Enhanced generation of reactive oxygen species in the limb skeletal muscles from a murine infarct model of heart failure

Association between worsening renal function severity during hospitalization and low physical function at discharge: a retrospective cohort study of older patients with heart failure and chronic kidney disease from Japan

BACKGROUND

The number of hospitalized older patients with chronic heart failure, chronic kidney disease, and worsening renal function is rising in Japan. This study aimed to clarify the impact of the severity of worsening renal function during hospitalization on low physical function at discharge of these patients.

METHODS

We included 573 consecutive heart failure patients who underwent phase I cardiac rehabilitation. Worsening renal function severity was defined according to elevation during hospitalization of baseline serum creatinine on admission: non-worsening renal function, serum creatinine < 0.2 mg/dL; worsening renal function II/I, serum creatinine ≥ 0.2 to < 0.5 mg/dL; worsening renal function III, and serum creatinine ≥ 0.5 mL/dL. Physical function was measured with the Short Performance Physical Battery. We compared background factors, clinical parameters, pre-hospitalization walking levels, Functional Independence Measure score, and physical function in the three renal function groups. Multiple regression analysis was performed with the Short Performance Physical Battery at discharge as the dependent variable.

RESULTS

The final analysis included 196 patients (mean age 82.7 years, male 51.5%) categorized into three groups based on worsening renal function: worsening renal function grade III group (n = 55), worsening renal function grade II/I group (n = 36), and non-worsening renal function group (n = 105). There is no significant difference in walking levels before hospitalization between the three groups, but physical function at discharge was significantly lower in the worsening renal function III group. Moreover, worsening renal function III was an independent factor for low physical function at discharge.

CONCLUSION

Worsening of renal function during hospitalization in older patients with heart failure and chronic kidney disease was strongly associated with low physical function at discharge, even after adjusting for other potentially confounding factors, such as pre-hospitalization walking levels, walking start day, and Geriatric Nutrition Risk Index at discharge. Notably, worsening renal function of mild or moderate severity (grade II/I) did not show a significant association with low physical function.

Systemic oxidative stress is associated with lower aerobic capacity and impaired skeletal muscle energy metabolism in heart failure patients

Oxidative stress plays a role in the progression of chronic heart failure (CHF). We investigated whether systemic oxidative stress is linked to exercise intolerance and skeletal muscle abnormalities in patients with CHF. We recruited 30 males: 17 CHF patients, 13 healthy controls. All participants underwent blood testing, cardiopulmonary exercise testing, and magnetic resonance spectroscopy (MRS). The serum thiobarbituric acid reactive substances (TBARS; lipid peroxides) were significantly higher (5.1 ± 1.1 vs. 3.4 ± 0.7 μmol/L, p < 0.01) and the serum activities of superoxide dismutase (SOD), an antioxidant, were significantly lower (9.2 ± 7.1 vs. 29.4 ± 9.7 units/L, p < 0.01) in the CHF cohort versus the controls. The oxygen uptake (VO₂) at both peak exercise and anaerobic threshold was significantly depressed in the CHF patients; the parameters of aerobic capacity were inversely correlated with serum TBARS and positively correlated with serum SOD activity. The phosphocreatine loss during plantar-flexion exercise and intramyocellular lipid content in the participants' leg muscle measured by ³¹phosphorus- and ¹proton-MRS, respectively, were significantly elevated in the CHF patients, indicating abnormal intramuscular energy metabolism. Notably, the skeletal muscle abnormalities were related to the enhanced systemic oxidative stress. Our analyses revealed that systemic oxidative stress is related to lowered whole-body aerobic capacity and skeletal muscle dysfunction in CHF patients.

Worsening renal function during hospitalization in elderly patients with heart failure: an independent factor of activities of daily living decline

This study aimed to clarify the effects of worsening renal function (WRF) during hospitalization on activities of daily living (ADL) at discharge of elderly heart failure (HF) patients. We included 323 consecutive patients hospitalized for HF who were prescribed phase I cardiac rehabilitation (CR) from November 2017 to April 2019. WRF was defined as a relative increase from baseline in serum creatinine of 25% or that in serum creatinine ≥ 0.3 mg/dL during hospitalization. The indices of ADL and physical function were the functional independence measure (FIM), short physical performance battery (SPPB) and 10-m comfortable gait speed as assessed at discharge. We compared background factors, clinical parameters, walking level before hospitalization, physical function, and FIM in two groups. Multiple regression analysis was performed with FIM at discharge as the dependent variable and items with P < 0.05 in bivariate correlation as independent variables. Ultimately, 160 patients were included and divided into the WRF group (n = 72) and non-WRF group (n = 88). FIM, SPPB, and 10-m comfortable walking speed were significantly lower in the WRF group. Moreover, even after adjustment for confounding factors (age, Hb, eGFR, CKD, GNRI, start day of standing), eGFR on admission (β = 0.12), WRF (β =  - 6.42) and walking level before hospitalization (β = - 10.00) were independent factors of ADL decline at discharge (adjusted R² = 0.46). WRF during hospitalization of elderly HF patients was a factor affecting ADL decline at discharge along with walking level before hospitalization and renal function at admission.

The Prognostic Impact of Circulating Regulatory T Lymphocytes on Mortality in Patients with Ischemic Heart Failure with Reduced Ejection Fraction

Background

Heart failure with reduced ejection fraction (HFrEF) constitutes a global health issue. While proinflammatory cytokines proved to have a pivotal role in the development and progression of HFrEF, less attention has been paid to the cellular immunity. Regulatory T lymphocytes (Tregs) seem to have an important role in the induction and maintenance of immune homeostasis. Therefore, we aimed to investigate the impact of Tregs on the outcome in HFrEF.

Methods

We prospectively enrolled 112 patients with HFrEF and performed flow cytometry for cell phenotyping. Individuals were stratified in ischemic (iHFrEF, n = 57) and nonischemic etiology (niHFrEF, n = 57) and nonischemic etiology (niHFrEF,

Results

Comparing patients with iHFrEF to niHFrEF, we found a significantly lower fraction of Tregs within lymphocytes in the ischemic subgroup (0.42% vs. 0.56%; p = 0.009). After a mean follow-up time of 4.5 years, 32 (28.6%) patients died due to cardiovascular causes. We found that Tregs were significantly associated with cardiovascular survival in the entire study cohort with an adjusted HR per one standard deviation (1-SD) of 0.60 (95% CI: 0.39-0.92; p = 0.009). After a mean follow-up time of 4.5 years, 32 (28.6%) patients died due to cardiovascular causes. We found that Tregs were significantly associated with cardiovascular survival in the entire study cohort with an adjusted HR per one standard deviation (1-SD) of 0.60 (95% CI: 0.39-0.92; p = 0.009). After a mean follow-up time of 4.5 years, 32 (28.6%) patients died due to cardiovascular causes. We found that Tregs were significantly associated with cardiovascular survival in the entire study cohort with an adjusted HR per one standard deviation (1-SD) of 0.60 (95% CI: 0.39-0.92; p = 0.009). After a mean follow-up time of 4.5 years, 32 (28.6%) patients died due to cardiovascular causes. We found that Tregs were significantly associated with cardiovascular survival in the entire study cohort with an adjusted HR per one standard deviation (1-SD) of 0.60 (95% CI: 0.39-0.92;

Conclusion

Our results indicate a potential influence of Tregs in the pathogenesis and progression of iHFrEF, fostering the implication of cellular immunity in iHFrEF pathophysiology and proving Tregs as a predictor for long-term survival among iHFrEF patients. A preview of this study has been presented at a meeting of the European Society of Cardiology earlier this year.

