An association study in the Taiwan Biobank elicits the GABAA receptor genes GABRB3, GABRA5, and GABRG3 as candidate loci for sleep duration in the Taiwanese population.

BACKGROUND: Gamma-aminobutyric acid type A (GABAA) receptors mainly mediate the effects of gamma-aminobutyric acid, which is the primary inhibitory neurotransmitter in the central nervous system. Abundant evidence suggests that GABAA receptors play a key role in sleep-regulating processes. No genetic association study has explored the relationships between GABAA receptor genes and sleep duration, sleep quality, and sleep timing in humans. METHODS: We determined the association between single-nucleotide polymorphisms (SNPs) in the GABAA receptor genes GABRA1, GABRA2, GABRB3, GABRA5, and GABRG3 and sleep duration, sleep quality, and sleep timing in the Taiwan Biobank with a sample of 10,127 Taiwanese subjects. There were 10,142 subjects in the original study cohort. We excluded 15 subjects with a medication history of sedative-hypnotics. RESULTS: Our data revealed an association of the GABRB3-GABRA5-GABRG3 gene cluster with sleep duration, which has not been previously identified: rs79333046 (beta = - 0.07; P = 1.21 × 10-3) in GABRB3, rs189790076 (beta = 0.92; P = 1.04 × 10-3) in GABRA5, and rs147619342 (beta = - 0.72; P = 3.97 × 10-3) in GABRG3. The association between rs189790076 in GABRA5 and sleep duration remained significant after Bonferroni correction. A variant (rs12438141) in GABRB3 was also found to act as a potential expression quantitative trait locus. Additionally, we discovered interactions between variants in the GABRB3-GABRA5-GABRG3 gene cluster and lifestyle factors, such as tea and coffee consumption, smoking, and physical activity, that influenced sleep duration, although some interactions became nonsignificant after Bonferroni correction. We also found interactions among GABRB3, GABRA5, and GABRG3 that affected sleep duration. Furthermore, we identified an association of rs7165524 (beta = - 0.06; P = 2.20 × 10-3) in GABRA5 with sleep quality and an association of rs79465949 (beta = - 0.12; P = 3.95 × 10-3) in GABRB3 with sleep timing, although these associations became nonsignificant after Bonferroni correction. However, we detected no evidence of an association of individual SNPs in GABRA1 and GABRA2. CONCLUSIONS: Our results indicate that rs189790076 in GABRA5 and gene-gene interactions among GABRB3, GABRA5, and GABRG3 may contribute to sleep duration in the Taiwanese population.

An association study in the Taiwan Biobank reveals RORA as a novel locus for sleep duration in the Taiwanese Population.

BACKGROUND: Sleep is a key factor for health-related quality of life since sleep disturbances are a significant and common problem for patients with various human diseases such as psychiatric disorders. While single nucleotide polymorphisms (SNPs) in circadian clock genes have been indicated to be associated with sleep duration, most of the association studies have been investigated in populations with European ancestry. It is believed that no studies have been conducted to investigate a link between sleep duration and the circadian clock genes RORA and RORB, which play a key role, with NR1D1, in an additional feedback loop for the circadian rhythm machinery. METHODS: In this study, we assessed the relationships between sleep duration and SNPs in the circadian clock genes NR1D1, RORA, and RORB in the Taiwan Biobank with a sample of 10,112 Taiwanese subjects. RESULTS: From our data, we revealed a novel significant association in sleep duration with the rs75981965 SNP (P = 9.93 × 10-5) in the RORA gene that has not been previously identified. The association of sleep duration with this SNP remained significant after performing Bonferroni correction. RORA is a potential candidate for sleep duration as RORA has been suggested to play a key role in the regulation of sleep disorders. Additionally, we pinpointed the effects of interactions between RORA rs75981965 and environmental factors such as tea consumption (P = 0.0015), coffee consumption (P = 0.0029), physical activity (P = 0.011), alcohol consumption (P = 0.0146), and smoking (P = 0.0223) in influencing sleep duration. We also found interactions between RORA and NR1D1 (P = 0.0023) as well as between RORA and RORB (P = 0.0061) in affecting sleep duration. CONCLUSIONS: Our results indicate that the circadian clock gene RORA may contribute to sleep duration independently as well as through gene-gene and gene-environment interactions in the Taiwanese population.

