Homocysteine and cardiovascular disease in diabetes mellitus

Association Between Elevated Total Homocysteine and Heart Failure Risk in the Multi-Ethnic Study of Atherosclerosis Cohort

BACKGROUND

Limited studies show an association between elevated total homocysteine (tHcy) and heart failure (HF) risk, but no studies have assessed whether this association differs by HF subtype. This study examines the relationship between tHcy, HF overall, and HF subtype (HF with preserved ejection fraction [HFpEF] and HF with reduced ejection fraction) in the Multi-Ethnic Study of Atherosclerosis cohort.

METHODS

Multi-Ethnic Study of Atherosclerosis participants with baseline tHcy and HF data were included (N=6765). Cox proportional hazards regression was used to calculate hazard ratios and 95% CI for tHcy and risk of HF. Models were stratified by impaired fasting glucose/type 2 diabetes status, and the combined impact of elevated tHcy and impaired fasting glucose/type 2 diabetes on HF incidence was examined.

RESULTS

Elevated tHcy (>12 μmol/L) was statistically significantly associated with HF overall and HFpEF, and conferred a higher risk for HF overall among individuals with dysglycemia impaired fasting glucose/type 2 diabetes compared with those with normoglycemia. Additionally, there was a statistically significant increased risk of HF overall and HF with reduced ejection fraction and a trend towards increased risk of HFpEF in individuals with both elevated tHcy and dysglycemia. tHcy appears to be a more significant contributor to HFpEF risk than dysglycemia, whereas dysglycemia seems to be more important in driving HF with reduced ejection fraction risk.

CONCLUSIONS

Our study confirms an association between hyperhomocysteinemia and HF risk in a large, multi-ethnic cohort. This is the first study to demonstrate that the impact of tHcy differs by HF subtype and appears to contribute more to HFpEF risk than HF with reduced ejection fraction risk.

The effect of diet-induced weight loss on circulating homocysteine levels in people with obesity and type 2 diabetes

BACKGROUND/AIMS

Having type 2 diabetes (T2D) in combination with being overweight results in an additional increase in cardiovascular disease (CVD) risk. In addition, T2D and obesity are associated with increased levels of total homocysteine (tHcy), possibly contributing to the CVD risk. Weight loss dieting has positive effects on several CVD risk factors, but whether it affects tHcy remains unclear. Therefore, the aim of this study was to determine the effect of a calorie restricted diet on tHcy in overweight people with T2D.

METHODS

In this post-hoc analysis of the POWER study, adults with T2D and a BMI greater than 27 kg/m² were included from the outpatient diabetes clinic of the Erasmus Medical Center, Rotterdam. The patients were subjected to a very low-calorie diet with fortified meal replacements for 20 weeks. Before and after this intervention, blood samples were collected to measure tHcy and other CVD risk factors like glycaemic and lipid parameters.

RESULTS

161 overweight participants with T2D were included, with a mean age of 54 years (range 26-74), mean weight of 104.6 ± 19.9 kg and mean HbA1c of 62.7 ± 14.3 mmol/mol. At baseline, men displayed higher tHcy than women, and tHcy level was positively correlated with body weight and triglyceride levels, while it was negatively correlated with renal function and HDL cholesterol. During the intervention, bodyweight was reduced by a mean of 9.7% (from 104.6 ± 19.9 to 94.5 ± 18.1 kg p < 0.001), and all measured glycaemic and lipid blood parameters improved significantly. However, tHcy remained unchanged (from 12.1 ± 4.1 to 12.1 ± 4.2 umol/L, p = 0.880). The change in tHcy during the intervention was negatively associated with the change in weight and BMI (p = 0.01 and p = 0.008, respectively). People who lost < 10 kg (n = 92) had a mean tHcy change of -0.47 umol/L, while people who lost more than ≥ 10 kg (n = 69) had a mean tHcy change of 0.60 umol/L (p = 0.021).

CONCLUSION

In conclusion, our data show that a calorie restricted diet does not affect tHcy in people with T2D and obesity, despite the use of meal replacements fortified with folic acid and vitamin B12. Our data showed a negative correlation between change in tHcy levels and weight loss, suggesting that people who lost more weight (> 10 kg) showed an increase in tHcy. Future studies should explore the potential increase in tHcy induced by weight loss dieting and target the question if tHcy reduction strategies during weight loss could be clinically beneficial.

The association of homocysteine level with the risk of diabetic nephropathy and diabetic retinopathy in NHANES

AIMS

To examine the association of homocysteine (Hcy) with diabetic nephropathy (DN) and diabetic retinopathy (DR) in a representative United States population.

METHODS

This was a cross-sectional study using data from participants in the National Health and Nutrition Examination Survey 2005-2006. Metrics including Hcy level, urinary albumin to creatinine ratio, estimated glomerular filtration rate, and retinopathy grading were collected. Multiple logistic regression models were employed to assess the association of Hcy with DN and DR.

RESULTS

630 participants were included in this study. The Hcy level was significantly higher in those with DN and DR than those without DN and DR. Hcy was associated with an increased risk of DN (OR = 1.31, 95% CI 1.18-1.46; P < 0.001). In the fully adjusted model of DN (model II), compared to participants in quartiles 1 of Hcy, the adjusted ORs for participants in quartiles 2-4 were 1.49 (95% CI 0.52-4.26; P = 0.426), 3.81 (95% CI 1.35-10.73; P = 0.015), and 14.08 (95% CI 3.84-51.66; P = 0.001), respectively. Hcy was also associated with an increased risk of DR (OR = 2.260, 95% CI 1.212-4.216; P = 0.014), but this association was non-significant in the fully adjusted model of DR (model II).

CONCLUSIONS

In diabetic patients, Hcy was associated with increased risk of DN in a non-linear manner. In addition, Hcy was associated with the risk of DR, but the association was attenuated after adjusting for confounders. In the future, Hcy can potentially be used as an early screening indicator for diabetic microvascular complications.

Dietary protein and amino acid restriction: Roles in metabolic health and aging-related diseases

The prevalence of obesity is a worldwide phenomenon in all age groups and is associated with aging-related diseases such as type 2 diabetes, as well metabolic and cardiovascular diseases. The use of dietary restriction (DR) while avoiding malnutrition has many profound beneficial effects on aging and metabolic health, and dietary protein or specific amino acid (AA) restrictions, rather than overall calorie intake, are considered to play key roles in the effects of DR on host health. Whereas comprehensive reviews of the underlying mechanisms are limited, protein restriction and methionine (Met) restriction improve metabolic health and aging-related neurodegenerative diseases, and may be associated with FGF21, mTOR and autophagy, improved mitochondrial function and oxidative stress. Circulating branched-chain amino acids (BCAAs) are inversely correlated with metabolic health, and BCAAs and leucine (Leu) restriction promote metabolic homeostasis in rodents. Although tryptophan (Trp) restriction extends the lifespan of rodents, the Trp-restricted diet is reported to increase inflammation in aged mice, while severe Trp restriction has side effects such as anorexia. Furthermore, inadequate protein intake in the elderly increases the risk of muscle-centric health. Therefore, the restriction of specific AAs may be an effective and executable dietary manipulation for metabolic and aging-related health in humans, which warrants further investigation to elucidate the underlying mechanisms.

Hyperhomocysteinemia: Metabolic Role and Animal Studies with a Focus on Cognitive Performance and Decline-A Review

Disturbances in the one-carbon metabolism are often indicated by altered levels of the endogenous amino acid homocysteine (HCys), which is additionally discussed to causally contribute to diverse pathologies. In the first part of the present review, we profoundly and critically discuss the metabolic role and pathomechanisms of HCys, as well as its potential impact on different human disorders. The use of adequate animal models can aid in unravelling the complex pathological processes underlying the role of hyperhomocysteinemia (HHCys). Therefore, in the second part, we systematically searched PubMed/Medline for animal studies regarding HHCys and focused on the potential impact on cognitive performance and decline. The majority of reviewed studies reported a significant effect of HHCys on the investigated behavioral outcomes. Despite of persistent controversial discussions about equivocal findings, especially in clinical studies, the present evaluation of preclinical evidence indicates a causal link between HHCys and cognition-related- especially dementia-like disorders, and points out the further urge for large-scale, well-designed clinical studies in order to elucidate the normalization of HCys levels as a potential preventative or therapeutic approach in human pathologies.

Plasma Levels of Homocysteine is Associated with Liver Fibrosis in Health Check-Up Population

Object

Studies have shown a link between homocysteine (Hcy) and heart diseases, kidney diseases, cerebrovascular diseases, liver diseases, and other pathological conditions. However, the relationship between Hcy and liver fibrosis (LF) is unclear. Here, we studied the link between plasma Hcy concentration and LF.

Methods

We determined and recorded the plasma Hcy concentration, general biochemical parameters, and liver stiffness measurement (LSM) in 1582 subjects, followed by statistical data analyses.

