Sex-based linkage analysis of alcoholism

A high degree of locus heterogeneity is likely in alcoholism, and linkage heterogeneity analysis may be helpful in mapping susceptibility loci. The genetic contribution to alcoholism in females may be higher than in males, and therefore sex of affected individuals was used in linkage analysis. Families with female alcoholics demonstrated evidence for linkage to chromosomes 10p11-p15 and 21q22.1-q22.2 while those with male alcoholics did not provide evidence for linkage to these regions. Sharing of maternal and paternal alleles was also investigated separately, and evidence for linkage of maternal alleles on chromosomes 1 and 8, and paternal alleles on chromosome 2 was observed, suggesting parental origin effects. Mapping of complex traits may benefit from tests of linkage heterogeneity based on sex, and parental origin.     

Mapping alcoholism genes using linkage/linkage disequilibrium analysis

Using a recently developed semiparametric method for combined linkage/linkage-disequilibrium analysis, we analyzed the Collaborative Study on the Genetics of Alcoholism data subset developed for Genetic Analysis Workshop 11 (GAW11). This semiparametric approach estimates recombination fractions for linkage, marker log odds ratios for linkage-disequilibrium, their product for combined linkage/linkage-disequilibrium, and corresponding z-scores. We used two outcomes: alcohol dependence and "alcoholism-free" and a genome-wide significance level of 4.1 (which corresponds to a genome-wide lod score of 3.6). For the alcohol dependence outcome, we observed significant linkage signals at D1S1588-D1S1631, D1S547, D2S399, D2S425, D4S2361, D7S1796, and D7S1824. We also found significant linkage-disequilibrium signals at D1S547 and D7S1795. For the "alcoholism-free" outcome, we found significant linkage signals at D4S2457, D41651 (both flank ADH3), D11S2359, and D16S47 and significant linkage-disequilibrium signals at D4S2361, FABP2, D11S2359, D19S431 and D19S47-D19S198-D19S601.     

Model-based and model-free multipoint genome-wide linkage analysis of alcoholism

We analyzed a subset of the Collaborative Study on the Genetics of Alcoholism (COGA) data set as provided by the 11th Genetic Analysis Workshop (GAW11). Linkage analyses were performed using each of the diagnostic criteria for alcoholism included in the data: the COGA criteria (DSM-III-R plus the Feighner criteria) and the narrower World Health Organization diagnosis ICD-10 criteria. Formal segregation analysis using these data was not attempted because only a subset of all the originally ascertained families was made available. Nevertheless, an attempt was made to estimate the best one-locus two-allele genetic model for these data. Model-based multipoint linkage analysis was performed using the results of our trait model fitting, and model-free multipoint linkage analysis was performed with an improved version of the Haseman and Elston linkage method for sib pairs.     

Association and linkage analysis of ICD-10 diagnosis for alcoholism

We analyzed the GAW11 data on alcoholism provided by the Collaborative Study on the Genetics of Alcoholism (COGA) using an extension of a new test of linkage and association for quantitative traits developed by George et al. [1999]. This method determines linkage between marker loci and quantitative traits, when allelic association is present between the trait and marker loci, by regressing the disease trait on the parental transmission of the allele of interest. We found no strong evidence of linkage to any markers. However, we found several markers suggestive of possible linkage that may deserve further investigation.     

Sib-pair linkage analyses of alcoholism: dichotomous and quantitative measures

We hypothesized that a quantitative alcoholism trait would have greater power than the Collaborative Study on the Genetics of Alcoholism (COGA) dichotomous alcoholism traits, ALDX1 and ALDX2, to detect putative alcoholism loci. To test this, we performed nonparametric sib-pair linkage analysis to screen 285 polymorphic autosomal markers for evidence of linkage to ALDX1, ALDX2, and a quantitative trait, QUANT, defined from the 11 COGA latent class variables. We also examined the effects on the analyses of including covariates (sex, age, and pack-years of smoking) and of transforming QUANT (log and square root). ALDX1 and ALDX2 showed the greatest evidence for linkage to markers on chromosome 1, by both the affected sib-pair and the Haseman-Elston tests. Regions of interest were also identified on chromosomes 4, 8, 16, and 17. QUANT showed little evidence for linkage to any chromosomal region, having no more significant results than were expected by chance. Including covariates or transforming QUANT had little effect on the analyses. A quantitative trait based on all 37 latent class variables, with each variable appropriately weighted, may have had more power than QUANT to detect genomic regions of relevance to alcoholism.     

