Genetic polymorphism of MTHFR G1793A in Chinese populations

Geographical distribution of MTHFR C677T gene polymorphisms among the reproductive-age women in Chinese Han populations: based on migration

BACKGROUND

Methylenetetrahydrofolate reductase (MTHFR) is essential for the metabolism of folic acid and homocysteine. The MTHFR C677T polymorphism is associated with several disorders. Our study aims to explore the geographical distributions of the MTHFR C677T polymorphism of women in China and how migration affected the polymorphism in Suzhou.

METHODS

A total of 7188 women of reproductive age were recruited in Suzhou of the study. Subjects were classified according to their native places after data extraction. MTHFR C677T gene polymorphisms were detected by quantitative PCR with genomic DNA isolated from blood samples.

RESULTS

The frequencies of the 677T allele and 677TT genotype were higher in northern China than that in southern China and decreased in geographical gradients from north to south. The frequencies were considerably higher in the migrant population than that in the indigenous population of Suzhou. The migrant population have gradually changed the prevalence in Suzhou.

CONCLUSIONS

Our study suggested that the prevalence of MTHFR C677T polymorphisms among women varied across different geographical regions in Chinese Han populations. The 677T allele frequencies of the northern populations were significantly higher than those of the southern populations. The migrant population gradually changed the prevalence of the MTHFR C677T polymorphism in Suzhou.

Homocysteine, an additional factor, is linked to osteoporosis in postmenopausal women with type 2 diabetes

We explored the relationship between plasma total homocysteine concentration and osteoporosis in postmenopausal patients with type 2 diabetes. Postmenopausal patients with type 2 diabetes (n = 258) were enrolled in a cross-sectional hospital-based study. Osteoporosis was documented by dual energy X-ray absorptiometry. Plasma total homocysteine concentration was measured using fluorescence polarization immunoassay. Risk factors for osteoporosis and determinants of homocysteine were obtained from blood samples and interviewer questionnaire. We found that plasma total homocysteine levels were higher in subjects with osteoporosis and diabetes than without [(9.5 ± 2.0) vs. (10.4 ± 2.4) μmol/l, p = 0.001]. The association of homocysteine with osteoporosis was independent of possible risk factors for osteoporosis in diabetes (e.g., duration of diabetes, HbA1c, body mass index, serum 25-hydroxyvitamin D, thiazolidinediones, and retinopathy) and determinants of homocysteine concentration (age, serum folate and vitamin B12, renal status, and biguanide use) [OR 1.40 (1.02-1.90), p = 0.036]. In addition, bone mineral density was closely correlated with homocysteine as a continuous variable after adjusting for age [r = -0.64 (-0.69 to -0.58), p = 0.002]. Furthermore, per increase of 5.0 μmol/l, plasma homocysteine was related to osteoporosis, after controlling for per unit increase of other factors [OR 1.42 (1.07-1.96), p = 0.027]. The optimal cut-off point for the plasma homocysteine level distinguishing diabetic patients with osteoporosis from without was 10.18 μmol/l. The results suggest that plasma total homocysteine concentration is independently associated with the occurrence of osteoporosis in postmenopausal patients with type 2 diabetes. Future prospective studies are warranted to clarify the relationship.

Fracture is additionally attributed to hyperhomocysteinemia in men and premenopausal women with type 2 diabetes

AIMS/INTRODUCTION

Data on hyperhomocysteinemia in relation to fractures in diabetes are limited. We aimed to explore the relationship between plasma total homocysteine concentrations and fractures in men and premenopausal women with type 2 diabetes.

MATERIALS AND METHODS

Diabetic and control participants (n = 292) were enrolled in a cross-sectional hospital-based study. Bone mineral density and fractures were documented by dual energy X-ray absorptiometry and X-ray film, respectively. Plasma total homocysteine concentrations were measured using fluorescence polarization immunoassay. Risk factors for low bone mineral density or fractures and determinants of homocysteine were obtained from blood samples and the interviewer questionnaire.

RESULTS

Plasma total homocysteine levels were higher in diabetic participants with fractures than without (8.6 [2.1] μmol/L vs 10.3 [3.0] μmol/L, P = 0.000). Diabetic participants with fractures had similar bone mineral densities as control participants. The association of homocysteine with the fracture was independent of possible risk factors for fractures (e.g., age, duration of diabetes, glycated hemoglobin, body mass index, thiazolidenediones and retinopathy) and determinants of homocysteine concentration (e.g., age, sex, serum folate and vitamin B12, renal status and biguanide use; odds ratio 1.41, 95% confidence interval 1.05-2.03, P = 0.020). Furthermore, per increase of 5.0 μmol/L plasma homocysteine was related to the fracture, after controlling for per unit increase of other factors (odds ratio 1.42, 95% confidence interval 1.12-1.78, P = 0.013).

CONCLUSIONS

Plasma total homocysteine concentration is independently associated with occurrence of fractures in men and premenopausal women with type 2 diabetes. Future prospective studies are warranted to clarify the relationship.

Homocysteine is linked to macular edema in type 2 diabetes

AIM

To explore the relationship between plasma total homocysteine concentration and diabetic macular edema in patients with type 2 diabetes.

METHODS

Patients with type 2 diabetes (n = 176) were enrolled in a cross-sectional hospital-based study. Diabetic macular edema status was documented by fundus photographs. Plasma total homocysteine concentration was measured using fluorescence polarization immunoassay. Normal control plasma homocysteine was established in 115 healthy subjects. Risk factors for diabetic macular edema were obtained from fasting blood samples and interviewer questionnaire.

