A comparative study of the glycemic control of various antidiabetic agents and the role of homocysteine in the therapy of type 2 diabetes mellitus

Folic acid effect on homocysteine, sortilin levels and glycemic control in type 2 diabetes mellitus patients

Aim

The present study aimed to determine the folic acid supplement (FAS) effects on serum homocysteine and sortilin levels, glycemic indices, and lipid profile in type II diabetic patients.

Method

A double-blind randomized controlled clinical trial have been performed on 100 patients with T2DM randomly divided into two groups that received either placebo or folic acid 5 mg/d for 12 weeks.

Results

FAS caused a significant decrease in homocysteine and sortilin serum levels (28.2% and 33.7%, P < 0.0001, respectively). After 3 months of intervention, 8.7% decrease in fasting blood glucose (P = 0.0005), 8.2% in HbA1c (P = 0.0002), 13.7% in serum insulin (P < 0.0001) and 21.7% in insulin resistance (P < 0.0001) were found in the folic acid group, however no significant difference was observed in the placebo group. Serum hs-CRP level showed significant positive associations with sortilin (r = 0.237, P = 0.018), homocysteine (r = 0.308, P = 0.002) and fasting blood glucose (r = 0.342, P = 0.000). There were no significant changes in lipid profile in both groups after 12 weeks.

Conclusion

FAS might be beneficial for reducing homocysteine and sortilin levels, enhancing glycemic control, and improved insulin resistance in patients with T2DM.

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.

Vascular Effects of Avocado Seed Glycosides during Diabetes-induced Endothelial Damage

BACKGROUND AND OBJECTIVES

The relationship between vascular damage and diabetes mellitus was exploited using avocado seed extracts. The purpose of the study was to understand the therapeutic relevance of glycosides compared to standard vascular and anti-diabetic drugs. Constituent Avocado Seed Glycosides (ASG) were analysed and administered to rats with Diabetes-Induced Vascular Damage (DIVD).

METHODS

The rats were first administered with streptozotocin and screened after seven days for alterations in blood glucose, insulin, vascular cell adhesion molecule (VCAM-1), Von Willebrand factor (VWF), Renin-Angiotensin-Aldosterone System (RAS), eNOx, and endothelin-1 (ET-1). Only rats that satisfied these criteria were recruited and treated with either glibenclamide, met.su + losart, or 200 mg/kg body weight ASG for 28 days.

RESULTS

There was an abundance of digitoxin (13.41 mg/100g), digoxin (17.98 mg/100g), avicularin (165.85 mg/100g), and hyperoside (282.51 mg/100g). ASG or met.su + losart exhibited slight modulatory properties on glucose homeostasis. Rats with DIVD showed elevated renin, angiotensin, VCAM-1 and Lp-PLA2 levels but slightly decreased with glibenclamide treatment and normalized with ASG or met.su + losart administration. All treatments normalized Hcy levels. DIVD caused the overproduction of CnT, LDH, Crt-K, LDL-c, TG, and TC and suppressed HDL-c but was completely normalized by the ASG. Water intake remained altered in treated rats.

CONCLUSION

The ASG had no relevant effect on glucose homeostasis during DIVD but showed significant vasoprotective properties.

Metformin Treatment and Homocysteine: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

The aim of this systematic review is to assess whether metformin could change the concentration of serum homocysteine (Hcy) with and without simultaneous supplementation of B-group vitamins or folic acid. A literature search was conducted in PubMed, EmBase, and Cochrane Central Register of Controlled Trials (CENTRAL) to identify randomized controlled trials (RCTs) reporting the concentration of serum Hcy in metformin-treated adults. Meta-analysis was applied to assess the association between metformin and the changes of Hcy concentration. Twelve publications were included in this study. In the overall analysis, metformin administration was not statistically associated with the change of Hcy when compared with the control treatment (mean difference (MD), 0.40 μmol/L; 95% confidence interval (CI), -0.07~0.87 μmol/L, p = 0.10). In the subgroup analysis, metformin was significantly associated with an increased concentration of Hcy in the absence of exogenous supplementation of folic acid or B-group vitamins (MD, 2.02 μmol/L; 95% CI, 1.37~2.67 μmol/L, p < 0.00001), but with a decreased concentration of serum Hcy in the presence of these exogenous supplementations (MD, -0.74 μmol/L; 95% CI, -1.19~-0.30 μmol/L, p = 0.001). Therefore, although the overall effect of metformin on the concentration of serum Hcy was neutral, our results suggested that metformin could increase the concentration of Hcy when exogenous B-group vitamins or folic acid supplementation was not given.

