Po-Min Chen

Critical roles of nardilysin in the maintenance of body temperature homoeostasis

Body temperature homoeostasis in mammals is governed centrally through the regulation of shivering and non-shivering thermogenesis and cutaneous vasomotion. Non-shivering thermogenesis in brown adipose tissue (BAT) is mediated by sympathetic activation, followed by PGC-1α induction, which drives UCP1. Here we identify nardilysin (Nrd1 and NRDc) as a critical regulator of body temperature homoeostasis. Nrd1−/− mice show increased energy expenditure owing to enhanced BAT thermogenesis and hyperactivity. Despite these findings, Nrd1−/− mice show hypothermia and cold intolerance that are attributed to the lowered set point of body temperature, poor insulation and impaired cold-induced thermogenesis. Induction of β3-adrenergic receptor, PGC-1α and UCP1 in response to cold is severely impaired in the absence of NRDc. At the molecular level, NRDc and PGC-1α interact and co-localize at the UCP1 enhancer, where NRDc represses PGC-1α activity. These findings reveal a novel nuclear function of NRDc and provide important insights into the mechanism of thermoregulation.

Nardilysin Is Required for Maintaining Pancreatic β-Cell Function.

Type 2 diabetes (T2D) is associated with pancreatic β-cell dysfunction, manifested by reduced glucose-stimulated insulin secretion (GSIS). Several transcription factors enriched in β-cells, such as MafA, control β-cell function by organizing genes involved in GSIS. Here we demonstrate that nardilysin (N-arginine dibasic convertase; Nrd1 and NRDc) critically regulates β-cell function through MafA. Nrd1−/− mice showed glucose intolerance and severely decreased GSIS. Islets isolated from Nrd1−/− mice exhibited reduced insulin content and impaired GSIS in vitro. Moreover, β-cell-specific NRDc-deficient (Nrd1delβ) mice showed a diabetic phenotype with markedly reduced GSIS. MafA was specifically downregulated in islets from Nrd1delβ mice, whereas overexpression of NRDc upregulated MafA and insulin expression in INS832/13 cells. Chromatin immunoprecipitation assay revealed that NRDc is associated with Islet-1 in the enhancer region of MafA, where NRDc controls the recruitment of Islet-1 and MafA transcription. Our findings demonstrate that NRDc controls β-cell function via regulation of the Islet-1–MafA pathway.

Association of serum levels of antibodies against MMP1, CBX1, and CBX5 with transient ischemic attack and cerebral infarction

Transient ischemic attack (TIA) is a predictor for cerebral infarction (CI), and early diagnosis of TIA is extremely important for the prevention of CI. We set out to identify novel antibody biomarkers for TIA and CI, and detected matrix metalloproteinase 1 (MMP1), chromobox homolog 1 (CBX1), and chromobox homolog 5 (CBX5) as candidate antigens using serological identification of antigens by recombinant cDNA expression cloning (SEREX) and Western blotting to confirm the presence of serum antibodies against the antigens. Amplified luminescent proximity homogeneous assay-linked immunosorbent assay (AlphaLISA) revealed that serum antibody levels were significantly higher in patients with TIA or acute-phase CI (aCI) compared with healthy donors (P < 0.01). Spearman’s correlation analysis and multivariate logistic regression analysis demonstrated that levels of anti-MMP1, anti-CBX1, and anti-CBX5 antibodies were associated with age, cigarette-smoking habits, and blood pressure. Thus, serum levels of antibodies against MMP1, CBX1, and CBX5 could potentially serve as useful tools for diagnosing TIA and predicting the onset of aCI.

Nardilysin is a promising biomarker for the early diagnosis of acute coronary syndrome

BACKGROUND Biomarkers for detection of transient myocardial ischemia in patients with unstable angina (UA) or for very early diagnosis of acute myocardial infarction (AMI) are not currently available. METHODS AND RESULTS We performed two sequential screenings of autoantibodies elevated shortly after the onset of acute coronary syndrome (ACS), and focused on metalloendopeptidase nardilysin (NRDC) among 19 identified candidate antigens. In a retrospective analysis among 93 ACS and 117 non-ACS patients, the serum level of NRDC was significantly increased in patients with ACS compared with that in patients with non-ACS (2073.5±189.8pg/ml versus 775.7±63.4pg/ml, P<0.0001). The area under the curve of NRDC for the diagnosis of ACS was 0.822 by the receiver operating characteristic curves analysis. In the time course analysis in 43 consecutive ACS patients (AMI: N=35 and UA: N=8), serum concentration of NRDC was significantly increased even in UA patients with a peak serum NRDC levels reached at admission both in AMI and UA patients. In a mouse model of AMI, we found an acute increase in serum NRDC and reduced NRDC expression in ischemic regions shortly after coronary artery ligation. NRDC expression was also reduced in infarcted regions in human autopsy samples from AMI patients. Moreover, the short treatment of primary culture of rat cardiomyocytes with H2O2 or A23187 induced NRDC secretion without cell toxicity. CONCLUSION NRDC is a promising biomarker for the early detection of ACS, even in UA patients without elevation of necrosis markers.

