Calcium paradox of aldosteronism and the role of the parathyroid glands

The prevalence of primary and secondary hyperparathyroidism and its cardiometabolic implications in primary aldosteronism

BACKGROUND

The aim of this study was to analyze the prevalence of primary and secondary hyperparathyroidism in patients with primary aldosteronism (PA), and its implication on cardiovascular and metabolic outcomes.

METHODS

A retrospective study of patients with PA (exposed cohort, N.=44) and all hypertensive (EH) patients with adrenal lesions without PA nor other adrenal hypersecretion (non-exposed cohort, N.=41) on follow-up at our center between 2016 and 2020.

RESULTS

The mean age of patients with PA and EH was 55.1±14.13 and 66.3±10.93 (P<0.001), and 50% of PA and 39.0% of EH were women (P=0.309). At diagnosis, the prevalence of primary hyperparathyroidism in PA was of 18.2%, and all were normocalcemic hyperparathyroidism cases. Globally, no differences were found in the prevalence of primary hyperparathyroidism compared to EH (18.2% vs. 29.3%, P=0.229), but hypercalcemic primary hyperparathyroidism was significantly more prevalent in EH patients than in PA (22.0% vs. 0%, P=0.001). There were 47.7% (N.=21) cases of secondary hyperparathyroidism in patients with PA (4 due to chronic kidney disease (CKD) and vitamin D deficiency, and 17 due to vitamin D deficiency alone). The cardiometabolic profile of patients with PA and hyperparathyroidism (N.=29) was similar to of those patients without hyperparathyroidism (N.=15) at diagnosis and after a median follow-up of 3.6 years (interquartile range 1.1-5.9).

CONCLUSIONS

Although primary and secondary hyperparathyroidism are common in patients with PA, their prevalence was similar than the observed in EH patients. Primary hyperparathyroidism is usually mild in PA, appearing as normocalcemic forms. No negative implications of the hyperparathyroidism in the cardiometabolic profile of PA were observed.

Blood Parameter Profiles and Their Clinical Implications in Hypertensive Patients: A Retrospective Chart Review

Introduction Hypertension (HTN) is a chronic condition that serves as a major risk factor for cardiovascular diseases, leading to increased mortality and morbidity. It is a frequent modifiable illness affecting global health, resulting in catastrophic fatalities and morbidity. Aim This study aims to investigate blood parameter profiles and their clinical implications in hypertensive patients at the Prince Faisal bin Khalid Cardiac Center in Abha, Saudi Arabia. Methods Utilizing retrospective data from 121 patients at the Prince Faisal bin Khalid Cardiac Center in Abha, Saudi Arabia. The hematological parameter examined were hemoglobin (HB), platelets, hematocrit (HCT), calcium, phosphorus, sodium, potassium, urea, creatinine, and uric acid. The SPSS version 28 software was used for data analysis. Results Significant correlations between various hematological parameters were found in the results, pointing to potential connections between kidney function, the production of blood cells, and electrolyte balance in hypertensive patients. The results align with earlier studies carried out in the area and offer insightful information for clinicians and researchers interested in managing HTN and its complications. Conclusion The study emphasized the significance of considering hypertensive patients' age, gender, and lifestyle when interpreting their blood parameter profiles. The findings imply that a thorough comprehension of these blood parameter values and their potential effects on HTN is necessary for effectively managing HTN in this population. This study on the blood parameter profiles in hypertensive patients in Saudi Arabia provides the relationships between various hematological parameter and their clinical implications. These findings should be considered when creating targeted interventions and strategies to address the specific requirements and difficulties of managing HTN and its associated complications in this population. More research is required to comprehend the underlying reasons for the observed variations in hematological parameter profiles and their effects on the management of HTN.

Native thiol decreases in patients with asymptomatic primary hyperparathyroidism, especially in the presence of surgery indication

BACKGROUND

Oxidative stress increases in many systemic and endocrine diseases. The effect of increased parathyroid hormone levels (PTH) and the effects of this hormone on oxidative stress in patients with primary hyperparathyroidism (pHPT) is unknown. We aimed to investigate the change of Thiol-disulfide (SH-SS), one of the oxidative stress parameters, in patients diagnosed with pHPT and the usability of this parameter in patients with pHPT.

METHODS

Forty-six patients who recently diagnosed with asymptomatic pHPT and 40 healthy controls were included in this prospective study. In addition to routine examinations for pHPT, serum SH-SS measurements were recorded. The pHPT patients included in the study were divided into two groups as patients with and without surgical treatment indication.

RESULTS

It was observed that the pHPT group had lower total SH and native SH values and higher SS values compared to the control group (P<0.05 for each). Native SH values were found to be lower in pHPT patients who were indicated for surgical treatment compared to those who did not (P<0.05). An independent relationship was found between Native SH and serum calcium, urine calcium and T scores in DEXA level in asymptomatic pHPT patients with surgical treatment indication (P<0.05).

CONCLUSIONS

In our study, native SH level decreases in patients with pHPT, especially in patients with surgical treatment indication for pHPT. The decrease in SH levels, which is a natural antioxidant that protects the body against oxidative stress, and the increase in SS levels in pHPT patients may be another metabolic effect of this disease. Native SH may be helpful in determining the indication for surgical treatment in asymptomatic pHPT patients.

Higher risk of chronic kidney disease and progressive kidney function impairment in primary aldosteronism than in essential hypertension. Case-control study

PURPOSE

To study the differences in the prevalence, risk, and grade of control of different cardiometabolic comorbidities in patients with primary aldosteronism (PA) and essential hypertension (EH) matched by age, sex, and blood pressure levels at diagnosis.

METHODS

Case-control study of a secondary base (PA patients in follow-up in a tertiary hospital between 2018 and 2020). Controls were patients with non-functioning adrenal incidentalomas and EH, matched by age, sex, and baseline diastolic blood pressure (DBP) and systolic blood pressure (SBP).

RESULTS

Fifty patients with PA and 50 controls were enrolled in the study. At diagnosis, PA patients had a higher prevalence of chronic kidney disease (CKD) than controls (18.4% vs. 2.1%, P = 0.008). No differences were detected in the prevalence of other cardiometabolic comorbidities nor in their degree of control (P > 0.05). All patients received antihypertensive medical treatment and 10 PA patients underwent unilateral laparoscopic adrenalectomy. After a median follow-up of 31.9 [IQR = 1.0-254.8] months, PA patients presented a greater degree of declination of kidney function than controls (average decrease in glomerular filtration rate (MDRD-4) -17.6 ± 3.1 vs. -2.8 ± 1.8 ml/min/1.73 m², P < 0.001). There were no differences in the grade of SBP (P = 0.840) and DBP control (P = 0.191), nor in the risk of developing other comorbidities or in their degree of control.

CONCLUSIONS

PA patients have a higher prevalence of CKD at the time of diagnosis when compared to EH matched by age, sex, and blood pressure levels. Furthermore, the risk of kidney function impairment throughout the follow-up is significantly greater in PA patients and is independent of the degree of blood pressure control.

Mechanisms coupling sodium and magnesium reabsorption in the distal convoluted tubule of the kidney

Hypomagnesaemia is a common feature of renal Na+ wasting disorders such as Gitelman and EAST/SeSAME syndrome. These genetic defects specifically affect Na+ reabsorption in the distal convoluted tubule, where Mg2+ reabsorption is tightly regulated. Apical uptake via TRPM6 Mg2+ channels and basolateral Mg2+ extrusion via a putative Na+ -Mg2+ exchanger determines Mg2+ reabsorption in the distal convoluted tubule. However, the mechanisms that explain the high incidence of hypomagnesaemia in patients with Na+ wasting disorders of the distal convoluted tubule are largely unknown. In this review, we describe three potential mechanisms by which Mg2+ reabsorption in the distal convoluted tubule is linked to Na+ reabsorption. First, decreased activity of the thiazide-sensitive Na+ /Cl- cotransporter (NCC) results in shortening of the segment, reducing the Mg2+ reabsorption capacity. Second, the activity of TRPM6 and NCC are determined by common regulatory pathways. Secondary effects of NCC dysregulation such as hormonal imbalance, therefore, might disturb TRPM6 expression. Third, the basolateral membrane potential, maintained by the K+ permeability and Na+ -K+ -ATPase activity, provides the driving force for Na+ and Mg2+ extrusion. Depolarisation of the basolateral membrane potential in Na+ wasting disorders of the distal convoluted tubule may therefore lead to reduced activity of the putative Na+ -Mg2+ exchanger SLC41A1. Elucidating the interconnections between Mg2+ and Na+ transport in the distal convoluted tubule is hampered by the currently available models. Our analysis indicates that the coupling of Na+ and Mg2+ reabsorption may be multifactorial and that advanced experimental models are required to study the molecular mechanisms.

PTH Modulation by Aldosterone and Angiotensin II is Blunted in Hyperaldosteronism and Rescued by Adrenalectomy

CONTEXT

Accumulating evidence suggests a link between adrenocortical zona glomerulosa and parathyroid gland through mechanisms that remain unexplored.

