Cataract: relationship between nutrition and oxidation

Opium Use and the Risk of Cataract: a Hospital-based, Group-matched, Case-control Study in Iran

PURPOSE

Cataract is the most prevalent cause of reversible blindness worldwide. Although studies have identified risk factors for cataract, its association with opium use has not been studied. This study aimed to evaluate the association between opium use and cataract in Iran in 2020.

METHODS

In a hospital-based, group-matched case-control study in Kerman, a city in southeast Iran, 160 new cases of cataract and 320 controls without cataract underwent ophthalmological examination and were interviewed. Logistic regression models tested the association between cataract and history of opium use, adjusting for demographic characteristics and history of hypertension, coronary heart disease, renal disease, smoking, alcohol use, and unprotected sun exposure.

RESULTS

After controlling for potential confounders, opium use increased the odds of cataract, exhibiting a dose-response relationship. The adjusted odds ratio (aOR) for mild use was 1.44 (95% confidence intervals [CI] 0.80-2.58), and 2.10 (95% CI 1.04-4.25) for heavy use. Exposure to opium juice use further increased the odds of cataract (aOR 2.24, 95% CI 1.00-5.10). Other significant associations with cataract were lower education level (aOR 5.46, 95% CI 2.45-11.29), being unmarried (aOR 2.88, 95% CI 1.65-5.00), both underweight (BMI <18.5, aOR 5.27, 95% CI 2.02-13.70) and overweight (BMI >25, aOR 1.82, 95% CI 1.15-2.87), and family history of cataract (aOR 2.07, 95% CI 1.32-3.23).

CONCLUSION

Our study provides evidence that opium use could increase the odds of cataract. Results also support the association of cataract with other modifiable risk factors, such as very low and high BMI and unprotected sun exposure.

The Relationship between Nutrient Intake and Cataracts in the Older Adult Population of Korea

Cataracts are a prevalent ophthalmic disease worldwide, and research on the risk factors for cataracts occurrence is actively being conducted. This study aimed to investigate the relationship between nutrient intake and cataracts in the older adult population in Korea. We analyzed data from Korean adults over the age of 60 years (cataract: 2137, non-cataract: 3497) using the Korean National Health and Nutrition Examination Survey. We performed univariate simple and multiple logistic regressions, adjusting for socio-demographic, medical history, and lifestyle, to identify the associations between nutrient intake and cataracts. A higher intake of vitamin B1 in the male group was associated with a lower incidence of cataracts. A lower intake of polyunsaturated fatty acids and vitamin A, and a higher intake of vitamin B2 in the female group were associated with a higher incidence of cataracts. Our study demonstrated that polyunsaturated fatty acids, vitamin A, and vitamin B2 could affect the incidence of cataracts according to sex. The findings could be used to control nutrient intake for cataract prevention.

Insights into the biochemical and biophysical mechanisms mediating the longevity of the transparent optics of the eye lens

In the human eye, a transparent cornea and lens combine to form the "refracton" to focus images on the retina. This requires the refracton to have a high refractive index "n," mediated largely by extracellular collagen fibrils in the corneal stroma and the highly concentrated crystallin proteins in the cytoplasm of the lens fiber cells. Transparency is a result of short-range order in the spatial arrangement of corneal collagen fibrils and lens crystallins, generated in part by post-translational modifications (PTMs). However, while corneal collagen is remodeled continuously and replaced, lens crystallins are very long-lived and are not replaced and so accumulate PTMs over a lifetime. Eventually, a tipping point is reached when protein aggregation results in increased light scatter, inevitably leading to the iconic protein condensation-based disease, age-related cataract (ARC). Cataracts account for 50% of vision impairment worldwide, affecting far more people than other well-known protein aggregation-based diseases. However, because accumulation of crystallin PTMs begins before birth and long before ARC presents, we postulate that the lens protein PTMs contribute to a "cataractogenic load" that not only increases with age but also has protective effects on optical function by stabilizing lens crystallins until a tipping point is reached. In this review, we highlight decades of experimental findings that support the potential for PTMs to be protective during normal development. We hypothesize that ARC is preventable by protecting the biochemical and biophysical properties of lens proteins needed to maintain transparency, refraction, and optical function.

Vitamin C and the Lens: New Insights into Delaying the Onset of Cataract

Cataracts or clouding of the lens is the leading cause of blindness in the world. Age and diabetes are major risk factors, and with an increasing aging and diabetic population, the burden of cataracts will grow. Cataract surgery is an effective way to restore vision; however, alternatives to cataract surgery are required to reduce the looming cataract epidemic. Since it is well established that oxidative damage plays a major role in the etiology of cataracts, antioxidants have been promoted as therapies to delay and/or prevent cataracts. However, many antioxidant interventions including vitamin C have produced mixed results as anti-cataract therapies. Progress has been made towards our understanding of lens physiology and the mechanisms involved in the delivery and uptake of antioxidants to the lens which may guide future studies aimed at addressing some of the inconsistencies seen in previous animal and human studies. Of interest is the potential for vitamin C based supplements in delaying the onset of cataracts post vitrectomy which occurs in up to 80% of patients within two years. These targeted approaches are required to reduce the burden of cataract on hospitals and improve the quality of life of our aging and diabetic population.

Activation of Sirtuin1 by lyceum barbarum polysaccharides in protection against diabetic cataract

ETHNOPHARMACOLOGICAL RELEVANCE

Lycium barbarum polysaccharide (LBP) extracted from the Lycium barbarum L. has been widely used to improve diabetes and its relative complications. However, the mechanisms have not fully understood. A recent study has demonstrated that LBP upregulates suituin 1 (SIRT1).

OBJECTIVE

This study was to define the role of Sirt1 and its downstream signaling pathways in diabetic cataract using in vitro and in vivo models.

MATERIALS AND METHODS

Human lens epithelial cell line SRA01/04 cells were cultured under high glucose (HG) medium with treatment of LBP or vehicle. Cell viability, apoptosis, protein and/or mRNA levels of Sirt1, BAX, Bcl-2, active-caspase-3, FOXO1, p27 and acetylated p53 were measured. SIRT1 upregulated- and knocked-down cells were generated and tested in high glucose culture. Diabetes mellitus was induced in rats by streptozotocin injection. Body weight, blood glucose levels, lens transparency and retinal function were assessed and SIRT1, as well as the aforementioned biomarkers were measured using Western blotting and qPCR in the animal lens samples.

RESULTS

The results showed that HG decreased cell viability and LBP prevented the decrease. The reduced viability in HG cultured SRA01/04 cells was associated with increased levels of BAX, active caspase 3, FOXO1, p27, and p53 and decreased levels of SIRT1 and Bcl-2. Further experiments using sirt1 gene modulated cells showed that upregulation of Sirt1 improved viability, increase cell division as reflected by an increased proportion of S phase in the cell cycle, reduced the number of apoptotic cell death and suppressed p53 acetylation and caspase 3 activation. Opposite results were observed in SIRT1 knock-down cells. Treating diabetic animals with LBP reduced body weight loss and blood glucose content in diabetic animals. Similarly, LBP hindered the development of cataract in lenses and improved retinal function. The beneficial effect of LBP on diabetic cataract was associated with the supression of p53, caspase 3, FOXO1, BAX, p27 and elevation of SIRT1 and Bcl-2, which were consistent with the in vitro findings.

CONCLUSION

Our findings showed that diabetes caused cataract is associated with suppression of SIRT1 and Bcl-2 and activation of other cell death related genes. LBP prevented diabetic cataract in animals by upregulating Sirt1 and Bcl-2 and suppressing cell death related genes.

