KLB is associated with alcohol drinking, and its gene product β-Klotho is necessary for FGF21 regulation of alcohol preference

Comparing Western and traditional Chinese medicine for male sexual dysfunction: can Klotho represent a silk road?

Traditional Chinese medicine (TCM) and Western Medicine both have shown efficacy in treating male sexual dysfunction (MSD). The aim of this perspective paper is to discuss a possible link between Western medicine and TCM in the MSD field as represented by the entity of Klotho. Klotho is a recently discovered protein, mainly expressed in the kidney, encoded by the anti-aging gene klotho. Not only is Klotho significantly correlated with the development and progression of kidney diseases and their complications, but increasing evidence indicates that it is also closely related to MSD. A comprehensive search within PubMed database was performed to retrieve available evidence on Klotho's roles, particularly in kidney and in MSD. Indeed, in the TCM theory, the concept of the "kidney" is entirely different from the Western medicine: it is closely related to metabolism and to the reproductive, nervous, endocrine systems, being more than just a urinary organ. According to the "Kidney storing essence (jīng) and governing reproduction" (KSEGR) theory, a cornerstone in TCM, the treatment of MSD mainly consists of restoring the kidney's function. Signs of decreasing kidney essence show a consistent similarity to deficiencies of Klotho, also for what regards the male sexual function. Based on the current evidence, Klotho may represent a potential biological indicator for sexual desire and sexual function and a kind of new scientific Silk Road between TCM and Western medicine for MSD; nevertheless, there is a need to conduct further high-quality research to prove this hypothesis.

Integrated Single-Cell Multiomic Profiling of Caudate Nucleus Suggests Key Mechanisms in Alcohol Use Disorder

Alcohol use disorder (AUD) is likely associated with complex transcriptional alterations in addiction-relevant brain regions. We characterize AUD-associated differences in cell type-specific gene expression and chromatin accessibility in the caudate nucleus by conducting a single-nucleus RNA-seq assay and a single-nucleus RNA-seq + ATAC-seq (multiome) assay on caudate tissue from 143 human postmortem brains (74 with AUD). We identified 17 cell types. AUD was associated with a higher proportion of microglia in an activated state and more astrocytes in a reactive state. There was widespread evidence for differentially expressed genes across cell types with the most identified in oligodendrocytes and astrocytes, including genes involved in immune response and synaptic regulation, many of which appeared to be regulated in part by JUND and OLIG2. Microglia-astrocyte communication via interleukin-1 beta, and microglia-astrocyte-oligodendrocyte interaction via transforming growth factor beta 1 were increased in individuals with AUD. Expression quantitative trait loci analysis revealed potential driver genes of AUD, including ADAL, that may protect against AUD in medium spiny neurons and interneurons. This work provides a thorough profile of the effects of AUD in the human brain and identifies several promising genes for further study.

Neutral sphingomyelinase controls acute and chronic alcohol effects on brain activity

Alcohol consumption is a widespread phenomenon throughout the world. However, how recreational alcohol use evolves into alcohol use disorder (AUD) remains poorly understood. The Smpd3 gene and its coded protein neutral sphingomyelinase (NSM) are associated with alcohol consumption in humans and alcohol-related behaviors in mice, suggesting a potential role in this transition. Using multiparametric magnetic resonance imaging, we characterized the role of NSM in acute and chronic effects of alcohol on brain anatomy and function in female mice. Chronic voluntary alcohol consumption (16 vol% for at least 6 days) affected brain anatomy in WT mice, reducing regional structure volume predominantly in cortical regions. Attenuated NSM activity prevented these anatomical changes. Functional MRI linked these anatomical adaptations to functional changes: Chronic alcohol consumption in mice significantly modulated resting state functional connectivity (RS FC) in response to an acute ethanol challenge (i.p. bolus of 2 g kg-1) in heterozygous NSM knockout (Fro), but not in WT mice. Acute ethanol administration in alcohol-naïve WT mice significantly decreased RS FC in cortical and brainstem regions, a key finding that was amplified in Fro mice. Regarding direct pharmacological effects, acute ethanol administration increased the regional cerebral blood volume (rCBV) in many brain areas. Here, chronic alcohol consumption otherwise attenuated the acute rCBV response in WT mice but enhanced it in Fro mice. Altogether, these findings suggest a differential role for NSM in acute and chronic functional brain responses to alcohol. Therefore, targeting NSM may be useful in the prevention or treatment of AUD.

A comprehensive multi-task deep learning approach for predicting metabolic syndrome with genetic, nutritional, and clinical data

Metabolic syndrome (MetS) is a complex disorder characterized by a cluster of metabolic abnormalities, including abdominal obesity, hypertension, elevated triglycerides, reduced high-density lipoprotein cholesterol, and impaired glucose tolerance. It poses a significant public health concern, as individuals with MetS are at an increased risk of developing cardiovascular diseases and type 2 diabetes. Early and accurate identification of individuals at risk for MetS is essential. Various machine learning approaches have been employed to predict MetS, such as logistic regression, support vector machines, and several boosting techniques. However, these methods use MetS as a binary status and do not consider that MetS comprises five components. Therefore, a method that focuses on these characteristics of MetS is needed. In this study, we propose a multi-task deep learning model designed to predict MetS and its five components simultaneously. The benefit of multi-task learning is that it can manage multiple tasks with a single model, and learning related tasks may enhance the model's predictive performance. To assess the efficacy of our proposed method, we compared its performance with that of several single-task approaches, including logistic regression, support vector machine, CatBoost, LightGBM, XGBoost and one-dimensional convolutional neural network. For the construction of our multi-task deep learning model, we utilized data from the Korean Association Resource (KARE) project, which includes 352,228 single nucleotide polymorphisms (SNPs) from 7729 individuals. We also considered lifestyle, dietary, and socio-economic factors that affect chronic diseases, in addition to genomic data. By evaluating metrics such as accuracy, precision, F1-score, and the area under the receiver operating characteristic curve, we demonstrate that our multi-task learning model surpasses traditional single-task machine learning models in predicting MetS.

The crosstalk between fibroblast growth factor 21 (FGF21) system and substance use

Existing literature indicates that communication between the central nervous system and the peripheral nervous system is disrupted by substance use disorders (SUDs), including alcohol use disorder (AUD). Fibroblast growth factor 21 (FGF21), a liver-brain axis hormone governing energy homeostasis, has been shown to modulate alcohol intake/preference and other substances. To further elucidate the relationship between FGF21, alcohol use, and other substance use, we conducted a scoping review to explore the association between FGF21 and SUDs. Increases in FGF21 reduce alcohol consumption while suppressing FGF21 increases alcohol consumption, demonstrating an inverse relationship. Alcohol elevates FGF21 levels primarily via the liver, subsequently promoting neuronal signals to curb alcohol intake. FGF21 activation engages molecular pathways that defend against alcohol-induced fat accumulation, oxidative stress, and inflammation. Considering the bidirectional association between FGF21 and alcohol, further studies on the FGF21 system as a potential pharmacotherapy for AUD and alcohol-associated liver disease are warranted.

Whole exome sequencing analysis identifies genes for alcohol consumption

Alcohol consumption is a heritable behavior seriously endangers human health. However, genetic studies on alcohol consumption primarily focuses on common variants, while insights from rare coding variants are lacking. Here we leverage whole exome sequencing data across 304,119 white British individuals from UK Biobank to identify protein-coding variants associated with alcohol consumption. Twenty-five variants are associated with alcohol consumption through single variant analysis and thirteen genes through gene-based analysis, ten of which have not been reported previously. Notably, the two unreported alcohol consumption-related genes GIGYF1 and ANKRD12 show enrichment in brain function-related pathways including glial cell differentiation and are strongly expressed in the cerebellum. Phenome-wide association analyses reveal that alcohol consumption-related genes are associated with brain white matter integrity and risk of digestive and neuropsychiatric diseases. In summary, this study enhances the comprehension of the genetic architecture of alcohol consumption and implies biological mechanisms underlying alcohol-related adverse outcomes.

A phenome-wide association and Mendelian randomisation study of alcohol use variants in a diverse cohort comprising over 3 million individuals

BACKGROUND

Alcohol consumption is associated with numerous negative social and health outcomes. These associations may be direct consequences of drinking, or they may reflect common genetic factors that influence both alcohol consumption and other outcomes.

