Effects of cilostazol on thrombospondin-1 (TSP-1) expression changes in the myocardium of diabetic rats

Adenosine Monophosphate-Activated Protein Kinase (AMPK) as a New Target for Antidiabetic Drugs: A Review on Metabolic, Pharmacological and Chemical Considerations

In view of the epidemic nature of type 2 diabetes and the substantial rate of failure of current oral antidiabetic drugs the quest for new therapeutics is intensive. The adenosine monophosphate-activated protein kinase (AMPK) is an important regulatory protein for cellular energy balance and is considered a master switch of glucose and lipid metabolism in various organs, especially in skeletal muscle and liver. In skeletal muscles, AMPK stimulates glucose transport and fatty acid oxidation. In the liver, it augments fatty acid oxidation and decreases glucose output, cholesterol and triglyceride synthesis. These metabolic effects induced by AMPK are associated with lowering blood glucose levels in hyperglycemic individuals. Two classes of oral antihyperglycemic drugs (biguanidines and thiazolidinediones) have been shown to exert some of their therapeutic effects by directly or indirectly activating AMPK. However, side effects and an acquired resistance to these drugs emphasize the need for the development of novel and efficacious AMPK activators. We have recently discovered a new class of hydrophobic D-xylose derivatives that activates AMPK in skeletal muscles in a non insulin-dependent manner. One of these derivatives (2,4;3,5-dibenzylidene-D-xylose-diethyl-dithioacetal) stimulates the rate of hexose transport in skeletal muscle cells by increasing the abundance of glucose transporter-4 (GLUT-4) in the plasma membrane through activation of AMPK. This compound reduces blood glucose levels in diabetic mice and therefore offers a novel strategy of therapeutic intervention strategy in type 2 diabetes. The present review describes various classes of chemically-related compounds that activate AMPK by direct or indirect interactions and discusses their potential for candidate antihyperglycemic drug development.

The renal protective effects of cilostazol on suppressing pathogenic thrombospondin-1 and transforming growth factor-beta expression in streptozotocin-induced diabetic rats

Diabetic nephropathy is a major complication facing patients with diabetes mellitus. The renal protective effects of the phosphodiesterase III inhibitor, cilostazol, were investigated in rats with streptozotocin-induced diabetes. Expression of thrombospondin-1 (TSP-1) and transforming growth factor-beta (TGF-beta) in the kidney was measured by immunohistochemistry and real-time reverse transcription-quantitative polymerase chain reaction analysis in diabetic rats, cilostazol-treated diabetic rats and control rats. Ultrastructural changes in the kidney were also analysed using microscopy. Four weeks after the induction of diabetes, TSP-1 and TGF-beta expression was significantly increased in the kidneys of diabetic rats compared with the control and was significantly lower in cilostazol-treated diabetic rats than in the untreated diabetic rats. Microscopy revealed characteristic renal pathology in the diabetic group, which was rarely seen in the cilostazol-treated diabetic rats. In conclusion, this study indicates that cilostazol treatment of diabetic rats effectively prevents pathological kidney changes, possibly via the down-regulation of TSP-1 and TGF-beta expression compared with untreated rats.