Glomerular hyperfiltration in morbid obesity
46 patients with BMI>35 kg/m2, without type-2-diabetes or hypertension, were evaluated at baseline and 6 months after bariatric surgery with oral glucose tollerance test, bioimpedance analysis and blood tests. The eGFR was calculated according to EPIcr-cys formula and insulin sensitivity by Oral Glucose Insulin Sensitivity. IL-1/Caspase-1 were measured with the ELISA-kit. HF was defined as eGFR 140 mL/min (non-indexed for BSA).

16 subjects at baseline had hyperfiltration, with a higher insulin resistance, BMI, lean mass and plasma levels of IL-1/Caspase-1. After surgery, there was a reduction in BMI and improvement in insulin resistance in all patients. However, in 8 of 16 patients hyperfiltration persisted and IL-1/Caspase-1 levels did not decrease (3.22±0.79 vs 3.13±1.03 and 23.7±12.1 vs 20.6±9.1, pre vs post, pg/ml), while cytokines normalized in all the other patients in parallel with the eGFR. In a logistic regression model, correcting for the main covariates, lean mass and IL-1 before surgery (p=0.01 and p =0.03, respectively), were the only predictors of hyperfiltration.

Weight loss is effective in reducing hyperfiltration in most, but not all patients. Hyperfiltration remains unchanged in subjects who do not have a reduction in IL-1/Caspase-1, suggesting a pathogenetic role of the inflammasome signaling in the early stages of nephropathy.