Flavonoid intake and the risk of age-related cataract in China's Heilongjiang Province

Background/objectives

Epidemiological evidence suggests that diets rich in flavonoids may reduce the risk of developing age-related cataract (ARC). Flavonoids are widely distributed in foods of plant origin, and the objective of this study was to evaluate retrospectively the association between the intakes of the five flavonoid subclasses and the risk of ARC.

Subjects/methods

A population-based case-control study (249 cases and 66 controls) was carried out in Heilongjiang province, which is located in the northeast of China, and where intakes and availability of fresh vegetables and fruits can be limited. Dietary data gathered by food-frequency questionnaire (FFQ) were used to calculate flavonoid intake. Adjusted odds ratio (OR) and 95% confidence interval (CI) were estimated by logistic regression.

Results

No linear associations between risk of developing ARC and intakes of total dietary flavonoids, anthocyanidins, flavon-3-ol, flavanone, total flavones or total flavonols were found, but quercetin and isorhamnetin intake was inversely associated with ARC risk (OR 11.78, 95% CI: 1.62–85.84, p<0.05, and OR 6.99, 95% CI: 1.12–43.44, p<0.05, quartile 4 vs. quartile 1, respectively).

Conclusion

As quercetin is contained in many plant foods and isorhamnetin in very few foods, we concluded that higher quercetin intake may be an important dietary factor in the reduction of the risk of ARC.

Altered ubiquitin causes perturbed calcium homeostasis, hyperactivation of calpain, dysregulated differentiation, and cataract

Although the ocular lens shares many features with other tissues, it is unique in that it retains its cells throughout life, making it ideal for studies of differentiation/development. Precipitation of proteins results in lens opacification, or cataract, the major blinding disease. Lysines on ubiquitin (Ub) determine fates of Ub-protein substrates. Information regarding ubiquitin proteasome systems (UPSs), specifically of K6 in ubiquitin, is undeveloped. We expressed in the lens a mutant Ub containing a K6W substitution (K6W-Ub). Protein profiles of lenses that express wild-type ubiquitin (WT-Ub) or K6W-Ub differ by only ∼2%. Despite these quantitatively minor differences, in K6W-Ub lenses and multiple model systems we observed a fourfold Ca(2+) elevation and hyperactivation of calpain in the core of the lens, as well as calpain-associated fragmentation of critical lens proteins including Filensin, Fodrin, Vimentin, β-Crystallin, Caprin family member 2, and tudor domain containing 7. Truncations can be cataractogenic. Additionally, we observed accumulation of gap junction Connexin43, and diminished Connexin46 levels in vivo and in vitro. These findings suggest that mutation of Ub K6 alters UPS function, perturbs gap junction function, resulting in Ca(2+) elevation, hyperactivation of calpain, and associated cleavage of substrates, culminating in developmental defects and a cataractous lens. The data show previously unidentified connections between UPS and calpain-based degradative systems and advance our understanding of roles for Ub K6 in eye development. They also inform about new approaches to delay cataract and other protein precipitation diseases.

Walking and running are associated with similar reductions in cataract risk

PURPOSE

Habitual running has been associated with reduced risk of cataract development in one prospective study. The purposes of the current analyses were to provide further evidence of this potentially important benefit of vigorous exercise and to test whether moderate exercise (e.g., walking) provides as significant and equivalent reduction in cataract risk as vigorous exercise (e.g., running).

METHODS

Cox proportional hazard analyses of self-reported, physician-diagnosed incident cataracts versus baseline energy expenditure (METs) in 32,610 runners and 14,917 walkers during a 6.2-yr follow-up. Results are reported as hazard ratios (HR), percent risk reductions (100 (HR - 1)), and 95% confidence intervals (95% CI).

RESULTS

Runners and walkers reported 733 and 1074 incident cataracts during follow-up, respectively. When adjusted for sex, race, age, education, smoking, and intakes of meat, fruit, and alcohol, lower cataract risk was significantly associated with both running (HR = 0.960 per MET·h·d, 95% CI 0.935-0.986) and walking (HR = 0.918 per MET·h·d, 95% CI = 0.881-0.956), with no significant difference in the risk reduction per MET-hours per day between running and walking or between men and women. Compared with running or walking at or below guideline levels (≤1.8 MET·h·d), incident cataract risk was significantly lower for running or walking 1.8-3.6 (16.4% lower, 95% CI = 6.4%-25.3%), 3.6-5.4 (19.0% lower, 95% CI = 5.6%-30.4%), 5.4-7.2 (26.2% lower, 95% CI = 11.2%-38.7%), 7.2-9.0 (34.1% lower, 95% CI = 10.0%-51.2%), and ≥9 MET·h·d (41.6% lower, 95% CI = 19.8%-57.4%).

CONCLUSION

Moderate (walking) and vigorous (running) exercise were both significantly associated with lower cataract risk and their effects similar. Cataract risk appears to decrease linearly with increasing exercise energy expenditure through 9 MET·h·d.

Waist circumference and dual-energy X-ray absorptiometry measures of overall and central obesity are similarly associated with systemic oxidative stress in women

Growing evidence suggests that overall and abdominal obesity might lead to oxidative stress (OxS), which, in turn, plays a key role in the pathogenesis of a wide spectrum of diseases. In this study, for the first time, we compared the correlations of indirect, i.e. anthropometric, and direct, by dual energy X-ray absorptiometry (DXA), measures of body fat with circulatory OxS markers in women. To address this issue, we assessed central and total body fat mass (FM) by DXA, and serum levels of advanced oxidation protein products (AOPP), thiols and hydroperoxides in 275 healthy women (age 21-65 years; body mass index [BMI] 21.1-32.0 kg/m(2); waist circumference [WC] 60.1-109.9 cm). Among the markers considered in the study, only hydroperoxides levels, i.e. by-products of lipid peroxidation, were significantly (p < 0.05 for all) and positively correlated to body fat accumulation after controlling for confounding factors. In particular, this marker was found to be similarly associated with DXA-derived total FM, total FM % and trunk FM as well as with WC. Of note, hydroperoxides appeared to be correlated with abdominal but not with general obesity, as classified according to standard WC and BMI cut-offs, respectively. In conclusion, taken together our data demonstrated that, at least in women, the measurement of body FM by DXA has no advantage over the simpler and cheaper WC with regard to their associations with systemic OxS markers. Moreover, WC emerged as a superior potential predictor of OxS compared to the other most commonly used anthropometric measures (including BMI and waist to hip ratio).

Lutein/zeaxanthin for the treatment of age-related cataract: AREDS2 randomized trial report no. 4

IMPORTANCE

Age-related cataract is a leading cause of visual impairment in the United States. The prevalence of age-related cataract is increasing, with an estimated 30.1 million Americans likely to be affected by 2020.

OBJECTIVE

To determine whether daily oral supplementation with lutein/zeaxanthin affects the risk for cataract surgery.

DESIGN, SETTING, AND PATIENTS

The Age-Related Eye Disease Study 2 (AREDS2), a multicenter, double-masked clinical trial, enrolled 4203 participants, aged 50 to 85 years, at risk for progression to advanced age-related macular degeneration.

INTERVENTIONS

Participants were randomly assigned to daily placebo; lutein/zeaxanthin, 10mg/2mg; omega-3 long-chain polyunsaturated fatty acids, 1 g; or a combination to evaluate the effects on the primary outcome of progression to advanced age-related macular degeneration.

