Homocysteine concentrations and vascular complications in patients with type 2 diabetes

Associations Between Serum Folate Level and HOMA-IR in Chinese Patients with Type 2 Diabetes Mellitus

Background

Adequate intake of folic acid (FA) has been proven essential for metabolism, cellular homeostasis, and antioxidant effects in diabetic patients. Our aim was to evaluate the association between serum folate levels and the risk of insulin resistance in patients with type 2 diabetes mellitus (T2DM) and to provide new ideas and approaches for reducing the risk of T2DM.

Methods

This was a case-control study involving 412 participants (206 with T2DM). Anthropometric parameters, islet function, biochemical parameters and body composition of T2DM group and control group were determined. Correlation analysis and logistic regression were used to evaluate the risk factors associated with the onset of insulin resistance in T2DM.

Results

The folate levels in type 2 diabetic patients with insulin resistance were significantly lower than those in patients without insulin resistance. Logistic regression showed that FA and high-density lipoprotein were independent influencing factors for insulin resistance in diabetic patients (P < 0.05). After adjusting for confounding factors, the degree of insulin resistance in diabetic patients was in a significant inverse relationship with folate levels (P< 0.05). We also found that below the serum FA threshold of 7.09 ng/mL insulin resistance was significantly more elevated.

Conclusion

Our findings suggest that the risk of insulin resistance increases with the decrease in serum FA levels in T2DM patients. Monitoring folate levels in these patients and FA supplementation are warranted preventive measures.

Unraveling the Crosstalk between Lipids and NADPH Oxidases in Diabetic Kidney Disease

Diabetic kidney disease (DKD) is a serious complication of diabetes mellitus and a leading cause of end-stage renal disease. Abnormal lipid metabolism and intrarenal accumulation of lipids have been shown to be strongly correlated with the development and progression of diabetic kidney disease (DKD). Cholesterol, phospholipids, triglycerides, fatty acids, and sphingolipids are among the lipids that are altered in DKD, and their renal accumulation has been linked to the pathogenesis of the disease. In addition, NADPH oxidase-induced production of reactive oxygen species (ROS) plays a critical role in the development of DKD. Several types of lipids have been found to be tightly linked to NADPH oxidase-induced ROS production. This review aims to explore the interplay between lipids and NADPH oxidases in order to provide new insights into the pathogenesis of DKD and identify more effective targeted therapies for the disease.

Hyperhomocysteinemia Promotes Carotid Artery Damage in Newly Diagnosed Type 2 Diabetic Patients Without Hypercholesterolemia

Background: The relationship between serum homocysteine levels and carotid artery damage in subjects with newly diagnosed type 2 diabetes mellitus remains unclear. The effect of hyperhomocysteinemia (HHCY) on carotid artery damage in patients with different cholesterol levels needs to be further investigated. Methods: In total 456 newly diagnosed type 2 diabetes from Beijing Chaoyang Hospital were recruited into the study. Patients were divided into four groups according to the levels of serum homocysteine and cholesterol. Carotid artery damage was defined as thickened intima-media and/or plaque formation. Results: In all the subjects, 80.2% patients had HHCY. The incidence of carotid artery injury was significantly lower in diabetic patients with normal homocysteine levels and nonhypercholesterolemia. Spearman correlation analysis showed homocysteine was positively correlated with free fatty acid and negatively correlated with glucose metabolism parameters. Logistic regression showed HHCY was correlated with carotid artery injury after adjusting for traditional cerebrovascular risk factors in type 2 diabetes without hypercholesterolemia (odds risk = 3.197, P = 0.022). Whereas HHCY was not associated with carotid artery injury in either total study population or hypercholesterolemia subgroup. Conclusions: HHCY was correlated with carotid artery damage in newly diagnosed type 2 diabetic subjects without hypercholesterolemia. How to improve the adverse vascular outcomes mediated by HHCY for diabetic patients needed further investigation.

