Effect of dietary omega-3 fatty acids and chronic ethanol consumption on reverse cholesterol transport in rats

We previously showed that chronic ethanol feeding leads to a decrease of apolipoprotein E (apoE) in high-density lipoprotein (HDL), whereas supplementing this diet with 2.8% of total dietary calories as omega3-fatty acids (omega3FAs) restores HDL-apoE to the control values. Since HDL containing apoE plays a major role in reverse cholesterol transport (RCT), we measured the effects chronic ethanol intake and omega3-FAs on RCT in the present study. Four groups of rats, control normal fat (CN), alcohol-normal fat (AN), control omega3FA fat (CF), and alcohol-omega3FA fat (AF), were fed their respective diets for 8 weeks, after which hepatocytes and HDLs from each group were evaluated for RCT capacity (cholesterol efflux from macrophages and uptake by liver cells). Compared with the control diet (CN), chronic ethanol (AN) feeding inhibited the cholesterol efflux capacity of HDL by 21% (P < .01), whereas omega3FA feeding (2.8% of total dietary calories) stimulated this capacity by 79% (P < .01) and 25% (P < .01) in CF and AF rats, respectively. With respect to cholesterol uptake by the liver, there were no significant 3-way or 4-way interactions between the 4 factors, HDL-alcohol, HDL-fish oil, hepatocyte-alcohol, and hepatocyte-fish oil. The main effects for HDL-alcohol, HDL-fish oil, and hepatocyte-alcohol were all highly significant (P = .0001, .0001, and .007, respectively). There was a significant HDL-alcohol and HDL-fish oil interaction (P = .0001). Hepatocyte-alcohol was not a factor in any 2-way interactions. Our study indicates no evidence of an interaction between the effects of omega3FAs and the effects of alcohol on hepatocytes in terms of RCT function. Thus, feeding as little as 2.8% of the total dietary calories as omega3FA not only restored the impaired RCT function of HDL caused by chronic ethanol intake, but also enhanced by severalfold the ability of HDL to promote RCT even in normal animals.     

Long-term ethanol consumption impairs reverse cholesterol transport function of high-density lipoproteins by depleting high-density lipoprotein sphingomyelin both in rats and in humans

Moderate alcohol consumption has been linked to lower incidence of coronary artery disease due to increased plasma high-density lipoprotein (HDL), whereas heavy drinking has the opposite effect. Because of the crucial role of HDL in reverse cholesterol transport and positive correlation of HDL sphingomyelin (SM) content with cholesterol efflux, we have compared HDL SM content with its reverse cholesterol transport capacity both in rats fed ethanol on long-term basis and alcoholic individuals. In rats, SM HDL content was decreased in the ethanol group (-15.4%, P < .01) with a concomitant efflux decrease (-21.0%, P < .01) compared to that in controls. Similarly, HDL from the ethanol group, when compared with HDL from the control group, exhibited 13.8% (P < .05) less cholesterol uptake with control-group hepatocytes and 35.0% (P < .05) less cholesterol uptake with ethanol-group hepatocytes. Conversely, hepatocytes from the ethanol group, when compared with hepatocytes from the control group, exhibited 31.0% (P < .01) less cholesterol uptake with control-group HDL and 48.0% (P < .01) less with ethanol-group HDL. In humans, SM content in plasma HDL was also decreased in chronically alcoholic individuals without liver disease (-51.5%, P < .01) and in chronically alcoholic individuals with liver disease (-51.3%, P < .01), compared with nondrinkers. Concomitantly, in alcoholic individuals without liver disease, both efflux and uptake were decreased by 83.0% and 54.0% (P < .01), respectively, and in chronically alcoholic individuals with liver disease by 84.0% and 61.0% (P < .01), respectively, compared with nondrinkers. Based on these findings, we conclude that long-term ethanol consumption significantly impairs not only cholesterol efflux function of HDL by decreasing its SM content but also cholesterol uptake by affecting presumably hepatocyte receptors for HDL.     

