Division of Animal and Nutritional Sciences, West Virginia University, Morgantown, WV, USA.
Department of Animal Science, Cornell University, Ithaca, NY, USA.
Animal. 2019 Nov;13(11):2547-2555. doi: 10.1017/S175173111900065X. Epub 2019 May 20.
Reductions in insulin sensitivity in periparturient dairy cows develop as a means to support lactation; however, excessive mobilization of fatty acids (FA) increases the risk for peripartal metabolic disorders. Our objectives were to investigate the effect of prepartum body condition score (BCS) on systemic glucose and insulin tolerance, and to compare direct and indirect measurements of insulin sensitivity in peripartal lean and overweight dairy cows. Fourteen multiparous Holstein cows were allocated into two groups according to their BCS at day -28 prepartum: lean (n = 7; BCS ≤ 3.0) or overweight; (n = 7; BCS ≥ 4.0). Liver biopsies were performed on day -27, -14 and 4, relative to expected parturition. Intravenous insulin or glucose tolerances tests were performed following each liver biopsy. Relative to lean cows, overweight cows exhibited lower dry matter intake, lost more BCS and displayed increased plasma FA and β-hydroxybutyrate concentrations and elevated liver lipid content during peripartum. Glucose clearance rate was lower for all cows postpartum. Prepartum BCS had minimal effects on insulin and glucose tolerance; however, the ability of the cow to restore blood glucose levels following an insulin challenge was suppressed by increased BCS. Glucose-dependent parameters of insulin and glucose tolerance were not correlated with surrogate indices of insulin sensitivity. We conclude that prepartum BCS had minimal effect on systemic insulin sensitivity following parturition. The observed inconsistency between surrogate indices of insulin sensitivity and direct measurements of insulin and glucose tolerance adds support to growing concerns regarding their usefulness as tools to estimate systemic insulin action in periparturient cows.
围产期奶牛的胰岛素敏感性降低是为了支持泌乳；然而，脂肪酸（FA）的过度动员会增加围产期代谢紊乱的风险。我们的目的是研究围产前体况评分（BCS）对全身葡萄糖和胰岛素耐量的影响，并比较围产期瘦牛和超重牛胰岛素敏感性的直接和间接测量。根据产前 28 天的 BCS，将 14 头经产荷斯坦奶牛分配到两组：瘦牛（n = 7；BCS ≤ 3.0）或超重牛（n = 7；BCS ≥ 4.0）。在产前第-27、-14 和 4 天进行肝活检。每次肝活检后进行静脉内胰岛素或葡萄糖耐量试验。与瘦牛相比，超重牛的干物质采食量较低，BCS 损失更多，围产期血浆 FA 和β-羟丁酸浓度升高，肝脂含量升高。所有奶牛产后葡萄糖清除率均降低。产前 BCS 对胰岛素和葡萄糖耐量的影响很小；然而，随着 BCS 的增加，奶牛在胰岛素冲击后恢复血糖水平的能力受到抑制。葡萄糖依赖性胰岛素和葡萄糖耐量参数与胰岛素敏感性的替代指标不相关。我们得出结论，产后产前 BCS 对全身胰岛素敏感性的影响很小。替代胰岛素敏感性的指标与直接测量胰岛素和葡萄糖耐量之间的观察到的不一致性，增加了对它们作为估计围产期奶牛全身胰岛素作用的工具的有用性的担忧。
