The short-term effect of a switch from glibenclamide to metformin on blood pressure and microalbuminuria in patients with type 2 diabetes mellitus.

BACKGROUND: Renal hyperfiltration and albuminuria have a deleterious effect on kidney function. Therefore, we studied the effect of metformin on blood pressure, renal hemodynamics, and microalbuminuria in type 2 diabetic patients.

METHODS: A clinical trial was designed in type 2 diabetic patients with incipient nephropathy. All patients were below the age of 65, normotensive, and without evidence of malignant, hepatic, or cardiovascular disorders. They were randomly allocated to receive glibenclamide or metformin. At baseline and 12 weeks thereafter we measured body mass index (BMI), serum insulin, blood glucose, lipid profile, glycosylated hemoglobin, blood pressure, glomerular filtration rate, renal plasma flow, and urine albumin.

RESULTS: We studied 23 patients in the glibenclamide group and 28 in the metformin group. There was no difference in baseline variables between the groups. Metabolic control was obtained in both groups. In the metformin group, all the following variables decreased: microalbuminuria was reduced by a mean of 24.2 mg/day (p = 0.008); systolic and diastolic blood pressure by a mean of 5.3 mmHg (p = 0.002) and 3.93 mmHg (p = 0.009), respectively; insulin levels by an average of 11.8 microIU/mL (p = 0.001), and total cholesterol levels and triglycerides by an average of 0.45 and 0.18 mmol/L, respectively. Insulin resistance measured by the homeostasis model decreased more in the metformin group than in the glibenclamide group. Patients treated with glibenclamide had an increase in HDL cholesterol of 0.082 mmol/L (p = 0.01).

CONCLUSIONS: Metformin significantly decreased the urine albumin excretion rate with none of the expected changes in renal hemodynamics, probably due to its favorable effects on blood pressure, lipid profile, metabolic control, and insulin resistance.