Dehong Cai

Glucagon-like peptide-1 (GLP-1) protects vascular endothelial cells against advanced glycation end products (AGEs) – induced apoptosis

Summary Background The peptide glucagon-like peptide-1 (GLP-1) is a hormone secreted by intestinal L cells in response to food intake. GLP-1 has been proposed as the basis of emerging therapy for patients with type 2 diabetes. However, the effects of GLP-1 on vascular injury in diabetes have not been identified. Advanced glycation end products (AGEs) induce endothelial cell apoptosis and have been implicated in the process of vascular complications from diabetes. Material/Methods The aim of this work was to investigate whether and how GLP-1 protects endothelial cells from apoptosis induced by AGEs. Human umbilical vein endothelial cells (HUVECs) were treated with AGEs (200 μg/mL) for 48 h in the presence or absence of GLP-1. Cell morphology, viability, apoptosis, ratio of Bcl-2 protein to Bax protein, cytochrome c release, and activity of caspase-9 and −3 were determined. Results Treatment of cells with AGEs led to cell morphology changes and decreased cell viability, resulting in apoptosis. GLP-1 alone increased cell viability in a concentration-dependent manner. GLP-1 partially inhibited AGEs-induced apoptosis in HUVECs. GLP-1 increased Bcl-2/Bax ratio, reduced cytochrome c levels in the cytoplasm, and reduced the activity of caspase-9 and −3 in AGEs-treated HUVECs. Conclusions AGEs induces apoptosis via the mitochondrion-cytochrome c-caspase protease pathway, and GLP-1 protects endothelial cells by interfering with this mechanism. GLP-1 may represent an anti-apoptotic agent in the treatment of vascular complications arising from diabetes.

The Cytotoxic Role of Intermittent High Glucose on Apoptosis and Cell Viability in Pancreatic Beta Cells

Objectives. Glucose fluctuations are both strong predictor of diabetic complications and crucial factor for beta cell damages. Here we investigated the effect of intermittent high glucose (IHG) on both cell apoptosis and proliferation activity in INS-1 cells and the potential mechanisms. Methods. Cells were treated with normal glucose (5.5 mmol/L), constant high glucose (CHG) (25 mmol/L), and IHG (rotation per 24 h in 11.1 or 25 mmol/L) for 7 days. Reactive oxygen species (ROS), xanthine oxidase (XOD) level, apoptosis, cell viability, cell cycle, and expression of cyclinD1, p21, p27, and Skp2 were determined. Results. We found that IHG induced more significant apoptosis than CHG and normal glucose; intracellular ROS and XOD levels were more markedly increased in cells exposed to IHG. Cells treated with IHG showed significant decreased cell viability and increased cell proportion in G0/G1 phase. Cell cycle related proteins such as cyclinD1 and Skp2 were decreased significantly, but expressions of p27 and p21 were increased markedly. Conclusions. This study suggested that IHG plays a more toxic effect including both apoptosis-inducing and antiproliferative effects on INS-1 cells. Excessive activation of cellular stress and regulation of cyclins might be potential mechanism of impairment in INS-1 cells induced by IHG.

Prevalence and determinants of hyperuricemia in type 2 diabetes mellitus patients with central obesity in Guangdong Province in China

This study investigated the prevalence and determinants of hyperuricemia in Chinese type 2 diabetes mellitus (T2DM) patients with central obesity. A multicentric hospital-based cross-sectional study was carried out in Guangdong Province between August 2011 and March 2012. At each hospital, Chinese T2DM patients with central obesity who were aged over 20 years, whose serum uric acid levels were measured, and who had lived in Guangdong Province for >=1 year, were recruited. Hyperuricemia was defined as serum uric acid >420 μmol/L in men and >360 μmol/L in women. Binary logistic regression was used to assess associated risk factors for hyperu-ricemia. A total of 2,917 T2DM patients with central obesity took part. The overall prevalence of hyperuricemia was 32.6% (36.1% for women, 28.4% for men). Binary logistic regression analyses demonstrated that women (OR: 1.576; 95% confidence interval (CI): 1.231, 2.018), high BMI (OR: 1.228; 95% CI: 1.094, 1.379), waist cir-cumference (OR: 1.135; 95% CI: 1.009, 1.276), hypertension (OR: 1.603; 95% CI: 1.263, 2.035), high total cho-lesterol (OR: 1.133; 95% CI: 1.002, 1.281), triglycerides (OR: 1.134; 95% CI: 1.069, 1.203), low HDL-cholesterol (OR: 0.820; 95% CI: 0.677, 0.995) and low estimated glomerular filtration rate (OR: 0.840; 95% CI: 0.815, 0.866) were risk factors associated with hyperuricemia. Hyperuricemia is prevalent in Chinese T2DM patients with central obesity and is significantly positively associated with women, cardiovascular risk factors such as obesity, hypertension and dyslipidemia, and low eGFR.

