The α(2C)-Del322-325 adrenoceptor polymorphism and the occurrence of left ventricular hypertrophy in hypertensives.

OBJECTIVES: Sympathetic activation has a role in the development of left ventricular hypertrophy (LVH). The presynaptic α(2C)-adrenoceptor inhibits the release of norepinephrine from sympathetic nerve terminals in the heart. A deletion polymorphism in the α(2C)-adrenoceptor (α(2C)Del322-325) generates a hypofunctional α(2C)-adrenoceptor, which may result in chronic adrenergic signalling. This study aimed to investigate whether the α(2C)Del322-325 polymorphism was associated with an increased prevalence of LVH in patients with systemic hypertension. METHODS: Left ventricular mass was measured in 205 patients with systemic hypertension and 60 normal volunteers using a 1.5-T Philips MRI system. Genotyping was performed using a restriction fragment length polymorphism assay. RESULTS: No significant difference was observed between the distribution of the α(2C)Del322-325 genotypes in hypertensive patients with LVH compared with those without LVH. Adjusting for confounding variables the odds ratio (OR) of being ins/del for the α(2C)Del322-325 and having LVH was 0.49 (95% CI 0.14-1.69, p = 0.256). CONCLUSIONS: These observations suggest that there is little evidence for an association between α(2C)Del322-325 polymorphism and an increased prevalence of LVH in patients with systemic hypertension.

Resting sympathetic nerve activity is related to age, sex and arterial pressure but not to α2-adrenergic receptor subtype.

OBJECTIVE: Sympathetic nerve hyperactivity has been associated with hypertension and heart failure and their cardiovascular complications. The α2-adrenergic receptors have been proposed to play a prominent role in the control of sympathetic neural output, and their malfunction to constitute a potential central mechanism for sympathetic hyperactivity of essential hypertension. Reports on the relationship between variant alleles of α2-adrenergic receptor subtypes and sympathetic drive or its effects, however, have not been consistent. Therefore, this study was planned to test the hypothesis that variant alleles of subtypes of α2-adrenergic receptors are associated with raised muscle sympathetic nerve activity (MSNA) in man. METHODS: One hundred and seventy-two individuals, with a wide range of arterial pressure, were prospectively examined. Resting MSNA was quantified from multiunit bursts and from single units, and α2-adrenergic receptor subtypes were genotyped from DNA extracted from leucocytes and quantified by spectrophotometry. RESULTS: No significant relationships between variant alleles of any of the α2A, α2B or α2C subtypes and raised muscle sympathetic activity were found. In contrast, MSNA showed a marked significant curvilinear relationship with age and systolic pressure; sex had a small but statistically significant effect. The α2-adrenergic receptor variants had a similar frequency when hypertensive and normotensive individuals were compared. CONCLUSION: Variant alleles of three α2-adrenergic receptor subtypes were not related to resting muscle sympathetic nerve hyperactivity, indicating that their functional differences shown in vitro are not reflected in sympathetic activity in man. Age had a marked effect likely influencing arterial pressure through sympathetic activity.

Polymorphisms of adrenoceptors are not associated with an increased risk of adverse event in heart failure: a MERIT-HF substudy.

BACKGROUND: Enhanced sympathetic activation has a central role in the development of heart failure (HF). We assessed whether the alpha(2C)-adrenoceptor (Del322-325) polymorphism exclusively or in combination with a beta(1)-adrenoceptor (Arg389) polymorphism, each with known independent effects on sympathetic function, were associated with an increased risk of adverse events in HF. METHODS AND RESULTS: A total of 526 patients enrolled in the Metoprolol CR/XL Randomized Intervention Trial in Congestive Heart Failure study were genotyped for both adrenoceptor polymorphisms. The distribution of alpha(2C) genotypes was similar between the event and nonevent groups. However, a reduced prevalence of the Del322-325 allele was found in individuals with ischemic congestive HF (P=.022). Patients possessing both the alpha(2C) Del322-325 and beta(1) Arg389 alleles had no increased risk of events. Adjusting for confounding variables and the beta(1) Arg389Gly polymorphism, the odds ratio of being ins/del + del/del for the alpha(2C) Del322-325 and having an event was 0.89 with 95% CI 0.49-1.63, P=.715. Similarly, adjusting for confounding variables and the alpha(2C) Del322-325 polymorphism the odds ratio of being Arg/Arg or Arg/Gly for the beta(1) Arg389Gly polymorphism and having an event was 1.13 with 95% CI 0.52-2.17, P=.864. CONCLUSIONS: The alpha(2C) Del322-325 polymorphism exclusively or in combination with the beta(1)Arg389 allele is not associated with an increased risk of adverse events in HF.