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Effects of Gabra2 Point Mutations on Alcohol Intake: Increased Binge-Like and Blunted Chronic Drinking by Mice.

ABSTRACT: BACKGROUND:Alcohol use disorders are associated with single-nucleotide polymorphisms in GABRA2, the gene encoding the GABAA receptor ?2-subunit in humans. Deficient GABAergic functioning is linked to impulse control disorders, intermittent explosive disorder, and to drug abuse and dependence, yet it remains unclear whether ?2-containing GABAA receptor sensitivity to endogenous ligands is involved in excessive alcohol drinking. METHODS:Male wild-type (Wt) C57BL/6J and point-mutated mice rendered insensitive to GABAergic modulation by benzodiazepines (BZD; H101R), allopregnanolone (ALLO) or tetrahydrodeoxycorticosterone (THDOC; Q241M), or high concentrations of ethanol (EtOH) (S270H/L277A) at ?2-containing GABAA receptors were assessed for their binge-like, moderate, or escalated chronic drinking using drinking in the dark, continuous access (CA) and intermittent access (IA) to alcohol protocols, respectively. Social approach by mutant and Wt mice in forced alcohol abstinence was compared to approach by EtOH-naïve controls. Social deficits in forced abstinence were treated with allopregnanolone (0, 3.0, 10.0 mg/kg, intraperitoneal [i.p.]) or midazolam (0, 0.56, 1.0 mg/kg, i.p.). RESULTS:Mice with BZD-insensitive ?2-containing GABAA receptors (H101R) escalated their binge-like drinking. Mutants harboring the Q241M point substitution in Gabra2 showed blunted chronic intake in the CA and IA protocols. S270H/L277A mutants consumed excessive amounts of alcohol but, unlike wild-types, they did not show forced abstinence-induced social deficits. CONCLUSIONS:These findings suggest a role for: (i) H101 in species-typical binge-like drinking, (ii) Q241 in escalated chronic drinking, and (iii) S270 and/or L277 in the development of forced abstinence-associated social deficits. Clinical findings report reduced BZD-binding sites in the cortex of dependent patients; the present findings suggest a specific role for BZD-sensitive ?2-containing receptors. In addition, amino acid residue 241 in Gabra2 is necessary for positive modulation and activation of GABAA receptors by ALLO and THDOC; we postulate that neurosteroid action on ?2-containing receptor may be necessary for escalated chronic EtOH intake.

SUBMITTER: Newman EL

PROVIDER: S-EPMC5073020 | biostudies-literature | 2016 Nov

REPOSITORIES: biostudies-literature

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Effects of Gabra2 Point Mutations on Alcohol Intake: Increased Binge-Like and Blunted Chronic Drinking by Mice.

Newman Emily L EL Gunner Georgia G Huynh Polly P Gachette Darrel D Moss Stephen J SJ Smart Trevor G TG Rudolph Uwe U DeBold Joseph F JF Miczek Klaus A KA

Alcoholism, clinical and experimental research 20160926 11

<h4>Background</h4>Alcohol use disorders are associated with single-nucleotide polymorphisms in GABRA2, the gene encoding the GABA<sub>A</sub> receptor α2-subunit in humans. Deficient GABAergic functioning is linked to impulse control disorders, intermittent explosive disorder, and to drug abuse and dependence, yet it remains unclear whether α2-containing GABA<sub>A</sub> receptor sensitivity to endogenous ligands is involved in excessive alcohol drinking.<h4>Methods</h4>Male wild-type (Wt) C57B ...[more]

