Nutrients, brain biochemistry, and behavior: a possible role for the neuronal membrane

Circulating Vitamin D Levels and Risk of Vitiligo: Evidence From Meta-Analysis and Two-Sample Mendelian Randomization

Background: The association between circulating vitamin D levels and risk of vitiligo was inconsistent among observational studies, and whether these observed associations were causal remained unclear. Therefore, we aimed to evaluate the effect of vitamin D on the risk of vitiigo using meta-analysis and Mendelian randomization (MR).

Methods: At the meta-analysis stage, literature search was performed in PubMed and Web of Science to identify eligible observational studies examining the association of circulating 25-hydroxyvitamin D [25(OH)D] or 25-hydroxyvitamin D₃ [25(OH)D₃] levels with risk of vitiligo up to April 30, 2021. Standardized mean differences (SMDs) with 95% confidence intervals (CIs) of 25(OH)D and 25(OH)D₃ in patients with vitiligo relative to controls were pooled. Then at the MR stage, genetic instruments for circulating 25(OH)D (N = 120,618) and 25(OH)D₃ (N = 40,562) levels were selected from a meta-analysis of genome-wide association studies (GWAS) of European descent, and summary statistics of vitiligo were obtained from a meta-analysis of three GWASs including 4,680 cases and 39,586 controls. We used inverse-variance weighted (IVW) as main method, followed by weighted-median and likelihood-based methods. Pleiotropic and outlier variants were assessed by MR-Egger regression and MR Pleiotropy RESidual Sum and Outlier (MR-PRESSO) test.

Results: In the meta-analysis, patients with vitiligo had a lower level of circulating 25(OH)D compared with controls [SMD = −1.40; 95% confidence interval (CI): −1.91, −0.89; P < 0.001], while no statistically significant difference of 25(OH)D₃ between vitiligo cases and controls was found (SMD = −0.63; 95% CI: −1.29, 0.04; P = 0.064). However, in the MR analyses, genetically predicted 25(OH)D [odds ratio (OR) = 0.93, 95% CI = 0.66–1.31, P = 0.66] and 25(OH)D₃ levels (OR = 0.95, 95% CI = 0.80–1.14, P = 0.60) had null associations with risk of vitiligo using the IVW method. Sensitivity analyses using alternative MR methods and instrumental variables (IV) sets obtained consistent results, and no evidence of pleiotropy or outliers was observed.

Conclusion: Our study provided no convincing evidence for a causal effect of 25(OH)D or 25(OH)D₃ levels on the risk of vitiligo. Further longitudinal and experimental studies, as well as functional studies are warranted to elucidate the role of vitamin D in the development of vitiligo.

Amino acids in cancer

Over 90 years ago, Otto Warburg's seminal discovery of aerobic glycolysis established metabolic reprogramming as one of the first distinguishing characteristics of cancer¹. The field of cancer metabolism subsequently revealed additional metabolic alterations in cancer by focusing on central carbon metabolism, including the citric acid cycle and pentose phosphate pathway. Recent reports have, however, uncovered substantial non-carbon metabolism contributions to cancer cell viability and growth. Amino acids, nutrients vital to the survival of all cell types, experience reprogrammed metabolism in cancer. This review outlines the diverse roles of amino acids within the tumor and in the tumor microenvironment. Beyond their role in biosynthesis, they serve as energy sources and help maintain redox balance. In addition, amino acid derivatives contribute to epigenetic regulation and immune responses linked to tumorigenesis and metastasis. Furthermore, in discussing the transporters and transaminases that mediate amino acid uptake and synthesis, we identify potential metabolic liabilities as targets for therapeutic intervention.

The Role of Essential Fatty Acids in Anorexia Nervosa and Obesity

The two basic questions in food intake study are what we eat, and how much do we eat. Most research is directed toward the control of how much is eaten. This is likely the result of the increased number of individuals with eating disorders in the Western world. Feeding behavior is highly complex, and is controlled by many psychological, physiological, biochemical, and immunological factors. The aim of this review is to clarify the involvement of fatty acids in eating disorders such as anorexia and binge eating disorder. The review will describe the modified fatty acid profile observed in individuals with anorexia or binge eating disorder, and discuss on what factors fatty acids can exert beneficial effects. In addition, the differences and similarities between anorexia and binge eating disorder will be discussed. We suggest that beneficial effects of essential fatty acids on both anorexia and binge eating disorder can be explained by the stabilizing effect of those fatty acids on the neuronal membrane fluidity index.

