Clinical determinants and prognostic impact of osteoporosis in patients with chronic heart failure

Background

Despite accumulating evidence of a close association between orthopedic fractures and chronic heart failure (CHF), the clinical risk factors of osteoporosis, defined as reduction in bone mineral densities (BMDs), in CHF patients have not been systematically analyzed. In addition, the impact of osteoporosis on prognosis of CHF remains unclear.

Aims

We aimed to clarify the prevalence, clinical risk factors, and prognostic impact of osteoporosis in CHF patients.

Methods

We retrospectively examined 303 CHF patients (75 years, [interquartile range (IQR), 66–82 years]; 41% female). BMDs at the lumber spine, femoral neck, and total femur were measured by dual-energy X-ray absorptiometry (DEXA), and osteoporosis was diagnosed when BMD at any of the three sites was less than 70% of Young Adult Mean.

Results

The prevalence of osteoporosis in the 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 lower body mass index (BMI). Loop diuretics and warfarin were used more frequently and direct oral anticoagulants (DOACs) were used less frequently in patients with osteoporosis than in patients without osteoporosis. Multivariate logistic regression analysis indicated that sex (odds ratio [OR] 5.07, 95% Confidence Interval [CI] 2.68–9.61, p<0.01), BMI (OR, 0.83; 95% CI, 0.75–0.91; p<0.01), gait speed (OR, 0.80; 95% CI, 0.70–0.92; p<0.01), loop diuretics use (OR, 2.52; 95% CI, 1.20–5.27; p=0.01) and no DOACs use (OR, 0.43; 95% CI, 0.19–0.96; p=0.04) were independently associated with osteoporosis. During the mean follow-up period of 290±254 days, 92 patients (30.4%) had adverse events. When patients with osteoporosis were divided into subgroups according to the number of sites with BMD of an osteoporosis level, Kaplan-Meier survival curves showed that the rate of adverse events (death and cardiovascular events) was higher in patients with osteoporotic BMD at two or more sites than in patients without osteoporosis (51% vs. 23%, p=0.03) (Figure). In multivariate Cox regression analyses, osteoporotic BMD at two or more sites was an independent predictor of adverse events after adjustment for age, sex, and NT-proBNP level (Hazard ratio, 1.74; 95% CI, 1.01–2.99; p=0.04).

Conclusion

The risk of osteoporosis may be increased in users of loop diuretics and may be decreased in users of DOACs in CHF patients. Extent of osteoporosis is a novel predictor of adverse events in CHF patients.

Funding Acknowledgement

Type of funding source: Public grant(s) – National budget only. Main funding source(s): The Japan Society for the Promotion of Science KAKENHI

Inhibition of xanthine oxidase ameliorates functional and metabolic impairment in type 2 diabetic hearts under pressure overload

Background

We recently reported that upregulated AMP deaminase (AMPD), via reduction in the tissue adenine nucleotide pool, contributes to exacerbation of diastolic dysfunction under pressure overload in OLETF, a rat model of obese type 2 diabetes (T2DM). Upregulated AMPD also possibly promotes xanthine oxidase (XO)-mediated ROS production, since AMPD deaminases AMP to IMP, which is further converted to inosine, providing substrates of XO, hypoxanthine and xanthine. Here, we examined the hypothesis that inhibition of XO ameliorates the pressure overload-induced diastolic dysfunction by suppression of ROS-mediated mitochondrial dysfunction and/or vascular dysfunction in T2DM rats.

