Exercise mitigates liver senescence but does not outmatch dietary restriction in obesity-related MASLD

The present study aims at deciphering the individual or combined benefits of aerobic exercise and dietary restriction on liver senescence, a state characterized by cell cycle arrest and simultaneous resistance to apoptosis, which is considered an established hallmark of metabolic dysfunction-associated steatotic liver disease (MASLD).

C57BL6 mice were subjected to a normal diet (ND) for 20 weeks or a high-fat diet (HFD) supplemented with 5 % High-fructose Corn Syrup (HFCS) for 12 weeks, followed by eight-week interventions, including dietary restriction (DR), aerobic exercise (EX), a combination of both (DREX) or continuation of a HFD-HFCS diet without intervention. Biomarkers of senescence were analyzed in terms of their liver mRNA expression levels, while GL13 and p21^WAF1/CIP1 immunohistochemical stainings were conducted to examine the levels of senescence-associated lipofuscin and p21^WAF1/CIP1 respectively, to finally investigate their relationship with the grade of hepatic steatosis and fibrosis observed in the studied mice.

DR and DREX groups exhibited significantly reduced features of obesity and MASLD-related hepatic steatosis and fibrosis, to a greater extent than the respective amelioration driven by aerobic exercise only in HFDEX animals. A statistically significant increase of mRNA expression was detected for cyclin-dependent kinase p21^WAF1/CIP1 in HFD livers as compared to ND, which was also reversed upon DR-inclusive interventions. Immunohistochemical stainings for GL13 and p21^WAF1/CIP1, as well as for p16^INK4A confirmed the aforementioned alterations of p21^WAF1/CIP1 at the tissular level while also revealed a p16^INK4A elevation in HFD livers which was reversed only upon DR/DREX.

Liver senescence is responsive both to exercise and dietary restriction, but its amelioration in the context of MASLD is more robust upon DR-inclusive interventions.