The Mechanism Research Of Free Fatty Acid-induced Insulin Resistance

Insulin resistance(IR)is a major metabolic abnormality in the great majority of patients with type 2 diabetes(T2DM),and the incidence of this disease has reached epidemic proportions around the globe.A series of changes on physical factors,including faltures of insulin signaling,abnormal functions of mitochondria and microvascular as well as inflammation induce IR.These changes induce accumulation of lipid metabolins such as DAG and/or ceramide which finally disturb insulin signaling and induce IR.The elevated level of free fatty acid(FFA)is the typical performance of lipid metabolism disorder and the main factor of obesity-induce IR.The present studies showed that the mechanisms of FFA-induced IR mainly include oxidative stress,inflammation,apoptosis,mitochondrial dysfunction,endoplasmic reticulum.The molecules involved in these progresses include JNK(Jun N-terminal kinase),ROS(reactive oxygen),PKC? and NLRP3 inflammasome.But most of these studies are conducted in cells or animal models where the related moleculars and signaling pathway are limited.So in this study we investigate the relationship between the level of FFA in blood and IR in T2 DM and pre-diabetes(Pre-DM).Then the microarray analysis is performed for peripheral blood RNA of T2 DM who exist IR and abnormally elevated level of FFA and healthy subjects whose level of FFA is normal.We want to screen the different expression genes which participate in the process of FFA-induced IR and find the potential moleculars.We hope to provide molecular targets and theoretical basis for early diagnosis and treatment of T2 DM.In this study we selected one hundred and fifty-four T2 DM and thirty-three pre-diabetes(Pre-DM)who were diagnosed and treated in our hospital.According to related diagnostic standards we divided T2 DM into two groups including obesity group(O group)and non-obesity group(N gourp).Similarly we divided Pre-DM into two groups including impaired fasting glucose group(IFG)and inpaired glucose tolerance group(IGT).Thirty-three healthy individuals were the controls(NC group).The levels of basic mass index,biochemical indexes,endocrine indexes and FFA were measured.The HOMA-IR was calculated by insulin homeostasis model.At last we analysed the datas by T test,Nonparametric rank sum test,Pearson correlation analysis and Multiple linear regression analysis.We extracted mRNA in peripheral blood and reversed and transcribed them into cDNA(four in O group,three in N group and three in NC group)The microarray analysis was performed in these ten samples to find genes which expressed differentially.qRT-PCR was performed in the rest cases of T2 DM and Pre-DM for the gene DOK1 which were found above to validate the gene chip results.In this study we found these four results:(1)The levels of FFA were significantly higher in T2 DM group,N gourp and O group than those in NC controls(p<0.05)HOMA-IR correlated significantly with FFA in N group(p<0.05)and the level of HOMA-IR would increase with the increase of FFA.The level of FFA is the most primary factor to the HOMA-IR in this study.(2)The levels of FFA were significantly higher in IFG group,IGT group and Pre-DM group than those in NC controls(p<0.05).HOMA-IR correlated significantly with FFA and the level of HOMA-IR would increase with the increase of FFA.The level of FFA is the most primary factor to the HOMA-IR in this study.(3)DNA array ananlysis showed that the level of FOS(FBJ murine osteosarcoma viral oncogene homolog)was significantly lower in O group than that in NC controls(p<0.05).The levels of FOS,HK2(hexokinase 2)and DOK1(docking protein 1)were significantly lower in N group than those in NC controls(p<0.05).The levels of FOS and MAPK1(mitogen-activated protein kinase1)were significantly higher in O group than those in N group(p<0.05).The level of AEBP1(AE binding protein 1)was significantly lower in O group than that in N group(p<0.05).(4)Fluorescence quantitative PCR results showed that the level of DOK1 was significantly lower in N group and Pre-DM groups that in NC controls(p<0.05),but there was no significantly changes in O group(p>0.05).In all words,we inferred that the abnormally high level of FFA might be related to the lower level of DOK1 in non obesity T2 DM and Pre-DM patients.The down-regulation of DOK1 might inhibit lipid synthesis and induce lipolysis which all induced or aggravate insulin resistance(IR).