Tinnitus Among Patients With Anxiety Disorder: A Nationwide Longitudinal Study.

OBJECTIVES: The association between tinnitus and anxiety disorder remains debated. We used a retrospective cohort study to investigate the relationship between anxiety disorder and tinnitus, aiming to decipher possible risk factors for tinnitus in patients with anxiety disorder. METHOD: Data on a total of 7,525 patients with anxiety disorder and 15,050 patients without (comparison cohort) were extracted from the Longitudinal Health Insurance Database 2005 in Taiwan. The Kaplan-Meier estimator with the log rank test and the Cox proportional-hazard regression model were used to compare the incidence of tinnitus in both groups and to identify risk factors that predicted tinnitus. RESULTS: After adjusting for related covariates, the hazard ratio for the development of tinnitus during the follow-up period was 3.54 (95% confidence interval: 3.11-4.02, P < .001) for anxiety disorder cohort relative to comparison cohort. Age ≧ 60 years, female sex, hypertension, and hyperlipidemia were statistically significant predictive risk factors of tinnitus in patients with anxiety disorder. CONCLUSION: A significant increase in the lifetime incidence of tinnitus was exhibited in patients with anxiety disorder. Elderly subjects, female sex, hypertension, and hyperlipidemia were risk factors. Clinicians should be alert to the possibility of tinnitus in subjects with anxiety disorder.

Cysteine-rich domain of scavenger receptor AI modulates the efficacy of surface targeting and mediates oligomeric Aß internalization.

BACKGROUND: Insufficient clearance of soluble oligomeric amyloid-ß peptide (oAß) in the central nervous system leads to the synaptic and memory deficits in Alzheimer's disease (AD). Previously we have identified scavenger receptor class A (SR-A) of microglia mediates oligomeric amyloid-ß peptide (oAß) internalization by siRNA approach. SR-A is a member of cysteine-rich domain (SRCR) superfamily which contains proteins actively modulating the innate immunity and host defense, however the functions of the SRCR domain remain unclear. Whether the SRCR domain of SR-AI modulates the receptor surface targeting and ligand internalization was investigated by expressing truncated SR-A variants in COS-7 cells. Surface targeting of SR-A variants was examined by live immunostaining and surface biotinylation assays. Transfected COS-7 cells were incubated with fluorescent oAß and acetylated LDL (AcLDL) to assess their ligand-internalization capabilities. RESULT: Genetic ablation of SR-A attenuated the internalization of oAß and AcLDL by microglia. Half of oAß-containing endocytic vesicles was SR-A positive in both microglia and macrophages. Clathrin and dynamin in SR-AI-mediated oAß internalization were involved. The SRCR domain of SR-AI is encoded by exons 10 and 11. SR-A variants with truncated exon 11 were intracellularly retained, whereas SR-A variants with further truncations into exon 10 were surface-targeted. The fusion of exon 11 to the surface-targeted SR-A variant lacking the SRCR domain resulted in the intracellular retention and the co-immunoprecipitation of Bip chaperon of the endoplasmic reticulum. Surface-targeted variants were N-glycosylated, whereas intracellularly-retained variants retained in high-mannose states. In addition to the collagenous domain, the SRCR domain is a functional binding domain for oAß and AcLDL. Our data suggest that inefficient folding of SR-AI variants with truncated SRCR domain was recognized by the endoplasmic reticulum associated degradation which leads to the immature N- glycosylation and intracellular retention. CONCLUSION: The novel functions of the SRCR domain on regulating the efficacy of receptor trafficking and ligand binding may lead to possible approaches on modulating the innate immunity in Alzheimer's disease and atherosclerosis.

Polymorphisms in LMNA and near a SERPINA13 gene are not associated with cognitive performance in Chinese elderly males without dementia.

