The role of taste receptor T1R1/T1R3 in autophagy regulation of spermatogenic cells and its association with spermatogenesis in Xiang pigs.

Male infertility is increasingly linked to impaired spermatogenesis, with emerging evidence implicating the umami taste receptor T1R1/T1R3 in male reproductive regulation. This study explored its role in regulating autophagy during spermatogenesis in Xiang pigs. Immunofluorescence confirmed T1R1/T1R3 co-localization in spermatogenic cells. Knockdown of TAS1R3 by RNAi triggered robust autophagy, characterized by increased autophagosomes, mitochondrial swelling, a significant accumulation of 2 C (diploid, spermatogonia) cells (increasing by ∼21%), a corresponding reduction 4 C (tetraploid, spermatocytes) cells (decreasing by ∼11%), a marked upregulation of Beclin 1 protein (by ∼8.0-fold) and the LC3-II/LC3-I ratio (by ∼2.9-fold), downregulation of mTOR, and suppression of key spermatogenic genes (POU5F1, SYCP3, STRA8). Conversely, the receptors activation by its natural ligand L-glutamate (L-Glu) suppressed autophagy, reducing Beclin 1 levels and the LC3-II/LC3-I ratio to approximately 0.7-fold of the control. This activation improved cellular function, upregulated mTOR, increased 1 C (haploid, spermatids) cell populations, and downregulated STRA8. Under H₂O₂-induced autophagy, L-Glu restored T1R3 expression, thereby reversing excessive autophagy and calcium overload, and rescuing the expression of autophagy-related (BECN1, mTOR) and spermatogenesis-related genes (SYCP3, STRA8). In vivo experiments, dietary supplementation with 0.5% L-Glu significantly increased seminiferous tubule diameter and epithelium thickness in Xiang pig testes, upregulating T1R1 and the autophagy substrate p62/SQSTM1. In conclusion, T1R1/T1R3 regulates spermatogenesis by modulating autophagy. Activation by L-Glu mitigates autophagic damage and promotes spermatogenesis, offering a novel strategy for enhancing male fertility by targeting T1R1/T1R3.