Low-density lipoproteins in hyperalphalipoproteinemic heavy alcohol drinkers have reduced affinity for the low-density lipoprotein receptor

A Proposal for the Optimal Management Target for Serum Non-High-Density Lipoprotein Cholesterol Level in Low-Risk Japanese Workers

AIM

The Japan Atherosclerosis Society Guidelines for the Diagnosis and Prevention of Atherosclerotic Cardiovascular Diseases 2012 (JAS Guidelines 2012) indicate that the management target for serum non-high-density lipoprotein cholesterol (non-HDLC) level is 30 mg/dL higher than that for low-density lipoprotein cholesterol (LDLC) level. However, it remains unclear whether this value is applicable to subjects at a low risk of cardiovascular disease. This study aimed to propose the optimal management target for serum non-HDLC level in low-risk Japanese subjects.

METHODS

Among 20,909 subjects who underwent annual medical checkup at a Japanese company in 2008, we analyzed the data of 17,023 subjects (14,352 men, mean age 37.8±8.6 years) in risk category I according to the JAS Guidelines 2012. The correlation between LDLC and non-HDLC levels was examined.

RESULTS

A strong correlation was found between LDLC and non-HDLC levels (r=0.95, p<0.001). The following regression equation for calculation of non-HDLC was obtained from linear regression analysis: non-HDLC (mg/dL)=1.09×LDLC (mg/dL)＋7.79. According to this equation, the optimal management target for non-HDLC level corresponding to that for LDLC level (160 mg/dL) was 180 mg/dL. A multiple logistic regression analysis revealed that age, obesity, habitual alcohol intake, and current smoking were significantly associated with non-HDLC ≥180 mg/dL.

CONCLUSIONS

The management target for non-HDLC level is recommended to be set at 20 mg/dL higher than that for the LDLC level (i.e., 180 mg/dL) in low-risk Japanese subjects.

Alcohol drinking determines the effect of the APOE locus on LDL-cholesterol concentrations in men: the Framingham Offspring Study

BACKGROUND

The effect of alcohol drinking on LDL-cholesterol concentrations is unclear. The reported variability may be due to interactions between genetic factors and alcohol intake.

OBJECTIVE

The purpose of the study was to examine whether variation at the apolipoprotein E gene (APOE) locus modulates the association between alcohol drinking and LDL cholesterol.

DESIGN

We used a cross-sectional design in a healthy population-based sample of 1014 men and 1133 women from the Framingham Offspring Study.

RESULTS

In male nondrinkers (n = 197), LDL cholesterol was not significantly different across APOE allele groups [APOE*E2 (E2), APOE*E3 (E3), and APOE*E4 (E4)]. However, in male drinkers (n = 817), differences were observed (P: < 0.001); those with the E2 allele had the lowest concentrations. LDL cholesterol in men with the E2 allele was significantly lower in drinkers than in nondrinkers but was significantly higher in drinkers than in nondrinkers in men with the E4 allele. This APOE-alcohol interaction remained significant (P < 0.001) after age, body mass index, smoking status, and fat and energy intakes were controlled for. In women, the expected effect of APOE alleles on LDL cholesterol occurred in both drinkers (n = 791; P < 0.001) and nondrinkers (n = 342; P < 0.001). Multiple linear regression models showed a negative association (P < 0.05) between alcohol and LDL cholesterol in men with the E2 allele but a positive association in men with the E4 allele. No significant associations were observed in men or women with the E3 allele.

CONCLUSION

In men, the effects of alcohol intake on LDL cholesterol are modulated in part by variability at the APOE locus.

The health benefits of wine

Epidemiologic studies from numerous disparate populations reveal that individuals with the habit of daily moderate wine consumption enjoy significant reductions in all-cause and particularly cardiovascular mortality when compared with individuals who abstain or who drink alcohol to excess. Researchers are working to explain this observation in molecular and nutritional terms. Moderate ethanol intake from any type of beverage improves lipoprotein metabolism and lowers cardiovascular mortality risk. The question now is whether wine, particularly red wine with its abundant content of phenolic acids and polyphenols, confers additional health benefits. Discovering the nutritional properties of wine is a challenging task, which requires that the biological actions and bioavailability of the >200 individual phenolic compounds be documented and interpreted within the societal factors that stratify wine consumption and the myriad effects of alcohol alone. Further challenge arises because the health benefits of wine address the prevention of slowly developing diseases for which validated biomarkers are rare. Thus, although the benefits of the polyphenols from fruits and vegetables are increasingly accepted, consensus on wine is developing more slowly. Scientific research has demonstrated that the molecules present in grapes and in wine alter cellular metabolism and signaling, which is consistent mechanistically with reducing arterial disease. Future research must address specific mechanisms both of alcohol and of polyphenolic action and develop biomarkers of their role in disease prevention in individuals.

