Role of AMP deaminase in diabetic cardiomyopathy.

Diabetes mellitus is one of the major causes of ischemic and nonischemic heart failure. While hypertension and coronary artery disease are frequent comorbidities in patients with diabetes, cardiac contractile dysfunction and remodeling occur in diabetic patients even without comorbidities, which is referred to as diabetic cardiomyopathy. Investigations in recent decades have demonstrated that the production of reactive oxygen species (ROS), impaired handling of intracellular Ca2+, and alterations in energy metabolism are involved in the development of diabetic cardiomyopathy. AMP deaminase (AMPD) directly regulates adenine nucleotide metabolism and energy transfer by adenylate kinase and indirectly modulates xanthine oxidoreductase-mediated pathways and AMP-activated protein kinase-mediated signaling. Upregulation of AMPD in diabetic hearts was first reported more than 30 years ago, and subsequent studies showed similar upregulation in the liver and skeletal muscle. Evidence for the roles of AMPD in diabetes-induced fatty liver, sarcopenia, and heart failure has been accumulating. A series of our recent studies showed that AMPD localizes in the mitochondria-associated endoplasmic reticulum membrane as well as the sarcoplasmic reticulum and cytosol and participates in the regulation of mitochondrial Ca2+ and suggested that upregulated AMPD contributes to contractile dysfunction in diabetic cardiomyopathy via increased generation of ROS, adenine nucleotide depletion, and impaired mitochondrial respiration. The detrimental effects of AMPD were manifested at times of increased cardiac workload by pressure loading. In this review, we briefly summarize the expression and functions of AMPD in the heart and discuss the roles of AMPD in diabetic cardiomyopathy, mainly focusing on contractile dysfunction caused by this disorder.

Optimal serum 25-hydroxyvitamin D level to prevent sarcopenia in patients with heart failure: Insights from a dose-response relationship.

BACKGROUND AND AIMS: Low serum 25-hydroxyvitamin D (25 [OH]D) levels have been associated with sarcopenia, frailty, and risk of cardiovascular disease, whereas high levels negatively impact clinical outcomes. We determined optimal serum 25(OH)D concentrations to minimise the probability of sarcopenia in patients with heart failure (HF) by examining the dose-dependent relationship between serum 25(OH)D levels and sarcopenia. METHODS AND RESULTS: We enrolled 461 consecutive patients with HF (mean age, 72 ± 15 years; 39% female) who underwent dual-energy X-ray absorptiometry. Serum 25(OH)D levels were measured using a chemiluminescence immunoassay. Sarcopenia was diagnosed according to the 2019 Asian Working Group for Sarcopenia criteria. Overall, 49% of enrolled patients were diagnosed with sarcopenia. Adjusted logistic regression with restricted cubic spline function revealed that the odds ratio (OR) of sarcopenia increased in patients with HF presenting serum 25(OH)D levels <14.6 ng/ml or > 31.4 ng/ml, reaching the lowest OR at ∼20 ng/ml. Multivariate logistic regression revealed that a serum 25(OH)D level below 14.6 ng/mL was independently associated with the presence of sarcopenia (adjusted OR: 2.16, 95% confidence interval [CI]: 1.24-3.78). Incorporating serum 25(OH)D levels <14.6 ng/ml, but not <20.0 ng/ml, in the baseline model improved continuous net reclassification (0.334, 95% CI: 0.122-0.546) in patients with HF. CONCLUSION: A U-shaped relationship exists between serum 25(OH)D levels and sarcopenia probability in patients with HF. Maintaining serum 25(OH)D levels between 14.6 and 31.4 ng/ml may help prevent sarcopenia in patients with HF.

Circulating level of ß-aminoisobutyric acid (BAIBA), a novel myokine-like molecule, is inversely associated with fat mass in patients with heart failure.