Homocysteine and diabetes: Role in macrovascular and microvascular complications

Diabetes mellitus (DM) can lead to the development of macro- and microvascular complications. Homocysteine (Hcy) may play a role in the development of cardiovascular (CV) diseases (CVDs). The role of Hcy in the development of the vascular complications associated with DM is not clearly defined. Despite a strong initial assumption regarding the importance of Hcy in DM and its complications, over time "enthusiasm has waned" because several studies showed unconvincing and occasionally contradictory results. A universal conclusion is not easy to draw given the diversity of studies (e.g. number of patients, design, folic acid and vitamin B status, ethnic differences, genetic background). For some complications, most results encourages further investigation. Impaired renal function is a major independent determinant of high total Hcy (tHcy) levels. However, the role of hyperhomocysteinaemia (HHcy) in the development of diabetic kidney disease (DKD) has yet to be determined. Hcy-lowering therapies can significantly decrease Hcy levels but their effects on CVD risk reduction are conflicting. Further studies are needed to determine the influence of Hcy-lowering therapy on CVD risk reduction, especially in patients with DM.

The effect of aerobic vs. resistance training on plasma homocysteine in individuals with type 2 diabetes

Elevated plasma homocysteine concentration is a risk factor for cardiovascular disease, which seems to be the main cause of increased mortality in patients with type 2 diabetes. Previous studies have demonstrated the effect of exercise on homocysteine levels and the magnitude of these benefits seems to depend on the type, mode and frequency of training. The present study aimed to compare the effects of aerobic and resistance training on plasma homocysteine in individuals with type 2 diabetes. The study included 15 individuals undergoing aerobic training, 14 subjects undergoing resistance training, and 18 individuals in the control group. Homocysteine, total cholesterol and fractions, glucose, and anthropometric measurements were conducted. The training program lasted 16 weeks. Aerobic training was performed twice a week and lasted 75 min, and resistance training was performed twice a week and lasted 75 min. Homocysteine levels were not significantly different between before and after training. High-density lipoprotein levels increased in both training groups and decreased in the control group. Glucose levels decreased after aerobic and resistance training. Body fat mass (percentage and total) decreased in both training group, but with more expression in the aerobic group. We conclude that 16-week aerobic and resistance training programs did not significantly affect plasma homocysteine levels in patients with type 2 diabetes. Nevertheless, these training programs yielded positive results in HDL control, plasma glucose, and body composition.

Effects of bromocriptine mesylate on homocysteine and high-sensitivity C-reactive protein levels in patients with type-2 diabetes mellitus

Introduction: Quick release bromocriptine (BROM-QR), currently approved for glycemic control, reduces the risk of cardiovascular events in adults with type-2 diabetes mellitus (T2DM). This study evaluates the effect of BROM-QR on homocysteine (HOMC) and high sensitive C-reactive protein (hs-CRP), the biochemical markers of coronary atherosclerosis/inflammation, in patients with uncontrolled T2DM.

Methods: In this non-randomized, before-and-after clinical trial, patients with uncontrolled T2DM on stable doses of two oral hypoglycemic agents received BROM-QR for 6 months. The change in serum concentrations of HOMC was the primary endpoint. Anthropometric measurements such as body mass index (BMI) and waist circumference were measured at the baseline and at the completion of treatment along with fasting plasma glucose (FPG), HbA1c, total cholesterol, triglyceride, creatinine and hs-CRP. Multivariate regression analysis was performed to identify factors associated with changes in the levels of HOMC.

Results: In 64 patients (46 completed 6 months of treatment), age was 55±7 years and the duration of T2DM was 8.0 ± 4.4 years. On enrollment, mean HbA1c, FPG, hs-CRP and HOMC levels were 9.0± 1.3 percent, 184 ± 42 mg/dL, 3.8± 3.4 mg/dl and 10.8 ± 6.2 micromole/L; respectively. Mean decrease of 0.7 ± 1.1 percent for HbA1c (P = 0.001) and 22 ± 44 mg/dL for FPG was observed (P = 0.002). HOMC levels decreased to 8.5 ± 5.2 micromole/L (P = 0.011) while hs-CRP levels remained unchanged at 3.7 ± 2.9 mg/dL (P = 0.835).

Conclusion: While HOMC and HbA1c levels decreased significantly after 6 months of treatment with BROM-QR in patients with T2DM, serum levels of hs-CRP, total cholesterol and triglyceride did not significantly change.

Homocysteine, cysteine, folate and vitamin B₁₂ status in type 2 diabetic patients with chronic kidney disease

BACKGROUND

Hyperhomocysteinemia (hHcy) is a risk factor in the progression of chronic kidney disease (CKD). In type 2 diabetes (T2D), hHcy is strongly associated with increased risk of cardiovascular disease. Vitamin B12 and folic acid supplementation have been reported to lower homocysteine (tHcy) levels, but no data on plasma tHcy, cysteine (Cys), folate and vitamin B12 levels in T2D-CKD patients are reported.

