ALOX15 Aggravates Metabolic Dysfunction-Associated Steatotic Liver Disease in Mice with Type 2 Diabetes via Activating the PPARγ/CD36 Axis

<b><i>Aims:</i></b> Metabolic dysfunction-associated steatotic liver disease (MASLD) is a prevalent hepatic disorder worldwide. Arachidonic acid 15-lipoxygenase (ALOX15), an enzyme catalyzing the peroxidation of polyunsaturated fatty acids, plays a crucial role in various diseases. Here, we sought to investigate the involvement of ALOX15 in MASLD. <b><i>Results:</i></b> In this study, we observed upregulation of ALOX15 in the liver of high-fat diet (HFD)- and streptozotocin (STZ)-induced mice. Metabolomic analysis revealed elevated levels of ALOX15 metabolites, 12(S)-hydroperoxyeicosatetraenoic acid and 15(S)-hydroperoxyeicosatetraenoic acid. Transcriptomic analysis showed that the increased fatty acid uptake regulated by the PPARγ/CD36 pathway predominated in lipid accumulation. To elucidate the mechanism underlying ALOX15-induced lipid accumulation, HepG2 cells were transfected with a lentivirus expressing ALOX15 or small interfering RNA targeting ALOX15 and exposed to palmitic acid (PA). Both ALOX15 overexpression and PA exposure led to increased intracellular free fatty acid and triglyceride, resulting in lipotoxicity. ALOX15 overexpression aggravated the effect of PA, while the knockdown of ALOX15 attenuated PA-induced lipotoxicity. Moreover, the treatment with PPARγ antagonist GW9662 or CD36 inhibitor sulfosuccinimidyl oleate sodium effectively reduced lipid accumulation and lipotoxicity resulting from ALOX15 overexpression and PA exposure, indicating the involvement of the PPARγ/CD36 pathway in ALOX15-mediated lipid accumulation. Furthermore, liraglutide, a widely used glucagon-like peptide 1 receptor (GLP-1R) agonist (GLP-1RA), improved hepatic lipid accumulation in HFD/STZ-induced mice by suppressing the ALOX15/PPARγ/CD36 pathway. <b><i>Innovation and Conclusion:</i></b> Our study underscores the potential of ALOX15 as an emerging therapeutic target for MASLD. In addition, the GLP-1RA may confer hepatoprotection by regulating ALOX15, enhancing our comprehension of the mechanisms underpinning their protection on MASLD. <i>Antioxid. Redox Signal.</i> 43, 37-55.