TitleA functional analysis of enterocyte fatty acid-binding proteins
NameLagakos, William Stacy (author), Storch, Judith (chair), Dixon, Joseph (internal member), Watford, Malcolm (internal member), Blaner, William (outside member), Rutgers University, Graduate School - New Brunswick,
Fatty acid-binding proteins
DescriptionIntestinal- and liver- fatty acid-binding proteins (IFABP and LFABP, respectively) are expressed at high levels in mammalian small intestinal enterocytes and bind the major products of dietary triacylglycerol (TG) digestion. The precise role of FABPs in processing these diet-derived lipids is unknown. We investigated the acute metabolism of fatty acids and monoacylglycerol in fasted WT and FABP-/- in small intestinal mucosa in vivo. Two minutes after intraduodenal administration of [14C]oleate or [3H]monoolein, mucosal radioactivity was recovered primarily in TG. Recovery of [14C]oleate in TG relative to phospholipids (PL) was significantly reduced in IFABP-/- mice. No changes were found in the expression of lipid synthetic genes, suggesting a non-transcriptional, trafficking defect. Recovery of [14C]oleate in lipid fractions was unaffected by LFABP ablation, although significantly less was oxidized. Oxidative capacity was unchanged in LFABP-/- intestinal mucosa homogenates, suggesting LFABP may target fatty acids toward catabolic fates. Incorporation of [3H]monoolein into TG relative to PL was markedly reduced in LFABP-/- despite no changes in the expression of lipid synthetic genes. While those results suggest a trafficking defect, reports on the binding of monoacylglycerol by LFABP are mixed. Therefore, the monoacylglycerol -binding capability of liver cytosol from wild-type and LFABP-/- mice was assessed by gel filtration chromatography. The [14C]oleate associated with ~14kDa proteins was absent in LFABP-/- liver cytosol. Interestingly, [3H]monoolein was present in the ~14kDa fractions from WT but not LFABP-/- cytosol. Immunoblotting confirmed the presence of LFABP in the ~14kDa fractions from WT, but not LFABP-/-. These results suggest that LFABP is a monoacylglycerol-binding protein in a physiological setting.
The systemic effects of enterocyte FABP deletion were examined by comparing body composition via dual energy X-ray absorptiometry and energy metabolism via indirect calorimetry. During food deprivation, IFABP-/- mice lost more fat mass and, accordingly, had a lower respiratory quotient than WT. LFABP-/- mice lost less fat-free mass and maintained a higher level of energy expenditure relative to WT. These findings suggest that ablation of enterocyte FABPs manifest specific cellular effects in their native tissues due to lipid trafficking defects, as well as systemic effects.
NoteIncludes bibliographical references (p. 149-161)
Noteby William Stacy Lagakos
CollectionGraduate School - New Brunswick Electronic Theses and Dissertations
Organization NameRutgers, The State University of New Jersey
RightsThe author owns the copyright to this work