Taku Rokutanda

Fat-derived Factor Omentin Stimulates Endothelial Cell Function and Ischemia-induced Revascularization via Endothelial Nitric Oxide Synthase-dependent Mechanism

Obesity-related diseases are associated with vascular dysfunction and impaired revascularization. Omentin is a fat-derived secreted protein, which is down-regulated in association with obese complications. Here, we investigated whether omentin modulates endothelial cell function and revascularization processes in vitro and in vivo. Systemic delivery of an adenoviral vector expressing omentin (Ad-omentin) enhanced blood flow recovery and capillary density in ischemic limbs of wild-type mice in vivo, which were accompanied by increased phosphorylation of Akt and endothelial nitric oxide synthase (eNOS). In cultured human umbilical vein endothelial cells (HUVECs), a physiological concentration of recombinant omentin protein increased differentiation into vascular-like structures and decreased apoptotic activity under conditions of serum starvation. Treatment with omentin protein stimulated the phosphorylation of Akt and eNOS in HUVECs. Inhibition of Akt signaling by treatment with dominant-negative Akt or LY294002 blocked the stimulatory effects of omentin on differentiation and survival of HUVECs and reversed omentin-stimulated eNOS phosphorylation. Pretreatment with the NOS inhibitor also reduced the omentin-induced increase in HUVEC differentiation and survival. Omentin protein also stimulated the phosphorylation of AMP-activated protein kinase in HUVECs. Transduction with dominant-negative AMP-activated protein kinase diminished omentin-induced phosphorylation of Akt and omentin-stimulated increase in HUVEC differentiation and survival. Of importance, in contrast to wild-type mice, systemic administration of Ad-omentin did not affect blood flow in ischemic muscle in eNOS-deficient mice in vivo. These data indicate that omentin promotes endothelial cell function and revascularization in response to ischemia through its ability to stimulate an Akt-eNOS signaling pathway.

Chronic C-Type Natriuretic Peptide Infusion Attenuates Angiotensin II-Induced Myocardial Superoxide Production and Cardiac Remodeling

Myocardial oxidative stress and inflammation are key mechanisms in cardiovascular remodeling. C-type natriuretic peptide (CNP) is an endothelium-derived cardioprotective factor, although its effect on cardiac superoxide generation has not been investigated in vivo. This study tested the hypothesis that suppression of superoxide production contributes to the cardioprotective action of CNP. Angiotensin II (Ang II) or saline was continuously infused subcutaneously into mice using an osmotic minipump. Simultaneously with the initiation of Ang II treatment, mice were infused with CNP (0.05 μg/kg/min) or vehicle for 2 weeks. The heart weight to tibial length ratio was significantly increased by Ang II in vehicle-treated mice. Treatment with CNP decreased Ang II-induced cardiac hypertrophy without affecting systolic blood pressure. Echocardiography showed that CNP attenuated Ang II-induced increase in wall thickness, left ventricular dilatation, and decrease in fractional shortening. CNP reduced Ang II-induced increases in cardiomyocyte size and interstitial fibrosis and suppressed hypertrophic- and fibrosis-related gene expression. Finally, CNP decreased Ang II-induced cardiac superoxide production. These changes were accompanied by suppression of NOX4 gene expression. Our data indicate that treatment with CNP attenuated Ang II-induced cardiac hypertrophy, fibrosis, and contractile dysfunction which were accompanied by reduced cardiac superoxide production.

Sirt7 Contributes to Myocardial Tissue Repair by Maintaining Transforming Growth Factor-β Signaling Pathway.

Background— Sirt7, 1 of the 7 members of the mammalian sirtuin family, promotes oncogenic transformation. Tumor growth and metastasis require fibrotic and angiogenic responses. Here, we investigated the role of Sirt7 in cardiovascular tissue repair process. Methods and Results— In wild-type mice, Sirt7 expression increased in response to acute cardiovascular injury, including myocardial infarction and hind-limb ischemia, particularly at the active wound healing site. Compared with wild-type mice, homozygous Sirt7-deficient (Sirt7−/−) mice showed susceptibility to cardiac rupture after myocardial infarction, delayed blood flow recovery after hind-limb ischemia, and impaired wound healing after skin injury. Histological analysis showed reduced fibrosis, fibroblast differentiation, and inflammatory cell infiltration in the border zone of infarction in Sirt7−/− mice. In vitro, Sirt7−/− mouse–derived or Sirt7 siRNA–treated cardiac fibroblasts showed reduced transforming growth factor-&bgr; signal activation and low expression levels of fibrosis-related genes compared with wild-type mice–derived or control siRNA–treated cells. These changes were accompanied by reduction in transforming growth factor receptor I protein. Loss of Sirt7 activated autophagy in cardiac fibroblasts. Transforming growth factor-&bgr; receptor I downregulation induced by loss of Sirt7 was blocked by autophagy inhibitor, and interaction of Sirt7 with protein interacting with protein kinase-C&agr; was involved in this process. Conclusion— Sirt7 maintains transforming growth factor receptor I by modulating autophagy and is involved in the tissue repair process.

