# Methionine Antagonizes Liver and Kidney Antioxidant Function Damage in Heat-Stressed Rex Rabbits

## TL;DR

Methionine helps protect the liver and kidneys of Rex rabbits from heat stress by boosting antioxidant defenses.

## Contribution

Methionine supplementation is shown to mitigate heat-induced oxidative damage in Rex rabbits via enhanced antioxidant activity.

## Key findings

- Methionine supplementation reduced oxidative stress markers like MDA and elevated antioxidant enzyme activities (SOD, CAT, GPx).
- 0.3% methionine improved liver and kidney health by suppressing amino acid catabolism and enhancing Nrf2/HO-1 and Nrf2/NQO1 pathways.
- Pathological analysis confirmed reduced tissue damage and fibrosis in supplemented rabbits.

## Abstract

Global climate warming has intensified extreme heat events, challenging intensive Rex rabbit farming. As economically valuable fur-meat hybrids, Rex rabbits are highly susceptible to heat stress due to underdeveloped sweat glands. This study explored methionine as a safe, eco-friendly dietary additive to counteract heat-induced damage. Using a heat stress model, we demonstrated that methionine supplementation effectively alleviated hepatic and renal oxidative injuries in heat-stressed rabbits. These findings propose methionine as a viable nutritional strategy to enhance thermotolerance in commercial rabbit production under escalating climatic stressors.

Heat stress triggers systemic oxidative stress that compromises physiological homeostasis. This study evaluated methionine’s effects on hepatic and renal antioxidant capacity in heat-stressed Rex rabbits. Rabbits were divided into five groups (30 replicates/group): control (20–25 °C, basal diet), heat stress (HS, 30–34 °C, basal diet), and HS +0.15%, 0.3%, or 0.45% methionine-supplemented groups. After 21 days, serum, skin, liver, and kidney samples were analyzed for biochemical parameters, oxidative stress markers, and gene expression. Results showed that 0.15–0.3% methionine supplementation under heat stress increased methionine apparent digestibility and suppressed amino acid catabolism; decreased serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels; reduced skin malondialdehyde (MDA) and elevated (MSRA) activity; attenuated hepatic central venous congestion and renal tubular vacuolization; enhanced hepatic superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx) activities (0.3% group); and modulated antioxidant gene expression via Nrf2/HO-1 and Nrf2/NQO1 pathways. Pathological analysis confirmed reduced fibrosis and cellular damage in liver/kidney tissues. Optimal methionine supplementation (0.3%) effectively mitigated heat-induced oxidative organ damage by enhancing endogenous antioxidant defenses and regulating redox-sensitive signaling pathways. These findings provide a nutritional strategy for alleviating heat stress-related metabolic disorders in rabbits.