Results of experimental studies have shown that ß-aminoisobutyric acid (BAIBA), an exercise-induced myokine-like molecule, is an endogenous negative regulator of fat mass in mice, but it remains unclear whether that is the case in humans, though an enhanced BAIBA concentration in patients receiving sodium-glucose cotransporter 2 inhibitors was found in our recent study. The objective of this study was to analyze the determinants of circulating BAIBA concentration in humans, with focus on the possible link between circulating BAIBA and body composition including fat mass. Data for 188 consecutive patients with heart failure (HF, 64 ± 13 years; 70% male) who received a dual energy X ray absorptiometry (DEXA) scan for assessment of body composition including fat mass index (FMI) and appendicular skeletal muscle mass index (ASMI) were used in this study. Plasma BAIBA concentration in a fasting state after stabilization of HF was determined using ultraperformance liquid chromatography. Plasma BAIBA was detected in 66% of the patients. In simple linear regression analyses of data from patients in whom plasma BAIBA was detected, plasma BAIBA concentration was positively correlated with uric acid and was negatively correlated with body mass index (BMI), estimated glomerular filtration rate (eGFR), FMI, and % body fat. There were no correlations between plasma BAIBA concentration and indexes of muscle mass and bone mass. The results of multiple linear regression analyses showed that FMI and % body fat in addition to BMI, but not ASMI, were independent explanatory factors for plasma BAIBA concentration. In conclusion, plasma BAIBA concentration is inversely correlated with indexes of fat mass, indicating that BAIBA may be a therapeutic target for excessive fat accumulation.

Downregulation of Mitochondrial Fusion Protein Expression Affords Protection from Canonical Necroptosis in H9c2 Cardiomyoblasts.

Necroptosis, a form of necrosis, and alterations in mitochondrial dynamics, a coordinated process of mitochondrial fission and fusion, have been implicated in the pathogenesis of cardiovascular diseases. This study aimed to determine the role of mitochondrial morphology in canonical necroptosis induced by a combination of TNFα and zVAD (TNF/zVAD) in H9c2 cells, rat cardiomyoblasts. Time-course analyses of mitochondrial morphology showed that mitochondria were initially shortened after the addition of TNF/zVAD and then their length was restored, and the proportion of cells with elongated mitochondria at 12 h was larger in TNF/zVAD-treated cells than in non-treated cells (16.3 ± 0.9% vs. 8.0 ± 1.2%). The knockdown of dynamin-related protein 1 (Drp1) and fission 1, fission promoters, and treatment with Mdivi-1, a Drp-1 inhibitor, had no effect on TNF/zVAD-induced necroptosis. In contrast, TNF/zVAD-induced necroptosis was attenuated by the knockdown of mitofusin 1/2 (Mfn1/2) and optic atrophy-1 (Opa1), proteins that are indispensable for mitochondrial fusion, and the attenuation of necroptosis was not canceled by treatment with Mdivi-1. The expression of TGFß-activated kinase (TAK1), a negative regulator of RIP1 activity, was upregulated and the TNF/zVAD-induced RIP1-Ser166 phosphorylation, an index of RIP1 activity, was mitigated by the knockdown of Mfn1/2 or Opa1. Pharmacological TAK1 inhibition attenuated the protection afforded by Mfn1/2 and Opa1 knockdown. In conclusion, the inhibition of mitochondrial fusion increases TAK1 expression, leading to the attenuation of canonical necroptosis through the suppression of RIP1 activity.

Independent Link Between Use of Mineralocorticoid Receptor Antagonists and Muscle Wasting in Heart Failure Patients Not Receiving Renin-Angiotensin System Inhibitors.

BACKGROUND: The renin-angiotensin system (RAS) activation is a proposed mechanism of muscle wasting (MW i.e., reduction in muscle mass). Although we reported that RAS inhibitors (RASIs) were associated with lower prevalence of MW in heart failure (HF) patients, the relationship between mineralocorticoid receptor (MR) signaling and MW has not been analyzed.Methods and Results: We analyzed data from 320 consecutive Japanese HF patients who underwent dual-energy X-ray absorptiometry scanning for assessment of appendicular skeletal muscle mass index (ASMI). In multiple linear regression analyses, plasma renin activity (PRA) was negatively correlated with ASMI in patients not receiving RASIs, indicating an untoward role of the RAS in MW. Results of analysis of covariance in which risk factors of MW served as covariates showed that use of MR antagonists (MRAs) was associated with lower ASMI and higher PRA in the non-RASIs group. The close relationship between use of MRAs and lower ASMI or higher PRA in the non-RASIs group was confirmed in analyses in which the differences in baseline characteristics between users and non-users of MRAs were minimized by using an inverse probability of treatment weighting. CONCLUSIONS: Increased PRA by MR inhibition without concurrent RAS inhibition, possibly contributing to upregulation of angiotensin II signaling, may be associated with reduction in muscle mass.

