Hyewon Chung

Ewha Womans University, Seoul, Seoul, South Korea

Are you Hyewon Chung?

Claim your profile

Publications (33)77.04 Total impact

  • Article: Is insulin resistance an intrinsic defect in asian polycystic ovary syndrome?
    [show abstract] [hide abstract]
    ABSTRACT: Purpose: Approximately 50% to 70% of women with polycystic ovary syndrome (PCOS) have some degree of insulin resistance, and obesity is known to worsen insulin resistance. Many metabolic consequences of PCOS are similar to those of obesity; therefore, defining the cause of insulin resistance in women can be difficult. Our objective was to clarify the factors contributing to insulin resistance in PCOS. Materials and Methods: We consecutively recruited 144 women with PCOS [age: 26±5 yr, body mass index, body mass index (BMI): 24.4±4.0 kg/m(2)] and 145 controls (age: 25±5 yr, BMI: 23.0±3.6 kg/m(2)), and divided them into overweight/obese (ow/ob, BMI ≥23 kg/m(2)) and lean (BMI <23 kg/m(2)) groups. Anthropometric measures and a 75-g oral glucose tolerance test were performed, and insulin sensitivity index (ISI) was calculated as an index of insulin sensitivity. Factors predictive of ISI were determined using regression analysis. Results: ISI was significantly lower in both lean and ow/ob women with PCOS compared to BMI-matched controls (p<0.05). Increasing BMI by 1 kg/m(2) decreased ISI by 0.169 in PCOS patients (p<0.05) and by 0.238 in controls (p<0.05); there was no significant difference between these groups. In lean PCOS patients and lean controls, BMI had no effect on ISI. Multiple regression analysis revealed that PCOS status (β=-0.423, p<0.001) and BMI (β=-0.375, p<0.001) were significantly associated with ISI. Conclusion: Insulin resistance is an intrinsic defect of PCOS, and a high BMI could exacerbate insulin resistance in all women, irrespective of whether they have PCOS.
    Yonsei medical journal 05/2013; 54(3):609-14. · 0.77 Impact Factor
  • Article: CORRELATION OF FOVEAL MICROSTRUCTURAL CHANGES WITH VISION AFTER ANTI-VASCULAR ENDOTHELIAL GROWTH FACTOR THERAPY IN AGE-RELATED MACULAR DEGENERATION.
    Hyun Jin Shin, Hyewon Chung, Hyung Chan Kim
    [show abstract] [hide abstract]
    ABSTRACT: PURPOSE:: To investigate the correlation of foveal microstructural changes with vision after intravitreal ranibizumab injection in eye with choroidal neovascularization (CNV) secondary to age-related macular degeneration. METHODS:: We retrospectively studied 40 eyes of 40 patients with neovascular age-related macular degeneration who had no previous treatment history of age-related macular degeneration. All patients were treated with 3 monthly intravitreal ranibizumab (0.5 mg/0.05 mL) injections. One month after the third consecutive injection, best-corrected visual acuity (BCVA) was evaluated and the eyes were categorized into 2 groups according to the change in BCVA (good function group: BCVA improvement ≥ logarithm of minimum angle of resolution 0.3; poor function group: BCVA improvement < logarithm of minimum angle of resolution 0.3). Changes of foveal photoreceptor layer integrity, CNV size (diameter and thickness), central macular thickness, center point thickness, outer nuclear layer thickness, and subretinal fluid in each group were also evaluated using spectral-domain optical coherence tomography. RESULTS:: The good function group is 20 eyes, and the poor function group is 20 eyes. No significant differences in baseline characteristics of variables including CNV type, initial BCVA, photoreceptor integrity, and CNV size were observed between the two groups. Best-corrected visual acuity in the good function group was 0.30 ± 0.17 (logarithm of minimum angle of resolution) and that in the poor function group was 0.48 ± 0.40 (logarithm of minimum angle of resolution). Decreased disrupted length of photoreceptor layer (1,020.80 ± 974.60) and decreased CNV thickness (78.86 ± 50.78) were found in the good function group at the end of follow-up. However, no significant differences in changes of CNV diameter, central macular thickness, center point thickness, outer nuclear layer thickness, and resolution of subretinal fluid were observed between the two groups. CONCLUSION:: Restoration of foveal photoreceptor integrity and decreased CNV thickness are closely associated with visual improvement in neovascular age-related macular degeneration after treatment.
