The beneficial effect of folate-enriched egg on the folate and homocysteine levels in rats fed a folate- and choline-deficient diet

Red blood cell folate level is associated with periodontitis in American adults: results from the NHANES 2009-2014

BACKGROUND

Red blood cell (RBC) folate is an indicator of long-term folate nutrition. Whether there is an association between RBC folate and periodontitis is unclear. This study aimed to use the NHANES database to determine whether RBC folate is associated with moderate/severe periodontitis.

METHODS

A cross-sectional analysis of 10,151 participants in the NHANES database from 2009 to 2014 was performed. Multivariate logistic regression was used to analyze the independent relationship between RBC folate and moderate/severe periodontitis. The generalized additive model (GAM), restricted cubic splines (RCS), smooth curve fitting, and threshold effect analysis were used to explore the dose-response relationship and the potential nonlinear relationship between RBC folate and periodontitis. Finally, subgroup analysis and interaction tests were performed to determine the effect of covariates on the relationship between RBC folate and moderate/severe periodontitis.

RESULTS

After adjusting for all confounders, there was a negative association between RBC folate concentration and moderate/severe periodontitis. The lowest fraction Q1 (< 360 ng/mL) of RBC folate concentration was used as the reference group, multivariable-adjusted ORs and 95% CIs of the second (360-463 ng/mL), third (464-569 ng/mL), fourth (570-732 ng/mL), and the highest quintile (> 733 ng/mL) categories were 0.88 (0.77, 1.01), 0.83 (0.72, 0.96), 0.77 (0.67, 0.90), 0.65 (0.56, 0.77) respectively. Additionally, a threshold nonlinear association was found between RBC folate (ng/mL) log2 transformation and moderate/severe periodontitis.

CONCLUSION

This cross-sectional study revealed a negative relationship between RBC folate and moderate/severe periodontitis within a certain threshold range. Dentists and policymakers should pay closer attention to oral hygiene and health care for people with low or high RBC folate levels. Further causal and longitudinal research mechanisms are needed to validate our findings.

Rat liver folate metabolism can provide an independent functioning of associated metabolic pathways

Folate metabolism in mammalian cells is essential for multiple vital processes, including purine and pyrimidine synthesis, histidine catabolism, methionine recycling, and utilization of formic acid. It remains unknown, however, whether these processes affect each other via folate metabolism or can function independently based on cellular needs. We addressed this question using a quantitative mathematical model of folate metabolism in rat liver cytoplasm. Variation in the rates of metabolic processes associated with folate metabolism (i.e., purine and pyrimidine synthesis, histidine catabolism, and influxes of formate and methionine) in the model revealed that folate metabolism is organized in a striking manner that enables activation or inhibition of each individual process independently of the metabolic fluxes in others. In mechanistic terms, this independence is based on the high activities of a group of enzymes involved in folate metabolism, which efficiently maintain close-to-equilibrium ratios between substrates and products of enzymatic reactions.

Red blood cell folate concentrations and coronary heart disease prevalence: A cross-sectional study based on 1999-2012 National Health and Nutrition Examination Survey

BACKGROUND AND AIM

Folate is involved in a number of metabolic pathways. Red blood cell (RBC) folate is a well-established indicator of folate intake. However, studies focused on the association between RBC folate and coronary heart disease (CHD) are limited. The aim of the current study was to investigate the effect of RBC folate concentrations on the presence of CHD in a nationally representative sample of American adults.

METHODS AND RESULTS

In the 1999-2012 National Health and Nutrition Examination Survey (NHANES), 22,499 subjects aged 30-74 years with RBC folate concentrations, CHD status and responses to co-variates questions were included; 822 (3.65%) participants were identified as having CHD. Bio-Rad Quanta Phase II radioassay and microbiological assay were used to measure RBC folate concentrations. Firstly, we treated RBC folate as a categorical variable, based on RBC folate tertiles, and used logistic regression analysis to display the RBC folate and CHD relationship. Secondly, we explored associations using a combination of restricted cubic spline and logistic regression models, stratified by sex. After adjusting for several well-established traditional CHD risk factors, RBC folate was positively related to CHD presence in the total population and the association was more pronounced among males than females. A J-shaped pattern was observed in RBC folate concentrations for females.