OBJECTIVES

To test the hypothesis that in vivo angiotensin II blockade affects PTH secretion in patients with hypertension and that aldosterone and angiotensim II directly stimulate PTH secretion ex vivo.

DESIGN AND SETTING

We investigated the changes of serum PTH levels induced by oral captopril (50 mg) administration in patients with primary essential hypertension (EH) and with primary aldosteronism (PA) caused by bilateral adrenal hyperplasia (BAH) or aldosterone-producing adenoma (APA), the latter before and after adrenalectomy. We also exposed primary cultures of human parathyroid cells from patients with primary hyperparathyroidism to angiotensin II (10-7 M) and/or aldosterone (10-7 M).

RESULTS

Captopril lowered PTH levels (in nanograms per liter) both in patients with EH (n = 63; 25.9 ± 8.3 baseline vs 24.4 ± 8.0 postcaptopril, P < 0.0001) and in patients with APA after adrenalectomy (n = 27; 26.3 ± 11.6 vs 24.0 ± 9.7 P = 0.021). However, it was ineffective in patients with full-blown PA caused by APA and BAH. In primary culture of human parathyroid cells, both aldosterone (P < 0.001) and angiotensin II (P = 0.002) markedly increased PTH secretion from baseline, by acting through mineralocorticoid receptor and angiotensin type 1 receptor, as these effects were abolished by canrenone and irbesartan, respectively.

CONCLUSION

These results collectively suggest an implication of the renin-angiotensin-aldosterone system in PTH regulation in humans, at least in PTH-secreting cells obtained from parathyroid tumors. Moreover, they further support the concept that mild hyperparathyroidism is a feature of human PA that is correctable with adrenalectomy.

Dynamic thiol/disulfide homeostasis and oxidant status in patients with hypoparathyroidism

Background

In this study, we aimed at determining the dynamic thiol/disulfide homeostasis and oxidant balance, and investigating the relation of these parameters to the severity of the disease and the serum calcium levels.

Methods

55 patients with iatrogenic hypoparathyroidism follow-ups and 40 healthy volunteers were included in the study. The blood dynamic thiol/sulfide balance, Total Antioxidant Status (TAS), Total Oxidant Status (TOS), Paraoxonase Enzyme Activity (PON) levels were measured in serum samples.

Results

In our study, it was found that the disulfide, disulfide/native thiol, disulfide/total thiol levels were higher in the hypoparathyroidism group. A negative correlation was found between 25-hydroxy vitamin D (25-OH vitamin D) and disulfide, disulfide/native thiol and disulfide/total thiol, and a positive correlation was found between native thiol and total thiol ratio; and the corrected calcium levels and PON levels were negatively correlated.

Conclusions

Consequently, a change in favour of disulfide was found in the dynamic thiol-disulfide homeostasis in the hypoparathyroidism group in our study.

Parathyroid Hormone Causes Endothelial Dysfunction by Inducing Mitochondrial ROS and Specific Oxidative Signal Transduction Modifications

Vitamin D deficiency contributes to cardiovascular risk (CVR), with hyperparathyroidism advocated as a putative mechanism. Indeed, mounting evidence supports the hypothesis that parathyroid hormone (PTH) impairs endothelial function, even though mechanisms are not fully elucidated. The present study was designed to verify in vitro the ability of sustained exposure to PTH to cause endothelial dysfunction, exploring the underlying mechanisms. In bovine aortic endothelial cells (BAECs), we evaluated the effects of PTH exposure (0.1 nM–24 hours) on both endothelial response to vasodilators, such as bradykinin (Bk (30 nM)) and acetylcholine (Ach (1 μM)), and angiogenic competence. Pretreatment with PTH impaired endothelial response to Bk but not to Ach, in terms of cytosolic calcium fluxes and NO production. In order to explore the underlying mechanisms, we assessed the production of total and mitochondrial ROS (tROS and mROS, respectively) in response to PTH (at 1 and 3 hours). PTH increased ROS generation, to an extent high enough to determine oxidation of Bk receptor B2. Conversely, the oxidation levels of M1 and M3 Ach receptors were not affected by PTH. A mROS selective scavenger (MitoTEMPO (5 μM)) restored the endothelial responsiveness to Bk while the well-known antioxidant properties of vitamin D (100 nM) failed to counteract PTH-mediated oxidative stress. PTH determined mitochondrial calcium fluxes ([Ca²⁺]_mt) and the mitochondrial calcium uniporter inhibitor Ru360 (10 μM) reduced mROS production and prevented the PTH-mediated endothelial dysfunction. Angiogenic competence was evaluated as tubular formations in the endothelial Matrigel assay and showed a significant impairment in PTH-pretreated cells (0.1 nM–24 hours), despite the increase in VEGF transcriptional levels. VEGFR2 oxidation occurred in response to PTH, suggesting that even the impairment of angiogenesis was due to the ROS surge. These results indicate that PTH affects endothelial function through ROS production, driven by mitochondrial calcium overload. PTH-induced oxidative stress might act as signaling modifiers, altering specific pathways (Bk and VEGF) and preserving others (Ach).

Adrenocortical incidentalomas and bone: from molecular insights to clinical perspectives

Adrenal incidentalomas constitute a common clinical problem with an overall prevalence of around 2-3%, but are more common with advancing age being present in 10% of those aged 70 years. The majority of these lesions are benign adrenocortical adenomas (80%), characterized in 10-40% of the cases by autonomous cortisol hypersecretion, and in 1-10% by aldosterone hypersecretion. Several observational studies have shown that autonomous cortisol and aldosterone hypersecretion are more prevalent than expected in patients with osteopenia and osteoporosis: these patients have accelerated bone loss and an increased incidence of vertebral fractures. In contrast to glucocorticoid action, the effects of aldosterone on bone are less well understood. Recent data, demonstrating a concomitant co-secretion of glucocorticoid metabolites in patients with primary aldosteronism, could explain some of the metabolic abnormalities seen in patients with aldosterone hypersecretion. In clinical practice, patients with unexplained osteoporosis, particularly when associated with other features such as impaired glucose tolerance or hypertension, should be investigated for the possible presence of autonomous cortisol or aldosterone secretion due to an adrenal adenoma. Randomized intervention studies are needed, however, to investigate the optimum interventions for osteoporosis and other co-morbidities in these patients.

Vitamin D deficiency is an independent predictor of mortality in patients with chronic heart failure

Purpose

Low 25-hydroxyvitamin D (25[OH]D) concentrations have been associated with adverse outcomes in selected populations with established chronic heart failure (CHF). However, it remains unclear whether 25[OH]D deficiency is associated with mortality and hospitalisation in unselected patients receiving contemporary medical and device therapy for CHF.

Methods

We prospectively examined the prevalence and correlates of 25[OH]D deficiency in 1802 ambulatory patients with CHF due to left ventricular systolic dysfunction (left ventricular ejection fraction ≤ 45%) attending heart failure clinics in the north of England.

Results

73% of patients were deficient in 25[OH]D (< 50 nmol/L). 25[OH]D deficiency was associated with male sex, diabetes, lower serum sodium, higher heart rate, and greater diuretic requirement. During a mean follow-up period of 4 years, each 2.72-fold increment in 25[OH]D concentration (for example from 32 to 87 nmol/L) is associated with 14% lower all-cause mortality (95% confidence interval (CI) 1, 26%; p = 0.04), after accounting for potential confounding factors.

Conclusions

Low 25-hydroxyvitamin D deficiency is associated with increased mortality in patients with chronic heart failure due to left ventricular systolic dysfunction. Whether vitamin D supplementation will improve outcomes is, as yet, unproven.

Electronic supplementary material

The online version of this article (10.1007/s00394-018-1806-y) contains supplementary material, which is available to authorized users.

Double hit! A unique case of resistant hypertension

A middle-aged woman with obesity, hyperlipidaemia and diet-controlled diabetes was referred for resistant hypertension. Her blood pressure (BP) was uncontrolled on five medications, including a diuretic. Physical exam revealed a systolic ejection murmur, and ECHO demonstrated moderate hypertrophy. Laboratory examination revealed elevated aldosterone level (20.7 ng/dL) and elevated aldosterone:renin ratio (41.4 (ng/dL)/(ng/mL/h)), meeting criteria for primary aldosteronism (PA), and confirmed by saline infusion testing. CT scan of the adrenals was non-localising. Adrenal venous sampling confirmed bilateral idiopathic adrenal hyperplasia. Concurrent primary hyperparathyroidism was demonstrated by elevated calcium and parathyroid hormone levels and localised by sestamibi scan. Idiopathic adrenal hyperplasia was treated medically with spironolactone. Her BP remained elevated until postparathyroidectomy. Evidence shows that a hyperfunctioning parathyroid gland may contribute to maintaining hyperaldosteronism in PA making this bidirectional link unique. The significance of this case is in the potential for further understanding of the pathophysiology of common causes of secondary hypertension.

