Demonstration of a role for insulin in the regulation of leptin in lactating dairy cows
Demonstration of a role for insulin in the regulation of leptin in lactating dairy cows
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DOI：
10.3168/jds.s0022-0302(03)73955-1
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发表时间：
2003-11-01
影响因子：
3.5
通讯作者：
Boisclair, YR
中科院分区：
文献类型：
--
作者：
Block, SS;Rhoads, RP;Boisclair, YR
在泌乳奶牛中，分娩时出现的负净能量平衡（EB）导致血浆瘦素减少，并与生长激素（GH）浓度升高和胰岛素浓度降低相关。这些观察结果提出了这样的可能性，即血浆胰岛素和GH的相反变化部分地导致了血浆瘦素的减少。为了验证这一假设，我们首先研究了营养不良的影响，而不混淆分娩的影响，使用后期泌乳奶牛喂养120%的营养需求或限制在33%的维护需求。血浆瘦素在限饲24小时内降低，并与血浆GH升高和血浆胰岛素降低相关。完全食物剥夺48小时引起类似的血浆瘦素浓度的变化。为了确定GH的升高是否是血浆瘦素下降的原因，在泌乳早期或泌乳晚期用赋形剂或牛生长激素处理奶牛。生长激素治疗对血浆瘦素无显着影响，无论阶段的哺乳期。最后，通过对泌乳中期奶牛进行正常血糖高胰岛素钳夹试验，研究了胰岛素的作用。高胰岛素血症96 h后，血浆瘦素水平显著升高。这些数据表明，胰岛素调节泌乳奶牛血浆瘦素。他们还认为，在营养不良的泌乳奶牛中，血浆胰岛素减少可能是血浆瘦素下降的一部分，但血浆GH升高不太可能产生重大影响。
In lactating dairy cows, the onset of negative net energy balance (EB) at parturition causes a reduction in plasma leptin and is also associated with increased concentration of growth hormone (GH) and decreased concentration of insulin. These observations raise the possibility that opposite changes in plasma insulin and GH are partly responsible for reduced plasma leptin. To test this hypothesis, we first examined the effects of undernutrition without the confounding influence of parturition by using late lactating dairy cows fed 120% of their nutrient requirements or restricted to 33% of maintenance requirements. Plasma leptin was reduced within 24 h of feed restriction, and was associated with increased plasma GH and decreased plasma insulin. Complete food deprivation for 48 h caused similar changes in the plasma concentration of leptin. To determine if an elevation in GH is responsible for the fall in plasma leptin, dairy cows were treated with excipient or bovine somatotropin in early lactation or in late lactation. Growth hormone treatment had no significant effect on plasma leptin irrespective of stage of lactation. Finally, the effects of insulin were studied by performing euglycemic hyperinsulinemic clamps in mid-lactating dairy cows. After 96 h of hyperinsulinemia, plasma leptin was increased significantly. These data indicate that insulin regulates plasma leptin in lactating dairy cows. They also suggest that, in undernourished lactating dairy cows, reduced plasma insulin could account for a portion of the decline in plasma leptin but that elevated plasma GH is unlikely to have a major effect.