Relation between oxidative stress, catecholamines, and impaired chronotropic response to exercise in patients with chronic heart failure secondary to ischemic or idiopathic dilated cardiomyopathy

The Impact of Pharmacotherapy for Heart Failure on Oxidative Stress-Role of New Drugs, Flozins

Heart failure (HF) is a multifactorial clinical syndrome involving many complex processes. The causes may be related to abnormal heart structure and/or function. Changes in the renin-angiotensin-aldosterone system, the sympathetic nervous system, and the natriuretic peptide system are important in the pathophysiology of HF. Dysregulation or overexpression of these processes leads to changes in cardiac preload and afterload, changes in the vascular system, peripheral vascular dysfunction and remodeling, and endothelial dysfunction. One of the important factors responsible for the development of heart failure at the cellular level is oxidative stress. This condition leads to deleterious cellular effects as increased levels of free radicals gradually disrupt the state of equilibrium, and, as a consequence, the internal antioxidant defense system is damaged. This review focuses on pharmacotherapy for chronic heart failure with regard to oxidation-reduction metabolism, with special attention paid to the latest group of drugs, SGLT2 inhibitors-an integral part of HF treatment. These drugs have been shown to have beneficial effects by protecting the antioxidant system at the cellular level.

Rate adaptive pacing in people with chronic heart failure increases peak heart rate but not peak exercise capacity: a systematic review

Rate adaptive cardiac pacing (RAP) allows increased heart rate (HR) in response to metabolic demand in people with implantable electronic cardiac devices (IECD). The aim of this work was to conduct a systematic review to determine if RAP increases peak exercise capacity (peak VO₂) in line with peak HR in people with chronic heart failure. We conducted a systematic literature search from 1980, when IECD and RAP were first introduced, until 31 July 2021. Databases searched include PubMed, Medline, EMBASE, EBSCO, and the Clinical Trials Register. A comprehensive search of the literature produced a total of 246 possible studies; of these, 14 studies were included. Studies and subsequent analyses were segregated according to comparison, specifically standard RAP (RAPON) vs fixed rate pacing (RAPOFF), and tailored RAP (TLD RAPON) vs standard RAP (RAPON). Pooled analyses were conducted for peak VO₂ and peak HR for RAPON vs RAPOFF. Peak HR significantly increased by 15 bpm with RAPON compared to RAPOFF (95%CI, 7.98-21.97, P < 0.0001). There was no significant difference between pacing mode for peak VO₂ 0.45 ml kg^-1 min^-1 (95%CI, - 0.55-1.47, P = 0.38). This systematic review revealed RAP increased peak HR in people with CHF; however, there was no concomitant improvement in peak VO₂. Rather RAP may provide benefits at submaximal intensities by controlling the rise in HR to optimise cardiac output at lower workloads. HR may be an important outcome of CHF management, reflecting myocardial efficiency.

8-Hydroxy-2-deoxyguanosine levels and heart failure: A systematic review and meta-analysis of the literature

BACKGROUND AND AIMS

The generation of reactive oxygen species (ROS) plays an important role in the etiology of several pathological conditions. High levels of 8-hydroxy-2-deoxyguanosine (8-OHdG), a biomarker of oxidative damage of DNA, have been found in patients with heart failure (HF). We performed a meta-analysis of the literature to investigate the association between 8-OHdG levels and HF.

METHODS AND RESULTS

A systematic search was performed in the PubMed, Web of Science, Scopus, EMBASE databases and studies evaluating 8-OHdG levels in HF patients and controls were included. Differences between cases and controls were expressed as standard mean difference (SMD) or mean difference (MD) with pertinent 95% confidence intervals (95%CI). Impact of clinical and demographic features on effect size was assessed by meta-regression. Six studies (446 HF patients and 140 controls) were included in the analysis. We found that HF patients showed higher 8-OHdG levels than controls (SMD:0.89, 95%CI: 0.68, 1.10). The difference was confirmed both in studies in which 8-OHdG levels were assessed in urine (MD:6.28 ng/mg creatinine, 95%CI: 4.01, 8.56) and in blood samples (MD:0.36 ng/ml, 95%CI: 0.04, 0.69). Interestingly, 8-OHdG levels progressively increased for increasing New York Heart Association (NYHA) class. Meta-regression models showed that none of clinical and demographic variables impacted on the difference in 8-OHdG levels among HF patients and controls.

