Fat absorption is not complete by midgut but dependent on load of
fat.
Lin, Henry C., Xiao-Tuan Zhao, and Lijie Wang.
Department of Medicine, Cedars-Sinai Research Institute, Cedars
-Sinai Medical Center, Los Angeles, California 90048; and School of
Medicine, University of California, Los Angeles, California 90024
APStracts 3:0012G, 1996.
Since the intubation study of Borgstrom et al in humans, the
completion of fat absorption within the proximal small intestine has
been widely accepted. Based on this report, it has been assumed that
the distal small intestine is exposed to fat only in the setting of
pathology. This concept may be flawed since completeness of fat
absorption was calculated from the recovery of a water soluble marker
but the aqueous phase is now known to move independently from fat. To
re-examine the question whether fat absorption is complete by midgut,
we measured the recovery of a fat-specific marker, 99m-Tc
-thiocyanate, in a canine model equipped with duodenal and midgut
fistulas. The fistulous output allowed for the measurement of the
amount of fat entering the small intestine and the amount of fat
entering the distal 1/2 of small intestine. Emulsion meals containing
15 or 60 g of corn oil were tested. The importance of fat exposure of
the distal 1/2 of the small intestine was further confirmed by
comparing the fistulous fat recovery under 2 different patterns of
exposure [allowing (All) or denying (150 cm) access to the distal
small intestine]. We found that fat recovery depended on 1. the dose
of fat (15 vs. 60 g, p<0.0005), 2. the pattern of exposure (150
cm vs. All, p<0.01), and 3. the fistulous position (duodenal vs.
midgut, p<0.005). Specifically, under 150 cm exposure pattern,
while 8.8 +/-1.8 g (mean + SE) of fat emptied into the duodenum after
the 15 g fat meal, 32.6 +/- 3.2 g emptied after the 60 g fat meal.
Correspondingly, while 3.5 +/- 1.5 g of fat was recoverable from the
midgut fistulous output after the 15 g meal, a much larger, 17.1 +/-
5.6 g of fat was recoverable and therefore, not absorbed by the
proximal 1/2 of small intestine after the 60 g meal. The amount of
fat recovery at each fistula was reduced when chyme was allowed
access to the whole gut (by triggering fat-induced ileal brake). We
conclude that the intestinal length required for fat absorption
depends on the load of fat in the meal so that, even after usual
meals, absorption of fat is not complete by midgut.
Received 10 August 1995; accepted in final form 21 December 1995.
APS Manuscript Number G347-5.
Article publication pending Am. J. Physiol. (Gastrointest. Liver
Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 22 January 96