YAP induces a neonatal-like pro-renewal niche in the adult heart

After myocardial infarction (MI), mammalian hearts do not regenerate, and the microenvironment is disrupted. Hippo signaling loss of function with activation of transcriptional co-factor YAP induces heart renewal and rebuilds the post-MI microenvironment. In this study, we investigated adult renewal-competent mouse hearts expressing an active version of YAP, called YAP5SA, in cardiomyocytes (CMs). Spatial transcriptomics and single-cell RNA sequencing revealed a conserved, renewal-competent CM cell state called adult (a)CM2 with high YAP activity. aCM2 co-localized with cardiac fibroblasts (CFs) expressing complement pathway component C3 and macrophages (MPs) expressing C3ar1 receptor to form a cellular triad in YAP5SA hearts and renewal-competent neonatal hearts. Although aCM2 was detected in adult mouse and human hearts, the cellular triad failed to co-localize in these non-renewing hearts. C3 and C3ar1 loss-of-function experiments indicated that C3a signaling between MPs and CFs was required to assemble the pro-renewal aCM2, C3+ CF and C3ar1+ MP cellular triad.

Endothelial cells adopt a pro-reparative immune responsive signature during cardiac injury

Modulation of the heart's immune microenvironment is crucial for recovery after ischemic events such as myocardial infarction (MI). Endothelial cells (ECs) can have immune regulatory functions; however, interactions between ECs and the immune environment in the heart after MI remain poorly understood. We identified an EC-specific IFN responsive and immune regulatory gene signature in adult and pediatric heart failure (HF) tissues. Single-cell transcriptomic analysis of murine hearts subjected to MI uncovered an EC population (IFN-ECs) with immunologic gene signatures similar to those in human HF. IFN-ECs were enriched in regenerative-stage mouse hearts and expressed genes encoding immune responsive transcription factors (Irf7, Batf2, and Stat1). Single-cell chromatin accessibility studies revealed an enrichment of these TF motifs at IFN-EC signature genes. Expression of immune regulatory ligand genes by IFN-ECs suggests bidirectional signaling between IFN-ECs and macrophages in regenerative-stage hearts. Our data suggest that ECs may adopt immune regulatory signatures after cardiac injury to accompany the reparative response. The presence of these signatures in human HF and murine MI models suggests a potential role for EC-mediated immune regulation in responding to stress induced by acute injury in MI and chronic adverse remodeling in HF.

Life expectancy associated with different ages at diagnosis of type 2 diabetes in high-income countries: 23 million person-years of observation

BACKGROUND

The prevalence of type 2 diabetes is increasing rapidly, particularly among younger age groups. Estimates suggest that people with diabetes die, on average, 6 years earlier than people without diabetes. We aimed to provide reliable estimates of the associations between age at diagnosis of diabetes and all-cause mortality, cause-specific mortality, and reductions in life expectancy.

METHODS

For this observational study, we conducted a combined analysis of individual-participant data from 19 high-income countries using two large-scale data sources: the Emerging Risk Factors Collaboration (96 cohorts, median baseline years 1961-2007, median latest follow-up years 1980-2013) and the UK Biobank (median baseline year 2006, median latest follow-up year 2020). We calculated age-adjusted and sex-adjusted hazard ratios (HRs) for all-cause mortality according to age at diagnosis of diabetes using data from 1 515 718 participants, in whom deaths were recorded during 23·1 million person-years of follow-up. We estimated cumulative survival by applying age-specific HRs to age-specific death rates from 2015 for the USA and the EU.

FINDINGS

For participants with diabetes, we observed a linear dose-response association between earlier age at diagnosis and higher risk of all-cause mortality compared with participants without diabetes. HRs were 2·69 (95% CI 2·43-2·97) when diagnosed at 30-39 years, 2·26 (2·08-2·45) at 40-49 years, 1·84 (1·72-1·97) at 50-59 years, 1·57 (1·47-1·67) at 60-69 years, and 1·39 (1·29-1·51) at 70 years and older. HRs per decade of earlier diagnosis were similar for men and women. Using death rates from the USA, a 50-year-old individual with diabetes died on average 14 years earlier when diagnosed aged 30 years, 10 years earlier when diagnosed aged 40 years, or 6 years earlier when diagnosed aged 50 years than an individual without diabetes. Using EU death rates, the corresponding estimates were 13, 9, or 5 years earlier.

INTERPRETATION

Every decade of earlier diagnosis of diabetes was associated with about 3-4 years of lower life expectancy, highlighting the need to develop and implement interventions that prevent or delay the onset of diabetes and to intensify the treatment of risk factors among young adults diagnosed with diabetes.

FUNDING

British Heart Foundation, Medical Research Council, National Institute for Health and Care Research, and Health Data Research UK.

Investigation of in-line filter replacement intervals for infusion

BACKGROUND

In-line filters in peripheral and central venous catheters are used to remove bacterial cells mechanically. A recent study indicated an extension of the use of infusion sets to 7 days. There is no evidence regarding replacement intervals for in-line filters.

AIM

To test in-line filters that were used continuously for 7 days in order to investigate their ability to remove bacteria and assess the flow rate.

METHODS

Three different in-line filters were attached to an ELNEOPA-NF No. 2 premixed infusion bag of intravenous hyperalimentation, into which Staphylococcus epidermidis ATCC12228 or Escherichia coli ATCC25922 was inoculated. These experiments were compared with a control infusion. The infusion was dropped at a flow rate of 40 mL/h and replaced at 24-h intervals for 7 days. Samples were collected 24 h after drop initiation.

FINDINGS

S. epidermidis was not detected in droplets between Days 1 and 6, but In-line filters 1 and 2 showed droplets containing 6-10 colony-forming units/mL on Day 7. E. coli was not detected in any of the filters after 7 days of continuous use. Flow rates <40 mL/h were observed on Day 7 for In-line filter 3 in studies of S. epidermidis, and on Days 4 and 3 for In-line filters 2 and 3, respectively, in studies of E. coli.

CONCLUSION

This study revealed differences in bacterial removal and flow rates under high inoculation between the three in-line filters tested. It is suggested that in-line filters can be used continuously for a maximum of 6 days, and reductions in flow rate after 48 h of continuous use should be noted carefully.

Integrated multi-omic characterization of congenital heart disease

The heart, the first organ to develop in the embryo, undergoes complex morphogenesis that when defective results in congenital heart disease (CHD). With current therapies, more than 90% of patients with CHD survive into adulthood, but many suffer premature death from heart failure and non-cardiac causes1. Here, to gain insight into this disease progression, we performed single-nucleus RNA sequencing on 157,273 nuclei from control hearts and hearts from patients with CHD, including those with hypoplastic left heart syndrome (HLHS) and tetralogy of Fallot, two common forms of cyanotic CHD lesions, as well as dilated and hypertrophic cardiomyopathies. We observed CHD-specific cell states in cardiomyocytes, which showed evidence of insulin resistance and increased expression of genes associated with FOXO signalling and CRIM1. Cardiac fibroblasts in HLHS were enriched in a low-Hippo and high-YAP cell state characteristic of activated cardiac fibroblasts. Imaging mass cytometry uncovered a spatially resolved perivascular microenvironment consistent with an immunodeficient state in CHD. Peripheral immune cell profiling suggested deficient monocytic immunity in CHD, in agreement with the predilection in CHD to infection and cancer2. Our comprehensive phenotyping of CHD provides a roadmap towards future personalized treatments for CHD.

