Kwang-Won Kim

Gachon University, 성남시, Gyeonggi-do, South Korea

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Publications (93)236.55 Total impact

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    ABSTRACT: The aim of this study was to investigate whether adjusting diabetic treatment regimens according to the information obtained from a continuous glucose monitoring system (CGMS) might lead to improved glycemic control in patients with type 2 diabetes. We reviewed the medical charts of 172 patients who used the CGMS for 1 year starting in December 2008 and the records of 1,500 patients who visited their regular outpatient clinics during December 2008. Of these patients, a total of 65 CGMS patients and 301 regular outpatients (control group) were enrolled in the study after propensity score matching. There were no differences in baseline glycated hemoglobin (HbA1c), age, and duration of diabetes between the CGMS and the control groups after propensity score matching. The changes in the HbA1c levels from baseline to 6 months were calculated. The CGMS group showed a significant improvement in the HbA1c level compared to the control group at 3 months (7.9%±1.6% vs. 7.4%±1.2%, P=0.001) and at 6 months (7.4%±1.2% vs. 7.9%±1.6%, P=0.010). There were significant differences in the treatment modality changes between the CGMS group and the control group. Using a 3-day CGMS was advantageous for improving glucose control in patients with type 2 diabetes and may help these patients to optimize glycemic control in clinical practice.
    Preview · Article · Dec 2014 · Diabetes & metabolism journal
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    ABSTRACT: Islet transplantation has been hampered by the shortage of islet donors available for diabetes therapy. However, pluripotent stem cells (PSCs) can be an alternative source of insulin-producing cells (IPCs) because of their capacity for self-renewal and differentiation. We described a method to efficiently differentiate PSCs into IPCs by co-culturing mature islets with directed-differentiated pancreatic endoderm (PE) cells from mouse and human PSCs. PE cells co-cultured with islet cells or islet cell-derived conditioned medium (CM) showed increased expression levels of β-cell markers; significantly higher levels of proinsulin- and Newport Green (NG)-positive cells, which revealed the characteristics of insulin producing cells; and increased insulin secretion upon glucose stimulation. Co-culturing human PE cells with islet cells was also effective to differentiate PE cells into IPCs. Diabetic nude mice transplanted with co-cultured cells exhibited restored euglycemia, human C-peptide release, and improved glucose tolerance. Immunohistochemistry revealed that insulin+/C-peptide + cells existed in the grafted tissues. These results suggest that mature islet cells can increase the differentiation efficiency of PE cells into mature IPCs via paracrine effects.
    No preview · Article · Aug 2014 · Stem Cell Reviews and Reports
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    ABSTRACT: While a few studies have demonstrated the benefit of PEGylation in islet transplantation, most have employed renal subcapsular models and none have performed direct comparisons of islet mass in intraportal islet transplantation using islet magnetic resonance imaging (MRI). In this study, our aim was to demonstrate the benefit of PEGylation in the early post-transplant period of intraportal islet transplantation with a novel algorithm for islet MRI. Islets were PEGylated after ferucarbotran labeling in a rat syngeneic intraportal islet transplantation model followed by comparisons of post-transplant glycemic levels in recipient rats infused with PEGylated (n = 12) and non-PEGylated (n = 13) islets. The total area of hypointense spots and the number of hypointense spots larger than 1.758 mm (2) of PEGylated and non-PEGylated islets were quantitatively compared. The total area of hypointense spots (P<0.05) and the number of hypointense spots larger than 1.758 mm (2) (P<0.05) were higher in the PEGylated islet group 7 and 14 days post translation (DPT). These results translated into better post-transplant outcomes in the PEGylated islet group 28 DPT. In validation experiments, MRI parameters obtained 1, 7, and 14 DPT predicted normoglycemia 4 wk post-transplantation. We directly demonstrated the benefit of islet PEGylation in protection against nonspecific islet destruction in the early post-transplant period of intraportal islet transplantation using a novel algorithm for islet MRI. This novel algorithm could serve as a useful tool to demonstrate such benefit in future clinical trials of islet transplantation using PEGylated islets.
