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

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.

The role of metabolites under the influence of genes and lifestyles in bone density changes

Purpose

Osteoporosis is a complex bone disease influenced by numerous factors. Previous studies have found that some metabolites are related to bone mineral density (BMD). However, the associations between metabolites and BMD under the influence of genes and lifestyle have not been fully investigated.

Methods

We analyzed the effect of metabolites on BMD under the synergistic effect of genes and lifestyle, using the data of 797 participants aged 55–65 years from the Taizhou Imaging Study. The cumulative sum method was used to calculate the polygenic risk score of SNPs, and the healthful plant-based diet index was used to summarize food intake. The effect of metabolites on BMD changes under the influence of genes and lifestyle was analyzed through interaction analysis and mediation analysis.

Results

Nineteen metabolites were found significantly different in the osteoporosis, osteopenia, and normal BMD groups. We found two high-density lipoprotein (HDL) subfractions were positively associated with osteopenia, and six very-low-density lipoprotein subfractions were negatively associated with osteopenia or osteoporosis, after adjusting for lifestyles and genetic factors. Tea drinking habits, alcohol consumption, smoking, and polygenic risk score changed BMD by affecting metabolites.

Conclusion

With the increased level of HDL subfractions, the risk of bone loss in the population will increase; the risk of bone loss decreases with the increased level of very-low-density lipoprotein subfractions. Genetic factors and lifestyles can modify the effects of metabolites on BMD. Our results show evidence for the precise prevention of osteoporosis.

Moderate alcohol consumption and lipoprotein subfractions: a systematic review of intervention and observational studies

CONTEXT

Moderate alcohol consumption is associated with decreased risk of cardiovascular disease (CVD) and improvement in cardiovascular risk markers, including lipoproteins and lipoprotein subfractions.

OBJECTIVE

To systematically review the relationship between moderate alcohol intake, lipoprotein subfractions, and related mechanisms.

DATA SOURCES

Following PRISMA, all human and ex vivo studies with an alcohol intake up to 60 g/d were included from 8 databases.

DATA EXTRACTION

A total of 17 478 studies were screened, and data were extracted from 37 intervention and 77 observational studies.

RESULTS

Alcohol intake was positively associated with all HDL subfractions. A few studies found lower levels of small LDLs, increased average LDL particle size, and nonlinear relationships to apolipoprotein B-containing lipoproteins. Cholesterol efflux capacity and paraoxonase activity were consistently increased. Several studies had unclear or high risk of bias, and heterogeneous laboratory methods restricted comparability between studies.

CONCLUSIONS

Up to 60 g/d alcohol can cause changes in lipoprotein subfractions and related mechanisms that could influence cardiovascular health.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO registration no. 98955.

Circulating high density lipoprotein distinguishes alcoholic hepatitis from heavy drinkers and predicts 90-day outcome: lipoproteins in alcoholic hepatitis

BACKGROUND

Alcohol-associated liver disease (ALD) and alcoholic hepatitis (AH) significantly impact the liver, an organ central to the lipid and lipoprotein metabolism.

OBJECTIVE

To define changes in the lipid and lipoprotein profiles in subjects with alcoholic hepatitis (AH) versus heavy drinkers with normal liver function and to determine the association of the AH-mediated lipoprotein phenotype with AH severity and outcomes.

METHODS

AH cases (n=196) and a heavy drinker control group (n=169) were identified in a multicenter, prospective cohort. The relationships between lipid panels and lipoprotein profiles among AH and heavy drinkers were interrogated using three common measurements: the conventional lipid panel, extended lipid panel by NMR, and NMR-based direct lipoprotein profiling. Predictive values for AH severity and mortality were determined using Harrell's C-Index.

RESULTS

Lipid and lipoprotein profiles were significantly different in AH compared to heavy drinkers. Among them, high density lipoprotein (HDL) particle concentration exhibited the most significant reduction in AH compared to heavy drinkers (5.3 ± 3.4 vs 22.3 ± 5.4 μmol/L, p < 0.001). Within AH patients, HDL particle concentration was inversely associated with Maddrey's Discriminant Function (DF) (p < 0.001), and independently associated with mortality at both 90 and 365 days even after adjustment for DF (p = 0.02, p = 0.05 respectively). HDL particle concentration less than 3.5 μmol/L and total cholesterol ≤ 96 mg/dL identified AH patients with higher 90-day mortality.

