Alcohol delays clearance of lipoproteins from the circulation

Effect of acute and chronic moderate red or white wine consumption on fasted and postprandial lipemia in the rat

The effects of acute and chronic (10 wk) red or white wine consumption on fasted and postprandial lipemia in the rat model are reported. Fasted rats, in the acute study, were loaded intragastrically with 5 ml of an olive oil emulsion (30% w/v) in the presence or absence of wine (8% v/v ethanol), and either mesenteric lymph or blood was collected 3 h postprandially. Animals in the chronic study received either red or white wine in drinking water for a period of 10 wk (3% v/v ethanol). Blood samples were collected from animals in either the fasted state or after fat-wine loading. Postprandially, wine delayed gastric emptying, reduced lymph triacylglycerol (TAG) secretion concomitantly with increased number and decreased chylomicron (CM) size, and increased plasma TAG and CM concentrations. Phospholipid and cholesterol contents of CM, but not very-low-density lipoprotein (VLDL), were increased, indicating enhanced liver bile secretion; however, a significant increase in plasma VLDL concentration was observed. In the chronic study, a wine-fat load resulted in increased high-density lipoprotein (HDL) cholesterol concentration and less pronounced postprandial hypertriglyceridemia and hyperchylomicronemia. In the fasted state, plasma TAG and total apolipoprotein B concentrations were not modified in these animals, and an increase in HDL and a decrease in low-density lipoprotein (LDL)/HDL cholesterol ratios were observed. No liver function or intestinal lipid absorption impairment was observed. In conclusion, unlike binge drinking, chronic moderate wine consumption appears to have a cardioprotective effect in the fasted state, an effect attenuated by the observed temporary postprandial hyperchylomicronemia and hypertriglyceridemia resulting from a direct effect of alcohol on CM size and number.

Effect of acute and chronic moderate alcohol consumption on fasted and postprandial lipemia in the rat

Effects of acute and chronic alcohol intake on fasted and postprandial lipemia in the rat model are reported. In the acute study, fasted rats are loaded with a 30% w/w olive oil emulsion with or without 8% alcohol in the form of ethanol, beer or whisky. After 3 h, either mesenteric lymph or blood is collected and the TAG-rich lipoprotein fractions are isolated. In the chronic study, animals received, for a period of 10 weeks, 3% alcohol in drinking water in the form of ethanol, beer or whisky. Blood samples were collected from animals in either the fasted state or after being loaded with the fat load as described above. Alcohol ingestion along with a fat load increases the number (increased net apoB48 secretion) and reduces the size (reduced TAG/apoB48 ratio) of CM secreted into the mesenteric lymph duct. It also delays gastric emptying, reduces trans-enterocyte TAG flux rates and increases plasma concentrations of TAG, cholesterol and CM. Similar conditions also results in increased total phospholipid and cholesterol content of CM but not of VLDL, indicating an enhanced liver bile secretion into the gut; however, a significant increase in plasma VLDL concentration is observed. Unlike the acute study, an alcohol-fat load in animals put on chronic alcohol intake results in increased HDL cholesterol concentrations and less pronounced postprandial hypertriglyceridemia and hypercholesterolemia but not hyperchylomicronemia. In the fasted state, plasma TAG and total apoB concentrations are not modified in these animals, and an increase in HDL and a decrease in total and LDL cholesterol concentrations are observed. No liver function impairment is observed following the 10-week period of chronic alcohol intake. In conclusion, unlike binge drinking, chronic moderate alcohol consumption appears to have a cardioprotective effect in the fasted state, an effect attenuated by the observed temporary postprandial hyperchylomicronemia and hypertriglyceridemia resulting from a direct effect of alcohol on CM size and number.

Alcohol-mediated enhancement of postprandial lipemia: a contributing factor to an increase in plasma HDL and a decrease in risk of cardiovascular disease

BACKGROUND

Moderate alcohol consumption increases plasma HDL and lowers cardiovascular disease risk while transiently enhancing postprandial lipemia.

OBJECTIVE

We hypothesized that the alcohol-mediated increase in postprandial triacylglycerol-rich lipoproteins (TRLs) and their clearance elevate HDL cholesterol and reverse cholesterol transport.

DESIGN

We determined the effect in normolipidemic humans (n = 14) of postprandial lipemia produced 4 h after a test meal (M) or a test meal + 0.5 g alcohol/kg body wt (M+A) on postprandial changes in plasma lipids and on the balance of cholesterol between TRL and the cholesterol-rich LDL and HDL fractions (CRL) or red blood cells (RBCs) in fresh and incubated plasma or blood.

