The beneficial metabolic effects of insulin sensitizers are not attenuated by mitochondrial pyruvate carrier 2 hypomorphism

Abstract

Rosiglitazone and pioglitazone are thiazolidinedione (TZD) compounds that have been used clinically as insulin-sensitizing drugs and are generally believed to mediate their effects via activation of the peroxisome proliferator-activated receptor γ (PPARγ). Recent work has shown that it is possible to synthesize TZD compounds with potent insulin-sensitizing effects and markedly-diminished affinity for PPARγ. Both clinically-used TZDs and investigational PPARγ-sparing TZDs, such as MSDC-0602, interact with the mitochondrial pyruvate carrier (MPC) and inhibit its activity. Two proteins, MPC1 and MPC2, comprise the MPC complex. Herein, we used mice expressing a hypomorphic MPC2 protein missing 16 amino acids in the N terminus (Mpc2Δ16 mice) to determine the effects of these residues in mediating the insulin-sensitizing effects of TZDs in diet-induced obese mice. We found that both pioglitazone and MSDC-0602 elicited their beneficial metabolic effects, including improving glucose tolerance, attenuating hepatic steatosis, reducing adipose tissue inflammation, and stimulating adipocyte browning, in both WT and Mpc2Δ16 mice after high fat diet feeding. In addition, truncation of MPC2 failed to attenuate the interaction between TZDs and the MPC in a BRET-based assay or to affect the suppression of pyruvate-stimulated respiration in cells. Collectively, these data suggest that the interaction between TZDs and MPC2 is not affected by loss of the N-terminal 16 amino acids nor are these residues required for the insulin-sensitizing effects of these compounds.

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