Association of the –1438G/A Polymorphism of the 5-HT2A Receptor Gene with Obstructive Sleep Apnea Syndrome

A Cross-Sectional Study on the Relationship Among Cytokines, 5-HT2A Receptor Polymorphisms, and Sleep Quality of Non-manual Workers in Xinjiang, China

BACKGROUND

Studies have shown that cytokine activity changes during the sleep-wake process, suggesting that inflammatory factors may be involved in a mechanism affecting sleep quality. Furthermore, the serotonergic system is also one of the essential components of airway relaxation during sleep, especially the serotonin 2A receptor (5-HTR2A) type that plays an important role in the sleep-wake process. Therefore, this research aimed to investigate the effects of cytokines and 5-HTR2A polymorphisms on sleep quality in non-manual workers in Urumqi, Xinjiang in order to explore the relationship between the three.

METHODS

This study used a cluster sampling method to randomly select non-manual workers who worked in Urumqi, Xinjiang for at least 1 year. From July 2016 and December 2017, this study recruited 1,500 non-manual workers for physical examination in the First Affiliated Hospital of Xinjiang Medical University. According to the inclusion and exclusion criteria, 1,329 non-manual workers were finally included in the questionnaire study. It used the Pittsburgh Sleep Quality Index questionnaire to assess sleep quality. Moreover, another 15% of respondents were randomly selected as the experimental study group. The polymerase chain reaction restriction fragment length polymorphism was used to detect 5-HTR2A gene genotypes. Simultaneously, the cytokine (IL-1β, IL-2, IL-6, and TNF-α) content was evaluated using an enzyme-linked immunoassay.

RESULTS

The results showed that among the 1,329 respondents, 870 had sleep quality problems, and the detection rate was 65.46%. The distribution of -1438G/A genotypes in the 5-HTR2A gene was significantly different among different sleep quality groups (p < 0.05), with no statistical significance present when comparing to T102C (p > 0.05). Logistic regression analysis showed that the AG [odds ratio (OR) = 2.771, 95% confidence interval (CI): 1.054-7.287] and GG (OR = 4.037, 95% CI: 1.244-13.105) genotypes at -1438G/A loci were both associated with poor sleep quality and were thus considered the susceptibility genotypes for sleep problems. Furthermore, IL-1β was shown to be a protective factor for sleep quality (OR = 0.949, 95% CI: 0.925-0.974). The interaction results showed that AG × IL-1β (OR = 0.952, 95% CI: 0.918-0.987) was associated with a lower risk of sleep problems than AA × IL-1β.

CONCLUSION

Cytokines and 5-HTR2A polymorphisms not only have independent effects on sleep but also may have cumulative effects. Therefore, it is necessary to further explore the related mechanisms affecting sleep quality to improve the sleep quality of non-manual workers.

Variants of candidate genes associated with the risk of obstructive sleep apnea

BACKGROUND

The researches on the associations between different candidate genes and obstructive sleep apnea (OSA) are inconsistent. Here, we performed a comprehensive qualitative and quantitative analysis to estimate the contribution of variants from candidate genes to the risk of OSA.

METHODS

Qualitative analysis was conducted to find the relationships for all included genes. Then, quantitative analysis of both allele models and genotype models was applied to evaluate the risk variants for OSA. Furthermore, a similar analysis was performed in different ethnic groups.

RESULTS

We included 152 publications containing 75 genes for qualitative analysis. Among them, we included 93 articles containing 28 variants from 16 genes for quantitative analysis. Through allele models, we found 10 risk variants for OSA (rs1801133 of MTHFR, ɛ4 of ApoE, -1438G/A of 5-HT2A, -308G/A of TNF-α, Pro1019Pro of LEPR, rs1130864 and rs2794521 of CRP, D/I of ACE, LPR and VNTR of 5-HTT) with the ORs of 1.21-2.07 in global population. We found that the variant of ɛ2 of ApoE could uniquely decrease the risk of OSA in the East Asian subgroup, while the other 6 variants, including ɛ4 in ApoE, -308G/A in TNF-α, Pro1019Pro in LEPR, D/I in ACE, LPR and VNTR in 5-HTT, could increase the risk of OSA. As for the European subpopulation, we only found that -308G/A in TNF-α could increase the risk for OSA.