METHODS

We performed exploratory phenome-wide association studies (PheWAS) of three of the best studied protective single nucleotide polymorphisms (SNPs) in genes encoding ethanol metabolising enzymes (ADH1B: rs1229984-T, rs2066702-A; ADH1C: rs698-T) using up to 1109 health outcomes across 28 phenotypic categories (e.g., substance-use, mental health, sleep, immune, cardiovascular, metabolic) from a diverse 23andMe cohort, including European (N ≤ 2,619,939), Latin American (N ≤ 446,646) and African American (N ≤ 146,776) populations to uncover new and perhaps unexpected associations. These SNPs have been consistently implicated by both candidate gene studies and genome-wide association studies of alcohol-related behaviours but have not been investigated in detail for other relevant phenotypes in a hypothesis-free approach in such a large cohort of multiple ancestries. To provide insight into potential causal effects of alcohol consumption on the outcomes significant in the PheWAS, we performed univariable two-sample and one-sample Mendelian randomisation (MR) analyses.

FINDINGS

The minor allele rs1229984-T, which is protective against alcohol behaviours, showed the highest number of PheWAS associations across the three cohorts (N = 232, European; N = 29, Latin American; N = 7, African American). rs1229984-T influenced multiple domains of health. We replicated associations with alcohol-related behaviours, mental and sleep conditions, and cardio-metabolic health. We also found associations with understudied traits related to neurological (migraines, epilepsy), immune (allergies), musculoskeletal (fibromyalgia), and reproductive health (preeclampsia). MR analyses identified evidence of causal effects of alcohol consumption on liability for 35 of these outcomes in the European cohort.

INTERPRETATION

Our work demonstrates that polymorphisms in genes encoding alcohol metabolising enzymes affect multiple domains of health beyond alcohol-related behaviours. Understanding the underlying mechanisms of these effects could have implications for treatments and preventative medicine.

FUNDING

MVJ, NCK, SBB, SSR and AAP were supported by T32IR5226 and 28IR-0070. SSR was also supported by NIDA DP1DA054394. NCK and RBC were also supported by R25MH081482. ASH was supported by funds from NIAAA K01AA030083. JLMO was supported by VA 1IK2CX002095. JLMO and JJMM were also supported by NIDA R21DA050160. JJMM was also supported by the Kavli Postdoctoral Award for Academic Diversity. EGA was supported by K01MH121659 from the NIMH/NIH, the Caroline Wiess Law Fund for Research in Molecular Medicine and the ARCO Foundation Young Teacher-Investigator Fund at Baylor College of Medicine. MSA was supported by the Instituto de Salud Carlos III and co-funded by the European Union Found: Fondo Social Europeo Plus (FSE+) (P19/01224, PI22/00464 and CP22/00128).

Understanding policy amenable risk factors: Alcohol consumption and long-term care use among people over 65 years old

OBJECTIVES

This study aims to explore the effect of past alcohol consumption frequency on formal and informal long-term care (LTC) use in old age and explore the different channels through which it may affect LTC use.

MOTIVATION

The existing literature has mainly focused on risk factors associated with a nursing home entry, but this evidence is outdated, not UK-focused, and does not look into other types of care, such as informal care. The results of this study will help in modelling the future demand for various types of care and the corresponding public spending.

METHODS

We use the English Longitudinal Study of Ageing (ELSA) (2002-2017) dataset to conduct longitudinal, individual-level analysis. We explore how the previous frequency of alcohol consumption affects formal and informal care use. We focus on people aged 65 and over with no previous LTC use and run regressions with and without instrumental variables (IV) to estimate how alcohol consumption patterns in the previous wave (2 years before) affect formal and informal care use. For IV regressions, we use the polygenic score for alcohol use, available for a subsample of ELSA respondents, as an instrument while also accounting for sociodemographic characteristics, lifestyle choices, and health conditions.

RESULTS

The main IV estimates suggest that frequent alcohol consumption has a weakly significant positive effect on the onset of formal LTC care use compared to none/rare drinking. This relationship diminishes and is not statistically significant when we directly control for health status. We find no statistically significant effect towards informal LTC use. These results contrast with the estimates without IV, which suggest that frequent alcohol consumption is negatively associated with informal care use and no or weakly negative association with formal care use.

DISCUSSION

Our findings suggest that unobserved confounding is important when studying the relationship between alcohol consumption and LTC. We hypothesise that primarily alcohol effects LTC through its adverse effect on health. In addition, unobserved factors like preferences towards seeking care, social behaviour may be related to alcohol consumption and affect access to care. We speculate alcohol may have a damaging effect on personal relationships and could indicate the burden eventually falling on formal care. In as far as the polygenic score IV can account for unobserved preference-behaviour differences, the results (weakly) support the hypothesis that these latter processes are relevant, especially for informal care use.

Genetic correlations of alcohol consumption and alcohol use disorder with sex hormone levels in females and males

Background

Alcohol consumption behaviors and alcohol use disorder risk and presentation differ by sex, and these complex traits are associated with blood concentrations of the steroid sex hormones, testosterone and estradiol, and their regulatory binding proteins, sex hormone binding globulin (SHBG) and albumin. Genetic variation is associated with alcohol consumption and alcohol use disorder, as well as levels of steroid sex hormones and their binding proteins.

Methods

To assess the contribution of genetic factors to previously described phenotypic associations between alcohol-use traits and sex-hormone levels, we estimated genetic correlations (rg) using summary statistics from prior published, large sample size genome-wide association studies (GWAS) of alcohol consumption, alcohol dependence, testosterone, estradiol, SHBG, and albumin.

Results

For alcohol consumption, we observed positive genetic correlation (i.e. genetic effects in the same direction) with total testosterone in males (rg = 0.084, p = 0.007) and trends toward positive genetic correlation with bioavailable testosterone (rg = 0.060, p = 0.084) and SHBG in males (rg = 0.056, p = 0.086) and with albumin in a sex-combined cohort (rg = 0.082, p = 0.015); however in females, we observed positive genetic correlation with SHBG (rg = 0.089, p = 0.004) and a trend toward negative genetic correlation (i.e. genetic effects in opposite directions) with bioavailable testosterone (rg = -0.064, p = 0.032). For alcohol dependence, we observed a trend toward negative genetic correlation with total testosterone in females (rg = -0.106, p = 0.024) and positive genetic correlation with BMI-adjusted SHBG in males (rg = 0.119, p = 0.017). Several of these genetic correlations differed between females and males and were not in the same direction as the corresponding phenotypic associations.

Conclusions

Findings suggest that shared genetic effects may contribute to positive associations of alcohol consumption with albumin in both sexes, as well as positive associations between alcohol consumption and bioavailable testosterone and between alcohol dependence and SHBG in males. However, relative contributions of heritable and environmental factors to associations between alcohol-use traits and sex-hormone levels may differ by sex, with genetic factors contributing more in males and environmental factors contributing more in females.

Functional 3'-UTR Variants Identify Regulatory Mechanisms Impacting Alcohol Use Disorder and Related Traits

Although genome-wide association studies (GWAS) have identified loci associated with alcohol consumption and alcohol use disorder (AUD), they do not identify which variants are functional. To approach this, we evaluated the impact of variants in 3' untranslated regions (3'-UTRs) of genes in loci associated with substance use and neurological disorders using a massively parallel reporter assay (MPRA) in neuroblastoma and microglia cells. Functionally impactful variants explained a higher proportion of heritability of alcohol traits than non-functional variants. We identified genes whose 3'UTR activities are associated with AUD and alcohol consumption by combining variant effects from MPRA with GWAS results. We examined their effects by evaluating gene expression after CRISPR inhibition of neuronal cells and stratifying brain tissue samples by MPRA-derived 3'-UTR activity. A pathway analysis of differentially expressed genes identified inflammation response pathways. These analyses suggest that variation in response to inflammation contributes to the propensity to increase alcohol consumption.