Curcumin improves exercise performance of mice with coronary artery ligation-induced HFrEF: Nrf2 and antioxidant mechanisms in skeletal muscle

A hallmark of chronic heart failure (HF) with low ejection fraction (HFrEF) is exercise intolerance. We hypothesized that reduced expression of nuclear factor E2-related factor 2 (Nrf2) in skeletal muscle contributes to impaired exercise performance. We further hypothesized that curcumin, a Nrf2 activator, would preserve or increase exercise capacity in HF. Experiments were carried out in mice with coronary artery ligation-induced HFrEF. Curcumin was deliveried by a subcutaneous osmotic minipump at a dose of 50 mg·kg^-1·day^-1 for 8 weeks. In vivo, in situ, and in vitro experiments were employed to evaluate exercise capacity, muscle function, and molecular mechanisms. We found that: 1) the maximal speed, running distance to exhaustion, and limb grip force were significantly lower in HFrEF mice compared with sham. Curcumin-treated HF mice displayed enhanced exercise performance compared with vehicle-treated HF mice; 2) both soleus (Sol) and extensor digitorum longus (EDL) muscles of HFrEF mice exhibited reduced force and rapid fatigue, which were ameliorated by curcumin; and 3) protein expression of Nrf2, hemeoxygenase-1, SOD2, myogenin, and MyoD were significantly lower, but total ubiquitinated proteins, MURF1, and atrogen-1 were higher in Sol and EDL of HFrEF compared with sham mice, whereas these alterations in Nrf2 signaling and antioxidant defenses in HFrEF were attenuated by curcumin, which had no effect on cardiac function per se in mice with severe HFrEF. These data suggest that impaired Nrf2 signaling intrinsic to skeletal muscle contributes to exercise intolerance in HFrEF. Skeletal muscle Nrf2 should be considered as a novel therapeutic target in severe HF. NEW & NOTEWORTHY These studies suggest that impaired nuclear factor E2-related factor 2 (Nrf2) signaling is a critical mechanism underlying the enhanced oxidative stress in skeletal muscle in heart failure with low ejection fraction (HFrEF). Curcumin prevents the decline in running performance in HFrEF mice by upregulating antioxidant defenses in skeletal muscle, likely mediated by activating Nrf2 signaling. These findings suggest a novel therapeutic target for the improvement of exercise capacity and quality of life in HFrEF patients.

Effect of Xanthine Oxidase Inhibition on Arterial Stiffness in Patients With Chronic Heart Failure

BACKGROUND

The xanthine oxidase inhibitor allopurinol improves endothelial function in different populations, including patients with chronic heart failure (CHF). Its effect on arterial stiffness parameters is less clear. We investigated the effect of short-term low-dose allopurinol therapy on arterial stiffness in Saudi patients with stable mild-moderate CHF.

METHODS

A prospective, randomized, double-blind, placebo-controlled study was performed on 73 patients with mild-moderate CHF. In all, 36 patients were randomized to allopurinol 300 mg daily for 3 months, while 37 patients were randomized to placebo. Arterial stiffness parameters, aortic pulse wave velocity (Ao-PWV) and heart rate corrected augmentation index (c-AIx), were assessed before and after treatment along with serum uric acid.

RESULTS

A total of 66 patients completed the study. Both groups were matched for age, sex, severity of heart failure, and arterial stiffness. Compared with placebo, allopurinol recipients had a significant fall in uric acid concentration from 6.31 ± 1.4 (SD) mg/dL to 3.81 ± 1.2 (P < .001). Despite that, there was no significant change in arterial stiffness parameters between allopurinol and placebo groups. Post-treatment Ao-PWV was 9.79 ± 2.6 m/s in the allopurinol group and 10.07 ± 3.4 m/s in the placebo group, P = .723. Post-treatment c-AIx was 24.0% ± 9.1% and 22.0% ± 9.9%, respectively, P = .403.

CONCLUSIONS

We have shown that allopurinol significantly reduced uric acid concentration in Saudi patients with CHF but was not associated with a change in arterial stiffness. Our cohort of patients had worse arterial stiffness values at baseline, which might make them more resistant to change using our study regimen.The study has been registered with the International Standard Randomized Controlled Trial Number registry with an identifier number of ISRCTN58980230.

Body temperature regulation and drugs of abuse

Phenethylamine-induced hyperthermia can occur following exposure to several different types of illicit stimulants, such as amphetamine, methamphetamine, 3,4-methylenedioxymethamphetamine ("Molly"), synthetic cathinones ("bath salts"), and N-methoxybenyl ("NBOMe"), to name a few. Peripheral norepinephrine release mediated by these sympathomimetic agents induces a double-edged sword of heat accumulation through β-adrenoreceptor-dependent activation of uncoupling protein (UCP1 and 3)-regulated thermogenesis and loss of heat dissipation through α₁-adrenoreceptor-mediated vasoconstriction. Additionally, thyroid hormones are important determinants of the capacity of thermogenesis induced by phenethylamines through the regulation of free fatty acid release and the transcriptional activation of a host of metabolic genes, including adrenergic receptors and mitochondrial uncoupling proteins. Here, we review the central and peripheral mechanistic "triggers" of phenethylamine-induced hyperthermia and outline potential pharmacologic interventions for managing phenethylamine-induced hyperthermia based on these recently discovered hyperthermia mediators.

Inflammation - Cause or Consequence of Heart Failure or Both?

PURPOSE OF REVIEW

With the intention to summarize the currently available evidence on the pathophysiological relevance of inflammation in heart failure, this review addresses the question whether inflammation is a cause or consequence of heart failure, or both.

RECENT FINDINGS

This review discusses the diversity (sterile, para-inflammation, chronic inflammation) and sources of inflammation and gives an overview of how inflammation (local versus systemic) can trigger heart failure. On the other hand, the review is outlined how heart failure-associated wall stress and signals released by stressed, malfunctioning, or dead cells (DAMPs: e.g., mitochondrial DNA, ATP, S100A8, matricellular proteins) induce cardiac sterile inflammation and how heart failure provokes inflammation in various peripheral tissues in a direct (inflammatory) and indirect (hemodynamic) manner. The crosstalk between the heart and peripheral organs (bone marrow, spleen, gut, adipose tissue) is outlined and the importance of neurohormonal mechanisms including the renin angiotensin aldosteron system and the ß-adrenergic nervous system in inflammation and heart failure is discussed. Inflammation and heart failure are strongly interconnected and mutually reinforce each other. This indicates the difficulty to counteract inflammation and heart failure once this chronic vicious circle has started and points out the need to control the inflammatory process at an early stage avoiding chronic inflammation and heart failure. The diversity of inflammation further addresses the need for a tailored characterization of inflammation enabling differentiation of inflammation and subsequent target-specific strategies. It is expected that the characterization of the systemic and/or cardiac immune profile will be part of precision medicine in the future of cardiology.

Mitochondrial dysfunction and oxidative stress in metabolic disorders - A step towards mitochondria based therapeutic strategies

Mitochondria are the powerhouses of the cell and are involved in essential functions of the cell, including ATP production, intracellular Ca2+ regulation, reactive oxygen species production & scavenging, regulation of apoptotic cell death and activation of the caspase family of proteases. Mitochondrial dysfunction and oxidative stress are largely involved in aging, cancer, age-related neurodegenerative and metabolic syndrome. In the last decade, tremendous progress has been made in understanding mitochondrial structure, function and their physiology in metabolic syndromes such as diabetes, obesity, stroke and hypertension, and heart disease. Further, progress has also been made in developing therapeutic strategies, including lifestyle interventions (healthy diet and regular exercise), pharmacological strategies and mitochondria-targeted approaches. These strategies were mainly focused to reduce mitochondrial dysfunction and oxidative stress and to maintain mitochondrial quality in metabolic syndromes. The purpose of our article is to highlight the recent progress on the mitochondrial role in metabolic syndromes and also summarize the progress of mitochondria-targeted molecules as therapeutic targets to treat metabolic syndromes. This article is part of a Special Issue entitled: Oxidative Stress and Mitochondrial Quality in Diabetes/Obesity and Critical Illness Spectrum of Diseases - edited by P. Hemachandra Reddy.