    Retina (Philadelphia, Pa.) 01/2013; · 2.93 Impact Factor
  • Article: Morphologic changes in acute central serous chorioretinopathy using spectral domain optical coherence tomography.
    Hyung Chan Kim, Won Bin Cho, Hyewon Chung
    [show abstract] [hide abstract]
    ABSTRACT: To investigate morphologic changes of acute central serous chorioretinopathy (CSC) using spectral domain optical coherence tomography (SD-OCT) and confocal scanning laser ophthalmoscopy. This retrospective study included 63 eyes of 63 patients with unilateral acute CSC. All patients underwent simultaneous SD-OCT and fluorescein angiography examination using Spectralis HRA+OCT. The external limiting membrane could be seen on SD-OCT, although the junction between photoreceptor inner and outer segments (IS/OS) was not detected in all eyes with retinal detachment (RD). However, IS/OS became visible after resolution of serous RD in 51 eyes (81.0%). SD-OCT images at the leakage sites showed a bump of retinal pigment epithelium (RPE) in in 47 cases (68.1%) and pigment epithelial detachment (PED) in 22 of 69 leakage sites (31.9%). In 14 of 69 leakage sites (20.3%), highly reflective areas suggesting fibrinous exudate were observed in the subretinal space. In nine leakage sites (13.0%), sagging or dipping of the posterior retinal layer was seen. Abnormal RPE changes such as RPE bump and PED were observed in 12 of 22 fellow eyes (54.5%). A variety of morphologic changes could be identified on SD-OCT, and those findings may contribute more information to our understanding of the pathophysiology of CSC.
    Korean Journal of Ophthalmology 10/2012; 26(5):347-54.
  • Article: Evaluation of changes in choroidal neovascularization secondary to age-related macular degeneration after anti-VEGF therapy using spectral domain optical coherence tomography.
    Ja Young You, Hyewon Chung, Hyung Chan Kim
    [show abstract] [hide abstract]
    ABSTRACT: To evaluate the changes in choroidal neovascularization (CNV) after anti-VEGF therapy for treatment of age-related macular degeneration (AMD) using spectral domain optical coherence tomography (SD OCT). This retrospective study included 65 eyes of 65 patients with CNV secondary to AMD. All patients underwent SD OCT before and 4 weeks after three intravitreal injections of bevacizumab (bevacizumab group) or ranibizumab (ranibizumab group). The diameter and thickness of CNV were measured from SD OCT images. Retinal edema was completely resolved in 57%, partially resolved in 28% and unchanged in 15% of all post-injection SD OCTs. The resolution rate of retinal edema was not significantly different between the bevacizumab and ranibizumab group (p = 0.960). In all CNV types, the diameter of CNV did not show significant change after treatment; the average diameter changed from 2923 to 2888 μm in classic CNV and from 2378 to 2338 μm in occult CNV in bevacizumab group; from 2691 to 2580 μm in classic CNV and from 2731 to 2337 μm in occult CNV in ranibizumab group. However, the thickness of CNV showed a significant reduction in classic CNV of both the bevacizumab group (from 301 to 233 μm, p = 0.012, reduction rate 22%) and the ranibizumab group (from 258 to 213 μm, p = 0.025, reduction rate 17%). In occult CNV, the thickness of CNV showed a significant reduction only in the ranibizumab group (from 163 to 146 μm, p = 0.033, reduction rate 10%). Anti-VEGF therapy for the treatment of AMD may reduce the thickness of CNV and thus result in morphologic stability of CNV. Although morphologic regression of CNV is not achieved, further CNV growth could be arrested with anti-VEGF therapy.
    Current eye research 05/2012; 37(5):438-45. · 1.51 Impact Factor
  • Article: Correlation of fundus autofluorescence with spectral-domain optical coherence tomography and vision in diabetic macular edema.
