Ganoderma lucidum protects against liver damage from high-fat diets

Background and objectives

A long-term high-fat diet (HFD) exerts lipotoxic effects on multiple organs, particularly the liver, leading to metabolic diseases. This study aimed to delineate the dynamic effects of HFD on lipid metabolism, elucidate the mechanisms underlying hepatic lipotoxicity, and investigate the protective effects of Ganoderma lucidum against lipotoxicity both in vitro and in vivo.

Methods

C57BL/6 mice were fed either a 45% or 60% HFD, followed by measurements of body composition, serum lipid profile, and liver pathology at four, eight, twelve, and sixteen weeks. Inflammatory responses, the unfolded protein response (UPR), and endoplasmic reticulum (ER)-phagy were examined in the livers of mice at 16 weeks. Male C57BL/6 mice were randomly assigned to four groups (n = 12 per group): normal diet, 45% HFD, and two HFD + Ganoderma lucidum water extract (GLE) groups (1 g/kg/d and 2 g/kg/d of crude drug, orally administered by gavage for eight weeks following a four-week HFD induction).

Results

Body weight, body fat, serum lipids, and hepatic steatosis increased progressively, accompanied by impaired glucose tolerance and liver injury, as indicated by elevated serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels. HFD also induced activation of the STING and NF-κB signaling pathways, as well as the PERK and IRE1 branches of the UPR. Similarly, ER-phagy selective receptors, particularly FAM134B, which is primarily expressed in hepatocytes as shown by single-cell sequencing, were upregulated after 16 weeks of HFD feeding. Furthermore, GLE mitigated palmitic acid-induced lipotoxicity in primary hepatocytes, as evidenced by improved cell viability, reduced ALT, AST, and lactate dehydrogenase levels in the culture supernatant, and decreased transferase dUTP nick-end labeling-positive cell counts. In 45% HFD-fed mice, GLE reduced serum total cholesterol, low-density lipoprotein, and hepatic triglyceride levels.

Conclusions

HFD-induced lipotoxicity causes hepatic tissue injury and inflammatory responses, which may be alleviated by coordinated regulation of compensatory UPR and ER-phagy. Ganoderma lucidum shows promise as a dietary supplement for managing metabolic disorders.