Mendelian randomization analysis in three Japanese populations supports a causal role of alcohol consumption in lowering low-density lipid cholesterol levels and particle numbers

Alcohol Consumption and Cerebral Small- and Large-Vessel Diseases: A Mendelian Randomization Analysis

AIMS

It remains inconclusive regarding alcohol intake and stroke risk because determining risk factors depends on the specific pathogenesis of stroke. We used the variant rs671 in the aldehyde dehydrogenase 2 gene (ALDH2) as an instrument to investigate the causal role of alcohol intake in cerebral small- and large-vessel diseases.

METHODS

We studied 682 men (mean age, 70.0 years), without stroke, in a cross-sectional Mendelian randomization analysis. We assessed small-vessel diseases (SVDs), which comprised lacunar infarcts, white matter hyperintensities (WMHs), and cerebral microbleeds, and large intracranial artery stenosis (ICAS) on brain magnetic resonance imaging.

RESULTS

The median (25%tiles, 75%tiles) alcohol consumption by ALDH2-rs671 inactive A allele (n=313 [45.9%]) and non-A allele (n=369 [54.1%]) carriers was 3.5 (0.0, 16.0) and 32.0 (12.9, 50.0) g/day, respectively. Non-A allele carriers had higher prevalent hypertension and lower low-density lipoprotein cholesterol concentrations than A allele carriers. In age-adjusted ordinal logistic regression for graded burden, odds ratios (95% confidence intervals) for total SVDs, lacunar infarcts, WMHs, cerebral microbleeds, and ICAS in non-Aallele carriers were 1.46 (1.09-1.94), 1.41 (0.95-2.08), 1.39 (1.05-1.85), 1.69 (1.06-2.69), and 0.70 (0.50-0.98), respectively, compared with A allele carriers. These associations attenuated to statistical non-significance after considering covariates and amount of alcohol intake.

CONCLUSIONS

Our findings suggest a positive association of alcohol consumption with risk of cerebral SVDs and its inverse association with risk of large-vessel disease through intermediaries, such as hypertension or low-density lipoprotein cholesterol. These findings provide insight into potential causal mechanisms linking alcohol consumption with stroke risk.

Association between Dietary Patterns and Serum Low Density Lipoprotein Cholesterol in Japanese Women and Men: The Japan Multi-Institutional Collaborative Cohort (J-MICC) Study

AIMS

The association between dietary patterns and serum low density lipoprotein (LDL) cholesterol would be changing in recent dietary habits in Japan. We investigated the relationship between dietary patterns and serum LDL cholesterol in a large general population.

METHODS

From the baseline survey of Japan Multi-Institutional Collaborative Cohort Study between 2005 and 2013, 27,237 participants (13,994 were women) aged 35-69 years were cross-sectionally analyzed. Using a semi-quantitative food frequency questionnaire, five major sex-specific dietary patterns were identified using factor analysis. We assessed serum LDL cholesterol by quintiles of dietary pattern factor score.

RESULTS

We identified dietary patterns; "vegetable rich pattern" , "meat and fried food rich pattern" and "high bread and low rice pattern" in women and men; "fish and shellfish rich pattern" and "high confectioneries and low alcohol pattern" in men; "healthy Japanese diet pattern" and "high alcohol and low rice pattern" in women. Serum LDL cholesterol in men was associated with "high bread and low rice pattern" score (Q5 was 4.2 mg/dL higher than Q1, p for trend ＜0.001) and "high confectioneries and low alcohol pattern" scores (Q5 was 9.5 mg/dL higher than Q1, p for trend ＜0.001). In women, serum LDL cholesterol was associated with "high bread and low rice pattern" score (Q5 was 7.1 mg/dL higher than Q1, p for trend ＜0.001).

CONCLUSION

Some recent dietary patterns in Japan were associated with serum LDL cholesterol. Serum LDL cholesterol was associated with high bread and low rice pattern in both sex, and high confectioneries and low alcohol pattern in men.

