Effects Of Perinatal Heat And Cold Stress On Glucose Homeostasis Regulation In Newborn

Background: Long-term cold and hot environments can decrease livestock productivity.Environmental temperature stress during gestation can lead to low birth weight and even increase mortality of newborn sheep.Our previous study in Chongqing also showed that environmental cold and hot factors had different negative effects on goat fetuses in the middle and later stages of pregnancy.Low birth weight livestock presents an unrecoverable metabolic disorder in infancy and adulthood,resulting in the reduction of feed utilization rate and meat quality,which seriously harms production.Although studies on environmental heat stress have been more in-depth in sheep,there are few studies on the effects of cold stress on goat production,and there has been no systematic study that investigates the effects of environmental cold stress during perinatal stage on metabolism and endocrinology in the acquired growth process of kids.Aim: To elucidate the growth of kids and mechanism of disordered glucose metabolism in peripheral tissues by perinatal ambient temperature.Methods: This research adopts Dazu county native newborn kids whose late pregnancy is in winter,summer,mild season which were divided into "cold group","heat group" and "moderate group" respectively.We detected the lamb growth after birth every day until euthanasia.Through the glucose tolerance test(GTT)and insulin tolerance test(ITT)method,insulin availability of kids was measured in vivo.Transcriptome sequencing analysis in skeletal muscle was utilized to explore the relevant regulation pathways.And the insulin signal transduction in the liver was determined by fluorescence quantitative PCR and western blot.Results and conclusion: Compared to moderate group,birth weight and body weight during 1-month age of cold and heat group of kids was markedly decreased.In vivo,blood glucose of Cold group during ITT was significantly higher than that in moderate group.In GTT graph,area under the curve(AUC)was 2.26-fold higher than that in the moderate group(P < 0.05).In ITT graph,area above curve(ABC)fell by 49.3%(P < 0.05),concentration plasma free fatty acid in the cold group was 1.48-fold than that in the moderate group(P < 0.05),the results of the heat group showed no significant difference in the moderate group.Thus,perinatal environmental cold stress resulted in impaired growth energy and decreased insulin sensitivity.In cold group liver of the,IRS2(-56.6%)and PPAR(+89.8%)had changed markedly,while FABP3,PGC1α and ANKRD2,which were related to lipid metabolism and oxidative stress,were 3.56-,3.14-and 4.39-fold higher in the skeletal muscles of the cold group than in the moderate group.To sum up,compared with the heat group,the low birth weight kids caused by ambient coldness in late gestation period showed reduced insulin sensitivity of the body and excessive fatty acids circulation,which was deeply caused by the down-regulation of insulin signal in the liver and the tendency of fat deposition,as well as excessive fat transportation and peroxidation in the skeletal muscles.Therefore,the perinatal environmental cold stress leaded to the injury of the growth ability of kids,and damaged the endocrine homeostasis of kids after birth,which had a negative impact on the feeding and meat quality of goats.Summary: In this study,the effects of perinatal environmental cold and heat stress on the regulation of glucose metabolism in newborn lambs were systematically described for the first time.At the same time,it provided a new cue for preventing and solving the harmful problems of extreme climate factors to animal husbandry in the future,and provided a theoretical basis for improving meat quality,developing healthy breeding,and improving the growth potential and efficiency of goats.