The 3111T/C polymorphism of the CLOCK gene confers a predisposition to a lifetime lower body weight in patients with anorexia nervosa and bulimia nervosa: a preliminary study

Chrono-Nutrition: Circadian Rhythm and Personalized Nutrition

The human circadian system has a period of approximately 24 h and studies on the consequences of "chornodisruption" have greatly expanded. Lifestyle and environmental factors of modern societies (i.e., artificial lighting, jetlag, shift work, and around-the-clock access to energy-dense food) can induce disruptions of the circadian system and thereby adversely affect individual health. Growing evidence demonstrates a complex reciprocal relationship between metabolism and the circadian system, in which perturbations in one system affect the other one. From a nutritional genomics perspective, genetic variants in clock genes can both influence metabolic health and modify the individual response to diet. Moreover, an interplay between the circadian rhythm, gut microbiome, and epigenome has been demonstrated, with the diet in turn able to modulate this complex link suggesting a remarkable plasticity of the underlying mechanisms. In this view, the study of the impact of the timing of eating by matching elements from nutritional research with chrono-biology, that is, chrono-nutrition, could have significant implications for personalized nutrition in terms of reducing the prevalence and burden of chronic diseases. This review provides an overview of the current evidence on the interactions between the circadian system and nutrition, highlighting how this link could in turn influence the epigenome and microbiome. In addition, possible nutritional strategies to manage circadian-aligned feeding are suggested.

CLOCK 3111TT Genotype Is Associated with Increased Total Cholesterol and Low-Density Lipoprotein Levels in Menopausal Women with a Body Mass Index of at Least 25 kg/m2

Lipid profile comparative analysis was performed to reveal the interdependence of lipids with Circadian locomoter output cycles protein kaput (CLOCK) 3111T/C gene polymorphism in menopausal women with/without a body mass index (BMI) of ≥25 kg/m². Methods: A total of 193 female volunteers aged 45 to 60 years were divided into two groups: Those with BMI < 25 kg/m² (control) and those with BMI ≥ 25 kg/m². Each group was then divided into two subgroups: Those with the CLOCK TT-genotype and those with the CLOCK TC-, CC-genotypes. Lipid metabolism parameters were determined by the enzymatic method. Single-nucleotide polymorphisms (SNPs) were detected via polymerase chain reaction–restriction fragment length polymorphism technology. Results: There were no differences in CLOCK 3111T/C genotypes or allele frequency between the control and main groups. In addition, there were no differences in lipid profile parameters between women of the control group and different CLOCK 3111T/C genotypes. The total cholesterol (p = 0.041) and low-density lipoprotein cholesterol (p = 0.036) levels were higher in the subgroup of women with a BMI ≥ 25 kg/m² and CLOCK TT-genotype as compared to the subgroup with a BMI ≥ 25 kg/m² and minor allele 3111C. Conclusions: SNP 3111T/C of the CLOCK gene is not associated with BMI however, data suggest that the minor allele of the CLOCK 3111T/C gene polymorphism may have a protective role in atherogenic lipid levels in women with a BMI greater than or equal to 25 kg/m².

CLOCK gene polymorphisms and quality of aging in a cohort of nonagenarians - The MUGELLO Study

A total of 356 elderly subjects [257F; 88–106 years] were genotyped for three polymorphisms of the CLOCK gene by TaqMan real-time PCR approach, in order to find associations with quality of aging. Subjects homozygous for the minor allele of rs1801260 were less frequently overweight (p = 0.046), had higher fasting glucose levels (p = 0.037), better scores at the Clock Drawing Test (CDT) (p = 0.047) and worse scores at the Geriatric Depression Scale (p = 0.032). Subjects homozygous for the minor allele of rs11932595 showed higher fasting glucose levels (p = 0.044) and better scores at CDT (p = 0.030). Conversely, subjects homozygous for the minor allele of rs4580704 showed higher triglyceride (p = 0.012), and LDL-cholesterol levels (p = 0.44), and a greater adherence to the Mediterranean diet (MD) (p = 0.044). In addition, AAC, AAG, GGC and AGC (rs1801260–rs11932595–rs4580704) haplotypes were analyzed: AAG was associated with higher risk of overweight (p = 0.008), hypertriglyceridemia (p = 0.040) and hypercholesterolemia (p = 0.036); GGC with lower risk of hyperglycemia (p = 0.022), better sleep pattern (p = 0.001) and with better score at mini-mental state examination (p = 0.010); AGC with lower risk of depression (p = 0.026) and AAC with lower adherence to the MD (p = 0.028). Therefore, CLOCK gene polymorphisms let us hypothesize an involvement in the quality of aging in a cohort of nonagenarians.