Effect of eplerenone on markers of bone turnover in patients with primary hyperparathyroidism - The randomized, placebo-controlled EPATH trial

Mineralocorticoid receptor (MR) antagonism may affect bone turnover via direct and indirect pathways involving parathyroid hormone, but randomized controlled trials are lacking. In a pre-specified analysis of the "Eplerenone in primary hyperparathyroidism" placebo-controlled, randomized trial (ISRCTN 33941607), effects of eight weeks MR-blockade with eplerenone on bone turnover markers in 97 patients with primary hyperparathyroidism were tested. Mean age was 67.5±9.5years, and 76 (78.4%) were females. In analysis of covariance with adjustment for baseline values, eplerenone had no significant effect on isoform 5b of the tartrate-resistant acid phosphatase (TRAP), beta-crosslaps, N-terminal propeptide of procollagen type 1 (P1NP), osteocalcin and bone-specific alkaline phosphatase. There was no significant cross-sectional correlation between plasma aldosterone concentration or the aldosterone-to-renin ratio and markers of bone turnover in multivariate linear regression models at baseline. These data provide first evidence from a randomized and placebo-controlled trial that short-term MR antagonism may not affect bone turnover, at least in patients with primary hyperparathyroidism.

Parathyroid hormone, aldosterone-to-renin ratio and fibroblast growth factor-23 as determinants of nocturnal blood pressure in primary hyperparathyroidism: the eplerenone in primary hyperparathyroidism trial

OBJECTIVES

The high prevalence of arterial hypertension in primary hyperparathyroidism (pHPT) is largely unexplained. Apart from parathyroid hormone (PTH), the mineral hormones fibroblast growth factor (FGF)-23 and aldosterone-to-renin ratio (ARR) are upregulated in pHPT. We aimed to determine whether nocturnal blood pressure (BP) is related with PTH, FGF-23 or ARR in a relatively large sample of pHPT patients.

METHODS

Cross-sectional data of the single-center "Eplerenone in Primary Hyperparathyroidism" trial were used. All patients with a biochemical diagnosis of pHPT who had both available 24-h ambulatory BP monitoring and valid laboratory data were included.

RESULTS

Full data were available in 136 patients (mean age 67 ± 10 years, 78% women). Median PTH was 99 (interquartile range: 82-124) pg/ml and mean calcium was 2.63 ± 0.15 mmol/l. ARR, but not PTH or FGF-23, was significantly and directly related with nocturnal SBP (Pearson's r = 0.241, P < 0.01) and DBP (r = 0.328, P < 0.01). In multivariate regression analyses, with adjustment for age, sex, PTH, FGF-23, traditional cardiovascular risk factors, antihypertensive medication and parameters of calcium metabolism ARR remained significantly and directly related with nocturnal BP (SBP: adjusted β-coefficient = 0.289, P < 0.01; DBP: β = 0.399, P < 0.01). The relationship between ARR and nocturnal SBP was exclusively present in patients with PTH levels above the median of 99 pg/ml.

CONCLUSION

ARR, but not FGF-23 or PTH, was independently and directly related with nocturnal BP parameters in patients with pHPT, and this relationship was dependent on pHPT disease severity. Inappropriately, elevated aldosterone may partially explain the high prevalence of arterial hypertension in pHPT.

Salt, Aldosterone, and Parathyroid Hormone: What Is the Relevance for Organ Damage?

Structured interventions on lifestyle have been suggested as a cost-effective strategy for prevention of cardiovascular disease. Epidemiologic studies demonstrate that dietary salt restriction effectively decreases blood pressure, but its influence on cardiovascular morbidity and mortality is still under debate. Evidence gathered from studies conducted in patients with primary aldosteronism, essential hypertension, or heart failure demonstrates that long-term exposure to elevated aldosterone results in cardiac structural and functional changes that are independent of blood pressure. Animal experiments and initial clinical studies indicate that aldosterone damages the heart only in the context of an inappropriately elevated salt status. Recent evidence suggests that aldosterone might functionally interact with the parathyroid hormone and thereby affect calcium homeostasis with important sequelae for bone mineral density and strength. The interaction between aldosterone and parathyroid hormone might have implications also for the heart. Elevated dietary salt is associated on the one hand with increased urinary calcium excretion and, on the other hand, could facilitate the interaction between aldosterone and parathyroid hormone at the cellular level. This review summarizes the evidence supporting the contribution of salt and aldosterone to cardiovascular disease and the possible cardiac and skeletal consequences of the mutual interplay between aldosterone, parathyroid hormone, and salt.

Oxidative stress and angiogenesis in primary hyperparathyroidism

Background

The inappropriate elevation of parathormone (PTH), which regulates the process of angiogenesis in parathyroid tissue, causes the changes of activity of enzymes responsible for the removal of free radicals. Parathyroidectomy (PTX) in patients with primary hyperparathyroidism (PHPT) lowers the level of PTH and leads to the reduction of risk of cardiovascular and all-cause mortality by normalization of the antioxidant status. Therefore, the aims of the study were to assess the activity of antioxidant enzymes and free radical reaction products in patients after parathyroidectomy, and to evaluate the correlation between the systemic oxidative stress and angiogenic parameters.

Materials and methods

Patients with PHPT treated surgically were enrolled into the study. Total antioxidant capacity (TAC), total oxidative status (TOS), oxidative stress index (OSI), superoxide dismutase (SOD), ceruloplasmin (CER), lipid hydroperoxides (LHP) and malondialdehyde (MDA) were measured before and after parathyroidectomy. The immunohistological expression of angiogenic factors in parathyroid specimens was assessed by the BrightVision method from ImmunoLogic using murine monoclonal anti-human: anti-VEGF, anti-CD31 and anti-CD106 antibodies.

Results

The significant increase of TAC, CER, reduction of TOS, MDA, SOD, especially for cytoplasmic form, and significant decrease of OSI, LHP were observed after PTX. There was no significant correlation between changes of oxidative stress markers and angiogenic parameters: VEGF, CD-31, CD-106 in parathyroid tissue. The correlation level was low and medium.

Conclusions

Parathyroidectomy causes down-regulation of lipid peroxidation processes and leads to reduction of oxidative stress in patients with PHPT. The decrease in the OSI is the results of down-regulation of oxidative stress in the postoperative period. The change of the antioxidant status has no impact on angiogenesis processes in parathyroid tissue.

Factors affecting parathyroid hormone levels in different types of primary aldosteronism

BACKGROUND

Recent studies have found that mild secondary hyperparathyroidism might be another clinical feature of patients with primary aldosteronims (PA), but whether serum parathyroid hormone level (PTH) is correlated with subtypes of PA and what contributes to the elevated PTH level remains unclear.

OBJECTIVE

To illustrate the changes of PTH in PA and to partly explain the mechanism of how the effects of aldosterone regulating the secretion of PTH in PA.

METHODS

We enrolled a total of 120 patients with primary hypertension (PH) and 242 patients with PA, which included 89 APAs (aldosterone-producing adenoma), 119 IHAs (idiopathic hyperaldosteronism) and 34 UAHs (unilateral adrenal hyperplasia). The plasma levels of aldosterone, renin activity, parathyroid hormone and markers associated with calcium metabolism were measured.

RESULTS

We found serum PTH level was significantly elevated in patients with PA compared with primary hypertension [9·0 (6·6, 11·7) vs 5·7 (4·4, 7·0)] pmol/l, P < 0·001]. However, no difference was found between the three PA subtypes (P > 0·05). Stepwise multiple regression analysis showed that in patients with PA, serum levels of K(+) and Ca(2+) were independently associated with serum PTH level. More importantly, elevated PTH level could be corrected either by unilateral adrenalectomy [9·9 (7·5, 12·8) vs 5·2 (4·4, 7·0) pmol/l, P < 0·001] or mineralocorticoid receptor (MR) antagonists treatment [11·7 (9·1, 13·4) vs 6·3 (5·1, 7·8) pmol/l, P < 0·001].

CONCLUSIONS

PTH level is elevated in PA patients and irrelevant with subtypes of PA. Serum K(+) and serum Ca(2+) level are main factors influence the plasma PTH level in PA patients. After medical or surgical treatment, PTH levels return to normal.

1,25-Dihydroxyvitamin D to PTH(1-84) Ratios Strongly Predict Cardiovascular Death in Heart Failure

OBJECTIVES

Vitamin D deficiency and hyperparathyroidism are common in patients with heart failure (HF). There is a growing body of evidence supporting the role of vitamin D and parathyroid hormone (PTH) in cardiac remodeling and worsening of HF. Lack of reliable automated testing of 1,25-dihydroxyvitamin D (1,25(OH)2D), the biologically active metabolite of vitamin D, has limited its contribution to the prognostic assessment of HF. Here, the association of 1,25(OH)2D and PTH(1-84) levels was evaluated for prediction of cardiovascular death in chronic HF patients.