PROCEDURES

tHcy and Cys levels were analyzed in 178 T2D-CKD patients by high performance liquid chromatography (HPLC) with fluorescence detection. In addition, we determined folate and vitamin B12 levels using a chemiluminescence method.

RESULTS

tHcy and Cys levels were increased in T2D patients, and this rise positively correlated with the CKD stage (P < 0.001). Folate levels were comparable to controls at various CKD stages, whereas vitamin B12 levels were lower, except at stage IV. We did not find any correlation between B-vitamins and levels of tHcy and Cys, regardless of the CKD stage.

CONCLUSIONS

This is the first study reporting tHcy, Cys and B-vitamins status in T2D-CKD patients. Although limited to our cohort of 178 patients, our findings could be helpful in clarifying the conflicting literature regarding B-vitamins supplementation. Further studies are necessary before any Hcy-lowering therapy can be safely established in T2D-CKD subjects.

Effect of lipopenic and hypotensive treatment on homocysteine levels in type 2 diabetics

Aim:

Evaluate the effect of lipopenic and hypotensive treatment on homocysteine levels.

Methods:

We recruited 145 type 2 diabetics and 130 control subjects. Thirty-seven diabetics had no complications, 54 had microvascular complications and 54 had macrovascular complications. We determined the parameters homocysteine of lipid, vitamin B12, triglycerides, and folates for all subjects. Associated treatments used one or more of the following drugs, statin, fibrate, angiotensin-converting enzyme inhibitor and beta-blockers.

Results:

Hyperhomocysteinemia was present in 35.6% of patients. Diabetics had elevated serum levels of triglycerides (P < 0.001), homocysteine (P < 0.01), folates (P < 0.01) and vitamin B12 (P < 0.001). A strong association was found between type 2 diabetes and hyperhomocysteinemia (P < 0.001). Diabetics with associated treatment had elevated homocysteine, vitamin B12 and folate levels when compared to diabetes-free controls. For diabetics with macrovascular complications, we found significant differences in homocysteine (P = 0.010) and folate (P = 0.014) between those taking associated drugs and those who did not. For diabetics with microvascular complications, a significant difference was found in folate only (P = 0.012).

Conclusion:

Drugs used for hypertension and hyperlipidemia may have an effect on homocysteine levels, for this reason the interaction between drug action and homocysteine levels should be taken into consideration.

Cardiovascular disease markers in type 2 diabetes: the effects of a moderate home-based exercise training programme

Patients with T2DM have an increased risk of CVD. Prevention of CVD represents the major goal of all treatment of T2DM, and early intervention in those patients at particularly high risk is important.We measured the insulin sensitivity and plasma biomarkers of CVD to determine whether a home-based exercise training program improves biomarker levels and insulin sensitivity. Patients with T2DM (n=12), IGT (n=4) and healthy control subjects (n=9) were studied before and after eight weeks of exercise training by rowing ergometry at 65-70% of peak oxygen uptake.

CONCLUSIONS

1) patients with T2DM have elevated plasma concentrations of CVD biomarkers compared to the matched control and IGT groups; 2) a moderate to vigorous intensity home-based training program did not reduce plasma concentrations of these CVD markers; 3) insulin sensitivity improved as a result of exercise training in the control group, but not in the T2DM group.

Hyperhomocysteinemia and lower extremity wounds

Chronic lower extremity wounds include ulceration of the leg and foot. The underlying pathology that causes these conditions includes venous insufficiency, arterial disease, diabetes, and other less common disorders. Since the introduction of the homocysteine theory more than 30 years ago, considerable evidence has demonstrated hyperhomocysteinemia to be an independent risk factor for venous and arterial thrombosis, atherosclerosis and cardiovascular disease. Although any cause-effect relationship remains to be determined, hyperhomocysteinemia as a risk factor for these events suggests that elevated levels of homocysteine may also be a marker of chronic lower limb ulceration. This review addresses the metabolism of homocysteine, mechanisms of vascular injury, a role for hyperhomocysteinemia in lower extremity wounds and possible means of treatment.

Microalbuminuria: risk factor and potential therapeutic target for stroke?

