Tom L. Smith

An expanded evaluation of the relationship of four alleles to the level of response to alcohol and the alcoholism risk.

BACKGROUND Alcoholism is a complex, genetically influenced disorder the cause of which may be better understood through the study of genetically influenced phenotypes that mediate the risk. One such intermediate phenotype is the low level of response (LR) to alcohol. This project used a case-control approach to search for genes that may contribute to LR. METHODS Data were available from alcohol challenges at approximately age 20 and regarding the development of alcohol use disorders over the subsequent 20 years for 85 men, including 40 reported in a previous genetic analysis. LR was evaluated using oral consumption of 0.75 ml/kg of alcohol, after which changes in subjective feelings of intoxication and body sway were measured. Alcohol abuse and dependence were diagnosed by DSM-III-R criteria through structured interviews administered to both the participant and an informant (usually the spouse) 10, 15, and 20 years after initial testing. Four polymorphisms were evaluated, including the serotonin transporter HTTLPR promoter ins/del, GABAAalpha6 Pro385Ser, NPY Leu7Pro, and catalase 262C>T. Two of these, HTTLPR and GABAAalpha6 Pro385Ser, had been previously associated with LR and alcoholism in a preliminary study. RESULTS The HTTLPR L allele was significantly related to both the LR and alcoholism in an allele-dosage (stepwise) manner. Furthermore, the association remained when L alleles were subdivided into recently reported functional subtypes: the lowest LR was associated with genotypes correlated with the highest serotonin transporter expression. The GABAAalpha6 Ser385 allele showed a nonsignificant trend for association to a low LR, as had been previously observed, although the Ser385 allele is uncommon, and only 18 heterozygotes were in the current group. However, the six men with both LL and Pro385/Ser385 genotypes had the lowest LR, and each had developed alcoholism during follow-up. Neither NPY nor catalase was associated with either LR or alcoholic outcomes, although the sample did not have sufficient power for definitive conclusions. CONCLUSIONS This report strengthens the support for a relationship between the HTTLPR L and GABAAalpha6 Ser385 alleles to low alcohol LR and to alcoholism in a prospectively studied cohort evaluated for LR in young adulthood and before the onset of alcohol dependence.

Reduction of immune function in life stress and depression

Reduced cell-mediated immune function has been found in depressed patients and in distressed persons undergoing threatening life events. The present study examines the interaction between severe life stress and major depression to produce immune alterations in 36 matched pairs of hospitalized depressed patients and nondepressed controls. Both major depressive disorder and the presence of threatening life events in control subjects are independently associated with a 50% reduction of natural killer (NK) cytotoxicity. A decrease in natural cytotoxicity is significantly associated with depressive symptoms but not with age, alcohol consumption, or tobacco smoking. These findings of altered immunity provide further evidence that the physiological responses in chronic stress parallel those found in the syndrome of depression.

Selective genotyping for the role of 5-HT2A, 5-HT2C, and GABAα6 receptors and the serotonin transporter in the level of response to alcohol: a pilot study

BACKGROUND The vulnerability to alcohol dependence appears to be genetically influenced through a variety of mechanisms. One potentially genetically mediated channel may be a low level of response (LR) to alcohol, which has been seen in children of alcoholics and noted to predict future alcohol abuse and dependence. This pilot study uses a case and control genetic association approach to evaluate the possible role of five genotypes in both LR and alcoholism in informative subgroups of men with high and low LR scores documented 15 years earlier. METHODS As part of a larger study, 41 men, about 39 years old, were selected from among the first 113, completed 15-year follow-ups in a prospective study. The 17 subjects whose LRs at age 20 were in the lower third were compared on five polymorphisms of four genes with 24 men whose reactions to alcohol had been above the median. RESULTS The 14 men with the LL genotype of the serotonin transporter (5-HTT) polymorphism and the seven with the Pro/Ser genotype of the GABAA alpha 6 polymorphism had demonstrated lower LR scores at about age 20, and had significantly higher proportions of alcoholics than the other genotypes for those loci. All four subjects with combined LL and Pro/Ser genotypes had developed alcoholism and demonstrated the lowest LR scores overall. There was no evidence that two polymorphisms of the 5-HT2A receptor gene and one of the 5-HT2C receptor gene were related to LR or alcoholism in this sample. CONCLUSIONS These results are consistent with animal and human studies suggesting a possible role for genetic variation in the GABAA alpha 6 and the serotonin transporter in the reaction to alcohol and the alcoholism risk.

