TGF-β-induced miR143/145 influences differentiation, insulin signaling and exercise response in human skeletal muscle [RNA-seq]

Physical training improves insulin sensitivity and can prevent type 2 diabetes. However, approximately 20% of individuals lack a beneficial outcome in glycemic control. TGF-β, identified as a possible upstream regulator involved in this low response is also a potent regulator of microRNAs (miRs). Aim of this study was to elucidate the potential impact of TGF-β-driven miRNAs on individual exercise response. Non-targeted long and sncRNA sequencing analyses of TGF-β1-treated human skeletal muscle cells corroborated the effects of TGF-β1 on muscle cell differentiation and the induction of extracellular matrix components, and identified several TGF-β1-regulated miRs. qPCR validated a potent upregulation of miR143/145 and miR181a2 by TGF-β1 in both human myoblasts and differentiating myotubes. Human skeletal muscle biopsy donors participating in a supervised 8-week endurance training intervention (n=40) were categorized as responder based on fold change ISIMats (≥ +1.1) or low responder. In skeletal muscle of low responders, TGF-β signaling and miR143/145 levels were stronger induced by training than in responders. Target-mining revealed HDACs, MYHs and insulin signaling components INSR and IRS1 as potential miR143/145 targets. All these targets were down-regulated in TGF-β1-treated myotubes. Transfection of miR mimics in differentiated myotubes validated MYH1, MYH4, and IRS1 as miR143/145 targets. Elevated TGF-β signaling and miR143/145 induction in skeletal muscle of low responders might obstruct improvements in insulin sensitivity by training in two ways: By negatively impacting cell fusion and myofiber functionality via miR143 suppressing its novel targets MYH1/4; by directly impairing insulin signaling via reduction of INSR by TGF-β and fine-tuned IRS1 suppression by miR143. Human skeletal muscle cells treated with TGF-β1, TGF-β1 + SB431542, or control cells. Data was analysed by RNAseq.