Synergistic reduction in albuminuria in type 2 diabetic mice by esaxerenone (CS-3150), a novel nonsteroidal selective mineralocorticoid receptor blocker, combined with an angiotensin II receptor blocker

Esaxerenone is a novel selective mineralocorticoid receptor (MR) blocker that was recently approved in Japan to treat hypertension. In phase II and III studies, esaxerenone plus a renin–angiotensin system inhibitor markedly reduced the urinary albumin-to-creatinine ratio (UACR) in hypertensive patients with diabetic nephropathy. To evaluate a direct renoprotective effect by MR blockade independent of an antihypertensive effect in the context of diabetic nephropathy, esaxerenone (3 mg/kg), olmesartan (an angiotensin II receptor blocker; 1 mg/kg), or both were orally administered to KK-Ay mice, a type 2 diabetes model, once daily for 56 days. Urinary albumin (Ualb), UACR, and markers, such as podocalyxin, monocyte chemoattractant protein-1 (MCP-1), and 8-hydroxy-2′-deoxyguanosine (8-OHdG), were measured, along with systolic blood pressure (SBP), fasting blood glucose, and serum K⁺ levels. Prior to the initiation of drug administration, KK-Ay mice showed higher blood glucose, insulin, Ualb excretion, and UACR levels than C57BL/6 J mice, a nondiabetic control, indicating the development of diabetic renal injury. Combined treatment with esaxerenone and olmesartan significantly reduced the change in UACR from baseline compared with the change associated with vehicle at week 8 (−1.750 vs. 0.339 g/gCre; P < 0.002) and significantly inhibited the change in Ualb from baseline compared with the change associated with vehicle at week 8 (P < 0.002). The combination treatment also reduced urinary excretion of podocalyxin and MCP-1, but did not influence 8-OHdG excretion, SBP, blood glucose, or serum K⁺ levels. Overall, esaxerenone plus olmesartan treatment ameliorated diabetic nephropathy in KK-Ay mice without affecting SBP, suggesting that the renoprotective effects of esaxerenone could be exerted independently of its antihypertensive effect.

YAP Partially Reprograms Chromatin Accessibility to Directly Induce Adult Cardiogenesis In Vivo

Specialized adult somatic cells, such as cardiomyocytes (CMs), are highly differentiated with poor renewal capacity, an integral reason underlying organ failure in disease and aging. Among the least renewable cells in the human body, CMs renew approximately 1% annually. Consistent with poor CM turnover, heart failure is the leading cause of death. Here, we show that an active version of the Hippo pathway effector YAP, termed YAP5SA, partially reprograms adult mouse CMs to a more fetal and proliferative state. One week after induction, 19% of CMs that enter S-phase do so twice, CM number increases by 40%, and YAP5SA lineage CMs couple to pre-existing CMs. Genomic studies showed that YAP5SA increases chromatin accessibility and expression of fetal genes, partially reprogramming long-lived somatic cells in vivo to a primitive, fetal-like, and proliferative state.

A unique phenotype of acquired Glanzmann thrombasthenia due to non-function-blocking anti-αIIbβ3 autoantibodies

Essentials Acquired Glanzmann thrombasthenia (aGT) is generally caused by function-blocking antibodies (Abs). We demonstrated a unique aGT case due to marked reduction of αIIbβ3 with anti-αIIbβ3 Abs. The anti-αIIbβ3 Abs of the patient did not inhibit platelet function but reduced surface αIIbβ3. Internalization of αIIbβ3 induced by the Abs binding may be responsible for the phenotype. SUMMARY: Background Acquired Glanzmann thrombasthenia (aGT) is a bleeding disorder generally caused by function-blocking anti-αIIbβ3 autoantibodies. Aim We characterize an unusual case of aGT caused by marked reduction of surface αIIbβ3 with non-function-blocking anti-αIIbβ3 antibodies (Abs). Methods A 72-year-old male suffering from immune thrombocytopenia since his 50s showed exacerbation of bleeding symptom despite mild thrombocytopenia. Platelet aggregation was absent with all agonists but ristocetin. Analysis of αIIbβ3 expression and genetic analysis were performed. We also analyzed effects of anti-αIIbβ3 Abs of the patient on platelet function and αIIbβ3 expression. Results Surface αIIbβ3 expression was markedly reduced to around 5% of normal, whereas his platelets contained αIIbβ3 to the amount of 40-50% of normal. A substantial amount of fibrinogen was also detected in his platelets. There were no abnormalities in ITGA2B and ITGB3 cDNA. These results indicated that reduced surface αIIbβ3 expression caused a GT phenotype, and active internalization of αIIbβ3 was suggested. Anti-αIIbβ3 IgG Abs were detected in platelet eluate and plasma. These Abs did not inhibit PAC-1 binding, indicating that the Abs were non-function-blocking. Surface αIIbβ3 expression of a megakaryocytic cell line and cultured megakaryocytes tended to be impaired by incubation with the patient's Abs. After 2 years of aGT diagnosis, his bleeding symptom improved and surface αIIbβ3 expression was recovered to 20% of normal with reduction of anti-αIIbβ3 Abs. Conclusion We demonstrated a unique aGT phenotype due to marked reduction of surface αIIbβ3. Internalization induced by anti-αIIbβ3 Abs may be responsible in part for the phenotype.

Pitx2 maintains mitochondrial function during regeneration to prevent myocardial fat deposition

Loss of the paired-like homeodomain transcription factor 2 (Pitx2) in cardiomyocytes predisposes mice to atrial fibrillation and compromises neonatal regenerative capacity. In addition, Pitx2 gain-of-function protects mature cardiomyocytes from ischemic injury and promotes heart repair. Here, we characterized the long-term myocardial phenotype following myocardial infarction (MI) in Pitx2 conditional-knockout (Pitx2 CKO) mice. We found adipose-like tissue in Pitx2 CKO hearts 60 days after MI induced surgically at postnatal day 2 but not at day 8. Molecular and cellular analyses showed the onset of adipogenic signaling in mutant hearts after MI. Lineage tracing experiments showed a non-cardiomyocyte origin of the de novo adipose-like tissue. Interestingly, we found that Pitx2 promotes mitochondrial function through its gene regulatory network, and that the knockdown of a key mitochondrial Pitx2 target gene, Cox7c, also leads to the accumulation of myocardial fat tissue. Single-nuclei RNA-seq revealed that Pitx2-deficient hearts were oxidatively stressed. Our findings reveal a role for Pitx2 in maintaining proper cardiac cellular composition during heart regeneration via the maintenance of proper mitochondrial structure and function.

