Genetics of diabetic nephropathy

Diabetic nephropathy is a clinical syndrome characterized by persistent albuminuria, a relentless decline in GFR, raised arterial blood pressure, and increased relative mortality for cardiovascular diseases. Diabetic nephropathy is a leading cause of end-stage renal failure. The pathogenesis of diabetic nephropathy is multifactorial, with contributions from metabolic abnormalities, hemodynamic alterations, and various growth factors and genetic factors. Epidemiologic and family studies have demonstrated that only a subset of the patients develop this complication, that family clustering of nephropathy is present, and that ethnicity plays an important role in the risk of developing this kidney disease. Short stature and low birth weight are both associated with increased risk of developing diabetic nephropathy, supporting the hypothesis that genetic predisposition or factors operating in utero, in early childhood, or both contribute to the development of diabetic nephropathy. Studies elucidating phenotypic markers such as parenteral hypertension and systemic blood pressure elevation have yielded conflicting results. The contribution from elevated blood pressure only plays a minor role in the majority of the patients developing diabetic nephropathy. The majority of the studies have demonstrated increased sodium/lithium countertransport activity in insulin-dependent diabetes mellitus patients with nephropathy, whereas studies of this phenotypic marker in parents of patients with and without nephropathy have yielded conflicting results. Recently, studies of genetic markers involved in the regulation of blood pressure and levels of cardiovascular risk factors have been conducted. Several studies have demonstrated that the deletion polymorphism in the angiotensin-I-converting enzyme acts as a risk factor for cardiovascular disease in diabetic patients. However, a meta-analysis does not support the suggestion that this factor plays any role for the initiation of diabetic nephropathy. Similar negative results have been obtained in relation to polymorphisms of the genes encoding for angiotensinogen and the angiotensin II Type 1 receptor. However, studies in diabetic and non-diabetic glomerulopathies have clearly demonstrated a deleterious effect of the deletion polymorphism in the angiotensin-converting enzyme on the progression of kidney function.