RESULTS

Postprandial lipemia after the M and M+A test meals caused a 56% and 89% increase in plasma triacylglycerol, a 30% and 74% increase in TRL cholesterol, and a 3.8% and 6.6% decrease in CRL cholesterol, respectively. In vitro reaction of endogenous lecithin:cholesterol acyltransferase (EC 2.3.1.43) and cholesteryl ester transfer proteins via incubation of fasting plasma samples and postprandial M and M+A plasma samples for 16 h increased TRL cholesterol by 22.8% (0.08 mmol/L), 32.6% (0.16 mmol/L), and 45.8% (0.28 mmol/L) in plasma and by 71.1% (0.27 mmol/L), 89.4% (0.45 mmol/L), and 112.5% (0.70 mmol/L) in RBC-enriched blood, respectively. After the in vitro lipolysis of TRL, the elevation of HDL cholesterol in postprandial M+A plasma, but not in postprandial M plasma, was significantly greater than in fasting plasma.

CONCLUSION

The alcohol-mediated increase in postprandial TRL flux and the hepatic removal of postprandial TRL after the acceptance of cholesterol from CRL and cell membranes contribute to increased HDL cholesterol and enhancement of reverse cholesterol transport in humans.

Effect of alcohol on lipids and lipoproteins in relation to atherosclerosis

Several studies indicate that light-to-moderate alcohol consumption is associated with a low prevalence of coronary heart disease. An increase in high-density lipoprotein (HDL) cholesterol is associated with alcohol intake and appears to account for approximately half of alcohol's cardioprotective effect. In addition to changes in the concentration and composition of lipoproteins, alcohol consumption may alter the activities of plasma proteins and enzymes involved in lipoprotein metabolism: cholesteryl ester transfer protein, phospholipid transfer protein, lecithin:cholesterol acyltransferase, lipoprotein lipase, hepatic lipase, paraoxonase-1 and phospholipases. Alcohol intake also results in modifications of lipoprotein particles: low sialic acid content in apolipoprotein components of lipoprotein particles (e.g., HDL apo E and apo J) and acetaldehyde modification of apolipoproteins. In addition, "abnormal" lipids, phosphatidylethanol, and fatty acid ethyl esters formed in the presence of ethanol are associated with lipoproteins in plasma. The effects of lipoproteins on the vascular wall cells (endothelial cells, smooth muscle cells, and monocyte/macrophages) may be modulated by ethanol and the alterations further enhanced by modified lipids. The present review discusses the effects of alcohol on lipoproteins in cholesterol transport, as well as the novel effects of lipoproteins on vascular wall cells.

The French paradox: possible involvement of ethanol in the protective effect against cardiovascular diseases

OBJECTIVES

This review surveyed the literature on the cardioprotective effects of moderate alcohol consumption.

METHODS

The putative cardioprotective effects of alcohol and other substances in alcoholic beverages are discussed by taking "the French paradox" as a starting point. A survey of the literature highlighted various hypotheses explaining the protective effects of moderate alcohol consumption.

RESULTS

The positive effects of moderate quantities of alcohol have been attributed in part to increased plasma levels of high-density lipoprotein, an inhibition of platelet aggregation, and improved endothelial function. Many investigators have claimed that wine is the significant factor explaining the French paradox. Red wine has been shown ex vivo to inhibit low-density lipoprotein oxidation, increase antioxidant capacity in humans, and reduce susceptibility of human plasma to lipid peroxidation. The non-alcoholic fraction of wine, represented mainly by phenolic compounds, may be the primary factor responsible for this protective effect. However, the protective effects are not restricted to a particular type of alcoholic drink, suggesting that alcohol per se rather than compounds specific to certain beverages reduces mortality risk.

CONCLUSIONS

It is difficult to explain the effect of alcohol on risk factors associated with cardiovascular diseases by a uniform biochemical mechanism. Moreover, its protective effects are counterbalanced by its addictive properties.

Alcohol consumption raises HDL cholesterol levels by increasing the transport rate of apolipoproteins A-I and A-II

BACKGROUND

Moderate alcohol intake is associated with lower atherosclerosis risk, presumably due to increased HDL cholesterol (HDL-C) concentrations; however, the metabolic mechanisms of this increase are poorly understood.

