Actin Cytoskeleton Dysregulation Links Testicular and Sperm Dysfunction in Type 1 Diabetes

Type 1 diabetes (T1D) is a systemic metabolic disorder associated with male reproductive dysfunction. Given the pivotal role of actin cytoskeleton remodeling in spermatogenesis and sperm function, this study investigated the effects of T1D on actin-regulating pathways in rat testis and spermatozoa (SPZ). Adult Wistar rats were rendered diabetic by streptozotocin administration (65 mg/kg, i.p.). Testicular analysis revealed a reduced F-/G-actin ratio together with marked F-actin disorganization, consistent with altered actin cytoskeleton remodeling. To investigate the molecular mechanisms underlying these alterations, key regulators of actin dynamics were examined. Diabetic animals displayed impaired expression of EPS8, Fascin, N-WASP, and the ARP2/3 complex, suggesting altered regulation of actin assembly, bundling, and branching. Further analyses demonstrated dysregulation of signaling pathways governing cytoskeletal organization. Reduced levels of phosphorylated Disheveled-2, DAAM1, RhoA-GTP, and ROCK1 indicated impairment of the planar cell polarity pathway. In parallel, changes in LIMK1/cofilin phosphorylation supported abnormal regulation of actin filament turnover. Alterations in the RICTOR/PKC/MARCKS signaling pathway further highlighted defects in cytoskeletal control. Similar abnormalities were observed in mature SPZ, where altered F-actin distribution and DAAM1 localization suggested persistent cytoskeletal defects. Moreover, diabetic SPZ exhibited a reduced ability to undergo acrosome reaction, accompanied by altered MARCKS phosphorylation, highlighting defects in actin-dependent processes essential for sperm function and fertilizing capacity. These findings indicate that disruption of actin cytoskeleton dynamics may represent a major mechanism contributing to testicular and sperm abnormalities in T1D, providing new insights into the mechanisms underlying diabetes-associated male reproductive dysfunction.