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 m(2) (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,.CrCl 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.CrCl 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.