STAT3/MTND4 Mediates Obesity-Related Seminal Vesicle Injury and Impaired Sperm Motility Via Reactive Oxygen Species /Mitochondrial Dysfunction.

Obesity induces male reproductive dysfunction. Mitochondrial dysfunction ranks among the mechanisms driving functional impairment. Notably, Mitochondrial NADH dehydrogenase subunit 4 (MTND4) exerts a pivotal role in sustaining the function of the mitochondrial electron transport chain and cellular energy metabolism. However, its molecular mechanism in obesity-associated seminal vesicle injury remains incompletely elucidated. In vivo and in vitro models of high-fat diet (HFD) were established, and the body weight changes of mice were recorded. Corresponding assay kits were applied to detect serum testosterone, total cholesterol (TC), and triglycerides (TG) levels, with changes in metabolic phenotypes analyzed. Hematoxylin-eosin staining, computer-aided sperm analysis system, qRT-PCR, Western blot, terminal deoxynucleotidyl transferase dUTP nick-end labeling, reactive oxygen species (ROS) detection, JC-1 staining, and superoxide dismutase/malondialdehyde assay kits were employed to evaluate seminal vesicle tissue structure, sperm function, cell viability, apoptosis, oxidative stress, and mitochondrial function, etc., respectively. The transcription factors upstream of MTND4 were forecast via the JASPAR database. The transcriptional regulation of MTND4 by STAT3 was verified via chromatin immunoprecipitation and dual-luciferase reporter assays. Finally, a STAT3-knockdown and MTND4-overexpression co-transfected HFD cell model was constructed to probe the effects of the STAT3/MTND4 on seminal vesicle injury and sperm motility. HFD induced obesity in mice, as evidenced by increased body weight, decreased serum testosterone level, and elevated levels of TC and TG. Concomitant manifestations included disorganized seminal vesicle tissue structure, epithelial exfoliation, impaired secretory function, together with marked reductions in sperm motility, progressive motility, and concentration. Meanwhile, the expression of MTND4 was markedly upregulated in mice with HFD. Overexpression of MTND4 promoted the accumulation of ROS, decreased mitochondrial membrane potential, and exacerbated oxidative stress, resulting in reduced motility and enhanced apoptosis of seminal vesicle cells. Furthermore, STAT3 transcriptionally activated MTND4; HFD induced a decrease in seminal vesicle cell viability via upregulating STAT3 to activate MTND4 transcription. HFD activates MTND4 transcription via upregulating STAT3, resulting in ROS production and mitochondrial dysfunction, which ultimately mediates obesity-related seminal vesicle injury and sperm dysfunction. The STAT3/MTND4 axis may be a novel target for regulating male reproductive health.