CONCLUSIONS

8-OHdG levels are higher in HF patients HF than in controls, with a progressive increase for increasing NYHA class. However, larger prospective studies are needed to test 8-OHdG as a biomarker of HF severity and progression.

Ischemia-modified albumin levels in patients with acute decompensated heart failure treated with dobutamine or levosimendan: IMA-HF study

OBJECTIVE

Ischemia-modified albumin (IMA) is a sensitive biomarker of myocardial ischemia. However, data on IMA levels in acute heart failure (HF) are still lacking. In this study, we aimed to evaluate serum IMA levels in acute decompensated HF and the effects of dobutamine and levosimendan treatments on IMA levels.

METHODS

This was a prospective, multicenter study that included 70 patients hospitalized with acute decompensated HF and left ventricular ejection fraction < 35%. Blood samples for IMA measurements were obtained on admission and 24-48 h after the initiation of HF therapy. Twenty-nine patients were treated with standard HF therapy, 18 received levosimendan, and 23 received dobutamine in addition to standard of care. A single serum specimen was also collected from 32 healthy individuals each. IMA concentrations were measured by the albumin cobalt binding colorimetric assay, and the results were given in absorbance units (AU). Independent and paired sample t-tests, Mann-Whitney U test, and Wilcoxon signed-rank test were used for the analysis.

RESULTS

In patients with acute decompensated HF, the serum concentration of IMA was significantly higher than those of healthy subjects (0.894 ± 0.23 AU vs. 0.379 ± 0.08 AU, p < 0.001). Overall, the IMA levels significantly decreased after 24-48 h of HF therapy (0.894 ± 0.23 AU and 0.832 ± 0.18 AU, p = 0.013). Furthermore, the IMA levels were also found to significantly decrease with standard HF therapy (1.041 ± 0.28 vs. 0.884 ± 0.15 AU, p = 0.041), with levosimendan (0.771 ± 0.18 vs. 0.728 ± 0.18 AU, p = 0.046) and also with dobutamine (0.892 ± 0.18 vs. 0.820 ± 0.13 AU, p = 0.035).

CONCLUSION

Patients with acute decompensated HF had elevated IMA levels, and appropriate HF therapy significantly reduced the serum IMA levels. Dobutamine or levosimendan did not increase the IMA levels, suggesting a lower potential in inducing myocardial ischemia when used in recommended doses.

Impact of utilizing a women-based formula for determining adequacy of the chronotropic response during exercise treadmill testing

BACKGROUND

A women-based formula for calculation of age-predicted maximum heart rate [age-predicted maximum heart rate=206-(0.88×age)] was established in asymptomatic volunteer women undergoing treadmill exercise tolerance testing (ETT). We sought to perform a comparison of the performance of this women-based formula for prediction of peak heart rate to the traditional formula [220-age] and our own database-generated prediction formula in a large database of women undergoing ETT.

METHODS

We performed a retrospective analysis of all consecutive women who underwent symptom-limited Bruce protocol ETT at the Mayo Clinic from 1994 to 2010. Women with known cardiovascular disease or those using beta blockers, calcium channel blockers, or digitalis were excluded. Separate analyses were performed according to symptomatic status.

RESULTS

The study included 11,029 women (89.4% Caucasian) with a mean age 52±12 years; 3,632 (33%) were referred specifically for evaluation of symptoms. Age-predicted maximum heart rate calculated by the traditional formula was achieved by 49.7% of women versus 69.9% by the women-based formula with most of the underestimation observed in older women. Average absolute deviation between achieved and predicted peak heart rate (HR) was 10.85±9.18 bpm for traditional versus 11.98±9.00 for women-based formulas (dependent t=-16.64, p<0.0001). The linear regression line calculated from our population [HR=201-(0.67×age)] was closer to the women-based formula, both in terms of intercept and slope than the traditional formula. Peak HR was shown to be slightly affected (-2.5 bpm) by symptom status at referral, whereas smoking and diabetes more significantly reduced achieved peak HR.

CONCLUSIONS

The women-based formula underestimated peak HR, especially in older women, but was observed to be closer in both intercept and slope to the regression line determined from our study in this large population of female patients. These sex-unique observations should be taken into account when determining adequacy and targets for ETT in women.