METHODS

We conducted a single center prospective cohort including 170 chronic HF patients (females n = 36; males n = 134; NYHA II-IV; mean age: 67 years; etiology: ischemic n = 119, dilated cardiomyopathy n = 51; mean LVEF: 23%). The primary outcome was cardiovascular death.

RESULTS

Serum levels of 1,25(OH)2D decreased markedly with increased HF severity. Medians were 33.3 pg/mL for NYHA-II patients, 23.4 pg/mL for NYHA-III, and 14.0 pg/mL for NYHA-IV patients (p<0.001). Most patients had levels of 25(OH)D below 30ng/mL, and stratification by NYHA functional class did not show significant differences (p = 0.249). The 1,25(OH)2D to PTH(1-84) ratio and the (1,25(OH)2D)2 to PTH(1-84) ratio were found to be the most significantly related to HF severity. After a median follow-up of 4.1 years, 106 out of 170 patients reached the primary endpoint. Cox proportional hazard modeling revealed 1,25(OH)2D and the 1,25(OH)2D to PTH(1-84) ratios to be strongly predictive of outcomes.

CONCLUSIONS

1,25(OH)2D and its ratios to PTH(1-84) strongly and independently predict cardiovascular mortality in chronic HF.

Small dedifferentiated cardiomyocytes bordering on microdomains of fibrosis: evidence for reverse remodeling with assisted recovery

With the perspective of functional myocardial regeneration, we investigated small cardiomyocytes bordering on microdomains of fibrosis, where they are dedifferentiated re-expressing fetal genes, and determined: (1) whether they are atrophied segments of the myofiber syncytium, (2) their redox state, (3) their anatomic relationship to activated myofibroblasts (myoFb), given their putative regulatory role in myocyte dedifferentiation and redifferentiation, (4) the relevance of proteolytic ligases of the ubiquitin-proteasome system as a mechanistic link to their size, and (5) whether they could be rescued from their dedifferentiated phenotype. Chronic aldosterone/salt treatment (ALDOST) was invoked, where hypertensive heart disease with attendant myocardial fibrosis creates the fibrillar collagen substrate for myocyte sequestration, with propensity for disuse atrophy, activated myoFb, and oxidative stress. To address phenotype rescue, 4 weeks of ALDOST was terminated followed by 4 weeks of neurohormonal withdrawal combined with a regimen of exogenous antioxidants, ZnSO4, and nebivolol (assisted recovery). Compared with controls, at 4 weeks of ALDOST, we found small myocytes to be: (1) sequestered by collagen fibrils emanating from microdomains of fibrosis and representing atrophic segments of the myofiber syncytia, (2) dedifferentiated re-expressing fetal genes (β-myosin heavy chain and atrial natriuretic peptide), (3) proximal to activated myoFb expressing α-smooth muscle actin microfilaments and angiotensin-converting enzyme, (4) expressing reactive oxygen species and nitric oxide with increased tissue 8-isoprostane, coupled to ventricular diastolic and systolic dysfunction, and (5) associated with upregulated redox-sensitive proteolytic ligases MuRF1 and atrogin-1. In a separate study, we did not find evidence of myocyte replication (BrdU labeling) or expression of stem cell antigen (c-Kit) at weeks 1-4 ALDOST. Assisted recovery caused complete disappearance of myoFb from sites of fibrosis with redifferentiation of these myocytes, loss of oxidative stress, and ubiquitin-proteasome system activation, with restoration of nitric oxide and improved ventricular function. Thus, small dedifferentiated myocytes bordering on microdomains of fibrosis can re-differentiate and represent a potential source of autologous cells for functional myocardial regeneration.

Multiple biomarker strategy based on parathyroid hormone and natriuretic peptides testing for improved prognosis of chronic heart failure

Biomarkers offer new perspectives for a more personalized management of patients with heart failure (HF). Hyperparathyroidism is common in HF patients and parathyroid hormone (PTH) testing might provide added value for the prognostication of HF patients. Our objectives were therefore to determine the efficiency of multiple biomarker strategy based on PTH and natriuretic peptides measurement for the risk stratification of patients with HF. Circulating concentrations of bioactive PTH 1-84 and natriuretic peptides, B-type natriuretic peptide (BNP) and N-terminal proBNP (NT-proBNP), were measured with automated immunoassays in 45 healthy individuals and 137 HF patients with reduced left ventricular ejection fraction. Circulating levels of PTH 1-84 and natriuretic peptides were significantly increased in HF patients in comparison to HF patients. Over a long-term follow-up, baseline PTH 1-84 levels were related to the risk of cardiovascular death. Furthermore, in multiple biomarker approach, PTH measurement was additive to BNP and NT-proBNP testing for the cardiovascular risk assessment of HF patients. In conclusion, the combination of PTH 1-84 and natriuretic peptides testing improves the prognostication of HF patients and might allowed more personalized approach for risk stratification and treatment selection in HF patients.

Nebivolol: a multifaceted antioxidant and cardioprotectant in hypertensive heart disease

Cardiomyocyte necrosis with attendant microscopic scarring is a pathological feature of human hypertensive heart disease (HHD). Understanding the pathophysiological origins of necrosis is integral to its prevention. In a rat model of HHD associated with aldosterone/salt treatment (ALDOST), myocyte necrosis is attributable to oxidative stress induced by cytosolic-free [Ca]i and mitochondrial [Ca]m overloading in which the rate of reactive oxygen species generation overwhelms their rate of detoxification by endogenous Zn-based antioxidant defenses. We hypothesized that nebivolol (Neb), unlike another β1 adrenergic receptor antagonist atenolol (Aten), would have a multifaceted antioxidant potential based on its dual property as a β3 receptor agonist, which activates endothelial nitric oxide synthase to stimulate nitric oxide (NO) generation. NO promotes the release of cytosolic Zn sequestered inactive by its binding protein, metallothionein. Given the reciprocal regulation between these cations, increased [Zn]i reduces Ca entry and attendant rise in [Ca]i and [Ca]m. Herein, we examined the antioxidant and cardioprotectant properties of Neb and Aten in rats receiving 4 weeks ALDOST. Compared with untreated age-/sex-matched controls, ALDOST alone or ALDOST with Aten, Neb cotreatment induced endothelial nitric oxide synthase activation, NO generation and a marked increase in [Zn]i with associated decline in [Ca]i and [Ca]m. Attendant antioxidant profile at subcellular and cellular levels included attenuation of mitochondrial H2O2 production and lipid peroxidation expressed as reduced 8-isoprostane concentrations in both mitochondria and cardiac tissue. Myocyte salvage was expressed as reduced microscopic scarring and tissue collagen volume fraction. Neb is a multifaceted antioxidant with unique properties as cardioprotectant in HHD.

PTH: Potential role in management of heart failure

Biomarkers play an important role for the diagnosis and prognosis of heart failure (HF), a disease with high morbidity and mortality as well as a huge impact on healthcare budgets. Parathyroid hormone (PTH) is a major systemic calcium-regulating hormone and an important regulator of bone and mineral homeostasis. PTH testing is important for differential diagnosis of calcemia related disorders and for the management of patients with chronic kidney disease. As secondary hyperparathyroidism has been evidenced in HF patients, PTH testing might be relevant in HF patients for risk stratification and more personalized selection of treatment.

Aldosterone and parathyroid hormone interactions as mediators of metabolic and cardiovascular disease

Inappropriate aldosterone and parathyroid hormone (PTH) secretion is strongly linked with development and progression of cardiovascular (CV) disease. Accumulating evidence suggests a bidirectional interplay between parathyroid hormone and aldosterone. This interaction may lead to a disproportionally increased risk of CV damage, metabolic and bone diseases. This review focuses on mechanisms underlying the mutual interplay between aldosterone and PTH as well as their potential impact on CV, metabolic and bone health. PTH stimulates aldosterone secretion by increasing the calcium concentration in the cells of the adrenal zona glomerulosa as a result of binding to the PTH/PTH-rP receptor and indirectly by potentiating angiotensin 2 induced effects. This may explain why after parathyroidectomy lower aldosterone levels are seen in parallel with improved cardiovascular outcomes. Aldosterone mediated effects are inappropriately pronounced in conditions such as chronic heart failure, excess dietary salt intake (relative aldosterone excess) and primary aldosteronism. PTH is increased as a result of (1) the MR (mineralocorticoid receptor) mediated calciuretic and magnesiuretic effects with a trend of hypocalcemia and hypomagnesemia; the resulting secondary hyperparathyroidism causes myocardial fibrosis and disturbed bone metabolism; and (2) direct effects of aldosterone on parathyroid cells via binding to the MR. This adverse sequence is interrupted by mineralocorticoid receptor blockade and adrenalectomy. Hyperaldosteronism due to klotho deficiency results in vascular calcification, which can be mitigated by spironolactone treatment. In view of the documented reciprocal interaction between aldosterone and PTH as well as the potentially ensuing target organ damage, studies are needed to evaluate diagnostic and therapeutic strategies to address this increasingly recognized pathophysiological phenomenon.

