Functional polymorphisms of circadian positive feedback regulation genes and clinical outcome of Chinese patients with resected colorectal cancer

Differences in circadian rhythmicity in CLOCK 3111T/C genetic variants in moderate obese women as assessed by thermometry, actimetry and body position

INTRODUCTION

Genetics is behind our circadian machinery. CLOCK (Circadian Locomotor Output Cycles Kaput) 3111T/C single-nucleotide polymorphism (SNP) has been previously related to obesity and weight loss. However, phenotypic association and functionality of CLOCK 3111 locus is still unknown. The aim of this study was to determine, in free-living conditions, if the presence of CLOCK 3111C in overweight women could be related to (a) circadian disorders, and (b) changes in sleep quality, to improve understanding of the previously demonstrated associations with obesity and reduced weight loss of the C carriers.

METHODS

Wrist temperature, actimetry and position (TAP) and TAP variables were measured as markers of circadian functionality during 8 consecutive days. A rest-activity and food diary was also completed, whereas sleep quality was determined by domiciliary polysomnography. We recruited 85 women who were overweight with body mass index (BMI) of 28.59±4.30 kg m(-2) and age 43±12 years. From this sample, we found that 43 women were carrying the minor allele (C) for CLOCK 3111T/C SNP and 42 women were TT carriers (major allele carriers). Both groups of patients were matched for number, age, obesity parameters and energy intake.

RESULTS

Compared with TT subjects, who showed more robust circadian rhythm profiles, patients with the C allele displayed significant circadian abnormalities: lower amplitude and greater fragmentation of the rhythm, a less stable circadian pattern and a significantly weakened circadian function, as assessed by the circadian function index (CFI). C subjects were also less active, started their activities later in the morning and were sleepier during the day, showing a delayed acrophase that characterizes 'evening-type' subjects.

CONCLUSION

C genetic variants in CLOCK 3111T/C display a less robust circadian rhythm than TT and a delayed acrophase that characterizes 'evening-type' subjects. We support the notion that identifying CLOCK genotypes in patients may assist the therapist in characterization of the roots of the metabolic problem.

A functional polymorphism in PER3 gene is associated with prognosis in hepatocellular carcinoma

BACKGROUND

Previous studies have revealed that circadian genes play important roles in cell proliferation, apoptosis, cell cycle control, DNA damage response and treatment response of chemotherapy agents in cancers.

AIMS

We hypothesized that the polymorphisms in circadian genes may be associated with prognosis of hepatocellular carcinoma (HCC) patients treated with transcatheter arterial chemoembolization (TACE).

METHODS

Twelve functional single nucleotide polymorphisms (SNPs) in circadian negative feedback regulation genes (including CRY1, CRY2, PER1, PER2 and PER3) were genotyped using Sequenom iPLEX genotyping method in 337 HCC patients treated with TACE and analysed for associations with overall survival.

RESULTS

Our data showed that one SNP rs2640908 in PER3 gene was significantly associated with overall survival of HCC patients (P = 0.027). Patients carrying at least one variant allele of rs2640908 (WV + VV) had a significantly decreased risk of death (hazard ratio, 0.71; 95% confidence interval, 0.53-0.90), when compared with those carrying homozygous wild-type alleles (WW). Kaplan-Meier analyses showed a significantly longer median survival time in patients with WV + VV genotypes of SNP rs2640908 than those with WW genotype (11.6 months vs. 8.1 months; log rank P = 0.030). In addition, we also observed a significant difference on the genotype distribution of SNP rs2640908 in patients with and without portal vein thrombus (P = 0.041).

CONCLUSIONS

Our study provides the first evidence that a single functional polymorphism of PER3 gene is significantly associated with overall survival in HCC patients treated with TACE.

[Physiological and pathophysiological role of the circadian clock system]

It has been well known for ages that in living organisms the rhythmicity of biological processes is linked to the ~ 24-hour light-dark cycle. However, the exact function of the circadian clock system has been explored only in the past decades. It came to light that the photosensitive primary "master clock" is situated in the suprachiasmatic photosensitive nuclei of the special hypothalamic region, and that it is working according to ~24-hour changes of light and darkness. The master clock sends its messages to the peripheral "slave clocks". In many organs, like pancreatic β-cells, the slave clocks have autonomic functions as well. Two essential components of the clock system are proteins encoded by the CLOCK and BMAL1 genes. CLOCK genes are in interaction with endonuclear receptors such as peroxisoma-proliferator activated receptors and Rev-erb-α, as well as with the hypothalamic-pituitary-adrenal axis, regulating the adaptation to stressors, energy supply, metabolic processes and cardiovascular system. Melatonin, the product of corpus pineale has a significant role in the functions of the clock system. The detailed discovery of the clock system has changed our previous knowledge about the development of many diseases. The most explored fields are hypertension, cardiovascular diseases, metabolic processes, mental disorders, cancers, sleep apnoe and joint disorders. CLOCK genes influence ageing as well. The recognition of the periodicity of biological processes makes the optimal dosing of certain drugs feasible. The more detailed discovery of the interaction of the clock system might further improve treatment and prevention of many disorders.