PURPOSE: A deletion of 287 bp Alu repeat of angiotensin converting enzyme (ACE) insertion/deletion (I/D) gene is associated with hypertension. Obstructive sleep apnea (OSA) is known to be associated with hypertension; however, frequency of this polymorphism has not been reported in the northern Indian population with OSA. The present study was done to determine the frequency of ACE (I/D) polymorphism in patients with OSA.
METHODS: Genotyping of ACE (I/D) gene polymorphism and estimation of serum angiotensin converting enzyme (SACE) activity were done in 813 subjects who underwent polysomnography. Of these, 395 were apneics and 418 were non-apneics.
RESULTS: The frequencies of II genotype [OR: 1.8 95% CI (1.26 to 2.60), p=0.001] and I allele [OR: 1.4 95% CI (1.13 to 1.69), p=0.001] of ACE gene were found to be significantly increased in patients with OSA as compared to patients without OSA. Frequency of II genotype was significantly decreased [OR: 0.46 95% CI (0.28 to 0.77), p=0.003] in OSA patients with hypertension. Whereas, frequencies of ID [OR=1.80 95%CI (1.08 to 2.99), p=0.024] and DD genotypes [OR=2.15 95% CI (1.30 to 3.57), p=0.003] were significantly increased in this group. The activity of SACE was significantly decreased in apneic group as compared to non-apneic group [OR=0.99 CI (0.98 to 1.00), p=0.04]. Additionally, the activity of SACE was significantly higher in subjects with DD genotype as compared to subjects with II genotype in order of DD>ID>II. Similar trend has been observed even after stratifying the genotypes in accordance with the presence or absence of OSA.
CONCLUSIONS: To the best of our knowledge this is the first Indian study on the association of ACE (I/D) polymorphism in patients with OSA and hypertension. The findings of the present study suggest that II genotype of ACE (I/D) polymorphism confers susceptibility towards development of OSA whereas DD genotype confers susceptibility towards hypertension irrespective of OSA.
CLINICAL IMPLICATIONS: The II genotype and decreased serum ACE activity could be used to predict and devise better precautionary measures and treatment strategies towards OSA.
DISCLOSURE: The following authors have nothing to disclose: Hemant Mishra, Surendra Sharma, Vishnubhatla Sreenivas
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