Therapeutic Strategies for Mitochondrial Dysfunction and Oxidative Stress in Age-Related Metabolic Disorders

Mitochondria are complex, intercellular organelles present in the cells and are involved in multiple roles including ATP formation, free radicals generation and scavenging, calcium homeostasis, cellular differentiation, and cell death. Many studies depicted the involvement of mitochondrial dysfunction and oxidative damage in aging and pathogenesis of age-related metabolic disorders and neurodegenerative diseases. Remarkable advancements have been made in understanding the structure, function, and physiology of mitochondria in metabolic disorders such as diabetes, obesity, cardiovascular diseases, and stroke. Further, much progress has been done in the improvement of therapeutic strategies, including lifestyle interventions, pharmacological, and mitochondria-targeted therapeutic approaches. These strategies were mainly focused to reduce the mitochondrial dysfunction caused by oxidative stress and to retain the mitochondrial health in various diseases. In this chapter, we have highlighted the involvement of mitochondrial dysfunction in the pathophysiology of various disorders and recent progress in the development of mitochondria-targeted molecules as therapeutic measures for metabolic disorders.

Aldosterone and cardiovascular remodelling: focus on myocardial failure

Heart failure is a clinical syndrome that may result from different disease states or conditions that injure the myocardium. The activation of circulating neurohormones, particularly aldosterone, may play a pivotal role in left ventricular (LV) remodelling. The Randomized Aldactone Evaluation Study and Eplerenone Post-Acute Myocardial Infarction Heart Failure Efficacy and Survival trial have emphasised the clinical importance of aldosterone. This review addresses some of the proposed mechanisms of LV remodelling in heart failure.

Wnt/β-Catenin Signaling Contributes to Skeletal Myopathy in Heart Failure via Direct Interaction With Forkhead Box O

Background—

There are changes in the skeletal muscle of patients with chronic heart failure (CHF), such as volume reduction and fiber type shift toward fatigable type IIb fiber. Forkhead box O (FoxO) signaling plays a critical role in the development of skeletal myopathy in CHF, and functional interaction between FoxO and the Wnt signal mediator β-catenin was previously demonstrated. We have recently reported that serum of CHF model mice activates Wnt signaling more potently than serum of control mice and that complement C1q mediates this activation. We, therefore, hypothesized that C1q-induced activation of Wnt signaling plays a critical role in skeletal myopathy via the interaction with FoxO.

Methods and Results—

Fiber type shift toward fatigable fiber was observed in the skeletal muscle of dilated cardiomyopathy model mice, which was associated with activation of both Wnt and FoxO signaling. Wnt3a protein activated FoxO signaling and induced fiber type shift toward fatigable fiber in C2C12 cells. Wnt3a-induced fiber type shift was inhibited by suppression of FoxO1 activity, whereas Wnt3a-independent fiber type shift was observed by overexpression of constitutively active FoxO1. Serum of dilated cardiomyopathy mice activated both Wnt and FoxO signaling and induced fiber type shift toward fatigable fiber in C2C12 cells. Wnt inhibitor and C1-inhibitor attenuated FoxO activation and fiber type shift both in C2C12 cells and in the skeletal muscle of dilated cardiomyopathy mice.

Conclusions—

C1q-induced activation of Wnt signaling contributes to fiber type shift toward fatigable fiber in CHF. Wnt signaling may be a novel therapeutic target to prevent skeletal myopathy in CHF.

Mitochondrial dysfunction in skeletal muscle during experimental Chagas disease

Trypanosoma cruzi invasion and replication in cardiomyocytes and other tissues induce cellular injuries and cytotoxic reactions, with the production of inflammatory cytokines and nitric oxide, both sources of reactive oxygen species. The myocyte response to oxidative stress involves the progression of cellular changes primarily targeting mitochondria. Similar alterations could be taking place in mitochondria from the skeletal muscle; if that is the case, a simple skeletal muscle biopsy would give information about the cardiac energetic production that could be used as a predictor of the chagasic cardiopathy evolution. Therefore, in the present paper we studied skeletal muscle mitochondrial structure and the enzymatic activity of citrate synthase and respiratory chain complexes I to IV (CI-CIV), in Albino Swiss mice infected with T. cruzi, Tulahuen strain and SGO Z12 and Lucky isolates, along the infection. Changes in the mitochondrial structure were detected in 100% of the mitochondria analyzed from the infected groups: they all presented at least 1 significant abnormality such as increase in their matrix or disorganization of their cristae, which are probably related to the enzymatic dysfunction. When we studied the Krebs cycle functionality through the measurement of the specific citrate synthase activity, we found it to be significantly diminished during the acute phase of the infection in Tulahuen and SGO Z12 infected groups with respect to the control one; citrate synthase activity from the Lucky group was significantly increased (p<0.05). The activity of this enzyme was reduced in all the infected groups during the chronic asymptomatic phase (p<0.001) and return to normal values (Tulahuen and SGO Z12) or increased its activity (Lucky) by day 365 post-infection (p.i.). When the mitochondrial respiratory chain was analyzed from the acute to the chronic phase of the infection through the measurement of the activity of complexes I to IV, the activity of CI remained similar to control in Tulahuen and Lucky groups, but was significantly augmented in the SGO Z12 one in the acute and chronic phases (p<0.05). CII increased its activity in Tulahuen and Lucky groups by day 75 p.i. and in SGO Z12 by day 365 p.i. (p<0.05). CIII showed a similar behavior in the 3 infected groups, remaining similar to control values in the first two stages of the infection and significantly increasing later on (p<0.0001). CIV showed an increase in its activity in Lucky throughout all stages of infection (p<0.0001) and an increase in Tulahuen by day 365days p.i. (p<0.0001); SGO Z12 on the other hand, showed a decreased CIV activity at the same time. The structural changes in skeletal muscle mitochondria and their altered enzyme activity began in the acute phase of infection, probably modifying the ability of mitochondria to generate energy; these changes were not compensated in the rest of the phases of the infection. Chagas is a systemic disease, which produces not only heart damage but also permanent skeletal muscle alterations.

Ventricular assist device implantation improves skeletal muscle function, oxidative capacity, and growth hormone/insulin-like growth factor-1 axis signaling in patients with advanced heart failure

BACKGROUND

Skeletal muscle dysfunction in patients with heart failure (HF) has been linked to impaired growth hormone (GH)/insulin-like growth factor (IGF)-1 signaling. We hypothesized that ventricular assist device (VAD) implantation reverses GH/IGF-1 axis dysfunction and improves muscle metabolism in HF.

METHODS

Blood and rectus abdominis muscle samples were collected during VAD implantation and explantation from patients with HF and controls. Clinical data were obtained from medical records, biomarkers measured by enzyme-linked immunosorbent assay (ELISA), and gene expression analyzed by reverse transcription and real-time polymerase chain reaction (RT-PCR). Grip strength was assessed by dynamometry. Oxidative capacity was measured using oleate oxidation rates. Muscle fiber type and size were assessed by histology.

RESULTS

Elevated GH (0.27 ± 0.27 versus 3.6 ± 7.7 ng/ml in HF; p = 0.0002) and lower IGF-1 and insulin-like growth factor binding protein (IGFBP)-3 were found in HF (IGF-1, 144 ± 41 versus 74 ± 45 ng/ml in HF, p < 0.05; and IGFBP-3, 3,880 ± 934 versus 1,935 ± 862 ng/ml in HF, p = 0.05). The GH/IGF-1 ratio, a marker of GH resistance, was elevated in HF (0.002 ± 0.002 versus 0.048 ± 0.1 pre-VAD; p < 0.0039). After VAD support, skeletal muscle expression of IGF-1 and IGFBP-3 increased (10-fold and 5-fold, respectively; p < 0.05) accompanied by enhanced oxidative gene expression (CD36, CPT1, and PGC1α) and increased oxidation rates (+1.37-fold; p < 0.05). Further, VAD implantation increased the oxidative muscle fiber proportion (38 versus 54 %, p = 0.031), fiber cross-sectional area (CSA) (1,005 ± 668 versus 1,240 ± 670 μm(2), p < 0.001), and Akt phosphorylation state in skeletal muscle. Finally, hand grip strength increased 26.5 ± 27.5 % at 180 days on-VAD (p < 0.05 versus baseline).

