The dihydrofolate reductase 19-bp deletion modifies the beneficial effect of B-vitamin therapy in mild cognitive impairment: Pooled study of two randomized placebo-controlled trials

Dysregulation of hepatic one-carbon metabolism in classical homocystinuria: Implications of redox-sensitive DHFR repression and tetrahydrofolate depletion for pathogenesis and treatment

Cystathionine beta-synthase-deficient homocystinuria (HCU) is a life-threatening disorder of sulfur metabolism. HCU can be treated by using betaine to lower tissue and plasma levels of homocysteine (Hcy). Here, we show that mice with severely elevated Hcy and potentially deficient in the folate species tetrahydrofolate (THF) exhibit a very limited response to betaine indicating that THF plays a critical role in treatment efficacy. Analysis of a mouse model of HCU revealed a 10-fold increase in hepatic levels of 5-methyl -THF and a 30-fold accumulation of formiminoglutamic acid, consistent with a paucity of THF. Neither of these metabolite accumulations were reversed or ameliorated by betaine treatment. Hepatic expression of the THF-generating enzyme dihydrofolate reductase (DHFR) was significantly repressed in HCU mice and expression was not increased by betaine treatment but appears to be sensitive to cellular redox status. Expression of the DHFR reaction partner thymidylate synthase was also repressed and metabolomic analysis detected widespread alteration of hepatic histidine and glutamine metabolism. Many individuals with HCU exhibit endothelial dysfunction. DHFR plays a key role in nitric oxide (NO) generation due to its role in regenerating oxidized tetrahydrobiopterin, and we observed a significant decrease in plasma NOx (NO2 + NO3) levels in HCU mice. Additional impairment of NO generation may also come from the HCU-mediated induction of the 20-hydroxyeicosatetraenoic acid generating cytochrome CYP4A. Collectively, our data shows that HCU induces dysfunctional one-carbon metabolism with the potential to both impair betaine treatment and contribute to multiple aspects of pathogenesis in this disease.

In vivo determination of the bioavailability of folic acid through the utilization of the PBPK model in conjunction with UPLC

This paper employed a physiologically based pharmacokinetic model (PBPK) to investigate the transformations of folic acid and its metabolites in vivo. Additionally, an ultra-performance liquid chromatography (UPLC) method was developed to accurately measure the body's retention rate and conversion rate of folic acid, tetrahydrofolate, and 5-methyltetrahydrofolate. Furthermore, the bioavailability of folic acid in the body was assessed by combining this method with an evaluation technique for animal models. The study found that the gastric metabolism time was 2 h, while the small intestinal metabolism duration was 4 h. The maximum conversion rate was observed in plasma and liver after 6 h, and in the brain after 8 h. This serves as a framework for creating a model to assess the bioavailability of folic acid in living organisms, to enhance the safety and efficacy of folic acid intake.

Dietary pattern, food, and nutritional supplement effects on cognitive outcomes in mild cognitive impairment: a systematic review of previous reviews

CONTEXT

Nutritional interventions may benefit cognition in people with mild cognitive impairment (MCI). However, evidence is yet to be synthesized in a way that can inform recommendations for clinical and public health settings.

OBJECTIVE

To systematically review evidence on the effect of dietary patterns, foods, and nutritional supplements on cognitive decline in individuals with MCI.

DATA SOURCES

Guided by the Preferred Reporting items for Systematic Review and Meta-Analysis Protocols 2015 statement, the Medline, EMBASE, and CINAHL databases, the JBI Database of Systematic Reviews and Implementation Reports, Cochrane Database of Systematic Reviews, and Database of Abstracts of Reviews of Effects were searched (publication years 2005 to 2020). Included studies were English-language systematic reviews and meta-analyses of randomized controlled trials and cohort studies reporting on the effectiveness of nutritional interventions on cognition of individuals with MCI.

DATA EXTRACTION

Two reviewers independently selected studies and extracted data on cognitive outcomes and adverse events. Review quality was assessed using AMSTAR 2 (A Measurement Tool to Assess Systematic Reviews-2). Primary study overlap was managed following Cochrane Handbook guidelines.

DATA ANALYSIS

Of the 6677 records retrieved, 20 reviews were included, which, in turn, reported on 43 randomized controlled trials and 1 cohort study that, together, addressed 18 nutritional interventions. Most reviews were limited by quality and the small number of primary studies with small sample sizes. Reviews were mostly positive for B vitamins, omega-3 fatty acids, and probiotics (including 12, 11 and 4 primary studies, respectively). Souvenaid and the Mediterranean diet reduced cognitive decline or Alzheimer's disease progression in single trials with <500 participants. Findings from studies with a small number of participants suggest vitamin D, a low-carbohydrate diet, medium-chain triglycerides, blueberries, grape juice, cocoa flavanols, and Brazil nuts may improve individual cognitive subdomains, but more studies are needed.