    Full-text · Article · Feb 2014 · Islets
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    ABSTRACT: Aims/Introduction The goal of the present study was to evaluate predictive factors for good efficacy and durability to sitagliptin with ongoing metformin or metformin plus glimepiride therapy in a real practice situation. The present observational study was carried out over a 60‐week period and involved Korean patients with type 2 diabetes mellitus. Materials and Methods A total of 100 mg of sitagliptin were added once daily to the two most popular therapy regimens (group 1: metformin, group 2: metformin plus glimepiride). Before adding sitagliptin, mean initial glycated hemoglobin (HbA1c) levels were 7.8% (62 mmol/mol) and mean diabetes duration was 8.3 years. Results After 60 weeks, the mean change in HbA1c from baseline was −0.9% (−10 mmol/mol) in group 1 and −1.0% (−11 mmol/mol) in group 2. Decreased HbA1c levels were significantly associated with higher initial HbA1c and lower log‐transformed C‐peptide levels in a multivariate regression analysis. Logistic regression analysis showed that a sustained reduction in HbA1c levels after 12 weeks was significantly associated with older age (≥60 years), higher baseline HbA1c (group 1 ≥ 7.0% [53 mmol/mol], group 2 ≥ 7.5% [58 mmol/mol]) and slower reduction of HbA1c (ΔHbA1c <1.0% [11 mmol/mol]) in group 1 and group 2. In group 2, a higher ratio of reduction of postprandial glucose/reduction of fasting plasma glucose (ΔPPG/ΔFPG) during 12 weeks was also associated with a sustained reduction in HbA1c levels after 12 weeks. Conclusions The effects of sitagliptin lasted more than 12 weeks in older patients with a higher baseline HbA1c, and slower reduction of HbA1c during 12 weeks.
    Full-text · Article · Feb 2014 · Journal of Diabetes Investigation
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    ABSTRACT: Aims/Introduction To evaluate whether hemoglobin A1c (HbA1c) levels are affected by hemoglobin level and gender. Materials and Methods A cross‐sectional analysis was carried out in a sample of 87,284 non‐diabetic Koreans without anemia who participated in comprehensive health check‐ups between January and December 2009 at the Kangbuk Samsung Hospital Total Healthcare Center in Seoul, Korea. We categorized men and women separately according to fasting plasma glucose and hemoglobin level to carry out the analysis. Results HbA1c increased steadily with increasing fasting plasma glucose level. Both men and women with lower hemoglobin had significantly higher HbA1c at a given fasting glucose level, and this result was consistent across the fasting glucose quintiles within the non‐diabetic range. Women had a lower mean hemoglobin value compared with men, and women had higher HbA1c levels at a given fasting glucose level consistently across the fasting glucose deciles. There was also a gender‐specific association between age and HbA1c (P < 0.001 for interaction). Conclusions HbA1c values were affected by hemoglobin level and gender in non‐anemic Koreans. Thus, hemoglobin level and gender should be considered in the diagnosis of diabetes using HbA1c.
    Full-text · Article · Feb 2014 · Journal of Diabetes Investigation
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    ABSTRACT: Role of impaired suppression of glucagon secretion in the pathogenesis of pancreatic cancer-associated diabetes has been suggested. We examined the correlation between glucagon/insulin ratio (G/I) after glucose challenge and hemoglobin A1C (A1C) in subjects with and without pancreatic cancer. Data were gathered from a preoperative screening 75-g oral glucose tolerance test in patients who would eventually undergo pancreatic resection. A multiple linear regression analysis was conducted using the following covariates: age, body mass index, hemoglobin, glucose and insulin levels at the corresponding time points, indices of insulin resistance, duration of diabetes, insulinogenic index, and use of glucose-lowering drugs. In subject group with pancreatic cancer (n = 45), but not in subject group without pancreatic cancer (n = 101), participants with A1C ≥6.5 % had significantly higher glucagon levels, lower insulin levels, and higher G/I ratios after the glucose challenge than those of the subjects with A1C <5.7 %. In the multiple linear regression analysis, there was an independent correlation between post-challenge G/I ratio and A1C in both groups. Some of the patients without pancreatic cancer had inappropriately elevated G/I ratios despite A1C <6.5 %. These patients were characterized by lower insulinogenic indices (p = 0.004) and less insulin resistance (p = 0.008). In conclusion, post-challenge G/I ratio independently correlated with A1C in patients with pancreatic cancer. Although significant, the degree of correlation was weakened in the subjects without pancreatic cancer because some had lower insulin secretory reserve compensated by less insulin resistance, resulting in inappropriately elevated G/I ratios relative to A1C.