Methods and results

Metabolomic analyses revealed that levels of xanthine and uric acid in the LV myocardium were significantly higher by 37% and 51%, respectively, in OLETF than in LETO, non-diabetic control rats, under the condition of phenylephrine-induced pressure overloading (200–230 mmHg). Myocardial XO activity in OLETF was 57.9% higher than that in LETO, which may be attributed to 31% higher level of inosine, a positive regulator of XO, in OLETF than in LETO. The activity of XO was significantly attenuated by administration of topiroxostat, an XO inhibitor at 0.5 mg/kg/day for 14 days. Pressure volume loop analyses showed that the pressure overloading resulted in significantly higher LVEDP in OLETF than in LETO (18.3±1.5 vs. 12.2±1.3 mmHg, p<0.05, n=7), though LVEDPs at baseline were comparable in OLETF and LETO (5.6±0.4 vs. 4.7±0.7 mmHg). Treatment with topiroxostat significantly suppressed the pressure overload-induced elevation of LVEDP in OLETF (18.3±1.5 vs. 11.3±1.1 mmHg, p<0.05) but not in LETO. Under the condition of pressure overloading, Ea/Ees, an index for ventricular-arterial coupling, was higher in OLETF than in LETO (2.3±0.3 vs. 1.6±0.3, p<0.05), and it was also improved by topiroxostat in OLETF (1.2±0.2, p<0.05). Myocardial ATP content was lower in OLETF than in LETO (2966±400 vs. 1818±171 nmol/g wet tissue, p<0.05), and treatment with topiroxostat significantly restored the ATP level (2629±307 nmol/g wet tissue). The LV myocardium of OLETF under pressure overload showed significantly higher level of malondialdehyde and 4-hydroxynonenal, an indicator of lipid peroxidation, than that of LETO. Measurement of oxygen consumption rate by Seahorse XFe96 Analyzer in mitochondria isolated from LV tissues revealed that state 3 respiration was significantly suppressed in OLETF by 43% compared to LETO, and it was restored by treatment with topiroxostat.

Conclusion

Both activity and substrates of XO are increased in T2DM hearts, in which upregulation of AMPD may play a role. Inhibition of XO ameliorates pressure overload-induced diastolic dysfunction and improves ventricular-arterial coupling in diabetic hearts, most likely through protection of mitochondrial function from ROS-mediated injury.

Funding Acknowledgement

Type of funding source: Public grant(s) – National budget only. Main funding source(s): Grant-in-aid for Scientific Research (#26461132, #17K09584) from the Japanese Society for the Promotion of Science

A Lynch syndrome-associated mutation at a Bergerat ATP-binding fold destabilizes the structure of the DNA mismatch repair endonuclease MutL

In humans, mutations in genes encoding homologs of the DNA mismatch repair endonuclease MutL cause a hereditary cancer that is known as Lynch syndrome. Here, we determined the crystal structures of the N-terminal domain (NTD) of MutL from the thermophilic eubacterium Aquifex aeolicus (aqMutL) complexed with ATP analogs at 1.69-1.73 Å. The structures revealed significant structural similarities to those of a human MutL homolog, postmeiotic segregation increased 2 (PMS2). We introduced five Lynch syndrome-associated mutations clinically found in human PMS2 into the aqMutL NTD and investigated the protein stability, ATPase activity, and DNA-binding ability of these protein variants. Among the mutations studied, the most unexpected results were obtained for the residue Ser34. Ser34 (Ser46 in PMS2) is located at a previously identified Bergerat ATP-binding fold. We found that the S34I aqMutL NTD retains ATPase and DNA-binding activities. Interestingly, CD spectrometry and trypsin-limited proteolysis indicated the disruption of a secondary structure element of the S34I NTD, destabilizing the overall structure of the aqMutL NTD. In agreement with this, the recombinant human PMS2 S46I NTD was easily digested in the host Escherichia coli cells. Moreover, other mutations resulted in reduced DNA-binding or ATPase activity. In summary, using the thermostable aqMutL protein as a model molecule, we have experimentally determined the effects of the mutations on MutL endonuclease; we discuss the pathological effects of the corresponding mutations in human PMS2.

Search for Electron Antineutrino Appearance in a Long-Baseline Muon Antineutrino Beam

Electron antineutrino appearance is measured by the T2K experiment in an accelerator-produced antineutrino beam, using additional neutrino beam operation to constrain parameters of the Pontecorvo-Maki-Nakagawa-Sakata (PMNS) mixing matrix. T2K observes 15 candidate electron antineutrino events with a background expectation of 9.3 events. Including information from the kinematic distribution of observed events, the hypothesis of no electron antineutrino appearance is disfavored with a significance of 2.40σ and no discrepancy between data and PMNS predictions is found. A complementary analysis that introduces an additional free parameter which allows non-PMNS values of electron neutrino and antineutrino appearance also finds no discrepancy between data and PMNS predictions.