Nuclear translocation of MLKL enhances necroptosis by a RIP1/RIP3-independent mechanism in H9c2 cardiomyoblasts.

Accumulating evidence suggests that necroptosis of cardiomyocytes contributes to cardiovascular diseases. Lethal disruption of the plasma membrane in necroptosis is induced by oligomers of mixed lineage kinase domain-like (MLKL) that is translocated to the membrane from the cytosol. However, the role played by cytoplasmic-nuclear shuttling of MLKL is unclear. Here, we tested the hypothesis that translocation of MLKL to the nucleus promotes the necroptosis of cardiomyocytes. Activation of the canonical necroptotic signaling pathway by a combination of TNF-α and zVAD (TNF/zVAD) increased nuclear MLKL levels in a RIP1-activity-dependent manner in H9c2 cells, a rat cardiomyoblast cell line. By use of site-directed mutagenesis, we found a nuclear export signal sequence in MLKL and prepared its mutant (MLKL-L280/283/284A), though a search for a nuclear import signal was unsuccessful. MLKL-L280/283/284A localized to both the cytosol and the nucleus. Expression of MLKL-L280/283/284A induced necroptotic cell death, which was attenuated by GppNHp, an inhibitor of Ran-mediated nuclear import, but not by inhibition of RIP1 activity or knockdown of RIP3 expression. GppNHp partly suppressed H9c2 cell death induced by TNF/zVAD treatment. These results suggest that MLKL that is translocated to the nucleus via RIP1-mediated necroptotic signaling enhances the necroptosis of cardiomyocytes through a RIP1-/RIP3-independent mechanism.

Early Commencement and Long-Term Continuation of Tolvaptan Treatment Attenuate Functional Impairment of Renal Vasopressin V2 Receptors and Improve Clinical Outcomes in Patients with Heart Failure.

Preserved urinary excretion of aquaporin 2, an index for the function of vasopressin V2 receptor (V2-R), has been reported to predict a favorable response of heart failure patients to treatment with tolvaptan. In this study, we investigated the long-term effects of tolvaptan treatment on clinical outcomes and V2-R function in patients with acute decompensated heart failure (ADHF). We enrolled 90 consecutive patients who were hospitalized in Sapporo Medical University Hospital for ADHF and treated with tolvaptan in the BOREAS-ADHF registry and analyzed patients who continued taking tolvaptan after discharge. The effect of tolvaptan treatment on rehospitalization for HF or death was investigated according to whether the V2-R function was preserved (first morning urine osmolarity ≥ 352 mOsm/L, High-Uosm) or impaired (Uosm < 352 mOsm/L, Low-Uosm). During a median follow-up period of 443 days, significantly fewer patients in the High-Uosm group experienced adverse events than did patients in the Low-Uosm group (P < 0.001). Among the patients with High-Uosm, early commencement of tolvaptan administration (on or before day 7 of hospitalization, Early/High-Uosm) significantly reduced adverse events compared to late administration (after day 7 of hospitalization, Late/High-Uosm). Uosm measured during the long-term follow-up period after discharge was significantly reduced compared to that before commencement of tolvaptan administration in the Late/High-Uosm group (from 468 ± 88 to 395 ± 108 mOsm, -18.3 ± 19.6%, P < 0.05) but not in the Early/High-Uosm group (from 478 ± 115 to 455 ± 133 mOsm, -0.50 ± 35.3%, P = 0.66). These findings indicate that early commencement and long-term continuation of tolvaptan treatment attenuate functional impairment of V2-R and improve clinical outcomes in ADHF patients with preserved V2-R function.

Elevated circulating level of ß-aminoisobutyric acid (BAIBA) in heart failure patients with type 2 diabetes receiving sodium-glucose cotransporter 2 inhibitors.