    [show abstract] [hide abstract]
    ABSTRACT: To investigate the correlation between fundus autofluorescence (FAF) and the results of spectral-domain optical coherence tomography (SD-OCT) as well as visual acuity (VA) in patients with diabetic macular edema (DME) and to determine the visual prognostic factors. Retrospective, interventional case series. Sixty-one patients with DME who underwent intravitreal injection of bevacizumab (IVB) as their first treatment. An assessment of VA and FAF and SD-OCT images were obtained before and after IVB (pre- and post-IVB). Foveal FAF was graded on a scale of 1 to 4. The presence or absence of FAF at the foveola was also determined. The association of FAF with VA and the SD-OCT results, including central macular thickness (CMT), outer nuclear layer thickness, the integrity of the external limiting membrane (ELM), and the integrity of the junction between the inner and outer segment of the photoreceptor (IS/OS). Better VA, preservation of the ELM, and IS/OS pre-IVB were associated with better VA post-IVB. Of the types of DME, cystoid macular edema significantly correlated with increased FAF at the foveola. A higher level of FAF was 5.6 times more likely to occur in DME with a defect in IS/OS and 10 times more likely to occur with each 10-μm increase in CMT. Each increase by a factor of 0.1 in the logarithm of the minimum angle of resolution (logMAR) pre-IVB increased the probability of high FAF by a factor of 1.73. Despite severe DME, fewer eyes with a low level of FAF exhibited an IS/OS defect and large logMAR VA than eyes with a high level of FAF with severe DME pre-IVB. The average grade of FAF pre-IVB was higher in patients with decreased vision during follow-up than in patients with increased or unchanged good vision. The strong association of FAF with SD-OCT parameters and VA in patients with DME could aid in the prediction of the restoration of photoreceptor integrity and subsequent visual recovery, especially in patients with severe DME, in whom photoreceptor integrity before treatment could not be adequately evaluated, even with SD-OCT.
    Ophthalmology 02/2012; 119(5):1056-65. · 5.45 Impact Factor
  • Article: Intravitreal bevacizumab alone versus in combination with photodynamic therapy for the treatment of neovascular maculopathy in patients aged 50 years or older: 1-year results of a prospective clinical study.
    [show abstract] [hide abstract]
    ABSTRACT: To compare the outcomes of treatment with intravitreal bevacizumab alone (BEVA group) or in combination with photodynamic therapy (PDT) (COMB group), in patients aged at least 50 years with neovascular maculopathy. Forty-one patients with neovascular age-related macular degeneration (AMD) (n = 31) or polypoidal choroidal vasculopathy (PCV) (n = 10) were randomized to either the BEVA group (n = 18) or the COMB group (n = 23). A total of three intravitreal bevacizumab injections (1.25 mg/0.05 ml) were given at 6-week intervals. In the COMB group, PDT was included near the time of one injection. Patients underwent best-corrected visual acuity (BCVA) measurement and optical coherence tomography (OCT) at every visit. Fluorescein angiography and indocyanine green angiography were repeated every 3 months. Overall BCVA (p = 0.001) and central foveal thickness (CFT) (p < 0.001) measured by OCT improved significantly at 12 months, and there was no between-group difference in BCVA or CFT between the BEVA and COMB groups. Whereas AMD patients showed significant improvement in BCVA (p = 0.001) and CFT (p = 0.004), PCV patients failed to improve. The effect of bevacizumab alone on neovascular AMD was similar to that of combination therapy, when measured by both BCVA and CFT. The total number of bevacizumab injections was not reduced when PDT was given, either among all patients or in a subgroup of naïve patients (p > 0.05). No serious complication was noted. The results of our 12-month prospective study indicate that intravitreal bevacizumab alone has similar efficacy and safety to bevacizumab plus PDT for treatment of patients with neovascular AMD, even treatment-naïve patients. The addition of PDT did not assist in reducing the required total number of bevacizumab injections.
    Acta ophthalmologica 02/2012; 90(1):61-7. · 2.44 Impact Factor
  • Article: Association between photoreceptor integrity and visual outcome in diabetic macular edema.
    [show abstract] [hide abstract]
    ABSTRACT: To investigate the correlation between foveal photoreceptor integrity and final visual acuity (VA) after treatment of eyes with diabetic macular edema (DME), and to determine the visual prognostic factors. We retrospectively studied 61 eyes of 52 patients with DME who were treated successfully with intravitreal triamcinolone injection (IVTA). Using spectral domain optical coherence tomography (SD-OCT), the eyes were categorized into three groups at the final visit according to restoration of the photoreceptor inner and outer segment junction (IS/OS) and the external limiting membrane (ELM): (1) the A group, with a completely visible IS/OS and ELM, (2) the B group, with a disrupted IS/OS and intact ELM, and (3) the C group, with a disrupted or loss of the IS/OS and ELM. Disrupted IS/OS length (DIL), disrupted ELM length (DEL), and mean disrupted IS/OS and ELM length (DIEL) were measured at the initial and final visits. Foveal thickness (FT), macular center thickness (MCT), and outer nuclear layer (ONL) thickness were also measured at the initial and final visits. Multivariate analysis testing was performed over the measured SD OCT variables. Final VA was closely associated with IS/OS integrity at the final visit; final VA (logMAR) in the A group (0.21 ± 0.14; 31 eyes) or B group (0.31 ± 0.21; 15 eyes) was significantly better than that in the C group (0.45 ± 0.33; 15 eyes) (p < 0.001). Shorter DIL, DEL, and DIEL at the final visit were associated with better final VA. Multivariate analysis showed that DIEL (r = 0.564) have the greatest correlation coefficient with final VA compared to DIL (r = 0.561) and DEL (r = 0.540). Better VA, preservation of the IS/OS and ELM at the initial visit were associated with intact photoreceptor integrity after resolution of DME. However, MCT, FT, and ONL thickness had no significant correlation with photoreceptor integrity. IS/OS and ELM are useful hallmarks for use in evaluation of foveal photoreceptor layer integrity, and are closely associated with final VA in DME. Pretreatment VA and photoreceptor status can predict potential restoration of photoreceptor integrity and subsequent visual recovery in DME.
