The Effect of Ethanol on Fatty Acid Metabolism; Stimulation of Hepatic Fatty Acid Synthesis in Vitro*

Abstract

Fatty infiltration of the liver is a common finding in alcoholic patients, but the mechanisms responsible for the accumulation of hepatic fat are not clear (2). In the present investigation, an attempt was made to clarify this relationship by studying the effect of ethanol on fatty acid metabolism in rat liver in vitro (3). MATERIALS AND METHODSSeventy-one male Sprague-Dawley rats weighing from 250 to 400 g were maintained on Purina Laboratory Chow, except for a 24 hour period immediately preceding the experiment. During this period, they were given 36.5 g glucose per kg together with 7.5 g ethanol per kg or, in the experiment shown in Table III, 50 g per kg fructose, administered by means of 5 gastric tube feedings of equal volume. Approximately 3 hours after the last gastric feeding, the animals were decapitated. The liver was quickly removed, and slices were prepared in the cold with a Stadie-Riggs slicer (4). The C14-labeled 1 and unlabeled substrates were dissolved in 5 ml isotonic KrebsRinger bicarbonate buffer, pH 7.4 (6), and the final concentration of the substrates was expressed as millimoles per liter. and the radioactivity counted in a Packard liquid scintillation counter. Randomized liver slices (approximately 0.5 g) were suspended in the incubation mixture in the main compartment of incubation flasks (8). The flasks were sealed with serum caps, gassed five minutes with a mixture of 95 per cent 02 and 5 per cent CO2, and then incubated for 3 hours at 37.50 C in a Dubnoff shaking water bath. Rat epididymal fat pads (0.5 to 1.0 g) were incubated in the same manner. At the end of the incubation, 0.2 ml of 10 N sulfuric acid was injected with a needle through the serum cap into the main compartment, and 1 ml of alkaline hyamine (9) into the center well. The, flasks were then shaken for 30 minutes in an ice bath to trap the evolving CO2 in the hyamine. The hyamine-C"4O. solution' was transferred into a volumetric flask and made up to 5 ml with toluene; 2 ml of this solution was mixed with 16 ml of toluene containing 0.4 per cent DPO and 0.005 per cent POPOP (9), and the radioactivity was measured in a Packard liquid scintillation counter. To calculate the disintegrations per minute (dpm), the obtained counts were multiplied by the efficiency of the counter which was determined separately for each experiment with an internal C"4 standard. C 40-2 was expressed in dpm per gram of wet tissue or per milligram of tissue nitrogen. The incubated tissue from each flask was homogenized in the incubation mixture, and an aliquot of this homogenate was used for determination of total nitrogen by the micro-Kjeldahl method (10). The rest of the homogenate was transferred to a screw-capped bottle, to which 0.4 ml of 90 per cent (wt/vol) potassium hydroxide per ml of homogenate was added. This mixture was saponified by autoclaving for 1 hour at 120°C. After cooling, ethanol was added to obtain a final concentration of 50 per cent. The mixture was vigorously shaken with 20 ml petroleum ether for 10 minutes to remove nonsa...

Effects of prolonged ethanol intake in man: role of dietary adipose, and endogenously synthesized fatty acids in the pathogenesis of the alcoholic fatty liver.

“…These results parallel closely the ones we obtained previously in rats studied under similar experimental conditions (1,6). Our previous observations of a decrease of fatty acid oxidation (18) in liver slices incubated with ethanol support the hypothesis that dietary lipids accumulate in the liver because of a reduction in their hepatic oxidation, but this possible mechanism for the hepatic accumulation of dietary fatty acids upon the ingestion of ethanol has not been investigated directly in the present study.…”

“…The mechanisms by which alcohol produced the accumulation of endogenously synthesized fatty acids under these experimental conditions have not been clarified. A plausible explanation would be increased hepatic fatty acid synthesis, decreased hepatic fatty acid oxidation, or both, shown previously to be produced by ethanol in the liver in vitro in association with a change in the cytoplasmic ratio of oxidized/reduced diphosphopyridine nucleotide (18,19). The relative importance of these two mechanisms, however, has not yet been dissociated (18,20).…”

“…Subsequently, after a second control period, subject J.S. was again given ethanol for 18 days, this time with a low fat diet ( Figure 4) similar to the low fat diet given the other subjects. Throughout the entire study, subject J.S.…”

Effects of Ethanol Infusion on the Redox State and Metabolite Levels in Rat Liver in vivo

“…Decreased hepatic acetyl CoA levels ( Table 2 ) suggestive of an increased lipogenesis [44] under the influence of ethanol may be of importance in understanding the role of ethanol in pathogenesis of ethanolinduced fatty livers. Intravenous infusion ofa number of alcohols and their aldehydes has recently been shown to inhibit the activity of CoA [45].…”

The Role of PI3K p110gamma in chronic liver injury

“…It has been known quite a while that ethanol stimulates hepatic fatty acid synthesis (Lieber and Schmidt, 1961). During the oxidation of ethanol to acetaldehyde NAD is reduced to NADH, which promotes fatty acid synthesis while counteracting lipid catabolism and consequently leads to fat accumulation in hepatocytes (Galli et al, 1999,Lieber andSchmidt, 1961).…”