AIMS: The mechanism by which a sodium-glucose cotransporter inhibitor (SGLT2i) induces favorable effects on diabetes and cardiovascular diseases including heart failure (HF) remains poorly understood. Metabolomics including amino acid profiling enables detection of alterations in whole body metabolism. The aim of this study was to determine whether plasma amino acid profiles are modulated by SGLT2i use in HF patients with type 2 diabetes mellitus (T2DM). METHODS: We retrospectively examined 81 HF patients with T2DM (68 ± 11 years old; 78% male). Plasma amino acid concentrations in a fasting state after stabilization of HF were determined using ultraperformance liquid chromatography. To minimize potential selection bias in the retrospective analyses, the differences in baseline characteristics between patients receiving an SGLT2i and patients not receiving an SGLT2i were controlled by using an inverse probability of treatment weighting (IPTW)-adjusted analysis. RESULTS: Of amino acids measurable in the present assay, plasma ß-aminoisobutyric acid (BAIBA), an exercise-induced myokine-like molecule also known as 3-aminoisobutyric acid or 3-amino-2-methyproponic acid, was detected in 77% of all patients and the proportion of patients in whom plasma BAIBA was detected was significantly higher in patients receiving an SGLT2i than in patients not receiving an SGLT2i (93% vs. 67%, p = 0.01). Analyses in patients in whom plasma BAIBA was detected showed that plasma BAIBA concentration was significantly higher in patients receiving an SGLT2i than in patients not receiving an SGLT2i (6.76 ± 4.72 vs. 4.56 ± 2.93 nmol/ml, p = 0.03). In multivariate logistic regression analyses that were adjusted for age and sex, SGLT2i use was independently associated with BAIBA detection. The independent association between BAIBA and SGLT2i use remained after inclusion of body mass index, HF with reduced ejection fraction, ischemic etiology, renal function, NT-proBNP, albumin, hemoglobin, and HbA1c into the Cox proportional hazards model. When the differences in baseline characteristics between patients receiving an SGLT2i and patients not receiving an SGLT2i were controlled by using an IPTW-adjusted analysis, least squares mean of plasma BAIBA concentration was significantly higher in patients receiving an SGLT2i than in patients not receiving an SGLT2i. CONCLUSION: SGLT2i use is closely associated with increased circulating BAIBA concentration in HF patients with T2DM.

Early Detection of Cardiac Amyloidosis in Transthyretin Mutation Carriers.

Diagnostic strategies for symptomatic transthyretin (ATTR) cardiac amyloidosis showing typical morphological features such as increased ventricular wall thickness and myocardial injury such as an elevation in serum troponin T level have been established, but those for subclinical cardiac amyloidosis are limited. In the era when effective therapies to suppress/delay progression of ATTR cardiac amyloidosis are available, early detection of cardiac involvement plays a crucial role in appropriate decision-making for treatment in TTR mutation carriers who have a family history of heart failure and death due to ATTR amyloidosis. Findings of three cases with known pathogenic transthyretin (TTR) mutations (p.Ser70Arg, p.Phe53Val, and p.Val50Met) and family histories of death for amyloidosis were presented. Two cases were asymptomatic, and a case carrying p.Phe53Val had gastrointestinal symptoms and autonomic neuropathy. Levels of plasma N-terminal fragment of pro-B-type natriuretic peptide and troponin T were within normal ranges in all cases, but results of cardiac magnetic resonance (CMR) and bone scintigraphy clearly revealed the presence of cardiac involvement in all cases, even in a case without echocardiographic abnormalities including left ventricular hypertrophy and relative apical sparing of longitudinal strain shown by two-dimensional speckle-tracking echocardiography. Electrocardiography revealed modest abnormalities including reduced R wave amplitude in V2 and a trend toward left axis deviation in all cases. In conclusion, CMR, bone scintigraphy, and electrocardiography are useful for early detection of ATTR cardiac amyloidosis in TTR mutation carriers. The role of comprehensive cardiac assessment in the early detection of cardiac amyloidosis in TTR mutation carriers is discussed.

Xanthine oxidoreductase-mediated injury is amplified by upregulated AMP deaminase in type 2 diabetic rat hearts under the condition of pressure overload.

