Roux-en-Y gastric bypass reverses renal glomerular but not tubular abnormalities in excessively obese diabetics

Obesity and type 2 diabetes are associated with renal dysfunction, which improves after Roux-en-Y gastric bypass (RYGB). During a 12-month follow-up period, we studied prospectively the changes in glomerular and tubular functions that occurred in excessively obese diabetic and non diabetic subjects after RYGB.

The cohort included 35 patients, 54% of whom had type 2 diabetes. Glomerular filtration rate (GFR) was estimated using creatinine clearance. Tubular function was studied by measuring the ratio of urinary cystatin C to urinary creatinine (UCC ratio).

Baseline renal parameters, anthropometric characteristics, and changes in body mass index after the surgical procedures were similar between the 2 cohorts. At 12 months after RYGB, creatinine clearance decreased 15% in diabetics (P = .02) and 21% in nondiabetics (P = .03). A change in GFR was seen earlier in the nondiabetics (-29% after 6 months; P = .003). The UCC ratio was increased at both 6- and 12-month follow-ups (P = .03 and .003, respectively) only in the diabetic group.

GFR was improved at 12 months after RYGB, with nondiabetics showing a greater propensity score. Tubular function remained unchanged in the nondiabetic subjects, but worsening occurred in the diabetic subjects. These results underscore the importance of reversal of excessive obesity before the onset of frank diabetes.