Molecular mechanisms, lipoprotein abnormalities and atherogenicity of hyperalphalipoproteinemia

Hyperalphalipoproteinemia (HALP) is caused by a variety of genetic and environmental factors. Among these, plasma cholesteryl ester transfer protein (CETP) deficiency is the most important and frequent cause of HALP in the Asian populations. CETP facilitates the transfer of cholesteryl ester (CE) from high density lipoprotein (HDL) to apolipoprotein (apo) B-containing lipoproteins, and is a key protein in the reverse cholesterol transport system. The deficiency of CETP causes various abnormalities in the concentration, composition, and function of both HDL and low density lipoprotein (LDL). The significance of CETP in terms of atherosclerosis had been controversial. However, the in vitro evidence showed large CE-rich HDL particles in CETP deficiency are defective in cholesterol efflux. Similarly, scavenger receptor BI (SR-BI) knockout mice show a marked increase in HDL-cholesterol but accelerated atherosclerosis in atherosclerosis-susceptible mice. Recent epidemiological studies in Japanese-Americans and in Omagari area where HALP subjects with the intron 14 splicing defect of CETP gene are markedly frequent, have demonstrated an increased incidence of coronary atherosclerosis in CETP-deficient patients. Thus, CETP deficiency is a state of impaired reverse cholesterol transport which may possibly lead to the development of atherosclerosis. The current review will focus on the molecular mechanisms and atherogenicity of HALP, especially CETP deficiency.

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.

Genetic cholesteryl ester transfer protein deficiency is extremely frequent in the Omagari area of Japan. Marked hyperalphalipoproteinemia caused by CETP gene mutation is not associated with longevity

Low levels of HDL cholesterol have been clearly demonstrated to be associated with an increased incidence of coronary heart disease, strongly suggesting that HDL particles have an antiatherogenic function. However, little information has been available concerning the atherogenicity of a marked hyperalphalipoproteinemia (HALP). There is no agreement about whether plasma cholesteryl ester transfer protein (CETP) deficiency is associated with an antiatherogenic state or not, although this disorder was reported to be one of the major causes of marked HALP. In the current study, we have found a unique area (Omagari City, Akita Prefecture, Japan) where CETP deficiency caused by a G-to-A mutation at the 5' splice donor site of intron 14 in the CETP gene is extremely frequent. In Omagari City, the mutation was detected more than 20 times more frequently and the prevalence of a marked HALP with plasma HDL cholesterol > or = 2.58 mmol/L (100 mg/dL) was 5 to 10 times higher than in other areas of Japan. This discovery has made it possible to perform a large population-based study concerning the atherogenicity of a marked elevation of HDL cholesterol in a genetically more homogeneous population. There was a statistically significant U-shaped relationship between HDL cholesterol levels and the incidence of ischemic changes in electrocardiograms. In cases of HDL cholesterol < 1.81 mmol/L (70 mg/dL), the incidence increased in proportion to the levels of HDL cholesterol. The frequency of the CETP gene mutation was higher in patients with coronary heart disease than in healthy control subjects. In subjects aged > 80 years, the prevalence of both marked HALP and the intron 14 splicing defect was significantly lower than in the younger generation. The current study indicated for the first time that a marked HALP caused by CETP gene mutation may not represent a longevity syndrome, suggesting the importance of reevaluation of the clinical significance and pathophysiology of a marked HALP.

