BACKGROUND AND PURPOSESmall-molecule glucokinase activators (GKAs) are currently being investigated as therapeutic options for the treatment of type 2 diabetes (T2D). Because liver overexpression of glucokinase is thought to be associated with altered lipid profiles, this study aimed at assessing the potential lipogenic risks linked to oral GKA administration. EXPERIMENTAL APPROACHNine GKA candidates were qualified for their ability to activate recombinant glucokinase and to stimulate glycogen synthesis in rat hepatocytes and insulin secretion in rat INS-1E cells. In vivo activity was monitored by plasma glucose and HbA1c measurements after oral administration in rodents. Risk-associated effects were assessed by measuring hepatic and plasma triglycerides and free fatty acids, as well as plasma aminotransferases, and alkaline phosphatase. KEY RESULTSGKAs, while efficiently decreasing glycaemia in acute conditions and HbA1c levels after chronic administration in hyperglycemic db/db mice, were potent inducers of hepatic steatosis. This adverse outcome appeared as soon as 4 days after daily oral administration at pharmacological doses and was not transient. GKA treatment similarly increased hepatic triglycerides in diabetic and normoglycaemic rats, together with a pattern of metabolic phenotypes including different combinations of increased plasma triglycerides, free fatty acids, alanine and aspartyl aminotransferases, and alkaline phosphatase. GKAs belonging to three distinct structural families induced hepatic steatosis in db/db mice, arguing in favour of a target-mediated, rather than a chemical class-mediated, effect. CONCLUSION AND IMPLICATIONSGiven the risks associated with fatty liver disease in the general population and furthermore in patients with T2D, these findings represent a serious warning for the use of GKAs in humans.

BACKGROUND AND PURPOSESmall molecule glucokinase activators (GKAs) have been associated with potent antidiabetic efficacy and hepatic steatosis in rodents. This study reports the discovery of S 50131 and S 51434, two novel GKAs with an original scaffold and an atypical pharmacological profile. EXPERIMENTAL APPROACHActivity of the compounds was assessed in vitro by measuring activation of recombinant glucokinase, stimulation of glycogen synthesis in rat hepatocytes and increased insulin secretion from rat pancreatic islets of Langerhans. Efficacy and safety in vivo were evaluated after oral administration in db/db mice by measuring glycaemia, HbA1c and dyslipidaemia-associated events. KEY RESULTSS 50131 and S 51434 activated GK and stimulated glycogen synthesis in hepatocytes and insulin secretion from pancreatic islets. Unexpectedly, while both compounds effectively lowered glycaemia after acute oral administration, they did not decrease HbA1c after a 4-week treatment in db/db mice. This lack of antidiabetic efficacy was associated with increased plasma free fatty acids (FFAs), contrasting with the effect of GKA50 and N00236460, two GKAs with sustained HbA1c lowering activity but neutral regarding plasma FFAs. S 50131, but not S 51434, also induced hepatic steatosis, as did GKA50 and N00236460. However, a shorter, 4-day treatment resulted in increased hepatic triglycerides without changing the plasma FFA levels, demonstrating dynamic alterations in the lipid profile over time. CONCLUSIONS AND IMPLICATIONSIn addition to confirming the occurrence of dyslipidaemia with GKAs, these findings provide new insights into understanding how such compounds may sustain or lose efficacy over time. AbbreviationsALAT, alanine aminotransferase; ASAT, aspartyl aminotransferase; FFA, free fatty acid; GCKR, glucokinase regulatory protein; GK, glucokinase; GKA, glucokinase activator; TG, triglyceride BJP British Journal of Pharmacology

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