Hippo pathway deficiency reverses systolic heart failure after infarction

Mammalian organs vary widely in regenerative capacity. Poorly regenerative organs, such as the heart are particularly vulnerable to organ failure. Once established, heart failure (HF) commonly results in mortality¹. The Hippo pathway, a kinase cascade that prevents adult cardiomyocyte proliferation and regeneration², is upregulated in human HF. We show that deletion of the Hippo pathway component Salvador (Salv) in mouse hearts with established ischemic HF after myocardial infarction (MI) induced a reparative genetic program with increased scar border vascularity, reduced fibrosis, and recovery of pumping function compared to controls. Using TRAP (translating ribosomal affinity purification), we isolated cardiomyocyte specific translating mRNA. Hippo deficient cardiomyocytes had increased expression of proliferative genes and stress response genes, such as the mitochondrial quality control (MQC) gene, Park2. Genetic studies indicated that Park2 was essential for heart repair suggesting a requirement for MQC in regenerating myocardium. Gene therapy with a virus encoding Salv shRNA improved heart function when delivered at the time of infarct or after ischemic HF post-MI was established. Our findings indicate that the failing heart has a previously unrecognized reparative capacity involving more than cardiomyocyte renewal.

Abstract 78: Hippo Pathway and Dystrophin Glycoprotein Complex Regulate Cardiomyocyte Proliferation

Regeneration of mammalian heart is limited due to the extremely low renewal rate of cardiomyocytes and their inability to reenter the cell cycle. The Hippo pathway controls heart size during development and represses postnatal heart regeneration by repressing cardiomyocyte proliferation. Our approach for activating adult heart regeneration is to uncover the mechanisms responsible for repression of cardiomyocyte proliferation. We have previously found that deletion of Salv, a modulator of the Hippo pathway, results in myocardial damage repair in postnatal and adult hearts. Deletion of Salv results in activation of the transcription factor, Yap, which positively regulates cytoskeleton and cell cycle genes. We also found that the components of dystrophin glycoprotein complex (DGC) are the target of Yap and DGC regulates heart regeneration. The dystrophin glycoprotein complex (DGC) is essential for muscle maintenance by anchoring the cytoskeleton and extracellular matrix. Disruption of the DGC results in muscular dystrophies, including Duchenne muscular dystrophy, resulting in both skeletal and cardiac myopathies. To explore the connection between DGC and the Hippo pathway, we conditionally deleted Salv in the mdx background, a mouse model of muscular dystrophy. We found that simultaneous disruption of the DGC and the Hippo pathway leads an increased cardiomyocyte proliferation after heart damage. This is associated with increased activity of Yap, suggesting DGC negatively regulate Yap to repress proliferation. We also found that one of the components DGC, dystroglycan directly binds Yap and anchors to the membrane. Our findings provide new insights into the mechanisms leading to heart repair through proliferation of endogenous cardiomyocytes.

Dystrophin-glycoprotein complex sequesters Yap to inhibit cardiomyocyte proliferation

The regenerative capacity of the adult mammalian heart is limited because of the reduced ability of cardiomyocytes (CMs) to progress through mitosis¹. The regenerative capacity of endogenous CMs exists at birth but is lost postnatally, with subsequent organ growth occurring through CM hypertrophy^2,3. The Hippo pathway, a conserved kinase cascade, inhibits CM proliferation in the developing heart to control heart size and in the adult heart to prevent regeneration^4,5. The dystrophin glycoprotein complex (DGC), a multicomponent transmembrane complex linking the actin cytoskeleton to extracellular matrix, is essential for CM homeostasis. DGC deficiency in humans results in muscular dystrophy, including lethal Duchenne muscular dystrophy (DMD). We found that the DGC component dystroglycan 1 (DAG1) directly binds to Hippo pathway effector Yap to inhibit CM proliferation. The Yap-DAG1 interaction was enhanced by Hippo-induced Yap phosphorylation, revealing a connection between Hippo pathway function and the DGC. After injury, Hippo-deficient postnatal hearts maintained organ size control by repairing the defect with correct dimensions, whereas postnatal hearts doubly deficient for Hippo and the DGC showed CM overproliferation at the injury site. In mature Mdx mouse hearts—a model of DMD—Hippo deficiency protected against overload-induced heart failure.

Chemical etching of silicon carbide in pure water by using platinum catalyst

Chemical etching of SiC was found to proceed in pure water with the assistance of a Pt catalyst. A 4H-SiC (0001) wafer was placed and slid on a polishing pad in pure water, on which a thin Pt film was deposited to give a catalytic nature. Etching of the wafer surface was observed to remove protrusions preferentially by interacting with the Pt film more frequently, thus flattening the surface. In the case of an on-axis wafer, a crystallographically ordered surface was obtained with a straight step-and-terrace structure, the height of which corresponds to that of an atomic bilayer of Si and C. The etching rate depended upon the electrochemical potential of Pt. The vicinal surface was observed at the potential at which the Pt surface was bare. The primary etching mechanism was hydrolysis with the assistance of a Pt catalyst. This method can, therefore, be used as an environmentally friendly and sustainable technology.

Skipping breakfast and 5-year changes in body mass index and waist circumference in Japanese men and women

OBJECTIVE

This study investigated the relationship between frequency of skipping breakfast and annual changes in body mass index (BMI) and waist circumference (WC).

METHODS

The participants were 4,430 factory employees. BMI and WC were measured repeatedly at annual medical examinations over a 5-year period. The association between frequency of skipping breakfast at the baseline examination and annual changes in anthropometric indices was evaluated using the generalized estimating equation method.

RESULTS

The mean (standard deviation) BMI was 23.3 (3.0) kg m^-2 for men and 21.9 (3.6) kg m^-2 for women; and the mean WC was 82.6 (8.7) cm for men and 77.8 (9.8) cm for women. During the follow-up period, mean BMI increased by 0.2 kg m^-2 for men and women, and mean WC increased by 1.1 cm for men and 1.0 cm for women. The annual change in the BMI of men who skipped breakfast four to six times per week was 0.061 kg m^-2 higher, and that of those who skipped breakfast seven times per week was 0.046 kg m^-2 higher, compared with those who did not skip breakfast. Annual changes in the WC of male participants who skipped breakfast seven times per week was 0.248 cm higher than that of those who did not skip breakfast. Skipping breakfast was not associated with changes in BMI or WC in women.

CONCLUSIONS

Skipping breakfast was closely associated with annual changes in BMI and WC among men, and eating breakfast more than four times per week may prevent the excessive body weight gain associated with skipping breakfast.