Unmasked renal impairment and prolonged hyperkalemia after unilateral adrenalectomy for primary aldosteronism coexisting with primary hyperparathyroidism: report of a case

We herein report the case of a patient with critical hyperkalemia after unilateral adrenalectomy (ADX) for aldosterone-producing adenomas, which were coexisting with primary hyperparathyroidism. A right adrenal tumor oversecreting mineral corticoid was identified in a 62-year-old female whose kidney function had been impaired due to primary hyperaldosteronism and hyperparathyroidism. The ADX improved her hypertension with normalization of the plasma aldosterone concentration, but without adequately increasing her plasma renin activity. Her eGFR further decreased postoperatively, hyperkalemia appeared and the serum potassium level rose to 6.3 mEq/L at 3 months after ADX. Then, treatment with calcium polystyrene sulfonate jelly was started. Eight months after ADX, a left lower parathyroidectomy was performed, and the serum calcium and intact parathyroid hormone levels decreased to the normal range. The hyperkalemia was difficult to control within 20 months postoperatively without treatment with calcium polystyrene sulfonate jelly or hydrocortisone. This suggests that unmasking the renal impairment and relative hypoaldosteronism after ADX might induce critical hyperkalemia.

Gene Expression Profiles of Peripheral Blood Mononuclear Cells Reveal Transcriptional Signatures as Novel Biomarkers for Cardiac Remodeling in Rats with Aldosteronism and Hypertensive Heart Disease

OBJECTIVES

In searching for a noninvasive surrogate tissue having mimicry with the prooxidant/-proinflammatory hypertensive heart disease (HHD) phenotype, we turned to peripheral blood mononuclear cells (PBMC). We tested whether iterations in [Ca²⁺]_i, [Zn²⁺]_i and oxidative stress in cardiomyocytes and PBMC would complement each other eliciting similar shifts in gene expression profiles in these tissues demonstrable during preclinical (wk 1) and pathologic (wk 4) stages of aldosterone/salt treatment (ALDOST).

BACKGROUND

Inappropriate neurohormonal activation contributes to pathologic remodeling of myocardium in HHD associated with aldosteronism. In rats receiving chronic ALDOST, evidence of reparative fibrosis replacing necrotic cardiomyocytes and coronary vasculopathy appears at wk 4 associated with the induction of oxidative stress by mitochondria that overwhelms endogenous, largely Zn²⁺-based, antioxidant defenses. Biomarker-guided prediction of risk prior to the appearance of cardiac pathology would prove invaluable.

METHODS

In PBMC and cardiomyocytes, quantitation of cytoplasmic free Ca²⁺ and Zn²⁺, H₂O₂ and 8-iosprostane levels, as well as isolation of RNA and gene expression, together with statistical and clustering analyses, and confirmation of genes by in situ hybridization and RT-PCR, were performed.

RESULTS

Compared to controls, at wk 1 and 4 ALDOST, we found comparable: increments in [Ca²⁺]_i, [Zn²⁺]_i and 8-isoprotane coupled to increased H₂O₂ production in cardiac mitochondria and PBMC, together with the common networks of expression profiles dominated by genes involved in oxidative stress, inflammation and repair. These included three central Ingenuity pathway-linked genes: p38MAPK, a stress-responsive protein; NFκB, a redox-sensitive transcription factor and a proinflammatory cascade it regulates; and TGF-β₁, a fibrogenic cytokine involved in tissue repair.

CONCLUSIONS

Significant overlapping demonstrated in the molecular mimicry of PBMC and cardiomyocytes during preclinical and pathologic stages of ALDOST implicates that transcriptional signatures of PBMC may serve as early noninvasive and novel sentinels predictive of impending pathologic remodeling in HHD.

Mineralocorticoid receptor antagonism confers cardioprotection in heart failure

The symptoms and signs constituting the congestive heart failure (CHF) syndrome have their pathophysiologic origins rooted in a salt-avid renal state mediated by effector hormones of the renin-angiotensin-aldosterone and adrenergic nervous systems. Controlled clinical trials, conducted over the past decade in patients having minimally to markedly severe symptomatic heart failure, have demonstrated the efficacy of a pharmacologic regimen that interferes with these hormones, including aldosterone receptor binding with either spironolactone or eplerenone. Potential pathophysiologic mechanisms, which have not hitherto been considered involved for the salutary responses and cardioprotection provided by these mineralocorticoid receptor antagonists, are reviewed herein. In particular, we focus on the less well-recognized impact of catecholamines and aldosterone on monovalent and divalent cation dyshomeostasis, which leads to hypokalemia, hypomagnesemia, ionized hypocalcemia with secondary hyperparathyroidism and hypozincemia. Attendant adverse cardiac consequences include a delay in myocardial repolarization with increased propensity for supraventricular and ventricular arrhythmias, and compromised antioxidant defenses with increased susceptibility to nonischemic cardiomyocyte necrosis.

Daily intake of vitamin D- or calcium-vitamin D-fortified Persian yogurt drink (doogh) attenuates diabetes-induced oxidative stress: evidence for antioxidative properties of vitamin D

BACKGROUND

Both poor vitamin D status and oxidative stress (OS) have been independently associated with late diabetic complications, including cardiovascular disease (CVD). The present study aimed to examine the effect of daily intake of vitamin D alone or in combination with calcium as a fortified Persian yogurt drink (doogh) on OS over 12 weeks.

METHODS

Ninety patients with type 2 diabetes aged 30-50 years from both sexes were randomly allocated to one of the three groups to receive two 250-mL bottles of doogh a day, which was either plain (PD; containing 150 mg per 250 mL of calcium and no detectable vitamin D), vitamin D-fortified (DD; containing 150 mg of calcium + 500 IU vitamin D per 250 mL) or calcium-vitamin D-fortified (CDD; 250 mg od calcium + 500 IU vitamin D per 250 mL).

RESULTS

Although mean (SD) serum concentrations of protein carbonyl significantly decreased in both DD and CDD groups [-2.07 (4.39) nm, P = 0.015 and -4.4 (7.64) nm, P = 0.003, respectively], the change in PD group was not significant [-0.54 (6.96) nm, P = 0.674]. A similar pattern was observed for cardiac myeloperoxidase [PD: -19.4 (75.9) μg L(-1) , P = 0.173; DD: -21.8 (54.2) μg L(-1) , P = 0.035, CDD: -48.5 (76.9) μg L(-1) , P = 0.002]. Superoxide dismutase increased significantly only in DD and CDD [56.9 (74.0) U L(-1) , P < 0.001 and 51.6 (119.9) U L(-1) , P = 0.025, respectively]. Changes of serum advanced glycation end-products showed a significant between-group difference among PD, DD and CDD [239.4 (388.4) U L(-1) , -58.1 (147.6) U L(-1) and -143.7 (475.9) U L(-1)  × 10(3) , respectively, P = 0.003], which remained significant after controlling for changes of fasting serum glucose (P = 0.013) and glycated haemoglobin (P = 0.015).

CONCLUSIONS

The findings of the present study demonstrated an OS attenuating effect of vitamin D. However, extra calcium did not convey additional benefit.

Disturbances in calcium metabolism and cardiomyocyte necrosis: the role of calcitropic hormones

A synchronized dyshomeostasis of extra- and intracellular Ca(2+), expressed as plasma ionized hypocalcemia and excessive intracellular Ca(2+) accumulation, respectively, represents a common pathophysiologic scenario that accompanies several diverse disorders. These include low-renin and salt-sensitive hypertension, primary aldosteronism and hyperparathyroidism, congestive heart failure, acute and chronic hyperadrenergic stressor states, high dietary Na(+), and low dietary Ca(2+) with hypovitaminosis D. Homeostatic responses are invoked to restore normal extracellular [Ca(2+)](o), including increased plasma levels of parathyroid hormone and 1,25(OH)(2)D(3). However, in cardiomyocytes these calcitropic hormones concurrently promote cytosolic free [Ca(2+)](i) and mitochondrial [Ca(2+)](m) overloading. The latter sets into motion organellar-based oxidative stress, in which the rate of reactive oxygen species generation overwhelms their detoxification by endogenous antioxidant defenses, including those related to intrinsically coupled increments in intracellular Zn(2+). In turn, the opening potential of the mitochondrial permeability transition pore increases, allowing for osmotic swelling and ensuing organellar degeneration. Collectively, these pathophysiologic events represent the major components to a mitochondriocentric signal-transducer-effector pathway to cardiomyocyte necrosis. From necrotic cells, there follows a spillage of intracellular contents, including troponins, and a subsequent wound healing response with reparative fibrosis or scarring. Taken together, the loss of terminally differentiated cardiomyocytes from this postmitotic organ and the ensuing replacement fibrosis each contribute to the adverse structural remodeling of myocardium and progressive nature of heart failure. In conclusion, hormone-induced ionized hypocalcemia and intracellular Ca(2+) overloading comprise a pathophysiologic cascade common to diverse disorders and that initiates a mitochondriocentric pathway to nonischemic cardiomyocyte necrosis.