CONCLUSION

Elevated RBC folate concentrations were associated with higher CHD risk. Further investigation is needed to test the association in large-scale follow-up studies.

Palm tocotrienol-rich fraction inhibits methionine-induced cystathionine β-synthase in rat liver

Oxidative stress plays an important role in cardiovascular diseases. The study investigated the effects of dietary palm tocotrienol-rich fraction on homocysteine metabolism in rats fed a high-methionine diet. Forty-two male Wistar rats were randomly assigned to six groups. Five groups were fed with high-methionine diet (1%) for 10 weeks. Groups 2 to 5 were also given dietary folate (8 mg/kg) and three doses of palm tocotrienol-rich fraction (30, 60 and 150 mg/kg) from week 6 to week 10. The last group was only given basal rat chow. High-methionine diet increased plasma homocysteine after 10 weeks, which was prevented by the supplementations of folate and high-dose palm tocotrienol-rich fraction. Hepatic S-adenosyl methionine (SAM) content was unaffected in all groups but S-adenosyl homocysteine (SAH) content was reduced in the folate group. Folate supplementation increased the SAM/SAH ratio, while in the palm tocotrienol-rich fraction groups, the ratio was lower compared with the folate. Augmented activity of hepatic cystathionine β-synthase and lipid peroxidation content by high-methionine diet was inhibited by palm tocotrienol-rich fraction supplementations (moderate and high doses), but not by folate. The supplemented groups had lower hepatic lipid peroxidation than the high-methionine diet. In conclusion, palm tocotrienol-rich fraction reduced high-methionine-induced hyperhomocysteinaemia possibly by reducing hepatic oxidative stress in high-methionine-fed rats. It may also exert a direct inhibitory effect on hepatic cystathionine β-synthase.

The application of a chemical determination of N-homocysteinylation levels in developing mouse embryos: implication for folate responsive birth defects

Elevated homocysteine levels have long been associated with various disease states, including cardiovascular disease and birth defects, including neural tube defects (NTDs). One hypothesis regarding the strong correlation between these various disorders and high levels of homocysteine is that a reactive form of this small molecule can attach to mammalian proteins in a phenomenon known as homocysteinylation. These posttranslational modifications may become antigenic or may even directly disrupt certain protein function. It remains to be determined whether dietary influences that can cause globally increased levels of circulating homocysteine confer negative effects maternally, or may otherwise negatively and materially impact the metabolic balance in developing embryos. Herein we present the application of a chemical method of determination of N-homocysteinylation to a set of neural tube closure stage mouse embryos and their mothers. We explore the uses of this newly described technique to investigate levels of maternal and embryonic N-homocysteinylation using dietary manipulations of one-carbon metabolism with two known folate-responsive NTD mouse models. The data presented reveal that although diet appeared to have significant effects on the maternal metabolic status, those effects did not directly correlate to the embryonic folate or N-homocysteinylation status. Our studies indicate that maternal diet and embryonic genotype most significantly affected the embryonic developmental outcome.

Organization of the human mitochondrial hydrogen sulfide oxidation pathway

Sulfide oxidation is expected to play an important role in cellular switching between low steady-state intracellular hydrogen sulfide levels and the higher concentrations where the physiological effects are elicited. Yet despite its significance, fundamental questions regarding how the sulfide oxidation pathway is wired remain unanswered, and competing proposals exist that diverge at the very first step catalyzed by sulfide quinone oxidoreductase (SQR). We demonstrate that, in addition to sulfite, glutathione functions as a persulfide acceptor for human SQR and that rhodanese preferentially synthesizes rather than utilizes thiosulfate. The kinetic behavior of these enzymes provides compelling evidence for the flow of sulfide via SQR to glutathione persulfide, which is then partitioned to thiosulfate or sulfite. Kinetic simulations at physiologically relevant metabolite concentrations provide additional support for the organizational logic of the sulfide oxidation pathway in which glutathione persulfide is the first intermediate formed.