Effect of Glycine-Conjugated Bile Acids with and without Lecithin on Water and Glucose Absorption in Perfused Human Jejunum

Abstract

A B S T R A C T Perfusion studies were performed in healthy volunteers to test whether the secretory effect of conjugated bile acids, previously shown for the colon, was also present in the jejunum. A perfusion system with a proximal occlusive balloon (and continuous aspiration of duodenal secretions) was used; isotonic test solutions contained glycine-conjugated bile acids with or without lecithin. Fluid movement was measured by changes in the concentration of polyethylene glycol (PEG, mol wt 4,000). Conjugated dihydroxy bile acids inhibited electrolyte and fluid absorption and, at higher concentrations, evoked secretion of an isotonic fluid. Glucose absorption continued, despite fluid secretion, but its rate decreased. The secretory effects of bile acids were abolished by the addition of lecithin to the bile acid solutions. A trihydroxy bile acid (cholylglycine) had no effect on jejunal absorption. Small amounts (6-9%) of conjugated bile acids were absorbed in the jejunum; lecithin was well absorbed (72-90%). The results indicate that dihydroxy bile acids influence salt and water transport in the human jejunum but that this effect may be abolished when a polar lipid such as lecithin is present. We speculate that this effect of bile acids may modify fluid movement in the small intestine postprandially after fat absorption has occurred.

Effects of dihydroxy bile acids and hydroxy fatty acids on the absorption of oleic acid in the human jejunum.

“…Net water and solute movements were calculated by standard formulas from the changes in PEG concentrations and solute concentrations between perfusion solutions and collected samples (21 Absorption of monosaccharides. As in previous studies (8,9,(11)(12)(13)16), absorption of glucose and xylose decreased whenever absorption changed to net fluid secretion in the presence of dihydroxy bile acids or fatty acids (Figs. 1, 2, and 3).…”

“…Our studies demonstrate that dihydroxy bile acids inhibit the absorption of fatty acids in addition to their established inhibitory effects on water transport and on absorption of nonmicellar solutes (8)(9)(10)(11)(12)(13)(14)(15)(16). They further document that the fractional absorption of fatty acids decreases with increasing fatty acid load and that this decrease correlates well with the simultaneously observed changes in glucose absorption and net water movement.…”

“…Dihydroxy bile acids and long-chain fatty acids induce net fluid secretion when perfused through the intestine of experimental animals (8)(9)(10)(11) and man (12)(13)(14). When water secretion is induced, electrolytes are secreted in parallel (9,11,(13)(14)(15), and in addition, absorption of organic solutes is reduced.…”

“…When water secretion is induced, electrolytes are secreted in parallel (9,11,(13)(14)(15), and in addition, absorption of organic solutes is reduced. Dihydroxy bile acids inhibit the absorption of glucose (8,9,12,13) and amino acids (10). Oleic acid (OA) inhibits the absorption of glucose (16); and ricinoleic acid (RA), a hydroxy fatty acid, inhibits the absorption of sugars (11,16), amino acids (16), taurocholate (11), and a lipid, 2-mono-olein (16).…”

Cholesterol reduces the effects of dihydroxy bile acids and fatty acids on water and solute transport in the human jejunum.

“…Dihydroxy bile acids and long-chain fatty acids inhibit intestinal transport of water and electrolytes and can induce intestinal net fluid secretion in man and experimental animals (1)(2)(3)(4)(5)(6)(7). In addition, they reduce absorption of organic solutes in the jejunum (2,6) and ileum (7) and enhance solute absorption in the colon (8,9).…”