Subacute ruminal acidosis (SARA) has been demonstrated to promote the development of mastitis, one of the most serious diseases in dairy farming worldwide, but the underlying mechanism is unclear. Using untargeted metabolomics, we found hexadecanamide (HEX) was significantly reduced in rumen fluid and milk from cows with SARA-associated mastitis. Herein, we aimed to assess the protective role of HEX in Staphylococcus aureus (S. aureus)- and SARA-induced mastitis and the underlying mechanism. We showed that HEX ameliorated S. aureus-induced mastitis in mice, which was related to the suppression of mammary inflammatory responses and repair of the blood-milk barrier. In vitro, HEX depressed S. aureus-induced activation of the NF-κB pathway and improved barrier integrity in mouse mammary epithelial cells (MMECs). In detail, HEX activated PPARα, which upregulated SIRT1 and subsequently inhibited NF-κB activation and inflammatory responses. In addition, ruminal microbiota transplantation from SARA cows (S-RMT) caused mastitis and aggravated S. aureus-induced mastitis, while these changes were reversed by HEX. Our findings indicate that HEX effectively attenuates S. aureus- and SARA-induced mastitis by limiting inflammation and repairing barrier integrity, ultimately highlighting the important role of host or microbiota metabolism in the pathogenesis of mastitis and providing a potential strategy for mastitis prevention.

中文翻译：

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十六酰胺通过抑制炎症反应和恢复血乳屏障完整性来减轻金黄色葡萄球菌引起的小鼠乳腺炎。

亚急性瘤胃酸中毒（SARA）已被证明可促进乳腺炎的发展，乳腺炎是全世界奶牛养殖中最严重的疾病之一，但其潜在机制尚不清楚。使用非靶向代谢组学，我们发现患有 SARA 相关乳腺炎的奶牛的瘤胃液和牛奶中十六酰胺 (HEX) 显着减少。在此，我们的目的是评估 HEX 在金黄色葡萄球菌 (S. aureus) 和 SARA 诱发的乳腺炎中的保护作用及其潜在机制。我们发现 HEX 可以改善金黄色葡萄球菌引起的小鼠乳腺炎，这与抑制乳腺炎症反应和修复血乳屏障有关。在体外，HEX 抑制金黄色葡萄球菌诱导的 NF-κB 通路激活，并改善小鼠乳腺上皮细胞 (MMEC) 的屏障完整性。具体来说，HEX 激活 PPARα，从而上调 SIRT1，随后抑制 NF-κB 激活和炎症反应。此外，SARA奶牛瘤胃微生物移植（S-RMT）引起乳腺炎并加重金黄色葡萄球菌引起的乳腺炎，而HEX可逆转这些变化。我们的研究结果表明，HEX 通过限制炎症和修复屏障完整性，有效减轻金黄色葡萄球菌和 SARA 诱导的乳腺炎，最终强调宿主或微生物代谢在乳腺炎发病机制中的重要作用，并为乳腺炎预防提供潜在策略。