title: Variation in the FABP2 promoter alters transcriptional activity and is associated with body composition and plasma lipid levels.
abstract: The fatty acid-binding proteins (FABPs) are cytoplasmic proteins involved in intracellular fatty acid transport and metabolism. FABP2, the intestinal-type FABP, is expressed exclusively in enterocytes in the small intestine. In previous studies of an Ala54Thr substitution in FABP2, the Thr-allele showed association with increased lipid oxidation, elevated plasma lipids, and impaired insulin sensitivity. We screened roughly 1 kb 5' of the FABP2 initiation codon and identified three insertion/deletion polymorphisms and four single nucleotide polymorphisms (SNPs). Three of the SNPs were in complete linkage disequilibrium with the three insertion/deletion polymorphisms, defining exactly two haplotypes (FABP2p-ID). We tested the hypothesis that this variation alters gene expression by transfecting Caco-2 cells with pGL3-Basic constructs containing opposite FABP2p-ID haplotypes. Luciferase assays showed a statistically significant two-fold increase in gene expression of the pGL3-insertion construct over the pGL3-deletion construct (P<0.001; n=5). We also tested for association between three FABP2 variants and measurements of body composition, plasma lipids, and insulin sensitivity in non-diabetic control subjects from the San Luis Valley Diabetes Study (n=714). The only informative variant, FABP2p-ID, was statistically significantly associated with body mass index (P=0.042) and marginally associated with fat mass (P=0.084), cholesterol (P=0.066), and HOMA IR (a derived measure of insulin resistance; P=0.062) in the entire cohort. Similar associations were seen only in non-Hispanics when the analysis was stratified by ethnicity. Within the non-Hispanic subgroup, the effects of FABP2p-ID on plasma lipids were sex-specific. These results suggest that genetic variation in the 5' region of FABP2 affects transcriptional activity, presumably leading to alterations in body composition and lipid processing.
authors.affiliation: Department of Human Genetics, University of Pittsburgh Graduate School of Public Health, Pittsburgh, Pa., USA. cdamcott@medicine.umaryland.edu
authors.forename: Coleen M
authors.initials: CM
authors.lastname: Damcott
authors.forename: Eleanor
authors.initials: E
authors.lastname: Feingold
authors.forename: Susan P
authors.initials: SP
authors.lastname: Moffett
authors.forename: M Michael
authors.initials: MM
authors.lastname: Barmada
authors.forename: Julie A
authors.initials: JA
authors.lastname: Marshall
authors.forename: Richard F
authors.initials: RF
authors.lastname: Hamman
authors.forename: Robert E
authors.initials: RE
authors.lastname: Ferrell
mesh_terms: D000704:Analysis of Variance; D001823:Body Composition / Q000235:genetics*; D002352:Carrier Proteins / Q000235:genetics* / Q000378:metabolism; D050556:Fatty Acid-Binding Proteins; D008055:Lipids / Q000097:blood*; D009363:Neoplasm Proteins; D011110:Polymorphism, Genetic; D011401:Promoter Regions, Genetic; D014158:Transcription, Genetic / Q000502:physiology*
chemical_list: D002352:Carrier Proteins; C493405:Fabp2 protein, mouse; D050556:Fatty Acid-Binding Proteins; D008055:Lipids; D009363:Neoplasm Proteins