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OBJECTIVESerum creatinine levels are lower in diabetic patients compared with their nondiabetic counterparts. Therefore, estimated glomerular filtration rate (eGFR) is higher in the former than in the latter group. Factors associated with overestimation of renal function in diabetic patients were examined, and new formulae reflecting precise eGFR were created. RESEARCH DESIGN AND METHODSEighty subjects (age 56.5 6 15.4 years; 35 males [43.8%]; 40 patients with diabetes and 40 nondiabetic subjects) were enrolled. GFR was evaluated by inulin clearance (C in ). eGFR values were calculated based on serum creatinine and/or serum cystatin C levels. The factors related to the dissociation between eGFR and C in in diabetic patients and the agreement among each of three eGFR and C in were compared. RESULTSAlthough C in was not significantly different between the diabetic and nondiabetic subjects (P = 0.2866), each of three eGFR measures from the diabetic patients was significantly higher than that of the nondiabetic subjects (P < 0.01). There were significant and positive correlations between the ratio of each eGFR/ C in , hemoglobin A 1c , and glycated albumin. The intraclass correlation coefficients in diabetic patients were weaker than those in the nondiabetic subjects, and the intercepts of the regression lines between each eGFR measure and C in in the diabetic patients were significantly higher than those of the nondiabetic subjects. New formulae for the calculation of eGFR corrected by the glycemic control indices were better than the original eGFR, particularly in diabetic patients. CONCLUSIONSeGFR overestimates C in as glycemic controls worsen. eGFR corrected by hemoglobin A 1c is considered to be clinically useful and feasible.

Background/Aims: Hyperuricemia has been reported to affect renal hemodynamics in rat models. We evaluate the relationship between serum uric acid and intrarenal hemodynamic parameters in humans, utilizing the plasma clearance of para-aminohippurate (C_PAH ) and inulin (C_in). Methods: Renal and glomerular hemodynamics were assessed by simultaneous measurement of C_PAH and C_in in 58 subjects. Of these, 19 subjects were planned to provide a kidney for transplantation; 26 had diabetes without proteinuria; and 13 had mild proteinuria. Renal and glomerular hemodynamics were calculated using Gomez`s formulae. Results: C_in was more than 60 ml/min/1.73m² in all subjects. Serum uric acid levels correlated significantly with vascular resistance at the afferent arteriole (R_a) (r = 0.354, p = 0.006) but not with that of the efferent arteriole (R_e). Serum uric acid levels (β = 0.581, p = <0.001) were significantly and independently associated with R_a after adjustment for several confounders (R² = 0.518, p = <0.001). Conclusions: These findings suggest, for the first time in humans, that higher serum uric acid levels are associated significantly with R_a in subjects with C_in > 60 ml/min/1.73m². The increase in R_a in subjects with higher uric acid levels may be related to dysfunction of glomerular perfusion.

Objective: Low thyroid function may be associated with a reduced glomerular filtration rate (GFR) calculated on the basis of creatinine metabolism. Thyroid hormone directly affects serum creatinine in muscle and low thyroid function might exert a similar direct effect in the kidney. The goal of the study was to evaluate this possibility by assessment of the inulin-based GFR and to examine the mechanism underlying the reduction of GFR. Patients and methods: Renal and glomerular hemodynamics were assessed by simultaneous measurements of plasma clearance of para-aminohippurate (C PAH ) and inulin (C in ) in 26 patients with serum creatinine !1.00 mg/dl and without thyroid disease. All subjects were normotensive with or without antihypertensive treatment and were kept in a sodium-replete state. Renal and glomerular hemodynamics were calculated using Gomez's formulae. Results: Serum TSH, including within the normal range (0.69-4.30 mIU/ml), was positively correlated with vascular resistance at the afferent arteriole (R a ) (rZ0.609, PZ0.0010), but not at the efferent arteriole (R e ). Serum TSH was significantly and negatively correlated with renal plasma flow (RPF), renal blood flow (RBF), and GFR (rZK0.456, PZ0.0192; rZK0.438, PZ0.0252; rZK0.505, PZ0.0086 respectively). In multiple regression analysis, serum TSH was significantly positively associated with R a after adjustment for age and mean blood pressure. Conclusions: These findings suggest that low thyroid function, even within the normal range, is associated with reduced RPF, RBF, and GFR, which might be caused by a preferential increase in R a .

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