BACKGROUND: The complexity of the galaninergic system is still not fully understood, especially under specific pre-existing comorbidities related to metabolic dysfunction. A plant-derived triterpenoid celastrol was demonstrated to exert a complex effect on the galaninergic system and to have hepatoprotective and anti-obesity properties. However, the exact molecular mechanisms responsible for these effects remain unclear. Specifically, there are no data on the impact of celastrol on the heart and liver galaninergic system. Therefore, this study aimed to investigate the effects of celastrol on the galaninergic system expression in the heart and liver of mice suffering from diet-induced obesity and metabolic dysfunction-associated steatotic liver disease and steatohepatitis (MASLD/MASH). METHODS: The male mice C57BL/6J were fed a Western-type high-fat diet for 16 and 20 weeks to induce obesity and MASLD/MASH. Celastrol was administered along with a specific diet for the last 4 weeks to evaluate its impact on the progression of these conditions. Moreover, the inhibitor of sterol regulatory element-binding protein 1/2 (SREBP1/2), fatostatin, was also tested to compare its influence on the galaninergic system with celastrol. RESULTS: The study demonstrates that celastrol treatment was safe and led to a reduction in food and energy intake, body fat and liver weights, and MASLD-to-MASH progression and improved glucose tolerance, serum biochemistry markers, and hepatic lipid peroxidation in mice. Quantitative gene expression originally showed significant regulation of galanin and all three of its receptors (GalR1/2/3) in the heart ventricles and only GalR2 in the liver of obese mice. Celastrol influenced the gene expression of galanin receptors: it downregulated Galr1 in the heart and upregulated Galr2 in the liver and Galr3 in the heart ventricles, potentially affecting energy metabolism, oxidative stress, and inflammation. Fatostatin suppressed gene expression of all the detected members of the galaninergic system in the heart ventricles, depicting the role of SREBP in this process. CONCLUSION: These findings suggest that celastrol may beneficially modulate the galaninergic system under obesity and MASLD-to-MASH progression, indicating its potential as a therapeutic agent for disorders associated with metabolic dysfunction.

• Keywords
• MASH, MASLD, celastrol, fatostatin, galanin receptor, heart, mouse, obesity,
• Publication type
• Journal Article MeSH

Although some clinical studies have reported increased mitochondrial respiration in patients with fatty liver and early non‑alcoholic steatohepatitis (NASH), there is a lack of in vitro models of non‑alcoholic fatty liver disease (NAFLD) with similar findings. Despite being the most commonly used immortalized cell line for in vitro models of NAFLD, HepG2 cells exposed to free fatty acids (FFAs) exhibit a decreased mitochondrial respiration. On the other hand, the use of HepaRG cells to study mitochondrial respiratory changes following exposure to FFAs has not yet been fully explored. Therefore, the present study aimed to assess cellular energy metabolism, particularly mitochondrial respiration, and lipotoxicity in FFA‑treated HepaRG and HepG2 cells. HepaRG and HepG2 cells were exposed to FFAs, followed by comparative analyses that examained cellular metabolism, mitochondrial respiratory enzyme activities, mitochondrial morphology, lipotoxicity, the mRNA expression of selected genes and triacylglycerol (TAG) accumulation. FFAs stimulated mitochondrial respiration and glycolysis in HepaRG cells, but not in HepG2 cells. Stimulated complex I, II‑driven respiration and β‑oxidation were linked to increased complex I and II activities in FFA‑treated HepaRG cells, but not in FFA‑treated HepG2 cells. Exposure to FFAs disrupted mitochondrial morphology in both HepaRG and HepG2 cells. Lipotoxicity was induced to a greater extent in FFA‑treated HepaRG cells than in FFA‑treated HepG2 cells. TAG accumulation was less prominent in HepaRG cells than in HepG2 cells. On the whole, the present study demonstrates that stimulated mitochondrial respiration is associated with lipotoxicity in FFA‑treated HepaRG cells, but not in FFA‑treated HepG2 cells. These findings suggest that HepaRG cells are more suitable for assessing mitochondrial respiratory adaptations in the developed in vitro model of early‑stage NASH.

• Keywords
• HepG2 cells, HepaRG cells, in vitro models, lipotoxicity, mitochondria, mitochondrial respiration, non‑alcoholic fatty liver disease, steatosis,
• MeSH
• Cell Line MeSH
• Hep G2 Cells MeSH
• Respiration MeSH
• Fatty Acids, Nonesterified MeSH
• Humans MeSH
• Mitochondria MeSH
• Non-alcoholic Fatty Liver Disease * MeSH
• Triglycerides MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Fatty Acids, Nonesterified MeSH
• Triglycerides MeSH