CONCLUSIONS

Eleven variants from the candidate genes are associated with the risk of OSA, which also show ethnicity differences in East Asian and European subgroups.

Molecular determinants of obstructive sleep apnea

Obstructive sleep apnea (OSA) is characterized as recurrent episodes of obstruction in the upper airway during the period of sleep. The condition occurs in approximately 11% and 4% of middle-aged men and middle-aged women, respectively. Polysomnography is a diagnostic procedure that involves the constant observation of oxygen saturation and unsaturation during sleep. Usually, positive airway pressure is considered a benchmark treatment for OSA. This review summarizes the recent developments and emerging evidence from molecular biology-based research studies that show that genetic factors have an influence on OSA. The genetic aspects of OSA that have been identified include heritability and other phenotypic co-factors such as anatomical morphology. It also draws attention to the results of a polymorphic-based study that was conducted to determine the causative single nucleotide mutations associated with obesity and adverse cardiovascular risk in OSA. However, the role of such mutations and their linkage to OSA can not yet be established. Nonetheless, a large body of evidence supports a strong association between inflammatory cytokine polymorphism and obesity in the development of OSA. There are also probable intermediate factors with several gene-gene interactions. Therefore, advanced applications and modern techniques should be applied to facilitate new findings and to minimize the risk of developing OSA.

Exome-Wide Meta-Analysis Identifies Rare 3'-UTR Variant in ERCC1/CD3EAP Associated with Symptoms of Sleep Apnea

Obstructive sleep apnea (OSA) is a common sleep breathing disorder associated with an increased risk of cardiovascular and cerebrovascular diseases and mortality. Although OSA is fairly heritable (~40%), there have been only few studies looking into the genetics of OSA. In the present study, we aimed to identify genetic variants associated with symptoms of sleep apnea by performing a whole-exome sequence meta-analysis of symptoms of sleep apnea in 1,475 individuals of European descent. We identified 17 rare genetic variants with at least suggestive evidence of significance. Replication in an independent dataset confirmed the association of a rare genetic variant (rs2229918; minor allele frequency = 0.3%) with symptoms of sleep apnea (p-value_meta = 6.98 × 10⁻⁹, β_meta = 0.99). Rs2229918 overlaps with the 3′ untranslated regions of ERCC1 and CD3EAP genes on chromosome 19q13. Both genes are expressed in tissues in the neck area, such as the tongue, muscles, cartilage and the trachea. Further, CD3EAP is localized in the nucleus and mitochondria and involved in the tumor necrosis factor-alpha/nuclear factor kappa B signaling pathway. Our results and biological functions of CD3EAP/ERCC1 genes suggest that the 19q13 locus is interesting for further OSA research.

5-HTR2A and IL-6 polymorphisms and obstructive sleep apnea-hypopnea syndrome

At present, variants of the 5-hydroxytryptamine receptor 2A (5-HTR2A) and interleukin-6 (IL-6) genes may be susceptible markers to develop for obstructive sleep apnea-hypopnea syndrome (OSAHS). Therefore, the aim of the present study was to explore the potential associations between the 5-HTR2A and IL-6 single-nucleotide polymorphisms (SNPs) and OSAHS. In total there were 130 cases and 136 controls collected for genotyping of 5-HTR2A (rs6311) and IL-6 (rs1800796) SNPs. The association of these SNPs with OSAHS risk were evaluated by computing the odds ratio (OR) and 95% confidence interval (CI) from multivariate unconditional logistic regression analyses with adjustment for gender and age. The results indicated that the genotype and allele frequencies in these two loci (rs6311 and rs1800796) were not significantly different between the cases and controls. However, carrying the 'C' allele of rs6311 has a protective effect against OSAHS via the gender-specific comparison (P=0.0409; OR, 1.744; 95% CI, 1.021-2.978). The 'G' allele and 'CG' genotype distribution of rs1800796, and 'C' allele and 'CT' genotype distribution of rs6311 have significant differences between the mild and moderate group (P<0.05). Similarly, the genotype distribution of rs6311 has differences between mild and severe cases (P=0.0026). The current research demonstrated that variants of rs6311 have an association with OSAHS in males. Additionally, polymorphisms of rs6311 and rs1800796 have relevance to the severity of OSAHS.

