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Background: Tibetan sheep grazing on the Qinghai-Tibet Plateau require dietary protein supplementation; however, they face economic constraints due to the high cost of feed transportation in this region. Given that the leucine metabolite β-hydroxy-β-methyl butyrate (HMB) enhances both protein synthesis and intestinal nutrient absorption, this study employed metagenomics and untargeted metabolomics to systematically evaluate HMB's effects on antioxidant capacity, immune response, microbiota, metabolites, and the health of the small intestine in Tibetan sheep. A total of 120 healthy weaned 60-day-old male Tibetan lambs were assigned to diets containing 0 mg/kg (control group, CON), 430 mg/kg (low HMB, L-HMB), 715 mg/kg (medium HMB, M-HMB), or 1,000 mg/kg (high HMB, H-HMB) for 90 d. At the end of the experiment, 6 lambs from each group were slaughtered for intestinal tissue and content sampling.

Results: The M-HMB treatment significantly increased average daily gain of the lambs without affecting feed intake, thereby improving feed utilization efficiency. M-HMB promoted the development of small intestinal morphological and elevated villus height, while also enhancing the activities of digestive enzyme and disaccharidase activities. Furthermore, M-HMB enhanced the antioxidant capacity, immune response, and barrier function of the small intestine. Metagenomic analysis revealed that M-HMB supplementation improved the composition of the small intestinal microbiota in Tibetan sheep, specifically increasing the relative abundance of Ruminococcus bacterium P7 and R. bromii, and enhanced microbial carbohydrate degradation capacity. Metabolomic analysis demonstrated that M-HMB supplementation significantly altered the small intestinal metabolite profile, enhancing carbohydrate metabolic pathways and increased the production of short-chain fatty acids (SCFAs). M-HMB upregulated PLCβ1 and ERK1/2 protein expression levels in small intestinal tissue and elevated the proportion of Ki67-positive cells at the basal crypt region of small intestinal crypts, suggesting enhanced proliferative activity of intestinal epithelial cells.

Conclusions: In summary, dietary supplementation with M-HMB (715 mg/kg) promoted small intestinal growth and development, enhanced digestive and absorptive functions, optimized the microbial composition, improved carbohydrate degradation, and increased the production of SCFAs, ultimately improving the growth performance of Tibetan sheep lambs.

Background: Nutritional strategies aimed at augmenting growth performance remain a central focus in poultry science. The liver, as a pivotal metabolic organ, exerts profound influence on skeletal muscle development. Nevertheless, the mechanistic interplay between hepatic metabolism and myogenesis has not been fully delineated. Here, by integrating multi-omics analyses with functional validation, we identified xanthosine, a metabolic derivative of hepatic caffeine catabolism, as a previously unrecognized regulator of broiler muscle growth. We further elucidated its mechanistic role in promoting myoblast proliferation.

Results: Comparative phenotypic assessment of high- and low-body-weight broilers revealed substantial differences in breast muscle mass. Metagenomic profiling of cecal microbiota demonstrated only a limited association between microbial composition and body weight. In contrast, untargeted plasma metabolomics uncovered a systemic upregulation of amino acid metabolism in high-body-weight broilers, concomitant with a pronounced activation of caffeine metabolism. Consistently, hepatic transcriptomic profiling revealed marked induction of cytochrome P450 family 1 subfamily A member 2 (CYP1A2), encoding a key enzyme catalyzing caffeine catabolism. Integrated KEGG pathway enrichment across metabolomic and transcriptomic datasets highlighted caffeine metabolism as a significantly perturbed pathway. Among its downstream metabolites, plasma xanthosine was robustly elevated in high-body-weight broilers. Functional validation via in ovo injection demonstrated that xanthosine administration significantly augmented post-hatch growth performance by increasing skeletal muscle mass. Mechanistic investigations further established that xanthosine drives myoblast proliferation through activation of the ERK/GSK3β/β-catenin signaling cascade.

Conclusions: Together, these findings delineate a liver-muscle metabolic axis in which hepatic CYP1A2-driven caffeine metabolism elevates circulating xanthosine, which in turn acts as a pivotal molecular effector of myogenic growth. This study uncovers a previously unappreciated metabolic mechanism by which hepatic activity orchestrates skeletal muscle development. It also highlights targeted modulation of xanthosine metabolism as a promising strategy to enhance broiler growth performance and production efficiency.