Down-regulation of liver Galβ1, 4GlcNAc α2, 6-sialyltransferase gene by ethanol significantly correlates with alcoholic steatosis in humans

Hepatic steatosis and steatohepatitis are frequent results of long-term ethanol exposure. We have previously demonstrated that long-term ethanol down-regulates Galβl, 4GlcNAc α2, 6-sialyltransferase (ST6Gal1), leading to defective glycosylation of a number of proteins including apolipoprotein (apo) E and apo J and the appearance of asialoconjugates in the blood of continuously alcohol-fed animals as well as in human alcoholics. In the current study, we have explored the possibility of whether ethanol-induced down-regulation of ST6Gal1 could contribute toward alcoholic steatosis in human alcoholics presumably because of impaired lipid and lipoprotein transport caused by this down-regulation. Real-time quantitative polymerase chain reaction analyses of liver samples from nondrinkers, moderate drinkers, and heavy drinkers as well as from subjects with and without alcoholic liver disease revealed direct evidence that the down-regulation of ST6Gal1 may be due to ethanol per se. The ST6Gal1 messenger RNA level was reduced by as much as 70% in moderate and heavy drinkers as well as in patients with alcoholic liver disease, but was not changed in subjects with liver disease due to causes other than alcohol exposure. Biochemical and histopathologic analysis demonstrated that the liver total cholesterol was increased by more than 30% (P < .05) and 75% (P < .01), respectively, in moderate and heavy drinkers compared with nondrinkers, with even more dramatic changes in triglyceride levels. Significantly, there was a strong inverse correlation between ST6Gal1 messenger RNA level and liver lipid deposit (F = 8.68, P < .001) by statistical analysis. Thus, it is suggested that alcohol-mediated down-regulation of hepatic ST6Gal1 gene leads to defective glycosylation of lipid-carrying apolipoproteins such as apo E and apo J, resulting in defective intracellular lipid and lipoprotein transport, which in turn may contribute to alcoholic steatosis.     

Therapeutic interventions targeted at the augmentation of reverse cholesterol transport

PURPOSE OF REVIEW: Serum high-density lipoproteins (HDLs) and reverse cholesterol transport (RCT) are important therapeutic targets in the management of atherosclerotic disease. This review summarizes the pathway of RCT and the currently available means by which investigators are attempting to modulate HDL levels and increase rates of RCT. RECENT FINDINGS: Low levels of HDL are commonly encountered in patients with atherosclerotic disease. HDLs mediate a substantial number of antiatherogenic effects along blood vessel walls. One of the most important of these antiatherogenic mechanisms is RCT, a series of reactions by which HDL is able to facilitate the net translocation of cholesterol from peripheral cells to the liver for excretion. There is scientific evidence supporting the concept of RCT in both animals and humans. To facilitate RCT, it is important that therapeutic effort be made to raise serum levels of HDL. Statins, fibrates, niacin, thiazolidinediones, and various combinations of these drugs all raise HDL levels. However, in many high-risk patients with established atherosclerotic disease, the elevations in HDL achieved with these medications are frequently inadequate. Newer agents designed to raise HDL and promote RCT are currently being developed, including infusible bioengineered HDL, edible HDL composed of D-amino acids, and agents capable of inhibiting cholesterol ester transfer protein, among others. SUMMARY: Established therapies for raising HDL can be effective either as monotherapy or when used in combination. Newer strategies are being developed to exploit more specifically the capacity of HDL to drive RCT and either prevent or reverse the course of atherosclerotic disease.     

Concentrations of apolipoprotein AI,AII, and E in plasma and lipoprotein fractions of alcoholic patients: Gender differences in the effects of alcohol