Genetic architecture of alcohol consumption identified by a genotype-stratified GWAS and impact on esophageal cancer risk in Japanese people

An East Asian-specific variant on aldehyde dehydrogenase 2 (ALDH2 rs671, G>A) is the major genetic determinant of alcohol consumption. We performed an rs671 genotype-stratified genome-wide association study meta-analysis of alcohol consumption in 175,672 Japanese individuals to explore gene-gene interactions with rs671 behind drinking behavior. The analysis identified three genome-wide significant loci (GCKR, KLB, and ADH1B) in wild-type homozygotes and six (GCKR, ADH1B, ALDH1B1, ALDH1A1, ALDH2, and GOT2) in heterozygotes, with five showing genome-wide significant interaction with rs671. Genetic correlation analyses revealed ancestry-specific genetic architecture in heterozygotes. Of the discovered loci, four (GCKR, ADH1B, ALDH1A1, and ALDH2) were suggested to interact with rs671 in the risk of esophageal cancer, a representative alcohol-related disease. Our results identify the genotype-specific genetic architecture of alcohol consumption and reveal its potential impact on alcohol-related disease risk.

Alcohol metabolism in alcohol use disorder: a potential therapeutic target

Ethanol metabolism plays an essential role in how the body perceives and experiences alcohol consumption, and evidence suggests that modulation of ethanol metabolism can alter the risk for alcohol use disorder (AUD). In this review, we explore how ethanol metabolism, mainly via alcohol dehydrogenase and aldehyde dehydrogenase 2 (ALDH2), contributes to drinking behaviors by integrating preclinical and clinical findings. We discuss how alcohol dehydrogenase and ALDH2 polymorphisms change the risk for AUD, and whether we can harness that knowledge to design interventions for AUD that alter ethanol metabolism. We detail the use of disulfiram, RNAi strategies, and kudzu/isoflavones to inhibit ALDH2 and increase acetaldehyde, ideally leading to decreases in drinking behavior. In addition, we cover recent preclinical evidence suggesting that strategies other than increasing acetaldehyde-mediated aversion can decrease ethanol consumption, providing other potential metabolism-centric therapeutic targets. However, modulating ethanol metabolism has inherent risks, and we point out some of the key areas in which more data are needed to mitigate these potential adverse effects. Finally, we present our opinions on the future of treating AUD by the modulation of ethanol metabolism.

ChREBP is activated by reductive stress and mediates GCKR-associated metabolic traits

Common genetic variants in glucokinase regulator (GCKR), which encodes GKRP, a regulator of hepatic glucokinase (GCK), influence multiple metabolic traits in genome-wide association studies (GWASs), making GCKR one of the most pleiotropic GWAS loci in the genome. It is unclear why. Prior work has demonstrated that GCKR influences the hepatic cytosolic NADH/NAD+ ratio, also referred to as reductive stress. Here, we demonstrate that reductive stress is sufficient to activate the transcription factor ChREBP and necessary for its activation by the GKRP-GCK interaction, glucose, and ethanol. We show that hepatic reductive stress induces GCKR GWAS traits such as increased hepatic fat, circulating FGF21, and circulating acylglycerol species, which are also influenced by ChREBP. We define the transcriptional signature of hepatic reductive stress and show its upregulation in fatty liver disease and downregulation after bariatric surgery in humans. These findings highlight how a GCKR-reductive stress-ChREBP axis influences multiple human metabolic traits.

Binge drinking episode causes acute, specific alterations in systemic and hepatic inflammation-related markers

BACKGROUND

Frequent binge drinking is a known contributor to alcohol-related harm, but its impact on systemic and hepatic inflammation is not fully understood. We hypothesize that changes in immune markers play a central role in adverse effects of acute alcohol intake, especially in patients with early liver disease.

AIM

To investigate the effects of acute alcohol intoxication on inflammation-related markers in hepatic and systemic venous plasma in people with alcohol-related liver disease (ArLD), non-alcoholic fatty liver disease (NAFLD) and healthy controls.

METHODS

Thirty-eight participants (13 with ArLD, 15 with NAFLD and 10 healthy controls) received 2.5 mL of 40% ethanol per kg body weight via a nasogastric tube. Seventy-two inflammation-related markers were quantified in plasma from hepatic and systemic venous blood, at baseline, 60 and 180 min after intervention.

RESULTS

Alcohol intervention altered the levels of 31 of 72 and 14 of 72 markers in the systemic and hepatic circulation. All changes observed in the hepatic circulation were also identified in the systemic circulation after 180 min. Only FGF21 and IL6 were increased after alcohol intervention, while the remaining 29 markers decreased. Differences in response to acute alcohol between the groups were observed for 8 markers, and FGF21 response was blunted in individuals with steatosis.

CONCLUSION

Acute alcohol intoxication induced changes in multiple inflammation-related markers, implicated in alcohol metabolism and hepatocellular damage. Differences identified between marker response to binge drinking in ArLD, NAFLD and healthy controls may provide important clues to disease mechanisms and potential targets for treatment.

CLINICAL TRIAL NUMBER

NCT03018990.

Single-cell DNA methylation and 3D genome architecture in the human brain

Delineating the gene-regulatory programs underlying complex cell types is fundamental for understanding brain function in health and disease. Here, we comprehensively examined human brain cell epigenomes by probing DNA methylation and chromatin conformation at single-cell resolution in 517 thousand cells (399 thousand neurons and 118 thousand non-neurons) from 46 regions of three adult male brains. We identified 188 cell types and characterized their molecular signatures. Integrative analyses revealed concordant changes in DNA methylation, chromatin accessibility, chromatin organization, and gene expression across cell types, cortical areas, and basal ganglia structures. We further developed single-cell methylation barcodes that reliably predict brain cell types using the methylation status of select genomic sites. This multimodal epigenomic brain cell atlas provides new insights into the complexity of cell-type-specific gene regulation in adult human brains.

Genome-Wide Association Studies of Coffee Intake in UK/US Participants of European Ancestry Uncover Gene-Cohort Influences

Coffee is one of the most widely consumed beverages. We performed a genome-wide association study (GWAS) of coffee intake in US-based 23andMe participants (N=130,153) and identified 7 significant loci, with many replicating in three multi-ancestral cohorts. We examined genetic correlations and performed a phenome-wide association study across thousands of biomarkers and health and lifestyle traits, then compared our results to the largest available GWAS of coffee intake from UK Biobank (UKB; N=334,659). The results of these two GWAS were highly discrepant. We observed positive genetic correlations between coffee intake and psychiatric illnesses, pain, and gastrointestinal traits in 23andMe that were absent or negative in UKB. Genetic correlations with cognition were negative in 23andMe but positive in UKB. The only consistent observations were positive genetic correlations with substance use and obesity. Our study shows that GWAS in different cohorts could capture cultural differences in the relationship between behavior and genetics.

Understanding the relationship between loneliness, substance use traits and psychiatric disorders: A genetically informed approach

Loneliness is a common, yet distressing experience associated with adverse outcomes including substance use problems and psychiatric disorders. To what extent these associations reflect genetic correlations and causal relationships is currently unclear. We applied Genomic Structural Equation Modelling (GSEM) to dissect the genetic architecture between loneliness and psychiatric-behavioural traits. Included were summary statistics from 12 genome-wide association analyses, including loneliness and 11 psychiatric phenotypes (range N: 9,537 - 807,553). We first modelled latent genetic factors amongst the psychiatric traits to then investigate potential causal effects between loneliness and the identified latent factors, using multivariate genome-wide association analyses and bidirectional Mendelian randomization. We identified three latent genetic factors, encompassing neurodevelopmental/mood conditions, substance use traits and disorders with psychotic features. GSEM provided evidence of a unique association between loneliness and the neurodevelopmental/mood conditions latent factor. Mendelian randomization results were suggestive of bidirectional causal effects between loneliness and the neurodevelopmental/mood conditions factor. These results imply that a genetic predisposition to loneliness may elevate the risk of neurodevelopmental/mood conditions, and vice versa. However, results may reflect the difficulty of distiguishing between loneliness and neurodevelopmental/mood conditions, which present in similar ways. We suggest, overall, the importance of addressing loneliness in mental health prevention and policy.