Chronic Life Stress Alters Sympathetic, Neuroendocrine, and Immune Responsivity to an Acute Psychological Stressor in Humans

Objective Life stress is hypothesized to alter the dynamic regulation of the autonomic, neuroendocrine, and immune systems. This study examined the effects of antecedent chronic life stress on psychological and physiological responsivity after acute challenge with a psychological stressor. Method Using a within-subject mixed design, male volunteers with (N = 12) and without chronic life stress (N = 11) were administered a 12-minute laboratory stressor (mental arithmetic) vs a video control. Results Acute psychological stress induced subjective distress, increases of circulating concentrations of epinephrine, norepinephrine, beta-endorphin, adrenocorticotropic hormone (ACTH), and cortisol, and a selective redistribution of natural killer (NK) cells into the peripheral blood as compared with the video control condition. Although the two groups were almost identical at baseline in psychological, sympathetic, neuroendocrine, and immune domains, the chronic stress group showed greater subjective distress, higher peak levels of epinephrine, lower peak levels of beta-endorphin and of NK cell lysis, and a more pronounced redistribution of NK cells in response to the acute psychological challenge than the controls. Furthermore, the acute stressor induced a protracted decline in NK lysis per NK cell in the chronic stress group but had no effect in the controls. Conclusions In summary, when persons who are undergoing chronic life stress are confronted with an acute psychological challenge, an exaggerated psychologic and peak sympathomedullary reactivity occurs that is associated with decrements in individual NK cell function and is protracted beyond termination of the stressor and sympathomedullary recovery.

Impaired natural killer cell activity during bereavement

Natural killer (NK) cell activity, a component of the immune surveillance system, was compared in women whose husbands had recently died with that found in age-matched women who had not experienced recent adverse life events. Bereaved women had significantly lower NK activity than women whose husbands were healthy. In a second study, depressive symptoms and NK activity were measured longitudinally in women before and after the death of their husbands. Our results suggest that depressive symptoms, not merely the death of the spouse, are related to a reduction in NK activity during bereavement.

Association of GABRG3 With Alcohol Dependence

BACKGROUND Evidence from human, animal, and in vitro cell models suggests that gamma-aminobutyric acid (GABA), the major inhibitory neurotransmitter in the human central nervous system, is involved in many of the neurochemical pathways that affect alcohol use, abuse, and dependence. Both linkage and association to the region on chromosome 15q that contains a cluster of GABAA receptor genes have previously been reported, but the role of these genes in alcoholism remains inconclusive. METHODS We conducted family-based association analyses by using a large sample of multiplex alcoholic families collected as part of the Collaborative Study on the Genetics of Alcoholism, to test for an association between alcohol dependence and the GABAA receptor genes clustered on chromosome 15q. Multiple single-nucleotide polymorphisms were tested in each of the three chromosome 15q GABAA receptor genes: GABRA5, GABRB3, and GABRG3. RESULTS Using both classic trio-based analyses and extended-family analyses, we found consistent evidence of association between alcohol dependence and GABRG3. Nearly all single-nucleotide polymorphisms across the gene yielded evidence of association, and haplotype analyses were highly significant. No consistent evidence of association was observed with either GABRA5 or GABRB3, nor was there evidence for parent-of-origin effects with any of the genes. CONCLUSIONS These analyses suggest that GABRG3 may be involved in the risk for alcohol dependence. These findings support the theory that the predisposition to alcoholism may be inherited as a general state of central nervous system disinhibition/hyperexcitability that results from an altered responsiveness to GABA.

The search for genes contributing to the low level of response to alcohol: Patterns of findings across studies

