Nutritional supplementation to prevent cataract formation

Antioxidant Nutraceutical Strategies in the Prevention of Oxidative Stress Related Eye Diseases

This review aims to discuss the delicate balance between the physiological production of reactive oxygen species and the role of antioxidant nutraceutical molecules in managing radicals in the complex anatomical structure of the eye. Many molecules and enzymes with reducing and antioxidant potential are present in different parts of the eye. Some of these, such as glutathione, N-acetylcysteine, α-lipoic acid, coenzyme Q10, and enzymatic antioxidants, are endogenously produced by the body. Others, such as plant-derived polyphenols and carotenoids, vitamins B2, C, and E, zinc and selenium, and omega-3 polyunsaturated fatty acids, must be obtained through the diet and are considered essential nutrients. When the equilibrium between the production of reactive oxygen species and their scavenging is disrupted, radical generation overwhelms the endogenous antioxidant arsenal, leading to oxidative stress-related eye disorders and aging. Therefore, the roles of antioxidants contained in dietary supplements in preventing oxidative stress-based ocular dysfunctions are also discussed. However, the results of studies investigating the efficacy of antioxidant supplementation have been mixed or inconclusive, indicating a need for future research to highlight the potential of antioxidant molecules and to develop new preventive nutritional strategies.

Current Approach to the Pathogenesis of Diabetic Cataracts

Cataracts remain the first or second leading cause of blindness in all world regions. In the diabetic population, cataracts not only have a 3–5 times higher incidence than in the healthy population but also affect people at a younger age. In patients with type 1 diabetes, cataracts occur on average 20 years earlier than in the non-diabetic population. In addition, the risk of developing cataracts increases with the duration of diabetes and poor metabolic control. A better understanding of the mechanisms leading to the formation of diabetic cataracts enables more effective treatment and a holistic approach to the patient.

Aryl Hydrocarbon Receptor in Oxidative Stress as a Double Agent and Its Biological and Therapeutic Significance

The aryl hydrocarbon receptor (AhR) has long been implicated in the induction of a battery of genes involved in the metabolism of xenobiotics and endogenous compounds. AhR is a ligand-activated transcription factor necessary for the launch of transcriptional responses important in health and disease. In past decades, evidence has accumulated that AhR is associated with the cellular response to oxidative stress, and this property of AhR must be taken into account during investigations into a mechanism of action of xenobiotics that is able to activate AhR or that is susceptible to metabolic activation by enzymes encoded by the genes that are under the control of AhR. In this review, we examine various mechanisms by which AhR takes part in the oxidative-stress response, including antioxidant and prooxidant enzymes and cytochrome P450. We also show that AhR, as a participant in the redox balance and as a modulator of redox signals, is being increasingly studied as a target for a new class of therapeutic compounds and as an explanation for the pathogenesis of some disorders.

Influence of Gender and Age of Brown Seaweed (Fucus vesiculosus) on Biochemical Activities of Its Aqueous Extracts

Fucus vesiculosus L. is a common coastal brown seaweed associated with various benefits to human health due to its phenolic content and nutrients and is used as food through different methods of consumption. This study aims to evaluate the influence of the seaweed’s gender and growth stage on different types of biological activities as well as its chemical constitution and elements present. Akin to food preparation, aqueous extracts of the seaweed were prepared at 25 °C (salad) and 100 °C (soup). Biological activities were determined by measuring total phenol content (TPC), antioxidant activity and inhibition of acetylcholinesterase (AChE). Liquid Chromatography High Resolution Mass Spectrometry (LC-HRMS/MS) was used for compound identification, and elemental analysis was carried out by using Total Reflection X-ray Fluorescence Spectrometry (TXRF). Older females and males had higher TPC compared to the new ones at 100 °C. Antioxidant activity depended on the extraction temperature but was higher for the youngest male at 100 °C. AChE inhibitory activity was higher for older males at 25 °C, but at 100 °C it was higher for older females. Primary metabolites and various phloroglucinol were the main compounds identified. Additionally, since this seaweed is often harvested in estuarine systems with high anthropogenic impacts, its safety was evaluated through the evaluation of the sample’s metal content. The heavy metals detected are within the limits established by various regulating entities, pointing to a safe food source.

