Objective: There is evidence that obesity and insulin sensitivity may alter renal function. The possible role of inflammation in this relationship is not fully known. We investigated relationships between renal function and insulin resistance, adiposity and other indicators of metabolic and cardiovascular disease risk, including plasma inflammation markers, in healthy individuals.
Methods: Renal function was estimated using eGFR (calculated using CKD-EPI formula). Also measured were waist-to-hip ratio (WHR), body mass index (BMI), adiposity (dual energy x-ray absorptiometry); fasting and 2 hour glucose (OGTT), insulin sensitivity (hyperinsulinemic-euglycemic clamp); systolic and diastolic blood pressure (SBP;DBP); fasting lipid profile; white blood cell count (WBC), circulating C-reactive protein, Interleukin-6 (ELISA); in 44 healthy, non-diabetic adults:17F/27M, age 31±10yrs (mean ± SD), percent body fat 29±9%, BMI median(IQR) 28(25, 31kg/m2)
Results: Mean eGFR was 114±16.3 mls/min/1.73m2 (higher in males, P=0.03) and was positively associated with % body fat (r=.38,P=0.01), 2 hour glucose after OGTT (r=.41,P=0.009), insulin sensitivity (r=-.52,P=0.001), SBP (r=.39,P=0.01) and WBC (r=.44,P=0.005) in age and sex-adjusted partial correlation analyses. eGFR was not associated with WHR, fasting glucose, nor fasting plasma lipids, inflammation markers or DBP (all p>0.05). Higher eGFR remained associated with insulin resistance after adjusting for age, sex, SBP and % body fat (hierarchical regression analysis, β=-.39,P=0.02 in final model). However the positive relationships between eGFR and WBC and 120min fasting glucose weakened marginally after inclusion of adiposity in the model (P=0.08, P=0.06 respectively).
Conclusions: We report for the first time an association between higher eGFR and insulin resistance independent of adiposity in a small cohort of clinically well-defined, non-diabetic participants. Direction of the relationship cannot be ascertained in these cross-sectional analyses. Appropriate screening and monitoring of patients for further changes in metabolic risk may be necessary to allow for early intervention to prevent deterioration in eGFR; such relationships merit further study.