Impact of morbid obesity on the kidney function of patients with type 2 diabetes

Type 2 diabetes and obesity impair kidney function. We examined their respective contributions to urinary albumin excretion (UAE) and glomerular filtration rate (GFR) in patients with type 2 diabetes and morbid obesity.

Cross-sectional, monocentric study of kidney function in patients with type 2 diabetes classified into four body mass index (BMI) stages: non-obese (<25 kg/m(2), n=157); overweight (25 to <30, n=311); obesity (30 to <40, n=310); and morbid obesity (≥40, n=77), with 84 similarly staged controls without diabetes. UAE classes were defined as normal (<30 μg/mg creatinine), microalbuminuria (30-299), or macroalbuminuria (≥300) from 3 consecutive urine samples. GFR was measured by (51)Cr EDTA plasma disappearance (adjusted and unadjusted to 1.73 m(2) body surface area, as obesity increases body surface).

Participants with type 2 diabetes had same age, diabetes duration, and HbA1c across BMI stages. UAE was higher in participants with type 2 diabetes (p<0.0001), and increased with obesity stages (p<0.0001). After adjustment for age, sex, systolic blood pressure and type 2 diabetes status, morbid obesity was associated with a risk of microalbuminuria (OR 1.99, 95%CI 1.35-2.98, p=0.0007) and macroalbuminuria (OR 2.33, 95%CI 1.25-4.22, p=0.006). The body surface adjusted GFR was lower in patients with type 2 diabetes than in controls (p<0.0001), and declined with obesity stages, contrary to controls. An interaction of diabetes and obesity was seen with unadjusted GFR values (p=0.002).

Morbid obesity interacts with type 2 diabetes to aggravate UAE and GFR. Treatment strategies should focus on both conditions to protect kidney function in these patients.