Hepatic Gluconeogenic Response to Single and Long-Term SGLT2 Inhibition in Lean/Obese Male Hepatic G6pc-Reporter Mice

Abstract

Sodium-glucose cotransporter 2 inhibitor (SGLT2i) consistently reduces blood glucose levels in type 2 diabetes mellitus but increases hepatic gluconeogenic gene expression and glucose production, offsetting its glucose-lowering effect. This study aimed to elucidate the effect of SGLT2i on hepatic gluconeogenic response and its mechanism in both insulin-sensitive and insulin-resistant states. A hepatic mouse model was generated to show liver-specific expression of Gaussia luciferase (GLuc) driven by the gluconeogenic enzyme gene G6pc promoter. Hepatic gluconeogenic response was evaluated by measuring plasma GLuc activity. SGLT2i was given to lean and obese mice in single gavage administration or 4-week dietary administration with controlled feeding every 3 hours. In lean mice, single-dose SGLT2i increased plasma GLuc activity from 2 hours after administration, decreasing blood glucose and plasma insulin from 1 to 2 hours after administration. In obese mice, which had higher plasma GLuc activity than lean ones, SGLT2i did not further increase GLuc activity despite decreased blood glucose and plasma insulin. Hepatic Akt and GSK3β phosphorylation was attenuated by single-dose SGLT2i in lean mice in accordance with the plasma insulin decrease, but not in obese mice. Long-term SGLT2i administration, which increased plasma GLuc activity in lean mice, decreased it in obese mice from 3 weeks after initiation, with increased hepatic Akt and GSK3β phosphorylation. In conclusion, single SGLT2i administration increases hepatic gluconeogenic response in lean insulin-sensitive mice, but not in obese insulin-resistant mice. Long-term SGLT2i administration relieves obesity-induced upregulation of the hepatic gluconeogenic response by restoring impeded hepatic insulin signaling in obese insulin-resistant mice.

Diet intake control is indispensable for the gluconeogenic response to sodium–glucose cotransporter 2 inhibition in male mice

“…SGLT2i was associated with a decreasing tendency of plasma insulin levels under controlled feeding, which was statistically significant until 2 weeks after the start of administration. Partly because controlled feeding itself showed a non-significant tendency for a decrease in plasma insulin levels in the control group of lean mice, as reported previously 10 , this significant decrease in plasma insulin was lost after 3 weeks. Although plasma insulin showed an increasing tendency in mice with SGLT2i administration after 1 week, this increase was not evident in a previous study carried out using the same regimen 10 .…”

“…AP-194033 and AP-163742). L-G6pc-GLuc male mice were generated by crossing liver-specific Cre recombinase-expressing mice 19,20 and G6pc-YFP/GLuc transgenic mice, which carry G6pc promoter and floxed yellow fluorescent protein followed by GLuc, as described previously 10 . Mice were housed in a temperature-controlled environment under a 12-h light/dark cycle with free access to normal chow (NC; CRF-1; Oriental Yeast Co., Ltd., Kyoto, Japan) and water under specific pathogen-free conditions.…”

“…Plasma concentrations of free fatty acids were determined by NEFA C-Test-Wako kits (Fujifilm Wako Pure Chemical Co.). Hepatic triglyceride and glycogen contents were measured as described previously 10,26 .…”

“…Quantitative polymerase chain reaction was carried out with the SYBR Select Master Mix (Thermo Fisher Scientific, Waltham, MA, USA), and the results were normalized using the Rplp0 gene as internal control. The sequence-specific primers used in the present study were described previously 10,27,28 and are available on request.…”

Autophagy stimulation and intracellular sodium reduction as mediators of the cardioprotective effect of sodium–glucose cotransporter 2 inhibitors

“…Other pathways that regulate autophagy (e.g. the serine/threonine kinase Akt) may also be involved in the action of SGLT2 inhibitors …”