Difficulties in maintaining potassium homeostasis in patients with heart failure

Controlled bio-inspired self-organised criticality

Complex biological systems are considered to be controlled using feedback mechanisms. Reduced systems modelling has been effective to describe these mechanisms, but this approach does not sufficiently encompass the required complexity that is needed to understand how localised control in a biological system can provide global stable states. Self-Organised Criticality (SOC) is a characteristic property of locally interacting physical systems, which readily emerges from changes to its dynamic state due to small nonlinear perturbations. These small changes in the local states, or in local interactions, can greatly affect the total system state of critical systems. It has long been conjectured that SOC is cardinal to biological systems, that show similar critical dynamics, and also may exhibit near power-law relations. Rate Control of Chaos (RCC) provides a suitable robust mechanism to generate SOC systems, which operates at the edge of chaos. The bio-inspired RCC method requires only local instantaneous knowledge of some of the variables of the system, and is capable of adapting to local perturbations. Importantly, connected RCC controlled oscillators can maintain global multi-stable states, and domains where power-law relations may emerge. The network of oscillators deterministically stabilises into different orbits for different perturbations, and the relation between the perturbation and amplitude can show exponential and power-law correlations. This can be considered to be representative of a basic mechanism of protein production and control, that underlies complex processes such as homeostasis. Providing feedback from the global state, the total system dynamic behaviour can be boosted or reduced. Controlled SOC can provide much greater understanding of biological control mechanisms, that are based on distributed local producers, with remote consumers of biological resources, and globally defined control.

NI956/QGC006, a Potent Orally Active, Brain-Penetrating Aminopeptidase A Inhibitor for Treating Hypertension

Brain renin-angiotensin system hyperactivity has been implicated in the development and maintenance of hypertension. We have shown that aminopeptidase A is involved in the formation of brain angiotensin III, which exerts tonic stimulatory control over blood pressure in hypertensive deoxycorticosterone acetate-salt rats and spontaneously hypertensive rats. We have also shown that injection of the specific and selective aminopeptidase A inhibitor, (3S)-3-amino-4-sulfanyl-butane-1-sulfonic acid (EC33), by central route or its prodrug, RB150/firibastat, by oral route inhibited brain aminopeptidase A activity and blocked the formation of brain angiotensin III, normalizing blood pressure in hypertensive rats. These findings identified brain aminopeptidase A as a potential new therapeutic target for hypertension. We report here the development of a new aminopeptidase A inhibitor prodrug, NI956/QGC006, obtained by the disulfide bridge-mediated dimerization of NI929. NI929 is 10× more efficient than EC33 at inhibiting recombinant mouse aminopeptidase A activity in vitro. After oral administration at a dose of 4 mg/kg in conscious deoxycorticosterone acetate-salt rats, NI956/QGC006 normalized brain aminopeptidase A activity and induced a marked decrease in blood pressure of -44±13 mm Hg 4 hours after treatment ( P<0.001), sustained over 10 hours (-21±12 mm Hg; P<0.05). Moreover, NI956/QGC006 decreased plasma arginine-vasopressin levels, and increased diuresis and natriuresis, that may participate to the blood pressure decrease. Finally, NI956/QGC006 did not affect plasma sodium and potassium concentrations. This study shows that NI956/QGC006 is a best-in-class central-acting aminopeptidase A inhibitor prodrug. Our results support the development of hypertension treatments targeting brain aminopeptidase A.

Abnormal serum potassium levels and 6-month all-cause mortality in patients co-treated with antipsychotic and diuretic drugs - A Danish register-based cohort study