P207 Synergetic effect of amino acid and ketone metabolism underlies empagliflozin-mediated cardioprotection in the type 2 diabetic heart

Funding Acknowledgements

Boehringer Ingelheim

Background

 Although emerging evidence has indicated that sodium glucose cotransporter 2 (SGLT2) inhibitors restore impaired cardiac energetics in type 2 diabetes mellitus (T2DM), the underlying molecular mechanisms have yet to be established.  Augmented utilization of ketone is one proposed hypothesis, but depletion of succinyl-CoA triggered by the conversion of ketone back to acetyl-CoA by SCOT (succinyl-CoA:3-oxoacid CoA transferase) may hamper oxidative capacity of the tricarboxylic acid (TCA) cycle, which also requires succinyl-CoA.  The recent finding that empagliflozin augments systemic amino acid metabolism in patients with T2DM led us to hypothesize that the anaplerotic effect of amino acid on the TCA cycle complements ketone oxidation.

Methods and Results

 Myocardial infarction (MI) was induced in T2DM rats (OLETF) and control rats (LETO).  Survival rate at 48 hours after MI was significantly lower in OLETF than in LETO (40% vs 84%), and empagliflozin treatment (10 mg/kg/day, 14 days) before MI improved the survival rate in OLETF to 70%.  Metabolome analysis was performed using heart tissues from the non-infarct region 12 hours after MI.  Using principal component analysis, data from 92 metabolites that were detected were compressed into 2 dimensions, and the first component (PC1) clearly separated empagliflozin-treated OLETF from non-treated LETO and OLETF.  Analysis of factor loading of each metabolite for PC1 revealed that branched chain amino acids leucine, isoleucine and valine, the latter two of which can be oxidized to succynyl-CoA, and β-hydroxybutyrate were the top four metabolites that characterized empagliflozin treatment.  Furthermore, in comparison to LETO, OLETF treated with empagliflozin showed 50% higher levels of glutamine and glutamate, both of which can replenish the TCA cycle at the level of α-ketoglutarate.  In OLETF, empagliflozin significantly increased the TCA cycle intermediates citrate, cis-aconitate and malate by 74%, 119% and 59%, respectively.  OLETF showed 86% higher lactate and 38% lower ATP than those in LETO, but levels of the metabolites were normalized by empagliflozin, suggesting improved glucose oxidation.

Conclusions

  The present analyses showed that amino acid and ketone metabolism are metabolic pathways that are most affected by empagliflozin.  Coordination of these "starvation-induced pathways" may underlie the favorable metabolic effect of empagliflozin in T2DM hearts.

Association of Dietary Variety and Appetite with Sleep Quality in Urban-Dwelling Older Japanese Adults

OBJECTIVES

Although it has been shown that specific foods and nutrients are associated with sleep quality, few studies have examined the association of dietary variety and appetite with sleep quality in older adults.

DESIGN AND SETTING

A cross-sectional study was conducted that examined the association of dietary variety and appetite with sleep quality in Japanese adults aged ≥70 years who resided in the metropolitan area of Tokyo, Japan.

PARTICIPANTS

Data were collected in two steps: a mailed interview survey and an on-site survey. Those who responded to the surveys and met the inclusion criteria were included.

MEASUREMENTS

Dietary variety, appetite, and sleep quality were assessed using a Dietary Variety Score (DVS), Council on Nutrition Appetite Questionnaire (CNAQ) score, and sleep efficiency, respectively. The sleep efficiency is the ratio of sleep duration to total time in bed (retiring time-awakening time). We defined the individuals with a sleep efficiency less than 75% as having poor sleep quality.

RESULTS

Mean DVS and CNAQ score were 3.8 and 29.6 points, respectively. The rate of individuals with poor sleep quality was 11.7%. In the fully adjusted model, the odds ratios (OR) for low sleep efficiency in the middle and highest group categories of the DVS were 0.83 (95% confidence interval [CI], 0.54-1.29) and 0.50 (95% CI, 0.28-0.90), respectively, in reference to the lowest group category (p for trend = 0.023). The OR for low sleep efficiency in the middle and highest group categories of the CNAQ score were 0.73 (95% CI, 0.47-1.14) and 0.54 (95% CI, 0.30-0.96), respectively, in reference to the lowest group category (p for trend = 0.031).

CONCLUSIONS

The higher DVS and CNAQ scores were significantly associated with higher sleep efficiency. Thus, dietary variety and good appetite might help maintain good sleep quality in urban-dwelling older Japanese adults.