Previous studies have shown that plasma levels of high-density lipoprotein (HDL) cholesterol and the two major protein components of HDLs, i.e., apolipoproteins AI and AII, were elevated in male alcoholic patients without serious liver injury. By contrast, alcohol effect on apolipoprotein E remains unclear. Apolipoprotein E is a major component of very low-density lipoprotein (VLDL) and a minor component of human high-density lipoprotein. It plays a critical role in lipoprotein metabolism through cellular lipoprotein receptors. Furthermore, previous works were carried out mostly with male subjects, whereas alcohol effects on serum apolipoproteins in female subjects have not yet been adequately addressed. In this study, we have raised antibodies specifically to recognize human apolipoprotein AI, All, and E, respectively, to quantify apolipoprotein concentrations in plasma and lipoprotein fractions of male and female alcoholic patients. We have also measured plasma apolipoprotein concentrations in patients who had abstained from alcohol while in the hospital. Our results showed the following: (1) plasma concentrations of apolipoprotein AI and All were significantly elevated yet plasma apolipoprotein E decreased (33%) significantly (P < .01) in male alcoholic patients; (2) apolipoprotein AI concentrations in female nondrinking control subjects were higher than in male controls, and the concentrations of apolipoprotein AI in female alcoholic patients were not significantly elevated over those of female controls; (3) similar to their male counterparts, female alcoholic patients exhibited higher plasma apolipoprotein All and lower apolipoprotein E; (4) changes in plasma apolipoproteins seen here were most likely attributable to a direct effect of alcohol but not a secondary effect of mild liver injury; (5) changes in plasma apo lipoprotein levels in alcoholic patients were reversible in 1 week after alcohol abstinence; and (6) the decrease of plasma apo E in alcoholic patients was indicated by the presence of apo E-deficient VLDL particles whereas the concentration of apo E in HDL particles of alcoholic patients remained unaffected.     

Serum apolipoprotein E in children and adolescents: the Bogalusa Heart Study

Serum apolipoprotein (apo) E levels and its relationship to lipids and lipoprotein cholesterol fractions were examined in a random subsample (n = 561) of children and adolescents (7 to 17 years of age) from a total biracial community. Mean (+/- SD) levels of apo E were higher in blacks (males 4.8 +/- 1.8 mg/dL; females 5.2 +/- 1.8 mg/dL) than in whites (males 3.9 +/- 1.2 mg/dL; females 4.3 +/- 1.0 mg/dL) irrespective of sex (P less than .001). The black-white difference in apo E persisted after controlling for the covariates: sexual maturation, age, adiposity, cigarette smoking, alcohol use, and oral contraceptive use (P less than .001). A sex differential (females greater than males, P less than .01) for apo E was seen in both racial groups. Apo E levels were inversely associated with age (P less than .01) and sexual maturation (P less than .05) only in white males. Apo E related positively and significantly to total cholesterol, low-density lipoprotein cholesterol, and high-density lipoprotein cholesterol fractions (HDL2-C and HDL3-C) in certain race-sex groups. Race, HDL2-C, triglycerides (very-low density lipoprotein cholesterol), HDL3-C, and sex were identified as predictor variables for apo E, in that order, and accounted for 21% of its variability in serum. It is conceivable that the observed race-sex differences in apo E may be related to apo E-HDL subfraction, which is thought to participate in the reverse cholesterol transport.     

High-density lipoprotein cholesterol in male alcoholics with and without severe liver disease

In a study of 26 male alcoholics, the subgroup without severe liver disease showed significant elevation in high-density lipoprotein cholesterol (HDL) in the immediate post-intoxication period; HDL levels decreased to control levels after one to two weeks of abstinence. Those patients with advanced liver disease failed to show this ethanol-induced rise in HDL. We were not able to correlate these observations with any variation in sex hormone levels, nutritional indices, age or quantity of alcohol intake. We concluded that ethanol consumption in alcoholics is associated with an increase in HDL levels, which is offset by the development of alcoholic liver disease.     

Desialylation of human apolipoprotein E decreases its binding to human high-density lipoprotein and its ability to deliver esterified cholesterol to the liver.