Background: β-Carotene exhibits distinct biological effects that enhance reproductive performance in mammals; however, the mechanisms underlying these effects remain poorly understood. This study aimed to evaluate the effect of β-carotene on ovarian development in replacement gilts and to investigate its potential mechanisms.

Results: A total of 20 gilts, aged 130 d, were randomly assigned to control group or β-carotene group (β-C group, diet containing 10 mg/kg of β-carotene). Each group consisted of 10 replicates, with one gilt per replicate, over a 60-d trial. β-Carotene significantly increased the number of follicles measuring 2-5 mm in diameter, elevated estradiol concentrations in both blood and follicular fluid of replacement gilts (P < 0.05). Compared to the control group, the β-C group exhibited a significant increase in β-carotene concentration within ovarian follicular fluid (P < 0.05). Transcriptomic analysis of GCs revealed that β-carotene could significantly upregulated the expression of Forkhead Box L2 (FOXL2). When β-carotene and its metabolic product were administered to granulosa cells (GCs), validation of differentially expressed genes in the transcriptome suggests the possibility that β-carotene, rather than its metabolic product, is responsible for the upregulation of FOXL2 in ovarian GCs, which subsequently may regulate StAR and enhance estradiol synthesis. Furthermore, β-carotene is likely to promote lipolysis, providing essential substrates for estradiol and adenosine triphosphate (ATP) production. Concurrently, β-carotene appears to increase the activity of the antioxidant enzymes superoxide dismutase 1 (SOD1) and glutathione peroxidase 4 (GPX4) in gilts, thereby reducing reactive oxygen species (ROS) (P < 0.05) and maintaining redox balance.

Conclusions: Our findings suggest that β-carotene could promote lipolysis, activate the FOXL2-StAR pathway to increase estradiol synthesis in GCs, and alleviate oxidative stress, thereby contributing to follicle development.

Background: Convergent evolution offers a unique lens through which to explore the molecular underpinnings of significant phenotypic transformations. Similar selective pressures likely drove the evolution of analogous milk traits in sheep and goats. Consequently, the current study aimed to identify common selection signals for milk traits across dairy and non-dairy breeds of sheep and goats worldwide.

Results: In this study, a total of 308 whole-genome sequences from diverse sheep (n = 108) and goat (n = 200) breeds, including both dairy and non-dairy types, across the world were utilized. The population structure and genetic diversity of dairy and non-dairy sheep and goat breeds were characterized. Species-specific genes associated with milk traits, such as POU2F1, ABCD2, TRNAC-GCA in sheep and PRPF6, VPS13C, TPD52L2, NFX1 and B4GALT1 in goats, were identified. Further gene annotation and bioinformatics analyses indicated that different biological pathways are important for milk traits in each species: fatty acid oxidation and AMP metabolic process in sheep, the U2-type spliceosomal complex and propanoate metabolism in goats. Additionally, common signatures of selection such as CLASP1, PDS5B, ZNF831, CCDC73 were found in sheep and goats. Haplotype and transcriptional analyses further confirmed the role of these genes in milk production and provided evidence for their analogous evolution in sheep and goats. The CLASP1 gene was identified as a target of convergent selection, representing a promising candidate for genetic improvement programs in dairy species.

Conclusions: These results provide insights into the genetic basis of convergent dairy traits, offering valuable targets for improving milk production and advancing dairy sheep and goat breeding programs.

Background: Mammalian spermatogenesis is critical for the transmission of male genetic information, and single-cell sequencing technology can reveal its complex process. However, at present, there is no research on the dynamic transcription of bovine germ cell population.

Results: In this study, we used Stereo-seq to construct a spatial transcription map of bovine testicular tissue at two ages. Four germ cell groups and five somatic cell groups were determined, and functional enrichment characterized their different biological functions and the differences between calves and adult bulls. At the same time, we also defined the subpopulations of cells and marker genes, then, clarified the communications between germ cells.

Conclusion: Our study constructed a spatial transcription map of bovine testicular tissue for the first time, and systematically described the dynamic transcription changes during spermatogenesis. These data laid the foundation for the study of spermatogenesis in large mammals and elucidated the transcriptional dynamics underlying male germ cell development.

