Biochemical diversity of human skeletal muscle

This is the authors' abstract. We don't add key points for this paper.

INTRODUCTION The molecular components largely responsible for muscle attributes such as passive tension development (titin and collagen), active tension development (myosin heavy chain [MHC]), and mechanosensitive signaling (titin) are well studied in animals but less is known about their roles in humans. METHODS 599 biopsies were obtained from 6 human cadaveric donors. Three assays were performed on each biopsy ‐ titin molecular weight determination, hydroxyproline content (a surrogate for collagen content), and MHC isoform distribution. RESULTS Discriminant function analysis (DFA) showed that titin MW was the strongest predictive factor of anatomic region and muscle functional group. On average, human muscles had more slow myosin than lower mammals. Average %MHC‐1 of muscles in this study was 65% (compare to 6% for mouse, 8% for rat, and 19% for rabbit). Overall, larger titins were associated with faster muscles. DISCUSSION The finding that titin was the strongest discriminating factor for DFA with anatomic region and muscle functional group as grouping variables is unexpected; titin is currently primarily considered to be a signal transduction cascade activator or determinant of passive tension. The titin‐MHC‐1 relationship we observed is opposite to that previously observed in rabbits, where large titins were associated with slower muscles.

Titin isoform mapping merits no immediate clinical use in muscle assessment; leaves open its integration into functional or disease models.