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N-AcetylCarnosine vs Cataracts / Glaucoma
https://pubmed.ncbi.nlm.nih.gov/12001824/
Efficacy of N-acetylcarnosine in the treatment of cataracts
Mark A Babizhayev, et al.
Abstract
Purpose: To evaluate the effects of 1% N-acetylcarnosine (NAC) solution on lens clarity over 6 and 24 months in patients with cataracts.
Trial design: Randomised, placebo-controlled study.
Participants: 49 subjects (76 affected eyes) with an average age of 65.3 +/- 7.0 years with a diagnosis of senile cataract with minimum to advanced opacification in various lens layers.
Methods: 26 patients (41 eyes) were allocated to topical NAC 1% eyedrops twice daily. The control group consisted of 13 patients (21 eyes) who received placebo eyedrops and 10 patients (14 eyes) who did not receive eyedrops.
Main outcome measures: All patients were evaluated at entry and followed up every 2 months for a 6-month period (trial 1), or at 6-month intervals for a 2-year period (trial 2), for best-corrected visual acuity and glare testing. In addition, cataract was measured using stereocinematographic slit-images and retro-illumination examination of the lens. Digital analysis of lens images displayed light scattering and absorbing centres in two- and three-dimensional scales.
Results: The overall intra-reader reproducibility of cataract measurements (image analysis) was 0.830, and glare testing 0.998. After 6 months, 90% of NAC-treated eyes showed improvement in best corrected visual acuity (7 to 100%) and 88.9% showed a 27 to 100% improvement in glare sensitivity. Topographic studies indicated fewer areas of posterior subcapsular lens opacity and 41.5% of treated eyes had improvement in image analysis characteristics. The overall ratios of image analysis characteristics at 6 months compared with baseline measures were 1.04 and 0.86 for the control and NAC-treated group, respectively (p < 0.001). The apparent benefits of treatment were sustained after 24 months' treatment. No treated eyes demonstrated worsening of vision. The overall visual outcome in the control group showed significant worsening after 24 months in comparison with both baseline and the 6-month follow-up examination. The overall clinical results observed in the NAC-treated group by the 24-month period of examination differed significantly (p < 0.001) from the control group in the eyes with cortical, posterior subcapsular, nuclear or combined lens opacities. Tolerability of NAC eyedrops was good in almost all patients, with no reports of ocular or systemic adverse effects.
Conclusion: Topical NAC shows potential for the treatment and prevention of cataracts.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6464029/
N‐acetylcarnosine (NAC) drops for age‐related cataract
...As part of normal metabolism, our bodies produce chemicals that contain oxygen and are reactive ("reactive oxygen species"). One theory of ageing is that these chemicals may be harmful and might lead to age‐related changes in our body, such as cataract. This is known as oxidative stress. N‐acetylcarnosine (NAC) is thought to be able to combat some of the effects of oxidative stress as it has anti‐oxidant properties. If NAC can stop the lens from becoming cloudy, or reduce the cloudiness, this might improve people's vision and quality of life.
What are the main results of the review?
The Cochrane researchers found two potentially relevant studies. The studies compared NAC eye drops with placebo or no treatment. These studies were from Russia and the United States and were conducted by the same research group.The Cochrane researchers were unable to find out enough information about these studies to include in the review. These studies are assigned as ‘awaiting classification’ in the review until sufficient information can be obtained from the authors...
https://www.sciencedirect.com/science/article/abs/pii/S0196978101004077
N-Acetylcarnosine, a natural histidine-containing dipeptide, as a potent ophthalmic drug in treatment of human cataracts
Abstract
A study was designed to document and quantify the changes in lens clarity over 6 and 24 months in 2 groups of 49 volunteers (76 eyes) with an average age of 65.3 ± 7.0 enrolled at the time of diagnosis of senile cataracts of minimal to advanced opacification.
The patients received N-acetylcarnosine, 1% sol (NAC) (26 patients, 41 eyes = Group II), placebo composition (13 patients, 21 eyes) topically (two drops, twice daily) to the conjunctival sac, or were untreated (10 patients, 14 eyes); the placebo and untreated groups were combined into the control (reference) Group I. Patients were evaluated upon entry, at 2-month (Trial 1) and 6-month (Trial 2)-intervals for best corrected visual acuity (b/c VA), by ophthalmoscopy and the original techniques of glare test (for Trial 1), stereocinematographic slit-image and retro-illumination photography with subsequent scanning of the lens. The computerized interactive digital analysis of obtained images displayed the light scattering/absorbing centers of the lens into 2-D and 3-D scales.
The intra-reader reproducibility of measuring techniques for cataractous changes was good, with the overall average of correlation coefficients for the image analytical data 0.830 and the glare test readings 0.998. Compared with the baseline examination, over 6 months 41.5% of the eyes treated with NAC presented a significant improvement of the gross transmissivity degree of lenses computed from the images, 90.0% of the eyes showed a gradual improvement in b/c VA to 7–100% and 88.9% of the eyes ranged a 27–100% improvement in glare sensitivity. Topographic studies demonstrated less density and corresponding areas of opacification in posterior subcapsular and cortical morphological regions of the lens consistent with VA up to 0.3. The total study period over 24 months revealed that the beneficial effect of NAC is sustainable. No cases resulted in a worsening of VA and image analytical readings of lenses in the NAC-treated group of patients. In most of the patients drug tolerance was good. Group I of patients demonstrated the variability in the densitometric readings of the lens cloudings, negative advance in glare sensitivity over 6 months and gradual deterioration of VA and gross transmissivity of lenses over 24 months compared with the baseline and 6-month follow-up examinations. Statistical analysis revealed the significant differences over 6 and 24 months in cumulative positive changes of overall characteristics of cataracts in the NAC-treated Group II from the control Group I.
The N-acetylated form of natural dipeptide L-carnosine appears to be suitable and physiologically acceptable for nonsurgical treatment for senile cataracts.
Introduction
Cataract is the leading cause of blindness worldwide, accounting for over 50% of the world’s blind population, affecting some 17 million people [36]. Although surgical extraction of the involved lens is effective, there is a considerable interest in identifying the risk and protective factors involved in cataractogenesis [35]. Age-related cataract is a multifactorial disease, and different risk factors appear to play a role for different cataract types. Numerous studies postulate that oxidative stress to the lens mediated by reactive oxygen species and lipid peroxides produced in the crystalline lens can initiate the process of cataractogenesis [2], [13], [18], [22], [23], [31], [34]. It is established that superoxide anion radical, hydroxyl radical, hydrogen peroxide, singlet oxygen and lipid peroxides can be generated by photochemical reactions in the lens surroundings triggering the development of different forms of cataract [7], [11], [30], [33], [38] and that the use of antioxidant supplements appears to be protective against cataract [29]. Peroxide damage to the lens plasma membranes may lead to disturbance of their permeability for ions, loss of thiol groups of the membrane-bound crystallins and the appearance of new fluorophores and also large protein aggregates with low solubility (scattering matrix) in the substance of the lens thus affecting the development of cortical (C), posterior subcapsular (PSC) and nuclear (N) cataracts [4], [10], [11], [20].
L-Carnosine (β-alanyl-L-histidine) and related β-alanyl histidyl dipeptides (anserine and balenine) are generally found in mM concentrations in several mammalian tissues, potentially exhibiting different metabolic activities [14]. The previously published data suggest that L-carnosine has excellent potential to act as a natural antioxidant with hydroxyl radical, singlet oxygen scavenging and lipid peroxidase activities [14], [21]. A striking effect of L-carnosine is its demonstrated ability to prevent, or partially reverse, lens cataract [3], [19]. Exogenous carnosine entering the organism intravenously, intraperitoneally, with food or topically to the eye, is not accumulated by the tissues but is excreted in the urine or destroyed by carnosinase, a dipeptidase enzyme that is present in blood plasma, liver, kidney and other tissues except muscle and probably lens [3], [24].