Background: Exosomes are crucial mediators of intercellular communication. As a key component of milk, milk-derived exosomes are abundant in genetic cargo, particularly microRNAs (miRNAs), indicating their potential role in regulating mammary gland physiology. Therefore, this study aimed to investigate the specificity of miRNAs in milk-derived exosomes and their regulatory roles in lipid synthesis in bovine mammary epithelial cells (BMECs).

Results: Based on 17,838 DHI records showing a significantly higher milk fat percentage (MFP) in late lactation (4.24% ± 1.07%), 10 high- (5.96% ± 0.26%, HMF) and 10 low-MFP (1.68% ± 0.23%, LMF) cows were selected during this stage for milk-derived exosome isolation and miRNA profiling. Exosomes isolated via differential ultracentrifugation were verified as 50-150 nm vesicles expressing CD9, CD81, and TSG101. miRNA sequencing identified 1,320 differentially expressed miRNAs (496 upregulated and 824 downregulated) between the HMF_EXO and LMF_EXO groups. Uptake assays confirmed that BMECs internalized these exosomes, and qRT-PCR validation showed that miR-423-5p and miR-125b were significantly upregulated and downregulated in HMF_EXO- and LMF_EXO-treated BMECs, respectively. Functionally, exosomal miR-423-5p promoted intracellular lipid accumulation and TG synthesis in BMECs by targeting APOA5, whereas miR-125b inhibited lipolysis and fatty acid oxidation by repressing SLC27A1.

Conclusions: This study demonstrates that milk-derived exosomal miRNAs represent a novel mechanism for regulating milk fat synthesis. Specifically, miR-423-5p and miR-125b directly modulated lipid metabolism in BMECs via the miR-423-5p/APOA5 and miR-125b/SLC27A1 pathways. These findings provide new insights into the molecular regulation of milk fat synthesis and highlight the importance of exosome-mediated intercellular communication in the lactating mammary gland.

Background: Rumen microbiota drive fermentation and contribute to variation in feed efficiency among ruminants, yet the underlying host-microbe mechanisms remain poorly understood. This study explores how rumen microbes shape feed conversion efficiency (FCR) through integrated interactions with multiple host organs.

Results: We applied a multi-omics strategy-combining rumen metagenomics and host multi-organ transcriptomics-in Hu sheep with divergent FCR. From a uniform cohort of 150 weaned male Hu lambs, 13 low-FCR (LFCR) and 13 high-FCR (HFCR) individuals were selected for integrated analyses. LFCR sheep exhibited greater growth performance and higher ruminal propionate concentrations compared with HFCR animals. The ruminal microbiomes were enriched in Saccharofermentans and Succinivibrionaceae_UBA2804, and showed functional convergence on amino acid biosynthesis, central carbon metabolism, and propionate-oriented fermentation in LFCR sheep. Carbohydrate-active enzyme profiles indicated that LFCR animals favored fiber- and starch-associated modules (GH126, CBM27, EPS-GT), whereas HFCR animals were enriched in host-glycan and uronic acid-degrading families (CE14, GH89, PL15). Hydrogen metabolism highlighted a clear dichotomy: LFCR animals redirected H₂ toward propionate and sulfate reduction, while HFCR animals retained greater butyrate-producing and methanogenic capacity. Transcriptomic profiling across rumen epithelium, liver, and muscle identified tissue-specific regulatory modules. Only the liver showed strong enrichment of carbohydrate metabolism, with a complete glycogen turnover and glucose export system (GYS2, PYGL, PGM2, G6PC1) and pathways linking microbial short-chain fatty acids to gluconeogenesis. In contrast, muscle efficiency modules were dominated by contractile and cytoskeletal genes (e.g., MYL2, TNNC1, TPM3), reflecting optimized energy expenditure rather than substrate metabolism. No efficiency-associated modules were detected in the rumen epithelium, consistent with its role in propionate absorption rather than metabolism.

Conclusions: The rumen microbiota of LFCR sheep possess highly efficient capacities for volatile fatty acid and amino acid synthesis, thereby enhancing energy utilization at its source. The resulting propionate further promotes hepatic gluconeogenesis, directly supplying energy for muscle cell growth and ultimately improving FCR. Thus, co-metabolism between rumen microbiota and the liver provides energy for muscle cell growth and is a key determinant of improved feed efficiency.