Glomerular Hyperfiltration and Renal Disease Progression in Type 2 Diabetes PIERO RUGGENENTI, MD1,2

OBJECTIVEdTo describe the prevalence and determinants of hyperfiltration (glomerular filtration rate [GFR] $120 mL/min/1.73 m2), GFR decline, and nephropathy onset or progres-sion in type 2 diabetic patients with normo- or microalbuminuria. RESEARCH DESIGN AND METHODSdWe longitudinally studied 600 hypertensive type 2 diabetic patients with albuminuria,200 mg/min and who were retrieved from two randomized trials testing the renal effect of trandolapril and delapril. Target blood pressure (BP) was,120/80 mmHg, and HbA1c was,7%. GFR, albuminuria, and glucose disposal rate (GDR) were centrally measured by iohexol plasma clearance, nephelometry in three consecutive overnight urine collections, and hyperinsulinemic euglycemic clamp, respectively. RESULTSdOver a median (range) follow-up of 4.0 (1.7–8.1) years, GFR declined by 3.37 (5.71–1.31) mL/min/1.73 m2 per year. GFR change was bimodal over time: a larger reduction at 6 months significantly predicted slower subsequent decline (coefficient:20.0054; SE: 0.0009), particularly among hyperfiltering patients. A total of 90 subjects (15%) were hyperfiltering at inclusion, and 11 of 47 (23.4%) patients with persistent hyperfiltration progressed to micro- or macroalbuminuria versus 53 (10.6%) of the 502 who had their hyperfiltration ameliorated at 6 months or were nonhyperfiltering since inclusion (hazard ratio 2.16 [95 % CI 1.13–4.14]). Amelioration of hyperfiltration was independent of baseline characteristics or ACE inhibition. It was significantly associated with improved BP and metabolic control, amelioration of GDR, and slower long-term GFR decline on follow-up. CONCLUSIONSdDespite intensified treatment, patients with type 2 diabetes have a fast GFR decline. Hyperfiltration affects a subgroup of patients and may contribute to renal function loss and nephropathy onset or progression. Whether amelioration of hyperfiltration is renopro-tective is worth investigating