The N-acetyl derivatives of histidine, carnosine and anserine exist in the cardiac and skeletal mammalian muscles and the total concentration of these imidazoles may lie within the measured range of L-carnosine in skeletal muscle (∼10 mM) [27]. The pharmaceutical compositions containing N-acetylcarnosine aluminum salt have been reported for the treatment of gastric ulcers [28]. Among 29 dipeptides of the carnosine family tested as potential substrates for a highly purified human serum carnosinase preparation, N-acetylcarnosine and few other compounds were not hydrolyzed, [24] thus promising a prolongation of physiological responses to the therapeutic treatments. A knowledge of corneal and iris/ciliary body esterase activity, in particular, acetylesterase (EC 3.1.1.6) and, in addition to esterase, the identified N-acetyltransferase activities [1] prompted the development of a prodrug of L-carnosine in its ophthalmic application as antioxidant such as the chemically characterized N-acetylated form of the dipeptide [16]. Experiments with N-acetylcarnosine (NAC) (1% sol) topically administered to the rabbit eyes (instillation, subconjunctival injection, ultrasound-induced administration) revealed its penetration into the eye and accumulation of the native form of L-carnosine in aqueous humor within 15–30 min of administration extending in order of the indicated therapeutic modalities [6], [8], [16]. The NAC molecule showed a moderate inhibiting activity for catalysis of phosphatidylcholine liposomal peroxidation in vitro, less pronounced than that of L-carnosine [16].
The advantage of NAC to act as an in vivo universal antioxidant with physiological and therapeutic relevance deals with its ability to give efficient protection against oxidative stress in the lipid phase of biological membranes and in aqueous environment due to turnover into L-carnosine [6], [8], [16]. Due to relative hydrophobicity compared with L-carnosine, NAC might penetrate through the cornea gradually, thus maintaining longer the active therapeutic concentration of L-carnosine in aqueous humor of the treated eye [16]. Different techniques of ocular administration of NAC showed its excellent tolerability to the eye, safety and the lack of possible side effects [16]. The clinical study was designed to be a prospective evaluation of the lens opacities and visual function in cataractous patients who applied topically to the eye (eye drops) the physiologically acceptable solution of NAC [6], [8].
Clinical design
The research was performed in agreement with the principles of Helsinki Declaration (ed. 1964 and following revisions) and the “Guidelines on the quality, safety and efficacy of pharmaceutical products used in European Community” (91/507/CEE). Each patient received verbal and written explanations about the object of the trial and the properties of the drugs which he would take. Each patient was also informed about his rights, particularly the right of withdrawing from the trial without any
Results
The distribution of cataracts in the examined patients is shown in Fig. 3, Fig. 4. There was a good concordance in the severity of cataract between slit-lamp, photograding, glare test readings and the b/c VA results (Table 2). High values of the linear correlation coefficients (r) for 34 examined eyes between VA and parameters of the glare test and image analytical grading ranged from −0.83 to −0.52 at initial study and from −0.80 to −0.55 at 5–6-months follow-up. Ophthalmic examinations
Discussion
L-Carnosine appeared to be suitable for the therapy and prophylaxis of cataracts as a water-soluble antioxidant inhibiting oxidative modification of proteins, accumulation of DNA damages and utilizing lipid peroxides in the lens as precursors to opacification [3], [14], [19]. A spectrum of physiological and antioxidant activities of L-carnosine in vivo is limited however, since this dipeptide readily becomes accessible for hydrolysis with human cytosolic and serum carnosinases, the latter being...
References (38)
https://worldwide.espacenet.com/publicationDetails/biblio?DB=EPODOC&II=0&ND=3&adjacent=true&locale=en_EP&FT=D&date=20070718&CC=CN&NR=100998863A&KC=A#
CN100998863
N-acetyl carnosine eye drops for preventing and treating cataract and its preparation method
An N-acetylcarnosine eyedrops for preventing and treating cataract is disclosed. Its preparing process features use of buffering liquid, lubricant, chelating agent, antiseptic agent and viscosity increaser for improving its osmotic pressure, stability and stay time in eye.
Technical areas:
The invention belongs to the technical field of pharmaceutical preparations.
Specifically related to N-acetyl carnosine eye drops for preventing and treating cataracts and preparation methods.
Background technique:
Cataract is one of the main causes of blindness. About 1/4 of the population over 65 years old is blind due to senile cataract. Senile cataract is a frequently-occurring and common disease among the elderly. As the population ages, the incidence rate is getting higher and higher. Senile cataract is a degenerative disease of the lens with a long course and progressive aggravation until the lens becomes completely cloudy and blind. Current cataract treatment methods mainly use drugs to delay the development of cataracts, and remove them through surgery when the cataracts are completely cloudy. However, about 2% of patients will develop postoperative syndrome after surgical treatment, and 30 to 50% of patients will relapse within two years.
The gradual oxidation of the eye lens cell membrane by free radicals is the main cause of senile cataracts. The surface of the eye lens is covered with epithelial cells, which contain a high content of antioxidants and can resist free radical damage.
After entering old age, the antioxidants in some people's lens epithelial cells gradually decrease, and free radicals can undergo oxidation reactions with the lens cell membrane through intercellular material exchange, making the lens increasingly turbid. Carnosine has a wide range of uses. As an effective antioxidant, it can prevent or delay cataract symptoms. At high doses, it can reverse cataracts and turn the lens from turbid to clear. However, carnosine is unstable in the eyeball and is degraded to histidine by carnosinase long before it enters the aqueous humor of the eye. N-acetyl carnosine (NAC) is a derivative of carnosine. Its chemical name is N-acetyl-β-alanine-L-histidine (N-Acetyl-β-alany-L-histidine). It has a strong It resists carnosinase hydrolysis and can pass through the cornea of the eyeball, reach the aqueous humor, and be converted into carnosine to protect against free radical damage.
WO95/10294 did some research on the pharmacological effects and pharmacokinetics of NAC in ophthalmology, confirmed that the drug has anti-lipid peroxidation effects in vitro, and proved that NAC is converted into acetylcarnosine in the aqueous humor of rabbit eyes.
The patent proposes the following eye drop formula
example 1:
100ml eye drops:
N-acetyl carnosine 1.00g
Disodium hydrogen phosphate 0.80g
Sodium dihydrogen phosphate 0.15g
Thimerosal 0.004g
Ethylenediaminetetraacetic acid calcium sodium salt 0.005g
Add sterile distilled water to 100ml
Example 2:
100ml eye drops:
N-acetyl carnosine 2.0g
Disodium hydrogen phosphate 1.6g
Sodium dihydrogen phosphate 0.3g
Thimerosal 0.004g
Ethylenediaminetetraacetic acid calcium sodium salt 0.005g
Add sterile distilled water to 100ml
After calculation and testing, the osmotic pressure of this 1% content formula is only about half of the normal human eye osmotic pressure, which will cause great irritation to human eyes.
Moreover, the preservative thimerosal used in both formulas is not suitable for long-term use due to mercury toxicity.
In addition, because ordinary eye drops are easily lost from the eyes, it affects the efficacy of the drug.
Contents of the invention:
The technical problem to be solved by the present invention is to overcome the above-mentioned defects and research and design an eye drop with low irritation and long retention time.
The invention provides an N-acetyl carnosine eye drop, which is composed of the following ingredients:
A buffer solution (or 0.8% ( m/v) anhydrous sodium phosphate dibasic and 0.9437% (m/v) anhydrous sodium phosphate disodium in a ratio of 10:90~30:70), 0.5~1% (m/v) glycerol , 0.01～0.25% (m/v) benzalkonium chloride (or benzalkonium bromide), 0.004～0.075% (m/v) chelating agent disodium ethylenediaminetetraacetate (or calcium sodium salt), tackifier Sodium hyaluronate (or polymer materials such as MC, HPMC, CMC-Na, etc.) and sterile water for injection.
The concentration of N-acetyl carnosine in the present invention can be 0.5 to 2% (m/v).
The present invention uses the above-mentioned borate or phosphate with a pH of about 7.0 as a buffer solution, and adjusts the osmotic pressure to isotonicity by increasing or decreasing the dosage.
The present invention uses glycerol as lubricant to increase eye comfort.
The present invention uses benzalkonium chloride or benzalkonium bromide as an antibacterial preservative, which can be used for a long time and has little irritation.
The present invention uses disodium ethylenediaminetetraacetate or calcium sodium salt of ethylenediaminetetraacetate as chelating agent to improve drug stability.
The present invention uses sodium hyaluronate (or polymer materials such as MC, HPMC, CMC-Na) as a thickening agent to adjust the viscosity to 10-60cp, prolonging the retention time of the drug in the eye, thereby improving the pharmacological effect and avoiding excessive loss of the drug. quick.
Sodium hyaluronate is preferred.
Sodium hyaluronate is mild and non-irritating within a certain range, has stable properties and has the same viscosity and elasticity as biological tears. It has good tolerance and has a lubricating effect, which is unmatched by other polymer materials. .
