Objective To explore the vascular endothelial function in individuals with normal glucose tolerance (NGT),impaired glucose tolerance (IGT),and type 2 diabetes mellitus,and to study the role played by PPARγcoactivator 1 α (PGC-1 α) in diabetic macrovascular function.Methods A total of 94 subjects with NGT,87with IGT,and 306 with type 2 diabetes mellitus were recruited in the study.Carotid flow-mediated vasodilatation (FMD),glyceryl trinitrate dilatation (GTN),and carotid intima-media thickness (CIMT) were assessed by highresolution B-mode color vascular Doppler instrument.Finally,correlation analysis was conducted.NO,Akt-Ser473phosphorylation levels,IL-β,and PGC-1 α mRNA expression levels were measured by means of nitrate reductase,western blot,and reverse transcriptase real-time fluorescence quantitative PCR assay methods in peripheral blood mononuclear cells respectively.Results FMD in newly-diagnosed type 2 diabetic group was significantly lower than that in NGT and IGT groups(P＜0.01).GTN and CIMT showed no difference.PGC-1 α mRNA transcription level in diabetic group was significantly lower than that in non-diabetic groups (P＜0.01).Correlation analysis showed that PGC-1 α was positively correlated with FMD and GTN (P＜0.05 or P＜0.01).Logistic regression analysis revealed that PGC-1 α was independently associated with FMD (P ＜ 0.01) after adjusting other influencing factors.Conclusion FMD is a more sensitive early warning indicator of endothelial function than CIMT and GTN.As indices of atherosclerosis,CIMT and GTN are more or less focused on the progression of macrovascular complications.PGC-1 α is a protective factor of macro-vasculature in diabetes mellitus,and its effect may be achieved through the protection of the vascular endothelium.