Mitochondrial function in heart failure: The impact of ischemic and non-ischemic etiology

Background Although cardiac mitochondrial dysfunction is associated with heart failure (HF), this is a complex syndrome with two predominant etiologies, ischemic HF (iHF) and non-ischemic HF (niHF), and the exact impact of mitochondrial dysfunction in these two distinct forms of HF is unknown. Methods and results To determine the impact of HF etiology on mitochondrial function, respiration was measured in permeabilized cardiac muscle fibers from patients with iHF (n = 17), niHF (n = 18), and healthy donor hearts (HdH). Oxidative phosphorylation capacity (OXPHOS), assessed as state 3 respiration, fell progressively from HdH to niHF, to iHF (Complex I + II: 54 ± 1; 34 ± 4; 27 ± 3 pmol·s− 1·mg− 1) as did citrate synthase activity (CSA: 206 ± 18; 129 ± 6; 82 ± 6 nmol·mg− 1·min− 1). Although still significantly lower than HdH, normalization of OXPHOS by CSA negated the difference in mass specific OXPHOS between iHF and niHF. Interestingly, Complex I state 2 respiration increased progressively from HdH, to niHF, to iHF, whether or not normalized for CSA (0.6 ± 0.2; 1.1 ± 0.3; 2.3 ± 0.3; pmol·mg− 1·CSA), such that the respiratory control ratio (RCR), fell in the same manner across groups. Finally, both the total free radical levels (60 ± 6; 46 ± 4 AU) and level of mitochondrial derived superoxide (1.0 ± 0.2; 0.7 ± 0.1 AU) were greater in iHF compared to niHF, respectively. Conclusions Thus, the HF-related attenuation in OXPHOS actually appears to be independent of etiology when the lower mitochondrial content of iHF is taken into account. However, these findings provide evidence of deleterious intrinsic mitochondrial changes in iHF, compared to niHF, including greater proton leak, attenuated OXPHOS efficiency, and augmented free radical levels

Altered skeletal muscle mitochondrial phenotype in COPD: disease vs. disuse

Patients with chronic obstructive pulmonary disease (COPD) exhibit an altered skeletal muscle mitochondrial phenotype, which often includes reduced mitochondrial density, altered respiratory function, and elevated oxidative stress. As this phenotype may be explained by the sedentary lifestyle that commonly accompanies this disease, the aim of this study was to determine whether such alterations are still evident when patients with COPD are compared to control subjects matched for objectively measured physical activity (PA; accelerometry). Indexes of mitochondrial density [citrate synthase (CS) activity], respiratory function (respirometry in permeabilized fibers), and muscle oxidative stress [4-hydroxynonenal (4-HNE) content] were assessed in muscle fibers biopsied from the vastus lateralis of nine patients with COPD and nine PA-matched control subjects (CON). Despite performing similar levels of PA (CON: 18 ± 3, COPD: 20 ± 7 daily minutes moderate-to-vigorous PA; CON: 4,596 ± 683, COPD: 4,219 ± 763 steps per day, P \u3e 0.70), patients with COPD still exhibited several alterations in their mitochondrial phenotype, including attenuated skeletal muscle mitochondrial density (CS activity; CON 70.6 ± 3.8, COPD 52.7 ± 6.5 U/mg, P \u3c 0.05), altered mitochondrial respiration [e.g., ratio of complex I-driven state 3 to complex II-driven state 3 (CI/CII); CON: 1.20 ± 0.11, COPD: 0.90 ± 0.05, P \u3c 0.05), and oxidative stress (4-HNE; CON: 1.35 ± 0.19, COPD: 2.26 ± 0.25 relative to β-actin, P \u3c 0.05). Furthermore, CS activity (r = 0.55), CI/CII (r = 0.60), and 4-HNE (r = 0.49) were all correlated with pulmonary function, assessed as forced expiratory volume in 1 s (P \u3c 0.05), but not PA (P \u3e 0.05). In conclusion, the altered mitochondrial phenotype in COPD is present even in the absence of differing levels of PA and appears to be related to the disease itself

Quadriceps exercise intolerance in patients with chronic obstructive pulmonary disease: the potential role of altered skeletal muscle mitochondrial respiration