Apolipoprotein E (apoE) plays a significant role in the delivery of high-density lipoprotein (HDL) cholesterol to the liver via the apoB/E receptor. The roles of the apoE sialylation status in its association with HDL and in the reverse cholesterol transport (RCT) function of HDL have not been well defined. Furthermore, long-term ethanol treatment impairs apoE sialylation and leads to its decreased content in HDL. Therefore, we investigated the association of either sialo apoE (SapoE) or desialo apoE (DSapoE) with HDL and its effect on the RCT function of HDL. The dextran sulfate precipitation method showed that [125I]DSapoE binding to HDL was 27.3% (P < .02) to 35.5% (P < .001) lower versus [125I]SapoE. Scatchard analysis of the specific binding data showed that [125I]SapoE had 11.2 times more affinity for HDL than [125I]DSapoE based on size-exclusion chromatography (Kd = 89.7 v 1,010 nmol/L). Similarly, [1251]HDL had 4.5 times more affinity for SapoE compared with DSapoE based on solid-phase binding (Kd = 21.9 v 104.4 nmol/L). Furthermore, esterified cholesterol uptake from reconstituted HDL particles (rHDLs) by HepG2 cells increased over basal uptake up to 153% when rHDLs contained SapoE, versus only 37% with DSapoE. Enzymatic resialylation of DSapoE completely restored its HDL-binding and RCT properties, identical to those of SapoE. It is therefore concluded that desialylation of apoE decreases its binding to plasma HDL, leading to an impaired RCT function.     

Alcohol consumption is associated with enrichment of high-density lipoprotein particles in polyunsaturated lipids and increased cholesterol esterification rate

BACKGROUND: Alcohol consumption is associated with high levels of high-density lipoproteins (HDLs). Moreover, changes in the fatty acid patterns of red blood cell phospholipids and plasma lipids have been observed in drinkers. The objectives of this study were to characterize the composition of HDL particles with respect to lipid molecular species in regular wine drinkers and to assess the functional properties of those HDLs as regards key steps of reverse cholesterol transport. METHODS: Forty-six subjects were recruited in the frame of a population study performed in Toulouse, southern France, and a nutritional investigation, including daily alcohol consumption, was performed. Subjects were sorted according to their daily alcohol intake (0, < or =35, and >35 g/day), mostly as red wine. The plasma HDL fraction was isolated, and neutral lipid molecular lipids and phospholipid fatty acids were analyzed by gas liquid chromatography. Efflux of cellular cholesterol and rates of cholesterol esterification and cholesteryl ester transfers between lipoproteins were assayed in a cell-plasma incubation system. RESULTS: Wine drinking, at 47 g/day, was associated with an increase in HDL cholesterol and apolipoprotein A-I, but not with triglycerides. Isolated HDL displayed a 27% increase in all cholesteryl ester molecular species. The particles were also enriched in unsaturated phospholipids and, particularly, in those containing arachidonic (+30%) and eicosapentaenoic (+90%) acids. The plasma cholesterol esterification rate, reflecting lecithin cholesterol acyl transferase activity on HDL, was found to be higher (+27%) in drinkers than in nondrinkers, whereas the rate of cellular cholesterol efflux to plasma was identical. CONCLUSIONS: Regular wine consumption is associated with high levels of polyunsaturated lipids in HDL and with increases in the cholesterol esterification rate.     

Mechanism of action of niacin on lipoprotein metabolism

It is generally accepted that the increased concentrations of apolipoprotein (apo) B containing very low-density lipoproteins (VLDL) and low-density lipoproteins (LDL), and decreased levels of apo AI containing high-density lipoproteins (HDL) are correlated to atherosclerotic cardiovascular disease. Current evidence indicates that the post-translational apo-B degradative processes regulate the hepatic assembly and secretion of VLDL and the subsequent generation of LDL particles. The availability of triglycerides (TG) for the addition to apo B during intracellular processing appears to play a central role in targeting apo B for either intracellular degradation or assembly and secretion as VLDL particles. Based on the availability of TG, the liver secretes either dense TG-poor VLDL2 or large TG-rich VLDL1 particles, and these particles serve as precursors for the formation of more buoyant or small, dense LDL particles by lipid transfer protein- and hepatic lipase-mediated processes. HDLs are a heterogenous class of lipoproteins, and apo AI (the major protein of HDL) participates in reverse cholesterol transport, a process by which excess cholesterol is eliminated. Recent studies indicate that HDL particles containing only apo A-I (LPA-I) are more effective in reverse cholesterol transport and more anti-atherogenic than HDL particles containing both apo A-I and apo A-II (LPA-I+A-II).     

