The cannabinoid receptor-1 gene interacts with stressful life events to increase the risk for problematic alcohol use.

Problematic alcohol use is a major contributor to the global burden of death and disabilities, and it represents a public health concern that has grown substantially following the COVID-19 pandemic. The available treatment options remain limited and to develop better pharmacotherapies for alcohol misuse we need to identify suitable biological targets. Previous research has implicated the brain's endocannabinoid system (ECS) in psychiatric and stress-related outcomes, including substance use and habituation to repeated stress. Moreover, genetic variants in the cannabinoid-1 receptor gene (CNR1; CB1R) have been associated with personality traits, which are in turn predictors of substance use disorders. To date, however, no human genome-wide association study has provided evidence for an involvement of the ECS in substance use outcomes. One reason for this ECS-related "missing heritability" may be unexamined gene-environment interactions. To explore this possibility, we conducted cross-sectional analyses using DNA samples and stress-exposure data from a longitudinal Swedish population-based study (N = 2,915). Specifically, we genotyped rs2023239, a functional C/T single nucleotide polymorphism in CNR1, previously reported to be associated with CNR1 binding in the brain, subjective reward following alcohol intake, and alcohol cue-elicited brain activation. Our two outcomes of interest were (i) problematic alcohol use based on the Alcohol Use Disorders Identification Test (AUDIT), and (ii) personality trait scores based on the Five Factor Model. We found no baseline association between rs2023239 and problematic alcohol use or personality traits. However, there was a clear trend for interaction between rs2023239's risk allele (C) and stressful life events (SLEs) in both childhood and adulthood, which predicted problematic alcohol use. Although not significant, there was also some indication that the risk allele interacted with child SLEs to increase scores on neuroticism. Our study supports the notion that the ECS can affect alcohol intake behaviors by interacting with life adversities and is-to the best of our knowledge-the first to focus on the interaction between CNR1 and stressors in both childhood and adulthood in humans. Further studies are warranted to confirm these findings.

Mendelian randomization analysis provides causality of smoking on the expression of ACE2, a putative SARS-CoV-2 receptor.

Background: To understand a causal role of modifiable lifestyle factors in angiotensin-converting enzyme 2 (ACE2) expression (a putative severe acute respiratory syndrome coronavirus 2 [SARS-CoV-2] receptor) across 44 human tissues/organs, and in coronavirus disease 2019 (COVID-19) susceptibility and severity, we conducted a phenome-wide two-sample Mendelian randomization (MR) study. Methods: More than 500 genetic variants were used as instrumental variables to predict smoking and alcohol consumption. Inverse-variance weighted approach was adopted as the primary method to estimate a causal association, while MR-Egger regression, weighted median, and MR pleiotropy residual sum and outlier (MR-PRESSO) were performed to identify potential horizontal pleiotropy. Results: We found that genetically predicted smoking intensity significantly increased ACE2 expression in thyroid (ß=1.468, p=1.8×10-8), and increased ACE2 expression in adipose, brain, colon, and liver with nominal significance. Additionally, genetically predicted smoking initiation significantly increased the risk of COVID-19 onset (odds ratio=1.14, p=8.7×10-5). No statistically significant result was observed for alcohol consumption. Conclusions: Our work demonstrates an important role of smoking, measured by both status and intensity, in the susceptibility to COVID-19. Funding: XJ is supported by research grants from the Swedish Research Council (VR-2018-02247) and Swedish Research Council for Health, Working Life and Welfare (FORTE-2020-00884).

Alcohol Consumption Is Associated with Poor Prognosis in Obese Patients with COVID-19: A Mendelian Randomization Study Using UK Biobank.

