Menopause modulates homocysteine levels in diabetic and non-diabetic women

Effects of MTHFR C677T polymorphism on homocysteine and vitamin D in women with polycystic ovary syndrome

OBJECTIVES

To evaluate the correlation between serum vitamin D, homocysteine and the methylene tetrahydrofolate reductase (MTHFR) C677T polymorphism in women with polycystic ovary syndrome (PCOS). Study design We retrospectively compared the serum homocysteine and vitamin D levels and the MTHFR C677T polymorphism in 104 PCOS patients and 104 controls. Parameters related to PCOS were statistically analysed.

RESULTS

Comparative analysis revealed that women with PCOS had significantly greater serum homocysteine levels (P = 0.002) and lower vitamin D concentrations (P = 0.040) than controls. The distribution frequency of the MTHFR C677T genotype did not significantly differ between the PCOS group and the control group. (P > 0.05). In the PCOS group, the serum level of homocysteine in the TT group was significantly greater than that in the CT (P = 0.003) and CC (P = 0.002) groups and the level of vitamin D in the TT group was significantly less than that in the CC (P < 0.001) and CT (P = 0.172) groups. The results were similar when the PCOS and control groups were divided according to whether they had insulin resistance. Vitamin D levels were significantly negatively correlated with homocysteine levels in all PCOS patients (r = -0.281, P = 0.004), similarly, vitamin D levels were negatively correlated with homocysteine levels in the CC, CT and TT of PCOS patients. According to multivariate analysis, vitamin D concentration was an independent risk factor for hyperhomocysteinaemia (adjusted OR 1.372, 95 % CI: 1.100-1.712).

CONCLUSIONS

No significant differences were found in the distributions of MTHFR C677T genotypes between the PCOS and control groups but these genotypes affected the patients' serum homocysteine and vitamin D concentrations. Women with the TT genotype have significantly lower vitamin D levels and higher homocysteine levels than women with the CC and CT genotypes. However, because of the limitations of this investigation, large-sample, high-quality prospective studies are needed to further verify these results in the future.

A Sex-Specific Comparative Analysis of Oxidative Stress Biomarkers Predicting the Risk of Cardiovascular Events and All-Cause Mortality in the General Population: A Prospective Cohort Study

Oxidative stress plays a pivotal role in cardiovascular (CV) disease, but current biomarkers used to predict CV events are still insufficient. In this study, we comparatively assessed the utility of redox-related biomarkers in predicting the risk of CV events and all-cause mortality in male and female subjects from the general population. Subjects (n = 5955) of the Prevention of REnal and Vascular ENd-stage Disease (PREVEND) population-based cohort study were included. Blood homocysteine, gamma-GT, HDL cholesterol, bilirubin and protein-adjusted free thiol (R-SH, sulfhydryl groups) levels were quantified at baseline and were prospectively analyzed in association with the risk of CV events and all-cause mortality. After adjustment for potentially confounding factors, protein-adjusted R-SH and homocysteine levels were significantly associated with the risk of CV events in men (HR 0.63 [0.40–0.99], p = 0.045 and HR 1.58 [1.20–2.08], p = 0.001, respectively). Protein-adjusted R-SH and HDL cholesterol levels were significantly associated with the risk of all-cause mortality in men (HR 0.52 [0.32–0.85], p = 0.009 and HR 0.90 [0.85–0.94], p < 0.001, respectively), while the same was observed for bilirubin and homocysteine levels in women (HR 0.68 [0.48–0.98], p = 0.040 and HR 2.30 [1.14–3.76], p < 0.001, respectively). Lower levels of protein-adjusted R-SH were robustly associated with an increased risk of CV events and all-cause mortality in men. Our results highlight the value of R-SH levels in cardiovascular risk assessment and their potential significance as being amenable to therapeutic intervention, while reaffirming the importance of other oxidative stress-related biomarkers, such as homocysteine, HDL cholesterol and bilirubin.

Association between Pro-oxidant-Antioxidant balance and high-sensitivity C-reactive protein in type 2 diabetes mellitus: A Study on Postmenopausal Women

INTRODUCTION

Oxidative stress known as a predictive marker for cardiovascular and metabolic diseases could be measured through pro-oxidant antioxidant balance (PAB). The present study aimed to evaluate PAB and its association with high-sensitivity C-reactive protein (hs-CRP) in the serum of postmenopausal women with diabetes mellitus.

METHODS

In this case-control study, 99 diabetic and 100 healthy postmenopausal women without diabetes mellitus were recruited. Serum PAB values, hs-CRP, lipid profile, insulin, and vitamin D levels were measured. Moreover, insulin resistance (HOMA-IR, HOMA-β and QUICKI), waist circumference (WC), waist-to-hip ratio (WHR), waist-to-height ratio (WHtR), and body mass index (BMI) were calculated.

