Abstract
Intracellular lipid binding proteins, including fatty acid binding proteins (FABPs) 1 and 2, are highly expressed in tissues involved in the active lipid metabolism. A zebrafish model was used to demonstrate differential expression levels of fabp1b.1, fabp1b.2, and fabp2 transcripts in liver, anterior intestine, and brain. Transcription levels of fabp1b.1 and fabp2 in the anterior intestine were upregulated after feeding and modulated according to diet formulation. Immunofluorescence and electron microscopy immunodetection with gold particles localized these FABPs in the microvilli, cytosol, and nuclei of most enterocytes in the anterior intestinal mucosa. Nuclear localization was mostly in the interchromatin space outside the condensed chromatin clusters. Native PAGE binding assay of BODIPY-FL-labeled FAs demonstrated binding of BODIPY-FLC(12) but not BODIPY-FLC(5) to recombinant Fabp1b.1 and Fabp2. The binding of BODIPY-FLC(12) to Fabp1b.1 was fully displaced by oleic acid. In vivo experiments demonstrated, for the first time, that intestinal absorption of dietary BODIPY-FLC(12) was followed by colocalization of the labeled FA with Fabp1b and Fabp2 in the nuclei. These data suggest that dietary FAs complexed with FABPs are able to reach the enterocyte nucleus with the potential to modulate nuclear activity.
Highlights
Intracellular lipid binding proteins, including fatty acid binding proteins (FABPs) 1 and 2, are highly expressed in tissues involved in the active lipid metabolism
Qualitative RT-PCR detected fabp1b.1 and fabp1b.2 transcripts in total RNA extracted from the anterior intestine in adult zebrafish, irrespective of the animals’ nutritional status (Fig. 1A). real-time quantitative RT-PCR (qRT-PCR) indicated high levels of transcripts for fabp1b.1 and fabp2 in the anterior intestine, by comparison with normalizing genes eef1a1 (Fig. 1B, D) and ppiaa
Zebrafish fabp1b.2 transcripts were detected in ovaries, testicles, kidneys, and heart, and trace amounts of fabp2 transcripts were found in kidneys
Summary
Intracellular lipid binding proteins, including fatty acid binding proteins (FABPs) 1 and 2, are highly expressed in tissues involved in the active lipid metabolism. A zebrafish model was used to demonstrate differential expression levels of fabp1b.1, fabp1b.2, and fabp transcripts in liver, anterior intestine, and brain. Transcription levels of fabp1b.1 and fabp in the anterior intestine were upregulated after feeding and modulated according to diet formulation. For the first time, that intestinal absorption of dietary BODIPYFLC12 was followed by colocalization of the labeled FA with Fabp1b and Fabp in the nuclei. These data suggest that dietary FAs complexed with FABPs are able to reach the enterocyte nucleus with the potential to modulate nuclear activity.—Esteves, A., A.
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