3111T/C Clock Gene Polymorphism in Women with Insomnia

Potential genetic and epigenetic mechanisms in insomnia: A systematic review

Insomnia is a stress-related sleep disorder conceptualised within a diathesis-stress framework, which it is thought to result from predisposing factors interacting with precipitating stressful events that trigger the development of insomnia. Among predisposing factors genetics and epigenetics may play a role. A systematic review of the current evidence for the genetic and epigenetic basis of insomnia was conducted according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) system. A total of 24 studies were collected for twins and family heritability, 55 for genome-wide association studies, 26 about candidate genes for insomnia, and eight for epigenetics. Data showed that insomnia is a complex polygenic stress-related disorder, and it is likely to be caused by a synergy of genetic and environmental factors, with stress-related sleep reactivity being the important trait. Even if few studies have been conducted to date on insomnia, epigenetics may be the framework to understand long-lasting consequences of the interaction between genetic and environmental factors and effects of stress on the brain in insomnia. Interestingly, polygenic risk for insomnia has been causally linked to different mental and medical disorders. Probably, by treating insomnia it would be possible to intervene on the effect of stress on the brain and prevent some medical and mental conditions.

Association between CLOCK Gene Polymorphisms and Insomnia Risk According to Food Groups: A KoGES Longitudinal Study

Food intake could mitigate or exacerbate the risk for insomnia associated with the CLOCK gene. This study investigated the associations between the clock circadian regulator (CLOCK) polymorphisms rs12649507 and rs4580704 and the risk of insomnia, as well as its interactions with food groups. Among 1430 adults, new insomnia cases were identified between 2005 and 2012. Single nucleotide polymorphisms were genotyped, and dietary intake was assessed. Next, Cox proportional hazard models were established. The fruit and meat groups significantly mitigated the risk of insomnia associated with rs12649507 among males (pinteraction = 0.006 in a recessive model; p = 0.010 in a dominant model). In contrast, among females the beverage group significantly increased the risk of insomnia (p = 0.041 in a dominant model). As for rs4580704, among males the fruit and meat groups modified the risk of insomnia (p = 0.006 in a recessive model; p = 0.001 in a dominant model). However, among females, the beverage group exacerbated the risk of insomnia associated with rs4580704 (p = 0.004 in a dominant model). In this longitudinal study, we observed a significantly modified insomnia risk associated with the CLOCK gene depending on food groups. Notably, in a general population the risks were modified according to both the fruit and meat intake among 775 males but exacerbated with beverage intake among 655 females.

Understanding neuron-glia crosstalk and biological clocks in insomnia

According to the World Health Organization, about one-third of the population experiences insomnia symptoms, and about 10-15% suffer from chronic insomnia, the most common sleep disorder. Sleeping difficulties associated with insomnia are often linked to chronic sleep deprivation, which has a negative health impact partly due to disruption in the internal synchronisation of biological clocks. These are regulated by clock genes and modulate most biological processes. Most studies addressing circadian rhythm regulation have focused on the role of neurons, yet glial cells also impact circadian rhythms and sleep regulation. Chronic insomnia and sleep loss have been associated with glial cell activation, exacerbated neuroinflammation, oxidative stress, altered neuronal metabolism and synaptic plasticity, accelerated age-related processes and decreased lifespan. It is, therefore, essential to highlight the importance of glia-neuron interplay on sleep/circadian regulation and overall healthy brain function. Hence, in this review, we aim to address the main neurobiological mechanisms involved in neuron-glia crosstalk, with an emphasis on microglia and astrocytes, in both healthy sleep, chronic sleep deprivation and chronic insomnia.

Gene polymorphisms (rs324957, rs324981) in NPSR1 are associated with increased risk of primary insomnia: A cross-sectional study