The diet factor in attention-deficit/hyperactivity disorder

This article is intended to provide a comprehensive overview of the role of dietary methods for treatment of children with attention-deficit/hyperactivity disorder (ADHD) when pharmacotherapy has proven unsatisfactory or unacceptable. Results of recent research and controlled studies, based on a PubMed search, are emphasized and compared with earlier reports. The recent increase of interest in this form of therapy for ADHD, and especially in the use of omega supplements, significance of iron deficiency, and the avoidance of the "Western pattern" diet, make the discussion timely. Diets to reduce symptoms associated with ADHD include sugar-restricted, additive/preservative-free, oligoantigenic/elimination, and fatty acid supplements. Omega-3 supplement is the latest dietary treatment with positive reports of efficacy, and interest in the additive-free diet of the 1970s is occasionally revived. A provocative report draws attention to the ADHD-associated "Western-style" diet, high in fat and refined sugars, and the ADHD-free "healthy" diet, containing fiber, folate, and omega-3 fatty acids. The literature on diets and ADHD, listed by PubMed, is reviewed with emphasis on recent controlled studies. Recommendations for the use of diets are based on current opinion of published reports and our practice experience. Indications for dietary therapy include medication failure, parental or patient preference, iron deficiency, and, when appropriate, change from an ADHD-linked Western diet to an ADHD-free healthy diet. Foods associated with ADHD to be avoided and those not linked with ADHD and preferred are listed. In practice, additive-free and oligoantigenic/elimination diets are time-consuming and disruptive to the household; they are indicated only in selected patients. Iron and zinc are supplemented in patients with known deficiencies; they may also enhance the effectiveness of stimulant therapy. In patients failing to respond or with parents opposed to medication, omega-3 supplements may warrant a trial. A greater attention to the education of parents and children in a healthy dietary pattern, omitting items shown to predispose to ADHD, is perhaps the most promising and practical complementary or alternative treatment of ADHD.

Mediation of cognitive function by high fat diet following stress and inflammation

In addition to commonly advertised hazards of obesity contributed by excess dietary fat, evidence of alterations in brain chemistry and structure are well documented. This brief review examines the role of nutrients, minerals and certain lipids, primarily the essential fatty acids (FA), that are beneficial to the maintenance of good health and that may offer therapeutic options by dietary supplementation. The review also considers the damaging effects of stress, especially in pre-existing conditions of obesity and diabetes, as studied in both animals and humans. The main focus of this brief review is to examine the effects of a high fat diet on stress and the immune system with particular emphasis on brain and cognitive function.

Essential fatty acids preparation (SR-3) improves Alzheimer's patients quality of life

In a number of previous reports we showed the salutary effects on rats of SR-3, a compound comprising a 1:4 ratio of n-3 and n-6 fatty acids. Improvements were noted in learning tasks, thermoregulation, recovery from neurotoxins, and seizure protection. Because we were impressed that these effects are related to changes in membrane fluidity and neuronal functioning and because Alzheimer's Disease is also associated with lipid defects, we undertook a short term (4 week) double blind study with 100 Alzheimer patients (60 received SR-3 and 40 in a placebo control). The results indicated improvements in mood, cooperation, appetite, sleep, ability to navigate in the home, and short term memory. Overall improvement was reported for 49 patients, and in no case did a guardian report adverse effects to the compound. While not uniform or permanent, and while no mode of action for SR-3 can be precisely identified at this time, the promising results in quality of life for the patient and caregiver warrant further clinical trials and continued basic research into the neuropsychological substrate of the disease and its response to SR-3.

The effect of manganese-induced hypercholesterolemia on learning in rats

Since the exact mechanism of manganese (Mn)-induced learning disability is not known, we investigated the role of elevated cholesterol in rats exposed daily to 357 and 714 micrograms Mn/kg for 39 d. Significant Mn accumulation was accompanied by increased cholesterol content in the hippocampal region of Mn-treated rats. The learning, which is based on the time needed to reach food placed at the exit of a T-maze after a 1-d training period, was significantly slower in exposed rats than in unexposed rats. The rats receiving 357 and 714 micrograms Mn/kg reached the food in 104.5 +/- 13.8 and 113.3 +/- 25.7 s, respectively, on d 30, whereas their untreated counterparts reached the food in 28.7 +/- 11.4 s. This delay was completely corrected to 29.3 +/- 7.8 and 30.7 +/- 6.0 s in rats with coadministration of an inhibitor of cholesterol biosynthesis with 357 and 714 micrograms/kg of Mn. The correction of impaired learning was associated with the normalization of hippocampal cholesterol, but the Mn level in this region of the brain was not influenced in rats treated with a drug that inhibits cholesterol biosynthesis. These results suggested that Mn-induced hypercholesterolemia is involved in Mn-dependent learning disability.

