BLOOD-PRESSURE, DIET AND THE PROGRESSION OF NEPHROPATHY IN PATIENTS WITH TYPE-1 DIABETES AND HYPERTENSION

To examine the relationships between the normal dietary intakes of pro tein and phosphate, blood pressure, and the progression of diabetic ne phropathy, we prospectively studied 20 Type 1 diabetic subjects of mea n age 43 +/- 10 years (SD) with early nephropathy (mean serum creatini ne 115 +/- 43 mumol l-1) over 1 year. Three monthly measurements of bl ood pressure, glycaemic control, and normal dietary intake (3-day weig hed food records) and 6-monthly measurements of glomerular filtration rate (using a single injection of chromium 51-EDTA) were made. GFR cha nged at a median rate of -0.89 ml min-1 1.73 m-2 month-1 (range + 0.85 to -2.55 ml min-1 1.73 m-2 month-1). Mean dietary protein intake (1.2 2 g kg-1; range 0.78 to 1.55 g kg-1) and phosphate intake (21.5 mg kg- 1; range 14.1 to 30.4 mg kg-1) were not significantly related to the r ate of change in GFR. Only mean systolic blood pressure was significan tly related to change in GFR, and accounted for 45 % of the variabilit y in GFR decline in the 18 subjects who completed the study (r = 0.67; R2 = 0.449; F1,16 = 13.2; p < 0.005; 95 % confidence interval for r0. 336-0.867). A mean systolic blood pressure of 140 mmHg or below was as sociated with no significant decline in GFR over a median period of 13 months. Systolic blood pressure accounted for nearly half of the vari ability in GFR and a mean systolic pressure of 140 mmHg or below may r epresent a marker for 'ideal' blood pressure treatment. The normal wid e variations in protein and phosphate intake between subjects did not significantly influence the rate at which renal function was lost.