Caveolin and β1-integrin coordinate angiotensinogen expression in cardiac myocytes

Background

The cardiac renin–angiotensin system (RAS) has been implicated in mediating myocyte hypertrophy and remodeling, although the biochemical mechanisms responsible for regulating the local RAS are poorly understood. Caveolin-1 (Cav-1)/Cav-3 double-knockout mice display cardiac hypertrophy, and in vitro disruption of lipid rafts/caveolae using methyl-β-cyclodextrin (MβCD) abolishes cardiac protection.

Methods

In this study, neonatal rat ventricular myocytes (NRVM) were used to determine whether lipid rafts/caveolae may be involved in the regulation of angiotensinogen (Ao) gene expression, a substrate of the RAS system.

Results

Treatment with MβCD caused a time-dependent upregulation of Ao gene expression, which was associated with differential regulation of mitogen-activated protein (MAP) kinases ERK1/2, p38 and JNK phosphorylation. JNK was highly phosphorylated shortly after MβCD treatment (2–30 min), whereas marked activation of ERK1/2 and p38 occurred much later (2–4 h). β_1D-Integrin was required for MβCD-induced activation of the MAP kinases. Pharmacologic inhibition of ERK1/2 and JNK enhanced MβCD-induced Ao gene expression, whereas p38 blockade inhibited this response. Adenovirus-mediated expression of wild-type p38α enhanced MβCD-induced Ao gene expression; conversely expression of dominant negative p38α blocked the stimulatory effects of MβCD. Expression of Cav-3 siRNA stimulated Ao gene expression, whereas overexpression of Cav-3 was inhibitory. Cav-1 and Cav-3 expression levels were found to be positively regulated by p38, but unaffected by ERK1/2 and JNK.

Conclusion

Collectively, these studies indicate that lipid rafts/caveolae couple to Ao gene expression through a mechanism that involves β₁-integrin and the differential actions of MAP kinase family members.     

Stretch-induced MAP kinase activation in cardiac myocytes: differential regulation through beta1-integrin and focal adhesion kinase

Mitogen-activated protein (MAP) kinases have been implicated in hemodynamic load induced heart failure. Both angiotensin II (Ang II) and mechanical stretch activate MAP kinases in cardiac myocytes. In this study, we used a neonatal rat ventricular myocyte (NRVM) model to determine the role of focal-adhesion kinase (FAK) in beta1 integrin mediated MAP kinase activation in response to mechanical stretch in presence and absence of Ang II receptor blockade (ATB). NRVM plated on deformable membranes coated with collagen IV were exposed to 20% equiaxial static-stretch. beta1 integrin signaling was blocked by adenovirus-mediated expression of a dominant-negative form of beta1D integrin (tac-beta1D). FAK signaling was disrupted by infecting NRVM with adenovirus expressing FAK-related non-kinase (FRNK). Western blot analysis was used to assess the phosphorylation of MAP kinases. In the presence and absence of ATB, mechanical stretch caused maximal phosphorylation of ERK, p38 and JNK at 5 min, which was significantly attenuated in NRVM expressing tac-beta1D. In the presence of ATB, FRNK overexpression significantly increased basal phosphorylation of ERK (40.2+/-8.6% P<0.05), p38 (39.5+/-11.7%, P<0.05), JNK (86+/-29.4%, P<0.05) and stretch-induced p38 (48.1+/-8.7%, P<0.05) and JNK (85.0+/-19.4%, P<0.05) phosphorylation. However, in the absence of ATB, FRNK overexpression significantly reduced basal and stretch-induced phosphorylation of only ERK. Examination of FAK activation revealed that beta1 integrin was required for stretch-induced phosphorylation of FAK at Y397 and Y925, but not Y861. In summary, mechanical stretch-activated ERK1/2, p38 and JNK through FAK independent and dependent mechanisms. Beta1 integrin was required for FAK independent activation of all three MAP kinases, whereas cross-talk between beta1 integrin and Ang II receptors mediated FAK dependent regulation of ERK1/2.     

