Metabolic syndrome is not a risk factor for kidney dysfunction in obese non-diabetic subjects

To investigate whether insulin resistance (IR) and the metabolic syndrome (MS) are associated with kidney dysfunction in obese non-diabetic (OND) subjects.

Three-hundred and eighty (113M/267F; age = 41 +/- 14 years) OND subjects (BMI > or = 30 kg/m(2); range = 43 +/- 8 kg/m(2)) were studied. Anthropometric measures, blood pressure, fasting glucose, insulin, lipid profile, and serum creatinine were evaluated. Glomerular filtration rate (GFR) was estimated (e-GFR) with the Modification of Diet in Renal Disease equation. Chronic kidney disease (CKD) was defined as e-GFR <60 ml/min/1.73 m(2).

e-GFR was associated with gender (being lower in women) (P = 0.001) and age (P < 0.0001). CKD was present in 32 subjects (8.4%), who were older (P < 0.0001) and more frequently affected by hypertension (P = 0.04) as compared to subjects without CKD. MS was present in 212 (55.8%) subjects. They were older (P< 0.001), had lower e-GFR (P = 0.02) and were more frequently affected by CKD (odds ratio (OR), 95% confidence interval (CI) = 2.3, 1.1-5.1) than those without MS. However, differences in e-GFR values and in the risk of CKD were no longer statistically significant after adjusting for age (P = 0.99 for e-GFR and OR, 95% CI = 1.2, 0.5-2.8 for the risk of CKD, respectively). Homeostasis model assessment of IR (HOMA(IR)) index was neither higher in subject with CKD (P = 0.1) nor inversely correlated with e-GFR (r = 0.1, P = 0.1).

In OND individuals the risk of CKD is independent of the MS and related abnormalities. This suggests that these individuals are not susceptible to a further deleterious role on kidney function on the top of that played by obesity itself.