P121 Pressure overload-induced functional and metabolic impairments in type 2 diabetic hearts are ameliorated by inhibition of xanthine oxidase

Funding Acknowledgements

SANWA KAGAKU KENKYUSHO Co., Ltd.

Background

  We have recently demonstrated that AMP deaminase (AMPD) is upregulated in OLETF, obese type 2 diabetic (T2DM) rats, and that the upregulated AMPD contributes to depletion of myocardial ATP at the time of pressure overload, leading to diastolic dysfunction.  On the other hand, AMPD promotes the formation of IMP from AMP, and IMP is in turn further converted to hypoxanthine and xanthine, substrates of xanthine oxidase (XO), which produces uric acid with ROS as a byproduct.  Based on these findings, we tested the hypothesis that inhibition of XO ameliorates the pressure overload-induced diastolic dysfunction in T2DM rats. 

Methods and results

Metabolomic analyses of the left ventricular myocardium revealed that levels of myocardial hypoxanthine and xanthine were significantly higher by 30% and 28%, respectively, in OLETF than in LETO, non-diabetic control rats, under the condition of pressure overloading (200-230 mmHg) induced by phenylephrine infusion. Myocardial XO activity in OLETF was 57.9% higher than that in LETO, and the activity was significantly attenuated by oral administration of topiroxostat, an XO inhibitor, at 0.1-0.5 mg/kg/day for 14 days in a dose-dependent manner.  Pressure volume loop analyses showed that the pressure overloading induced by phenylephrine infusion resulted in significantly higher LVEDP in OLETF than in LETO (18.3 ± 1.5 vs. 12.2 ± 1.3 mmHg, p < 0.05, n = 7), though LVEDPs at baseline were comparable in OLETF and LETO (5.6 ± 0.4 vs. 4.7 ± 0.7 mmHg).  Treatment with topiroxostat significantly suppressed the pressure overload-induced elevation of LVEDP in OLETF (18.3 ± 1.5 vs. 11.3 ± 1.1 mmHg, p < 0.05) but not in LETO.  Tau, the time constant of LV pressure decay, was significantly prolonged to 14.7 ± 0.7 ms (p < 0.05) by pressure overloading in OLETF but not in LETO, though baseline Tau values were similar in LETO and OLETF (6.1 ± 0.2 vs. 8.0 ± 0.4 ms).  The prolongation of Tau by pressure overloading in OLETF was significantly attenuated by treatment with topiroxostat.  Ea/Ees, an index for ventricular-arterial coupling, was higher in OLETF than in LETO (2.3 ± 0.3 vs. 1.6 ± 0.3, p < 0.05) under the condition of pressure overloading, and it was also improved by topiroxostat in OLETF (1.2 ± 0.2, p < 0.05).  Myocardial ATP content was lower in OLETF than in LETO under the condition of pressure overloading (2966 ± 400 vs. 1818 ± 171 nmol/g wet tissue, p < 0.05), but treatment with topiroxostat significantly restored the ATP level (2629 ± 307 nmo/g wet tissue). Conclusion:  In T2DM hearts, not only XO activity but also XO substrates are upregulated and upregulated AMPD may be involved in the upregulation.  Inhibition of XO ameliorates pressure overload-induced diastolic dysfunction and improves ventricular-arterial coupling most likely through augmented ATP preservation.

Determination of Walnut Protein in Processed Foods by Enzyme-Linked Immunosorbent Assay: Interlaboratory Study

Because food allergens from tree nuts, including walnuts, are a frequent cause of adverse food reactions for allergic patients, the labeling of foods containing ingredients derived from tree nuts is required in numerous countries. According to Japanese regulations, the labeling of food products containing walnuts is recommended. To ensure proper labeling, a novel sandwich ELISA kit for the determination of walnut protein in processed foods (Walnut Protein [2S-Albumin] Kit; Morinaga Institute of Biological Science, Inc.; walnut kit) has been developed. We prepared seven types of incurred samples (model processed foods: biscuits, bread, sponge cake, orange juice, jelly, chicken meatballs, and rice gruel) containing 10 g walnut soluble protein/g of food for use in interlaboratory evaluations of the walnut kit. The walnut kit displayed sufficient reproducibility relative standard deviations (interlaboratory precision: 5.89.9 RSDR) and a high level of recovery (81119) for all the incurred samples. All the repeatability relative standard deviation (RSDr) values for the incurred samples that were examined were less than 6.0. The results of this interlaboratory evaluation suggested that the walnut kit could be used as a precise and reliable tool for determination of walnut protein in processed foods.