Results

During different stages of LF, we found a considerable difference (p <0.001 unless specified) in body mass index (BMI), sex, age, Hcy, the levels of alanine transaminase (ALT), gamma-glutamyl transpeptidase (GGT; P = 0.012), triglycerides (TG; P = 0.006), low-density lipoprotein cholesterol (LDL-C), fasting blood glucose (FBS), and platelet count (PLT). There was a strong association between the plasma Hcy concentration and the serum biomarkers of LF (P <0.001) and the values of LSM (P <0.001).

Conclusion

The plasma Hcy concentration was substantially different among different stages of LF. The higher the plasma Hcy concentration, the more evident was the degree of LF.

Diabetes associated residual atherosclerotic cardiovascular risk in statin-treated patients with prior atherosclerotic cardiovascular disease

AIM

In statin-treated persons with atherosclerotic cardiovascular disease (ASCVD) the further ASCVD risk that diabetes mellitus (DM) adds is not well-quantified. We examined this residual risk for initial and total recurrent ASCVD events.

METHODS

We studied 3271 patients with ASCVD on statin therapy in the AIM-HIGH clinical trial cohort. Cox regression and the Prentice, Williams, and Peterson model examined the excess risk of initial and total recurrent ASCVD events associated with DM over a 3- year mean follow-up. Predictors of first and total ASCVD events in those with and without DM were also examined.

RESULTS

Of our cohort with ASCVD on statin therapy 40% also had DM. Those with vs. without DM were older, were less likely to be male or white. They had higher systolic blood pressure, lower HDL-C, LDL-C, lipoprotein (a), but higher triglycerides and BMI (all p < 0.01). Adjusted HRs were 1.21 (95% CI; 1.01-1.46, p = 0.038) and 1.23 (95% CI: 1.05-1.44, p = 0.012) for first and total recurrent ASCVD events, respectively. Homocysteine and lipoprotein(a) most strongly predicted events in those with and without DM, respectively.

CONCLUSION

In statin-treated patients with ASCVD, DM was associated with significantly greater residual risk over ASCVD alone for both first and total recurrent ASCVD events.

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.

Hyperhomocysteinemia and dyslipidemia in point mutation G307S of cystathionine β-synthase-deficient rabbit generated using CRISPR/Cas9

Background

Congenital hyper-homocysteinemia (HHcy) is caused by a defective cystathionine β-synthase (CBS) gene, and is frequently associated with dyslipdemia. The aim of this study was to further elucidate the effect of mutated CBS gene on circulating lipids using a rabbit model harboring a homozygous G307S point mutation in CBS.

Methods

CRISPR/Cas9 system was used to edit the CBS gene in rabbit embryos. The founder rabbits were sequenced, and their plasma homocysteine (Hcy) and lipid profile were analyzed.

Results

Six CBS-knockout (CBS-KO) founder lines with biallelic modifications were obtained. Mutation in CBS caused significant growth retardation and high mortality rates within 6 weeks after birth. In addition, the 6-week old CBS-KO rabbits showed higher plasma levels of Hcy, triglycerides (TG), total cholesterol (TC) and low-density lipoprotein cholesterol (LDL-C) compared to the age-matched wild-type (WT) controls. Histological analysis of the mutants showed accumulation of micro-vesicular cytoplasmic lipid droplets in the hepatocytes. However, gastric infusion of vitamin B and betaine complex significantly decreased the plasma levels of TG, TC and LDL-C in the CBS-KO rabbits, and alleviated hepatic steatosis compared to the untreated animals.

Conclusion

A CBS^G307S rabbit model was generated that exhibited severe dyslipidemia when fed on a normal diet, indicating that G307S mutation in the CBS gene is a causative factor for dyslipidemia.

Dietary intake, clinical-nutritional status, and homocysteine in hemodialysis subjects: the mediating role of inflammation (NUGE-HD study)

The aim of the present study was to test the hypothesis that inflammation mediates the associations among food intake, clinical-nutritional status, and plasma homocysteine (Hcys) in hemodialysis (HD) subjects. This was a cross-sectional analysis of data on 129 subjects undergoing HD (58.9% male, 61.8 ± 15.5 years of age) from the cohort Nutrition and Genetics on HD outcomes (NUGE-HD study). Sociodemographic, anthropometric, and metabolic data were collected, and food intake was assessed using a quantitative food frequency questionnaire. Plasma C-reactive protein (CRP) was used as an inflammatory marker. Data were analyzed by structural equation modeling. Regarding the direct effects, complex B vitamin intake was negatively associated with body mass index, and diabetes mellitus was positively associated with CRP. Plasma CRP also showed a negative association with Hcys, and the ratio of saturated and polyunsaturated fatty acids intake showed a positive association with Hcys. Regarding indirect effects, the results showed that the relationship between the presence of diabetes mellitus and Hcys is mediated by plasma CRP. In conclusion, the ratio of saturated and polyunsaturated fatty acids had a direct effect on plasma Hcys, whereas inflammation had a direct and mediating effect on the relationship between Hcys and diabetes mellitus in HD subjects. Novelty In end-stage renal disease, CRP influences plasma Hcys directly and also indirectly through its mediating effect. The quantity and quality of dietary fatty acids influence plasma Hcys concentrations in HD subjects.

Inhibition of soluble epoxide hydrolase ameliorates hyperhomocysteinemia-induced hepatic steatosis by enhancing β-oxidation of fatty acid in mice

Hepatic steatosis is the beginning phase of nonalcoholic fatty liver disease, and hyperhomocysteinemia (HHcy) is a significant risk factor. Soluble epoxide hydrolase (sEH) hydrolyzes epoxyeicosatrienoic acids (EETs) and other epoxy fatty acids, attenuating their cardiovascular protective effects. However, the involvement of sEH in HHcy-induced hepatic steatosis is unknown. The current study aimed to explore the role of sEH in HHcy-induced lipid disorder. We fed 6-wk-old male mice a chow diet or 2% (wt/wt) high-metnionine diet for 8 wk to establish the HHcy model. A high level of homocysteine induced lipid accumulation in vivo and in vitro, which was concomitant with the increased activity and expression of sEH. Treatment with a highly selective specific sEH inhibitor (0.8 mg·kg^-1·day^-1 for the animal model and 1 μM for cells) prevented HHcy-induced lipid accumulation in vivo and in vitro. Inhibition of sEH activated the peroxisome proliferator-activated receptor-α (PPAR-α), as evidenced by elevated β-oxidation of fatty acids and the expression of PPAR-α target genes in HHcy-induced hepatic steatosis. In primary cultured hepatocytes, the effect of sEH inhibition on PPAR-α activation was further confirmed by a marked increase in PPAR-response element luciferase activity, which was reversed by knock down of PPAR-α. Of note, 11,12-EET ligand dependently activated PPAR-α. Thus increased sEH activity is a key determinant in the pathogenesis of HHcy-induced hepatic steatosis, and sEH inhibition could be an effective treatment for HHcy-induced hepatic steatosis. NEW & NOTEWORTHY In the current study, we demonstrated that upregulation of soluble epoxide hydrolase (sEH) is involved in the hyperhomocysteinemia (HHcy)-caused hepatic steatosis in an HHcy mouse model and in murine primary hepatocytes. Improving hepatic steatosis in HHcy mice by pharmacological inhibition of sEH to activate peroxisome proliferator-activated receptor-α was ligand dependent, and sEH could be a potential therapeutic target for the treatment of nonalcoholic fatty liver disease.

Cardiovascular Protective Effects of Salvianic Acid A on db/db Mice with Elevated Homocysteine Level

The onsets of left ventricular hypertrophy (LVH) and endothelial dysfunction (ED) in diabetics, especially in those with elevated homocysteine (Hcy), precede the development of cardiovascular (CV) events. Salvianic acid A (SAA) is a renowned Traditional Chinese Medicine (TCM) that has been applied in the treatment of cardiovascular disease for many decades. In this study, we aimed (1) to investigate the CV protective effects of SAA on ameliorating LVH and ED in db/db mice with elevated blood Hcy level and (2) to decipher whether the observed CV protective effects of SAA are associated with Hcy metabolism by modulating the methylation potential and redox status in the liver of the db/db mice with elevated blood Hcy level. Our results found that the administration of SAA could significantly slow down the build-up of left ventricular mass and ameliorate ED. Immunological assay analysis on the mouse liver tissue also indicated that SAA treatment on db/db mice with elevated Hcy was associated with reduced methylation potential but improved redox status. In conclusion, we revealed that SAA has the potential to protect against the hyperglycemia- and hyperhomocysteinemia-induced oxidative stress on diabetic mice via modulation in Hcy metabolism.