CONCLUSION

Our data demonstrate that VAD implantation corrects GH/IGF-1 signaling, improves muscle structure and function, and enhances oxidative muscle metabolism in patients with advanced HF.

Heart failure and mitochondrial dysfunction: the role of mitochondrial fission/fusion abnormalities and new therapeutic strategies

The treatment of heart failure (HF) has evolved during the past 30 years with the recognition of neurohormonal activation and the effectiveness of its inhibition in improving the quality of life and survival. Over the past 20 years, there has been a revolution in the investigation of the mitochondrion with the development of new techniques and the finding that mitochondria are connected in networks and undergo constant division (fission) and fusion, even in cardiac myocytes. This has led to new molecular and cellular discoveries in HF, which offer the potential for the development of new molecular-based therapies. Reactive oxygen species are an important cause of mitochondrial and cellular injury in HF, but there are other abnormalities, such as depressed mitochondrial fusion, that may eventually become the targets of at least episodic treatment. The overall need for mitochondrial fission/fusion balance may preclude sustained change in either fission or fusion. In this review, we will discuss the current HF therapy and its impact on the mitochondria. In addition, we will review some of the new drug targets under development. There is potential for effective, novel therapies for HF to arise from new molecular understanding.

The influence of low-level laser therapy on parameters of oxidative stress and DNA damage on muscle and plasma in rats with heart failure

In heart failure (HF), there is an imbalance between the production of reactive oxygen species and the synthesis of antioxidant enzymes, causing damage to the cardiovascular function and increased susceptibility to DNA damage. The aim of this study was to evaluate the influence of low-level laser therapy (LLLT) on parameters of oxidative stress and DNA damage in skeletal muscle and plasma of rats with HF. Wistar rats were allocated into six groups: "placebo" HF rats (P-HF, n = 9), "placebo" Sham rats (P-sham, n = 8), HF rats at a dose 3 J/cm(2) of LLLT (3 J/cm(2)-HF, n = 8), sham rats at a dose 3 J/cm(2) of LLLT (3 J/cm(2)-sham, n = 8), HF rats at a dose 21 J/cm(2) of LLLT (21 J/cm(2)-HF, n = 8) and sham rats at a dose 21 J/cm(2) of LLLT (21 J/cm(2)-sham, n = 8). Animals were submitted to a LLLT protocol for 10 days at the right gastrocnemius muscle. Comparison between groups showed a significant reduction in superoxide dismutase (SOD) activity in the 3 J/cm(2)-HF group (p = 0.03) and the 21 J/cm(2)-HF group (p = 0.01) compared to the P-HF group. 2',7'-Dihydrodichlorofluorescein (DCFH) oxidation levels showed a decrease when comparing 3 J/cm(2)-sham to P-sham (p = 0.02). The DNA damage index had a significant increase either in 21 J/cm(2)-HF or 21 J/cm(2)-sham in comparison to P-HF (p = 0.004) and P-sham (p = 0.001) and to 3 J/cm(2)-HF (p = 0.007) and 3 J/cm(2)-sham (p = 0.037), respectively. Based on this, laser therapy appears to reduce SOD activity and DCFH oxidation levels, changing the oxidative balance in the skeletal muscle of HF rats. Otherwise, high doses of LLLT seem to increase DNA damage.

Functional and structural alterations of cardiac and skeletal muscle mitochondria in heart failure patients

BACKGROUND AND AIMS

The fundamental mechanisms involved in the genesis and progression of heart failure are not clearly understood. The present study was conducted to analyze the cardiac mitochondrial involvement in heart failure, the possible parallelism between cardiac and skeletal muscle and if there is a link between clinical symptoms and mitochondrial damage.

METHODS

Left ventricle and pectoral biopsies were obtained from patients with heart failure (n: 21) and patients with inter-auricular communication as the unique diagnosis for surgery (n: 6). Mitochondria were isolated from these tissues and studied through electron microscopy, spectrophotometry to measure the activity of respiratory complex III and immunohistochemistry to determine the presence of reactive oxygen species.

RESULTS

More than 90% of cardiac and skeletal muscle mitochondria presented structural and functional alterations in relation to an increment in the reactive oxygen species production, even in patients without the presence of any clinical Framingham criteria.

CONCLUSIONS

We demonstrated some parallelism between cardiac and skeletal muscle mitochondrial alterations in patients with heart failure and that these alterations begin before the major clinical Framingham criteria are installed, pointing to mitochondria as one of the possibly responsible factors for the evolution of cardiac disease.

Mitochondrial proteome remodeling in ischemic heart failure

AIMS

Mitochondrial dysfunction is an important part of the decline in cardiac function in heart failure. We hypothesized for hypothesized that there would be specific abnormalities in mitochondrial function and proteome with the progression of ischemic heart failure (HF).

MAIN METHODS

We used a high left anterior descending artery (LAD) ligation in 3-4month old male rats to generate HF. Rats were studied 9weeks post-ligation.

KEY FINDINGS

Electron microscopy of left ventricle samples showed mitochondrial changes including decreased size, increased number, abnormal distribution, and cristae loss. Mitochondria in ischemic HF exhibited decreased total ATP, impaired mitochondrial respiration, as well as reduced complex I activity. Analysis of LV mitochondrial proteins by mass spectrometry was performed, and 31 differentially expressed proteins (p<0.05) of more than 500 total proteins were identified. Of these proteins, 15 were up-regulated and 16 were down-regulated in the failing heart. A set of complex I proteins was significantly decreased, consistent with the impairment of complex I activity. There were distinct changes in mitochondrial function and proteome in ischemic HF. Although there were similarities, the distinction between the reported proteomic changed with TAC pressure overload induced HF and ischemic HF in the current study suggested different pathological mechanisms.

SIGNIFICANCE

Specific changes in mitochondrial protein expression, which correlate with changes in mitochondrial function, have been identified in ischemic HF for the first time.

The cardiorenal syndrome in heart failure: cardiac? renal? syndrome?

There has been increasing interest on the so-called cardiorenal syndrome (CRS), defined as a complex pathophysiological disorder of the heart and kidneys whereby acute or chronic dysfunction in one organ may induce acute or chronic dysfunction in the other. In this review, we contend that there is lack of evidence warranting the adoption of a specific clinical construct such as the CRS within the heart failure (HF) syndrome by demonstrating that: (a) the approaches and tools regarding the definition of kidney involvement in HF are suboptimal; (b) development of renal failure in HF is often confounded by age, hypertension, and diabetes; (c) worsening of renal function (WRF) in HF may be largely independent of alterations in cardiac function; (d) the bidirectional association between HF and renal failure is not unique and represents one of the several such associations encountered in HF; and (e) inflammation is a common denominator for HF and associated noncardiac morbidities. Based on these arguments, we believe that dissecting one of the multiple bidirectional associations in HF and constructing the so-called cardiorenal syndrome is not justified pathophysiologically. Fully understanding of all morbid associations and not only the cardiorenal is of great significance for the clinician who is caring for the patient with HF.

Effects of shear stresses and antioxidant concentrations on the production of reactive oxygen species in lung cancer cells

Reactive oxygen species (ROS) are known to be a key factor in the development of cancer, and many exogenous sources are supposed to be related to the formation of ROS. In this paper, a microfluidic chip was developed for studying the production of ROS in lung cancer cells under different chemical and physical stimuli. This chip has two unique features: (1) five relative concentrations of 0, 1/8, 1/2, 7/8, and 1 are achieved in the culture regions; (2) a shear stress gradient is produced inside each of the five culture areas. Lung cancer cells were seeded inside this biocompatible chip for investigating their response to different concentrations of H2O2, a chemical stimulus known to increase the production of ROS. Then the effect of shear stress, a physical stimulus, on lung cancer cells was examined, showing that the production of ROS was increased in response to a larger shear stress. Finally, two antioxidants, α-tocopherol and ferulic acid, were used to study their effects on reducing ROS. It was found that high-dose α-tocopherol was not able to effectively eliminate the ROS produced inside cells. This counter effect was not observed in cells cultured in a traditional chamber slide, where no shear stress was present. This result suggests that the current microfluidic chip provides an in vitro platform best mimicking the physiological condition where cells are under circulating conditions.

