Time-restricted Feeding Affects Body Weight And Behavior In Post-weaning Socially Isolated Mice

BackgroundIn mammals,several aspects of behavior and physiology,such as blood pressure,body temperature,hormone secretion,sleep-wake cycle,and rest-activity rhythms exhibit daily oscillations known as circadian rhythms,allowing life to anticipate and adapt to the continual changes that occur in an organism's environment.So the limited resources and energy are made use of to sustain all life activities normally.However,if the synchronization of organism and the environment is long-term disturbed,it would bring many negative consequences,even closely related to endocrine disorders,metabolic imbalance,tumorigenesis and emotional dysregulation.The regulation of circadian rhythms is mainly dependent on the suprachiasmatic nucleus in the hypothalamus.It is the main brain regions controlling circadian clock,also known as central circadian rhythms oscillator.It receives light signals from the retina to impact the transcription rhythms of the clock control gene by molecular clock,a kind of cellular feedback regulation mechanism,and uses the rhythms signals from neurotransmitters and hormones and other signals to control the organs and tissues,to achieve the central and peripheral rhythms synchronization.The core molecular clockwork is composed of a transcriptional/post-translational feedback loop in which clock genes and their protein products periodically suppress their own transcription.Entrainment factors are environmental factors affecting the circadian clock,such as light,social activities,food intake.With the development of modern society and lifestyle changes,the influence made by nature entrainment factors becomes smaller and smaller,and social zeitgeber play a more important role.The social zeitgeber disorder cause metabolic disorders and emotional dysregulation susceptibility.Social rhythms disruption is common in the population.However,the impact on the rhythms of eating is often ignored by people,and the relationship between it and diseases failed to attract people's attention.Eating rhythms can affect the balance of energy metabolism by signaling pathways,including AMPK,CREB,and AKT,which is closely related to obesity and diabetes.Preserving natural feeding rhythms can prevent high-fat diet-induced metabolic diseases,and reduce cardiovascular accidents.So eating rhythms can enhance the synchronization to peripheral and central pacemaker,which is important to the balance of energy metabolism.Although there are some studies displayed that eating rhythms influence metabolic disorders,cardiovascular disease and Huntington's disease,but it has not been well studied on the specific relationship between eating rhythms and depression.Currently,there is some emerging evidence supporting the use of interpersonal and social rhythms therapy(IPSRT)to target social rhythms to promote mood stability.It requires a patient according to the social clues,to form more stable social habits.However,the mechanism of circadian rhythms antidepressant is not clear.Mice are social mammals as a method used to support research about social isolation.Some studies have found that post-weaning social isolation could lead to weight gain,anxiety and depression-like behaviors in mice,,also found that the mice hormone secretion rhythms disorders.So,in order to study the relationship between circadian rhythms disorders,social isolation and depression,we selected post-weaning isolation-reared mouse model for the experiment.The aim of our study is to investigate the influence of the body weight change and abnormal behavior caused by the time-restricted feeding in post-weaning socially isolated mice,to explore the relationship between depression and circadian rhythms.Our study attempts to understand the pathogenesis of depression and to find new ways to prevent and treat it.Methods(1)Four-week-old male C57BL/6J mice were randomly divided into three group.Control group(Control)was group-housed,the social isolated ad labium group(SI+FA)mice were exposed to food freely and social isolation,and the social isolated time-restricted feeding group(SI+FT)access to food during their natural feeding time from ZT12(8 p.m.)to ZTO(8 a.m.).Body weight and food intake were measured weekly.(2)Four weeks after treatment,the three groups of mice were tested behavior,including anxiety-like behavior,depression-like behavior,hedonic behavior and learning and memory by open-field test(OFT),elevated plus maze teat(EPMT),forced swimming test(FST),sucrose preference test(SPT)and morris water maze test(MWMT).(3)To explore the potential mechanism of the impact of social isolation to animal behavior.We used RT-QPCR to detect the transcription rhythms of Clock,Bmall,Perl,Per2,Cryl and PPARy gene on hypothalamus,and to test the expression of PPARy and MAOA on amygdal.(4)We use Luciferase reporter assay system to detect the lucigeraase signal of MAOA promoter plasmid effected by PPARy and BMAL1/NPAS2.Results(1)We found isolation could lead to weakened the rhythms of feeding,as early as the first week,SI+FA mice consumed a high percentage of daily food intake during the rest(light)period than the Control mice.Time-restricted feeding could reduce weight gain caused by isolation.(2)In the behavioral test,OFT showed that SI+FA mice increased the total distance and decreased the centre time compared with Control mice in 5 min,but no difference was found between SI+FA group and SI+FT group.In the EPMT,the duration time in the open arms of SI+FA group significant longer than control group,but no difference was found between SI+FA group and SI+FT group.In the last 4 min of the FST,the immobility time of SI+FA group was significantly longer than that of the control group,but the SI+FT group showed short time than SI+FA group.In the sucrose preference test,the SI+FA group increased the percentage compared with Control mice of the sucrose preference,but no difference was found between SI+FA group and SI+FT group.In the MWMT,the swimming velocity showed no significant difference.With regard to spatial learning training,the latency time in each group showed a decreasing trend.The SI+FA group mice tended to take longer time to find the platform.For the probe test phase,the SI+FA group had fewer crossing times to through the data of platform site than the Control group,and the SI+FT group was showed increased the crossing times than SI+FA group.(3)Transcripts of the core circadian clock genes in the hypothalamus Clock,Bmall was no difference in each group,but Perl,Per2 and Cry 1 had showed been affected by social isolation,but not time-restricted feeding.The mRNA level of PPARy was showed difference in social isolation mice,and it could be reverse by time-restricted feeding.In amygdale,the protein and mRNA level of MAOA in the SI+FA mice was showed increased than Control group and the SI+FT group.The expression level of PPARy in the SI+FA group was decreased than control group,and it could be reverse by time-restricted feeding.(4)The promoter of MAOA was activated by BMAL1/NPAS2.However,PPARy could dampened the activation by BMAL1/NPAS2 in neuroblastoma cells.ConclusionThose findings suggest that post-weaning socially isolated in mice attenuated the diurnal pattern of feeding behavior,lead to weight gain and abnormal behavior.Time-restricted feeding could prevent those changes.The diurnal rhythms expression of PPARy,Perl,Per2 and Cry1 could be changed by social isolation,but only the rhythms of PPAR? could be reversed by time-restricted feeding.Tine-restricted feeding could also recover the expression rhythms of MAOA and PPAR? in amygdale in social isolated mice.PPAR? could dampen the MAOA promoter activation by BMAL1/NPAS2 in neuroblastoma cells.