Enzyme-Linked Immunosorbent Assay Kit for the Determination of Soybean Protein in Processed Foods: Interlaboratory Evaluation

The labeling of foods containing ingredients derived from soybean is recommended in Japan because of an increasing number of patients who are allergic to soybeans. To ensure proper labeling, a novel sandwich ELISA kit for the determination of soybean protein in processed foods (FASTKIT Ver. II, Soybean, Nippon Meat Packers, Inc.; soy kit) has been developed. Five types of incurred samples (model processed foods: rice gruel, sausage, sweet adzuki bean soup, sweet potato cake, and tomato sauce) containing 10 g soybean soluble protein/g food were prepared for use in interlaboratory evaluations of the soy kit. The soy kit displayed a sufficient RSDR value (interlaboratory precision: 9.313.4 RSDR) and a high level of recovery (97114) for all the incurred samples. The RSDr value for the incurred samples was mostly <4.8. The results of this interlaboratory evaluation suggest that the soy kit can be used as a precise and reliable tool for the determination of soybean proteins in processed foods.

Automatic detection of early gastric cancer in endoscopic images using a transferring convolutional neural network

Endoscopic image diagnosis assisted by machine learning is useful for reducing misdetection and interobserver variability. Although many results have been reported, few effective methods are available to automatically detect early gastric cancer. Early gastric cancer have poor morphological features, which implies that automatic detection methods can be extremely difficult to construct. In this study, we proposed a convolutional neural network-based automatic detection scheme to assist the diagnosis of early gastric cancer in endoscopic images. We performed transfer learning using two classes (cancer and normal) of image datasets that have detailed texture information on lesions derived from a small number of annotated images. The accuracy of our trained network was 87.6%, and the sensitivity and specificity were well balanced, which is important for future practical use. We also succeeded in presenting a candidate region of early gastric cancer as a heat map of unknown images. The detection accuracy was 82.8%. This means that our proposed scheme may offer substantial assistance to endoscopists in decision making.

P4537Impact of body composition analysis on prediction of short-term readmission events in heart failure: muscle wasting vs. obesity

Background

Obesity, defined as higher body mass index (BMI), is associated with better prognosis in patients with chronic heart failure (CHF), though the presence of obesity is a risk factor of development of CHF (Obesity paradox). On the other hand, muscle wasting, i.e. reduction in skeletal muscle mass, is frequently observed in CHF, leading to lower exercise capacity and poor cardiovascular outcome.

Purpose

The aim of this study was to examine whether analysis of body composition improves prediction of short-term readmission rates in patients with CHF.

Methods

We retrospectively analyzed data for 167 consecutive HF patients who were admitted to our institute for management of HF and received a Dual-energy X-ray absorptiometry (DEXA) scan. Muscle wasting was defined as DEXA-measured appendicular skeletal muscle mass index <7.0 kg/m2 in male and <5.4 kg/m2 in female according to the Asian Working Group for Sarcopenia criteria. Obesity was defined according to the criteria by the use of DEXA-measured percent body fat mass: >25% in male, >30% in female. The primary endpoint was readmission due to cardiac events including worsening heart failure, arrhythmia, and cardiopulmonary arrest during a 180-days follow-up period after discharge.

Results

The mean age of the patients was 74±13 years and 46% of them were male. The mean BMI was 21.8±3.8 kg/m2. Forty-seven percent of the patients were classified as NYHA functional class III. The most frequent etiology of HF was cardiomyopathy (30%), followed by ischemic heart disease (27%) and valvular heart disease (27%). The prevalence of muscle wasting and that of obesity were 69% and 59%, respectively. Patients with muscle wasting had lower BMI level, higher prevalence of NYHA functional class III and diabetes mellitus compared with those without muscle wasting. On the other hand, patients with obesity had higher prevalence of hypertension and dyslipidemia, higher level of BMI, fasting plasma insulin and triglyceride, and lower level of HDL-cholesterol compared with those without obesity. During the follow-up period, 34 patients (19%) were re-hospitalized due to cardiac events. Kaplan-Meier survival curves showed that patients with obesity had a significantly lower readmission rate during a 180-days follow-up period than did the patients without obesity (14.3% vs. 29.0%, Log-Rank test, p<0.01). There was no difference in readmission rates between patients with and without muscle wasting (20.0% vs. 21.2%, p=0.88). In multivariate Cox regression analyses adjusted for age, sex, diabetes, and renal function, obesity was independently associated with lower readmission rates (hazard ratio 0.45, 95% confidence interval 0.22–0.93). However, the association between obesity and readmission rate was lost after the adjustment for NT-proBNP levels.