Effects of Pro12Ala polymorphism in peroxisome proliferator-activated receptor-γ2 gene on metabolic syndrome risk: A meta-analysis

BACKGROUND Associations between peroxisome proliferator-activated receptor γ2 (PPARγ2) gene polymorphism and metabolic syndrome risk remained controversial and ambiguous. Thus, we performed a meta-analysis to assess the association between Pro12Ala polymorphism in PPARγ2 gene and metabolic syndrome susceptibility. METHODS An electronic literature search was conducted on Medline, OVID, Cochrane Library database, and the China National Knowledge Internet up to March 2013. Odds ratios (ORs) with 95% confidence intervals (CIs) were used to calculate the strength of association in the fixed or random effects model. RESULTS Ten studies involving a total of 4456 cases and 10343 controls were included in this meta-analysis. No statistical evidence of association was found between Pro12Ala polymorphism and metabolic syndrome risk in all genetic models (homozygote model: OR=0.83, 95% CI=0.62-1.12; heterozygote model: OR=1.04, 95% CI=0.94-1.14; dominant model: OR=1.02, 95% CI=0.93-1.12; recessive model: OR=0.83, 95% CI=0.62-1.11). No statistical evidence of significant association was observed when stratified by ethnicity, definition of metabolic syndrome, source of control groups and quality score of the selected articles. All in all, the results did not support a major role of the Pro12Ala variant of the PPARγ2 gene in metabolic syndrome risk. CONCLUSIONS This meta-analysis suggested that the effect of Pro12Ala polymorphism in PPARγ2 gene may not be related to metabolic syndrome as an entity. However, Pro12Ala may affect the single component of metabolic syndrome. A large, well designed study is required to more adequately assess the role for Pro12Ala polymorphism on metabolic syndrome.

Lipopolysaccharide-induced apoptosis in a murine intestinal endocrine cell line by modulation of Bcl-2, Bax and caspase-3

Numerous studies have focused on how to modulate the secretion of glucagon-like peptide 1 (GLP-1) due to its marked anti-diabetic function. However, few studies have investigated the apoptosis of enteroendocrine L cells, which secrete GLP-1. The aim of this study was to determine whether lipopolysaccharide (LPS), a gut bacterial product, is capable of inducing apoptosis in the intestinal endocrine cell line STC-1. We found that LPS is capable of reducing the viability of STC-1 cells in a concentration-dependent manner. annexin V/propidium iodide (PI) double staining detected by fluorescence microscopy and flow cytometry revealed a strong apoptosis-inducing ability for LPS in STC-1 cells. Furthermore, western blotting revealed that exposure to LPS significantly decreased the expression of Bcl-2 and increased the expression of Bax and caspase-3. In conclusion, LPS induced the apoptosis of STC-1 cells in a dose-dependent manner, which may be responsible for the reduced secretion of GLP-1 in diabetes.

Cardiometabolic risk profiles associated with chronic complications in overweight and obese type 2 diabetes patients in South China.

