New oral therapies for type 2 diabetes mellitus: The glitazones or insulin sensitizers

Type 2 diabetes mellitus is a growing problem not only in the United States but also across the world. There is now strong evidence that intensive control of blood glucose can significantly reduce and retard the microvascular complications of retinopathy, nephropathy, and neuropathy. Ultimately however, up to 80% of type 2 diabetics die from macrovascular cardiovascular disease. This increased incidence of atherosclerotic disease is intricately associated with insulin resistance, which is a major pathophysiologic abnormality in type 2 diabetes. There is strong evidence that insulin resistance is involved in the development of not only hyperglycemia, but also dyslipidemia, hypertension, hypercoagulation, vasculopathy, and ultimately atherosclerotic cardiovascular disease. This cluster of metabolic abnormalities has been termed the insulin resistance or cardiovascular dysmetabolic syndrome. The thiazolidinediones (rosiglitazone and pioglitazone), a new class of oral antidiabetic agents, are insulin sensitizers and exert direct effects on the mechanisms of insulin resistance. These effects not only improve insulin sensitivity and glycemic control with reduced insulin requirements, but also have potentially favorable effects on other components of the cardiovascular dysmetabolic syndrome. Long-term studies are needed to determine whether the insulin-sensitizing effects of the glitazones can prevent or delay premature atherosclerotic cardiovascular disease, morbidity, and death.