Leonore M. DeCarli

Ethanol Oxidation by Hepatic Microsomes: Adaptive Increase after Ethanol Feeding

Hepatic microsomes contain an ethanol-oxidizing system distinct from alcohol dehydrogenase. In vitro, it has characteristics comparable to those of microsomal drug-detoxifying enzymes and, in vivo, it is capable of adaptation to the administration of ethanol. The existence of this microsomal ethanol-oxidizing system may explain ultrastructural, pharmacological, and biochemical effects of ethanol.

Phosphatidylcholine Protects Against Fibrosis and Cirrhosis in the Baboon

BACKGROUND/AIMS Polyunsaturated soybean lecithin (55%-60% phosphatidylcholine [PC]) protects against fibrosis in alcohol-fed baboons. The present study was undertaken to determine whether PC is the active agent. METHODS Virtually pure PC (equivalent to that contained in the lecithin) was administered for up to 6.5 years with or without alcohol, and the results were compared with those of unsupplemented groups. RESULTS Control livers remained normal, whereas 10 of 12 baboons fed alcohol without PC developed septal fibrosis or cirrhosis with transformation of 81% +/- 3% of the hepatic lipocytes to collagen-producing transitional cells. By contrast, none of the eight animals fed alcohol with PC developed septal fibrosis or cirrhosis, and only 48% +/- 9% of their lipocytes were transformed, indicating that PC was indeed the protective compound. Ethanol feeding also resulted in decreased liver phospholipids and PC, and both were corrected by the supplementation. Furthermore, PC stimulated collagenase activity in cultured lipocytes. This PC consisted of several species, mainly dilinoleoylphosphatidylcholine (40%-52%) and palmitoyl-linoleoylphosphatidylcholine (23%-24%). Only dilinoleoylphosphatidylcholine duplicated the effect of the PC on collagenase. Other species of PC, phosphatidylethanolamine, free fatty acids, or choline were without effect. CONCLUSIONS PC prevents alcohol-induced fibrosis and cirrhosis in nonhuman primates, and dilinoleoylphosphatidylcholine appears to be the active species, possibly by promoting collagen breakdown.

[58] Animal models of chronic ethanol toxicity

Publisher Summary This chapter introduces an experimental model for the toxic effect created by overcoming the natural aversion of the rodent for alcohol by incorporating the ethanol in a totally liquid diet. This technique provides flexibility to adjust to special experimental or physiological needs by allowing for various substitutions, including changes in lipids, proteins, or other dietary constituents. This procedure is thereby ideally suited for the study of the interactions of alcohol with deficiency or excess of various nutrients. The technique also facilitates the comparison with controls by simplifying pair-feeding procedures. The optimal amount of ethanol for the rat liquid diet is found to be 5 g% or 36% of total energy. With lesser amounts of alcohol, intake falls below a critical threshold; blood levels of alcohol then become negligible, and the model becomes irrelevant to clinical conditions. The first experimental model of alcoholic cirrhosis made it possible to clarify the pathogenesis of alcohol-induced fibrosis and has revealed precirrhotic lesions that have now found applicability to the human condition.

Difference in hepatic metabolism of long- and medium-chain fatty acids: the role of fatty acid chain length in the production of the alcoholic fatty liver.

Replacement of dietary triglycerides containing long-chain fatty acids (LCFA) by triglycerides containing medium-chain fatty acids (MCFA) markedly reduced the capacity of alcohol to produce fatty liver in rats. After 24 days of ethanol and MCFA, the increase in hepatic triglycerides was only 3 times that of controls, whereas an 8-fold rise was observed after ethanol and LCFA. The triglyceride fatty acids that accumulated in the liver after feeding of ethanol with MCFA contained only a small percentage of the MCFA; their composition also differed strikingly from that of adipose lipids. To study the mechanism of the reduction in steatosis, we compared oxidation to CO(2) and incorporation into esterified lipids of (14)C-labeled chylomicrons or palmitate-(14)C (representing LCFA), and of octanoate-(14)C (as MCFA) in liver slices and isolated perfused livers, in the presence or absence of ethanol. Ethanol depressed the oxidation of all substrates to CO(2); MCFA, however, was much more oxidized and reciprocally much less esterified than LCFA, with a 100-fold difference in the ratio of esterified lipid-(14)C to (14)CO(2). Furthermore, in hepatic microsomal fractions incubated with alpha-glycerophosphate, octanoate was much less esterified than palmitate. This propensity of MCFA to oxidation rather than esterification represents a likely explanation for the reduction in alcoholic steatosis upon replacement of dietary LCFA by MCFA.

Silymarin retards the progression of alcohol-induced hepatic fibrosis in baboons.

Goal/Background Hepatoprotective effects of silymarin in patients with alcoholic liver disease are controversial. For strict control, this was assessed in non-human primates. Study Twelve baboons were fed alcohol with or without silymarin for 3 years with a nutritionally adequate diet. Results Silymarin opposed the alcohol-induced oxidative stress (assessed by plasma 4-hydroxynonenal) and the rise in liver lipids and circulating ALT. Alcohol also increased hepatic collagen type I by 50% over the 3 years with a significant rise in mRNA for &agr;1 (I) procollagen, both prevented by silymarin. There were corresponding morphologic changes: at 36 months, 2 of 6 animals fed alcohol had cirrhosis and 2 septal fibrosis, with perivenular fibrosis in 2, whereas with alcohol + silymarin, there was only 1 cirrhosis and 1 septal fibrosis, with perivenular fibrosis in 2, and virtually no lesions in the remaining 2. Conclusions Silymarin retards the development of alcohol-induced hepatic fibrosis in baboons, consistent with several positive clinical trials. The negative outcome observed in other trials possibly reflects poor compliance resulting in irregular or low silymarin intake. Thus, in view of the innocuity of silymarin, it might be advisable in future clinical studies to insure the controlled administration of sufficient amounts of silymarin.