Conclusion

Body composition analysis by DEXA enables to find CHF patients with increased fat mass who have lower risk of short-term readmission.

P1538Low energy intake predicts readmission of elderly heart failure patients independently of nutritional status

Background

Malnutrition is frequently present and closely associated with poor clinical outcomes in elderly heart failure (HF) patients. Our previous study showed that low energy intake (EI) is associated with worse functional status in elderly HF inpatients after cardiac rehabilitation, but significance of EI in prediction of hospital readmission has not been elucidated fully.

Purpose

We examined whether low EI is a predictor of readmission for cardiac events in elderly HF patients.

Methods

We retrospectively retrieved data for 298 HF patients aged ≥65 years (median age of 77 years, interquartile range [IQR]: 71 - 82, female: 53%) who admitted to our institute for diagnosis and treatment of HF. Medical records were reviewed with regard to demography, medical history, comorbidities, medications, laboratory data, echocardiograms, functional status, nutritional status and total energy intake. Nutritional status was assessed using the Mini Nutritional Assessment Short Form (MNA-SF) and total EI per day were calculated at discharge by a registered dietitian and a trained physical therapist. The primary endpoint was readmission due to cardiovascular events including worsening HF, arrhythmia, angina pectoris and myocardial infarction during a 1-year follow-up period.

Results

The median period of follow-up was 235 days (IQR: 78–365 days). The 1-year readmission rate for cardiovascular events was 54.4%. The cutoff values of MNA-SF score and EI, calculated by ROC curve analysis to predict the primary endpoint, were 7 points (area under the curve [AUC]: 0.59, sensitivity: 0.65, specificity: 0.50) and 31.8 kcal/kg/day (AUC: 0.59, sensitivity: 0.83, specificity: 0.35), respectively. Patients with low MNF-SF score (≤7) or low EI (≤31.8 kcal/kg/day) had significantly higher readmission rate during a 1-year follow-up period than did the patients with high MNF-SF score or EI (MNA-SF: 60.7% vs. 45.6%, p<0.01, EI: 60.4% vs. 36.8%, p<0.01), respectively. When patients were classified into four groups using cutoff values of MNA-SF score and EI, 1-year readmission rate was significantly higher in patients with low EI than in those with high EI regardless of MNF-SF scores. In multivariate Cox proportional hazard analyses adjusted for known prognostic factors in addition to age and gender, hazard ratios (HR) were significantly higher in patients with high MNA-SF score and low EI (adjusted HR: 2.81, 95% confidential interval [CI]: 1.15 - 9.32, p=0.02) and low MNA-SF score (≤7) and low EI (adjusted HR: 4.16, 95% CI: 1.72 - 13.72, p<0.01) than those with high MNA-SF score and high EI.

Kaplan-Meier curves of readmission rates

Conclusions

Low energy intake is a nutritional status-independent predictor of 1-year readmission rate in elderly HF patients.

P6453Activation of necroptotic pathway by downregulated caspase-8 expression is associated with progression of left ventricular remodeling in nonischemic dilated cardiomyopathy

Background

Necroptosis, a form of programmed necrosis, has been suggested to be involved in the pathogenesis of various pathological conditions including heart failure. Protein expression of caspase-8, an endogenous inhibitor of necroptosis, is reported to be downregulated in human failing hearts, but its clinical significance remains unclear.

Methods

Endomyocardial biopsy specimens were obtained from patients with nonischemic dilated cardiomyopathy (n=57, 56.2±14.5 years old, 70% male). The area stained with antibodies against caspase-8 and phospho-MLKL-Ser358 was calculated using an image analyzer, and fibrotic and cardiomyocyte areas were determined by Masson's Trichrome staining. Using a level of median caspase-8 expression (6.04% of the area of the myocardium with caspase-8 signal), patients were classified into a high caspase-8 expression group (H-cas8) and a low caspase-8 expression group (L-cas8).

