Association of functional dopamine-beta-hydroxylase (DBH) 19 bp insertion/deletion polymorphism with smoking severity in male schizophrenic smokers

Interaction of oxidative stress and BDNF on executive dysfunction in patients with chronic schizophrenia

Executive dysfunction is increasingly recognized as one of the widely observed dimensions of cognitive impairments in the course of schizophrenia (SCZ). However, the potential molecular pathological mechanisms remain elusive. Previous studies have demonstrated that decreased brain-derived neurotrophic factor (BDNF) and oxidative damage may be associated with the psychopathology and cognitive impairment of SCZ. The present study aims to assess whether the interaction between BDNF and oxidative damage is involved in the disruption of executive function (EF) in patients with chronic SCZ. Serum BDNF and plasma oxidative stress markers were measured in 189 patients and 60 control subjects. EFs were evaluated by Wisconsin card sorting tests (WCST), Stroop word/color test (Stroop), and verbal fluency tests (VFT). The results showed that patients performed worse in the VFT, WCST and Stroop tests than healthy subjects. Moreover, patients had lower activities of glutathione peroxidase (GSH-Px) and superoxide dismutase (SOD) and lower BDNF levels, but higher malondialdehyde (MDA) levels than healthy controls. In patients, BDNF was negatively correlated with SOD (p < 0.01). For patients, catalase (CAT) activity was negatively associated with WCST error score (p = 0.02) and BDNF was positively correlated to VFT score (p = 0.02). However, all these correlations between biomarkers and EF domains did not pass Bonferroni corrections. Finally, multiple regression analyses identified BDNF × SOD activity and BDNF × MDA as influencing factors for VFT score in patients (both p < 0.05). Our results highlight the complex interplay between OS parameters and BDNF in the pathophysiology of EF impairment in SCZ, consistent with its neurodevelopmental hypothesis.

Tobacco smoking and schizophrenia: re-examining the evidence

Tobacco smoking among people with mental illnesses can be explained by biological, psychological and social factors. The prevalence of smoking in people diagnosed with schizophrenia is higher than in people with other mental disorders and in the general population. This article explores three current hypotheses that explain this higher prevalence of smoking in schizophrenia. The first, the self-medication hypothesis, is increasingly countered by a growing body of evidence indicating that smokers experience more severe symptoms of schizophrenia. Numerous researchers have already identified smoking as a possible risk factor for the development of schizophrenia, which is the second hypothesis. The third hypothesis (shared genetic vulnerability) identifies certain genes that confer vulnerability for both schizophrenia and nicotine dependence. Understanding the reasons behind the higher prevalence of smoking among people with schizophrenia is vital in planning effective primary, secondary and tertiary smoking prevention for these individuals.

LEARNING OBJECTIVES

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Cross-Sectional Study to Characterise Nicotine Dependence in Central Vietnamese Men

Tobacco is legally permitted for adults, easily available, and the prevalence of smoking is high. Tobacco use is the largest preventable risk factor for human disease. To reduce smoking, many countries have introduced public policy to restrict the distribution of tobacco. The aim of this study was to analyse tobacco smoking and nicotine dependence in Central Vietnamese men around Hue and Da Nang cities. Nicotine dependence was measured using the Fagerström Test for Nicotine Dependence (FTND) score. The cohort contained total of 1822 Central Vietnamese men from Hue and Da Nang: 1453 smokers and 369 non-smokers. Individuals completed a questionnaire and factors such as smoking initiation, quitting behaviour, and success in quitting were also recorded. In the smoking group, the average amount of time in which the individual had smoked was 26.4 years. Average FTND value was 4.02, median was 4, the first quartile was 2, and the third quartile was 6. In all, 431 smokers (30%) had an FTND score of 6 or higher; an FTND score of this value is considered to equate to an individual having high nicotine dependence. Therefore, it could be noted that high nicotine dependence is very common in Central Vietnam. High nicotine dependence was significantly correlated with years of smoking. The longer the smoking period, the higher the FTND score. A high FTND score correlated with the individual being less likely to successfully quit smoking. The results of the questionnaire demonstrate that even when there is no restriction in public policy concerning the distribution of tobacco, individuals still wish to quit smoking. This study identified a high prevalence of severe nicotine dependence in Central Vietnamese men and the majority smokers wished to quit smoking. Consequently, the results of this study highlight the acute need for a specific programme to aid smokers in Central Vietnam to quit smoking.