Angiotensin II-induced reduction in exercise capacity is associated with increased oxidative stress in skeletal muscle

Angiotensin II (ANG II)-induced oxidative stress has been known to be involved in the pathogenesis of cardiovascular diseases. We have reported that the oxidative stress in skeletal muscle can limit exercise capacity in mice ( 16 ). We thus hypothesized that ANG II could impair the skeletal muscle energy metabolism and limit exercise capacity via enhancing oxidative stress. ANG II (50 ng·kg−1·min−1) or vehicle was infused into male C57BL/6J mice for 7 days via subcutaneously implanted osmotic minipumps. ANG II did not alter body weight, skeletal muscle weight, blood pressure, cardiac structure, or function. Mice were treadmill tested, and expired gases were analyzed. The work to exhaustion (vertical distance × body weight) and peak oxygen uptake were significantly decreased in ANG II compared with vehicle. In mitochondria isolated from skeletal muscle, ADP-dependent respiration was comparable between ANG II and vehicle, but ADP-independent respiration was significantly increased in ANG II. Furthermore, complex I and III activities were decreased in ANG II. NAD(P)H oxidase activity and superoxide production by lucigenin chemiluminescence were significantly increased in skeletal muscle from ANG II mice. Treatment of ANG II mice with apocynin (10 mmol/l in drinking water), an inhibitor of NAD(P)H oxidase activation, completely inhibited NAD(P)H oxidase activity and improved exercise capacity, mitochondrial respiration, and complex activities in skeletal muscle. ANG II-induced oxidative stress can impair mitochondrial respiration in skeletal muscle and limit exercise capacity.

Immunoglobulin treatment ameliorates myocardial injury in experimental autoimmune myocarditis associated with suppression of reactive oxygen species

AIMS

We tested the hypothesis that immunoglobulin ameliorated experimental autoimmune myocarditis (EAM) in mice attributing to the suppression of reactive oxygen species (ROS)-mediated myocardial injury.

METHODS

We intraperitoneally administered intact type of human immunoglobulin (Ig) or F(ab')2 fragments of human immunoglobulin, 1g/kg/day daily for 3 weeks, to male BALB/c mice with heart failure due to EAM.

RESULTS

The results showed that intact type of Ig, but not F(ab')2 type, reduced the severity of myocarditis by comparing the heart weight/body weight and lung weight/body weight ratios, pericardial effusion score, macroscopic and microscopic scores. Tissue superoxide production was marked in untreated mice with EAM, which was suppressed by the treatment of immunoglobulins. The cytotoxic activities of lymphocytes in mice with EAM treated with Ig were reduced compared with untreated controls. The shift from Th1 toward Th2 cytokine balance was demonstrated by the treatment of immunoglobulins both in vitro and in vivo.

CONCLUSION

ROS may be involved in the development of myocarditis. Intact Ig ameliorates myocardial damage in mice with myocarditis associated with suppression of ROS and cytotoxic activity of lymphocytes.

Oxidative stress and enhanced sympathetic vasoconstriction in contracting muscles of nitrate-tolerant rats and humans

Sympathetic vasoconstriction is normally attenuated in exercising muscle, but this functional sympatholysis is impaired in rats with hypertension or heart failure due to elevated levels of reactive oxygen species (ROS) in muscle. Whether ROS have a similar effect in the absence of cardiovascular disease or whether these findings extend to humans is not known. We therefore tested the hypothesis that chronic treatment with nitroglycerin (NTG) to induce nitrate tolerance, which is associated with excessive ROS production, impairs functional sympatholysis in healthy rats and humans. NTG treatment increased ethidium fluorescence in rat muscles and urinary F(2)-isoprostanes in humans, demonstrating oxidative stress. In vehicle-treated rats, sympathetic nerve stimulation (1 to 5 Hz) evoked decreases in femoral vascular conductance at rest (range, -30 to -63%) that were attenuated during hindlimb contraction (range, -2 to -31%; P < 0.05). In NTG-treated rats, vasoconstrictor responses were similar at rest, but were enhanced during contraction (range, -17 to -50%; P < 0.05 vs. vehicle). Infusion of the ROS scavenger tempol restored sympatholysis in these rats. In humans, reflex sympathetic activation during lower body negative pressure (LBNP) evoked decreases in muscle oxygenation in resting forearm (-12 ± 1%) that were attenuated during handgrip exercise (-3 ± 1%; P < 0.05). When these subjects became nitrate tolerant, LBNP-induced decreases in muscle oxygenation were unaffected at rest, but were enhanced during exercise (-9 ± 1%; P < 0.05 vs. before NTG). Collectively, these data indicate that functional sympatholysis is impaired in otherwise healthy nitrate-tolerant rats and humans by a mechanism probably involving muscle oxidative stress.

Cardiovascular regulation by skeletal muscle reflexes in health and disease

Heart rate and blood pressure are elevated at the onset and throughout the duration of dynamic or static exercise. These neurally mediated cardiovascular adjustments to physical activity are regulated, in part, by a peripheral reflex originating in contracting skeletal muscle termed the exercise pressor reflex. Mechanically sensitive and metabolically sensitive receptors activating the exercise pressor reflex are located on the unencapsulated nerve terminals of group III and group IV afferent sensory neurons, respectively. Mechanoreceptors are stimulated by the physical distortion of their receptive fields during muscle contraction and can be sensitized by the production of metabolites generated by working skeletal myocytes. The chemical by-products of muscle contraction also stimulate metaboreceptors. Once activated, group III and IV sensory impulses are transmitted to cardiovascular control centers within the brain stem where they are integrated and processed. Activation of the reflex results in an increase in efferent sympathetic nerve activity and a withdrawal of parasympathetic nerve activity. These actions result in the precise alterations in cardiovascular hemodynamics requisite to meet the metabolic demands of working skeletal muscle. Coordinated activity by this reflex is altered after the development of cardiovascular disease, generating exaggerated increases in sympathetic nerve activity, blood pressure, heart rate, and vascular resistance. The basic components and operational characteristics of the reflex, the techniques used in human and animals to study the reflex, and the emerging evidence describing the dysfunction of the reflex with the advent of cardiovascular disease are highlighted in this review.

Chronic heart failure and exercise intolerance: the hemodynamic paradox

Heart failure represents a major source of morbidity and mortality in industrialized nations. As the leading hospital discharge diagnosis in the United States in patients over the age of 65, it is also associated with substantial economic costs. While the acute symptoms of volume overload frequently precipitate inpatient admission, it is the symptoms of chronic heart failure, including fatigue, exercise intolerance and exertional dyspnea, that impact quality of life. Over the last two decades, research into the enzymatic, histologic and neurohumoral alterations seen with heart failure have revealed that hemodynamic derangements do not necessarily correlate with symptoms. This “hemodynamic paradox” is explained by alterations in the skeletal musculature that occur in response to hemodynamic derangements. Importantly, gender specific effects appear to modify both disease pathophysiology and response to therapy. The following review will discuss our current understanding of the systemic effects of heart failure before examining how exercise training and cardiac resynchronization therapy may impact disease course.