Results

Caspase-8 signals were detected in cytoplasm and intercalated disks of cardiomyocytes. Patients in the L-cas8 group was younger (51.3±13.1 vs. 61.2±14.3 years old) and had larger left ventricular end-diastolic volume (LVEDV: 174±49 vs. 131±41 ml), larger left ventricular end-systolic volume (LVESV: 123±51 vs. 87±39 ml), and higher ratio of mitral peak velocity of early filling to late diastolic filling (E/A: 1.94±1.48 vs. 1.12±0.66) compared with the H-cas8 group. Caspase-8 expression level was positively correlated with age (r=0.34, p=0.01) and negatively correlated with LVEDV (r=−0.47, p<0.01), LVESV (r=−0.40, p<0.01), and E/A (r=−0.39, p<0.01) in simple linear regression analysis. The extent of myocardial fibrosis was not correlated with caspase-8 expression level. Multiple regression analysis indicated that LVEDV, LVESV, and E/A were independent explanatory factors of caspase-8 expression level after adjusting age and sex. Phospho-MLKL signals, an index of activation of necroptotic pathway, were frequently observed in cytoplasm, intercalated disks, and nuclei in the L-cas8 group but not in the H-cas8 group.

Conclusion

Lower caspase-8 expression in cardiomyocytes was associated with increased phosphorylation of MLKL and larger left ventricular volume, suggesting that downregulated caspase-8 may contribute to progression of myocardial remodeling via activation of MLKL in human dilated cardiomyopathy.

P6273Inhibitory phosphorylation of RIP1 at Ser320 induces nuclear translocation of TFEB, leading to suppression of necroptosis in cardiomyocytes

Background

Necroptosis, a form of programmed necrosis, has been shown to contribute to the pathogenesis of various diseases including ischemia/reperfusion injury and heart failure. We recently reported that necroptotic signals suppresses autophagy in cardiomyocytes and that rapamycin, an mTORC1 inhibitor, not only promotes autophagy but also protect the cells from necroptosis.

Purpose

We examined the mechanism by which rapamycin suppresses necroptosis of cardiomyocytes, focusing on regulation of RIP1 activity and autophagic flux.

Methods and results

In H9c2 cardiomyoblasts, necroptosis was induced by treatment with TNF and z-VAD-fmk (zVAD) for 24 h, and cell death was determined by LDH release (as % of total). The treatment with TNF/zVAD increased LDH release from 3.4±1.3% to 46.1±2.3%, and LDH release was suppressed by necrostatin-1 (5.9±0.9%), a RIP1 inhibitor, and by rapamycin (23.5±1.4%). The protective effect of rapamycin was mimicked by Ku-0063794, an mTORC1/2 inhibitor. TNF/zVAD induced RIP1-RIP3 complex formation, together with suppression of TNF-induced RIP1 cleavage, which was mitigated by rapamycin. In addition, rapamycin not only suppressed TNF/zVAD-induced phosphorylation of RIP1-Ser166, an index of RIP1 activation, but also increased phosphorylation of RIP1-Ser320, an inhibitory phosphorylation site. In cells transfected with RIP1-S320A, which lack Ser320 for inhibitory phosphorylation, rapamycin failed to suppress TNF/zVAD-induced RIP1-RIP3 binding and cell death. Immunoblot analyses showed that TNF/zVAD significantly increased level of LC3-II. The accumulation of LC3-II protein was not further increased by bafilomycin A1 (100 nM), an inhibitor of lysosomal protein degradation, indicating that accumulation of LC3-II by TNF/zVAD reflected suppression of autophagic flux. Inhibition of RIP1 by necrostatin-1 attenuated TNF/zVAD-induced accumulation of LC3 II. The restoration of autophagic flux in TNF/zVAD-treated cells by necrostatin-1 was confirmed by monitoring tandem RFP-GFP-LC3 transfected cells; necrostatin-1 increased a ratio of RFP-LC3-puncta (autolysosomes) to RFP-GFP-LC3-puncta (autophagosomes) in TNF/zVAD-treated cells. In addition, necrostatin-1 and rapamycin induced nuclear translocation of TFEB, a regulator of lysosome biogenesis, which was associated with upregulation of MCOLN1 mRNA, a downstream target of TFEB. Restoration of autophagic flux in TNF/zVAD-treated cells by necrostatin-1 was inhibited by siRNA-mediated knockdown of TFEB.

