The gastrointestinal microbiota plays a key role in the host physiology and health through a complex host-microbiota co-metabolism. Metabolites produced by microbial metabolism can travel through the bloodstream to reach distal organs and affect their function, ultimately influencing the development of relevant production traits such as meat quality. Meat quality is a complex trait made up of a number of characteristics and intramuscular fat content (IMF) is considered to be one of the most important parameters. In this study, 52 rabbits from two lines divergently selected for IMF (high-IMF (H) and low-IMF (L) lines) were used to perform an untargeted metabolomic analysis of their caecal content, with the aim to obtain information on genetically determined microbial metabolism related to IMF. A large, correlated response to selection was found in their caecal metabolome composition. Partial least squares discriminant analysis was used to identify the pathways differentiating the lines, which showed a classification accuracy of 99%. On the other hand, two linear partial least squares analyses were performed, one for each line, to extract evidence on the specific pathways associated with IMF deposition within each line, which showed predictive abilities (estimated using the Q2) of approximately 60%. The most relevant pathways differentiating the lines were those related to amino acids (aromatic, branched-chain and gamma-glutamyl), secondary bile acids, and purines. The higher content of secondary bile acids in the L-line was related to greater lipid absorption, while the differences found in purines suggested different fermentation activities, which could be related to greater nitrogen utilisation and energy efficiency in the L-line. The linear analyses showed that lipid metabolism had a greater relative importance for IMF deposition in the L-line, whereas a more complex microbial metabolism was associated in the H-line. The lysophospholipids and gamma-glutamyl amino acids were associated with IMF in both lines; the nucleotide and secondary bile acid metabolisms were mostly associated in the H-line; and the long-chain and branched-chain fatty acids were mostly associated in the L-line. A metabolic signature consisting of two secondary bile acids and two protein metabolites was found with 88% classification accuracy, pointing to the interaction between lipid absorption and protein metabolism as a relevant driver of the microbiome activity influencing IMF.

中文翻译：

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两种不同选择的兔子品系的盲肠代谢组学揭示了与肌内脂肪沉积相关的微生物机制


胃肠道微生物群通过复杂的宿主-微生物群共代谢在宿主生理和健康中起关键作用。微生物代谢产生的代谢物可以通过血液到达远端器官并影响其功能，最终影响相关生产性状（如肉质）的发展。肉质是一个复杂的性状，由许多特征组成，肌内脂肪含量 （IMF） 被认为是最重要的参数之一。在这项研究中，来自两个品系（高 IMF （H） 和低 IMF （L） 品系）的 52 只兔子被用于对其盲肠内容物进行非靶向代谢组学分析，目的是获得与 IMF 相关的遗传决定微生物代谢的信息。在它们的盲肠代谢组组成中发现了对选择的巨大、相关的反应。偏最小二乘判别分析用于识别区分线的途径，显示分类准确率为 99%。另一方面，进行了两次线性偏最小二乘分析，每行一次，以提取每行内与 IMF 沉积相关的特定途径的证据，结果显示预测能力（使用 Q2 估计）约为 60%。区分这些谱系的最相关途径是与氨基酸（芳香族、支链和 γ-谷氨酰）、次级胆汁酸和嘌呤相关的途径。L 系中次级胆汁酸含量较高与脂质吸收增加有关，而嘌呤中发现的差异表明发酵活性不同，这可能与 L 系中更高的氮利用和能源效率有关。 线性分析表明，脂质代谢对 L 线中 IMF 沉积的相对重要性更大，而在 H 线中与更复杂的微生物代谢相关。溶血磷脂和 γ-谷氨酰氨基酸在两个品系中都与 IMF 相关;核苷酸和次级胆汁酸代谢主要与 H 线相关;长链和支链脂肪酸主要与 L 线相关。发现由两种次级胆汁酸和两种蛋白质代谢物组成的代谢特征具有 88% 的分类准确率，表明脂质吸收和蛋白质代谢之间的相互作用是影响 IMF 的微生物组活性的相关驱动因素。