Effects of folic acid supplementation on serum homocysteine levels, lipid profiles, and vascular parameters in post-menopausal Korean women with type 2 diabetes mellitus

BACKGROUND/OBJECTIVES

Complications of diabetes, such as cardiovascular disease, are associated with increased mortality among type 2 diabetes mellitus patients. Homocysteine has been recently identified as a predictor of cardiovascular disease-related complications in diabetes. We investigated whether or not supplementation with folic acid tablets can lower homocysteine levels and improve parameters related with vascular complications.

SUBJECTS/METHODS

We conducted a non-randomized 8-week trial involving postmenopausal diabetic women (n = 25) supplemented with 800 µg of folic acid (400 µg twice a day) daily. Subjects' serum levels of folate, homocysteine, and vitamin B₁₂ were measured, along with vascular function and brachial-ankle pulse wave velocity.

RESULTS

Folic acid supplementation significantly increased serum folate levels (P < 0.0001), reduced homocysteine levels (P < 0.0001), and increased vitamin B₁₂ levels (P = 0.0063). There were significant decreases in low-density lipoprotein cholesterol levels as well as the ratios of low-density lipoprotein cholesterol to high-density lipoprotein cholesterol and total cholesterol to high-density lipoprotein cholesterol. Brachial-ankle pulse wave velocities were not altered by supplementation. Changes in serum vitamin B₁₂ after folic acid supplementation were negatively correlated with changes in brachial-ankle pulse wave velocity.

CONCLUSIONS

In this study on postmenopausal Korean women with type 2 diabetes mellitus, folic acid supplementation reduced serum homocysteine levels, increased serum folate and vitamin B₁₂ levels, and lowered lipid parameters.

Homocysteine and Its Relationship to Asymptomatic Carotid Stenosis in a Chinese Community Population

Little is known about the association between homocysteine (Hcy) and asymptomatic CAS in the healthy population. The purpose of this study was to investigate the relationship between Hcy levels and asymptomatic CAS in a Chinese community population. The current study included 5393 participants who were age of 40 years or older, and free of stroke, transient ischemic attack, and coronary artery disease. Demographic and clinical variables were investigated, and the presence of CAS was assessed by Color Doppler Ultrasound. A multivariate logistic regression was used to examine the association between Hcy levels and asymptomatic CAS. 361 (6.69%) participants were diagnosed with asymptomatic CAS, who had higher Hcy levels compared with those without (p-value for trend = 0.0001). After adjusting other possible risk factors, Hcy > 19.3μmol/L was considered as an independent indicator of asymptomatic CAS (OR 1.53, 95%CI 1.05–2.23; p-value for trend = 0.0265), but with a difference between participants with diabetes and without [OR (95%CI): 2.89(1.02–8.22) vs. 1.42(0.95–2.12); P interaction < 0.05]. In this large-population, community-based study, Hcy is an independent indicator of asymptomatic CAS, especially in patients with diabetes.

Fractions of Total Plasma Homocysteine in Patients with Ischemic Stroke Before the Age of 55 Years

The mechanism responsible for the association between elevated circulating homocysteine levels and ischemic stroke remains unclear. Therefore, the authors assessed total plasma homocysteine (tHcy) and its fractions (free [fHcy] and protein-bound [bHcy] homocysteine) in patients with ischemic stroke before the age of 55 years. Fifty patients (23 men, mean age 46.8 ±7.6 years) with ischemic stroke or transient ischemic attacks, with symptoms lasting <72 hours were enrolled. In this group: 32 (64%) patients had hypertension; 12 (24%), ischemic heart disease (IHD); and 20 (40%), type 2 diabetes mellitus (DM). The control group consisted of 30 matched healthy individuals (17 men, mean age 44.6 ±6.2 years). The tHcy, fHcy, and bHcy levels were determined by high-performance liquid chromatography. tHcy and its fractions did not differ significantly between patients and controls. However, stroke patients with hypertension had significantly higher concentrations of tHcy and bHcy compared to stroke patients without hypertension (tHcy 13.0 ±3.3 vs 10.7 ±3.2 µmol/L, p<0.05; bHcy 9.7 ±2.6 vs 7.8 ±2.3 µmol/L, p<0.01, respectively); fHcy was borderline significant: 3.1 (1.5-6.5) vs 2.5 (1.8-5.3) µmol/L, p=0.05. The presence of IHD, DM, hyperlipoproteinemia, clinical subtypes of stroke, smoking, and family history of stroke did not influence these parameters. In the group of 50 patients, tHcy correlated with mean systolic blood pressure (BP) ( r =0.3, p<0.05) and bHcy correlated with mean systolic and mean diastolic BP ( r =0.3, p<0.05). These findings suggest an association between hypertension and redox status of Hcy in patients with ischemic stroke before the age of 55 years. This observation supports the hypothesis that elevated BP may contribute to Hcy-related vascular injury.

Hyperhomocysteinemia activates the aryl hydrocarbon receptor/CD36 pathway to promote hepatic steatosis in mice

Hyperhomocysteinemia (HHcy) is associated with liver diseases such as fatty liver and hepatic fibrosis; however, the underlying mechanism is still largely unknown. The current study aimed to explore the signaling pathway involved in HHcy-induced hepatic steatosis (HS). C57BL/6 mice were fed a high-methionine diet (HMD) for 4 and 8 weeks to establish the HHcy mouse model. Compared to a chow diet, the HMD induced hepatic steatosis and elevated hepatic expression of CD36, a fatty acid transport protein. The increased CD36 expression was associated with activation of the aryl hydrocarbon receptor (AHR). In primary cultured hepatocytes, high levels of homocysteine (Hcy) treatment up-regulated CD36 and increased subsequent lipid uptake; both were significantly attenuated by small interfering RNA (siRNA) knockdown of CD36 and AHR. Chromatin immunoprecipitation assay revealed that Hcy promoted binding of AHR to the CD36 promoter, and transient transfection assay demonstrated markedly increased activity of the AHR response element by Hcy, which was ligand dependent. Mass spectrometry revealed significantly increased hepatic content of lipoxin A4 (LXA4 ), a metabolite of arachidonic acid, in HMD-fed mice. Furthermore, overexpression of 15-oxoprostaglandin 13-reductase 1, a LXA4 inactivation enzyme, inhibited Hcy-induced AHR activation, lipid uptake, and lipid accumulation. Moreover, LXA4 -induced up-regulation of CD36 and lipid uptake was inhibited by AHR siRNA in vitro in hepatocytes. Finally, treatment with an AHR antagonist reversed HHcy-induced lipid accumulation by inhibiting the AHR-CD36 pathway in mice.

CONCLUSION

HHcy activates the AHR-CD36 pathway by increasing hepatic LXA4 content, which results in hepatic steatosis. (Hepatology 2016;64:92-105).

Hyperhomocysteinemic Diabetic Cardiomyopathy: Oxidative Stress, Remodeling, and Endothelial-Myocyte Uncoupling

Accumulation of oxidized-matrix (fibrosis) between the endothelium (the endothelial cells embedded among the myocytes) and cardiomyocytes is a hallmark of diabetes mellitus and causes diastolic impairment. In diabetes mellitus, elevated levels of homocysteine activate matrix metalloproteinase and disconnect the endothelium from myocytes. Extracellular matrix functionally links the endothelium to the cardiomyocyte and is important for their synchronization. However, in diabetes mellitus, a disconnection is caused by activated metalloproteinase, with subsequent accumulation of oxidized matrix between the endothelium and myocyte. This contributes to endothelial-myocyte uncoupling and leads to impaired diastolic relaxation of the heart in diabetes mellitus. Elevated levels of homocysteine in diabetes are attributed to impaired homocysteine metabolism by glucose and insulin and decreased renal clearance. Homocysteine induces oxidative stress and is inversely related to the expression of peroxisome proliferators activated receptor (PPAR). Several lines of evidence suggest that ablation of the matrix metalloproteinase (MMP-9) gene ameliorates the endothelial-myocyte uncoupling in diabetes mellitus. Homocysteine competes for, and decreases the PPARγ activity. In diabetes mellitus, endothelial-myocyte uncoupling is associated with matrix metalloproteinase activation and decreased PPARγ activity. The purpose of this review is to discuss the role of endothelial-myocyte uncoupling in diabetes mellitus and increased levels of homocysteine, causing activation of latent metalloproteinases, decreased levels of thioredoxin and peroxiredoxin, and cardiac tissue inhibitor of metalloproteinase (CIMP) in response to antagonizing PPARγ.

