Gluconeogenesis, But Not Glycogenolysis, Contributes to the Increase in Endogenous Glucose Production by SGLT-2 Inhibition

OBJECTIVE Recent studies indicate that sodium-glucose cotransporter 2 (SGLT-2) inhibition increases endogenous glucose production (EGP), potentially counteracting the glucose-lowering potency, and stimulates lipid oxidation and lipolysis. However, the acute effects of SGLT-2 inhibition on hepatic glycogen, lipid, and energy metabolism have not yet been analyzed. We therefore investigated the impact of a single dose of dapagliflozin (D) or placebo (P) on hepatic glycogenolysis, hepatocellular lipid (HCL) content and mitochondrial activity (kATP). RESEARCH DESIGN AND METHODS Ten healthy volunteers (control [CON]: age 30 ± 3 years, BMI 24 ± 1 kg/m2, HbA1c 5.2 ± 0.1%) and six patients with type 2 diabetes mellitus (T2DM: age 63 ± 4 years, BMI 28 ± 1.5 kg/m2, HbA1c 6.1 ± 0.5%) were investigated on two study days (CON-P vs. CON-D and T2DM-P vs. T2DM-D). 1H/13C/31P MRS was performed before, 90–180 min (MR1), and 300–390 min (MR2) after administration of 10 mg dapagliflozin or placebo. EGP was assessed by tracer dilution techniques. RESULTS Compared with CON-P, EGP was higher in CON-D (10.0 ± 0.3 vs. 12.4 ± 0.5 μmol kg−1 min−1; P < 0.05) and comparable in T2DM-D and T2DM-P (10.1 ± 0.7 vs. 10.4 ± 0.5 μmol kg−1 min−1; P = not significant [n.s.]). A strong correlation of EGP with glucosuria was observed (r = 0.732; P < 0.01). The insulin-to-glucagon ratio was lower after dapagliflozin in CON-D and T2DM-D compared with baseline (P < 0.05). Glycogenolysis did not differ between CON-P and CON-D (−3.28 ± 0.49 vs. −2.53 ± 0.56 μmol kg−1 min−1; P = n.s.) or T2DM-P and T2DM-D (−0.74 ± 0.23 vs. −1.21 ± 0.33 μmol kg−1 min−1; P = n.s.), whereas gluconeogenesis was higher after dapagliflozin in CON-P compared with CON-D (6.7 ± 0.6 vs. 9.9 ± 0.6 μmol kg−1 min−1; P < 0.01) but not in T2DM. No significant changes in HCL and kATP were observed. CONCLUSIONS The rise in EGP after SGLT-2 inhibition is due to increased gluconeogenesis, but not glycogenolysis. Changes in glucagon and the insulin-to-glucagon ratio are not associated with an increased hepatic glycogen breakdown. HCL and kATP are not significantly affected by a single dose of dapagliflozin.