Canadian researchers have found that abdominal fat may actually make people gain weight by making them hungrier.
In a study published in a recent edition of The FASEB Journal, scientists from the Lawson Health Research Institute, part of the University of Western Ontario, concluded that abdominal fat cells can produce an appetite-inducing hormone known as Neuropeptide Y (NPY).
In his lab research, lead study author Dr. Kaiping Yang, found that the abdominal fat in obese rats in fact produced the hormone.
Researchers had previously believed that only the brain produces NPY, and that a primary reason that those who are overweight eat in excess is the brain's excessive production of the hormone.
In addition to being the strongest appetite-stimulating hormone, NPY also stimulates fat-cell production.
"This may lead to a vicious cycle where NPY produced in the brain causes you to eat more and therefore gain more fat around your middle. And then that fat produces more NYP hormone, which leads to even more fat cells," Yang said in a statement.
This new research adds to the growing number of studies that point to the detrimental health effects caused by carrying extra weight around the mid-section. The so-called "spare tire" can elevate a person's risk for heart disease, diabetes and hypertension.
The next step for Yang and his research team is to investigate if NPY produced by abdominal fat is circulated into the bloodstream. If so, it's possible that it could move to the brain, where it might further stimulate hunger pangs. Such findings could lead to a blood test for NPY levels.
"If you can detect NPY early and identify those at risk for abdominal obesity, we can then target therapy to turn off NPY," Yang said. "It would be much easier to use drugs to prevent obesity than to treat the diseases caused by obesity."
Abstract:
Neuropeptide Y is produced in visceral adipose tissue and promotes proliferation of adipocyte precursor cells via the Y1 receptor
Kaiping Yang, Haiyan Guan, Edith Arany, David J. Hill, and Xiang Cao
Neuropeptide Y (NPY) is synthesized in neural tissue of the central and peripheral nervous systems and has a number of important functions besides regulating appetite and energy homeostasis. Here we identify a novel site of NPY biosynthesis and a role for NPY in promoting proliferation of adipocyte precursor cells. We show that NPY mRNA is not only expressed in visceral adipose tissue (VAT) but that its levels are up-regulated 6-fold in our early-life programmed rat model of increased visceral adiposity. This is accompanied by a parallel rise in NPY protein, demonstrating that VAT is a novel peripheral site of NPY biosynthesis. Furthermore, NPY mRNA expression is also elevated >2-fold in VAT of obese Zucker rats. Importantly, NPY stimulates proliferation of primary rat preadipocytes as well as 3T3-L1 preadipocytes in vitro. This mitogenic effect appears to be mediated by the Y1 receptor and involves the activation of extracellular related kinase 1/2. In addition, insulin and glucocorticoid up-regulate VAT NPY expression in lean but not obese Zucker rats. Taken together, these results suggest that an enhanced local expression of NPY within VAT may be a common feature of and contribute to the molecular mechanisms underlying increased visceral adiposity.--Yang, K., Guan, H., Arany, E., Hill, D. J., Cao, X. Neuropeptide Y is produced in visceral adipose tissue and promotes proliferation of adipocyte precursor cells via the Y1 receptor.
(requires registration)