Tumor necrosis factor-α produced in cardiomyocytes mediates a predominant myocardial inflammatory response to stretch in early volume overload

Acute stretch caused by volume overload (VO) of aorto-caval fistula (ACF) induces a variety of myocardial responses including mast cell accumulation, matrix metalloproteinase (MMP) activation, and collagen degradation, all of which are critical in dictating long-term left ventricle (LV) outcome to VO. Meanwhile, these responses can be part of myocardial inflammation dictated by tumor necrosis factor-α (TNF-α), which is elevated after acute ACF. However, it is unknown whether TNF-α mediates a major myocardial inflammatory response to stretch in early VO. In 24-h ACF and sham rats, microarray gene expression profiling and subsequent Ingenuity Pathway Analysis identified a predominant inflammatory response and a gene network of biologically interactive genes strongly linked to TNF-α. Western blot demonstrated increased local production of TNF-α in the LV (1.71- and 1.66-fold in pro- and active-TNF-α over control, respectively, P < 0.05) and cardiomyocytes (2- and 4-fold in pro- and active-TNF-α over control, respectively, P < 0.05). TNF-α neutralization with infliximab (5.5 mg/kg) attenuated the myocardial inflammatory response to acute VO, as indicated by inhibition of inflammatory gene upregulation, myocardial infiltration (total CD45+ cells, mast cells, and neutrophils), MMP-2 activation, collagen degradation, and cardiac cell apoptosis, without improving LV remodeling and function. These results indicate that TNF-α produced by cardiomyocytes mediates a predominant inflammatory response to stretch in the early VO in the ACF rat, suggesting an important role of TNF-α in initiating pathophysiological response of myocardium to VO.     

Caveolin-3 expression and caveolae are required for isoflurane-induced cardiac protection from hypoxia and ischemia/reperfusion injury

Volatile anesthetics protect the heart from ischemia/reperfusion injury but the mechanisms for this protection are poorly understood. Caveolae, sarcolemmal invaginations, and caveolins, scaffolding proteins in caveolae, localize molecules involved in cardiac protection. We tested the hypothesis that caveolae and caveolins are essential for volatile anesthetic-induced cardiac protection using cardiac myocytes (CMs) from adult rats and in vivo studies in caveolin-3 knockout mice (Cav-3^−/−). We incubated CM with methyl-β-cyclodextrin (MβCD) or colchicine to disrupt caveolae formation, and then exposed the myocytes to the volatile anesthetic isoflurane (30 min, 1.4%), followed by simulated ischemia/reperfusion (SI/R). Isoflurane protected CM from SI/R [23.2 ± 1.6% vs. 71.0 ± 5.8% cell death (assessed by trypan blue exclusion), P < 0.001] but this protection was abolished by MβCD or colchicine (84.9 ± 5.5% and 64.5 ± 6.1% cell death, P < 0.001). Membrane fractionation by sucrose density gradient centrifugation of CM treated with MβCD or colchicine revealed that buoyant (caveolae-enriched) fractions had decreased phosphocaveolin-1 and caveolin-3 compared to control CM. Cardiac protection in vivo was assessed by measurement of infarct size relative to the area at risk and cardiac troponin levels. Isoflurane-induced a reduction in infarct size and cardiac troponin relative to control (infarct size: 26.5% ± 2.6% vs. 45.3% ± 5.4%, P < 0.01; troponin: 27.7 ± 4.4 vs. 77.7 ± 11.8 ng/ml, P < 0.05). Isoflurane-induced cardiac protection was abolished in Cav-3^−/− mice (infarct size: 53.4% ± 6.1% vs. 53.2% ± 3.5%, P < 0.01; troponin: 102.1 ± 22.3 vs. 105.9 ± 8.2 ng/ml, P < 0.01). Isoflurane-induced cardiac protection is thus dependent on the presence of caveolae and the expression of caveolin-3. We conclude that caveolae and caveolin-3 are critical for volatile anesthetic-induced protection of the heart from ischemia/reperfusion injury.     