    Albrecht von Graæes Archiv für Ophthalmologie 08/2011; 250(1):61-70. · 2.17 Impact Factor
  • Source
    Article: Association between foveal microstructure and visual outcome in age-related macular degeneration.
    Hyun Jin Shin, Hyewon Chung, Hyung Chan Kim
    [show abstract] [hide abstract]
    ABSTRACT: To investigate the correlation between foveal photoreceptor integrity and final visual acuity after treatment of eyes with neovascular age-related macular degeneration, and to determine the visual prognostic factors. We retrospectively studied 40 eyes of 40 patients with neovascular age-related macular degeneration who were treated successfully with intravitreal anti-vascular endothelial growth factor injection. Using spectral-domain optical coherence tomography, the eyes were categorized into three groups at the final visit, the V group with a completely visible photoreceptor inner and outer segment junction (IS/OS), the P group with a partially detected IS/OS, and the I group with an invisible IS/OS. The length of disrupted IS/OS and external limiting membrane, central macular thickness, and choroidal neovascularization size at the initial and final visits were measured. Retinal pigment epithelium regularity and outer nuclear layer thickness at the final visit were also evaluated. Final visual acuity was closely associated with IS/OS integrity at the final visit. Final visual acuity (logarithm of minimum angle of resolution) in the V group (0.13 ± 0.10) was better than that in the P group (0.41 ± 0.31), and final visual acuity in the P group was better than that in the I group (0.97 ± 0.51) (P < 0.001). Shorter disrupted IS/OS and external limiting membrane length at the final visit were closely associated with better final visual acuity. Preservation of the IS/OS and external limiting membrane, thinner central macular thickness, and shorter choroidal neovascularization height before treatment were associated with intact photoreceptor integrity after resolution of exudation. However, central macular thickness, outer nuclear layer thickness, and retinal pigment epithelium regularity at the final visit had no significant correlation with photoreceptor integrity. Foveal photoreceptor integrity was closely associated with final visual acuity in neovascular age-related macular degeneration after treatment. Initial visual acuity, IS/OS and external limiting membrane integrity, central macular thickness, and choroidal neovascularization height were correlated with final photoreceptor integrity, and they would be visual prognostic factors after resolution of exudation.
    Retina (Philadelphia, Pa.) 05/2011; 31(8):1627-36. · 2.93 Impact Factor
  • Article: Association between integrity of foveal photoreceptor layer and visual outcome in retinal vein occlusion.
    Hyun Jin Shin, Hyewon Chung, Hyung Chan Kim
    [show abstract] [hide abstract]
    ABSTRACT: To investigate the correlation between integrity of foveal photoreceptor layer and initial as well as final visual acuity (VA) after successful resolution of macular oedema (ME) associated with retinal vein occlusion (RVO). We retrospectively studied 31 eyes of 31 patients with resolved ME secondary to RVO. The integrity of foveal photoreceptor layer was studied using the junction between photoreceptor inner and outer segment (IS/OS) on spectral domain optical coherence tomography (SD OCT). The study eyes were categorized into three groups at final visit; V group with completely visible IS/OS, P group with partially detected IS/OS and I group with invisible IS/OS. Disrupted length of IS/OS and external limiting membrane (ELM) were measured. Final VA (logMAR) was closely associated with the IS/OS integrity at final visit; final VA in V group (0.03 ± 0.05) was better than that in P group (0.21 ± 0.23) (p = 0.027) and final VA in P group was better than that in I group (0.70 ± 0.36) (p = 0.004). Better initial VA (logMAR) and shorter length of disrupted IS/OS at initial visit were closely associated with better final VA (logMAR). In addition, final VA (logMAR) was closely associated with the length of disrupted IS/OS and ELM at final visit.   After resolution of ME associated with RVO, the final VA is associated with the integrity of foveal photoreceptor layer. Better VA and the smaller length of disrupted IS/OS on SD OCT at initial visit are indicators of better visual outcome in patients with RVO.
