Small molecule glucokinase activators disturb lipid homeostasis and induce fatty liver in rodents: a warning for therapeutic applications in humans

Investigational anti-hyperglycemic agents: the future of type 2 diabetes therapy?

As the pandemic of type 2 diabetes spreads globally, clinicians face many challenges in treating an increasingly diverse patient population varying in age, comorbidities, and socioeconomic status. Current therapies for type 2 diabetes are often unable to alter the natural course of the disease and provide durable glycemic control, and side effects in the context of individual patient characteristics often limit treatment choices. This often results in the progression to insulin use and complex regimens that are difficult to maintain. Therefore, a number of agents are being developed to better address the pathogenesis of type 2 diabetes and to overcome limitations of current therapies. The hope is to provide more options for glucose lowering and complication reduction with less risk for hypoglycemia and other adverse effects. These agents include newer incretin-based therapies and PPAR agonists, as well as new therapeutic classes such as sodium-coupled glucose cotransporter 2 inhibitors, free fatty acid receptor agonists, 11-β-hydroxysteroid dehydrogenase type 1 inhibitors, glucokinase activators, and several others that may enter clinical use over the next decade. Herein we review these agents that are advancing through clinical trials and describe the rationale behind their use, mechanisms of action, and potential for glucose lowering, as well as what is known of their limitations.

Treatment with exendin-4 improves the antidiabetic efficacy and reverses hepatic steatosis in glucokinase activator treated db/db mice

The glucokinase activators improve the fasting as well as postprandial glucose control and are important investigational drugs for the treatment of diabetes. However, recent studies have implicated that continuous activation of glucokinase with a small molecule activator can increase hepatic triglycerides and the long term glucose control is not achieved. In this study, we investigated the effect of combination of glucokinase activator (GKA, Piragliatin) with GLP-1 receptor agonist exendin-4 (Ex-4) in male db/db mice. Twelve weeks combination treatment in the db/db mice resulted in a significant decrease in body weight gain, food consumption, random glucose and %HbA1c. The decrease in serum glucose and %HbA1c in combination group was more profound and significantly different than that of individual treatment (GKA or Ex-4) group. GKA treatment increased hepatic triglycerides, whereas combination of Ex-4 with GKA attenuated hepatic steatosis. The combination of GKA with Ex-4 reduced the hepatic lipid accumulation, improved the insulin sensitivity, and reduced hepatic glucose production in db/db mice. Overall, our data indicate that combination of GKA and GLP-1 receptor agonist Ex-4 improves glucose homeostasis, shows antiobesity activity, without causing harmful side effects like fatty liver.

Small molecular glucokinase activators: has another new anti-diabetic therapeutic lost favour?

Glucokinase activators (GKAs) represent one of the leading hopes for the next generation of type 2 diabetes (T2D) therapeutics, showing efficacy in reducing blood glucose and HbA1c levels in animal models of T2D and short-term human trials. While the hypoglycaemic risks of GCK activation in pancreatic beta-cells have long been appreciated, the hepatic effects of GKAs have generally been perceived to be without significant side effect. In this issue of the British Journal of Pharmacology, De Ceuninck et al. report that acute and chronic GKA treatment of normoglycaemic and hyperglycaemic rodent models results in significant accumulation of triglycerides in the liver. This suggests GKA-mediated activation of hepatic glucose uptake and suppression of endogenous glucose production may come at a significant cost; namely, the development of hepatic steatosis. This raises important questions regarding the safety of GKAs and emphasizes that both plasma and hepatic lipid profiles should be carefully monitored in on-going and future studies of these molecules.

LINKED ARTICLE

This article is a commentary on De Ceuninck et al., pp. 339-353 of this issue. To view this paper visit http://dx.doi.org/10.1111/j.1476-5381.2012.02184.x.