The role of aldehyde dehydrogenase 2 in cardiovascular disease

Aldehyde dehydrogenase 2 (ALDH2) is a mitochondrial enzyme involved in the detoxification of alcohol-derived acetaldehyde and endogenous aldehydes. The inactivating ALDH2 rs671 polymorphism, present in up to 8% of the global population and in up to 50% of the East Asian population, is associated with increased risk of cardiovascular conditions such as coronary artery disease, alcohol-induced cardiac dysfunction, pulmonary arterial hypertension, heart failure and drug-induced cardiotoxicity. Although numerous studies have attributed an accumulation of aldehydes (secondary to alcohol consumption, ischaemia or elevated oxidative stress) to an increased risk of cardiovascular disease (CVD), this accumulation alone does not explain the emerging protective role of ALDH2 rs671 against ageing-related cardiac dysfunction and the development of aortic aneurysm or dissection. ALDH2 can also modulate risk factors associated with atherosclerosis, such as cholesterol biosynthesis and HDL biogenesis in hepatocytes and foam cell formation and efferocytosis in macrophages, via non-enzymatic pathways. In this Review, we summarize the basic biology and the clinical relevance of the enzymatic and non-enzymatic, tissue-specific roles of ALDH2 in CVD, and discuss the future directions in the research and development of therapeutic strategies targeting ALDH2. A thorough understanding of the complex roles of ALDH2 in CVD will improve the diagnosis, management and prognosis of patients with CVD who harbour the ALDH2 rs671 polymorphism.

Low cholesterol states: clinical implications and management

INTRODUCTION

Hypocholesterolemia results from genetic - both monogenic and polygenic - and non-genetic causes and can sometimes be a source of clinical concern. We review etiologies and sequelae of hypocholesterolemia and therapeutics inspired from genetic hypocholesterolemia.

AREAS COVERED

Monogenic hypocholesterolemia disorders caused by the complete absence of apolipoprotein (apo) B-containing lipoproteins (abetalipoproteinemia and homozygous hypobetalipoproteinemia) or an isolated absence of apo B-48 lipoproteinemia (chylomicron retention disease) lead to clinical sequelae. These include gastrointestinal disturbances and severe vitamin deficiencies that affect multiple body systems, i.e. neurological, musculoskeletal, ophthalmological, and hematological. Monogenic hypocholesterolemia disorders with reduced but not absent levels of apo B lipoproteins have a milder clinical presentation and patients are protected against atherosclerotic cardiovascular disease. Patients with heterozygous hypobetalipoproteinemia have somewhat increased risk of hepatic disease, while patients with PCSK9 deficiency, ANGPTL3 deficiency, and polygenic hypocholesterolemia typically have anunremarkable clinical presentation.

EXPERT OPINION

In patients with severe monogenic hypocholesterolemia, early initiation of high-dose vitamin therapy and a low-fat diet are essential for optimal prognosis. The molecular basis of monogenic hypocholesterolemia has inspired novel therapeutics to help patients with the opposite phenotype - i.e. elevated apo B-containing lipoproteins. In particular, inhibitors of PCSK9 and ANGPTL3 show important clinical impact.

Effects of the genetic variants of alcohol-metabolizing enzymes on lipid levels in Asian populations: a systematic review and meta-analysis

CONTEXT

Emerging evidence indicates that variants of alcohol-metabolizing enzymes may influence lipid metabolism.

OBJECTIVE

This study aimed to investigate whether the rs671 and rs1229984 variants affect lipid levels in East Asian individuals.

DATA SOURCES

PubMed, Foreign Medical Journal Service, Embase, Cochrane Library, Scopus, MEDLINE, Web of Science, Web of Knowledge, Wanfang, and Chinese Biomedical Literature databases were searched until December 31, 2021.

DATA EXTRACTION

Meta-analyses of studies that examined the effects of alcohol-metabolizing enzyme variants on lipid levels, as well as the interaction with alcohol intake, were selected. Data extraction was conducted independently by two investigators and confirmed by the third.

DATA ANALYSIS

In total, 86 studies (179 640 individuals) were analyzed. The A allele of rs671 (a functional variant in the ALDH2 gene) was linked to higher levels of low-density lipoprotein cholesterol (LDL-C) and lower levels of triglycerides and high-density lipoprotein cholesterol. In contrast, the A allele of the rs1229984 (a functional variant in the ADH2 gene) was associated only with lower levels of LDL-C. The effects of rs671 and rs1229984 on lipid levels were much stronger in Japanese than in Chinese individuals and in males than in females. Regression analysis indicated that the effects of rs671 on lipid levels were independent of alcohol intake in an integrated East Asian population (ie, Japanese, Chinese, and Korean individuals). Intriguingly, alcohol intake had a statistical influence on lipid levels when the sample analyzed was restricted to Japanese individuals or to males.

CONCLUSIONS

The rs671 and rs1229984 variants of alcohol-metabolizing enzymes have significant effects on lipid levels and may serve as genetic markers for lipid dyslipidemia in East Asian populations. Circulating lipid levels in Japanese individuals and in males were modulated by the interaction between rs671 and alcohol intake.

Alcohol consumption and subclinical and clinical coronary heart disease: A Mendelian randomization analysis

AIMS

The potential effect of alcohol consumption on coronary heart disease (CHD) remains unclear. We used the variant rs671 in the aldehyde dehydrogenase 2 gene (ALDH2) as an instrument to investigate the causal role of alcohol intake in subclinical and clinical CHD.

