Glomerular hyperfiltration is associated with blood pressure abnormalities in normotensive normoalbuminuric IDDM patients

OBJECTIVE - To analyze the blood pressure patterns in normoalbuminuric IDDM patients with glomerular hyperfiltration. RESEARCH DESIGN AND METHODS - A controlled cross-sectional study of 38 normotensive normoalbuminuric (urinary albumin excretion rate <20 mu g/min) IDDM patients (18 hyperfiltering [glomerular filtration rate > 134 ml . min(-1) . 1.73 m(-2)] and 20 normofiltering) and 20 normal individuals matched for age, sex, and BMI was performed. The 24-h ambulatory blood pressure was monitored using an auscultatory technique (Pressurometer IV, Del Mar Avionics), the glomerular filtration rate was measured by Cr-51-labeled EDTA method, extracellular volume by the distribution volume of Cr-51-labeled EDTA, and the 24-h urinary albumin excretion rate by radioimmunoassay. RESULTS - Mean nocturnal diastolic blood pressure was higher in hyperfiltering IDDM patients (70.4 +/- 7.8 mmHg), when compared with the control group (65.1 +/- 5.3 mmHg, P = 0.04). Diastolic blood pressure night:day ratio was higher in hyperfiltering IDDM patients (92.0 +/- 8.6%), when compared with normofiltering IDDM patients (85.9 +/- 4.8%) and control subjects (87.0 +/- 6.8%, P = 0.02). In IDDM patients, the glomerular filtration rate significantly correlated with the diastolic blood pressure night:day ratio (r = 0.5, P = 0.002), extracellular volume (r = 0.4, P = 0.002), and HbA(1) (r = 0.3, P = 0.03). In stepwise multiple regression analysis, factors associated with glomerular filtration rate were diastolic blood pressure night:day ratio, extracellular volume, and HbA(1) (adjusted r(2) = 0.27, P = 0.003). CONCLUSIONS - Glomerular hyperfiltration is associated with higher nocturnal diastolic blood pressure and with a blunted nocturnal decrease in diastolic blood pressure levels in normotensive and normoalbuminuric IDDM patients.