BACKGROUND: We previously reported that upregulated AMP deaminase (AMPD) contributes to diastolic ventricular dysfunction via depletion of the adenine nucleotide pool in a rat model of type 2 diabetes (T2DM), Otsuka Long-Evans-Tokushima Fatty rats (OLETF). Meanwhile, AMPD promotes the formation of substrates of xanthine oxidoreductase (XOR), which produces ROS as a byproduct. Here, we tested the hypothesis that a functional link between upregulated AMPD and XOR is involved in ventricular dysfunction in T2DM rats. METHODS AND RESULTS: Pressure-volume loop analysis revealed that pressure overloading by phenylephrine infusion induced severer left ventricular diastolic dysfunction (tau: 14.7 ± 0.8 vs 12.5 ± 0.7 msec, left ventricular end-diastolic pressure: 18.3 ± 1.5 vs 12.2 ± 1.3 mmHg, p < 0.05) and ventricular-arterial uncoupling in OLETF than in LETO, non-diabetic rats, though the baseline parameters were comparable in the two groups. While the pressure overload did not affect AMPD activity, it increased XOR activity both in OLETF and LETO, with OLETF showing significantly higher XOR activity than that in LETO (347.2 ± 17.9 vs 243.2 ± 6.1 µg/min/mg). Under the condition of pressure overload, myocardial ATP level was lower, and levels of xanthine and uric acid were higher in OLETF than in LETO. Addition of exogenous inosine, a product of AMP deamination, to the heart homogenates augmented XOR activity. OLETF showed 68% higher tissue ROS levels and 47% reduction in mitochondrial state 3 respiration compared with those in LETO. Overexpression of AMPD3 in H9c2 cells elevated levels of hypoxanthine and ROS and reduced the level of ATP. Inhibition of XOR suppressed the production of tissue ROS and mitochondrial dysfunction and improved ventricular function under the condition of pressure overload in OLETF. CONCLUSIONS: The results suggest that increases in the activity of XOR and the formation of XOR substrates by upregulated AMPD contribute to ROS-mediated diastolic ventricular dysfunction at the time of increased cardiac workload in diabetic hearts.

Barthel Index Score Predicts Mortality in Elderly Heart Failure　- A Goal of Comprehensive Cardiac Rehabilitation.

BACKGROUND: A strategy to predict mortality in elderly heart failure (HF) patients has not been established.Methods and Results:We retrospectively enrolled 413 HF patients aged ≥65 years (mean age 78 years) who had received comprehensive cardiac rehabilitation (CR) during hospitalization. Basic activities of daily life were assessed before discharge using the Barthel index (BI). Of 413 HF patients, 116 (28%) died during a median follow-up period of 1.90 years (interquartile range 1.20-3.23 years). An adjusted dose-dependent association analysis showed that the hazard ratio (HR) of mortality increased in an almost linear manner as the BI score decreased, and that a BI score of 85 corresponded to an HR of 1.0. Kaplan-Meier survival curves showed that the survival rate was lower for patients with a low BI (<85) than for those with a high BI (≥85; 65% vs. 74%, respectively; P=0.007). In multivariate Cox regression analyses, low BI was independently associated with higher mortality after adjusting for predictors, including B-type natriuretic peptide. Inclusion of the BI into the adjusted model improved the accuracy of the prediction of mortality. CONCLUSIONS: A BI score <85 at the time of discharge is associated with increased mortality independent of known prognostic markers, and achieving functional status with a BI score ≥85 by comprehensive CR during hospitalization may contribute to favorable outcomes in elderly HF patients.

High percent body fat mass predicts lower risk of cardiac events in patients with heart failure: an explanation of the obesity paradox.

BACKGROUND: Although high body mass index (BMI) is a risk factor of heart failure (HF), HF patients with a higher BMI had a lower mortality rate than that in HF patients with normal or lower BMI, a phenomenon that has been termed the "obesity paradox". However, the relationship between body composition, i.e., fat or muscle mass, and clinical outcome in HF remains unclear. METHODS: We retrospectively analyzed data for 198 consecutive HF patients (76 years of age; males, 49%). Patients who were admitted to our institute for diagnosis and management of HF and received a dual-energy X-ray absorptiometry scan were included regardless of left ventricular ejection fraction (LVEF) categories. Muscle wasting was defined as appendicular skeletal muscle mass index < 7.0 kg/m2 in males and < 5.4 kg/m2 in females. Increased percent body fat mass (increased FM) was defined as percent body fat > 25% in males and > 30% in females. RESULTS: The median age of the patients was 76 years (interquartile range [IQR], 67-82 years) and 49% of them were male. The median LVEF was 47% (IQR, 33-63%) and 33% of the patients had heart failure with reduced ejection fraction. Increased FM and muscle wasting were observed in 58 and 67% of the enrolled patients, respectively. During a 180-day follow-up period, 32 patients (16%) had cardiac events defined as cardiac death or readmission by worsening HF or arrhythmia. Kaplan-Meier survival curves showed that patients with increased FM had a lower cardiac event rate than did patients without increased FM (11.4% vs. 22.6%, p = 0.03). Kaplan-Meier curves of cardiac event rates did not differ between patients with and those without muscle wasting (16.5% vs. 15.4%, p = 0.93). In multivariate Cox regression analyses, increased FM was independently associated with lower cardiac event rates (hazard ratio: 0.45, 95% confidence interval: 0.22-0.93) after adjustment for age, sex, diabetes, muscle wasting, and renal function. CONCLUSIONS: High percent body fat mass is associated with lower risk of short-term cardiac events in HF patients.

