Sulfated polysaccharides from Sargassum swartzii ameliorates glucose and lipid metabolism and enhance fertility potential by reducing testicular apoptosis and oxidative stress in diabetic mice

Diabetes mellitus increasingly threatens male fertility through hormonal dysregulation, oxidative stress, and impaired spermatogenesis. The present study aimed to investigate the effects of sulfated polysaccharides (SPs) isolated from Sargassum swartzii against diabetes-induced infertility and in vitro fertilization (IVF) outcomes. SPs were extracted, purified, and their chemical composition and antioxidant activity were characterized by evaluating total carbohydrate, phenol, and flavonoid content and DPPH radical scavenging assay. Male mice were made diabetic through streptozotocin injection (45 mg/kg) and subsequently divided into six groups that received different daily doses of SPs (50, 200, and 400 mg/kg) for 30 days. Various reproductive markers were assessed, including sperm count, motility, viability, and IVF success, as well as testicular structure, hormone levels, oxidative stress markers. The Sargassum swartzii extract contained 0.148 g/g carbohydrates and 0.197 g/g proteins, 47.18 mg phenolics and 35.12 mg flavonoids. The animal experiment revealed that diabetes led to a significant reduction in reproductive capacity, hormonal balance, and antioxidant defense, accompanied by increased testicular apoptosis and oxidative damage. Treatment with SPs significantly improved these reproductive parameters, such as a significant increase in sperm quality and embryonic development, as well as biochemical factors, including the secretion of testosterone, LH, and FSH hormones in a dose-dependent manner. These improvements were mediated through increased antioxidant enzyme activity and regulation of caspase-3, Bax, Bcl-2 genes expression. Overall, findings suggest that SPs from Sargassum swartzii offer strong therapeutic potential as a safe marine-derived bioactive compound for preventing or treating diabetes-related infertility.