Cristian A. Carvajal

Primary Aldosteronism and Hypertensive Disease

Abstract—Recent studies in hypertensive populations that have used the serum aldosterone (SA) to plasma renin activity (PRA) ratio as a screening test have demonstrated a high prevalence of primary aldosteronism (PA). This frequency is higher than that previously described when hypokalemia was used as a screening tool. However, other factors, such as the characteristics of hypertensive disease, could also influence the prevalence of PA. We studied 609 essential hypertensive patients, classified according to the Joint National Committee VI (JNC VI), in 3 different stages depending on the severity of their hypertensive disease. We measured SA and PRA and calculated the SA-PRA ratio for all patients. An SA-PRA ratio >25 was detected in 63 of 609 patients, and the fludrocortisone test confirmed the PA diagnoses in 37 of 609 (6.1%) cases. PA prevalence according to hypertension stage was as follows: stage 1, 6 of 301 cases (1.99%); stage 2, 15 of 187 cases (8.02%); and stage 3, 16 of 121 cases (13.2%). PA patients were slightly younger than the other hypertensive patients (48.4±10.5 vs 53.6±10.2 years; P <0.05). Serum potassium levels were normal in 36 of 37 PA patients; only 1 patient had minor hypokalemia. Computed tomography scans showed bilateral adrenal enlargement in 7 and an adrenal nodule in 2 cases. In summary, we found a high frequency of PA in essential hypertensives classified in stages 2 and 3 according to the JNC VI. The low frequency of computed tomography scan abnormalities and hypokalemia suggests that the diagnosis for most PA patients corresponds to attenuated forms of the disease.

Endothelial cell oxidative stress and signal transduction

Endothelial dysfunction (ED) is an early event in atherosclerotic disease, preceding clinical manifestations and complications. Increased reactive oxygen species (ROS) have been implicated as important mechanisms that contribute to ED, and ROSs may function as intracellular messengers that modulate signaling pathways. Several intracellular signal events stimulated by ROS have been defined, including the identification of two members of the mitogen activated protein kinase family (ERK1/2 and big MAP kinase, BMK1), tyrosine kinases (Src and Syk) and different isoenzymes of PKC as redox-sensitive kinases. ROS regulation of signal transduction components include the modification in the activity of transcriptional factors such as NFkB and others that result in changes in gene expression and modifications in cellular responses. In order to understand the intracellular mechanisms induced by ROS in endothelial cells (EC), we are studying the response of human umbilical cord vein endothelial cells to increased ROS generation by different pro-atherogenic stimuli. Our results show that Homocysteine (Hcy) and oxidized LDL (oxLDL) enhance the activity and expression of oxidative stress markers, such as NFkB and heme oxygenase 1. These results suggest that these pro-atherogenic stimuli increase oxidative stress in EC, and thus explain the loss of endothelial function associated with the atherogenic process.

High sodium intake is associated with increased glucocorticoid production, insulin resistance and metabolic syndrome

High sodium (HS) diet is associated with hypertension (HT) and insulin resistance (IR). We evaluated whether HS diet was associated with a dysregulation of cortisol production and metabolic syndrome (MetS).

A possible association between primary aldosteronism and a lower β-cell function

Objective Primary aldosteronism (PA) is the most common secondary cause of hypertension and recently has been implicated as a cause of impaired glucose tolerance. We investigated the glucose insulin sensitivity and insulin secretion in patients with idiopathic primary aldosteronism. Design Thirty PA patients and 60 essential hypertensive (EH) patients as controls were included, matched (1: 2) by their body mass index (BMI) (29.9 ± 4.3 versus 29.8 ± 5.8 m/kg2), age (53.7 ± 9.4 versus 59.9 ± 8.6 years old) and gender (male/female: 8/22 versus 17/43). In all patients, we measured insulin, total cholesterol, triglycerides, C-peptide and fasting glucose levels. Homeostasis model assessment for insulin resistance (HOMA-IR) and HOMA of pancreatic β-cell function (HOMA-βF) indexes were calculated. We also evaluated the response to spironolactone in 19 PA patients. Results PA patients had higher levels of glucose (5.2 ± 0.7 versus 4.9 ± 0.7 mmol/l; P = 0.017). Insulin levels (10.7 ± 6.5 versus 11.5 ± 5.8 uUI/ml, P = 0.525) and HOMA-IR (2.51 ± 1.59 versus 2.45 ± 1.29 uUI/ml × mmol/l, P = 0.854) were similar in both groups. HOMA-βF index (138.9 ± 89.8 versus 179.8 ± 100.2%, P = 0.049) and C-peptide (0.83 ± 0.63 versus 1.56 ± 0.84 ng/dl, P = 0.0001) were lower in PA patients. Potassium was normal in both groups. Negative correlations between serum aldosterone/plasma renin activity (SA/PRA) ratio and HOMA-βF, and between C-peptide and SA levels were found in all patients. After the spironolactone treatment, we found an increase of C-peptide and insulin levels without changes in HOMA-IR or HOMA-βF. Conclusion Our results showed differences in glucose metabolism between PA patients and those with hypertension suggesting that these findings could probably be determined by a lower β-cell function influenced by aldosterone. These findings highlight the importance of aldosterone in glucose metabolism.

