| Heat stress(HS)is loss of balance between heat dissipation and heat production caused by the stimulation of high temperature environment of the animal body.In severe cases,it leads to the decline of animal body weight,depression,low quality of animal products,and the decline of immunity and reproductive ability.Spermatogenesis requires a temperature 2～7℃ lower than the core temperature.When HS occurs,excess heat accumulates in the scrotum,which affects the germ cells in testis and epididymis,and eventually leads to the arrest or death of spermatogenic cells,the decrease of sperm count,sperm motility and acrosomal integrity,and the reduction of semen quality.HS also cause the destruction of tight junctions between Sertoli cells,which leads to the loss of protection of testis spermatogenic environment.Besides,intestine is another target organ of HS.HS destructs of intestinal mucosal epithelium microstructure,increases intestinal permeability,disorders gut microbiota,and makes bacterial endotoxins enter the circulation from the intestinal cavity(metabolic endotoxemia).In conclusion,compares to short-term acute HS,the influence factors of testis are more complex under chronic systemic HS,endotoxin,inflammation and other potential stimuli.The purpose of this study is to explore the crosstalk between testis and intestine when systemic heat stress occurs,with a view to alleviating the load of heat stress on testis by feeding probiotics to relieve intestinal inflammation and providing necessary nutrients.In this study,40 male ICR mice were divided into two groups randomly: control(CON)group and heat stress(HS)group.The systemic HS mice of daytime high temperature and high humidity was established in the HS group,and the mice in the CON group were fed at room temperature.The testis injury of mice induced by HS was observed at different time points.According to the phenomena obtained in the previous step,Enterococcus faecium(EF)and Clostridium butyricum(CB)were fed orally to HS mice as treatment method.60 male ICR mice were divided into 6 groups randomly:CON group,EF+CON group,CB +CON group,HS group,EF +HS group,CB +HS group.In EF+CON group,CB +CON group,EF +HS group and CB +HS group,two kinds of probiotic suspensions were fed orally,and then continued normal or HS treatment.While the CON group and HS group were fed the same amount of phosphate buffer solution.RT-q PCR,protein western blotting,enzyme-linked immunosorbent assay,and high-throughput sequencing were used to detect testis,intestinal tissues and microbiota,and serum.Results are as follows:(1)After systemic HS,testicular size decreased,testicular cell loss,and mature sperm count decreased.The intestinal wall was thinner,the intestinal permeability was enhanced,and the gut microbiota was disordered with inflammation;(2)In HS group,the serum concentrations of follicle stimulating hormone,luteinizing hormone were increased,while testosterone concentration was decreased.The concentrations of pro-inflammatory factors and bacterial endotoxin were increased,and the inflammatory response pathway in testis was activated;(3)After pre-feeding with EF and CB,the gut microbiota of HS mice was nearly recoverd,the inflammation of intestinal tissue was relieved,the concentration of proinflammatory in serum was decreased,the status of testicular cells was improved,and the number of mature sperm was increased significantly.This study revealed that systemic HS induces testicular inflammation via circulatory system by promoting the intestinal inflammation.Reshaping gut microbiota by probiotics reduces intestinal inflammation,improves testicular health,and improves semen quality.The study elucidates the mechanism of probiotics in relieving testicular dysfunction caused by systemic HS based on the gut-testis axis,and provides theoretical basis for the application of probiotics in saving the spermatogenic dysfunction caused by summer high temperature in domestic animals. |
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