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1.  In Memoriam 
PMCID: PMC4273025
2.  A Gut Feeling to Cure Diabetes: Potential Mechanisms of Diabetes Remission after Bariatric Surgery 
Diabetes & Metabolism Journal  2014;38(6):406-415.
A cure for type 2 diabetes was once a mere dream but has now become a tangible and achievable goal with the unforeseen success of bariatric surgery in the treatment of both obesity and type 2 diabetes. Popular bariatric procedures such as Roux-en-Y gastric bypass and sleeve gastrectomy exhibit high rates of diabetes remission or marked improvement in glycemic control. However, the mechanism of diabetes remission following these procedures is still elusive and appears to be very complex and encompasses multiple anatomical and physiological changes. In this article, calorie restriction, improved β-cell function, improved insulin sensitivity, and alterations in gut physiology, bile acid metabolism, and gut microbiota are reviewed as potential mechanisms of diabetes remission after Roux-en-Y gastric bypass and sleeve gastrectomy.
PMCID: PMC4273026  PMID: 25541603
Bariatric surgery; Diabetes mellitus, type 2; Obesity; Roux-en-Y gastric bypass; Sleeve gastrectomy
3.  Current Concepts in Diabetic Retinopathy 
Diabetes & Metabolism Journal  2014;38(6):416-425.
For the past several decades, tremendous efforts have been made to decrease the complications of diabetes, including diabetic retinopathy. New diagnostic modalities like ultrawide field fundus fluorescein angiography and spectral domain optical coherence tomography has allowed more accurate diagnosis of early diabetic retinopathy and diabetic macular edema. Antivascular endothelial growth factors are now extensively used to treat diabetic retinopathy and macular edema with promising results. There remains uncertainty over the long term effects and the socioeconomic costs of these agents.
PMCID: PMC4273027  PMID: 25541604
Diabetic retinopathy; Epidemiology; Vascular endothelial growth factor
4.  Therapeutic Approaches for Preserving or Restoring Pancreatic β-Cell Function and Mass 
Diabetes & Metabolism Journal  2014;38(6):426-436.
The goal for the treatment of patients with diabetes has today shifted from merely reducing glucose concentrations to preventing the natural decline in β-cell function and delay the progression of disease. Pancreatic β-cell dysfunction and decreased β-cell mass are crucial in the development of diabetes. The β-cell defects are the main pathogenesis in patients with type 1 diabetes and are associated with type 2 diabetes as the disease progresses. Recent studies suggest that human pancreatic β-cells have a capacity for increased proliferation according to increased demands for insulin. In humans, β-cell mass has been shown to increase in patients showing insulin-resistance states such as obesity or in pregnancy. This capacity might be useful for identifying new therapeutic strategies to reestablish a functional β-cell mass. In this context, therapeutic approaches designed to increase β-cell mass might prove a significant way to manage diabetes and prevent its progression. This review describes the various β-cell defects that appear in patients with diabetes and outline the mechanisms of β-cell failure. We also review common methods for assessing β-cell function and mass and methodological limitations in vivo. Finally, we discuss the current therapeutic approaches to improve β-cell function and increase β-cell mass.
PMCID: PMC4273028  PMID: 25541605
β-Cell function; β-Cell mass; Therapeutic agents
5.  Is GDF15 a Novel Biomarker to Predict the Development of Prediabetes or Diabetes? 
Diabetes & Metabolism Journal  2014;38(6):437-438.
PMCID: PMC4273029  PMID: 25541606
6.  Arterial Stiffness by Aerobic Exercise Is Related with Aerobic Capacity, Physical Activity Energy Expenditure and Total Fat but not with Insulin Sensitivity in Obese Female Patients with Type 2 Diabetes 
Diabetes & Metabolism Journal  2014;38(6):439-448.
Arterial stiffness is an important factor in atherosclerosis. Thus we examined whether aerobic exercise could reduce arterial stiffness in obese women with type 2 diabetes without diabetic complication.
A total of 35 women with type 2 diabetes (body mass index, 26.6±2.8 kg/m2; age, 56.4±1.9 years; duration of diabetes, 4.7±4.8 years) were assigned to aerobic exercise group (AEG) or control group (CG). AEG completed a 12-week exercise program (3.6 to 5.2 metabolic equivalents, 3 day/week, 60 min/day), with their exercise activities monitored by accelerometers. We measured abdominal total fat area (TFA), visceral fat area (VFA), and subcutaneous fat area (SFA) by computed tomography, insulin sensitivity by insulin tolerance test (KITT), and augmentation index (AIx) by SphygmoCor at baseline and at the end of the 12-week program.
The AIx was improved in the AEG compared with the CG (P<0.001). The percent change of AIx had significant correlation with the improvement of physical activity energy expenditure (PAEE), aerobic capacity, TFA, and SFA (r=-0.416, P=0.013; r=0.560, P<0.001; r=0.489, P=0.003; r=0.531, P=0.001, respectively), but not with insulin sensitivity, energy intake, or VFA.
Improvement in aortic stiffness by aerobic exercise is related with the improvement of aerobic capacity, PAEE, and total fat but not with insulin sensitivity or energy intake in obese women with type 2 diabetes.
PMCID: PMC4273030  PMID: 25541607
Abdominal fat; Augmentation index; Diabetes mellitus, type 2; Moderate aerobic exercise; Vascular stiffness
7.  Effectiveness of 3-Day Continuous Glucose Monitoring for Improving Glucose Control in Type 2 Diabetic Patients in Clinical Practice 
Diabetes & Metabolism Journal  2014;38(6):449-455.
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.
