Effects of Dietary Sodium and Protein Intake on Glomerular Filtration Rate in Subjects with Type 2 Diabetes Treated with Sodium-Glucose Cotransporter 2 Inhibitors.

Background: Approximately one-fourth of patients treated with sodium-glucose cotransporter 2 inhibitors (SGLT2i) experience an acute estimated glomerular filtration rate (eGFR) reduction of more than 10% ("dippers"). High sodium and protein intake can increase intraglomerular pressure and predispose to a decline in renal function. We investigated whether measured creatinine clearance (CrCl) is a sensitive enough method to detect the initial dip of GFR and if dietary sodium and protein intake might influence the extent of the early change in GFR.

Methods: 28 subjects with type 2 diabetes (T2D) were enrolled. For sodium and urea determination, 24-h urinary samples were collected to estimate sodium and protein intake respectively before and 1, 3 and 6 months after SGLT2i initiation.

Results: Mean CrCl was 83.23±25.52 mL/min/1.73 m² (eGFR 67.32±16.07) and dropped by 19% at month 1 (eGFR by 6%). Dippers were 64 and 40%, according to CrCl and eGFR, respectively. Exploring the potential correlation between changes in renal function and salt intake, ΔCrCl and baseline urinary sodium were inversely related at month 1 (r=-0,61; p<0.01), at month 3 (r=-0.51; p=0.01) and month 6 (r=-0,48; p<0.05). Likewise, an inverse correlation between ΔCrCl and baseline urinary urea was demonstrated at months 1 and 3 (r=-0.46; p<0.05 for both); at month 6, a similar trend was observed (r=-0.47; p=0.054).

Conclusions: The present study suggests that a higher dietary sodium and protein intake may amplify the extent of the early dip in GFR, as detected with measured CrCl, in diabetic patients undergoing SGLT2i treatment.