Shrimp-derived peptides restore spermatogenesis by activating the GDNF/GFRα1/c-RET pathway in a rat model of NAFLD.

OBJECTIVE

The present study was carried out to investigate the protective effects of peptides derived from Pacific white shrimp (Litopenaeus vannamei) by-products on spermatogenesis and spermatogonial stem cell (SSC) self-renewal in a rat model of non-alcoholic fatty liver (NAFLD).

DESIGN

Experimental study.

SETTING

Urmia University, Urmia, Iran.

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 50°C, yielding 70-75% low molecular weight peptides (<500 Da), and administered via oral gavage for 10 weeks.

MAIN OUTCOME MEASURES: The expressions of Glial cell line-derived neurotrophic factor (GDNF), GDNF family receptor alpha-1 (GFRα1), c-RET and BCL6b were evaluated by qPCR and immunohistochemistry. Spermatogenesis and tubular differentiation indices, tubular differentiation index (TDI), spermiogenesis index (SPI), histological alterations, oxidative stress biomarkers (malondialdehyde [MDA], reduced glutathione [GSH], oxidized glutathione [GSSG], and insulin resistance (HOMA-IR), were assessed.

RESULTS

HFD markedly reduced SSC self-renewal markers, impaired spermatogenesis, increased oxidative stress and HOMA-IR, compared with the control group (p < 0.05). Peptide supplementation, especially at 300 mg/kg, upregulated the expression of GDNF, GFRα1, c-RET and BCL6B, improved spermatogenic indices, partially restored redox balance, reduced HOMA-IR, and ameliorated histological damage in the testes.

CONCLUSIONS

In conclusion, these findings provide new evidence that shrimp-derived peptide supplementation was associated with reduced oxidative-stress markers, enhanced GDNF/GFRα1/c-RET-related measures, and improved spermatogenic indices and support SSC self-renewal in NAFLD-induced male reproductive dysfunction.