MAIN OUTCOMES AND MEASURES

Cataract surgery was documented at annual study examination with the presence of pseudophakia or aphakia, or reported during telephone calls at 6-month intervals between study visits. Annual best-corrected visual acuity testing was performed. A secondary outcome of AREDS2 was to evaluate the effects of lutein/zeaxanthin on the subsequent need for cataract surgery.

RESULTS

A total of 3159 AREDS2 participants were phakic in at least 1 eye and 1389 of 6027 study eyes underwent cataract surgery during the study, with median follow-up of 4.7 years. The 5-year probability of progression to cataract surgery in the no lutein/zeaxanthin group was 24%. For lutein/zeaxanthin vs no lutein/zeaxanthin, the hazard ratios for progression to cataract surgery was 0.96 (95% CI, 0.84-1.10; P = .54). For participants in the lowest quintile of dietary intake of lutein/zeaxanthin, the hazard ratio comparing lutein/zeaxanthin vs no lutein/zeaxanthin for progression to cataract surgery was 0.68 (95% CI, 0.48-0.96; P = .03). The hazard ratio for 3 or more lines of vision loss was 1.03 (95% CI, 0.93-1.13; P = .61 for lutein/zeaxanthin vs no lutein/zeaxanthin).

CONCLUSIONS AND RELEVANCE

Daily supplementation with lutein/zeaxanthin had no statistically significant overall effect on rates of cataract surgery or vision loss.

TRIAL REGISTRATION

clinicaltrials.gov Identifier: NCT00345176.

Effect of aqueous extract of the leaves of Acalypha wilkesiana 'Godseffiana' Muell Arg (Euphorbiaceae) on the hematology, plasma biochemistry and ocular indices of oxidative stress in alloxan induced diabetic rats

ETHNOPHARMACOLOGICAL RELEVANCE

The leaves of Acalypha wilkesiana are used in Southern Nigeria for the management of hypertension and diabetes mellitus. In this study, the effect of aqueous extract of the leaves of Acalypha wilkesiana on the hematology, plasma biochemistry and ocular indices of oxidative stress was investigated in alloxan induced diabetic rats.

METHODOLOGY

Diabetes mellitus was induced by injection of alloxan (80 mg/kg body weight), via the tail vein. The extract was administered orally at 100, 200 and 300 mg/kg (both to normal and diabetic rats), and metformin at 50mg/kg.

RESULTS

On gas chromatographic analysis of the extract, twenty nine known flavonoids were detected, consisting mainly of 29.77% apigenin, 14.97% quercetin, 11.12% naringenin, 10.62% kaempferol, 9.05% (-)-epicatechin and 4.04% (+)-catechin. Tannic acid and β-sitosterol were also detected. Compared to test control, the treatment lowered (significantly, P < 0.05) plasma glucose, triglyceride, conjugated bilirubin levels, atherogenic index of plasma, plasma alanine transaminase activity, total protein and total bilirubin, aspartate transaminase activity and unconjugated bilirubin, plasma urea, blood urea nitrogen and ocular malondialdehyde contents, lymphocyte and monocyte counts, and not significantly, plasma very low density lipoprotein cholesterol, but increased (significantly, P < 0.05) plasma calcium contents, total white cell and platelet counts, mean cell volume and ocular ascorbic acid content, and (though not significantly) plasma high density lipoprotein cholesterol level, red cell and neutrophil counts.

CONCLUSIONS

This study showed that the extract was hypoglycemic, positively affected the hemopoietic system and integrity and function (dose dependently) of the liver and kidney of the diabetic rats; improved the lipid profile and had no deleterious effect on red cell morphology. It also protected against oxidative stress in ocular tissues. This study also revealed the presence of pharmacologically active compounds in the leaf extract. All of these highlights the cardioprotective potential of the leaves of Acalypha wilkesiana and support its use in traditional health practices for the management of diabetes mellitus.

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.

Diet quality scores and oxidative stress in Korean adults

BACKGROUND/OBJECTIVES

The purpose of diet-quality indices is to assess and guide individual dietary intake for the promotion of health and prevention of disease, and food based dietary-quality indices need to be applied by using each country's own unique diet. We assessed the relationships between relatively simple dietary quality scores modified for a Korean diet, such as the Recommended Food Score (RFS) and alternate Mediterranean Diet Score (aMDS), and oxidative stress biomarkers in Korean adults.

SUBJECTS/METHODS

A total of 976 adults were recruited for the Biomarker Monitoring for Environmental Health Study between April and December 2005 in Seoul and Incheon, Korea. RFS and aMDS were calculated by using a food-frequency questionnaire. We used regression analyses to assess the associations between diet quality scores and urinary malondialdehyde (MDA) and 8-hydroxy-2'-deoxyguanosine (8-OHdG).

RESULTS

RFS and aMDS were negatively associated with urinary MDA concentrations (P=0.032 for RFS, P=0.043 for aMDS), but not with 8-OHdG after adjusted for potential covariates. After stratified analyses by sex, negative associations between the both scores and urinary MDA concentrations were not significant in both men and women. There were no significant associations of RFS and aMDS with urinary 8-OHdG concentrations.

CONCLUSIONS

Higher RFS and aMDS scores were related to lower oxidative stress. Therefore, good quality of diet may be useful in reducing oxidative stress.

Poly(2-hydroxyethyl methacrylate)-quercetin Conjugate as Biomaterial in Ophthalmology: An "ab initio" Study

A novel polymeric material with antioxidant properties and suitable for ophthalmic application was synthesized by free radical grafting reaction between 2-hydroxyethyl methacrylate and quercetin. The presence of quercetin in the polymeric chain was confirmed by FT-IR and UV-Vis analyses, while an estimation of the amount of quercetin bound per gram of polymer was obtained by the Folin-Ciocalteu assay. The conjugate shows high biocompatibility (HET-CAM assay) and antioxidant and anti-inflammatory properties which were extensively investigated by specific in vitro tests.

Age-related cataract in a randomized trial of vitamins E and C in men

OBJECTIVE

To test whether supplementation with alternate-day vitamin E or daily vitamin C affects the incidence of age-related cataract in a large cohort of men.

METHODS

In a randomized, double-masked, placebo-controlled trial, 11,545 apparently healthy US male physicians 50 years or older without a diagnosis of cataract at baseline were randomly assigned to receive 400 IU of vitamin E or placebo on alternate days and 500 mg of vitamin C or placebo daily.

MAIN OUTCOME MEASURE

Incident cataract responsible for a reduction in best-corrected visual acuity to 20/30 or worse based on self-report confirmed by medical record review.

APPLICATION TO CLINICAL PRACTICE

Long-term use of vitamin E and C supplements has no appreciable effect on cataract.

RESULTS

After 8 years of treatment and follow-up, 1174 incident cataracts were confirmed. There were 579 cataracts in the vitamin E-treated group and 595 in the vitamin E placebo group (hazard ratio, 0.99; 95% confidence interval, 0.88-1.11). For vitamin C, there were 593 cataracts in the treated group and 581 in the placebo group (hazard ratio, 1.02; 95% confidence interval, 0.91-1.14).

CONCLUSION

Long-term alternate-day use of 400 IU of vitamin E and daily use of 500 mg of vitamin C had no notable beneficial or harmful effect on the risk of cataract.

TRIAL REGISTRATION

clinicaltrials.gov Identifier: NCT00270647.

Effect of curcumin on selenite-induced cataractogenesis in Wistar rat pups

PURPOSE

The present study was aimed at investigating the possible antioxidant potential of curcumin at a dose of 75 mg/kg body weight on selenite-induced cataract in experimental rat pups.

