Hypertension and Renal Complications in Type 2 Diabetes

Diabetes mellitus and arterial hypertension are the leading causes of end-stage renal disease in industrialized countries. Although attention has focused on renal disease and insulin-dependent diabetes mellitus (type 1 diabetes), a silent epidemic of renal disease caused by type 2, noninsulin-dependent diabetes mellitus is rapidly developing. The course of renal function is heterogeneous in type 2 diabetic patients and reflects heterogeneous patterns of renal lesions. A subset of patients with microalbuminuria and proteinuria is characterized by the typical diabetic glomerulopathy usually observed in type 1 diabetic patients, with altered albumin excretion rate (AER), for example, glomerular basement membrane thickening and mesangial fractional volume expansion. These patients also have diabetic retinopathy and rapidly lose renal function despite tight blood pressure control. In contrast, a second subset of type 2 diabetic patients has normal or near-normal patterns of glomerular structure, despite abnormalities of AER comparable to those of the patients with diabetic glomerulopathy. Thus abnormalities of AER have a different renal prognostic value depending on the underlying renal structure. The patients with worse clinical prognosis and typical diabetic glomerulopathy also have diabetic retinopathy, whereas those with a better course of renal function quite often have no diabetic retinopathy. Several findings, albeit not unanimous, suggest that HbA1c levels above 7.5 to 8.0 % are closely associated with a rapid decay of renal function in type 2 diabetes. Tight blood pressure control plays a further important role in determining the progression of renal a damage in type 2 diabetes mellitus. Convincing evidence has been provided that drugs capable of inhibiting the renin-angiotensin hormonal system are quite effective in preventing and delaying the evolution of renal damage in both type 1 and 2 diabetes. Equally strong data support the view that other antihypertensive compounds such as beta-blockers and calcium antagonists also delay the progression of renal damage in diabetes mellitus. Whatever the drug used to treat hypertension, the majority of the authors conclude that blood pressure levels should be maintained below 130/85 mmHg in diabetic patients. While it is well established that uncontrolled diabetes underlies the development of diabetic nephropathy, newer evidence suggests that genetically determined susceptibility to hyperglycemia-caused glomerular injury is also necessary. More information on this issue will help to design new therapeutical approaches to treat hypertension and renal complications in type 2 diabetes.