Oxidative stress impairs insulin signal in skeletal muscle and causes insulin resistance in postinfarct heart failure

Insulin resistance has been shown to occur as a consequence of heart failure. However, its exact mechanisms in this setting remain unknown. We have previously reported that oxidative stress is enhanced in the skeletal muscle from mice with heart failure after myocardial infarction (MI) (30). This study is aimed to investigate whether insulin resistance in postinfarct heart failure is due to the impairment of insulin signaling in the skeletal muscle caused by oxidative stress. Mice were divided into four groups: sham operated (sham); sham treated with apocynin, an inhibitor of NAD(P)H oxidase activation (10 mmol/l in drinking water); MI; and MI treated with apocynin. After 4 wk, intraperitoneal insulin tolerance tests were performed, and skeletal muscle samples were obtained for insulin signaling measurements. MI mice showed left ventricular dilation and dysfunction by echocardiography and increased left ventricular end-diastolic pressure and lung weight. The decrease in glucose level after insulin load significantly attenuated in MI compared with sham. Insulin-stimulated serine phosphorylation of Akt and glucose transporter-4 translocation were decreased in MI mice by 61 and 23%, respectively. Apocynin ameliorated the increase in oxidative stress and NAD(P)H oxidase activities measured by the lucigenin assay in the skeletal muscle after MI. It also improved insulin resistance and inhibited the decrease of Akt phosphorylation and glucose transporter-4 translocation. Insulin resistance was induced by the direct impairment of insulin signaling in the skeletal muscle from postinfarct heart failure, which was associated with the enhanced oxidative stress via NAD(P)H oxidase.

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.

Oxidative stress in cardiac and skeletal muscle dysfunction associated with diabetes mellitus

Diabetes mellitus increases the risk of heart failure independently of underlying coronary artery disease. It also causes skeletal muscle dysfunction, which is responsible for reduced exercise capacity commonly seen in heart failure. The underlying pathogenesis is partially understood. Several factors may contribute to the development of cardiac and skeletal muscle dysfunction in heart failure and diabetes mellitus. Based on the findings in animal models, this review discusses the role of oxidative stress that may be involved in the development and progression of cardiac and skeletal dysfunction associated with diabetes.

Effects of reactive oxygen species scavenger on the protective action of 100% oxygen treatment against sterile inflammation in mice

Sepsis/multiple organ dysfunction syndrome (MODS) is a major cause of high mortality in the intensive care unit. We have recently reported that 100% oxygen treatment is beneficial to mice with zymosan-induced sterile inflammation by increasing antioxidant enzymatic activities. Yet, the use of hyperoxia is hindered by concerns that it could exacerbate organ injury by increasing free radical formation. It is believed that systemic inflammation and overproduction of reactive oxygen species (ROS) contribute to the mechanism underlying sepsis/MODS. A ROS scavenger has been proven to protect against sepsis/MODS in some animal models. Therefore, we hypothesized that ROS scavenger pretreatment might enhance the protective action of 100% oxygen treatment against zymosan-induced sterile inflammation in mice. In the present study, we showed that 100% oxygen treatment prevented the abnormal changes in serum biochemical parameters, tissue oxygenation, and organ histopathology, and improved the 14-day survival rate in zymosan-stimulated mice, indicating that 100% oxygen treatment had a protective action on sterile inflammation. We found that pretreatment with a ROS scavenger (N-acetylcysteine, vitamin C, or dimethylthiourea) abolished this protective action of 100% oxygen treatment. We also showed that 100% oxygen treatment decreased the levels of serum proinflammatory cytokines (TNF-alpha, IL-6, and high-mobility group box 1), increased the level of serum anti-inflammatory cytokine (IL-10), and upregulated the activities of serum and tissue antioxidant enzymes (superoxide dismutase, catalase, and glutathione peroxidase) in zymosan-stimulated mice, which were reversed by the pretreatment with a ROS scavenger (N-acetylcysteine, vitamin C, or dimethylthiourea). We thus conclude that ROS scavenger pretreatment partly abolishes the protective effects of 100% oxygen treatment on sterile inflammation in mice by regulating inflammatory cytokines as well as antioxidant enzymes.

Oxidative stress and the muscle reflex in heart failure

Muscle contraction stimulates thin fibre muscle afferents and evokes a reflex increase in blood pressure. In heart failure (HF) this reflex is accentuated. Of note, superoxide and other reactive oxygen species are increased in HF. In this report, we tested the hypothesis that excess superoxide contributes to the exaggerated muscle reflex in HF. HF was induced in rats by coronary artery ligation. Electrically induced 30 s hindlimb muscle contraction in decerebrate rats with myocardial infarction (MI) (left ventricular fractional shortening (FS) = 24 +/- 1%; n = 15) evoked larger (P < 0.05) increases in mean arterial pressure (MAP) and renal sympathetic nerve activity (RSNA) as compared to control rats (FS = 47 +/- 1%; n = 14). In the MI rats, the pressor and RSNA responses to contraction were reduced by intra-arterial injection into the hindlimb circulation of tempol (10 mg), a superoxide dismutase mimetic (DeltaMAP: 22 +/- 2 vs. 11 +/- 1 mmHg; integral DeltaRSNA: 1032 +/- 204 vs. 431 +/- 73 arbitrary units (a.u.); before vs. after tempol; P < 0.05). Tempol also attenuated the RSNA response to 1 min intermittent (1-4 s stimulation to relaxation) bouts of static contraction in the MI rats (116 +/- 17 vs. 72 +/- 11 a.u.; P < 0.05; n = 16). In the control rats, tempol had no effect on these responses. These results suggest that excess superoxide in HF sensitizes mechanically sensitive muscle afferents engaged during contraction. We hypothesize that oxidative stress contributes to the exaggerated muscle reflex in HF.

Muscle wastage in heart failure: orphan of the heart failure

The patients with heart failure (HF) often exhibit some degree of muscle wasting restricted to the lower limbs. This loss of tissue may become more extensive in some patients, usually when their HF is more advanced, and may affect all body compartments. The underlying metabolic causes are very complex and differ from patient to patient. Three essential contributors are dietary deficiency and loss of nutrients through the digestive tract and metabolic dysfunction. The development of cachexia is an ominous sign and new drugs will be added into our therapeutic armamentarium to fight against cardiac cachexia in the near-future.

NADPH oxidase-derived reactive oxygen species in skeletal muscle modulates the exercise pressor reflex

Muscle metabolic by-products during exercise, such as K+, lactic acid, ATP, H+, and phosphate, are well established to be involved in the reflex cardiovascular response to static muscle contraction. However, the role of muscle reactive oxygen species (ROS), a metabolic by-product during muscle contraction, in the exercise pressor reflex (EPR) has not been investigated in detail. In the present study, we evaluated the role of muscle ROS in the EPR in a decerebrate rat model. We hypothesized that muscle NADPH oxidase-derived ROS contributes to sensitization of the EPR. Thus the rise in blood pressure and heart rate in response to a 30-s static contraction induced by electrical stimulation of L4/L5 ventral roots was compared before and after hindlimb arterial infusion of the redox agents: diethyldithiocarbamate, a superoxide dismutase inhibitor; the superoxide dismutase mimetic 4-hydroxy-2,2,6,6-tetramethyl piperidine 1-oxyl (tempol); the free radical scavenger dimethylthiourea; a NADPH oxidase inhibitor, apocynin; and a xanthine oxidase inhibitor, allopurinol. The EPR-induced pressor response was augmented after treatment with diethyldithiocarbamate and was attenuated after treatment with tempol, dimethylthiourea, and apocynin. Treatment with allopurinol did not affect the EPR function. None of the drug's affected the EPR heart rate response. In addition, neither the pressor response to electrical stimulation of the central end of dorsal roots, nor femoral blood flow was affected by any treatment. These data suggest that NADPH oxidase-derived muscle ROS plays an excitatory role in the EPR control of blood pressure.

