Objective-Adiponectin is adipose-specific secretory protein and acts as anti-diabetic and anti-atherosclerotic molecule.We previously found peroxisome proliferators response element in adiponectin promoter region, suggesting that peroxisome proliferator-activated receptor (PPAR) ligands elevate adiponectin. Fibrates are known to be PPAR␣ ligands and were shown to reduce risks of diabetes and cardiovascular disease. Effect of fibrates on adiponectin has not been clarified, whereas thiazolidinediones enhance adiponectin. Thus, we explored the possibility and mechanism that fibrates enhance adiponectin in humans, mice, and cells. Methods and Results-Significant increase of serum adiponectin was observed in bezafibrate-treated subjects compared with placebo group in patients enrolled in The Bezafibrate Infarction Prevention study. Higher baseline adiponectin levels were strongly associated with reduced risk of new diabetes. Fibrates, bezafibrate and fenofibrate, significantly elevated adiponectin levels in wild-type mice and 3T3-L1 adipocytes. Such an effect was not observed in PPAR␣-deficient mice and adipocytes. Fibrates activated adiponectin promoter but failed to enhance its activity when the point mutation occurred in peroxisome proliferators response element site and the endogenous PPAR␣ was knocked down by PPAR␣-RNAi. Conclusions-Our results suggest that fibrates enhance adiponectin partly through adipose PPAR␣ and measurement of adiponectin might be a useful tool for searching subjects at high risk for diabetes. Key Words: adipocyte Ⅲ adiponectin Ⅲ fibrate Ⅲ metabolic syndrome Ⅲ peroxisome proliferator-activated receptor F ibrates have been used in clinical practice for Ͼ4 decades as a class of agents known to decrease triglyceride levels. Fibrates are also known to be peroxisome proliferator-activated receptor (PPAR)␣ ligands. Several clinical studies of fibrates have been performed in large populations. The Bezafibrate Infarction Prevention study (BIP) suggested that bezafibrate prevented cardiovascular events in the subgroup of coronary artery disease patients with high triglycerides. 1 Moreover, further subanalyses demonstrated that the administrations of bezafibrate significantly reduced new-onset diabetes 2,3 and myocardial infarction in the patients with the metabolic syndrome (MS). 4 The Fenofibrate Intervention and Event Lowering in Diabetes (FIELD) study showed that fenofibrate significantly reduced nonfatal myocardial infarctions and coronary revascularizations, a secondary endpoint, among patients with type 2 diabetes. 5 These favorable clinical outcomes in fibrate studies might be explained by not only its triglyceride-lowering effect but also its various PPAR␣-mediated pleiotropic effects.Adiponectin is an adipose-specific secretory protein and acts as an anti-diabetic and anti-atherosclerotic molecule. 6 Furthermore, a number of clinical trials showed that subjects with high levels of circulating adiponectin tend to be protected against type 2 diabetes and myocardial infarction. 7,8 Thiazolidi...