Fat around arteries may actually keep them healthy

Fat around our arteries play an important role in keeping blood vessels healthy, according to new research.

Known as Perivascular Adipose Tissue, or PVAT the fat helps arteries let go of muscular tension while under constant strain. This is similar to the bladder, which expands to accommodate more liquid while at the same time keeping it from spilling out.

The finding of the study, led by researchers at Michigan State University was published in the journal Scientific Reports.

"In our study, PVAT reduced the tension that blood vessels experience when stretched. And that's a good thing because the vessel then expends less energy. It's not under as much stress," said Stephanie Watts, MSU professor of pharmacology and toxicology in the College of Osteopathic Medicine.

PVAT has largely been ignored by researchers who have thought its main job was to store lipids and do little more.

Scientists only divide blood vessels into three parts, the innermost layer called the tunica intima, the middle layer called the tunica media and the outermost layer called the tunica adventitia.

Watts wanted scientists to recognize PVAT as the fourth layer, which others have called tunica adiposa as tunica means a membranous sheath enveloping or lining an organ and adiposa is a synonym for fat.

"For years, we ignored this layer - in the lab it was thrown out; in the clinic it wasn't imaged. But now we're discovering it may be integral to our blood vessels. Our finding redefines what the functional blood vessels are and is part of what can be dysfunctional in diseases that afflict us, including hypertension. We need to pay attention to this layer of a blood vessel because it does far more than we originally thought," Watts added.

Other investigators have shown that PVAT plays a role in the functioning of blood vessels, finding that it secretes substances that can cause blood vessels to relax as well as substances that can cause it to contract.

However, Watts and her colleagues wanted to test whether PVAT itself, rather than the substances it secretes, might play a role in how blood vessels perform. So, they decided to test whether PVAT provides a structural benefit to arteries by assisting the function of stress relaxation.

The team tested the thoracic aorta in rats and found those with intact PVAT had more stress relaxation than those without.

Watts further mentioned, "My mind was blown. I made every single person in my lab come and look and I asked, 'Tell me if I'm hallucinating...do you think this is real?'" as the pieces with surrounding fat had measurably relaxed more than those without.

Watts and her colleagues also tested other arteries and were able to duplicate the same response.

"It's not something you see only in this particular vessel or this particular species or this particular strain. But that maybe it's a general phenomenon," she added.