Donghyuk Shin

Relation between obesity and bone mineral density and vertebral fractures in Korean postmenopausal women.

Purpose The traditional belief that obesity is protective against osteoporosis has been questioned. Recent epidemiologic studies show that body fat itself may be a risk factor for osteoporosis and bone fractures. Accumulating evidence suggests that metabolic syndrome and the individual components of metabolic syndrome such as hypertension, increased triglycerides, and reduced high-density lipoprotein cholesterol are also risk factors for low bone mineral density. Using a cross sectional study design, we evaluated the associations between obesity or metabolic syndrome and bone mineral density (BMD) or vertebral fracture. Materials and Methods A total of 907 postmenopausal healthy female subjects, aged 60-79 years, were recruited from woman hospitals in Seoul, South Korea. BMD, vetebral fracture, bone markers, and body composition including body weight, body mass index (BMI), percentage body fat, and waist circumference were measured. Results After adjusting for age, smoking status, alcohol consumption, total calcium intake, and total energy intake, waist circumference was negatively related to BMD of all sites (lumbar BMD p = 0.037, all sites of femur BMD p < 0.001) whereas body weight was still positively related to BMD of all sites (p < 0.001). Percentage body fat and waist circumference were much higher in the fracture group than the non-fracture group (p = 0.0383, 0.082 respectively). Serum glucose levels were postively correlated to lumbar BMD (p = 0.016), femoral neck BMD (p = 0.0335), and femoral trochanter BMD (p = 0.0082). Serum high density lipoprotein cholesterol (HDLC) was positively related to femoral trochanter BMD (p = 0.0366) and was lower in the control group than the fracture group (p = 0.011). Conclusion In contrast to the effect favorable body weight on bone mineral density, high percentage body fat and waist circumference are related to low BMD and a vertebral fracture. Some components of metabolic syndrome were related to BMD and a vertebral fracture.

Increasing Incidence of Inflammatory Bowel Disease Among Young Men in Korea Between 2003 and 2008

Background and AimsTemporal trends in incidence rates of Crohn’s disease (CD) and ulcerative colitis (UC) can provide valuable clues about etiology. Korea has a draft system, and every male must fulfill his military service. However, according to military rules, patients with CD and UC are not conscripted into the army, and when the disease is diagnosed during military service, patients are relieved from military duties. Such policies provide a unique opportunity to determine the incidence of CD and UC among young men in Korea. We studied the incidence of CD and UC over time in Korea, a rapidly developing country.MethodsThe Armed Forces Medical Command of the Republic of Korea Army provided lists of members who were relieved from military duties due to diagnoses of CD and UC between 2003 and 2008.ResultsDuring this 6-year period, there were 96 incident cases of CD and 104 incident cases of UC. For the 6-year period, the adjusted mean annual incidence rates of CD and UC per 100,000 persons were 3.2 and 3.5, respectively. When analyzed by 2-year intervals, the mean annual incidence of CD and UC increased, from 1.8 and 1.7 per 100,000 persons in 2003–2004, to 2.7 and 3.3 per 100,000 persons in 2005–2006, and to 5.1 and 5.4 per 100,000 persons in 2007–2008, respectively.ConclusionsIncidence of CD and UC among young men is rapidly increasing in Korea, which strongly suggests an environmental contribution to the disease.

Differential Physiological Roles of ESCRT Complexes in Caenorhabditis elegans

Endosomal sorting complex required for transport (ESCRT) complexes are involved in endosomal trafficking to the lysosome, cytokinesis, and viral budding. Extensive genetic, biochemical, and structural studies on the ESCRT system have been carried out in yeast and mammalian systems. However, the question of how the ESCRT system functions at the whole organism level has not been fully explored. In C. elegans, we performed RNAi experiments to knock-down gene expression of components of the ESCRT system and profiled their effects on protein degradation and endocytosis of YP170, a yolk protein. Targeted RNAi knock-down of ESCRT-I (tsg-101 and vps-28) and ESCRT-III (vps-24, and vps-32.2) components interfered with protein degradation while knock-down of ESCRT-II (vps-25 and vps-36) and ESCRT-III (vps-20 and vps-24) components hampered endocytosis. In contrast, the knockdown of vps-37, another ESCRT-I component, showed no defect in either YP170 uptake or degradation. Depletion of at least one component from each complex — ESCRT-0 (hgrs-1), ESCRT-I (tsg-101, vps-28, and vps-37), ESCRT-II (vps-36), ESCRT-III (vps-24), and Vps4 (vps-4) — resulted in abnormal distribution of embryos in the uterus of worms, possibly due to abnormal ovulation, fertilization, and egglaying. These results suggest differential physiological roles of ESCRT-0, -I, -II, and -III complexes in the context of the whole organism, C. elegans.