Self-management with alcohol over lifespan: psychological mechanisms, neurobiological underpinnings, and risk assessment

Self-management includes all behavioural measures and cognitive activities aimed at coping with challenges arising throughout the lifespan. While virtually all of these challenges can be met without pharmacological means, alcohol consumption has long been instrumentalized as a supporting tool to help coping with problems arising selectively at adolescence, adulthood, and ageing. Here, we present, to our knowledge, the first systematic review of alcohol instrumentalization throughout lifespan. We searched MEDLINE, Google Scholar, PsycINFO and CINAHL (from Jan, 1990, to Dec, 2022) and analysed consumption patterns, goals and potential neurobiological mechanisms. Evidence shows a regular non-addictive use of alcohol to self-manage developmental issues during adolescence, adulthood, and ageing. Alcohol is selectively used to overcome problems arising from dysfunctional personality traits, which manifest in adolescence. A large range of psychiatric disorders gives rise to alcohol use for the self-management of distinct symptoms starting mainly in adulthood. We identify those neuropharmacological effects of alcohol that selectively serve self-management under specific conditions. Finally, we discuss the adverse effects and associated risks that arise from the use of alcohol for self-management. Even well-controlled alcohol use adversely impacts health. Based on these findings, we suggest the implementation of an entirely new view. Health policy action may actively embrace both sides of the phenomenon through a personalized informed use that allows for harm-controlled self-management with alcohol.

Hepatokines, bile acids and ketone bodies are novel Hormones regulating energy homeostasis

Current views show that an impaired balance partly explains the fat accumulation leading to obesity. Fetal malnutrition and early exposure to endocrine-disrupting compounds also contribute to obesity and impaired insulin secretion and/or sensitivity. The liver plays a major role in systemic glucose homeostasis through hepatokines secreted by hepatocytes. Hepatokines influence metabolism through autocrine, paracrine, and endocrine signaling and mediate the crosstalk between the liver, non-hepatic target tissues, and the brain. The liver also synthetizes bile acids (BAs) from cholesterol and secretes them into the bile. After food consumption, BAs mediate the digestion and absorption of fat-soluble vitamins and lipids in the duodenum. In recent studies, BAs act not simply as fat emulsifiers but represent endocrine molecules regulating key metabolic pathways. The liver is also the main site of the production of ketone bodies (KBs). In prolonged fasting, the brain utilizes KBs as an alternative to CHO. In the last few years, the ketogenic diet (KD) became a promising dietary intervention. Studies on subjects undergoing KD show that KBs are important mediators of inflammation and oxidative stress. The present review will focus on the role played by hepatokines, BAs, and KBs in obesity, and diabetes prevention and management and analyze the positive effects of BAs, KD, and hepatokine receptor analogs, which might justify their use as new therapeutic approaches for metabolic and aging-related diseases.

Biological and pharmacological functions of the FGF19- and FGF21-coreceptor beta klotho

Beta klotho (KLB) is a fundamental component in fibroblast growth factor receptor (FGFR) signaling as it serves as an obligatory coreceptor for the endocrine hormones fibroblast growth factor 19 (FGF19) and fibroblast growth factor 21 (FGF21). Through the development of FGF19- and FGF21 mimetics, KLB has emerged as a promising drug target for treating various metabolic diseases, such as type 2 diabetes (T2D), non-alcoholic fatty liver disease (NAFLD), and cardiovascular disease. While rodent studies have significantly increased our understanding of KLB function, current clinical trials that test the safety and efficacy of KLB-targeting drugs raise many new scientific questions about human KLB biology. Although most KLB-targeting drugs can modulate disease activity in humans, individual patient responses differ substantially. In addition, species-specific differences in KLB tissue distribution may explain why the glucose-lowering effects that were observed in preclinical studies are not fully replicated in clinical trials. Besides, the long-term efficacy of KLB-targeting drugs might be limited by various pathophysiological conditions known to reduce the expression of KLB. Moreover, FGF19/FGF21 administration in humans is also associated with gastrointestinal side effects, which are currently unexplained. A better understanding of human KLB biology could help to improve the efficacy and safety of existing or novel KLB/FGFR-targeting drugs. In this review, we provide a comprehensive overview of the current understanding of KLB biology, including genetic variants and their phenotypic associations, transcriptional regulation, protein structure, tissue distribution, subcellular localization, and function. In addition, we will highlight recent developments regarding the safety and efficacy of KLB-targeting drugs in clinical trials. These insights may direct the development and testing of existing and future KLB-targeting drugs.

Multi-trait genome-wide association analyses leveraging alcohol use disorder findings identify novel loci for smoking behaviors in the Million Veteran Program

Smoking behaviors and alcohol use disorder (AUD), both moderately heritable traits, commonly co-occur in the general population. Single-trait genome-wide association studies (GWAS) have identified multiple loci for smoking and AUD. However, GWASs that have aimed to identify loci contributing to co-occurring smoking and AUD have used small samples and thus have not been highly informative. Applying multi-trait analysis of GWASs (MTAG), we conducted a joint GWAS of smoking and AUD with data from the Million Veteran Program (N = 318,694). By leveraging GWAS summary statistics for AUD, MTAG identified 21 genome-wide significant (GWS) loci associated with smoking initiation and 17 loci associated with smoking cessation compared to 16 and 8 loci, respectively, identified by single-trait GWAS. The novel loci for smoking behaviors identified by MTAG included those previously associated with psychiatric or substance use traits. Colocalization analysis identified 10 loci shared by AUD and smoking status traits, all of which achieved GWS in MTAG, including variants on SIX3, NCAM1, and near DRD2. Functional annotation of the MTAG variants highlighted biologically important regions on ZBTB20, DRD2, PPP6C, and GCKR that contribute to smoking behaviors. In contrast, MTAG of smoking behaviors and alcohol consumption (AC) did not enhance discovery compared with single-trait GWAS for smoking behaviors. We conclude that using MTAG to augment the power of GWAS enables the identification of novel genetic variants for commonly co-occuring phenotypes, providing new insights into their pleiotropic effects on smoking behavior and AUD.

Tgr5-/- mice are protected from ethanol-induced metabolic alterations through enhanced leptin and Fgf21 signaling

BACKGROUND

Alcohol-associated liver disease (ALD) is caused by chronic use of alcohol and ranges from hepatic steatosis to fibrosis and cirrhosis. Bile acids are physiological detergents that also regulate hepatic glucose and lipid homeostasis by binding to several receptors. One such receptor, Takeda G protein-coupled receptor 5 (TGR5), may represent a therapeutic target for ALD. Here, we used a chronic 10-day + binge ethanol-feeding model in mice to study the role of TGR5 in alcohol-induced liver injury.

METHODS

Female C57BL/6J wild-type mice and Tgr5-/- mice were pair-fed Lieber-DeCarli liquid diet with ethanol (5% v/v) or isocaloric control diet for 10 days followed by a gavage of 5% ethanol or isocaloric maltose control, respectively, to represent a binge-drinking episode. Tissues were harvested 9 hours following the binge, and metabolic phenotypes were characterized through examination of liver, adipose, and brain mechanistic pathways.

RESULTS

Tgr5-/- mice were protected from alcohol-induced accumulation of hepatic triglycerides. Interestingly, liver and serum levels of Fgf21 were significantly increased during ethanol feeding in Tgr5-/- mice, as was phosphorylation of Stat3. Parallel to Fgf21 levels, increased leptin gene expression in white adipose tissue and increased leptin receptor in liver were detected in Tgr5-/- mice fed ethanol diet. Adipocyte lipase gene expression was significantly increased in Tgr5-/- mice regardless of diet, whereas adipose browning markers were also increased in ethanol-fed Tgr5-/- mice, indicating potential for enhanced white adipose metabolism. Lastly, hypothalamic mRNA targets of leptin, involved in the regulation of food intake, were significantly increased in Tgr5-/- mice fed ethanol diet.

CONCLUSIONS

Tgr5-/- mice are protected from ethanol-induced liver damage and lipid accumulation. Alterations in lipid uptake and Fgf21 signaling, and enhanced metabolic activity of white adipose tissue, may mediate these effects.