RESULTS

Serum PAB, hs-CRP, insulin resistance, HOMA-β, QUICKI, low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), and triglycerides (TG) levels were significantly higher in the postmenopausal women with diabetes mellitus, while there was no significant difference in the total cholesterol (TC), serum insulin, WC, WHR, WHtR and vitamin D levels between the groups. Pearson correlation coefficient showed that HDL-C and insulin levels were directly correlated with serum PAB. Also, there was a significant direct relationship between LDL-C and insulin levels and hs-CRP. There was no meaningful relationship between serum insulin and vitamin D levels and other assessed parameters. Backward logistic regression showed a positive relationship between diabetes mellitus and serum PAB and an inverse relationship with serum HDL levels.

CONCLUSIONS

Serum PAB, hs-CRP concentration, and lipid profile were significantly different between postmenopausal women with and without diabetes mellitus. These differences may contribute to the development of coronary complications.

Type II diabetes mellitus and hyperhomocysteinemia: a complex interaction

BACKGROUND

Elevated homocysteine (Hc) levels have a well-established and clear causal relationship to epithelial damage leading to coronary artery disease. Furthermore, it is strongly associated with other metabolic syndrome variables, such as hypertension, which is correlated with type II diabetes mellitus (T2DM). Studies on T2DM in relation to Hc levels have shown both positive and negative associations. The aim of the present study is to examine the relationship between Hc levels and risk of T2DM in the Lebanese population.

METHODS

We sought to identify whether Hc associates positively or negatively with diabetes in a case-control study, where 2755 subjects enrolled from patients who had been catheterized for coronary artery diagnosis and treatment. We further sought to identify whether the gene variant MTHFR 667C>T is associated with T2DM, and how Hc and MTHFR 667C>T also impact other correlates of T2DM, including the widely used diuretics in this study population.

RESULTS

We found that Hc levels were significantly reduced among subjects with diabetes compared to those without diabetes when adjusted for all potential confounders (OR 0.640; 95% CI [0.44-0.92]; p = 0.0200). The associations between Hc levels and other variates contradicted the result: hypertension associates positively with high Hc levels, and with T2DM. The MTHFR 667C>T only associated significantly with high Hc levels.

CONCLUSION

These results suggest population-specific variations among a range of mechanisms that modulate the association of Hc and T2DM, providing a probe for future studies.

Fracture Risk in Type 2 Diabetes: Current Perspectives and Gender Differences

Type 2 diabetes mellitus (T2DM) is associated with an increased risk of osteoporotic fractures, resulting in disabilities and increased mortality. The pathophysiological mechanisms linking diabetes to osteoporosis have not been fully explained, but alterations in bone structure and quality are well described in diabetic subjects, likely due to a combination of different factors. Insulin deficiency and dysfunction, obesity and hyperinsulinemia, altered level of oestrogen, leptin, and adiponectin as well as diabetes-related complications, especially peripheral neuropathy, orthostatic hypotension, or reduced vision due to retinopathy may all be associated with an impairment in bone metabolism and with the increased risk of fractures. Finally, medications commonly used in the treatment of T2DM may have an impact on bone metabolism and on fracture risk, particularly in postmenopausal women. When considering the impact of hypoglycaemic drugs on bone, it is important to balance their potential direct effects on bone quality with the risk of falling-related fractures due to the associated hypoglycaemic risk. In this review, experimental and clinical evidence connecting bone metabolism and fracture risk to T2DM is discussed, with particular emphasis on hypoglycaemic treatments and gender-specific implications.

Lipid and non-lipid cardiovascular risk factors in postmenopausal type 2 diabetic women with and without coronary heart disease

BACKGROUND

Coronary heart disease (CHD) is the leading cause of death in diabetic women. In addition to hyperglycemia, other factors may contribute to the excessive cardiovascular risk.

AIM

In this study we evaluated common and emerging risk factors in a selected group of postmenopausal type 2 diabetic women with (n = 36) and without CHD (n = 59), not taking lipid-lowering medications.

METHODS

Clinical and lifestyle data were collected, and metabolic and lipid profile, as well as fasting plasma levels of total homocysteine (tHcy), folate, vitamin B12, C-reactive protein (hsCRP), interleukin 6 (IL-6), and vascular cell adhesion molecule-1 (VCAM-1) were measured in all participants.

RESULTS

Age, menopause and diabetes duration, family history for cardiovascular disease, prevalence of hypertension and current insulin use were greater in diabetic women with than without CHD (P < 0.05 for all comparisons). CHD women also showed higher levels of triglycerides, small dense LDL (sdLDL), remnant-like particle cholesterol, tHcy, and VCAM-1, and a lower creatinine clearance (P < 0.05 all). Conversely, the two groups were comparable for BMI, waist circumference, smoking habit, fasting plasma glucose, HbA1c, total cholesterol, low-density lipoprotein cholesterol (LDL-C), HDL cholesterol, folate, vitamin B12, hsCRP and IL-6 levels. At multivariate analysis, lower creatinine clearance (OR = 0.932, P = 0.017) and higher sdLDL serum concentration (OR = 1.224, P = 0.037) were the strongest risk factors associated with CHD in this population, whereas no significant association was noted with LDL-C.

CONCLUSIONS

Our data suggest that beyond LDL-C, a lower creatinine clearance and more subtle alterations of LDL particles, together with a constellation of several well known and emerging cardiovascular risk factors, are stronger contributors to the high CHD risk of diabetic women.

