Gender and single nucleotide polymorphisms in MTHFR, BHMT, SPTLC1, CRBP2, CETP, and SCARB1 are significant predictors of plasma homocysteine normalized by RBC folate in healthy adults

Association of Maternal Betaine-Homocysteine Methyltransferase (BHMT) and BHMT2 Genes Polymorphisms with Congenital Heart Disease in Offspring

To systematically explore the association of single nucleotide polymorphisms (SNPs) of maternal BHMT and BHMT2 genes with the risk of congenital heart disease (CHD) and its three subtypes including atrial septal defect (ASD), ventricular septal defect (VSD), and patent ductus arteriosus (PDA) in offspring. A hospital-based case-control study involving 683 mothers of CHD children and 740 controls was performed. Necessary exposure information was captured through epidemiological investigation. Totally twelve SNPs of maternal BHMT and BHMT2 genes were detected and analyzed systematically. The study showed that maternal BHMT gene polymorphisms at rs1316753 (CG vs. CC: OR = 1.96 [95% CI 1.41-2.71]; GG vs. CC: OR = 1.99 [95% CI 1.32-3.00]; dominant model: OR = 1.97 [95% CI 1.44-2.68]) and rs1915706 (TC vs. TT: OR = 1.93 [95% CI 1.44-2.59]; CC vs. TT: OR = 2.55 [95% CI 1.38-4.72]; additive model: OR = 1.77 [95% CI 1.40-2.24]) were significantly associated with increased risk of total CHD in offspring. And two haplotypes were observed to be significantly associated with risk of total CHD, including C-C haplotype involving rs1915706 and rs3829809 in BHMT gene (OR = 1.30 [95% CI 1.07-1.58]) and C-A-A-C haplotype involving rs642431, rs592052, rs626105, and rs682985 in BHMT2 gene (OR = 0.71 [95% CI 0.58-0.88]). Besides, a three-locus model involving rs1316753 (BHMT), rs1915706 (BHMT), and rs642431 (BHMT2) was identified through gene-gene interaction analyses (P < 0.01). As for three subtypes including ASD, VSD, and PDA, significant SNPs and haplotypes were also identified. The results indicated that maternal BHMT gene polymorphisms at rs1316753 and rs1915706 are significantly associated with increased risk of total CHD and its three subtypes in offspring. Besides, significant interactions between different SNPs do exist on risk of CHD. Nevertheless, studies with larger sample size in different ethnic populations and involving more SNPs in more genes are expected to further define the genetic contribution underlying CHD and its subtypes.

Betaine consumption as a new clinical approach to treatment and prophylaxis of folate-related pathologies

The most important pathway in the development of folate-related pathologies is an increase in the level of homocysteine (HC). HC, a cytotoxic and neurotoxic amino acid (when its level is ≥12 μmol/L), is 1 of the most widely studied compounds in cardiology, neurobiology, oncology, and embryology for the last 20 years. Given its toxicity, the processes of endogenous detoxification of HC are of particular interest to medicine. To date, the most studied pathway is that of remethylation (the conversion of HC to methionine), with the participation of B12- and B9-dependent methionine synthase. Less studied is remethylation with the participation of the choline derivatives betaine and betaine-HC-S-methyltransferase (BHMT). Therefore, the aim of this review was to conduct a theoretical analysis of available information regarding the contribution of betaine metabolism, its enzyme, and its genetic polymorphism to folate metabolism disturbances, and the development of folate-related pathologies. This review emphasizes the potential clinical significance of 2 factors that can influence the remethylation reaction of HC: the use of betaine and identifying the BHMT gene variants and their impact on the risk for developing certain folate-related pathologies, and treatment options. Moreover, with a high level of methylation of the BHMT gene and in the presence of its low-function variants (eg, rs3733890), it is necessary to use betaine as an additional methyl donor, especially during folate therapy. More clinical research is needed to identify the effects of the different BHMT gene variants on the individual risk for folate-related pathologies to better assess the clinical significance, the need for genetic testing, and betaine consumption.