METHODS

We conducted two Mendelian randomization studies: a cross-sectional study of coronary artery calcification (CAC) on computed tomography of 1029 healthy men (mean age, 63.8 years) and a case-control study of 421 men with CHD (acute coronary syndrome [ACS] or stable angina pectoris) who underwent coronary revascularization and 842 age-matched male controls.

RESULTS

In the CAC study, medians (25%tiles, 75%tiles) of alcohol consumption by ALDH2-rs671 *2 homozygotes (n = 86 [8.4%]), *1*2 heterozygotes (n = 397 [38.5%]), and *1 homozygotes (n = 546 [53.1%]) were 0.0 (0.0, 0.0), 28.0 (0.0, 129.0), and 224.0 (84.0, 350.0) g/week, respectively. In age-adjusted Poisson regression with robust error variance, compared with *2 homozygotes, relative risks for prevalent CAC score >0, ≥100, and ≥300 in *1 homozygotes were 1.29 (95% confidence interval, 1.06-1.57), 1.76 (1.05-2.96), and 1.81 (0.80-4.09), respectively. In age-adjusted ordinal logistic regression for CAC distributions, we observed higher odds among *1 homozygotes (odds ratio, 2.19 [1.39-3.46]) and even among *1*2 heterozygotes (1.77 [1.11-2.82]) compared with *2 homozygotes. In the case-control study, conditional logistic regression revealed lower prevalence of *1 homozygotes among men with CHD (odds ratio, 0.54 [0.35-0.82]), especially ACS (0.46 [0.27-0.77]), than controls.

CONCLUSION

Our findings indicate a positive association of alcohol consumption with CAC burden but an inverse association with clinical CHD, especially ACS.

Pretransplant and Posttransplant Alcohol Consumption and Outcomes in Kidney Transplantation: A Prospective Multicenter Cohort Study

The impact of pretransplant and posttransplant alcohol consumption on outcomes in kidney transplant recipients (KTRs) is uncertain. Self-reported alcohol consumption was obtained at the time of transplant and 2 years after transplant in a prospective cohort study. Among 907 KTRs, 368 (40.6%) were drinkers at the time of transplant. Compared to non-drinkers, alcohol consumption did not affect the risk of death-censored graft failure (DCGF), biopsy-proven acute rejection (BPAR), cardiovascular events, or all-cause mortality. Compared to persistent non-drinkers, the development of DCGF, BPAR, cardiovascular events, all-cause mortality, or posttransplant diabetes mellitus was not affected by the alcohol consumption pattern (persistent, de novo, or stopped drinking) over time. However, de novo drinkers had a significantly higher total cholesterol (p < 0.001) and low-density lipoprotein cholesterol levels (p = 0.005) compared to persistent non-drinkers 5 years after transplant, and had significantly higher total cholesterol levels (p = 0.002) compared to the stopped drinking group 7 years after transplant, even after adjusting for the use of lipid-lowering agents, age, sex, and body mass index. Although pretransplant and posttransplant alcohol consumption were not associated with major outcomes in KTRs during the median follow-up of 6.0 years, a new start of alcohol use after KT results in a relatively poor lipid profile.

Clinical Trial Registration:clinicaltrials.gov, identifier NCT02042963.

Alcohol consumption in relation to cardiovascular diseases and mortality: a systematic review of Mendelian randomization studies

The causal effects of alcohol-in-moderation on cardiometabolic health are continuously debated. Mendelian randomization (MR) is an established method to address causal questions in observational studies. We performed a systematic review of the current evidence from MR studies on the association between alcohol consumption and cardiometabolic diseases, all-cause mortality and cardiovascular risk factors. We performed a systematic search of the literature, including search terms on type of design and exposure. We assessed methodological quality based on key elements of the MR design: use of a full instrumental variable analysis and validation of the three key MR assumptions. We additionally looked at exploration of non-linearity. We reported the direction of the studied associations. Our search yielded 24 studies that were eligible for inclusion. A full instrumental variable analysis was performed in 17 studies (71%) and 13 out of 24 studies (54%) validated all three key assumptions. Five studies (21%) assessed potential non-linearity. In general, null associations were reported for genetically predicted alcohol consumption with the primary outcomes cardiovascular disease (67%) and diabetes (75%), while the only study on all-cause mortality reported a detrimental association. Considering the heterogeneity in methodological quality of the included MR studies, it is not yet possible to draw conclusions on the causal role of moderate alcohol consumption on cardiometabolic health. As MR is a rapidly evolving field, we expect that future MR studies, especially with recent developments regarding instrument selection and non-linearity methodology, will further substantiate this discussion.