Ballota nigra L. – an overview of pharmacological effects and traditional uses

Ballota nigra, also known as black horehound is a common medical herb used in folk medicine around the world. First reported mentions of its medical properties and use goes as far as the 13th century. The use of black horehound depends on regions and countries. It is used mostly to treat e.g. mild sleep disorders, nervousness, upset stomach, wound healing. It can be used as an anti-inflammatory, antibacterial, antiprotozoal, antifungal drug. Moreover, it has been reported as a potential cancer drug. This extensive usage is particularly interesting for us. The aim of this review is to present available data on B. nigra pharmacological effects and known traditional uses gathered from a wide range of scientific articles published in 1997–2020.

A Mechanistic Review of β-Carotene, Lutein, and Zeaxanthin in Eye Health and Disease

Carotenoids are natural lipid-soluble antioxidants abundantly found as colorful pigments in fruits and vegetables. At least 600 carotenoids occur naturally, although about 20 of them, including β-carotene, α-carotene, lycopene, lutein, zeaxanthin, meso-zeaxanthin, and cryptoxanthin, are detectable in the human blood. They have distinct physiological and pathophysiological functions ranging from fetal development to adult homeostasis. β-carotene is a precursor of vitamin A that essentially functions in many biological processes including vision. The human macula lutea and eye lens are rich in lutein, zeaxanthin, and meso-zeaxanthin, collectively known as macular xanthophylls, which help maintain eye health and prevent ophthalmic diseases. Ocular carotenoids absorb light from the visible region (400-500 nm wavelength), enabling them to protect the retina and lens from potential photochemical damage induced by light exposure. These natural antioxidants also aid in quenching free radicals produced by complex physiological reactions and, consequently, protect the eye from oxidative stress, apoptosis, mitochondrial dysfunction, and inflammation. This review discusses the protective mechanisms of macular xanthophylls in preventing eye diseases such as cataract, age-related macular degeneration, and diabetic retinopathy. Moreover, some preclinical animal studies and some clinical trials are discussed briefly to understand carotenoid safety and efficacy.

Oxidative stress-induced diseases and tea polyphenols

Reactive oxide species are the middle products of normal metabolism, and play a crucial role in cell signaling transduction. On the contrary, accumulation of excess reactive oxide species results in oxidative stress that often brings multifarious impairment to cells, including decrease of ATP level in cells, elevation of cytosolic Ca2+, DNA damage, dysfunction of biological function in lipid bilayer and so on. These effects will finally lead to all kinds of diseases. Tea polyphenols are widely considered as a kind of excellent antioxidant agents. It can be antioxidants by directly scavenging reactive oxide species or chelating transition metals, and indirectly upregulating the activity of antioxidant enzymes. In addition, tea polyphenols have also been observed a potent pro-oxidant capacity, which directly leads to the generation of reactive oxide species, and indirectly induces apoptosis and death of cancer cells. The underlying characters of its pro-oxidant activity in some diseases is not well understood. The present review we will discuss the dual character of tea polyphenols, both antioxidant and pro-oxidant properties, in some human diseases induced by oxidative stress.

Photoperiodic regime influences onset of lens opacities in a non-human primate

Background

Opacities of the lens are typical age-related phenomena which have a high influence on photoreception and consequently circadian rhythm. In mouse lemurs, a small bodied non-human primate, a high incidence (more than 50% when >seven years) of cataracts has been previously described during aging. Previous studies showed that photoperiodically induced accelerated annual rhythms alter some of mouse lemurs’ life history traits. Whether a modification of photoperiod also affects the onset of age dependent lens opacities has not been investigated so far. The aim of this study was therefore to characterise the type of opacity and the mouse lemurs’ age at its onset in two colonies with different photoperiodic regimen.

Methods

Two of the largest mouse lemur colonies in Europe were investigated: Colony 1 having a natural annual photoperiodic regime and Colony 2 with an induced accelerated annual cycle. A slit-lamp was used to determine opacities in the lens. Furthermore, a subset of all animals which showed no opacities in the lens nucleus in the first examination but developed first changes in the following examination were further examined to estimate the age at onset of opacities. In total, 387 animals were examined and 57 represented the subset for age at onset estimation.

