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

Perfusion studies of the normal human jejunum were performed to test whether dihydroxy bile acids and hydroxy fatty acids inhibit the absorption of oleic acid, since previous reports documented their inhibitory effects on the absorption of several other organic solutes. 3 mM deoxycholate and 7 mM glycodeoxycholate inhibited the absorption of 3 mM oleic acid in isotonic micellar solutions while inducing net fluid secretion. Similarly, fractional absorption of oleic acid decreased in the presence of hydroxy fatty acids. However, only the changes induced by 2 mM ricinoleic acid could be distinguished from changes induced by an increase in total fatty acid concentration. Under all experimental conditions, close linear relationships existed between net water movement and fractional absorption of glucose, xylose, and fatty acids, as well as between the absorption rates of these solutes. In contrast, net fluid secretion induced by hypertonic D-mannitol (450 mosmol/liter) had no effect on solute absorption. Our data and observations in the literature do not allow formulation of a hypothesis which would adequately define all effects of dihydroxy bile acids and fatty acids on intestinal transport processes. The observations help explain the malabsorption of fat and other nutrients in patients with the blind loop syndrome.

Inhibition of ileal water absorption by intraluminal fatty acids. Influence of chain length, hydroxylation, and conjugation of fatty acids.

The influence of fatty acids on ileal absorption of water, electrolytes, glucose, and taurocholate was examined in Thirty-Vella fistulas in five mongrel dogs. Fatty acid absorption also was measured. Segments of terminal ileum were perfused at steady state with isotonic electrolyte solutions containing 11.2 mM glucose, 4.5 mM taurocholate, and 0.1-5.0 mM fatty acid. Three C(18) fatty acids, oleic acid, 10(9)-hydroxystearic acid, and ricinoleic acid, completely inhibited water absorption at 5 mM. Sodium, chloride, and potassium absorptions were inhibited in parallel with absorption of water. Differences between the potencies of C(18) fatty acids were apparent when lesser concentrations were perfused. Dodecanoic and decanoic acids were as effective as C(18) fatty acids at 5 mM but octanoic and hexanoic acids were ineffective. The polar group of C(18) fatty acids was modified by conjugating oleic and ricinoleic acids with taurine. When these compounds and a substituted C(18) fatty acid, p-n-decylbenzenesulfonate, were perfused, water absorption was also inhibited. Short-chain fatty acids (C(3) and C(4)) and their hydroxylated derivatives were ineffective at 5 mM. When water absorption was inhibited, absorption of glucose and taurocholate was decreased. We speculate that the phenomenon of inhibition of water and electrolyte absorption by fatty acids may be relevant to steatorrhea and diarrhea in man.

Effects of oleic and ricinoleic acids on net jejunal water and electrolyte movement. Perfusion studies in man.

To examine the effects of oleic acid and ricinoleic acid on jejunal absorption, steady-state jejunal perfusions were performed in healthy volunteers. Taurocholate, used to solubilize the fatty acids, did not influence absorption. Both fatty acids (concentration, 10 mM) reversed electrolyte and water net movement; that is, they induced fluid secretion; this effect was rapidly reversible. Ricinoleic acid (the active principle of castor oil) was the more potent, producing fluid secretion when perfused at concentrations at which oleic acid was without effect. However, ricinoleic acid was absorbed more slowly than was oleic acid, and hence was associated with higher intraluminal concentrations. Addition of lecithin and monoolein did not diminish the secretory effect of ricinoleic acid; addition of a secretory bile acid (taurodeoxycholate) did not enhance the effect. The response of the jejunal mucosa to a known cathartic provides observations pertinent to the pathophysiology of steatorrheal diseases in man. Dietary fatty acid also has secretory properties with respect to the human intestine; bacterial hydration, to hydroxy fatty acids, is not required to induce fluid secretion.