Association of apolipoprotein (Apo)E genotype with plasma apo E levels

The purpose of this study was to investigate the effects of apolipoprotein (apo) E genotype on plasma apo E levels as well as serum total, low-density lipoprotein (LDL) cholesterol, high-density lipoprotein (HDL) cholesterol, triglyceride, and glucose values in 734 middle-aged and elderly, female and male subjects. Apo E allele frequencies were similar to those reported in other Caucasian populations. After adjustment for medications, alcohol use, smoking, age, and body mass index, apo E genotype was noted to have significant effects on apo E, total cholesterol, LDL cholesterol, and glucose levels in females, and on apo E, LDL cholesterol, and HDL cholesterol levels, as well as the total cholesterol (TC)/HDL cholesterol ratio in males. Female and male subjects with the apo E4 allele had significantly (P<0.05) lower plasma apo E (25 and 15%) and higher LDL cholesterol levels (5 and 2%), while those with the apo E2 allele had significantly (P<0.05) higher apo E (32 and 27%) and lower LDL cholesterol levels (10 and 10%) than the apo E3/3 group. Moreover, female apo E4 carriers had significantly (P<0.05) lower glucose values (11%) than the apo E3/3 group. These data are consistent with the concept that, in addition to the well known effects of apo E genotype on LDL-C values, this locus plays a very significant role in modulating plasma apo E levels.     

Effects of intravenous apolipoprotein A-I/phosphatidylcholine discs on paraoxonase and platelet-activating factor acetylhydrolase in human plasma and tissue fluid

We have previously shown that intravenous apolipoprotein (apo) A-I/phosphatidylcholine (apo A-I/PC) discs increase plasma high-density lipoprotein (HDL) concentration in humans. We have now studied the associated changes in two enzymes, paraoxonase (PON) and platelet-activating factor acetylhydrolase (PAF-AH) that are carried in whole or in part by HDLs, and are thought to influence atherogenesis by hydrolyzing oxidized phospholipids in lipoproteins. Apo A-I/PC discs (40 mg/kg over 4 h) were infused into eight healthy males. Although plasma apo A-I and HDL cholesterol increased on average by 178 and 158%, respectively, plasma total PON and total PAF-AH concentrations did not rise. By the end of the infusion, HDL-associated PAF-AH had increased by 0.56 +/- 0.14 microg/mL (mean +/- S.D., P < 0.01), and nonHDL-associated PAF-AH had decreased by 0.84 +/- 0.11 microg/mL (P < 0.05). These changes were accompanied by an increase in the HDL-associated PAF-AH/apo A-I ratio from 0.19 to 0.35 (P < 0.05), and by a decrease in the nonHDL-associated PAF-AH/apo B ratio from 2.1 to 1.4 (P < 0.05). No changes in PON or PAF-AH concentrations were detected in prenodal lymph (tissue fluid), collected continuously from the leg. Our results show that the total concentrations of PON and PAF-AH in plasma are uninfluenced by plasma HDL concentration. PAF-AH transfers readily between HDLs and LDLs in vivo, and its distribution between them is determined partly by their relative concentrations and partly by HDL composition.     

Chronic hypothyroidism induces abnormal structure of high-density lipoproteins and impaired kinetics of apolipoprotein A-I in the rat

Abnormal levels of plasma high-density lipoproteins (HDL) commonly reflect altered metabolism of the major HDL-apolipoprotein A-I (apo A-I). It is well known that thyroid hormones are involved in the regulation of lipoprotein metabolism, inducing significant changes in the concentration, size, and composition of plasma HDL. The purpose of this study was to evaluate the mechanisms responsible of the decreased HDL-apo A-I in chronic thyroidectomized rats (Htx) and to assess the role of HDL structure in apo A-I turnover. Htx rats were found to have a 3-fold increase in low-density lipoprotein-cholesterol (LDL-C), whereas HDL-C and apo A-I showed a 25.9% and 22.6% decrease compared to controls (P <.05), thus suggesting a defect in HDL metabolism. Turnover studies of apo A-I incorporated into normal HDL, using exogenous (125)I-radiolabeling, confirmed an altered fractional catabolic rate (FCR) in Htx rats (0.097 +/- 0.009 d(-1) v 0.154 +/- 0.026 d(-1) for Htx and control rats, respectively, P <.005). Apo A-I production rates calculated with autologous HDL data showed that apo A-I synthesis was decreased to a higher extent than the already reduced apo A-I catabolism, thus explaining the low apo A-I plasma levels in Htx rats. Composition analysis of HDL-Htx revealed increased phospholipid and apo E content, whereas apo A-IV was diminished. Such structural changes contribute to the reduced apo A-I catabolism as demonstrated with further kinetic turnover studies in normal rats treated with (125)I-radiolabeled apo A-I reincorporated into HDL isolated from plasma of Htx rats (FCR, 0.102 +/- 0.017 v 0.154 +/- 0.026 d(-1), for Htx and normal rats, respectively, P <.005). In summary, chronic hypothyroidism in rat a species that lacks cholesteryl ester transfer protein (CETP) activity is characterized by low HDL-C and apo A-I plasma levels as a result of a low apo A-I production rate that exceeds a decreased FCR. Both structural abnormalities of HDL and changes induced in the animal that affect HDL catabolism contribute to the low FCR of apo A-I in the hypothyroid state.     