Turkish propolis supresses MCF-7 cell death induced by homocysteine

Elevated plasma homocysteine (Hcy) level is a most important risk factor for various vascular diseases including coronary, cerebral and peripheral arterial and venous thrombosis. Propolis is produced by honeybee from various oils, pollens and wax materials. Therefore, it has various biological properties including antioxidant, antitumor and antimicrobial activities. This study investigated the effects of propolis and Hcy on apoptosis in cancer cells. According to our findings, Hcy induced apoptosis in human breast adenocarcinoma (MCF-7) cells by regulating numerous genes and proteins involved in the apoptotic signal transduction pathway. In contrast, treatment with propolis inhibited caspase- 3 and -9 induced by Hcy in MCF-7 cells. It can be concluded that Hcy may augment the activity of anticancer agents that induce excessive reactive oxygen species (ROS) generation and apoptosis in their target cells. In contrast to the previous studies herein we found that propolis in low doses protected cancer cells inhibiting cellular apoptosis mediated by intracellular ROS-dependent mitochondrial pathway.

Diabetic neuropathy is not associated with homocysteine, folate, vitamin B12 levels, and MTHFR C677T mutation in type 2 diabetic outpatients taking metformin

BACKGROUND

Hyperhomocysteinemia and vitamin B12 deficiency may be involved in the development of diabetic peripheral neuropathy (DPN). Metformin therapy may reduce vitamin B12 plasma levels, thus contributing to DPN.

AIM AND METHODS

The purposes of this cross-sectional study were to assess (1) the potential associations of DPN with serum levels of homocysteine (tHcy), B-vitamins, and/or the common methylenetetrahydrofolate reductase (MTHFR) C677T mutation; (2) the influence of chronic treatment with metformin on tHcy and B-vitamins concentrations and, finally, (3) to evaluate whether, by this influence, metformin is a risk factor for DPN in a group of type 2 diabetic outpatients.

RESULTS

Our data showed that fasting tHcy, folate, and vitamin B12 levels and the MTHFR C677T genotype distribution were comparable between subjects with (n = 79, 30 %) and without DPN (n = 184, 70 %). Metformin-treated subjects (n = 124, 47 %) showed significantly lower levels of vitamin B12 (P < 0.001), but the prevalence of DPN was not different when compared to those not treated with this drug (33 vs. 27 %, P = NS). At univariate regression analysis, DPN was associated with age, duration of diabetes, HbA1c, creatinine levels, and the presence of coronary heart disease (CHD), and negatively with HDL-C concentrations (P < 0.05 all), but at multivariate regression analysis, high creatinine levels (P = 0.06), low HDL-C levels (P = 0.013), and a higher prevalence of CHD (P = 0.001) were the only variables independently associated with DPN in this population.

CONCLUSIONS

In conclusion, in these type 2 diabetic outpatients circulating levels of tHcy, folate, and the MTHFR C677T mutation are not associated with DPN, which was predicted by creatinine levels, CHD, and dyslipidemia. Metformin therapy is associated with a mild vitamin B12 level reduction, but not with DPN.

Evaluation of the role of N-methyl-D-aspartate (NMDA) receptors in insulin secreting beta-cells

The possibility that antagonism of N-methyl-D-aspartate (NMDA) receptors represent a novel drug target for diabetes prompted the current studies probing NMDA receptor function in the detrimental actions of homocysteine on pancreatic beta-cell function. Cellular insulin content and release, changes in membrane potential and intracellular Ca(2+) and gene expression were assessed following acute (20min) and long-term (18h) exposure of pancreatic clonal BRIN-BD11 beta-cells to known NMDA receptor modulators in the absence and presence of cytotoxic concentrations of homocysteine. As expected, acute or long-term exposure to homocysteine significantly suppressed basal and secretagogue-induced insulin release. In addition, NMDA reduced glucose-stimulated insulin secretion (GSIS). Interestingly, the selective NMDA receptor antagonist, MK-801, had no negative effects on GSIS. The effects of the NMDA receptor modulators were largely independent of effects on membrane depolarisation and increases of intracellular Ca(2+). However, combined culture of the NMDA antagonist, MK-801, with homocysteine did enhance intracellular Ca(2+) levels. Actions of NMDA agonists/antagonists and homocysteine on signal transduction pathways were independent of changes in cellular insulin content, cell viability, DNA damage or expression of key beta-cell genes. Taken together, the data support a role for NMDA receptors in controlling pancreatic beta-cell function. However, modulation of NMDA receptor function was unable to prevent the detrimental beta-cell effects of homocysteine.

Homocysteine downregulates gene expression of heme oxygenase-1 in hepatocytes

Background

Hyperhomocysteinemia (HHcy) is an independent risk factor for liver diseases, such as fatty liver and hepatic fibrosis. However, the mechanisms underlying this pro-oxidative effect of homocysteine (Hcy) in hepatocytes remain largely unknown. Thus, we investigated the effect of Hcy on the gene expression of heme oxygenase-1 (HO-1), the primary rate-limiting enzyme in heme catabolism and a key anti-oxidant detoxification enzyme in maintaining cellular redox homeostasis.

Methods

In vivo, twenty male C57BL/6 mice at 8 weeks of age were randomly divided into two groups. One group was fed a chow diet (chow group; n = 10), the other group of mice was fed a methionine-supplemented diet (Met group, 1 mg kg⁻¹ day⁻¹ L-methionine in drinking water; n = 10) for 4 weeks. In vitro, HepG2 cells were stimulated with different doses of homocysteine (Hcy).

Results

Four weeks’ methionine supplementation caused a significant increase of plasma Hcy concentration and a decrease of HO-1 expression in the liver of C57BL/6 mice than mice received chow diet. Besides, SOD enzyme activities were impaired and the level of oxidative stress markers, such as malondialdehyde (MDA) were elevated in the liver from mice supplemented with methionine compared with control mice. In cultured hepatocytes, Hcy treatment reduced both the mRNA and protein levels of HO-1 dose-dependently. However, Hcy had no effect on the gene expression of Nrf2, the major transcriptional regulator of HO-1. Instead, Hcy induced the expression of Bach1, a transcriptional repressor of HO-1. In addition, Hcy stimulated the nuclear localization of Bach1 but prevented that of Nrf2. Furthermore, we found that knockdown of Bach1 attenuated the suppression of the HO-1 expression by Hcy.

Conclusions

Collectively, our results demonstrated that Bach1 plays an important role in Hcy-triggered ROS generations through inhibiting HO-1 expression, likely, resulting from the disturbed interplay between Bach1 and Nrf2.

Electronic supplementary material

The online version of this article (doi:10.1186/1743-7075-11-55) contains supplementary material, which is available to authorized users.

Does the MTHFR C677T gene polymorphism indicate cardiovascular disease risk in type 2 diabetes mellitus patients?

Objective:

Diabetes mellitus is a major risk factor for cardiovascular disease (CVD). We investigated the relationship among biochemical and cardiac risk parameters with the methylenetetrahydrofolate reductase (MTHFR) C677T genotype in type 2 diabetes mellitus (T2DM) patients.

Methods:

One hundred seven T2DM subjects with severe CVD diagnosed by angiography were included consecutively in this cross-sectional study. Biochemical and clinical parameters were obtained from patients who were not positive for nephropathy and retinopathy. MTHFR C677T genotypes were analyzed using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) methods. Normally and abnormally distributed continuous variables were analyzed using student t- and Mann-Whitney U tests. Categorical variables were analyzed using chi-square test.

Results:

In the study, 31 T2DM subjects had the CC (29.0%), 62 had the CT (57.9%), and 14 had the TT (13.1%) genotypes. There were no significant differences between subjects with wild-type (677CC) and with mutant (677CT+677TT) alleles in terms of diabetes duration, visceral fat area, total cholesterol, triglyceride, fasting plasma glucose, systolic blood pressure, diastolic blood pressure, high-sensitivity C-reactive protein, homocysteine (Hcy), and carotid intima-media thickness values.

Conclusion:

This study suggests that MTHFR gene polymorphisms can not be used as a marker for the assessment of cardiovascular risk in T2DM patients.

Higher homocysteine and lower betaine increase the risk of microangiopathy in patients with diabetes mellitus carrying the GG genotype of PEMT G774C

BACKGROUND

Diabetes represents one of the greatest medical and socioeconomic threats worldwide. The pathogenesis involved is complicated. The effect of methyl donors and genetic polymorphisms in metabolic enzymes on the risk of microangiopathy in patients with diabetes is not well understood. This study investigates the association of homocysteine, choline and betaine levels and phosphatidylethanolamine N-methyltransferase (PEMT) G774C (rs12325817) genotypes with the risk of diabetes and its related microangiopathic complications.

METHODS

Between January 2009 and June 2010, 184 diabetic patients and 188 non-diabetic control subjects were enrolled in the hospital-based case-control study. Serum concentrations of betaine and choline were determined by high-performance liquid chromatography (HPLC)-mass spectrometry. Serum concentrations of homocysteine were assayed using HPLC. PEMT gene mutations were detected by polymerase chain reaction and restriction fragment length polymorphism.

