Caloric restriction exacerbates renal post-ischemic injury and fibrosis by modulating mTORC1 signaling and autophagy.

Abstract

Objective: This study investigates the effects of caloric restriction (CR) on renal injury and fibrosis following ischemia-reperfusion injury (IRI), with a focus on the roles of the mechanistic/mammalian target of rapamycin complex 1 (mTORC1) signaling and autophagy.

Methods: A mouse model of unilateral IRI with or without CR was used. Renal function was assessed through serum creatinine and blood urea nitrogen levels, while histological analysis and molecular assays evaluated tubular injury, fibrosis, mTORC1 signaling, and autophagy activation. Inducible renal tubule-specific Atg7 knockout mice and autophagy inhibitor 3-MA were used to elucidate autophagy's role in renal outcomes.

Results: CR exacerbated renal dysfunction, tubular injury, and fibrosis in IRI mice, associated with suppressed mTORC1 signaling and enhanced autophagy. Rapamycin, an mTORC1 inhibitor, mimicked the effects of CR, further supporting the involvement of mTORC1-autophagy pathway. Tubule-specific Atg7 knockout and autophagy inhibitor 3-MA mitigated these effects, indicating a central role for autophagy in CR-induced renal damage. Glucose supplementation, but not branched-chain amino acids (BCAAs), alleviated CR-induced renal fibrosis and dysfunction by restoring mTORC1 activation. Finally, we identified leucyl-tRNA synthetase 1 (LARS1) as a key mediator of nutrient sensing and mTORC1 activation, demonstrating its glucose dependency under CR conditions.

Conclusion: Our study provides novel insights into the interplay between nutrient metabolism, mTORC1 signaling, and autophagy in IRI-induced renal damages, offering potential therapeutic targets for mitigating CR-associated complications after renal IRI.