Family density of alcoholism and linkage information in the analysis of the COGA data

In this study of GAW11 Problem 1, we analyzed the genome scan data in families weighted according to the density of alcoholism among the probands' siblings. We hypothesized that certain disease-predisposing alleles may be common in the general population, rendering high-density sibships less informative for linkage. Three types of families were found in the data, with the prevalence of alcoholism of 1.0, 0.78, and 0.24 in the probands' sibships. The linkage results showed several peak lod scores on chromosomes 1, 2, 4, 8, 11, 19, and 21, the majority of which originated in only one or two types of families. However, for almost all markers, the maximum lod scores observed without the weights were equal to or exceeded the values obtained for any single type of family. These results indicate that although the stratification of families may be theoretically justified, in practice the best strategy is to use all available information.     

Platelet monoamine oxidase activity in alcoholism subtypes: relationship to personality traits and executive functions

- AIMS: The purpose of the present study was to compare alcoholic subtypes (type 1 versus type 2) with regard to platelet monoamine oxidase (MAO) activity. A possible relationship between enzyme activity, personality traits and executive functions was also investigated. METHODS: Seventeen type 1 and 16 type 2 in-patient male chronic alcoholic patients and 17 healthy male volunteers were included in the study. The personality traits were investigated by the Minnesota Multiphasic Personality Inventory-2 (MMPI-2). Executive functions were assessed by the Wisconsin Card Sorting Test (WCST). RESULTS: When compared to the healthy subjects, platelet MAO activity was reduced in both alcoholic groups. The enzyme activity of the type 2 group was significantly lower than that of type 1 patients. Both groups of alcoholic patients also displayed impairment in executive functions. The comparison of the MMPI-2 scores of the study groups revealed that type 2 alcoholics had more severe psychopathology. CONCLUSIONS: The results support previous evidence suggesting that platelet MAO activity is a useful biochemical measure for the subtyping of alcoholics.     

Exploring linkage for alcoholism using affection status and quantitative event related potential phenotypes

Using genome-scan data from the Collaborative Study on the Genetics of Alcoholism (COGA), we compared results of linkage analyses using a qualitative alcoholism phenotype to results of linkage analyses using event related potential (ERP) quantitative phenotypes, and compared our results to the results of Reich et al. [1998] and Begleiter et al. [1998]. We describe a general and simple strategy for identifying regions of the genome which may harbor genes involved in alcohol dependence which takes into consideration the results of both the affection status and ERP linkage analyses.     

The prevention of alcoholism and economic alcoholism

In this paper the author presents the social-health approach to the prevention of alcoholism which was recommended by the Liquor Regulations Committee of the Saskatchewan Legislature. This approach very strongly suggested the need for a pricing policy to reduce overall alcohol consumption and thereby reduce alcoholism. The paper deals with the Erroll Committee's references to pricing policy. The author concludes with reference to the government-industrial complex which must be overcome if alcoholism is to be controlled in North America and expresses concern that we have entered an era of “economic alcoholism” in North America.     

Evidence for linkage and association to alcohol dependence on chromosome 19

An association study on markers showing suggestive evidence for linkage to severe alcoholism was performed on the Collaborative Study on the Genetics of Alcoholism (COGA) data set. Our linkage study was restricted to the autosomal markers on chromosomes 2, 3, 4, 13, and 19, with low homozygosity (below 30%) and high identity-by-state sharing in affected sib pairs (ASPs). We used a strict phenotype definition, only individuals diagnosed as affected both on the ALDX1 (COGA criterion) and ALDX2 (ICD-10) scales were used in the analyses. Linkage was assessed by excess identity-by-descent allele sharing in ASPs. The strongest evidence of linkage was detected on chromosome 19, in particular at markers D19S49 (p < 0.0001) and D19S431 (p < 0.002). An association study of allele and haplotype data was then carried out on chromosome 19 markers using affected-family-based controls. A haplotype defined by alleles at markers D19S49, D19S43, and D19S200 in chromosome 19 shows significant association (p < 0.003, odds ratio 2.82). Further, significant differences were observed in the distribution of the harm avoidance subscale among genotypes defined by D19S49 (p < 0.0001). These results provide evidence for the existence of a locus in chromosome 19 potentially involved in alcohol dependence susceptibility.     