Reversibility of manganese-induced learning defect in rats

In this study the mechanism by which manganese (Mn) induces learning defect and its reversibility has been investigated in rats. Female albino rats were dosed orally with 357 micrograms Mn/kg body weight for 15 or 30 days. Attempts were made to correct the Mn-induced learning defect by (1) co-administration of mevinolin and Mn for 30 days; (2) administration of mevinolin for 15 days after 15 days of dosing with Mn, and (3) by withdrawal of Mn treatment (15 days dosing with Mn followed by 15 days without Mn). Mevinolin was given orally at 235.7 micrograms/kg body weight. Significant increases in the Mn and cholesterol levels in the hippocampus were accompanied by an obvious slowness in learning of rats exposed to Mn. After one training period (day 29) the time required to reach the exit of a T-maze was 104.5 +/- 13.8 sec for rats dosed with Mn for 30 days, whereas that of the controls was 28.7 +/- 11.4 sec on day 30. This delay was completely corrected (to 30.7 +/- 6.0 sec) in rats co-administered mevinolin (an inhibitor of cholesterol biosynthesis) with Mn. Withdrawal of Mn, with or without inhibiting the cholesterol biosynthesis, also corrected the Mn-induced learning defect. These results suggest that Mn toxicity produces learning disability by increasing cholesterol biosynthesis and this reversible disability in learning can be corrected by withdrawal of Mn exposure.

Modulation of learning, pain thresholds, and thermoregulation in the rat by preparations of free purified alpha-linolenic and linoleic acids: determination of the optimal omega 3-to-omega 6 ratio

Ingested polyunsaturated fatty acids are postulated to lead to changes in central nervous system activity, presumably by altering the lipid composition of neuronal membranes. In support of this hypothesis, we and other investigators have previously demonstrated cognitive effects in rats fed oils that contain both alpha-linolenic acid (18:3 omega 3) and linoleic acid (18:2 omega 6), with the relative content of alpha-linolenic acid being seen as the critical variable. The present study in rats examined the effects of preparations containing different ratios of highly purified free alpha-linolenic acid to linoleic acid (about 25 mg/kg of body weight daily) on learning performance (Morris water tank), pain thresholds (heated plate), and thermoregulatory control of d-amphetamine-induced hypothermia during 4 weeks of treatment. Preparations with omega 3-to-omega 6 ratios ranging from 1:3.5 to 1:5 (specifically a ratio of 1:4) produced significant favorable effects on all of these variables. Although the specific mode of action remains to be elucidated, these results suggest that such preparations of free fatty acids should be evaluated in the treatment of memory disorders and pain conditions.

Do essential fatty acids play a role in brain and behavioral development?

The membrane phospholipids of the brain contain high levels of polyunsaturated fatty acids (PUFA), particularly arachidonic acid, 20:4n-6 and docosahexaenoic acid, 22:6n-3. These long-chain PUFA are synthesized from their respective essential fatty acid (EFA) precursors, linoleic acid, 18:2n-6 and linolenic acid, 18:3n-3. Although the necessity of n-6 fatty acids for optimum growth has been established, a similar requirement for those of the n-3 family is less clear. The rapid accumulation of the long-chain n-3 PUFA in the brain during prenatal and preweaning development suggests that the provision of n-3 fatty acids to the developing brain may be necessary for normal growth and functional development. The intent of this review is to assess the experimental work which addresses this question, most of which has been conducted on rodents. The emphasis will be on studies which measure behavioral outcomes, and particular attention will be paid to methodological issues which affect the interpretation of these data. An integration of the research findings will be presented and discussed in light of possible implications for therapeutic interventions.

The effects of iron deficiency and electric shock on learning in rats

It is hypothesized that electric shock can compensate for the learning deficit caused by iron deficiency in the experimental rat population, and that this effect will be sustained over a 3-week "rehabilitation" period. Forty-seven female Sprague-Dawley rats served as the experimental subjects. The learning capacity of the rats was assessed using a water Y-maze. The dependent variables were assessed twice, once after half had been made iron deficient, and again after the iron deficiency had been corrected. A 2 x 2 x 2 analysis of variance with repeated measures was employed, along with post-hoc tests, to assess the effects of the experimental manipulations on the rats' performance. The experimental results replicated previous findings regarding the damaging effects of iron deficiency on learning capacity in rats and confirmed that shock improves the performance of rats in the water Y-maze. Furthermore, it was found that shock and iron deficiency interact, such that the performance of iron-deficient rats subjected to electric shock is superior to that of rats not made iron deficient. This trend persists even after the hematological effects of iron deficiency are corrected, although to a less dramatic degree. A possible explanation for these findings is advanced.