Bone involvement in aldosteronism

In rats with aldosteronism, a reduction of bone mineral density (BMD) and cortical bone strength has been reported. Our study was aimed to evaluate bone involvement in patients with primary aldosteronism (PA). A total of 188 consecutive subjects with adrenal incidentaloma, observed between November 2009 and October 2011, were screened for PA with aldosterone-to-renin ratio. After confirmatory tests, in those who screened positive, 11 patients were diagnosed as PA and 15 patients were not (nPA). A serum/urinary biochemical profile, parathyroid hormone (PTH), BMD measured at lumbar spine (LS) and total and femoral neck (TN and FN) by dual X-ray absorptiometry, and conventional spinal radiographs (T(4) -L(4) ) were obtained in all subjects. PA patients had a significantly higher 24-hour urinary calcium (6.28 ± 1.85 versus 4.28 ± 1.18 mmol/d; p < 0.01), and PTH (9.8 [5.8-14.6], median [range] versus 5.3 [2.5-10.8] pmol/L; p < 0.01) than nPA patients. BMD expressed as Z-value at LS (-1.18 ± 0.99 versus 0.22 ± 1.12), FN (-0.85 ± 0.73 versus 0.01 ± 0.82), and TN (-0.49 ± 0.61 versus 0.39 ± 0.93) was lower in PA than in nPA (p = 0.003, p = 0.011, and p = 0.012, respectively). The prevalence of osteoporosis was higher in PA than in nPA (8/11, 72.7% versus 3/15, 20.0%; Fisher's exact test: p = 0.015). Vertebral fractures tended to be more prevalent in PA than in nPA (5/11, 45.5% versus 2/15, 13.3%; Fisher's exact test: p = 0.095). Logistic regression analysis showed that osteoporosis and morphometric vertebral fractures were associated with PA (odds ratio [OR], 15.4; 95% confidence interval [CI] = 1.83-130, p = 0.012; and OR, 30.4; 95%CI, 1.07-862, p = 0.045, respectively) regardless of age, body mass index (BMI), and LS-BMD. In 9 of 11 PA patients, 6 months after beginning of treatment (surgery or spironolactone) there was a significant reduction of urinary calcium excretion (p < 0.01) and PTH (p < 0.01), whereas in 5 of 11 PA patients, 1 year after beginning of treatment, BMD was significantly increased at LS, p < 0.01). In conclusion, PA is associated with osteoporosis, vertebral fractures, and increased urinary calcium excretion.

Vitamin D and Parathyroid Hormone Relationships with Urinary Nitric Oxide Metabolites and Plasma Isoprostanes in African-Americans

BACKGROUND: Vitamin D deficiency and secondary rises in parathyroid hormone (PTH) are highly prevalent in obese African-Americans. Endothelial dysfunction related to oxidative stress is more common in African-Americans compared to whites. Currently, the association of vitamin D (25-hydroxyvitamin D, 25-OH D) and PTH to nitric oxide metabolites (NOx) - nitrate and nitrite - and oxidative stress in African-Americans is unknown. Objective: A cross-sectional design was utilized to determine the association of 25-OH D and PTH with urinary NOx (UNOx) (n = 101) and plasma isoprostanes (n = 125), an oxidative stress marker, in overweight (body mass index of 25-39.9), normotensive African-Americans aged ≥35 years. Measurements: Multivariable linear regression analysis adjusted for age, sex, body mass index, and season was used to determine the relationship of 25-OH D and PTH to UNOx and isoprostanes. General linear models, adjusted for the same covariates, contrasted UNOx across three mutually exclusive vitamin D/PTH groups: (1) normal 25-OH D (51-249 nmol/l) and normal PTH (≤65 pg/ml); (2) low 25-OH D and normal PTH, and (3) low 25-OH D and high PTH. RESULTS: 25-OH D was directly associated with UNOx before (p = 0.02) and after (p = 0.03) adjustment for PTH levels. A borderline significant association was observed between PTH and isoprostanes (p = 0.08). UNOx was 424, 290, and 270 μmol/8 h, respectively, across vitamin D/PTH groups 1-3 (p = 0.08). CONCLUSION: 25-OH D was directly associated with NO availability and PTH was positively, though borderline, associated with isoprostanes in overweight, normotensive adult African-Americans.

Coronary microvascular dysfunction induced by primary hyperparathyroidism is restored after parathyroidectomy

BACKGROUND

Symptomatic primary hyperparathyroidism (PHPT) is associated with increased cardiovascular mortality. However, data on the association between asymptomatic PHPT and cardiovascular risk are lacking. We assessed coronary flow reserve (CFR) as a marker of coronary microvascular function in asymptomatic PHPT of recent onset.

METHODS AND RESULTS

We studied 100 PHPT patients (80 women; age, 58±12 years) without cardiovascular disease and 50 control subjects matched for age and sex. CFR in the left anterior descending coronary artery was detected by transthoracic Doppler echocardiography, at rest, and during adenosine infusion. CFR was the ratio of hyperemic to resting diastolic flow velocity. CFR was lower in PHPT patients than in control subjects (3.0±0.8 versus 3.8±0.7; P<0.0001) and was abnormal (≤2.5) in 27 patients (27%) compared with control subjects (4%; P=0.0008). CFR was inversely related to parathyroid hormone (PTH) levels (r=-0.3, P<0.004). In patients with CFR ≤2.5, PTH was higher (26.4 pmol/L [quartiles 1 and 3, 16 and 37 pmol/L] versus 18 [13-25] pmol/L; P<0.007), whereas calcium levels were similar (2.9±0.1 versus 2.8±0.3 mmol/L; P=0.2). In multivariable linear regression analysis, PTH, age, and heart rate were the only factors associated with CFR (P=0.04, P=0.01, and P=0.006, respectively). In multiple logistic regression analysis, only PTH increased the probability of CFR ≤2.5 (P=0.03). In all PHPT patients with CFR ≤2.5, parathyroidectomy normalized CFR (3.3±0.7 versus 2.1±0.5; P<0.0001).

CONCLUSIONS

PHPT patients have coronary microvascular dysfunction that is completely restored after parathyroidectomy. PTH independently correlates with the coronary microvascular impairment, suggesting a crucial role of the hormone in explaining the increased cardiovascular risk in PHPT.

Mitochondriocentric pathway to cardiomyocyte necrosis in aldosteronism: cardioprotective responses to carvedilol and nebivolol

Foci of fibrosis, footprints of cardiomyocyte necrosis, are scattered throughout the failing myocardium and are a major component to its pathologic remodeling. Understanding pathogenic mechanisms contributing to hormone-mediated necrosis is therefore fundamental to developing cardioprotective strategies. In this context, a mitochondriocentric signal-transducer-effector pathway to necrosis is emerging. Our first objective, using cardiomyocytes and subsarcolemmal mitochondria (SSM) harvested from rats receiving a 4-week aldosterone/salt treatment (ALDOST), was to identify the major components of this pathway. Second, to validate this pathway, we used mitochondria-targeted pharmaceutical interventions as cardioprotective strategies using 4-week cotreatment with either carvedilol (Carv) or nebivolol (Nebiv). Compared with controls, we found the 4-week ALDOST to be accompanied by elevated cardiomyocyte free [Ca(2+)]i and SSM free [Ca(2+)]m; increased H(2)O(2) production and 8-isoprostane in SSM, cardiac tissue, and plasma; and enhanced opening of mitochondrial permeability transition pore (mPTP) and myocardial scarring. Increments in the antioxidant capacity augmented by increased cytosolic free [Zn(2+)]i were overwhelmed. Cotreatment with either Carv or Nebiv attenuated [Ca(2+)]i and [Ca(2+)]m overloading, prevented oxidative stress, and reduced mPTP opening while augmenting [Zn(2+)]i and conferring cardioprotection. Thus, major components of the mitochondriocentric signal-transducer-effector pathway to cardiomyocyte necrosis seen with ALDOST include intracellular Ca overloading coupled to oxidative stress and mPTP opening. This subcellular pathway can be favorably regulated by Carv or Nebiv cotreatment to salvage cardiomyocytes and prevent fibrosis.

Aldosterone and parathyroid hormone: a precarious couple for cardiovascular disease

Animal and human studies support a clinically relevant interaction between aldosterone and parathyroid hormone (PTH) levels and suggest an impact of the interaction on cardiovascular (CV) health. This review focuses on mechanisms behind the bidirectional interactions between aldosterone and PTH and their potential impact on the CV system. There is evidence that PTH increases the secretion of aldosterone from the adrenals directly as well as indirectly by activating the renin-angiotensin system. Upregulation of aldosterone synthesis might contribute to the higher risk of arterial hypertension and of CV damage in patients with primary hyperparathyroidism. Furthermore, parathyroidectomy is followed by decreased blood pressure levels and reduced CV morbidity as well as lower renin and aldosterone levels. In chronic heart failure, the aldosterone activity is inappropriately elevated, causing salt retention; it has been argued that the resulting calcium wasting causes secondary hyperparathyroidism. The ensuing intracellular calcium overload and oxidative stress, caused by PTH and amplified by the relative aldosterone excess, may increase the risk of CV events. In the setting of primary aldosteronism, renal and faecal calcium loss triggers increased PTH secretion which in turn aggravates aldosterone secretion and CV damage. This sequence explains why adrenalectomy and blockade of the mineralocorticoid receptor tend to decrease PTH levels in patients with primary aldosteronism. In view of the reciprocal interaction between aldosterone and PTH and the potentially ensuing CV damage, studies are urgently needed to evaluate diagnostic and therapeutic strategies addressing the interaction between the two hormones.