Abstract 396: Regulation of Cardiomyocyte Proliferation by the Hippo Pathway and Dystrophin Complex

Regeneration in mammalian hearts is limited due to the extremely low renewal rate of cardiomyocytes and their inability to reenter the cell cycle. In rodent hearts, endogenous regenerative capacity exists during development but is rapidly repressed after birth, at which time growth is by hypertrophy. During the developmental and neonatal periods, heart regeneration occurs through proliferation of pre-existing cardiomyocytes. Our approach of activating heart regeneration is to uncover the mechanisms responsible for repression of cardiomyocyte proliferation. The Hippo pathway controls heart size by repressing cardiomyocyte proliferation during development. By deleting Salv , a modulator of the Hippo pathway, we found that myocardial damage in postnatal and adult hearts was repaired both anatomically and functionally. This heart repair occurred primary through proliferation of preexisting cardiomyocytes. During repair, cardiomyocytes reenter the cell cycle; de novo DNA synthesis, karyokinesis, and cytokinesis all take place. The dystrophin glycoprotein complex (DGC) is essential for muscle maintenance by anchoring the cytoskeleton and extracellular matrix. Disruption of the DGC results in muscular dystrophies, including Duchenne muscular dystrophy, resulting in both skeletal and cardiac myopathies. Recently the DGC was shown to regulate cardiomyocyte proliferation and we found that the DGC and the Hippo pathway components directly interact. To address if the DGC and the Hippo pathway coordinately regulate cardiomyocyte proliferation, we conditionally deleted Salv in the mouse model of muscular dystrophy, the mdx line. We found that simultaneous disruption of both the DGC and Hippo pathway leads an increased de novo DNA synthesis and cytokinesis in cardiomyocytes after heart damage. Our findings provide new insights into the mechanisms leading to heart repair through proliferation of endogenous cardiomyocytes.

CS-3150, a Novel Nonsteroidal Mineralocorticoid Receptor Antagonist, Shows Preventive and Therapeutic Effects On Renal Injury in Deoxycorticosterone Acetate/Salt-Induced Hypertensive Rats

The present study was designed to assess both preventive and therapeutic effects of (S)-1-(2-Hydroxyethyl)-4-methyl-N-[4-(methylsulfonyl) phenyl]-5-[2-(trifluoromethyl) phenyl]-1H-pyrrole-3-carboxamide (CS-3150), a novel nonsteroidal mineralocorticoid receptor antagonist, on renal injury in deoxycorticosterone acetate (DOCA)/salt-induced hypertensive rats (DOCA rats). From 7 weeks of age, DOCA was subcutaneously administered once a week for 4 weeks to uninephrectomized rats fed a high-salt diet. In experiment 1, CS-3150 (0.3-3 mg/kg) was orally administered once a day for 4 weeks coincident with DOCA administration. In experiment 2, after establishment of renal injury by 4 weeks of DOCA/salt loading, CS-3150 (3 mg/kg) was orally administered once a day for 4 weeks with or without continuous DOCA administration. In experiment 1, DOCA/salt loading significantly increased systolic blood pressure (SBP), which was prevented by CS-3150 in a dose-dependent manner. Development of renal injury (proteinuria, renal hypertrophy, and histopathological changes in glomeruli and tubule) was also suppressed by CS-3150 with inhibition of mRNA expression of fibrosis, inflammation, and oxidative stress markers. In experiment 2, under continuous DOCA treatment, CS-3150 clearly ameliorated existing renal injury without lowering SBP, indicating that CS-3150 regressed renal injury independent of its antihypertensive action. Moreover, CS-3150 treatment in combination with withdrawal of DOCA showed further therapeutic effect on renal injury accompanied by reduction in SBP. These results demonstrate that CS-3150 not only prevents but also ameliorates hypertension and renal injury in DOCA rats. Therefore, CS-3150 could be a promising agent for the treatment of hypertension and renal disorders, and may have potential to promote regression of renal injury.

Pitx2 promotes heart repair by activating the antioxidant response after cardiac injury

Myocardial infarction results in compromised myocardial function and heart failure owing to insufficient cardiomyocyte self-renewal. Unlike many vertebrates, mammalian hearts have only a transient neonatal renewal capacity. Reactivating primitive reparative ability in the mature mammalian heart requires knowledge of the mechanisms that promote early heart repair. By testing an established Hippo-deficient heart regeneration mouse model for factors that promote renewal, here we show that the expression of Pitx2 is induced in injured, Hippo-deficient ventricles. Pitx2-deficient neonatal mouse hearts failed to repair after apex resection, whereas adult mouse cardiomyocytes with Pitx2 gain-of-function efficiently regenerated after myocardial infarction. Genomic analyses indicated that Pitx2 activated genes encoding electron transport chain components and reactive oxygen species scavengers. A subset of Pitx2 target genes was cooperatively regulated with the Hippo pathway effector Yap. Furthermore, Nrf2, a regulator of the antioxidant response, directly regulated the expression and subcellular localization of Pitx2. Pitx2 mutant myocardium had increased levels of reactive oxygen species, while antioxidant supplementation suppressed the Pitx2 loss-of-function phenotype. These findings reveal a genetic pathway activated by tissue damage that is essential for cardiac repair.

Abstract 13: Hippo Signaling Deletion During Heart Failure Reverses Functional Decline

The heart has long been thought of as a static organ incapable of repair. Recent findings have challenged this view of the heart, and have demonstrated that mature cardiomyocytes are capable of re-entering the cell-cycle. However, there is still paucity in understanding endogenous mechanisms preventing cardiomyocyte self-renewal. Our approach is to apply developmental mechanisms of cardiomyocyte cell-cycle control to the damaged heart by altering the Hippo signaling pathway.

During development Hippo signaling regulates intrinsic organ size. The core mammalian Hippo pathway includes the Ste20-like serine/threonine kinases Mst1 and Mst2, homologous to the Drosophila Hippo kinase. A subsequent kinase cascade leads to the phosphorylation of the transcription factor Yap. Phosphorylated Yap is sequestered in the cytoplasm, thus preventing transcriptional activity. We previously demonstrated Hippo signaling controls cardiomyocyte proliferation during development to restrain heart size. Additionally, using both the Apex resection (AR) and LAD-ligation (MI) models of cardiac damage, in a Hippo signaling deletion mouse, we demonstrated cardiac regeneration. Indicated by preserved cardiac function and reduced fibrotic scar formation. Additionally, these hearts display cardiomyocyte proliferation as marked by EDU incorporation, pHH3, AurkB, and Ki67 staining.

We are taking a new approach to determine the effect of Hippo signaling deletion on the failing heart, by inducing Hippo deletion after fibrotic scar formation has already occurred. To Thus far our results indicate functional recovery of the failing heart only after inducible deletion of Hippo signaling. Consistent with our previous data, preliminary results indicate adult cardiomyocytes after Hippo deletion re-enter the cell cycle. By altering Hippo signaling during heart failure and subsequently inducing cardiomyocyte proliferation we have established recovery of cardiac function. These results will greatly advance strategies to induce cardiac repair.