mRNA-binding protein tristetraprolin is essential for cardiac response to iron deficiency by regulating mitochondrial function.

Cells respond to iron deficiency by activating iron-regulatory proteins to increase cellular iron uptake and availability. However, it is not clear how cells adapt to conditions when cellular iron uptake does not fully match iron demand. Here, we show that the mRNA-binding protein tristetraprolin (TTP) is induced by iron deficiency and degrades mRNAs of mitochondrial Fe/S-cluster-containing proteins, specifically Ndufs1 in complex I and Uqcrfs1 in complex III, to match the decrease in Fe/S-cluster availability. In the absence of TTP, Uqcrfs1 levels are not decreased in iron deficiency, resulting in nonfunctional complex III, electron leakage, and oxidative damage. Mice with deletion of Ttp display cardiac dysfunction with iron deficiency, demonstrating that TTP is necessary for maintaining cardiac function in the setting of low cellular iron. Altogether, our results describe a pathway that is activated in iron deficiency to regulate mitochondrial function to match the availability of Fe/S clusters.

Abrupt Onset of Cardiac Tamponade in Sarcoidosis.

Sarcoidosis is a systemic inflammatory disease characterized by the formation of noncaseating epithelioid granulomas. Multiple organs, including the lung, eyes, and skin, are involved in this disorder, and cardiac involvement is a major cause of morbidity and mortality in patients with this disorder. We present the case history of a 22-year-old man with neurosarcoidosis complicated by abrupt onset of cardiac tamponade. Cardiac tamponade is a rare but potentially fatal manifestation of sarcoidosis, which is treatable with glucocorticoid therapy. Including the present case, previously reported cases of sarcoidosis with cardiac tamponade are reviewed to delineate its clinical characteristics.

Clinical Risk Factors and Prognostic Impact of Osteoporosis in Patients With Chronic Heart Failure.

BACKGROUND: The clinical significance of osteoporosis in chronic heart failure (CHF) remains unclear.Methods and Results:A total of 303 CHF patients (75 years, [interquartile range (IQR) 66-82 years]; 41% female) were retrospectively examined. Bone mineral densities (BMDs) at the lumbar spine, femoral neck, and total femur were measured by using dual-energy X-ray absorptiometry (DEXA), and osteoporosis was diagnosed when the BMD at any of the 3 sites was <70% of the Young Adult Mean percentage (%YAM). The prevalence of osteoporosis in CHF patients was 40%. Patients with osteoporosis were older (79 [IQR, 74-86] vs. 72 [IQR, 62-80] years), included a large percentage of females, had slower gait speed and had a lower body mass index. Multivariate logistic regression analysis indicated that sex, BMI, gait speed, loop diuretics use and no use of direct oral anticoagulants (DOACs) were independently associated with osteoporosis. Kaplan-Meier survival curves showed that the rate of death and heart failure hospitalization was higher in patients with osteoporotic BMD at 2 or 3 sites than in patients without osteoporosis (hazard ratio 3.45, P<0.01). In multivariate Cox regression analyses, osteoporotic BMD at 2 or 3 sites was an independent predictor of adverse events after adjustment for prognostic markers. CONCLUSIONS: Loop diuretics use and no DOACs use are independently associated with osteoporosis in CHF patients. Osteoporosis is a novel predictor of worse outcome in patients with CHF.

Assessment of prognosis in immunoglobulin light chain amyloidosis patients with severe heart failure: a predictive value of right ventricular function.

