Decrease in glomerular filtration rate in Japanese patients with type 2 diabetes is linked to atherosclerosis

OBJECTIVE - We assessed the effects of atherosclerosis on the glomerular filtration rate (GFR) in patients with type 2 diabetes and who had micro- or normoalbuminuria. RESEARCH DESIGN AND METHODS - A total of 61 Japanese patients with type 2 diabetes were recruited from inpatients of Osaka City University Hospital. They ranged in age from 40 to 69 years (28 men and 33 women). Each subject collected a 24-h urine sample for quantitative analysis of albumin. Absence of albuminuria was defined as a urinary albumin excretion level of <30 mg/24 h (n = 36) and microalbuminuria as a level of 30-300 mg/24 h. The GFR was estimated using Tc-99m diethylenetriamine pentaacetic renogram method. As indexes of atherosclerosis, we measured the intimal-medial thickness (IMT) and distensibility of the carotid artery using high-resolution B-mode ultrasonagraphy and an echo-tracking system. We measured the resistance index (RI) of the renal interlobar arteries by pulsed Doppler sonography. RESULTS - The clinical characteristics of type 2 diabetic patients with and without microalbuminuria did not differ except for duration of diabetes, which was longer in the patients with microalbuminuria. GFR also did not differ between the patients with and without microalbuminuria. GFR was significantly correlated with the patient's age (r = -0.256, P < 0.05), carotid IMT (r = -0.326, P < 0.05), carotid stiffness beta (r = -0.449, P < 0.001), and renal arterial RI (r = -0.365, P < 0.05). In multiple regression analysis, independent factors associated with GFR were carotid IMT (R-2 = 0.108, P = 0.0102), carotid stiffness beta (R-2 = 0.208, P = 0.0003), and renal artery RI (R-2 = 0.130, P = 0.0043). CONCLUSIONS - The decline in GFR in type 2 diabetic patients in the early stages of nephropathy may be due in part to atherosclerosis.