Intracellular toxic advanced glycation end-products (TAGE) in myoblasts may cause sarcopenia: Research article of a non-clinical study
Abstract Background: Sarcopenia is a progressive disease that is characterized by decreases in skeletal muscle mass and function. Skeletal muscle consists of myotubes that differentiated from myoblasts. Although sarcopenia is associated with non-alcoholic steatohepatitis (NASH) and type 2 diabetes mellitus (T2DM), the underlying mechanisms remain unclear. We considered that glyceraldehyde (GA), a glucose/fructose metabolism intermediate, plays a crucial role in sarcopenia. We previously designated GA-derived advanced glycation end-products (AGEs) as toxic AGEs (TAGE) because of their cytotoxicity and involvement in lifestyle-related diseases (LSRD), such as NASH and T2DM. We hypothesized that TAGE induce cytotoxicity in myoblasts. Methods: C2C12 cells, which are murine myoblasts, were treated with 0, 0.5, 1, 1.5, and 2 mM GA for 24 h, and cell viability and intracellular TAGE were measured using WST-8 and slot blot assays. Cells were pretreated with 8 mM aminoguanidine (AG), an inhibitor of AGE production, for 2 h followed by 0, 1.5, and 2 mM GA for 24 h. Cell viability and intracellular TAGE were then measured. Serum TAGE levels in STAM mice, in which there were four stages (pre-simple steatosis, simple steatosis, steatohepatitis, and fibrosis), were measured using an enzyme-linked immunosorbent assay. Results were expressed as TAGE units (U) per milliliter of serum, with 1 U corresponding to 1.0 μg of GA-derived AGE-bovine serum albumin (BSA) (TAGE-BSA). The viabilities of cells treated with 20 μg/mL non-glycated BSA (NG-BSA) and TAGE-BSA for 24 h were assessed using the WST-8 assay. Results: In C2C12 cells treated with 1.5 and 2 mM GA, cell viability decreased to 47.7 and 5.0% and intracellular TAGE increased to 6.0 and 15.9 μg/mg protein, respectively. Decreases in cell viability and TAGE production were completely inhibited by 8 mM AG. Serum TAGE levels at the steatohepatitis and fibrosis stages were 10.51 ±1.16 and 10.44±0.95 U/mL, respectively, and increased from the pre-simple steatosis stage. The viabilities of C2C12 cells treated with 20 μg/mL NG-BSA and TAGE-BSA were 99.7 and 88.3%, respectively. Conclusion: Intracellular TAGE were generated in C2C12 cells and induced cell death more strongly than extracellular TAGE. Intracellular TAGE in myoblasts may cause sarcopenia in patients with LSRD.