The 100 Most Cited Turkish Papers in the Otorhinolaryngology Journals of Web of Science

Objective

The aim of the study was to analyze the 100 most cited publications with Turkish origin in the Web of Science Otorhinolaryngology (ORL) journals.

Methods

The Web of Science database was searched in terms of citations for publications originating from Turkey in ORL journals since 1983. After the identification of the 100 most cited articles, analysis was performed for the first author, institution, city, publication type, subject related to subspecialty, and journals having the most cited articles. Moreover, the number of ORL publications and citations of countries was determined in descending order using the same database.

Results

A total of 3948 ORL articles with Turkish origin was identified. The number of citations was 181 for the first and 28 for the last in the 100 most cited articles. As there was more than one article with 28 citations, 101 articles were analyzed. The number of the articles was 76, 22, and 3 for the university, education/research, and state hospitals, respectively. Hacettepe University, Ankara Numune Hospital, and Gazi University were the three leading institutions having the most cited articles, and Ankara was the first city. While 98 of 101 articles were original research, the number of case reports and review articles were 2 and 1, respectively. Thirty-five articles were related to otology, 23 to pediatric ORL, 20 to rhinology and head and neck surgery, and 3 to facial plastic surgery. Laryngoscope, Otolaryngology-Head and Neck Surgery, and International Journal of Pediatric Otorhinolaryngology were the leading 3 journals with the most cited articles coming from Turkey. The evaluation of countries revealed that Turkey was among the first 10 countries in terms of number of ORL articles but fell behind for the number of citations.

Conclusion

This bibliometric study is the first one regarding the contribution of Turkish authors and institutions to ORL literature. Similar studies might be periodically repeated to determine national development in the field of ORL and place of Turkey in the world.

The association of 5-HT2A, 5-HTT, and LEPR polymorphisms with obstructive sleep apnea syndrome: a systematic review and meta-analysis

Objective

A consensus has not been reached regarding the association of several different gene polymorphisms and susceptibility to obstructive sleep apnea syndrome (OSAS). We performed a meta-analysis to better evaluate the associations between 5-HT2A, 5-HTT, and LEPR polymorphisms, and OSAS.

Method

5-HT2A, 5-HTT, and LEPR polymorphisms and OSAS were identified in PubMed and EMBASE. The pooled odd rates (ORs) with 95%CIs were estimated using a fixed-effect or random-effect models. The associations between these polymorphisms and OSAS risk were assessed using dominant, recessive and additive models.

Results

Twelve publications were included in this study. The -1438 “A” allele of 5-HT2A was identified as a candidate genetic risk factor for OSAS (OR: 2.33, 95%CI 1.49–3.66). Individuals carrying the -1438 “G” allele had a nearly 70% reduced risk of OSAS when compared with AA homozygotes (OR: 0.30, 95%CI 0.23–0.40). There was no significant association between 5-HT2A 102C/T and OSAS risk, using any model. The “S” allele of 5-HTTLPR conferred protection against OSAS (OR: 0.80, 95%CI 0.67–0.95), while the “10” allele of 5-HTTVNTR contributed to the risk of OSAS (OR: 2.08, 95%CI: 1.58–2.73). The “GG” genotype of LEPR was associated with a reduced risk of OSAS (OR: 0.39, 95%CI 0.17–0.88).

Conclusion

The meta-analysis demonstrated that 5-HTR-1438 “A” and 5-HTTVNTR “10” alleles were significantly associated with OSAS. The “S” allele of 5-HTTLPR and the “GG” genotype of LEPR conferred protection against OSAS. Further studies, such as Genome-Wide Association study (GWAS), should be conducted in a large cohort of OSAS patients to confirm our findings.

A systematic review and meta-analysis of the association between serotonergic gene polymorphisms and obstructive sleep apnea syndrome

Background

5-Hydroxytryptamine receptor (5-HTR) and 5-hydroxytryptamine transporter (5-HTT) gene polymorphisms have been reported to be associated with susceptibility to obstructive sleep apnea syndrome (OSAS). The associations, derived from sporadic, inconsistent, small-sample-size studies, need to be evaluated further in a meta-analysis.