PMID: 27717041

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Project description:BackgroundBinge drinking (BD) refers to a pattern of alcohol consumption characterized by the consumption of large amounts of alcohol in a short period of time followed by periods of abstinence. This drinking pattern is prevalent worldwide, mainly among young people. Excessive alcohol consumption is the spectrum of consumption patterns that may have or have had health consequences, and includes the concepts of risky alcohol use, harmful alcohol use and alcohol dependence according to Diagnostic and Statistical Manual of Mental Disorders, fourth edition (DSM-IV), the latter two are currently grouped into alcohol use disorder (AUD) according to the fifth edition of the DSM (DSM-5). Due to the high prevalence of BD among young people, especially university students, as well as the important consequences of its practice, a study was conducted to evaluate excessive alcohol consumption and its relationship with the practice of BD in university students.MethodsA cross-sectional study was conducted among students (aged 18-30 years) enrolled in the academic year 2018-2019 at the Faculty of Nursing at a university in northern Spain. Data collection included sociodemographic information, and alcohol use information, collected using a semi-structured questionnaire. To measure the excessive alcohol consumption, this study used the Alcohol Use Disorders Identification Test (AUDIT).ResultsA total of 142 participants were included, of which 88.03% were women. Up to 38.03% were classified as BD. Up to 14.77% of non-BD participants and 66.67% of BD participants were classified as risky drinkers (AUDIT Total geq 8 in men or geq 6 in women) (p < 0.001). Up to 3.41% of the non-BD and 24.07% of the BD were drinkers with harmful alcohol use and probable alcohol dependence (AUDIT Total geq 13) (p < 0.001). A total of 5.68% of non-BD and 42.59% of BD were AUD drinkers (AUDIT Total geq 9 in males or geq 8 in females) (p < 0.001). In addition, statistically significant differences were found between the BD and non-BD groups in the responses to each of the AUDIT items, as well as in the total score and also in the scores of the three domains of the questionnaire.ConclusionsExcessive alcohol consumption is frequent among university students, especially among those who practice BD.

Project description:ObjectiveExcessive alcohol consumption is a leading cause of global morbidity and mortality. However, knowledge of the biological factors that influence ad libitum alcohol intake may be incomplete. Two large studies recently linked variants in the KLB locus with levels of alcohol intake in humans. KLB encodes ?-klotho, co-receptor for the liver-derived hormone fibroblast growth factor 21 (FGF21). In mice, FGF21 reduces alcohol intake, and human Fgf21 variants are enriched among heavy drinkers. Thus, the liver may limit alcohol consumption by secreting FGF21. However, whether full-length, active plasma FGF21 (FGF21 (1-181)) levels in humans increase acutely or sub-chronically in response to alcohol ingestion is uncertain.MethodsWe recruited 10 healthy, fasted male subjects to receive an oral water or alcohol bolus with concurrent blood sampling for FGF21 (1-181) measurement in plasma. In addition, we measured circulating FGF21 (1-181) levels, liver stiffness, triglyceride, and other metabolic parameters in three healthy Danish men before and after consuming an average of 22.6 beers/person/day (4.4 g/kg/day of ethanol) for three days during Oktoberfest 2017 in Munich, Germany. We further correlated fasting FGF21 (1-181) levels in 49 healthy, non-alcoholic subjects of mixed sex with self-reports of alcohol-related behaviors, emotional responses, and problems. Finally, we characterized the effect of recombinant human FGF21 injection on ad libitum alcohol intake in mice.ResultsWe show that alcohol ingestion (25.3 g or ?2.5 standard drinks) acutely increases plasma levels of FGF21 (1-181) 3.4-fold in fasting humans. We also find that binge drinking for three days at Oktoberfest is associated with a 2.1-fold increase in baseline FGF21 (1-181) levels, in contrast to minor deteriorations in metabolic and hepatic biomarkers. However, basal FGF21 (1-181) levels were not correlated with differences in alcohol-related behaviors, emotional responses, or problems in our non-alcoholic subjects. Finally, we show that once-daily injection of recombinant human FGF21 reduces ad libitum alcohol intake by 21% in mice.ConclusionsFGF21 (1-181) is markedly increased in circulation by both acute and sub-chronic alcohol intake in humans, and reduces alcohol intake in mice. These observations are consistent with a role for FGF21 as an endocrine inhibitor of alcohol appetite in humans.

Dataset Information

Effects of Gabra2 Point Mutations on Alcohol Intake: Increased Binge-Like and Blunted Chronic Drinking by Mice.

Publications

Effects of Gabra2 Point Mutations on Alcohol Intake: Increased Binge-Like and Blunted Chronic Drinking by Mice.

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