Effect of folic acid supplementation on biochemical indices in overweight and obese men with type 2 diabetes

AIMS

This study performed to determine the effects of folate supplementation on indices of glycemic control, insulin resistance and lipid profile in overweight and obese men with type 2 diabetes under metformin (at least 1500 mg daily) treatment.

METHODS

The study was a double-blind randomized controlled clinical trial. Forty-eight overweight and obese men (aged 58.2±8.9 years; BMI=28.6±2.9 kg/m(2)) with type 2 diabetes participated in the study. Patients were divided randomly into two groups of folic acid (5 mg/d) and placebo. All patients received the tablets for eight weeks.

RESULTS

Supplementation with folic acid led to 8% decrease in HbA1C (p=0.048), 7.5% in fasting blood glucose (p=0.051), 16.2% in serum insulin (p=0.021), 20.5% in insulin resistance (p=0.041) and 21.2% in plasma homocysteine (p=0.000). A significant increase in serum folate and B12 levels (19% and 17.3%, p=0.000, respectively) were observed in the folic acid group, whereas no significant changes occurred in the placebo group. Also, in the folic acid and placebo groups, there were no significant changes in body weight.

CONCLUSIONS

Folic acid supplementation lowered plasma level of homocysteine, improved glycemic control and insulin resistance in patients with type 2 diabetes.

Risk of fatal and nonfatal lactic acidosis with metformin use in type 2 diabetes mellitus

BACKGROUND

Metformin is an oral anti-hyperglycemic agent that has been shown to reduce total mortality compared to other anti-hyperglycemic agents, in the treatment of type 2 diabetes mellitus. Metformin, however, is thought to increase the risk of lactic acidosis, and has been considered to be contraindicated in many chronic hypoxemic conditions that may be associated with lactic acidosis, such as cardiovascular, renal, hepatic and pulmonary disease, and advancing age.

OBJECTIVES

To assess the incidence of fatal and nonfatal lactic acidosis, and to evaluate blood lactate levels, for those on metformin treatment compared to placebo or non-metformin therapies.

SEARCH STRATEGY

A comprehensive search was performed of electronic databases to identify studies of metformin treatment. The search was augmented by scanning references of identified articles, and by contacting principal investigators.

SELECTION CRITERIA

Prospective trials and observational cohort studies in patients with type 2 diabetes of least one month duration were included if they evaluated metformin, alone or in combination with other treatments, compared to placebo or any other glucose-lowering therapy.

DATA COLLECTION AND ANALYSIS

The incidence of fatal and nonfatal lactic acidosis was recorded as cases per patient-years, for metformin treatment and for non-metformin treatments. The upper limit for the true incidence of cases was calculated using Poisson statistics. In a second analysis lactate levels were measured as a net change from baseline or as mean treatment values (basal and stimulated by food or exercise) for treatment and comparison groups. The pooled results were recorded as a weighted mean difference (WMD) in mmol/L, using the fixed-effect model for continuous data.

MAIN RESULTS

Pooled data from 347 comparative trials and cohort studies revealed no cases of fatal or nonfatal lactic acidosis in 70,490 patient-years of metformin use or in 55,451 patients-years in the non-metformin group. Using Poisson statistics the upper limit for the true incidence of lactic acidosis per 100,000 patient-years was 4.3 cases in the metformin group and 5.4 cases in the non-metformin group. There was no difference in lactate levels, either as mean treatment levels or as a net change from baseline, for metformin compared to non-metformin therapies.

AUTHORS' CONCLUSIONS

There is no evidence from prospective comparative trials or from observational cohort studies that metformin is associated with an increased risk of lactic acidosis, or with increased levels of lactate, compared to other anti-hyperglycemic treatments.

