Vascular PPARγ Controls Circadian Variation in Blood Pressure and Heart Rate through Bmal1

Thiazolidinediones (TZDs) are PPAR gamma activators that exhibit vasculoprotective properties. To determine the vascular function of PPAR gamma, we analyzed Tie2-Cre/flox and SM22Cre/flox mice. Unexpectedly, both knockout strains exhibited a significant reduction of circadian variations in blood pressure and heart rate in parallel with diminished variations in urinary norepinephrine/epinephrine excretion and impaired rhythmicity of the canonical clock genes, including Bmal1. PPAR gamma expression in the aorta exhibited a robust rhythmicity with a more than 20-fold change during the light/dark cycle. Rosiglitazone treatment induced aortic expression of Bmal1 mRNA, and ChIP and promoter assays revealed that Bmal1 is a direct PPAR gamma target gene. These studies have uncovered a role for vascular PPAR gamma as a peripheral factor participating in regulation of cardiovascular rhythms.