BACKGROUND Alcoholism is a complex genetically influenced disorder in which multiple phenotypes [e.g., disinhibition, alcohol-metabolizing patterns, and the low level of response (LR) to alcohol] contribute to the risk. A low LR to alcohol is one of the more thoroughly studied risk phenotypes; data indicate that LR relates to the risk status, predicts future alcoholism, and has a heritability as high as 60%. This article reviews data from animal and human studies regarding the LR to alcohol, searching for a convergence of results that might lead to the identification of relevant genes. METHODS A literature search was performed regarding animal and human genetic studies focusing on genes that might affect the LR to alcohol as a risk factor for alcoholism. The goal was to synthesize these results and highlight potential patterns. RESULTS Focusing on both genetic linkage and association studies, a number of chromosomal regions and genes potentially relevant to findings across two or more sources were identified. The genes of potential interest fell into several categories, including second-messenger systems (e.g., G proteins, adenylyl cyclase, and protein kinases); neurotransmitters or drug-related receptors (e.g., gamma-aminobutyric acid-A, glutamate, serotonin, and cannabinoid and opioid receptors); genes that affect alcohol metabolism; and genes that might relate to an overlap in the risk for alcoholism and some psychiatric conditions (e.g., catechol-O-methyltransferase regarding schizophrenia and bipolar disorder). CONCLUSIONS The review identifies several genes that may contribute to a low LR to alcohol and, thus, to an increased risk for alcohol use disorders. The chromosomal regions and genes highlighted here may form the basis for more focused genetic studies of alcohol use disorders, with the goals of developing more specific and effective prevention and treatment approaches.

Lack of association between an RFLP near the D2 dopamine receptor gene and severe alcoholism

Blum et al (1990) have recently examined a restriction fragment length polymorphism (RFLP) detected by TaqI RFLP to the dopamine D2 receptor gene (DRD2) in deceased alcoholics and nonalcoholics, and reported an association between alcoholism and the A1 allele. Subsequent studies, however, by other investigators have failed to confirm this. We have examined the DRD2 TaqI RFLP in 47 living Caucasian males with severe alcoholism. All alcoholic subjects were thoroughly characterized by a structured interview, and met DSM-III-R criteria for alcohol dependence. Only 9/47 (19%) (1990) of these alcoholics had the AI allele compared to 14/22 (64%) reported by Blum et al. This rate was not significantly different from the rates reported in control populations by Blum et al (1990), CEPH, or Bolos et al (1990), and differed only slightly from those reported by Grandy et al (1990). Alcoholics selected for severe medical complications also displayed a similar rate. Our data do not support an association between alcoholism and the D2 dopamine receptor gene in this population.

EEG sleep studies in “pure” primary alcoholism during subacute withdrawal: Relationships to normal controls, age, and other clinical variables

Electroencephalogram (EEG) sleep recordings were compared in 34 normal controls and 31 inpatients with relatively pure primary alcoholism who had been abstinent for about 17 days. Compared with normal controls, primary alcoholics took longer to fall asleep, slept less, and had poor sleep efficiency. Sleep loss reflected reduced non-rapid eye movement (NREM) sleep, especially stage 2 sleep, stage 4 sleep, and total delta (stage 3 and 4) sleep. Alcoholic patients had higher REM density of the first REM period. Sleep deteriorated with age in both normal controls and patients, with younger alcoholics showing sleep patterns typical of older controls. Among other clinical-demographic variables examined, the shorter the duration of sobriety at the time of the study, the later patients went to bed and fell asleep. The number of drinks per drinking day in the 3 months before admission was directly related to the duration of the first REM period. In addition, the maximum number of withdrawal symptoms the patient had ever experienced was inversely related to the amount of delta sleep. Sleep measures were not correlated with depression rating, liver enzymes, or other measures of alcohol consumption.

The search for genes related to a low-level response to alcohol determined by alcohol challenges.

BACKGROUND A low level of response (LR) to alcohol seems to relate to a substantial proportion of the risk for alcoholism and to have significant heritability. METHODS This report describes the results of a genome-wide segregation analysis for the first 139 pairs of full siblings by using an alcohol challenge protocol as a direct measure of LR. Subjects from 18 to 29 years old were selected if the original screen indicated they had an alcohol-dependent parent, reported a personal history of drinking but had no evidence of alcohol dependence, and had a full sibling with similar characteristics. Body sway and Subjective High Assessment Scale scores were measured at baseline and at regular intervals after the administration of a measured dose of alcohol. Participants and available parents were genotyped for 811 microsatellite markers, and resulting data were analyzed with a variance component method. RESULTS Nine chromosome regions with logarithm of the odds ratio (LOD) between 2.2 and 3.2 were identified; several had previously been implicated regarding phenotypes relevant to alcoholism and the LR to alcohol. Several regions identified in the previous linkage study by using a retrospective self-report questionnaire were potentially confirmed by this study. The strongest evidence was on chromosomes 10, 11, and 22. CONCLUSIONS Several chromosomal areas seem to relate to the low LR to alcohol as a risk factor for alcohol dependence.