Omega-3 polyunsaturated fatty acids ameliorate high-fat-diet-induced structural and functional impairments of testicular tissue via ER stress inhibition.

Obesity is a well-established risk factor for male infertility. Recent studies have demonstrated that endoplasmic reticulum (ER) stress is a key contributor to spermatogenic disorder associated with obesity. Omega-3 polyunsaturated fatty acids (n-3 PUFAs) have been shown to mitigate ER stress, thereby alleviating insulin resistance. However, their specific role in obesity-induced reproductive disorders remains unclear. In this study, we used the transgenic fat-1 mice (TG mice) that are capable of endogenously converting Omega-6 polyunsaturated fatty acids (n-6 PUFAs) to n-3 PUFAs. The mice were divided into four groups according to their diet: a control group (WT + ND, n = 8), a wild type high-fat diet group (WT + HFD, n = 8), a transgenic control group (TG + ND, n = 8), and a transgenic high-fat diet group (TG + HFD, n = 8). After 18 weeks of feeding, the mice were anesthetized and euthanized to examine indicators related to obesity and reproductive function. High-fat diet (HFD) induced significant obesity in WT mice, and we observed significant alteration mitophagy in the reproductive function of WT mice (P < 0.001), primarily manifested as abnormal testicular morphology, decreased sperm quantity and motility (P < 0.01), and reduced testosterone levels (P < 0.01). TG mice exhibited a significant attenuation of these pathological changes (P < 0.05). Markers of ER stress and mitophagy were significantly reduced in the testes of TG mice (P < 0.01), accompanied by an increased expression of phosphorylated AMP-activated protein kinase (AMPK) (P < 0.01), compared to WT mice. Concurrently, TG mice exhibited significantly elevated levels of mitochondrial biogenesis markers and key enzymes involved in testosterone synthesis in the testes, compared to those in WT mice (P < 0.01). Furthermore, TG mice displayed notable resistance to testicular inflammation induced by HFD compared with WT mice (P < 0.01). Our findings suggest that HFD-induced obesity is associated with impaired testicular morphology and function in mice. n-3 PUFAs may ameliorate these impairments by activating AMPK to suppress ER stress, restore mitochondrial dysfunction, and alleviate inflammation, thereby improving testicular morphology and function.