Neuropeptide S and neuropeptide S receptor (NPSR1) are associated with sleep regulation. Herein, the possible contribution of 6 polymorphisms in NPSR1 on the chromosome to primary insomnia (PI) and objective sleep phenotypes was investigated.The study included 157 patients with PI and 133 age- and sex-matched controls. All subjects were investigated by polysomnography for 3 consecutive nights. The genotyping of 6 polymorphisms was carried out by polymerase chain reaction-restriction fragment length polymorphism method.A significant difference was detected for rs324957 and rs324981 between PI and controls. The PI patients had a higher frequency of AA than controls in rs324957 (P = .02) and rs324981 (P = .04). However, for other single nucleotide polymorphisms (rs323922, rs324377, rs324396, and rs324987), no significant differences were observed between PI patients and controls. There were 2 different allelic combinations that were associated with PI susceptibility (CATGTC, GCCAAT) and its risk factor. A significant difference in sleep latency was observed among 3 genotype carriers of NPSR1 gene polymorphism rs324957 in PI group (P = .04), with carriers of the A/A genotype having the longest sleep latency (mean ± SD: 114.80 ± 58.27), followed by the A/G genotype (112.77 ± 46.54) and the G/G genotype (92.12 ± 42.72).This study provided the evidence that the NPSR1 gene polymorphisms (rs324957, rs324981) might be susceptibility loci for PI. Further studies are needed to explore the role of NPSR1 gene polymorphisms in molecular mechanisms of PI in a larger sample size.

Circadian Clock, Time-Restricted Feeding and Reproduction

The goal of this review was to seek a better understanding of the function and differential expression of circadian clock genes during the reproductive process. Through a discussion of how the circadian clock is involved in these steps, the identification of new clinical targets for sleep disorder-related diseases, such as reproductive failure, will be elucidated. Here, we focus on recent research findings regarding circadian clock regulation within the reproductive system, shedding new light on circadian rhythm-related problems in women. Discussions on the roles that circadian clock plays in these reproductive processes will help identify new clinical targets for such sleep disorder-related diseases.

The Relationship Between Tryptophan Hydroxylase-2 Gene with Primary Insomnia and Depressive Symptoms in the Han Chinese Population

Background:

Insomnia often coexists with depression, and there is compelling evidence for a genetic component in the etiologies of both disorders.

Aims:

To investigate the relationship between exonic variant (rs4290270) in the tryptophan hydroxylase-2 gene and primary insomnia and symptoms of depression in Han Chinese.

Study Design:

Case-control study.

Methods:

This study included 152 patients with primary insomnia and 164 age- and gender-matched normal controls. All patients were investigated by polysomnography for 2 consecutive nights. The depressive symptoms were measured by using a 20-item Zung Self-rating Depression Scale. Sleep quality was assessed with the Pittsburgh Sleep Quality index. The genotypes of the TPH-2 gene polymorphism rs4290270 were determined by the polymerase chain reaction-restriction fragment length polymorphism method.

Results:

The genotype distributions of the tryptophan hydroxylase-2 gene polymorphism rs4290270 were in Hardy-Weinberg equilibrium in both patients and controls (p>0.05). The allele and genotype distributions of this variant were comparable between patients and controls in all subjects and between genders (all p>0.05). The impact of rs4290270 on self-rating depression scale score changes was statistically significant (p=0.002), with carriers of the A/A genotype having the highest self-rating depression scale score (mean ± standard deviation: 52.73±12.88), followed by the A/T genotype (50.94±11.29, p=0.35) and the T/T genotype (43.48±7.78, p<0.01), and this impact was more obvious in women (p<0.001).

Conclusion:

The tryptophan hydroxylase-2 gene polymorphism rs4290270 may not be a susceptibility locus for primary insomnia in Han Chinese, but it may be a marker of depressive symptoms.

Association of 3111T/C Polymorphism of the Clock Gene with Circadian Rhythm of Melatonin in Menopausal Women with Insomnia

We carried out a comparative analysis of circadian rhythms of melatonin secretion in Caucasian menopausal women with and without insomnia depending on the 3111T/C polymorphism of the Clock gene. Melatonin levels was measured in the saliva 4 times a day (06.00-07.00, 12.00-13.00, 18.00-19.00, and 23.00-00.00 h). Carriers of the TT genotype with insomnia demonstrated significantly higher level of melatonin in the early morning hours compared to the carriers of the minor allele C (12.60±7.58 and 8.98±8.62 pg/ml, respectively, p=0.023). In the control group, no statistically significant differences were revealed. The carriers of the TT genotype with sleep disorders have higher morning melatonin level compared to control group women (12.60±7.58 and 5.48±4.74 pg/ml, respectively, p=0.005) and low nocturnal melatonin level (6.42±4.97 and 12.52±10.40 pg/ml, respectively, p=0.039).