Renin-Angiotensin-Aldosterone System (RAAS) gene polymorphisms and antihypertensive response to irbesartan in Chinese hypertensives

Interactive Effect of the KCNJ11 Ile337Val Polymorphism and Cigarette Smoking on the Antihypertensive Response to Irbesartan in Chinese Hypertensive Patients

OBJECTIVE

This study was designed to detect the association of the potassium inwardly rectifying channel, subfamily J, member 11 (KCNJ11) gene polymorphism with antihypertensive therapeutic response to irbesartan in a large-scale Chinese hypertensive population.

METHODS

A total of 1,099 patients with essential hypertension were enrolled to receive a daily dose of 150 mg irbesartan for 27 days. Pretreatment baseline blood pressure (BP) and posttreatment BP on the 28th day were measured. Plasma irbesartan concentrations were measured by high-performance liquid chromatography-fluorescence. The KCNJ11 I337V gene polymorphism was determined using high-throughput TaqMan technology.

RESULTS

The HapMap data in the Han Chinese population showed that the I337V was used as a representative for 4 common functional polymorphisms. Our results showed that the association of antihypertensive response to irbesartan and the KCNJ11 genetic variant in the total sample was not significant. However, in nonsmokers, relative to the GG genotype, subjects with the homozygous AA genotype had a significantly higher therapeutic response to irbesartan (adjusted beta ± SE: 4.7±1.9 mm Hg, P = 0.015). In smokers, the subjects with the homozygous AA genotype had a significantly lower therapeutic response to irbesartan (adjusted beta ± SE: -5.6±2.5 mm Hg, P = 0.026). A multivariate linear regression model confirmed that there was a significant interactive effect between the KCNJ11 gene and smoking on irbesartan treatment (interaction P = 0.001).

CONCLUSION

The interactive effect of smoking status and the KCNJ11 genotype may influence the antihypertensive effects of irbesartan, which indicates a consideration for future individualized antihypertensive drug treatment.

Renin-angiotensin system blocking drugs

The two major classes of drugs that target the RAS are the angiotensin-converting enzyme (ACE) inhibitors and the selective AT1 receptor blockers (ARBs). Although both of these drug classes target angiotensin II, the differences in their mechanisms of action have implications for their effects on other pathways and receptors that may have therapeutic implications. Both ACEIs and ARBs are effective antihypertensive agents that have been shown to reduce the risk of cardiovascular and renal events. Direct inhibition of renin -the most proximal aspect of the RAS -became clinically feasible from 2007 with the introduction of aliskiren. This latter drug has been shown to be efficacious for the management of hypertension. Combined therapy of direct renin-inhibitors with ACEIs or ARBs has been tested in some clinical situations as congestive HF and proteinuria with diverse results. This article tries to offer an updated review of current knowledge on the use of RAS blocking drugs in clinical settings.

Non-adherence to antihypertensive medication and impaired cognition: which comes first?

OBJECTIVE

Antihypertensive medications are important in the prevention of serious consequences of hypertension, such as stroke and heart failure. Up to one-third of elderly hypertensive patients, however, do not adhere to their medication. Adherence to medication decreases with increasing age, and with decreasing cognitive ability, thus elderly, cognitively-impaired patients have poorer control of blood pressure. Good control of blood pressure is associated with decreased prevalence of dementia and Alzheimer's disease. This study assessed the evidence that antihypertensive medications have effects on the prevalence or severity of mild cognitive impairment, dementia or Alzheimer's disease.

METHODS

The ISI Web of Knowledge database was searched; including replicates, the nine searches identified 14400 publications since 1952, of which 9.9% had been published in 2009. This review considers the 18 studies meeting the set criteria published in 2009 or later.

KEY FINDINGS

Not all antihypertensive medications are equivalent in their positive cognitive effects, with brain-penetrating angiotensin-converting-enzyme inhibitors and possibly angiotensin receptor antagonists being the most effective.

CONCLUSIONS

Based on evidence of blood-pressure control and cost, UK National Institute for Health and Clinical Excellence guidelines recommend calcium-channel blockers or thiazide-type diuretics for the treatment of hypertension in patients over 55 years. These guidelines take no account of the potential cognitive effects of the antihypertensive therapies, consideration of which might lead to a review. There may be benefit in stressing that adherence to antihypertensive medication not only decreases the risk of cardiovascular disease and death, but may also decrease the risk or severity of mild cognitive impairment, dementia and Alzheimer's disease.

Haplotypes of the adrenergic system predict the blood pressure response to beta-blockers in women with essential hypertension

AIMS

To analyze the association of haplotypes of the adrenergic system with essential hypertension and with the blood pressure response to beta-blockers.

MATERIALS & METHODS

In 1112 never-treated essential hypertension patients and 203 normotensive controls, tightly linked SNPs of beta-adrenergic receptors (ADRB1 - Ser49Gly and Arg389Gly; ADRB2 - Cys19Arg, Gly16Arg and Gln27Glu) and the G-protein beta3-subunit (GNB3 - A3882C, G5249A and C825T) were genotyped. Association of haplotypes with essential hypertension and with the blood pressure response to atenolol 50 mg twice daily in a subgroup of essential hypertension patients (n = 340) was evaluated (Haploview 3.2).

RESULTS

No SNPs or haplotypes were associated with essential hypertension. In females only, GNB3 SNPs and haplotypes were associated with the blood pressure response (p < 0.05).

CONCLUSION

Our study confirmed the sex-specific association of GNB3 with the blood pressure response to atenolol with no substantial advantage of the analysis of haplotypes over SNPs.