    Acta ophthalmologica 02/2011; 89(1):e35-40. · 2.44 Impact Factor
  • Article: Light-induced phosphorylation of crystallins in the retinal pigment epithelium.
    [show abstract] [hide abstract]
    ABSTRACT: Protein phosphorylations have essential regulatory roles in visual signaling. Previously, we found that phosphorylation of several proteins in the retina and retinal pigment epithelium (RPE) is involved in anti-apoptotic signaling under oxidative stress conditions, including light exposure. In this study, we used a phosphoprotein enrichment strategy to evaluate the light-induced phosphoproteome of primary bovine RPE cells. Phosphoprotein-enriched extracts from bovine RPE cells exposed to light or dark conditions for 1h were separated by 2D SDS-PAGE. Serine and tyrosine phosphorylations were visualized by 2D phospho Western blotting and specific phosphorylation sites were analyzed by tandem mass spectrometry. Light induced a marked increase in tyrosine phosphorylation of beta crystallin A3 and A4. The most abundant light-induced up-regulated phosphoproteins were crystallins of 15-25 kDa, including beta crystallin S and zeta crystallin. Phosphorylation of beta crystallin suggests an anti-apoptotic chaperone function of crystallins in the RPE. Other chaperones, cytoskeletal proteins, and proteins involved in energy balance were expressed at higher levels in the dark. A detailed analysis of RPE phosphoproteins provides a molecular basis for understanding of light-induced signal transduction and anti-apoptosis mechanisms. Our data indicates that phosphorylation of crystallins likely represents an important mechanism for RPE shielding from physiological and pathophysiological light-induced oxidative injury.
    International journal of biological macromolecules 01/2011; 48(1):194-201. · 2.37 Impact Factor
  • Source
    Article: Prohibitin as an oxidative stress biomarker in the eye.
    [show abstract] [hide abstract]
    ABSTRACT: Identification of biomarker proteins in the retina and retinal pigment epithelium (RPE) under oxidative stress may imply new insights into signaling mechanisms of retinal degeneration at the molecular level. Proteomic data from an in vivo mice model in constant light and an in vitro oxidative stress model are compared to controls under normal conditions. Our proteomic study shows that prohibitin is involved in oxidative stress signaling in the retina and RPE. The identity of prohibitin in the retina and RPE was studied using 2D electrophoresis, immunohistochemistry, western blot, and mass spectrometry analysis. Comparison of expression levels with apoptotic markers as well as translocation between mitochondria and the nucleus imply that the regulation of prohibitin is an early signaling event in the RPE and retina under oxidative stress. Immunohistochemical analysis of murine aged and diabetic eyes further suggests that the regulation of prohibitin in the RPE/retina is related to aging- and diabetes-induced oxidative stress. Our proteomic approach implies that prohibitin in the RPE and the retina could be a new biomarker protein of oxidative stress in aging and diabetes.
    International journal of biological macromolecules 12/2010; 47(5):685-90. · 2.37 Impact Factor
  • Article: Early biosignature of oxidative stress in the retinal pigment epithelium.
    [show abstract] [hide abstract]
    ABSTRACT: The retinal pigment epithelium (RPE) is essential for retinoid recycling and phagocytosis of photoreceptors. Understanding of proteome changes that mediate oxidative stress-induced degeneration of RPE cells may provide further insight into the molecular mechanisms of retinal diseases. In the current study, comparative proteomics has been applied to investigate global changes of RPE proteins under oxidative stress. Proteomic techniques, including 2D SDS-PAGE, differential gel electrophoresis (DIGE), and tandem time-of-flight (TOF-TOF) mass spectrometry, were used to identify early protein markers of oxidative stress in the RPE. Two biological models of RPE cells revealed several differentially expressed proteins that are involved in key cellular processes such as energy metabolism, protein folding, redox homeostasis, cell differentiation, and retinoid metabolism. Our results provide a new perspective on early signaling molecules of redox imbalance in the RPE and putative therapeutic target proteins of RPE diseases caused by oxidative stress.