    Full-text · Article · Jan 2014 · Endocrine
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    ABSTRACT: One aspect of the effects of metformin on glucagon-like peptide (GLP)-1 might be at least associated with the mechanism by which the cross-talk between insulin and Wnt signaling enhances GLP-1 secretion, due to the action of metformin as an insulin sensitizer. However, it remains completely unknown. Here, we have investigated the mechanisms underlying effects of metformin on cross-talk between insulin and Wnt signaling. GLP-1 enhancement by meformin was determined in human NCI-H716 intestinal L-cells and hyperglycemic db/db mice treated with metformin (0.25 and 0.5mM and/or 12.5mg/kg body wet.) for 24 h and 2 mo. Metformin increased GLP-1 secretion in L-cells and db/db mice. Metformin stimulated the nuclear translocation of β-catenin and the TOP flash activity, and gene depletion of β-catenin or mutation of transcription factor 7 like 2 binding site offset GLP-1 enhancement by metformin. In addition, insulin receptor substrate-2 gene depletion blocked the metformin-enhanced β-catenin translocation. These effects were preceded by the increase in glucose utilization and calcium influx, the activation of calcium-dependent protein kinase, and, in turn, the activation of insulin signaling and the inhibition of glycogen synthase kinase 3β, a potent inhibitor of β-catenin. Furthermore, high blood glucose levels were controlled via GLP-1 receptor-dependent insulinotropic pathways in db/db mice, which were evidenced by the increase in GLP-1 and insulin levels at 30min after oral glucose loading and pancreatic insulinotropic genes expression. Our findings suggest that the cooperation between Wnt and its upstream insulin signaling pathways might be a novel and important mechanism underlying the effects of metformin on GLP-1 production.
    No preview · Article · Nov 2013 · Journal of Endocrinology
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    ABSTRACT: We investigated the clinical characteristics and follow-up findings of subjects with adrenal incidentalomas in a single, tertiary-care hospital in South Korea. The study consisted of a retrospective analysis of 282 adrenal incidentaloma patients who underwent radiographic and endocrinological evaluations at Samsung Medical Center in Seoul, South Korea, between January 2004 and July 2011. Most (86.2%) of the subjects were found to have nonfunctioning tumors. Functioning tumors were seen in 39 patients (13.8%). Among them, 28 (9.9%) had subclinical Cushing syndrome (SCS), six (2.1%) had pheochromocytoma, and five (1.8%) had primary hyperaldosteronism. Malignant adrenal tumors were discovered in three cases: two (0.7%) were primary adrenal cancers, and one (0.4%) was a secondary metastasis from a lung cancer. Significant risk factors for functional tumors were female gender (odds ratio [OR], 3.386; 95% confidence interval [CI], 1.611 to 7.117; p = 0.0013) and a noncontrast attenuation value of > 10 Hounsfield units (OR, 2.806; 95% CI, 1.231 to 6.397; p = 0.0141). During follow-up (mean, 22.5 months) of 72 of the patients, three (4.2%) developed hormonal changes due to functional tumors. One was confirmed as pheochromocytoma by histopathology, and the others were diagnosed with SCS and followed routinely without surgical intervention. No malignant transformation was found in these patients. Based on these findings, initial hormonal and radiographic evaluations for adrenal incidentalomas appear to be more important than follow-up tests because functional or malignant changes are rare.
    Full-text · Article · Sep 2013 · The Korean Journal of Internal Medicine
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    ABSTRACT: Purpose Although the presence of cannabinoid type 1 (CB1) receptor in islets has been reported, the major contributor to the protective effect of rimonabant on islet morphology is unknown. We determined whether the protective effect of rimonabant on pancreatic islet morphology is valid in established diabetes and also whether any effect was independent of decreased food intake. Materials and Methods After diabetes was confirmed, Otsuka Long-Evans Tokushima Fatty rats, aged 32 weeks, were treated with rimonabant (30 mg/kg/d, rimonabant group) for 6 weeks. Metabolic profiles and islet morphology of rats treated with rimonabant were compared with those of controls without treatment (control group), a pair-fed control group, and rats treated with rosiglitazone (4 mg/kg/d, rosiglitazone group). Results Compared to the control group, rats treated with rimonabant exhibited reduced glycated albumin levels (p<0.001), islet fibrosis (p<0.01), and improved glucose tolerance (p<0.05), with no differences from the pair-fed control group. The retroperitoneal adipose tissue mass was lower in the rimonabant group than those of the pair-fed control and rosiglitazone groups (p<0.05). Rimonabant, pair-fed control, and rosiglitazone groups showed decreased insulin resistance and increased adiponectin, with no differences between the rimonabant and pair-fed control groups. Conclusion Rimonabant had a protective effect on islet morphology in vivo even in established diabetes. However, the protective effect was also reproduced by pair-feeding. Thus, the results of this study did not support the significance of islet CB1 receptors in islet protection with rimonabant in established obesity-associated type 2 diabetes.