Hypothalamic paraventricular nucleus activation contributes to neurohumoral excitation in rats with heart failure

Heart failure (HF) is a serious cardiovascular disease and is characterized by exaggerated sympathetic activity. In this paper, we review these limited studies, with particular emphasis on examining the role of the paraventricular nucleus (PVN) in the neurohumoral excitation in HF. The PVN is an important neuroendocrine and preautonomic output nucleus, and is considered as the important central site for integration of sympathetic nerve activity. Accumulating evidences demonstrate that a number of neurohumoral processes are involved in the pathophysiology of HF, such as renin-angiotensin system (RAS), proinflammatory cytokines (PICs), neurotransmitters, and reactive oxygen species (ROS). Recent studies about neurohumoral regulation indicate that angiotensin II type1 receptor (AT₁-R) is the important product mediated by cytoplasmic nuclear factor-kappa B (NF-κB) which is up-regulated along with elevated PICs and angiotensin II (ANG II) in the PVN of HF rats. These findings suggest that the NF-κB mediates the cross-talk between RAS and PICs in the PVN in HF. The further studies indicate that the interaction between AT₁-R and NF-κB in the PVN contributes to oxidative stress and sympathoexcitation by modulating neurotransmitters in heart failure, and the superoxide activates NF-κB in the PVN and contributes to neurohumoral excitation. In conclusion, the neurohumoral excitation in HF is based on the interaction of RAS, PICs, ROS, NF-κB and neurotransmitters in the PVN; and the activated NF-κB in the PVN modulates the neurotransmitters and contributes to sympathoexcitation in rats with heart failure.

Beyond gout: uric acid and cardiovascular diseases

OBJECTIVES

This article discusses the results of clinical and experimental studies that examine the association of hyperuricemia and gout with cardiovascular (CV) disease.

METHODS

Key papers for inclusion were identified by a PubMed search, and articles were selected for their relevance to the topic, according to the authors' judgment.

RESULTS AND CONCLUSIONS

Significant progress has been made in confirming an association, possibly causal, between hyperuricemia and CV outcomes. Xantine-oxidase (XO) inhibitors appear to be the most promising agents for prevention and treatment of CV consequences associated with hyperuricemia. Several small and medium sized studies have examined the effect of these agents on CV function in a variety of patient populations. Improvements in measures of endothelial function, oxidative stress, cardiac function, hemodynamics, and certain inflammatory indices have been demonstrated. Compounds for XO inhibition with more specific clinical effects and fewer side effects than allopurinol may be promising options to further explore the therapeutic potential in patients with CV disease. It is too early to make clinical recommendations with regard to the benefits of using XO inhibitor allopurinol or the novel febuxostat in patients with asymptomatic increased UA levels and high CV risk because only a small number of studies have shown that they may be beneficial in terms of CV outcomes. More studies are therefore needed to determine the potential of these drugs for reducing the risk of developing CV disease.

Pheochromocytoma and markers of oxidative stress

High levels of catecholamines in pheochromocytoma (PHEO) are associated with risk of cardiovascular complications. In this study, we looked for potential differences in markers of oxidative stress - vitamin C, superoxide dismutase (SOD) and malondialdehyde (MDA) in PHEO before and after the operation. We studied 18 subjects with PHEO who were examined before and approximately one year after the successful tumor removal (free of disease). All subjects had elevated urinary epinephrine and/or norepinephrine levels before the operation. Vitamin C levels increased significantly after the operation from 61+/-27 to 77+/-20 micromol/l (P=0.02), and MDA decreased significantly after the tumor removal from 2.6+/-0.4 to 2.0+/-0.6 micromol/l (P=0.01). However, no changes were found in SOD activity before and after the operation. In conclusion, increased catecholamine production in PHEO is accompanied by decreased levels of vitamin C and increased levels of MDA which may indicate the activation of oxidative stress in PHEO. Successful operation was associated with lowering of oxidative stress by using both biomarkers. On the contrary, no changes in SOD activity before and after the tumor removal were noted.

