The intestinal fatty acid binding protein is not essential for dietary fatabsorption in mice

The intestinal fatty acid binding protein (I-FABP) belongs to a family of 1 5 kDa clamshell-like proteins that are found in many different tissues. So far, nine types have been identified. Their primary structures are highly c onserved between species but somewhat less so among the different types. Th e function of these proteins, many of which are highly expressed, is not we b understood. Their ability to bind lipid ligands suggests a role in lipid metabolism, but direct evidence for this idea is still lacking. We tested t he hypothesis that I-FABP serves an essential role in the assimilation of d ietary fatty acids by disrupting its gene (Fabpi) in the mouse. We discover ed that Fabpi(-/-) mice are viable, but they display alterations in body we ight and are hyperinsulinemic. Male Fabpi(-/-) mice had elevated plasma tri acylglycerols and weighed more regardless of the dietary fat content. In co ntrast, female Fabpi(-/-) mice gained less weight in response to a high-fat diet. The results clearly demonstrate that I-FABP is not essential for die tary fat absorption. We propose that I-FABP functions as a lipid-sensing co mponent of energy homeostasis that alters body weight gain in a gender-spec ific fashion.