Nicotine dependence is associated with depression and childhood trauma in smokers with schizophrenia: results from the FACE-SZ dataset

In a perspective of personalized care for smoking cessation, a better clinical characterization of smokers with schizophrenia (SZ) is needed. The objective of this study was to determine the clinical characteristics of SZ smokers with severe nicotine (NIC) dependence. 240 stabilized community-dwelling SZ smokers (mean age = 31.9 years, 80.4% male gender) were consecutively included in the network of the FondaMental Expert Centers for Schizophrenia and assessed with validated scales. Severe NIC dependence was defined by a Fagerstrom questionnaire score ≥ 7. Depression was defined by a Calgary score ≥ 6. Childhood trauma was self-reported by the Childhood Trauma Questionnaire score (CTQ). Ongoing psychotropic treatment was recorded. Severe NIC dependence was identified in 83 subjects (34.6%), depression in 60 (26.3%). 44 (22.3%) subjects were treated by antidepressants. In a multivariate model, severe NIC dependence remained associated with depression (OR = 3.2, p = 0.006), male gender (OR = 4.5, p = 0.009) and more slightly with childhood trauma (OR = 1.03, p = 0.044), independently of socio-demographic characteristics, psychotic symptoms severity, psychotropic treatments and alcohol disorder. NIC dependence was independently and strongly associated with, respectively, depression and male gender in schizophrenia, and only slightly with history of childhood trauma. Based on these results, the care of both nicotine dependence and depression should be evaluated for an effective smoking cessation intervention in schizophrenia.

Association of the DBH Polymorphism rs3025343 With Smoking Cessation in a Large Population-Based Sample

Introduction

Genetic variations in DBH-gene and its surroundings have been shown to associate with smoking behavior including smoking cessation in several studies. In this study we replicate and measure the effect size for association between DBH polymorphism rs3025343 and smoking cessation in a large population-based sample while examining environmental factors that could relate to the association.

Methods

We studied 11 926 adult subjects from four surveys of the National FINRISK Study. The analysis was restricted to either current or former smokers. Logistic and linear regression analyses were conducted to investigate the relationships of the single nucleotide polymorphism (SNP), covariates, smoking cessation, and smoking severity (cotinine, CPD). Gene-environment interactions were tested by likelihood-ratio test.

Results

The association between rs3025343 and smoking cessation (prevalence odds ratio, OR = 1.12, p = .094, 95%CI = 0.98-1.30) was replicated identically with the GWAS study of The Tobacco and Genetics Consortium (OR = 1.12, 95%CI = 1.08-1.18). None of our tested phenotypes significantly influenced the association between rs3025343 and smoking cessation. Overall, marital status, education, depression, alcohol use, self-rated health, and chronic obstructive pulmonary disease (COPD) showed phenotypic associations with smoking cessation, but the association of various phenotypes with smoking cessation did not vary by genotype.

Conclusions

The current study replicates the effect size for the association between rs3025343 and smoking cessation despite lack of overall significance due to smaller sample size. We could not show environmental influences on the association of rs3025343 with smoking cessation.

Implications

Our study replicates the direction and strength of the association of DBH polymorphism rs3025343 with smoking cessation. We could not detect environmental influences on the strength of the association of rs3025343 with smoking cessation, but the limited power of our analysis needs to be taken into account.

Focused Analysis of Exome Sequencing Data for Rare Germline Mutations in Familial and Sporadic Lung Cancer

INTRODUCTION

The association between smoking-induced chronic obstructive pulmonary disease (COPD) and lung cancer (LC) is well documented. Recent genome-wide association studies (GWAS) have identified 28 susceptibility loci for LC, 10 for COPD, 32 for smoking behavior, and 63 for pulmonary function, totaling 107 nonoverlapping loci. Given that common variants have been found to be associated with LC in genome-wide association studies, exome sequencing of these high-priority regions has great potential to identify novel rare causal variants.

METHODS

To search for disease-causing rare germline mutations, we used a variation of the extreme phenotype approach to select 48 patients with sporadic LC who reported histories of heavy smoking-37 of whom also exhibited carefully documented severe COPD (in whom smoking is considered the overwhelming determinant)-and 54 unique familial LC cases from families with at least three first-degree relatives with LC (who are likely enriched for genomic effects).

RESULTS

By focusing on exome profiles of the 107 target loci, we identified two key rare mutations. A heterozygous p.Arg696Cys variant in the coiled-coil domain containing 147 (CCDC147) gene at 10q25.1 was identified in one sporadic and two familial cases. The minor allele frequency (MAF) of this variant in the 1000 Genomes database is 0.0026. The p.Val26Met variant in the dopamine β-hydroxylase (DBH) gene at 9q34.2 was identified in two sporadic cases; the minor allele frequency of this mutation is 0.0034 according to the 1000 Genomes database. We also observed three suggestive rare mutations on 15q25.1: iron-responsive element binding protein neuronal 2 (IREB2); cholinergic receptor, nicotinic, alpha 5 (neuronal) (CHRNA5); and cholinergic receptor, nicotinic, beta 4 (CHRNB4).