Allopurinol reduces antigen-specific and polyclonal activation of human T cells

Allopurinol is the most popular commercially available xanthine oxidase inhibitor and it is widely used for treatment of symptomatic hyperuricaemia, or gout. Although, several anti-inflammatory actions of allopurinol have been demonstrated in vivo and in vitro, there have been few studies on the action of allopurinol on T cells. In the current study, we have assessed the effect of allopurinol on antigen-specific and mitogen-driven activation and cytokine production in human T cells. Allopurinol markedly decreased the frequency of IFN-γ and IL-2-producing T cells, either after polyclonal or antigen-specific stimulation with Herpes Simplex virus 1, Influenza (Flu) virus, tetanus toxoid and Trypanosoma cruzi-derived antigens. Allopurinol attenuated CD69 upregulation after CD3 and CD28 engagement and significantly reduced the levels of spontaneous and mitogen-induced intracellular reactive oxygen species in T cells. The diminished T cell activation and cytokine production in the presence of allopurinol support a direct action of allopurinol on human T cells, offering a potential pharmacological tool for the management of cell-mediated inflammatory diseases.

Severity of oxidative stress and inflammatory activation in end-stage heart failure patients are unaltered after 1 month of left ventricular mechanical assistance

This study investigates the impact of early left ventricular (LV)-mechanical unloading on systemic oxidative stress and inflammation in terminal heart failure patients and their impact both on multi organ failure and on intensive care unit (ICU) stay. Circulating levels of urinary 15-isoprostane-F(2t) (8-epi-PGF2(α)) and pro-inflammatory markers [plasma interleukin (IL)-6, IL-8, and urinary neopterin, a monocyte activation index] were analyzed in 20 healthy subjects, 22 stable end-stage heart failure (ESHF) patients and in 23 LV assist device (LVAD) recipients at pre-implant and during first post-LVAD (PL) month. Multi-organ function was evaluated by total Sequential Organ Failure Assessment (tSOFA) score. In LVAD recipients the levels of oxidative-inflammatory markers and tSOFA score were higher compared to other groups. After device implantation 8-epi-PGF2(α) levels were unchanged, while IL-6, and IL-8 levels increased during first week, and at 1month returned to pre-implant values, while neopterin levels increased progressively during LVAD support. The tSOFA score worsened at 1 PL-week with respect to pre-implant value, but improved at 1 PL-month. The tSOFA score related with IL-6 and IL-8 levels, while length of ICU stay related with pre-implant IL-6 levels. These data suggest that hemodynamic instability in terminal HF is associated to worsening of systemic inflammatory and oxidative milieu that do not improve in the early phase of hemodynamic recovery and LV-unloading by LVAD, affecting multi-organ function and length of ICU stay. This data stimulate to evaluate the impact of inflammatory signals on long-term outcome of mechanical circulatory support.

Neurohumoral stimulation

The temporal relationship between the development of heart failure and activation of the neurohumoral systems involved in chronic heart failure (CHF) has not been precisely defined. When a compensatory mechanism switches to a deleterious contributing factor in the progression of the disease is unclear. This article addresses these issues through evaluating the contribution of various cardiovascular reflexes and cellular mechanisms to the sympathoexcitation in CHF. It also sheds light on some of the important central mechanisms that contribute to the increase in sympathetic nerve activity in CHF.

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

BACKGROUND

Patients with primary aldosteronism experience greater left ventricular hypertrophy and a higher frequency of cardiovascular events than do essential hypertensive patients with comparable blood pressure levels. Aldosterone has been correlated with increased oxidative stress, endothelial inflammation, and fibrosis, particularly in patients with heart disease.

AIM

To evaluate oxidative stress, subclinical endothelial inflammation, and myocardial fibrosis markers in patients with primary aldosteronism and essential hypertension. DESIGN AND INDIVIDUALS: We studied 30 primary aldosteronism patients and 70 control essential hypertensive patients, matched by age, sex and median blood pressure. For all patients, we measured the serum levels of aldosterone, plasma renin activity, malondialdehyde (MDA), xanthine oxidase, metalloproteinase-9, ultrasensitive C-reactive protein and amino terminal propeptides of type I (PINP), and type III procollagen. We also evaluated the effect of PA treatment in 19 PA individuals.

RESULTS

PA patients showed elevated levels of MDA (1.70 ± 0.53 versus 0.94 ± 0.65 μmol/l, P <0.001) and PINP (81.7 ± 50.6 versus 49.7 ± 27 mg/l, P = 0.002) compared with essential hypertensive controls. We found a positive correlation between MDA, PINP, and the serum aldosterone/plasma renin activity ratio in primary aldosteronism patients. Clinically, treating primary aldosteronism patients decreased MDA and PINP levels.

CONCLUSION

We detected higher levels of MDA and PINP in primary aldosteronism patients, suggesting increased oxidative stress and myocardial fibrosis in these individuals. Treating primary aldosteronism patients reduced MDA and PINP levels, which may reflect the direct effect of aldosterone greater than endothelial oxidative stress and myocardial fibrosis, possibly mediated by a mineralocorticoid receptor.

