The Anxiolytic Effect Of Short-term High-fat Diet In Male Mice And Its Epigenetic Mechanism

With the improvement of living standard,overweight and obesity are becoming more and more popular,not only causing metabolic diseases,but also closely related to mental health.As we know,anxiety disorder is one of the most common mental problems with a prevalence about 7%in one’s lifetime.Children and adolescents are at high risk.It is characterized by excessive worry about school,family,and working etc.There are many risk factors,including the environment,diet,microbiota,parental care and so on.Current treatments(such as Pharmacological treatment and cognitive behavioral therapies)appear to be effective in a short time but have poor effects in long-term and are prone to recurrence.Therefore,it is important to look for the biomarkers or targets during the development of this disease.In recent years,some studies have revealed that epigenetic mechanisms are closely related to the emotional behavior of offspring.To explore the relationship between the diet and anxiety,we selected obesity models induced by high-fat diet(5weeks old mice,19-20g,60%energy from fat for 6 weeks).To test whether the short-term high-fat diet caused mental disorders such as anxiety and depression in mice,the open field test(OFT),the light dark box test(LDT),and the elevated plus maze(EPM)were used to detect the anxiety-like behavior,while the sucrose preference test(SPT),tail suspension test(TST)and forced swimming test(FST)were used to detect the depression-like behavior.It was found that the HFD group spent more time in the open arm of EPM and the light box of LDT,respectively,which represents anxiolytic-like behaviors.However,there is no difference in the locomotor ability and depression-like behavior.Next,we designed the following experiments with 6-weeks’ high fat diet mice(11 weeks old)mating with the same age females which fed a control diet.The offspring were fed with control diet and behavioral tests were performed when they grown up.The results showed that male offspring of HFD mice also displayed anxiolytic-like behavior compared with the offspring of CD mice.In order to explore the epigenetic mechanism of the paternal HFD on the offspring behavior,We use DNA methylation microarray to detect the genes of parental sperm,combined with the method of MeDIP,qPCR to verify the methylation of some related genes in the paternal sperm and offspring brain regions.We found that the methylation of BDNF and HOMER decreased in the paternal sperm and offspring mPFC,while the methylation of MAOA increased and GRIN3B did not changed significantly.Expression of the methytransferases in both of them decreased.At the mRNA level,the expression of BDNF increased in the paternal mPFC,hippocampus and offspring mPFC,while the expression of MAOA decreased in the paternal mPFC and amygdala.After the administration of ANA12 to male offspring of HFD,the antagonist of BDNF receptor TrkB,the anxiolytic behaviors were abolished.Furthermor,We found that the protein level of MAOA decreased in the paternal mPFC/amygdala by the western blot analysis.In recent years,the theory that intestinal microorganisms influence the function of the brain(gut-brain axis)has been proved by many studies.We extracted the flora from the fecal from the CD/HFD mice and transplanted them to the SPF mice.Mice displayed anxiolytic-like behavior after transplanting HFD microbiota compare to the group which transplanted CD microbiota.In order to identify which microbiota might influence the behavior,we used 16SrDNA analysis to detect the distribution and difference of intestinal flora between different group mice.It was found that the relative abundances of Lactobacillus were significantly increased in the HFD group and the FMT-HFD group.It is suggested that changes in the relative abundance of Lactobacillus may be involved in the regulation of anxiolytic-like behavior in the mice.For all the results,the following conclusions can be drawn.1)Short-term highfat diet can cause anxiolytic-like behavior in mice and their male offspring.2)The methylation level BDNF and HOMER decreased in the paternal sperm and offspring mPFC,while MAOA increased,and the expression of DNMT decreased.3)At the mRNA level,the expression of BDNF increased in the paternal mPFC,hippocampus and offspring mPFC;the expression of MAOA decreased in the paternal mPFC and agmydala.4)ANA 12 can abolish the anxiolytic behaviors of male offspring of HFD.5)The protein level of MAOA decreased in the paternal mPFC and amygdala.6)Lactobacillus may be involved in the regulation of anxiolytic-like behavior in mice fed short-term high-fat diets.