A significant association was found between the CLOCK gene variants and in a sample of 405 patients from North India.
Two specific variants in the CLOCK gene (rs1801260 and rs34789226) are statistically significantly associated with essential hypertension.
The rs1801260 variant demonstrated significant associations under multiple genetic models (codominant, dominant, and recessive).
The rs34789226 variant showed significant negative associations under codominant and dominant models.
The distribution of certain genotypes and haplotypes differed significantly between hypertensive cases and healthy controls.
In hypertensive males, specific genotypes and haplotypes were found to be more common than in females.
Simplified
BACKGROUND: Hypertension (HTN) is a medical condition characterized by persistent systolic and diastolic blood pressures of ≥ 140 mmHg and ≥ 90 mmHg, respectively. With more than 1200 million adult patients aged 30-79 years worldwide according to the latest WHO data, HTN is a major health risk factor; more importantly, 46% of patients are unaware of this condition. (EH), also known as primary hypertension, is the predominant subtype and has a complex etiology that involves both genetic and non-genetic factors. Majority of living organisms are influenced by the light and dark cycle of a day and respond to these changes through an intricate clock referred to as the "biological clock" or "circadian rhythm". The connection between circadian rhythm and blood pressure is well established, with many studies supporting the role of circadian rhythm gene mutation(s)/polymorphism(s) in EH. To date, no such data are available from any Indian population.
METHODS: This case‒control study was conducted on 405 EH patients and 505 healthy controls belonging to the Jammu region of North India after an informed consent was obtained from the participants. A total of three single nucleotide variants, two in the CLOCK gene (rs1801260 and rs34789226) and one in the BMAL1/ARNTL gene (rs6486121), were selected for genotyping. Genotyping was performed via the RFLP technique, and the applicable statistical analyses were performed via the SPSS and SNPStats programs.
RESULTS: Logistic regression analysis revealed a statistically significant association of both CLOCK gene variants rs1801260 (T > C 3'UTR) and rs34789226 (C > T Exon 9) and a nonsignificant association of the BMAL1/ARNTL intronic variant rs6486121 (C > T) with EH. The 3'UTR variant showed a statistically significant association under the codominant (p < 0.0001), dominant (p < 0.0001), and recessive (p = 0.0004) models. In contrast, the exon 9 variant showed a statistically significant negative association under the codominant (p = 0.003) and dominant (p = 0.015) models only. The rs6486121/rs1801260 and rs1801260/rs34789226/rs6486121 haplotypes showed significant differences in their distribution between cases and controls (p < 0.0001). Certain genotypes and haplotypes were found more common in hypertensive males than females.
CONCLUSION: This is a first report linking circadian rhythm gene polymorphisms with EH in any Indian population. The statistically significant association of the CLOCK gene 3'UTR and exon 9 polymorphisms with EH, highlight the potential role of this gene and probably other genes of the circadian pathway in the etiology of EH in the study population. Additionally, our study also revealed that certain genotypes are making males more susceptible to EH.
Key numbers
2.69
Increase in Risk for CC Genotype
Odds Ratio for rs1801260 TT vs. CC under codominant model
0.69
Decrease in Risk for TC Genotype
Odds Ratio for rs34789226 TT vs. TC under dominant model
1.60
Significant Association in Males
Odds Ratio for haplotypes C/C and C/T in males
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Declarations. Ethics approval and consent to participate: This study was approved by the Central University Jammu human ethics committee (notification no. IHEC/CUJ/CMB-23/01). A written and informed consent was taken from all the participants. Consent for publication: Not applicable. Competing interests: The authors declare no competing interests.
