Wound healing impairment is increasingly recognized to be a consequence of hyperglycemia-induced dysfunction of endothelial precursor cells (EPCs) in type 2 diabetes mellitus (T2DM). Metformin exhibits potential for the improvement of endothelial function and the wound healing process. However, the underlying mechanisms for the observed beneficial effects of metformin application remain to be completely understood. The present study assessed whether metformin, a widely used therapeutic drug for T2DM, may accelerate wound closure in T2DM db/db mice. Genetically hyperglycemic db/db mice were used as the T2DM model. Metformin (250 mg/kg/day; intragastric) was administered for two weeks prior to EPC collection and wound model creation in db/db mice. Wound healing was evaluated by alterations in the wound area and the number of platelet endothelial cell adhesion molecule-positive cells. The function of the isolated bone marrow-derived EPCs (BM-EPCs) was assessed by a tube formation assay. The number of circulating EPCs, and the levels of intracellular nitric oxide (NO) and superoxide (O2−) were detected by flow cytometry. Thrombospondin-1 (TSP-1) expression was determined by western blot analysis. It was observed that treatment with metformin accelerated wound healing, improved angiogenesis and increased the circulating EPC number in db/db mice. In vitro, treatment with metformin reversed the impaired BM-EPC function reflected by tube formation, and significantly increased NO production while decreasing O2− levels in BM-EPCs from db/db mice. In addition, TSP-1 expression was markedly attenuated by treatment with metformin in cultured BM-EPCs. Metformin contributed to wound healing and improved angiogenesis in T2DM mice, which was, in part, associated with stimulation of NO, and inhibition of O2− and TSP-1 in EPCs from db/db mice.

Proliferation of human retinal endothelial cells (HRECs) is an important event in the development of diabetic retinopathy. Glucose fluctuations are strong predictor of diabetic vascular complications. In this study we have investigated the effect of intermittent high glucose on proliferation and expression of vascular endothelial growth factor (VEGF) in HRECs. The possible involvement of mitochondrial reactive oxygen species (ROS) was assessed. HRECs were incubated for 72 h in media containing different glucose concentrations: 5, 25, 5 mmol/l alternating with 25 mmol/l glucose, with or without Mn(III)tetrakis(4-benzoic acid) porphyrin chloride (MnTBAP) and thenoyltri-fluoroacetone (TTFA). The cell proliferation, VEGF expression, mitochondrial ROS, nitrotyrosine and 8-hydroxydeoxyguanosine (8-OHdG) were measured. In cultured HRECs, treatment with constant or intermittent high glucose significantly increased [(3)H]thymidine incorporation in a time-dependent manner. Treatment with constant high glucose for 48 h resulted in significant increases in [(3)H]thymidine incorporation, mRNA and protein levels of VEGF compared with HRECs treated with the normal glucose, which were markedly enhanced in cells exposed to intermittent high glucose. The levels of mitochondrial ROS, nitrotyrosine and 8-OhdG were significantly elevated under both intermittent and constant high glucose conditions, the effect being greater under intermittent high glucose. In addition, the antioxidants MnTBAP or TTFA can effectively prevent cell proliferation and overexpression of VEGF, as well as overproduction of mitochondrial ROS, nitrotyrosine and 8-OhdG in HRECs induced by constant or intermittent high glucose. Intermittent high glucose enhances cell proliferation and overexpression of VEGF through reactive oxygen species (ROS) overproduction at the mitochondrial transport chain level in HRECs, indicating that glycemic variability have important pathological effects on the development of diabetic retinopathy dependent of mitochondrial ROS.

These results indicate that methylglyoxal-induced insulin resistance and salt sensitivity at least in part by increasing oxidative stress and/or AGEs formation in Sprague-Dawley rats. The present study provides further evidence for methylglyoxal as one of the causative factors in the pathogenesis of insulin resistance and salt-sensitive hypertension.

Genetic variants of FTO and MC4R have been linked with obesity and T2DM in populations of Europeans. In this study, we have investigated the association of FTO rs9939609 and MC4R rs17782313 with obesity and T2DM in the Chinese population and analyzed the relationship between rs9939609 and rs17782313. 2351 individuals were recruited. We tested the rs9939609 and rs17782313 by sequences retrieval method. Clinical and biochemical characteristics were measured. The rs9939609 per-A allele and rs17782313 per-C allele increases of OR for obesity was 1.42 (95% CI 1.39-3.74) and 1.39 (95% CI 1.21-3.53).The genotypic OR for obesity was 1.92 (95% CI 1.81-4.67) for AA genotype, 1.71 (95% CI 1.47-4.54) for AT genotype, 1.87 (95% CI 1.72-4.00) for CC genotype, and 1.44 (95% CI 1.20-3.18) for CT genotype. BMI of participants carrying neither FTO nor MC4R risk allele was 25.9 ± 4.9, one risk allele was 26.4 ± 5.1, two risk alleles was 28.1 ± 5.5, and there or four risk alleles was 33.2 ± 6.3. We found no association between FTO and MC4R and the Chinese population with T2DM (P > 0.05). Our data support that the rs9939609 and rs17782313 are strongly associated with obesity and BMI. Their combined effects were significant in Chinese population. No association between FTO and MC4R and Chinese population with T2DM was found.

Elevated circulating concentrations of interleukin-18 (IL-18), monocyte chemoattractant protein-1 (MCP-1), and plasminogen activator inhibitor-1 (PAI-1) and decrease of adiponectin are associated with obesity-related diseases. The mechanism that mediates the aberrant production of the adipokines remains poorly understood. The aim of this study was to investigate the effect of intermittent high glucose on the expression of IL-18, MCP-1, and PAI-1 and adiponectin in 3T3-L1 adipocytes. 3T3-L1 adipocytes were incubated for 24 h in media containing different glucose concentrations: 5 mmol/l, 20 mmol/l and a daily alternating 5 or 20 mmol/l glucose, with or without the addition of1.0 mmol/l N-acetylcysteine (NAC). The expression and secretion of IL-18, MCP-1, PAI-1, and adiponectin were determined by real-time RT-PCR and ELISA, respectively.The production of reactive oxygen species (ROS) and 8-hydroxydeoxyguanosine(8-OHdG) were measured. Stable high glucose significantly increased expression and secretion of IL-18, MCP-1, and PAI-1, and reduced adiponectin expression and secretion compared to normal glucose conditions.These effects were significantly greater under intermittent high glucose conditions compared to stable high glucose. The level of ROS and 8-OHdG were significantly elevated under both intermittent and stable high glucose conditions, the effect being greater under intermittent high glucose. The intermittent glucose was more effective in triggering the generation of ROS than stable high glucose. The adding of the NAC, aspecific pharmacological inhibitor of ROS, normalized the expression of these adipokines and the levels of ROS and 8-OHdG under both stable and intermittent glucose conditions.Intermittent high glucose induces a greater aberrant production of key adipokines than stable high glucose, and this effect seems to be related to over-production of ROS.