Results

The first and most commonly observable opacity in the lens was nuclear sclerosis. Mouse lemurs from Colony 1 showed a delayed onset of nuclear sclerosis compared to mouse lemurs from Colony 2 (4.35 ± 1.50 years vs. 2.75 ± 0.99 years). For colony 1, the chronological age was equivalent to the number of seasonal cycles experienced by the mouse lemurs. For colony 2, in which seasonal cycles were accelerated by a factor of 1.5, mouse lemurs had experienced 4.13 ± 1.50 seasonal cycles in 2.75 ± 0.99 chronological years.

Discussion

Our study showed clear differences in age at the onset of nuclear sclerosis formation between lemurs kept under different photoperiodic regimes. Instead of measuring the chronological age, the number of seasonal cycles (N = four) experienced by a mouse lemur can be used to estimate the risk of beginning nuclear sclerosis formation. Ophthalmological examinations should be taken into account when animals older than 5–6 seasonal cycles are used for experiments in which unrestricted visual ability has to be ensured. This study is the first to assess and demonstrate the influence of annual photoperiod regime on the incidence of lens opacities in a non-human primate.

Topical nutraceutical Optixcare EH ameliorates experimental ocular oxidative stress in rats

PURPOSE

Based on the hypothesis that oral nutraceuticals do not adequately reach all ocular tissues in the anterior segment, we evaluated the ability of a 3% concentration of the ingredients in a topical nutraceutical antioxidant formulation called Optixcare Eye Health (Optixcare EH) to ameliorate oxidative stress in rat models of age-related ocular diseases.

METHODS

Diabetes was induced by tail-vein injection of streptozotocin, and the development of cataracts was monitored by slit lamp. Young rats were exposed to ultraviolet (UV) light, and the reduction in lens glutathione (GSH) levels and increase in 4-hydroxynonenol (4-HNE) were measured. Oxidative stress in the neural retina was generated by exposure of dark-adapted rats to 1,000 lx of light, and oxidative stress markers were measured. Dry eye was induced in rats by twice daily (b.i.d.) subcutaneous scopolamine injections. Topical Optixcare EH was administered b.i.d. and compared in select experiments to the multifunctional antioxidant JHX-4, the topical aldose reductase inhibitor (ARI) Kinostat™, oral Ocu-GLO™, and the topical ocular comfort agents Optixcare Eye Lube, Optixcare Eye Lube + Hyaluron, and Idrop Vet Plus hyaluronic acid.

RESULTS

In diabetic rats, topical ARI treatment prevented cataract formation while the nutraceuticals delayed their development with Optixcare EH>Ocu-GLO. In UV-exposed rats, the reduction of GSH and increase in 4-HNE in the lens were normalized in order JHX-4>Optixcare EH>Ocu-GLO. In the retina, oxidative stress markers were reduced better by oral JHX-4 compared with topical Optixcare EH. In the scopolamine-induced dry-eye rats, tear flow was maintained by Optixcare EH treatment, while none of the comfort agents examined altered tear flow.

CONCLUSIONS

Topical administration of a 3% concentration of the ingredients in Optixcare EH reduces experimentally induced reactive oxygen species in rats exposed to several sources of ocular oxidative stress. In addition, Optixcare EH maintains tear volume in scopolamine-induced dry eye. This suggests that in the anterior segment, the ingredients in Optixcare EH may have clinical potential against ocular oxidative stress.

Advances in lens implant technology

Cataract surgery is one of the oldest and the most frequent outpatient clinic operations in medicine performed worldwide. The clouded human crystalline lens is replaced by an artificial intraocular lens implanted into the capsular bag. During the last six decades, cataract surgery has undergone rapid development from a traumatic, manual surgical procedure with implantation of a simple lens to a minimally invasive intervention increasingly assisted by high technology and a broad variety of implants customized for each patient’s individual requirements. This review discusses the major advances in this field and focuses on the main challenge remaining – the treatment of presbyopia. The demand for correction of presbyopia is increasing, reflecting the global growth of the ageing population. Pearls and pitfalls of currently applied methods to correct presbyopia and different approaches under investigation, both in lens implant technology and in surgical technology, are discussed.