According to literature reports, eye drops containing sodium hyaluronate can reduce the contact angle by more than 10°, have good corneal wettability, are easier to spread evenly on the corneal surface, and can improve local bioavailability.
Another object of the present invention is to provide a method for preparing N-acetyl carnosine eye drops. The method is to dissolve the viscosity-increasing agent with water for injection one day in advance, and then add the ingredients in the order of the formula during preparation (solid ingredients are Add after dissolving in water for injection), mix evenly, filter with microporous filter membrane or sand core funnel, sterilize with flowing steam at 100°C for 30 minutes, cool and pack aseptically to prepare the N-acetyl carnosine eye drops of the present invention. .
The N-acetyl carnosine eye drops of the present invention are isotonic with tears, have excellent stability, are comfortable to use and non-irritating, and add a viscosity increasing agent to extend the residence time of the drug in the eyes, thereby improving the pharmacological effect and preventing the drug from being lost too quickly , which has good clinical application value in preventing and treating cataract disease.
Pharmacodynamic test of N-acetyl carnosine eye drops
1 material
1.1 Animals
84 healthy Wistar rats, weighing 60-80 grams, half male and half female, were provided by the Animal Center of Zhejiang University of Traditional Chinese Medicine.
1.2 Sample
1% N-acetyl carnosine eye drops, Shanghai New Drug Development Center, batch number: 050420, 050427; Binaide eye drops (pirenoxine sodium eye drops), Wuhan Wujing Pharmaceutical Co., Ltd., batch number: 05040204; Shapuaisi (benzyda lysine eye drops), Zhejiang Pinghu Shapuaisi Pharmaceutical Co., Ltd., batch number: 050419; 1% atropine eye drops, Hangzhou No. 1 Hospital Preparation, batch number: 050125; D-galactose Liquid, Shanghai Hengxin Chemical Reagent Co., Ltd., batch number: 030926; MDA, SOD, GSH-PX, CAT reagents, Nanjing Jiancheng Bioengineering Institute, MDA batch number 20050716, SOD batch number 20050602, GSH-PX batch number 20050719, CAT batch number 20050725.
2Experimental methods
2.1 Grouping
After no abnormality in the eyes of each group was detected by slit lamp, the rats in each group were divided into 7 groups randomly according to gender and weight, with 12 rats in each group.
The 1st group is the normal control group; the 2nd group is the model group; the 3rd and 4th groups are the positive control groups of Bronidine and Shapuis respectively; the 5th and 6th groups are respectively the N-acetyl carnosine eye drops, Low dose (medium dose 6 times/day, low dose 3 times/day) treatment group.
2.2 Cataract model preparation
2.2.Preparation of 150% galactose
Dissolve galactose in distilled water to prepare a 50% solution, and sterilize it at high temperature before use.
2.2.2 Modeling
Animals in each group were intraperitoneally injected with 50% galactose solution in the morning and evening at doses of 12g/kg and 8.4g/kg, respectively, for 29 consecutive days. The blank group was intraperitoneally injected with the same volume of normal saline.
All experimental animals were fed balanced diets by the Animal Center of our hospital.
2.3 Administration
Each group of animals was instilled 0.1 ml of their respective eye drops into the conjunctival sacs on both sides. After administration, the animal's eyelids were passively closed by hand for 5-10 seconds.
Among them, the animals in the 1st and 2nd groups were treated with physiological saline drops on both eyes, 6 times a day; the animals in the 3rd and 4th groups were treated with intravenous sodium eye drops (pirenoxine sodium eye drops), Shapuaisi (benzdalai), respectively. N-acetyl carnosine eye drops were applied to both eyes, 6 times a day; animals in groups 5 and 6 were all treated with N-acetyl carnosine eye drops, and the number of eye drops was 6 and 3 times a day respectively.
Administration was started 3 days before modeling and continued for 31 days.
2.4 Efficacy evaluation
2.4.1 Observation and scoring of crystal turbidity
From the 3rd day after the start of modeling, 1% atropine was used to dilate the pupils every other day. The rats' crystals were observed with a slit lamp microscope under ether anesthesia. The time when the lens opacity appeared and the degree of opacity were recorded and drawn. At the same time, a Nikon 4500 digital camera was used. Take photos.
The degree of crystal opacity is scored according to Table 1.
Table 1 Rat lens opacity scoring criteria
2.4.2 Determination of crystal biochemical indicators
2.4.2.1 Preparation of crystal homogenate: One day after stopping the drug, the rats were killed by pulling their necks. Take out the eyeballs of both eyes, cut off the back wall of the eyeballs, completely separate the crystals, peel off the vitreous body, use filter paper to absorb the water on the surface of the crystals, and quickly weigh it. And record the crystal weight.
Immediately put the crystals into the homogenization tube, add 1.2 ml of physiological saline, grind thoroughly for 5 minutes in an ice bath to prepare crystal homogenate, centrifuge (speed 3600 rpm, 10 minutes), and take the supernatant to measure various indicators.
2.4.2.2 Determination of the contents of superoxide dismutase (SOD), glutathione peroxidase (GSH-PX), catalase (CAT) and malondialdehyde (MDA) in crystals.
Take 0.2ml of the supernatant from each tube, and measure its content according to the methods shown in the SOD, GSH-PX, CAT and MDA kits.
2.5 Statistical processing
The data is represented by <img file="A20061002326600091.TIF" he="16" id="idf0001" img-content="drawing" img-format="tif" wi="39"/>. Use SPSS statistical software to conduct variance analysis on the results. P＜0.05 and P＜0.01 are the signs of significant difference.
3 results
(1) Effect of N-acetyl carnosine eye drops on lens opacity in rats
The crystals were observed under a slit lamp microscope. After the first week of galactose administration, vacuoles appeared in the crystals of some rats in the model group, and then the crystal opacity developed progressively. By the fourth week, the crystal opacity scores of the rats in the model group had reached 4. points and above, the crystal turbidity of each group is shown in Table 2.
It can be seen from Table 2: ① Compared with the normal control group and the model group, on the 12th, 19th and 31st days after administration, the crystal opacity score of the model group was significantly higher than that of the normal control group (p<0.01), indicating that the modeling was successful. .
On the 12th day after administration, the crystal opacity scores of the medium and low dose N-acetyl carnosine eye drops groups were significantly lower than those of the model group (p<0.01); on the 19th day after administration, the middle and low dose N-acetyl carnosine eye drops The lens opacity score of the dose group was significantly lower than that of the model group (p<0.01). On the 31st day after administration, the lens opacity score of the N-acetylcarnosine eye drops medium-dose group was lower than that of the model group (p<0.01). , the lens opacity score of the low-dose N-acetylcarnosine eye drops group was lower than that of the model group (p<0.05).
On the 12th, 19th, and 31st days after administration, the crystal turbidity scores of the leucine and saprois groups were significantly lower than those of the model group (p<0.01).
The above results show that N-acetyl carnosine eye drops can delay the formation and development of cataracts in rats.
Table 2 Effect of N-acetyl carnosine eye drops on lens opacity scores in rats
Compared with the model group: 1〕p＜0.05, 2〕p＜0.01.
(2) Effect of N-acetyl carnosine eye drops on the contents of SOD, GSH-PX, CAT and MDA in rat lens
The results can be seen in Table 3:
① The activity of crystalline SOD in the model group was significantly lower than that in the blank control group (p<0.01); the middle and low dose groups of N-acetyl carnosine eye drops were significantly higher than those in the model group (p<0.01); The thinking group was also significantly higher than the model group (p<0.01).
[0073]
② The activity of crystalline CAT in the model group was significantly lower than that in the blank control group (p<0.01); the middle and low doses of N-acetyl carnosine eye drops in the three dose groups were significantly higher than those in the model group (p<0.01); The thinking group was also significantly higher than the model group (p<0.01).
③The activity of crystalline GSH-PX in the model group was significantly lower than that in the blank control group (p<0.01); the middle and low dose groups of N-acetyl carnosine eye drops were significantly higher than the model group (p<0.01); The Puaisi group was also significantly higher than the model group (p<0.01).
④The content of crystalline MDA in the model group was significantly higher than that in the blank control group (p<0.01); the middle and low dose groups of N-acetyl carnosine eye drops were significantly lower than those in the model group (p<0.01); Bronine and Shapuai The thinking group was also significantly lower than the model group (p<0.01).