Mitochondria play a central role in nonischemic cardiomyocyte necrosis: common to acute and chronic stressor states

The survival of cardiomyocytes must be ensured as the myocardium adjusts to a myriad of competing physiological and pathophysiological demands. A significant loss of these contractile cells, together with their replacement by stiff fibrillar collagen in the form of fibrous tissue accounts for a transition from a usually efficient muscular pump into one that is failing. Cellular and subcellular mechanisms involved in the pathogenic origins of cardiomyocyte cell death have long been of interest. This includes programmed molecular pathways to either necrosis or apoptosis, which are initiated from ischemic or nonischemic origins. Herein, we focus on the central role played by a mitochondriocentric signal-transducer-effector pathway to nonischemic cardiomyocyte necrosis, which is common to acute and chronic stressor states. We begin by building upon the hypothesis advanced by Albrecht Fleckenstein and coworkers some 40 years ago based on the importance of calcitropic hormone-mediated intracellular Ca(2+) overloading, which predominantly involves subsarcolemmal mitochondria and is the signal to pathway activation. Other pathway components, which came to be recognized in subsequent years, include the induction of oxidative stress and opening of the mitochondrial inner membrane permeability transition pore. The ensuing loss of cardiomyocytes and consequent replacement fibrosis, or scarring, represents a disease of adaptation and a classic example of when homeostasis begets dyshomeostasis.

Hyperparathyroidism in patients with primary aldosteronism: cross-sectional and interventional data from the GECOH study

CONTEXT

Experimental studies suggest that aldosterone induces hypercalciuria and might contribute to hyperparathyroidism.

OBJECTIVE

We aimed to test for differences in PTH levels and parameters of calcium and vitamin D metabolism in patients with primary aldosteronism (PA) compared with patients with essential hypertension (EH) and to evaluate the impact of PA treatment on these laboratory values.

DESIGN, SETTING, AND PARTICIPANTS

The Graz Endocrine Causes of Hypertension study includes hypertensive patients referred for screening for endocrine hypertension at a tertiary care center in Graz, Austria.

MAIN OUTCOME MEASURES

Differences in PTH levels between patients with PA and EH.

RESULTS

Among 192 patients, we identified 10 patients with PA and 182 with EH. PTH levels (mean ± sd in picograms per milliliter) were significantly higher in PA patients compared with EH (67.8 ± 26.9 vs. 46.5 ± 20.9; P = 0.002). After treatment of PA with either adrenal surgery (n = 5) or mineralocorticoid receptor antagonists (n = 5), PTH concentrations decreased to 43.9 ± 14.9 (P = 0.023). Serum 25-hydroxyvitamin D concentrations were similar in both groups. Compared with EH, serum calcium concentrations were significantly lower (2.35 ± 0.10 vs. 2.26 ± 0.10 mmol/liter; P = 0.013), and there was a nonsignificant trend toward an increased spot urine calcium to creatinine ratio in PA [median (interquartile range) 0.19 (0.11-0.31) vs. 0.33 (0.12-0.53); P = 0.094].

CONCLUSIONS

Our results suggest that PA contributes to secondary hyperparathyroidism. Further studies are warranted to evaluate whether PTH has implications for PA diagnostics and whether mineralocorticoid receptor antagonists have a general impact on PTH and calcium metabolism.

Stressor states and the cation crossroads

Neurohormonal activation involving the hypothalamic-pituitary-adrenal axis and adrenergic nervous and renin-angiotensin-aldosterone systems is integral to stressor state-mediated homeostatic responses. The levels of effector hormones, depending upon the degree of stress, orchestrate the concordant appearance of hypokalemia, ionized hypocalcemia and hypomagnesemia, hypozincemia, and hyposelenemia. Seemingly contradictory to homeostatic responses wherein the constancy of extracellular fluid would be preserved, upregulation of cognate-binding proteins promotes coordinated translocation of cations to injured tissues, where they participate in wound healing. Associated catecholamine-mediated intracellular cation shifts regulate the equilibrium between pro-oxidants and antioxidant defenses, a critical determinant of cell survival. These acute and chronic stressor-induced iterations in extracellular and intracellular cations are collectively referred to as the cation crossroads. Intracellular cation shifts, particularly excessive accumulation of Ca2+, converge on mitochondria to induce oxidative stress and raise the opening potential of their inner membrane permeability transition pores (mPTPs). The ensuing loss of cationic homeostasis and adenosine triphosphate (ATP) production, together with osmotic swelling, leads to organellar degeneration and cellular necrosis. The overall impact of iterations in extracellular and intracellular cations and their influence on cardiac redox state, cardiomyocyte survival, and myocardial structure and function are addressed herein.

Mitochondria-targeted cardioprotection in aldosteronism

Chronic aldosterone/salt treatment (ALDOST) is accompanied by an adverse structural remodeling of myocardium that includes multiple foci of microscopic scarring representing morphologic footprints of cardiomyocyte necrosis. Our previous studies suggested that signal-transducer-effector pathway leading to necrotic cell death during ALDOST includes intramitochondrial Ca overloading, together with an induction of oxidative stress and opening of the mitochondrial permeability transition pore (mPTP). To further validate this concept, we hypothesized that mitochondria-targeted interventions will prove to be cardioprotective. Accordingly, 8-week-old male Sprague-Dawley rats receiving 4 weeks ALDOST were cotreated with either quercetin, a flavonoid with mitochondrial antioxidant properties, or cyclosporine A (CsA), an mPTP inhibitor, and compared with ALDOST alone or untreated, age/sex-matched controls. We monitored mitochondrial free Ca and biomarkers of oxidative stress, including 8-isoprostane and H2O2 production; mPTP opening; total Ca in cardiac tissue; and collagen volume fraction to quantify replacement fibrosis, a biomarker of cardiomyocyte necrosis, and employed terminal deoxynucleotidyl transferase dUTP nick end labeling assay to address apoptosis in coronal sections of ventricular myocardium. Compared with controls, at 4 weeks ALDOST we found a marked increase in mitochondrial H2O2 production and 8-isoprostane levels, an increased propensity for mPTP opening, and greater concentrations of mitochondrial free [Ca]m and total tissue Ca, coupled with a 5-fold rise in collagen volume fraction without any terminal deoxynucleotidyl transferase dUTP nick end labeling-based evidence of cardiomyocyte apoptosis. Each of these pathophysiologic responses to ALDOST was prevented by quercetin or cyclosporine A cotreatment. Thus, mitochondria play a central role in initiating the cellular-subcellular mechanisms that lead to necrotic cell death and myocardial scarring. This destructive cycle can be interrupted and myocardium salvaged with its structure preserved by mitochondria-targeted cardioprotective strategies.

Eplerenone potentiates protective effects of amlodipine against cardiovascular injury in salt-sensitive hypertensive rats

The clinical value of the combination of amlodipine and eplerenone is unclear. This study was undertaken to test whether eplerenone potentiates the protective effects of amlodipine against hypertensive cardiovascular injury. Salt-loaded Dahl salt-sensitive hypertensive rats (DS rats) were given (1) vehicle, (2) an antihypertensive dose of amlodipine, (3) a non-antihypertensive dose of eplerenone or (4) combined amlodipine and eplerenone for 6 weeks, and the effects on cardiovascular injuries were compared. There was no significant difference among the four groups regarding plasma aldosterone, urine volume or urinary electrolytes. A subpressor dose of eplerenone markedly ameliorated vascular endothelial dysfunction, cardiac inflammation and fibrosis in DS rats to a similar degree as an antihypertensive dose of amlodipine. Addition of eplerenone to amlodipine, without affecting blood pressure, enhanced the improvement by amlodipine of vascular endothelial function, cardiac inflammation, fibrosis and diastolic dysfunction in DS rats. Additive beneficial effects of eplerenone were attributed to additive potentiation of eNOS and Akt phosphorylation and additive reduction of oxidative stress. Eplerenone significantly attenuated cardiovascular NADPH oxidase activity by reducing gp91(phox) upregulation and attenuated the upregulation of cardiovascular AT1 receptor, but amlodipine failed to affect them. Thus, the normalization by eplerenone of gp91(phox) and AT1 receptor upregulation seems to be at least partially responsible for the additive benefits of eplerenone in the prevention of hypertensive cardiovascular injury. The combination of amlodipine and eplerenone may be a promising therapeutic strategy for cardiovascular disease in salt-sensitive hypertension.

