Falk Kiefer

Genome-wide Association Study of Alcohol Dependence

CONTEXT Alcohol dependence is a serious and common public health problem. It is well established that genetic factors play a major role in the development of this disorder. Identification of genes that contribute to alcohol dependence will improve our understanding of the mechanisms that underlie this disorder. OBJECTIVE To identify susceptibility genes for alcohol dependence through a genome-wide association study (GWAS) and a follow-up study in a population of German male inpatients with an early age at onset. DESIGN The GWAS tested 524,396 single-nucleotide polymorphisms (SNPs). All SNPs with P < 10(-4) were subjected to the follow-up study. In addition, nominally significant SNPs from genes that had also shown expression changes in rat brains after long-term alcohol consumption were selected for the follow-up step. SETTING Five university hospitals in southern and central Germany. PARTICIPANTS The GWAS included 487 male inpatients with alcohol dependence as defined by the DSM-IV and an age at onset younger than 28 years and 1358 population-based control individuals. The follow-up study included 1024 male inpatients and 996 age-matched male controls. All the participants were of German descent. MAIN OUTCOME MEASURES Significant association findings in the GWAS and follow-up study with the same alleles. RESULTS The GWAS produced 121 SNPs with nominal P < 10(-4). These, together with 19 additional SNPs from homologues of rat genes showing differential expression, were genotyped in the follow-up sample. Fifteen SNPs showed significant association with the same allele as in the GWAS. In the combined analysis, 2 closely linked intergenic SNPs met genome-wide significance (rs7590720, P = 9.72 x 10(-9); rs1344694, P = 1.69 x 10(-8)). They are located on chromosome region 2q35, which has been implicated in linkage studies for alcohol phenotypes. Nine SNPs were located in genes, including the CDH13 and ADH1C genes, that have been reported to be associated with alcohol dependence. CONCLUSIONS This is the first GWAS and follow-up study to identify a genome-wide significant association in alcohol dependence. Further independent studies are required to confirm these findings.

Genetic variation in the PNPLA3 gene is associated with alcoholic liver injury in caucasians.

A recent genome‐wide study revealed an association between variation in the PNPLA3 gene and liver fat content. In addition, the PNPLA3 single‐nucleotide polymorphism rs738409 (M148I) was reported to be associated with advanced alcoholic liver disease in alcohol‐dependent individuals of Mestizo descent. We therefore evaluated the impact of rs738409 on the manifestation of alcoholic liver disease in two independent German cohorts. Genotype and allele frequencies of rs738409 (M148I) were determined in 1,043 alcoholic patients with or without alcoholic liver injury and in 376 at‐risk drinkers from a population‐based cohort. Relative to alcoholic patients without liver damage (n = 439), rs738409 genotype GG was strongly overrepresented in patients with alcoholic liver cirrhosis (n = 210; OR 2.79; Pgenotype = 1.2 × 10−5; Pallelic = 1.6 × 10−6) and in alcoholic patients without cirrhosis but with elevated alanine aminotransferase levels (n = 219; OR 2.33; Pgenotype = 0.0085; Pallelic = 0.0042). The latter, biochemically defined association was confirmed in an independent population‐based cohort of at‐risk drinkers with a median alcohol intake of 300 g/week (OR 4.75; Pgenotype = 0.040; Pallelic = 0.022), and for aspartate aminotransferase (AST) levels. Frequencies of allele PNPLA3 rs738409(G) in individuals with steatosis and normal alanine aminotransferase (ALT) and AST levels were lower than in alcoholics without steatosis and normal ALT/AST (Pcombined = 0.03). The population attributable risk of cirrhosis in alcoholic carriers of allele PNPLA3 rs738409(G) was estimated at 26.6%. Conclusion: Genotype PNPLA3 rs738409(GG) is associated with alcoholic liver cirrhosis and elevated aminotransferase levels in alcoholic Caucasians. (HEPATOLOGY 2011)