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

Jejunal perfusion studies were performed in 16 healthy volunteers to test the hypothesis that intraluminal cholesterol can mitigate the fluid secretion induced by dihydroxy bile acids and fatty acids. Fluid secretion in the presence of 5 mM taurodeoxycholate was somewhat reduced by 4 mM mono-olein which was used for the solubilization of cholesterol. Addition of 0.8 mM cholesterol reduced fluid secretion further (P less than 0.05). Fluid secretion induced by 4 mM oleic acid was changed to net absorption in a linear fashion with increasing cholesterol concentration in the perfusion solutions. 1 mM cholesterol reduced fluid secretion induced by 6 mM oleic acid (P less than 0.005), but had no effect on fluid secretion induced by 6 mM linolenic acid. Glucose absorption was generally affected in a similar manner as water transport. In vitro, 1 mM cholesterol reduced monomer activity of 6 mM oleic acid to 72.3 +/- 0.9% of control and that of linolenic acid to 81.1 +/- 1.7% of control. Although statistically significant (P less than 0.001), the difference in the effects of cholesterol on monomer activities of the two fatty acids was rather small and it is unlikely that changes in monomer concentration of fatty acids and bile acids account for the protective effect of cholesterol. The in vivo observations point to a new physiological role for biliary cholesterol: the modification of the response of the small intestine to the effects of dihydroxy bile acids and fatty acids.

Cl- secretion induced by bile salts. A study of the mechanism of action based on a cultured colonic epithelial cell line.

When applied to the basolateral (serosal) side of the T84 colonic epithelial monolayer, taurodeoxycholate caused net Cl- secretion in a dose-dependent manner with a threshold effect observed at 0.2 mM. In contrast, when applied to the apical (luminal) surface, concentrations of taurodeoxycholate below 1 mM had little or no effect. Only when the concentration of taurodeoxycholate present on the apical side was greater than or equal to 1 mM did apical addition results in an electrolyte transport effect. This apical effect on electrolyte transport was associated with an abrupt increase in the permeability of the monolayer. Cyclic AMP and cyclic GMP in the T84 monolayers were not increased by the bile salt, but in the presence of extracellular Ca2+, free cytosolic Ca2+ increased with a graded dose effect and time course that corresponded approximately to the changes in short circuit current (Isc). The results suggest that luminal bile salts at a relatively high concentration (greater than or equal to 1 mM) increase tight junction permeability. Once tight junction permeability increases, luminal bile salts could reach the basolateral membrane of the epithelial cells where they act to increase free cytosolic Ca2+ from extracellular sources. The resulting increases in free cytosolic Ca2+, rather than in cyclic nucleotides, appear to be involved in transcellular Cl- secretion.

Effects of lysophosphatidylcholine on jejunal water and solute transport in the rat in vivo.

The effects of lysophosphatidylcholine on jejunal water and solute transport were studied in vivo in the rat. Five mM lysophosphatidylcholine significantly reduced absorption of water, electrolytes and glucose (P less than 0.05) and 10 mM lysophosphatidylcholine induced net fluid secretion. The effects of 10 mM lysophosphatidylcholine were significantly reduced in the presence of 5 mM phosphatidylcholine (P less than 0.05) and 2 mM cholesterol (P less than 0.05). The fractional absorption of lysophosphatidylcholine decreased with increasing concentration of the detergent in the perfusion solution. Increasing concentrations of taurocholate in the perfusion solutions potentiated the effects of lysophosphatidylcholine (P less than 0.01), although 10 mM taurocholate by itself had no significant effect on intestinal water and electrolyte transport. The data establish that lysophosphatidylcholine, a zwitterionic detergent, affects intestinal transport in the same way as bile acids, fatty acids and synthetic cationic or nonionic detergents. By comparison with the response of the human jejunum to taurodeoxycholate, it is likely that lysophosphatidylcholine generated during the normal process of digestion has an effect on intestinal water and solute transport in man.

Effect of lecithin on jejunal absorption of micellar lipids in man and on their monomer activity in vitro.