Aging is associated with cognitive deterioration. A recent study showed two polymorphisms (rs505058 in LMNA and rs11622883 near a SERPINA13 gene), identified in a genome-wide association study of late-onset Alzheimer's disease, to be associated with cognitive function (Mini Mental State Examination) in a UK elderly population. This study replicated these findings in Chinese elderly males without dementia. A total of 358 elderly subjects were assessed by the Cognitive Abilities Screening Instruments (CASI) and the Wechsler Digit Span Task tests. Analysis of covariance was used to compare cognitive scores among genotypic groups, with age and total education years as covariates. The two polymorphisms were not associated with the global cognitive function or specific cognitive domains in the elderly without dementia. Our data argue against that these two polymorphisms may affect cognitive function in the elderly.

Differential regulation of neurotrophin S100B and BDNF in two rat models of depression.

Several clinical studies have demonstrated that serum brain-derived neurotrophic factor (BDNF) levels are decreased and serum S100B levels are increased in patients with major depression. In this study, we investigated whether these findings could be replicated in animal models of depression. We measured BDNF and S100B protein levels in the serum, prefrontal cortex, striatum and hippocampus of rats in models of depression, i.e., olfactory bulbectomy (OBX) and chronic unpredictable stress (CUS) models. Serum BDNF levels were significantly increased in the OBX rats, as were hippocampal BDNF levels in the CUS rats, in comparison with their respective controls. Significant increases in serum S100B levels were observed in both the OBX and CUS rats as compared with their respective controls; however, S100B levels were decreased in the prefrontal cortex of the CUS rats. No significant correlation was found between serum and regional brain S100B/BDNF levels. Our findings suggest that both of these animal models of depression, in which similar serum S100B level changes to those in depressed patients were observed, could be used as valid models to explore the role of S100B underlying major depression. Neither serum S100B nor BDNF levels reflect their levels in the brain, and changes in their levels in patients with neuropsychiatric diseases should be interpreted cautiously.

Interleukin-1 beta (C-511T) genetic polymorphism is associated with cognitive performance in elderly males without dementia.

Interleukin-1 beta (IL-1 beta), a proinflammatory cytokine, plays a significant role in age-related changes in long-term potentiation (a biological substrate for learning and/or memory) in the hippocampus of experimental animals. This study tests the hypothesis that a biallelic functional polymorphism in the promoter region (position-511) (rs16944) of the IL-1 beta gene is associated with cognitive performance in elderly males without dementia. A total of 161 elderly male subjects without major psychiatric disorders or dementia participated in this research. Cognitive functions were assessed by the Cognitive Abilities Screening Instruments (CASI) test as well as The Wechsler Digit Span Task test. A significant association was found between the IL-1 beta C-511T polymorphism and CASI score (p=0.008), particularly in the abstraction and judgment subtest (p=0.010), and the backward digit span test (p=0.004). Post hoc tests indicated that the C/C genotype gained better cognitive function test results than T/T carriers, mainly in the non-apolipoprotein E allele epsilon 4 carriers. These results suggest that genetic variants of the IL-1 beta C-511T polymorphism may play a role in specific cognitive functions in normal aged males. Considering that cognitive decline in the elderly is associated with local inflammation processes, genetic variants of cytokines and their receptors should be tested to improve gene-based prediction of general cognitive function in the elderly.

Haplotype analysis of single nucleotide polymorphisms in the vascular endothelial growth factor (VEGFA) gene and antidepressant treatment response in major depressive disorder.