    Journal of proteomics 11/2010; 74(2):254-61. · 5.07 Impact Factor
  • Article: Correlation of microperimetry with fundus autofluorescence and spectral-domain optical coherence tomography in repaired macular holes.
    [show abstract] [hide abstract]
    ABSTRACT: To investigate the correlation of microperimetry with fundus autofluorescence (FAF), spectral-domain optical coherence tomography (SD-OCT), and visual acuity (VA) in order to better characterize visual outcomes after successful macular hole (MH) surgery. Cross-sectional case series. Postoperative VA, microperimetry, FAF, and SD-OCT images from 23 eyes of 23 patients who underwent successful MH surgery were obtained. FAF images were examined using the Heidelberg retina angiograph 2, and foveal structure and macular sensitivity were evaluated with SD-OCT and microperimetry. The mean retinal sensitivities within the central 9 degrees (microperimetry, mean), the retinal sensitivity of the foveal center (microperimetry, center), and the difference between the values obtained for the foveal center or mean of study and fellow eyes (microperimetry, centerdiff and microperimetry, meandiff, respectively) were measured with microperimetry. Microperimetry (mean) was well correlated with microperimetry (center) in both study and fellow eyes. Poor postoperative VA was correlated with large microperimetry (meandiff). Following successful MH surgery, FAF of all eyes decreased markedly. There was a positive correlation between microperimetry (centerdiff) and degree of FAF of study eyes. However, a decrease in FAF after MH surgery was not correlated well with either degree of defect in the junction between photoreceptor inner and outer segment (IS/OS) or central retinal thickness on SD-OCT. The amount of remaining FAF is related to macular sensitivity as measured by microperimetry after successful MH surgery. Function of photoreceptors and retinal pigment epithelium as well as integrity can be estimated by measuring the decrease in FAF after successful MH surgery. Moreover, functional correlation with microperimetry provides both morphologic and functional information on repaired MHs.
    American journal of ophthalmology 10/2010; 151(1):128-136.e3. · 3.83 Impact Factor
  • Article: The Drosophila homolog of methionine sulfoxide reductase A extends lifespan and increases nuclear localization of FOXO.
    [show abstract] [hide abstract]
    ABSTRACT: Methionine sulfoxide reductase A (msrA) was previously found to increase resistance to oxidative stress and longevity in animals. We identified Drosophila msrA (dmsrA), a Drosophila homolog of human msrA, as a downstream effector of forkhead box O (FOXO) signaling in Drosophila, which enhances resistance to oxidative stress and increases survival under stressed conditions. Additionally, overexpression of dmsrA in neurons extended the lifespan of flies. Moreover, overexpression of dmsrA in fat body cells caused FOXO to translocate to the nucleus, implying that this possible positive feedback loop between dmsrA and FOXO could potentiate the antioxidant activity of dmsrA and increase the lifespan in Drosophila.
    FEBS letters 08/2010; 584(16):3609-14. · 3.54 Impact Factor
  • Article: Cleavage of the retinal pigment epithelium-specific protein RPE65 under oxidative stress.
    [show abstract] [hide abstract]
    ABSTRACT: The regeneration of the 11-cis-retinyl imine chromophore of rhodopsin during the visual cycle and mechanisms that control this process are central questions in the field of vision research. The retinal pigment epithelium (RPE)-specific protein RPE65 is centrally involved in the isomerization and hydrolysis of all-trans-retinyl esters. In this study, we investigated RPE65 cleavage and potential regulatory mechanisms under oxidative stress conditions. The D407 RPE cell cultures were exposed to H(2)O(2) (100-1000 microM). Changes in the levels of RPE65 and proteins related to apoptosis were investigated using gel electrophoresis and western blotting. Mass spectrometry was used to confirm the identity of RPE65. C57BL/6J (M450) and C3HeB/FeJ (L450) mice were used for in vivo experiments. We found that a novel 45kDa truncated fragment of the RPE65 protein, designated RPE45, appears in RPE cells upon light exposure or oxidative stress. RPE45 is generated in vitro by recombinant caspases via an ubiquitination-dependent mechanism. Collectively, our results indicate that oxidative stress during the visual cycle results in cleavage of RPE65.
    International journal of biological macromolecules 08/2010; 47(2):104-8. · 2.37 Impact Factor
  • Article: Early Detection of Tamoxifen-induced Maculopathy in Patients With Low Cumulative Doses of Tamoxifen.
