 Sample Size and Data Analysis Methods. We will perform correlation analyses to examine the relationships between the increment in skin and forearm blood flow following acetylcholine infusion and the improvements in plasma hemoglobin A1c levels and whole body insulin sensitivity before and after pioglitazone therapy using ANOVA with repeated measures over time. We anticipate that pioglitazone treatment will improve glycemic control and tissue insulin sensitivity and that the improvements in hemoglobin A1c and insulin action will be closely related to improvements in acetylcholine-stimulated increments in skin and forearm blood flow. Changes in insulin sensitivity insulin clamp data, insulin signaling pathways activity, nitric oxide production in vivo, endothelial function, FPG and HbA1c will be compared. Further, we anticipate that plasma levels of endothelial damage markers ICAMVCAM, p-Selectin, s-Selectin and PAI-1 and inflammatory markers C-reactive protein and interleukins, which are elevated in diabetic patients, will be reduced following pioglitazone, and that the reduction will correlate with the improvements in skin and muscle endothelial function. We also expect to observe an improvement in the plasma lipid profile, especially triglycerides and free fatty acids after pioglitazone treatment. Similar correlations between improved endothelial-independent blood flow nitroprusside-stimulated following pioglitazone treatment and enhanced insulin sensitivity, glycemic control, nitric oxide production and insulin signaling pathways will also be performed. We expect that improved insulin sensitivity insulin clamp and increased NO production in vivo following pioglitazone treatment will be closely related to enhanced IRS-1 tyrosine phosphorylation and total IRS-1 associated PI-3 kinase activity, which we previously have shown to be markedly impaired in type 2 diabetic individuals 39. In contrast, we expect that the MAP-kinase mitogenic pathway, which regulates vascular smooth muscle cell growthproliferation and which we have shown to be normal or upregulated in type 2 diabetics, may be inhibited following pioglitazone treatment. It would be of great pathogenic significance if reduction in the MAP kinase activity correlated with the improved endothelial function following pioglitazone therapy. 