Effect of chronic alcohol consumption on Hepatic SIRT1 and PGC-1α in rats

The nuclear genes, NAD-dependent deacetylase Sirtuis 1 (SIRT1) and the peroxisome proliferator-activated receptor-gamma coactivator1alpha (PGC-1alpha) are regulators of energy metabolism. Here, we studied the role of alcohol consumption in expression of these sensing molecules. Alcohol significantly reduced hepatic SIRT1 mRNA by 50% and PGC-1alpha mRNA by 46% and it significantly inhibited the protein expression of SIRT1 and PGC-1alpha, while the transcription factor PPAR-gamma remained unchanged. However, when the lipid composition of the alcohol diet was changed by replacing long-chain triglycerides (LCT) with medium chain triglycerides (MCT), SIRT1 and PGC-1alpha mRNA were restored to near control levels. This study demonstrates that alcohol reduces key energy sensing proteins and that replacement of LCT by MCT affects the transcription of these genes. Since there is a pathophysiological link between SIRT1 and PGC-1alpha and mitochondrial energy, the implication of the study is that mitochondrial dysfunction due to alcohol abuse can be treated by dietary modifications.

Alcohol alters hepatic FoxO1, p53, and mitochondrial SIRT5 deacetylation function

Chronic alcohol consumption affects the gene expression of a NAD-dependent deacetylase Sirtuis 1 (SIRT1) and the peroxisome proliferator-activated receptor-gamma coactivator1alpha (PGC-1alpha). Our aim was to verify that it also alters the forkhead (FoxO1) and p53 transcription factor proteins, critical in the hepatic response to oxidative stress and regulated by SIRT1 through its deacetylating capacity. Accordingly, rats were pair-fed the Lieber-DeCarli alcohol-containing liquid diets for 28 days. Alcohol increased hepatic mRNA expression of FoxO1 (p=0.003) and p53 (p=0.001) while corresponding protein levels remained unchanged. However phospho-FoxO1 and phospho-Akt (protein kinase) were both decreased by alcohol consumption (p=0.04 and p=0.02, respectively) while hepatic p53 was found hyperacetylated (p=0.017). Furthermore, mitochondrial SIRT5 was reduced (p=0.0025), and PGC-1alpha hyperacetylated (p=0.027), establishing their role in protein modification. Thus, alcohol consumption disrupts nuclear-mitochondrial interactions by post-translation protein modifications, which contribute to alteration of mitochondrial biogenesis through the newly discovered reduction of SIRT5.

Hepatic lipid in morbid obesity. Assessment at and subsequent to jejunoileal bypass.

Abstract Twenty-three massively obese patients (mean excess of ideal body weight of 137 per cent) underwent end-to-end jejunoileal bypass because of dietary treatment failure and complications of obesity. Histologic assessment was done on liver biopsies taken at operation and an average of 13 months later. Chemical measurement showed a mean (± S.D.) increase in total lipids from 110.7 ± 62.8 to 221.7 ± 180.2 mg per gram, and in triglycerides from 79.9 ± 63.3 to 177.2 ± 151.2 mg per gram (p<0.05). Phospholipid, free cholesterol and cholesterol esters were not significantly increased. Thus, controlled histologic estimates can provide a rough guide of lipid mass present in a given biopsy specimen within the range of 50 per cent. For purposes of experimental study, this degree of sensitivity and precision may be inadequate. Secondly, hepatic lipid accumulation does not correlate with degree of obesity. Thirdly, jejunoileal bypass for obesity is accompanied during the period of weight loss by a threefold incre...

Effect of ethanol on fatty acid metabolism in liver slices

Abstract It has been demonstrated that in rats, administration of ethanol increases the fat content of the liver ( Mallov and Bloch, 1956 ), but the mechanism of this effect is unknown. In the present study, liver slices and adipose tissue were incubated with various labeled substrates and the effect of ethanol on the incorporation of the label into fatty acids was studied.

[37] The Microsomal ethanol oxidizing systems (MEOS)

Publisher Summary This chapter describes procedures for assaying the activities of microsomal ethanol oxidizing system (MEOS) in total liver tissue, in microsomes, and in partially purified microsomal fractions. It is assumed that ethanol metabolism proceeds exclusively via alcohol dehydrogenase (ADH), an enzyme of the cell sap of the hepatocyte. Indeed, this concept is satisfactory at low ethanol concentrations because the oxidation of ethanol is almost completely abolished under these conditions by pyrazole, a potent inhibitor of alcohol dehydrogenase activity. Recent studies have shown that, in addition to ADH, ethanol can also be metabolized by the microsomal fraction of the hepatocyte, which comprises the endoplasmic reticulum. MEOS is also differentiated from ADH, in contrast to ADH the microsomal ethanol oxidation is more active with NADPH than with NAD, has a neutral pH optimum, and shows a relative insensitivity to the ADH inhibitors pyrazole and 4- methylpyrazole.