Vascular endothelial growth factor (VEGF) has been implicated in neurotrophy and neurogenesis, which play a pivotal role in brain development and may be involved in antidepressant therapeutic mechanisms. Recent animal studies demonstrate that VEGF levels are increased by several antidepressants, including selective serotonin reuptake inhibitors, and that VEGF signalling is required for antidepressant-induced behavioural response. We hypothesized that common genetic variants in the VEGF gene (official gene name: VEGFA) may be associated with the therapeutic response to antidepressants in major depressive disorders (MDD). Seven VEGFA polymorphisms were genotyped in 351 patients with MDD who were treated with selective serotonin reuptake inhibitor (fluoxetine or citalopram) antidepressants and who were were studied in a therapeutic evaluation for at least 4 weeks. Of the 351 patients, 158 completed an 8-week therapeutic evaluation. No significant association with either 4-week or 8-week antidepressant therapeutic effect was shown in the alleles and genotypes of single loci, or haplotypes from two blocks constructed from these polymorphisms. Our findings suggested that VEGFA genetic variants do not play a major role in the response to selective serotonin reuptake inhibitors.

Tryptophan hydroxylase 2 gene is associated with major depression and antidepressant treatment response.

Tryptophan hydroxylase-2 (TPH2) is the rate-limiting biosynthetic isoenzyme for serotonin that is preferentially expressed in the brain and has been implicated in the pathogenesis of major depressive disorder (MDD) and in the mechanism of antidepressant action. This study aimed to investigate whether common genetic variation in the TPH2 gene is associated with MDD and therapeutic response to antidepressants in a Chinese population. A total of 508 MDD patients and 463 unrelated controls were recruited. Among the MDD patients, 187 accepted selective serotonin reuptake inhibitor (fluoxetine or citalopram) antidepressant treatment for 8 weeks with therapeutic evaluation before and after treatment. Five TPH2 polymorphisms were genotyped and their association with MDD or treatment response was assessed by haplotype and single-marker analysis. In single-marker-based analysis, the rs17110747-G homozygote polymorphism was found to be more frequent in the MDD patients than in the controls (P=0.002). Genotype analysis in responders (defined as those with a 50% reduction in baseline Hamilton score) and non-responders after 8 weeks of antidepressant treatment showed that the proportion of rs2171363 heterozygote carriers was higher in the responders than the non-responders (P=0.009). No significant association with MDD or antidepressant therapeutic response was discovered in haplotype analyses. Our findings show that TPH2 genetic variants may play a role in MDD susceptibility and in acute therapeutic response to selective serotonin reuptake inhibitors.

Is dysfunction of the tissue plasminogen activator (tPA)-plasmin pathway a link between major depression and cardiovascular disease?

Epidemiological, genetic and clinical studies have demonstrated an association between major depressive disorder (MDD) and cardiovascular disease (CVD). For example, MDD is a risk factor for the development of CVD, while around one fifth of patients with CVD have MDD and a significantly larger percentage have subsyndromal symptoms of depression. Furthermore, patients with CVD and depression have an increased risk of future cardiac events compared to similar cohorts without depression, independent of baseline cardiac dysfunction. Despite evidence that CVD and MDD are epidemiologically linked, the cause of this correlation is still unknown. Several risk factors including physical and psychological stress, smoking, physical inactivity and inflammation have been proposed to mediate the interaction between MDD and CVD. The tissue-type plasminogen activator (tPA)-plasminogen proteolytic cascade is widely expressed in the brain. Accumulating evidence from preclinical and clinical studies suggests that tPA and its inhibitor, plasminogen activator inhibitor-1, are related to stress reaction and depression. In addition, brain-derived neurotrophic factor (BDNF) is important for the pathogenesis of MDD and the tPA-plasminogen proteolytic cascade has been implicated in the cleavage of proBDNF to BDNF in the brain, by which the direction of BDNF action is controlled. Thus, it is proposed that tPA-plasmin pathway dysfunction may play a role in the link between MDD and CVD. Future study of the components in the tPA-plasminogen system in CVD patients comorbid with MDD may lead to new, potentially important insights into the link between MDD and CVD, and might also contribute to novel strategies for the management of these two common and devastating diseases.

Association study of polymorphisms in the mitochondrial aspartate/glutamate carrier SLC25A12 (aralar) gene with schizophrenia.