Growth differentiation factor-15 is a useful prognostic marker in patients with heart failure with preserved ejection fraction.

BACKGROUND Circulating growth differentiation factor 15 (GDF-15) levels correlate with heart mass and fibrosis; however, little is known about its value in predicting the prognosis of patients with heart failure with preserved ejection fraction (HFpEF). METHODS We measured serum GDF-15 levels in 149 consecutive patients with left ventricular diastolic dysfunction (LVDD) and normal LV ejection fraction (>50%) and followed them for cardiovascular events. LVDD was defined according to the European Society of Cardiology guidelines. RESULTS The New York Heart Association functional class and circulating B-type natriuretic peptide (BNP) levels were significantly higher in the high-GDF-15 group (n = 75; greater than or equal to the median value [3694 pg/mL]) than in the low-GDF-15 group (n = 74). Patients were divided into HFpEF and LVDD groups according to the presence or absence of HF. Serum GDF-15 levels were significantly higher in the HFpEF group (n = 73) than in the LVDD group (n = 76) (median, 4215 [interquartile range, 3382-5287] vs 3091 [interquartile range, 2487-4217 pg/mL]; P < 0.0001). Kaplan-Meier curve analysis showed a significantly higher probability of cardiovascular events in the high-GDF-15 group than in the low-GDF-15 group for data of all patients (log-rank test P = 0.006) and data of patients in the HFpEF group only (P = 0.014). Multivariate Cox hazard analysis identified age (hazard ratio [HR], 0.92; 95% confidence interval [CI], 0.87-0.98; P = 0.008), atrial fibrillation (HR, 7.95; 95% CI, 1.98-31.85, P = 0.003), lnBNP (HR, 3.37; 95% CI, 1.73-6.55; P < 0.0001), and GDF-15 (ln[GDF-15]) (HR, 4.74; 95% CI, 1.26-17.88, P = 0.022) as independent predictors of primary end points. CONCLUSIONS GDF-15 is a potentially useful prognostic biomarker in patients with HFpEF.

Sirt7 Contributes to Myocardial Tissue Repair by Maintaining TGF-β Signaling Pathway

Background— Sirt7, 1 of the 7 members of the mammalian sirtuin family, promotes oncogenic transformation. Tumor growth and metastasis require fibrotic and angiogenic responses. Here, we investigated the role of Sirt7 in cardiovascular tissue repair process. Methods and Results— In wild-type mice, Sirt7 expression increased in response to acute cardiovascular injury, including myocardial infarction and hind-limb ischemia, particularly at the active wound healing site. Compared with wild-type mice, homozygous Sirt7-deficient (Sirt7−/−) mice showed susceptibility to cardiac rupture after myocardial infarction, delayed blood flow recovery after hind-limb ischemia, and impaired wound healing after skin injury. Histological analysis showed reduced fibrosis, fibroblast differentiation, and inflammatory cell infiltration in the border zone of infarction in Sirt7−/− mice. In vitro, Sirt7−/− mouse–derived or Sirt7 siRNA–treated cardiac fibroblasts showed reduced transforming growth factor-&bgr; signal activation and low expression levels of fibrosis-related genes compared with wild-type mice–derived or control siRNA–treated cells. These changes were accompanied by reduction in transforming growth factor receptor I protein. Loss of Sirt7 activated autophagy in cardiac fibroblasts. Transforming growth factor-&bgr; receptor I downregulation induced by loss of Sirt7 was blocked by autophagy inhibitor, and interaction of Sirt7 with protein interacting with protein kinase-C&agr; was involved in this process. Conclusion— Sirt7 maintains transforming growth factor receptor I by modulating autophagy and is involved in the tissue repair process.