RESULTS

After adjustment for potential confounders, serum total homocysteine had a significant dose-dependent positive association, and serum choline had an inverse association with the risks of diabetes and its microangiopathic complications (both p < 0.001). Although serum betaine was not associated with the risk of diabetes, it had a significant inverse association with diabetic microangiopathy. Compared with GG genotype, the CC genotype of PEMT G774C was associated with a decreased risk of diabetes (OR 0.559, 95% CI 0.338, 0.926) and its microangiopathy (OR 0.452, 95% CI 0.218, 0.937).

CONCLUSION

The GG genotype of the PEMT G774C polymorphism, higher levels of serum homocysteine and lower levels of serum betaine are associated with an increased risk of microangiopathy in patients with diabetes.

Association of MTHFR and PPARγ2 gene polymorphisms in relation to type 2 diabetes mellitus cases among north Indian population

BACKGROUND

Type 2 diabetes mellitus is a multifactorial and polygenic disease, which is considered as a major life threatening problem all over the world. There has been a worldwide effort in the identification of susceptibility genes for type 2 diabetes mellitus and its complications. At present, adequate data is not available dealing with MTHFR (rs1801133) and PPARγ2 (rs1801282) gene polymorphisms and its association with type 2 diabetes mellitus cases among north Indian populations. Thus, we conceived the need for further studies to investigate MTHFR and PPARγ2 gene polymorphisms and their susceptibility to type 2 diabetes mellitus in north Indian population.

MATERIALS AND METHODS

In this study, a total 175 subjects including 87 type 2 diabetes mellitus cases and 88 controls were enrolled. MTHFR and PPARγ2 gene polymorphisms in the cases and controls were evaluated by polymerase chain reaction and restriction fragment length polymorphism (PCR-RFLP).

RESULTS

The MTHFR gene CC, CT, TT genotype frequencies obtained were 40%, 43%, and 17% in type 2 diabetes mellitus cases and 56%, 29%, and 15% in healthy controls respectively. The OR for CC was 0.54 (95%CI 0.29-0.98, P=0.041, χ(2)=4.18, power=0.98), for CT 1.76 (95%CI 0.94-3.30, P=0.07, χ(2)=3.2, power=0.96), and for TT 1.2 (95%CI 0.53-2.70, P=0.66, χ(2)=0.198, power=0.76). The PPARγ2 gene GG CG, CC genotype frequencies obtained were 28%, 41%, and 31% in cases and 40%, 39%, and 21% in healthy controls respectively. OR for GG was 0.58 (95%CI 0.30-1.09, P=0.08, χ(2)=2.9, power=0.96), for CG 1.12 (95%CI 0.61-2.05, P=0.71, χ(2)=0.137, power=0.778), and for CC 1.63 (95%CI 0.82-3.23, P=0.156, χ(2)=2.01, power=0.92).

CONCLUSION

It might be recommended that MTHFR CC genotype seems to be a good marker for the early identification of population at risk of type 2 diabetes mellitus. While we have detected significant difference in allelic frequencies of PPARγ2 C (Proline) and G (Alanine), but at genotypic level significant difference was not detected in this case-control study. Further study with larger groups may be required to validate the study.

Homocysteine inhibits adipogenesis in 3T3-L1 preadipocytes

Hyperhomocysteinemia (HHcy) is a characteristic metabolic abnormality in several pathological conditions, including hypertension, diabetes and alcoholic liver disease. Emerging evidence indicates that adipose tissue contributes to HHcy and homocysteine (Hcy) conversely affects adipose tissue function. However, the specific effect of Hcyon adipogenesis is poorly understood. In the present study, we investigated the effects and mechanisms of Hcy on adipogenic process using 3T3-L1 preadipocytes, a well-established in vitro model for the study of adipogenesis. Confluent mouse embryo 3T3-L1 preadipocytes (D0) were exposed to differentiation cocktail for three days (D3). Then, cells were transferred to insulin-containing medium and re-fed every two days. Maturation of adipocytes was confirmed by Oil Red O staining of lipid droplets on day 7. Exogenous Hcy was added to the culture medium on either D0 or D3. At day 7, adipogenesis indices were measured. Our data indicated that both Hcy addition protocols suppressed adipogenic process, evidenced by decreased lipid accumulation and downregulated gene expressions of adipocyte protein 2 and peroxisome proliferator-activated receptor gamma (PPAR-gamma), implying that Hcy exerted inhibitory effects on both mitotic clonal expansion (MCE) stage and differentiation stage. Further study showed that Hcy suppresses MCE via decreasing retinoblastoma protein phosphorylation and E2F-1 protein expression. To delineate the critical involvement of PPAR-gamma in Hcy-induced suppression on adipogenesis, we employed rosiglitazone, a specific PPAR-gamma agonist, to replace insulin for the inductive stimulus of adipogenesis. Our results showed that Hcy suppressed rosiglitazone-induced adipogenesis in a similar fashion as this by insulin, suggesting that inhibition of PPAR-gamma transactivation was critically involved in the Hcy-induced inhibitory effect on adipogenesis. Taken together, our data indicate that Hcy suppressed adipogenesis in 3T3-L1 preadipocytes and the inhibition of PPAR-gamma transactivity may, at least partially, contribute to the suppressive effect.

Relation of homocysteinemia to contrast-induced nephropathy in patients undergoing percutaneous coronary intervention

Hyperhomocysteinemia induces oxidative stress and endothelial dysfunction, which share the proposed pathophysiologic mechanisms of contrast-induced nephropathy (CIN). However, no study has investigated the relation between hyperhomocysteinemia and CIN. The aim of the present study was to evaluate the effects of hyperhomocysteinemia on CIN in patients undergoing percutaneous coronary intervention. This was an observational cohort study that included 572 patients who underwent percutaneous coronary intervention. CIN was defined as an absolute ≥0.5 mg/dl or a relative ≥25% increase in the serum creatinine level at 48 hours after the procedure. The incidence of CIN was significantly greater in patients in the third homocysteine tertile (from lowest to highest, 4.7%, 7.3%, and 24.2%, p <0.001). Furthermore, the homocysteine levels were significantly greater in patients with CIN than in those without CIN (16.9 ± 4.9 vs 13.5 ± 4.2 μmol/L, p <0.001). In multiple logistic regression models, hyperhomocysteinemia was an independent risk factor for CIN (per the SD change in the plasma homocysteine level [4.44 μmol/L], odds ratio 1.70, 95% confidence interval 1.07 to 2.71, p = 0.025) after adjusting for major risk factors such as age, diabetes, and baseline cardiac and renal function. In subgroup analyses according to diabetes, acute coronary syndrome, or baseline estimated glomerular filtration rate, significant, graded associations were found between the homocysteine level and the incidence of CIN. In conclusion, hyperhomocysteinemia is independently associated with a greater risk of CIN in patients undergoing percutaneous coronary intervention.

Functional aspects of cytidine-guanosine dinucleotides and their locations in genes

Originally, the finding of a particular distribution of cytidine-guanosine dinucleotides (CpGs) in genomic DNA was considered to be an interesting structural feature of eukaryotic genome organization. Despite a global depletion of CpGs, genes are frequently associated with CpG clusters called CpG islands (CGIs). CGIs are prevalently unmethylated but often found methylated in pathologic situations. On the other hand, CpGs outside of CGIs are generally methylated and are found mainly in the heterochromatic fraction of the genome. Hypomethylation of those CpGs is associated with genomic instability in malignancy. Additionally, CpG-rich and CpG-poor regions, as well as CpG-shores, are defined. Usually, the methylation status inversely correlates with gene expression. Methylation of CpGs, as well as demethylation and generation of hydroxmethyl-cytosines, is strictly regulated during development and differentiation. This review deals with the relevance of the organizational features of CpGs and their relation to each other.

Carotid intimal-medial thickness is not increased in women with previous gestational diabetes mellitus

BACKGROUND

Gestational diabetes mellitus (GDM) is known to increase the risk of cardiovascular diseases. Measuring the carotid artery intimal-medial thickness (CIMT) is a non-invasive technique used to evaluate early atherosclerosis and to predict future cardiovascular diseases. We examined the association between CIMT and cardiovascular risk factors in young Korean women with previous GDM.

METHODS

One hundred one women with previous GDM and 19 women who had normal pregnancies (NP) were recruited between 1999 and 2002. At one year postpartum, CIMT was measured using high-resolution B-mode ultrasonography, and oral glucose tolerance tests were performed. Fasting glucose, glycated hemoglobin A1c (HbA1c), insulin levels and lipid profiles were also measured. CIMTs in the GDM and NP groups were compared, and the associations between CIMT and cardiovascular risk factors were analyzed in the GDM group.

RESULTS

CIMT results of the GDM group were not significantly different from those of the NP group (GDM, 0.435±0.054 mm; NP, 0.460±0.046 mm; P=0.069). In the GDM group, a higher HbA1c was associated with an increase in CIMT after age adjustment (P=0.011). CIMT results in the group with HbA1c >6.0% were higher than those of the normal HbA1c (HbA1c ≤6.0%) (P=0.010). Nine of the patients who are type 2 diabetes mellitus converters within one year postpartum but showed no significant difference in CIMT results compared to NP group.