Psychiatric patients have excess mortality compared to the general population, and several potential mechanisms may explain this increased risk. This study examined the relationship between serum potassium levels and risk of all-cause mortality in patients co-treated with antipsychotic and diuretic drugs. Using a register-based cohort design, we identified patients between 1995 and 2012 who received a combination of an antipsychotic and a diuretic drug and who further had a serum potassium measurement within 90 days. During the study period, we included the most frequently redeemed antipsychotic drugs with regard to the propensity of corrected QT (QTc) prolongation: zuclopenthixol (unknown/mild), flupentixol (mild), levomepromazine (moderate), and quetiapine (moderate/severe). Patients co-treated with antidepressant drugs, lithium, and other antipsychotic drugs were excluded. Outcome was 6-month all-cause mortality, estimated with multivariable Cox regression. Patients were divided into seven serum potassium levels using restricted cubic splines (reference: 4.2-4.4 mmol/L) and stratified according to the included antipsychotic drugs. Of 6729 patients (median age: 74.0 years; women: 65.3%), 10.8% had hypokalemia and 4.9% had hyperkalemia. Hyperkalemia (>5.0 mmol/L, HR 2.82 [95% CI 2.25-3.54]), hypokalemia (<3.5 mmol/L, HR 1.59 [95% CI 1.29-1.95]), and high normal potassium levels (4.5-4.7 mmol/L, HR 1.44 [95% CI 1.19-1.75]; 4.8-5.0 mmol/L, HR 1.60 [95% CI 1.26-2.04]) were associated with an increased risk of 6-month all-cause mortality. This risk was independent of antipsychotic drugs (interaction: P = 0.06). Our findings imply that excess mortality in patients co-treated with antipsychotic and diuretic drugs is related to serum potassium levels and independent of antipsychotic drugs.

Micronutrient Deficiency Independently Predicts Adverse Health Outcomes in Patients With Heart Failure

BACKGROUND

Despite growing evidence on the important role of micronutrients in prognosis of heart failure (HF), there has been limited research that micronutrient deficiency predicts health outcomes in patients with HF.

PURPOSE

The aim of this study was to determine whether micronutrient deficiency independently predicts adverse health outcomes.

METHODS

A total of 113 consecutive outpatients with HF completed a 3-day food diary to measure intake of 15 micronutrients. The Computer Aided Nutrition Analysis Program for Professionals was used to analyze the food diaries and determine dietary micronutrient deficiencies. Patients completed the Minnesota Living With HF Questionnaire to assess health-related quality of life (HRQoL) and were followed up for 1 year to determine cardiac-related hospitalization or cardiac death. Hierarchical multiple linear regressions and Cox proportional hazard regressions were used to determine whether micronutrient deficiencies predicted health outcomes.

RESULTS

Fifty-eight patients (51%) had at least 3 micronutrient deficiencies (range, 0-14). Calcium, magnesium, and vitamin D were the most common micronutrient deficiencies. Micronutrient deficiency was independently associated with worse HRQoL (β = .187, P = .025) in hierarchical multiple linear regression. Thirty-nine patients were hospitalized or died during 1-year follow-up because of cardiac problems. The number of micronutrient deficiencies independently predicted cardiac event-free survival (hazard ratio, 1.14; 95% confidence interval, 1.02-1.28).

CONCLUSIONS

These findings show that micronutrient deficiency independently predicted poor HRQoL and earlier cardiac event-free survival in patients with HF. Further research is needed to provide for specific dietary guidelines for better health outcomes in HF patients.

The meaning of hypokalemia in heart failure

Maintenance of normal potassium (K(+)) homeostasis has become an increasingly important limiting factor in the therapy of heart failure (HF). With the application of loop diuretics and digoxin, hypokalemia has become a frequent and feared side effect of treatment. Low serum K(+) in HF may be also a marker of increased neurohormonal activity and disease progression. To gain the maximum benefit from treatment, we need to individualize drug use and carefully monitor electrolytes. Symptomatic HF patients (New York Heart Association class III-IV) should be prescribed the lowest dose of diuretic necessary to maintain euvolemia. Mild hypokalemia may be corrected by the use of aldosterone receptor antagonists such as spironolactone or eplerenone. However, a more severe hypokalemia should preferably be corrected using K(+) supplement. Serum K levels should be frequently checked and maintained between 4.0 and 5.5 mEq/l (mmol/l).

What is the risk of hyperkalaemia in heart failure?

INTRODUCTION

Chronic heart failure (CHF) is the only major cardiovascular disease whose prevalence and incidence are thought to be increasing. Potassium balance may be lost both through the neurohormonal mechanisms involved in cardiovascular diseases and through the drugs used in their treatment. Avoiding both hypo- and hyperkalemia is difficult but beneficial in CHF.

AREAS COVERED

Aldosterone production is decreased in the elderly, diabetic patients, and those receiving drugs that block the production or action of renin and angiotensin II. As a result, these groups, as well as those with already impaired potassium excretion due to progressive age or disease-related decline in glomerular filtration rate, are particularly vulnerable to the development of hyperkalemia.