A human laboratory study on the link between alcohol administration and circulating fibroblast growth factor 21 (FGF21) in individuals with alcohol use disorder

Growing evidence indicates that the crosstalk between the central nervous system and the periphery plays an important role in the pathophysiology of neuropsychiatric conditions, including addictive disorders. Fibroblast growth factor 21 (FGF21) is part of the liver-brain axis and regulates energy homeostasis, metabolism, and macronutrient intake. In addition, FGF21 signaling modulates alcohol intake and preference, and changes in FGF21 levels are observed following alcohol consumption. To further elucidate the relationship between alcohol use and FGF21, we assessed serum FGF21 concentrations in 16 non-treatment seeking individuals with alcohol use disorder (AUD) in a naturalistic outpatient setting, as well as a controlled laboratory experiment that included alcohol cue-reactivity, alcohol priming, and alcohol self-administration in a bar-like setting. FGF21 levels were stable during the outpatient phase when participants received placebo and had no significant lifestyle changes. During the bar-like laboratory experiment, a robust increase in serum FGF21 concentrations was found after the 2-hr alcohol self-administration session (F3, 49 = 23.39, p < 0.001). Percent change in FGF21 levels positively correlated with the amount of alcohol self-administered but did not reach statistical significance. No significant changes in FGF21 levels were found after exposure to alcohol cues or consuming the priming drink. Given the bidirectional link between FGF21 and alcohol, targeting the FGF21 system may be further examined as a potential pharmacotherapy for AUD.

Protection from alcohol intoxication: Must be FGF21 to enter

Fibroblast growth factor 21 (FGF21) is generally known as a stress-induced metabolic regulator with enormous therapeutic potential to treat metabolic diseases, but a more specific role of FGF21 concerns physiological handling of alcohol in mammals. In this issue of Cell Metabolism, Choi et al. demonstrate that FGF21 mediates the recovery from alcohol intoxication by directly activating noradrenergic neurons in mice, thus advancing our knowledge on FGF21 biology and further diversifying its therapeutic potential.

FGF21 counteracts alcohol intoxication by activating the noradrenergic nervous system

Animals that consume fermenting fruit and nectar are at risk of exposure to ethanol and the detrimental effects of inebriation. In this report, we show that the hormone FGF21, which is strongly induced by ethanol in murine and human liver, stimulates arousal from intoxication without changing ethanol catabolism. Mice lacking FGF21 take longer than wild-type littermates to recover their righting reflex and balance following ethanol exposure. Conversely, pharmacologic FGF21 administration reduces the time needed for mice to recover from ethanol-induced unconsciousness and ataxia. FGF21 did not counteract sedation caused by ketamine, diazepam, or pentobarbital, indicating specificity for ethanol. FGF21 mediates its anti-intoxicant effects by directly activating noradrenergic neurons in the locus coeruleus region, which regulates arousal and alertness. These results suggest that this FGF21 liver-brain pathway evolved to protect against ethanol-induced intoxication and that it might be targeted pharmaceutically for treating acute alcohol poisoning.

The Promise of an Evolutionary Perspective of Alcohol Consumption

The urgent need for medical treatments of alcohol use disorders has motivated the search for novel molecular targets of alcohol response. Most studies exploit the strengths of lab animals without considering how these and other species may have adapted to respond to alcohol in an ecological context. Here, we provide an evolutionary perspective on the molecular and genetic underpinnings of alcohol consumption by reviewing evidence that alcohol metabolic enzymes have undergone adaptive evolution at 2 evolutionary junctures: first, to enable alcohol consumption accompanying the advent of a frugivorous diet in a primate ancestor, and second, to decrease the likelihood of excessive alcohol consumption concurrent with the spread of agriculture and fermentation in East Asia. By similarly considering how diverse vertebrate and invertebrate species have undergone natural selection for alcohol responses, novel conserved molecular targets of alcohol are likely be discovered that may represent promising therapeutic targets.

A Genome-Wide Association Study Reveals a BDNF-Centered Molecular Network Associated with Alcohol Dependence and Related Clinical Measures

At least 50% of factors predisposing to alcohol dependence (AD) are genetic and women affected with this disorder present with more psychiatric comorbidities, probably indicating different genetic factors involved. We aimed to run a genome-wide association study (GWAS) followed by a bioinformatic functional annotation of associated genomic regions in patients with AD and eight related clinical measures. A genome-wide significant association of rs220677 with AD (p-value = 1.33 × 10^-8 calculated with the Yates-corrected χ² test under the assumption of dominant inheritance) was discovered in female patients. Associations of AD and related clinical measures with seven other single nucleotide polymorphisms listed in previous GWASs of psychiatric and addiction traits were differently replicated in male and female patients. The bioinformatic analysis showed that regulatory elements in the eight associated linkage disequilibrium blocks define the expression of 80 protein-coding genes. Nearly 68% of these and of 120 previously published coding genes associated with alcohol phenotypes directly interact in a single network, where BDNF is the most significant hub gene. This study indicates that several genes behind the pathogenesis of AD are different in male and female patients, but implicated molecular mechanisms are functionally connected. The study also reveals a central role of BDNF in the pathogenesis of AD.

Phosphorylation of RXRα mediates the effect of JNK to suppress hepatic FGF21 expression and promote metabolic syndrome

The cJun NH₂-terminal kinase (JNK) signaling pathway in the liver promotes systemic changes in metabolism by regulating peroxisome proliferator-activated receptor α (PPARα)-dependent expression of the hepatokine fibroblast growth factor 21 (FGF21). Hepatocyte-specific gene ablation studies demonstrated that the Mapk9 gene (encoding JNK2) plays a key mechanistic role. Mutually exclusive inclusion of exons 7a and 7b yields expression of the isoforms JNK2α and JNK2β. Here we demonstrate that Fgf21 gene expression and metabolic regulation are primarily regulated by the JNK2α isoform. To identify relevant substrates of JNK2α, we performed a quantitative phosphoproteomic study of livers isolated from control mice, mice with JNK deficiency in hepatocytes, and mice that express only JNK2α or JNK2β in hepatocytes. We identified the JNK substrate retinoid X receptor α (RXRα) as a protein that exhibited JNK2α-promoted phosphorylation in vivo. RXRα functions as a heterodimeric partner of PPARα and may therefore mediate the effects of JNK2α signaling on Fgf21 expression. To test this hypothesis, we established mice with hepatocyte-specific expression of wild-type or mutated RXRα proteins. We found that the RXRα phosphorylation site Ser²⁶⁰ was required for suppression of Fgf21 gene expression. Collectively, these data establish a JNK-mediated signaling pathway that regulates hepatic Fgf21 expression.

Genes regulating levels of ω-3 long-chain polyunsaturated fatty acids are associated with alcohol use disorder and consumption, and broader externalizing behavior in humans

BACKGROUND

Individual variation in the physiological response to alcohol is predictive of an individual's likelihood to develop alcohol use disorder (AUD). Evidence from diverse model organisms indicates that the levels of long-chain polyunsaturated omega-3 fatty acids (ω-3 LC-PUFAs) can modulate the behavioral response to ethanol and therefore may impact the propensity to develop AUD. While most ω-3 LC-PUFAs come from diet, humans can produce these fatty acids from shorter chain precursors through a series of enzymatic steps. Natural variation in the genes encoding these enzymes has been shown to affect ω-3 LC-PUFA levels. We hypothesized that variation in these genes could contribute to the susceptibility to develop AUD.

METHODS

We identified nine genes (FADS1, FADS2, FADS3, ELOVL2, GCKR, ELOVL1, ACOX1, APOE, and PPARA) that are required to generate ω-3 LC-PUFAs and/or have been shown or predicted to affect ω-3 LC-PUFA levels. Using both set-based and gene-based analyses we examined their association with AUD and two AUD-related phenotypes, alcohol consumption, and an externalizing phenotype.

RESULTS

We found that the set of nine genes is associated with all three phenotypes. When examined individually, GCKR, FADS2, and ACOX1 showed significant association signals with alcohol consumption. GCKR was significantly associated with AUD. ELOVL1 and APOE were associated with externalizing.

CONCLUSIONS

Taken together with observations that dietary ω-3 LC-PUFAs can affect ethanol-related phenotypes, this work suggests that these fatty acids provide a link between the environmental and genetic influences on the risk of developing AUD.

