Impact of initial treatment on renal function in newly-diagnosed Type 2 (non-insulin-dependent) diabetes mellitus

Summary The impact of improved glycaemic control on renal function in newly-presenting Type 2 (non-insulin-dependent) diabetic patients has not been adequately researched. Consequently, glomerular filtration rate and effective renal plasma flow and urinary albumin excretion rates were determined in 76 subjects (age (mean (SD)): 54 (9.5) years; 50 male) of an original cohort of 110 newly-presenting normotensive non-proteinuric Type 2 diabetic patients following 6 months treatment with diet alone (n=42) or with oral hypoglycaemic agents (n=34). Significant reductions were observed in (presentation vs 6 months): body mass index (p<0.01); fasting plasma glucose (p<0.001); glycated haemoglobin (HbA₁) (p<0.001); systolic blood pressure (p<0.01); and diastolic blood pressure (p<0.001). Glomerular filtration rate declined from 117 (22) to 112 (21) ml·min^–1 (p<0.01), with unchanged effective renal plasma flow (534 (123) vs 523 (113) ml·min^–1) and filtration fraction (22.4 (3.0) vs 21.8 (3.4)%). Albumin excretion rate (median (range)) declined from 1.1 (0.1–34.7) to 0.5 (0.1–29.9) g·min^–1 (p<0.01). Changes in glomerular filtration rate ( values) were inversely correlated with presentation values (p<0.001), and positive relationships were observed with effective renal plasma flow (p<0.01), and glycated haemoglobin (p<0.05). Type 2 diabetic patients with glomerular filtration rate values at presentation over 120 ml·min^–1 demonstrated significant reduction in glomerular filtration rate (n=31; p<0.001), whilst those with original values less than 120 ml·min^–1 remained unchanged (n=45). Glomerular filtration rate, effective renal plasma flow and filtration fraction for the Type 2 diabetic patients remained elevated compared with age-controlled normal subjects (p<0.01-0.001). Albumin excretion rate at presentation and 6 months were positively correlated with fasting plasma glucose levels (p<0.05) but not renal haemodynamics. Thus, glomerular filtration rate and albumin excretion rate in newly-presenting Type 2 diabetic patients are influenced by metabolic control. Improved glycaemia for 6 months produces a reduction in glomerular filtration rate, mainly in the younger patients with values greater than 120 ml·min^–1 at diagnosis of diabetes. Despite these changes, renal haemodynamic parameters remain elevated compared with age-matched normal subjects.