Relationships of Alcohol Consumption with Coronary Risk Factors and Macro- and Micro-Nutrient Intake in Japanese People: The INTERLIPID Study

Several studies have reported a J-shaped relationship between alcohol consumption and coronary heart disease (CHD) risk. However, the mechanisms of this relationship remain unclear. This study aimed to evaluate the relationships of alcohol consumption with established CHD risk factors and with macro-/micro-nutrient intake among Japanese people. Participants were 1,090 Japanese men and women aged 40-59 y enrolled in the INTERLIPID study, excluding former drinkers. Based on two 7-d alcohol records, participants were classified as non-drinkers (0 g/wk), light-drinkers (<100 g/wk), moderate-drinkers (100-299 g/wk), or heavy-drinkers (≥300 g/wk). Detailed macro-/micro-nutrient intake was evaluated using four in-depth 24-h dietary recalls and adjusted for total energy intake excluding alcohol. We analyzed the associations of CHD risk factors and nutrient intake with alcohol consumption. Serum high-density lipoprotein cholesterol and blood pressure were higher and low-density lipoprotein cholesterol was lower among those with higher alcohol consumption. J-shaped relationships with alcohol consumption were observed for the proportion of current smokers, number of cigarettes smoked, and prevalence of hypertension; these risk factors were lowest among light-drinkers. Carbohydrate and total fiber intakes were lower and protein and dietary cholesterol intakes were higher among those with higher alcohol consumption. These associations were similar for men and women. Alcohol consumption was related to nutrient intake as well as established CHD risk factors. Non-drinkers were higher on some CHD risk factors than were light-drinkers. These findings may influence the J-shaped relationship between alcohol consumption and CHD risk.

Benefits and hazards of alcohol-the J-shaped curve and public health

Purpose

The purpose of this paper is a review of updated evidence of a J-shaped association between alcohol consumption and the risk of coronary heart disease (CHD) and all-cause mortality in relation to public health issues to create a basis for sensible individual health deliberations.

Design/methodology/approach

A review of the evidence from the first observation of a J-shaped association between a moderate alcohol intake and CHD in 1926 to recent studies of the effect of healthy lifestyles (including moderate alcohol intake) on life expectancy free of cardiovascular disease (CVD), cancer and Type 2 diabetes. An update on the biological plausibility of the J-shaped association with focus on recent findings of the association of alcohol intake and blood lipid levels.

Findings

Plausible J-shaped relations between light to moderate alcohol consumption and the risk of CHD, CVD mortality and all-cause mortality have been found in a large number of robust epidemiological studies. Among the potential mechanisms underlying the proposed protective effects are higher levels of high-density lipoprotein lacking apolipoprotein C3, reduced platelet aggregability, increased level of endothelial cell fibrinolysis, increased insulin sensitivity and decreased inflammation.

Originality/value

The existence of a J-shaped association between alcohol consumption and the risk of CHD and all-cause mortality is based on observational evidence and accordingly challenged by a degree of uncertainty leading some public health circles to state: “there is no safe level of alcohol consumption.” The authors propose that communication on the pros and cons of alcohol intake should emphasize the nadir of a J-shaped curve as a healthy range for the general population while advice regarding the consumption of alcohol should be adjusted to factor in the risks and potential benefits for each individual patient considering age, sex, family history, personal drinking history and specific medical history.

Alcohol consumption combined with dietary low-carbohydrate/high-protein intake increased the left ventricular systolic dysfunction risk and lethal ventricular arrhythmia susceptibility in apolipoprotein E/low-density lipoprotein receptor double-knockout mice

Alcohol abuse is positively associated with cardiovascular disease. Dietary low-carbohydrate/high-protein (LCHP) intake confers a greater mortality risk. Here, the impact of ethanol consumption in combination with dietary LCHP intake on left ventricular (LV) systolic function and lethal ventricular arrhythmia susceptibility were investigated in apolipoprotein E/low-density lipoprotein receptor double-knockout (AL) mice. The underlying mechanisms, cardiac sympathovagal balance, beta-adrenergic receptor (ADRB) levels, and gap junction channel protein connexin 43 (Cx43) expression, were examined. Male AL mice fed an LCHP diet with or without ethanol were bred for 16 weeks. Age-matched male AL and wild-type mice received standard chow diet and served as controls. The following were used to assess LV systolic function, lethal ventricular arrhythmia susceptibility, cardiac sympathovagal balance, Cx43 expression, and ADRB levels: The results demonstrated that ethanol consumption in combination with dietary LCHP intake worsened LCHP-induced LV systolic dysfunction in AL mice and enhanced their susceptibility in the ventricular arrhythmia-evoked test. There were concomitant increases in LV weight, LF/HF ratio shown by HRV, TH, ADRB1, ADRB2, and Cx43 expressions by LV fluorescence immunohistochemistry, and LV Cx43 messenger ribonucleic acid expression by PCR. In AL mice, alcohol consumption combined with dietary LCHP intake may thus promote a shift in cardiac sympathovagal balance toward sympathetic predominance, the increases in beta-adrenergic receptors (ADRB1 and ADRB2), and then affect the gap junction channel protein Cx43, which in turn could contribute to increased risks of LV systolic dysfunction and susceptibility to lethal ventricular arrhythmia.

