IMPACT OF INITIAL TREATMENT ON RENAL-FUNCTION IN NEWLY-DIAGNOSED TYPE-2 (NON-INSULIN-DEPENDENT) DIABETES-MELLITUS

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 1 17 (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) mug.min-1 (p < 0.01). Changes in glomerular filtration rate (DELTA values) were inversely correlated with presentation values (p < 0.001), and positive relationships were observed with DELTA effective renal plasma flow (p < 0.01), and DELTA 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 < 0.010. 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.