Communicated by Ju ¨rgen Horst
The human intestinal fatty acid binding protein 2 (FABP2) mediates fat absorption by binding and intracellular trafficking of long-chain free fatty acids. Studies with knockout mice and association analysis of polymorphisms revealed that FABP2 is a susceptibility gene for type 2 diabetes (noninsulin dependent diabetes mellitus [NIDDM]) and related traits.
-471G4A (rs2282688), and c.-778G4T (rs10034579) result in two haplotypes A and B, whereby B possesses two-to three-fold lower transcriptional activity than A. We show in luciferase reporter gene assays by a series of chimeric FABP2 promoter constructs in intestinal Caco-2 cells that polymorphism c.-80_-79insT essentially determines different activities of the FABP2 promoter. In accordance, in electrophoretic mobility shift assays (EMSAs), transcriptional factors GATA-5 and -6 bind with higher binding affinities to the FABP2 promoter region containing the À80A allele compared to B. As functional consequence, haplotype A is twice as much more activated by GATA factors than haplotype B in liver Huh7 cells. Additionally, a construct bearing the À80B allele in the background of haplotype A reversed the activity from A to B. Thus, the GATA mediated differential activation of FABP2 haplotypes depends on polymorphism c.-80_-79insT. This provides the molecular basis for the variant specific transcriptional regulation of the diabetes type 2-associated FABP2 gene.