Methylenetetrahydrofolate reductase gene polymorphism and risk of type 2 diabetes mellitus

OBJECTIVE

This review aimed to comprehensively assess the literature examining a possible link between the rs1801133 polymorphism (677C → T) in the gene encoding the methylenetetrahydrofolate reductase (MTHFR) gene and risk of type 2 diabetes mellitus (DM).

RESEARCH DESIGN AND METHODS

Several research databases were systematically searched for studies examining the genotype at the rs1801133 polymorphism in healthy control individuals and individuals with type 2 DM. Genotype frequency data were examined across all studies and across subsets of studies according to ethnicity and presence of serious DM-related complications. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated.

RESULTS

A total of 4855 individuals with type 2 DM and 5242 healthy controls from 15 countries comprising Asian, Caucasian and African ethnicities were found to satisfy the inclusion criteria and included in the review. Genotype at the rs1801133 polymorphism was not consistently associated with either increased or reduced risk of type 2 DM; the OR across all studies was 0.91 (95%CI 0.82 to 1.00) for the C- vs. T-allele, 0.88 (0.75 to 1.03) for CC vs. CT+TT, 0.82 (0.71 to 0.95) for CC vs. TT, and 1.15 (1.03 to 1.29) for TT vs. CC+CT. Similar results were found when the meta-analysis was repeated separately for each ethnic subgroup, and for subgroups with or without serious DM-related complications.

CONCLUSIONS

There does not appear to be compelling evidence of an association between the genotype at the rs1801133 polymorphism of the MTHFR gene and risk of type 2 DM.

Raloxifene ameliorates detrimental enzymatic and nonenzymatic collagen cross-links and bone strength in rabbits with hyperhomocysteinemia

We demonstrate a reduction in enzymatic divalent immature and trivalent pyridinium cross-links and an increase in the nonenzymatic cross-link, pentosidine (Pen), in rabbits with methionine (Met)-induced hyperhomocysteinemia. Such detrimental cross-link formation in bone was ameliorated by raloxifene (RLX) treatment.

INTRODUCTION

Collagen cross-links are determinants of bone quality. Homocysteine (Hcys) interferes with collagen cross-linking. Because RLX is thought to ameliorate bone quality, we investigated whether RLX ameliorated hyperhomocysteinemia-induced cross-link abnormalities using a Met-rich diet rabbit model.

METHODS

We divided New Zealand white rabbits into six groups (n = 6 per group): baseline control, sham operation, sham + 1% Met diet, ovariectomy (OVX), 1% Met diet + OVX, OVX + RLX (10 mg/kg/day), and 1% Met diet + OVX + RLX. RLX was administered for 16 weeks. We measured the amount of enzymatic immature and mature pyridinium cross-links and the nonenzymatic cross-link, Pen, and correlated the cross-link content to bone strength.

RESULTS

Hcys levels were significantly higher in the Met diet groups than in the normal diet groups. Met-fed rabbits with or without OVX showed a significant reduction of enzymatic cross-links, whereas an increase in Pen was observed in Met-fed rabbits with OVX. The cross-link content of the RLX-treated Met-fed rabbits with OVX was restored to similar levels as the sham group, accompanied by an improvement of bone strength.

CONCLUSION

These results demonstrate that hyperhomocysteinemia reduced bone strength via a reduction of enzymatic cross-links and an increase of nonenzymatic cross-links. RLX may ameliorate hyperhomocysteinemia-induced detrimental cross-linking in rabbits with OVX and may improve bone strength via the amelioration of collagen cross-links.

Association analyses suggest multiple interaction effects of the methylenetetrahydrofolate reductase polymorphisms on timing of menarche and natural menopause in white women

OBJECTIVE

This study aimed to investigate whether polymorphisms of the methylenetetrahydrofolate reductase (MTHFR) gene are associated with age at menarche and age at natural menopause in white women.

METHODS

In a cross-sectional study, a total of 305 randomly selected unrelated white women were genotyped for six single nucleotide polymorphisms (SNPs) of the MTHFR gene (including one common replacement, rs1801133). This sample was comprehensively analyzed for the association of the SNPs with age at menarche. Then a subsample of 210 women who experienced natural menopause was analyzed for the association of the MTHFR gene with age at natural menopause.

RESULTS

Duration of breast-feeding was a significant predictor of earlier natural menopause (P < 0.05). No individual SNPs were associated with either age at menarche or age at natural menopause. However, three significant (P < 0.05) SNP-SNP interaction effects (rs2066470/rs1476413, rs2066470/rs4846049, and rs17037390/rs4846049) on the onset of menarche were determined. Three haplotypes were significantly associated with age at menopause (P < 0.05). Four SNPs (rs2066470, rs17037390, rs1801133, and rs4846048) indicated significant interaction effects with various lifestyle factors on age at natural menopause.

CONCLUSIONS

The results of our study suggest that the MTHFR gene may influence the onset of menarche and natural menopause. This effect is probably due to the multiple SNP-SNP and SNP-environment interactions. More independent studies are needed to further clarify the possible contribution of this gene to the timing of menarche and menopause.