Deﬁning the contribution of skeletal muscle pyruvate dehydrogenase (cid:2) 1 to exercise performance and insulin action

the contribution of skeletal muscle pyruvate dehydrogenase (cid:2) 1 to exercise performance and insulin action. Am Physiol Metab 315: 2018. —The pyruvate dehydrogenase complex (PDC) converts pyruvate to acetyl-CoA and is an important control point for carbohydrate (CHO) oxidation. However, the importance of the PDC and CHO oxidation to muscle metabolism and exercise performance, particu- larly during prolonged or high-intensity exercise, has not been fully deﬁned especially in mature skeletal muscle. To this end, we deter- mined whether skeletal muscle-speciﬁc loss of pyruvate dehydrogenase alpha 1 ( Pdha1 ), which is a critical subunit of the PDC, impacts resting energy metabolism, exercise performance, or metabolic adap- tation to high-fat diet (HFD) feeding. For this, we generated a tamoxifen (TMX)-inducible Pdha1 knockout (PDHmKO) mouse, in which PDC activity is temporally and speciﬁcally ablated in adult skeletal muscle. We assessed energy expenditure, ex vivo muscle contractile performance, and endurance exercise capacity in PDH- mKO mice and wild-type (WT) littermates. Additionally, we studied glucose homeostasis and insulin sensitivity in muscle after 12 wk of HFD feeding. TMX administration largely ablated PDH (cid:2) in skeletal muscle of adult PDHmKO mice but did not impact energy expendi- ture, muscle contractile function, or low-intensity exercise performance. Additionally, there were no differences in muscle insulin sensitivity or body composition in PDHmKO mice fed a control or HFD, as compared with WT mice. However, exercise capacity during high-intensity exercise was severely impaired in PDHmKO mice, in parallel with a large increase in plasma lactate concentration. In conclusion, although skeletal muscle PDC is not a major contributor to resting energy expenditure or long-duration, low-intensity exercise performance, it is necessary for optimal performance during high-intensity exercise. one ﬂoxed (FL) Pdha1 allele ( Pdha1Ex8 FL/Y ) whereas female mice had two ﬂoxed alleles ( Pdha1Ex8 FL/FL ). Studies were conducted on male or female PDHmKO mice on a C57BL/6J background, with ﬂoxed but iHSA-Cre -negative littermates used as experimental controls [referred to as wild-type (WT)]. TMX (2 mg) was administered via oral gavage to all mice for 5 consecutive days, starting at 4–5 wk of age. Experimental interventions were conducted a minimum of 4 wk after TMX administration. For diet studies, 2 wk after TMX administration mice were switched to an HFD (20 kcal% protein, 20 kcal% CHOs, 60 kcal% fat) (cat. no. D-12492, Research Diets, Inc., New Brunswick, NJ) or remained on a normal chow diet (25 kcal% protein, 58 kcal% CHOs, 17 kcal% fat) (CHOW; cat. no. 7912 irradiated, Envigo Teklad, East Millstone, NJ) for 12 wk. Diet and exercise studies were done in separate cohorts of mice. Tissues were excised from fasted (4 h) and anesthetized animals, snap-frozen in liquid nitrogen, and stored at (cid:4) 80°C for subsequent analysis. All experiments were approved by and conducted in accordance with the Animal Care Program at the University of California, San Diego.