    Full-text · Article · Sep 2013 · Yonsei medical journal
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    ABSTRACT: Background: Several retrospective studies with short-term follow-up have demonstrated a low rate of new-onset diabetes after distal pancreatectomy for benign pancreatic tumors. We sought to determine the long-term diabetes-free survival of patients who underwent islet autotransplantation (IAT) after distal pancreatectomy and to identify any associations between the isolation parameters of autologous islets and diabetes-free survival. Methods: Among the 37 nondiabetic patients who underwent 50% to 60% partial pancreatectomy, 20 underwent IAT (IAT group; median follow-up period, 61 months). In the IAT group, diabetes-free survival was determined based on annual oral glucose tolerance tests, fasting blood glucose, and hemoglobin A1C. Results: The 7-year diabetes-free survival rate was 51% in the IAT group (median follow-up period, 61 months) and 45% in the 37 study subjects. Diabetes-free survival was significantly prolonged when islet yield per gram of pancreas weight was more than 5154 islet equivalents (IEQ)/g, even in patients with prediabetes and high insulin resistance who had a markedly high rate of diabetes development. The proportion of patients with impaired glucose tolerance at 2 years after distal pancreatectomy was 12 of 16 in the control group, 6 of 7 in patients with islet yields of less than 5154 IEQ/g, and 3 of 11 in patients with islet yields of more than 5154 IEQ/g (P=0.019). Conclusions: Partial (50%-60%) pancreatectomy for benign pancreatic tumors had a major metabolic consequence, especially in patients with prediabetes and high insulin resistance. In this setting, prolonged diabetes-free survival was observed in patients who underwent IAT when a high islet yield per gram of pancreas was achieved.
    No preview · Article · Apr 2013 · Transplantation
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    ABSTRACT: Background: The ratio of apolipoprotein B (apoB) to apolipoprotein A1 (apoA1) has been reported to be associated with metabolic syndrome (MetS) and insulin resistance (IR). Non-HDL-C is regarded as a surrogate marker for apoB in routine clinical practice. However, it is unclear whether the ratio of non-HDL-C to HDL-C is an equal or a better predictor than the apoB/apoA1 ratio for the identification of MetS and IR. Methods: We performed a retrospective study of 41,821 Korean adults who participated in a routine health screening examination. Anthropometry, fasting glucose, fasting insulin, HOMA-IR, CRP, lipid profiles, apoB, and apoA1 were measured. Results: To compare the predictive value for MetS between different lipid ratios, we analyzed the ROC curves of apoB/apoA1 and non-HDL-C/HDL-C ratios. ROC analysis showed that the AUCs of non-HDL-C/HDL-C (0.75 [95% CI=0.74-0.76] in men and 0.84 [95% CI=0.83-0.85] in women) were significantly higher than those of apoB/apoA1 (0.66 [95% CI=0.65-0.67] in men and 0.77 [95% CI=0.76-0.78] in women). The non-HDL-C/HDL-C ratio also showed a significantly stronger association with HOMA-IR than the apoB/apoA1 ratio. The optimal cutoff value of the non-HDL-C/HDL-C ratio for detection of MetS in men was 3.39, with a sensitivity of 66.7% and a specificity of 71.8%, whereas the optimal ratio cutoff value in women was 2.89, with a sensitivity of 75.7% and a specificity of 78.1%. Conclusions: Our findings indicate that the non-HDL-C/HDL-C ratio is a better marker than the apoB/apoA1 ratio for identifying IR and MetS in Koreans.