This study sought to determine if qualitative alterations in skeletal muscle mitochondrial respiration, associated with decreased mitochondrial efficiency, contribute to exercise intolerance in patients with chronic obstructive pulmonary disease (COPD). Using permeabilized muscle fibers from the vastus lateralis of 13 patients with COPD and 12 healthy controls, complex I (CI) and complex II (CII)-driven State 3 mitochondrial respiration were measured separately (State 3:CI and State 3:CII) and in combination (State 3:CI+CII). State 2 respiration was also measured. Exercise tolerance was assessed by knee extensor exercise (KE) time to fatigue. Per milligram of muscle, State 3:CI+CII and State 3:CI were reduced in COPD (P \u3c 0.05), while State 3:CII and State 2 were not different between groups. To determine if this altered pattern of respiration represented qualitative changes in mitochondrial function, respiration states were examined as percentages of peak respiration (State 3:CI+CII), which revealed altered contributions from State 3:CI (Con 83.7 ± 3.4, COPD 72.1 ± 2.4%Peak, P \u3c 0.05) and State 3:CII (Con 64.9 ± 3.2, COPD 79.5 ± 3.0%Peak, P \u3c 0.05) respiration, but not State 2 respiration in COPD. Importantly, a diminished contribution of CI-driven respiration relative to the metabolically less-efficient CII-driven respiration (CI/CII) was also observed in COPD (Con 1.28 ± 0.09, COPD 0.81 ± 0.05, P \u3c 0.05), which was related to exercise tolerance of the patients (r = 0.64, P \u3c 0.05). Overall, this study indicates that COPD is associated with qualitative alterations in skeletal muscle mitochondria that affect the contribution of CI and CII-driven respiration, which potentially contributes to the exercise intolerance associated with this disease

Salt restriction lowers blood pressure at rest and during exercise without altering peripheral hemodynamics in hypertensive individuals

Dietary salt restriction is a well-established approach to lower blood pressure and reduce cardiovascular disease risk in hypertensive individuals. However, little is currently known regarding the effects of salt restriction on central and peripheral hemodynamic responses to exercise in those with hypertension. Therefore, this study sought to determine the impact of salt restriction on the central and peripheral hemodynamic responses to static-intermittent handgrip (HG) and dynamic single-leg knee extension (KE) exercise in individuals with hypertension. Twenty-two subjects (14 men and 8 women, 51 ± 10 yr, 173 ± 11 cm, 99 ± 23 kg) forewent their antihypertensive medication use for at least 2 wk before embarking on a 5-day liberal salt (LS: 200 mmol/day) diet followed by a 5-day restricted salt (RS: 10 mmol/day) diet. Subjects were studied at rest and during static intermittent HG exercise at 15, 30, and 45% of maximal voluntary contraction and KE exercise at 40, 60, and 80% of maximum KE work rate. Salt restriction lowered resting systolic blood pressure (supine: −12 ± 12 mmHg, seated: −17 ± 12 mmHg) and diastolic blood pressure (supine: −3 ± 9 mmHg, seated: −5 ± 7 mmHg, P \u3c 0.05). Despite an ~8 mmHg lower mean arterial blood pressure during both HG and KE exercise following salt restriction, neither central nor peripheral hemodynamics were altered. Therefore, salt restriction can lower blood pressure during exercise in subjects with hypertension, reducing the risk of cardiovascular events, without impacting central and peripheral hemodynamics during either arm or leg exercise

Single passive leg movement-induced hyperemia: a simple vascular function assessment without a chronotropic response.

Passive leg movement (PLM)-induced hyperemia is a novel approach to assess vascular function, with a potential clinical role. However, in some instances, the varying chronotropic response induced by PLM has been proposed to be a potentially confounding factor. Therefore, we simplified and modified the PLM model to require just a single PLM (sPLM), an approach that may evoke a peripheral hemodynamic response, allowing a vascular function assessment, but at the same time minimizing central responses. To both characterize and assess the utility of sPLM, in 12 healthy subjects, we measured heart rate (HR), stroke volume, cardiac output (CO), mean arterial pressure (MAP), leg blood flow (LBF), and calculated leg vascular conductance (LVC) during both standard PLM, consisting of passive knee flexion and extension performed at 1 Hz for 60 s, and sPLM, consisting of only a single passive knee flexion and extension over 1 s. During PLM, MAP transiently decreased (5 \ub1 1 mmHg), whereas both HR and CO increased from baseline (6.0 \ub1 1.1 beats/min, and 0.8 \ub1 0.01 l/min, respectively). Following sPLM, MAP fell similarly (5 \ub1 2 mmHg; P = 0.8), but neither HR nor CO responses were identifiable. The peak LBF and LVC response was similar for PLM (993 \ub1 189 ml/min; 11.9 \ub1 1.5 ml\ub7min-1\ub7mmHg-1, respectively) and sPLM (878 \ub1 119 ml/min; 10.9 \ub1 1.6 ml\ub7min-1\ub7mmHg-1, respectively). Thus sPLM represents a variant of the PLM approach to assess vascular function that is more easily performed and evokes a peripheral stimulus that induces a significant hyperemia, but does not generate a potentially confounding, chronotropic response, which may make sPLM more useful clinically. NEW & NOTEWORTHY: Using the single passive leg movement (PLM) technique, a variant of the vascular function assessment PLM, we have identified a novel peripheral vascular assessment method that is more easily performed than PLM, which, by not evoking potentially confounding central hemodynamic responses, may be more useful clinically