Aralar is a mitochondrial calcium-regulated aspartate-glutamate carrier mainly distributed in brain and skeletal muscle, and involved in the transport of aspartate from mitochondria to the cytosol of a cell. Studies have shown that the brain N-acetyl aspartate (NAA) levels are greatly decreased in aralar-deficient mice, suggesting that aralar plays an important role in the synthesis of NAA in neuronal cells. Since magnetic resonance spectroscopy studies have revealed consistently reduced NAA levels in various brain regions of schizophrenic patients and their unaffected relatives, genes that affect aralar levels or NAA metabolism in the brain may be implicated in the pathogenesis of schizophrenia. Aralar is encoded by the SLC25A12 gene. In the past this gene has been found to be associated with susceptibility to autism; in this study we tested the hypothesis that SLC25A12 genetic variants confer susceptibility to schizophrenia. Six SLC25A12 polymorphisms were studied in a sample population of 253 people with schizophrenia and 216 normal controls. Significant linkage disequilibrium was obtained among the six polymorphisms. However, neither single marker nor haplotype analysis revealed an association between variants at the SLC25A12 locus and schizophrenia, suggesting that it is unlikely that the SLC25A12 polymorphisms investigated play a substantial role in conferring susceptibility to schizophrenia in the Chinese population. Further studies with SLC25A12 variants relating to brain NAA levels in patients with schizophrenia are suggested.

Association study of adenosine A2a receptor (1976C>T) genetic polymorphism and mood disorders and age of onset.

Evidence suggests that the adenosine A2a receptor (A2aAR) may be implicated in the pathogenesis of mood disorders. We tested the hypothesis that the A2aAR 1976C>T genetic variant confers susceptibility to mood disorders by comparing 192 mood disorder patients and 216 normal controls. The distribution of the A2aAR genotypes and alleles did not differ significantly comparing the two groups, suggesting that it is unlikely that the A2aAR 1976C>T polymorphism plays a major role in the development of mood disorders.

Family-based association study between G72/G30 genetic polymorphism and schizophrenia.

Genetic variations in G72/G30 have been reported to be associated with schizophrenia and bipolar disorders in several case-control studies. This gene is located in a genomic region known to contain susceptibility genes for schizophrenia. As case-control studies carry an increased risk of confounding through population stratification, we investigate whether the rs947267 (A/C) polymorphism is associated with schizophrenia in a family-based association study. This polymorphism is located within the G72/G30 gene and has been previously associated with bipolar disorders. The sample consisted of a total of 216 Chinese families that included an affected offspring and parents. Transmission disequilibrium analysis revealed a significant association between the G72/G30 rs947267 polymorphism and schizophrenia (P=0.016), with the A allele more commonly transmitted to patients. Further analysis stratified by sex showed that the A allele was significantly more overtransmitted than nontransmitted in the trios of male probands (P=0.031), but not in the trios of female probands. Our family-based association study supports the suggestion that the G72/G30 gene may be implicated in susceptibility to schizophrenia and there may be an interaction between this gene and sex in the pathogenesis of schizophrenia.

X-box binding protein 1 (XBP1) C--116G polymorphisms in bipolar disorders and age of onset.

X-box binding protein 1 (XBP1), a critical gene in the endoplasmic reticulum stress response, is located on chromosome 22q12, which has been linked with bipolar disorders in several studies. Recently, associations have been reported between a polymorphism (-116C --> G) in the promoter region of XBP1, and bipolar disorders in both case-control study and family-based association study, however, this finding is not yet confirmed by other research using independent sample populations. To replicate this finding and determine the association between onset age of bipolar disorders and the XBP1 C--116G polymorphism, we investigated the prevalence of this polymorphism in a Chinese population (153 bipolar disorder patients and 174 controls). We were unable, however, to demonstrate a significant association between the C--116G polymorphism and bipolar disorders (P = 0.674 for genotype and P = 0.436 for allele frequency) or age at onset (P = 0.563). Further, no association was demonstrated between this polymorphism and family history in bipolar disorder patients. These negative findings suggest that the XBP1 C--116G polymorphism does not play a major role in the pathogenesis of bipolar disorders in Chinese populations.