Empagliflozin Counters Metolazone-Induced Hypomagnesemia and Modifies Renal Ion Transporters and Channels

Background: Hypomagnesemia can be caused by NaCl-cotransporter (NCC) inhibition by thiazide-like diuretics including metolazone (MET). The mechanism involves atrophy of the distal convoluted tubule, which lowers capacity for Mg2+ reabsorption through the TRPM6/7 channel. Anti-diabetic Na+-glucose cotransporter 2 inhibitors (SGLT2i) have been reported to correct hypomagnesemia and to also activate NCC. We hypothesized that the SGLT2i empagliflozin (EMPA) suppresses hypomagnesemia induced by MET and modifies expression and activities of renal ion transporters. Methods: 64 male C57BL/6 mice were randomized into 4 groups of 16 mice (1: control, 2: MET, 3: EMPA, 4: MET+EMPA) and placed on a 0.08% Mg2+ diet. For the entire study, mice in group 1 had no drugs, while mice in groups 3 & 4 had MET (250 mg/kg diet) in their diet. From day 7 to day 28, mice in groups 2 and 4 had EMPA (300 mg/kg diet) in their diets. On day 28, 24-hour urine was collected and on day 29 mice were euthanized. Plasma and urine Mg2+ and other electrolytes were measured. Kidneys were homogenized for Western blots for selected renal ion transporters and channels. Diuretic response tests were carried out to assess the in vivo activities of NCC, NKCC2, and ENaC. Results: Plasma Mg2+ was significantly lower in MET and higher in EMPA mice; in MET+EMPA mice it was significantly higher than in MET mice and not different to controls, suggesting EMPA reversed MET-induced hypomagnesemia. EMPA did not reverse MET-induced metabolic alkalosis and caused strong diuresis. Compared with controls, abundances of total NCC, TRPM6, tNKCC2, and calbindin were significantly lower in both MET and MET+EMPA mice but did not differ for EMPA mice, suggesting effects on other segments contribute to correction of hypomagnesemia. Hydrochlorothiazide response test showed EMPA did not reverse MET-induced NCC inhibition, while furosemide response test showed NKCC2 activity did not differ among the treatment groups. However, amiloride response test suggests EMPA may further inhibit ENaC-dependent K+ secretion. Abundance of pAQP2 was significantly lower in MET and higher in EMPA mice. Conclusion: EMPA could correct drug-induced hypomagnesemia, though it exerts complex effects on renal ion channels and transporters in response to polyuria. Funding: NIDDK Support, Private Foundation Support