Multiancestry Genome-Wide Association Study of Lipid Levels Incorporating Gene-Alcohol Interactions

A person's lipid profile is influenced by genetic variants and alcohol consumption, but the contribution of interactions between these exposures has not been studied. We therefore incorporated gene-alcohol interactions into a multiancestry genome-wide association study of levels of high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, and triglycerides. We included 45 studies in stage 1 (genome-wide discovery) and 66 studies in stage 2 (focused follow-up), for a total of 394,584 individuals from 5 ancestry groups. Analyses covered the period July 2014-November 2017. Genetic main effects and interaction effects were jointly assessed by means of a 2-degrees-of-freedom (df) test, and a 1-df test was used to assess the interaction effects alone. Variants at 495 loci were at least suggestively associated (P < 1 × 10-6) with lipid levels in stage 1 and were evaluated in stage 2, followed by combined analyses of stage 1 and stage 2. In the combined analysis of stages 1 and 2, a total of 147 independent loci were associated with lipid levels at P < 5 × 10-8 using 2-df tests, of which 18 were novel. No genome-wide-significant associations were found testing the interaction effect alone. The novel loci included several genes (proprotein convertase subtilisin/kexin type 5 (PCSK5), vascular endothelial growth factor B (VEGFB), and apolipoprotein B mRNA editing enzyme, catalytic polypeptide 1 (APOBEC1) complementation factor (A1CF)) that have a putative role in lipid metabolism on the basis of existing evidence from cellular and experimental models.

Genetic determinants of beverage consumption: Implications for nutrition and health

Beverages make important contributions to nutritional intake and their role in health has received much attention. This review focuses on the genetic determinants of common beverage consumption and how research in this field is contributing insight to what and how much we consume and why this genetic knowledge matters from a research and public health perspective. The earliest efforts in gene-beverage behavior mapping involved genetic linkage and candidate gene analysis but these approaches have been largely replaced by genome-wide association studies (GWAS). GWAS have identified biologically plausible loci underlying alcohol and coffee drinking behavior. No GWAS has identified variants specifically associated with consumption of tea, juice, soda, wine, beer, milk or any other common beverage. Thus far, GWAS highlight an important behavior-reward component (as opposed to taste) to beverage consumption which may serve as a potential barrier to dietary interventions. Loci identified have been used in Mendelian randomization and gene×beverage interaction analysis of disease but results have been mixed. This research is necessary as it informs the clinical relevance of SNP-beverage associations and thus genotype-based personalized nutrition, which is gaining interest in the commercial and public health sectors.

The Joint Effects of Smoking and Alcohol Drinking on Lipid-Related Indices among Chinese Males-Comparing Exercise and Non-Exercise Groups

BACKGROUND

Smoking and drinking are two predisposing factors for dyslipidemia. Exercise has been proposed as a strategy to improve the blood lipids. However, it remains unclear how smoking and drinking jointly affect blood lipids and whether exercise influences their effects.

OBJECTIVES

To evaluate the effects of smoking and drinking, either alone or in combination, on lipid-related indices in both exercise and non-exercise groups among Chinese men.

METHODS

This study was conducted in a health examination center between 2015 and 2016. A sample of 6,179 male subjects was divided into exercise and non-exercise groups. Logistic and linear regression analyses were used to calculate the odds ratios for abnormal lipid-related indices and correlation coefficients between smoking/drinking and lipid-related indices.

RESULTS

In the study population, the percentage of stable smokers and stable drinkers was 46.3% (2,860/6,179) and 77.6% (4,795/6,179), respectively. An increased smoking amount was significantly associated with an elevated triglyceride (TG) level and a decreased high-density lipoprotein cholesterol (HDL-C) level. Heavier smokers had higher odds ratios for high TG and low HDL-C. Heavier drinkers had higher levels of total cholesterol (TC), TG, and HDL-C and higher odds ratios for high TC and high TG but lower odds ratio for low HDL-C. The exercise group had lower TG levels and higher HDL-C levels than did the non-exercise group.