Aminothiol redox alterations in patients with chronic heart failure of ischaemic or non-ischaemic origin

OBJECTIVE

Oxidative stress plays a role in the progression of chronic heart failure (CHF), but whether and how ischaemic heart disease (IHD) or non-IHD aetiology may account for differential redox alterations is currently unclear. We assessed the relation between thiol redox state and lipid peroxidation, as a marker of oxidative stress, in patients with CHF of ischaemic or non-ischaemic origin.

METHODS

Blood reduced glutathione, plasma total and reduced cysteine, cysteinylglycine, homocysteine, glutathione, plasma alpha-tocopherol, ascorbic acid, and free malondialdehyde were assessed in 43 CHF heart transplant candidates (24 IHD and 19 non-IHD) and 30 controls matched for age, gender and number of atherosclerotic risk factors.

RESULTS

Reduced cysteine was increased in CHF patients compared with controls. The highest levels were found in IHD versus non-IHD patients versus controls. Malondialdehyde levels were significantly higher in IHD patients than in controls, whereas antioxidant vitamins did not differ among the three groups.

CONCLUSIONS

Specific abnormalities in the thiol pattern are associated with heart failure aetiology in CHF patients. Our findings point to the possible role of reduced cysteine in the progression of chronic IHD to heart failure status, as an additional pro-oxidant stimulus for worsening oxidative stress.

Effects of carvedilol on oxidative stress and chronotropic response to exercise in patients with chronic heart failure

BACKGROUND

Our previous studies suggest that the increase in heart rate from rest to peak exercise is reduced in patients with chronic heart failure (CHF) and this is associated with increased oxidative stress, as determined by malondialdehyde (MDA) plasma levels.

AIM

To investigate the effects of carvedilol on the heart rate response to exercise and oxidative stress in patients with CHF.

METHODS AND RESULTS

Thirty stable NYHA classes II-III CHF patients received carvedilol therapy for 6 months, at a mean maintenance dose of 25 mg (range 6.25-50 mg/day). After treatment, the patients showed a significant improvement in their functional NYHA class (p=0.013), increased left ventricular ejection fraction (LVEF) (24+/-1.4% to 31+/-2.3%, p=0.003) and 6-min walk distance (499+/-18 to 534+/-18 m, p=0.03), without changes in the peak VO2. At baseline, norepinephrine (NE) plasma levels increased with exercise (510+/-51 to 2513+/-230 pg/mL, p<0.001), and these levels were not affected by carvedilol. Chronotropic responsiveness index (increase in heart rate divided by the increase in NE from rest to peak exercise) was not changed by carvedilol (0.049+/-0.001 to 0.042+/-0.001, p=0.6). MDA levels of CHF patients decreased after treatment with carvedilol (2.4+/-0.2 to 1.1+/-0.2 microM, p<0.001), without changes in antioxidant enzyme activities.

CONCLUSIONS

Carvedilol treatment in patients with CHF results in reduced oxidative stress without restoration of the chronotropic responsiveness index.

Blood glutathione as independent marker of lipid peroxidation in heart failure

BACKGROUND

Aminothiols have a critical function as intracellular redox buffers and constitute furthermore an important extracellular redox system. Lipid peroxidation is increased in chronic heart failure (CHF), but the contribution of each thiol to oxidative stress in this syndrome has not been evaluated.

AIM

To assess the correlation between blood and plasma concentrations of aminothiols and lipid peroxidation as marker of oxidative stress in CHF patients.

METHODS

Blood reduced glutathione (GSH), plasma total and reduced cysteine, cysteinylglycine, homocysteine, GSH, alpha-tocopherol, ascorbic acid, and free malondialdehyde (MDA) were assessed in samples obtained from 26 CHF heart transplant candidates and 26 age- and gender-matched controls with atherosclerotic risk factors and no history of cardiovascular disease. Results are expressed as median and interquartile range (I-III).

