Reduced stem cell aging in exercised human skeletal muscle is enhanced by ginsenoside Rg1

Abstract

Background: Stem cell aging, characterized by elevated p16^INK4a expression, decreases cell repopulating and self-renewal abilities, which results in elevated inflammation and slow recovery against stress.

Methods: Biopsied muscles were analyzed at baseline and 24 h after squat exercise in 12 trained men (22 ± 2 y). Placebo (PLA) and immunostimulant Rg1 (5 mg) were supplemented 1 h before a squat exercise, using a double-blind counterbalanced crossover design.

Results: Perceived exertion at the end of resistance exercise session was significantly lowered after Rg1 supplementation. Exercise doubled endothelial progenitor cells (EPC) (p < 0.001) and decreased p16^INK4a mRNA to 50% of baseline (d = 0.865, p < 0.05) in muscle tissues, despite p16^INK4a+ cell and beta-galactosidase⁺ (ß-Gal⁺) cell counts being unaltered. Rg1 further lowered p16INK4a mRNA to 35% of baseline with greater effect size than the PLA level (d = 1.302, p < 0.01) and decreased myeloperoxidase (MPO) mRNA to 39% of baseline (p < 0.05). A strong correlation between MPO and p16^INK4a expression in muscle tissues was observed (r = 0.84, p < 0.001).

Conclusion: EPC in skeletal muscle doubled 1 d after an acute bout of resistance exercise. The exercised effects in lowering EPC aging and tissue inflammation were enhanced by immunostimulant Rg1, suggesting the involvement of immune stimulation on EPC rejuvenation.

Keywords: CD4; Rg1; cellular senescence; p16INK4a; resistance exercise; senolytic.

Figure 1

Biomarkers of cellular senescence in human skeletal muscle 24 h after squat exercise. The p16^INK4a+ cells (A) and ß-Gal⁺ cells (B) are indicated by brown precipitates surrounding myofibers in the immunohistochemical stains of muscle cross-sections. No significant changes in quantity of p16^INK4a+ cells (C) and ß-Gal⁺ cells (D) Were observed post exercise during PLA- and Rg1-supplemented trials. Squat exercise decreased p16^INK4a mRNA (E) While no effect on ß-Gal mRNA (F) in vastus lateralis muscle of young men with training experience. ^*denotes significant difference against Pre, p < 0.05; ^**denotes significant difference against Pre, p < 0.01. Abbreviations: Pre: before exercise; Post: 24 h after exercise. ß-Gal⁺: ß-Galactosidase; PLA: Placebo; Rg1: Ginsenoside Rg1.

Figure 2

Myeloperoxidase mRNA in human skeletal muscle 24 h after squat exercise. Myeloperoxidase mRNA (neutrophil marker) decreased post exercise when immunostimulant Rg1 was supplemented 1 h before exercise (A). Myeloperoxidase mRNA is highly correlated with p16^INK4a mRNA (B) In muscle tissues. ^**denotes significant difference against Pre, p < 0.01. Abbreviations: Pre: before exercise; Post: 24 h after exercise. MPO: Myeloperoxidase; PLA: Placebo; Rg1: Ginsenoside Rg1.

Figure 3

Endothelial progenitor cell expansion (CD34⁺ cells) in human skeletal muscle 24 h after squat exercise. The CD34⁺ cells and p16^INK4a+ cells (B) are indicated by brown precipitates surrounding myofibers in immunohistochemical stains of muscle cross-section. (A) CD34⁺ cells were nearly doubled post exercise (C). Approximately 65% of CD34⁺ cells were colocalized with p16^INK4a+ cells. This ratio was not much affected after exercise (60%) in the trained men. ^*denotes significant difference against Pre, p < 0.05; ^**denotes significant difference against Pre, p < 0.01. Abbreviations: Pre: before exercise; Post: 24 h after exercise. PLA: Placebo; Rg1: Ginsenoside Rg1.

Figure 4

Rating of perceived exertion (RPE) at the end of resistance exercise session was significantly lowered after 1 h after Rg1 supplementation. ^*Significant difference between PLA and Rg1, p < 0.05.