Natural flavonoids as potential multifunctional agents in prevention of diabetic cataract

Cataract is one of the earliest secondary complications of diabetes mellitus. The lens is a closed system with limited capability to repair or regenerate itself. Current evidence supports the view that cataractogenesis is a multifactorial process. Mechanisms related to glucose toxicity, namely oxidative stress, processes of non-enzymatic glycation and enhanced polyol pathway significantly contribute to the development of eye lens opacity under conditions of diabetes. There is an urgent need for inexpensive, non-surgical approaches to the treatment of cataract. Recently, considerable attention has been devoted to the search for phytochemical therapeutics. Several pharmacological actions of natural flavonoids may operate in the prevention of cataract since flavonoids are capable of affecting multiple mechanisms or etiological factors responsible for the development of diabetic cataract. In the present paper, natural flavonoids are reviewed as potential agents that could reduce the risk of cataract formation via affecting multiple pathways pertinent to eye lens opacification. In addition, the bioavailability of flavonoids for the lens is considered.

Dietary supplementation: effects on visual performance and occurrence of AMD and cataracts

OBJECTIVE

To evaluate results of studies that have provided information regarding the effects of dietary supplementation on visual performance, development and progression of age-related macular degeneration (AMD), and risk for cataracts.

RESEARCH DESIGN AND METHODS

Studies with information about the effects of dietary supplementation were identified via PubMed searches that combined (in separate searches) the terms 'supplement' OR 'supplementation' OR 'diet' AND 'cataract' or 'macular degeneration' or 'visual' OR 'vision'. Additional references concerned with biologic effects of specific agents, measurement of visual function, and the etiology and epidemiology of cataracts and AMD were identified on the basis of PubMed conventional literature searches.

RESULTS

Studies of the effects of dietary supplementation, primarily with preparations including lutein and zeaxanthin, have demonstrated improvements in contrast sensitivity and visual performance under glare conditions that, in some studies, have been correlated with effects of treatment on macular pigment optical density. Results from both observational and prospective interventional studies generally support the conclusion that dietary supplements including these xanthophylls significantly decrease the occurrence of AMD and the development of nuclear lens opacities. However, there is variability in results regarding effects of dietary supplementation that may be related to limitations of long-term observational or interventional studies and which cannot be easily controlled or which may also be related in some studies to other important, yet unrecorded, diet- and lifestyle-related factors that are capable of influencing the risks for AMD and/or cataracts.

CONCLUSIONS

The multiple benefits of dietary supplementation support the development and use of these preparations to promote optimal visual function and decrease risk for AMD and cataracts. Increasing understanding of the optimal approach to supplementation will depend upon results from interventional studies that also carefully evaluate and analyze well-established factors for these two conditions.

Diabetic cataract-pathogenesis, epidemiology and treatment

Cataract in diabetic patients is a major cause of blindness in developed and developing countries. The pathogenesis of diabetic cataract development is still not fully understood. Recent basic research studies have emphasized the role of the polyol pathway in the initiation of the disease process. Population-based studies have greatly increased our knowledge concerning the association between diabetes and cataract formation and have defined risk factors for the development of cataract. Diabetic patients also have a higher risk of complications after phacoemulsification cataract surgery compared to nondiabetics. Aldose-reductase inhibitors and antioxidants have been proven beneficial in the prevention or treatment of this sightthreatening condition in in vitro and in vivo experimental studies. This paper provides an overview of the pathogenesis of diabetic cataract, clinical studies investigating the association between diabetes and cataract development, and current treatment of cataract in diabetics.

Carbon nanotubes: promising agents against free radicals

The potential role of carbon nanotubes (CNTs) as free-radical scavengers is still an emerging area of research. So far some promising results have been reported strongly suggesting that CNTs can be very efficient for that task. The implications of such a valuable property for applications aimed at biomedical and environmental uses are encouraging. There are still abundant open questions related to the possible use of CNTs for scavenging free radicals. Thus much more work needs to be devoted to this fascinating topic. In this mini review the progress made so far is reviewed and some future perspectives are provided.

Preventive effect of onion juice on selenite-induced experimental cataract

Purpose:

To evaluate the effects of onion juice on sodium-selenite induced cataract formation.