Methods

Relevant studies were identified by searching PubMed, Embase, The Cochrane Library, China National Knowledge Infrastructure (CNKI), Wanfang, and Weipu. Eligible data were extracted from each included study. Odds ratios (ORs) were calculated using a fixed-effects or a random-effects model. The ORs and 95% confidence interval (CI) were used to assess the strength of the association between serotonergic gene polymorphisms and OSAS in the dominant and recessive models, as well as alleles. The Q statistic was used to evaluate homogeneity and Begg’s test was used to assess publication bias.

Results

Eight studies were finally included in the meta-analysis of the association between 5-HTR2A gene variants (including 102T/C and 1438G/A), 5-HTT gene polymorphisms (including 5-HTT gene-linked promoter region (5-HTTLRP), and serotonin transporter intron 2 variable number tandem repeat (STin2VNTR) and OSAS risk. The G allele of 5-HTR2A 1438G/A, long 5-HTTLPR, and 10-tandem-repeats STin2VNTR were shown to increase OSAS susceptibility, with ORs of 2.33 (A vs. G, 95% CI 1.48–3.66), 1.24 (L vs. S, 95% CI: 1.04–1.49), and 2.87 (10 vs. 12, 95% CI: 1.38–5.97), respectively. These significant differences were determined in both dominant and recessive models. Of the 5-HTR2A 1438G/A gene polymorphism, the AA genotype increased the OSAS risk, with an OR of 4.21 (95% CI: 2.83–6.25) in a recessive model in male OSAS patients, but no significant association was found in females.

Conclusions

Our meta-analysis demonstrated that polymorphisms in the 5-HTR2A 1438G/A and 5-HTT genes contributed to susceptibility to OSAS. The A allele of the 1438G/A gene polymorphism is predominantly distributed in males and increased the OSAS risk significantly.

Association between the -1438G/A and T102C polymorphisms of 5-HT2A receptor gene and obstructive sleep apnea: a meta-analysis

The serotonin 2A (5-HT2A) receptor has been implicated in obstructive sleep apnea (OSA). Single nucleotide polymorphisms (SNPs) in the 5-HT2A gene have been found in OSA, the most common being -1438G/A and T102C; however, studies of the association between 5-HT2A SNPs and OSA risk have reported inconsistent findings. A meta-analysis was performed to quantitatively review the association between -1438G/A and T102C SNPs and OSA. Five studies, including 791 subjects for -1438G/A genotype and 1,068 subjects for T102C genotype, were selected. Pooled data analysis of the -1438G/A genotype indicated a significantly increased OSA risk was associated with two variant genotypes (AA vs. AG+GG: OR 3.023, 95 % CI 2.169-4.213, P = 0.506 for heterogeneity; A allele carriers vs. GG: OR 1.938, 95 % CI 0.879-4.274, P = 0.012 for heterogeneity). Stratification analysis by gender supported the association in males, but not females. For the T102C genotype, no significantly increased OSA risk was associated with the two variant genotypes (CC vs. CT+TT: OR 1.065, 95 % CI 0.787-1.442, P = 0.361 for heterogeneity; C allele carriers vs. TT: OR 0.979, 95 % CI 0.737-1.3, P = 0.9 for heterogeneity).In conclusions, meta-analysis indicated that the -1438G/A, and not T102C, polymorphism of 5-HT2A is a positive risk factor of OSA, especially in males.

Association between 5-HT2A receptor polymorphisms and risk of obstructive sleep apnea and hypopnea syndrome: a systematic review and meta-analysis