METHODS

Group I: Control rat pups receiving physiological saline; Group II: Selenite-induced group (15 microM/kg body wt); Group III: Selenite-induced group co-treated with curcumin (single dose of curcumin orally 75 mg/kg body wt); Group IV: Selenite-induced animals post-treated (after 24 hrs) with curcumin at a dose mentioned for group III; Group V: Rat pups were pretreated with curcumin (dose as mentioned in Group III), 24 hrs before the administration of selenite. Encapsulated lenses liver, kidney, and serum were analyzed for antioxidant enzymes and malondialdehyde, a marker of lipid peroxidation.

RESULTS

Intraperitoneal injection of sodium selenite (15 microM/kg body wt) to 8-10-day-old rat pups led to severe oxidative stress in eye lens as evidenced by enhanced LPO levels that led to cataract formation. Sodium selenite also led to decrease in activities of SOD, GST, GPx, CAT with simultaneous decrease in the levels of GSH, vitamin C, and vitamin E. Treatment with curcumin (75 mg/kg body wt) led to a significant decrease in the levels of LPO, enzymic antioxidants, and nonenzymic antioxidants, which were similar to that of control.

CONCLUSIONS

Curcumin suppressed selenite-induced oxidative stress and cataract formation in rat pups. The presence of oxidative stress in selenite cataract development and its prevention by curcumin support the possibility that the natural consumption of curcumin in food can help prevent the onset of senile cataract.

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.

Association of oxidative stress, iron, and centralized fat mass in healthy postmenopausal women

OBJECTIVE

Centralized adiposity, insulin resistance, excess iron, and elevated oxidative stress place postmenopausal women at risk for atherosclerotic cardiovascular disease (CVD). The objective of this study was to determine the relationship among excess iron, oxidative stress, and centralized fat mass in healthy postmenopausal women.

METHODS

The parent project recruited healthy women for a randomized, double-blind, clinical trial designed to examine the effect of soy isoflavones on bone. At baseline (n = 122), we measured three antioxidant enzymes, iron status indices (serum ferritin among others), oxidative stress indices (oxidized low-density lipoprotein [oxLDL], urinary isoprostanes [PGF(2alpha)], protein carbonyls, DNA damage), and waist, hip, and thigh fat mass using dual-energy x-ray absorptiometry (DXA). We calculated insulin resistance using the homeostasis model assessment (HOMA). Multiple regression analysis was used to determine the CVD risk factors that contributed to oxidative stress and centralized fat mass (waist + hip/thigh = AndGynFM ratio).

RESULTS

Almost 14% (p < 0.0005) of the variability in oxLDL was accounted for by AndGynFM ratio (6.1%, p < 0.0005), age (4.0%, p = 0.012), and serum iron (2.8%, p = 0.053). Similarly, 16% (p < 0.0001) of the variability in PGF(2alpha) was accounted for by the AndGynFM ratio (4.8%, p = 0.011), HOMA (3.9%, p = 0.021), and serum iron (2.7%, p = 0.054). We accounted for 33% (p

CONCLUSIONS

Our study suggests that reducing centralized fat mass and maintaining a favorable lipid profile, antioxidant status, and iron status all may be important in protecting postmenopausal women from atherosclerotic CVD.

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Key Words Collapse

MESH Headings

• Aged
• Biomarkers/blood
• Body Fat Distribution/adverse effects
• Body Mass Index
• Bone Density/drug effects
• Bone and Bones/drug effects
• Coronary Artery Disease/blood
• Coronary Artery Disease/etiology
• Coronary Artery Disease/prevention & control
• Double-Blind Method
• Female
• Ferritins/blood
• Folic Acid/blood
• Humans
• Iron/metabolism
• Middle Aged
• Oxidative Stress/drug effects
• Postmenopause/blood
• Reference Values
• Soybean Proteins/administration & dosage
• Soybean Proteins/pharmacology
• Waist-Hip Ratio

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Grants

• R01 AR046922-01A2 NIAMS NIH HHS
• R01 AR046922 A2 NIAMS NIH HHS
• P01 ES012020 NIEHS NIH HHS
• 95P50AT004155 NCCIH NIH HHS

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Affiliation(s)

Betsy L. Crist Department of Food Science and Human Nutrition, Iowa State University, Ames, Iowa
D. Lee Alekel Department of Food Science and Human Nutrition, Iowa State University, Ames, Iowa Nutrition and Wellness Research Center, Iowa State University, Ames, Iowa
Laura M. Ritland Department of Food Science and Human Nutrition, Iowa State University, Ames, Iowa
Laura N. Hanson Department of Food Science and Human Nutrition, Iowa State University, Ames, Iowa
Ulrike Genschel Department of Statistics, Iowa State University, Ames, Iowa
Manju B. Reddy Department of Food Science and Human Nutrition, Iowa State University, Ames, Iowa

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A randomized, double-masked, placebo-controlled clinical trial of multivitamin supplementation for age-related lens opacities. Clinical trial of nutritional supplements and age-related cataract report no. 3

OBJECTIVE

To evaluate the effect of a multivitamin/mineral supplement on development or progression of age-related lens opacities.

DESIGN

Randomized, double-masked, single center, placebo-controlled clinical trial.

PARTICIPANTS

One thousand twenty participants, 55 to 75 years old and with early or no cataract, were randomly assigned to a daily tablet of a multivitamin/mineral formulation or a placebo.

METHODS

Baseline and annual lens photographs were graded for severity of lens opacities according to a modification of the Age-Related Eye Disease Study system for classifying cataracts.

MAIN OUTCOME MEASURES

The primary outcome was a prespecified increase from baseline in nuclear, cortical, or posterior subcapsular cataract (PSC) opacity grades or cataract surgery. Secondary outcomes included an increase in type-specific opacity grades, cataract surgery, and visual acuity (VA) loss from baseline > or =15 letters.

RESULTS

Participants were observed for an average of 9.0+/-2.4 years. There was a decrease in total lens events in participants assigned to the multivitamin/mineral formulation compared with those assigned to the placebo (hazard ratio [HR], 0.82; 95% confidence interval [CI], 0.68-0.98; P = 0.03). Nuclear events were significantly less common (HR, 0.66; 95% CI, 0.50-0.88; P = 0.004) and PSC events significantly more common (HR, 2.00; 95% CI, 1.35-2.98; P<0.001) in participants taking the multivitamin/mineral formulation than in those assigned to the placebo. No statistically significant treatment effects were seen for cortical opacities, moderate VA loss, or cataract surgery.

CONCLUSIONS

Lens events were less common in participants who took the multivitamin/mineral formulation, but treatment had opposite effects on the development or progression of nuclear and PSC opacities, the 2 most visually important opacity subtypes.

Prospective epidemiological cohort study of reduced risk for incident cataract with vigorous physical activity and cardiorespiratory fitness during a 7-year follow-up

PURPOSE

To test whether greater vigorous physical activity (kilometers per week run) and greater cardiorespiratory fitness (10-km race performance in meters per second) reduce the incidence of clinically diagnosed cataract.

METHODS

Prospective cohort study of self-reported clinical diagnosis of cataract in nondiabetic, nonvegetarian, and nonsmoking male (n = 29,025) and female runners (n = 11,967).

RESULTS

Incident cataracts were reported by 733 (2.53%) men and 179 (1.50%) women during (mean +/- SE) 7.74 +/- 0.01 and 7.42 +/- 0.02 years of follow-up, respectively. The risk for incident cataract increased with BMI, such that the risk in men > 27.5 kg/m(2) was 88% larger than in men < 20 kg/m(2). Men's cataract risk declined significantly in relation to running distance (P = 0.01), even when adjusted for BMI. Men who ran > or = 64 km/wk had 35% lower risk for cataract than those reporting < 16 km/wk (28% lower risk when adjusted for BMI). In addition, men with greater cardiorespiratory fitness were at significantly less risk for development of cataract than were the least fit men. This result was not accounted for by adjustment for running distance or BMI. Compared with the least fit men, those who ran faster than 4.75 m/s had 50% lower risk for incident cataract (43% lower when adjusted for km/wk and BMI).