Association of the melatonin circadian rhythms with clock 3111T/C gene polymorphism in Caucasian and Asian menopausal women with insomnia

A comparative analysis of melatonin circadian rhythms in Caucasian (incoming population) and Asian (indigenous population) menopausal women with/without sleep disorders depending on the genotype of Clock 3111T/C gene polymorphism was realized.The melatonin level in the saliva was determined four times a day (6:00-7:00, 12:00-13:00, 18:00-19:00, 23:00-00:00 h). The Caucasian women-carriers of the TT-genotype with insomnia as compared to control group-had a higher morning melatonin level and a lower night melatonin level. The Asian women with TT-genotype and insomnia had a lower levels of melatonin as compared to control at daytime, evening and night. A significantly higher melatonin level in the early morning hours was detected in the Caucasian women-carriers of the TT-genotype with insomnia as compared to group womencarriers of the minor 3111C-allele. There were no statistically significant differences in the circadian rhythms of melatonin in the Asian women depending on the genotype of the Clock 3111T/C polymorphism. An assumption with respect to the protective role of the minor allele 3111C in the development of insomnia associated with the displacement of melatonin circadian rhythms in the representatives of the incoming population was made.

Discussing the putative role of obesity-associated genes in the etiopathogenesis of eating disorders

In addition to the identification of mutations clearly related to Mendelian forms of obesity; genome-wide association studies and follow-up studies have in the last years pinpointed several loci associated with BMI. These genetic alterations are located in or near genes expressed in the hypothalamus that are involved in the regulation of eating behavior. Accordingly, it seems plausible that these SNPs, or others located in related genes, could also help develop aberrant conduct patterns that favor the establishment of eating disorders should other susceptibility factors or personality dimensions be present. However, and somewhat surprisingly, with few exceptions such as BDNF, the great majority of the genes governing these pathways remain untested in patients with anorexia nervosa, bulimia nervosa or binge-eating disorder. In the present work, we review the few existing studies, but also indications and biological concepts that point to these genes in the CNS as good candidates for association studies with eating disorder patients.

Diversity of human clock genotypes and consequences

The molecular clock consists of a number of genes that form transcriptional and posttranscriptional feedback loops, which function together to generate circadian oscillations that give rise to circadian rhythms of our behavioral and physiological processes. Genetic variations in these clock genes have been shown to be associated with phenotypic effects in a repertoire of biological processes, such as diurnal preference, sleep, metabolism, mood regulation, addiction, and fertility. Consistently, rodent models carrying mutations in clock genes also demonstrate similar phenotypes. Taken together, these studies suggest that human clock-gene variants contribute to the phenotypic differences observed in various behavioral and physiological processes, although to validate this requires further characterization of the molecular consequences of these polymorphisms. Investigating the diversity of human genotypes and the phenotypic effects of these genetic variations shall advance our understanding of the function of the circadian clock and how we can employ the clock to improve our overall health.

Physical activity and sex modulate obesity risk linked to 3111T/C gene variant of the CLOCK gene in an elderly population: the SUN Project

