Role of p110a subunit of PI3-kinase in skeletal muscle mitochondria

Skeletal muscle insulin resistance, decreased phosphatidylinositol 3-kinase (PI3K) activation and altered mitochondrial function are hallmarks of type 2 diabetes. We created mice with a muscle-specific knockout of p110a or p110ß, the two major catalytic subunits of PI3K. We find that mice with muscle-specific knockout of p110a, but not p110ß, display impaired muscle insulin signaling and reduced muscle size due to enhanced proteasomal and autophagic activity. Despite insulin resistance and muscle atrophy, M-p110aKO mice show decreased serum myostatin, increased mitochondrial mass, increased mitochondrial fusion visualized by intravital microscopy, and increased PGC1a expression, especially PCG1a2 and PCG1a3. This leads to enhanced mitochondrial oxidative capacity, striking increases in muscle NADH content, and higher muscle free radical release measured in vivo using pMitoTimer reporter. Thus, p110a is the dominant catalytic isoform of PI3K in muscle in control of insulin sensitivity and muscle mass, and has a unique role in mitochondrial homeostasis in skeletal muscle. Overall design: All studies were performed in male mice on C57BL/6J background. Muscle-specific p110alpha or p11beta knockout mice were generated by crossing mice carrying the Cre recombinase gene driven by the human alpha-skeletal actin (HSA) promoter (Jackson Laboratories Stock Number: 006149) with mice carrying either floxed p110alpha or p110beta alleles in which exon 1 of p110alpha or exon 2 of p110bet was flanked with loxP sites. Skeletal muscle from 2-3-month-old male mice was harvested and RNA was extracted using Trizol. Gene expression profiling was performed using NEBNext mRNA Sample Prep Master Mix kit (NEB) by BioPolymers Facility at Harvard Medical School. Reads were aligned to the mouse genome (GRCm38) using STAR aligner and counted with Subread featureCounts.

29

Li ME, Lauritzen HPMM, O'Neill BT, Wang CH, Cai W, Brandao BB, Sakaguchi M, Tao R, Hirshman MF, Softic S, Kahn CR