Study On The Source Of Reducing Power In Lipid Synthesis In Obese Mice And Adipocytes Models

Obesity is a worldwide epidemic that can cause a range of chronic diseases such as cardivasular disease,type 2 diabetes,dyslipidemia and certain cancers.NADPH is the key factor in fatty acid synthesis and the main reducing power in this process.It is believed that the main source of cytoplasmic NADPH is predominantly the oxidized pentose pathway(PPP),and other possible cytoplasmic pathways include isocitrate dehydrpgenase(IDH),malate(ME)and isoforms of methylenetetrahydrofolate dehydrogenase(MTHFD).However,it is not clear the role of these NADPH producing enzymes in the process of fatty acid synthesis of obesity.In this study,we investigated the effects of different NADPH producing enzymes on fatty acid synthesis during the process of obesity tissues and adipocyte formation,and explored the main source of NADPH.RT-qPCR was used to analyze the transcriptional level of genes related to NADPH.The levels of cell total fatty acid production,NADPH,and mRNA levels of adiposeproducing genes were analyzed after silencing the key genes.The main conclusions we made are as follows:(1)RT-qPCR results of ob/ob mice and db/db mice showed that the transcriptional level of MTHFD2,G6 PD,PGD and ME1 were upregulated.In diet-induced obese mice(DIO),the transcriptional level of MTHFD2,IDH1,G6 PD and PGD were upregulated.It indicated MTHFD2 in folate metabolism,G6 PD and PGD in PPP,ME1 are the potential NADPH sources in obese mice.(2)RT-qPCR results in induced op9 showed that the transcriptional levels of ALDH4A1,MTHFD2,ME1,ME3,G6 PD,PGD were upregulated.Both 3 types of obese models and adipocyte results indicated that MTHFD2 in folate metabolism,PGD in PPP metabolism and ME1 might be the main sources of NADPH production in lipid formation.(3)Lipid droplets accumulation,expression level of adipogenesis related transcriptional factors and NADPH content were significantly reduced in MTHFD2 siliencing group after siliencing the key genes.It suggests that MTHFD2 may play a very critical role in fat formation.In studing the effects of folate metabolism on lipid synthesis,cell viability and lipid droplet accumulation were all decreased after adding folate synthesis inhibitor and folate metabolic balance inhibitor.It suggests that folate metabolism plays an important role in cell differentiation.It indicates that MTHFD2 is probably the main reducing power for NADPH production in fat synthesis and folate metabolism pathway plays a very important role in fat formtion.