CONCLUSIONS

Our results demonstrated highly disruptive risk-conferring CCDC147 and DBH mutations.

An association between the PPARα-L162V polymorphism and nicotine dependency among patients with schizophrenia

OBJECTIVE

Patients with schizophrenia are more likely to be smokers than the general population, which makes them an interesting group with which to study the etiology of nicotine dependency. We studied the prevalence of a gene variant of peroxisome proliferator-activated receptor alpha (PPARα) in schizophrenia, together with nicotine dependency, to investigate whether the PPARα-L162V polymorphism (rs1800206) influences nicotine dependency in schizophrenia. Given evidence suggesting that smoking influences the severity of schizophrenia, together with our recent data linking the PPARα-L162V polymorphism to clinical manifestations of schizophrenia (in the Croatian population), we hypothesized that interactions between the two (smoking and the PPARα-L162V polymorphism) might contribute to disease onset and scores for the Positive and Negative Syndrome Scale. To the best of our knowledge, this is the first study to investigate the possible associations between the PPARα gene and nicotine dependency.

PATIENTS AND METHODS

Genotyping was performed for 267 chronically ill schizophrenia patients (males/females: 140/127) by polymerase chain reaction.

RESULTS

A significant excess of PPARα-L162V genotypes and PPARα-162V alleles were detected among female smokers in comparison to female nonsmokers (18.2% vs. 2.0%, and 9.1% vs. 1.0%, p<0.01, respectively). We also revealed a significant PPARα genotype-smoking interaction that predicted positive symptom severity among male patients (F=4.43, p<0.05). These data indicated that the PPARα-L162V heterozygous genotype, depending on smoking status, might be of relevance as either protective, or a risk factor, for the severity of positive symptoms. No interaction between the PPARα-L162V polymorphism and smoking for the time of onset of schizophrenia was detected (p>0.05, respectively).

CONCLUSION

We demonstrated two significant yet weak effects. The first showed an effect of the PPARα-L162V polymorphism on the risk of nicotine dependency. The second linked the PPARα genotype-smoking interaction to positive symptoms severity among schizophrenia patients; both effects manifested in a gender-specific fashion.

Genetic Relationship between Schizophrenia and Nicotine Dependence

It is well known that most schizophrenia patients smoke cigarettes. There are different hypotheses postulating the underlying mechanisms of this comorbidity. We used summary statistics from large meta-analyses of plasma cotinine concentration (COT), Fagerström test for nicotine dependence (FTND) and schizophrenia to examine the genetic relationship between these traits. We found that schizophrenia risk scores calculated at P-value thresholds of 5 × 10⁻³ and larger predicted FTND and cigarettes smoked per day (CPD), suggesting that genes most significantly associated with schizophrenia were not associated with FTND/CPD, consistent with the self-medication hypothesis. The COT risk scores predicted schizophrenia diagnosis at P-values of 5 × 10⁻³ and smaller, implying that genes most significantly associated with COT were associated with schizophrenia. These results implicated that schizophrenia and FTND/CPD/COT shared some genetic liability. Based on this shared liability, we identified multiple long non-coding RNAs and RNA binding protein genes (DA376252, BX089737, LOC101927273, LINC01029, LOC101928622, HY157071, DA902558, RBFOX1 and TINCR), protein modification genes (MANBA, UBE2D3, and RANGAP1) and energy production genes (XYLB, MTRF1 and ENOX1) that were associated with both conditions. Further analyses revealed that these shared genes were enriched in calcium signaling, long-term potentiation and neuroactive ligand-receptor interaction pathways that played a critical role in cognitive functions and neuronal plasticity.

To quit or not: Vulnerability of women to smoking tobacco

Tobacco smoking is currently on the rise among women, and can pose a greater health risk. In order to understand the nature of the increase in smoking prevalence among women, we focused on the vulnerability of women to smoking behaviors--smoking cessation or tobacco addiction--and performed a systematic review of the socioeconomic and intrinsic factors as well as tobacco ingredients that affect women's susceptibility to smoking tobacco. We observed that nicotine and other tobacco components including cocoa-relatives, licorice products, and menthol aggravate tobacco addiction in women rather than in men. Various genetic and epigenetic alterations in dopamine pathway and the pharmaco-kinetics and -dynamic factors of nicotine also showed potential evidences for high susceptibility to tobacco addiction in women. Therefore, we suggest systemic approaches to prevent tobacco smoking-related health risks, considering gene-environment-gender interaction.