Although the benefit of updated therapeutic regimens, including bortezomib, on the survival of immunoglobulin light chain (AL) amyloidosis patients with heart failure (HF) has been reported, predictors of mortality in the patients treated with the updated therapy remain unclear. We retrospectively enrolled AL amyloidosis patients who had severe HF at the time of diagnosis and received the updated therapy, including bortezomib (n = 19, 61 ± 6 years old, 68% male). Severe HF was defined as the presence of both NYHA functional class III or IV and BNP > 200 pg/ml or NT-pro-BNP > 900 pg/ml. One-year mortality rate during follow-up after commencement of the treatment was 37%. Left ventricular morphological parameters and indexes of left ventricular diastolic function on admission were similar in the non-survivors and survivors. However, non-survivors had higher incidences of atrial fibrillation and ventricular tachycardia, higher serum total bilirubin levels (1.34 ± 0.55 vs. 0.61 ± 0.29 mg/dl), higher right atrial volume index (RAVI 49.7 ± 29.9 vs. 27.3 ± 6.8 ml/m2), lower tricuspid annular peak velocities during systole (RVs' 8.0 ± 1.8 vs. 11.6 ± 3.7 cm/sec) and late diastole (RVa' 3.4 ± 0.9 vs. 11.4 ± 5.3 cm/sec), and larger inferior vena cava dimension (22.7 ± 6.4 vs. 16.3 ± 4.9 mm) than those in survivors. Kaplan-Meier curve analyses showed that larger RAVI and lower RVs' and RVa', but not left ventricular systolic/diastolic dysfunction, predicted higher mortality during 1-year follow-up. The present results suggest that the presence of right-sided heart abnormality on admission is associated with high 1-year mortality in AL amyloidosis patients with severe HF under the updated therapeutic regimens.

Risk classification of pulmonary arterial hypertension by echocardiographic combined assessment of pulmonary vascular resistance and right ventricular function.

Which combination of clinical parameters improves the prediction of prognosis in patients with pulmonary arterial hypertension (PAH) remains unclear. We examined whether combined assessment of pulmonary vascular resistance and right ventricular function by echocardiography is useful for classifying risks in PAH. In 41 consecutive patients with PAH (mean age of 48.9 ± 17.3 years, 31 females), a 6-min walk test, pulmonary function test, and echocardiography were performed at baseline and during PAH-specific therapies. The study endpoint was defined as a composite of cardiovascular death and hospitalization for PAH and/or right ventricular failure. During a follow-up period of 9.2 ± 8.7 months, 18 patients reached the endpoint. Multivariate regression analysis showed that the ratio of tricuspid regurgitation pressure gradient to the time-velocity integral of the right ventricular outflow tract (TRPG/TVI) and tricuspid annular plane systolic excursion (TAPSE) during PAH-specific treatment were independent prognostic predictors of the endpoint. Using cutoff values indicated by receiver operating characteristic analysis, the patients were divided into four subsets. Multivariate analyses by Cox's proportional hazards model adjusted for age, sex and body mass index indicated that subset 4 (TRPG/TVI ≥ 3.89 and TAPSE ≤ 18.9 mm) had a significantly higher event risk than did subset 1 (TRPG/TVI < 3.89 and TAPSE > 18.9 mm): HR = 25.49, 95% CI 4.70-476.97, p < 0.0001. Combined assessment of TRPG/TVI and TAPSE during adequate PAH-specific therapies enables classification of risks for death and/or progressive right heart failure in PAH.

Translational regulation by miR-301b upregulates AMP deaminase in diabetic hearts.

AMP deaminase (AMPD) plays a crucial role in adenine nucleotide metabolism. Recently we found that upregulated AMPD activity is associated with ATP depletion and contractile dysfunction under the condition of pressure overloading in the heart of a rat model of type 2 diabetes mellitus (T2DM), OLETF. Here we examined the mechanism of AMPD upregulation by T2DM. The protein level of 90-kDa full-length AMPD3 was increased in whole myocardial lysates by 55% in OLETF compared to those in LETO, a non-diabetic control. In contrast, the mRNA levels of AMPD3 in the myocardium were similar in OLETF and LETO. AMPD3 was comparably ubiquitinated in OLETF and LETO, and its degradation ex vivo was more sensitive to MG-132, a proteasome inhibitor, in OLETF than in LETO. MicroRNA array analysis revealed downregulation (>50%) of 57 microRNAs in OLETF compared to those in LETO, among which miR-301b was predicted to interact with the 3'UTR of AMPD3 mRNA. AMPD3 protein level was significantly increased by a miR-301b inhibitor and was decreased by a miR-301b mimetic in H9c2 cells. A luciferase reporter assay confirmed binding of miR-301b to the 3'UTR of AMPD3 mRNA. Transfection of neonatal rat cardiomyocytes with a miR-301b inhibitor increased 90-kDa AMPD3 and reduced ATP level. The results indicate that translational regulation by miR-301b mediates upregulated expression of cardiac AMPD3 protein in OLETF, which potentially reduces the adenine nucleotide pool at the time of increased work load. The miR-301b-AMPD3 axis may be a novel therapeutic target for intervening enegy metabolism in diabetic hearts.

