Glycemia, MTHFR genotype and low homocysteine in uncomplicated type 2 diabetic patients

The role and importance of gene polymorphisms in the development of atherosclerosis

The development of atherosclerosis is a multifactorial process. The purpose of the study was to examine three genetic polymorphisms playing a role in the metabolic processes underlying the disease. We compared the data of 348 atherosclerotic non-diabetic patients with 260 atherosclerotic diabetic patients and 384 healthy controls. We analyzed the prevalence of myocardial infarction and stroke in three different groups of patients carrying different polymorphisms. It was proved that if the mutant TT eNOS Glu298ASP variant is present, a significantly higher number of myocardial infarctions can be observed than in patients carrying heterozygote GT or normal GG genotype. We proved that in the case of MTHFR 677CT heterozygote variants, the occurrence of myocardial infarction is significantly higher and the difference is also significant in case of the 677TT homozygote variant. It was verified that among patients with the mutant TNF-α AA genotype the occurrence of cardiovascular events was significantly higher. Screening the genetically high risk groups on the long run should be considered as an early detection opportunity that may give better chances for prevention and treatment. Understanding the inflammatory mechanisms of the atherosclerosis may give new therapeutical targets to pharmacologists.

The role of B vitamins in preventing and treating cognitive impairment and decline

Many epidemiologic studies have considered whether markers of B-vitamin status are associated with cognitive function and cognitive decline. This avenue of research was sparked by the homocysteine (Hcy) theory of cardiovascular disease, which was extended to Alzheimer's disease when a link between vascular dementia and Alzheimer's disease was discovered. Hcy could cause cognitive impairment via direct neurotoxicity. However, decreased remethylation of Hcy to methionine might also compromise cognitive function by means other than mere Hcy lowering. Folate and vitamin B-12 participate in Hcy remethylation and largely determine Hcy status. Consequently, much of the relevant research has focused on these 2 B vitamins. The many subtly different hypotheses that investigators have addressed by attempting to link several B-vitamin status indicators to diverse cognition-related outcomes have created a confusing body of conflicting studies that seems to defy summarization. Nevertheless, themes are discernible that aid interpretation, foster hypothesis generation, and inform future study design. For example, despite a shared metabolic pathway, Hcy, vitamin B-12, and folate are differently related to specific cognitive outcomes. Although consistency of findings across studies is often touted as essential to distinguishing causal from coincidental relationships, discrepancies among study findings can be even more informative.

Methylentetrahydrofolate reductase and nitric oxide synthase polymorphism in patients with atherosclerosis and diabetes

The development of the atherosclerosis is based on multifactorial causes. In addition to the traditional risk factors, gene polymorphisms can play a role in the disease. Therefore in this study we investigated whether the eNOS and MTHFR gene polymorphisms is associated with myocardial infarction and stroke in patients with or without diabetes. We have identified polymorphisms in the NOS 3 gene and one of these polymorphisms, Glu(298-->)Asp, was found to be a major risk factor for carotid artery disease and myocardial infarction. Our results indicate that the MTHFR G677T allele is significantly associated with MI. MTHFR 677 G/T genotyping may be of clinical importance as a prognostic and therapeutic marker, although further studies are needed to substantiate this hypothesis.

Inverse association between plasma homocysteine, sulphonylurea exposure and physical activity: a community-based sample of type 2 diabetes patients in the Skaraborg hypertension and diabetes project

AIM

This study aimed to investigate levels of Homocysteine (tHcy) and folate in a population-based sample of patients with type 2 diabetes. In particular, the study explored modifiable determinants such as treatment for diabetes, life style, glucose control and kidney function.

PATIENTS AND METHODS

In a community-based surveillance of patients with type 2 diabetes, 196 men and 191 women were consecutively identified in primary care and characterized by cardiovascular disease (CVD) risk factors focusing on components in the metabolic syndrome. For categorical associations plasma tHcy was dichotomized using the upper 10 percentiles of the distribution.

RESULTS

Treatment with sulphonylurea was associated with lower serum levels of tHcy compared to those on diet alone. The association was confined to women [odds ratio 0.14; confidence interval 0.03-0.8] and remained significant when differences in factors related to the metabolic syndrome, life style and previous CVD were accounted for, but was lost when adjusted for HbA1c. There was an inverse dose-related association between physical activity and plasma levels of tHcy (men p = 0.006, women p = 0.034), and a positive association with serum levels of creatinine (men p = 0.004, women p < 0.001).

