Effect of acute ethanol ingestion on fat absorption

Regulation of intestinal apo A-IV mRNA abundance in rat pups during fasting and refeeding

The amount of intestinal apolipoprotein (apo) A-IV mRNA was examined in rat pups during fasting and refeeding. When 14-day old pups were fasted for 15 h, apo A-IV mRNA levels in the whole intestine decreased to 20% of the prefasting level. Refeeding casein and lactose, and the artificial milk composed of Intralipid, casein and lactose, caused an elevation of the apo A-IV mRNA after 3 h, without accompanying an elevation of serum triacylglycerols and apo A-IV (fat-independent elevation of apo A-IV mRNA). Refeeding Intralipid alone simultaneously elevated the apo A-IV mRNA, and serum triacylglycerols and apo A-IV after 3 h (fat-dependent elevation of apo A-IV mRNA). Administration of physiological saline during fasting partly suppressed the reduction of the apo A-IV mRNA (40% of the prefasting level), and the dietary fat-independent elevation of the message disappeared. Refeeding dam's milk to the pups, fasted without water administration, increased the apo A-IV mRNA after 3 and 15 h, although the elevation of serum triacylglycerols and apo A-IV occurred only after 15 h. Refeeding the milk increased the apo A-IV mRNA after 3 h and 15 h. Refeeding dam's milk to the pups fasted with saline administration accelerated the fat-dependent elevation of the apo A-IV mRNA. Simultaneously refeeding Intralipid and Pluronic L-81, an inhibitor of lymphatic fat transport, delayed the elevation of the apo A-IV mRNA and serum triacylglycerols and apo A-IV. Transcription rates of the apo A-IV mRNA, determined by nuclear run/on assay, were similar before and after fasting and refeeding Intralipid. During fasting, administration of puromycin, as compared with actinomycin D, enhanced the disappearance rate of the apo A-IV message. Intestinal mRNA for apo B, but not for apo A-I and beta-actin, similarly changed to the apo A-IV message. Thus, it can be concluded that: (1) dietary fat-dependent and -independent factors are involved in the elevation of the intestinal apo A-IV message; (2) the elevation of the message is not mediated by lipid uptake in the enterocytes but rather stimulated by the events leading to secretion of chylomicrons; and, (3) dietary fat-dependent elevation of the message appears to be due to the stabilization of the message.

Effect of ethanol on intestinal uptake of fatty acids, fatty alcohols, and cholesterol

The effect of acute exposure of the rabbit jejunum to ethanol on the uptake of fatty acids, fatty alcohols, and cholesterol was examined using a previously validated in vitro technique. The effective resistance of the intestinal unstirred water layer was determined from the rate of uptake of a homologous series of fatty alcohols. The addition of ethanol to the incubation or preincubation solutions had no effect on the uptake of these probes when the bulk phase was stirred at 600 rpm, but uptake was higher in the ethanol-exposed samples when the bulk phase was unstirred. Increasing the concentration of ethanol in the bulk phase was associated with a progressive decline in the rate of uptake of acetic, lauric, myristic, and palmitic acids, whereas the uptake of hexanoic, octanoic, and decanoic acids was unaffected, and the uptake of cholesterol was increased. Acute exposure of the intestine to ethanol was associated with an increase in the electrical conductance of the tissue, with no associated change noted in the tight junctions on transmission electron microscopy or in the surface epithelium on scanning electron microscopy. The results suggest that acute exposure of the rabbit intestine to ethanol is associated with a selective decline in the passive permeability properties of the membrane towards only certain lipids and that the effective resistance of the unstirred layer is influenced by ethanol only when the bulk phase is unstirred and the resistance is high.

Effect of ethanol on transport from rat intestine during high and low rates of oleate absorption

Long-chain fatty acids (LCFA) are transported predominantly in the intestinal lymph when rates of LCFA absorption are high, and oral ethanol has been shown to enhance this lymphatic transport. A greater proportion of absorbed LCFA is transported via portal blood when rates of LCFA absorption are low. We tested the hypothesis in unanesthetized lymph-fistula rats that ethanol might also enhance the mucosal absorption and lymphatic transport of oleic acid when oleate absorption rates were low. The results did not support this hypothesis. Ethanol enhanced oleate absorption and transport from the intestine when 360 mumol, but not when 8 mumol of [14C] oleate was infused intraduodenally over 4 hr. There were major differences in intestinal mucosal metabolism of high and low loads of oleic acid. After the high load, the proportion of intestinal [14C] phospholipid to [14C] neutral lipid was 8:92. This ratio changed to 37:63, and the percentage of neutral 14C as triglyceride decreased from 87 to 68% when the low load of oleate was infused. We suggest that a portion of absorbed LCFA is incorporated into phospholipid and transported as high-density lipoproteins in portal blood. This portal pathway for LCFA was uninfluenced by ethanol in the present experiments.

The effect of various dietary factors on the size distribution of lymph fat particles in rat

By means of cellulose acetate electrophoresis and measurement of radio-activity, lipoproteins (d less than or equal to 1,006) of lymph collected from rats fed a diet containing fats added to labeled fatty acids for 20-24 hr, have been separated into two kinds differing in their size. Fats with different saturated and unsaturated fatty acid content were tested: corn oil, lard, mutton tallow, tripalmitin, corn oil-lard mixture, and randomized palmitic-linoleic triglycerides. Factors studied were: (a) increased amounts of these fats given alone or included in a test meal; (b) added amounts of nutrients (other than fats) in the test meal; (c) adaptation to a diet containing 20% fat for 10 days. The major part of the labeled lymph lipid was always transported by the smaller particles. Size distribution of lymph fat particles was influenced by some of the factors studied. Generally, unsaturated fats produced higher amounts of larger particles.