    No preview · Article · Mar 2013 · International journal of cardiology
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    ABSTRACT: We report the case of a 36-year-old woman who presented with headache, fever, and amenorrhea. Laboratory analysis revealed hypopituitarism and autoimmune thyroiditis, while a cerebrospinal fluid study suggested concurrent aseptic meningitis. A magnetic resonance image (MRI) scan revealed a 1.0×0.9 cm cystic mass enlarging the sella turcica. Surgical resection via an endoscopic transsphenoidal route was performed. The histological finding of the excised tissue revealed foamy histiocytes with vacuolated cytoplasm, supporting the diagnosis of xanthomatous hypophysitis. Although a residual soft lesion was observed on the MRI image postoperatively, the patient's headache and fever improved. Ten months after surgery, the patient complained of visual impairment and headache, and the residual mass had enlarged into the suprasellar area. High dose (500 mg intravenous) methylprednisolone was administered for 3 days. During the methylprednisolone pulse therapy, the patient's visual acuity and headache improved. A follow-up MRI taken after methylprednisolone therapy showed a marked mass reduction. Our case supports an autoimmune pathophysiology for xanthomatous hypophysitis and suggests that high dose glucocorticoid therapy as a treatment option.
    Preview · Article · Mar 2013
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    ABSTRACT: Background It has been reported that peroxisome proliferator-activated receptor (PPAR)-γ and their synthetic ligands have direct effects on pancreatic β-cells. We investigated whether PPAR-γ activation stimulates insulin secretion through the up-regulation of GPR40 in pancreatic β-cells. Methods Rat insulinoma INS-1 cells and primary rat islets were treated with rosiglitazone (RGZ) and/or adenoviral PPAR-γ overexpression. OLETF rats were treated with RGZ. Results PPAR-γ activation with RGZ and/or adenoviral PPAR-γ overexpression increased free fatty acid (FFA) receptor GPR40 expression, and increased insulin secretion and intracellular calcium mobilization, and was blocked by the PLC inhibitors, GPR40 RNA interference, and GLUT2 RNA interference. As a downstream signaling pathway of intracellular calcium mobilization, the phosphorylated levels of CaMKII and CREB, and the downstream IRS-2 and phospho-Akt were significantly increased. Despite of insulin receptor RNA interference, the levels of IRS-2 and phospho-Akt was still maintained with PPAR-γ activation. In addition, the β-cell specific gene expression, including Pdx-1 and FoxA2, increased in a GPR40- and GLUT2-dependent manner. The levels of GPR40, phosphorylated CaMKII and CREB, and β-cell specific genes induced by RGZ were blocked by GW9662, a PPAR-γ antagonist. Finally, PPAR-γ activation up-regulated β-cell gene expressions through FoxO1 nuclear exclusion, independent of the insulin signaling pathway. Based on immunohistochemical staining, the GLUT2, IRS-2, Pdx-1, and GPR40 were more strongly expressed in islets from RGZ-treated OLETF rats compared to control islets. Conclusion These observations suggest that PPAR-γ activation with RGZ and/or adenoviral overexpression increased intracellular calcium mobilization, insulin secretion, and β-cell gene expression through GPR40 and GLUT2 gene up-regulation.
    Full-text · Article · Jan 2013 · PLoS ONE
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    ABSTRACT: Diabetes self-management education has an important role in diabetes management. The efficacy of education has been proven in several randomized trials. However, the status of diabetes education programs in real Korean clinical practice has not yet been evaluated in terms of patient compliance with the education prescription. We retrospectively analyzed clinical and laboratory data from all patients who were ordered to undergo diabetes education during 2009 at Samsung Medical Center, Seoul, Korea (n=2,291). After excluding ineligible subjects, 588 patients were included in the analysis. Among the 588 patients, 433 received education. The overall compliance rate was 73.6%, which was significantly higher in the subjects with a short duration or living in a rural area compared to those with a long duration (85.0% vs. 65.1%, respectively; P<0.001) or living in an urban area (78.2% vs. 70.4%, respectively; P=0.037). The hemoglobin A1c decreased greater in the compliant group (from 7.84±1.54 at baseline to 6.79±1.06 at 3 months and 6.97±1.20 at 12 months after prescription in the compliant group vs. from 7.74±1.25 to 7.14±1.02 and 7.24±1.24 in the non-compliant group; P=0.001). The decrease in hemoglobin A1c was greater in the subjects with a short duration (P=0.032). In our study a large percent of patients refuse to get education despite having a prescription from their physician. This refusal rate was higher in the patients with long-standing diabetes or in urban residence. Furthermore, education was more effective in patients with a short duration of diabetes in clinical practice.