CONCLUSION

Lipid and lipoprotein profiles are profoundly altered in AH and can help in prognosticating disease severity and mortality.

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.

Gut microbiota of adults with different metabolic phenotypes

OBJECTIVE

The aim of this study was to investigate the gut microbiota of individuals with different metabolic phenotypes and to compare their characteristics.

METHODS

This was a cross-sectional study with 109 adults, classified according to metabolic status, by body mass index, and homeostasis model assessment. Anthropometric and biochemical characteristics and blood pressure were evaluated. Level of physical activity was evaluated by means of a questionnaire, and dietary consumption was evaluated using a 3-d food record. Feces samples were collected from each participant, and gut microbiota profile was analyzed by sequencing of the 16S rRNA gene. The Kruskal-Wallis and χ² tests were used, according to the scale of measurement of the variables, on the statistical program SPSS version 25, with significance level of 5%.

RESULTS

Significantly lower values of saturated fat intake and fasting glycemia were observed in metabolically healthy individuals who were overweight and obese compared with their unhealthy counterparts. Diversity and richness of bacterial communities were lower in individuals who were obese and in the unhealthy phenotype. The genus Eubacterium rectale and genera of the family Prevotellaceae were more abundant in the metabolically healthy obese and metabolically healthy overweight groups than in the metabolically healthy normal weight one, whereas Bifidobacterium was more abundant in the metabolically healthy normal weight group. The genera Coprococcus and Ruminococcus were more abundant in the metabolically healthy overweight group than in the metabolically unhealthy overweight one.

CONCLUSIONS

We observed distinct characteristics in the gut microbiota of different metabolic phenotypes. The intestines of individuals with unhealthy phenotypes hosted inflammation-associated microbiota, with lower butyrate production potential and reduced bacterial diversity.

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.

Association between alcohol consumption and metabolic syndrome among Chinese adults

OBJECTIVE

To assess the prevalence of metabolic syndrome (MetS) in Chinese adults living in Ningbo and to examine the association between alcohol consumption and MetS and its medical components.

DESIGN

A representative survey in Ningbo was conducted in 2015 covering socio-demography. A FFQ together with additional questionnaires was used to collect information on alcohol consumption, diet, demography, lifestyle and medical information. Multivariable logistic regression and generalised linear models were used to examine the association between alcohol consumption and both MetS and its medical components, respectively.

SETTING

Ningbo, China.

PARTICIPANTS

A total of 2853 adults ≥ 20 years (44 % men) in this final analysis.

RESULTS

The prevalence of frequent alcohol drinkers and MetS was 29·9 % and 28·0 %, respectively. Significantly higher prevalence of MetS and mean values of medical components were found in the group of frequent alcohol drinkers with an exception for HDL-cholesterol, compared with less or non-alcohol drinkers. Frequent alcohol consumption was associated with higher odds of developing MetS and positively associated with medical components excepting waist circumference.

CONCLUSIONS

Frequent alcohol consumption contributed to a higher prevalence of MetS and unfavourable influence on MetS and its medical components among Chinese adults. A public health intervention on alcohol restriction is necessary for the prevention and control of the ongoing epidemic MetS.

Dietary habits, lipoprotein metabolism and cardiovascular disease: From individual foods to dietary patterns

Cardiovascular disease (CVD) remains the first cause of mortality in Western countries. Among cardiometabolic risk factors, dyslipidemia, and especially high low-density lipoprotein cholesterol (LDL-C) concentrations, have been extensively linked to the development and progression of atherosclerosis and to CVD events. Recent evidence has shown that the prevention of unhealthy dietary habits and sedentarism is crucial in the management of dyslipidemia. In this sense, a number of scientific societies recommend the adherence to certain healthy dietary patterns (DPs), such as the Mediterranean diet (MedDiet), the Dietary Approaches to Stop Hypertension (DASH), the Portfolio diet, the Vegetarian diet, the Nordic diet and low-carbohydrate diets, as well as increased physical activity between others. This nutritional and lifestyle advice could be adopted by government bodies and implemented in different health programs as a reliable way of providing health-care professionals with efficient tools to manage cardiometabolic risk factors and thus, prevent CVD. In this narrative review, we will discuss recent data about the effects of nutrition on dyslipidemia, mainly focusing on high LDL-C concentrations and other lipid particles related to atherogenic dyslipidemia such as triglycerides (TG) and non-high density lipoprotein cholesterol (non-HDL-C), that are related to CVD. On the other hand, we also comment on other cardiometabolic risk factors such as type 2 diabetes mellitus (T2DM), high blood pressure (HBP), inflammation and endothelial dysfunction. This review includes food groups as well as different healthy DPs.