Distinct Z-DNA binding mode of a PKR-like protein kinase containing a Z-DNA binding domain (PKZ)

Double-stranded ribonucleic acid-activated protein kinase (PKR) downregulates translation as a defense mechanism against viral infection. In fish species, PKZ, a PKR-like protein kinase containing left-handed deoxyribonucleic acid (Z-DNA) binding domains, performs a similar role in the antiviral response. To understand the role of PKZ in Z-DNA recognition and innate immune response, we performed structural and functional studies of the Z-DNA binding domain (Zα) of PKZ from Carassius auratus (caZαPKZ). The 1.7-Å resolution crystal structure of caZαPKZ:Z-DNA revealed that caZαPKZ shares the overall fold with other Zα, but has discrete structural features that differentiate its DNA binding mode from others. Functional analyses of caZαPKZ and its mutants revealed that caZαPKZ mediates the fastest B-to-Z transition of DNA among Zα, and the minimal interaction for Z-DNA recognition is mediated by three backbone phosphates and six residues of caZαPKZ. Structure-based mutagenesis and B-to-Z transition assays confirmed that Lys56 located in the β-wing contributes to its fast B-to-Z transition kinetics. Investigation of the DNA binding kinetics of caZαPKZ further revealed that the B-to-Z transition rate is positively correlated with the association rate constant. Taking these results together, we conclude that the positive charge in the β-wing largely affects fast B-to-Z transition activity by enhancing the DNA binding rate.

Polyubiquitin recognition by AtSAP5, an A20-type zinc finger containing protein from Arabidopsis thaliana

Stress associated proteins (SAPs) in plants contain A20-type zinc finger (A20_ZF) domains and are involved with abiotic stress response. A20-type zinc finger domains in animals reportedly recognize ubiquitin as a regulatory signal in cell. However, it remains unclear whether A20_ZF domains in plants perform similar roles. AtSAP5, a SAP from Arabidopsis thaliana, exhibits a unique sequence feature among 10 AtSAPs harboring A20_ZF domains. The highly conserved diaromatic patch is replaced by the dialipathic patch. Here we investigated whether AtSAP5 recognizes ubiquitin and the roles of the dialipathic patch in ubiquitin binding in vitro. GST pulldown assay reveals that AtSAP5 binds polyubiquitin rather than monoubiquitin. AtSAP5 shows preferences for linear and K63-linked polyubiquitin chains to K48-linked one. The A20_ZF domain of AtSAP5 is sufficient for linkage-specific polyubiquitin recognition. The dialipathic patch in AtSAP5 plays an important role in K48-linked polyubiquitin recognition. Taken together, our results suggest that AtSAP5 participates in polyubiquitin recognition in plants and that the dialipathic patch in AtSAP5 is critical in binding K48-linked polyubiquitn chains.

The speed of eating and functional dyspepsia in young women.

BACKGROUND/AIMS Little information is available on whether the speed of eating differs between individuals with and without dyspepsia, mainly because controlled studies are usually not feasible. METHODS A survey was applied to 89 individuals with relatively controlled eating patterns, using questionnaires that assessed eating time and functional dyspepsia (FD) based on the Rome III criteria. RESULTS The prevalence of FD was 12% (11 of 89 participants), and 7% (6 of 89) were diagnosed with gastroesophageal reflux disease (GERD). The proportion of individuals reporting that they ate their meals rapidly was higher for those with FD than for those without FD or GERD (control) (46% vs 17%, p=0.043), as was the reported eating speed (7.1+/-1.5 vs 5.8+/-2.0 [mean+/-SD], p=0.045; visual analog scale on which a higher score indicated faster eating). However, the measured eating time did not differ significantly between FD and controls (11.0+/-2.8 vs 12.8+/-3.3 minutes, p=0.098). The proportion of individuals who ate their meals within 13 minutes was significantly higher for those with FD than for controls (91% vs 51%, p=0.020). CONCLUSIONS The results of this study suggest that eating speed affects dyspepsia. Further studies are warranted.

Differential contribution of the mitochondrial translation pathway to the survival of diffuse large B-cell lymphoma subsets.

Diffuse large B-cell lymphomas (DLBCLs) are a highly heterogeneous group of tumors in which subsets share molecular features revealed by gene expression profiles and metabolic fingerprints. While B-cell receptor (BCR)-dependent DLBCLs are glycolytic, OxPhos-DLBCLs rely on mitochondrial energy transduction and nutrient utilization pathways that provide pro-survival benefits independent of BCR signaling. Integral to these metabolic distinctions is elevated mitochondrial electron transport chain (ETC) activity in OxPhos-DLBCLs compared with BCR-DLBCLs, which is linked to greater protein abundance of ETC components. To gain insights into molecular determinants of the selective increase in ETC activity and dependence on mitochondrial energy metabolism in OxPhos-DLBCLs, we examined the mitochondrial translation pathway in charge of the synthesis of mitochondrial DNA encoded ETC subunits. Quantitative mass spectrometry identified increased expression of mitochondrial translation factors in OxPhos-DLBCL as compared with the BCR subtype. Biochemical and functional assays indicate that the mitochondrial translation pathway is required for increased ETC activity and mitochondrial energy reserves in OxPhos-DLBCL. Importantly, molecular depletion of several mitochondrial translation proteins using RNA interference or pharmacological perturbation of the mitochondrial translation pathway with the FDA-approved inhibitor tigecycline (Tigecyl) is selectively toxic to OxPhos-DLBCL cell lines and primary tumors. These findings provide additional molecular insights into the metabolic characteristics of OxPhos-DLBCLs, and mark the mitochondrial translation pathway as a potential therapeutic target in these tumors.