CONCLUSIONS

Both heavier smoking and heavier drinking were associated with poorer TG levels, and the results suggest that drinking may be helpful for HDL-C. Exercise may relieve the negative effects of smoking and drinking.

Association of longitudinal alcohol consumption trajectories with coronary heart disease: a meta-analysis of six cohort studies using individual participant data

BACKGROUND

Studies have shown that alcohol intake trajectories differ in their associations with biomarkers of cardiovascular functioning, but it remains unclear if they also differ in their relationship to actual coronary heart disease (CHD) incidence. Using multiple longitudinal cohort studies, we evaluated the association between long-term alcohol consumption trajectories and CHD.

METHODS

Data were drawn from six cohorts (five British and one French). The combined analytic sample comprised 35,132 individuals (62.1% male; individual cohorts ranging from 869 to 14,247 participants) of whom 4.9% experienced an incident (fatal or non-fatal) CHD event. Alcohol intake across three assessment periods of each cohort was used to determine participants' intake trajectories over approximately 10 years. Time to onset for (i) incident CHD and (ii) fatal CHD was established using surveys and linked medical record data. A meta-analysis of individual participant data was employed to estimate the intake trajectories' association with CHD onset, adjusting for demographic and clinical characteristics.

RESULTS

Compared to consistently moderate drinkers (males: 1-168 g ethanol/week; females: 1-112 g ethanol/week), inconsistently moderate drinkers had a significantly greater risk of incident CHD [hazard ratio (HR) = 1.18, 95% confidence interval (CI) = 1.02-1.37]. An elevated risk of incident CHD was also found for former drinkers (HR = 1.31, 95% CI = 1.13-1.52) and consistent non-drinkers (HR = 1.47, 95% CI = 1.21-1.78), although, after sex stratification, the latter effect was only evident for females. When examining fatal CHD outcomes alone, only former drinkers had a significantly elevated risk, though hazard ratios for consistent non-drinkers were near identical. No evidence of elevated CHD risk was found for consistently heavy drinkers, and a weak association with fatal CHD for inconsistently heavy drinkers was attenuated following adjustment for confounding factors.

CONCLUSIONS

Using prospectively recorded alcohol data, this study has shown how instability in drinking behaviours over time is associated with risk of CHD. As well as individuals who abstain from drinking (long term or more recently), those who are inconsistently moderate in their alcohol intake have a higher risk of experiencing CHD. This finding suggests that policies and interventions specifically encouraging consistency in adherence to lower-risk drinking guidelines could have public health benefits in reducing the population burden of CHD. The absence of an effect amongst heavy drinkers should be interpreted with caution given the known wider health risks associated with such intake.

TRIAL REGISTRATION

ClinicalTrials.gov, NCT03133689 .

Associations of High-Density Lipoprotein Particle and High-Density Lipoprotein Cholesterol With Alcohol Intake, Smoking, and Body Mass Index - The INTERLIPID Study

BACKGROUND

Recently, high-density lipoprotein particles (HDL-P) have been found to be more strongly inversely associated with coronary artery disease (CAD) risk than their counterpart, HDL cholesterol (HDL-C). Given that lifestyle is among the first targets in CAD prevention, we compared the associations of HDL-P and HDL-C with selected lifestyle factors. Methods and Results: We examined 789 Japanese participants of the INTERLIPID Study: men (n=386) and women (n=403) aged 40-59 years in 1996-1998. Participants treated for dyslipidemias were excluded. Lifestyle factors included alcohol intake, smoking amount, and body mass index (BMI). Multivariable linear regression was used for cross-sectional analyses of these factors with HDL-P, HDL-C, HDL-P size subclasses (small, medium and large) and mean HDL-P size. In men, higher alcohol intake was associated with higher HDL-P and higher HDL-C. The associations of alcohol, however, were strongest with HDL-P. A higher smoking amount tended to be associated with lower HDL-P and HDL-C. In contrast, BMI was not associated with HDL-P, but was strongly inversely associated with HDL-C. While alcohol intake favored larger mean HDL-P size, smoking and BMI favored a lipid profile with smaller HDL-P subclasses and overall smaller mean HDL-P size. Similar, but generally weaker results were observed in women.

CONCLUSIONS

Although both HDL-P and HDL-C are parameters of HDL, they have different associations with alcohol, smoking and BMI.

