Sedentary behavior in mice induces metabolic inflexibility by suppressing skeletal muscle pyruvate metabolism
Piyarat Siripoksup, … , Jared Rutter, Katsuhiko Funai
Piyarat Siripoksup, … , Jared Rutter, Katsuhiko Funai
Published April 23, 2024
Citation Information: J Clin Invest. 2024;134(11):e167371. https://doi.org/10.1172/JCI167371.
View: Text | PDF
Research Article Metabolism

Sedentary behavior in mice induces metabolic inflexibility by suppressing skeletal muscle pyruvate metabolism

Abstract

Carbohydrates and lipids provide the majority of substrates to fuel mitochondrial oxidative phosphorylation. Metabolic inflexibility, defined as an impaired ability to switch between these fuels, is implicated in a number of metabolic diseases. Here, we explore the mechanism by which physical inactivity promotes metabolic inflexibility in skeletal muscle. We developed a mouse model of sedentariness, small mouse cage (SMC), that, unlike other classic models of disuse in mice, faithfully recapitulated metabolic responses that occur in humans. Bioenergetic phenotyping of skeletal muscle mitochondria displayed metabolic inflexibility induced by physical inactivity, demonstrated by a reduction in pyruvate-stimulated respiration (JO2) in the absence of a change in palmitate-stimulated JO2. Pyruvate resistance in these mitochondria was likely driven by a decrease in phosphatidylethanolamine (PE) abundance in the mitochondrial membrane. Reduction in mitochondrial PE by heterozygous deletion of phosphatidylserine decarboxylase (PSD) was sufficient to induce metabolic inflexibility measured at the whole-body level, as well as at the level of skeletal muscle mitochondria. Low mitochondrial PE in C2C12 myotubes was sufficient to increase glucose flux toward lactate. We further implicate that resistance to pyruvate metabolism is due to attenuated mitochondrial entry via mitochondrial pyruvate carrier (MPC). These findings suggest a mechanism by which mitochondrial PE directly regulates MPC activity to modulate metabolic flexibility in mice.

Authors

Piyarat Siripoksup, Guoshen Cao, Ahmad A. Cluntun, J. Alan Maschek, Quentinn Pearce, Marisa J. Brothwell, Mi-Young Jeong, Hiroaki Eshima, Patrick J. Ferrara, Precious C. Opurum, Ziad S. Mahmassani, Alek D. Peterlin, Shinya Watanabe, Maureen A. Walsh, Eric B. Taylor, James E. Cox, Micah J. Drummond, Jared Rutter, Katsuhiko Funai

×

Figure 2

SMC housing reduces pyruvate-dependent respiration without altering palmitate-stimulated respiration.

Options: View larger image (or click on image) Download as PowerPoint
SMC housing reduces pyruvate-dependent respiration without altering palm...
(A) Dot plot representing gene set enrichment analysis (GSEA) pathway analysis (Kyoto Encyclopedia of Genes and Genomes) of differentially expressed genes (FDR < 0.05) in skeletal muscle of sham and SMC mice. Normalized enrichment scores are represented by a darker color (negatively enriched) and lighter color (positively enriched), while a larger dot diameter indicates a smaller adjusted P value. Dot plot was generated with R Studio. (B) Representative Western blot of respiratory complexes (I–V) of whole muscle tissue of sham and SMC mice (n = 3–4 per group). (C) Ratio of nuclear to mitochondrial DNA in gastrocnemius muscle (n = 8 per group). (D) O2 utilization in isolated mitochondria from gastrocnemius muscle measured in the presence of 2 mM ADP, 0.5 mM malate (Mal), 5 mM pyruvate (Pyr), 10 mM succinate, 1 μM carbonyl cyanide-p-trifluoromethoxyphenylhydrazone (FCCP) of sham and SMC mice (n = 4–6 per group). (E) O2 utilization in isolated mitochondria measured in the presence of 2 mM ADP (adenosine diphosphate), 0.5 mM malate, 0.02 mM palmitoyl-l-carnitine (PLC) (n = 4–6 per group). (F) Representative Western blot of respiratory complex proteins in isolated muscle mitochondria of sham and SMC mice (n = 5–6 per group). (G) Reduced (GSH) and oxidized (GSSG) glutathione levels in plantaris muscle of sham and SMC mice (n = 6 per group). (H) Electron leak (JH2O2/O2) with succinate in isolated muscle mitochondria from gastrocnemius muscle of sham and SMC mice (n = 3–6 per group). Data represent mean ± SEM. P values generated by 2-way ANOVA with Tukey’s post hoc test (C–E, G, and H).