Relationship between hypertension and subtle and overt abnormalities of carbohydrate metabolism

In patients with type II diabetes mellitus, the prevalence of hypertension is increased as much as twofold over that in the nondiabetic population. Hypertension in diabetic patients increases the risk and accelerates the course of development of cardiac disease, stroke, peripheral vascular disease, retinopathy, and nephropathy. Despite the importance of hypertension in type II diabetics, the basic mechanisms that initiate and sustain hypertension in these patients are poorly understood. Contributing factors discussed in this review include the following: obesity, insulin resistance, hyperinsulinemia, genetic factors, and abnormalities of cellular cation homeostasis. Also discussed are the features of hypertension in type II diabetic individuals which are reminiscent of the hemodynamic abnormalities characterizing hypertension in the elderly, including increased vascular reactivity and increased atherosclerotic vascular disease. Recent evidence has shown that insulin resistance and hyperinsulinemia exist in as many as 50 to 70% of adult nonobese individuals with untreated hypertension. These observations strongly suggest that the disease known as hypertension is characterized by fundamental abnormalities of metabolism as well as by hemodynamic alterations. This review discusses the mechanisms by which hyperinsulinemia and/or insulin resistance may lead to hypertension. Elevated levels of triglycerides in plasma and suppressed high-density lipoprotein cholesterol concentrations are often observed in hypertensive individuals. These elevations may result, in part, from hyperinsulinemia and/or insulin resistance. Information will be presented suggesting that subtle abnormalities of carbohydrate metabolism that exist in patients with hypertension may contribute to the accelerated cardiovascular disease that accompanies the hypertension state. This review also addresses both special concerns about metabolic consequences of antihypertensive therapy in hypertensive patients with subtle carbohydrate intolerance as well as those in hypertensive patients with overt diabetes.