Genetic factors may interact with physical activity levels to modify obesity risk. Our aim was to explore the influence of rs1801260 single-nucleotide polymorphism (SNP) (3111T/C) of CLOCK gene on obesity risk, and to examine its potential interaction with lifestyle factors in an elderly population within the SUN ("Seguimiento Universidad de Navarra") Project. Subjects (n = 903, aged 69 ± 6 yrs) were recruited from the SUN Project. DNA was obtained from saliva, whereas lifestyle and dietary data were collected by validated self-report questionnaires. Genotype was assessed by reverse transcriptase-polymerase chain reaction (RT-PCR) plus allele discrimination. A significant interaction was observed between the 3111T/C SNP of CLOCK gene and sex for overweight/obesity risk (p for sex × CLOCK interaction <.001). Our results showed that women carrying the C allele of CLOCK gene had a marginally significant lower risk of overweight/obesity compared with noncarrier-TT-subjects (odds ratio [OR]: .61, 95% confidence interval [CI]: .36-1.04; p = .069). Moreover, this association of the C allele with a decreased overweight/obesity risk might be enhanced in those women with a high physical activity level. Women practicing more than 16.8 metabolic equivalent tasks (hours per week) had a significantly lower overweight/obesity risk (OR: .36, 95% CI: .17-.79; p = .011). Furthermore, a significant interaction between the 3111T/C gene variant and physical activity (PA) for overweight/obesity risk was observed but only in women (p for PA × CLOCK interaction <.050). In conclusion, it appears that physical activity levels may act by modifying the association of the 3111T/C SNP (rs1801260) of the CLOCK gene with overweight/obesity risk in elderly women in the SUN Project.

Body weight, metabolism and clock genes

Biological rhythms are present in the lives of almost all organisms ranging from plants to more evolved creatures. These oscillations allow the anticipation of many physiological and behavioral mechanisms thus enabling coordination of rhythms in a timely manner, adaption to environmental changes and more efficient organization of the cellular processes responsible for survival of both the individual and the species. Many components of energy homeostasis exhibit circadian rhythms, which are regulated by central (suprachiasmatic nucleus) and peripheral (located in other tissues) circadian clocks. Adipocyte plays an important role in the regulation of energy homeostasis, the signaling of satiety and cellular differentiation and proliferation. Also, the adipocyte circadian clock is probably involved in the control of many of these functions. Thus, circadian clocks are implicated in the control of energy balance, feeding behavior and consequently in the regulation of body weight. In this regard, alterations in clock genes and rhythms can interfere with the complex mechanism of metabolic and hormonal anticipation, contributing to multifactorial diseases such as obesity and diabetes. The aim of this review was to define circadian clocks by describing their functioning and role in the whole body and in adipocyte metabolism, as well as their influence on body weight control and the development of obesity.

Genome-wide association scan for five major dimensions of personality

Personality traits are summarized by five broad dimensions with pervasive influences on major life outcomes, strong links to psychiatric disorders and clear heritable components. To identify genetic variants associated with each of the five dimensions of personality we performed a genome-wide association (GWA) scan of 3972 individuals from a genetically isolated population within Sardinia, Italy. On the basis of the analyses of 362 129 single-nucleotide polymorphisms we found several strong signals within or near genes previously implicated in psychiatric disorders. They include the association of neuroticism with SNAP25 (rs362584, P=5 x 10(-5)), extraversion with BDNF and two cadherin genes (CDH13 and CDH23; Ps<5 x 10(-5)), openness with CNTNAP2 (rs10251794, P=3 x 10(-5)), agreeableness with CLOCK (rs6832769, P=9 x 10(-6)) and conscientiousness with DYRK1A (rs2835731, P=3 x 10(-5)). Effect sizes were small (less than 1% of variance), and most failed to replicate in the follow-up independent samples (N up to 3903), though the association between agreeableness and CLOCK was supported in two of three replication samples (overall P=2 x 10(-5)). We infer that a large number of loci may influence personality traits and disorders, requiring larger sample sizes for the GWA approach to confidently identify associated genetic variants.

Sleep disturbance as transdiagnostic: consideration of neurobiological mechanisms

Sleep disturbance is increasingly recognized as an important, but understudied, mechanism in the complex and multi-factorial causation of the symptoms and functional disability associated with psychiatric disorders. This review proposes that it is biologically plausible for sleep disturbance to be mechanistically transdiagnostic. More specifically, we propose that sleep disturbance is aetiologically linked to various forms of psychopathology through: its reciprocal relationship with emotion regulation and its shared/interacting neurobiological substrates in (a) genetics--genes known to be important in the generation and regulation of circadian rhythms have been linked to a range of disorders and (b) dopaminergic and serotonergic function--we review evidence for the interplay between these systems and sleep/circadian biology. The clinical implications include potentially powerful and inexpensive interventions including interventions targeting light exposure, dark exposure, the regulation of social rhythms and the reduction of anxiety. We also consider the possibility of developing a 'transdiagnostic' treatment; one treatment that would reduce sleep disturbance across psychiatric disorders.