Chronic intermittent fasting improves the survival following large myocardial ischemia by activation of BDNF/VEGF/PI3K signaling pathway

Chronic heart failure (CHF) is the major cause of death in the developed countries. Calorie restriction is known to improve the recovery in these patients; however, the exact mechanism behind this protective effect is unknown. Here we demonstrate the activation of cell survival PI3kinase/Akt and VEGF pathway as the mechanism behind the protection induced by intermittent fasting in a rat model of established chronic myocardial ischemia (MI). Chronic MI was induced in rats by occlusion of the left coronary artery. Two weeks later, the rats were randomly assigned to a normal feeding group (MI-NF) and an alternate-day feeding group (MI-IF). After 6 weeks of observation, we evaluated the effect of intermittent fasting on cellular and ventricular remodeling and long-term survival after CHF. Compared with the normally fed group, intermittent fasting markedly improved the survival of rats with CHF (88.5% versus 23% survival, P < 0.05). The heart weight body weight ratio was significantly less in the MI-IF group compared to the MI-NF group (3.4 ± 0.17 versus 3.9 ± 0.18, P < 0.05). Isolated heart perfusion studies exhibited well preserved cardiac functions in the MI-IF group compared to the MI-NF group (P < 0.05). Molecular studies revealed the upregulation of angiogenic factors such asHIF-1-α (3010 ± 350% versus 650 ± 151%), BDNF (523 ± 32% versus 110 ± 12%), and VEGF (450 ± 21% versus 170 ± 30%) in the fasted hearts. Immunohistochemical studies confirmed increased capillary density (P < 0.001) in the border area of the ischemic myocardium and synthesis VEGF by cardiomyocytes. Moreover fasting also upregulated the expression of other anti-apoptotic factors such as Akt and Bcl-2 and reduced the TUNEL positive apoptotic nuclei in the border zone. Chronic intermittent fasting markedly improves the long-term survival after CHF by activation through its pro-angiogenic, anti-apoptotic and anti-remodeling effects.     

机械应力对MG63成骨样细胞结缔组织生长因子表达的影响

目的 观察力学刺激对MG63成骨样细胞的结缔组织生长因子(CTGF)表达的影响以及丝裂原活化蛋白激酶(MAPK)信号途径在这一过程中的作用.方法 应用Western印迹法检测MG63细胞CTGF蛋白表达及细胞外信号调节激酶(ERK)、c-Jun氨基末端激酶(JNK)、p38磷酸化水平,应用RT-PCR检测CTGF mRNA表达.结果 环状应力刺激可显著上调CFGF蛋白及mRNA表达,3～6 h达高峰,升高2～3倍;并且激活ERK及JNK信号途径,刺激10 min开始活化,ERK在60 min达高峰,而JNK在15～30min达高峰,对p38信号途径没有明显活化作用.JNK信号通路阻断剂SP600125能够阻断应力刺激对CTGF的上调作用,而ERK信号阻断剂PD98059及p38信号阻断剂SB203580却无此作用.结论 环状机械应力通过JNK依赖的途径上调了MG63细胞的CTGF表达.     

Coronary artery calcium scoring: Influence of adaptive statistical iterative reconstruction using 64-MDCT

Objective

Assessment of coronary artery calcification is increasingly used for cardiovascular risk stratification. We evaluated the reliability of calcium-scoring results using a novel iterative reconstruction algorithm (ASIR) on a high-definition 64-slice CT scanner, as such data is lacking.

Methods and results

In 50 consecutive patients Agatston scores, calcium mass and volume score were assessed. Comparisons were performed between groups using filtered back projection (FBP) and 20–100% ASIR algorithms. Calcium score was measured in the coronary arteries, signal and noise were measured in the aortic root and left ventricle. In comparison with FBP, use of 20%, 40%, 60%, 80%, and 100% ASIR resulted in reduced image noise between groups (7.7%, 18.8%, 27.9%, 39.86%, and 48.56%, respectively; p < 0.001) without difference in signal (p = 0.60). With ASIR algorithms Agatston coronary calcium scoring significantly decreased compared with FBP algorithms (837.3 ± 130.3; 802.2 ± 124.9, 771.5 ± 120.7; 744.7 ± 116.8, 724.5 ± 114.2, and 709.2 ± 112.3 for 0%, 20%, 40%, 60%, 80%, and 100% ASIR, respectively, p < 0.001). Volumetric score decreased in a similar manner (p < 0.001) while calcium mass remained unchanged. Mean effective radiation dose was 0.81 ± 0.08 mSv.

Conclusion

ASIR results in image noise reduction. However, ASIR image reconstruction techniques for HDCT scans decrease Agatston coronary calcium scores. Thus, one needs to be aware of significant changes of the scoring results caused by different reconstruction methods.     