Passive Exercise Using Whole-Body Periodic Acceleration Enhances Blood Supply to Ischemic Hindlimb

Objective—Whole-body periodic acceleration (WBPA) has been developed as a passive exercise technique to improve endothelial function by increasing shear stress through repetitive movements in spinal axis direction. We investigated the effects of WBPA on blood flow recovery in a mouse model of hindlimb ischemia and in patients with peripheral arterial disease. Methods and Results—After unilateral femoral artery excision, mice were assigned to either the WBPA (n=15) or the control (n=13) group. WBPA was applied at 150 cpm for 45 minutes under anesthesia once a day. WBPA significantly increased blood flow recovery after ischemic surgery, as determined by laser Doppler perfusion imaging. Sections of ischemic adductor muscle stained with anti-CD31 antibody showed a significant increase in capillary density in WBPA mice compared with control mice. WBPA increased the phosphorylation of endothelial nitric oxide synthase (eNOS) in skeletal muscle. The proangiogenic effect of WBPA on ischemic limb was blunted in eNOS-deficient mice, suggesting that the stimulatory effects of WBPA on revascularization are eNOS dependent. Quantitative real-time polymerase chain reaction analysis showed significant increases in angiogenic growth factor expression in ischemic hindlimb by WBPA. Facilitated blood flow recovery was observed in a mouse model of diabetes despite there being no changes in glucose tolerance and insulin sensitivity. Furthermore, both a single session and 7-day repeated sessions of WBPA significantly improved blood flow in the lower extremity of patients with peripheral arterial disease. Conclusion—WBPA increased blood supply to ischemic lower extremities through activation of eNOS signaling and upregulation of proangiogenic growth factor in ischemic skeletal muscle. WBPA is a potentially suitable noninvasive intervention to facilitate therapeutic angiogenesis.

Akt1-Mediated Fast/Glycolytic Skeletal Muscle Growth Attenuates Renal Damage in Experimental Kidney Disease

Muscle wasting is frequently observed in patients with kidney disease, and low muscle strength is associated with poor outcomes in these patients. However, little is known about the effects of skeletal muscle growth per se on kidney diseases. In this study, we utilized a skeletal muscle-specific, inducible Akt1 transgenic (Akt1 TG) mouse model that promotes the growth of functional skeletal muscle independent of exercise to investigate the effects of muscle growth on kidney diseases. Seven days after Akt1 activation in skeletal muscle, renal injury was induced by unilateral ureteral obstruction (UUO) in Akt1 TG and wild-type (WT) control mice. The expression of atrogin-1, an atrophy-inducing gene in skeletal muscle, was upregulated 7 days after UUO in WT mice but not in Akt1 TG mice. UUO-induced renal interstitial fibrosis, tubular injury, apoptosis, and increased expression of inflammatory, fibrosis-related, and adhesion molecule genes were significantly diminished in Akt1 TG mice compared with WT mice. An increase in the activating phosphorylation of eNOS in the kidney accompanied the attenuation of renal damage by myogenic Akt1 activation. Treatment with the NOS inhibitor L-NAME abolished the protective effect of skeletal muscle Akt activation on obstructive kidney disease. In conclusion, Akt1-mediated muscle growth reduces renal damage in a model of obstructive kidney disease. This improvement appears to be mediated by an increase in eNOS signaling in the kidney. Our data support the concept that loss of muscle mass during kidney disease can contribute to renal failure, and maintaining muscle mass may improve clinical outcome.

A Pilot Study: The Beneficial Effects of Combined Statin-exercise Therapy on Cognitive Function in Patients with Coronary Artery Disease and Mild Cognitive Decline

Objective Hypercholesterolemia, a risk factor in cognitive impairment, can be treated with statins. However, cognitive decline associated with “statins” (HMG-CoA reductase inhibitors) is a clinical concern. This pilot study investigated the effects of combining statins and regular exercise on cognitive function in coronary artery disease (CAD) patients with prior mild cognitive decline. Methods We recruited 43 consecutive CAD patients with mild cognitive decline. These patients were treated with a statin and weekly in-hospital aerobic exercise for 5 months. We measured serum lipids, exercise capacity, and cognitive function using the mini mental state examination (MMSE). Results Low-density lipoprotein cholesterol levels were significantly decreased, and maximum exercise capacity (workload) was significantly increased in patients with CAD and mild cognitive decline after treatment compared with before. Combined statin-exercise therapy significantly increased the median (range) MMSE score from 24 (22-25) to 25 (23-27) across the cohort (p<0.01). Changes in body mass index (BMI) were significantly and negatively correlated with changes in the MMSE. After treatment, MMSE scores in the subgroup of patients that showed a decrease in BMI were significantly improved, but not in the BMI-increased subgroup. Furthermore, the patients already on a statin at the beginning of the trial displayed a more significant improvement in MMSE score than statin-naïve patients, implying that exercise might be the beneficial aspect of this intervention as regards cognition. In a multivariate logistic regression analysis adjusted for age >65 years, sex, and presence of diabetes mellitus, a decrease in BMI during statin-exercise therapy was significantly correlated with an increase in the MMSE score (odds ratio: 4.57, 95% confidence interval: 1.05-20.0; p<0.05). Conclusion Statin-exercise therapy may help improve cognitive dysfunction in patients with CAD and pre-existing mild cognitive decline.

