Mechanisms of lipid loss from the small intestinal mucosa.

Abstract

SUMMARY Many water-soluble compounds have been shown to pass from the small intestinal mucosa into the lumen. In this work, the loss of lipids from the mucosa was investigated by perfusion experiments in rats, using 0 15M NaCl or buffer solutions over a range of pH, with or without the addition of 5 7 or 11'4 mM taurocholic acid. Perfusates were extracted for the estimation of individual lipids and for DNA, which is a measure of cell loss.The results suggest that free fatty acids reach the lumen by diffusion and that their solubility in the luminal fluid is a factor determining their rate of loss. Triglycerides, cholesterol, phosphatidyl ethanolamine, and phosphatidyl choline are present only as the result of desquamation of mucosal cells.The accumulation of lipid in the lumen of intestinal loops (Blitstein and Erenthal, 1891;Angevine, 1929) shows that endogenous lipid passes from the mucosa into the lumen. In man the faeces contain 0-7-1 -0 g lipid/day during fasting (Bouchier, Kellock, and Manousos, 1963; Blomstrand, 1963), but this is no indication of the amount of endogenous lipid. In the fasting dog, faecal lipids rise approximately threefold when bile is diverted (Sperry, 1927;Pessoa, Kim, and Ivy, 1953) indicating that bile is not the most important source of endogenous lipid, and that a high proportion is normally reabsorbed.Other authors have claimed that neutral lipids (Burr, MacPherson, and Tidwell, 1960; Lough, Felinski, and Garton, 1963; Brenner, Vazza, and De Toma's. 1963) and sterols (Wilson and Reinke, 1968;Simmonds, Hofmann, and Theodor, 1967) pass from the mucosa into the lumen, but Cotton (1972) made the first systematic study. Using a perfusion technique in rats, he measured deoxyribonucleic acid, a measure of cell loss (Davidson, Leslie, and White, 1951), and lipids in saline perfusates of the small bowel, and concluded that triglycerides, cholesterol, phosphatidyl ethanolamine, and phosphatidyl choline in perfusates were wholly derived from desquamated cells, but fatty acids 'exuded' from the mucosa. but loss of the other lipids was not. Gas-liquid chromatography showed that the principal fatty acids were palmitic, oleic, stearic, and linoleic.In these experiments the perfusion fluid was normal saline in which lipids are almost insoluble. The small bowel lumen in the normal animal contains bile salt micelles in which fatty acids, phospholipids, and, to a lesser extent, cholesterol dissolve. In addition, the solubility of long-chain fatty acids depends on the pH, which increases from 5 to 6 in the duodenum to 7 to 8 in the ileum. Loss of lipids by mechanisms other than desquamation may have been limited in Cotton's experiments by the use of saline, and the present experiments were done to show whether loss of lipids is related to their solubility in the perfusing fluid. Methods ANIMAL EXPERIMENTSSixteen adult male Wistar rats, fed on Spiller's autoclave diet, and weighing 250-280 g were used.Half the animals were fasted of food for 24 hr before the experiment and they were kept in false b...

Parenteral lipids shape gut bile acid pools and microbiota profiles in the prevention of cholestasis in preterm pigs

“…The finding of both the FAs and their carnitine esters suggest that they originated from lipids incorporated into host cells, likely hepatocytes or intestinal epithelial cells, and were then secreted in bile or sloughed into the gut lumen, respectively. Even during fasting or on a lipid-free diet, significant amounts of lipids are excreted in feces (56). This is consistent with our previous finding that the body tissue FA composition is strongly influenced by the FA composition of administered parenteral lipid emulsion (26).…”

Digestion et absorption intestinale des phosphatildycholines

“…The lysophosphatidylcholines were either completely hydrolysed or acylated to form new phosphatidylcholine molecules, while the unsaturated fatty acids were used for triglyceride synthesis. These (Clément et a/., 1955 ;Raulin et Lefort, 1960 ;Clément, 1961 ;Di Costanzo et Waldram, 1975 ;Reisser, 1978) ; chez le Mouton (Zamytchkina et Grodsensky, 1955 (Hauton et Laurent 1965 ;Lairon et al, 1972 ;Nalbone et al, 1973Nalbone et al, , 1978Nalbone et al, , 1979 (Nalbone et al, 1978Vigne et al, 1979Vigne et al, , 1981. L'existence de ce complexe est compatible avec la théorie de l'organisation micellaire des constituants biliaires.…”

<i>In vivo </i>Plasma Cholesterol Exchanges in the Digestive Tract of the Rat: Effect of <i>L</i>-Thyroxine

“…Although these data support our hypothesis, it remains to be seen whether in testinal cholesterol comes only from cell sloughing or whether additional cholesterol ex changes occur between cells and lumen. Using 30-min perfusions in rat intestine, Cotton (10) and then Waldram (26) concluded that trigly cerides. cholesterol and phospholipids are lost only by desquamated mucosal cells.…”