Ventricular K currents are reduced in mice with elevated levels of serum TNFα

In the present study mice were treated with tumor necrosis factor alpha (TNFα) for 6 weeks to determine if chronic TNFα treatment could produce serum levels of TNFα similar to what has been observed in disease states (heart failure, HIV) and to determine if these levels of TNFα alter ventricular K⁺ currents. Mice chronically treated with TNFα and sham treated mice were utilized for experiments. Serum levels were measured with a Searchlight® protein array. Patch-clamp techniques, real-time PCR and Western blot analysis were used to study K⁺ current densities and K⁺ channel expression. Results showed that serum concentrations of TNFα were significantly higher in TNFα treated mice compared to controls (control: 9.5 ± 1.5 pg/ml, TNFα: 27.4 ± 5.0 pg/ml; p < 0.05) and comparable to serum TNFα levels observed in heart failure and HIV models. In ventricular myocytes from TNFα treated mice the outward K⁺ currents I_to and I_Kur were significantly reduced (at + 30 mV: I_to: control: 45.0 ± 2.9 pA/pF, TNFα: 34.5 ± 2.9 pA/pF; p < 0.05; I_Kur: control 34.1 ± 2.7 pA/pF, TNFα: 25.0 ± 2.2 pA/pF; p < 0.05). Expression studies revealed that ventricular mRNA and protein expression for the channels underlying I_to and I_Kur did not differ between the two groups. However, the recovery from inactivation for I_Kur was significantly longer in TNFα treated mice. Overall, this study shows that pathologically relevant levels of serum TNFα modulate K⁺ currents in mouse ventricle. These findings could help to explain the role of TNFα in the pathogenesis of cardiac arrhythmia.     

Cardiac myofibroblast differentiation is attenuated by α3 integrin blockade: Potential role in post-MI remodeling

Cardiac fibroblasts and myofibroblasts are responsible for post-MI remodeling which occurs via regulation of extracellular matrix (ECM). Accelerated post-MI remodeling leads to excessive ECM deposition and fibrosis, contributing to impaired contractile function, arrhythmias, and heart failure. We have previously reported that type VI collagen induces myofibroblast differentiation in cultured cardiac fibroblasts, and that type VI collagen and myofibroblast content were both elevated in the myocardium 20 weeks post-MI. The purpose of this study was to determine the expression patterns of type VI collagen and myofibroblast content in early post-myocardial infarction (MI) remodeling to gain insight into whether type VI collagen induces in vivo myofibroblast differentiation via specific matrix-receptor interactions. Adult male Sprague-Dawley rats were anesthetized and left coronary arteries were permanently ligated. Histological tissue sections and whole tissue protein lysates were obtained from infarcted and non-infarcted areas of MI hearts and sham operated controls. At 3 days post-MI, we observed a significant increase in α₃ integrin expression (2.02 ± 0.18 fold); at 7 days post-infarction both type VI collagen (2.27 ± 0.18 fold) and myofibroblast (4.65 ± 0.6 fold) content increased. By 14 days myofibroblast content returned to sham control levels, although type VI collagen (2.42 ± 0.11 fold) was still elevated. In vitro cross-linking confirmed that the α₃ integrin interacts with type VI collagen, and α₃ integrin function blocking antibodies inhibited the differentiation of isolated cardiac fibroblasts. Collectively, our in vitro results indicate that the α₃ integrin receptor interacts with type VI collagen to promote myofibroblast differentiation, and that this interaction may impact in vivo post-MI remodeling.     

Histone-deacetylase inhibition reverses atrial arrhythmia inducibility and fibrosis in cardiac hypertrophy independent of angiotensin

