The effect of HY7715 treatment on physiological fatigue in aged mice. (A) Blood was sampled from the tail vein after the treadmill test, and lactate was analyzed using a lactate sensor. After sacrifice, (B) plasma lactate, (C) plasma aspartate aminotransferase (AST), (D) plasma alanine aminotransferase (ALT), (E) plasma blood urea nitrogen (BUN), and (F) plasma creatinine concentrations were detected using a commercial colorimetric enzyme-linked immunosorbent assay (ELISA) kit. Statistical significance was determined using one-way ANOVA followed by Tukey’s post hoc test (N = 5). Datasets denoted by different letters are significantly different; p < 0.05 (a > b > c > d). YM, young mice; OM, old mice; OM + C, creatine-treated old mice; OM + HY, HY7715-treated old mice.