Actin cytoskeletal remodeling with protrusion formation is essential for heart regeneration in Hippo-deficient mice

The mammalian heart regenerates poorly, and damage commonly leads to heart failure. Hippo signaling is an evolutionarily conserved kinase cascade that regulates organ size during development and prevents adult mammalian cardiomyocyte regeneration by inhibiting the transcriptional coactivator Yap, which also responds to mechanical signaling in cultured cells to promote cell proliferation. To identify Yap target genes that are activated during cardiomyocyte renewal and regeneration, we performed Yap chromatin immunoprecipitation sequencing (ChIP-Seq) and mRNA expression profiling in Hippo signaling-deficient mouse hearts. We found that Yap directly regulated genes encoding cell cycle progression proteins, as well as genes encoding proteins that promote F-actin polymerization and that link the actin cytoskeleton to the extracellular matrix. Included in the latter group were components of the dystrophin glycoprotein complex, a large molecular complex that, when defective, results in muscular dystrophy in humans. Cardiomyocytes near the scar tissue of injured Hippo signaling-deficient mouse hearts showed cellular protrusions suggestive of cytoskeletal remodeling. The hearts of mdx mutant mice, which lack functional dystrophin and are a model for muscular dystrophy, showed impaired regeneration and cytoskeleton remodeling, but normal cardiomyocyte proliferation, after injury. Our data showed that, in addition to genes encoding cell cycle progression proteins, Yap regulated genes that enhance cytoskeletal remodeling. Thus, blocking the Hippo pathway input to Yap may tip the balance so that Yap responds to mechanical changes associated with heart injury to promote repair.

Contribution of glucan-binding protein A to firm and stable biofilm formation by Streptococcus mutans

Glucan-binding proteins (Gbps) of Streptococcus mutans, a major pathogen of dental caries, mediate the binding of glucans synthesized from sucrose by the action of glucosyltransferases (GTFs) encoded by gtfB, gtfC, and gtfD. Several stress proteins, including DnaK and GroEL encoded by dnaK and groEL, are related to environmental stress tolerance. The contribution of Gbp expression to biofilm formation was analyzed by focusing on the expression levels of genes encoding GTFs and stress proteins. Biofilm-forming assays were performed using GbpA-, GbpB-, and GbpC-deficient mutant strains and the parental strain MT8148. The expression levels of gtfB, gtfC, gtfD, dnaK, and groEL were evaluated by reverse transcription-quantitative polymerase chain reaction (RT-qPCR). Furthermore, the structure of biofilms formed by these Gbp-deficient mutant strains was observed using confocal laser scanning microscopy (CLSM). Biofilm-forming assay findings demonstrated that the amount formed by the GbpA-deficient mutant strain (AD1) was nearly the same as that by the parental strain, while the GbpB- and GbpC-deficient mutant strains produced lower amounts than MT8148. Furthermore, RT-qPCR assay results showed that the expressions of gtfB, dnaK, and groEL in AD1 were elevated compared with MT8148. CLSM also revealed that the structure of biofilm formed by AD1 was prominently different compared with that formed by the parental strain. These results suggest that a defect in GbpA influences the expression of genes controlling biofilm formation, indicating its importance as a protein for firm and stable biofilm formation.

2,3,7,8-Tetrachlorodibenzo-p-dioxin in breast milk increases autistic traits of 3-year-old children in Vietnam

Dioxin levels in the breast milk of mothers residing near a contaminated former airbase in Vietnam remain much higher than in unsprayed areas, suggesting high perinatal dioxin exposure for their infants. The present study investigated the association of perinatal dioxin exposure with autistic traits in 153 3-year-old children living in a contaminated area in Vietnam. The children were followed up from birth using the neurodevelopmental battery Bayley-III. The high-2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) exposed groups (⩾3.5 pg per g fat) showed significantly higher Autism Spectrum Rating Scale (ASRS) scores for both boys and girls than the mild-TCDD exposed groups, without differences in neurodevelopmental scores. In contrast, the high total dioxin-exposed group, indicated by polychlorinated dibenzo-p-dioxins/furans (PCDDs/Fs)--the toxic equivalents (TEQ) levels⩾17.9 pg-TEQ per g fat, had significantly lower neurodevelopmental scores than the mild-exposed group in boys, but there was no difference in the ASRS scores. The present study demonstrates a specific impact of perinatal TCDD on autistic traits in childhood, which is different from the neurotoxicity of total dioxins (PCDDs/Fs).

Nitric oxide confers cisplatin resistance in human lung cancer cells through upregulation of aldo-keto reductase 1B10 and proteasome

In this study, we show that exposure of human lung cancer A549 cells to cisplatin (cis-diamminedichloroplatinum, CDDP) promotes production of nitric oxide (NO) through generation of reactive oxygen species (ROS) and resulting upregulation of inducible NO synthase (iNOS). The incubation of the cells with a NO donor, diethylenetriamine NONOate, not only reduced the CDDP-induced cell death and apoptotic alterations (induction of CCAAT-enhancer-binding protein homologous protein and caspase-3 activation), but also elevated proteolytic activity of 26S proteasome, suggesting that the activation of proteasome function contributes to the reduction of CDDP sensitivity by NO. Monitoring expression levels of six aldo-keto reductases (AKRs) (1A1, 1B1, 1B10, 1C1, 1C2, and 1C3) during the treatment with the NO donor and subsequent CDDP sensitivity test using the specific inhibitors also proposed that upregulation of AKR1B10 by NO is a key process for acquiring the CDDP resistance in A549 cells. Treatment with CDDP and NO increased amounts of nitrotyrosine protein adducts, indicative of peroxynitrite formation, and promoted the induction of AKR1B10, inferring a relationship between peroxynitrite formation and the enzyme upregulation in the cells. The treatment with CDDP or a ROS-related lipid aldehyde, 4-hydroxy-2-nonenal, facilitated the iNOS upregulation, which was restored by increasing the AKR1B10 expression. In contrast, the facilitation of NO production by CDDP treatment was hardly observed in AKR1B10-overexpressing A549 cells and established CDDP-resistant cancer cells (A549, LoVo, and PC3). Collectively, these results suggest the NO functions as a key regulator controlling AKR1B10 expression and 26S proteasome function leading to gain of the CDDP resistance.

