Effects Of Salt Intake On Cognitive Function,Intestinal Inflammation And Gut Microbiota In Mongolian Gerbil (Meriones Unguiculatus)

Objective:This study took the mongolian gerbil(Meriones Unguiculatus)as a model to explore the effects of high-salt food and high-salt water on its cognition,intestinal inflammation,gut microbiota and the physiological mechanism of its response to high salt intake.Methods : Fifty 4-month-old mongolian gerbils were divided into 5 groups and 10 animals as a group,They were fed salty food or saline water for 8 weeksthe,5 groups are CON group,SF4% group,SF8% group,SW4%group and SW8% group.The CON group was given normal food and water,SF4%group was given 4% salty food and normal drinking water,SF8% group was given 8%salty food and normal drinking water,SW4% group was given normal food and 4%saline water,SW8% group was given normal food and 8% saline water,feeding for eight weeks.The food intake,water intake and body weight were measured once every three days.The open field experiment,Y-maze experiment,Elevated cross maze experiment and Novel object recognition experiment were carried out to measure the behavior of animals such as learning and memory function,the anxiety index since the sixth week.The resting metabolic rate(RMR)was slso measured,the urine was collected.The animals were sacrificed and the blood samples were taken since the 9th week.Separating the serum to measure the osmotic pressure,the concentration of corticosterone(CORT)and antidiuretic hormone(ADH).The concentration of malondialdehyde(MDA),the activity of superoxide dismutase(SOD),the expression of brain-derived neurotrophic factor(BDNF)in hippocampal tissues were measured.Colonic feces were collected and gut microbiota was measured.The colon was taken to measure the inflammatory cytokines such as interleukin-17(IL-17)and tumor necrosis factor(TNF-α),the expression of nuclear transcription factor kappa B(NF-κB)was measured.Results:(1)Compared with CON group,SF4% and SF8% group had no difference in food intake and body weight,but water intake was significantly increased(P<0.001);Compared with CON group,SW4% group had no difference in food intake and body weight,while water intake decreased(P<0.05);Compared with CON group,Food intake of SW8% group(P<0.001),water intake(P<0.001)and body weight(P<0.05)were significantly increased;Compared with CON group,RMR of all treatments had no significant difference.(2)Compared with CON group,the ratio of the total distance,the proportion of the moving time in the food arm and the proportion of the moving distance in the food arm of all treatments in Y-maze had no significant difference.Compared with the CON group,there was no significant difference in the total movement distance between the central area and the peripheral area,the frequency of crossing the central area and the time of movement in the central area in the open field experiment.Compared with the CON group,the time staying in the open and closed arm and the number of central entry had no significant difference in the elevated cross maze experiment.Compared with CON group,the ratio of contact frequency,time to familiar object and ratio of contact frequency,time to the unfamiliar object in all treatments had no significant difference in the novelty-seeking test.Compared with CON group,the SOD activity in hippocampal region of SF8% was significantly decreased(P<0.01),there was no difference in SOD activity in the hippocampus of other treatment groups;Compared with CON group,there was no significant difference in the concentration of MDA in the hippocampus of all treatment groups.(3)Compared with CON group,there was no significant difference in the serum osmotic pressure of all treatment groups.Compared with CON group,the urine osmotic pressure of SW8% group was significantly increased(P<0.001),and the urine osmotic pressure of SW8% group was significantly higher than that of SW4% group(P<0.01).(4)Compared with the CON group,there was no significant difference in the concentration of ADH among the other groups.The concentration of ADH in SW8% group was significantly lower than that in SW4%group(P<0.05);compared with CON group,the concentration of CORT in SF8%group(P<0.01),SW4% group(P<0.001),SW8% group(P<0.01)were significantly decreased,and there was no significant difference in the concentration of CORT in SF4% group.(5)Compared with CON group,the concentration of IL-17 in the colon of SF8% group(P<0.001)and SW4% group(P<0.01)was significantly decreased,and there was no significant difference in the content of IL-17 in the colon of other groups;Compared with CON group,there was no significant difference in the concentration of TNF-α and the expression of NF-KB in colon of all groups.(6)The analysis of gut microbiota showed that salt in food and water would affect gut microbiota of mongolian gerbils.The number of OTU in SF8%,SW4%,SW8% group increased,and the number of OTU in gut microbiota of SW8% group increased most obviously.The SW8% group had the largest proportion of special flora,most of which belonged to Firmicutes,while the other four groups had fewer dominant flora.High salt in water and food had opposite effects on the abundance of gut microbiota at phylum and family levels in mongolian gerbils.Conclusion:(1)The intake of high salty food and water had no effect on the food intake and body weight of mongolian gerbils,and the water intake increased significantly.(2)The intake of high-salty food and water did not cause the impairment of cognitive function such as learning and memory,and will not produce anxiety and other adverse emotions.(3)The intake of high salty food and water did not induce colonic and systemic inflammation in mongolian gerbils.(4)The high salty food and water affected the composition and diversity of gut microbiota in mongolian gerbils.