RESULTS

MDA levels were significantly higher in CHF patients than in controls [1.03 (0.56-1.60) microM vs. 0.70 (0.40-0.83) microM, p=0.006]. Blood reduced GSH concentrations were significantly higher [662 (327-867) microM vs. 416 (248-571) microM, p=0.016], while alpha-tocopherol levels were significantly lower [15 (13-19) microM vs. 21 (17-32) microM, p=0.001] in CHF patients than in controls. By multivariate logistic regression analysis, the only independent predictors of lipid peroxidation, as expressed by MDA levels > or = 1.00 microM, were increased blood GSH concentrations (OR 1.003 per unit, 95% CI 1.001 to 1.006, p=0.008), ischemic (OR 20, 95% CI 2.6 to 155, p=0.004) and non ischemic CHF etiology (OR 11, 95% CI 1.3 to 99, p=0.026).

CONCLUSIONS

Abnormalities in intracellular GSH cycling are associated to increased lipid peroxidation in CHF.

Elevated levels of oxidative DNA damage in serum and myocardium of patients with heart failure

BACKGROUND

Oxidative stress has been implicated in the pathogenesis of chronic heart failure. The present study investigated whether the levels of 8-hydroxy-2-deoxyguanosine (8-OHdG), a marker of oxidative DNA damage, were elevated in the serum and myocardium of patients with dilated cardiomyopathy (DCM), and furthermore whether carvedilol, a vasodilating beta-blocker with antioxidant activity, could reduce the levels.

METHODS AND RESULTS

Serum levels of 8-OHdG were measured by enzyme immunoassay in 56 patients with DCM and in 20 control subjects. DCM patients had significantly elevated serum levels of 8-OHdG compared with control subjects. Endomyocardial biopsy samples obtained from 12 DCM patients and 5 control subjects with normal cardiac function were studied immunohistochemically for the expression of 8-OHdG. Positive 8-OHdG staining was found in the nuclei of cardiomyocytes from DCM patients but not in those from control subjects. After treatment with carvedilol, the serum levels of 8-OHdG in DCM patients significantly decreased by 19%, together with amelioration of heart failure.

CONCLUSIONS

Levels of 8-OHdG are elevated in the serum and myocardium of patients with heart failure. Treatment with carvedilol might be effective for decreasing the oxidative DNA damage.

Increased systemic inflammation and oxidative stress in patients with worsening congestive heart failure: improvement after short-term inotropic support

In the present study, we evaluated circulating pro-inflammatory mediators and markers of oxidative stress in patients with decompensated CHF (congestive heart failure) and assessed whether clinical recompensation by short-term inotropic therapy influences these parameters. Patients with worsening CHF (n=29, aged 61.9+/-2.7 years), NYHA (New York Heart Association) class III-IV, and left ventricular ejection fraction of 23.7+/-1.8% were studied. Controls comprised age-matched healthy volunteers (n=15; 54.1+/-3.2 years). Plasma levels of cytokines [IL (interleukin)-6 and IL-18], chemokines [MCP-1 (monocyte chemotactic protein-1)], adhesion molecules [sICAM (soluble intercellular adhesion molecule), sE-selectin (soluble E-selectin)], systemic markers of oxidation [TBARS (thiobarbituric acid-reactive substances), 8-isoprostaglandin F(2alpha) and nitrotyrosine] and hs-CRP (high-sensitivity C-reactive protein) were measured by ELISA and colorimetric assays at admission and 30 days following 72-h milrinone (n=15) or dobutamine (n=14) infusion. Plasma IL-6, IL-18, sICAM, E-selectin, hs-CRP and oxidative markers were significantly higher in patients on admission before inotropic treatment compared with controls (P<0.05). Short-term inotropic support improved clinical status as assessed by NYHA classification and by the 6-min walk test and significantly decreased plasma levels of IL-6, IL-18, sICAM, hs-CRP and markers of oxidation (P<0.05) at 30 days. The effects of milrinone and dobutamine were similar. In conclusion, our results demonstrate that patients with decompensated CHF have marked systemic inflammation and increased production of oxygen free radicals. Short-term inotropic support improves functional status and reduces indices of inflammation and oxidative stress in patients with decompensated CHF.

Exercise, caloric restriction, and systemic oxidative stress

BACKGROUND

In humans, the main sources of reactive oxygen species (ROS), the molecules causing oxidative stress, are mitochondrial superoxide ions and neutrophil-derived oxidative radicals. Circulating antioxidants contribute to the protection against oxidative stress. Although the formation of ROS and secretion of antioxidants are independently regulated by exercise and diet, little is known about their combined effect. We hypothesized that relatively brief, intense exercise training may reduce systemic oxidation via an intrinsic mechanism, independent of changes in circulating antioxidants and of neutrophil-derived enzymes (as may be caused by concomitant caloric restriction).