Effects of metformin with or without supplementation with folate on homocysteine levels and vascular endothelium of women with polycystic ovary syndrome

OBJECTIVE

To evaluate whether the administration of metformin exerts any effects on serum homocysteine (Hcy) levels in patients with polycystic ovary syndrome (PCOS) and whether supplementation with folate enhances the positive effects of metformin on the structure and function of the vascular endothelium.

RESEARCH DESIGN AND METHODS

A total of 50 patients affected by PCOS, without additional metabolic or cardiovascular diseases, were enrolled in a prospective nonrandomized placebo-controlled double-blind clinical study. They were grouped into two treatment arms that were matched for age and BMI. Patients were treated with a 6-month course of metformin (1,700 mg daily) plus folic acid (400 microg daily; experimental group, n = 25) or placebo (control group, n = 25). Complete hormonal and metabolic patterns, serum Hcy, folate, vitamin B12, endothelin-1 levels, brachial artery diameter at the baseline (BAD-B) and after reactive hyperemia (BAD-RH), flow-mediated dilation, and intima-media thickness in both common carotid arteries were evaluated.

RESULTS

After treatment, a significant increase in serum Hcy levels was observed in the control group compared with the baseline values and the experimental group. A beneficial effect was observed in the concentrations of BAD-B, BAD-RH, flow-mediated dilation, intima-media thickness, and serum endothelin-1 in both groups. However, the results were improved more significantly in the experimental group than in the control subjects.

CONCLUSIONS

Metformin exerts a slight but significant deleterious effect on serum Hcy levels in patients with PCOS, and supplementation with folate is useful to increase the beneficial effect of metformin on the vascular endothelium.

Risk of fatal and nonfatal lactic acidosis with metformin use in type 2 diabetes mellitus

BACKGROUND

Metformin is an oral anti-hyperglycemic agent that has been shown to reduce total mortality compared to other anti-hyperglycemic agents, in the treatment of type 2 diabetes mellitus. Metformin, however, is thought to increase the risk of lactic acidosis, and has been considered to be contraindicated in many chronic hypoxemic conditions that may be associated with lactic acidosis, such as cardiovascular, renal, hepatic and pulmonary disease, and advancing age.

OBJECTIVES

To assess the incidence of fatal and nonfatal lactic acidosis, and to evaluate blood lactate levels, for those on metformin treatment compared to placebo or non-metformin therapies.

SEARCH STRATEGY

A comprehensive search was performed of electronic databases to identify studies of metformin treatment. The search was augmented by scanning references of identified articles, and by contacting principal investigators.

SELECTION CRITERIA

Prospective trials and observational cohort studies in patients with type 2 diabetes of least one month duration were included if they evaluated metformin, alone or in combination with other treatments, compared to placebo or any other glucose-lowering therapy.

DATA COLLECTION AND ANALYSIS

The incidence of fatal and nonfatal lactic acidosis was recorded as cases per patient-years, for metformin treatment and for non-metformin treatments. The upper limit for the true incidence of cases was calculated using Poisson statistics. In a second analysis lactate levels were measured as a net change from baseline or as mean treatment values (basal and stimulated by food or exercise) for treatment and comparison groups. The pooled results were recorded as a weighted mean difference (WMD) in mmol/L, using the fixed-effect model for continuous data.

MAIN RESULTS

Pooled data from 347 comparative trials and cohort studies revealed no cases of fatal or nonfatal lactic acidosis in 70,490 patient-years of metformin use or in 55,451 patients-years in the non-metformin group. Using Poisson statistics the upper limit for the true incidence of lactic acidosis per 100,000 patient-years was 4.3 cases in the metformin group and 5.4 cases in the non-metformin group. There was no difference in lactate levels, either as mean treatment levels or as a net change from baseline, for metformin compared to non-metformin therapies.

AUTHORS' CONCLUSIONS

There is no evidence from prospective comparative trials or from observational cohort studies that metformin is associated with an increased risk of lactic acidosis, or with increased levels of lactate, compared to other anti-hyperglycemic treatments.