BACKGROUND: Acute and chronic alcohol abuse has adverse impacts on both the innate and adaptive immune response, which may result in reduced resistance to severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection and promote the progression of coronavirus disease 2019 (COVID-19). However, there are no large population-based data evaluating potential causal associations between alcohol consumption and COVID-19. METHODS: We conducted a Mendelian randomization study using data from UK Biobank to explore the association between alcohol consumption and risk of SARS-CoV-2 infection and serious clinical outcomes in patients with COVID-19. A total of 12,937 participants aged 50-83 who tested for SARS-CoV-2 between 16 March to 27 July 2020 (12.1% tested positive) were included in the analysis. The exposure factor was alcohol consumption. Main outcomes were SARS-CoV-2 positivity and death in COVID-19 patients. We generated allele scores using three genetic variants (rs1229984 (Alcohol Dehydrogenase 1B, ADH1B), rs1260326 (Glucokinase Regulator, GCKR), and rs13107325 (Solute Carrier Family 39 Member 8, SLC39A8)) and applied the allele scores as the instrumental variables to assess the effect of alcohol consumption on outcomes. Analyses were conducted separately for white participants with and without obesity. RESULTS: Of the 12,937 participants, 4496 were never or infrequent drinkers and 8441 were frequent drinkers. Both logistic regression and Mendelian randomization analyses found no evidence that alcohol consumption was associated with risk of SARS-CoV-2 infection in participants either with or without obesity (All q > 0.10). However, frequent drinking, especially heavy drinking (HR = 2.07, 95%CI 1.24-3.47; q = 0.054), was associated with higher risk of death in patients with obesity and COVID-19, but not in patients without obesity. Notably, the risk of death in frequent drinkers with obesity increased slightly with the average amount of alcohol consumed weekly (All q < 0.10). CONCLUSIONS: Our findings suggest that alcohol consumption has adverse effects on the progression of COVID-19 in white participants with obesity, but was not associated with susceptibility to SARS-CoV-2 infection.

Network Meta-Analysis on the Mechanisms Underlying Alcohol Augmentation of COVID-19 Pathologies.

BACKGROUND: The coronavirus disease 2019 (COVID-19) pandemic is a worldwide crisis caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Many COVID-19 patients present with fever in the early phase, with some progressing to a hyperinflammatory phase. Ethanol (EtOH) exposure may lead to systemic inflammation. Network meta-analysis was conducted to examine possible relationships between EtOH consumption and COVID-19 pathologies. METHODS: Molecules affected by EtOH exposure were identified by analysis with QIAGEN Knowledge Base. Molecules affected by COVID-19 were identified from studies in MEDLINE, bioRxiv, and medRxiv reporting gene expression profiles in COVID-19 patients, QIAGEN Coronavirus Network Explorer, and analysis of the RNA-sequencing data of autopsied lungs of COVID-19 patients retrieved from the GEO database. Network meta-analysis was then conducted on these molecules using QIAGEN Ingenuity Pathway Analysis (IPA). RESULTS: Twenty-eight studies reporting significant gene expression changes in COVID-19 patients were identified. One RNA-sequencing dataset on autopsied lungs of COVID-19 patients was retrieved from GEO. Our network meta-analysis suggests that EtOH exposure may augment the effects of SARS-CoV-2 infection on hepatic fibrosis signaling pathway, cellular metabolism and homeostasis, inflammation, and neuroinflammation. EtOH may also enhance the activity of key mediators including cytokines, such as IL-1ß, IL-6, and TNF, and transcription factors, such as JUN and STAT, while inhibiting the activity of anti-inflammatory mediators including glucocorticoid receptor. Furthermore, IL-1ß, IL-6, TNF, JUN, and STAT were mapped to 10 pathways predicted to associate with SARS-CoV-2 proteins, including HMGB1, IL-1, and IL-6 signaling pathways. CONCLUSIONS: Our meta-analyses demonstrate that EtOH exposure may augment SARS-CoV-2-induced inflammation by altering the activity of key inflammatory mediators. Our findings suggest that it is important for clinicians to caution patients about the risk of alcohol consumption, which has increased during the COVID-19 pandemic. The findings also call for further investigation into how alcohol exposure affects viral infections.