Cellular and molecular pathways to myocardial necrosis and replacement fibrosis

Fibrosis is a fundamental component of the adverse structural remodeling of myocardium present in the failing heart. Replacement fibrosis appears at sites of previous cardiomyocyte necrosis to preserve the structural integrity of the myocardium, but not without adverse functional consequences. The extensive nature of this microscopic scarring suggests cardiomyocyte necrosis is widespread and the loss of these contractile elements, combined with fibrous tissue deposition in the form of a stiff in-series and in-parallel elastic elements, contributes to the progressive failure of this normally efficient muscular pump. Cellular and molecular studies into the signal-transducer-effector pathway involved in cardiomyocyte necrosis have identified the crucial pathogenic role of intracellular Ca2+ overloading and subsequent induction of oxidative stress, predominantly confined within its mitochondria, to be followed by the opening of the mitochondrial permeability transition pore that leads to the destruction of these organelles and cells. It is now further recognized that Ca2+ overloading of cardiac myocytes and mitochondria serves as a prooxidant and which is counterbalanced by an intrinsically coupled Zn2+ entry serving as antioxidant. The prospect of raising antioxidant defenses by increasing intracellular Zn2+ with adjuvant nutriceuticals can, therefore, be preferentially exploited to uncouple this intrinsically coupled Ca2+ - Zn2+ dyshomeostasis. Hence, novel yet simple cardioprotective strategies may be at hand that deserve to be further explored.

Cation dyshomeostasis and cardiomyocyte necrosis: the Fleckenstein hypothesis revisited

An ongoing loss of cardiomyocytes to apoptotic and necrotic cell death pathways contributes to the progressive nature of heart failure. The pathophysiological origins of necrotic cell loss relate to the neurohormonal activation that accompanies acute and chronic stressor states and which includes effector hormones of the adrenergic nervous system. Fifty years ago, Albrecht Fleckenstein and coworkers hypothesized the hyperadrenergic state, which accompanies such stressors, causes cardiomyocyte necrosis based on catecholamine-initiated excessive intracellular Ca(2+) accumulation (EICA), and mitochondrial Ca(2+) overloading in particular, in which the ensuing dysfunction and structural degeneration of these organelles leads to necrosis. In recent years, two downstream factors have been identified which, together with EICA, constitute a signal-transducer-effector pathway: (i) mitochondria-based induction of oxidative stress, in which the rate of reactive oxygen metabolite generation exceeds their rate of detoxification by endogenous antioxidant defences; and (ii) the opening of the mitochondrial inner membrane permeability transition pore (mPTP) followed by organellar swelling and degeneration. The pathogenesis of stress-related cardiomyopathy syndromes is likely related to this pathway. Other factors which can account for cytotoxicity in stressor states include: hypokalaemia; ionized hypocalcaemia and hypomagnesaemia with resultant elevations in parathyroid hormone serving as a potent mediator of EICA; and hypozincaemia with hyposelenaemia, which compromise antioxidant defences. Herein, we revisit the Fleckenstein hypothesis of EICA in leading to cardiomyocyte necrosis and the central role played by mitochondria.

Congestive heart failure: where homeostasis begets dyshomeostasis

Despite today's standard of care, aimed at preventing homeostatic neurohormonal activation, one in every five patients recently hospitalized with congestive heart failure (CHF) will be readmitted within 30 days of discharge because of a recurrence of their symptoms and signs. In light of recent pathophysiological insights, it is now propitious to revisit CHF with a view toward complementary and evolving management strategies. CHF is a progressive systemic illness. Its features include: oxidative stress in diverse tissues; an immunostimulatory state with circulating proinflammatory cytokines; a wasting of soft tissues; and a resorption of bone. Its origins are rooted in homeostatic mechanisms gone awry to beget dyshomeostasis. For example, marked excretory losses of Ca2+ and Mg2+ accompany renin-angiotensin-aldosterone system activation, causing ionized hypocalcemia and hypomagnesemia that lead to secondary hyperparathyroidism with consequent bone resorption and a propensity to atraumatic fractures. Parathyroid hormone accounts for paradoxical intracellular Ca2+ overloading in diverse tissues and consequent systemic induction of oxidative stress. In cardiac myocytes and mitochondria, these events orchestrate opening of the mitochondrial permeability transition pore with an ensuing osmotic-based destruction of these organelles and resultant cardiomyocyte necrosis with myocardial scarring. Contemporaneous with Ca2+ and Mg2+ dyshomeostasis is hypozincemia and hyposelenemia, which compromise metalloenzyme-based antioxidant defenses, whereas hypovitaminosis D threatens Ca2+ stores needed to prevent secondary hyperparathyroidism. An intrinsically coupled dyshomeostasis of intracellular Ca2+ and Zn2+, representing pro-oxidant and antioxidant, respectively, is integral to regulating the mitochondrial redox state; it can be uncoupled by a Zn2+ supplement in favor of antioxidant defenses. Hence, the complementary use of nutriceuticals to nullify dyshomeostatic responses involving macro- and micronutrients should be considered. Evolving strategies with mitochondria-targeted interventions interfering with their uptake of Ca2+ or serving as selective antioxidant or mitochondrial permeability transition pore inhibitor may also prove efficacious in the overall management of CHF.

Fibrosis in hypertensive heart disease: molecular pathways and cardioprotective strategies

Fibrosis is a fundamental component of the adverse structural remodelling of myocardium found in hypertensive heart disease (HHD). A replacement fibrosis appears at sites of previous cardiomyocyte necrosis to preserve the structural integrity of the myocardium. Such scarring has adverse functional consequences. The extensive distribution of fibrosis involving the right and left heart suggests cardiomyocyte necrosis is widespread. Together, the loss of these contractile elements and fibrous tissue deposition in the form of stiff in-series and in-parallel elastic elements contribute to the progressive failure of this normally efficient muscular pump. Pathogenic mechanisms modulating fibrous tissue formation at sites of repair include auto/paracrine properties of locally generated angiotensin II and endothelin-1. This study focuses on the signal-transducer-effector pathway involved in cardiomyocyte necrosis and the crucial pathogenic role of intracellular calcium overloading, and the subsequent induction of oxidative stress originating within its mitochondria that dictates the opening of the mitochondrial permeability transition pore. The ensuing osmotic destruction of these organelles is followed by necrotic cell death. It is now further recognized that calcium overloading of cardiac myocytes and mitochondria functioning as pro-oxidant is pathophysiologically counterbalanced by an intrinsically coupled zinc entry, which serves as an antioxidant. The prospect of raising intracellular zinc by adjuvant nutriceutical supplementation can, therefore, be preferentially exploited to uncouple this intrinsically coupled calcium-zinc dyshomeostasis in favour of endogenous antioxidant defences. Novel cardioprotective strategies may thus be at hand and deserve to be explored further in the overall management of patients with HHD.

Calcium and zinc dyshomeostasis during isoproterenol-induced acute stressor state

Acute hyperadrenergic stressor states are accompanied by cation dyshomeostasis, together with the release of cardiac troponins predictive of necrosis. The signal-transducer-effector pathway accounting for this pathophysiological scenario remains unclear. We hypothesized that a dyshomeostasis of extra- and intracellular Ca2+ and Zn2+ occurs in rats in response to isoproterenol (Isop) including excessive intracellular Ca2+ accumulation (EICA) and mitochondrial [Ca2+]m-induced oxidative stress. Contemporaneously, the selective translocation of Ca2+ and Zn2+ to tissues contributes to their fallen plasma levels. Rats received a single subcutaneous injection of Isop (1 mg/kg body wt). Other groups of rats received pretreatment for 10 days with either carvedilol (C), a β-adrenergic receptor antagonist with mitochondrial Ca2+ uniporter-inhibiting properties, or quercetin (Q), a flavonoid with mitochondrial-targeted antioxidant properties, before Isop. We monitored temporal responses in the following: [Ca2+] and [Zn2+] in plasma, left ventricular (LV) apex, equator and base, skeletal muscle, liver, spleen, and peripheral blood mononuclear cells (PBMC), indices of oxidative stress and antioxidant defenses, mitochondrial permeability transition pore (mPTP) opening, and myocardial fibrosis. We found ionized hypocalcemia and hypozincemia attributable to their tissue translocation and also a heterogeneous distribution of these cations among tissues with a preferential Ca2+ accumulation in the LV apex, muscle, and PBMC, whereas Zn2+ declined except in liver, where it increased corresponding with upregulation of metallothionein, a Zn2+-binding protein. EICA was associated with a simultaneous increase in tissue 8-isoprostane and increased [Ca2+]m accompanied by a rise in H2O2 generation, mPTP opening, and scarring, each of which were prevented by either C or Q. Thus excessive [Ca2+]m, coupled with the induction of oxidative stress and increased mPTP opening, suggests that this signal-transducer-effector pathway is responsible for Isop-induced cardiomyocyte necrosis at the LV apex.