Monitoring dynamic alterations in calcium homeostasis by T (1)-weighted and T (1)-mapping cardiac manganese-enhanced MRI in a murine myocardial infarction model

Manganese has been used as a T(1)-weighted MRI contrast agent in a variety of applications. Because manganese ions (Mn(2+)) enter viable myocardial cells via voltage-gated Ca(2+) channels, manganese-enhanced MRI is sensitive to the viability and inotropic state of the heart. In spite of the established importance of Ca(2+) regulation in the heart both before and after myocardial injury, monitoring strategies to assess Ca(2+) homeostasis in affected cardiac tissues are limited. This study implements a T(1)-mapping method to obtain quantitative information both dynamically and over a range of MnCl(2) infusion doses. To optimize the current Mn(2+) infusion protocols, we performed both dose-dependent and temporal washout studies. A non-linear relationship between infused MnCl(2) solution dose and increase in left ventricular wall relaxation rate (DeltaR(1)) was observed. Control mice also exhibited significant Mn(2+) clearance over time, with a decrease in DeltaR(1) of approximately 50% occurring in just 2.5 h. The complicated efflux time dependence possibly suggests multiple efflux mechanisms. With the use of the measured relationship between infused Mn(2+) dose, DeltaR(1), and inductively coupled plasma mass spectrometry data analysis provided a means of estimating the absolute heart Mn concentration in vivo. We show that this technique has the sensitivity to observe or monitor potential alterations in Ca(2+) handling in vivo because of the physiological remodeling after myocardial infarction. Left ventricular free wall DeltaR(1) values were significantly lower (P = 0.005) in the adjacent zone, surrounding the injured myocardial tissue, than in healthy tissue. This inferred reduction in Mn concentration can be used to estimate potentially salvageable myocardium in vivo for future treatment or evaluation of disease progression.

Mitochondrial oxidative stress and dysfunction in myocardial remodelling

Recent experimental and clinical studies have suggested that oxidative stress is enhanced in myocardial remodelling and failure. The production of oxygen radicals is increased in the failing heart, whereas normal antioxidant enzyme activities are preserved. Mitochondrial electron transport is an enzymatic source of oxygen radical generation and can be a therapeutic target against oxidant-induced damage in the failing myocardium. Chronic increases in oxygen radical production in the mitochondria can lead to a catastrophic cycle of mitochondrial DNA (mtDNA) damage as well as functional decline, further oxygen radical generation, and cellular injury. Reactive oxygen species induce myocyte hypertrophy, apoptosis, and interstitial fibrosis by activating matrix metalloproteinases. These cellular events play an important role in the development and progression of maladaptive myocardial remodelling and failure. Therefore, oxidative stress and mtDNA damage are good therapeutic targets. Overexpression of the genes for peroxiredoxin-3 (Prx-3), a mitochondrial antioxidant, or mitochondrial transcription factor A (TFAM), could ameliorate the decline in mtDNA copy number in failing hearts. Consistent with alterations in mtDNA, the decrease in mitochondrial function was also prevented. Therefore, the activation of Prx-3 or TFAM gene expression could ameliorate the pathophysiological processes seen in mitochondrial dysfunction and myocardial remodelling. Inhibition of oxidative stress and mtDNA damage could be novel and effective treatment strategies for heart failure.

Cinacalcet and the prevention of secondary hyperparathyroidism in rats with aldosteronism

BACKGROUND

In rats receiving aldosterone/salt treatment (ALDOST), increased Ca2+ excretion leads to a fall in plasma-ionized Ca2+ and appearance of secondary hyperparathyroidism (SHPT) with parathyroid hormone (PTH)-mediated intracellular Ca2+ overloading inducing oxidative stress in diverse tissues. Parathyroidectomy prevents this scenario. Rats with ALDOST were cotreated with cinacalcet (Cina), a calcimimetic that raises the threshold of the parathyroids' Ca(2+)-sensing receptor.

METHODS AND RESULTS

We monitored plasma-ionized [Ca2+]o, PTH, and total Ca2+ in heart and peripheral blood mononuclear cells (PBMC), and evidence of oxidative stress in heart, PBMC, and plasma. Cina-treated rats for 4 weeks were compared with 4 weeks of ALDOST alone and with untreated age-/gender-matched controls. In comparison to controls, ALDOST led to a fall (P < 0.05) in Ca2+ (1.16 +/- 0.01 vs 1.03 +/- 0.01 mmol/L), which was not prevented by Cina (1.01 +/- 0.03 mmol/L); a rise (P < 0.05) in plasma PTH (36 +/- 7 vs 134 +/- 19 pg/mL) that was attenuated by Cina (69 +/- 12 pg/mL); increased (P < 0.05) cardiac [Ca2+] (3.92 +/- 0.25 vs 6.78 +/- 0.35 nEq/mg FFDT) and PBMC [Ca2+]i (29.8 +/- 2.3 vs 50.2 +/- 2.3 nmol/L), each of which was prevented with Cina (3.65 +/- 0.10 nEq/mg FFDT and 32.5 +/- 6.0 nmol/L, respectively); increased cardiac MDA (0.56 +/- 0.03 vs 0.94+/-0.07 nmol/mg protein) and PBMC H2O2 production (63.5 +/- 7.5 vs 154.0 +/- 25.2 mcb) and reduced (P < 0.05) plasma alpha1-AP activity (39.8 +/- 0.6 vs 29.6 +/- 1.8 mM), each prevented by Cina (0.66 +/- 0.04 mmol/mg protein, 58.2 +/- 12.7 mcb and 37.0 +/- 1.2 mM, respectively).

CONCLUSIONS

PTH-mediated intracellular Ca2+ overloading accounts for the induction of oxidative stress in diverse tissues in rats with aldosteronism and which can be prevented by Cina.

Stressed out: the skeletal muscle ryanodine receptor as a target of stress

Over the past century, understanding the mechanisms underlying muscle fatigue and weakness has been the focus of much investigation. However, the dominant theory in the field, that lactic acidosis causes muscle fatigue, is unlikely to tell the whole story. Recently, dysregulation of sarcoplasmic reticulum (SR) Ca(2+) release has been associated with impaired muscle function induced by a wide range of stressors, from dystrophy to heart failure to muscle fatigue. Here, we address current understandings of the altered regulation of SR Ca(2+) release during chronic stress, focusing on the role of the SR Ca(2+) release channel known as the type 1 ryanodine receptor.

Skeletal muscle contractile protein function is preserved in human heart failure

Skeletal muscle weakness is a common finding in patients with chronic heart failure (CHF). This functional deficit cannot be accounted for by muscle atrophy alone, suggesting that the syndrome of heart failure induces a myopathy in the skeletal musculature. To determine whether decrements in muscle performance are related to alterations in contractile protein function, biopsies were obtained from the vastus lateralis muscle of four CHF patients and four control patients. CHF patients exhibited reduced peak aerobic capacity and knee extensor muscle strength. Decrements in whole muscle strength persisted after statistical control for muscle size. Thin filaments and myosin were isolated from biopsies and mechanically assessed using the in vitro motility assay. Isolated skeletal muscle thin-filament function, however, did not differ between CHF patients and controls with respect to unloaded shortening velocity, calcium sensitivity, or maximal force. Similarly, no difference in maximal force or unloaded shortening velocity of isolated myosin was observed between CHF patients and controls. From these results, we conclude that skeletal contractile protein function is unaltered in CHF patients. Other factors, such as a decrease in total muscle myosin content, are likely contributors to the skeletal muscle strength deficit of heart failure.

Mitochondrial-nuclear cross-talk in the aging and failing heart

HYPOTHESIS

Damage to heart mitochondrial structure and function occur with aging, and in heart failure (HF). However, the extent of mitochondrial dysfunction, the expression of mitochondrial and nuclear genes, and their cross-talk is not known.

OBSERVATIONS

Several observations have suggested that somatic mutations in mitochondrial DNA (mtDNA), induced by reactive oxygen species (ROS), appear to be the primary cause of energy decline, and that the generation of ROS is mainly the product of the mitochondrial respiratory chain. The free radical theory of aging, that could also be applied to HF, and in particular the targeting of mtDNA is supported by a plurality of observations from both animal and clinical studies showing decreased mitochondrial function, increased ROS levels and mtDNA mutations in the aging heart.

DISCUSSION

Aging and HF with their increased ROS-induced defects in mtDNA, including base modifications and frequency of mtDNA deletions, might be expected to cause increased errors or mutations in mtDNA-encoded enzyme subunits, resulting in impaired oxidative phosphorylation and defective electron transport chain (ETC) activity which in turn creates more ROS. These events in both the aging and failing heart involve substantial nuclear-mitochondrial interaction, which is further illustrated in the progression of myocardial apoptosis. In this review the cross-talk between the nucleus and the mitochondrial organelle will be examined based on a number of animal and clinical studies, including our own.