Conclusion

Activation of TFEB by inhibitiory phosphorylation of RIP1-Ser320 is a primary mechanism of cytoprotection afforded by mTORC1 inhibition against necroptosis.

Coherence between oscillations in the cardiorespiratory system and tissue oxygen index in muscle recovering from intensive exercise in humans

It has been shown that the tissue oxygen index (TOI) measured by near-infrared spectroscopy oscillates at very low frequencies during recovery after exercise and that this oscillation is derived from interactions among biochemical substances involved in oxidative metabolism in skeletal muscle. As a further step, we examined whether TOI in muscle interacts through oscillation with factors related to oxygen in the cardiorespiratory system. For this examination, coherence and phase difference between the TOI in the vastus lateralis and heart rate (HR) and between TOI and arterial oxygen saturation (SpO₂) were sequentially determined during recovery (2-60 min) after severe cycle exercise with a workload of 7.5% of body weight for 20 s. Significant coherence between TOI and HR was obtained in the very low-frequency band (approximate range: 0.002-0.03 Hz) and in the low-frequency band (approximate range: 0.06-0.12 Hz). The phase difference was negative in the low-frequency band and positive in the very low-frequency band. The coherence between TOI and SpO₂ was significant in the very low-frequency band. The phase difference was negative. There were no sequential changes in these coherences and phase differences. The results suggest that TOI in skeletal muscle interrelates with factors related to the heart and lungs.

tRNA Wobble Modification Affects Leaf Cell Development in Arabidopsis thaliana

The tRNA modification at the wobble position of Lys, Glu and Gln (wobbleU* modification) is responsible for the fine-tuning of protein translation efficiency and translation rate. This modification influences organism function in accordance with growth and environmental changes. However, the effects of wobbleU* modification at the cellular, tissue, or individual level have not yet been elucidated. In this study, we show that sulfur modification of wobbleU* of the tRNAs affects leaf development in Arabidopsis thaliana. The sulfur modification was impaired in the two wobbleU*-modification mutants: the URM1-like protein-defective mutant and the Elongator complex-defective mutants. Analyses of the mutant phenotypes revealed that the deficiency in the wobbleU* modification increased the airspaces in the leaves and the leaf size without affecting the number and the area of palisade mesophyll cells. On the other hand, both mutants exhibited increased number of leaf epidermal pavement cells but with reduced cell size. The deficiency in the wobbleU* modification also delayed the initiation of the endoreduplication processes of mesophyll cells. The phenotype of ASYMMETRIC LEAVES2-defective mutant was enhanced in the Elongator-defective mutants, while it was unchanged in the URM1-like protein-defective mutant. Collectively, the findings of this study suggest that the tRNA wobbleU* modification plays an important role in leaf morphogenesis by balancing the development between epidermal and mesophyll tissues.

The crystal structure of homoserine dehydrogenase complexed with l-homoserine and NADPH in a closed form

Homoserine dehydrogenase from Thermus thermophilus (TtHSD) is a key enzyme in the aspartate pathway that catalyses the reversible conversion of l-aspartate-β-semialdehyde to l-homoserine (l-Hse) with NAD(P)H. We determined the crystal structures of unliganded TtHSD, TtHSD complexed with l-Hse and NADPH, and Lys99Ala and Lys195Ala mutant TtHSDs, which have no enzymatic activity, complexed with l-Hse and NADP+ at 1.83, 2.00, 1.87 and 1.93 Å resolutions, respectively. Binding of l-Hse and NADPH induced the conformational changes of TtHSD from an open to a closed form: the mobile loop containing Glu180 approached to fix l-Hse and NADPH, and both Lys99 and Lys195 could make hydrogen bonds with the hydroxy group of l-Hse. The ternary complex of TtHSDs in the closed form mimicked a Michaelis complex better than the previously reported open form structures from other species. In the crystal structure of Lys99Ala TtHSD, the productive geometry of the ternary complex was almost preserved with one new water molecule taking over the hydrogen bonds associated with Lys99, while the positions of Lys195 and l-Hse were significantly retained with those of the wild-type enzyme. These results propose new possibilities that Lys99 is the acid-base catalytic residue of HSDs.