Insufficient activation of Akt upon reperfusion because of its novel modification by reduced PP2A-B55α contributes to enlargement of infarct size by chronic kidney disease.

Chronic kidney disease (CKD) increases myocardial infarct size by an unknown mechanism. Here we examined the hypothesis that impairment of protective PI3K-PDK1-Akt and/or mTORC-Akt signaling upon reperfusion contributes to CKD-induced enlargement of infarct size. CKD was induced in rats by 5/6 nephrectomy (SNx group) 4 weeks before myocardial infarction experiments, and sham-operated rats served as controls (Sham group). Infarct size as a percentage of area at risk after ischemia/reperfusion was significantly larger in the SNx group than in the Sham group (56.3 ± 4.6 vs. 41.4 ± 2.0%). In SNx group, myocardial p-Akt-Thr308 level at baseline was elevated, and reperfusion-induced phosphorylation of p-Akt-Ser473, p-p70s6K and p-GSK-3ß was significantly suppressed. Inhibition of Akt-Ser473 phosphorylation upon reperfusion by Ku-0063794 significantly increased infarct size in the Sham group but not in the SNx group. There was no difference between the two groups in activities of mTORC2 and PDK1 and protein level of PTEN. However, the PP2A regulatory subunit B55α, which specifically targets Akt-Thr308, was reduced by 24% in the SNx group. Knockdown of B55α by siRNA increased baseline p-Akt-Thr308 and blunted Akt-Ser473 phosphorylation in response to insulin-like growth factor-1 (IGF-1) in H9c2 cells. A blunted response of Akt-Ser473 to IGF-1 was also observed in HEK293 cells transfected with a p-Thr308-mimetic Akt mutant (T308D). These results indicate that increased Akt-Thr308 phosphorylation by down-regulation of B55α inhibits Akt-Ser473 phosphorylation upon reperfusion in CKD and that the impaired Akt activation by insufficient Ser473 phosphorylation upon reperfusion contributes to infarct size enlargement by CKD.

Excessive degradation of adenine nucleotides by up-regulated AMP deaminase underlies afterload-induced diastolic dysfunction in the type 2 diabetic heart.

Type 2 diabetes mellitus (T2DM) is often complicated with diastolic heart failure, which decompensates under increased afterload. Focusing on cardiac metabolomes, we examined mechanisms by which T2DM augments ventricular diastolic stiffness in response to pressure overloading. Pressure-volume relationships (PVRs) and myocardial metabolomes were determined at baseline and during elevation of aortic pressure by phenylephrine infusion in a model of T2DM, OLETF, and its non-diabetic control, LETO. Pressure overloading augmented diastolic stiffness without change in systolic reserve in OLETF as indicated by a left-upward shift of end-diastolic PVR. In contrast, PVRs under cardioplegic arrest in buffer-perfused isolated hearts were similar in OLETF and LETO, indicating that extracellular matrix or titin remodeling does not contribute to the afterload-induced increase in stiffness of the beating ventricle of OLETF. Metabolome analyses revealed impaired glycolysis and facilitation of the pentose phosphate pathway in OLETF. Pressure overloading significantly reduced ATP and total adenine nucleotides by 34% and 40%, respectively, in OLETF but not in LETO, while NADH-to-NAD(+) ratios were similar in the two groups. The decline in ATP by pressure overloading in OLETF was associated with increased inosine 5-monophosphate and decreased adenosine levels, being consistent with the 2.5-times higher activity of cardiac AMP deaminase in OLETF. Tissue ATP level was negatively correlated with tau of LV pressure and LVEDP. These results suggest that ATP depletion due to excessive degradation of adenine nucleotides by up-regulated AMP deaminase underlies ventricular stiffening during acute pressure overloading in T2DM hearts.