Increased levels of oxidative stress, subclinical inflammation, and myocardial fibrosis markers in primary aldosteronism patients.

Background Patients with primary aldosteronism experience greater left ventricular hypertrophy and a higher frequency of cardiovascular events than do essential hypertensive patients with comparable blood pressure levels. Aldosterone has been correlated with increased oxidative stress, endothelial inflammation, and fibrosis, particularly in patients with heart disease. Aim To evaluate oxidative stress, subclinical endothelial inflammation, and myocardial fibrosis markers in patients with primary aldosteronism and essential hypertension. Design and individuals We studied 30 primary aldosteronism patients and 70 control essential hypertensive patients, matched by age, sex and median blood pressure. For all patients, we measured the serum levels of aldosterone, plasma renin activity, malondialdehyde (MDA), xanthine oxidase, metalloproteinase-9, ultrasensitive C-reactive protein and amino terminal propeptides of type I (PINP), and type III procollagen. We also evaluated the effect of PA treatment in 19 PA individuals. Results PA patients showed elevated levels of MDA (1.70 ± 0.53 versus 0.94 ± 0.65 μmol/l, P <0.001) and PINP (81.7 ± 50.6 versus 49.7 ± 27 mg/l, P = 0.002) compared with essential hypertensive controls. We found a positive correlation between MDA, PINP, and the serum aldosterone/plasma renin activity ratio in primary aldosteronism patients. Clinically, treating primary aldosteronism patients decreased MDA and PINP levels. Conclusion We detected higher levels of MDA and PINP in primary aldosteronism patients, suggesting increased oxidative stress and myocardial fibrosis in these individuals. Treating primary aldosteronism patients reduced MDA and PINP levels, which may reflect the direct effect of aldosterone greater than endothelial oxidative stress and myocardial fibrosis, possibly mediated by a mineralocorticoid receptor.

Epigenetics and arterial hypertension: the challenge of emerging evidence.

Epigenetic phenomena include DNA methylation, post-translational histone modifications, and noncoding RNAs, as major marks. Although similar to genetic features of DNA for their heritability, epigenetic mechanisms differ for their potential reversibility by environmental and nutritional factors, which make them potentially crucial for their role in complex and multifactorial diseases. The function of these mechanisms is indeed gaining interest in relation to arterial hypertension (AH) with emerging evidence from cell culture and animal models as well as human studies showing that epigenetic modifications have major functions within pathways related to AH. Among epigenetic marks, the role of DNA methylation is mostly highlighted given the primary role of this epigenetic feature in mammalian cells. A lower global methylation was observed in DNA of peripheral blood mononuclear cells of hypertensive patients. Moreover, DNA hydroxymethylation appears modifiable by salt intake in a Dahl salt-sensitive rat model. The specific function of DNA methylation in regulating the expression of AH-related genes at promoter site was described for hydroxysteroid (11-beta) dehydrogenase 2 (HSD11B2), somatic angiotensin converting enzyme (sACE), Na+/K+/2Cl- cotransporter 1 (NKCC1), angiotensinogen (AGT), α-adducin (ADD1), and for other crucial genes in endocrine hypertension. Post-translational histone methylation at different histone 3 lysine residues was also observed to control the expression of genes related to AH as lysine-specific demethylase-1(LSD1), HSD11B2, and epithelial sodium channel subunit α (SCNN1A). Noncoding RNAs including several microRNAs influence genes involved in steroidogenesis and the renin-angiotensin-aldosterone pathway. In the present review, the current knowledge on the relationship between the main epigenetic marks and AH will be presented, considering the challenge of epigenetic patterns being modifiable by environmental factors that may lead toward novel implications in AH preventive and therapeutic strategies.

Biochemical and genetic characterization of 11 beta-hydroxysteroid dehydrogenase type 2 in low-renin essential hypertensives.