Abstract 258: Pitx2 Promotes Murine Myocardial Regeneration after Myocardial Injury

Myocardial infarction is the leading cause of morbidity and mortality in the United States. Compromised myocardial function, due to the lack of self-renewal capacity in mature hearts, is a major reason for heart failure. Available therapies can only ameliorate, but not reverse the loss of functional myocardium. With heart transplantation as the only available cure, design of an effective regenerative therapy has become imperative for cardiovascular research. To repopulate the heart with de novo cardiomyocytes, most attempts have been based on the transplantation of cardiac, non-cardiac stem cells or their derivatives, however a more profound knowledge of stem cells is required for achieving significant progress. Meanwhile, triggering endogenous regenerative capacity is a compelling strategy for cardiac repair. It has been reported that proliferation of pre-existing cardiomyocytes strongly contributes to regeneration. Thus, efforts have been made to reintroduce mature cardiomyocytes into mitotic cycle. The mechanisms underlying the proliferation of cardiomyocytes during development and their homeostasis during adulthood are not fully understood, but likely require tight regulation of transcription factors in specific cell types. We have previously shown that the mouse Hippo kinase cascade is a major heart-size control pathway during development. In addition, activation of Yap, a transcriptional cofactor inhibited by Hippo, by genetically disrupting Hippo signaling is sufficient to induce juvenile and adult myocardial regeneration after surgery-induced myocardial infarction. Here we identified the paired-like homeodomain transcription factor 2 (pitx2) as a potential downstream target and cofactor of Yap in mouse heart. Our data indicates that Pitx2 expression is induced by myocardial injury, and is required for neonatal myocardial regeneration in a postnatal day 1 (P1) apex resection model. Further studies show that over-expression of pitx2 in adult cardiomyocytes is sufficient to promote the restoration of myocardial structure and function after myocardial infarction. Together, we show that pitx2 is a new manipulator of myocardial regeneration and could serve as a novel therapeutic target in cardiac regenerative therapy.

Abstract 170: Hippo Signaling Regulates Epicardial Derived Cell Fate through Controlling Mechanical Property

Epicardium is the outmost layer of heart and regulates heart development by contributing to the heart tissue and secreting signaling molecules. Epicardial-derived cells, EPDC, is a group of multi-potent cells mainly derive into cardiac fibroblasts and smooth muscle cells. Hippo signaling pathway controls organ growth through regulating cell proliferation. Yap, the effector of Hippo pathway has been shown to regulate mechanosensing and cell fate. However, the function of Hippo signaling in EPDC development has not been studied yet.

To study the role of Hippo signaling in development of epicardium and EPDC, we used epicardial specific line, Wt1 CreERT2 , to conditionally delete the components of the pathway, Lats1/2. Cre activity was induced at embryonic day (E)11.5 and Lats1/2 CKO hearts exhibited disorganized coronary vasculature. We used genetic lineage tracing approach to track EPDC and revealed increased endothelial cells deriving from EPDC, suggesting that EPDC changed cell fate. We observed that shape of the epicardial cells became rounded with decreased F-actin in Lats1/2 CKO, which suggested that cell tension was reduced. Since mechanical properties of cellular microenvironment are known to regulate cell shape and influence cell fate determination, we hypothesize that Hippo pathway regulates mechanical property to control cell fate in EPDC. Transcription analysis showed that signals regulating cytoskeleton organization were disrupted, which suggests Hippo regulates cytoskeleton gene expression and affects mechanical force that cell sensed autonomously. Proliferation assay using EdU incorporation showed increased proliferation in EPDC of Lats1/2 CKO was observed, which suggests the changes of external tension cell sensed. To recapitulate the changes of external tension, we plated EPDC onto different stiffness substrate. EPDC of Lats1/2 CKO differentiated into endothelial cells on the soft substrate. On the other hand, Lats1/2 CKO did not derive endothelial cells on the hard substrate and wild type EPDC did not differentiate into endothelial cells on neither soft nor hard substrate.

Taken together, our results suggested that Hippo pathway affected EPDC fate determination through controlling internal and external mechanical cues.

Noncontact quantitative biomechanical characterization of cardiac muscle using shear wave imaging optical coherence tomography

We report on a quantitative optical elastographic method based on shear wave imaging optical coherence tomography (SWI-OCT) for biomechanical characterization of cardiac muscle through noncontact elasticity measurement. The SWI-OCT system employs a focused air-puff device for localized loading of the cardiac muscle and utilizes phase-sensitive OCT to monitor the induced tissue deformation. Phase information from the optical interferometry is used to reconstruct 2-D depth-resolved shear wave propagation inside the muscle tissue. Cross-correlation of the displacement profiles at various spatial locations in the propagation direction is applied to measure the group velocity of the shear waves, based on which the Young's modulus of tissue is quantified. The quantitative feature and measurement accuracy of this method is demonstrated from the experiments on tissue-mimicking phantoms with the verification using uniaxial compression test. The experiments are performed on ex vivo cardiac muscle tissue from mice with normal and genetically altered myocardium. Our results indicate this optical elastographic technique is useful as a noncontact tool to assist the cardiac muscle studies.

Hippo signaling impedes adult heart regeneration

Heart failure due to cardiomyocyte loss after ischemic heart disease is the leading cause of death in the United States in large part because heart muscle regenerates poorly. The endogenous mechanisms preventing mammalian cardiomyocyte regeneration are poorly understood. Hippo signaling, an ancient organ size control pathway, is a kinase cascade that inhibits developing cardiomyocyte proliferation but it has not been studied postnatally or in fully mature adult cardiomyocytes. Here, we investigated Hippo signaling in adult cardiomyocyte renewal and regeneration. We found that unstressed Hippo-deficient adult mouse cardiomyocytes re-enter the cell cycle and undergo cytokinesis. Moreover, Hippo deficiency enhances cardiomyocyte regeneration with functional recovery after adult myocardial infarction as well as after postnatal day eight (P8) cardiac apex resection and P8 myocardial infarction. In damaged hearts, Hippo mutant cardiomyocytes also have elevated proliferation. Our findings reveal that Hippo signaling is an endogenous repressor of adult cardiomyocyte renewal and regeneration. Targeting the Hippo pathway in human disease might be beneficial for the treatment of heart disease.

Bmp signaling represses Vegfa to promote outflow tract cushion development

Congenital heart disease (CHD) is a devastating anomaly that affects ∼1% of live births. Defects of the outflow tract (OFT) make up a large percentage of human CHD. We investigated Bmp signaling in mouse OFT development by conditionally deleting both Bmp4 and Bmp7 in the second heart field (SHF). SHF Bmp4/7 deficiency resulted in defective epithelial to mesenchymal transition (EMT) and reduced cardiac neural crest ingress, with resultant persistent truncus arteriosus. Using a candidate gene approach, we found that Vegfa was upregulated in the Bmp4/7 mutant hearts. To determine if Vegfa is a downstream Bmp effector during EMT, we examined whether Vegfa is transcriptionally regulated by the Bmp receptor-regulated Smad. Our findings indicate that Smad directly binds to Vegfa chromatin and represses Vegfa transcriptional activity. We also found that Vegfa is a direct target for the miR-17-92 cluster, which is also regulated by Bmp signaling in the SHF. Deletion of miR-17-92 reveals similar phenotypes to Bmp4/7 SHF deletion. To directly address the function of Vegfa repression in Bmp-mediated EMT, we performed ex vivo explant cultures from Bmp4/7 and miR-17-92 mutant hearts. EMT was defective in explants from the Bmp4/7 double conditional knockout (dCKO; Mef2c-Cre;Bmp4/7(f/f)) and miR-17-92 null. By antagonizing Vegfa activity in explants, EMT was rescued in Bmp4/7 dCKO and miR-17-92 null culture. Moreover, overexpression of miR-17-92 partially suppressed the EMT defect in Bmp4/7 mutant embryos. Our study reveals that Vegfa levels in the OFT are tightly controlled by Smad- and microRNA-dependent pathways to modulate OFT development.