    [show abstract] [hide abstract]
    ABSTRACT: Pathogenic macula determined by techniques including 3-dimensional optical coherence tomography OCT (3D-OCT), in six breast cancer patients who had received low cumulative doses (4.2 to 9.6 g) of tamoxifen is described. Fluorescein angiography showed varying amounts of foveolar hyperfluorescence. 3-dimensional OCT revealed one or several foveal cystoid spaces in 10 of 12 eyes with or without focal disruption of the photoreceptor transition zones. Time-domain OCT did not indicate cystoid spaces in two of the eyes that clearly showed intraretinal cysts on 3D-OCT. Tiny disruptions of photoreceptor transition zones were also more clearly visible on 3D-OCT. Previous studies have clearly shown retinopathy following long-term or high dosages of tamoxifen. Our results indicate that patients with low cumulative doses of tamoxifen can also suffer visual symptom-related foveal cystoid spaces and/or macular thinning. 3D-OCT is very effective in detecting early subtle changes in tamoxifen-induced maculopathy that can occur in asymptomatic patients.
    Ophthalmic Surgery Lasers and Imaging 03/2010; · 0.62 Impact Factor
  • Source
    Article: Serum C-reactive protein levels in normal-weight polycystic ovary syndrome.
    [show abstract] [hide abstract]
    ABSTRACT: Serum levels of highly sensitive C-reactive protein (hsCRP), a vascular inflammatory marker, may predict the development of cardiovascular disease (CVD) and type 2 diabetes. Women with polycystic ovary syndrome (PCOS) are at greater risk for type 2 diabetes and CVD. The aim of this study was to compare hsCRP levels between normal weight women with PCOS and controls with a normal menstrual cycle and to determine the factors associated with serum hsCRP levels. Thirty-nine lean PCOS patients and 24 healthy, regular cycling women were enrolled in this study. We performed anthropometric measurements, fat computed tomography (CT), and blood sampling to determine blood chemistry and levels of hsCRP, gonadotropins, testosterone, and sex-hormone binding globulin. We also conducted 75-g oral glucose-tolerance test and euglycemic hyperinsulinemic clamp to assess insulin sensitivity. Serum hsCRP concentrations were higher in women with PCOS than in women with regular mensturation. However, this difference was no longer significant after adjusting for body mass index (BMI). hsCRP levels were correlated with waist circumference (r=0.46, p<0.01), BMI (r=0.46, p<0.01), visceral fat area (r=0.45, p<0.01), and systolic (r=0.42, p<0.05) and diastolic blood pressure (r=0.39, p<0.05). hsCRP also tended to be negatively associated with insulin-mediated glucose uptake (IMGU) (r=-0.31, p=0.07). A multiple regression analysis revealed that BMI (beta=0.29, p<0.05), systolic blood pressure (beta=0.39, p<0.01), and IMGU (beta=-0.31, p<0.05) predicted serum hsCRP levels in women with PCOS. PCOS by itself does not seem to be associated with increased hsCRP levels, whereas known CVD risk factors affect serum hsCRP levels in PCOS.
    The Korean Journal of Internal Medicine 12/2009; 24(4):350-5.
  • Article: The prevalence and risk factors for glucose intolerance in young Korean women with polycystic ovary syndrome.
    [show abstract] [hide abstract]
    ABSTRACT: Insulin resistance and hyperinsulinemia play important roles in the pathogenesis of polycystic ovary syndrome (PCOS). In addition, some women with PCOS have been shown to have insulin secretory defects and can be predicted to be at an increased risk for glucose intolerance. We performed the present study to determine the prevalence and risk factors for glucose intolerance in Korean women with PCOS. We consecutively recruited 194 women with PCOS diagnosed by American Society for Reproductive Medicine/European Society of Human Reproduction and Embryology (ASRM/ESHRE) criteria. Anthropometric measures, 75 g oral glucose tolerance test (OGTT), and measurement of insulin sensitivity (insulin mediated glucose uptake; IMGU) using euglycemic hyperinsulinemic clamp technique were performed. In women with PCOS, the prevalence of impaired glucose tolerance (IGT) and/or impaired fasting glucose (IFG) was 17.0% and type 2 diabetes 1.0%, and in lean women with PCOS, the prevalence of IGT and/or IFG was 5.9%. The prevalence of glucose intolerance was 28-fold higher in women with PCOS, and 9.8-fold higher in lean women with PCOS compared to age-matched Korean women. Women with glucose intolerance had higher BMI, waist circumference, free testosterone, fasting insulin, 2-h post-load insulin, total cholesterol, LDL cholesterol, triglyceride and lower sex hormone binding globulin and IMGU than women with normal glucose tolerance (NGT) (P < 0.05). IMGU was the most powerful predictor for glucose intolerance after adjustment for age, BMI, waist circumference, and hyperandrogenemia. The 2-h OGTT was the best screening measure for glucose intolerance and diagnosis of diabetes in women with PCOS. Young Korean women with PCOS have high prevalence for glucose intolerance and type 2 diabetes, and insulin resistance is the most important factor associated with glucose intolerance.
