Transient Overexpression of VEGF-A in Adipose Tissue Promotes Energy Expenditure via Activation of the Sympathetic Nervous System

Abstract

Adipose-derived VEGF-A stimulates functional blood vessel formation in obese fat pads which in turn facilitates healthy expansion of the adipose tissue. However, the detailed mechanism(s) governing the process remains largely unknown. Here, we investigated the role of sympathetic nervous system activation in the process. To this end, we induced overexpression of VEGF-A in an adipose-specific doxycycline (Dox)-inducible transgenic mouse model for a short period of time during high fat-diet (HFD) feeding. We found that local overexpression of VEGF-A in adipose tissue stimulated lipolysis and browning rapidly after Dox induction. Immunofluorescent staining against tyrosine hydroxylase (TH) indicated higher levels of sympathetic innervation in adipose tissue of transgenic mice. In response to the increased norepinephrine (NE) level, expression of {beta}3-andrenoceptor was significantly upregulated and the downstream protein kinase A (PKA) pathway was activated, as indicated by the enhanced phosphorylation of the whole PKA substrates, in particular the hormone sensitive lipase (HSL) in adipocytes. As the result, the adipose tissue exhibited increased lipolysis, browning, and energy expenditure. Importantly, all these effects were abolished upon the treatment with {beta}3-adrenoceptor antagonist SR59230A. Collectively, these results demonstrate that transient overexpressed VEGF-A activates sympathetic nervous system which hence promotes lipolysis and browning in adipose tissue.