Genome-wide meta-analysis of alcohol use disorder in East Asians

Alcohol use disorder (AUD) is a leading cause of death and disability worldwide. Genome-wide association studies (GWAS) have identified ~30 AUD risk genes in European populations, but many fewer in East Asians. We conducted GWAS and genome-wide meta-analysis of AUD in 13,551 subjects with East Asian ancestry, using published summary data and newly genotyped data from five cohorts: (1) electronic health record (EHR)-diagnosed AUD in the Million Veteran Program (MVP) sample; (2) DSM-IV diagnosed alcohol dependence (AD) in a Han Chinese-GSA (array) cohort; (3) AD in a Han Chinese-Cyto (array) cohort; and (4) two AD Thai cohorts. The MVP and Thai samples included newly genotyped subjects from ongoing recruitment. In total, 2254 cases and 11,297 controls were analyzed. An AUD polygenic risk score was analyzed in an independent sample with 4464 East Asians (Genetic Epidemiology Research in Adult Health and Aging (GERA)). Phenotypes from survey data and ICD-9-CM diagnoses were tested for association with the AUD PRS. Two risk loci were detected: the well-known functional variant rs1229984 in ADH1B and rs3782886 in BRAP (near the ALDH2 gene locus) are the lead variants. AUD PRS was significantly associated with days per week of alcohol consumption (beta = 0.43, SE = 0.067, p = 2.47 × 10-10) and nominally associated with pack years of smoking (beta = 0.09, SE = 0.05, p = 4.52 × 10-2) and ever vs. never smoking (beta = 0.06, SE = 0.02, p = 1.14 × 10-2). This is the largest GWAS of AUD in East Asians to date. Building on previous findings, we were able to analyze pleiotropy, but did not identify any new risk regions, underscoring the importance of recruiting additional East Asian subjects for alcohol GWAS.

Common and distinguishing genetic factors for substance use behavior and disorder: an integrated analysis of genomic and transcriptomic studies from both human and animal studies

BACKGROUND AND AIMS

Genomic and transcriptomic findings greatly broaden the biological knowledge regarding substance use. However, systematic convergence and comparison evidence of genome-wide findings is lacking for substance use. Here, we combined all the genome-wide findings from both substance use behavior and disorder (SUBD) and identified common and distinguishing genetic factors for different SUBDs.

METHODS

Systemic literature search for genome-wide association (GWAS) and RNA-seq studies of alcohol/nicotine/drug use behavior (partially meets or not reported diagnostic criteria) and alcohol use behavior and disorder (AUBD), nicotine use behavior and disorder (NUBD) and drug use behavior and disorder (DUBD) was performed using PubMed and the GWAS catalog. Drug use was focused upon cannabis, opioid, cocaine and methamphetamine use. GWAS studies required case-control or case/cohort samples. RNA-seq studies were based on brain tissues. The genes which contained significant single nucleotide polymorphism (P ≤ 1 × 10^-6 ) in GWAS and reported as significant in RNA-seq studies were extracted. Pathway enrichment was performed by using Metascape. Gene interaction networks were identified by using the Protein Interaction Network Analysis database.

RESULTS

Total SUBD-related 2910 genes were extracted from 75 GWAS studies (2 773 889 participants) and 17 RNA-seq studies. By overlapping the genes and pathways of AUBD, NUBD and DUBD, four shared genes (CACNB2, GRIN2B, PLXDC2 and PKNOX2), four shared pathways [two Gene Ontology (GO) terms of 'modulation of chemical synaptic transmission', 'regulation of trans-synaptic signaling', two Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways of 'dopaminergic synapse', 'cocaine addiction'] were identified (significantly higher than random, P < 1 × 10^-5 ). The top shared KEGG pathways (Benjamini-Hochberg-corrected P-value < 0.05) in the pairwise comparison of AUBD versus DUBD, NUBD versus DUBD, AUBD versus NUBD were 'Epstein-Barr virus infection', 'protein processing in endoplasmic reticulum' and 'neuroactive ligand-receptor interaction', respectively. We also identified substance-specific genetic factors: i.e. ADH1B and ALDH2 were unique for AUBD, while CHRNA3 and CHRNA4 were unique for NUBD.

CONCLUSIONS

This systematic review identifies the shared and unique genes and pathways for alcohol, nicotine and drug use behaviors and disorders at the genome-wide level and highlights critical biological processes for the common and distinguishing vulnerability of substance use behaviors and disorders.

New developments in the biology of fibroblast growth factors

The fibroblast growth factor (FGF) family is composed of 18 secreted signaling proteins consisting of canonical FGFs and endocrine FGFs that activate four receptor tyrosine kinases (FGFRs 1-4) and four intracellular proteins (intracellular FGFs or iFGFs) that primarily function to regulate the activity of voltage-gated sodium channels and other molecules. The canonical FGFs, endocrine FGFs, and iFGFs have been reviewed extensively by us and others. In this review, we briefly summarize past reviews and then focus on new developments in the FGF field since our last review in 2015. Some of the highlights in the past 6 years include the use of optogenetic tools, viral vectors, and inducible transgenes to experimentally modulate FGF signaling, the clinical use of small molecule FGFR inhibitors, an expanded understanding of endocrine FGF signaling, functions for FGF signaling in stem cell pluripotency and differentiation, roles for FGF signaling in tissue homeostasis and regeneration, a continuing elaboration of mechanisms of FGF signaling in development, and an expanding appreciation of roles for FGF signaling in neuropsychiatric diseases. This article is categorized under: Cardiovascular Diseases > Molecular and Cellular Physiology Neurological Diseases > Molecular and Cellular Physiology Congenital Diseases > Stem Cells and Development Cancer > Stem Cells and Development.

The potential effects of HECTD4 variants on fasting glucose and triglyceride levels in relation to prevalence of type 2 diabetes based on alcohol intake

Excessive alcohol intake is an important cause of major public health problem in East Asian countries. Growing evidence suggests that genetic factors are associated with alcohol consumption and the risk for alcohol-associated disease, and these factors contribute to the risk of developing chronic diseases, including diabetes. This study aims to investigate the association of type 2 diabetes with genetic polymorphisms within HECTD4 based on alcohol exposure. We performed a genome-wide association study involving the cohorts of the KoGES-HEXA study (n = 50,028) and Ansan and Ansung study (n = 7,980), both of which are prospective cohort studies in Korea. The top three single-nucleotide polymorphisms (SNPs) of the HECTD4 gene, specifically rs77768175, rs2074356 and rs11066280, were found to be significantly associated with alcohol consumption. We found that individuals carrying the variant allele in these SNPs had lower fasting blood glucose, triglyceride, and GGT levels than those with the wild-type allele. Multiple logistic regression showed that statistically significant associations of HECTD4 gene polymorphisms with an increased risk of type 2 diabetes were found in drinkers. Namely, these SNPs were associated with decreased odds of diabetes in the presence of alcohol consumption. As a result of examining the effect of alcohol on the expression of the HECTD4 gene, ethanol increased the expression of HECTD4 in cells, but the level was decreased by NAC treatment. Similar results were obtained from liver samples of mice treated with alcohol. Moreover, a loss of HECTD4 resulted in reduced levels of CYP2E1 and lipogenic gene expression in ethanol-treated cells, while the level of ALDH2 expression increased, indicating a reduction in ethanol-induced hepatotoxicity.

Back-translating GWAS findings to animal models reveals a role for Hgfac and Slc39a8 in alcohol and nicotine consumption

Alcohol and tobacco are the most commonly used addictive substances, with high comorbidity rates between alcohol use disorder and tobacco use disorder. Risk for alcohol and nicotine addiction is highly heritable, and they share common genetic factors. A GWAS in over 1 million individuals has revealed 566 genetic variants in 406 loci associated with multiple stages of alcohol and tobacco use. Three novel genes-SLC39A8, GRK4 and HGFAC-within loci associated with altered alcoholic drinks per week (ADW) or cigarettes per day (CPD) were selected to further study their role in alcohol and tobacco use disorder. The role of these genes was assessed using the two-bottle choice addiction paradigm in transgenic mice for each of the genes. We found significant decreases in chronic alcohol consumption and preference in female Hgfac knockout (KO) mice, and decreased nicotine preference in male Hgfac KO compared with wild-type (WT) mice. Additionally, male Slc39a8 hypomorph mice showed greater overall nicotine preference compared with WT mice, while no differences were detected for Grk4 KO mice in alcohol or nicotine consumption and preference in either sex. Thus, this study implicates Hgfac and Slc39a8 in alcohol and tobacco use in a sex-specific manner.

Depression with atypical neurovegetative symptoms shares genetic predisposition with immuno-metabolic traits and alcohol consumption

BACKGROUND

Depression is a highly prevalent and heterogeneous disorder. This study aims to determine whether depression with atypical features shows different heritability and different degree of overlap with polygenic risk for psychiatric and immuno-metabolic traits than other depression subgroups.