Influence of dietary fats on Ecstasy-induced hyperthermia

BACKGROUND AND PURPOSE

Studies were designed to examine the effects of dietary fats on metabolic effects of 3,4-methylenedioxymethamphetamine (MDMA, Ecstasy). These effects included hyperthermia, expression of uncoupling protein (UCP1 and 3) in brown adipose tissue or skeletal muscle and plasma free fatty acid (FFA) levels.

EXPERIMENTAL APPROACH

Male Sprague-Dawley rats were fed either a high-fat diet (HFD, 60% kcal) or a lower fat isocaloric controlled diet (LFD, 10% kcal) for 28 days before MDMA challenge.

KEY RESULTS

No significant differences were observed between LFD and HFD groups in terms of body weight, plasma thyroxine (T4) levels and expression of brown fat UCP1 or skeletal muscle UCP3 protein. HFD significantly raised levels of circulating FFA and potentiated the thermogenesis induced by MDMA (10 mg kg(-1), s.c.), compared to the effects of the LFD. Moreover, 30 and 60 min after MDMA administration, plasma FFA levels decreased in HFD animals, but were markedly elevated in the LFD group.

CONCLUSIONS AND IMPLICATIONS

These results indicate that high-fat feeding regulates MDMA-induced thermogenesis by augmenting the activation of UCP rather than its expression.

Micronutrients in African-Americans with decompensated and compensated heart failure

Heart failure is thought to be more common and of greater severity in African-Americans (AAs). Potential mechanisms remain uncertain. The importance of micronutrient deficiencies in the pathophysiologic expression of congestive heart failure (CHF) in AAs remains to be explored, including hypovitaminosis D, which can promote secondary hyperparathyroidism (SHPT), together with hypozincemia and hyposelenemia, the 2 most crucial trace minerals integral to diverse biologic functions. Serum parathyroid hormone (PTH), 25-hydroxyvitamin D (25(OH)D), Zn, and Se were monitored in 30 AAs hospitalized during June through December 2005, with decompensated failure and reduced ejection fraction (EF) (<35%) of predominantly nonischemic origin treated with an angiotensin-converting enzyme (ACE) inhibitor or an angiotensin receptor blocker (ARB), furosemide, and spironolactone. Based on their symptomatic status before hospitalization, 15 patients were stratified as having protracted (>or=4 weeks) CHF, whereas 15 patients had short-term (1-2 weeks) CHF. These hospitalized patients were compared with 10 AA outpatients with stable, similarly treated compensated failure and comparable EF, and 9 AA normal volunteers without cardiovascular disease. Serum PTH was elevated in all patients with protracted CHF and in 60% of patients with short-term CHF, but not in compensated patients or normal volunteers. However, serum 25(OH)D was reduced in all patients with >or=4 weeks and 80% with either 1-2 weeks CHF or compensated failure compared with volunteers. Serum Zn was below normal in 11 of 15 patients with protracted CHF, in 8 of 15 patients with shorter duration CHF, and in 5 of 10 patients with compensated failure. Serum Se was reduced in all patients with >or=4 weeks, 60% with short-term CHF, and 90% of compensated patients. Concomitant to hypovitaminosis D, hypozincemia, and hyposelenemia, SHPT is a covariant of CHF in housebound AAs.

Macro- and micronutrients in African-Americans with heart failure

An emerging body of evidence suggests secondary hyperparathyroidism (SHPT) may be an important covariant of congestive heart failure (CHF), especially in African-Americans (AA) where hypovitaminosis D is prevalent given that melanin, a natural sunscreen, mandates prolonged exposure of skin to sunlight and where a housebound lifestyle imposed by symptomatic CHF limits outdoor activities and hence sunlight exposure. In addition to the role of hypovitaminosis D in contributing to SHPT is the increased urinary and fecal losses of macronutrients Ca(2+) and Mg(2+) associated with the aldosteronism of CHF and their heightened urinary losses with furosemide treatment of CHF. Thus, a precarious Ca(2+) balance seen with reduced serum 25(OH)D is further compromised when AA develop CHF with circulating RAAS activation and are then treated with a loop diuretic. SHPT accounts for a paradoxical Ca(2+) overloading of diverse tissues and the induction of oxidative stress at these sites which spills over to the systemic circulation. In addition to SHPT, hypozincemia and hyposelenemia have been found in AA with compensated and decompensated heart failure and where an insufficiency of these micronutrients may have its origins in inadequate dietary intake, altered rates of absorption or excretion and/or tissue redistribution, and treatment with an ACE inhibitor or AT(1) receptor antagonist. Zn and Se deficiencies, which compromise the activity of several endogenous antioxidant defenses, could prove contributory to the severity of heart failure and its progressive nature. These findings call into question the need for nutriceutical treatment of heart failure and which is complementary to today's pharmaceuticals, especially in AA.

Diagnostic usefulness of B-type natriuretic peptide and functional consequences of muscle alterations in COPD and chronic heart failure

COPD affects up to one third of patients with chronic heart failure. The coexistence of COPD and chronic heart failure presents clinicians with diagnostic and therapeutic challenges. Measurement of B-type natriuretic peptide plasma levels facilitates the diagnosis of acute dyspnea in patients known to have both COPD and chronic heart failure. Patients with COPD or chronic heart failure have skeletal muscle abnormalities that limit functional capacity independently from primary organ failure. Exercise training reverses skeletal muscle abnormalities in patients with COPD or chronic heart failure and may be particularly indicated in patients with coexistent COPD and chronic heart failure.

Secondary hyperparathyroidism and hypovitaminosis D in African-Americans with decompensated heart failure

OBJECTIVE

We previously noted secondary hyperparathyroidism (SHPT) in African-American patients hospitalized during February, 2005 with either untreated or treated congestive heart failure (CHF) due to ischemic or idiopathic cardiomyopathy. Herein, we hypothesized that housebound African-American patients hospitalized during the period of June 1 through August 31, 2005, with CHF would have SHPT and hypovitaminosis D.

METHODS

Twenty-five African-American patients with an ejection fraction (EF) less than 35% due to ischemic or dilated (idiopathic) cardiomyopathy were monitored: 20 were hospitalized with CHF, stratified on historical grounds as of 4 weeks' or longer duration or of 1 to 2 weeks' duration in 11 and 9 patients, respectively, despite medical care that included furosemide; serum parathyroid hormone (PTH) and 25(OH)D at the time of admission in these patients were compared to five asymptomatic outpatients seen during the summer with stable, compensated failure.

RESULTS

Serum PTH was elevated (127 +/- 13; 82-243 pg/mL) in all patients with CHF of 4 weeks' or longer duration (normal, 12-65 pg/mL) and was elevated in three of nine patients (59 +/- 8; 18-99 pg/mL) with CHF of 1 to 2 weeks' duration. Ionized hypocalcemia (1.09 +/- 0.03 and 1.08 +/- 0.02 mmol/L; normal, 1.12-1.30) and hypomagnesemia (0.47 +/- 0.02 and 0.46 +/- 0.03 mmol/L; normal, 0.53-0.67) were respectively found in long- or short-duration CHF. No compensated patient had elevated PTH (42 +/- 5; 17-53). Hypovitaminosis D (< or =30 ng/mL) was universally present in patients with CHF of 4 weeks' or longer duration (15.1 +/- 1.4; 7.0-23.8 ng/mL) and was also prevalent in the other groups (20.3 +/- 5.1, 7.0-54.1 ng/mL in CHF of 1 to 2 weeks' duration and 23.1 +/- 4.9; 17.2-42.7 ng/mL in compensated failure).

CONCLUSIONS

In African-American patients with CHF, hypovitaminosis D, aldosteronism, and loop diuretic treatment each exaggerate Ca and Mg losses to stress a fragile Ca balance leading to ionized hypocalcemia and hypomagnesemia with SHPT.