METHODS AND RESULTS

We tested the hypothesis that ethanol increases HDL-C by raising transport rates (TRs) of the major HDL apolipoproteins apoA-I and -II. We measured the turnover of these apolipoproteins in vivo in paired studies with and without alcohol consumption in 14 subjects. The fractional catabolic rate (FCR) and TR of radiolabeled apoA-I and -II were determined in the last 2 weeks of a 4-week Western-type metabolic diet, without (control) or with alcohol in isocaloric exchange for carbohydrates. Alcohol was given as vodka in fixed amounts ranging from 0.20 to 0.81 g. kg(-1). d(-1) (mean+/-SD 0.45+/-0.19) to reflect the usual daily intake of each subject. HDL-C concentrations increased 18% with alcohol compared with the control (Wilcoxon matched-pairs test, P=0.002). The apoA-I concentrations increased by 10% (P=0.048) and apoA-II concentrations increased by 17% (P=0.005) due to higher apoA-I and -II TRs, respectively, whereas the FCR of both apoA-I and -II did not change. The amount of alcohol consumed correlated with the degree of increase in HDL-C (Pearson's r=0.66, P=0.01) and apoA-I TR (r=0.57, P=0.03). The increase in HDL-C also correlated with the increase in apoA-I TR (r=0.61, P=0.02).

CONCLUSIONS

Alcohol intake increases HDL-C in a dose-dependent fashion, associated with and possibly caused by an increase in the TR of HDL apolipoproteins apoA-I and -II.

Carbohydrate-deficient transferrin and gamma-glutamyltransferase are inversely associated with lipid markers of cardiovascular risk

BACKGROUND

A variety of epidemiological studies have suggested a U-shaped association between alcohol consumption and atherosclerosis progression and incidence events. Moderate intake of alcohol is considered beneficial, whereas heavy drinking increases cardiovascular disease risk.

METHODS

Alcohol and cardiovascular risk-related laboratory tests were carried out in 70 consecutive male employees in connection with an occupational health survey in 1996. Carbohydrate-deficient transferrin (CDT) and gamma-glutamyltransferase (GGT) were used as markers for alcohol consumption. The subjects were divided into quartiles on the basis of CDT or GGT value.

RESULTS

The highest CDT quartile had significantly higher serum high-density lipoprotein (HDL)-cholesterol (P < 0.05) than the lowest quartile. The highest GGT quartile had significantly higher serum total cholesterol (P < 0. 01), lower serum HDL-cholesterol (P < 0.05), higher serum low-density lipoprotein (LDL)-cholesterol (P < 0.01) and higher serum triglyceride (P < 0.01) than the lowest quartile.

CONCLUSIONS

An explanation for the findings is that high alcohol consumption without significant liver induction increases the level of HDL-cholesterol, whereas high alcohol consumption with induction of liver may have adverse effects on lipoprotein metabolism. The results were interpreted to indicate that CDT and GGT detect different populations of drinkers in regard to cardiovascular lipid risk factors.

Alcohol and lipids

Alcoholic fatty liver and hyperlipemia result from the interaction of ethanol and its oxidation products with hepatic lipid metabolism. An early target of ethanol toxicity is mitochondrial fatty acid oxidation. Acetaldehyde and reactive oxygen species have been incriminated in the pathogenesis of the mitochondrial injury. Microsomal changes offset deleterious accumulation of fatty acids, leading to enhanced formation of triacylglycerols, which are partly secreted into the plasma and partly accumulate in the liver. However, this compensatory mechanism fades with progression of the liver injury, whereas the production of toxic metabolites increases, exacerbating the lesions and promoting fibrogenesis. The early presence of these changes confers to the fatty liver a worse prognosis than previously thought. Alcoholic hyperlipemia results primarily from increased hepatic secretion of very-low-density lipoprotein and secondarily from impairment in the removal of triacylglycerol-rich lipoproteins from the plasma. Hyperlipemia tends to disappear because of enhanced lipolytic activity and aggravation of the liver injury. With moderate alcohol consumption, the increase in high-density lipoprotein becomes the predominant feature. Its mechanism is multifactorial (increased hepatic secretion and increased extrahepatic formation as well as decreased removal) and explains part of the enhanced cholesterol transport from tissues to bile. These changes contribute to, but do not fully account for, the effects on atherosclerosis and/or coronary heart disease attributed to moderate drinking.

Effects of alcohol on plasma lipoprotein metabolism

Alcohol consumption affects a number of steps in plasma lipoprotein metabolism: it serves as a substrate for lipoprotein triglyceride synthesis, alters synthesis of apolipoproteins, and affects the activity of the key enzymes of lipoprotein metabolism, namely lipoprotein lipase and hepatic lipase, and cholesterol ester transfer protein. In addition, alcohol consumption may increase tissue sensitivity to insulin. The specific effects of alcohol consumption vary and depend on the amount ingested, type of drinking (as opposed to moderate regular alcohol consumption, binge drinking results in an unfavourable serum lipoprotein profile), body composition of the drinkers and a number of gene/environment interactions. Modification of lipoproteins by acetaldehyde, the product of ethanol metabolism or by antioxidants present in some alcoholic beverages also influences the lipoprotein alterations due to alcohol consumption. Moderate alcohol consumption increases serum high density lipoprotein cholesterol and may decrease the concentration of lipoprotein(a).