Obstructive sleep apnea and hypopnea syndrome (OSAHS) is a common disorder with several predisposing factors, which may include genetic causes. Studies of the association of susceptibility to and severity of OSAHS with the polymorphisms of the 5-HTR 2A/2C genes have had low statistical power and have yielded inconsistent results. To clarify the association we perform a meta-analysis that combines the genotyping data from all eligible published studies. We quantitatively analyzed five publications, which included a pool of 633 cases and 512 controls, addressing the 5-HT receptor polymorphism and the risk of OSAHS. Hardy-Weinberg equilibrium (HWE) and the minor allele frequency of genetic frequency distributions for the controls were calculated. Differences in the distribution of genotypes between cases and controls were compared by odds ratios (ORs) with their 95% confidence intervals (CIs). For each genetic model, data were pooled using fixed- or random-effects models, depending on the inter-publication heterogeneity. Our results from pooled data showed that individuals carrying the 5-HTR 2A -1438G/A AA genotype had an increased risk of OSAHS (OR=3.69, 95% CI=1.92-7.08) compared with those carrying the GG genotype. Significant results were also reached under a recessive model (OR=3.16, 95% CI=2.33-4.30, p<0.01). However, the results declined to an OR of 2.16 (95% CI=0.9-5.21) in a homozygote model when the studies were restricted to HWE. No statistically significant results concerning an association of the 102C/T polymorphism of the 5-HTR 2A gene with OSAHS were reached (p>0.05 for each genetic model). This meta-analysis suggested that the 5-HTR 2A -1438G/A genotype might modulate an elevated risk of OSAHS. No association of the 5-HTR 2A 102C/T genotype polymorphism with OSAHS was established. However, some publications exhibited HWE bias, which might influence the reliability of pooled data. Further studies in this field, using larger samples, better designs and additional ethnicities, are warranted.

Polymorphisms of the 5-hydroxytryptamine 2A/2C receptor genes and 5-hydroxytryptamine transporter gene in Chinese patients with OSAHS

BACKGROUND

It is known that there is a genetic predisposition to OSAHS. Polymorphisms of the 5-hydroxytryptamine (5-HT) 2A/2C receptors (5-HTR 2A/2C) genes and 5-HT transporter (5-HTT) gene may be associated with the pathogenesis of obstructive sleep apnea-hypopnea syndrome (OSAHS).

OBJECTIVES

In this study, we aimed to investigate the prevalence of polymorphisms of the 5-HTR 2A/2C genes and the 5-HTT gene in the Chinese Han OSAHS population.

METHODS

A total of 226 unrelated subjects of the Chinese Han population, including 121 OSAHS patients and 105 healthy controls, were involved in the study. The A1438G and T102C polymorphisms of the 5-HTR 2A gene, G796C polymorphisms of the 5-HTR 2C gene, and two polymorphisms (gene-linked polymorphic region [LPR] and variable number tandem repeat [VNTR]) of the 5-HTT gene were identified by polymerase chain reaction (PCR)-RFLP.

RESULTS

Compared with the control group, the OSAHS group had significantly higher AA genotype and A allele frequencies in the A1438G polymorphisms of the 5-HTR 2A gene, and had significantly higher frequencies of 10/10, 12/10 genotypes and the allele 10 of 5-HTT-VNTR. There were no significant differences between the genotype distribution and allele frequencies of the OSAHS group and the control group regarding the T102C polymorphisms of the 5-HTR 2A gene and the G796C polymorphisms of the 5-HTR 2C gene, the frequencies of the S or L allele and the S/S, S/L or L/L genotypes in 5-HTT-LPR.

CONCLUSIONS

The A1438G polymorphism of the 5-HTR 2A gene might be involved in the pathogenesis in OSAHS subjects of the Chinese Han population. Meanwhile, our findings support the argument that 5-HTT polymorphism appears to be associated with susceptibility to OSAHS, because the allele 10 of 5-HTT-VNTR might be a susceptible factor.

Association of the 5-HT2A receptor gene polymorphisms with obstructive sleep apnea hypopnea syndrome in Chinese Han population

CONCLUSIONS

The -1438G/A polymorphism of 5-HT2A receptor gene may associate with obstructive sleep apnea hypopnea syndrome (OSAHS) in a Chinese Han population. Different genotypes of -1438G/A polymorphism may influence the ventilatory activity in response to hypoxia, and in turn the sleep breath status.

OBJECTIVE

This study was designed to assess the association of polymorphisms in all exons and promoter region of the 5-HT2A receptor gene with OSAHS in a Chinese Han population.

METHODS

A total of 315 subjects (210 patients and 105 controls) were included for genetic analyses of polymorphisms in all exons and promoter region of the 5-HT2A receptor gene.