Atrial fibrosis influences the development of atrial fibrillation (AF), particularly in the setting of structural heart disease where angiotensin-inhibition is partially effective for reducing atrial fibrosis and AF. Histone-deacetylase inhibition reduces cardiac hypertrophy and fibrosis, so we sought to determine if the HDAC inhibitor trichostatin A (TSA) could reduce atrial fibrosis and arrhythmias. Mice over-expressing homeodomain-only protein (HopX^Tg), which recruits HDAC activity to induce cardiac hypertrophy were investigated in 4 groups (aged 14-18 weeks): wild-type (WT), HopX^Tg, HopX^Tg mice treated with TSA for 2 weeks (TSA-HopX) and wild-type mice treated with TSA for 2 weeks (TSA-WT). These groups were characterized using invasive electrophysiology, atrial fibrosis measurements, atrial connexin immunocytochemistry and myocardial angiotensin II measurements. Invasive electrophysiologic stimulation, using the same attempts in each group, induced more atrial arrhythmias in HopX^Tg mice (48 episodes in 13 of 15 HopX^Tg mice versus 5 episodes in 2 of 15 TSA-HopX mice, P < 0.001; versus 9 episodes in 2 of 15 WT mice, P < 0.001; versus no episodes in any TSA-WT mice, P < 0.001). TSA reduced atrial arrhythmia duration in HopX^Tg mice (1307 ± 289 ms versus 148 ± 110 ms, P < 0.01) and atrial fibrosis (8.1 ± 1.5% versus 3.9 ± 0.4%, P < 0.001). Atrial connexin40 was lower in HopX^Tg compared to WT mice, and TSA normalized the expression and size distribution of connexin40 gap junctions. Myocardial angiotensin II levels were similar between WT and HopX^Tg mice (76.3 ± 26.0 versus 69.7 ± 16.6 pg/mg protein, P = NS). Therefore, it appears HDAC-inhibition reverses atrial fibrosis, connexin40 remodeling and atrial arrhythmia vulnerability independent of angiotensin II in cardiac hypertrophy.     

Expression of spliceosome assembly factor SC-35 in TUNEL-positive atrial cardiomyocytes in mitral and tricuspid regurgitation: Viability of atrial cardiomyocytes

Background

Most of the atrial cardiomyocytes with positive terminal deoxynucleotidyl transferase (TdT)-mediated dUTP in situ nick end-labelling (TUNEL) reaction are not apoptotic in patients with mitral and tricuspid valve diseases. The TUNEL-positive myocytes with expression of spliceosome assembly factor SC-35, an indicator of increased RNA synthesis, should be living cardiomyocytes.

Methods

This study analyzed twenty-three patients with significant mitral and tricuspid regurgitation. Fifteen patients had persistent atrial fibrillation, and eight had sinus rhythm. Atrial appendageal tissues were obtained during surgery. Immunohistochemical study was performed.

Results

Immunohistochemical study of fibrillating right atrial myocardium demonstrated that 44.8 ± 24.6% of myocytes had TUNEL-positive nuclei whereas 39.4 ± 21.4% of myocytes had TUNEL-positive nuclei in sinus right atrial myocardium (p = 0.682). However, most (81.6%) nuclei of TUNEL-positive myocytes in the fibrillating right atria also expressed proliferating cell nuclear antigen (PCNA), an indicator of DNA replication and repair, and most nuclei (91.8%) of TUNEL-positive myocytes also expressed SC-35. In fibrillating left atria, most (88.1%) nuclei of TUNEL-positive myocytes also expressed SC-35. Similarly, in sinus right atrial myocardium, most (78.0%) nuclei of TUNEL-positive myocytes expressed PCNA, and most (91.4%) nuclei of TUNEL-positive myocytes also expressed SC-35, but none expressed Ki-67, a replication-associated antigen. Additionally, the percentage of TUNEL-positive myocytes in the right atria significantly and positively correlated with the percentage of PCNA-positive myocytes (r = 0.826, p < 0.001) and SC-35 positive myocytes (r = 0.713, p < 0.001).

Conclusions

Most TUNEL-positive atrial cardiomyocytes in patients with mitral and tricuspid regurgitation are living cardiomyocytes.     

Mechanisms of maintained exercise capacity in adults with repaired tetralogy of Fallot

Background

The mechanisms whereby cardiac output is augmented with exercise in adult repaired tetralogy of Fallot (TOF) are poorly characterised.

Methods

16 repaired TOF patients (25 ± 7 years of age) and 8 age and sex matched controls (25 ± 4 years of age) underwent cardiopulmonary exercise testing and then real-time cardiac MRI (1.5 T) at rest and whilst exercising within the scanner, aiming for 30% heart rate reserve (Level 1) and 60% heart rate reserve (Level 2), using a custom-built MRI compatible foot pedal device.

