The Effect Of Folic Acid Supplementation On High-fat Diet-fed Induced Obese Mice And The Underlying Mechanisms

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Folic acid supplementation alters the DNA methylation profile and improves insulin resistance in high-fat diet-fed miceBackground:Obesity is a major contributor to the global burden of disabilities and chronic diseases including high blood pressure,insulin resistance,type 2diabetes,and heart diseases.Insulin resistance is regulated by both genetic and environmental factors.The interaction between these factors during disease development can be mediated by epigenetic modifications.Epigenetic markers might explain the link between lifestyle and the risk of disease.White adipose tissue(WAT),such as epididymal fat,appears to play an important role in the development and maintenance of obesity-associated insulin resistance.However,the exact mechanisms by which WAT becomes dysfunctional and promotes obesity-related complications such as insulin resistance are poorly understood.Folate is required for provides the single-carbon moiety in the synthesis pathway for S-adenosylmethionine.Supplementation with FA alters global DNA methylation profiles,protects against DNA damage,and optimizes DNA repair and the fidelity of DNA replication.Notably,some studies showed that FA supplementation decreased insulin resistance and the plasma levels of homocysteine(Hcy),and also improved blood glucose control in obese patients with type 2 diabetes.However,systematic studies of the role of FA supplementation on the risk of obesity and insulin resistance have barely been conducted.We thus adopted a genome-wide approach to directly examine whether FA supplementation affects the DNA methylation profile of mouse adipose tissue and identify the functional consequences of these changes.Methods:Mice were fed a high-fat diet(HFD),normal diet(ND),or a HFD supplemented with folic acid(FAD)for 10 weeks,epididymal fat was harvested,and genome-wide DNA methylation analyses were performed using methylated DNA immunoprecipitation sequencing(MeDIP-seq).RT-qPCR and bisulfite sequencing were then performed to assess mRNA expression and DNA methylation,respectively,of Adcy3 and Rapgef4.Results:Mice exposed to the HFD progressively expanded their adipose mass,which was accompanied by a significant increase in circulating glucose and insulin levels.FA supplementation reduced the fat mass and serum glucose levels and improved insulin resistance in HFD-fed mice.MeDIP-seq revealed distribution of differentially methylated regions(DMRs)throughout the adipocyte genome,with more hypermethylated regions in HFD mice.Methylome profiling identified DMRs associated with 3787 annotated genes from HFD mice in response to FA supplementation.Pathway analyses showed novel DNA methylation changes in adipose genes associated with insulin secretion,pancreatic secretion,and type 2 diabetes.The differential DNA methylation corresponded to changes in the adipose tissue gene expression of Adcy3 and Rapgef4 in mice exposed to a diet containing FA.Conclusions:FA supplementation improved insulin resistance,decreased the fat mass,and induced DNA methylation and gene expression changes in genes associated with obesity and insulin secretion in obese mice fed a HFD.Part ? Folic acid prevents cardiac dysfunction and reduces myocardial fibrosis in a mouse model of high-fat diet-induced obesityBackground:Obesity is regard as an energy balance disorder in which inappropriate expansion and dysfunction of adipose tissue caused a prevalence of type 2 diabetes and cardiovascular diseases.Accumulated studies have demonstrated that the impact of obesity on cardiac remodeling with structural and functional abnormalities.However,the underlying mechanisms contributing to these changes remain incompletely understood.Oxidative stress and inflammation has considered as involve in the pathogenesis and progression of many forms of cardiovascular disease.Several evidence indicate that oxidative stress plays a pivotal role in the development of obesity-induced cardiovascular disease.Previous study also demonstrated that cardiac fibrosis and inflammation are ameliorated by treatment with antioxidant in the diabetic heart.FA is an antioxidant,recently reported to be reducing reactive oxygen species generation,and blunts cardiac dysfunction during ischemia.A meta-analysis of randomized controlled trials have shown that FA supplementation can reduce the risk of cardiovascular diseases.The antioxidant activity is thought to be involved in these effects of FA on cardiovascular disorders.In addition,Hyperhomocysteinemia was found to be associated with a higher risk of cardiovascular disease in previous studies,and dietary folate fortification lowers plasma Hey levels through converting Hey to methionine.Therefore,FA is consider as have an antioxidant effect against ROS and an alleviating role in hyperhomocysteinemia and its associated cardiac dysfunction.However,the direct effects of FA on obesity-related cardiomyopathy have not yet been studied.Methods:To test our hypothesis,six-week-old C57BL/6J mice were fed a HFD,ND,or a FAD for 14 weeks.Cardiac function was measured using a transthoracic echocardiographic exam.Phenotypic analysis included measurements of body and heart weight,blood glucose and tissue Hey content,and heart oxidative stress status.Results:HFD consumption elevated fasting blood glucose levels,caused obesity and heart enlargement.FA supplementation in HFD fed mice resulted in reduced fasting blood glucose,heart weight and heart tissue Hey content.We also observed a significant cardiac systolic dysfunction when mice were subjected to HFD feeding,as indicated by a reduction in LV ejection fraction and fractional shortening,however,FAD treated improved cardiac function.FA supplementation protected against cardiac fibrosis induced by HFD.In addition,HFD increased heart tissue MDA concentration,and reduced the activity of antioxidant enzyme,GSH and CAT.HFD consumption induced myocardial oxidant stress with amelioration by FA treatment.Conclusions:FA supplementation significantly lowers blood glucose levels,heart tissue Hcy content,and reverses cardiac dysfunction induced by HFD in mice.These functional improvements of the heart may be mediated by the alleviation of oxidative stress and myocardial fibrosis.