Tracheal intubation during chest compressions performed by qualified emergency physicians unfamiliar with the Pentax-airwayscope

Objective Experienced emergency physicians were recruited and a randomized crossover trial was conducted to compare the performance of the Pentax-Airwayscope (AWS) video-laryngoscope with the Macintosh laryngoscope (McL) for tracheal intubation during continuous chest compressions under three different scenarios: (1) normal airway, (2) limited neck mobility, and (3) tongue edema. Methods Thirty-six experienced emergency physicians performed intubations on a manikin in each of three scenarios. The sequences of scenarios and intubating devices were randomized. Time to complete intubation (primary end point), time to visualization of the vocal cords, the overall success rate, percentage of glottic opening, dental compression, and ease of intubation were determined. Results The times (median [interquartile range]) to complete tracheal intubation were significantly shorter with the AWS than the McL in all three scenarios (11.6 [8.0-14.7] vs. 15.1 [12.8-17.9] s, 13.5 [10.5-20.9] vs. 17.0 [14.1-19.9] s, and 13.6 [11.1-20.9] vs. 15.1 [18.6-37.5] s, respectively). The overall success rates were higher with the AWS than the McL in the difficult intubation scenario (77.8 vs. 100%). The AWS was also more effective than the McL with respect to the percentage of glottic opening, dental compression, and ease of intubation in all three scenarios. Conclusion Although participants were experienced emergency physicians familiar with the McL and unfamiliar with the AWS, the AWS proved to be a better tool than the McL to perform tracheal intubation during continuous chest compressions on a manikin. The AWS should be considered as an initial intubating tool to perform tracheal intubation during continuous chest compressions rather than the McL.

A20 promotes metastasis of aggressive basal-like breast cancers through multi-monoubiquitylation of Snail1

Although the ubiquitin-editing enzyme A20 is a key player in inflammation and autoimmunity, its role in cancer metastasis remains unknown. Here we show that A20 monoubiquitylates Snail1 at three lysine residues and thereby promotes metastasis of aggressive basal-like breast cancers. A20 is significantly upregulated in human basal-like breast cancers and its expression level is inversely correlated with metastasis-free patient survival. A20 facilitates TGF-β1-induced epithelial–mesenchymal transition (EMT) of breast cancer cells through multi-monoubiquitylation of Snail1. Monoubiquitylated Snail1 has reduced affinity for glycogen synthase kinase 3β (GSK3β), and is thus stabilized in the nucleus through decreased phosphorylation. Knockdown of A20 or overexpression of Snail1 with mutation of the monoubiquitylated lysine residues into arginine abolishes lung metastasis in mouse xenograft and orthotopic breast cancer models, indicating that A20 and monoubiquitylated Snail1 are required for metastasis. Our findings uncover an essential role of the A20–Snail1 axis in TGF-β1-induced EMT and metastasis of basal-like breast cancers.

New conformations of linear polyubiquitin chains from crystallographic and solution-scattering studies expand the conformational space of polyubiquitin.

The conformational flexibility of linkage-specific polyubiquitin chains enables ubiquitylated proteins and their receptors to be involved in a variety of cellular processes. Linear or Met1-linked polyubiquitin chains, associated with nondegradational cellular signalling pathways, have been known to adopt multiple conformations from compact to extended conformations. However, the extent of such conformational flexibility remains open. Here, the crystal structure of linear Ub2 was determined in a more compact conformation than that of the previously known structure (PDB entry 3axc). The two structures differ significantly from each other, as shown by an r.m.s.d. between C(α) atoms of 3.1 Å. The compactness of the linear Ub2 structure in comparison with PDB entry 3axc is supported by smaller values of the radius of gyration (Rg; 18 versus 18.9 Å) and the maximum interatomic distance (Dmax; 55.5 versus 57.8 Å). Extra intramolecular hydrogen bonds formed among polar residues between the distal and proximal ubiquitin moieties seem to contribute to stabilization of the compact conformation of linear Ub2. An ensemble of three semi-extended and extended conformations of linear Ub2 was also observed by small-angle X-ray scattering (SAXS) analysis in solution. In addition, the conformational heterogeneity in linear polyubiquitin chains is clearly manifested by SAXS analyses of linear Ub3 and Ub4: at least three distinct solution conformations are observed in each chain, with the linear Ub3 conformations being compact. The results expand the extent of conformational space of linear polyubiquitin chains and suggest that changes in the conformational ensemble may be pivotal in mediating multiple signalling pathways.