The above results show that the activities of SOD, CAT and GSH-PX in the lens of the N-acetyl carnosine eye drops, medium and low dose groups were significantly higher or higher than the model group, while the content of lipid peroxidation product MDA was lower than the model group. It shows that N-acetyl carnosine eye drops can increase the activity of antioxidant enzymes in the lens of rats and reduce oxidative damage to the lens.
Table 3 Effect of N-acetyl carnosine eye drops on the contents of SOD, CAT, GSH-PX and MDA in rat lens
Compared with the model group: 1〕p＜0.05, 2〕p＜0.01
**Number of crystals: normal control group (24), model group (24), leucine control group (22), Shapuaisi control group (22), N-acetyl carnosine eye drops medium dose group (24) , N-acetyl carnosine eye drops low-dose group (20).
[0081]
*Number of crystals: In addition to the normal control group (21), model group (23), leucine control group (21), Shapuaisi control group (21), and N-acetyl carnosine eye drops medium dose group (23) , the remaining groups are the same as above.
in conclusion
Observation of lens turbidity under a slit lamp microscope showed that N-acetyl carnosine eye drops significantly reduced the score of lens opacity in the rat D-galactose cataract model, indicating that it has the effect of delaying the occurrence and development of cataracts.
Crystal biochemical measurements show that N-acetyl carnosine eye drops can significantly increase the activities of SOD, CAT, and GSH-Px and reduce the content of MDA.
Oxidative damage is the main factor inducing senile cataract (SC) [3]. Aging leads to a decrease in crystal antioxidant enzyme activity and an increase in free radicals in the crystal, which denatures and turbids the crystal protein, leading to cataracts.
N-acetyl carnosine eye drops can delay the occurrence and development of cataracts, possibly by increasing the activity of antioxidant enzymes in the lens of rats, reducing the production of peroxidation products, and enhancing the protective effect on the lens.
Test on eye irritation of acetyl carnosine eye drops in rabbits
1. Experimental purpose:
Observe the irritation reaction and recovery of rabbit eyes after multiple exposures to acetyl carnosine eye drops.
2. Animals and materials
Animals: Adult healthy rabbits, weighing 2~3kg, half male and half female.
Provided by the Animal Center of Zhejiang University of Traditional Chinese Medicine.
Test drugs: homemade acetyl carnosine eye drops: batch number 051026, control patent formula: batch number: 051102, normal saline eye drops: batch number 20051205
3. Test method:
As a congenital self-control, 8 healthy adult rabbits were selected and randomly divided into two groups, with four rabbits in each group, half male and half female.
Raised in a single cage.
The temperature of the rabbit's animal room is 20°C (±3°C), and the relative humidity is 30%-70%.
Artificial light, 12 hours of daylight, 12 hours of darkness.
No restriction on food and water.
Observe and record the condition of the cornea, iris and conjunctiva within 24 hours before medication. Those with existing lesions or inflammation will be discarded.
One group of rabbits received homemade acetyl carnosine eye drops (0.1ml/eye) in the left conjunctival sac of rabbits; another group of rabbits received control patented formula eye drops (0.1ml/eye) in the left conjunctival sac of the right eye. An equal amount of normal saline was dripped onto both sides as a control, 4 times a day (10:00, 12:00, 14:00, 16:00) for 9 consecutive days.
Compress the nasolacrimal duct during each administration. After administration, the animal's eyelids are passively closed by hand for 5 to 10 seconds.
Eyes were examined with a hand-held slit lamp before daily dosing and 1, 2, 4, 24, 48 and 72 hours after the last dose, and recorded accordingly.
If no irritation symptoms occur, continue observation for 7 days.
4. Test results:
The results of the eye irritation test were judged and evaluated according to the "Research Guidelines for New Traditional Chinese Medicines" of the Pharmaceutical Administration of the Ministry of Health of the People's Republic of China. According to the requirements of Appendix 1 (Eye Irritation Response Scoring Standard), each animal and subject were compared at each observation time. The sum of the irritation reaction scores of the cornea, iris and conjunctiva after drug exposure is the total score of the irritation reaction of the test drug. The sum of the irritation reaction scores of each group of test animals is divided by the number of animals, which is the total score of the irritation reaction of the subject. The final score of the irritation of the test animal is determined based on the highest score, and the degree of eye irritation of the test drug is determined according to Appendix 2 (Eye Irritation Evaluation Standard).
The experimental results are shown in Table 1 and Table 2.
5. Conclusion:
As can be seen from Table 1, the comprehensive average score of eye irritation of rabbits after multiple administrations of homemade acetyl carnosine eye drops for 9 consecutive days is 0.5. According to the (Eye Irritation Evaluation Standard), the comprehensive average score of eye irritation is 0.5. The range of 0 to 3.9 is non-irritating. Therefore, it is believed that the eye drops have no irritating reaction to the cornea, iris and conjunctiva of rabbits.
As can be seen from Table 2, the comprehensive average score of irritation to rabbit eyes after multiple administrations of the control patented formula eye drops for 9 consecutive days is 1. Similarly, it can be considered that the control formula eye drops are irritating to the cornea and iris of rabbits. There was no irritation reaction to the skin and conjunctiva.
Table 1 Results of scoring of eye irritation reaction of homemade acetyl carnosine eye drops on rabbits
Table 2 Results of the irritation reaction scores of rabbit eyes compared with patented formula eye drops
Schedule
Appendix Table 1 Eye Irritation Reaction Scoring Criteria
Appendix 2 Eye Irritation Evaluation Criteria
Eye drops stability test
According to the requirements of the Guiding Principles of Drug Stability Testing in Appendix XIX C of Part II of the Chinese Pharmacopoeia 2000 Edition, the stability of acetyl carnosine eye drops was investigated.
Three batches of eye drops were examined.
1.1 Source of samples and reference materials
Three batches of acetyl carnosine eye drops (031009, 031013, 031015) were all provided by the preparation room of the New Drug Center, and all test results met the tentative quality standards.
Acetyl carnosine reference substance was provided by the synthesis laboratory of the Center for New Drugs.
1.2 Sample packaging: medicinal high-pressure polyethylene eye drops in bottles
1.3 Inspection items: content, related substances, osmotic pressure, pH value, appearance, etc.
1.4 Inspection method: The above inspection items are all inspected according to the draft quality standard of Acetyl Carnosine Eye Drops
1.5 Inspection results:
(1) Test of influencing factors
1. High temperature test:
Take a batch of this product (030909), remove the outer packaging, place it at 60°C, take samples for inspection on the 5th day and the 10th day, and compare with the 0 day.
Conclusion: This product was placed at 60°C for 10 days, and there was no significant change in various indicators. This product is stable to high heat.
2. Strong light exposure test:
Take a batch of this product (030909), remove the outer packaging, place it under the conditions of 4500lx±500lx, take samples for inspection on the 5th day and the 10th day, and compare with the 0 day.
Conclusion: This product was placed under the conditions of 4500lx±500lx for 10 days, and there was no significant change in various indicators. This product is stable to strong light.
(2) Accelerated test
1. Take three batches of this product (031009, 031013, 031015), simulate the packaging for the market, place it at 40°C and a relative humidity of 75%, and take samples for inspection at 1 month, 2 months, 3 months, and 6 months respectively. 0 month comparison.
Conclusion: This product was placed at 40°C and relative humidity of 75% for 6 months, and the results showed no significant changes, indicating that the quality of this product is stable at 40°C and relative humidity of 75%.
2. Take three batches of this product (031009, 031013, 031015), simulate the packaging for the market, place them at 25°C and relative humidity of 20%, and take samples for inspection at 1 month, 2 months, 3 months, and 6 months respectively. 0 month comparison.
Conclusion: This product was placed at 25°C and relative humidity of 20% for 6 months, and the results showed no significant changes, indicating that the quality of this product is stable at 25°C and relative humidity of 20%.
(3) Long-term test of retained samples at room temperature
Take three batches of this product (031009, 031013, 031015), simulate market packaging, place them at 25°C and relative humidity of 60%, and take samples for inspection at 3, 6, 9, 12, 18, and 24 months respectively, and 0 months Compare.
Conclusion: This product was placed at 25°C and relative humidity of 60% for 24 months, and the results showed no significant changes, indicating that the quality of this product is stable at 25°C and relative humidity of 60%.