Sugar-sweetened beverage and diet soda consumption and the 7-year risk for type 2 diabetes mellitus in middle-aged Japanese men

PURPOSE

This cohort study investigated the association between sugar-sweetened beverage (SSB) and diet soda consumption and the incidence of type 2 diabetes in Japanese men.

METHODS

The participants were 2,037 employees of a factory in Japan. We measured consumption of SSB and diet soda using a self-administered diet history questionnaire. The incidence of diabetes was determined in annual medical examinations over a 7-year period. Hazard ratios (HRs) with 95 % confidence intervals (CIs) for diabetes were estimated after adjusting for age, body mass index, family history, and dietary and other lifestyle factors.

RESULTS

During the study, 170 participants developed diabetes. The crude incidence rates (/1,000 person-years) across participants who were rare/never SSB consumers, <1 serving/week, ≥ 1 serving/week and <1 serving/day, and ≥ 1 serving/day were 15.5, 12.7, 14.9, and 17.4, respectively. The multivariate-adjusted HR compared to rare/never SSB consumers was 1.35 (95 % CI 0.80-2.27) for participants who consumed ≥ 1 serving/day SSB. Diet soda consumption was significantly associated with the incident risk of diabetes (P for trend = 0.013), and multivariate-adjusted HRs compared to rare/never diet soda consumers were 1.05 (0.62-1.78) and 1.70 (1.13-2.55), respectively, for participants who consumed <1 serving/week and ≥ 1 serving/week.

CONCLUSIONS

Consumption of diet soda was significantly associated with an increased risk for diabetes in Japanese men. Diet soda is not always effective at preventing type 2 diabetes even though it is a zero-calorie drink.

Serum gamma-glutamyltransferase and the risk of hyperuricemia: a 6-year prospective study in Japanese men

We conducted a longitudinal study to investigate whether increased serum gamma-glutamyltransferase independently predicts subsequent development of hyperuricemia. The study participants included 3,310 Japanese men without hyperuricemia, aged 20-54 years. The participants had annual heath examinations for 6 years to assess incident hyperuricemia (defined as serum uric acid>416.4 μmol/l and/or taking medication for hyperuricemia). The risk of incident hyperuricemia was compared in participants grouped according to their baseline serum gamma-glutamyltransferase level. During follow-up, there were 529 incident cases of hyperuricemia. A positive, dose-response relationship was observed between serum gamma-glutamyltransferase and the risk of incident hyperuricemia. The hazard ratios (95% confidence intervals) for hyperuricemia, compared with a serum gamma-glutamyltransferase level ≤19 U/l, were 1.32 (1.05-1.67) for 20-39 U/l, 1.28 (0.90-1.83) for 40-59 U/l, 1.56 (0.98-2.47) for 60-79 U/l, and 1.57 (1.02-2.41) for ≥80 U/l after adjustment for baseline serum uric acid, creatinine, total cholesterol, and glycated hemoglobin levels, ln(serum alanine aminotransferase), age, systolic blood pressure, medications for hypertension, hypercholesterolemia, and diabetes, body mass index, and smoking and exercise habits. A similar positive relationship was observed regardless of the presence or absence of alcohol drinking, obesity, metabolic disorders (any combination of hypertension, hypercholesterolemia and/or diabetes), or clinically high serum aminotransferases, without evidence of a significant interaction between increased serum gamma-glutamyltransferase and risk factors for incident hyperuricemia. These findings indicate that increased serum gamma-glutamyltransferase is an independent predictor of subsequent development of hyperuricemia.

Alcohol intake and the risk of hyperuricaemia: a 6-year prospective study in Japanese men

BACKGROUND AND AIMS

Since there is little information derived from prospective studies on the amount of alcohol drinking required to induce hyperuricaemia, we attempted to address this issue in a Japanese population.

METHODS AND RESULTS

A total of 3310 Japanese men aged 20-54 years that were free of hyperuricaemia were classified according to their alcohol intake per week at baseline. Incident hyperuricaemia, defined as >7.0 mg/dl and/or taking medication for hyperuricaemia, was assessed through annual heath examinations for 6 years after the baseline examination. During follow-up, 529 incident cases of hyperuricaemia occurred. There was a positive, dose-response relationship between alcohol intake and the risk of incident hyperuricaemia. The hazard ratio (95% confidence interval) for hyperuricaemia in drinkers compared with non-drinkers was 1.10 (0.85-1.42) for <10.0 drinks/week, 1.40 (1.07-1.84) for 10.0-19.9 drinks/week, 1.64 (1.23-2.21) for 20.0-29.9 drinks/week and 1.98 (1.40-2.80) for ≥30.0 drinks/week (one drink contained 11.5 g of ethanol) after adjusting for age, baseline serum uric acid, body mass index, smoking habits, exercise habits, serum creatinine, blood pressure, serum cholesterol and blood glucose. The fraction of hyperuricaemia in the population attributable to alcohol intake was 21.6%. A clear dose-response pattern was observed for both beer and sake, when the consumption of these two beverages was analysed separately.

CONCLUSION

Habitual alcohol intake significantly contributed to the development of hyperuricaemia in Japanese men, regardless of type of alcoholic beverage consumed. Therefore, it is essential to reduce excessive alcohol intake to prevent and manage hyperuricaemia.

A new frequency-multiplied interferometer system in the GAMMA 10 tandem mirror

A new interferometer is installed on the west anchor cell of the GAMMA 10 tandem mirror. In GAMMA 10, we have used a heterodyne-type interferometer with a 70-GHz IMPATT oscillator and a 150-MHz oscillator for frequency modulation. The new interferometer consists of a 17.5-GHz phase locked dielectric resonator oscillator and a 37.5-MHz temperature-compensated crystal oscillator, as well as frequency multipliers. The main motivation for the new interferometer using frequency multipliers is to achieve a stable and cost effective interferometer. Direct anchor heating experiments with new anchor ion cyclotron range of frequency antennas in both the west and the east anchor cells are carried out. Density increases in both anchor cells are clearly observed using the new interferometer.

Expression level of Hand2 affects specification of enteric neurons and gastrointestinal function in mice

BACKGROUND & AIMS

Hand2 is a basic helix-loop-helix transcription factor required for terminal differentiation of enteric neurons. We studied Hand2 haploinsufficient mice, to determine whether reduced expression of Hand2 allows sufficient enteric neurogenesis for survival, but not for development of a normal enteric nervous system (ENS).