Acute high-intensity exercise and skeletal muscle mitochondrial respiratory function: role of metabolic perturbation

Recently it was documented that fatiguing, high-intensity exercise resulted in a significant attenuation in maximal skeletal muscle mitochondrial respiratory capacity, potentially due to the intramuscular metabolic perturbation elicited by such intense exercise. With the utilization of intrathecal fentanyl to attenuate afferent feedback from group III/IV muscle afferents, permitting increased muscle activation and greater intramuscular metabolic disturbance, this study aimed to better elucidate the role of metabolic perturbation on mitochondrial respiratory function. Eight young, healthy males performed high-intensity cycle exercise in control (CTRL) and fentanyl-treated (FENT) conditions. Liquid chromatography-mass spectrometry and high-resolution respirometry were used to assess metabolites and mitochondrial respiratory function, respectively, pre- and postexercise in muscle biopsies from the vastus lateralis. Compared with CTRL, FENT yielded a significantly greater exercise-induced metabolic perturbation (PCr: −67% vs. −82%, Pi: 353% vs. 534%, pH: −0.22 vs. −0.31, lactate: 820% vs. 1,160%). Somewhat surprisingly, despite this greater metabolic perturbation in FENT compared with CTRL, with the only exception of respiratory control ratio (RCR) (−3% and −36%) for which the impact of FENT was significantly greater, the degree of attenuated mitochondrial respiratory capacity postexercise was not different between CTRL and FENT, respectively, as assessed by maximal respiratory flux through complex I (−15% and −33%), complex II (−36% and −23%), complex I + II (−31% and −20%), and state 3CI+CII control ratio (−24% and −39%). Although a basement effect cannot be ruled out, this failure of an augmented metabolic perturbation to extensively further attenuate mitochondrial function questions the direct role of high-intensity exercise-induced metabolite accumulation in this postexercise response

Angiotensin II potentiates α-adrenergic vasoconstriction in the elderly

Abstract Aging is characterized by increased sympatho-excitation, expressed through both the α-adrenergic and RAAS (renin-angiotensin-aldosterone) pathways. Although the independent contribution of these two pathways to elevated vasoconstriction with age may be substantial, significant cross-talk exists that could produce potentiating effects. To examine this interaction, 14 subjects (n = 8 young, n = 6 old) underwent brachial artery catheterization for administration of AngII (angiotensin II; 0.8-25.6 ng/dl per min), NE [noradrenaline (norepinephrine); 2.5-80 ng/dl per min] and AngII with concomitant α-adrenergic antagonism [PHEN (phentolamine); 10 μg/dl per min]. Ultrasound Doppler was utilized to determine blood flow, and therefore vasoconstriction, in both infused and contralateral (control) limbs. Arterial blood pressure was measured directly, and sympathetic nervous system activity was assessed via microneurography and plasma NE analysis. AngII sensitivity was significantly greater in the old, indicated by both greater maximal vasoconstriction ( − 59 + − 4 % in old against − 48 + − 3 % in young) and a decreased EC 50 (half-maximal effective concentration) (1.4 + − 0.2 ng/dl per min in old against 2.6 + − 0.7 μg/dl per min in young), whereas the maximal NE-mediated vasoconstriction was similar between these groups ( − 58 + − 9 % in old and − 62 + − 5 % in young). AngII also increased venous NE in the old group, but was unchanged in the young group. In the presence of α-adrenergic blockade (PHEN), maximal AngII-mediated vasoconstriction in the old was restored to that of the young ( − 43 + − 8 % in old and − 39 + − 6 % in young). These findings indicate that, with healthy aging, the increased AngII-mediated vasoconstriction may be attributed, in part, to potentiation of the α-adrenergic pathway, and suggest that cross-talk between the RAAS and adrenergic systems may be an important consideration in therapeutic strategies targeting these two pathways

Strong Relationship Between Vascular Function in the Coronary and Brachial Arteries: A Clinical Coming of Age for the Updated Flow-Mediated Dilation Test?