Possible linkage of alcoholism, monoamine oxidase activity and P300 amplitude to markers on chromosome 12q24

Multipoint linkage analysis was used to screen for evidence of linkage between alcoholism and five alcoholism-related quantitative traits. The results suggest that a susceptibility locus that influences monoamine oxidase activity and P300 amplitude at the Pz lead, and increases the risk of alcohol dependence may be linked to markers in the 12q24 region. Furthermore, the susceptibility for alcoholism may be associated with allele 3 (allele size 144) of D12S392.     

Evidence about the use of naltrexone and for different ways of using it in the treatment of alcoholism

Eight double-blind placebo-controlled clinical trials in five countries have demonstrated the safety and efficacy of naltrexone as an adjunct in alcoholism treatment. The efficacy depends, however, on how naltrexone is used. Three of the trials tested naltrexone in two ways: (1) with supportive therapy, i.e. support of complete abstinence; (2) with therapy tacitly accepting that relapses may occur and teaching how to cope with them. Although all found benefits from naltrexone with the coping therapy, none of them found any significant benefit of naltrexone over placebo when combined with support for abstinence. These results are consistent with our pre-clinical studies in which naltrexone, naloxone, and nalmefene were effective when paired with drinking but ineffective when given during abstinence. This supported the hypothesis that the primary mechanism involved is extinction (as had been concluded earlier for the effects of naltrexone in opiate addiction treatment), because extinction only weakens responses that are made while reinforcement is blocked. On this basis, it was proposed that: (1) naltrexone should be administered to patients who were still currently drinking; (2) the instructions should be to take naltrexone only when drinking was anticipated; (3) this treatment should continue indefinitely. Subsequently, clinical trials have found that naltrexone used in this manner is safe and effective.     

Etiologic heterogeneity in alcoholism

Etiologic heterogeneity in alcohol abuse was evaluated in 195 extended pedigrees, comprising 288 nuclear families of 140 male and 55 female Caucasian American hospitalized alcoholics. Previous adoption studies in Sweden demonstrated differential heritability of two patterns of alcohol abuse in men: type-2 alcoholism exhibited early onset of abuse associated with criminal behavior, while type-1 abuse began at a later age, uncomplicated by antisocial traits. Alcohol abuse in female Swedish adoptees was relatively homogeneous and similar to the late-onset, type-1 abuse. The notion of etiologic heterogeneity, as suggested by the Stockholm Adoption Studies, was examined in the American pedigrees by contrasting the models of familial transmission of susceptibility to alcoholism obtained via segregation analyses of families of male versus female probands. Families of male probands demonstrated significant familial resemblance, accounted for by a multifactorial-polygenic background in addition to a major (gene) effect. In contrast, familial resemblance in the pedigrees of female probands was attributed solely to a multifactorial-polygenic effect. We considered whether some families of male alcoholics were similar to families of female probands, who expressed type-1 abuse predominantly. Pedigrees of male probands were separated in two groups: (1) "female-like" families had a better likelihood for the model obtained for families of female probands than the one for families of all male probands, (2) "male-like" families had a better likelihood for the model of familial transmission describing families of all male probands. A statistically significant difference in the pattern of familial transmission was observed between the "male-like" and "female-like" groups. Discriminant function analysis of alcohol-related symptoms showed that the familial subtypes differed in clinical features as well. Alcohol abuse by male relatives in "male-like" families was characterized by the early onset of inability to abstain entirely from alcohol or lack of desire to stop drinking; in contrast, abuse in "female-like" families was characterized by late onset of guilt feelings and loss of control over binge drinking.     

Nutritional status in alcoholism

An intensive study of 39 alcoholic patients with liver disease indicated a wide range of nutritional status; severe malnutrition was uncommon.
Normal values for all measurements of anthropometry and vitamin status were observed in 41 and 13% of 39 subjects respectively. Mild protein-energy malnutrition (by anthropometry) was observed in 22%. The incidence of abnormal biochemical levels of the micronutrients were: riboflavin (69%), magnesium (54%), zinc (50%). thiamin (44%), pyridoxine (21%), ascorbate (19%), and folate (18%).