Effects of alcohol consumption on pharmacokinetics, efficacy, and safety of fluvastatin

Alcohol consumption is known to have beneficial effects on cardiac mortality, probably by increasing high density lipoprotein cholesterol (HDL-C). Alcohol also increases triglycerides and, in some studies, total cholesterol and low density lipoprotein cholesterol (LDL-C). Nothing is known, however, of the effects of alcohol on the pharmacokinetics and efficacy of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors. Consequently, 2 studies have been carried out to determine the effects of alcohol consumption on the pharmacokinetics and efficacy of the HMG-CoA reductase inhibitor fluvastatin. Firstly, the effects of acute alcohol consumption on a single, oral 40 mg dose of fluvastatin were examined in a reference-controlled, randomized, crossover study in 10 healthy volunteers. Measurements were made after ingestion of 70 g of ethanol diluted to 20% with lemonade and, following a 7-day period, after ingestion of lemonade alone (reference). The half-life (t1/2) of a single dose of fluvastatin was significantly reduced by acute alcohol consumption compared with reference, whereas the area under the time-concentration curve (AUC), peak concentration (Cmax), and time to peak concentration (tmax) did not differ from the reference group. The lipid profile, measured 8 hr after administration, did not differ significantly from baseline in the reference group, apart from a slight reduction in apolipoprotein (apo)-AI. Triglyceride levels increased with alcohol, probably due to impaired fatty acid oxidation. Surprisingly, total cholesterol and LDL-C fell significantly, possibly due to altered pharmacokinetics, as reflected by the lower t1/2.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of alcohol on lipoprotein lipase, hepatic lipase, cholesteryl ester transfer protein, and lecithin:cholesterol acyltransferase in high-density lipoprotein cholesterol elevation

The mechanism whereby alcohol increases high-density lipoprotein cholesterol (HDL-C) levels is unclear. Lipoprotein lipase (LPL), hepatic lipase (HL), cholesteryl ester transfer protein (CETP) and lecithin:cholesterol acyltransferase (LCAT) act on lipoprotein metabolism. The purpose of the present study is to determine which one or what combination of these factors is responsible for the rise in HDL-C levels following alcohol ingestion. After 3 weeks of abstinence, 12 men consumed 0.5 g/kg bw of alcohol per day for 4 weeks; 13 abstaining men served as controls. Mean plasma total cholesterol (TC) levels were unchanged in either group throughout the study. Among the alcohol consumers, plasma triglycerides (TG), HDL-C, apolipoprotein (apo) A-I and A-II levels increased significantly after 3 weeks of alcohol loading but were unchanged in the control group. High-density lipoprotein3 cholesterol (HDL3-C) levels increased significantly in the alcohol consumers after 4 weeks of alcohol loading whereas high-density lipoprotein2 cholesterol (HDL2-C) levels were unaffected. In the controls, neither HDL2-C nor HDL3-C changed significantly. Post-heparin plasma (PHP) LPL activity and mass increased significantly (P < 0.01) after the alcohol ingestion (controls remained unchanged) without changing LPL specific activity. HL, CETP and LCAT activities were unaffected in both groups. We conclude that of the factors considered, LPL contributed the most to the alcohol-induced rise in HDL-C.

Drug control of reverse cholesterol transport

Reverse cholesterol transport identifies a series of metabolic events resulting in the transport of excess cholesterol from peripheral tissues to the liver. High-density lipoproteins (HDL) are the vehicle of cholesterol in this reverse transport, a function believed to explain the inverse correlation between plasma HDL levels and atherosclerosis. An attempt to stimulate, by the use of drugs, this transport process may hold promise in the prevention and treatment of arterial disease. Among the agents affecting lipoprotein metabolism, only probucol exerts significant effects on reverse cholesterol transport, by stimulating the activity of the cholesteryl ester transfer protein and, consequently, altering HDL subfraction composition/distribution. Another approach to the stimulation of reverse cholesterol transport consists of raising plasma HDL levels; studies in animals, either by exogenous supplementation or by endogenous overexpression, have shown a consistent benefit in terms of atherosclerosis regression and/or non-progression. Thus, it is time to consider different future treatments of atherosclerosis, combining the classical lipid-lowering treatments with innovative methods to promote cholesterol removal from the arterial wall.