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

•Urinary albumin excretion increased with obesity stages.•Morbid obesity increases the risk of micro- and macroalbuminuria.•Adjusted glomerular filtration rate declined with obesity stages.•Morbid obesity interacts with type 2 diabetes to impair kidney function.

AimsType 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.MethodsCross-sectional, monocentric study of kidney function in patients with type 2 diabetes classified into four body mass index (BMI) stages: non-obese (<25 kg/m2, 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 51Cr EDTA plasma disappearance (adjusted and unadjusted to 1.73 m2 body surface area, as obesity increases body surface).ResultsParticipants 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).ConclusionsMorbid 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.