CONCLUSION

Higher HbA1c is associated with an increase in CIMT in women with previous GDM. However, CIMT at one year postpartum was not increased in these women compared to that in NP women.

Mild hyperhomocysteinemia, C677T polymorphism on methylenetetrahydrofolate reductase gene and the risk of macroangiopathy in type 2 diabetes: a prospective study

The role of hyperhomocysteinemia as a risk factor for diabetic long-term complications has not been sufficiently evaluated in prospective studies, considering specific correlates of homocysteine (tHcy) concentration and traditional cardiovascular disease (CVD) risk factors. Fasting tHcy, vitamin B12 and folate plasma levels, the common methylenetetrahydrofolate reductase (MTHFR) C677T gene polymorphism, as well as clinical and lifestyle information were assessed in 216 type 2 diabetic patients attending two outpatient clinics, who had a follow-up evaluation at 65 ± 9 months for the incidence of macroangiopathy. At basal evaluation, mild hyperhomocysteinemia (tHcy ≥ 15 μmol/l) was diagnosed in 21.3% of participants. At follow-up, hyperhomocysteinemia and the distribution of MTHFR C677T genotype did not significantly differ according to the incidence of macroangiopathy. Multiple variables adjusted ORs (95% CI) for CVD associated with mild hyperhomocysteinemia were 1.01 (0.37-2.82); P > 0.05; those associated with MTHFR TT genotype were 0.46 (0.15-1.38); P > 0.05. Although the prevalence of hyperhomocysteinemia was higher in diabetic men (26.9%) than in women (16.1%; P > 0.05), similar results were also observed in a separate sex-analysis. At the multivariate analysis, including in the model other potential CVD risk factors, only creatinine clearance was a significant risk factor for the development of macroangiopathy. In this cohort of diabetic subjects, mild hyperhomocysteinemia and the MTHFR TT genotype are not significant risk factors for the development of macroangiopathy; impaired renal function was confirmed as a significant predictor of this complication.

Cobalamin status in children

Cobalamin and the metabolic markers methylmalonic acid and total homocysteine undergo marked changes during childhood. In breastfed infants a metabolic profile indicative of cobalamin deficiency is common. Symptoms of cobalamin deficiency in children differ with age, presenting a continuum from subtle developmental delay to life-threatening clinical conditions. The symptoms may be difficult to detect, particularly in infants, and there tends to be a diagnostic delay of several months in this age group. Several reports show that even moderate deficiency in children may be harmful, and long-term consequences of neurological deterioration may persist after cobalamin deficiency has been treated. Given the crucial role of cobalamin for normal growth and development, possible widespread infantile deficiency needs attention. Cobalamin deficiency should be considered a differential diagnosis in children with subtle symptoms, and strategies to prevent cobalamin deficiency in mothers and children should be addressed.

Homocysteine suppresses the expression of the collagen cross-linker lysyl oxidase involving IL-6, Fli1, and epigenetic DNA methylation

Elevated homocysteine (Hcys) serum levels represent a risk factor for several chronic pathologies, including cardiovascular disease, atherosclerosis, and chronic renal failure, and affect bone development, quality, and homeostasis. Hcys influences the formation of a stable bone matrix directly through the inhibition of the collagen cross-linking enzyme lysyl oxidase (Lox) and, as we have shown recently, by repressing its mRNA expression. The aim of this study was to investigate the mechanisms involved in this process. Through evaluation of gene arrays, quantitative RT-PCR, immunoblots, and ELISA, we identified a Hcys-dependent stimulation of interleukin 6 (IL-6) and genes involved in IL-6/Janus kinase 2 (JAK2)-dependent signal transduction pathways in pre-osteoblastic MC3T3-E1 cells. Moreover, up-regulation of genes essential for epigenetic DNA methylation (DNA (cytosine-5)-methyltransferases and helicase lymphoid-specific (Hells) was observed. Further investigations demonstrated that Hcys increased via IL-6/JAK2 the expression of Fli1 (Friend leukemia virus integration 1), a transcription factor, which we found essential for IL-6-dependent Dnmt1 stimulation. CpG methylation analysis of CpG-rich Lox proximal promoter revealed an increased CpG methylation status after treatment of the cells with Hcys indicating an epigenetic origin for Hcys-dependent Lox repression. Inhibition of the IL-6/JAK2 pathway or of CpG methylation reversed the repressive effect of Hcys on Lox expression. In conclusion, we demonstrate that Hcys stimulates IL-6 synthesis in osteoblasts, which is known to affect bone metabolism via osteoclasts. Furthermore, IL-6 stimulation results via JAK2, Fli1, and Dnmt1 in down-regulation of Lox expression by epigenetic CpG methylation revealing a new mechanism negatively affecting bone matrix formation.

Synergism in hyperhomocysteinemia and diabetes: role of PPAR gamma and tempol

BACKGROUND

Hyperhomocysteinemia (HHcy) and hyperglycemia cause diabetic cardiomyopathy by inducing oxidative stress and attenuating peroxisome proliferator- activated receptor (PPAR) gamma. However, their synergistic contribution is not clear.

METHODS

Diabetic Akita (Ins2+/-) and hyperhomocysteinemic cystathionine beta synthase mutant (CBS+/-) were used for M-mode echocardiography at the age of four and twenty four weeks. The cardiac rings from WT, Akita and hybrid (Ins2+/-/CBS+/-) of Akita and CBS+/- were treated with different doses of acetylcholine (an endothelial dependent vasodilator). High performance liquid chromatography (HPLC) was performed for determining plasma homocysteine (Hcy) level in the above groups. Akita was treated with ciglitazone (CZ) - a PPAR gamma agonist and tempol-an anti-oxidant, separately and their effects on cardiac remodeling were assessed.

RESULTS

At twenty four week, Akita mice were hyperglycemic and HHcy. They have increased end diastolic diameter (EDD). In their heart PPAR gamma, tissue inhibitor of metalloproteinase-4 (TIMP-4) and anti-oxidant thioredoxin were attenuated whereas matrix metalloproteinase (MMP)-9, TIMP-3 and NADPH oxidase 4 (NOX4) were induced. Interestingly, they showed synergism between HHcy and hyperglycemia for endothelial-myocyte (E-M) uncoupling. Additionally, treatment with CZ alleviated MMP-9 activity and fibrosis, and improved EDD. On the other hand, treatment with tempol reversed cardiac remodeling in part by restoring the expressions of TIMP-3,-4, thioredoxin and MMP-9.

CONCLUSIONS

Endogenous homocysteine exacerbates diabetic cardiomyopathy by attenuating PPAR gamma and inducing E-M uncoupling leading to diastolic dysfunction. PPAR gamma agonist and tempol mitigates oxidative stress and ameliorates diastolic dysfunction in diabetes.

Chronic pancreatitis is associated with hyperhomocysteinemia and derangements in transsulfuration and transmethylation pathways

OBJECTIVES

Homocysteine has been implicated in vascular dysfunction and thrombosis, as well as inflammatory conditions. This study was aimed to find out whether chronic pancreatitis (CP) is associated with hyperhomocysteinemia and derangements of transmethylation and transsulfuration pathways.

METHODS

We estimated homocysteine and its metabolites in 45 alcoholic CP patients, 45 tropical CP patients, and 48 healthy controls.

RESULTS

Significant increases in plasma total homocysteine and decreases in red blood cell folate, reduced glutathione, plasma methionine, cysteine, and urinary inorganic sulfate/creatinine ratio were observed in both alcoholic and tropical CP patients in comparison with healthy controls. Red blood cell glutathione and plasma cysteine levels were significantly lower in alcoholic than in tropical CP patients. However, plasma vitamin B12 levels were comparable between CP patients and controls. No significant differences in these parameters were observed between diabetic patients and nondiabetic patients. Multivariate regression analysis showed a significant negative correlation between homocysteine and folate (r = -0.415, P = 0.001) and a positive correlation between glutathione and cysteine levels (r = 0.37, P = 0.003).

CONCLUSIONS

Chronic pancreatitis is associated with hyperhomocysteinemia and derangements in transmethylation and transsulfuration pathways. Low folate levels observed in these patients seem to have a key role in this derangement.

Atorvastatin attenuates homocysteine-induced apoptosis in human umbilical vein endothelial cells via inhibiting NADPH oxidase-related oxidative stress-triggered p38MAPK signaling

AIM

To examine the effect of atorvastatin on homocysteine (Hcy)-induced reactive oxygen species (ROS) production and apoptosis in human umbilical vein endothelial cells (HUVECs).