Microalbuminuria (MA), a microvascular irregularity of the blood-urine interface within kidney glomeruli, may reflect the renal sign of global endothelial dysfunction, and has been associated with an elevated risk of serious cardiovascular events including stroke. This relationship appears graded, with higher levels of MA being independently associated with a greater magnitude of vascular risk over time. Furthermore, the presence of MA appears to independently predict poorer clinical outcomes following acute stroke. Screening for MA is relatively easy and inexpensive and could be effective in identifying stroke patients at risk for unfavorable outcomes. Reduction of subclinical albuminuria in stroke patients could be a clinically relevant endpoint worthy of pursuit by pharmacological treatment since the antiproteinuric effects of several established therapies appear to parallel better cardiovascular prognosis including better stroke outcomes, among subjects at high vascular risk. This review depicts the compelling epidemiological and clinical evidence relating MA to stroke, and presents the rationale for conducting future studies to assess the role of MA as a potential therapeutic target in persons with, or at risk for stroke.

Intercellular adhesion molecule-1 (ICAM-1) expression is necessary for monocyte adhesion to the placental bed endothelium and is increased in type 1 diabetic human pregnancy

BACKGROUND

That adhesion molecule expression is upregulated in endothelial cells of the placental bed in pregnancies complicated by type 1 diabetes mellitus, and that this is associated with increased adherence of peripheral blood monocytes, which can be reversed by reduction in activity or expression of relevant adhesion molecules. Specific aims were to compare the adherence of monocytes from normal pregnancies to decidual endothelial cells from both normal and diabetic pregnancies, and to examine the involvement of intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) in regulation of such adhesion.

METHODS

We examined adhesion of peripheral blood monocytes (isolated by density gradient centrifugation) of normal third trimester pregnant women, to cultured endothelial cells (isolated from decidual biopsies collected at elective caesarean section) from both normal women and those with type 1 diabetes. Adhesion molecule expression was determined by flow cytometry. The role of ICAM-1 was further investigated by monoclonal antibody-blocking experiments and gene-silencing methodology.

RESULTS

There was a significant increase in monocyte adhesion to decidual endothelial cells from diabetic pregnancies, associated with increased endothelial cell expression of ICAM-1, but not VCAM-1. ICAM-1 expression in normal decidual endothelial cells was stimulated by pro-atherogenic and pro-inflammatory stimuli. Following ICAM-1 antibody blockade, monocyte adhesion was decreased by > 70%. ICAM-1 silencing by small interfering RNAs also inhibited monocyte adhesion and ICAM-1 expression.

CONCLUSIONS

These findings implicate upregulation of ICAM-1 in decidual endothelial cells in the development of placental bed vascular pathology in diabetic pregnancy.

High-throughput multiplex single-nucleotide polymorphism (SNP) analysis in genes involved in methionine metabolism

Hyperhomocysteinemia is a well-known independent marker factor for atherothrombotic diseases and may result from acquired and genetic influences. Several polymorphisms are suspected to be associated with hyperhomocysteinemia, but data are limited and inconsistent. High-throughput genotyping technologies, such as GenomeLab SNPStream, are now available. Moreover, an appropriate selection of SNPs to be analyzed could represent a strong resource to define the role of genetic risk factors. We developed a multiplex PCR-oligonucleotide extension approach by GenomeLab platform. We selected 72 SNPs based on their putative function and frequency in the candidate genes AHCY, BHMT, BHMT2, CBS, ENOSF1, FOLH1, MTHFD1, MTHFR, MTR, MTRR, NNMT, PON1, PON2, SLC19A1, SHMT1, TCN2, and TYMS. We were able to analyze 57 of the SNPs (79%). For MTHFR C677T and A1298C and MTR A2756G SNPs, we compared data obtained with an electronic microchip technology and found 99.2% concordance. We also performed a haplotype analysis. This approach could represent a useful tool to investigate the genotype-phenotype correlation and the association of these genes with hyperhomocysteinemia and correlated diseases.

Hyperhomocysteinemia and elevated ox-LDL in Tunisian type 2 diabetic patients: Role of genetic and dietary factors

INTRODUCTION

Total plasma homocysteine (tHcy) is an emerging risk factor for the development of atherosclerosis. However, its relationship with diabetes is still unclear.

OBJECTIVES

We evaluated the association between tHcy levels and methylenetetrahydrofolate reductase (MTHFR) 677C-->T genotype in a type 2 diabetes mellitus (DM) population and their relationship with oxidized LDL (ox-LDL) according to dietary habits and vascular complications.

DESIGN AND METHODS

Eighty-six DM patients were compared to 120 healthy volunteers.