METHODS

Data included 30 069 European ancestry individuals from the UK Biobank who met criteria for lifetime major depression. Participants reporting both weight gain and hypersomnia were classified as ↑WS depression (N = 1854) and the others as non-↑WS depression (N = 28 215). Cases with non-↑WS depression were further classified as ↓WS depression (i.e. weight loss and insomnia; N = 10 142). Polygenic risk scores (PRS) for 22 traits were generated using genome-wide summary statistics (Bonferroni corrected p = 2.1 × 10-4). Single-nucleotide polymorphism (SNP)-based heritability of depression subgroups was estimated.

RESULTS

↑WS depression had a higher polygenic risk for BMI [OR = 1.20 (1.15-1.26), p = 2.37 × 10-14] and C-reactive protein [OR = 1.11 (1.06-1.17), p = 8.86 × 10-06] v. non-↑WS depression and ↓WS depression. Leptin PRS was close to the significance threshold (p = 2.99 × 10-04), but the effect disappeared when considering GWAS summary statistics of leptin adjusted for BMI. PRS for daily alcohol use was inversely associated with ↑WS depression [OR = 0.88 (0.83-0.93), p = 1.04 × 10-05] v. non-↑WS depression. SNP-based heritability was not significantly different between ↑WS depression and ↓WS depression (14.3% and 12.2%, respectively).

CONCLUSIONS

↑WS depression shows evidence of distinct genetic predisposition to immune-metabolic traits and alcohol consumption. These genetic signals suggest that biological targets including immune-cardio-metabolic pathways may be relevant to therapies in individuals with ↑WS depression.

Spatial distribution of beta-klotho mRNA in the mouse hypothalamus, hippocampal region, subiculum, and amygdala

Beta-klotho (KLB) is a co-receptor required for endocrine fibroblast growth factor (FGF) 15/19 and FGF21 signaling in the brain. Klb is prominent within the hypothalamus, which is consistent with its metabolic functions, but diverse roles for Klb are now emerging. Central Klb expression is low but discrete and may govern FGF-targeted sites. However, given its low expression, it is unclear if Klb mRNA is more widespread. We performed in situ hybridization to label Klb mRNA to generate spatial maps capturing the distribution and level of Klb within the mouse hypothalamus, hippocampal region, subiculum, and amygdala. Semi-quantitative analysis revealed that Klb-labeled cells may express low, medium, or high levels of Klb mRNA. Hypothalamic Klb hybridization was heterogeneous and varied rostrocaudally within the same region. Most Klb-labeled cells were found in the lateral hypothalamic zone, but the periventricular hypothalamic region, including the suprachiasmatic nucleus, contained the greatest proportion of cells expressing medium or high Klb levels. We also found heterogeneous Klb hybridization in the amygdala and subiculum, where Klb was especially distinct within the central amygdalar nucleus and ventral subiculum, respectively. By contrast, Klb-labeled cells in the hippocampal region only expressed low levels of Klb and were typically found in the pyramidal layer of Ammon's horn or dentate gyrus. The Klb-labeled regions identified in this study are consistent with reported roles of Klb in metabolism, taste preference, and neuroprotection. However, additional identified sites, including within the hypothalamus and amygdala, may suggest novel roles for FGF15/19 or FGF21 signaling. The central expression of beta-klotho (Klb) is essential for the physiological actions of endocrine fibroblast growth factors. Klb mRNA was widely expressed throughout the hypothalamus, hippocampus, and amygdala. However, the level of Klb expression varied between cells and contributed to a distinctive pattern of distribution within each brain structure. This article is protected by copyright. All rights reserved.

Predicting Alcohol Use From Genome-Wide Polygenic Scores, Environmental Factors, and Their Interactions in Young Adulthood

OBJECTIVE

Alcohol use during emerging adulthood is associated with adverse life outcomes, but its risk factors are not well known. Here, we predicted alcohol use in 3153 young adults aged 22 years from a) genome-wide polygenic scores (GPS) based on genome-wide association studies for the target phenotypes number of drinks per week and Alcohol Use Disorders Identification Test scores, b) 30 environmental factors, and c) their interactions (i.e., G × E effects).

METHODS

Data were collected from 1994 to 2018 as a part of the UK Twins Early Development Study.

RESULTS

GPS accounted for up to 1.9% of the variance in alcohol use (i.e., Alcohol Use Disorders Identification Test score), whereas the 30 measures of environmental factors together accounted for 21.1%. The 30 GPS by environment interactions did not explain any additional variance, and none of the interaction terms exceeded the significance threshold after correcting for multiple testing.

CONCLUSIONS

GPS and some environmental factors significantly predicted alcohol use in young adulthood, but we observed no GPS by environment interactions in our study.

FGF21 suppresses alcohol consumption through an amygdalo-striatal circuit

Excessive alcohol consumption is a major health and social issue in our society. Pharmacologic administration of the endocrine hormone fibroblast growth factor 21 (FGF21) suppresses alcohol consumption through actions in the brain in rodents, and genome-wide association studies have identified single nucleotide polymorphisms in genes involved with FGF21 signaling as being associated with increased alcohol consumption in humans. However, the neural circuit(s) through which FGF21 signals to suppress alcohol consumption are unknown, as are its effects on alcohol consumption in higher organisms. Here, we demonstrate that administration of an FGF21 analog to alcohol-preferring non-human primates reduces alcohol intake by 50%. Further, we reveal that FGF21 suppresses alcohol consumption through a projection-specific subpopulation of KLB-expressing neurons in the basolateral amygdala. Our results illustrate how FGF21 suppresses alcohol consumption through a specific population of neurons in the brain and demonstrate its therapeutic potential in non-human primate models of excessive alcohol consumption.

Fibroblast Growth Factor 21 Facilitates the Homeostatic Control of Feeding Behavior

Fibroblast growth factor 21 (FGF21) is a stress hormone that is released from the liver in response to nutritional and metabolic challenges. In addition to its well-described effects on systemic metabolism, a growing body of literature now supports the notion that FGF21 also acts via the central nervous system to control feeding behavior. Here we review the current understanding of FGF21 as a hormone regulating feeding behavior in rodents, non-human primates, and humans. First, we examine the nutritional contexts that induce FGF21 secretion. Initial reports describing FGF21 as a 'starvation hormone' have now been further refined. FGF21 is now better understood as an endocrine mediator of the intracellular stress response to various nutritional manipulations, including excess sugars and alcohol, caloric deficits, a ketogenic diet, and amino acid restriction. We discuss FGF21's effects on energy intake and macronutrient choice, together with our current understanding of the underlying neural mechanisms. We argue that the behavioral effects of FGF21 function primarily to maintain systemic macronutrient homeostasis, and in particular to maintain an adequate supply of protein and amino acids for use by the cells.

Genetic analysis of dietary intake identifies new loci and functional links with metabolic traits

Dietary intake is a major contributor to the global obesity epidemic and represents a complex behavioural phenotype that is partially affected by innate biological differences. Here, we present a multivariate genome-wide association analysis of overall variation in dietary intake to account for the correlation between dietary carbohydrate, fat and protein in 282,271 participants of European ancestry from the UK Biobank (n = 191,157) and Cohorts for Heart and Aging Research in Genomic Epidemiology Consortium (n = 91,114), and identify 26 distinct genome-wide significant loci. Dietary intake signals map exclusively to specific brain regions and are enriched for genes expressed in specialized subtypes of GABAergic, dopaminergic and glutamatergic neurons. We identified two main clusters of genetic variants for overall variation in dietary intake that were differently associated with obesity and coronary artery disease. These results enhance the biological understanding of interindividual differences in dietary intake by highlighting neural mechanisms, supporting functional follow-up experiments and possibly providing new avenues for the prevention and treatment of prevalent complex metabolic diseases.