Serum SH3BP5-specific Antibody Level is a Biomarker of Atherosclerosis

Abstract Background: The discovery and development of novel biomarkers that could facilitate early diagnosis and thus prevent the progression of atherosclerosis-related diabetes mellitus (DM), cerebral infarction (CI), and cardiovascular disease (CVD) has garnered much research interest. Notably, recent reports have described a number of highly sensitive antibody markers. In this study, we aimed to identify additional antibody markers that would facilitate screening. Methods: The amplified luminescent proximity homogeneous assay (AlphaLISA) method, which incorporates glutathione- or streptavidin-donor beads and anti-human-IgG-acceptor beads, was used to evaluate serum antibody levels in serum samples. The protein array method was used for the initial screening, and peptide arrays were used to identify epitope sites. Results: The protein array identified SH3 domain-binding protein 5 (SH3BP5) as a target antigen of serum IgG antibodies in the sera of patients with atherosclerosis. We prepared recombinant glutathione S-transferase (GST)- fused SH3BP5 protein. Peptide arrays revealed that the epitope site recognized by serum antibodies is located within amino acids 161–174 of SH3BP5. AlphaLISA revealed significantly higher serum antibody levels against both the SH3BP5 protein and peptide in patients with DM, acute-phase CI, transient ischemic attack, CVD or chronic kidney disease (CKD), than in healthy donors. Furthermore, areas under the receiver operating characteristic curves of these antibodies were higher in patients with CKD and DM than in other patients. Spearman correlation analysis revealed associations between the serum antibody levels against SH3BP5 peptide and artery stenosis, hypertension, and smoking. Conclusions: The serum anti-SH3BP5 antibody marker appears to be useful for estimating the progress of atherosclerosis and may discriminate atherosclerosis associated with hypertension and/or habitual smoking.

Elevated Levels of Autoantibodies against ATP2B4 and BMP-1 in Sera of Patients with Atherosclerosis-related Diseases

Background: Atherosclerosis-related life-style diseases such as cerebral infarction (CI), cardiovascular disease (CVD), diabetes mellitus (DM), and chronic kidney disease (CKD) are a serious problem in the recently aging society. The development of novel and sensitive diagnostic markers is necessary and expected for the early treatment. Methods and Results: Through the first screening by phage expression cloning, we identified ATPase, Ca++ transporting, plasma membrane 4 (ATP2B4) and bone morphogenetic protein 1 (BMP-1) as antigens recognized by IgG antibodies in the sera of patients with atherosclerosis. The presence of autoantibodies against these antigens in serum specimens was confirmed by Western blotting. We then compared serum antibody levels against recombinant ATP2B4 and BMP-1 proteins between healthy donors (HD) and patients with atherosclerotic diseases, such as CI, transient ischemic attack (TIA), CVD, DM, or CKD, by the Alpha (amplified luminescent proximity homogeneous assay)-LISA method. The results revealed that both antibody levels were significantly higher in patients with these diseases than in HD and exhibited most prominent differences in CKD vs. HD. Correlation analysis showed that both antibody levels were well correlated with the degree of artery stenosis, such as maximum intima-media thickness with some different patterns, i.e., anti-ATP2B4 antibody levels were related to hypertension, whereas anti-BMP-1 antibodies were related to smoking habits. Conclusions: The serum antibody levels against ATP2B4 and BMP-1 can be useful diagnostic markers for atherosclerosis and its related diseases caused by hypertension and smoking habits, respectively.

