As cows transition from pregnancy to lactation, free fatty acids (FFA) are mobilized from adipose tissues (AT) through lipolysis to counter energy deficits. In clinically healthy cows, lipolysis intensity is reduced throughout lactation; however, if FFA release exceeds tissue demands or the liver’s metabolic capacity, lipid byproducts accumulate, increasing cows’ risk of metabolic and infectious disease. Endocannabinoids (eCBs) and their congeners, N-acylethanolamines (NAEs), are lipid-based compounds that modulate metabolism and inflammation. Their synthesis and release depend upon the availability of FFA precursors and the abundance of synthesizing and degrading enzymes and transporters. Therefore, we hypothesized that eCB production and transcription of endocannabinoid system components are modulated by lipolysis pathways in adipocytes. To test this hypothesis, we stimulated canonical (isoproterenol, 1 µmol/L; ISO) and inflammatory (lipopolysaccharide, 1 µg/mL; LPS) lipolysis pathways in adipocytes isolated from the AT of 5 Holstein dairy cows. Following, we assessed lipolysis intensity, adipocytes’ release of eCBs, and transcription of endocannabinoid system components. We found that ISO and LPS stimulated lipolysis at comparable intensities. Exposure to either treatment tended to elevate the release of eCBs and NAEs by cultured adipocytes; however, specific eCBs and NAEs and the transcriptional profiles differed by treatment. On one hand, ISO enhanced adipocytes’ release of 2-arachidonoylglycerol (2-AG) but reduced NAE production. Notably, ISO enhanced the cells’ expression of enzymes associated with 2-AG biosynthesis (INPP5F, GDPD5, GPAT4), transport (CD36), and adipogenesis (PPARG). Conversely, LPS enhanced adipocytes’ synthesis and release of N-arachidonoylethanolamide (AEA). This change coincided with enhanced transcription of the NAE-biosynthesizing enzyme, PTPN22, and adipocytes’ transcription of genes related to eCB degradation (PTGS2, MGLL, CYP27B1). Furthermore, LPS enhanced adipocytes’ transcription of eCB and NAE transporters (HSPA1A, SCP2) and the expression of the anti-adipogenic ion channel, TRPV3. Our data provide evidence for distinct modulatory roles of canonical and inflammatory lipolysis pathways over eCB release and transcriptional regulation of biosynthesis, degradation, transport, and ECS signaling in cows’ adipocytes. Based on our findings, we conclude that, within adipocytes, eCB production and ECS component expression are, at least in part, mediated by lipolysis in a pathway-dependent manner. These findings contribute to a deeper understanding of the molecular mechanisms underlying metabolic regulation in dairy cows’ AT, with potential implications for prevention and treatment of inflammatory and metabolic disorders.

中文翻译：

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脂解途径调节奶牛脂肪细胞中的脂质介质释放和内源性大麻素系统信号传导


当奶牛从怀孕期过渡到哺乳期时，游离脂肪酸 (FFA) 通过脂肪分解从脂肪组织 (AT) 中动员出来，以应对能量不足。在临床健康的奶牛中，整个哺乳期脂肪分解强度降低；然而，如果 FFA 释放超过组织需求或肝脏代谢能力，脂质副产物就会积聚，增加奶牛患代谢性疾病和传染病的风险。内源性大麻素 (eCB) 及其同源物 N-酰基乙醇胺 (NAE) 是调节代谢和炎症的脂质化合物。它们的合成和释放取决于 FFA 前体的可用性以及合成和降解酶和转运蛋白的丰度。因此，我们假设内源性大麻素系统成分的 eCB 产生和转录受到脂肪细胞中脂解途径的调节。为了检验这一假设，我们刺激了从 5 头荷斯坦奶牛的 AT 中分离的脂肪细胞中的典型（异丙肾上腺素，1 µmol/L；ISO）和炎症（脂多糖，1 µg/mL；LPS）脂肪分解途径。接下来，我们评估了脂肪分解强度、脂肪细胞释放的 eCB 以及内源性大麻素系统成分的转录。我们发现 ISO 和 LPS 以相当的强度刺激脂肪分解。接受任何一种治疗都会增加培养脂肪细胞释放的 eCB 和 NAE；然而，特定的 eCB 和 NAE 以及转录谱因治疗而异。一方面，ISO 增强脂肪细胞释放 2-花生四烯酸甘油 (2-AG)，但减少 NAE 的产生。值得注意的是，ISO 增强了细胞与 2-AG 生物合成（INPP5F、GDPD5、GPAT4）、运输（CD36）和脂肪生成（PPARG）相关的酶的表达。 相反，LPS 增强脂肪细胞的 N-花生四烯酰乙醇酰胺 (AEA) 的合成和释放。这种变化与 NAE 生物合成酶 PTPN22 的转录增强以及脂肪细胞与 eCB 降解相关的基因（PTGS2、MGLL、CYP27B1）转录的增强相一致。此外，LPS 增强脂肪细胞 eCB 和 NAE 转运蛋白（HSPA1A、SCP2）的转录以及抗脂肪形成离子通道 TRPV3 的表达。我们的数据提供了证据，证明经典脂肪分解途径和炎症脂肪分解途径对奶牛脂肪细胞中 eCB 释放和生物合成、降解、运输和 ECS 信号传导的转录调节具有不同的调节作用。根据我们的发现，我们得出结论，在脂肪细胞内，eCB 的产生和 ECS 成分的表达至少部分是由脂解以途径依赖性方式介导的。这些发现有助于更深入地了解奶牛 AT 代谢调节的分子机制，对预防和治疗炎症和代谢紊乱具有潜在意义。