The Impact of Education and Age on Metabolic Disorders

Metabolic disorders, such as obesity, elevated blood pressure, dyslipidemias, insulin resistance, hyperglycemia, and hyperuricemia have all been identified as risk factors for an epidemic of important and widespread chronic-degenerative diseases, such as type 2 diabetes and cardiovascular disease, that constitute some of the world's most important public health challenges. Their increasing prevalence can be associated with an aging population and to lifestyles within an obesogenic environment. Taking educational level as a proxy for lifestyle, and using both logistic and linear regressions, we study the relation between a wide set of metabolic biomarkers, and educational level, body mass index (BMI), age, and sex as correlates, in a population of 1,073 students, academic and non-academic staff at Mexico's largest university (UNAM). Controlling for BMI and sex, we consider educational level and age as complementary measures-degree and duration-of exposure to metabolic insults. Analyzing the role of education across a wide spectrum of educational levels (from primary school to doctoral degree), we show that higher education correlates to significantly better metabolic health when compared to lower levels, and is associated with significantly less risk for waist circumference, systolic blood pressure, glucose, glycosylated hemoglobin, triglycerides, high density lipoprotein and metabolic syndrome (all p < 0.05); but not for diastolic blood pressure, basal insulin, uric acid, low density lipoprotein, and total cholesterol. We classify each biomarker, and corresponding metabolic disorder, by its associated set of statistically significant correlates. Differences among the sets of significant correlates indicate various aetiologies and the need for targeted population-specific interventions. Thus, variables strongly linked to educational level are candidates for lifestyle change interventions. Hence, public policy efforts should be focused on those metabolic biomarkers strongly linked to education, while adopting a different approach for those biomarkers not linked as they may be poor targets for educational campaigns.

Interaction between adipocytes and high-density lipoprotein:new insights into the mechanism of obesity-induced dyslipidemia and atherosclerosis

Obesity is the most common nutritional disorder worldwide and is associated with dyslipidemia and atherosclerotic cardiovascular disease. The hallmark of dyslipidemia in obesity is low high density lipoprotein (HDL) cholesterol (HDL-C) levels. Moreover, the quality of HDL is also changed in the obese setting. However, there are still some disputes on the explanations for this phenomenon. There is increasing evidence that adipose tissue, as an energy storage tissue, participates in several metabolism activities, such as hormone secretion and cholesterol efflux. It can influence overall reverse cholesterol transport and plasma HDL-C level. In obesity individuals, the changes in morphology and function of adipose tissue affect plasma HDL-C levels and HDL function, thus, adipose tissue should be the main target for the treatment of HDL metabolism in obesity. In this review, we will summarize the cross-talk between adipocytes and HDL related to cardiovascular disease and focus on the new insights of the potential mechanism underlying obesity and HDL dysfunction.

Effects of moderate red wine on cardiovascular risk factors in diabetics: a systematic review and meta-analysis of randomized controlled trials