Genetically-Guided Medical Nutrition Therapy in Type 2 Diabetes Mellitus and Pre-diabetes: A Series of n-of-1 Superiority Trials

Type 2 diabetes mellitus (T2DM) is a heterogeneous metabolic disorder of multifactorial etiology that includes genetic and dietary influences. By addressing the latter, medical nutrition therapy (MNT) contributes to the management of T2DM or pre-diabetes toward achieving glycaemic control and improved insulin sensitivity. However, the clinical outcomes of MNT vary and may further benefit from personalized nutritional plans that take into consideration genetic variations associated with individual responses to macronutrients. The aim of the present series of n-of-1 trials was to assess the effects of genetically-guided vs. conventional MNT on patients with pre-diabetes or T2DM. A quasi-experimental, cross-over design was adopted in three Caucasian adult men with either diagnosis. Complete diet, bioclinical and anthropometric assessment was performed and a conventional MNT, based on the clinical practice guidelines was applied for 8 weeks. After a week of “wash-out,” a precision MNT was prescribed for an additional 8-week period, based on the genetic characteristics of each patient. Outcomes of interest included changes in body weight (BW), fasting plasma glucose (FPG), and blood pressure (BP). Collectively, the trials indicated improvements in BW, FPG, BP, and glycosylated hemoglobin (HbA1c) following the genetically-guided precision MNT intervention. Moreover, both patients with pre-diabetes experienced remission of the condition. We conclude that improved BW loss and glycemic control can be achieved in patients with pre-diabetes/T2DM, by coupling MNT to their genetic makeup, guiding optimal diet, macronutrient composition, exercise and oral nutrient supplementation in a personalized manner.

Interaction analysis of gene variants related to one-carbon metabolism with chronic hepatitis B infection in Chinese patients

BACKGROUND

The risk of chronic hepatitis B (CHB) infection is influenced by aberrant DNA methylation and altered nucleotide synthesis and repair, possibly caused by polymorphic variants in one-carbon metabolism genes. In the present study, we investigated the relationship between polymorphisms belonging to the one-carbon metabolic pathway and CHB infection.

METHODS

A case-control study using 230 CHB patients and 234 unrelated healthy controls was carried out to assess the genetic association of 24 single nucleotide polymorphisins (SNPs) determined by mass spectrometry.

RESULTS

Three SNPs, comprising rs10717122 and rs2229717 in serine hydroxymethyltransferase1/2 (SHMT2) and rs585800 in betaine-homocysteine S-methyltransferase (BHMT), were associated with the risk of CHB. Patients with DEL allele, DEL.DEL and DEL.T genotypes of rs10717122 had a 1.40-, 2.00- and 1.83-fold increased risk for CHB, respectively. Cases inheriting TA genotype of rs585800 had a 2.19-fold risk for CHB infection. The T allele of rs2229717 was less represented in the CHB cases (odds ratio = 0.66, 95% confidence interval = 0.48-0.92). The T allele of rs2229717 was less in patients with a low hepatitis B virus-DNA level compared to the control group (odds ratio = 0.49, 95% confidence interval = 0.25-0.97) and TT genotype of rs2229717 had a significant correlation with hepatitis B surface antigen level (p = 0.0195). Further gene-gene interaction analysis showed that subjects carrying the rs10717122 DEL.DEL/DEL.T and rs585800 TT/TA genotypes had a 2.74-fold increased risk of CHB.

CONCLUSIONS

The results of the present study suggest that rs10717122, rs585800 and rs2229717 and gene-gene interactions of rs10717122 and rs585800 affect the outcome of CHB infection, at the same time as indicating their usefulness as a predictive and diagnostic biomarker of CHB infection.

MTHFR Polymorphisms in Girls with Anorexia Nervosa: Implications on Body Weight

The development of atypical vs typical anorexia nervosa (AN) might be explained by the genetic background. We assessed the link between the subtypes of AN and the genetic polymorphisms of the thrombotic panel and the methyltetrahydrofolate reductase (MTHFR) gene. This cross-sectional pilot study recruited 48 girls with AN and 10 age-matched control girls with normal menstruation. We recorded anthropometric parameters and obtained blood samples for genotyping and hormonal assessment. Classification of AN was performed according to the DSM-V criteria. Girls with AN had 2.66 times higher odds of carrying at least one genetic polymorphism from the MTHFR panel (C677T and A1298C) compared with girls without AN (OR = 2.660, p-value = 0.041; CI 95% 1.057-6.720). The presence of atypical vs typical AN was associated independently with the presence of any of the assessed MTHFR polymorphisms (C677T, OR = 4.929, 95% CI 1.076-22.579, p-value = 0.040; A1298C, OR = 0.097, 95% CI 0.011-0.866, p-value = 0.037) in age and estrogen adjusted models. The atypical presentation of AN is mainly linked with higher prevalence of the MTHFR C677T and lower prevalence of the A1298C polymorphism.

