Effect of liver fatty acid binding protein (FABP) T94A missense mutation on plasma lipoprotein responsiveness to treatment with fenofibrate

Fenofibrate, a peroxisome proliferated activated receptor alpha (PPARalpha) agonist, has been shown to decrease plasma triglyceride (TG) and increase plasma high-density lipoprotein (HDL) cholesterol levels despite a large interindividual variation in the response. Fenofibrate-activated PPARalpha binds to a DNA sequence element termed PPAR response element (PPRE) present in regulatory regions of target genes. A PPRE has been identified in the proximal 5' flanking region of the gene encoding the liver fatty acid binding protein (LFABP). LFABP is a small cytosolic protein of 14 kDa present in the liver and the intestine and is a member of the superfamily of the fatty acid binding proteins (FABPs). FABPs play a role in the solubilization of long-chain fatty acids (LCFAs) and their CoA-ester to various intracellular organelles. FABPs serves as intracellular acceptors of LCFAs, and they may also have an impact in ligand-dependent transactivation of PPARs in trafficking LCFAs to the nucleus. Since PPARs are known to regulate the transcription of many genes involved in lipid metabolism, the importance of LFABP in fatty acid uptake has to be considered. The aim of this study was to verify whether genetic variations in the LFABP gene may impact on plasma lipoprotein/lipid levels in the fasting state as well as on the response to a lipid-lowering therapy with fenofibrate on plasma lipids and obesity variables. We also wanted to verify whether the presence of the PPARalpha L162V mutation interacts with genetic variants in LFABP gene. To achieve this goal, we first determined the genomic structure of the human LFABP gene and then designed intronic primers to sequence the coding regions, all exon-intron splicing boundaries, and the promoter region of the gene in 24 patients showing divergent plasma lipoprotein/lipid response to fenofibrate. Sequence analysis revealed the presence of a T94A missense mutation in exon 3. Interspecies comparison revealed that threonine 94 is conserved among species. We subsequently screened another sample of 130 French Canadian subjects treated with fenofibrate for the presence of the LFABP T94A mutation. Carriers of the A94 allele were at increased risk to exhibit plasma TG levels above 2.00 mmol/l after treatment with fenofibrate [2.75 (1.03-7.34); OR 95% confidence interval (CI)]. In addition, carriers of the A94 allele were characterized by higher baseline plasma-free fatty acid levels (FFA) (p=0.01) and by a lower body mass index (BMI) (p=0.05) and waist circumference (p=0.005) than T94 homozygotes. Moreover, PPARalpha L162V and LFABP T94A showed to have a synergistic effect on BMI (p interaction=0.03). These results suggest that the LFABP T94A missense mutation could influence obesity indices as well as the risk to exhibit residual hypertriglyceridmia following a lipid-lowering therapy with fenofibrate.