    Full-text · Article · Dec 2012 · Diabetes & metabolism journal
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    ABSTRACT: Congenital adrenal hyperplasia (CAH) is characterized by decreased adrenal hormone production due to enzymatic defects and subsequent rise of adrenocorticotrophic hormone that stimulates the adrenal cortex to become hyperplastic, and sometimes tumorous. As the pathophysiology is basically a defect in the biosynthesis of cortisol, one may not consider CAH in patients with hypercortisolism. We report a case of a 41-yr-old man with a 4 cm-sized left adrenal tumorous lesion mimicking Cushing's syndrome who was diagnosed with CAH. He had central obesity and acanthosis nigricans involving the axillae together with elevated 24-hr urine cortisol level, supporting the diagnosis of Cushing's syndrome. However, the 24-hr urine cortisol was suppressed by 95% with the low dose dexamethasone suppression test. CAH was suspected based on the history of precocious puberty, short stature and a profound suppression of cortisol production by dexamethasone. CAH was confirmed by a remarkably increased level of serum 17-hydroxyprogesterone level. Gene mutation analysis revealed a compound heterozygote mutation of CYP21A2 (I173N and R357W).
    Preview · Article · Nov 2012 · Journal of Korean medical science
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    ABSTRACT: We evaluated the association of regular physical exercise with the presence of non-alcoholic fatty liver disease (NAFLD) and liver enzymes in relation to obesity and insulin resistance. A cross-sectional analysis was conducted in 72,359 healthy Korean adults without diabetes who participated in a comprehensive health check-up. Subjects who have been exercising regularly (more than 3 times per week, at least for 30 minutes each time and for consecutive 3 month) were categorized into exercise group. All subjects were categorized into deciles based on their body mass index (BMI) and we estimated the odds ratios (ORs) for having NAFLD according to exercise regularity in each decile. The diagnosis of NAFLD was based on ultrasonography findings. Individuals with NAFLD (n = 19,921) were analyzed separately to evaluate ORs for having elevated liver enzymes based on regularity of exercise. The risk for NAFLD was significantly reduced in exercise group with age- and sex-adjusted ORs of 0.53-0.72 for all BMI deciles except at BMI categories of <19.6 and 20.7-21.6 kg/m(2). While no difference was seen in BMI between subjects in exercise and non-exercise group across the BMI deciles, the values of body fat percentage and metabolic risk factors differed. Among NAFLD patients, subjects in exercise group had a lower risk for having elevated liver enzymes with multivariable adjusted OR of 0.85 (95% CI 0.74-0.99, for AST) and 0.74 (95% CI 0.67-0.81, for ALT) than did subjects in non-exercise group. Regular exercise was associated with a reduced risk for having NAFLD and decreased liver enzymes in patients with NAFLD, and this relationship was also independent of obesity.
    Full-text · Article · Oct 2012 · PLoS ONE
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    ABSTRACT: FasL, perforin, TNFα, IL-1 and NO have been considered as effector molecule(s) leading to β-cell death in autoimmune diabetes. However, the real culprit(s) of β-cell destruction have long been elusive despite intense investigation. Previously we have suggested IFNγ/TNFα synergism as the final effector molecules in autoimmune diabetes of NOD mice. A combination of IFNγ and TNFα but neither cytokine alone, induced classical caspase-dependent apoptosis in murine insulinoma and pancreatic islet cells. IFNγ treatment conferred susceptibility to TNFα-induced apoptosis on otherwise resistant murine insulinoma cells by STAT1 activation followed by IRF-1 induction. Here we report that IFNγ/TNFα synergism induces apoptosis of human pancreatic islet cells. We also observed STAT1 activation followed by IRF-1 induction by IFNγ treatment in human islet cells. Taken together, we suggest that IFNγ/TNFα synergism could be involved in human islet cell death in type 1 diabetes, similar to murine type 1 diabetes.
    Preview · Article · Jun 2012 · Immune Network
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    ABSTRACT: Autophagy is a catabolic cellular process involving the degradation of the cell's own components. Although the role of autophagy of diverse tissues in body metabolism has been investigated, the importance of autophagy in hypothalamic proopiomelanocortin (POMC) neurons, key regulators of energy balance, has not been addressed. The role of autophagy in leptin sensitivity that is critical for the control of body weight and appetite has also not been investigated. We produced mice with specific deletion of autophagy-related 7 (Atg7), an essential autophagy gene, in hypothalamic POMC neurons (Atg7(ΔPOMC) mice). Atg7 expression was deficient in the arcuate nucleus of the hypothalamus of Atg7(ΔPOMC) mice. p62, a specific substrate of autophagy, accumulated in the hypothalamus of Atg7(ΔPOMC) mice, which colocalized with ubiquitin. Atg7(ΔPOMC) mice had increased body weight due to increased food intake and decreased energy expenditure. Atg7(ΔPOMC) mice were not more prone to diet-induced obesity compared with control mice but more susceptible to hyperglycemia after high-fat diet. The ability of leptin to suppress fasting-elicited hyperphagia and weight gain during refeeding was attenuated in Atg7(ΔPOMC) mice. Deficient autophagy did not significantly affect POMC neuron number but impaired leptin-induced signal transducer and activation of transcription 3 activation. Our findings indicate a critical role for autophagy of POMC neurons in the control of energy homeostasis and leptin signaling.