The effect of lecithin on jejunal absorption of fatty acids and octadecenoylglycerol was studied in healthy volunteers with a jejunal perfusion system which excluded pancreatic and biliary secretions from the test segment. Lecithin significantly reduced the absorption of oleic acid (P less than 0.05) and octadecenoylglycerol (P less than 0.01), while it had no effect on the absorption of ricinoleic acid. In vitro, lecithin reduced monomer activities of all three lipids; the changes were greater for oleic acid and octadecenoylglycerol than for ricinoleic acid (P less than 0.02). From these data it is concluded that lecithin reduces monomer activity of fatty acids in mixed micellar solutions and that it can thereby reduce the absorption rates of micellar lipids. Intact lecithin is not absorbed under these conditions. Maldigestion of lecithin in pancreatic insufficiency may, therefore, aggravate the steatorrhea observed in this condition.

Effect of taurine conjugated bile salts with and without lecithin on water and electrolyte transport in the canine gallbladder in vivo.

Because dihydroxy bile salts alter water and electrolyte transport in the intestine, we tested the effects of taurine conjugated bile salts on water and electrolyte transport in the canine gallbladder in vivo. 16.7 mM taurodeoxycholate or taurochenodeoxycholate completely abolished net absorption of water (P less than 0.01). 40 mM taurocholate significantly reduced net water absorption (P less than 0.05), whereas 16.7 mM taurocholate had no significant effect. Net movement of electrolytes was closely related to net water movement. Water and electrolyte absorption continued undisturbed when the gallbladders were exposed to 16.7 mM taurodeoxycholate together with 5.6 mM lecithin. Biliary lecithin, therefore, is important for the protection of the mucosa of the gallbladder from the potentially damaging effects of bile salts.

[Absorption and malabsorption of fat and bile acids (author's transl)]. / Resorption und Malabsorption von Fetten und Gallensäuren.

The current concepts of normal fat absorption and the entero-hepatic circulation of bile acids are being reviewed with emphasis on the steps which are clinically important. Based on an understanding of normal physiology, diseases associated with steatorrhea can be classified according to pathogenetic mechanisms. In some diseases the pathogenesis of the steatorrhea is not understood. Malabsorption of fat and bile salts can have characteristic consequences such as nutritional deficiencies, diarrhea, hyperoxaluria with nephrolithiasis, and cholelithiasis. For quantitative assessment of steatorrhea chemical analysis of fecal fat is necessary.

Effect of glucose on jejunal water and solute absorption in the presence of glycodeoxycholate and oleate in man.

Jejunal perfusion studies were performed in 12 healthy volunteers to study the effects of 14 and 56 mM glucose on fluid secretion induced by 5 mM glycodeoxycholate on 7 mM oleate. Glucose enhanced water absorption under control conditions and reduced water secretion induced by glycodeoxycholate or oleate (P less than 0.01). As has been observed previously, glycodeoxycholate and oleate inhibited glucose absorption (P less than 0.001) and significant linear relationships existed between net water movement and glucose absorption. Glycodeoxycholate also reduced the absorption of 14 mM arabinose (P less than 0.05) and oleate reduced the absorption of 56 mM mannitol (P less than 0.05). Reduced solute absorption in the presence of glycodeoxycholate and oleate, therefore, cannot be attributed to an effect on active transport alone. The relationships between sodium transport and water absorption varied with the glucose concentration in the perfusion solutions. Similarly, the relationships between glucose absorption and sodium absorption varied with glucose concentration. The data suggest that a significant amount of glucose can be absorbed without concomitant absorption of sodium. The data indicate that glucose absorption can stimulate water absorption directly without the mediation of sodium and that water movement follows glucose at a rate which maintains isotonicity.

Comparison of cholesterol and beta-sitosterol: effects on jejunal fluid secretion induced by oleate, and absorption from mixed micellar solutions.