Detailed ways
Example 1:
100ml eye drops formula:
NAC 1g
Boric acid 0.848g
Borax 0.146g
Glycerin 1.0g
Benzalkonium chloride 0.01g
EDTA-2Na 0.004g
Sodium hyaluronate 0.11g
Add water for injection to 100ml
Dissolve 0.11g sodium hyaluronate with 25ml of water for injection one day in advance, accurately weigh 1.0g of NAC, dissolve it in about 40ml of borate buffer (containing 0.848g of boric acid, 0.146g of borax), and add 1.0g of glycerin and 1% Mix 1 ml of benzalkonium chloride solution and 1 ml of 0.4% EDTA disodium salt. After mixing, add sodium hyaluronate solution. After mixing thoroughly, filter through a 0.8 μm microporous membrane, sterilize with steam at 100°C for 30 minutes, and cool. Then sterilely dispense it into 10ml eye drop bottles.
According to the osmotic pressure measurement, it is isotonic with tears, and the eye drops are comfortable and non-irritating.
Viscosity 13.5cp (25℃, Brookfeild viscometer, ultra-low viscosity adapter).
Around PH6.2, the appearance is clear.
Example 2
100ml eye drops formula:
NAC 2.0g
Sodium dihydrogen phosphate 0.156g
Disodium hydrogen phosphate 2.017g
Glycerin 0.5g
Benzalkonium Bromide 0.01g
EDTA calcium sodium salt 0.004g
Hydroxypropyl methylcellulose 2g
Add water for injection to 100ml
Dissolve 2g of hydroxypropyl methylcellulose with 25ml of water for injection one day in advance and set aside. Accurately weigh 2.0g of NAC and dissolve it in about 50ml of phosphate buffer (containing 0.156g of sodium dihydrogen phosphate and 2.017g of disodium hydrogenphosphate). Add 0.5g of glycerin, 1ml of 1% benzalkonium bromide solution and 1ml of 0.4% EDTA calcium sodium salt. After mixing, add hydroxypropyl methylcellulose solution. After mixing thoroughly, filter with 0.8μm microporous filter membrane, 100 Sterilize with circulating steam at ℃ for 30 minutes, cool and then aseptically dispense into 10ml eye drop bottles.
According to the osmotic pressure measurement, it is isotonic with tears, and the eye drops are comfortable and non-irritating.
Viscosity 17.5cp (25℃, Brookfeild viscometer, ultra-low viscosity adapter).
PH is about 6.7 and the appearance is clear.
Example 3
100ml eye drops formula:
NAC 0.5g
Boric acid 1.283g
Borax 0.220g
Glycerin 0.5g
Benzalkonium chloride 0.01g
EDTA disodium salt 0.004g
Sodium carboxymethyl cellulose 0.76g
Add water for injection to 100ml
Dissolve 0.76g sodium carboxymethylcellulose with 25ml of water for injection one day in advance and set aside. Accurately weigh 0.5g of NAC and dissolve it in about 50ml of borate buffer (containing 1.283g of boric acid and 0.220g of borax). Add 0.5g of glycerol and 1 ml of 1% benzalkonium bromide solution and 1 ml of 0.4% EDTA disodium salt. After mixing, add sodium carboxymethyl cellulose solution. After mixing thoroughly, filter through a No. 3 sand core funnel and sterilize with steam at 100°C for 30 minutes. , cool and then sterilely dispense into 10ml eye drop bottles.
According to the osmotic pressure measurement, it is isotonic with tears, and the eye drops are comfortable and non-irritating.
Viscosity 27.7cp (25℃, Brookfeild viscometer, ultra-low viscosity adapter).
PH is about 6.7 and the appearance is clear.
https://en.wikipedia.org/wiki/Acetylcarnosine
N-Acetylcarnosine (NAC)
N-Acetylcarnosine (NAC) (Not to confuse with N-Acetylcysteine) is a naturally occurring[1] compound chemically related to the dipeptide carnosine. The NAC molecular structure is identical to carnosine with the exception that it carries an additional acetyl group. The acetylation makes NAC more resistant to degradation by carnosinase, an enzyme that breaks down carnosine to its constituent amino acids, beta-alanine and histidine.[2]
Actions
Carnosine and metabolic derivatives of carnosine, including NAC, are found in a variety of tissues but particularly muscle tissue.[1] These compounds have varying degrees of activity as free radical scavengers.[1] It has been suggested that NAC is particularly active against lipid peroxidation in the different parts of the lens in the eye.[3] It is an ingredient in eye drops that are marketed as a dietary supplement (not a drug) and have been promoted for the prevention and treatment of cataracts. There is scant evidence on its safety, and no convincing evidence that the compound has any effect on ocular health.
Research
Most of the clinical research on NAC has been conducted by Mark Babizhayev of the US-based company Innovative Vision Products (IVP), which markets NAC treatments.
During early experiments performed at the Moscow Helmholtz Research Institute for Eye Diseases, it was shown that NAC (1% concentration), was able to pass from the cornea to the aqueous humour after about 15 to 30 minutes.[4] In a 2004 trial of 90 canine eyes with cataracts, NAC was reported to have performed better than placebo in positively affecting lens clarity.[5] An early human study NAC reported that NAC was effective in improving vision in cataract patients and reduced the appearance of cataract.[6]
The Babizhayev group later published a placebo-controlled clinical trial of NAC in 76 human eyes with mild to advanced cataracts and reported similar positive results for NAC. However, a 2007 scientific review of the current literature discussed the limitations of the clinical trial, noting that the study had low statistical power, a high dropout rate and "insufficient baseline measurement to compare the effect of NAC", concluding that "a separate larger trial is needed to justify the benefit of long-term NAC therapy".[7]
Babizhayev and colleagues published a further human clinical trial in 2009. They reported positive results for NAC as well as arguing "only certain formulas designed by IVP... are efficacious in the prevention and treatment of senile cataract for long-term use."[8]
Commentary
The Royal College of Ophthalmologists remains very skeptical about claims of efficacy in cataract reversal. It issued the following public statement about NAC in August 2008:
The evidence for the effectiveness of N-acetyl carnosine eye drops is based on experience on a small number of cases carried out by a Russian research team [Babizhayev]. To date, the research has not been corroborated and the results replicated by others. The long-term effect is unknown. Unfortunately, the evidence to date does not support the 'promising potential' of this drug in cataract reversal. More robust data from well conducted clinical trials on adequate sample sizes will be required to support these claims of efficacy. Furthermore, we do not feel the evidence base for the safety is in any way sufficient to recommend its use in the short term. More research is needed.[9]
In a 2010 book on ocular disease, the current state of this subject is summarized as follows:
Carnosine (β-alanyl-L-histidine), and its topical prodrug formulation N-acetylcarnosine (NAC), is advertised (especially on the internet) to treat a range of ophthalmic disorders associated with oxidative stress, including age-related and diabetic cataracts. No convincing animal studies or masked clinical trials have been reported.[10]
A Cochrane review summarizing research up to June 2016 has concluded that there is "no convincing evidence that NAC reverses cataract, nor prevents progression of cataract".[11] The authors did not include the studies conducted by the Babizhayev group because they were unable to establish that the research used scientific methods appropriate for clinical
References
Boldyrev A, Abe H (February 1999). "Metabolic transformation of neuropeptide carnosine modifies its biological activity". Cell. Mol. Neurobiol. 19 (1): 163–75. doi:10.1023/a:1006914028195. PMID 10079975.
Pegova A, Abe H, Boldyrev A (December 2000). "Hydrolysis of carnosine and related compounds by mammalian carnosinases". Comp. Biochem. Physiol. B. 127 (4): 443–6. doi:10.1016/S0305-0491(00)00279-0. PMID 11281261.
Bonnefont-Rousselot D (2001). "Antioxidant and anti-AGE therapeutics". J Soc Biol. 195 (4): 391–398. doi:10.1051/jbio/2001195040391. PMID 11938556. S2CID 90728419.
Babizhayev MA, Yermakova VN, Sakina NL, et al. (1996). "N alpha acetylcarnosine as a pro-drug of L-carnosine in ophthalmic application as antioxidant". Clin Chim Acta. 254 (1–2): 1–21. doi:10.1016/0009-8981(96)06356-5. PMID 8894306.
Babizhayev MA, Deyev AI, Yermakova VN, Brikman IV, Bours J (2004). "Lipid peroxidation and cataracts: N-acetylcarnosine as a therapeutic tool to manage age-related cataracts in human and in canine eyes". Drugs in R&D. 5 (3): 125–39. doi:10.2165/00126839-200405030-00001. PMID 15139774. S2CID 68176996.
