Researchers Find a New Marker of Deep Belly Fat
Recently, a study of the abdominal fat of 196 people demonstrated that such visceral fat produces something called retinol (vitamin A)-binding protein 4 (RBP4), a carrier protein that transports vitamin A around your body. There was sixty times more RBP4 gene activity in the belly fat of obese people than in the belly fat of lean people, and twice as much in people with impaired glucose tolerance or type 2 diabetes as in people with normal blood glucose.
The amount of RBP4 in the blood accurately reflected the amount of fat around the central organs. In obese people, the blood level of RBP4 was double or triple that of normal-weight people. RBP4 in the blood also correlated inversely with insulin sensitivity and inversely with gene activity of GLUT4, an important insulin-regulated glucose transporter.
The study authors noted that because of its close correlation with central fat levels, RBP4 could perhaps be used as a marker to predict risk of disease. Previous research has indicated that blood RBP4 can be reduced by exercise and that RBP4 levels drop in association with improved insulin sensitivity.
In another study, teens who ate low carb diets and exercised also lowered their RBP4 levels. In mouse experiments, RBP4 has been found to decrease the insulin sensitivity of muscle and liver tissue.
Sources: Cell Metabolism, July 2007