CONCLUSIONS

The association with physical activity might be one contributing explanation for its well-known protective effect on cardiovascular disease. The over risk for vascular complications in diabetic patients with kidney disease may be partially explained by high levels of tHcy and should be further explored. Prospective studies are particularly needed on various treatment for type 2 diabetes and tHcy to explore possible implications for clinical procedures and for public health.

Correlates of total homocysteine plasma concentration in type 2 diabetes

BACKGROUND

Although well-defined in the general population, correlates of total homocysteine (tHcy) plasma concentration have not been sufficiently evaluated in diabetes. We investigated factors potentially associated with tHcy concentration in a cohort of type 2 diabetic subjects.

MATERIALS AND METHODS

The common methylene tetrahydrofolate reductase (MTHFR) C677T polymorphism, fasting tHcy, vitamin B12 and folate plasma levels were assessed in 312 diabetic subjects, whose clinical, metabolic and lifestyle information was also available.

RESULTS

The MTHFR genotype distribution was comparable to the Hardy-Weinberg equilibrium, with an overall TT homozygous frequency of 22%. Fasting tHcy concentration was significantly higher in men than in women (P < 0.001). Multivariate-adjusted tHcy concentration was significantly different across the quartiles of age (P < 0.001), folate (P = 0.01), vitamin B12 (P = 0.03), creatinine concentrations (P = 0.001) and smoking (P = 0.02). Overall, significant trends were noted for creatinine clearance (P for trend = 0.02) and systolic blood pressure (BP) (unadjusted P for trend = 0.01), whereas no differences were noted according to BMI, diastolic BP, presence of hypertension, and diabetes-related variables, such as diabetes duration, fasting glucose and glycated haemoglobin concentrations, current treatment and diabetes long-term complications. Total homocysteine levels significantly correlated with age, systolic BP, vitamin B12, creatinine and creatinine clearance, but only age, creatinine, folate and vitamin B12 levels were independently associated with tHcy concentration in stepwise regression analysis.

CONCLUSIONS

Age, creatinine, folate, vitamin B12, and to a minor extent, sex, smoking, TT genotype and systolic BP were significantly associated with Hcy plasma concentration in type 2 diabetes, whereas no significant associations were noted with diabetes-related variables.

Association of methylenetetrahydrofolate reductase gene polymorphism with carotid atherosclerosis depending on smoking status in a Japanese general population

BACKGROUND AND PURPOSE

The association of the methylenetetrahydrofolate reductase gene (MTHFR) with carotid atherosclerosis remains inconsistent. This may be due to small sample size and inappropriate analysis. We investigated the association of C677T/MTHFR with blood pressure and carotid atherosclerosis in a Japanese general population.

METHODS

Subjects (30 to 89 years of age; 1693 women, 1554 men) who gave informed consent were randomly selected from a general population in Suita, Japan. MTHFR genotypes were determined by TaqMan polymerase chain reaction. Carotid atherosclerosis was evaluated by high-resolution ultrasonography with atherosclerotic indexes of intimal-medial thickness (IMT), maximum IMT in the common carotid artery (CCA), plaque score, and stenosis (>50%).

RESULTS

Age-adjusted diastolic blood pressure was significantly higher in women with the TT genotype than in those with the CC genotype. In a recessive model (CC+CT versus TT), all adjusted odds ratios for hypertension and >50% stenosis in women were 1.42 and 3.42 (95% confidence intervals, 1.01 to 1.99 and 1.23 to 9.53), respectively. In women, maximum IMT in CCA for smokers with the TT genotype was significantly higher than for smokers with the CC genotype and nonsmokers with the TT genotype (P<0.05).

CONCLUSIONS

Our study suggests that the MTHFR TT genotype is a risk factor for hypertension and carotid stenosis in women. Significant interactions between C677T/MTHFR and smoking on maximum IMT in CCA were observed in women but not in men. Smoking cessation for subjects with the TT genotype is important in the prevention of cerebrovascular disease.

Diabetes and other coronary heart disease risk equivalents

The close association between diabetes and cardiovascular disease suggests that current predictions of a massive increase in the prevalence of type 2 diabetes foreshadow an equally daunting rise in the incidence of vascular disease. The limited cardiovascular benefits obtained by glucose-lowering treatments, although perhaps not surprising, indicate that other cardiovascular risk factors must be given serious consideration as therapeutic targets. The impressive reductions in the number of vascular events observed in diabetic patients, albeit in small patient populations, participating in various drug trials amply justify such an approach. A necessary prerequisite, however, is a clear understanding of the clinical importance of individual risk factors to the occurrence of vascular disease in type 2 diabetic patients. This would appear essential for defining treatment strategies in the face of a bewildering array of potential therapeutic targets. The present review considers recent studies that have assessed the predictive value of risk factors against a diabetic background.