Babizhayev MA, Deyev AI, Yermakova VN, et al. (2002). "Efficacy of N-acetylcarnosine in the treatment of cataracts". Drugs in R&D. 3 (2): 87–103. doi:10.2165/00126839-200203020-00004. PMID 12001824. S2CID 5696698.
Toh T, Morton J, Coxon J, Elder MJ (2007). "Medical treatment of cataract". Clin. Experiment. Ophthalmol. 35 (7): 664–71. doi:10.1111/j.1442-9071.2007.01559.x. PMID 17894689. S2CID 43125880.
Babizhayev MA, Burke L, Micans P, Richer SP (2009). "N-Acetylcarnosine sustained drug delivery eye drops to control the signs of ageless vision: glare sensitivity, cataract amelioration and quality of vision currently available treatment for the challenging 50,000-patient population". Clin Interv Aging. 4: 31–50. doi:10.2147/cia.s4090. PMC 2685223. PMID 19503764.
"N-Acetyl Carnosine for cataracts". Archived from the original on 2011-09-29. Retrieved July 15, 2012.
"Clinical Guidelines". Archived from the original on 2012-06-23. Retrieved August 16, 2012.
Levin LA, Albert DM (2010). Ocular Disease: Mechanisms and Management: Expert Consult - Online and Print, 1e. Saunders. p. 249. ISBN 978-0702029837.
Dubois VD, Bastawrous A (2017). "N-acetylcarnosine (NAC) drops for age-related cataract". Cochrane Database of Systematic Reviews. 2017 (2): CD009493. doi:10.1002/14651858.CD009493.pub2. ISSN 1465-1858. PMC 6464029. PMID 28245346.
https://www.naturalmedicinejournal.com/journal/l-carnosines-effects-cataract-development
January 15, 2014
L-Carnosine's Effects on Cataract Development
Cataract is the opacification of the ocular lens or capsule.
Tina Kaczor, ND, FABNO
Abstract
Cataracts are the leading cause of blindness worldwide. With an aging population, the incidence and prevalence of cataract-induced blindness is expected to rise considerably. L-carnosine (β-alanyl-L-histidine) is an endogenous dipeptide compound in vertebrates that has been designated an “antiaging” molecule due to its ability to delay senescence of cells. L-carnosine and N-acetyl-L-carnosine have demonstrated a reduction in opacification of the lens when used as a direct instillation to the eye. These compounds represent a promising new means of addressing cataracts.
Introduction
Cataract is the opacification of the ocular lens or capsule. According to the World Health Organization, in the year 2002, the last year that statistics were estimated, cataracts caused nearly half of the 37 million cases of blindness worldwide.1 In the United States, 20.5 million Americans over the age of 40 are affected in at least one eye, with an estimated increase to over 30 million Americans by the year 2020.2 Surgery is the only treatment option available and, while highly successful at restoring sight, it is not feasible in many developing countries that lack the infrastructure for adequate access to care.3 Ultimately, an easily disseminated medication that is economical and convenient could have a profound impact on the prevalence of the disease.4 Currently no agent is approved for use in preventing or delaying the onset of cataracts. There is evidence, however, that the natural agent L-carnosine (β-alanyl-L-histidine) effectively delays cataract development. The uniformity of benefit from preliminary evidence on carnosine and lens health, combined with a low toxicity profile make this endogenous dipeptide an intriguing candidate for prevention of cataract formation.
Background
Lens fiber cells are long, transparent cells continually produced by epithelial cells in the anterior portion of the lens and growing around the periphery (like longitudinal lines on a globe) to reach the posterior aspect. This process begins embryologically with the first lens fiber cells essentially providing the nexus upon which fetal and then adult lens fibers are built. Anatomically, these cells accumulate like layers in an onion, with the center becoming the nuclear region, outside of which is the cortical region. Aptly named, the subcapsular region is found between the cortical region and capsule that encompasses the lens.
Of note, all mature lens fiber cells lack nuclei or organelles, necessitating diffusion of many molecules, including nutrients, into the cells. The lack of intracellular structures and complete solubility of proteins, predominantly proteins called crystallins, within the lens cells is necessary for light rays to penetrate to the back of the eye.
Cataracts are classified into 3 types, depending on the region of the eye in which they originate. Nuclear cataracts begin at the center of the lens and affect distant vision in particular. These are the most common type of cataract and are thought to occur due to the aging process—thus the common term “age-related” or “senile” cataracts. Cortical cataracts are also called “diabetic cataracts”; they begin in the periphery of the lens and progress inward in a spoke-like fashion. Subcapsular cataracts usually begin at the back of the lens (posterior subcapsular cataracts) and are found in patients with a history of diabetes, steroid use, retinitis pigmentosa, or severe nearsightedness.
While symptomology varies between type and degree of cataract, the main symptoms of cloudy vision and sensitivity to glare is common to all forms at some stage of development. Double vision or multiple images in one eye can also occur. Unique to the development of nuclear cataracts, there may be a period of “second sight,” when the focus of near objects improves. This ability to see close objects more clearly is short lived, however, as the lens becomes more opaque and cloudy vision more severe. Cortical cataracts affect both distant and near vision and, while blurring occurs, sensitivity to glare and loss of contrast are more significant in this type of cataract. Subcapsular cataracts usually occur concomitantly with nuclear or cortical, and this type is marked by a more rapid progression.
Before any agents, synthetic or natural, are considered it is prudent to address known risk factors for cataract development. Risk factors include aging, diabetes, obesity, exposure to UVB radiation, smoking, previous eye surgery, prolonged use of some drugs (eg, corticosteroids, some diuretics, antipsychotics), and previous eye injury or inflammation. While many of these can be actively addressed through lifestyle modifications, others such as aging and eye injury clearly cannot be controlled. In addition to these established risk factors, epidemiological data suggests dietary intake of several nutrients can be protective. Nutrients such as taurine, carotenoiods, tocopherol, and acsorbate have shown a protective role from the development of some types of cataracts.5,6
Carnosine is an endogenous dipeptide synthesized by carnosine synthase in an ATP-dependent reaction that links amino acid substrates histidine and β-alanine. A high concentration is found in skeletal muscle fibers. As such, L-carnosine is also obtained from meat in the diet, although it appears to undergo rapid degradation by serum carnosinase. L-carnosine is also found in neural tissue, with a larger concentration in the olfactory bulb. Its biological role is not known conclusively, but the higher concentrations in these long-living cells is in keeping with its putative role as an antisenescence molecule.7
The presence of endogenous carnosine in the lens of the eye suggests it is needed in normal physiological processes.8 Of note, there is no evidence that the eye contains carnosine synthase. Therefore carnosine, like many other nutrients, must be derived from systemic circulation, diffusing into the aqueous humor then subsequently into the lens cells themselves. Carnosinase, the enzyme that degrades carnosine into its component amino acids, is found in the eye. The presence of carnosinase may result in rapid degradation of carnosine into its component amino acids.
L- Carnosine versus N-acetylcarnosine
Currently, N-acetylcarnosine (NAC), not L-carnosine, eye drops are commercially available. NAC was found to be a prodrug of L-carnosine within the eye, as it undergoes deacetylation to release carnosine into the aqueous humor.9 Since carnosine is thought to be rapidly degraded by resident carnosinase in the lens, and NAC appears to be protected from this enzyme, the instillation of NAC was proposed as a means of achieving a more effective delivery of L-carnosine to the lens. Furthermore, NAC is a less hydrophobic molecule, so it may more readily pass through the membrane lipid bilayer of lens cells. While the data on these compounds is certainly not interchangeable, when considering the compounds as an instillation directly into the eye, the molecular effects of L-carnosine can be extrapolated to include that seen with NAC as well, since the latter compound is completely deacetylated in situ to render L-carnosine.
Overview of Cataractogenesis and Carnosine
The development of cataracts, or cataractogenesis, is marked by many of the same processes that are involved in the senescence of cells. Namely, reactive oxygen species (ROS), advanced glycation end products (AGEs), and deleterious aldehydes and thiols accumulate intracellularly. In excess, these incendiary molecules lead to changes in lipid and protein structures that are the hallmark of aging cells. Two morphological changes that directly result in increasing opacification are peroxidation of the lipid bilayer of cellular membranes of the lens and crosslinking of otherwise soluble crystallin proteins forming insoluble aggregates within the lens fiber cells. Each of these macromolecular changes leads to disruption in the passage of light through the lens by scattering light rays, and with adequate accumulation, this eventually can obscure light passage completely.
