Both type 1 and type 2 diabetes are associated with increased risk of cardiovascular disease. This is in part attributed to the effects of hyperglycemia on vascular endothelial and smooth muscle cells, but the underlying mechanisms are not fully understood. In diabetic animal models, hyperglycemia results in hypercontractility of vascular smooth muscle possibly due to increased activation of Rho-kinase. The aim of the present study was to investigate the regulation of contractile smooth muscle markers by glucose and to determine the signaling pathways that are activated by hyperglycemia in smooth muscle cells. Microarray, quantitative PCR, and Western blot analyses revealed that both mRNA and protein expression of contractile smooth muscle markers were increased in isolated smooth muscle cells cultured under high compared with low glucose conditions. This effect was also observed in hyperglycemic Akita mice and in diabetic patients. Elevated glucose activated the protein kinase C and Rho/Rho-kinase signaling pathways and stimulated actin polymerization. Glucose-induced expression of contractile smooth muscle markers in cultured cells could be partially or completely repressed by inhibitors of advanced glycation end products, L-type calcium channels, protein kinase C, Rho-kinase, actin polymerization, and myocardin-related transcription factors. Furthermore, genetic ablation of the miR-143/145 cluster prevented the effects of glucose on smooth muscle marker expression. In conclusion, these data demonstrate a possible link between hyperglycemia and vascular disease states associated with smooth muscle contractility.Diabetes confers a 2-4-fold excess risk for a wide range of cardiovascular diseases, including macrovascular complications leading to coronary heart disease and ischemic stroke, as well as microvascular diseases, such as nephropathy and retinopathy (1, 2). Based on current trends, the rising incidence of diabetes (expected to reach 333 million people worldwide by 2025) will undoubtedly equate to increased cardiovascular mortality. Chronic hyperglycemia has long been recognized as an independent risk factor for cardiovascular disease (3, 4). Importantly, the progressive relationship between glucose levels and cardiovascular risk extends below the threshold for diabetes diagnosis (fasting plasma glucose Ն7.0 mmol/liter or 2-h plasma glucose Ն11.1 mmol/liter (2, 3)), and more recently, even transient hyper-and hypoglycemia have emerged as important determinants of cardiovascular disease (5). Despite the vast clinical and epidemiological experience linking blood glucose and poor glucose control to the development and progression of cardiovascular disease, the underlying molecular mechanisms leading to vascular dysfunction and disease are poorly understood (6).It has been well established that hyperglycemia results in vascular hyperreactivity in diabetic patients (7) and animal models (8 -10). Part of this effect may be attributed to a decrease in nitric oxide (NO) bioavailability as well as a reduced respon...