State Key Laboratory of Grassland Agro-Ecosystems, International Centre for Tibetan Plateau Ecosystem Management, School of Life Sciences, Lanzhou University, Lanzhou730000, People's Republic of China.
College of Pastoral Agriculture Science and Technology, Lanzhou University, Lanzhou730020, People's Republic of China.
Br J Nutr. 2022 Apr 28;127(8):1132-1142. doi: 10.1017/S0007114521001902. Epub 2021 Jun 4.
Seasonal energy intake of Tibetan sheep on the harsh Qinghai-Tibetan Plateau (QTP) fluctuates greatly and is often well below maintenance requirements. The aim of this study was to gain insight into how the hypothalamus regulates energy homoeostasis in Tibetan sheep. We compared Tibetan and Small-tailed Han sheep (n 24 of each breed), which were each allocated randomly into four groups and offered one of four diets that differed in digestible energy densities: 8·21, 9·33, 10·45 and 11·57 MJ/kg DM. Sheep were weighed every 2 weeks, and it was assumed that the change in body weight (BW) reflected the change in energy balance. The arcuate nucleus of the hypothalamus in Tibetan sheep had greater protein expressions of neuropeptide Y (NPY) and agouti-related peptide (AgRP) when in negative energy balance, but lesser protein expressions of proopiomelanocortin (POMC) and cocaine and amphetamine-regulated transcript (CART) when in positive energy balance than Small-tailed Han sheep. As a result, Tibetan sheep had a lesser BW loss when in negative energy balance and stored more energy and gained more BW when in positive energy balance than Small-tailed Han sheep with the same dietary intake. Moreover, in the hypothalamic adenosine monophosphate-activated protein kinase (AMPK) regulation pathway, Tibetan sheep had greater adenosine monophosphate-activated protein kinase-α 2 protein expression than Small-tailed Han sheep, which supported the premise of a better ability to regulate energy homoeostasis and better growth performance. These differences in the hypothalamic NPY/AgRP, POMC/CART and AMPK pathways between breeds conferred an advantage to the Tibetan over Small-tailed Han sheep to cope with low energy intake on the harsh QTP.
藏绵羊生活在高寒的青藏高原，其季节性能量摄入波动很大，常常远低于维持需求。本研究旨在深入了解下丘脑如何调节藏绵羊的能量稳态。我们比较了藏绵羊和小尾寒羊（每种羊各 24 只），将它们随机分为四组，分别提供四种不同消化能密度的日粮：8.21、9.33、10.45 和 11.57MJ/kgDM。每两周称重一次，假设体重变化（BW）反映了能量平衡的变化。当处于负能量平衡时，藏绵羊下丘脑弓状核的神经肽 Y（NPY）和刺鼠相关肽（AgRP）的蛋白表达增加，但当处于正能量平衡时，前阿黑皮素原（POMC）和可卡因和安非他命调节转录物（CART）的蛋白表达减少。因此，当处于负能量平衡时，藏绵羊的 BW 损失较少，当处于正能量平衡时，其储存的能量更多，BW 增加更多，而摄入相同日粮的小尾寒羊则相反。此外，在下丘脑腺苷酸活化蛋白激酶（AMPK）调节通路中，藏绵羊的 AMPK-α2 蛋白表达高于小尾寒羊，这支持了其更好地调节能量稳态和更好的生长性能的前提。这些品种间下丘脑 NPY/AgRP、POMC/CART 和 AMPK 通路的差异赋予了藏绵羊在青藏高原恶劣环境下应对低能量摄入的优势。