CONCLUSIONS

These data suggest that the men's cataract risk decreased in association with lower BMI, greater physical activity, and greater cardiorespiratory fitness, the latter being statistically independent of both BMI and physical activity. The study limitations include the absence of confirmation of the clinical diagnosis and the lack of specificity of the type of cataract.

Effect of Supplemented and Topically Applied Antioxidant Substances on Human Tissue

Systemic and topical application of antioxidant substances for the medical treatment and prophylaxis of many diseases as well as additional protection of the skin against the destructive action of free radicals and other reactive species has become very popular during the past years. Stimulated by the positive results of a fruit and vegetable diet in supporting medical treatment and in cosmetics, artificial and extracted antioxidant substances have been broadly applied. Surprisingly, not only positive but also strong negative results have been obtained by different authors. According to study reports artificial and extracted antioxidant substances support different kinds of medical therapies, if they are applied in mixtures of different compounds at low concentration levels. In the case of the application of high concentration of some single compounds, side effects were often observed. Regarding skin treatment by systemically applied antioxidant substances for cosmetic purposes, positive cosmetic effects as well as no effects, but almost no side effects, apart from a number of allergic reactions, were reported. One reason for this seems to be the lower concentration of systemically applied antioxidant substances in comparison with a medical application. Topical application of antioxidant substances is closely related to cosmetic treatment for skin protection and anti-aging. Positive results were also obtained in this case. The present review is an attempt to classify and summarize the published literature concerning the efficiency of action of systemic and topical applications of antioxidant substances, such as carotenoids and vitamins, on human organism and especially on the skin. The available literature on this topic is very extensive and the results are often contradictory. Nevertheless, there are some clear tendencies concerning systemic and topical application of antioxidant substances in medicine and cosmetics, and we summarize them in the present paper.

Vitamin E supplementation in Alzheimer's disease, Parkinson's disease, tardive dyskinesia, and cataract: Part 2

OBJECTIVE

To review clinical trials evaluating the safety and efficacy of vitamin E supplementation in Alzheimer's disease, Parkinson's disease, tardive dyskinesia, and cataract.

DATA SOURCES

Using the MeSH terms alpha-tocopherol, tocopherols, vitamin E, Parkinson disease, tardive dyskinesia, Alzheimer disease, cataract, and clinical trials, a literature review was conducted to identify peer-reviewed articles in MEDLINE (1966-July 2005).

STUDY SELECTION AND DATA EXTRACTION

Published materials including original research, review articles, and meta-analyses were reviewed. Only English-language articles and trials that included vitamin E alone or in combination with other vitamins or minerals were reviewed. Emphasis was placed on prospective, randomized, double-blind, placebo-controlled clinical trials.

DATA SYNTHESIS

The clinical studies demonstrated contradicting results regarding the benefits of vitamin E in Parkinson's disease, tardive dyskinesia, and cataract. The study reviewed for Alzheimer's disease seemed to show benefit when vitamin E was used; however, the statistical methods employed are questionable. There is enough evidence from large, well-designed studies to discourage the use of vitamin E in Parkinson's disease, cataract, and Alzheimer's disease. We recommend that vitamin E be considered a treatment option in patients with tardive dyskinesia only if they are newly diagnosed.

CONCLUSIONS

We encourage patients to supplement with vitamin E-rich foods. The use of a daily multivitamin, which usually contains 30 IU of alpha-tocopherol, may be beneficial; however, we discourage individual vitamin E supplements that usually contain 400 IU of alpha-tocopherol.

Vitamin C protects HL60 and U266 cells from arsenic toxicity

Although there is no compelling evidence that vitamin C has antitumor activity in humans, clinical trials are testing the hypothesis that ascorbic acid (AA) will enhance the efficacy of arsenic trioxide (As2O3) in myeloma. In vitro, AA cytotoxicity depends on its interaction with free transition metal ions in culture media leading to the generation of H2O2 and other reactive oxygen species (ROSs). Therefore, to circumvent the extracellular in vitro pro-oxidant effects of AA, we loaded HL60, U266, and RPMI-8226 cells with vitamin C by incubation with dehydroascorbic acid (DHA). Loading cells in this manner resulted in prominent, dose-dependent protection of As2O3-treated cells as measured by viability, colony formation, and apoptosis assays. Glutathione depletion enhanced cell sensitivity to the cytotoxic effects of As2O3 and vitamin C loading provided protection. AA was found to generate cytotoxic concentrations of H2O2 in culture medium without cells and copper/iron chelators inhibited this reaction. However, AA did not generate H2O2 in simple buffer or human plasma. Direct incubation with AA resulted in increased intracellular ROSs, whereas DHA incubation decreased it. These results clarify an apparent paradox and indicate that vitamin C loading in HL60, U266, and RPMI-8226 cells ameliorates As2O3 cytotoxicity.

Antioxidants and Prevention of Chronic Disease

The generation of reactive oxygen species (ROS) and other free radicals (R) during metabolism is a necessary and normal process that ideally is compensated for by an elaborate endogenous antioxidant system. However, due to many environmental, lifestyle, and pathological situations, excess radicals can accumulate, resulting in oxidative stress. Oxidative stress has been related to cardiovascular disease, cancer, and other chronic diseases that account for a major portion of deaths today. Antioxidants are compounds that hinder the oxidative processes and thereby delay or prevent oxidative stress. This article examines the process of oxidative stress and the pathways by which it relates to many chronic diseases. We also discuss the role that endogenous and exogenous antioxidants may play in controlling oxidation and review the evidence of their roles in preventing disease.

Capillary high-performance liquid chromatographic determination of lutein and zeaxanthin in aqueous humor from a single mouse eye

To protect the eye from ultraviolet phototoxicity caused by free radicals, ocular components such as the aqueous humor accumulate antioxidants, such as the carotenoids. Lutein and zeaxanthin are the only carotenoids known to be present in the aqueous humor. Due to the small sample volume, pooling of samples from an undesirable large number of animals is often required for sufficient sensitivity and statistically significant differences to be achieved. In this paper we present a rapid, sensitive and robust packed capillary high-performance liquid chromatographic visible detection method for the quantification of lutein and zeaxanthin in the aqueous humor of single mouse eyes.

Antioxidant nutrients and chronic disease: use of biomarkers of exposure and oxidative stress status in epidemiologic research

Oxidation of lipid, nucleic acids or protein has been suggested to be involved in the etiology of several chronic diseases including cancer, cardiovascular disease, cataract, age-related macular degeneration and aging in general. A large body of research has investigated the potential role of antioxidant nutrients in the prevention of these and other chronic diseases. This review concentrates on the following antioxidant nutrients: beta-carotene and other carotenoids, vitamin E, vitamin C and selenium. The first part of the review emphasizes the utility of biological markers of exposure for these nutrients and the relationship to dietary intake data. The second part considers functional assays of oxidative stress status in humans including the strengths and limitations of various assays available for use in epidemiologic research. A wide variety of functional assays both in vivo and ex vivo, are covered, including various measures of lipid oxidation (thiobarbituric acid reactive substances, exhaled pentane/ethane, low-density lipoprotein resistance to oxidation, isoprostanes), DNA oxidation (oxidized DNA bases such as 8-OHdG, autoantibodies to oxidized DNA, modified Comet assay) and protein oxidation (protein carbonyls). Studies that have examined the effects of antioxidant nutrients on these functional markers are included for illustrative purposes. The review concludes with a discussion of methodologic issues and challenges for studies involving biomarkers of exposure to antioxidant nutrients and of oxidative stress status.