    Endocrine 08/2009; 36(2):326-32. · 1.42 Impact Factor
  • Source
    Article: Ocular sarcoidosis in a Korean population.
    [show abstract] [hide abstract]
    ABSTRACT: The aim of current study was to evaluate the incidence and characteristics of ocular sarcoidosis in a Korean population. We conducted a retrospective study of 104 consecutive patients with biopsy-proven sarcoidosis seen at Asan Medical Center in Seoul, Korea, from 1993 to 2007. Medical records, photographs, and fluorescein angiograms were reviewed. Of 104 patients, 22 (21%) had intraocular involvement with female predominance (86%, M:F=3:19). Of the 39 eyes with ocular involvement, 16 (41%) eyes had isolated anterior uveitis, 12 (31%) eyes had intermediate uveitis, 6 eyes (15%) had panuveitis with retinal vasculitis, and 5 (13%) eyes had panuveitis with punched multifocal choroiditis. Mean duration of ophthalmologic follow-up was 62 months. All ocular inflammation was well managed with topical steroid and/or systemic steroid with relatively good final visual outcomes. Ocular complications such as cataract (12 eyes, 30%), glaucoma (6 eyes, 15%), vitreous opacity (1 eye, 3%), cystoid macular edema (3 eyes, 7%), neovascularization (2 eye, 5%), and epiretinal membrane (4 eye, 10%) were related to ocular sarcoidosis. In Korea, where sarcoidosis is very rare, our study indicates relatively low ocular and predominantly non posterior segment involvement with relatively good visual prognosis.
    Journal of Korean medical science 07/2009; 24(3):413-9. · 0.84 Impact Factor
  • Article: Neuroprotective role of erythropoietin by antiapoptosis in the retina.
    [show abstract] [hide abstract]
    ABSTRACT: Erythropoietin (EPO) stimulates red blood cell production, in part by inhibiting apoptosis of the red blood cell precursors. The erythropoietic effects of EPO are circadian stage dependent. Retinal injury due to light occurs through oxidative mechanisms and is manifest by retinal and retinal pigment epithelium (RPE) cells apoptosis. The visual cycle might be circadian coordinated as a means of effectively protecting the retina from the detrimental effects of light-induced, oxygen-dependent, free radical-mediated damage, especially at the times of day when light is more intense. We show that the retinal expression of EPO and its receptor (EPOR), as well as subsequent Janus kinase 2 (Jak2) phosphorylations, are each tightly linked to a specific time after oxidative stress and in anticipation of daily light onset. This is consistent with physiological protection against daily light-induced, oxidatively mediated retinal apoptosis. In vitro, we verify that EPO protects RPE cells from light, hyperoxia, and hydrogen peroxide-induced retinal cell apoptosis, and that these stimuli increase EPO and EPOR expression in cultured RPE cells. Together, these data support the premise that EPO and its EPOR interactions represent an important retinal shield from physiologic and pathologic light-induced oxidative injury.
    Journal of Neuroscience Research 04/2009; 87(10):2365-74. · 2.74 Impact Factor

Institutions

  • 2013
    • Ewha Womans University
      • Department of Internal Medicine
      Seoul, Seoul, South Korea
  • 2010–2013
    • Konkuk University Medical Center
      Changnyeong, South Gyeongsang, South Korea
  • 2012
    • Konkuk University
      • Department of Ophthalmology
      Seoul, Seoul, South Korea
  • 2006–2012
    • University of Ulsan
      • Asan Medical Center
      Ulsan, Ulsan, South Korea
  • 2010–2011
    • University of South Carolina
      • Department of Ophthalmology
      Columbia, SC, USA
  • 2008–2009
    • Asan Medical Center
      Seoul, Seoul, South Korea
    • Ulsan University Hospital
      Ulsan, Ulsan, South Korea