RESULTS

Associated higher tHcy levels and significantly higher ox-LDL levels (p<0.001) were found in DM patients compared to healthy subjects. Homozygosity for the T allele of MTHFR was more frequent in diabetics than in healthy subjects (12.8% vs. 7.2%) and it was associated with higher tHcy levels. Moreover, this elevated level was associated with significantly higher ox-LDL levels in DM patients with hypertension (p<0.05). Improving folate and vitamin C intakes could have beneficial effects on lowering the tHcy and ox-LDL levels.

CONCLUSIONS

The interplay of genetic and dietary factors modulates the effect of homocysteine on cardiovascular risk factors.

High glucose and homocysteine synergistically affect the metalloproteinases-tissue inhibitors of metalloproteinases pattern, but not TGFB expression, in human fibroblasts

AIMS/HYPOTHESIS

Atherosclerosis is particularly aggressive in patients with diabetes. Hyperhomocysteinaemia causes oxidative stress and cytokine secretion: its atherogenic effect is mediated by an enhanced inflammatory response. Matrix metalloproteinases (MMPs) regulate extracellular matrix degradation and remodelling, and contribute to the vulnerability of the atherosclerotic lesion. Fibroblasts contribute to collagen biosynthesis and participate in plaque remodelling via expression and release of MMP2 and MMP9. To explore the role of hyperhomocysteinaemia in cellular pathways involved in plaque growth and stability in diabetic patients, we studied the effect of hyperhomocysteinaemia in human fibroblasts grown in the presence of normal or high glucose concentrations.

MATERIALS AND METHODS

In fibroblasts of five normal subjects, grown at 5.5 or 22 mmol/l glucose and treated with homocysteine, we determined: (1) MMP2, MMP9 and tissue inhibitor of metalloproteinases (TIMP)-1 (an MMP inhibitor) production by western blot analysis; (2) their activity by zymography; (3) TGFB1 expression by real-time PCR; and (4) TGFB, fibronectin and IL6 release by ELISA.

RESULTS

Hyperhomocysteinaemia increased the production and enzymatic activity of MMP2 and MMP9, the effect being more pronounced in high glucose. Conversely, TIMP1 production was reduced by hyperhomocysteinaemia in both conditions, especially in high glucose. Hyperhomocysteinaemia also stimulated IL6 release, at least in part through nuclear factor-kappaB activation. TGFB1 expression was not affected by hyperhomocysteinaemia either in normal or in high glucose.

CONCLUSIONS/INTERPRETATION

Homocysteine upregulates the MMP-TIMP pathway and IL6 release, the effect being stronger in the presence of high glucose. These actions of homocysteine may contribute to the increased atherogenesis observed in diabetic patients with poor metabolic control.

Mining literature for a comprehensive pathway analysis: a case study for retrieval of homocysteine related genes for genetic and epigenetic studies

Homocysteine is an independent risk factor for cardiovascular diseases. It is also known to be associated with a variety of complex disorders. While there are a large number of independent studies implicating homocysteine in isolated pathways, the mechanism of homocysteine induced adverse effects are not clear. Homocysteine-induced modulation of gene expression through alteration of methylation status or by hitherto unknown mechanisms is predicted to lead to several pathological conditions either directly or indirectly. In the present manuscript, using literature mining approach, we have identified the genes that are modulated directly or indirectly by an elevated level of homocysteine. These genes were then placed in appropriate pathways in an attempt to understand the molecular basis of homocysteine induced complex disorders and to provide a resource for selection of genes for polymorphism screening and analysis of mutations as well as epigenetic modifications in relation to hyperhomocysteinemia. We have identified 135 genes in 1137 abstracts that either modulate the levels of homocysteine or are modulated by elevated levels of homocysteine. Mapping the genes to their respective pathways revealed that an elevated level of homocysteine leads to the atherosclerosis either by directly affecting lipid metabolism and transport or via oxidative stress and/or Endoplasmic Reticulum (ER) stress. Elevated levels of homocysteine also decreases the bioavailability of nitric oxide and modulates the levels of other metabolites including S-adenosyl methionine and S-adenosyl homocysteine which may result in cardiovascular or neurological disorders. The ER stress emerges as the common pathway that relates to apoptosis, atherosclerosis and neurological disorders and is modulated by levels of homocysteine. The comprehensive network collated has lead to the identification of genes that are modulated by homocysteine indicating that homocysteine exerts its effect not only through modulating the substrate levels for various catalytic processes but also through regulation of expression of genes involved in complex diseases.