RESULTS

Diabetic patients had increased plasma homocysteine compared with normal control. Plasma homocysteine levels were higher in subjects with diabetic macular edema than without ((11.4 ± 2.7) versus (8.5 ± 1.9) (μmol/l), p = 0.000). The association of homocysteine with diabetic macular edema was independent of major risk factors for diabetic macular edema (duration of diabetes, HbA1c, lipid) and determinants of higher homocysteine concentration (age, gender, serum folate and vitamin B12, renal status, and biguanide use) (OR: 1.63 (1.02-2.14), p = 0.018). Furthermore, per increase of 5.0 μmol/l plasma homocysteine was related to macular edema, after controlling for per unit increase of other factors (OR: 1.64 (1.04-2.16), p = 0.019).

CONCLUSIONS

Plasma total homocysteine concentration is independently associated with the occurrence of macular edema in type 2 diabetes. Future prospective studies are warranted to clarify the relationship.

Association of homocysteine with peripheral neuropathy in Chinese patients with type 2 diabetes

AIM

To explore the relationship between plasma total homocysteine concentration and diabetic neuropathy in Chinese patients with type 2 diabetes.

METHODS

Chinese patients with type 2 diabetes (n=249) were enrolled in a cross-sectional hospital based study. Diabetic neuropathy status was documented by presence of clinical signs and confirmed by electromyography. Plasma total homocysteine concentration was measured using fluorescence polarization immunoassay. Traditional risk factors for diabetic neuropathy were obtained from fasting blood samples and interviewer-questionnaire.

RESULTS

Plasma total homocysteine levels were higher in subjects with diabetic neuropathy than without (12.8 (9.2-14.8) μmol/l vs. 8.0 (7.7-9.1) μmol/l, p=0.005). The association of homocysteine with diabetic neuropathy was independent of major traditional risk factors for diabetic neuropathy (duration of diabetes, HbA1c) and determinants of higher homocysteine concentration (age, gender, serum folate and vitamin B12, renal status, and Biguanide use) (OR: 1.12 (1.00-1.25), p=0.042). Furthermore, per increase of 4.0 μmol/l plasma homocysteine was related to neuropathy, after controlling for per unit increase of other factors (OR: 1.17 (0.94-1.33), p=0.045).

CONCLUSION

Plasma total homocysteine concentration was independently associated with occurrence of diabetic neuropathy in Chinese people. Future prospective studies are warranted to clarify the relationship.

Association study between methylenetetrahydrofolate reductase gene polymorphisms and Graves' disease

5,10-Methylenetetrahydrofolate reductase (MTHFR) catalyzes the metabolism of folate and nucleotides, which are essential for DNA synthesis and methylation. It is highly polymorphic, and its variant genotypes result in lower enzymatic activity and higher plasma homocysteine. Previous studies have provided evidence that a high prevalence of MTHFR gene polymorphisms is frequently detected in patients with autoimmune disease, suggesting a novel genetic association with autoimmune disorders. However, the genetic association between MTHFR and Graves' disease (GD), one of the most common autoimmune diseases, has not been studied. Here, we designed a clinic-based case-control study including 199 GD cases and 235 healthy controls to examine the associations between three common MTHFR polymorphisms (i.e., C677T, A1298C, and G1793A) and GD. Surprisingly, logistic regression analysis shows MTHFR 677CT + TT genotypes are associated with an approximately 42% reduction in the risk of GD in women (adjusted OR = 0.58, 95% CI = 0.3-0.9), compared to the CC genotype, indicating a significant protective effect of 677CT + TT genotypes. Our result provides epidemiological evidence that MTHFR mutation (C677T) protects women from GD. The protective effect, possibly obtained by influencing DNA methylation, should be confirmed in a large number of cohorts.

The Shanghai Changfeng Study: a community-based prospective cohort study of chronic diseases among middle-aged and elderly: objectives and design

The Shanghai Changfeng Study is a community-based prospective cohort study of chronic diseases ongoing since February 2009 in Shanghai, China. The study focuses on multiple chronic diseases, including obesity and metabolic syndrome, diabetes, osteoporosis, liver diseases, cardiovascular diseases and neurologic diseases. 15,000 subjects of 40 years or over are planned to be recruited. The rationale, objectives and design of this study are described in this paper.

Early influences on cardiovascular and renal development

The hypothesis that a developmental component plays a role in subsequent disease initially arose from epidemiological studies relating birth size to both risk factors for cardiovascular disease and actual cardiovascular disease prevalence in later life. The findings that small size at birth is associated with an increased risk of cardiovascular disease have led to concerns about the effect size and the causality of the associations. However, recent studies have overcome most methodological flaws and suggested small effect sizes for these associations for the individual, but an potential important effect size on a population level. Various mechanisms underlying these associations have been hypothesized, including fetal undernutrition, genetic susceptibility and postnatal accelerated growth. The specific adverse exposures in fetal and early postnatal life leading to cardiovascular disease in adult life are not yet fully understood. Current studies suggest that both environmental and genetic factors in various periods of life may underlie the complex associations of fetal growth retardation and low birth weight with cardiovascular disease in later life. To estimate the population effect size and to identify the underlying mechanisms, well-designed epidemiological studies are needed. This review is focused on specific adverse fetal exposures, cardiovascular adaptations and perspectives for new studies.

The Rotterdam Study: 2010 objectives and design update

The Rotterdam Study is a prospective cohort study ongoing since 1990 in the city of Rotterdam in The Netherlands. The study targets cardiovascular, endocrine, hepatic, neurological, ophthalmic, psychiatric and respiratory diseases. As of 2008, 14,926 subjects aged 45 years or over comprise the Rotterdam Study cohort. The findings of the Rotterdam Study have been presented in close to a 1,000 research articles and reports (see www.epib.nl/rotterdamstudy). This article gives the rationale of the study and its design. It also presents a summary of the major findings and an update of the objectives and methods.