Separation of three compositionally distinct subclasses of rat high density lipoproteins by heparin-affinity chromatography

The composition of 3 subclasses of plasma high density lipoproteins (HDL) separated by heparin-affinity chromatography was characterized. Plasma was obtained from Fischer-344 adult male rats fed a semi-purified diet containing 1 % cholesterol. HDL particles were isolated by ultracentrifugation and agarose column chromatography. The purified HDL fraction was applied to a column (1.0 × 28 cm) packed with heparin-Sepharose CL-6B and eluted at 4°C with 5 mM Tris buffer (pH 7.4) with varying concentrations of NaCl. The first peak (PI) eluted with 50 mM NaCl and 25 mM MnCl₂ was albumin; the second peak (P2) eluted at 70 mM NaCl accounted for 78% of total plasma HDL-cholesterol (HDL-C) and 82% of total HDL protein. The particles of this HDL subclass measured 113 A in diameter and were devoid of apolipoprotein (apo) E, but high in apo A-1. The third peak (P3) eluted with 290 mM NaCl represented 4.3% of total HDL-C and 6.0% of total HDL protein, and contained apo E (25% of its protein). The average size of the particles was 126 Å. The last peak (P4) eluted at 0.6 M NaCl accounted for 18% of total HDL-C and 12% of HDL protein. The particles of P4 were considerably larger in size (156 Å) relative to those of P2 and P3, and rich in apo E (73% of its protein) with relatively low concentrations of apo A-1 and C. Based on the compositional characteristics and sizes of the particles, the HDL subclasses of P2, P3 and P4 were designated as HDL₂ with no apo E, HDL₂ with moderate apo E, and HDL₁ (or HDL_c), respectively. The above results provide evidence for the existence of 3 compositionally distinct subclasses of plasma HDL in the rat, which may differ with regard to their roles in the transport and metabolism of cholesterol.     

Accelerated turnover of very low density lipoprotein triglycerides in chronic alcohol users. A possible mechanism for the up-regulation of high density lipoprotein by ethanol

The concentration of high density lipoproteins (HDL) is related to the catabolism of triglyceride-rich lipoproteins. In order to elucidate the mechanisms by which alcohol increases plasma HDL levels we measured the turnover kinetics of very low density lipoprotein (VLDL) triglycerides in 10 alcoholic men without liver disease and in nonalcoholic control men matched for age, weight and plasma VLDL triglyceride level. The study was repeated in the alcoholics after a 2-week abstinence period. The alcoholic men had elevated HDL cholesterol but reduced low density lipoprotein (LDL) cholesterol as compared to the controls. The fractional catabolic rate and the total turnover (production) rate of VLDL triglycerides were both significantly increased (P less than 0.05) in the alcoholic men before abstinence. After withdrawal of alcohol both the synthetic rate and the catabolic rate of VLDL triglycerides returned to normal and the HDL (HDL2 and HDL3) cholesterol fell. The per cent decrease in HDL2 cholesterol during abstinence was positively correlated to the respective fall of VLDL triglyceride fractional catabolic rate (r = +0.51). The results suggest that the absence of hypertriglyceridemia and the elevated levels of HDL in regular alcohol users may be partly based on increased metabolic clearance of VLDL particles and on subsequent accelerated transfer of the VLDL surface components to HDL.     

