2759-LB: Aerobic Exercise Modulates Fibrotic Signaling without Excess Collagen Accumulation in Skeletal Muscle of Adults with Type 2 Diabetes

Introduction and Objective: Skeletal muscle fibrosis contributes to impaired muscle regeneration, reduced strength, and metabolic dysfunction in type 2 diabetes (T2DM). Transforming growth factor-β1 (TGF-β1) signaling regulates extracellular matrix (ECM) remodeling, but human data linking transcriptional changes to protein-level ECM adaptations following exercise are limited. Our objective was to determine whether exercise-induced transcriptional changes in fibrotic signaling correspond to alterations in collagen and fibrotic pathway protein abundance in skeletal muscle of adults with T2DM. Methods: Twenty adults with T2DM underwent vastus lateralis muscle biopsies at baseline and after 12-wks of aerobic exercise training (AE: 60min/d, 5 d/wk, ~70% VO2max; NCT03021252) or standard of care (CON). Muscle biopsies were taken 48 hrs after the last training session. RNA sequencing (>100M paired-end reads) identified differential expression of fibrosis-related genes and TGF-β1 signaling pathways. Protein abundance of ECM markers was measured by western blot and normalized to total protein. Data were analyzed using a linear mixed-effects model (group, time, group × time). Results: RNA-seq identified 27 differentially expressed (AE vs CON) fibrosis-related genes following AE training (padj <0.05, |log2FC|>0.5) including increased SMAD7 expression. AE training also increased expression of structural ECM genes including COL1A1, COL1A2, COL3A1, and COL4A1. Despite these transcriptional changes, mixed-effects analysis revealed no significant main effects of group or time and no group × time interactions for COL1, COL3, SMAD, pSMAD, or TGFB1 protein abundance. Conclusion: AE altered transcriptional regulation of fibrotic signaling pathways in skeletal muscle of adults with T2DM without corresponding changes in collagen protein abundance, indicating regulated ECM remodeling rather than fibrotic accumulation. Future work should define ECM remodeling mechanisms with AE. Disclosure C.A. Lutz: None. J.F. Horowitz: None. A.T. Ludlow: None. J. Haus: None. Funding NIH (DK109948)