Results

At rest, TOF patients had severely dilated RVs (indexed RV end-diastolic volume: 149 ± 37 mL/m²), moderate-severe PR (regurgitant fraction 35 ± 12%), normal RV fractional area change (FAC) (52 ± 7%) and very mildly impaired exercise capacity (83 ± 15% of predicted maximal work rate). Heart rate and RV FAC increased significantly in TOF patients (75 ± 10 vs 123 ± 17 beats per minute, p < 0.001; 44 ± 7 vs 51 ± 10%, p = 0.025), and similarly in control subjects (70 ± 11 vs 127 ± 12 beats per minute, p < 0.001; 49 ± 7 vs 61 ± 9%, p = 0.003), when rest was compared to Level 2. PR fraction decreased significantly but only modestly, from rest to Level 2 in TOF patients (37 ± 15 to 31 ± 15%, p = 0.002). Pulmonary artery net forward flow was maintained and did not significantly increase from rest to Level 2 in TOF patients (70 ± 19 vs 69 ± 12 mL/beat, p = 0.854) or controls (93 ± 9 vs 95 ± 21 mL/beat, p = 0.648).

Conclusions

During exercise in repaired TOF subjects with dilated RV and free PR, increased total RV output per minute was facilitated by an increase in heart rate, an increase in RV FAC and a decrease in PR fraction.     

Perioperative administration of enoximone and renal function after cardiac surgery: A propensity-matched analysis

Background

Perioperative administration of enoximone has been shown to improve hemodynamics, organ function, and inflammatory response. Aim of the present study is to evaluate the impact of enoximone on postoperative renal function after on-pump cardiac surgery.

Methods

A total of 3727 patients undergoing cardiac surgery at one Institution between May 2004 and November 2010 were reviewed. A propensity score was built and a 1:1 perfect matching was performed, providing two fairly comparable cohorts of 712 patients each, receiving or not enoximone after surgery. Renal function was evaluated by lower glomerular filtration rate (GFR) value reached postoperatively.

Results

Overall 30-day mortality rate was 4.3% (62/1424). Cumulative incidence of postoperative renal failure (RF) was 157/1424(11%), of which 99/1424(7%) needed renal replacement therapy. Mean lower postoperative GFR in patients who received or not enoximone was 63 ± 30.1 and 53.5 ± 26.1 ml/min/1.73 m² (p < 0.0001), respectively. At multivariable analysis age (OR2.75, p = 0.0004), diabetes (OR1.82, p = 0.006), preoperative GFR (OR3.81, p < 0.0001), preoperative cardiogenic shock (OR1.65, p = 0.004), previous cardiac surgery (OR2.12, p = 0.0002), type of intervention (OR1.96, p = 0.005), and enoximone (OR0.38, p = 0.001) were found to be independently associated with postoperative RF. Logistic regression analysis showed that the administration of enoximone (OR0.41, p = 0.0001), and of no inotropes (OR0.27, p < 0.0001) were protective vs. the occurrence of postoperative RF.

Conclusion

Patients perioperatively receiving enoximone showed a statistically significant better renal function after cardiac surgery.     

Le degré de l’insuffisance rénale chronique est associé aux taux de cytokines pro-inflammatoires, à l’hyperhomocystéinémie et au stress oxydant

Aim

To evaluate pro-inflammatory cytokines, homocysteinemia and markers of oxidative status in the course of chronic renal failure.

Patients and methods

One hundred and two patients (male/female: 38/64; age: 45 ± 07 years) with chronic renal failure were divided into 4 groups according to the National Kidney Foundation classification. They included 28 primary stage renal failure patients, 28 moderate stage renal failure, 28 severe stage renal failure and 18 end stage renal failure. The inflammatory status was evaluated by the determination of pro-inflammatory cytokines (tumor necrosis factor-α, interleukin-1β, interleukin-6) and total homocysteine. Pro-oxidant status was assessed by assaying thiobarbituric acid reactive substances, hydroperoxides, and protein carbonyls. Antioxidant defence was performed by analysis of superoxide dismutase, catalase, glutathione peroxidase, glutathione reductase.

Results

Inflammatory markers were elevated in the end stage renal failure group compared to the other groups (P < 0.001). Indeed, an increase in thiobarbituric acid reactive substances, hydroperoxides and protein carbonyls was noted in the end stage renal failure group in comparison with the other groups (P < 0.001), while the levels of antioxidants enzymes activity were decreased in the study population (P < 0.001).

Conclusion

Impaired renal function is closely associated with the elevation of inflammatory markers leading to both increased markers of oxidative stress and decreased antioxidant defense.     

