Shrimp peptides mitigate fatty liver-linked testicular dysfunction in rats via oxidative stress, autophagy, and energy pathways

OBJECTIVE: To study the protective effects of bioactive peptides derived from whiteleg shrimp (Litopenaeus vannamei) by-products on testicular function in a rat model of nonalcoholic fatty liver disease. DESIGN: Experimental study. ANIMALS: Twenty-four adult male Wistar rats (8 weeks old, average weight 230.2 ± 23 g). EXPOSURE: Rats were divided into four groups (n = 6): control (standard chow), high-fat diet (HFD), HFD + 20 mg peptide/kg body weight (BW), and HFD + 300 mg peptide/kg BW. Peptides were enzymatically hydrolyzed at 40 °C-60 °C, yielding 60%-70% low-molecular-weight peptides (<500 Da), and administered via oral gavage for 10 weeks. MAIN OUTCOME MEASURES: Spermatogenic indices (tubule diameter, Sertoli/Leydig cell counts, tubular differentiation index, and spermiogenesis index), oxidative stress markers (malondialdehyde [MDA], reduced glutathione [GSH], oxidized glutathione [GSSG], total antioxidant capacity), autophagy-related gene expression (Beclin-1, Atg7, LC3-I, and p62), and glucose/lactate transporter expression (GLUT1/3, MCT1/4) assessed via quantitative polymerase chain reaction and immunohistochemistry. RESULTS: High-fat diet significantly reduced tubule diameter, Sertoli/Leydig cell numbers, tubular differentiation index, and spermiogenesis index while increasing MDA (11.7 ± 2.9 vs. 8.3 ± 1.0 nmol/mL) and disrupting GSH/GSSG ratio (78.6 ± 8.7 vs. 48.2 ± 9.3). Autophagy genes were upregulated, and GLUT/MCT expression decreased at messenger ribonucleic acid and protein levels. Peptide supplementation, particularly at 300 mg/kg BW, dose-dependently reversed these effects by preserving tubular structure, normalizing oxidative markers (MDA: 8.8 ± 0.55 nmol/mL; GSH/GSSG: 51.5 ± 3.0), reducing autophagy gene expression, and enhancing GLUT/MCT expression in germ and Sertoli cells, with superior efficacy at the higher dose. CONCLUSION: Shrimp-derived bioactive peptides mitigate nonalcoholic fatty liver disease-induced testicular dysfunction by modulating oxidative stress, autophagy pathways, and energy metabolism. They are promising natural therapeutics for preserving male fertility under metabolic stress and warrant clinical investigation.