RESULTS

Six single nucleoside polymorphism (SNP) sites were identified in the sequencing of the promoter and exons of the 5-HT2A receptor gene; however, genotypes and allele frequencies of the SNPs did not show significant differences between the patients and controls except the -1438G/A polymorphism. For SNP of -1438G/A, the A/A genotype was over-represented and the allele A was more frequent in the patients, while the G/A genotype was over-represented and the allele G was more frequent in the controls (p < 0.001, p = 0.005, respectively). In the patients, the A/A and G/A genotypes were over-represented in the subgroups with lowest nocturnal SaO(2) (LSaO(2)) ≤75% and LSaO(2) >75%, respectively (p = 0.006).

Relationship of obstructive sleep apnea syndrome with the 5-HT2A receptor gene in Brazilian patients

BACKGROUND

Serotonin (5-HT) regulates a variety of visceral and physiological functions, including sleep. Polymorphisms in the 5-HT2A receptor gene can alter its transcription, affecting the number of receptors in the serotoninergic system, contributing to obstructive sleep apnea syndrome (OSAS).

OBJECTIVE

The aim of this study was to determine the prevalence of the 102T-C and -1438G-A polymorphisms in the 5-HTR2A gene in Brazilian patients with and without OSAS.

SUBJECTS AND METHODS

A cross-sectional study performed at the Otorhinolaryngology and Sleep Disorder Out Clinics, São José do Rio Preto Medical School, FAMERP. One hundred patients were examined as index cases and 100 persons as controls, of both genders to both groups. DNA was extracted from peripheral blood leukocytes, and the sites that encompassed both polymorphisms were amplified by PCR-RFLP.

RESULTS

There was a significant prevalence of the male gender in index cases compared with the control group gender (p < 0.0001). There was no significant genotypic difference in the 102T-C polymorphism between the case and control groups (p = 1.000). The AA genotype of the -1438G-A polymorphism was more prevalent in the patients with OSAS compared with the controls (OR, 2.3; CI 95% 1.20-4.38; p = 0.01).

CONCLUSIONS

There was no difference in the prevalence of the 102T-C polymorphism between patients with OSAS and the control group. Serotoninergic system dysfunction appeared to be related to OSAS. The -1438G-A polymorphism and OSAS are related in this studied Brazilian population.

The impact of atypical antipsychotic use on obstructive sleep apnea: a pilot study and literature review

BACKGROUND

Limited evidence links atypical antipsychotics (AAs) use to sleep related respiratory dysfunction and greater severity of obstructive sleep apnea (OSA). The present paper reviews the published evidence and examines the impact of AA use on the presence and severity of OSA among subjects with clinically suspected OSA after adjusting for several confounds.

METHODS

Archives of the University of Iowa Sleep Laboratory from 2005 to 2009 were searched for patients using AAs at the time of diagnostic polysomnogram (PSG). PSG data of the 84 AA users with heterogeneous psychiatric disorders (of these 20 diagnosed only with depression) were subsequently compared to PSG data of two randomly selected, non-AA user groups from the same patient pool: (i) 200 subjects with a depressive disorder as the only psychiatric diagnosis, and (ii) 331 mentally healthy controls. PSG data were analyzed adjusting for known demographic, medical, and psychiatric risk factors for OSA.

RESULTS

Prevalence and severity of OSA did not differ significantly across three groups. Sex, age, body mass index (BMI), and neck circumference (NC) independently predicted OSA. Odds ratio for OSA in the subset of AA users carrying the diagnosis of depression (n=20) compared with subjects without mental illness was 4.53 (p<.05). By contrast, AA users without depression or those with multiple psychiatric diagnoses including depression did not show a statistically significantly elevated OSA risk.

CONCLUSIONS

AA use in subjects with depression appears to increase the risk of OSA after controlling for known predisposing factors.

The genetics of obstructive sleep apnoea

PURPOSE OF REVIEW

Obstructive sleep apnoea syndrome (OSAS) is a highly prevalent disorder associated with reduced quality of life and adverse cardiovascular and metabolic sequelae. Recent years have seen an intensification of the research effort to establish the genetic contribution to the development of OSAS and its sequelae. This review explores emerging evidence in this field.

RECENT FINDINGS

A genetic basis for sleep-disordered breathing has been demonstrated for discrete disorders such as Treacher-Collins and Down syndromes, but the picture is less clear in so-called idiopathic OSAS. A degree of heritability appears likely in some of the intermediate phenotypes that lead to OSAS, particularly craniofacial morphology. However, only sparse and often contradictory evidence exists regarding the role of specific polymorphisms in causing OSAS in the general population. Similarly, investigations of the cardiovascular sequelae of OSAS have in general failed to consistently find single causative genetic mutations. Nonetheless, evidence suggests a role for tumour necrosis factor-α polymorphisms in particular, and large-scale family studies have suggested shared pathogenetic pathways for the development of obesity and OSAS.