Background The 11β-hydroxysteroid dehydrogenase type 2 (11βHSD2) catalyzes the conversion of cortisol (F) to cortisone (E), avoiding the interaction of cortisol with the mineralocorticoid receptor. If it fails, cortisol will stimulate sodium and water reabsorption, increasing the intravascular volume that suppresses renin and secondarily increase the blood pressure. Objective To look for the possible contribution of a decreased ability of 11βHSD2 to convert cortisol to its inactive metabolite cortisone in the pathogenesis of low renin hypertension (LREH). Patients and methods We studied 64 LREH patients (plasma renin activity, PRA < 1 ng/ml per h), eighty normo-renin essential hypertensives (NREH) (PRA: 1–2.5 ng/ml per h) and 74 normotensives. Serum aldosterone (SA), F, E and serum F/E ratio was determined in all patients. A serum F/E ratio was considered high when it was higher than X + 2SD from the normotensive value. Cytosine-adenine (CA)-repeat microsatellite region in intron 1 of HSD11B2 gene was genotyped in all patients and normotensives volunteers. In 13 LREH with high F/E ratio we performed HSD11B2 gene sequencing. Results LREH had serum F/E ratio higher than NREH and normotensive controls (3.6 (2.9–4.3) versus 2.9 (2.2–4.3) versus 3.0 (2.4–3.7) (P = 0.004), respectively). We observed an inverse relation between F/E ratio and SA and PRA. In NREH and normotensives we did not find correlation between these variables. In the LREH subset the longer 155 bp CA-allele showed the highest serum F/E ratio. No mutations in coding region or short introns were found in LREH patients. Conclusion In this study we show that low-renin essential hypertensives had increased serum cortisol/cortisone ratios as compared with normotensive subjects. This suggest that some essential hypertensives, with suppressed renin activity, may have an impairment in the cortisol inactivation catalyzed by the enzyme 11βHSD2, whose low activity in LREH patients could be associated with the length of CA-repeat microsatellite in intron 1 of the HSD11B2 gene.

Overexpression of 11β-hydroxysteroid dehydrogenase type 1 in visceral adipose tissue and portal hypercortisolism in non-alcoholic fatty liver disease.

The enzyme 11β‐hydroxysteroid‐dehydrogenase type 1 (11β‐HSD1) catalyses the reactivation of intracellular cortisol. We explored the potential role of 11β‐HSD1 overexpression in visceral adipose tissue (VAT) in non‐alcoholic fatty liver disease (NAFLD) assessing sequential changes of enzyme expression, in hepatic and adipose tissue, and the occurrence of portal hypercortisolism in obese mice. 11β‐HSD1 expression was also assessed in tissues from obese patients undergoing bariatric surgery.

Birth weight is inversely associated with blood pressure and serum aldosterone and cortisol levels in children

Context  Low birth weight has been independently associated with adult hypertension, and renin‐angiotensin system (RAS) plays a role in this connection.

Overexpression of hepatic 5α-reductase and 11β-hydroxysteroid dehydrogenase type 1 in visceral adipose tissue is associated with hyperinsulinemia in morbidly obese patients

11-β-Hydroxysteroid dehydrogenase type 1 (11β-HSD1) converts cortisone to cortisol, mainly in the liver and visceral adipose tissue (VAT), and has been implicated in several metabolic disorders. The absence of systemic hypercortisolism in central obesity could be due to increased inactivation of cortisol to its tetrahydrometabolites by the hepatic enzymes 5α- and 5β-reductases. Our aim was to assess the expression of the reductases in the liver and of 11β-HSD1 in the liver and VAT in morbidly obese patients and to analyze their association with clinical, anthropometric, and biochemical parameters. Hepatic and VAT samples were obtained during bariatric surgery. 5α- and 5β-reductases, 11β-HSD1, and 18S expression was measured using real-time polymerase chain reaction. Anthropometric and biochemical variables were analyzed. Forty-one patients were recruited (age, 41.8 ± 10.6 years; body mass index, 42.1 ± 6.6 kg/m(2); 71% women). The expression of hepatic 5α- and 5β-reductases was positively correlated (r = +0.53, P = .004), and their expression levels were correlated with hepatic 11β-HSD1 expression (r = +0.61, P < .001 for 5α-reductase and r = +0.50, P < .001 for 5β-reductase). Hepatic 5α-reductase was associated with insulin (r = +0.34, P = .015). Visceral adipose tissue 11β-HSD1 expression was associated with glucose (r = +0.37, P = .025) and insulin (r = +0.54, P = .002). Our results showed that 5α-reductase and VAT 11β-HSD1 expressions were associated with insulinemia. These findings suggest that overexpression of 5α-reductase, through a higher inactivation of cortisol in the liver, could have a protective role in preserving hepatic sensitivity to insulin. The overexpression of liver reductases in obesity could be an adaptive response to an increase in cortisol production by the liver and visceral 11β-HSD1 to avoid systemic hypercortisolism.