Suppression of the HPA Axis Stress-Response: Implications for Relapse

This article presents the proceedings of a symposium held at the meeting of the International Society for Biomedical Research on Alcoholism (ISBRA) in Mannheim, Germany, in October 2004. This symposium explored the potential role of hypothalamic-pituitary-adrenal (HPA) axis dysregulation upon relapse. HPA axis stimulation induces the release of the glucocorticoid cortisol, a compound with profound effects upon behavior and emotion. Altered stress-responses of the HPA axis in abstinent alcohol-dependent subjects, therefore, may influence their affective and behavioral regulation, thus impacting their potential for relapse. Bryon Adinoff began the symposium with a review of HPA axis dysfunction in alcohol-dependent subjects, including recent studies from his lab demonstrating an attenuated glucocorticoid response to both endogenous and exogenous stimulation in one-month abstinent men. Klaus Junghanns presented his work demonstrating that a blunted ACTH or cortisol response to subjective stressors (social stressor or alcohol exposure) is predictive of a return to early drinking. The final two presenters examined the interaction between naltrexone and HPA responsiveness in alcohol-dependent or at-risk subjects, as naltrexone induces an increase in ACTH and cortisol. Falk Kiefer discussed the relationship between basal HPA axis responsivity and clinical outcome following treatment with naltrexone or acamprosate. Plasma ACTH significantly decreased over the course of the study in the placebo group, but not the medication groups [corrected] Lower basal concentrations of ACTH and cortisol were associated with quicker relapse in the placebo group only. Suchitra Krishnan-Sarin described her preliminary work, in which family-history positive (FH+) and family history negative (FH-) subjects were administered naltrexone, followed by an assessment of alcohol-induced craving. The cortisol response to alcohol was significantly and inversely related to craving in the FH+, but not the FH-, subjects. Alterations in HPA axis responsivity may therefore have a negative impact upon clinical outcome in alcohol-dependent subjects, and disinhibition of the axis with medication may have therapeutic potential.

Drugs for relapse prevention of alcoholism: ten years of progress

Multiple neurochemical pathways are involved in mediating craving and relapse to alcohol. Opioidergic and glutamatergic systems have a key role in alcoholism, as demonstrated by the clinically effective compounds naltrexone and acamprosate acting through these systems. The dopaminergic system has long featured in alcoholism research; hitherto disappointing results from clinical studies could improve following the discovery that dopamine D3 receptor antagonism produces consistent and robust results in preclinical studies. Corticotropin-releasing factor signalling and the endocannabinoid system integrate stress-related events and thereby mediate relapse behaviour. Overall, these new targets have yielded several compounds that are undergoing clinical testing. However, the heterogeneity in treatment response makes it necessary to characterize genetic and protein markers and endophenotypes for individualized pharmacotherapy.

Translational magnetic resonance spectroscopy reveals excessive central glutamate levels during alcohol withdrawal in humans and rats.

BACKGROUND In alcoholism, excessive glutamatergic neurotransmission has long been implicated in the acute withdrawal syndrome and as a key signal for dependence-related neuroplasticity. Our understanding of this pathophysiological mechanism originates largely from animal studies, but human data are needed for translation into successful medication development. METHODS We measured brain glutamate levels during detoxification in alcohol-dependent patients (n = 47) and in healthy control subjects (n = 57) as well as in a rat model of alcoholism by state-of-the-art ¹H-magnetic magnetic resonance spectroscopy at 3 and 9.4 T, respectively. RESULTS We found significantly increased glutamate levels during acute alcohol withdrawal in corresponding prefrontocortical regions of treatment-seeking alcoholic patients and alcohol-dependent rats versus respective control subjects. The augmented spectroscopic glutamate signal is likely related to increased glutamatergic neurotransmission because, enabled by the high field strength of the animal scanner, we detected a profoundly elevated glutamate/glutamine ratio in alcohol-dependent rats during acute withdrawal. All dependence-induced metabolic alterations normalize within a few weeks of abstinence in both humans and rats. CONCLUSIONS Our data provide first-time direct support from humans for the glutamate hypothesis of alcoholism, demonstrate the comparability of human and animal magnetic resonance spectroscopy responses, and identify the glutamate/glutamine ratio as potential biomarker for monitoring disease progression.

Effects of Cue-Exposure Treatment on Neural Cue Reactivity in Alcohol Dependence: A Randomized Trial

BACKGROUND In alcohol-dependent patients, alcohol-associated cues elicit brain activation in mesocorticolimbic networks involved in relapse mechanisms. Cue-exposure based extinction training (CET) has been shown to be efficacious in the treatment of alcoholism; however, it has remained unexplored whether CET mediates its therapeutic effects via changes of activity in mesolimbic networks in response to alcohol cues. In this study, we assessed CET treatment effects on cue-induced responses using functional magnetic resonance imaging (fMRI). METHODS In a randomized controlled trial, abstinent alcohol-dependent patients were randomly assigned to a CET group (n = 15) or a control group (n = 15). All patients underwent an extended detoxification treatment comprising medically supervised detoxification, health education, and supportive therapy. The CET patients additionally received nine CET sessions over 3 weeks, exposing the patient to his/her preferred alcoholic beverage. Cue-induced fMRI activation to alcohol cues was measured at pretreatment and posttreatment. RESULTS Compared with pretreatment, fMRI cue-reactivity reduction was greater in the CET relative to the control group, especially in the anterior cingulate gyrus and the insula, as well as limbic and frontal regions. Before treatment, increased cue-induced fMRI activation was found in limbic and reward-related brain regions and in visual areas. After treatment, the CET group showed less activation than the control group in the left ventral striatum. CONCLUSIONS The study provides first evidence that an exposure-based psychotherapeutic intervention in the treatment of alcoholism impacts on brain areas relevant for addiction memory and attentional focus to alcohol-associated cues and affects mesocorticolimbic reward pathways suggested to be pathophysiologically involved in addiction.

