Pharmacologically induced glycosuria elicits adaptive responses in glucose homeostasis and hormone release. In type 2 diabetes (T2D), along with decrements in plasma glucose and insulin levels and increments in glucagon release, sodium-glucose cotransporter 2 (SGLT2) inhibitors induce stimulation of endogenous glucose production (EGP) and a suppression of tissue glucose disposal (TGD). We measured fasting and postmeal glucose fluxes in 25 subjects without diabetes using a double glucose tracer technique; in these subjects and in 66 previously reported patients with T2D, we also estimated lipolysis (from [ 2 H 5 ]glycerol turnover rate and circulating free fatty acids, glycerol, and triglycerides), lipid oxidation (LOx; by indirect calorimetry), and ketogenesis (from circulating b-hydroxybutyrate concentrations). In both groups, empagliflozin administration raised EGP, lowered TGD, and stimulated lipolysis, LOx, and ketogenesis. The pattern of glycosuria-induced changes was similar in subjects without diabetes and in those with T2D but quantitatively smaller in the former. With chronic (4 weeks) versus acute (first dose) drug administration, glucose flux responses were attenuated, whereas lipid responses were enhanced; in patients with T2D, fasting b-hydroxybutyrate levels rose from 246 6 288 to 561 6 596 mmol/L (P < 0.01). We conclude that by shunting substantial amounts of carbohydrate into urine, SGLT2-mediated glycosuria results in a progressive shift in fuel utilization toward fatty substrates. The associated hormonal milieu (lower insulin-to-glucagon ratio) favors glucose release and ketogenesis.When large quantities of glucose are pharmacologically forced into urinary excretion, whole-body metabolism undergoes adaptive changes involving glucose fluxes, hormonal responses, fuel selection, and energy expenditure (1,2). In previous work (3), we used empagliflozin to investigate the physiological response to forced glycosuria in patients with type 2 diabetes (T2D). By combining a mixed meal with the double-tracer technique, we found that after acute or chronic empagliflozin administration endogenous glucose production (EGP) rose, tissue glucose disposal (TGD) decreased, and lipid utilization increased. The aims of the present work were to measure the full spectrum of changes in lipolysis, lipid levels, and substrate availability consequent upon empagliflozininduced glycosuria in patients with T2D and to test whether and to what extent these changes occur in subjects without diabetes.
RESEARCH DESIGN AND METHODS
PopulationSixty-six patients with T2D were recruited into the study; their inclusion criteria are detailed in Ferrannini et al. (3). Twenty-five subjects without diabetes (12 with normal glucose tolerance [NGT] and 13 with impaired glucose tolerance [IGT]) served as control subjects (Supplementary Table 1). The glucose and hormone data for the patients with T2D have been reported (3) and are repeated here for comparison purposes. The study (clinicaltrials.gov identifier NCT01248364; EudraCT number 2010-...