Circulating biomarkers of collagen type I metabolism mark the right ventricular fibrosis and adverse markers of clinical outcome in adults with repaired tetralogy of Fallot

Background

Right ventricular (RV) fibrosis is common in patients with repaired tetralogy of Fallot (rTOF). Although accumulating evidence indicates the role of circulating biomarkers of collagen metabolism in left ventricular fibrosis, rTOF data are lacking. This study examined the expression profile and clinical relevance of circulating biomarkers of collagen type I metabolism in rTOF patients.

Methods

Serum biomarkers of collagen type I synthesis (carboxy-terminal propeptide of procollagen type I, PICP), degradation (carboxy-terminal telopeptide of collagen type I, CITP), and enzymes regulating collagen degradation (matrix metalloproteinases, and type I tissue inhibitor, TIMP-1) were measured in 70 rTOF and 91 control adults. All patients had complete clinical data and received cardiovascular magnetic resonance scans with late gadolinium enhancement (LGE).

Results

Compared to the controls, rTOF patients had higher PICP levels (p < 0.001), PICP:CITP ratios (p < 0.001), and TIMP-1 concentrations (p < 0.001). Increasing PICP levels correlated with higher RV LGE scores (r = 0.427, p < 0.001), lower VO₂max (r = − 0.428, p = 0.002), and larger RV volumes. Furthermore, stepwise multivariate linear regression analysis identified RV end-diastolic volume index > 150 mL/m² (β = 40.52, p = 0.016), RV LGE score (β = 3.94, p = 0.008), and age (β = − 1.77, p = 0.011) as independent correlates of circulating PICP levels.

Conclusions

Patients with rTOF exhibited a profibrotic state with excessive collagen type I synthesis and dysregulated degradation. Elevated circulating PICP levels might reflect RV fibrosis, and link to adverse markers of clinical outcome.     

A flavonoid fraction purified from Rutaceae aurantiae (Daflon) inhibiting AGE formation,reduces urinary albumin clearance and corrects hypoalbuminemia in normotensive and hypertensive diabetic rats

Aim

Advanced glycation endproducts (AGEs) have been shown to contribute to alteration of glomerular permselectivity to proteins in diabetes. Oxidative stress is required for AGE formation. Therefore we studied the effect of an antioxidant micronized purified flavonoid fraction (MPFF, Daflon^R 500 mg), on urinary albumin clearance in diabetic rats.

Methods

Hyperglycaemia was induced by streptozotocin 55 mg/kg IM at days 0 and 7 in normotensive Wistar rats (NWR, diabetes duration 5 months) or hypertensive Wistar Kyoto rats (SHR, diabetes duration 2 months). MPFF was administered at 300 mg/kg/day, from day −2 until sacrifice.

Results

After 5 months of diabetes in NWR, MPFF reduced albumin clearance from 729 ± 92 to 392 ± 60 nl/min/kg, p < 0.01, and restored albuminemia from 20.4 ± 0.9 to 24.0 ± 1 g/l, p < 0.05; albumin fractional clearance was significantly diminished in the flavonoid-treated diabetic rats (0.360 ± 0.037‰ versus 1.335 ± 0.430‰ in the diabetic controls, p < 0.001); MPFF did not significantly modify blood glucose and plasma fructosamine levels. After 2 months of diabetes in SHR, MPFF reduced albumin clearance from 243 ± 121 to 101 ± 47 nl/min/kg, p < 0.05, and restored albuminemia from 21.1 ± 1.6 to 26.7 ± 2.2 g/l (p < 0.05); MPFF also decreased plasma fluorescence characteristic of AGEs (p < 0.02). Besides hesperetin, a main metabolite of MPFF recovered in plasma, inhibited in vitro the formation of the crosslinking AGE pentosidine in collagen incubated with high glucose (p < 0.001).

Conclusion

Our results confirm the role of glycoxidative stress in diabetic nephropathy. MPFF might be useful as complementary treatment for preventing diabetic microangiopathy.     

Prevalence of risk factors for atrial fibrillation and stroke among 1210 patients with sleep disordered breathing

Aims

This study sought to identify the prevalence of risk factors for atrial fibrillation and stroke in a sleep apnea population.

Methods

Study participants included 1210 consecutive adults who were referred with suspicion of sleep apnea. Statistical analysis was used to determine the relationship between sleep apnea syndrome and risk factors for atrial fibrillation and stroke.