Materials and Methods:

Thirty-two 10-day-old Wistar-albino rat pups were divided into four equal groups. Group 1 received only subcutaneous saline injection. In Group 2, sodium-selenite (30 nmol/g body weight) was injected subcutaneously. In Group 3, subcutaneous sodium-selenite was injected and one drop 50% diluted fresh juice of crude onion was instilled every 8 h into the right eye for 14 days; the left eye received no treatment. Group 4 rats were similar to those of Group 3, the only difference being that of undiluted fresh juice of crude onion. The development of cataract was assessed. Rat lenses were analyzed for total antioxidant (TA) level, and for activities of glutathione peroxidase (GPX) and superoxide dismutase (SOD).

Results:

Both eyes of all rats in Group 1 did not exhibit cataract formation. In Group 2, all rats developed Grade 3 cataract in the lenses of both eyes. The difference in exhibited cataract in the lens of the right eyes in all rats between Group 2 and any eyes of groups 3 or 4 were significant (P = 0.001). The mean TA level and mean activities of SOD and GPX in Group 2 rat lenses were significantly lower than the values in lenses of all rats in Group 1 (P = 0.001, 0.003, 0.001), and in the lenses of the right eyes of rats in Groups 3 and 4 (P = 0.001, 0.020, 0.001).

Conclusion:

Instillation of onion juice into the rat eyes can effectively prevent selenite-induced cataract formation. This effect was associated with increased TA level, SOD and GPX activities in the lens.

Comparative study of plasma ascorbic acid levels in senile cataract patients and in normal individuals

OBJECTIVE

Dietary antioxidant vitamins, in particular vitamin C, could play a role in preventing the onset or progression of age-related visual impairment. The aim of this study was to determine the plasma ascorbic acid levels in normal individuals and in senile cataract patients.

METHOD

The test group included 50 cataract patients, while the control group members were selected among medical staff and patients' companions after age matching with the test group. Questionnaire forms contained age, sex, and location of residency (urban or rural) inquiries. Five milliliters of drawn blood was centrifuged, and plasma ascorbic acid level was measured by spectrophotometer. Statistical analysis of plasma ascorbic acid concentrations were done by paired test.

RESULTS

The mean plasma ascorbic acid level in the test group was 0.96 +/- 0.08 mg/dl and 1.12 +/- 0.15 mg/dl in the control group. Ascorbic acid level in the test group was significantly lower than the control group and p value = 0.00001. Aging had a reverse relation with plasma ascorbic acid level in males, while it showed no significant alterations in females. Rural compared with urban and females compared to males showed higher levels of plasma ascorbic acid.

CONCLUSION

This study revealed that plasma ascorbic acid level in cataract patients was lower than normal individuals. Antioxidant vitamins, in particular vitamin C, found in Mediterranean fruits and vegetables, can help with the prevention of cataracts, which is a major health service burden in many countries.

Metabolites from algae with economical impact

In order to survive in a highly competitive environment, freshwater or marine algae have to develop defense strategies that result in a tremendous diversity of compounds from different metabolic pathways. Recent trends in drug research from natural sources have shown that algae are promising organisms to furnish novel biochemically active compounds. The current review describes the main substances biosynthesized by algae with potential economic impact in food science, pharmaceutical industry and public health. Emphasis is given to fatty acids, steroids, carotenoids, polysaccharides, lectins, mycosporine-like amino acids, halogenated compounds, polyketides and toxins.

Vitamina C

Vitamin C or ascorbic acid is a hydrosoluble vitamin derived from glucose metabolism. It acts as a reductor agent required for synthesis of collagen fibers through hydroxylation of proline and lysine. It also protects the body against damage caused by the free radicals. Humans cannot synthesize ascorbic acid as they lack an enzyme called gulonolactone oxidase. Concentrations in plasma and leukocytes reflect the levels of the diet and body deposits respectively of this vitamin. Among foods with high vitamin C levels are tomatoes, potatoes, and citrus fruits such as limes, oranges and lemons. The current recommendation of daily intake of vitamin C is 90 mg/d for men and 75 mg/d for women. Patients with chronic diseases such as cancer or diabetes or those who smoke need higher doses in their usual diet. Ascorbic acid deficiency gives rise to the appearance of scurvy. This disease is rarely seen in developed countries. The symptoms develop with plasma levels below 0.15 mg/dL. Scurvy is characterized by the presence of weakness, joint pain or skin lesions in form of petechias, gum bleeding, ease of developing bruises or delay in wound healing. The most characteristic skin manifestations are purpuric perifollicular hyperkeratotic papules and the presence of kinky hair.