Quercetin metabolism in the lens: role in inhibition of hydrogen peroxide induced cataract

Oxidative stress is implicated in the initiation of maturity onset cataract. Quercetin, a major flavonol in the diet, inhibits lens opacification in a lens organ culture oxidative model of cataract. The aim of this research was to investigate the metabolism of quercetin in the lens and show how its metabolism affects the ability to prevent oxidation-induced opacity. The LOCH model (Free Radical Biology & Medicine 26:639; 1999) was employed, using rat lenses to investigate the effects of quercetin and metabolites on hydrogen peroxide-induced opacification. High-performance liquid chromatography analysis showed that the intact rat lens is capable of converting quercetin aglycone to 3'-O-methyl quercetin (isorhamnetin). Over a 6 h culture period no further metabolism of the 3'-O-methyl quercetin occurred. Loss of quercetin in the lens was accounted for by the increase in 3'-O-methyl quercetin. Incubation with 3,5-dinitrocatechol (10 microM), a catechol-O-methyltransferase (COMT) inhibitor, prevented the conversion of quercetin to 3'-O-methyl quercetin. The presence of both membrane-bound and soluble COMT was confirmed by immunoblotting. The results demonstrate that in the rat lens COMT methylates quercetin and that the product accumulates within the lens. Quercetin (10 microM) and 3'-O-methyl quercetin (10 microM) both inhibited hydrogen peroxide- (500 microM) induced sodium and calcium influx and lens opacification. Incubation of lenses with quercetin in the presence of COMT inhibitor revealed that the efficacy of quercetin is not dependent on its metabolism to 3'-O-methyl quercetin. The results indicate dietary quercetin and metabolites are active in inhibiting oxidative damage in the lens and thus could play a role in prevention of cataract formation.

Vitamin C prevents hyperbaric oxygen-induced growth retardation and lipid peroxidation and attenuates the oxidation-induced up-regulation of glutathione in guinea pigs

Hyperbaric oxygen therapy is used to treat various clinical conditions, but it also causes oxidative damage. The objectives of this study are to determine if increased vitamin C intake can prevent hyperbaric oxygen-induced damage and to determine interactions among vitamin C, glutathione and vitamin E in response to oxidative stress. The growth rates of unexposed guinea pigs fed 1.25 mg vitamin C/day were indistinguishable from that of guinea pigs fed 50 mg vitamin C/day. In contrast, hyperbaric oxygen exposure resulted in growth retardation in guinea pigs fed 1.25 mg vitamin C/day, but it had little effect on the growth rates of guinea pigs fed 50 mg vitamin C/day. Increased vitamin C intake also prevented hyperbaric oxygen-induced lipid peroxidation in the liver. In guinea pigs not exposed to hyperbaric oxygen, levels of vitamin C in tissues were closely related to vitamin C intake, but tissue levels of glutathione and vitamin E were not related to vitamin C intake. However, interactions between vitamin C and glutathione were observed upon chronic hyperbaric oxygen exposure. Chronic hyperbaric oxygen exposure resulted in >2-fold increases in the levels of glutathione in liver and lung of guinea pigs fed 1.25 mg vitamin C/day. In comparison, the oxidation-induced increases in glutathione were significantly attenuated in guinea pigs fed 50 mg vitamin C/day. These data show that increased intake of vitamin C can prevent or alleviate the hyperbaric oxygen-induced damage. The interactions between vitamin C and glutathione upon hyperbaric oxygen exposure indicate that there is a homeostatic regulation of antioxidant capacity in guinea pig tissues.

Removal of oxidatively damaged proteins from lens cells by the ubiquitin-proteasome pathway

Understanding how oxidized proteins are removed is important since accumulation of such damaged proteins is causally related to cellular and organismic dysfunction, disease and aging. Previous work showed that activity of the ubiquitin-proteasome pathway (UPP) in lens cells increased during recovery from oxidative stress ( Shang et al., 1997b : J. Biol. Chem. 272, 23086-93). In this study we sought to determine if the up-regulation of the UPP during recovery from oxidative stress has a role in selective removal of oxidized proteins from the cells. In cells which were not exposed to peroxide, inhibition of the proteasome with MG132 or clasto-lactacystin beta-lactone had little effect on protein carbonyl levels. However, inhibition of the proteasome in the 20 microM peroxide-treated cells caused an approximate 60% increase in levels of protein carbonyl and an approximate 100% increase in levels of ubiquitin conjugates. The carbonyl-containing proteins that accumulated in the presence of the proteasome inhibitor co-localized with high molecular mass ubiquitin-protein conjugates. Furthermore, isolated carbonyl-containing proteins from H2O2-treated cells were ubiquitinated, and ubiquitin-conjugates were enriched with carbonyl-containing proteins. The diminished effect of proteasome inhibitors on protein carbonyl levels, together with the robust increase in ubiquitin-protein conjugates and accompanied increases in oxidized proteins, upon exposure to 60 microM H2O2 indicate that the proteasomal step of the UPP is more susceptible to oxidative inactivation than the ubiquitination step. In fact, oxidative stress is associated with a hyperactivation of the ubiquitin-activating enzyme. These data indicate that the UPP plays a role in removal of oxidatively damaged proteins from cells and that attenuation of the UPP activity may result in cytotoxic accumulation of damaged proteins, possibly including the ubiquitinated forms.

Studies on trypsin-modified bovine and human lens acylpeptide hydrolase

Acylpeptide hydrolase removes the N -acetylated amino acids from the peptide substrates but not from intact proteins. Cleavage between amino acid residues 203--204 of the native acylpeptide hydrolase results in the formation of a 55 kDa truncated active enzyme in the bovine lens, in vivo. In this study we explored the hydrolytic properties of the truncated enzyme using lens beta- and gamma-crystallins as substrates. SDS--PAGE analysis indicated that the beta B2-crystallin was cleaved by truncated acylpeptide hydrolase into several protein fragments (10--26 kDa). No cleavage of the gamma-crystallins was observed under similar conditions. Both the acylpeptide hydrolase activity and the protease activity of the 55 kDa enzyme were completely inhibited by diisopropylfluorophosphate, p -chloromercuribenzoate and ebelactone, and moderately inhibited by N -tosyl phenylalanine chloromethyl ketone. SDS--PAGE analysis followed by fluorography of ((3)H) diisopropylfluorophosphate labeled human lens acylpeptide hydrolase preparation showed the presence of the 55 kDa truncated form of the enzyme, as observed in the bovine lens. The peptide (d)-AIKGDQFL-NH(2)--the amino acid sequence 200--207 of the native bovine acylpeptide hydrolase with an in vivo cleavage site of native protein--was hydrolysed by the lens protease(s) suggesting that the in vivo generation of the 55 kDa acylpeptide hydrolase may be mediated through a proteolytic processing. The protease(s) responsible for the cleavage of this peptide was inhibited by diisopropylfluorophosphate and p -chloromercuribenzoate.

