Immune, Oxidative, and Morphological Changes in the Livers of Tibetan Sheep after Feeding Resveratrol and β-Hydroxy-β-methyl Butyric Acid: A Transcriptome–Metabolome Integrative Analysis

This study investigated the effects of dietary resveratrol (RES) and β-Hydroxy-β-methyl butyric acid (HMB) on immune, oxidative, and morphological changes in the livers of Tibetan sheep using transcriptomics and metabolomics. One hundred and twenty male Tibetan lambs of a similar initial weight (15.5 ± 0.14 kg) were randomly divided into four groups with thirty lambs per treatment: (1) H group (basal diet without RES or HMB); (2) H-RES group (1.5 g/day of RES); (3) H-HMB group (1250 mg/day of HMB); (4) H-RES-HMB group (1.5 g/day of RES and 1250 mg/day of HMB). The experiment was conducted for 100 days, including a pre-test period of 10 days and a formal period of 90 days. The results showed significantly increased concentrations of glutathione peroxidase, superoxide dismutase, and IgM in the H-RES-HMB group (<i>p</i> < 0.05), while the malondialdehyde levels were significantly decreased (<i>p</i> < 0.05). The glycolytic indices including creatinine kinase (CK), malate dehydrogenase (MDH), and succinate dehydrogenase (SDH) were significantly increased in the H-RES-HMB group compared with the others (<i>p</i> < 0.05). A histological analysis showed that the hepatic plate tissue in the H-RES-HMB group appeared normal with multiple cells. The transcriptomic analysis showed that the expression of genes associated with the calcium signaling pathway (<i>MYLK2</i>, <i>CYSLTR2</i>, <i>ADCY1</i>, <i>HRH1</i>, <i>ATP2B2</i>, <i>NOS2</i>, <i>HRC</i>, <i>ITPR1</i>, and <i>CAMK2B</i>) and the NF-κB signaling pathway (<i>BCL2</i> and <i>CARD14</i>) in the H-RES-HMB group were upregulated. The key differential metabolites (d-pyroglutamic acid, DL-serine, DL-threonine, fumarate, and glyceric acid) were enriched in the pathways associated with D-amino acid metabolism, the citrate cycle (TCA cycle), and carbon metabolism. The combined transcriptomic and non-targeted metabolomic analyses showed the co-enrichment of differential genes (<i>NOS2</i> and <i>GLUD1</i>) and metabolites (fumarate) in arginine biosynthesis-regulated glycolytic activity, whereas the differential genes (<i>ME1</i>, <i>SCD5</i>, <i>FABP2</i>, <i>RXRG</i>, and <i>CPT1B</i>) and metabolites (Leukotriene b4) co-enriched in the PPAR signaling pathway affected the immune response by regulating the PI3K/AKT and cGMP/PKG signaling. In conclusion, the dietary RES and HMB affected the hepatic antioxidant capacity, immune response, and glycolytic activity through modulating the transcriptome (<i>BCL2</i>, <i>CAMK2B</i>, <i>ITPR1</i>, and <i>IL1R1</i>) and metabolome (DL-serine, DL-threonine, fumaric acid, and glycolic acid).