EXPERT OPINION

Evidence from several studies suggests that, in patients with CHF, serum potassium should be maintained between 4.0 and 5.5 mEq/L. To gain the maximum benefit from aldosterone antagonists it is necessary to individualize their use; it is also necessary to carefully monitor electrolytes.

Effect of amino acid infusion on potassium serum levels in neuroendocrine tumour patients treated with targeted radiopeptide therapy

PURPOSE

Administration of positively charged amino acids has been introduced to reduce the nephrotoxicity of targeted radiopeptide therapy (TRT). However, the amino acid solution may have side effects, including hyperkalaemia. The aim of this study was to evaluate the frequency and the magnitude of hyperkalaemia in neuroendocrine tumour (NET) patients undergoing TRT.

METHODS

Enrolled in the study were 31 patients with NET eligible for TRT with [(90)Y-DOTA(0),Tyr(3)]octreotide ((90)Y-DOTATOC). Their mean age was 54 ± 14 years. Of these 31 patients, 21 (67%) were referred for the first treatment cycle, while 10 (33%) were referred for a subsequent therapy cycle. Patients were treated with therapeutic doses of (90)Y-DOTATOC ranging from 7,030 to 35,520 MBq. To inhibit tubular reabsorption of (90)Y-DOTATOC, 1 l of physiological saline solution containing 25 g of arginine hydrochloride and 25 g of lysine hydrochloride was given over 4 h starting 1 h before (90)Y-DOTATOC injection. All patients underwent a standard biochemical blood analysis at baseline, and 4 h and 24 h after the beginning of the amino acid infusion.

RESULTS

ANOVA repeated measures showed a significant overall effect on K(+) levels over time (F = 118.2, df = 2, P < 0.0001). Mean serum levels of K(+) were 4.00 ± 0.33 mmol/l at baseline, 5.47 ± 0.57 mmol/l at 4 h, and 4.38 ± 0.63 mmol/l at 24 h after the beginning of the infusion. Post-hoc analysis showed that K(+) levels at 4 h were significantly (P < 0.05) higher than at baseline. K(+) levels at 24 h were significantly (P < 0.05) lower than at 4 h but they were still significantly (P < 0.05) higher than K(+) levels at baseline. On a subject-by-subject basis, none of the 31 patients had increased K(+) levels at baseline. At 4 h, 24 of the 31 patients (77%) had K(+) levels above the normal range, and 6 patients (19%) experienced severe hyperkalaemia (K(+) ≥ 6 mmol/l). All patients with increased K(+) levels were clinically asymptomatic. At 24 h, only 4 patients (13%) had increased K(+) serum levels. The magnitude of the increase in K(+) levels between baseline and 4 h was relatively homogeneous over the whole group (1.41 ± 0.50 mmol/l) and it was not related (linear regression, P>0.05) to baseline K(+) levels. Intravenous administration of 40 mg furosemide 1 h after the beginning of the amino acid infusion did not have a significant effect on K(+) levels (P>0.05). No clinical characteristic was predictive for the increase in K(+) levels (chi-squared test, P > 0.05).

CONCLUSION

Hyperkalaemia is a frequent, potentially life-threatening side effect of basic amino acid infusion during TRT. K(+) levels 4 h after the beginning of the infusion should be monitored in patients at risk of complications, such as those with heart disease and those with risk factors for nephrotoxicity.

Nutritional inadequacies in patients with stable heart failure

Sodium restriction is the primary nutritional strategy in heart failure; however, other diet-related concerns may also occur. We characterized dietary intake among stable patients with heart failure and a non-heart-failure cardiac control group to quantify and determine prevalence of inadequate micronutrient intake. Two 3-day food records were completed by 123 patients with heart failure and 58 controls. A subset of each group provided two 24-hour urine collections. Mean intake of sodium (2,540+/-1,122 vs 2,596+/-1,184 mg/day) and potassium (3,190+/-980 vs 3,114+/-828 mg/day) was similar between the heart failure and control groups. Prevalence of inadequate potassium intake was 94% among patients with heart failure and 91% among controls. More than 50% in each group had inadequate intakes of calcium, magnesium, folate, and vitamins D and E. In stable patients with heart failure, sodium intake was not excessive. However, we demonstrated widespread dietary inadequacies of other vitamins and minerals. These findings highlight the importance of diet beyond that of sodium restriction.