Reduced levels of rat lens antioxidant vitamins upon in vitro UVB irradiation

Ultraviolet (UV) radiation is one of the major risk factors of cataractogenesis. UV radiation induced damage to the eye lens is believed to be mediated through reactive oxygen species. Antioxidant defense systems, enzymatic and non-enzymatic, resist this damage. In the present study, the levels of rat lens endogenous antioxidants, L-ascorbic acid, alpha-tocopherol and beta-carotene, have been determined by HPLC upon in vitro UVB irradiation. UVB irradiation for 24 h (300 nm; 100 µW/cm(2)) of three months old rat lens suspended in RPMI medium, leads to 69-89% decrease in endogenous levels of these antioxidants. The addition of ascorbic acid (2 mM), alpha-tocopherol (2.5 µM) or beta-carotene (10 µM), separately to the medium during irradiation significantly prevented the decrease in their endogenous levels, thereby suggesting a protective role for these antioxidant micronutrients against photodamage to the eye lens.

4-Hydroxy-2-nonenal-mediated impairment of intracellular proteolysis during oxidative stress. Identification of proteasomes as target molecules

Oxidative stress is associated with important pathophysiological events in a variety of diseases. It has been postulated that free radicals and lipid peroxidation products generated during the process may be responsible for these effects because of their ability to damage cellular components such as membranes, proteins, and DNA. In the present study, we provide evidence that oxidative stress causes a transient impairment of intracellular proteolysis via covalent binding of 4-hydroxy-2-nonenal (HNE), a major end product of lipid peroxidation, to proteasomes. A single intraperitoneal treatment with the renal carcinogen, ferric nitrilotriacetate, caused oxidative stress, as monitored by accumulation of lipid peroxidation products and 8-hydroxy-2'-deoxyguanosine, in the kidney of mice. In addition, transient accumulation of HNE-modified proteins in the kidney was also found by competitive enzyme-linked immunosorbent assay and immunohistochemical analyses. This and the observation that the HNE-modified proteins were significantly ubiquitinated suggested a crucial role of proteasomes in the metabolism of HNE-modified proteins. In vitro incubation of the kidney homogenates with HNE indeed resulted in a transient accumulation of HNE-modified proteins, whereas the proteasome inhibitor significantly suppressed the time-dependent elimination of HNE-modified proteins. We found that, among three proteolytic activities (trypsin, chymotrypsin, and peptidylglutamyl peptide hydrolase activities) of proteasomes, both trypsin and peptidylglutamyl peptide hydrolase activities in the kidney were transiently diminished in accordance with the accumulation of HNE-modified proteins during oxidative stress. The loss of proteasome activities was partially ascribed to the direct attachment of HNE to the protein, based on the detection of HNE-proteasome conjugates by an immunoprecipitation technique. These results suggest that HNE may contribute to the enhanced accumulation of oxidatively modified proteins via an impairment of ubiquitin/proteasome-dependent intracellular proteolysis.

Decreasing ascorbate intake does not affect the levels of glutathione, tocopherol or retinol in the ascorbate-requiring osteogenic disorder shionogi rats

Levels of glutathione in liver and kidney, and other nutrients in plasma were evaluated in male and female ascorbate-requiring osteogenic disorder Shionogi (ODS) rats fed semipurified diets in which the concentrations of ascorbate were gradually decreased from 1965 to 180 mg/kg. Plasma ascorbate levels in ODS rats were unaffected when ascorbate levels in the diet were decreased from 1965 to 768 mg/kg. However, plasma ascorbate levels decreased progressively when levels of ascorbate in the diet were decreased from 527 to 180 mg/kg. Plasma ascorbate levels decreased up to 77% when the dietary ascorbate concentration decreased from 1965 to 180 mg/kg. Ascorbate levels in liver and kidney fell as much as 60-70% when the dietary ascorbate levels were reduced from 1965 to 180 mg/kg. However, the glutathione levels in these tissues were not affected. Plasma retinol and vitamin E levels were not affected by decreasing dietary ascorbate intake. Total cholesterol levels increased significantly in female rats as dietary ascorbate intake declined. Levels of glycated hemoglobin decreased significantly when dietary ascorbate levels decreased from 1965 to 527 mg/kg. This study suggests that levels of vitamin E, retinol and glutathione are not affected by decreased dietary intake of ascorbate under nonscorbutic conditions, whereas elevated ascorbate intake is associated with a decrease in levels of plasma cholesterol in female ODS rats. However, excessive intake of ascorbate may be associated with elevated glycation of hemoglobin. To achieve the maximal health benefit of ascorbate supplementation, further studies are necessary to define optimal ascorbate intakes.

The relationship between cataract, cell swelling and volume regulation

The cause of cataracts is not known. Data from epidemiological and case-control studies have suggested various risk factors, among them; sunlight, diabetes, diarrhoea, oxidative stress, smoking and alcohol. Many reports in the literature suggest that the hydrated state of the lens is linked to cataract and recently direct evidence has emerged linking lens swelling to cataract. This review attempts to collate the various strands of evidence relating the hydrated state of the lens in cataract and to construct a common pathway for cataractogenesis. This common pathway involves lens swelling, membrane permeabilization, vacuole and cleft formation, disturbance to the intracellular environment, protein aggregation/modification and light scatter. This hypothesis gives rise to some testable predictions amongst which is that under certain conditions the lens axial diameter will increase raising the possibility that pre-cataractous changes could be detected (e.g., by ultrasound) and, with appropriate action, the cataract could be prevented or delayed. There are encouraging signs from animal studies that certain types of lens opacification can be delayed or prevented, lending credibility to the objective of cataract prevention in humans. Even a delay in the onset of cataract would have a huge global impact. The incidence of cataract correlates with poverty, poor diet and poor hygiene and the vast majority of cataract is found in developing countries. Economic factors and a lack of cataract surgeons in these countries mean that surgery is not the long-term answer. Prevention is the only realistic global approach. This review concludes that detection of pre-cataractous changes and cataract prevention are achievable objectives and funds should be directed towards their realization.

Functional food science and defence against reactive oxidative species

This paper assesses critically the science base that underpins the argument that oxidative damage is a significant causative factor in the development of human diseases and that antioxidants are capable of preventing or ameliorating these disease processes. The assessment has been carried out under a number of headings, and some recommendations for future research are made based on the present day knowledge base. The knowledge database (1) Consideration of the basic science that underlies understanding of the role of free radicals in causing cellular pathologies, and the role of antioxidants in preventing this, shows that an imbalance of reactive oxygen species and antioxidant defence systems may lead to chemical modifications of biologically relevant macromolecules. This imbalance provides a logical pathobiochemical mechanism for the initiation and development of several disease states. Experimental data obtained in vivo provide evidence that antioxidants function in systems that scavenge reactive oxygen species and that these are relevant to what occurs in vivo. The relevance in vivo of these observations depends inter alia on knowledge of the uptake and distribution of the antioxidant within the human body, and on what tissue levels of the antioxidant may be expected in relation to dietary levels. (2) There is some way to go until validated precise methods are available for measuring biomarkers of oxidative damage in human subjects in vivo under minimally invasive conditions. With respect to oxidative damage in DNa, HPLC and GC-mass spectrophotometry methods have both merits and limitations. Lipid oxidation products in plasma are best measured as isoprostanes or as lipid hydroperoxides using specific HPLC techniques. Development of isoprostane measurement will advance specificity and precision. The measurement of oxidative damage to proteins has some potential but such methods have not been effectively exploited. (3) Epidemiological studies support the hypothesis that the major antioxidant nutrients vitamin E and vitamin C, and beta-carotene (which may or may not be acting as an antioxidant in vivo), may play a beneficial role in prevention of several chronic disorders. More research is needed on the impact of other non-nutrient compounds, such as other carotenoids and flavonoids, on human health. In general, human intervention studies using hard end-points are the gold standard. Trials are restricted mainly to the major antioxidants and do not allow firm conclusions because of inconsistent findings, an insufficient number of studies and the use of varying doses. There is evidence that large doses of beta-carotene may be deleterious to the health of certain subgroups of the population such as heavy habitual smokers. (4) With respect to the safety of administration of supplementary vitamins, vitamin C is safe at levels of supplementation up to 600 mg/d, and higher levels, up to 2000 mg/d, are without risk. Vitamin E has a very low human toxicity and an intake of 1000 mg/d is without risk; 3200 mg/d has been shown to be without any consistent risk. Large intakes of beta-carotene must be viewed with caution because they have been shown to confer detriment to a population at high risk of lung cancer when administered after many years of high risk (smoking) behaviour. Until further work clarifies the situation in heavy smokers with respect to taking supplements, larger doses should be avoided by such individuals. There is little reliable information about the human toxicology of flavonoids and related non-nutrient antioxidant constituents of the diet. (5) The food industry has long experience in the control of oxidative damage in foods and this experience can be used to advantage for the protection of food antioxidants which are beneficial. Some of these, such as vitamins C and E and beta-carotene, are well known, and strategies for their protection in foods are already exploited by food technologies. (ABSTRACT TRUNCATED)