Impact of Alcohol Consumption on Male Fertility Potential: A Narrative Review

Alcohol abuse disorder is a serious condition, implicating more than 15 million people aged 12 years and older in 2019 in the United States. Ethanol (or ethyl alcohol) is mainly oxidized in the liver, resulting in the synthesis of acetaldehyde and acetate, which are toxic and carcinogenic metabolites, as well as in the generation of a reductive cellular environment. Moreover, ethanol can interact with lipids, generating fatty acid ethyl esters and phosphatidylethanol, which interfere with physiological cellular pathways. This narrative review summarizes the impact of excessive alcohol consumption on male fertility by describing its metabolism and how ethanol consumption may induce cellular damage. Furthermore, the impact of alcohol consumption on hormonal regulation, semen quality, and genetic and epigenetic regulations is discussed based on evidence from animal and human studies, focusing on the consequences on the offspring. Finally, the limitations of the current evidence are discussed. Our review highlights the association between chronic alcohol consumption and poor semen quality, mainly due to the development of oxidative stress, as well as its genotoxic impact on hormonal regulation and DNA integrity, affecting the offspring’s health. New landscapes of investigation are proposed for the identification of molecular markers for alcohol-associated infertility, with a focus on advanced OMICS-based approaches applied to the analysis of semen samples.

Protein Appetite at the Interface between Nutrient Sensing and Physiological Homeostasis

Feeding behavior is guided by multiple competing physiological needs, as animals must sense their internal nutritional state and then identify and consume foods that meet nutritional needs. Dietary protein intake is necessary to provide essential amino acids and represents a specific, distinct nutritional need. Consistent with this importance, there is a relatively strong body of literature indicating that protein intake is defended, such that animals sense the restriction of protein and adaptively alter feeding behavior to increase protein intake. Here, we argue that this matching of food consumption with physiological need requires at least two concurrent mechanisms: the first being the detection of internal nutritional need (a protein need state) and the second being the discrimination between foods with differing nutritional compositions. In this review, we outline various mechanisms that could mediate the sensing of need state and the discrimination between protein-rich and protein-poor foods. Finally, we briefly describe how the interaction of these mechanisms might allow an animal to self-select between a complex array of foods to meet nutritional needs and adaptively respond to changes in either the external environment or internal physiological state.

A systems omics-based approach to decode substance use disorders and neuroadaptations

Substance use disorders (SUDs) are a group of neuropsychiatric conditions manifesting due to excessive dependence on potential drugs of abuse such as psychostimulants, opioids including prescription opioids, alcohol, inhalants, etc. Experimental studies have generated enormous data in the area of SUDs, but outcomes from such data have remained largely fragmented. In this review, we attempt to coalesce these data points providing an important first step towards our understanding of the etiology of SUDs. We propose and describe a 'core addictome' pathway that behaves central to all SUDs. Besides, we also have made some notable observations paving way for several hypotheses; MECP2 behaves as a master switch during substance use; five distinct gene clusters were identified based on respective substance addiction; a central cluster of genes serves as a hub of the addiction pathway connecting all other substance addiction clusters. In addition to describing these findings, we have emphasized the importance of some candidate genes that are of substantial interest for further investigation and serve as high-value targets for translational efforts.

Alcohol and the brain: from genes to circuits

Alcohol use produces wide-ranging and diverse effects on the central nervous system. It influences intracellular signaling mechanisms, leading to changes in gene expression, chromatin remodeling, and translation. As a result of these molecular alterations, alcohol affects the activity of neuronal circuits. Together, these mechanisms produce long-lasting cellular adaptations in the brain that in turn can drive the development and maintenance of alcohol use disorder (AUD). We provide an update on alcohol research, focusing on multiple levels of alcohol-induced adaptations, from intracellular changes to changes in neural circuits. A better understanding of how alcohol affects these diverse and interlinked mechanisms may lead to the identification of novel therapeutic targets and to the development of much-needed novel and efficacious treatment options.

The Interaction of Single Nucleotide Polymorphisms on Fibroblast Growth Factor 19 Superfamily Genes Is Associated With Alcohol Dependence-Related Aggression

Alcohol dependence (AD) is characterized by compulsive alcohol consumption, which involves behavioral impairments such as aggression. Members of fibroblast growth factor (FGF) 19 superfamily, including FGF19, FGF21, and FGF23, are major endocrine mediators that play an important role in alcohol metabolism and alcohol related disorders. The objective of the present study is to explore the possible associations among the interaction of single nucleotide polymorphisms (SNPs) of the FGF 19 superfamily, AD occurrence, and aggression in patients with AD. A total of 956 subjects were enrolled in this study, including 482 AD patients and 474 healthy controls (HCs). Michigan alcoholism screening test (MAST) was used to measure the level of AD, a Chinese version of the Buss–Perry Aggression Questionnaire was used to evaluate the aggressive behavior of subjects, and MassARRAY^@ system was used to genotype rs948992 of FGF19, rs11665841 and rs11665896 of FGF21, rs7955866 and rs11063118 of FGF23. The results showed that AD patients presented a significantly higher level of aggression compared to HCs, and MAST scores were significantly positively associated Buss–Perry aggression scores (r = 0.402, p < 0.001) in AD patients. The interaction of FGF19 rs948992 TC × FGF21 rs11665896 GG presented the high-risk genotype combination predicting the high level of AD. In addition, the interaction of FGF19 rs948992 TC × FGF21 rs11665896 TG × FGF23 rs11063118 TT presented the high-risk genotype combination predicting the high level of aggression in AD patients. Our results added evidence linking the combination of rs948992 TC × rs11665896 TG × rs11063118 TT to aggressive behavior in AD patients and pointed out the potential usefulness of the SNPs of FGF19 superfamily as a predictor for the aggression in AD patients.

Novel characterization of the multivariate genetic architecture of internalizing psychopathology and alcohol use

Genetic correlations suggest that the genetic relationship of alcohol use with internalizing psychopathology depends on the measure of alcohol use. Problematic alcohol use (PAU) is positively genetically correlated with internalizing psychopathology, whereas alcohol consumption ranges from not significantly correlated to moderately negatively correlated with internalizing psychopathology. To explore these different genetic relationships of internalizing psychopathology with alcohol use, we performed a multivariate genome-wide association study of four correlated factors (internalizing psychopathology, PAU, quantity of alcohol consumption, and frequency of alcohol consumption) and then assessed genome-wide and local genetic covariance between these factors. We identified 14 significant regions of local, largely positive, genetic covariance between PAU and internalizing psychopathology and 12 regions of significant local genetic covariance (including both positive and negative genetic covariance) between consumption factors and internalizing psychopathology. Partitioned genetic covariance among functional annotations suggested that brain tissues contribute significantly to positive genetic covariance between internalizing psychopathology and PAU but not to the genetic covariance between internalizing psychopathology and quantity or frequency of alcohol consumption. We hypothesize that genome-wide genetic correlations between alcohol use and psychiatric traits may not capture the more complex shared or divergent genetic architectures at the locus or tissue specific level. This study highlights the complexity of genetic architectures of alcohol use and internalizing psychopathology, and the differing shared genetics of internalizing disorders with PAU compared to consumption.

Associations of Alcohol Consumption with Cerebrospinal Fluid Biomarkers of Alzheimer's Disease Pathology in Cognitively Intact Older Adults: The CABLE Study

BACKGROUND

The relationship between alcohol consumption and Alzheimer's disease (AD) pathology is unclear. Amyloid-β (Aβ) and tau biomarkers in cerebrospinal fluid (CSF) have been proven valuable in establishing prognosis in pre-clinical AD.

OBJECTIVE

We sought to examine the associations between alcohol consumption and CSF AD biomarkers in cognitive intact subjects.

METHODS

A total of 806 cognitively intact participants who had measurements of CSF Aβ, pTau, and total Tau proteins and drinking characteristics were included from the Chinese Alzheimer's Biomarker and Lifestyle (CABLE) study. Linear and logistic regression analyses were utilized to explore the associations of alcohol consumption with CSF AD biomarkers. We examined the interaction effects of age, gender, and apolipoprotein epsilon (APOE) ɛ4 status on the relationships between the frequency of drinking and CSF biomarkers.

RESULTS

The multiple linear regression analyses revealed significant differences in CSF AD biomarkers between infrequent drinking (< 1 times/week) and frequent drinking groups (≥1 times/week). Participants in frequent drinking group had higher CSF p-tau/Aβ42 and tTau/Aβ42. Frequent drinking was significantly associated with greater pTau and tTau abnormalities compared to the infrequent drinking group in older (> 65 years) participants.

CONCLUSION

The present study showed significant associations between drinking frequency and CSF AD biomarkers in cognitively intact older adults. Alcohol consumption may have an influence on AD by modulating amyloid deposition and tau phosphorylation in the preclinical stage.