SUMMARY

As with other common disorders, OSAS is likely to result from multiple gene-gene interactions occurring in a suitable environment. The application of modern genetic investigative techniques, such as genome-wide association studies, may facilitate new discoveries in this field.

A candidate gene study of obstructive sleep apnea in European Americans and African Americans

RATIONALE

Obstructive sleep apnea (OSA) is hypothesized to be influenced by genes within pathways involved with obesity, craniofacial development, inflammation, and ventilatory control.

OBJECTIVES

We conducted the first candidate gene study of OSA using family data from European Americans and African Americans, selecting biologically plausible genes from within these pathways.

METHODS

A total of 1,080 single nucleotide polymorphisms (SNPs) were genotyped in 729 African Americans and 505 SNPs were genotyped in 694 European Americans. Coding for SNPs additively, association testing on the apnea-hypopnea index (AHI) as a continuous trait, and OSA as a dichotomous trait (AHI ≥15) was conducted using methods that account for familial correlations in models adjusted for age, age-squared, and sex, with and without body mass index.

MEASUREMENTS AND MAIN RESULTS

In European Americans, variants within C-reactive protein (CRP) and glial cell line-derived neurotrophic factor (GDNF) were associated with AHI (CRP: β = 4.6; SE = 1.1; P = 0.0000402) (GDNF: β = 4.3; SE = 1; P = 0.0000201) and with the dichotomous OSA trait (CRP: odds ratio = 2.4; 95% confidence interval, 1.5-3.9; P = 0.000170) (GDNF: odds ratio = 2; 95% confidence interval, 1.4-2.89; P = 0.0000433). In African Americans, rs9526240 within serotonin receptor 2a (HTR2A: odds ratio = 2.1; 95% confidence interval, 1.5-2.9; P = 0.00005233) was associated with OSA.

CONCLUSIONS

This candidate gene analysis identified the potential role of genes operating through intermediate disease pathways to influence sleep apnea phenotypes, providing a framework for focusing future replication studies.

Sleep and circadian rhythm disturbances: multiple genes and multiple phenotypes

Sleep is regulated by two broad mechanisms: the circadian system, which generates 24-h rhythms of sleep propensity and a wake-dependent homeostatic sleep process whereby sleep pressure increases during wake and dissipates during sleep. These, in turn, regulate multiple brain structures and neurotransmitter systems. In view of the complexity of sleep it is not surprising that there is considerable variation between individuals in both sleep timing and propensity. Furthermore, marked abnormalities in sleep are commonly encountered in psychiatric and neurodegenerative disorders. Teasing apart the genetic versus environmental contributions to normal and abnormal sleep is complex. Here we attempt to summarise what recent progress has been made, and what will be needed in the future to gain a more complete understanding of this fundamental aspect of physiology.

Using linkage analysis to identify quantitative trait loci for sleep apnea in relationship to body mass index

To understand the genetics of sleep apnea, we evaluated the relationship between the apnea hypopnea index (AHI) and body mass index (BMI) through linkage analysis to identify genetic loci that may influence AHI and BMI jointly and AHI independent of BMI. Haseman-Elston sibling regression was conducted on AHI, AHI adjusted for BMI and BMI in African-American and European-American pedigrees. A comparison of the magnitude of linkage peaks was used to assess the relationship between AHI and BMI. In EAs, the strongest evidence for linkage to AHI was on 6q23-25 and 10q24-q25, both decreasing after BMI adjustment, suggesting loci with pleiotropic effects. Also, a promising area of linkage to AHI but not BMI was observed on 6p11-q11 near the orexin-2 receptor, suggesting BMI independent pathways. In AAs the strongest evidence of linkage for AHI after adjusting for BMI was on chromosome 8p21.3 with linkage increasing after BMI adjustment and on 8q24.1 with linkage decreasing after BMI adjustment. Novel linkage peaks were also observed in AAs to both BMI and AHI on chromosome 13 near the serotonin-2a receptor. These analyses suggest genetic loci for sleep apnea that operate both independently of BMI and through BMI-related pathways.

