Paradoxical roles of perivascular adipose tissue in atherosclerosis and hypertension

Perivascular adipose tissue (PVAT) is the fat tissue surrounding most of the vasculature and it has long been considered solely as vessel-supporting connective tissue. There are 2 major types of adipose tissue widely distributed throughout the body: white (WAT) and brown (BAT). PVAT is similar to BAT in rodents, but it was believed that only WAT existed in adult humans and BAT was present only in infants. However, the presence of functional BAT in adult humans is now accepted. The main function of BAT is to generate heat, and it is essential for adaptive thermogenesis and energy expenditure, whereas the main function of WAT is to store lipids. Besides the different functions of WAT and BAT, growing evidence suggests that different depots of adipose tissue have different functions. Similar to other fat depots, PVAT produces various adipokines, growth factors and inhibitors that affect functions of adjacent layers of the vasculature. Pathophysiological conditions such as obesity, vascular injury, aging and infection could cause PVAT dysfunction, leading to vascular endothelial and smooth muscle cell dysfunctions. In this review, we discuss the function and dysfunction of PVAT on atherosclerosis and hypertension.