Differential enterocyte partitioning of fatty acids in intestinal fatty acid‐binding protein‐null mice (IFABP‐/‐)

Abstract

IFABP is expressed at high levels in the mammalian small intestine (SI) and binds the major product of dietary triacylglycerol (TG) digestion, fatty acids (FA). The precise role of IFABP in processing these diet‐derived lipids is unknown. IFABP‐null mice grow normally but have a modest increase in food intake. We investigated the acute metabolism of FA in fasted WT and IFABP−/− SI mucosa in vivo. Two min after intraduodenal administration of [14C]‐oleate, mucosal [14C] was recovered primarily in TG, with no difference between WT and IFABP−/−. However, recovery of [14C] in the phospholipid (PL) fraction was greater in IFABP−/− mice (p<0.01), resulting in a reduced TG/PL ratio. No changes were found in the expression of LFABP or lipid synthetic genes, suggesting the results may be due to a non‐transcriptional, trafficking function of IFABP. Appearance of TG and [14C] in the plasma after an oral gavage of [14C]‐oleate in olive oil was unaffected by IFABP‐ablation, confirming that dietary PL is not a major source for chylomicron PL. Food deprivation increased [14C]‐oleate oxidation in WT and IFABP−/− mucosa similarly, and the expression of genes involved in mitochondrial and peroxisomal FA oxidation were also unchanged. Overall, given the absence of transcriptional changes, the effects of IFABP−/− on metabolism suggest it may be involved in FA trafficking into complex lipids. Source of research support: NIHDK38389 (JS)