Antidepressant-like Effects Of Fasting With Estrogen In Female Mice And The Potential Mechanisms

In the recent decades of years,some antidepressants came up into clinical application.However,some individuals are resistant to the clinical therapy of antidepressants or even have adverse effects.Therefore,the development of new antidepressant-like therapy is needed.Our previous study has shown that acute 9 h fasting produces antidepressant-like effects in male mice,the antidepressant-like effects of acute fasting in female mice is still unknown.It has been reported that there are gender differences in depression,women are more vulnerable to depressive disorders,and occurrence of depression in women is affected by estrogen deficiency.Several clinical studies have reported that estrogen replacement therapy exerts anti-depressive actions in perimenopausal women with depression.Furthermore,estrogen combined with other antidepressants produces additive antidepressant-like effects.It is unclear whether estrogen produces additive effects with fasting.Therefore,by behavioral tests,the present study investigated the antidepressant-like effects of fasting combined with estrogen treatment;the potential mechanisms underlying these effects were investigated using several biochemistry methods and RNA-sequencing.1 The antidepressant-like effects of fasting with estrogen in female mice(1)Fasting had antidepressant-like effects in female mice.Firstly,we did force swimming test and open field test to explore the antidepressant-like activity induced by acute 9 h fasting.The results showed that acute 9 h fasting reduced the immobility time in forced swimming test of female mice without influencing the locomotor activity in open field test,indicating that acute 9 h fasting provided significant antidepressant-like effects in female mice.(2)The additive antidepressant-like effects of fasting with estrogen.The behavioral test showed that the immobility time in forced swimming test also decreased by single 17?-estradiol injection.Fasting combined with estradiol produced an additive effect on immobility time.The results suggest that acute fasting combined with estradiol produced better anti-depressant like actions compared with individual treatment.These antidepressant-like effects were blocked by an estrogen receptor antagonist,tamoxifen,indicating that estrogen receptors may be involved in the mood improvement induced by acute fasting as well as estradiol.2 The potential biochemistry mechanisms of antidepressant-like effects induced by fasting with estrogen(1)The CREB-BDNF pathways of prefrontal cortex and hippocampus are involved in the antidepressant-like effects of fasting with estrogen.Results of western blot revealed that protein levels of total CREB,p-CREB and BDNF were enhanced by both fasting and estradiol treatment.Acute 9 fasting combined with estradiol treatment enhanced the activity of CREB-BDNF pathway more obvious.Above all,CREB-BENF pathway may be a potential mechanism mediated with the antidepressant-like effects of acute 9 fasting with estradiol.(2)Fasting and estrogen treatment significantly improve the hippocampal neurogenesis in female mice.The mice pretreated with BrdU were obtained to fast for 9 h,inject with estradiol or temoxifen.Immunoflurorescence histochemistry was used to observe cell proliferation in hippocampus.BrdU-positive cells in dentate gyrus of hippocampus were increased by acute fasting,and the addition of estradiol had additive effects.Hippocampal neurogenesis appeared to play a role in the additive antidepressant-like effects of fasting with estrogen.(3)Ghrelin(induced by fasting)and estrogen are positively related to each other.Serum ghrelin,estrogen and corticosterone levels were examined by ELISA kit.Ghrelin and estradiol levels were significant changed by fasting,and the additive of estradiol further enhanced the level of ghrelin compared with fasting alone group.The results demonstrated that ghrelin induced by acute 9 h fasting has mutual promoting effect with estradiol.Furthermore,corticosterone levels were decreased by estradiol treatment but no significant influenced by fasting,indicating that HPA asis may be mainly involved in antidepressant-like effects of estrogen.3 The differences in gene expression of prefrontal cortex and hippocampus in female mice after fasting and estrogen treatment(1)There are differential expressed genes(DEGs)after fasting or estrogen treatment in both prefrontal cortex and hippocampus,and some of which are co-expressed.The results showed that there are DEGs after fasting or estradiol treatment in both prefrontal cortex and hippocampus.The upregulated or downregualted gene numbers were similar induced by two treatments.Venn diagram showed that there were co-expression genes by two treatments,and hearmap showed that the co-DEGs were upregualted or downregulated in common.(2)The DEGs induced by fasting or estrogen can be enriched in GO terms and KEGG pathways related to the central nervous system,and some are co-enriched.The results of GO entrichment showed that there were many neurological functions co-enriched in DEGs after fasting or E2 treatment in both prefrontal cortex and hippocampus.Moreover,there were co-enriched KEGG pathways after fasting and E2 treatment.The common-enriched KEGG pathways were mentioned by previous studies to be associated with neurological functions.We suppose that co-enriched GO terms and KEGG pathways may be involved in the additive antidepressant-like effects of fasting with estrogen.(3)Drd2 is picked as a key gene,the function of dopaminergic system and the activity of its receptor may be crucial to the additive antidepressant-like effects of fasting with estrogen.27 DEGs in prefrontal cortex and 2 DEGs in hippocampus commented by KEGG pathways were found to be overlapped in Venn diagram.There were several studies explored that these genes may be related to depression disorders,and interestingly,most of them were associated with dopamine system.Further PPI analysis screened out Drd2 as a hub gene of sub networks in both prefrontal cortex and hippocampus,indicating Drd2 may interact with multiple genes and play a key role of biological pathways associated with depression.In conclusion,our study confirmed the antidepressant-like effects of fasting in female mice,and estrogen produced additive effects,providing a novel non-pharmalogical therapy for clinical treatment of women with depression disorders.