Difference in sensitivities of blood HDL cholesterol and LDL cholesterol levels to alcohol in middle-aged Japanese men

Blood HDL cholesterol and LDL cholesterol levels are known to be higher and lower, respectively, in drinkers than in nondrinkers, and the beneficial effects of alcohol on cholesterol metabolism are thought to mainly explain the lower risk for ischemic heart disease in light-to-moderate drinkers than in nondrinkers. However, it remains unknown whether sensitivities of HDL and LDL cholesterol levels to alcohol are different or not. The subjects of this study were 21,572 middle-aged Japanese men, and they were divided into three tertile groups for blood HDL cholesterol levels. The relationships between habitual alcohol intake and LDL cholesterol levels were investigated in each tertile for HDL cholesterol. In all of the tertile groups for HDL cholesterol, mean LDL cholesterol levels were significantly lower in the drinking subgroups than in the nondrinking subgroup and tended to be lower with an increase of alcohol intake. In all of the tertile groups for HDL cholesterol, odds ratios for high LDL cholesterol of each drinking subgroup vs. the nondrinking subgroup were significantly lower than the reference level of 1.00, and also tended to be lower with an increase of alcohol intake. The odds ratios of each drinking subgroup tended to be lower in the 1st tertile group for HDL cholesterol than in the 3rd tertile group. Drinkers in the 1st tertile for HDL cholesterol are thought to have relatively low sensitivity of HDL cholesterol to alcohol, but clearly showed lower LDL cholesterol levels than those found in nondrinkers. Therefore, the sensitivity of LDL cholesterol level to alcohol is different from the sensitivity of HDL cholesterol level to alcohol.

Exploring the utility of alcohol flushing as an instrumental variable for alcohol intake in Koreans

Previous studies have indicated an association of higher alcohol intake with cardiovascular disease and related traits, but causation has not been definitively established. In this study, the causal effect of alcohol intake on hypertension in 2,011 men and women from the Ansan-Ansung cohort was estimated using an instrumental variable (IV) approach, with both a phenotypic and genotypic instrument for alcohol intake: alcohol flushing and the rs671 genotype (in the alcohol dehydrogenase 2 [ALDH2] gene), respectively. Both alcohol flushing and the rs671 genotype were associated with alcohol intake (difference in alcohol intake with alcohol flushers vs. non-flushers: −9.07 g/day; 95% confidence interval [CI]: −11.12, −7.02; P-value: 8.3 × 10⁻¹⁸ and with the rs671 GA + AA vs. GG genotype: −7.94 g/day; 95% CI: −10.20, −5.69; P-value: 6.1 × 10⁻¹²). An increase in alcohol intake, as predicted by both the absence of alcohol flushing and the presence of the rs671 GG genotype in the IV analyses, was associated with an increase in blood pressure in men from this Korean population. In conclusion, this study supports a causal effect of alcohol intake on hypertension and indicated that alcohol flushing may be a valid proxy for the ALDH2 rs671 polymorphism, which influences alcohol intake in this Korean population.

Alcohol Consumption, Aldehyde Dehydrogenase 2 Gene Polymorphisms, and Cardiovascular Health in Korea

Alcohol consumption is a serious health issue in Korea in terms of the amount consumed and the behavior related to its consumption. Aldehyde dehydrogenase 2 (ALDH2) is a key enzyme in alcohol metabolism that degrades acetaldehyde to nontoxic acetic acid. The enzyme is coded by the ALDH2 gene, which is commonly polymorphic in East Asian populations. A point mutation in the ALDH2 gene (the rs671 allele) yields an inactive form of ALDH2 that causes acetaldehyde accumulation in the body after alcohol consumption, thereby inhibiting normal alcohol metabolism. Individuals who are homozygous for polymorphism in ALDH2 tend to refrain from drinking alcohol, decreasing their chances of developing alcoholism and exposure to the associated risks. Mendelian randomization (MR) studies have demonstrated that alcohol consumption predicted by ALDH2 genotype is causally related to cardiovascular risks. Moreover, recent MR studies suggest that the ALDH2 variant has mechanistic effects on some disease outcomes or mortality through increased blood levels of acetaldehyde, showing differences therein between heterozygotes (ALDH2*2*2) and homozygotes (ALDH2*1*2) in those who consume alcohol. Accordingly, consideration of ALDH2 genotype in alcohol prevention programs is warranted. In conclusion, strategies that incorporate genetic information and provide an evidential basis from which to help people make informed decisions on alcohol consumption are urgently required.