Evaluation of H-type hypertension prevalence and its influence on the risk of increased carotid intima-media thickness among a high-risk stroke population in Hainan Province, China

H-type hypertension, defined as a combination of hypertension and hyperhomocysteinemia (Hhcy), is associated with atherosclerosis and, therefore, increased stroke risk. However, the role of hypertension and Hhcy in high-risk stroke populations has not been studied. The present study investigated the prevalence of H-type hypertension in a high-risk stroke population of Hainan Province, China and to assess possible joint effects between hypertension and Hhcy for increased carotid intima-media thickness (CIMT). In this community-based cross-sectional study, 959 high-risk stroke subjects (age, 65.8 ± 10.8 years; 46.6% men) were recruited from Hainan Province, China. The demographic and clinical characteristics were collected, and blood samples were obtained. Analysis of variance or chi-square tests were performed to compare variates among groups based on both homocysteine levels and blood pressure status. The associations of hypertension and Hhcy with increased CIMT were evaluated through logistic regression. The prevalence of H-type hypertension was 34.8% in this population, with a higher ratio of H-type hypertension in men than in women. Compared with the normotension and normal homocysteine subgroup, the risk of increased CIMT was significantly higher in the subgroup with hypertension and Hhcy (odds ratio [OR] = 2.639; 95% confidence interval [CI], 1.690-4.091) after adjusting for age and sex. Increased CIMT was affected by an additive synergetic interaction between Hhcy and hypertension (synergy index = 1.105). It emphasized the clinical importance of anti-hypertension and lowering Hhcy in the high-risk stroke population.

Retinol-binding protein 2 (RBP2): biology and pathobiology

Retinol-binding protein 2 (RBP2; originally cellular retinol-binding protein, type II (CRBPII)) is a 16 kDa cytosolic protein that in the adult is localized predominantly to absorptive cells of the proximal small intestine. It is well established that RBP2 plays a central role in facilitating uptake of dietary retinoid, retinoid metabolism in enterocytes, and retinoid actions locally within the intestine. Studies of mice lacking Rbp2 establish that Rbp2 is not required in times of dietary retinoid-sufficiency. However, in times of dietary retinoid-insufficiency, the complete lack of Rbp2 gives rise to perinatal lethality owing to RBP2 absence in both placental (maternal) and neonatal tissues. Moreover, when maintained on a high-fat diet, Rbp2-knockout mice develop obesity, glucose intolerance and a fatty liver. Unexpectedly, recent investigations have demonstrated that RBP2 binds long-chain 2-monoacylglycerols (2-MAGs), including the canonical endocannabinoid 2-arachidonoylglycerol, with very high affinity, equivalent to that of retinol binding. Crystallographic studies establish that 2-MAGs bind to a site within RBP2 that fully overlaps with the retinol binding site. When challenged orally with fat, mucosal levels of 2-MAGs in Rbp2 null mice are significantly greater than those of matched controls establishing that RBP2 is a physiologically relevant MAG-binding protein. The rise in MAG levels is accompanied by elevations in circulating levels of the hormone glucose-dependent insulinotropic polypeptide (GIP). It is not understood how retinoid and/or MAG binding to RBP2 affects the functions of this protein, nor is it presently understood how these contribute to the metabolic and hormonal phenotypes observed for Rbp2-deficient mice.

Genetic Association of Plasma Homocysteine Levels with Gastric Cancer Risk: A Two-Sample Mendelian Randomization Study

BACKGROUND

The association of plasma homocysteine level (PHL) with gastric cancer risk was reported in observational studies. However, the causality is challenging due to confounding factors and the lack of evidence from well-designed cohort studies. Herein, we performed a two-sample Mendelian randomization (MR) analysis to investigate whether PHL is causally related to gastric cancer risk.