Chronobiology, genetics and metabolic syndrome

PURPOSE OF REVIEW

Circadian rhythms are such an innate part of our lives that we rarely pause to speculate why they even exist. Recently, some studies have suggested that the disruption of the circadian system may be causal for the manifestations of metabolic syndrome (MetS). This review summarizes the latest evidence of the existing interaction among chronobiology, genetics and MetS.

RECENT FINDINGS

Shift work, sleep deprivation and bright light exposure at night are related to increased adiposity and prevalence of MetS. Animal models have revealed that mice with circadian locomotor output cycles kaput (clock) gene disruption are prone to develop a phenotype resembling MetS. Moreover, studies in humans have shown that clock genes are expressed in adipose tissue, and that both their levels of expression and their genetic variants correlate with different components of the MetS. Current studies are illustrating the particular role of different clock gene variants and their predicted haplotypes in MetS.

SUMMARY

The circadian system has an important impact on metabolic disturbances and vice versa. Although the precise mechanism linking the MetS to chronodisruption is not well known, hypotheses point to the internal desynchronization between different circadian rhythms. The novelty of this area of research is contributing to the development of new and intriguing studies, particularly those focused on the association between different clock genes polymorphisms and MetS traits.

Managing jet lag: Some of the problems and possible new solutions

Jet lag is due to the misalignment of the internal circadian clock(s) with external time cues. For short stopovers (1-2 days) adapting the circadian system is not advised, and at present immediate circadian adaptation is virtually impossible. The use of short-term measures such as judicious naps, caffeine and short acting hypnotics to maintain alertness and sleep is preferred. For intermediate length stays (3-5 days) a phase position with the circadian nadir situated within the sleep period is desirable but difficult to achieve. For longer stays (more than 4-5 days) strategies to hasten adaptation include timed exposure to and avoidance of light. The use of artificial light enriched with short wavelengths may be beneficial. The American Academy of Sleep Medicine recommends the timed use of the chronobiotic melatonin to hasten adaptation. Large individual differences in rate and direction of adaptation make timing treatment according to individual circadian phase difficult. Individual differences in tolerance to the sleep deprivation of jet lag may relate to a length polymorphism in the human clock gene PER3. The maximum efficacy for jet lag avoidance is by pre-flight adaptation, however, this requires time and commitment.

Genetic susceptibility to eating disorders: associated polymorphisms and pharmacogenetic suggestions

Anorexia nervosa (AN), bulimia nervosa (BN) and binge-eating disorder (BED) are characterized by abnormal eating behaviors often resulting in dramatic physical consequences for the patients. The etiology of eating disorders (EDs) is currently unknown; however, a strong genetic contribution is likely to be involved. To date, the majority of genetic studies have focused on candidate genes, and polymorphic variants of genes coding for substances likely to be involved in the etiopathogenesis of EDs have been assessed for association with AN, BN, BED and/or ED-related phenotypic traits. Results have been generally inconsistent and cannot be considered conclusive because of several methodological flaws and differences, such as small sample sizes, ethnic heterogeneity of studied populations, lack of statistical correction for multiple testing, adoption of different diagnostic criteria and population stratification. Although, at present, no convincing evidence for associations of candidate genes with EDs has been provided, the 5-HT2A receptor gene and the BDNF gene seem to be promising candidates for genetic influences on AN, since polymorphic variants of these genes have been found quite consistently, although not specifically, linked to AN restricting subtype in large sample studies. Moreover, pharmacogenetic investigations have suggested a possible role of some gene polymorphisms in predicting the response to treatment with selective serotonin reuptake inhibitors in BN, but results are still preliminary. The heterogeneity of ED phenotypes is believed to represent the most relevant variable responsible for contradictory and not conclusive results. Future studies should focus on more homogeneous subgroups, either relying on specific ED traits or identifying endophenotypes. This will be useful also for prevention and treatment of EDs.