Melatonin Alleviates High-Fructose-Induced Renal Injury in Male Mice, Which Might Be Associated with the Regulation of Mitophagy and Fatty Acid Oxidation

<b>Objective</b>: To explore the preventive effect and mechanism of melatonin on high-fructose-induced renal injury in mice. <b>Methods</b>: A total of forty male C57BL/6J mice aged six weeks were randomly assigned to four groups: control group (CON), melatonin group (MLT), fructose group (FRU), and fructose + melatonin group (FRU + MLT). The concentration of the fructose solution was 30%, and the dose of melatonin was 10 mg/kg/day by intragastric administration. The experiment lasts for 10 weeks. <b>Results</b>: Liquid intake and energy intake were comparable between the FRU and FRU + MLT, both of which were significantly higher than that in the CON and MLT. MLT inhibited fructose-induced increased levels in serum creatinine (Cre), serum urea nitrogen (BUN), serum uric acid (UA), serum triglyceride (TG), renal kidney injury molecule-1 (KIM-1), and renal TG. Hematoxylin and Eosin (H&E) staining and Oil Red O (ORO) staining showed that MLT alleviated renal tubular dilatation, loss of brush border, epithelial cell detachment and lipid accumulation. Transmission electron microscope (TEM) observations showed that MLT increased autophagic vacuoles among mitochondria. Western blot analysis showed that, compared with the FRU, the FRU + MLT had elevated expression of AMP-activated protein kinase (AMPK) phosphorylation, along with a significant increase in the expression of its downstream mitophagy-related proteins (including PINK1, Parkin, LC3 II, and Beclin1), whereas the expression of p62 was markedly decreased. Furthermore, the expression levels of FAO-related proteins (including PPARα and CPT1A) in the FRU + MLT were significantly upregulated. <b>Conclusions</b>: MLT alleviates renal injury caused by high-fructose exposure in male mice and its mechanism might be associated with the regulation of mitophagy and fatty acid oxidation.