Pathogenesis and treatment of hypertension associated with diabetes mellitus

The pathogenesis of hypertension associated with diabetes mellitus (DM) involves an interplay of hereditary and acquired mechanisms. A familial trait for essential hypertension appears to be a risk factor for the development of both hypertension and nephropathy in type I DM and coexists commonly with impaired insulin sensitivity, relative hyperinsulinemia, and dyslipidemia, which can already be detected before the appearance of hypertension, obesity, or upper abdominal redistribution of body fat. The latter finding helps explain the frequent development of hypertension as well as dyslipidemia and/or type II DM in given individuals. Obesity is an important factor promoting these complications. Type I or II DM but not uncomplicated essential hypertension is characteristically accompanied by excess body Na+. This abnormality complements a tendency toward vascular hyperreactivity and a presumably morphologic and functional vasculopathy, thereby promoting the pathogenesis of hypertension in diabetic patients. For the treatment of hypertension in diabetic patients, nonpharmacologic measures are indispensable. If drugs are needed, angiotensin-converting enzyme (ACE) inhibitors and some but not all calcium antagonists are the preferred agents. Monotherapy or a combination of these drug types allows effective blood pressure control in most diabetic patients without further metabolic impairment; ACE inhibitors even tend to improve glucose control. Ketanserin may be a potential alternative, and if a diuretic is also needed, the metabolically neutral indapamide is a reasonable choice. If these agents do not allow satisfactory blood pressure highly selective beta 1-blockers or alpha 1-blockers may be introduced as a second choice. In diabetic patients with nephropathy, effective antihypertensive therapy can reduce proteinuria and slow the progression of the nephropathy; ACE inhibitors may improve diabetic proteinuria even at unchanged systemic blood pressure levels. Unless diuretics are needed for reasons other than hypertension, the treatment of diabetic patients with thiazides or loop diuretics in conventional dosage should probably be avoided until clarification of their influence on prognosis. Nevertheless, whether and to what extent other agents and nonpharmacologic measures can modify the prognosis in diabetic patients is also unclear, and the approach to antihypertensive therapy is therefore still largely empiric.