Adam C L, Findlay P A, Kyle C E, Young P, Mercer J G
Molecular Neuroendocrinology Group, Rowett Research Institute, Bucksburn, Aberdeen, UK.
J Endocrinol. 1997 Feb;152(2):329-37. doi: 10.1677/joe.0.1520329.
Castrate male sheep (wethers, average liveweight 38 +/- 0.6 kg) were given one of the following diets for 10 weeks followed by euthanasia (n = 8/group): high-energy high-protein providing 1-5 times the energy required to maintain liveweight (maintenance) (group 1.5 M), low-energy low-protein at 0.5 maintenance (0.5 M), or low-energy high-protein at 0.5 maintenance (0.5 M + P). 1.5 M wethers gained 22% liveweight whereas 0.5 M and 0.5 M + P wethers lost 18 and 13% liveweight respectively. Relative to the 1.5 M group, the 0.5 M and 0.5 M + P groups had similar plasma concentrations of glucose and cortisol throughout, but elevated non-esterified fatty acids (P < 0.001) and reduced IGF-I and insulin (P < 0.05, 0.01 or 0.001) from 1 week onwards. Each week blood samples were taken every 12 min for 4 h and plasma assayed for LH. Mean concentration over 4 h, LH pulse frequency and LH pulse amplitude showed no progressive change in 1.5 M sheep. However, in both 0.5 M and 0.5 M + P groups mean LH increased (P < 0.001 and P < 0.01 respectively), pulse frequency decreased (P < 0.01 and P < 0.01) and pulse amplitude increased (P < 0.001 and P < 0.01) over the 10-week period. Anterior pituitary. LH content was greater in 0.5 M (P < 0.01) and 0.5 M + P (P < 0.05) than in 1.5 M sheep. Coronal sections (20 microns) of hypothalamic brain tissue were subjected to in situ hybridisation to determine gene expression for neuropeptide Y (NPY). NPY mRNA was concentrated in the arcuate nucleus and median eminence, with total amounts greater in both 0.5 M (310%, P < 0.001) and 0.5 M + P (333%, P < 0.01) groups than in 1.5 M sheep (100%). These data reveal that chronic low dietary energy intake by long-term castrates, with high or low protein intake, reduces LH pulse frequency but increases the circulating levels of LH by virtue of an increase in pulse amplitude, and concomitantly increases hypothalamic NPY gene expression.
对去势公羊（阉羊，平均体重38±0.6千克）给予以下日粮之一，持续10周，随后实施安乐死（每组n = 8）：高能量高蛋白日粮，提供维持体重所需能量的1 - 5倍（维持量）（1.5M组）；低能量低蛋白日粮，为维持量的0.5倍（0.5M组）；或低能量高蛋白日粮，为维持量的0.5倍（0.5M + P组）。1.5M组的阉羊体重增加了22%，而0.5M组和0.5M + P组的阉羊体重分别下降了18%和13%。与1.5M组相比，0.5M组和0.5M + P组在整个实验过程中血浆葡萄糖和皮质醇浓度相似，但从第1周起非酯化脂肪酸水平升高（P < 0.001），胰岛素样生长因子-I（IGF-I）和胰岛素水平降低（P < 0.05、0.01或0.001）。每周采集一次血样，每隔12分钟采集一次，共采集4小时，测定血浆中的促黄体生成素（LH）。1.5M组绵羊4小时的平均浓度、LH脉冲频率和LH脉冲幅度均无渐进性变化。然而，在0.5M组和0.5M + P组中，10周内平均LH均升高（分别为P < 0.001和P < 0.01），脉冲频率降低（P < 0.01和P < 0.01），脉冲幅度增加（P < 0.001和P < 0.01）。垂体前叶。0.5M组（P < 0.01）和0.5M + P组（P < 0.05）的LH含量高于1.5M组绵羊。对下丘脑脑组织的冠状切片（20微米）进行原位杂交，以确定神经肽Y（NPY）的基因表达。NPY mRNA集中在弓状核和正中隆起，0.5M组（310%，P < 0.001）和0.5M + P组（333%，P < 0.01）的总量均高于1.5M组绵羊（100%）。这些数据表明，长期去势公羊长期摄入低能量日粮，无论蛋白质摄入量高低，都会降低LH脉冲频率，但由于脉冲幅度增加而使LH循环水平升高，并同时增加下丘脑NPY基因表达。
