Reciprocal interactions of obstructive sleep apnea and hypertension associated with ACE I/D polymorphism in males.

BACKGROUND: The angiotensin-converting enzyme (ACE) insertion/deletion (I/D) polymorphism gene contributes to the genesis of hypertension (HTN) and may help explain the relationship between obstructive sleep apnea (OSA) and HTN. However, ACE is a pleiotropic gene that has several influences, including skeletal muscle and control of ventilation. We therefore tested the hypothesis that ACE polymorphism influences OSA severity. METHODS: Male OSA patients (apnea-hypopnea index [AHI]>5 events/h) from 2 university sleep centers were evaluated by polysomnography and ACE I/D polymorphism genotyping. RESULTS: We studied 266 males with OSA (age=48+/-13 y, body mass index=29+/-5 kg/m(2), AHI=34+/-25 events/h). HTN was present in 114 patients (43%) who were older (p<0.01), heavier (p<0.05) and had more severe OSA (p<0.01). The I allele was associated with HTN in patients with mild to moderate OSA (p<0.01), but not in those with severe OSA. ACE I/D polymorphism was not associated with apnea severity among normotensive patients. In contrast, the only variables independently associated with OSA severity among patients with hypertension in multivariate analysis were BMI (OR=1.12) and II genotype (OR=0.27). CONCLUSIONS: Our results indicate reciprocal interactions between OSA and HTN with ACE I/D polymorphism, suggesting that among hypertensive OSA males, the homozygous ACE I allele protects from severe OSA.

Validation of commonly used reference genes for sleep-related gene expression studies.

BACKGROUND: Sleep is a restorative process and is essential for maintenance of mental and physical health. In an attempt to understand the complexity of sleep, multidisciplinary strategies, including genetic approaches, have been applied to sleep research. Although quantitative real time PCR has been used in previous sleep-related gene expression studies, proper validation of reference genes is currently lacking. Thus, we examined the effect of total or paradoxical sleep deprivation (TSD or PSD) on the expression stability of the following frequently used reference genes in brain and blood: beta-actin (b-actin), beta-2-microglobulin (B2M), glyceraldehyde-3-phosphate dehydrogenase (GAPDH), and hypoxanthine guanine phosphoribosyl transferase (HPRT). RESULTS: Neither TSD nor PSD affected the expression stability of all tested genes in both tissues indicating that b-actin, B2M, GAPDH and HPRT are appropriate reference genes for the sleep-related gene expression studies. In order to further verify these results, the relative expression of brain derived neurotrophic factor (BDNF) and glycerol-3-phosphate dehydrogenase1 (GPD1) was evaluated in brain and blood, respectively. The normalization with each of four reference genes produced similar pattern of expression in control and sleep deprived rats, but subtle differences in the magnitude of expression fold change were observed which might affect the statistical significance. CONCLUSION: This study demonstrated that sleep deprivation does not alter the expression stability of commonly used reference genes in brain and blood. Nonetheless, the use of multiple reference genes in quantitative RT-PCR is required for the accurate results.

Casein kinase I epsilon (CKIvarepsilon) N408 allele is very rare in the Brazilian population and is not involved in susceptibility to circadian rhythm sleep disorders.

Circadian rhythms are regulated by clock proteins through post-translational modifications. Indeed, Casein kinase I epsilon (CKIvarepsilon) promotes reversible phosphorylation of PER proteins, and a deficiency in this phosphorylation has been implicated in human sleep disorders. Here, we investigated the CKIvarepsilon S408N polymorphism in a Brazilian population sample. The N408 allele was previously described to be much less frequent in individuals with Delayed Sleep-Phase Syndrome (DSPS), than in the general Japanese population, suggesting a protective function for the allele against the disease. We found that this polymorphism is very rare in the Brazilian population (1.37%), indicating that it has no influence on susceptibility to circadian rhythm sleep disorders. Therefore, it is necessary to account for adaptative influences in genetic background, analyzing different groups with different photoperiods, to validate the effects of this and other polymorphisms on sleep and circadian disorders.

Simple detection of large InDeLS by DHPLC: the ACE gene as a model.

Insertion-deletion polymorphism (InDeL) is the second most frequent type of genetic variation in the human genome. For the detection of large InDeLs, researchers usually resort to either PCR gel analysis or RFLP, but these are time consuming and dependent on human interpretation. Therefore, a more efficient method for genotyping this kind of genetic variation is needed. In this report, we describe a method that can detect large InDeLs by DHPLC (denaturating high-performance liquid chromatography) using the angiotensin-converting enzyme (ACE) gene I/D polymorphism as a model. The InDeL targeted in this study is characterized by a 288 bp Alu element insertion (I). We used DHPLC at nondenaturating conditions to analyze the PCR product with a flow through the chromatographic column under two different gradients based on the differences between D and I sequences. The analysis described is quick and easy, making this technique a suitable and efficient means for DHPLC users to screen InDeLs in genetic epidemiological studies.

Cognitive performance of patients with mesial temporal lobe epilepsy is not associated with human prion protein gene variant allele at codons 129 and 171.

Cognitive impairment has long been recognized in people with medically refractory epilepsies. Mesial temporal lobe epilepsy related to hippocampal sclerosis (MTLE-HS), the most common surgically remediable epileptic syndrome, has been associated with a cellular prion protein (PrPc) gene (Prnp) variant allele at codon 171. The polymorphism consisting of a methionine-for-valine substitution at codon 129 has been associated with early cognitive deterioration in elderly people and patients with Down syndrome. The same variant allele in homozygosis (V129V) has been associated to a lower long-term memory in healthy humans. PrPc mediates several processes related to neuroplasticity, and its role in cognitive processes remains unknown. In this study, we evaluated the genetic contribution of Prnp alleles to cognitive performance in patients with MTLE-HS. Cognitive performance, measured with 19 neuropsychological tests, of patients with refractory MTLE-HS with the normal Prnp genotypes was compared with that of patients with the variant alleles at codons 129 and 171. With the effects of clinical, demographic, electrophysiological, and neuroimaging variable interactions controlled by multiple linear regression analysis and adjustment for multiple test comparisons, the presence of Prnp variant alleles was found not to be significantly associated to cognitive performance of patients with MTLE-HS. The presence of variant alleles at codons 129 and 171 is not associated to cognitive performance of patients with refractory MTLE-HS.