Increased catabolic rate of low density lipoproteins in humans with cholesteryl ester transfer protein deficiency

The cholesteryl ester transfer protein (CETP) transfers lipids among lipoprotein particles and plays a central role in lipoprotein metabolism. Humans with genetic deficiency of CETP have both elevated HDL cholesterol and apolipoprotein A-I concentrations as well as decreased LDL cholesterol and apolipoprotein B levels. The present study was undertaken to elucidate the metabolic basis for the decreased LDL cholesterol and apo B levels in CETP deficiency. We conducted a series of in vivo apo B kinetic studies in tow unrelated homozygotes with CETP deficiency and in control subjects. A primed constant infusion of stable isotopically labeled phenylalanine was administered to the two CETP deficient subjects and control subjects and apo B kinetic parameters in VLDL, intermediate density lipoproteins, and LDL were obtained by using a multicompartmental model. The fractional catabolic rates (FCR) of LDL apo B were significantly increased in the CETP-deficient subjects (0.56 and 0.75/d) compared with the controls (mean FCR of 0.39/d). Furthermore, the production rates of apo B in VLDL and intermediate density lipoprotein were decreased by 55% and 81%, respectively, in CETP deficiency compared with the controls. In conclusion, CETP-deficient subjects were demonstrated to have substantially increased catabolic rates of LDL apo B as the primary metabolic basis for the low plasma levels of LDL apo B. This result indicates that the LDL receptor pathway may be up-regulated in CETP deficiency.

Increased plasma cholesteryl ester transfer protein in obese subjects. A possible mechanism for the reduction of serum HDL cholesterol levels in obesity

It is well known that obesity is frequently associated with low levels of serum high-density lipoprotein (HDL) cholesterol. However, the mechanism for this reduction has not been fully clarified. Cholesteryl ester transfer protein (CETP) transfers cholesteryl ester from HDL to apolipoprotein B-containing lipoproteins and plays an important role in regulating the concentration and composition of HDL. To elucidate the mechanism for the reduction of serum HDL cholesterol in obesity, we analyzed serum lipoproteins, CETP, and postheparin lipoprotein lipase (LPL) and hepatic triglyceride lipase (HTGL) activities in 30 obese subjects (17 women and 13 men, age 44 +/- 14 years, mean +/- SD). We also investigated the relationship between these variables, total adiposity, and indices of body fat distribution. The average body mass index of the obese subjects was 33.1 +/- 4.8 kg/m2 (range, 26.4 to 43.8 kg/m2). The obese subjects showed significantly lower serum HDL cholesterol levels than control subjects (1.04 +/- 0.28 versus 1.50 +/- 0.34 mmol/L, P < .01). In the obese subjects, both activities and protein mass of CETP and postheparin HTGL activities were significantly increased, whereas postheparin LPL activities were significantly decreased. CETP activities, independent of postheparin HTGL and LPL activities, were correlated negatively with HDL cholesterol (r = -.39, P < .05) and the cholesteryl ester to triglyceride ratio of HDL2 and HDL3 (r = -.36, P < .05; r = -.46, P < .05, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

Frequency of intron 14 splicing defect of cholesteryl ester transfer protein gene in the Japanese general population--relation between the mutation and hyperalphalipoproteinemia

Cholesteryl ester transfer protein (CETP) deficiency, which has been found only in Japan, is characterized by marked hyperalphalipoproteinemia (HALP) and abnormalities of both low density and high density lipoproteins. We have reported that this deficiency is commonly associated with a G-->A mutation at the intron 14 splice donor site of the CETP gene (Yamashita et al., Biochem. Biophys. Res. Commun., 170 (1990) 1346-1351). In the current study, we determined the frequency of this mutation in Japanese subjects by using polymerase chain reaction. A single primer-template mismatch of one base pair from the CETP gene mutation permitted the introduction of a cleavage site for Nde I in mutant alleles but not in normal ones. Out of 171 patients with marked HALP whose serum HDL-cholesterol was more than 100 mg/dl, 6 (3.5%) subjects were homozygous and 48 (28.1%) were heterozygous for this mutation. Furthermore, in unrelated 512 healthy Japanese subjects, 5 (0.98%) were identified as heterozygotes. Relative allelic frequency of A at the intron 14 splice donor site was 0.0049 and the frequency of homozygous CETP deficiency was estimated to be approximately 1/42,000. These results demonstrate that this common mutation may be frequent in the Japanese population. Although HALP is very heterogenous, this mutation could be one of the major causes of marked HALP.