Hydrogen administration improves the growth performance of juvenile largemouth bass (Micropterus salmoides) by increasing feed intake, reducing serum lipids, activating mTOR and Nrf2 signaling pathways, and altering the intestinal microbiota

Abstract

Hydrogen (H2) gas is recognized for its anti-oxidative, anti-apoptotic, and anti-inflammatory properties in multiple plant and animal models. Nevertheless, there is a lack of research on the effects of H2 administration on fish. This research seeks to investigate how H2 administration affects the growth performance, mammalian target of rapamycin (mTOR) and nuclear factor erythroid 2-related factor 2 (Nrf2) signaling pathways, and intestinal microbiota of juvenile largemouth bass under normal feeding conditions. The research randomly allocated 240 fish (3.55 ± 0.01 g) into two treatment groups, each comprising 4 replicate tanks with 30 fish per tank. The control group was maintained in regular water, while the experimental group (referred to as H2 group) was treated with H2-dissolved water for 1 h per day for 6 weeks. Upon analysis of both groups, it was revealed that the weight gain, final weight, feed intake, specific growth rate, and survival rate were significantly improved by H2 treatment (P < 0.05). In addition, administration of H2 significantly reduced the triglyceride content and increased the high-density lipoprotein-cholesterol content in the serum (P < 0.05). Moreover, administration of H2 led to a significant increase in the expression of genes associated with mTOR (PI3K, AKT, TOR, S6K1, and 4EBP1) and Nrf2 (Nrf2, SOD, and GPX) signaling pathways (P < 0.05). Furthermore, H2 significantly increased the expression of growth hormone receptor (GHR) and neuropeptide Y (NPY) genes in the brain of juvenile largemouth bass. H2 did not significantly affect intestinal histology. However, it significantly increased the relative abundance of Sulfuritalea, Bradyrhizobium, and norank_f__Beggiatoaceae (P < 0.05) and reduced the relative abundance of Brevundimonas, unclassified_o__Chlamydiales, and Delftia in the intestinal microbiota (P < 0.05). Thus, these results suggested that providing juvenile largemouth bass with H2-dissolved water for 1 h per day can lead to a significantly increasing in growth performance, stimulating feed intake, activating mTOR and Nrf2 signaling pathways, and augmenting the abundance of beneficial bacteria in the intestines of juvenile largemouth bass. These findings provided a valuable support for the H2 application in the largemouth bass healthy culture.