Periadventitial fat releases a vascular relaxing factor

Area of Science:

• Cardiovascular Biology
• Adipose Tissue Biology
• Vascular Physiology

Background:

• Blood vessels are enveloped by adventitial fat, containing adipocytes that secrete vasoactive substances.
• These substances may play a role in modulating vascular smooth muscle contraction.

Purpose of the Study:

• To investigate the modulatory effect of perivascular adipose tissue on aortic ring contraction.
• To identify the mechanism behind the anticontractile properties of perivascular fat.

Main Methods:

• Studied aortic ring preparations from Sprague-Dawley rats with and without periadventitial adipose tissue.
• Assessed contractile responses to angiotensin II, serotonin, and phenylephrine.
• Utilized inhibitors for ATP-dependent K+ channels (glibenclamide) and tyrosine kinases (genistein), as well as blockers for NOS, cyclo-oxygenase, cytochrome P450, and adenosine receptors.

Main Results:

• Intact aortic rings with periadventitial fat exhibited significantly reduced contractile responses (95%, 80%, 30%) to various agonists compared to denuded vessels.
• The anticontractile effect was attenuated by glibenclamide and genistein.
• Blocking other pathways (NOS, COX, CYP450, adenosine) did not restore vascular contractility.
• The effect was observed in Zucker fa/fa rats, indicating leptin receptor independence.
• Transfer of solutions from perivascular fat or adipocytes induced relaxation in denuded vessels.

Conclusions:

• Perivascular adipose tissue releases a transferable adventitium-derived relaxing factor.
• This factor likely acts through tyrosine kinase-dependent activation of K+ channels in vascular smooth muscle cells.
• Perivascular fat plays a significant role in regulating vascular tone.