Early detection of coronary artery dysfunction is of paramount cardiovascular clinical importance, but a noninvasive assessment is lacking. Indeed, the brachial artery flow-mediated dilation test only weakly correlated with acetylcholine-induced coronary artery function (r=0.36). However, brachial artery flow-mediated dilation methodologies have, over time, substantially improved. This study sought to determine if updates to this technique have improved the relationship with coronary artery function and the noninvasive indication of coronary artery dysfunction. Coronary artery and brachial artery function were assessed in 28 patients referred for cardiac catheterization (61±11 years). Coronary artery function was determined by the change in artery diameter with a 1.82 μg/min intracoronary acetylcholine infusion. Based on the change in vessel diameter, patients were characterized as having dysfunctional coronary arteries (\u3e5% vasoconstriction) or relatively functional coronary arteries (\u3c5% vasoconstriction). Brachial artery function was determined by flow-mediated dilation, adhering to current guidelines. The acetylcholine-induced change in vessel diameter was smaller in patients with dysfunctional compared with relatively functional coronary arteries (−11.8±4.6% versus 5.8±9.8%, P\u3c0.001). Consistent with this, brachial artery flow-mediated dilation was attenuated in patients with dysfunctional compared with relatively functional coronaries (2.9±1.9% versus 6.2±4.2%, P=0.007). Brachial artery flow-mediated dilation was strongly correlated with the acetylcholine-induced change in coronary artery diameter (r=0.77, P\u3c0.0001) and was a strong indicator of coronary artery dysfunction (receiver operator characteristic=78%). The current data support that updates to the brachial artery flow-mediated dilation technique have strengthened the relationship with coronary artery function, which may now provide a clinically meaningful indication of coronary artery dysfunction

Something is definitely better than nothing: simple strategies to prevent vascular dysfunction

Understanding the negative health consequences of a physical inactivity has been the topic of much investigation as an alarming number of adults have adopted a sedentary lifestyle. With the rise in sedentarism the field of inactivity physiology has emerged. The goal of inactivity physiology is to identify the impact in inactivity on health and develop strategies that effectively minimize the risk of a sedentary lifestyle. Arising from this field is the finding that excessive sitting is linked to increased cardiovascular and metabolic disease and all-cause mortality. Most importantly, these relationships exist even in individuals that are physically active. Clearly, excessive sitting is an occupational hazard with significant health consequences. Through a series of investigations, including research published this issue of Clinical Science, Padilla and colleagues have identified that prolonged sitting evokes vascular dysfunction and that this dysfunction is caused by reduced shear stress. This commentary highlights this series of investigations and culminates with an overview of how prior exercise and standing are effective strategies to circumvent vascular dysfunction that is caused by excessive sitting. Excessive sitting is now considered by many to be an occupational and societal hazard due to the alarming evidence linking this sedentary behavior to increased cardiovascular and metabolic disease and all-cause mortality [1][2][3][4]. Strategies to circumvent these negative health outcomes are critical as sedentarism continues to rise in the workplace and leisure time physical activity continues to decline. Longitudinal and epidemiological investigations provide evidence that even in individuals meeting the recommended levels of moderate-to-vigorous physical activity, excessive sitting is independently associated with negative health outcomes [1,[4][5][6][7][8][9]. The recognition of these negative outcomes has led to the emergence of the field of inactivity physiology in order to better understand the mechanisms leading to disease progression as a result of sedentary behavior and to provide recommendations to mitigate the deleterious impact of sedentary behavior and in particular, excessive sitting [2,10]. In this issue of the Clinical Science, Padilla and colleagues expand upon their previous work and explore how prior exercise and standing affect sitting-induced endothelial dysfunction [11]. Before diving head first into the findings of the present study, we must first appreciate the link between atherosclerosis, endothelial dysfunction, and shear rate. Endothelial dysfunction presents prior to the onset of overt cardiovascular disease (CVD) and is an established risk factor for the development of future CVD [12

Heterogeneity of blood flow: impact of age on muscle specific tissue perfusion during exercise

Merced Theater (1870) and Masonic Hall (1858); Olvera Street (La Placita Olvera) is in the oldest part of Downtown Los Angeles, California, and is part of the El Pueblo de Los Angeles Historic Monument (Los Angeles Plaza Historic District). Since 1911 it was described as Sonora Town. Having started as a short lane, Wine Street, it was extended and renamed in honor of Agustín Olvera, a prominent local judge, in 1877. There are 27 historic buildings lining Olvera Street, including the Avila Adobe, the Pelanconi House and the Sepulveda House. In 1930, it was converted to a colorful Mexican marketplace. Source: Wikipedia; http://en.wikipedia.org/wiki/Main_Page (accessed 8/11/2013