The ability of L-carnosine to attenuate the products of lipid peroxidation within the ocular lens was first suggested by Dr. Alan Babizhayev and colleagues in 1987.10 Indeed, much research has since confirmed that carnosine reduces the formation of lipid peroxides within the lens.11,12,13
In addition to directly attenuating membrane structure damage through lessening peroxidation of lipids, reduction of lipid peroxides also reduces the formation of its highly reactive metabolite, malondialdehyde (MDA). MDA interacts with amino acid moieties on crystallin proteins within the lens to cause crosslinking of these proteins, resulting in insoluble aggregate molecules.14
In cataracts, many enzymes that normally provide defense against ROS overproduction, including superoxide dismutase and catalase, are depleted.15 Exacerbating this effect, the nuclear region of the lens is normally dependent on the production and subsequent diffusion of glutathione from the cortical region, but this diffusion process becomes less efficient as we age.16 Carnosine has been shown to preserve levels of these enzymes in cataract lenses, thus improving their antioxidative capacity.17 There is also postulation that carnosine lessens ROS damage through its ability to chelate free metal ions, which are required to generate O2-.18
Separately, carnosine has been shown to act as an alternative target for glycation, a “sacrificial transglycation,” that effectively binds sugars to itself rendering them unavailable to bind proteins. This leads to a measurable decrease in AGEs and may be responsible for much of carnosine’s antisenescence action apart from its antioxidant capacity.19
Another mechanism by which carnosine is able to reduce protein adducts is by directly binding to carbonyl groups on proteins. Carbonyl groups increase in high oxidation and glycation environments; thus they often coincide with aging of cells. Carnosine’s binding to reactive carbonyls, a process called “carnosinylation,” prevents proteins from binding to one another and forming adducts.20
Remarkably, L-carnosine has been shown capable of deaggregating the crystalline lens proteins that directly result in opacity. Methylglyoxal-induced glycation of α-crystallin aggregates was reversed with the addition of carnosine to the media.21 The ability of carnosine to denatured protein aggregates was also demonstrated in an in vitro study of rat lenses. Both L- and D-carnosine had a “disassembling” effect on α-crystallin fibrils and restored the transparency of cataractous lenses. This was accompanied by a reduction in the average size of the proteins, confirming that disassembly did take place.22
A dominant pathway of cataractogenesis in diabetic patients, in addition to those discussed above, is the polyol pathway. This is the sequential transformation of glucose into sorbitol and subsequently fructose within the lens by the enzymes aldose reductase and sorbitol dehydrogenase, respectively.23 Aldose reductase inhibitors have been found to prevent sugar-induced cataracts, thus confirming the integral role of this pathway on cataract formation.24 The fructose molecule is highly reactive and, together with oxidized proteins and a direct reduction of esterase activity, leads to AGEs. Carnosine has been shown to directly inhibit aldehyde reductase, thus lowering the concentration of fructose and AGEs.25 Further, the addition of carnosine to lens media abrogated fructose induced deactivation of esterase activity.26
In Vivo Studies
In one study using rats with streptozocin-induced diabetes, cataract development was shown to progress in a biphasic manner, with a slow progression in the first 8 weeks followed by a rapid increase in the next 5 weeks. Carnosine delayed the onset of lens opacification in the early stages of cataract development, reaching statistical significance at week 4 (P<0.05), but failed to affect later progression of the disease. This rodent study also demonstrated a reduction in the levels of AGEs in treated eyes versus untreated, which was concordant with better preservation of glutathione and catalase levels in the treated groups.27
NAC may not only act as a progdrug but may itself be involved in the antiaggregation effects observed with NAC-containing eye drops. A rodent study using UV-induced cataractogenesis supported this finding and suggested that a mixture of D-pantethine and NAC is even more effective than NAC alone in its antiaggregate effects.28
A recent study using rats with streptozocin-induced diabetes showed a delay in the development of cataracts using an instillation of aspirin (1%), L-carnosine (1%), or an alternating combination of the 2. Both single agent interventions delayed cataracts while the combination was more effective than either agent alone. In addition, there was an increase in the levels of soluble protein in the lenses of the treated groups versus controls.29
In a small study, 30 dogs of various breeds with existing lens opacities were administered a combination product containing 2% NAC. Additional ingredients in the proprietary formula include glutathione, cysteine ascorbate, L-taurine, and riboflavin (Ocluvet™, by Practivet, Arizona, USA). 58 eyes of 30 dogs were evaluated, 22 with mature cataract, 13 with immature cataract, 9 with cataract associated with eye inflammation, and 14 with nuclear sclerosis. Images of the lenses were taken at weeks 2, 4, and 8. Objective measurement of lens opacification was determined by a lens opacification index (LOI) using computerized integration of the grayscale level of each pixel across the lens image. There was a reduction in the level of LOI in all groups, although this was only statistically significant in the immature cataract and nuclear sclerosis groups. Subjectively, owners perceived improvement in 80% of the dogs studied. The greater benefit in early cataract development supports in vitro data that suggests later stages of cataract development appear to overwhelm the benefits of antioxidant support.30
Another canine study using 1.0% NAC in its patented formulation (Can-C®, Innovative Vision Products, Delaware, USA) used 30 dogs in the treatment group, 15 dogs in placebo-controlled group, and 10 dogs without treatment. All dogs had cataracts at the start and all eyes were assessed. Placebo consisted of all ingredients in the drops except NAC. After 6 months of treatment, 96% of eyes in the treatment group showed improvement in the slit image and retroillumination photographs. No mention is given in the publication of the statistical analysis or of the results of the 2 nontreatment groups.31
Babizhayev and colleagues have shown beneficial effects of 1.0% NAC instillation in the eyes in several small human clinical trials. In a randomized study of 49 subjects with senile cataracts (76 affected eyes), 26 (41 affected eyes) were given NAC (1.0%) eyedrops twice daily. There were 2 control groups: a placebo group of 13 patients (21 affected eyes) who received an eye drop formulation containing all ingredients but NAC and an untreated group of 10 patients (14 eyes) who did not receive any eye drops. For statistical analysis, the control groups were pooled. The 6-month outcome showed 90% of patients in the treated group had improved visual acuity and 89% showed improved glare sensitivity. Image analysis of the cataracts at 6 months showed a statistically significant difference (P<.0001) using an in-house imaging that included slit-lamp assessment and retroillumination of the lenes to assess.32
In a continuation of the above study, the participants were assessed every 6 months for a total of 24 months. At 24 months no one in the treatment group had declining visual acuity, while overall there was a decline in the control group. Overall, reductions in glare sensitivity and visual acuity were sustained for the 24 month duration of the study; this difference was statistically significant (P< .0001).33
In another trial by the same group, 65 older drivers with 1 or both eyes affected by cataract and 72 older adult controls without cataract were recruited to participate in a double-blind, placebo-controlled trial. Assessment of glare sensitivity (halos) at red and green targets was made using an in-house test. At 4 months participants receiving NAC had a statistically significant improvement in visual acuity and glare sensitivity (P<0.001).34
In 2009 another trial of 75 patients with cataracts and 72 without, 1.0% NAC was instilled daily for 9 months. In both groups visual acuity and reduction in glare sensitivity reached statistical significance (P<0.001) at 9 months.35
Discussion
A growing body of evidence suggests that L-carnosine attenuates aging processes, ultimately culminating in delayed senescence of the organism as a whole, as suggested in Drosophila and mouse models.36 Mechanisms of carnosine’s antiaging effects include its role as an antioxidant, antiglycating agent, metal chelating agent, aldehyde scavenger, carbonyl scavenger, and stimulator of nitric oxide synthase.37 Many of these are relevant to the development of cataracts, and it is a reasonable assumption that carnosine’s beneficial effects in the lens are largely due to these mechanisms of cellular self-preservation. For a thorough review of carnosine’s biological effects throughout the body, the reader is referred to a recent publication by Alan Hipkiss.38
Much of the clinical research demonstrating the efficacy of carnosine in preventing or treating cataracts in humans has been done by Dr. Babizhayev of Innovative Vision Products (IVP), Delaware, USA. His group proposed the use of NAC as a prodrug for L-carnosine in 1996.39 Since then, IVP has manufactured a patented formula called Can-C (private label, Nu-Eyes) which consists of deionized water, glycerin (1.0%), NAC (1.0%), carboxymethylcellulose (0.3%), benzyl alcohol (0.3%), and potassium borate and bicarbonate buffers.40 Babizhayev’s group proposes this particular formulation obtains superior absorption through the cornea and that acetylation of carnosine optimizes the delivery of carnosine into the lens in several ways: protection from degradation by carnosinase in the aqueous humor, a more lipophilic molecule that allows for easier penetration into the lens, and, due to the pharmacokinetics of deacetylation, “timed release” of the carnosine molecule.41,42
Babizhayev and colleagues reported that instillation of non-acetylated L-carnosine (1%) to rabbit eyes did not lead to an increase of L-carnosine concentration in the anterior compartment versus placebo, an effect they speculate is due to carnosinase degradation of the dipeptide.43 While this is in keeping with the assumption that carnosinases in the eye rapidly degrade L-carnosine, there is recent evidence of L-carnosine accumulation in the eyes of rabbits using a 5.0% instillation.44 Further, Babisheyev asserts that not only is L-carnosine less effective than NAC, but that there may be risk of harm to the eye due to the byproduct of histamine that ultimately results from the degradation of carnosine. These predictions are disputed, at least in part, by data in animals that demonstrates reduced cataractogenesis with the use of L-carnosine eye drops.45 There is no in vivo data that directly compares the efficacy of L-carnosine versus NAC eyedrops. More definite studies are needed to unequivicably conclude whether NAC is superior to L-carnosine.
