Lipid processing and lipoprotein synthesis by the developing human
fetal colon.
E, Levy, Loirdighi N, Thibault L, Nguyen Td, Labuda D, Delvin E, and
M[acute]enard D.
Depts of Nutrition, Pediatrics and Biochemistry, Centre de
Recherche, H[circumflex]opital Ste-Justine, Universit[acute]e de
Montr[acute]eal and Groupe de Recherche en Biologie du
D[acute]eveloppement, Department of Anatomy and Cellular Biology,
Universit[acute]e de Sherbrooke, Qu[acute]ebec, Canada
APStracts 2:0233G, 1995.
Despite significant progress in the elucidation of the ontogeny of
gastrointestinal function, little attention has been given to colonic
lipid processing during development. The major purpose of this study
was to explore the intracellular phase of fat absorption, lipid
synthesis and secretion in the human fetal colon, compared to the
jejunum originating from the same fetuses. The synthesis of lipids
and major apolipoproteins was examined using cultured fetal colonic
explants incubated with [14C]-oleic acid and [35S] methionine,
respectively. Fetal colonic explants demonstrated substantial ability
to incorporate [14C] oleic acid (dpm/mg protein) into phospholipids
(48,743+/-4,783), triglycerides (25,687+/-2,469) and cholesteryl
esters (6,751+/-1,227). The total amount of radiolabeled lipids was
much higher within the tissue (87,472+/-9,142) than in the medium
(51,916+/-4,970), indicating a limited capacity of the fetal colon to
export newly synthesized lipids. The limited colonic lipid secretory
processes was even more evident when compared with homologous fetal
jejunum's de novo synthesized lipids present in tissue (133,975+/
-13,836) and medium (279,858+/-1,610) respectively. Similarly to the
jejunum, the colon was able to elaborate all the phospholipid
classes, phosphatidylcholine accounting for more than 70% of tissue
phospholipids. However, their individual levels were present in
lesser amounts in the colon (p<0.001). Colonic explants
elaborated most of the major lipoprotein classes, but were less
efficient than jejunal explants in exporting chylomicrons (x33), VLDL
(x1.5) and HDL (x9) into the medium. Apo-B synthesis and apo-B mRNA
editing were comparable in colonic and jejunal explants, thus not
responsible for the defective lipoprotein secretion in the fetal
large bowel. These results establish for the first time the
capability of the human fetal colon to form, but not to efficiently
transport lipids, lipoproteins and apoproteins.
Received 5 May 1995; accepted in final form 4 November 1995.
APS Manuscript Number G187-5.
Article publication pending Am. J. Physiol. (Gastrointest. Liver
Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 30 November 95