The metabolic syndrome is strongly associated with insulin resistance and has been recognized as a cluster of risk factors for cardiovascular diseases such as visceral obesity, hypertension, and diabetes. There is a growing body of evidence to show that nonalcoholic steatohepatitis (NASH) is the hepatic manifestation of insulin resistant patients with the metabolic syndrome. Indeed, insulin resistance increases adipocyte lipolysis and subsequently elevates circulating free fatty acids, thus stimulating the accumulation of fatty acids in the liver (hepatic steatosis). Fatty acids elicit reactive oxygen species generation, thereby promoting disease progression to NASH by both lipid peroxidation and inflammatory cytokine production. Postprandial hyperglycemia, one of the characteristic features of insulin resistance, also induces oxidative stress generation, being involved in dysfunction of pancreatic beta cells and vascular wall cells in the metabolic syndrome. Recently, STOP-NIDDM trial revealed that acarbose (Glucobay®), an α-glucosidase inhibitor, improved postprandial hyperglycemia and subsequently reduced the risk of development of type 2 diabetes and newly diagnosed hypertension in patients with impaired glucose tolerance. In this study, acarbose treatment was also found to reduce body mass index and waist circumference in these patients. Furthermore, a meta-analysis of seven long-term studies has also shown that intervention with acarbose improved triglyceride levels, body weight and systolic blood pressure and subsequently prevented myocardial infarction in type 2 diabetic patients. Since acarbose improves postprandial hyperglycemia by delaying the release of glucose from complex carbohydrates in the absence of an increase in insulin secretion, the beneficial aspects of acarbose could be ascribed to improvement of insulin sensitivity in these patients. Given the pathological link between NASH and insulin resistance, we would like to hypothesize here that acarbose may become a promising therapeutic strategy for the treatment of patients with NASH. Does acarbose treatment improve steatohepatitis histologically? Is the extent of histological improvement by acarbose parallel to that of insulin sensitivity in these patients? Large clinical trials will provide us with more definite information whether acarbose treatment can improve insulin sensitivity and resultantly reduce the risk of progression of liver diseases in patients with NASH.
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