TGF contributes to impaired exercise response by suppression of mitochondrial key regulators in skeletal muscle

substantial number of people at risk to develop type 2 diabetes could not improve insulin sensitivity by physical training intervention. We studied the mechanisms of this impaired exercise response in 20 middle-aged individuals who performed a controlled eight weeks cycling and walking training at 80 % individual VO2max. Participants identified as non-responders in insulin sensitivity (based on Matsuda index) did not differ in pre-intervention parameters compared to high responders. The failure to increase insulin sensitivity after training correlates with impaired up-regulation of mitochondrial fuel oxidation genes in skeletal muscle, and with the suppression of the upstream regulators PGC1 and AMPK2. The muscle transcriptome of the non-responders is further characterized by an activation of TGF and TGF target genes, which is associated with increases in inflammatory and macrophage markers. TGF1 as inhibitor of mitochondrial regulators and insulin signaling is validated in human skeletal muscle cells. Activated TGF1 signaling down-regulates the abundance of PGC1, AMPK2, mitochondrial transcription factor TFAM, and of mitochondrial enzymes. Thus, increased TGF activity in skeletal muscle can attenuate the improvement of mitochondrial fuel oxidation after training and contribute to the failure to increase insulin sensitivity.

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Böhm A, Hoffmann C, Irmler M, Schneeweiss P, Schnauder G, Sailer C, Schmid V, Hudemann J, Machann J, Schick F, Beckers J, Hrabě de Angelis M, Staiger H, Fritsche A, Stefan N, Nieß AM, Häring HU, Weigert C