Diet and nutrition in primary care. From antioxidants to zinc

This article reviews the role of diet in primary prevention based on current epidemiologic and clinical studies. Special consideration is given to circumstances which may require individualizing the dietary prescription. The role of dietary supplements in primary care is discussed. Particular emphasis is given to studies highlighting the clinical importance of specific minerals. Additionally, the practical application of antioxidant vitamins is presented in light of recent research findings.

Will the 'good fairies' please prove to us that vitamin E lessens human degenerative disease?

Recent research about the role of free radical derivatives of oxygen and nitrogen in biological systems has highlighted the possibility that antioxidants, such as vitamin E, that prevent these processes in vitro may be capable of carrying out a similar function in living organisms in vivo. There is increasing evidence that free radical reactions are involved in the early stages, or sometimes later on, in the development of human diseases, and it is therefore of particular interest to inquire whether vitamin E and other antioxidants, which are found in the human diets, may be capable of lowering the incidence of these diseases. Put simply, the proposition is that by improving human diets by increasing the quantity in them of antioxidants, it might be possible to reduce the incidence of a number of degenerative diseases. Of particular significance to these considerations is the likely role of the primary fat-soluble dietary antioxidant vitamin E in the prevention of degenerative diseases such as arteriosclerosis, which is frequently the cause of consequent heart attacks or stroke, and prevention of certain forms of cancer, as well as several other diseases. Substantial evidence for this proposition now exists, and this review is an attempt to give a brief account of the present position. Two kinds of evidence exist; on the one hand there is very substantial basic science evidence which indicates an involvement of free radical events, and a preventive role for vitamin E, in the development of human disease processes. On the other hand, there is also a large body of human epidemiological evidence which suggests that incidence of these diseases is lowered in populations having a high level of antioxidants, such as vitamin E, in their diet, or who have taken steps to enhance their level of intake of the vitamin by taking dietary supplements. There is also some evidence which suggests that intervention with dietary supplements of vitamin E can result in a lowered risk of disease, in particular of cardiovascular disease, which is a major killer disease among the developed nations of the world. The intense interest in this subject recently has as its objective the possibility that, by making some simple alterations to dietary lifestyle, or by enhancing the intake of vitamin E by fortification of foods, or by dietary supplements, it may be possible to reduce substantially the risk of a large amount of common, highly disabling human disease. By this simple means, therefore it may be possible to improve substantially the quality of human life, in particular for people of advancing years.

Will the 'good fairies' please prove to us that vitamin E lessens human degenerative disease?

Recent research about the role of free radical derivatives of oxygen and nitrogen in biological systems has highlighted the possibility that antioxidants, such as vitamin E, that prevent these processes in vitro may be capable of carrying out a similar function in living organisms in vivo. There is increasing evidence that free radical reactions are involved in the early stages, or sometimes later on, in the development of human diseases, and it is therefore of particular interest to inquire whether vitamin E and other antioxidants, which are found in the human diets, may be capable of lowering the incidence of these diseases. Put simply, the proposition is that by improving human diets by increasing the quantity in them of antioxidants, it might be possible to reduce the incidence of a number of degenerative diseases. Of particular significance to these considerations is the likely role of the primary fat-soluble dietary antioxidant vitamin E in the prevention of degenerative diseases such as arteriosclerosis, which is frequently the cause of consequent heart attacks or stroke, and prevention of certain forms of cancer, as well as several other diseases. Substantial evidence for this proposition now exists, and this review is an attempt to give a brief account of the present position. Two kinds of evidence exist; on the one hand there is very substantial basic science evidence which indicates an involvement of free radical events, and a preventive role for vitamin E, in the development of human disease processes. On the other hand, there is also a large body of human epidemiological evidence which suggests that incidence of these diseases is lowered in populations having a high level of antioxidants, such as vitamin E, in their diet, or who have taken steps to enhance their level of intake of the vitamin by taking dietary supplements. There is also some evidence which suggests that intervention with dietary supplements of vitamin E can result in a lowered risk of disease, in particular of cardiovascular disease, which is a major killer disease among the developed nations of the world. The intense interest in this subject recently has as its objective the possibility that, by making some simple alterations to dietary lifestyle, or by enhancing the intake of vitamin E by fortification of foods, or by dietary supplements, it may be possible to reduce substantially the risk of a large amount of common, highly disabling human disease. By this simple means, therefore it may be possible to improve substantially the quality of human life, in particular for people of advancing years.

Did the loss of endogenous ascorbate propel the evolution of Anthropoidea and Homo sapiens?

It has been previously theorized that free-radical reactions led to the first life on Earth, and their ability to randomly cause mutations may have subsequently led to the evolution of life. One of the most efficient free-radical quenchers is ascorbate, which most animals manufacture endogenously. It is generally believed that, approximately 25 million years ago, an ancestor of the Anthropoidea primate suborder, which includes Homo sapiens, lost the ability to produce its own ascorbate, and all descending species inherited this genetic defect. The first of three hypotheses presented here proposes that a genetic defect, caused by either free radicals or a virus, deleted the gene needed by Anthropoidea to manufacture endogenous ascorbate. The second hypothesis proposes that this evolutionary accident permitted large numbers of free radicals to remain metabolically unquenched. The third hypothesis proposes that the presence of these excessive free radicals increased the likelihood of free-radical-induced genetic mutations, and these mutations propelled the evolution of Anthropoidea, leading to Homo sapiens.

Changes in the age dependence of mortality and disability: Cohort and other determinants

Though the general trend in the United States has been toward increasing life expectancy both at birth and at age 65, the temporal rate of change in life expectancy since 1900 has been variable and often restricted to specific population groups. There have been periods during which the age- and gender-specific risks of particular causes of death have either increased or decreased. These periods partly reflect the persistent effects of population health factors on specific birth cohorts. It is important to understand the ebbs and flows of cause-specific mortality rates because general life expectancy trends are the product of interactions of multiple dynamic period and cohort factors. Consequently, we first review factors potentially affecting cohort health back to 1880 and explore how that history might affect the current and future cohort mortality risks of major chronic diseases. We then examine how those factors affect the age-specific linkage of disability and mortality in three sets of birth cohorts assessed using the 1982, 1984, and 1989 National Long Term Care Surveys and Medicare mortality data collected from 1982 to 1991. We find large changes in both mortality and disability in those cohorts. providing insights into what changes might have occurred and into what future changes might be expected.