METHODS

Nineteen volunteers exercised for 7 days, 3 hours/day at 75% of oxygen uptake. Caloric intake was either 110% of caloric expenditure (high calorie, n=10) or 75% of caloric expenditure (low calorie, n=9). Blood samples for F2-isoprostanes, catalase, myeloperoxidase (MPO), interleukin-x (IL-x), white blood cells (WBCs), and other metabolic variables were taken at baseline, at the end of training, and 1 week after completion of the study.

RESULTS

Serum F2-isoprostanes (microg/mL), markers of lipid peroxidation, were similarly reduced after 7 days of exercise in the high-calorie (from 35+/-4 to 27+/-2) and low-calorie (from 35+/-3 to 24+/-2) groups. Similar reductions were observed in IL-x concentrations. Conversely, no change was observed in circulating concentrations of the antioxidant catalase. Whereas total WBCs and neutrophil counts were significantly reduced in the low-calorie group only, no difference in neutrophil-derived MPO was measured between groups.

CONCLUSION

A significant reduction in systemic oxidation may occur relatively early during intense exercise training in healthy young men, independent of caloric intake. The potential contribution to these effects of circulating antioxidants and neutrophil-derived oxidative enzymes will require further investigation.

Improvement of sympathetic response to exercise by oral administration of ascorbic acid in patients after myocardial infarction

BACKGROUND

Recent studies indicated that excessive oxidative stress in an animal heart failure model injures both the sympathetic nerve endings and receptors, resulting in disturbance of norepinephrine release and sensitivity to norepinephrine. However, it has not been clarified whether this phenomenon is expressed clinically in patients with heart disease. Therefore, we examined the efficacy of ascorbic acid administration as an antioxidant vitamin in relation to the heart rate and norepinephrine response to exercise in patients after myocardial infarction.

METHODS

In this randomized crossover trial, 21 male patients who had had myocardial infarction underwent symptom-limited ergometer cardiopulmonary exercise testing twice, that is, without and with ascorbic acid (2 g) administration. Plasma norepinephrine concentrations were assessed at rest and at peak exercise, and heart rate responsiveness to the norepinephrine increment from rest to peak exercise (DeltaHR/logDeltaNE) was calculated.

RESULTS

In the exercise test after ascorbic acid administration, peak oxygen consumption (VO(2)) improved over baseline. Ascorbic acid administration significantly increased the change in heart rate and norepinephrine from rest to peak exercise and DeltaHR/logDeltaNE. The increment in heart rate was significantly correlated with peak VO(2) in each test.

CONCLUSION

Ascorbic acid intake before exercise improved exercise capacity through enhancement of the heart rate and norepinephrine response to exercise in patients after myocardial infarction. These findings suggest that ascorbic acid intake improves sympathetic dysfunction resulting from injury by excessive oxidative stress after myocardial infarction.

Exercise, stress, and inflammation in the growing child: from the bench to the playground

PURPOSE OF REVIEW

It is becoming increasingly clear that physical activity in children plays a critical role in growth and development, therapy for certain chronic diseases and disabilities, and in the pediatric origins of a variety of bone, metabolic, and cardiovascular diseases. New mechanistic insights have created the opportunity for a phase shift in understanding of the links between exercise and health in the context of the growing child.

RECENT FINDINGS

Exercise even in healthy children profoundly alters stress, immune, and inflammatory mediators including peripheral blood mononuclear cells and circulating pro- and anti-inflammatory cytokines (like interleukin-6). Moreover, exercise even in healthy adults stimulates the production of reactive oxygen species (ROS) and mediators that attenuate them. Oxidative stress, in turn, alters growth and stress mediators. Both ROS and stress/inflammatory factors interact with powerful growth mediators like growth hormone and insulinlike growth factor-I. These findings suggest specific ways in which the balance between pro- and anti-inflammatory, catabolic, and anabolic factors associated with exercise can influence health and growth in children.

SUMMARY

To address the current epidemic of physical inactivity and obesity in children and to optimize the therapeutic effects of exercise in children with disease and disability will require real changes in environments (eg, schools and playgrounds); innovative approaches to rehabilitation of children with chronic disease and disability; and enlightened training of child health professionals. Identifying novel exercise mechanisms involving stress, inflammation, and growth factors will help guide these efforts.