METHODS

HUVECs were cultured with Hcy (0.1-5 mmol/L) in the presence or absence of atorvastatin (1-100 micromol//L) or various stress signaling inhibitors, including the nicotinamide adenine dinucleotide phosphate (NADPH) oxidase inhibitor diphenylene iodonium (DPI, 10 micromol/L), the p38 mitogen-activated protein kinase (p38 MAPK) inhibitor SB203580 (10 micromol/L) and antioxidants N-acetyl cysteine (NAC, 1 mmol/L). Cell apoptosis was evaluated by Annexin V/propidium iodide staining and flow cytometry. ROS were detected by 2',7'-dichlorodihydrofluorescein diacetate (H(2)DCFH-DA). NADPH oxidases were evaluated with lucigenin-enhanced chemiluminescence. Hcy-induced expression of p38MAPK protein was measured by Western blotting analysis.

RESULTS

Atorvastatin inhibited endothelial cell apoptosis induced by 1 mmol/L Hcy in a dose-dependent manner and the maximal inhibitory effect was reached at 100 micromol/L. Atorvastatin (10 micromol/L) significantly suppressed Hcy (1 mmol/L for 30 min) induced ROS accumulation (3.17+/-0.33 vs 4.34+/-0.31, P<0.05). Atorvastatin (10 micromol/L) also antagonized Hcy (1 mmol/L for 30 min) induced activation of NADPH oxidase (2.57+/-0.49 vs 3.33+/-0.6, P<0.05). Furthermore, atorvastatin inhibited Hcy-induced phosphorylation of p38 MAPK (1.7+/-0.1 vs 2.22+/-0.25, P<0.05), similar effects occurred with DPI, NAC and SB203580.

CONCLUSION

Atorvastatin may inhibit Hcy-induced ROS accumulation and endothelium cell apoptosis through an NADPH oxidase and/or p38MAPK-dependent mechanisms, all of which may contribute to atorvastatin-induced beneficial effect on endothelial function.

MTHFR (Ala 222 Val) polymorphism and AMI in patients with type II diabetes mellitus

The prevalent Ala222Val single nucleotide polymorphism of the MTHFR gene has been shown to be associated with type II diabetes. The objective of the present study was to find out whether there is genetic predisposition for development of acute myocardial infarction in type II diabetes mellitus among South Indian Tamil population. PCR-based restriction enzyme analysis was performed in DNA isolated from 120 acute myocardial infarction patients with diabetes mellitus and 100 non diabetic healthy individuals with no documented cardiovascular diseases. The results indicate that the MTHFR 677TT genotype is absent in both case and controls. The MTHFR 677CT genotype was observed among 32 (26.7 %) cases and 20 (20%) controls and the MTHFR 677CC genotype among 88 (73.3%) cases and 80 (80%) controls. The allelic frequencies were in accordance to Hardy Weinberg equilibrium. There was no statistical difference in genotype distribution between cases and controls. In conclusion, we suggest that the analysis of MTHFR genotyping for C677T polymorphism alone need not be considered to find out whether there is genetic predisposition for development of acute myocardial infarction in type II diabetes mellitus among South Indian Tamil population.

Late cardiovascular consequences of gestational diabetes mellitus

Gestational diabetes mellitus (GDM), defined as carbohydrate intolerance of any degree first recognized during pregnancy, complicates approximately 4% of all pregnancies in the United States. Several factors can increase one's risk of developing GDM, including obesity, family history of type 2 diabetes mellitus (T2DM), and race/ethnicity. Conversely, a history of GDM can increase the risk of developing not only T2DM but also cardiovascular disease (CVD) independent of a diagnosis of T2DM. Several investigations have explored GDM relationships with CVD risk factors, CVD surrogate markers, and clinically evident CVD. These studies have included evaluations of biochemical parameters, such as inflammatory and endothelial biomarkers; endothelial dysfunction, such as that seen in impaired brachial artery flow-mediated vasodilation; and vascular dysfunction, manifest as cardiac dysfunction or in diseases such as hypertension. This article will review these studies and examine factors considered to be responsible for promoting CVD in women with a history of GDM, such as T2DM and metabolic syndrome and its components. In addition, studies evidencing CVD in women with a history of GDM will be explored.

Menopause modulates homocysteine levels in diabetic and non-diabetic women

High total homocysteine (tHcy) plasma levels may contribute to the increased cardiovascular risk of Type 2 diabetic women. However, to date, data on factors modulating tHcy concentration in this population are scarce. Fasting tHcy, vitamin B12, folate plasma levels, and the methylene tetrahydrofolate reductase (MTHFR) C677T genotype as well as clinical, biochemical, and lifestyle variables were compared in 91 Type 2 diabetic and 91 matched non-diabetic women (40 pre- and 51 post-menopausal, in each group). Fasting tHcy concentration did not differ between diabetic and control women, even after multivariable adjustment. In both groups, tHcy levels increased after menopause, but the differences were weakened after multivariable adjustment. The MTHFR genotype distribution was in accordance with the Hardy-Weinberg equilibrium, with a similar TT frequency in diabetic (22.2 %) and control women (19.8%). Overall, tHcy plasma concentration was higher in TT homozygous compared to other genotypes. We found a menopause-genotype interaction on tHcy levels (p=0.068 for menopause*genotype interaction); overall, the increase of tHcy concentration in TT subjects was limited to pre-menopause (p<0.0001; adjusted p=0.024), and this was confirmed after considering diabetic and control women separately (p=0.001 and p=0.01, respectively). At multivariate analysis, menopause was an independent correlate of tHcy concentration, together with creatinine, folate and MTHFR genotype. Our data show that menopause has a strong influence on tHcy concentration even in Type 2 diabetic women and demonstrate, for the first time, that it may modulate the association between tHcy and the common MTHFR polymorphism both in diabetic and non-diabetic women.

Measuring subclinical atherosclerosis: is homocysteine relevant?

OBJECTIVES

We systematically reviewed published studies looking at the relationship between total serum homocysteine (tHcy) and subclinical markers of atherosclerosis, such as carotid intimal-medial thickness (C-IMT), coronary artery calcium (CAC) and ankle-brachial index (ABI) in asymptomatic individuals. We analyzed these studies to examine this relationship as well as to guide future avenues of investigation by identifying studies that will help in the inclusion of tHcy levels in current guidelines on atherosclerotic disease management.

BACKGROUND

tHcy has been known to be associated with clinically evident atherosclerotic disease. However, tHcy is not incorporated in current guidelines for diagnosis of subclinical disease in high-risk asymptomatic individuals.

METHODS

We searched online databases (e.g., PUBMED, MEDLINE) for published articles assessing the relationship between tHcy and C-IMT, CAC and ABI. We limited the studies to asymptomatic populations, and excluded any study including symptomatic patients or individuals with a history of coronary, peripheral or cerebrovascular disease.

RESULTS

A systemic review of 19 articles revealed a significant association between elevated levels of tHcy and subclinical markers of atherosclerosis in asymptomatic individuals in most studies. Mean tHcy levels were consistently found to be higher in men compared to women. A total of 12 studies showed a significant association between tHcy and other risk markers of atherosclerosis, even after adjusting for age, sex and conventional risk factors. There were seven studies in unique populations that showed no significant relationship. We also observed that studies lowering baseline tHcy levels did not lead to an improvement in C-IMT, CAC or ABI scores. This might indicate that tHcy has a stronger role as a marker of atherosclerotic disease than as a risk factor for the same.

CONCLUSIONS

Based on our review, we conclude that there is a significant association between the subclinical atherosclerotic process and tHcy, and it shows potential as a cheap marker for risk stratification of asymptomatic patients. However, future studies further elucidating this association and elaborating the exact role of tHcy in the atherosclerotic disease process are required. The results of these studies suggest the incorporation of plasma tHcy levels in future risk reduction protocols for identification of individuals at higher risk of atherosclerotic events, and thus to categorize them for more aggressive treatment with established preventive and therapeutic measures.

Effect of folic acid in women with and without insulin resistance who have hyperhomocysteinemic polycystic ovary syndrome

OBJECTIVE

To study the effect of folic acid on homocysteine (Hcy) levels in women with insulin resistance and polycystic ovary syndrome (PCOS) in a prospective clinical trial.

METHOD

Of 210 women with PCOS, 70 were hyperhomocysteinemic; and of these, 32 were insulin resistant and 38 were not. The 70 women were treated with folic acid for 3 months. Baseline and serum levels of Hcy and insulin were measured in both groups.

RESULTS

In both groups Hcy concentrations were significantly decreased following folic acid supplementation. The mean+/-SD levels before and after treatment were 14.03+/-1.5 micromol/L and 12.53+/-1.72 micromol/L in group 1 (P<0.001), and they were 12.07+/-0.87 micromol/L and 8.83+/-0.78 micromol/L in group 2 (P<0.001).