CONCLUSIONS

Few nutritional interventions were found to convincingly improve cognition of individuals with MCI. More high-quality research in MCI populations is required to determine if nutritional treatments improve cognition and/or reduce progression to dementia.

SYSTEMATIC REVIEW REGISTRATION

Open Science Framework protocol identifier DOI:10.17605/OSF.IO/BEP2S.

B Vitamin Supplementation Slows Cognitive Decline in Mild Cognitive Impairment Patients with Frontal Lobe Atrophy

BACKGROUND

The effects of B vitamins on mild cognitive impairment (MCI) patients' cognition have been mixed, suggesting the existence of moderating factors.

OBJECTIVE

A post hoc analysis of a negative B vitamin trial was performed to examine the potential modulating effect of regional brain atrophy on the cognitive response to B vitamins in MCI patients.

METHODS

In the 24-month randomized trial, 279 MCI outpatients took 500μ#x03BC;g methylcobalamin and 400μ#x03BC;g folic acid once per day or placebo tablets once per day. Sixty-four aspirin users were excluded from analysis as aspirin use has been found to have significant negative interaction effects. Subjects were followed up at months 12 and 24. The primary cognitive outcome was clinical dementia rating scale sum of boxes (CDR_SOB). In a subgroup of 83 subjects, MRI brain scans were performed at baseline to estimate regional brain atrophy ratios.

RESULTS

Among the trial subjects who had MRI data, B vitamin supplementation had no significant effect on CDR_SOB, despite having significant homocysteine lowering effects. The atrophy ratio of the left frontal lobe significantly moderated the effect of B vitamin supplementation on CDR_SOB, after adjusting for confounders, in that B vitamin supplementation was associated with lower CDR_SOB scores (i.e., better cognitive function) at the 24th month among those patients with above median atrophy ratios, but not among those with lower atrophy ratios, in the left frontal lobe.

CONCLUSION

B vitamins may be more effective in slowing down cognitive decline in MCI patients with atrophy in the left frontal lobe.

Problem in the Recent American Heart Association Guideline on Secondary Stroke Prevention: B Vitamins to Lower Homocysteine Do Prevent Stroke

In this article, we discuss a problem in the most recent American Heart Association guideline on secondary stroke prevention that apparently arose from the rules of evidence imposed on the guideline panel. We are told by the cochair of the panel that American Heart Association rules about guidelines for secondary prevention prohibited consideration of primary prevention studies and secondary analyses of secondary prevention studies. However, evidence-based medicine should consider all the best external evidence available and also clinical judgement. The most important problem in the guideline was the recommendation that B vitamins to lower homocysteine do not prevent recurrent stroke. When considering all the best external evidence, it is clear that B vitamins do prevent stroke, but in the early secondary stroke prevention studies, the benefit of B vitamins in participants with good renal function was apparently offset by harm from cyanocobalamin among participants with renal failure (level B-R evidence). We review the evidence that B vitamins should be used to prevent stroke, both in primary and secondary stroke prevention (class 2a recommendation). We also review issues in folate metabolism that require further study, with regard to the form of folate to be used for stroke prevention. We recommend that the guideline be revised to say that B vitamins to lower homocysteine prevent stroke and that methylcobalamin or hydroxycobalamin should be used instead of cyanocobalamin.

Metabolic Basis of Cognitive Improvement Associated With Active B Vitamin Supplementation in Cognitively Impaired Elderly Subjects – A Metabolomics Study

Intervention studies with active B vitamin supplementation in cognitively impaired individuals have yielded varying results in randomized controlled trials. In addition, a negative interaction of active B vitamin supplementation with aspirin usage on cognitive outcome was noted, but the molecular basis of the interaction has largely remained unknown. To investigate the metabolic basis of cognitive improvement brought about by active B vitamin supplementation, we conducted an extensive metabolomics analysis covering 302 identified metabolites on the baseline and 24-month serum samples from a cohort of 137 subjects randomly assigned to active supplementation or placebo. Pathway analysis uncovered enhanced gluconeogenesis and War-burg effects underlying cognitive improvement in non-aspirin users supplemented with active B vitamins. In addition, metabolomics revealed that aspirin usage may interact with B vitamin supplementation by altering gut microbial metabolism, particularly in terms of propionate production. Lastly, our omics data suggest that varying capacities to assimilate B vitamins at baseline, possibly mediated by differences in gut microbial composition, may underlie variations in inter-individual responses to active B vitamin supplementation.