Tilbrook Alan J, Rivalland Elizabeth A T, Turner Anne I, Lambert Gavin W, Clarke Iain J
Department of Physiology, Monash University, Monash, Vic., Australia.
Neuroendocrinology. 2008;87(4):193-205. doi: 10.1159/000117576. Epub 2008 Feb 18.
There is evidence that levels of adipose tissue can influence responses of the hypothalamopituitary-adrenal (HPA) axis to stress in humans and rats but this has not been explored in sheep. Also, little is known about the sympathoadrenal responses to stress in individuals with relatively different levels of adipose tissue. We tested the hypothesis that the stress-induced activation of the HPA axis and sympathoadrenal system is lower in ovariectomized ewes with low levels of body fat (lean) than ovariectomized ewes with high levels of body fat (fat). Ewes underwent dietary manipulation for 3 months to yield a group of lean ewes (n = 7) with a mean (+/-SEM) live weight of 39.1 +/- 0.9 kg and body fat of 8.9 +/- 0.6% and fat ewes (n = 7) with a mean (+/-SEM) live weight of 69.0 +/- 1.8 kg and body fat of 31.7 +/- 3.4%. Fat ewes also had higher circulating concentrations of leptin than lean ewes. Blood samples were collected every 15 min over 8 h when no stress was imposed (control day) and on a separate day when 4 h of isolation/restraint was imposed after 4 h of pretreatment sampling (stress day). Plasma concentrations of adrenocorticotropic hormone (ACTH), cortisol, epinephrine and norepinephrine did not change significantly over the control day and did not differ between lean and fat ewes. Stress did not affect plasma leptin levels. All stress hormones increased significantly during isolation/restraint stress. The ACTH, cortisol and epinephrine responses were greater in fat ewes than lean ewes but norepinephrine responses were similar. Our results suggest that relative levels of adipose tissue influence the stress-induced activity of the hypothalamopituitary-adrenal axis and some aspects of the sympathoadrenal system with fat animals having higher responses than lean animals.
有证据表明，脂肪组织水平会影响人类和大鼠下丘脑 - 垂体 - 肾上腺（HPA）轴对应激的反应，但尚未在绵羊身上进行过此类研究。此外，对于脂肪组织水平相对不同的个体对应激的交感 - 肾上腺反应了解甚少。我们检验了以下假设：与体脂水平高的去卵巢母羊（肥胖组）相比，体脂水平低的去卵巢母羊（消瘦组）应激诱导的HPA轴和交感 - 肾上腺系统激活程度更低。母羊接受了3个月的饮食控制，以产生一组消瘦母羊（n = 7），平均（±标准误）活重为39.1±0.9千克，体脂为8.9±0.6%，以及肥胖母羊（n = 7），平均（±标准误）活重为69.0±1.8千克，体脂为31.7±3.4%。肥胖母羊的循环瘦素浓度也高于消瘦母羊。在无应激状态下（对照日）的8小时内，每隔15分钟采集一次血样，在另一天，在预处理采样4小时后施加4小时的隔离/束缚应激（应激日）。促肾上腺皮质激素（ACTH）、皮质醇、肾上腺素和去甲肾上腺素的血浆浓度在对照日没有显著变化，消瘦母羊和肥胖母羊之间也没有差异。应激不影响血浆瘦素水平。在隔离/束缚应激期间，所有应激激素均显著增加。肥胖母羊的ACTH、皮质醇和肾上腺素反应大于消瘦母羊，但去甲肾上腺素反应相似。我们的结果表明，脂肪组织的相对水平会影响应激诱导的下丘脑 - 垂体 - 肾上腺轴的活动以及交感 - 肾上腺系统的某些方面，肥胖动物的反应高于消瘦动物。
