Mechanism Of NPY Action On The Adaptation To Extreme Habitats In Qinghai-tibet Plateau Yak

ObjectiveIn order to investigate the adaption mechanism of plateau animals to extreme environment of the Qinghai-Tibet plateau, such as severe cold, hypoxia, and lengthy grass-withering period, this paper centred on NPY to discuss the effect of energy metabolism on maintaining homeostasis for yak. This study applied gene cloning techniques and analysis of sequence alignment, quantitative analysis of mRNA and protein, positioning analysis of NPY, and construction of eukaryotic expression of NPY. The results are as follows:1. The CDS of yak NPY contained a complete ORF(294bp) encoding 97 amino acids. Deduced amino acid sequences of NPY gene between yak and cattle, sheep, and tibetan antelope were high in homology, which were 100%, 99%, 99% and 97.9%, respectively. While the homology of human, rat and mouse were 94.8%, 91.8% and 90.7% compared with yak, respectively. And the phylogenetic distance consistented with their genetic relationship.2. The eukaryotic expression plasmid pEGFP-NPY of the yak NPY CDS coding sequence was successfully constructed.3. The distribution of NPY mRNA in the "hypothalamus-pituitary-alimentary canal" axis between the yak and cattle was almost the same, but the quantity was not. NPY mRNA content of hypothalamus and pituitary of the yak was significantly higher in yak than cattle(P<0.001). However, NPY content in the yak duodenum was significantly lower in than that of cattle(P<0.001), and the mRNA in the yak abomasum also was lower than that of cattle(P>0.05).4.The distribution of the NPY protein in the "hypothalamus-pituitary-alimentary canal" axis between the yak and cattle was almost the same, however the quantity was not. However,NPY immunoreactive cell numbers of ARC in yak was significantly less than cattle(P<0.01). The mean IOD(intensity optical density) of DMN, PVN and pituitary of NPY immunoreactive product in yak was significantly higher than that of cattle(P<0.01). The mean IOD in the yak duodenum was significantly higher than that of cattle(P<0.05), and the IOD in the yak abomasum also was higher than that of cattle(P>0.05).Conclusion1. Similar to the low altitude animals, the amino acid sequence of NPY of the Qinghai-Tibet Plateau yak had strong evolutionary consevation, the differential expression of NPY played a role in the regulation of appetite, energy metabolism and so on.2 In the long and extremely cold hay period, the low expression of the hypothalamus NPY in the arcuate nucleus of the yak possibly reduces appetite and slow feed movement, further to reduce energy consumption by inhibiting appetite pathway; the high expression of the hypothalamus NPY in the paraventricular and dorsomedial nucleus of the yak reduces energy consumption by lowering energy and fat metabolism; the high expression in the pituitary NPY increases their expression in the digestive tract, and the high expression of NPY in the digestive tract can reduce gastrointestinal peristalsis, further slow gastric emptying, and enhance the absorption and utilization of nutrients.