Preventive Regulation Of L-Theanine On Nutrient Metabolism In Rats Under Heat Stress And Its Mechanism

Heat stress is mainly the sum of non-specific response of the organism when it is stimulated by a stimulus that exceeds its body temperature can be regulable capacity.Severe heat stress can lead to a significant decrease in growth and production performance,nutrient metabolism,immune function and tissue damage.L-theanine is a characteristic non-protein amino acid in tea which can promote growth and development,regulate nutrient metabolism,and alleviate heat stress and other biological activities.Whether L-theanine can alleviate heat stress through nutrient metabolism and how the mechanism of action remains to be investigated.For this reason,In this study,7 SPF SD male rats aged 7 weeks were fed L-theanine at three different doses:(100mg·kg^-1·d^-1),medium(200mg·kg^-1·d^-1)and high(400mg·kg^-1·d^-1)L-theanine for 35d in normal rats,saline for 28d in normal rats,and saline for 29-35d in normal rats.heat treatment for 7d（pre-prevention）,and 35d of normal rats fed with heat treatment for 7d at 29-35d（long-term intervention）.and the rats were treated with enzyme-linked immunoassay,Western bolt,Through the rat body weight,diet,key enzymes in the serum and liver tissue and physiological and biochemical index determination,histopathological changes and HSP70 protein in liver tissue and the expression of related proteins,AMPK pathway L-theanine prevention of heat stress on effect and mechanism of nutrient metabolism in rats,The main results and conclusions of the study are as follows:1.The preventive effect of L-theanine on nutrient metabolism in heat-stressed rats.Compared with the normal group,the food intake and body weight,serum GLU content,and serum TP and ALB content of the heat stress group were significantly reduced（p<0.05）,and serum COR,LDL-C,TG,L-CHO,BUN,liver Glycogen content and liver index increased significantly（p<0.05）,serum AST,ALT,LDH,and liver PEPCK,FAS enzyme activities significantly increased（p<0.05）;compared with heat stress group,L-theanine prophase The feed intake of the prevention group and the L-theanine long-term intervention group was significantly increased（p<0.05）,the weight gain was not significant（p>0.05）,the serum GLU content,and the serum TP and ALB content significantly increased（p<0.05）,Serum COR,LDL-C,TG,T-CHO,BUN,liver glycogen content and rat liver index were significantly reduced（p<0.05）,serum AST,ALT,LDH,and liver PEPCK and FAS enzyme activities（p<0.05）Significantly lower（p<0.05）.The effect of the L-theanine long-term intervention group is better than that of the pre-prevention group,and the medium-dose long-term intervention group has better effect.2.The mechanism of action of L-theanine in prophylactically regulating nutrient metabolism in heat-stressed rats.Compared with the normal group,liver HSP70,TORC2,m TORC1 protein expression was significantly up-regulated（p<0.05）,ACC protein expression was not significantly（p>0.05）,LKB1 protein expression was significantly down-regulated（p<0.05）in the L-theanine group,liver LKB1 protein expression was significantly up-regulated（p<0.05）,HSP70,ACC,m TORC1 protein expression was significantly downregulated（p<0.05）,and TORC2 protein expression was not significantly downregulated（p>0.05）;compared with the heat stress group,the protein expression of LKB1 and the phosphorylation of AMPK protein were significantly upregulated in the liver of the L-theanine pre-prevention group and the L-theanine long-term intervention group（p<0.05）,and the protein expression of HSP70,TORC2,ACC,and m TORC1 were significantly down-regulated（p<0.05）.Among them,the effect of L-theanine long-term intervention group was better than than the pre-prevention group,and the effect was better with the medium dose(200mg·kg^-1·d^-1).In summary,the preventive regulation of nutrient metabolism by L-theanine in heat-stressed rats and its mechanism:it can inhibit hepatic gluconeogenesis and regulate gluconeogenesis by activating LKB1/AMPK/TORC2/PEPCK pathway;it can promote lipolysis,inhibit lipid synthesis and reduce lipid deposition by activating LKB1/AMPK/SREBP-1c/ACC or LKB1/AMPK/SREBP-1c/FAS pathway;it can promote protein synthesis,increase serum TP and ALB content,inhibit protein catabolism and reduce serum BUN content by activating LKB1/AMPK/m TORC1pathway.It can promote protein synthesis,increase serum TP and ALB content,inhibit protein catabolism,reduce serum BUN content and improve growth performance of heat-stressed rats through activating LKB1/AMPK/m TORC1pathway.