Association of GABA(B)R1 receptor gene polymorphism with obstructive sleep apnea syndrome

OBJECTIVE

GABA(B)R (gamma-amino butyric acid B receptor)-mediated neurotransmission has been implicated in the pathophysiology of a variety of neuropsychiatric disorders. GABA(B)R1 gene variants were identified by single-strand conformation analysis. The nucleotide exchanges cause a substitution of alanine to valine in exon 1a1 (Ala20Val), a substitution of glycine to serine in exon 7 (Gly489Ser) and a silent C to G nucleotide exchange encoding the amino acid phenylalanine in exon 11 (Phe658Phe). The significance of GABA(B)R1a gene polymorphism in obstructive sleep apnea syndrome (OSAS) as well as the association of these polymorphisms with the polysomnography findings in OSAS patients are not known. In this study, we aimed to assess the significance of 3 different GABA(B)R1 gene polymorphisms (Ala20Val, Gly489Ser and Phe658Phe) in OSAS.

METHODS

Seventy-five patients (23 female and 52 male) with OSAS and 99 healthy volunteers (51 female, 48 male) were included in the study to assess Ala20Val, Gly489Ser and Phe658Phe polymorphisms of the GABA(B)R1 gene.

RESULTS

For the Ala20Val variants, there was no significant difference between the genotypes and allele frequencies of the patients and controls, nor between both genders (p > 0.05). For Phe658Phe polymorphism, there was no significant difference between genotypes and allele frequencies of the patients and controls (p > 0.05). However, the C/C genotype was overrepresented and the T/C genotype was less frequent in male than female patients (p = 0.03). The C/C genotype was overrepresented and the T/C genotype was less frequent in male patients than male controls (p = 0.01). For GABA(B)R1-Gly489Ser polymorphism, all of the patients and controls had G/G genotype. The apnea arousal index scores of the male patients with C/C genotype were significantly higher than in the patients with C/T genotype (p = 0.01). The percent total sleep time in non-REM 1 scores of the male patients with T/T genotype were significantly higher than in the patients with T/C genotype (p = 0.021). The percent total sleep time in non-REM 2 scores of the female patients with C/C genotype were significantly higher than in the patients with C/T genotype (p = 0.006).

CONCLUSION

The Ala20Val polymorphism of the GABA(B)R1 gene may be associated with OSAS, whereas Gly489Ser polymorphism does not seem to be involved in OSAS. The C/C variant of the Phe658Phe polymorphism GABA(B)R1 gene seems associated with the occurrence of OSAS and is also associated with some sleep related parameters (apnea arousal index and percent total sleep time in non-REM) recorded by polysomnography.

Insulin receptor substrate gene polymorphism is associated with obstructive sleep apnea syndrome in men

OBJECTIVE

The objective of this study was to assess significance of insulin receptor substrate (IRS) -1 gene polymorphism (Gly972Arg) at codon 972 in obstructive sleep apnea syndrome (OSAS).

METHODS

Using the polymerase chain reaction technique, the codon 972 polymorphism of the IRS-1 gene was analyzed in the DNA obtained from leukocytes of 50 patients and 143 healthy controls.

RESULTS

An overall comparison between the genotypes and allele frequencies of the patients and controls did not reveal any statistically significant difference between the patients and controls (P > .05). Gender-specific comparisons were not significantly different except for a significant difference between the genotypes and allele frequencies of the male patients and male controls (P < .05). The heterozygous, Gly/Arg variant of the IRS-1 gene was overrepresented and the homozygous, Gly/Gly variant was less frequent in male patients compared with male controls. In the patients with OSAS, there was no correlation between the genotypes and polysomnography parameters on correlation analyses (P > .05). There was no relationship between the genotypes and diabetes mellitus (P > .05). Body mass indices and polysomnography parameters of the patients with and without diabetes mellitus were not significantly different (P > .05).

CONCLUSION

The polymorphism of the IRS-1 gene at codon 972, especially Gly/Arg variant, or the presence of the allele for Arg appears to be associated with occurrence of OSAS in male patients, whereas this polymorphism is not related to severity of OSAS.