Background Type 2 diabetes is often accompanied by altered cardiometabolic risk profiles, including abdominal obesity, hypertension, and dyslipidaemia. The association of altered cardiometabolic risk profiles with chronic complications of diabetes is not well investigated. Methods We recruited 2954 type 2 diabetes patients with a body mass index ≥25 kg/m2 who visited the diabetes clinics of 62 hospitals in 21 cities in Guangdong province of China from August 2011 to March 2012. Demographic characteristics, personal and family medical histories, and data on chronic complications of diabetes were collected. Clinical examinations and laboratory assessment were conducted. Results Abdominal obesity was found in 91.6% of the study population, elevated blood pressure in 78.3%; elevated serum triacylglycerols in 57.8%, and reduced serum HDL-C in 55.9%. Among the cardiometabolic risk factors, elevated blood pressure was significantly associated with almost all the chronic complications of diabetes. After adjusting for age, gender, duration of diabetes, and HbA1c, elevated blood pressure was significantly associated with diabetic retinopathy (OR 1.63, 95% CI: 1.22–2.19), diabetic nephropathy (OR 3.16, 95% CI: 2.25–4.46), cardiovascular disease (OR 2.71, 95% CI: 1.70–4.32), and stroke (OR 1.90, 95% CI: 1.15–3.12). Abdominal adiposity was significantly associated with diabetic nephropathy (OR 1.39, 95% CI: 1.11–1.74). Elevated triacylglycerols was significantly associated with diabetic retinopathy (OR 1.29, 95% CI: 1.05–1.58) and diabetic nephropathy (OR 1.30, 95% CI: 1.05–1.58). Reduced HDL-C was significantly associated with stroke (OR 1.41, 95% CI: 1.05–1.88). Conclusions Altered cardiometabolic risk profiles, and elevated blood pressure in particular, were significantly associated with chronic complications in overweight and obese patients with type 2 diabetes. Future studies on the prevention of chronic complications of diabetes might make lowering blood pressure a primary target.

The performance of a diabetic retinopathy risk score for screening for diabetic retinopathy in Chinese overweight/obese patients with type 2 diabetes mellitus.

Abstract Introduction. Diabetic retinopathy (DR) is a common chronic microvascular diabetic complication. The presence of DR may indicate microcirculatory dysfunction in other organ systems besides visual morbidity. The objective of this study was to develop a simple diabetic retinopathy risk score to identify DR in Chinese overweight/obese patients with type 2 diabetes mellitus (T2DM). Patients and methods. A multicentre hospital-based cross-sectional study was carried out in Guangdong Province between August 2011 and March 2012. The evaluated 2699 patients included 1263 males and 1436 females, with an average age of 59.4 ± 13.0 years. Results. The diabetic retinopathy risk score was conducted by age, duration of DM, history of antihypertensive drug treatment, and waist circumference. The area under the receiver operating characteristics curve for DR was 0.700 (95% CI 0.671–0.729). Comparing Youdens index of different values, the optimal cut-off point was 20 to predict DR. The odds ratio for one unit increase in the diabetic retinopathy risk score associated with the risk of DR was 1.104 (95% CI 1.089–1.120). Conclusions. Our data suggest that the diabetic retinopathy risk score could be a reliable primary screening tool for the presence of DR in Chinese overweight/obese patients with T2DM.

Cutoff value of HbA1c for predicting diabetes and prediabetes in a Chinese high risk population aged over 45.

OBJECTIVE To evaluate the cutoff value of HbA1c for predicting diabetes and prediabetes in a Chinese high risk population aged over 45. METHODS A total of 619 people aged over 45 without diabetes were randomly recruited to complete Finnish Diabetes Risk Score (FINDRISC) questionnaire. 208 high-risk individuals (defined by Diabetes Risk Score >=9) had OGTT and HbA1c determined at the same time. RESULTS In a Chinese population aged over 45, the best cutoff value of HbA1c for detecting diabetes and prediabetes was 5.8% and 5.4% respectively. The area under the receiver operating characteristic (AUROC) curve of HbA1c for detecting diabetes was 0.85 (95% CI: 0.80-0.90) and prediabetes was 0.62 (95% CI: 0.54-0.70). The combined use of HbA1c and fasting blood glucose (FPG) had larger AUROC than HbA1c alone (0.88, 95%CI: 0.83-0.92 in detecting diabetes vs 0.75, 95% CI: 0.67-0.82 in prediabetes), and had a higher sensitivity in predicting diabetes and higher specificity and positive predictive value (PPV) in predicting prediabetes. However, the AUROC between HbA1c alone and combined use in predicting diabetes was not significantly different (p=0.173). CONCLUSIONS FINDRISC is feasible tool to screen people who are at high risk of diabetes. The cutoff values of HbA1c to diagnose diabetes and prediabetes in a Chinese high risk population aged over 45 were 5.8% and 5.4%, respectively. The sensitivity and specificity of HbA1c for detecting diabetes and prediabetes was relatively low, so that the combined use of HbA1c and FPG may be more effective in prediction.