New Test for Bad Belly Fat?
Diabetes-Linked Protein Warns of Dangerous Deep Belly Fat
July 10, 2007 -- Rising blood levels of a protein called RBP4 indicate
ballooning growth of deep belly fat -- which is strongly linked to type 2
diabetes and heart disease.
Recently, a research team led by Barbara B. Kahn, MD, head of the diabetes
division at Beth Israel Deaconess Medical Center, showed that
rising RBP4 levels predict insulin resistance. Insulin resistance is an
early sign of type 2 diabetes and rising heart disease risk.
Another major risk factor for diabetes and heart disease is deep belly fat.
Doctors call this accumulation of fat around the organs of the abdomen
"visceral adiposity." Could belly fat explain the link between RBP4 and
diabetes/heart disease risk?
To find out, Kahn's team joined forces with researchers Matthias Blüher, MD,
and colleagues at the University of Leipzig, Germany. They obtained deep belly
fat samples from 196 German patients undergoing abdominal surgery. Sixty-six
study participants were lean and 130 were obese.
- There was 60 times more RBP4 gene activity in the belly fat of obese
patients than in the belly fat of lean patients.
- Blood levels of RBP4 were two to three times higher in obese patients than
in lean patients.
- Regardless of whether a patient was lean or obese, higher blood levels of
RBP4 meant more deep belly fat and more insulin resistance.
"This suggests a potential role for RBP4 as a convenient marker not only
for type 2 diabetes but also for [heart disease] risk," the researchers
conclude in the July issue of the journal Cell Metabolism.
The body uses RBP4 -- retinol (vitamin A)-binding-protein 4 -- to carry
vitamin A in the blood. In a news release, Kahn says it's not yet clear whether
these newly discovered roles for RBP4 are due to vitamin A or to the protein
In earlier studies, Kahn and colleagues showed that RBP4 causes insulin
resistance in mice. If it works the same way in people, it might be the target
of new diabetes drugs. Interestingly, a cancer drug called fenretinide reduces
RBP4 levels. In obese mice, this drug improves insulin sensitivity and blood
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