Background: Diabetes mellitus is of major public health concerns; its incidence is continuously increasing. Diabetes mellitus is associated with a high risk of cardiovascular complications such as hypertension. Red wine has been reported to reduce cardiovascular risk factors. We quantified the effects of red wine on cardiovascular factors. Methods: We retrieved English-language articles published from January 1990 to April 2019. Cardiovascular risk factors were compared using means with 95% confidence intervals (95% CIs). Results: We identified five eligible randomized controlled trials. Diabetic patients who drank red wine exhibited significantly reduced systolic blood pressure (BP) (mean difference [MD] -1.33, 95% CI -1.81, -0.85) and diastolic BP (MD -1.31, 95% CI -1.80, -0.83) than those who did not. Compared to the observations for diabetics who did not drink red wine, the high-density lipoprotein (HDL) level was significantly higher in red wine drinkers (MD -0.24, 95% CI -0.39, -0.09). However, red wine had no effect on the body mass index (BMI) (MD -0.27, 95% CI -1.80, 1.25), the total cholesterol level (MD 0.13, 95% CI -0.17, 0.44), or the low-density lipoprotein (LDL) level (MD 0.08, 95% CI -0.21, 0.37). Conclusions: Red wine consumption significantly lowered BP and increased the HDL level in diabetics. Red wine had no significant effect on BMI or cholesterol and LDL levels. Given the heterogeneity of the studied populations and the lack of standardization and completeness across the published studies, caution is required while interpreting these findings.

Lipoprotein metabolism in liver diseases

PURPOSE OF REVIEW

The liver is the central hub of lipoprotein metabolism. A complex relationship exists between dyslipidemia and chronic liver diseases (CLDs). Recent advances in the genetics of nonalcoholic fatty liver disease (NAFLD) and alcoholic liver disease (ALD) exemplify the pivotal role of lipoprotein metabolism in the pathogenesis of CLD. We review these relationships in four quintessential forms of CLD: NAFLD, ALD, cholestatic liver disease and cirrhosis, with a focus on recent discoveries.

RECENT FINDINGS

An I148 M variant in patatin-like phospholipase domain-containing protein 3 (PNPLA3) and an E167K variant in transmembrane 6 superfamily 2 (TM6SF2) are major genetic risk factors for the development and progression of NAFLD. These genetic variants also increase the risk of ALD. Both PNPLA3 and TM6SF2 are involved in the hepatic assembly of very low-density lipoprotein. The discovery of these two genetic variants highlights the risk of CLD when environmental factors are combined with functional modifications in the lipoprotein metabolism pathway.

SUMMARY

The relationship between CLD and lipoprotein metabolism is reciprocal. On the one hand, the progression of CLD impairs lipoprotein metabolism; on the other hand, modifications in lipoprotein metabolism can substantially increase the risk of CLD. These relationships are at play among the most common forms of CLD affecting a significant proportion of the population.

Peripheral Acid Sphingomyelinase Activity Is Associated with Biomarkers and Phenotypes of Alcohol Use and Dependence in Patients and Healthy Controls

By catalyzing the hydrolysis of sphingomyelin into ceramide, acid sphingomyelinase (ASM) changes the local composition of the plasma membrane with effects on receptor-mediated signaling. Altered enzyme activities have been noted in common human diseases, including alcohol dependence. However, the underlying mechanisms remain largely unresolved. Blood samples were collected from early-abstinent alcohol-dependent in-patients (n[♂] = 113, n[♀] = 87) and matched healthy controls (n[♂] = 133, n[♀] = 107), and analyzed for routine blood parameters and serum ASM activity. We confirmed increased secretory ASM activities in alcohol-dependent patients compared to healthy control subjects, which decreased slightly during detoxification. ASM activity correlated positively with blood alcohol concentration, withdrawal severity, biomarkers of alcohol dependence (liver enzyme activities of gamma-glutamyl transferase, alanine aminotransferase, aspartate aminotransferase; homocysteine, carbohydrate-deficient transferrin; mean corpuscular volume, and creatine kinase). ASM activity correlated negatively with leukocyte and thrombocyte counts. ASM and gamma-glutamyl transferase were also associated in healthy subjects. Most effects were similar for males and females with different strengths. We describe previously unreported associations between ASM activity and markers of liver damage and myelosuppression. Further research should investigate whether this relationship is causal, or whether these parameters are part of a common pathway in order to gain insights into underlying mechanisms and develop clinical applications.

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.

Serum paraoxonase-1 activity is associated with light to moderate alcohol consumption: the PREVEND cohort study

Background

Paraoxonase-1 (PON-1) is a high-density lipoprotein (HDL)-associated enzyme with antioxidative properties, which may protect against the development of cardiovascular disease. Alcohol consumption increases HDL cholesterol, but the extent to which alcohol consumption gives rise to higher serum PON-1 activity is uncertain.