Results

Among 1210 enrolled patients, 65.8% had severe sleep apnea (Apnea/hypopnea Index — AHI > 30), 25.2% had mild to moderate sleep apnea (AHI 5 to 30), and 8.8% had no sleep apnea (AHI < 5). At baseline, the mean apnea–hypopnea index in patients with sleep apnea syndrome was 35. Compared to patients with an AHI < 5, those with an AHI > 30 were older (47.3 ± 11.4 vs. 52.74 ± 12.4, p < 0.001) and had a higher body mass index (BMI) (30.7 ± 7.3 vs. 33.83 ± 10.1, p < 0.001), a higher prevalence of hypertension (38 vs. 16%, p < 0.001), and a higher CHADS₂ (congestive heart failure, hypertension, age, diabetes and prior stroke) score (0.59 ± 0.8 vs. 0.28 ± 0.64, p < 0.001).

Conclusions

Patients with severe sleep apnea have a higher prevalence of risk factors for atrial fibrillation and stroke when compared with subjects without sleep apnea.     

Mitochondrial biogenesis and angiogenesis in skeletal muscle of the elderly

The aim of this study was to test the hypotheses that 1) skeletal muscles of elderly subjects can adapt to a single endurance exercise bout and 2) endurance trained elderly subjects have higher expression/activity of oxidative and angiogenic proteins in skeletal muscle than untrained elderly people. To investigate this, lifelong endurance trained elderly (ET; n = 8) aged 71.3 ± 3.4 years and untrained elderly subjects (UT; n = 7) aged 71.3 ± 4 years, performed a cycling exercise bout at 75% VO_2max with vastus lateralis muscle biopsies obtained before (Pre), immediately after exercise (0h) and at 2 h of recovery. Capillarization was detected histochemically and oxidative enzyme activities were determined on isolated mitochondria. GLUT4, HKII, Cyt c and VEGF protein expression was measured on muscle lysates from Pre-biopsies, phosphorylation of AMPK and P38 on lysates from Pre and 0h biopsies, while PGC-1α, VEGF, HKII and TFAM mRNA content was determined at all time points. ET had ~ 40% higher PDH, CS, SDH, α-KG-DH and ATP synthase activities and 27% higher capillarization than UT, reflecting increased skeletal muscle oxidative capacity with lifelong endurance exercise training. In addition, acute exercise increased in UT PGC-1α mRNA 11-fold and VEGF mRNA 4-fold at 2 h of recovery, and AMPK phosphorylation ~ 5-fold immediately after exercise, relative to Pre, indicating an ability to adapt metabolically and angiogenically to endurance exercise. However, in ET PGC-1α mRNA only increased 5 fold and AMPK phosphorylation ~ 2-fold, while VEGF mRNA remained unchanged after the acute exercise bout. P38 increased similarly in ET and UT after exercise. In conclusion, the present findings suggest that lifelong endurance exercise training ensures an improved oxidative capacity of skeletal muscle, and that skeletal muscle of elderly subjects maintains the ability to respond to acute endurance exercise.     

Early development of leaks in the CoreValve percutaneous aortic valve prosthesis: echocardiographic assessment

The study investigated echocardiographic findings after 1 month in 22 patients who received a CoreValve prostheses to treat aortic valve stenosis. Particular attention was paid to the evaluation of valvular leaks and the left ventricular wall thickness. Echocardiograms were obtained prior to implantation, at discharge and 1 month later. The patients’ mean age was 77 ± 4 years. At discharge, 16 patients (76%) had aortic regurgitation: 8 grade I and 8 grade II. At 1 month, only 13 (62%) presented with the condition: 10 grade I and 3 grade II, with 8 patients (38%) demonstrating a reduction of at least one grade (P < .005). The septal thickness decreased (from 14.2 ± 2 mm at baseline to 11 ± 2.4 mm at 1 month; P < .001), as did the posterior wall thickness (from 10.9 ± 2.4 mm at baseline to 8.3 ± 1.2 mm at 1 month; P < .001). In our patient series, the frequency and grade of residual aortic regurgitation after implantation of the CoreValve prosthesis decreased within 1 month, and favorable left ventricular remodeling was also observed.Full English text available from:www.revespcardiol.org