METHODS

Enteric transcripts that encode Hand2 and the neuron-specific embryonic lethal abnormal vision proteins HuB, HuC, and HuD were quantified. Immunocytochemistry was used to identify and quantify neurons. Apoptosis was analyzed with the terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling procedure. Intracellular microelectrodes were used to record inhibitory junction potentials. Gastrointestinal transit and colonic motility were measured in vivo.

RESULTS

Levels of of enteric Hand2 transcripts were associated with genotypes of mice, in the following order: Hand2(+/+) > Hand2(LoxP/+) > Hand2(+/-) > Hand2(LoxP/-). Parallel reductions were found in expression of HuD and in regional and phenotypic manners. Numbers of neurons, numbers of neuronal nitric oxide synthase(+) and calretinin(+), but not substance P(+) or vasoactive intestinal peptide(+) neurons, decreased. No effects were observed in stomach or cecum. Apoptosis was not detected, consistent with the concept that Hand2 inhibits neuronal differentiation, rather than regulates survival. The amplitude of inhibitory junction potentials in colonic circular muscle was similar in Hand2 wild-type and haploinsufficient mice, although in haploinsufficient mice, the purinergic component was reduced and a nitrergic component appeared. The abnormal ENS of haploinsufficient mice slowed gastrointestinal motility but protected mice against colitis.

CONCLUSIONS

Reduced expression of factors required for development of the ENS can cause defects in the ENS that are subtle enough to escape detection yet cause significant abnormalities in bowel function.

Hand2 loss-of-function in Hand1-expressing cells reveals distinct roles in epicardial and coronary vessel development

RATIONALE

The basic helix-loop-helix (bHLH) transcription factors Hand1 and Hand2 are essential for embryonic development. Given their requirement for cardiogenesis, it is imperative to determine their impact on cardiovascular function.

OBJECTIVE

To deduce the role of Hand2 within the epicardium.

METHOD AND RESULTS

We engineered a Hand1 allele expressing Cre recombinase. Cardiac Hand1 expression is largely limited to cells of the primary heart field, overlapping little with Hand2 expression. Hand1 is expressed within the septum transversum, and the Hand1 lineage marks the proepicardial organ and epicardium. To examine Hand factor functional overlap, we conditionally deleted Hand2 from Hand1-expressing cells. Hand2 mutants display defective epicardialization and fail to form coronary arteries, coincident with altered extracellular matrix deposition and Pdgfr expression.

CONCLUSIONS

These data demonstrate a hierarchal relationship whereby transient Hand1 septum transversum expression defines epicardial precursors that are subsequently dependent on Hand2 function.

A Tlx2-Cre mouse line uncovers essential roles for hand1 in extraembryonic and lateral mesoderm

Hand1 regulates development of numerous tissues within the embryo, extraembryonic mesoderm, and trophectoderm. Systemic loss of Hand1 results in early embryonic lethality but the cause has remained unknown. To determine if Hand1 expression in extraembryonic mesoderm is essential for embryonic survival, Hand1 was conditionally deleted using the HoxB6-Cre mouse line that expresses Cre in extraembryonic and lateral mesoderm. Deletion of Hand1 using HoxB6-Cre resulted in embryonic lethality identical to systemic knockout. To determine if lethality is due to Hand1 function in extraembryonic mesoderm or lateral mesoderm, we generated a Tlx2-Cre mouse line expressing Cre in lateral mesoderm but not extraembryonic tissues. Deletion of Hand1 using the Tlx2-Cre line results in embryonic survival with embryos exhibiting herniated gut and thin enteric smooth muscle. Our results show that Hand1 regulates development of lateral mesoderm derivatives and its loss in extraembryonic mesoderm is the primary cause of lethality in Hand1-null embryos.

Homeostasis model assessment of insulin resistance and the risk of cardiovascular events in middle-aged non-diabetic Japanese men

AIMS/HYPOTHESIS

Little is known about the relationship between the HOMA of insulin resistance (HOMA-IR) and the risk of cardiovascular events in Asian populations, which have lower levels of HOMA-IR than Western populations. Accordingly, we determined the predictive value of HOMA-IR for cardiovascular risk in a Japanese population that was apparently free of diabetes, addressing whether insulin resistance itself increases cardiovascular risk independently of other relevant metabolic disorders.

METHODS

We followed 2,548 non-diabetic men aged 35 to 59 years for 11 years. The hazard ratios for the incidence of cardiovascular events due to increased HOMA-IR were estimated using a Cox proportional hazards model that was adjusted for potential confounding factors.

RESULTS

The multivariate-adjusted hazard ratio for cardiovascular events compared with the first quartile of HOMA-IR (<or=0.66) was 1.07 (95% CI 0.44-2.64) for the second (HOMA-IR 0.67-1.01), 1.36 (0.56-3.28) for the third (HOMA-IR 1.02-1.51) and 2.50 (1.02-6.10) for the fourth quartile (HOMA-IR >or=1.52). The hazard ratio associated with a one SD (0.61) increment in log-transformed HOMA-IR was 1.51 (1.13-2.02). A similar positive relationship was observed for coronary events and stroke. In addition, the relationship between HOMA-IR and cardiovascular risk was broadly similar in participants with and without hypertension, dyslipidaemia (elevated triacylglycerol and/or reduced HDL-cholesterol), abdominal obesity and current smoking.

CONCLUSIONS/INTERPRETATION

Increased HOMA-IR predicted subsequent cardiovascular events in non-diabetic Japanese men. The association was independent of traditional cardiovascular risk factors and other relevant metabolic disorders.

Purification and Characterization of Exo-beta-d-Glucosaminidase from a Cellulolytic Fungus, Trichoderma reesei PC-3-7

Chitosan-degrading activities induced by glucosamine (GlcN) or N-acetylglucosamine (GlcNAc) were found in a culture filtrate of Trichoderma reesei PC-3-7. One of the chitosan-degrading enzymes was purified to homogeneity by precipitation with ammonium sulfate followed by anion-exchange and hydrophobic-interaction chromatographies. The enzyme was monomeric, and its molecular mass was 93 kDa. The optimum pH and temperature of the enzyme were 4.0 and 50 degrees C, respectively. The activity was stable in the pH range 6.0 to 9.0 and at a temperature below 50 degrees C. Reaction product analysis from the viscosimetric assay and thin-layer chromatography and H nuclear magnetic resonance spectroscopy clearly indicated that the enzyme was an exo-type chitosanase, exo-beta-d-glucosaminidase, that releases GlcN from the nonreducing end of the chitosan chain. H nuclear magnetic resonance spectroscopy also showed that the exo-beta-d-glucosaminidase produced a beta-form of GlcN, demonstrating that the enzyme is a retaining glycanase. Time-dependent liberation of the reducing sugar from partially acetylated chitosan with exo-beta-d-glucosaminidase and the partially purified exo-beta-d-N-acetylglucosaminidase from T. reesei PC-3-7 suggested that the exo-beta-d-glucosaminidase cleaves the glycosidic link of either GlcN-beta(1-->4)-GlcN or GlcN-beta(1-->4)-GlcNAc.