Mitochondrial pyruvate carrier inhibitors improve metabolic parameters in diet-induced obese mice

Wesley T Hodges,Chaowapong Jarasvaraparn,Daniel Ferguson,Kristine Griffett,Lauren E Gill,Yana Chen,Ma Xenia G Ilagan,Lamees Hegazy,Bahaa Elgendy,Kevin Cho,Gary J Patti,Kyle S Mccommis,Brian N Finck

doi:10.1016/j.jbc.2021.101554

Abstract

The mitochondrial pyruvate carrier (MPC) is an inner mitochondrial membrane complex that plays a critical role in intermediary metabolism. Inhibition of the MPC, especially in liver, may have efficacy for treating type 2 diabetes mellitus. Herein, we examined the antidiabetic effects of zaprinast and 7ACC2, small molecules which have been reported to act as MPC inhibitors. Both compounds activated a bioluminescence resonance energy transfer–based MPC reporter assay (reporter sensitive to pyruvate) and potently inhibited pyruvate-mediated respiration in isolated mitochondria. Furthermore, zaprinast and 7ACC2 acutely improved glucose tolerance in diet-induced obese mice in vivo. Although some findings were suggestive of improved insulin sensitivity, hyperinsulinemic–euglycemic clamp studies did not detect enhanced insulin action in response to 7ACC2 treatment. Rather, our data suggest acute glucose-lowering effects of MPC inhibition may be due to suppressed hepatic gluconeogenesis. Finally, we used reporter sensitive to pyruvate to screen a chemical library of drugs and identified 35 potentially novel MPC modulators. Using available evidence, we generated a pharmacophore model to prioritize which hits to pursue. Our analysis revealed carsalam and six quinolone antibiotics, as well as 7ACC1, share a common pharmacophore with 7ACC2. We validated that these compounds are novel inhibitors of the MPC and suppress hepatocyte glucose production and demonstrated that one quinolone (nalidixic acid) improved glucose tolerance in obese mice. In conclusion, these data demonstrate the feasibility of therapeutic targeting of the MPC for treating diabetes and provide scaffolds that can be used to develop potent and novel classes of MPC inhibitors.

Highlights

Diabetes employ a number of approaches for lowering blood glucose including augmenting the release of insulin by pancreatic beta cells, decreasing reabsorption of glucose by the kidneys, suppressing the production of glucose by the liver, or enhancing the sensitivity of target tissues to the effects of insulin
We have shown that mitochondrial pyruvate carrier (MPC) inhibitors induce a strong increase in bioluminescence resonance energy transfer (BRET) signal likely due to MPC complex conformational changes in response to engagement of the pyruvate binding site (Fig. 1A) [8, 9]
Consistent with an in vivo effect of the MPC inhibitors on gluconeogenesis, we found that administration of zaprinast or 7ACC2 to lean C57BL6/J mice 30 min prior to conducting a lactate/pyruvate tolerance test blunted the gluconeogenic response compared to vehicle-treated mice (Fig. 4D)

Summary

Introduction

Diabetes employ a number of approaches for lowering blood glucose including augmenting the release of insulin by pancreatic beta cells, decreasing reabsorption of glucose by the kidneys, suppressing the production of glucose by the liver, or enhancing the sensitivity of target tissues to the effects of insulin. To determine if these MPC inhibitors might elicit metabolic improvements similar to the effects of TZD-based MPC inhibitors, WT and LS-Mpc2−/− mice were fed a HF diet for 12 weeks and treated with a single injection of 30 mg/kg zaprinast 18 h prior to assessing glucose tolerance.

Results

Conclusion