METHODS

We performed the MR analysis based on the results from genome-wide association studies consisting of 2,631 patients with gastric cancer and 4,373 controls. An externally weighted genetic risk score (wGRS) was constructed with 15 SNPs with well-established associations with PHL. We utilized logistic regression model to estimate associations of PHL-related SNPs and wGRS with gastric cancer risk in total population and in strata by sex, age, and study site, in addition to a series of sensitivity analyses.

RESULTS

High genetically predicted PHL was associated with an increased gastric cancer risk (per SD increase in the wGRS: OR = 1.07; 95% confidence interval, 1.01-1.12; P = 0.011), which was consistent in sensitivity analyses. Subgroup analyses provided evidence of a stronger association with gastric cancer risk in women than in men. MR-Egger and weighted median regression suggested that potentially unknown pleiotropic effects were not biasing the association between PHL and gastric cancer risk.

CONCLUSIONS

These results revealed that genetically predicted high PHL was associated with an increased gastric cancer risk, suggesting that high PHL may have a causal role in the etiology of gastric cancer.

IMPACT

These findings provide causal inference for PHL on gastric cancer risk, suggesting a causal role of high PHL in the etiology of gastric cancer.

Association between BHMT and CBS gene promoter methylation with the efficacy of folic acid therapy in patients with hyperhomocysteinemia

Both betaine homocysteine methyltransferase (BHMT) and cystathionine β-synthase (CBS) are major enzymes in the metabolism of plasma homocysteine (Hcy). Abnormal methylation levels of BHMT and CBS are positively associated with Hcy levels. The present study is performed to explore the association between the methylation levels in the promoter regions of the BHMT and CBS genes and the efficacy of folic acid therapy in patient with hyperhomocysteinemia (HHcy). A prospective cohort study recruiting HHcy (Hcy ≥ 15 μmol/L) patients was performed. The subjects were treated with oral folic acid (5 mg/d) for 90 days, and the patients were divided into the success group (Hcy < 15 μmol/L) and the failure group (Hcy ≥ 15 μmol/L) according to their Hcy levels after treatment. In the logistic regression model with adjusted covariates, the patients with lower total methylation levels in the BHMT and CBS promoter regions exhibited 1.627-fold and 1.671-fold increased risk of treatment failure compared with higher methylation individuals, respectively. Similarly, subjects who had lower methylation levels (<methylation mean) in BHMT CpG1 had 1.792 times higher risks. Stratified analysis by sex found that lower CBS methylation levels were associated with a 2.128-fold increased risk for treatment failure in males with HHcy. Lower levels of BHMT or CBS promoter total methylation might be associated with increased the risk of treatment failure. These studies suggest that lower levels of BHMT and CBS methylation are all predictors of failure in folic acid therapy for HHcy. However, due to some limitations of this study, such as the small number of the loci tested, further large-scale studies are necessary to verify our observations.

Associations of cholesteryl ester transfer protein (CETP) gene variants with pituitary adenoma

AIM

The aim was to evaluate the association of CETP (rs5882 and rs708272) single nucleotide polymorphisms with the presence, invasiveness, hormonal activity and recurrence of pituitary adenoma (PA).

METHODS

The study group included 142 patients with PA and the control group, 753 healthy subjects. The genotyping of CETP (rs5882 and rs708272) was performed using a real-time PCR method.

RESULTS

After statistical analysis we found that CETP rs708272 genotype G/A under the over-dominant model was associated with the decreased odds of PA (OR=0.637; 95%CI: 0.443-0.917; P=0.015), active PA (OR=0.538; 95%CI: 0.335-0.865; P =0.01) and non-recurrent PA (OR=0.602; 95% CI: 0.402 - 0.902; P =0.014). When compared to controls, the rs708272 genotype G/A was less frequent in the active PA subgroup (37.5% vs 52.7%, P =0.009) and the non-recurrent PA subgroup (40.2% vs 52.7%, P=0.013), while the rs5882 genotype A/A was less frequent in the non-recurrent PA subgroup (37.5% vs 46.2%, P=0.015).