Jejunal fluid secretion induced by perfusion with oleic acid can be reduced by the addition of cholesterol. The present study was performed to test the specificity of this effect by comparing the effects of cholesterol with that of a plant sterol, beta-sitosterol during perfusion of the jejunum in healthy volunteers. In addition, we compared the solubilities of cholesterol and beta-sitosterol in micellar solutions and their jejunal absorption rates. One millimolar beta-sitosterol was as effective as 1 mM cholesterol in reducing jejunal fluid secretion induced by 6 mM oleate (n = 7). In mixed micellar solutions consisting of 10 mM taurocholate and 6 mM oleate, solubility of beta-sitosterol is about one third of cholesterol solubility. When cholesterol was gradually replaced by beta-sitosterol in the incubation mixture, beta-sitosterol reduced cholesterol solubility to a greater extent than would be expected from an equimolar replacement of cholesterol by beta-sitosterol. Absorption of beta-sitosterol was limited by its solubility in mixed micellar solutions and both sterols were absorbed at equal rates as long as their solubility limits were not exceeded (n = 5).

Failure of customary treatment in chronic active liver disease: causes and management.

Among 134 patients with chronic active liver disease, selected by identical clinical, biochemical and morphologic criteria, assigned to standard treatment programs and followed at regular intervals, 21 of 105 failed treatment with standard regimens containing steroids. Treatment failure was more common in patients whose serum contained hepatitis B surface antigen, those with more severe liver disease as judged by liver function tests (prothrombin time) and hepatic morphology (subacute hepatitis or cirrhosis). Early diagnosis of treatment failure, based on changes in liver function tests rather than on clinical features of deterioration, coupled with the immediate administration of higher doses of prednisone with or without higher doses of azathioprine, resulted in disappearance of clinical and biochemical features of disease activity in the majority of patients. These results were greatly superior to those earlier reported by us from patients chosen by identical criteria but treated by conventional measures. However, when endogenous encephalopathy developed the outlook was grave, regardless of previous or subsequent therapy. We recommend that patients at risk for failing conventional treatment be identified early, followed carefully with serial liver function tests, and be treated promptly with higher doses of medication when deterioration occurs.

Effects of long chain fatty acids on solute absorption: perfusion studies in the human jejunum.

Perfusion studies were performed in healthy volunteers to test the hypothesis that net fluid secretion induced by fatty acids is accompanied by parallel reduction in solute transport. Ricinoleic acid provoked a marked net secretion of fluid and concomitantly inhibited the absorption of all solutes tested; these included glucose, xylose, L-leucine, L-lysine, Folic acid, and 2-mono-olein. Oleic acid also reduced net fluid and solute transport, but was less potent in reducing solute absorption than was ricinoleic acid. When fluid secretion was induced osmotically with mannitol, glucose and xylose absorption was not affected. The mechanism for this generalised effect of fatty acids on solute absorption is uncertain, possibly nonspecific, and might be related to mucosal damage and altered mucosal permeability induced by these agents.

Clinical features and prognosis of severe chronic active liver disease (CALD) after corticosteroid-induced remission.

Disappearance of symptoms, resolution of most biochemical abnormalities, and histologic improvement to mild chronic inflammation were accomplished in 69 of 123 patients (56%) with severe chronic active liver disease treated with corticosteroids for up to 6.5 yr. Remission of at least 6 mo duration was possible in 35 of the 69 (51%) after discontinuation of therapy while others relapsed promptly and required retreatment. The likelihood of sustained remission was not predicted by initial clinical or biochemical features, although patients developing cirrhosis during treatment invariably relapsed. Subsequent courses of treatment after relapse were equally effective in again inducing remission, but the probability of another relapse increased after each successive therapy and was 86% after three treatments. Six of twenty-two patients (27%) followed for at least 4 yr after initial remission had three or more relapses. Although patients who relapsed were more likely to develop cirrhosis, manifestations of portal hypertension and immediate survival were not affected by relapse. Complete disappearance of all manifestations of active disease was possible in 12 of the patients entering remission (17%), but only patients without cirrhosis consistently sustained this improvement. We conclude that relapse after cessation of therapy frequently follows corticosteroid-induced remission of severe CALD, especially if cirrhosis develops, but does not jeopardize response to subsequent treatments or alter early prognosis.

