Sodium-glucose cotransporter 2 inhibitors (SGLT2i) reduce glucose levels in diabetes by inhibiting renal glucose reabsorption in the proximal tubule (PT), resulting in urinary glucose excretion. A recent large cardiovascular outcomes trial suggested that the SGLT2i empagliflozin may also decrease risk of renal dysfunction. Because sodium (Na) and glucose reabsorption are coupled through SGLT2, it is hypothesized that the renal benefits may be derived from lowering Na reabsorption in the PT, which would lead to favorable renal hemodynamic changes. However, the quantitative contribution of SGLT2 to PT Na reabsorption, as well as the differences between healthy and diabetic subjects, and the impact of SGLT2i on PT Na reabsorption are unknown. In this study we extended an existing mathematical model of glucose dynamics to account for renal glucose filtration and excretion. We utilized this model to quantify glucose and Na reabsorption through SGLT2 in healthy, controlled, and uncontrolled diabetes and following treatment with canagliflozin. In healthy, controlled diabetic, and uncontrolled diabetic states, Na reabsorption through SGLT2 was found to be 5.7%, 11.5%, and 13.7% of total renal Na reabsorption, and 7.1% to 9.5%, 14.4% to 19.2%, and 17.1% to 22.8% of sodium reabsorption in the PT alone. The model predicted that treatment of controlled diabetes with canagliflozin returns PT Na reabsorption through SGLT2 to normal levels. The degree of increased PT Na reabsorption due to SGLT2 is likely sufficient to drive pathologic changes in renal hemodynamics, and restoration of normal Na reabsorption through SGLT2 may contribute to beneficial renal effects of SGLT2 inhibition.
Keywords: canagliflozin; mechanistic model; sodium-glucose cotransporter 2 inhibitors; type 2 diabetes; urinary glucose excretion.
© 2017, The American College of Clinical Pharmacology.