CONCLUSION

Our study showed that CETP rs708272 genotype G/A may be associated with a decreased risk of PA.

Opposite Expression of SPARC between the Liver and Pancreas in Streptozotocin-Induced Diabetic Rats

Secreted protein acidic and rich in cysteine (SPARC) is a matricellular protein that regulates several cellular events, including inflammation and tissue remodelling. In this study, we investigated the tissue-specific expression of SPARC in streptozotocin (STZ)-induced diabetes, and found that SPARC was significantly up-regulated in the liver while down-regulated in the pancreas of STZ-induced diabetic rats. Chronic inflammation occurred in the diabetic pancreas accompanied by up-regulation of CCAAT/enhancer-binding protein beta (C/EBPβ) and its targets (TNFα, Il6, CRP, and Fn1) as well as myeloperoxidase (Mpo) and C-X-C chemokine receptor type 2 (Cxcr2). Diabetic liver showed significant up-regulation of Tgfb1 as well as moderately less up-regulated TNFα and reduced Fn1, resulting in elevated fibrogenesis. PARP-1 was not up-regulated during CD95-mediated apoptosis, resulting in restoration of high ATP levels in the diabetic liver. On the contrary, CD95-dependent apoptosis was not observed in the diabetic pancreas due to up-regulation of PARP-1 and ATP depletion, resulting in necrosis. The cytoprotective machinery was damaged by pancreatic inflammation, whereas adequate antioxidant capacity indicates low oxidative stress in the diabetic liver. High and low cellular insulin content was found in the diabetic liver and pancreas, respectively. Furthermore, we identified six novel interacting partner proteins of SPARC by co-immunoprecipitation in the diabetic liver and pancreas, and their interactions with SPARC were predicted by bioinformatics tools. Taken together, opposite expression of SPARC in the diabetic liver and pancreas may be related to inflammation and immune cell infiltration, degrees of apoptosis and fibrosis, cytoprotective machinery, and cellular insulin levels.

Genome-wide association study of selenium concentrations

Selenium (Se) is an essential trace element in human nutrition, but its role in certain health conditions, particularly among Se sufficient populations, is controversial. A genome-wide association study (GWAS) of blood Se concentrations previously identified a locus at 5q14 near BHMT. We performed a GW meta-analysis of toenail Se concentrations, which reflect a longer duration of exposure than blood Se concentrations, including 4162 European descendants from four US cohorts. Toenail Se was measured using neutron activation analysis. We identified a GW-significant locus at 5q14 (P < 1 × 10(-16)), the same locus identified in the published GWAS of blood Se based on independent cohorts. The lead single-nucleotide polymorphism (SNP) explained ∼1% of the variance in toenail Se concentrations. Using GW-summary statistics from both toenail and blood Se, we observed statistical evidence of polygenic overlap (P < 0.001) and meta-analysis of results from studies of either trait (n = 9639) yielded a second GW-significant locus at 21q22.3, harboring CBS (P < 4 × 10(-8)). Proteins encoded by genes at 5q14 and 21q22.3 function in homocysteine (Hcy) metabolism, and index SNPs for each have previously been associated with betaine and Hcy levels in GWAS. Our findings show evidence of a genetic link between Se and Hcy pathways, both involved in cardiometabolic disease.

[Folic acid intake before and after mandatory fortification: a population-based study in São Paulo, Brazil]

This study analyzed folic acid intake before and since mandatory fortification. Dietary data were collected by 24-hour recall in a health survey in São Paulo (ISA-Capital) in 2003 and 2007-2008, stratifying the population according to life stage and gender. Estimated average requirement (EAR) and tolerable upper intake level (UL) were used to assess intake. Prevalence of inadequate folic acid intake decreased in all groups, especially adolescents and adult males (72% to < 1% and 76% to 6%, respectively) but remained high in adult women (38%). Beans were the main source of folic acid before fortification. With fortification, bread became the main source, but beans remained important. Fortification was successful (increased intake within safe levels), but it raised concerns about the high proportion in the target group (adult women) who still fail to meet the recommended intake.