CONCLUSION

The Hcy levels of hyperhomocysteinemic women with PCOS were reduced after 3 months of folic acid supplementation, and the rate of reduction was higher among women without insulin resistance. No change was found in fasting insulin levels.

Homocysteine metabolism in diabetes

An increase in the plasma level of Hcy (homocysteine), an intermediate in the catabolism of methionine, has been identified as a risk factor for many diseases including CVD (cardiovascular disease). CVD is the major cause of death in patients with diabetes mellitus. Therefore the study of Hcy metabolism in diabetes mellitus has been a major focus of current research. Studies conducted in our laboratory were able to show that in both Type 1 and Type 2 diabetes with no renal complications, the plasma Hcy levels were lower than in controls. In Type 1 diabetes, increased activities of the trans-sulfuration enzymes were the major cause for the reduction in plasma Hcy. In Type 2 diabetes, BHMT (betaine:homocysteine methyltransferase) was also observed to play a major role in the increased catabolism of Hcy in addition to the trans-sulfuration enzymes. We were also able to demonstrate the direct effect of insulin and the counter-regulatory hormones on the regulation of cystathionine beta-synthase and BHMT, which accounts for the changes in the activities of these two enzymes seen in diabetes mellitus.

Relation of plasma homocysteine levels to atherosclerotic vascular disease and inflammation markers in type 2 diabetic patients

OBJECTIVE

Both hyperhomocysteinemia and increased inflammatory activity are shown to be associated with atherosclerosis. The relation of inflammatory activity to homocysteine (Hcy) levels is not well established. In the present study, we aimed to evaluate the relation of plasma Hcy levels to atherosclerotic vascular disease and inflammatory activity in type 2 diabetic patients.

DESIGN AND METHODS

In total 90 type 2 diabetic patients were included in the study. Of these patients, 41 had established atherosclerotic vascular disease and 49 had no evidence of atherosclerotic vascular disease. Hcy levels and markers of inflammation, namely C-reactive protein, fibrinogen, erythrocyte sedimentation rate, interleukin-6, and tumor necrosis factor alpha (TNFalpha), were measured. Glucose regulation, C-peptide, lipid parameters, and renal functions were also studied.

RESULTS

Both Hcy levels and inflammation markers were all significantly elevated in patients with atherosclerotic vascular disease when compared with patients without vascular disease. Reduced renal functions were responsible for the majority of Hcy elevation in patients with vascular disease. Also, renal functions were significantly associated with both Hcy levels and inflammatory markers. There was no correlation between Hcy levels and inflammation markers except for TNFalpha.

CONCLUSIONS

Inflammatory activity and Hcy levels are increased in type 2 diabetic patients with atherosclerotic vascular disease. Impairment of renal functions is the key factor that affects both Hcy levels and inflammation markers. Inflammation is not involved in the process by which Hcy leads atherosclerosis in type 2 diabetes.

Serum gamma-glutamyl transferase is associated with plasma total homocysteine in Japanese patients with type 2 diabetes

Serum gamma-glutamyl transferase (gamma-GT), a marker of oxidative stress, predicts morbidity and mortality from cardiovascular disease. Plasma total homocysteine (tHcy), a pro-oxidant and also an independent risk factor for cardiovascular disease, correlates with gamma-GT among some populations. It is not known whether tHcy correlates with gamma-GT among type 2 diabetic patients in whom oxidative stress is increased and implicated for the development of diabetic complications. In the present study, we analyzed the association between gamma-GT, tHcy and related vitamins cross-sectionally among patients with type 2 diabetes without overt nephropathy (age range 17-76 years; n = 110). In a univariate regression analysis model, gamma-GT (logarithm) was positively associated with tHcy (beta = 0.288, P = 0.002) but not with folate or vitamin B(12). The association between tHcy and gamma-GT (logarithm) remained significant in a multivariate analysis model including age, lifestyle factors, folate, vitamin B(12), creatinine, HbA(1c) and medical history (beta = 0.219, P = 0.027). These results suggest that tHcy generates oxidative stress among type 2 diabetic patients and may partly explain the reported association between gamma-GT and cardiovascular disease.

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.

Cardiac synchronous and dys-synchronous remodeling in diabetes mellitus

Glucose-mediated impairment of homocysteine (Hcy) metabolism and decrease in renal clearance contribute to hyperhomocysteinemia (HHcy) in diabetes. The Hcy induces oxidative stress, inversely relates to the expression of peroxisome proliferators activated receptor (PPAR), and contributes to diabetic complications. Extracellular matrix (ECM) functionally links the endothelium to the myocyte and is important for cardiac synchronization. However, in diabetes and hyperhomocysteinemia, a "disconnection" is caused by activated matrix metalloproteinase with subsequent accumulation of oxidized matrix (fibrosis) between the endothelium and myocyte (E-M). This contributes to "endothelial-myocyte uncoupling," attenuation of cardiac synchrony, leading to diastolic heart failure (DHF), and cardiac dys-synchronizatrion. The decreased levels of thioredoxin and peroxiredoxin and cardiac tissue inhibitor of metalloproteinase are in response to antagonizing PPARgamma.

Homocysteine and vitamin B(12) concentrations and mortality rates in type 2 diabetes

OBJECTIVE

To assess the role of homocysteine as a risk factor for mortality in diabetic subjects.

METHODS

Homocysteine, vitamin B(12), and folate concentrations were measured in stored sera of 396 diabetic Pima Indians aged > or = 40 years when examined between 1982 and 1985. Vital status was assessed through 2001.

RESULTS AND CONCLUSIONS

Over a median follow-up of 15.7 years, there were 221 deaths-76 were due to cardiovascular disease (CVD), 36 to diabetes/nephropathy and 34 to infections. Homocysteine was positively associated with mortality from all causes (hazard rate ratio (HRR) for highest versus lowest tertile of homocysteine = 1.70, 95% confidence interval (CI) 1.18-2.46), from diabetes/nephropathy (HRR = 2.39, 95% CI 0.94-6.11) and from infectious diseases (HRR = 3.39, 95% CI 1.19-9.70), but not from CVD (HRR = 1.16, 95% CI 0.62-2.17) after adjustment for age, sex and diabetes duration. Homocysteine correlated with serum creatinine (r = 0.50), and the relationships with mortality rates were not significant after adjustment for creatinine. Vitamin B(12) was positively associated with all-cause mortality (HRR for 100 pg/mL difference adjusted for age, sex and diabetes duration = 1.15, 95% CI 1.08-1.22) and death from diabetes/nephropathy (HRR = 1.27, 95% CI 1.10-1.46). The association between homocysteine and mortality in type 2 diabetes is not causal, but is confounded by renal disease in Pima Indians.

Plasma homocysteine and polycystic ovary syndrome: the missed link

OBJECTIVE

The objective was to investigate the relationship between insulin resistance and increased serum homocysteine in women with polycystic ovarian syndrome (PCOS).

DESIGN

Prospective controlled trial.

SETTING

Department of Obstetrics & Gynecology, Mansoura Faculty of Medicine, Mansoura, Egypt.

PATIENTS

Ninety PCOS women as a study group and 35 women with infertility due to other causes as a control group.

OUTCOME MEASURES

Serum homocysteine levels in the presence and absence of insulin resistance in PCOS patients.

RESULTS

Homocysteine levels were significantly higher in PCOS patients than in the controls. Considering 11 micromol/l as the cut-off level for a normal homocysteine level, 41.1% of PCOS patients (37 out of 90) and 2.9% of control group (1 out of 35) had high homocysteine levels. With regard to insulin resistance, 23% of PCOS patients without insulin resistance (9 out of 39) had a high homocysteine level, while 47% of PCOS patients with insulin resistance (24 out of 51) had this, thus demonstrating the effect of insulin resistance on the homocysteine level.

CONCLUSION

There is a strong association between serum homocysteine and insulin resistance in women with PCOS that contributes to the long-term complications of PCOS.

Progressive glycosylation of albumin and its effect on the binding of homocysteine may be a key step in the pathogenesis of vascular damage in diabetes mellitus

The majority of diabetes research to date has rightly focussed on the direct effects of hyperglycaemia on tissues and a number of theories relating to the pathogenesis of vascular disease have been proposed. This research is important as until methods are found to achieve glycaemic control in all diabetic patients, prophylactic interventions to prevent vasculopathy will be required. One of the major blood proteins, human albumin is known to be covalently modified by extended incubation with glucose, leading to an impairment of ligand binding. One of the important ligands bound by albumin is homocysteine. There is increasing and compelling clinical, experimental and epidemiological evidence that homocysteine, and in particular the free unbound fraction, is vasculotoxic. If homocysteine binding to albumin is impaired by increasing glycosylation of albumin then either drugs which reduce homocysteine levels (pyridoxine, folic acid and cobalamin) or inhibit glycosylation (aminoguanidines) may be of benefit in the prevention of vascular damage in diabetic patients.