Liver Galbeta1,4GlcNAc alpha2,6-sialyltransferase is down-regulated in human alcoholics: possible cause for the appearance of asialoconjugates

Galbetal,4GlcNAc alpha2,6-sialyltransferase (ST6GalI) mediates the glycosylation of proteins and lipids to form functionally important glycoproteins and glycolipids in the Golgi compartment. Our previous work demonstrated that long-term ethanol feeding in rats caused a marked 59% decrease in ST6GalI activity as well as ST6GalI messenger RNA (mRNA) level in the liver that was due to decreased stability of the mRNA. Clinical observations show that down-regulation of ST6GalI gene and consequent impaired activity of ST6GalI seems to be the major cause for the appearance of asialoconjugates in the blood of long-term alcoholics. The plasma carbohydrate-deficient transferrin (CDT) and sialic acid index of plasma apolipoprotein J were also altered in the alcoholic group compared with the nondrinkers. We have now investigated how alcohol affects the gene regulation of ST6GalI and the possible mechanism in postmortem human liver specimens taken from nondrinkers, moderate alcohol drinkers, and heavy alcohol drinkers. Real-time polymerase chain reaction analyses of the liver RNA extract showed that ST6GalI mRNA level was progressively decreased by 49% in moderate drinkers (P < .01) and by 69% in heavy drinkers (P < .01) compared with nondrinkers. Western blot analysis showed that liver ST6GalI protein level was negligibly decreased in moderate drinkers but decreased by 30% (P < .05) in heavy drinkers compared with nondrinkers. We further demonstrated a single ST6GalI mRNA-binding protein complex in the normal human liver extract, which progressively decreased in the liver extracts of moderate and heavy alcohol drinkers. Thus, it is concluded that the appearance of asialoconjugates in alcoholics is possibly due to the down-regulation of ST6GalI gene expression.     

Reverse cholesterol transport: High-density lipoprotein’s magnificent mile

High-density lipoproteins (HDLs) are among the most structurally complex and functionally versatile forms of circulating serum lipoproteins. HDLs undergo extensive enzymatic remodeling during their maturation in serum, interact with highly specific receptors in peripheral tissues and the liver, and are able to exert a variety of antiatherogenic effects (eg, inhibit inflammation, oxidation, and apoptosis). Considerable epidemiologic, clinical, and basic scientific investigation supports the conclusion that HDLs as a molecular class are atheroprotective. One of the most important antiatherogenic functions of HDL is its capacity to drive reverse cholesterol transport, the process by which excess cholesterol in peripheral tissues is extracted and delivered to the liver for disposal. Despite the rapid expansion in our understanding of how HDL antagonizes many of mechanisms etiologic for atherosclerosis and the observation that a low serum level of HDL is the most frequent lipid abnormality in patients with premature coronary artery disease, many physicians still focus inadequate attention on recognizing and treating hypoalphalipoproteinemia. Our current understanding of reverse cholesterol transport reinforces the clinical importance of including HDL screening when evaluating any given patient’s risk for cardiovascular disease.     

Independent effects of liver disease and chronic alcoholism on thyroid function and size: the possibility of a toxic effect of alcohol on the thyroid gland

In an autopsy study we found thyroid volume significantly decreased in alcoholics with liver cirrhosis as compared to matched controls: 15 mL (range, 7 to 37 mL) v 25 mL (range, 13 to 90 mL) (P less than .01). At the same time the amount of fibrosis of the thyroid glands was higher in the alcoholics as compared to the matched controls: 20% (range, 6% to 40%) v 12% (range, 6% to 23%) (P less than .01). In order to evaluate the relative importance of alcohol consumption and liver disease on thyroid function and ultrasonically determined size, three groups of patients and matched controls (sex, age, weight, and smoking habits) were investigated: group 1, 18 patients with nonalcoholic liver cirrhosis; group 2, 21 consecutive chronic alcoholics (greater than 100 g of alcohol daily for greater than 5 years) without liver cirrhosis (all had biopsy proven fatty change or normal liver); group 3, 31 nonalcoholic patients with chronic nonhepatic, nonrenal disease. In group 1 median thyroid volume and serum FT4I, FT3I, and TSH levels were unchanged compared with the controls. In group 2 median thyroid volume was 13 mL (range, 9 to 32 mL) compared with 27 mL (range, 12 to 44 mL) in the controls (P less than .005). Serum T3 and FT3I levels were reduced, while T4, FT4I, and TSH levels were unaltered. In group 3 serum T3 and FT3I levels were reduced while serum FT4I and TSH levels and thyroid volume were unaltered compared with the controls. It is suggested that alcohol may have a toxic effect on the thyroid gland independent of the degree of liver damage.     