Effects of amphotericin B and cholera toxin on intestinal transport in the rat. An in vivo model for the effects of dihydroxy bile acids and fatty acids on intestinal transport.

In vivo perfusion experiments were performed in the rat jejunum and colon to test the hypothesis that the changes in intestinal solute transport induced by dihydroxy bile acids and fatty acids are the result of the combined effects of fluid secretion and enhancement of mucosal permeability. The hypothesis predicts that absorption of organic solutes will be reduced in inverse relationship to the absorption rates under control conditions and that absorption of small, nonabsorbable solutes such as mannitol will be enhanced by these agents. Fluid secretion was induced either by administering cholera toxin or by increasing the osmolality of the perfusion solution to 365 mOsm/L. Permeability was enhanced by adding amphotericin B, 50 micrograms/ml, to the perfusion solutions. The isotonic perfusion solutions contained 11.2 mM glucose and 4 mM triethylene, tetraethylene, pentaethylene, and hexaethylene glycol or mannitol as probes of passive permeability. In the jejunum cholera toxin induced fluid and electrolyte secretion and reduced organic solute absorption to a small but significant degree (p less than 0.05). Amphotericin B alone enhanced absorption of organic solutes, water, and electrolytes (p less than 0.01). In the presence of fluid secretion induced by an osmotic load, only absorption of triethylene and pentaethylene glycol was reduced. Addition of amphotericin B after exposure to cholera toxin or to the hypertonic solutions resulted in a further significant reduction of absorption of glucose and ethylene glycols (p less than 0.05). The combination of amphotericin B and cholera toxin resulted in enhanced absorption of mannitol (p less than 0.02). Similarly, 5 mM deoxycholate enhanced jejunal absorption of mannitol (p less than 0.01) and reduced the absorption of glucose and the low-molecular-weight ethylene glycols (p less than 0.01). In the colon the administration of amphotericin B after the exposure to cholera toxin resulted in enhanced absorption of glucose (p less than 0.05) in spite of continuing fluid secretion. The combination of fluid secretion and enhancement of mucosal permeability, therefore, reproduced all in vivo effects of bile acids and fatty acids on intestinal transport of organic solutes.

Acid pH enhances the effects of taurodeoxycholate on water and solute transport in the human and rat jejunum.

The relative rate of unspecific binding of bile acids to brush border membrane vesicles resembles their relative potencies as intestinal secretagogues. This interaction of bile acids with brush border membranes is enhanced in an acid environment. We, therefore, studied the effects of taurodeoxycholate and taurocholate on water and solute transport at pH 7.6 and pH 4.0 in the human and rat jejunum. Five mM taurodeoxycholate induced significantly greater fluid secretion in the human jejunum at pH 4.0 than at pH 7.6 (p less than 0.02; n = 5), 10 mM taurocholate (n = 4) had no effect at either pH. In the rat 15 mM taurodeoxycholate at pH 4.0 induced greater fluid secretion (p less than 0.01; n = 6), released more phospholipid (p less than 0.001; n = 4) and enhanced absorption of mannitol more than at pH 7.6 (p less than 0.05; n = 6). In contrast fluid secretion and release of phospholipids induced by Triton X-100 were not affected by pH (n = 6), nor was fluid secretion induced by cholera toxin (n = 8). The data suggest that the enhancement of the secretory effect of taurodeoxycholate in an acid environment is due to its increased interaction with the mucosal surface, and support the concept that the ability of detergents to interact with the intestinal brush border membrane determines their effectiveness as intestinal secretagogues.

Effects of taurodeoxycholate on in vivo water and solute transport in rat jejunum in absence and presence of calcium.