Early diastolic overinflation in diastolic mitral regurgitation.

An 81-year-old man presented with exertional dyspnea at our hospital. An electrocardiogram was recorded, which showed 2:1 atrioventricular (AV) block. Transthoracic 2-dimensional echocardiography showed that the left ventricular (LV) wall thickness and wall motion were normal. Color Doppler echocardiography showed no significant valvular heart disease. Pulsed Doppler echocardiography at the mitral valve showed a high early diastolic inflow (E) wave (111 cm/s) with a short deceleration time (125 ms) and diastolic mitral regurgitation (MR) in early diastole (Fig. 1, right panel, arrow). By raising the baseline to reveal the full profile of the diastolic regurgitant flow, pulsed Doppler echocardiography showed that the pressure gradient at the mitral cusp was 8.3 mmHg (Fig. 1, left panel, arrow). There have been reports about the mechanisms of diastolic MR. As coaptation of the mitral valve is not isolated to the tips but, rather, is the result of the overlap of several millimeters of tissue, LV contraction is necessary for definite mitral valve closure. Thus, AV block of any degree may become a cause of diastolic MR [1]. The reversed AV pressure gradient during atrial relaxation may also contribute to this. Without AV block, diastolic MR may be present in a high LV diastolic pressure setting, such as that during aortic regurgitation [2]. In the present case, a longitudinal global strain from speckle tracking showed that the left ventricle was already dilated to the level of end-diastole (Fig. 2, dotted line, arrow). This suggests that LV early diastolic pressure might be as high as end-diastolic pressure. Along with the decrease in left atrial pressure after atrial contraction, there might be a reversed pressure gradient between the left ventricle and the left atrium. The global strain decreased during mid-diastole, suggesting gradual decrease in LV size due to diastolic MR (Fig. 2). Thus, global strain was useful in estimating the LV volume change during diastole in this patient.

Deceased left ventricular compliance contributing to diastolic mitral regurgitation in a patient with atrioventricular block

A 79-year-old woman temporarily lost consciousness and was admitted to our hospital. She had been treated for hypertension and diabetes mellitus. Upon admission, her blood pressure was 112/51 mm Hg; pulse rate, 37/min; and pulse oxygen saturation, 95 %. On auscultation, her heart and breath sounds were normal. Blood examination results showed normal cardiac enzyme levels but high plasma B-type natriuretic peptide levels (381.7 pg/mL). A 12-lead electrocardiogram showed advanced atrioventricular (AV) block. Slight ST-segment elevation and terminal T inversion were observed in leads III and aVF. A chest radiograph showed a cardiothoracic ratio of 57 %. Twodimensional transthoracic echocardiography showed normal left ventricular (LV) wall thickness and hypokinesis at the inferior wall. LV end-diastolic and end-systolic dimensions and fractional shortening were normal (44 mm, 26 mm, and 41 %, respectively). A pulsed Doppler echocardiogram of the mitral inflow (Fig. 1, arrows) and color Doppler imaging (Fig. 2, top, arrow) showed diastolic mitral regurgitation (DMR). The estimated peak pressure gradient of DMR was 8 mm Hg. The patient underwent cardiac catheterization. Simultaneous recording of pulmonary artery wedge (PAW) and LV pressures showed that the LV pressure was elevated abruptly by atrial contraction and remained elevated until late diastole (Fig. 2, bottom). As the PAW pressure decreased after the atrial contraction, AV pressure reversal occurred and continued to late diastole. Coronary arteriography revealed severe stenosis at the right coronary artery, for which percutaneous coronary intervention was performed. The next day, the AV block was abolished. A transthoracic echocardiogram showed that the DMR had disappeared. Complete mitral valve closure needs effective LV contraction, and mitral regurgitation may occur whenever the LV pressure exceeds the left atrial (LA) pressure during diastole. In any degree of AV block, atrial relaxation without succeeding LV contraction may cause reversed AV pressure gradient and DMR [1]. In the present case, we recorded the PAW and LV pressures simultaneously. The LV pressure abruptly elevated to higher than 15 mm Hg in mid-diastole by atrial contraction and decreased LV compliance owing to myocardial ischemia. However, the LA volume was already so small in atrial systole that the LA and PAW pressures became lower in mid-diastole. This case suggests that early atrial emptying and decreased LV compliance might play pivotal roles in the DMR in AV block.