Objective

In a population-based study, we determined the relation of serum PON-1 activity with alcohol consumption when taking account of HDL cholesterol and apolipoprotein A-I (apoA-I), its major apolipoprotein.

Design

A cross-sectional study was performed in 8224 participants of the Prevention of Renal and Vascular End-Stage Disease (PREVEND) cohort. Alcohol consumption was categorized as 1) no/rarely (25.3%); 2) 0.1-10 g/d (49.3%); 3) 10-30 g/d (20.1%); and 4) >30 g/d (5.2%) with 1 drink equivalent to 10 g alcohol. Serum PON-1 activity was measured as its arylesterase activity (phenyl acetate as substrate).

Results

Median serum PON-1 activity was 50.8, 53.1, 54.4, and 55.7 U/L in the 4 categories of alcohol consumption, respectively (P < 0.001). Its increase paralleled the increments in HDL cholesterol and apoA-I. Notably, there was no further increase in PON-1 activity, HDL cholesterol, and apoA-I when alcohol consumption was increased from 10-30 g/d to >30 g/d. Multivariable linear regression analysis demonstrated that PON-1 activity was related to alcohol consumption independently from clinical covariates, high sensitivity C-reactive protein, and lipid concentrations, including HDL cholesterol (P < 0.001 for each category of alcohol consumption with no alcohol consumption as the reference category). Notably, as inferred from standardized β-coefficients, there was no difference in PON-1 activity between 10-30 g alcohol/d and >30 g alcohol/d.

Conclusions

Alcohol consumption is associated with an increase in serum PON-1 activity, but its effect seems to reach a plateau with alcohol consumption of 10-30 g/d.

Comprehensive Metabolic Profiling Reveals a Lipid-Rich Fingerprint of Free Thyroxine Far Beyond Classic Parameters

OBJECTIVE

Thyroid hormones are ubiquitously involved in human metabolism. However, the precise molecular patterns associated with alterations in thyroid hormones levels remain to be explored in detail. A number of recent studies took great advantage of metabolomics profiling to outline the metabolic actions of thyroid hormones in humans.

METHODS

Among 952 participants in the Study of Health in Pomerania, data on serum free thyroxine (FT4) and thyrotropin and comprehensive nontargeted metabolomics data from plasma and urine samples were available. Linear regression analyses were performed to assess the association between FT4 or thyrotropin and metabolite levels.

RESULTS AND CONCLUSION

After accounting for major confounders, 106 of 613 plasma metabolites were significantly associated with FT4. The associations in urine were minor (12 of 587). Most of the plasma metabolites consisted of lipid species, and subsequent analysis of highly resolved lipoprotein subclasses measured by proton nuclear magnetic resonance spectroscopy revealed a consistent decrease in several of these species (e.g., phospholipids) and large low-density lipoprotein and small high-density lipoprotein particles. The latter was unique to men. Several polyunsaturated and saturated fatty acids displayed an association with FT4 in women only. A random forest-based variable selection approach using phenotypic characteristics revealed higher alcohol intake in men and an adverse thyroid state and menopause in women as the putative mediating factors. In general, our observations have confirmed the lipolytic and lipogenic effect of thyroid hormones even in the physiological range and revealed different phenotypic characteristics (e.g., lifestyle differences) as possible confounders for sex-specific findings.

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.

A human PSMB11 variant affects thymoproteasome processing and CD8+ T cell production

The Psmb11-encoded β5t subunit of the thymoproteasome, which is specifically expressed in cortical thymic epithelial cells (cTECs), is essential for the optimal positive selection of functionally competent CD8+ T cells in mice. Here, we report that a human genomic PSMB11 variation, which is detectable at an appreciable allele frequency in human populations, alters the β5t amino acid sequence that affects the processing of catalytically active β5t proteins. The introduction of this variation in the mouse genome revealed that the heterozygotes showed reduced β5t expression in cTECs and the homozygotes further exhibited reduction in the cellularity of CD8+ T cells. No severe health problems were noticed in many heterozygous and 5 homozygous human individuals. Long-term analysis of health status, particularly in the homozygotes, is expected to improve our understanding of the role of the thymoproteasome-dependent positive selection of CD8+ T cells in humans.