Diabetic Nephropathy: Metabolic versus hemodynamic considerations

Not all patients with diabetes develop clinically significant nephropathy and, for this reason, attention has begun to focus on the risk factors for development of this serious complication. These risk factors have not been quantified to the same degree as those factors associated with more common progressive vascular diseases, such as atherosclerosis. However, studies of pathogenesis and clinical and epidemiological surveys of diabetic nephropathy point to numerous risk categories. Glycemic control, genetic and familial predispositions, renal and glomerular enlargement, glomerular hyperfiltration, and capillary and systemic hypertension can be invoked as contributors to this disease process. This review focuses on hemodynamic alterations and their role in the development and progression of diabetic nephropathy. Increases in GFR, largely driven by increases in plasma flow and capillary pressure, appear in early IDDM and NIDDM. This abnormality of renal vascular control probably is derived from alterations in several vasoactive control systems. In addition, the elevations in capillary pressure may be damaging to the glomerular capillaries. Arterial hypertension is not necessarily present before clinical nephropathy appears; however, it is a usual concomitant of progressive diabetic renal disease. The strongest evidences for the roles of altered systemic and renal hemodynamics in the progression of diabetic renal disease are clinical and experimental studies demonstrating attenuation of the disease process by lowering systemic and capillary pressures with antihypertensive agents, and dietary and glycemic modifications. Thus, although multiple factors probably interact to determine risk for the development of diabetic nephropathy, hemodynamic forces are a particularly important contributor and are especially amenable to therapeutic intervention.