ACTH and Polymorphisms at Steroidogenic Loci as Determinants of Aldosterone Secretion and Blood Pressure

11β-Hydroxylase (CYP11B1) gene variants and new-onset depression in later life

BACKGROUND

Cumulative exposure to high glucocorticoid levels is detrimental for the brain and may have particular implications in later life. A feature of late-life depression is increased cortisol secretion. Variants in the CYP11B1 gene, which codes for the enzyme responsible for cortisol synthesis, could influence risk of late-life depression, but this hypothesis has not been examined. We investigated the associations between variants in the CYP11B1 gene and late-life depression, taking into account history of depression and potential sex-specific effects.

METHODS

We assessed depression in 1007 community-dwellers aged 65 years or older (60% women) at baseline and over a 14-year follow-up. A clinical level of depression was defined as a score of ≥ 16 on the Centre for Epidemiology Studies Depression scale or a diagnosis of current major depression based on the Mini-International Neuropsychiatric Interview and according to the criteria of the Diagnostic and Statistical Manual of Mental Disorders, 4th edition (DSM-IV). We examined incident and recurrent depression in participants without or with a history of major depression, respectively. We genotyped 5 single-nucleotide polymorphisms (SNPs) spanning CYP11B1. We used multivariable analyses to adjust for age, body mass index, cardiovascular ischemic pathologies, hypertension, cognitive impairment and anxiety.

RESULTS

In women, rs6471580 and rs7016924 were associated with a 50% lower rate of incident (new-onset) late-life depression, and rs11783855 was associated with a 2.4-fold higher rate of late-life depression. These associations remained after correction for multiple testing, but we found no associations for recurrent depression in women or men.

LIMITATIONS

This study focused on the major gene involved in corticosteroid biosynthesis, but other genes may also be implicated in this pathway.

CONCLUSION

Variants of the CYP11B1 gene appear to be susceptibility factors for late-life depression in a sex-specific manner.

Regulation of Aldosterone Secretion

Secretion of the major mineralocorticoid aldosterone from the adrenal cortex is a tightly-regulated process enabling this hormone to regulate sodium homeostasis and thereby contribute to blood pressure control. The circulating level of aldosterone is the result of various regulatory mechanisms, the most significant being those controlled by the renin-angiotensin system and plasma potassium levels. The importance of maintaining tight control over aldosterone secretion is demonstrated by cases of dysregulation, which can result in severe hypertension and significantly increased cardiovascular risk. In this article we summarize current knowledge of the major regulatory mechanisms, focusing particularly on the systems operating within the adrenocortical zona glomerulosa cells; we also describe some of the other factors that influence aldosterone production to a lesser but still significant extent. Finally, we discuss the influence of common genetic polymorphisms on aldosterone secretion in large sections of the population and also the emerging role of microRNA as significant regulators of this system.

Somatic and inherited mutations in primary aldosteronism

Primary aldosteronism (PA), the most common form of secondary hypertension, is caused in the majority of cases by unilateral aldosterone-producing adenoma (APA) or bilateral adrenal hyperplasia. Over the past few years, somatic mutations in KCNJ5, CACNA1D, ATP1A1 and ATP2B3 have been proven to be associated with APA development, representing more than 50% of sporadic APA. The identification of these mutations has allowed the development of a model for APA involving modification on the intracellular ionic equilibrium and regulation of cell membrane potential, leading to autonomous aldosterone overproduction. Furthermore, somatic CTNNB1 mutations have also been identified in APA, but the link between these mutations and APA development remains unknown. The sequence of events responsible for APA formation is not completely understood, in particular, whether a single hit or a double hit is responsible for both aldosterone overproduction and cell proliferation. Germline mutations identified in patients with early-onset PA have expanded the classification of familial forms (FH) of PA. The description of germline KCNJ5 and CACNA1H mutations has identified FH-III and FH-IV based on genetic findings; germline CACNA1D mutations have been identified in patients with very early-onset PA and severe neurological abnormalities. This review summarizes current knowledge on the genetic basis of PA, the association of driver gene mutations and clinical findings and in the contribution to patient care, plus the current understanding on the mechanisms of APA development.