Validation of simplified PESI score for identification of low-risk patients with pulmonary embolism: From the COMMAND VTE Registry

Background: The simplified pulmonary embolism severity index (sPESI) score has been reported to be useful in predicting 30-day mortality for patients with pulmonary embolism, which helps the identification of low-risk patients for early hospital discharge or home treatment. However, therapeutic decision-making should also be based on the risks of adverse events other than mortality. Methods: The COMMAND VTE Registry is a multicentre registry enrolling consecutive patients with acute symptomatic venous thromboembolism in Japan between January 2010 and August 2014, and the current study population consisted of 1715 patients with pulmonary embolism. We calculated the sPESI score for each patient, and compared 30-day rates of mortality, recurrent venous thromboembolism and major bleeding between sPESI scores of 0 and 1 or greater. Results: Patients with a sPESI score of 0 accounted for 383 (22%) patients, and 110 (6.4%) patients died within 30 days. The cumulative 30-day incidence of mortality was lower in patients with a sPESI score of 0 than those with a sPESI score of 1 or greater (0.5% vs. 8.1%, log rank P<0.001). There was no significant difference in the cumulative 30-day incidence of recurrent venous thromboembolism between patients with a sPESI score of 0 and 1 or greater (1.3% vs. 2.8%, log rank P=0.11). The cumulative 30-day incidence of major bleeding was lower in patients with a sPESI score of 0 than those with a sPESI score of 1 or greater (1.1% vs. 4.0%, log rank P=0.005). Conclusions: In patients with a sPESI score of 0, the 30-day mortality, recurrent venous thromboembolism and major bleeding rates were reasonably low. The sPESI score could be useful to identify candidates for early hospital discharge or home treatment.

Influence of Baseline Platelet Count on Outcomes in Patients With Venous Thromboembolism (from the COMMAND VTE Registry)

The influence of thrombocytopenia on the long-term clinical outcomes has not been thoroughly evaluated in patients with venous thromboembolism (VTE). This study sought to elucidate association of baseline thrombocytopenia with bleeding, recurrent VTE, and mortality risk. We evaluated the influence of baseline thrombocytopenia among 3,012 patients whose baseline platelet counts were available in the COMMAND VTE Registry in Japan with a median follow-up period of 1,219 days. Baseline thrombocytopenia was classified as follows: mild: 100,000 to 150,000/μl; moderate: 50,000 to 99,999/μl; and severe: <50,000/μl. The primary outcome measurement was International Society of Thrombosis and Hemostasis major bleeding, and the secondary outcome measurements were recurrent VTE and all-cause death. There were 167 patients (5.5%) with moderate or severe thrombocytopenia (moderate: 144 patients and severe: 23 patients), 523 patients (17.4%) with mild thrombocytopenia, and 2,322 patients (77.1%) without thrombocytopenia. The cumulative 5-year incidence of major bleeding was markedly higher in patients with moderate or severe thrombocytopenia (moderate or severe 29.4% vs mild: 14.1% vs no thrombocytopenia: 10.6%, p <0.001). After adjusting the confounders, the risk of or thrombocytopenia relative to no thrombocytopenia for major bleeding remained significant (adjusted hazard ratio [HR] 2.15, 95% confidence interval [CI] 1.43 to 3.13, p <0.001). The excess risk of moderate or severe thrombocytopenia relative to no thrombocytopenia was also significant for mortality (adjusted HR 1.54, 95% CI 1.18 to 1.97, p = 0.002), but the risk was neutral for recurrent VTE (adjusted HR 1.05, 95% CI 0.55 to 1.81, p = 0.87). In conclusion, VTE patients with baseline moderate or severe thrombocytopenia had higher risk for major bleeding events and mortality without significant excess risk for recurrent VTE events.

Elevated Adiponectin Antibody Levels in Sera of Patients with Atherosclerosis-Related Coronary Artery Disease, Cerebral Infarction and Diabetes Mellitus

Adiponectin secreted from the adipocytes plays pleiotropic, anti-atherosclerotic roles, such as enhancement of insulin secretion and an increase in energy expenditure. The measurement of levels of circulating adiponectin is useful to evaluate the progression of atherosclerosis-related diseases, such as coronary artery disease (CAD), cerebral infarction (CI) and diabetes mellitus (DM). We examined the serum antibody levels against recombinant adiponectin protein via the amplified luminescent proximity homogeneous assay-linked immunosorbent assay (AlphaLISA) method. The results revealed that the antibody levels were significantly higher in patients with CAD, CI and type 2 DM, than in healthy donors. Receiver operating curve analysis showed that the sensitivity was in a range of 41–48% for CAD, CI and DM. Thus, the serum anti-adiponectin antibody levels could be a common marker for atherosclerosis-related diseases.