Recombinant bovine somatotropin (rBST) changes metabolism to spare glucose for milk synthesis in cows. Ceramides inhibit insulin responsiveness in bovine adipocytes and are associated with insulin resistance and milk production in cows. The mechanisms by which rBST supports lactation may involve ceramide. Eight multiparous lactating Holstein cows were enrolled in a 2 × 2 replicated Latin square design with 14-d periods. Cows received a single rBST injection (Posilac; Elanco Animal Health, Indianapolis, IN; 0.062 mg/kg BW) or no injection (CON). An epinephrine challenge, insulin tolerance test, and liver biopsy were performed. Somatotropin enhanced the conversion of feed nutrients into milk components and increased plasma free fatty acid (FFA) concentrations (P < 0.01). Area-under-the-curves for FFA in response to epinephrine and insulin were greater in rBST-treated cows. In response to insulin, glucose concentrations (20- and 30-min post-challenge) and insulin area-under-the-curve were higher with rBST treatment (P < 0.05, <0.10, and <0.01), suggesting insulin resistance. Somatotropin modified the plasma lipidome. For example, rBST decreased plasma di- and triacylglycerol levels (eg, DG-50:1 and TG-18:0/16:0/16:1), phosphatidylcholines and sphingomyelins (P < 0.05). Somatotropin increased plasma total and very-long-chain (C22:0-, C24:0-, C26:0-) ceramide concentrations (P < 0.01). Liver ceramide concentrations were not modified. Plasma ceramides were positively correlated with circulating FFA (r ~ 0.57; P < 0.05) and milk yield (r ~ 0.63; P < 0.05). We conclude that rBST administration modifies the bovine lipidome and increases plasma ceramide concentrations in association with increased milk production in cows.

重组牛生长激素 (rBST) 改变新陈代谢，为奶牛的牛奶合成腾出葡萄糖。神经酰胺抑制牛脂肪细胞的胰岛素反应性，并与奶牛的胰岛素抵抗和产奶量有关。rBST 支持泌乳的机制可能涉及神经酰胺。八头经产泌乳荷斯坦奶牛被纳入 2 × 2 重复拉丁方设计，周期为 14 天。奶牛接受单次 rBST 注射（Posilac；Elanco Animal Health，Indianapolis，IN；0.062 mg/kg BW）或不注射 (CON)。进行了肾上腺素激发试验、胰岛素耐受试验和肝活检。生长激素促进饲料营养物质向牛奶成分的转化，并增加血浆游离脂肪酸 (FFA) 浓度（P< 0.01)。在 rBST 治疗的奶牛中，FFA 对肾上腺素和胰岛素的反应曲线下面积更大。在对胰岛素的反应中，rBST 治疗后葡萄糖浓度（攻击后 20 分钟和 30 分钟）和胰岛素曲线下面积更高（P < 0.05、<0.10 和 <0.01），表明存在胰岛素抵抗。生长激素修饰血浆脂质组。例如，rBST 降低了血浆二酰甘油和三酰甘油水平（例如，DG-50:1 和 TG-18:0/16:0/16:1）、磷脂酰胆碱和鞘磷脂（P < 0.05）。生长激素增加血浆总神经酰胺和超长链（C22:0-、C24:0-、C26:0-）神经酰胺浓度（P < 0.01）。肝脏神经酰胺浓度没有改变。血浆神经酰胺与循环 FFA 呈正相关（r~ 0.57; P < 0.05) 和产奶量 ( r ~ 0.63; P < 0.05)。我们得出结论，rBST 给药会改变牛脂质组并增加血浆神经酰胺浓度，这与奶牛的产奶量增加有关。