Bile acids and fatty acids enhance the permeability of brush-border membrane vesicles for calcium. It has been postulated that increased influx of calcium into the enterocyte might be responsible for the fluid secretion induced by dihydroxy bile acids and fatty acids. During in vivo perfusion studies of the rat jejunum, 15 mM taurodeoxycholate induced secretion of electrolytes and water (P less than 0.001), reduced glucose absorption (P less than 0.001), and enhanced the absorption of mannitol (P less than 0.0125) and calcium (P less than 0.001). Calcium absorption continued to be enhanced during perfusion of a CaCl2-containing solution following the perfusion with taurodeoxycholate (P less than 0.05). In view of the previously demonstrated enhanced permeability of the apical brush-border membrane in the presence of bile acids, it is very likely that some calcium enters the enterocyte along the steep concentration gradient in the presence of taurodeoxycholate. In spite of enhanced calcium absorption, 15 mM CaCl2 had no effect on control absorption rates or on fluid secretion induced by taurodeoxycholate. The data indicate that the effects of bile acids on intestinal transport are not mediated by an influx of calcium into the enterocyte.

Protection by dietary proteins against the effects of bile acids on rat jejunum and stomach.

Because bile acids bind to certain proteins we examined whether the effect of dihydroxy bile acids on jejunal water transport and gastric mucosal function could be blocked by the presence of protein. In the rat jejunum 2.5% bovine serum albumin blocked the secretion of water and electrolytes induced by 2 mM deoxycholate, whereas 5% ovalbumin, which does not bind bile acids, had no effect. Bovine serum albumin protected large unilamellar liposomes from damage by taurodeoxycholate and reduced the monomer concentration of taurodeoxycholate, whereas ovalbumin afforded no protection. In equilibrium dialysis studies whey protein and bovine serum albumin reduced the free taurodeoxycholate concentration (150 mM HCl enhanced this effect). In the rat stomach taurodeoxycholate (2.5 or 10 mM) in the presence of 150 mM HCl reduced potential difference and enhanced sodium secretion and hydrogen ion loss. These effects were reduced in the presence of whey protein. We conclude that proteins that bind bile acids have the potential to protect mucosal membranes from the adverse effects of bile acids.

Quantification of carcinoembryonic antigen-like activities in normal, human gastrointestinal secretions.

The secretion of carcinoembryonic antigen-like (CEA-like) material into the gastrointestinal tract of 28 fasting normal men was quantified by using intestinal perfusion techniques. CEA-like material was recovered from all levels of the gastrointestinal tract. The highest secretory rate was in the colon (mean +/- SE, 2.41 +/- 2.0 mug/minute per colon), followed by pancreatobiliary secretion and pancreatic secretion. The secretory rate from the stomach, duodenum, jejunum, and ileum was less than 20 ng/minute. After perchloric acid extraction, the CEA-like material from the colon had the same chromatographic and radioimmunologic properties as [125I] CEA. These data suggest that the CEA-like material is normally secreted into the gastrointestinal tract and particularly into the colon.

Prednisone for chronic active liver disease: dose titration, standard dose, and combination with azathioprine compared.

Among 120 consecutive patients with chronic active liver disease (CALD) randomized to different treatments, those receiving maintenance doses of prednisone 20 mg daily (Pred), prednisone in doses given on alternate days and titrated to secure resolution of clinical and biochemical abnormalities (Pred-Titrad), or a combination of prednisone 10 mg and azathioprine 50 mg daily (Comb) survived and underwent resolution of clinical and biochemical features of disease more often than a control group receiving placebo or azathioprine 100 mg daily. Histological remission occurred significantly more often with Pred and Comb than with other regimens. Major side-effects of therapy were commoner with Pred than with Comb or Pred-Titrad, which did not differ. We conclude that Comb is the initial treatment of choice for CALD, since clinical, biochemical, and histological resolution of disease activity occurs as often as with Pred, whereas early side-effects are significantly less frequent.