Mechanism of arachidic acid alleviating cold-induced liver metabolic stress via lysosome-mediated lipid degradation and mitochondrial oxidation

ZHAO Zhiwei; ZHU Sijin; LIU Zongcai; LIU Fengshuo; LU Huanyu; CHEN Jingyuan

doi:10.13276/j.issn.2097-1656.2025.05.002

Abstract：Objective To investigate the underlying mechanism of arachidic acid(AA)in alleviating cold-induced metabolic stress in the liver.Methods Forty 8-week-old male C57BL/6 mice were selected to establish an animal model exposed to a 4 ℃ low-temperature environment.The mice were fed either a control diet or an AA-enriched diet for one week.The treatment group was exposed to 4 ℃ for 18 h followed by a 6-hour fasting period;the control group underwent the same procedures but at 22℃.Rectal thermometers and infrared thermography were used to monitor body temperature in the mice.Lipid droplet staining was employed to observe lipid accumulation in liver tissue,while HE staining was used to observe morphological changes in liver tissue.Confocal imaging was utilized to label lysosomes and mitochondria within hepatocytes.Targeted fatty acid lipidomics was applied to analyze changes in liver fatty acid content and composition during acute cold exposure.Cellular respiration and tissue oxygen consumption rates(OCR)in liver tissue were measured using cell culture and tissue respiration assay techniques.Mitochondrial isolation and OCR measurements were conducted to assess the activities of mitochondrial oxidative phosphorylation coupling complexes Ⅰ and Ⅱ.Results Under 24 h of acute cold exposure,the abdominal infrared thermography signals of the mice were significantly reduced,accompanied by a substantial decrease in rectal temperature(P＜0.01).Metabolomic analysis suggested that acute cold exposure significantly induced the expression of Elovll,Elovl3,and Elovl6(P＜0.01).Cellular experiments demonstrated that treatment with a combination of palmitic acid(PA)and oleic acid(OA)inhibited both the basal and maximal OCR of AML12 hepatocytes(P＜0.01).Tissue respiration assays and mitochondrial OCR measurements found that AA treatment enhanced the basal OCR in liver tissue and increased the OCR of hepatocytes' mitochondria(P＜0.01).Confocal imaging showed that AA-treated cells exhibited lower red C12 and green lipid droplet fluorescence signals,and inhibited the accumulation of C12-labeled fatty acids into lipid droplets(P＜0.01).When lysosomal acid lipase inhibitor Lalistat-1 was injected and lipid droplet staining was performed,the results indicated increased accumulation of lipid droplets in AML12 cells under PA+OA stress conditions(P＜0.01).Conclusion Acute cold exposure induces the synthesis pathway of very long-chain saturated fatty acids in the liver.AA inhibits lipid droplet accumulation,enhances mitochondrial oxidative function,alleviates cold-induced lipid droplet deposition in the liver,promotes the contact between lipid droplets and lysosomes,and improves liver metabolism through lysosome-mediated lipid droplet degradation.