While there is no data on dietary consumption of carnosine and cataract development, serum carnosine levels do decrease with age.46 Given carnosine’s multiple antisenescent actions, this correlation may be part of the aging process itself. Carnosine levels can be increased through the consumption of meat, and a carnivorous diet has been postulated to have possible antiaging effects.47 Strict vegetarian diets are devoid of the peptide, so a diet high in carnosine precursors histidine and alanine, with emphasis on the more rate-limiting alanine, may be the closest simulation. Oral supplementation of carnosine or its substrates has not been studied in regard to eye health. There is also no data to suggest a diet high in carnosine will effectively diminish cataract formation.
Conclusion
The endogenous dipeptide carnosine (β-alanyl-L-histidine) is recognized as an antiaging molecule at both cellular and whole animal levels. Overall, the state of the evidence on carnosine’s role in delaying or treating cataractogenesis is preliminary. However, the role of carnosine as a universal antiaging molecule is fairly well established. This larger body of evidence, along with the uniformity of beneficial effects on cataractous lenses in the limited studies that have been published, provide rationale for consideration of this nontoxic agent in delay of cataract development, particularly in early stage cataracts.
References
1 Resnikoff S, Pascolini D, Etya’ale D, et al. Global data on visual impairment in the year 2002. Bulletin of the World Health Organization. 2004;82:844-851.
2 Congdon N, Vingerling JR, Klein BE, et al. Prevalence of cataract and pseudophakia/aphakia among adults in the United States. Arch Ophthalmol. Apr 2004;122(4):487-494.
3 Chang M, Congdon N, Baker S, Bloem M, Savage H, Sommer A. The surgical management of cataract: barriers, best practices and outcomes. International Ophthalmology. 2008;28(4):247-260.
4 Toh T, Morton J, Coxon J, Elder MJ. Medical treatment of cataract. Clin Experiment Ophthalmol. Sep-Oct 2007;35(7):664-671.
5 Taylor A, Jacques P, Chylack L, et al. Long-term intake of vitamins and carotenoids and odds of early age-related cortical and posterior subcapsular lens opacities. Am J Clin Nutr. 2002;75(3):540-549.
6 Christen W, Liu S, Glynn R, Gaziano M, Buring J. Dietary Carotenoids, Vitamins C and E, and Risk of Cataract in Women: A Prospective Study. Arch Ophthalmol. 2008;126(1):102-109.
7 Hipkiss AR. Chapter 3 Carnosine and Its Possible Roles in Nutrition and Health. In: Steve LT, ed. Advances in Food and Nutrition Research. Vol Volume 57: Academic Press; 2009:87-154.
8 Quinn PJ, Boldyrev AA, Formazuyk VE. Carnosine: Its properties, functions and potential therapeutic applications. Molecular Aspects of Medicine. 1992;13(5):379-444.
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14 Bhuyan KC, Bhuyan DK. Molecular mechanism of cataractogenesis: III. Toxic metabolites of oxygen as initiators of lipid peroxidation and cataract. Curr Eye Res. Jan 1984;3(1):67-81.
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32 Babizhayev MA, Deyev AI, Yermakova VN, et al. Efficacy of N-acetylcarnosine in the treatment of cataracts. Drugs R D. 2002;3(2):87-103.
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36 Hipkiss AR. Chapter 3 Carnosine and Its Possible Roles in Nutrition and Health. In: Steve LT, ed. Advances in Food and Nutrition Research. Vol Volume 57: Academic Press; 2009:87-154.
37 Ibid.
38 Ibid.
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40 Babizhayev MA, Burke L, Micans P, Richer SP. N-Acetylcarnosine sustained drug delivery eye drops to control the signs of ageless vision: glare sensitivity, cataract amelioration and quality of vision currently available treatment for the challenging 50,000-patient population. Clin Interv Aging. 2009;4:31-50.
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43 Babizhayev MA. Analysis of lipid peroxidation and electron microscopic survey of maturation stages during human cataractogenesis: pharmacokinetic assay of Can-C N-acetylcarnosine prodrug lubricant eye drops for cataract prevention. Drugs R D. 2005;6(6):345-369.
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45 Yan H, Guo Y, Zhang J, Ding Z, Ha W, Harding JJ. Effect of carnosine, aminoguanidine, and aspirin drops on the prevention of cataracts in diabetic rats. Mol Vis. 2008;14:2282-2291.
46 Hipkiss AR. Chapter 3 Carnosine and Its Possible Roles in Nutrition and Health. In: Steve LT, ed. Advances in Food and Nutrition Research. Vol Volume 57: Academic Press; 2009:87-154.
47 Hipkiss A. Would carnosine or a carnivorous diet help suppress aging and associated pathologies? Annals of the New York Academy of Sciences. 2006;1067:369-374.
NMJ_APR10_NP
Efficacy of N-Acetylcarnosine in the Treatment of Cataracts
March 2002Drugs in R & D 3(2):87-103
DOI:10.2165/00126839-200203020-00004
Authors: Mark A Babizhayev, et al.
Abstract
To evaluate the effects of 1% N-acetylcarnosine (NAC) solution on lens clarity over 6 and 24 months in patients with cataracts. Randomised, placebo-controlled study. 49 subjects (76 affected eyes) with an average age of 65.3 +/- 7.0 years with a diagnosis of senile cataract with minimum to advanced opacification in various lens layers. 26 patients (41 eyes) were allocated to topical NAC 1% eyedrops twice daily. The control group consisted of 13 patients (21 eyes) who received placebo eyedrops and 10 patients (14 eyes) who did not receive eyedrops. All patients were evaluated at entry and followed up every 2 months for a 6-month period (trial 1), or at 6-month intervals for a 2-year period (trial 2), for best-corrected visual acuity and glare testing. In addition, cataract was measured using stereocinematographic slit-images and retro-illumination examination of the lens. Digital analysis of lens images displayed light scattering and absorbing centres in two- and three-dimensional scales. The overall intra-reader reproducibility of cataract measurements (image analysis) was 0.830, and glare testing 0.998. After 6 months, 90% of NAC-treated eyes showed improvement in best corrected visual acuity (7 to 100%) and 88.9% showed a 27 to 100% improvement in glare sensitivity. Topographic studies indicated fewer areas of posterior subcapsular lens opacity and 41.5% of treated eyes had improvement in image analysis characteristics. The overall ratios of image analysis characteristics at 6 months compared with baseline measures were 1.04 and 0.86 for the control and NAC-treated group, respectively (p < 0.001). The apparent benefits of treatment were sustained after 24 months' treatment. No treated eyes demonstrated worsening of vision. The overall visual outcome in the control group showed significant worsening after 24 months in comparison with both baseline and the 6-month follow-up examination. The overall clinical results observed in the NAC-treated group by the 24-month period of examination differed significantly (p < 0.001) from the control group in the eyes with cortical, posterior subcapsular, nuclear or combined lens opacities. Tolerability of NAC eyedrops was good in almost all patients, with no reports of ocular or systemic adverse effects. Topical NAC shows potential for the treatment and prevention of cataracts.