Pharmacological Relapse Prevention of Alcoholism: Clinical Predictors of Outcome

Objective: The efficacy of pharmacological relapse prevention in alcoholism with acamprosate and naltrexone has been supported by several controlled trials. It remains uncertain whether any differential indication for treatment exists. Methods: We evaluated outcome data of a controlled trial on acamprosate and naltrexone in patients with low vs. high baseline somatic distress, depression and anxiety (Symptom Checklist-90, SCL-90), low vs. high baseline craving, and according to typological differentiation as proposed by Cloninger and Lesch. These variables have previously been suggested to be predictors of outcome. Results: Comparing the course of abstinence rates, acamprosate was mainly efficacious in patients with low baseline somatic distress, whereas naltrexone was effective especially in patients with high baseline depression. Baseline craving showed no predictive value. Pharmacological treatment was efficacious in type II alcoholics according to Cloninger. Applying Lesch’s typological differentiation, acamprosate was shown to be mainly effective in type I, whereas naltrexone revealed best treatment effects in type III and IV. Conclusion: The study supports the hypothesis that different subgroups of alcohol dependent subjects might benefit from a differential treatment with either naltrexone or acamprosate. Baseline psychopathology and especially typological differentiation might be useful in matching patients to distinct pharmacotherapeutic interventions.

Leptin: a modulator of alcohol craving?

BACKGROUND Leptin has been shown to regulate food intake and energy expenditure. Because leptin acts via regulation of appetite, we studied the hypothesis that suggests leptin modulates craving for alcohol as well. METHODS We studied leptin plasma concentrations (RIA) both in alcoholic subjects during inpatient detoxification (day 1: n = 78, day 14: n = 60) and in healthy control subjects (n = 30). To rule out interference with the activation of the HPA axis during alcohol withdrawal, we also evaluated cortisol plasma levels (RIA). RESULTS We found plasma leptin and cortisol elevated at onset of withdrawal, decreasing significantly up to day 14. Leptin (and the body-mass corrected ratio leptin/BMI) was highly correlated with self-rated craving. No correlations of craving with cortisol and BMI were observed. CONCLUSIONS We suggest that leptin may modulate withdrawal-induced craving in alcoholic subjects.

Neuroendocrine pathways of addictive behaviour

Alcohol intake is known to modulate plasma concentrations of neuroendocrine peptides. However, recent results suggest that the endocrine system may not only respond passively to alcohol intake but that, vice versa, it also actively modulates alcohol intake behaviour. The most coherent body of data concerns the hypothalamo ‐ pituitary ‐ adrenocortical (HPA) axis, with low corticotrophin‐releasing hormone (CRH) being associated with more intense craving and increased probability of relapse after acute detoxification. Leptin, β‐endorphin and atrial natriuretic peptide (ANP), which indirectly regulate the HPA system, also may modulate the intensity of craving or the intensity of the alcohol withdrawal syndrome. Although most of the currently available data demonstrate association rather than causality between neuroendocrine changes and alcohol‐related behaviours, they do provide testable hypotheses and open up perspectives of treating alcohol dependence via manipulation of the neuroendocrine axis.

A genome-wide association study confirms PNPLA3 and identifies TM6SF2 and MBOAT7 as risk loci for alcohol-related cirrhosis

Alcohol misuse is the leading cause of cirrhosis and the second most common indication for liver transplantation in the Western world. We performed a genome-wide association study for alcohol-related cirrhosis in individuals of European descent (712 cases and 1,426 controls) with subsequent validation in two independent European cohorts (1,148 cases and 922 controls). We identified variants in the MBOAT7 (P = 1.03 × 10−9) and TM6SF2 (P = 7.89 × 10−10) genes as new risk loci and confirmed rs738409 in PNPLA3 as an important risk locus for alcohol-related cirrhosis (P = 1.54 × 10−48) at a genome-wide level of significance. These three loci have a role in lipid processing, suggesting that lipid turnover is important in the pathogenesis of alcohol-related cirrhosis.