    No preview · Article · Feb 2012 · Endocrinology
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    ABSTRACT: The aim of this study was to assess the prevalence of diabetes and to study the effects of excess growth hormone (GH) on insulin sensitivity and β-cell function in Korean acromegalic patients. One hundred and eighty-four acromegalic patients were analyzed to assess the prevalence of diabetes, and 52 naïve acromegalic patients were enrolled in order to analyze insulin sensitivity and insulin secretion. Patients underwent a 75 g oral glucose tolerance test with measurements of GH, glucose, insulin, and C-peptide levels. The insulin sensitivity index and β-cell function index were calculated and compared according to glucose status. Changes in the insulin sensitivity index and β-cell function index were evaluated one to two months after surgery. Of the 184 patients, 17.4% were in the normal glucose tolerance (NGT) group, 45.1% were in the pre-diabetic group and 37.5% were in the diabetic group. The insulin sensitivity index (ISI(0,120)) was significantly higher and the HOMA-IR was lower in the NGT compared to the diabetic group (P = 0.001 and P = 0.037, respectively). The ISI(0,120) and disposition index were significantly improved after tumor resection. Our findings suggest that both insulin sensitivity and β-cell function are improved by tumor resection in acromegalic patients.
    Full-text · Article · Feb 2012 · Journal of Korean medical science
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    ABSTRACT: We have reported that apoptotic β cells undergoing secondary necrosis, called "late apoptotic (LA) β cells," stimulated APCs and induced diabetogenic T cell priming through TLR2, which might be one of the initial events in autoimmune diabetes. Indeed, diabetogenic T cell priming and the development of autoimmune diabetes were significantly inhibited in TLR2-null NOD mice, suggesting the possibility that TLR2 blockade could be used to inhibit autoimmune diabetes. Because prolonged TLR stimulation can induce TLR tolerance, we investigated whether repeated TLR2 administration affects responses to LA β cells and inhibits autoimmune diabetes in NOD mice by inducing TLR2 tolerance. Treatment of primary peritoneal macrophages with a TLR2 agonist, Pam3CSK(4), suppressed cytokine release in response to LA insulinoma cells or further TLR2 stimulation. The expression of signal transducer IRAK-1 and -4 proteins was decreased by repeated TLR2 stimulation, whereas expression of IRAK-M, an inhibitory signal transducer, was enhanced. Chronic Pam3CSK(4) administration inhibited the development of diabetes in NOD mice. Diabetogenic T cell priming by dendritic cells and upregulation of costimulatory molecules on dendritic cells by in vitro stimulation were attenuated by Pam3CSK(4) administration in vivo. Pam3CSK(4) inhibited diabetes after adoptive transfer of diabetogenic T cells or recurrence of diabetes after islet transplantation by pre-existing sensitized T cells. These results showed that TLR2 tolerance can be achieved by prolonged treatment with TLR2 agonists, which could inhibit priming of naive T cells, as well as the activity of sensitized T cells. TLR2 modulation could be used as a novel therapeutic modality against autoimmune diabetes.
    Full-text · Article · Nov 2011 · The Journal of Immunology

Publication Stats

1k Citations
236.55 Total Impact Points

Institutions

  • 2013-2014
    • Gachon University
      • Department of Internal Medicine
      성남시, Gyeonggi-do, South Korea
  • 2004-2014
    • Samsung Medical Center
      • • Department of Endocrinology and Metabolism
      • • Department of Surgery
      Sŏul, Seoul, South Korea
  • 1999-2014
    • Sungkyunkwan University
      • • Samsung Medical Center
      • • School of Medicine
      Sŏul, Seoul, South Korea
  • 2003
    • Gyeongsang National University
      • Department of Internal Medicine
      Shinshū, Gyeongsangnam-do, South Korea