Apolipoprotein E polymorphism modulates the association between obesity and dyslipidemias during young adulthood: The Bogalusa Heart Study

To elucidate to what extent apolipoprotein (apo) E polymorphism modulates obesity-induced dyslipidemias during young adulthood, longitudinal data on 759 individuals (72% white/28% black; initial and follow-up mean age, 25.9 and 32.7 years) were examined. Among both races and the total sample, the apo E2 group (with E2/2 or E2/3 phenotype) had significantly lower and the apo E4 (with E4/4 or E3/4 phenotype) group higher low-density lipoprotein (LDL) cholesterol than the apo E3 (with E3/3 phenotype) group at both examinations. In addition, the apo E2 group displayed higher high-density lipoprotein (HDL) cholesterol in the total sample. No allele-specific effect was noted for the longitudinal changes (Delta). An increase in Delta adiposity, measured as Delta body mass index (BMI), was accompanied by higher increase in Delta LDL cholesterol in the e4 carriers than the e2 carriers among the whites (P <.05) and the total sample (P <.01); an increase in Delta triglycerides and decrease in Delta HDL cholesterol in the e2 carriers than the e4 carriers among all the groups (P <.05 to.001). Among the apo E phenotype groups, the incidence of high (>75th percentile specific for race and sex) LDL cholesterol at follow-up was in the order E4 > E3 > E2 both in the obese (BMI > 30; P for trend =.033) and the nonobese (BMI < 25; P for trend =.035) groups. Although the increase of low (<25th percentile specific for race and sex) HDL cholesterol or high triglycerides showed no apo E phenotype-specific trend, the incidence of high triglycerides without high LDL cholesterol was in the order E2 > E3 > E4 only in the obese group (P for trend =.025). The prevalence trend for dyslipidemias at follow-up among the persistently obese and nonobese groups also gave similar results. Thus, apo E gene locus influences not only the levels of certain lipoprotein variables during young adulthood, but also modulates the association between obesity and dyslipidemias.     

Effect of Apolipoprotein E Phenotype on Plasma Lipids and Lipoproteins in Alcohol Abusers

The effect of apolipoprotein (apo) E phenotype on the concentration and chemical composition of plasma lipoproteins was studied in 73 male alcohol abusers and 50 male controls. The apo E phenotype was confirmed by genotyping to avoid possible effects of posttrans-lational modifications by alcohol or its metabolites. The lipid and protein concentrations of both intermediate density lipoprotein and low density lipoprotein were lower among the alcohol abusers than among the controls, those with E4 having the highest low density lipoprotein masses in both groups. In the alcohol abusers with E4 only the high density lipoprotein (HDL)-2 lipid and protein concentrations were higher than in the controls with respective phenotype group, whereas both HDL₂ and HDL₃ were higher in alcohol abusers with other apo E phenotypes, suggesting that apo E modulates the alcohol-effect on HDL subfractions. This effect was not explained by cholestetyl ester transfer protein activity, which was lower in the alcohol abusers (25 to 34%, p < cOm), but without significant difference between the apo E groups. In conclusion, alcohol abuse does not cause major changes in the electric charge of apo E in humans. Heavy alcohol intake seems to have a beneficial effect on plasma lipids and lipoproteins, regardless of the apo E phenotype, but the modulation of the alcohol-induced increase in HDL by apo E phenotype should be taken into consideration in future studies. Key Words: Alcohol, Apolipoprotein E, HDL, LDL, VLDL.