Hepatic scavenger receptor BI protects against polymicrobial-induced sepsis through promoting LPS clearance in mice

Recent studies revealed that scavenger receptor BI (SR-BI or Scarb1) plays a critical protective role in sepsis. However, the mechanisms underlying this protection remain largely unknown. In this study, using Scarb1(I179N) mice, a mouse model specifically deficient in hepatic SR-BI, we report that hepatic SR-BI protects against cecal ligation and puncture (CLP)-induced sepsis as shown by 75% fatality in Scarb1(I179N) mice, but only 21% fatality in C57BL/6J control mice. The increase in fatality in Scarb1(I179N) mice was associated with an exacerbated inflammatory cytokine production. Further study demonstrated that hepatic SR-BI exerts its protection against sepsis through its role in promoting LPS clearance without affecting the inflammatory response in macrophages, the glucocorticoid production in adrenal glands, the leukocyte recruitment to peritoneum or the bacterial clearance in liver. Our findings reveal hepatic SR-BI as a critical protective factor in sepsis and point out that promoting hepatic SR-BI-mediated LPS clearance may provide a therapeutic approach for sepsis.

Vitamin B6 deficiency, genome instability and cancer

Vitamin B6 functions as a coenzyme in >140 enzymatic reactions involved in the metabolism of amino acids, carbohydrates, neurotransmitters, and lipids. It comprises a group of three related 3-hydroxy-2-methyl-pyrimidine derivatives: pyridoxine (PN), pyridoxal (PL), pyridoxamine (PM) and their phosphorylated derivatives [pyridoxal 5'-phosphate (PLP) and pyridoxamine 5'-phosphate (PMP)], In the folate metabolism pathway, PLP is a cofactor for the mitochondrial and cytoplasmic isozymes of serine hydroxymethyltransferase (SHMT2 and SHMT1), the P-protein of the glycine cleavage system, cystathionine β-synthase (CBS) and γ-cystathionase, and betaine hydroxymethyltransferase (BHMT), all of which contribute to homocysteine metabolism either through folate- mediated one-carbon metabolism or the transsulfuration pathway. Folate cofactors carry and chemically activate single carbons for the synthesis of purines, thymidylate and methionine. So the evidence indicates that vitamin B6 plays an important role in maintenance of the genome, epigenetic stability and homocysteine metabolism. This article focuses on studies of strand breaks, micronuclei, or chromosomal aberrations regarding protective effects of vitamin B6, and probes whether it is folate-mediated one-carbon metabolism or the transsulfuration pathway for vitamin B6 which plays critical roles in prevention of cancer and cardiovascular disease.

Single nucleotide polymorphisms in CETP, SLC46A1, SLC19A1, CD36, BCMO1, APOA5, and ABCA1 are significant predictors of plasma HDL in healthy adults

Background

In a marker-trait association study we estimated the statistical significance of 65 single nucleotide polymorphisms (SNP) in 23 candidate genes on HDL levels of two independent Caucasian populations. Each population consisted of men and women and their HDL levels were adjusted for gender and body weight. We used a linear regression model. Selected genes corresponded to folate metabolism, vitamins B-12, A, and E, and cholesterol pathways or lipid metabolism.

Methods

Extracted DNA from both the Sacramento and Beltsville populations was analyzed using an allele discrimination assay with a MALDI-TOF mass spectrometry platform. The adjusted phenotype, y, was HDL levels adjusted for gender and body weight only statistical analyses were performed using the genotype association and regression modules from the SNP Variation Suite v7.

Results

Statistically significant SNP (where P values were adjusted for false discovery rate) included: CETP (rs7499892 and rs5882); SLC46A1 (rs37514694; rs739439); SLC19A1 (rs3788199); CD36 (rs3211956); BCMO1 (rs6564851), APOA5 (rs662799), and ABCA1 (rs4149267). Many prior association trends of the SNP with HDL were replicated in our cross-validation study. Significantly, the association of SNP in folate transporters (SLC46A1 rs37514694 and rs739439; SLC19A1 rs3788199) with HDL was identified in our study.

Conclusions

Given recent literature on the role of niacin in the biogenesis of HDL, focus on status and metabolism of B-vitamins and metabolites of eccentric cleavage of β-carotene with lipid metabolism is exciting for future study.