Impaired lipolysis and mitochondrial dysfunction in the epididymal tissues of high-fat diet-fed mice

A high-fat diet (HFD) is associated with low fertility in male mice, characterized by reduced sex hormone levels and impaired sperm quality. The epididymis is crucial for sperm maturation, yet its vulnerability to metabolic disturbances remains poorly understood. METHODS AND RESULTS: Twelve C57BL/6J mice were randomly assigned to either a HFD (60% kcal from fat; Research Diets, D12492) or a standard diet group. The dietary intervention started at 5 weeks of age and was maintained for 10 weeks. Epididymal tissues from both groups were studied using immunofluorescence and Western blotting. Compared to the control group, HFD-fed mice exhibited significant increases in body weight, epididymal fat pad weight, serum lipids, along with decreased serum testosterone. Epididymal tissues from the HFD group showed marked lipid droplet accumulation and elevated oxidative stress. Consistently, the activity and expression of key lipolytic enzymes-hormone-sensitive lipase (HSL) and adipose triglyceride lipase (ATGL)-were significantly downregulated. Furthermore, HFD feeding disrupted mitochondrial dynamics, as indicated by reduced levels of fusion proteins (MFN1/MFN2) and altered expression of fission markers (p-DRP1(Ser616) and FIS1). Moreover, autophagy-particularly mitophagy and lipophagy-was impaired, evidenced by a significant reduction in autophagosomes and dysregulation of autophagy-related proteins.

This study provides a mechanistic explanation for diet-induced male infertility, demonstrating that HFD impairs epididymal function and creates an adverse microenvironment for sperm maturation by disrupting lipid metabolism, mitochondrial function, and autophagy processes.