Clinical Nephrology – Epidemiology – Clinical Trials
Kidney International (2004) 65, 259–265; doi:10.1111/j.1523-1755.2004.00351.x
Body mass index is associated with altered renal hemodynamics in non-obese healthy subjects
RENATE J BOSMA, JAAP J HOMAN, VAN DER HEIDE, ERIC J OOSTEROP, PAUL EDE JONG and GERJAN NAVIS
Department of Medicine, Division of Nephrology, University Hospital Groningen, The Netherlands
Correspondence: G.J. Navis, Department of Medicine, University Hospital, Hanzeplein 1, NL-9700 RB Groningen, The Netherlands. E-mail: g.j.navis@int.azg.nl
Received 9 January 2003; Revised 15 May 2003; Re-revised 7 July 2003; Accepted 6 August 2003.
Abstract
Body mass index is associated with altered renal hemodynamics in non-obese healthy subjects.
Background
Weight excess is associated with increased renal risk. Data in overt obesity suggest a role for altered renal hemodynamics. Whether body mass index (BMI) is also relevant to renal function in non-obese subjects is unknown.
Methods
We studied the relation between BMI and renal hemodynamics in 102 healthy, non-obese (BMI <30 kg/m2) subjects [59 males, 43 females, mean age 39 (18–69) years] in a post-hoc analysis of subjects evaluated as prospective kidney donors or as healthy volunteers in renal hemodynamic studies.
Results
Mean (
SD) BMI was 24.0 2.8 kg/m2, mean arterial pressure (MAP) 93 11 mm Hg, glomerular filtration rate (GFR, iothalamate clearance) 111 19 mL/min/1.73m2, effective renal plasma flow (ERPF, hippuran clearance) 458 108 mL/min/1.73m2, FF (GFR/ERPF) 0.25 0.04. On univariate analysis, BMI correlated negatively with ERPF/1.73m2 body surface area (BSA) (r=-0.46; P < 0.001), GFR/1.73m2 BSA (r=-0.24, P = 0.013) and positively with FF (r = 0.45, P < 0.001), and age (r = 0.47, P < 0.001). On multivariate analysis both BMI and age were independent predictors of ERPF/1.73m2 BSA (negative) and FF (positive, all P < 0.05). Age was the only predictor of GFR/1.73m2 BSA (negative). Analyzed for renal function indexed for height (h), BMI correlated negatively with ERPF/h (r=-0.274, P = 0.005), but not with GFR/h (r = 0.13, P = 0.899). On multivariate analysis both BMI (positive) and age (negative) were independent predictors for GFR/h (both P < 0.001). Age was the only predictor for ERPF/h (negative). Predictors for FF (BMI and age, both positive) were by definition unaltered.
Conclusion
The impact of BMI on renal function is not limited to overt obesity, as in subjects with BMI <30 kg/m2 a higher BMI is associated with higher FF, that is, a higher GFR relative to ERPF. This suggests an altered afferent/efferent balance and higher glomerular pressure (i.e., a potentially unfavorable renal hemodynamic profile) that may confer enhanced renal susceptibility when other factors, such as hypertension or diabetes are superimposed.
Keywords:
body mass index, obesity, renal hemodynamics, renal function, renal risk
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