Mendelian randomization in cardiometabolic disease: challenges in evaluating causality

Mendelian randomization (MR) is a burgeoning field that involves the use of genetic variants to assess causal relationships between exposures and outcomes. MR studies can be straightforward; for example, genetic variants within or near the encoding locus that is associated with protein concentrations can help to assess their causal role in disease. However, a more complex relationship between the genetic variants and an exposure can make findings from MR more difficult to interpret. In this Review, we describe some of these challenges in interpreting MR analyses, including those from studies using genetic variants to assess causality of multiple traits (such as branched-chain amino acids and risk of diabetes mellitus); studies describing pleiotropic variants (for example, C-reactive protein and its contribution to coronary heart disease); and those investigating variants that disrupt normal function of an exposure (for example, HDL cholesterol or IL-6 and coronary heart disease). Furthermore, MR studies on variants that encode enzymes responsible for the metabolism of an exposure (such as alcohol) are discussed, in addition to those assessing the effects of variants on time-dependent exposures (extracellular superoxide dismutase), cumulative exposures (LDL cholesterol), and overlapping exposures (triglycerides and non-HDL cholesterol). We elaborate on the molecular features of each relationship, and provide explanations for the likely causal associations. In doing so, we hope to contribute towards more reliable evaluations of MR findings.

Different inverse association of large high-density lipoprotein subclasses with exacerbation of insulin resistance and incidence of type 2 diabetes: The Nagahama study

AIMS

In addition to its antiatherogenic action, high-density lipoprotein (HDL) may also have an antidiabetes function. Although the biological actions of small HDL (HDL3) and large HDL (HDL2) subclasses may be different, evidence in support of that hypothesis is lacking. The aim of this study was to clarify the difference in prognostic significance of HDL subclasses for exacerbation of insulin resistance and incidence of type 2 diabetes in the general population.

METHODS

Study participants included 8365 community residents 52±13years of age not taking lipid lowering drugs. Serum HDL cholesterol subclasses and low-density lipoprotein subclasses, were measured by a homogeneous assay. Insulin resistance was assessed by homeostasis model assessment of insulin resistance (HOMA-IR).

RESULTS

Cross-sectional analysis adjusted for possible covariates found that HDL2 cholesterol (HDL2-C) levels were inversely associated with HOMA-IR (β=-0.169, p<0.001), whereas HDL3-C had the opposite association (β=0.054, p<0.001). Similar results were found in an analysis for type 2 diabetes (HDL2-C, odds ratio=0.96, p=0.001; HDL3-C, odds ratio=1.04, p=0.181). In a longitudinal analysis with 5.0years of follow-up, HDL2-C was inversely associated with exacerbation of insulin resistance (β=-0.163, p<0.001); HDL3-C had the opposite association (β=0.026, p=0.037). During follow-up, 205 individuals were newly diagnosed with diabetes, and HDL2-C level was associated with an inverse risk of type 2 diabetes incidence (odds ratio=0.98, p=0.006).

CONCLUSIONS

HDL may have an antidiabetic function; the prognostic value of HDL2-C for diabetes and insulin resistance might be better than that of HDL3-C.

The causal effects of alcohol on lipoprotein subfraction and triglyceride levels using a Mendelian randomization analysis: The Nagahama study

BACKGROUND

Light-to-moderate alcohol consumption may increase circulating high-density lipoprotein cholesterol (HDL-C) levels and decrease low-density lipoprotein cholesterol (LDL-C) levels. However, the effect of alcohol on biologically important lipoprotein subfractions remains largely unknown. Here we aimed to clarify the effects of alcohol on lipoprotein subfractions using a Mendelian randomization analysis.

METHODS

The study subjects consisted of 8364 general Japanese individuals. The rs671 polymorphism in aldehyde dehydrogenase 2 gene, a rate-controlling enzyme of alcohol metabolism, was used as an instrumental variable. Lipoprotein subfractions were measured by a homogeneous assay.

RESULTS

The biologically active *1 allele of the ALDH2 genotype was strongly associated with alcohol consumption in men (p < 0.001). In a regression analysis adjusted for possible covariates, the *1 allele was positively associated with HDL-C even in a sub-analysis for HDL subfractions (HDL2-C: β = 0.082, p < 0.001; HDL3-C: β = 0.195, p < 0.001). In contrast, the *1 allele was inversely associated with total LDL-C levels (β = -0.049, p = 0.008), while its association with large-buoyant LDL-C (β = -0.124, p < 0.001) and small-dense LDL-C (β = 0.069, p < 0.001) was opposite. Therefore, the ratio of small-dense LDL to large-buoyant LDL exhibited a linear increase with the number of *1 alleles carried (β = 0.127, p < 0.001). Furthermore, the *1 allele was inversely associated with triglyceride levels in an analysis adjusted for LDL subfractions (β = -0.097, p < 0.001), but not for the total LDL (β = 0.014, p = 0.410).

CONCLUSIONS

Alcohol may increase HDL-C levels irrespective of the particle size. Moreover, alcohol may decrease the total LDL-C, although the proportion of atherogenic small-dense LDL-C increased partially due to a potential inter-relationship with decreased triglyceride levels.