PMCID: PMC4273031  PMID: 25541608
Continuous glucose monitoring; Diabetes mellitus, type 2; Hemoglobin A, glycosylated
8.  The Glycated Albumin to Glycated Hemoglobin Ratio Might Not Be Associated with Carotid Atherosclerosis in Patients with Type 1 Diabetes 
Diabetes & Metabolism Journal  2014;38(6):456-463.
The ratio of glycated albumin to glycated hemoglobin (GA/A1c) is known to be elevated in subjects with type 2 diabetes mellitus (T2DM) who had decreased insulin secretion. Additionally, the carotid intima media thickness (IMT) is greater in T2DM patients with higher GA/A1c ratios. We investigated whether increased GA/A1c ratio and IMT are also associated in type 1 diabetes mellitus (T1DM), which is characterized by lack of insulin secretory capacity.
In this cross-sectional study, we recruited 81 T1DM patients (33 men, 48 women; mean age 44.1±13.0 years) who underwent carotid IMT, GA, and HbA1c measurements.
The mean GA/A1c ratio was 2.90. Based on these results, we classified the subjects into two groups: group I (GA/A1c ratio <2.90, n=36) and group II (GA/A1c ratio ≥2.90, n=45). Compared with group I, the body mass indexes (BMIs), waist circumferences, and IMTs were lower in group II. GA/A1c ratio was negatively correlated with BMI, urine albumin to creatinine ratio (P<0.001 for both), and both the mean and maximal IMT (P=0.001, both). However, after adjusting the confounding factors, we observed that IMT was no longer associated with GA/A1c ratio.
In contrast to T2DM, IMT was not significantly related to GA/A1c ratio in the subjects with T1DM. This suggests that the correlations between GA/A1c ratio and the parameters known to be associated with atherosclerosis in T2DM could be manifested differently in T1DM. Further studies are needed to investigate these relationships in T1DM.
PMCID: PMC4273032  PMID: 25541609
Diabetes mellitus, type 1; Carotid intima-media thickness; Glycated albumin to glycated hemoglobin ratio; Glycosylated serum albumin
9.  A Cross-Sectional Study of the Phenotypes of Obesity and Insulin Resistance in Adults with Down Syndrome 
Diabetes & Metabolism Journal  2014;38(6):464-471.
Despite the confluence of multiple cardiovascular risk factors, subclinical atherosclerotic damage and cardiovascular events remain extremely rare in adults with Down syndrome (DS). We aim to determine the prevalence of obesity and metabolic disorders in an adult cohort with DS and to compare our findings with adults without DS.
Cross-sectional study of 51 consecutively selected adults with DS living in the community and 51 healthy controls in an outpatient clinic of a tertiary care hospital in Madrid, Spain. Epidemiological data (age and gender), anthropometric data (body mass index and waist-to-height ratio), coexisting clinical conditions, and laboratory data (fasting glucose, insulin, glycated hemoglobin, creatinine, thyroid hormones, vitamins, and lipid profile) were measured and compared between the groups.
Adults with DS were significantly younger and more often men with a higher prevalence of overweight and obesity than controls. Their waist-to-height ratio was higher, and they more frequently had abdominal obesity. The results of an analysis adjusted for age and gender revealed no differences in fasting insulin levels, homeostatic model assessment indexes, or lipid profile between adults with DS and controls.
Adults with DS presented a high prevalence of overweight and obesity. However, we found no differences in lipid profile, prevalence of insulin resistance, or metabolic syndrome between adults with DS and controls.
PMCID: PMC4273033  PMID: 25541610
Down syndrome; Hypothyroidism; Insulin resistance; Metabolic syndrome; Obesity, abdominal
10.  GDF15 Is a Novel Biomarker for Impaired Fasting Glucose 
Diabetes & Metabolism Journal  2014;38(6):472-479.
Growth differentiation factor-15 (GDF15) is a protein that belongs to the transforming growth factor β superfamily. An elevated serum level of GDF15 was found to be associated with type 2 diabetes mellitus (T2DM). T2DM is an inflammatory disease that progresses from normal glucose tolerance (NGT) to impaired fasting glucose (IFG). Hence, we aimed to validate the relationship between GDF15 and IFG.
The participants were divided into the following three groups: NGT (n=137), IFG (n=29), and T2DM (n=75). The controls and T2DM outpatients visited the hospital for routine health check-ups. We used fasting blood glucose to detect IFG in nondiabetic patients. We checked the body mass index (BMI), C-reactive protein level, metabolic parameters, and fasting serum GDF15 level.
Age, BMI, triglyceride, insulin, glucose, homeostatic model assessment-insulin resistance (HOMA-IR), and GDF15 levels were elevated in the IFG and T2DM groups compared to the NGT group. In the correlation analysis between metabolic parameters and GDF15, age and HOMA-IR had a significant positive correlation with GDF15 levels. GDF15 significantly discriminated between IFG and NGT, independent of age, BMI, and HOMA-IR. The serum levels of GDF15 were more elevated in men than in women. As a biomarker for IFG based on the receiver operating characteristic curve analysis, the cutoff value of GDF15 was 510 pg/mL in males and 400 pg/mL in females.
GDF15 had a positive correlation with IR independent of age and BMI, and the serum level of GDF15 was increased in the IFG and T2DM groups. GDF15 may be a novel biomarker for detecting IFG in nondiabetic patients.
PMCID: PMC4273034  PMID: 25541611
Biological markers; Diabetes mellitus, type 2; Growth differentiation factor 15; Prediabetic state
11.  Glycated Hemoglobin Value for Fasting Plasma Glucose of 126 mg/dL in Korean: The 2011 Korea National Health and Nutrition Examination Survey 
Diabetes & Metabolism Journal  2014;38(6):480-483.
We aimed to estimate the cutoff value of glycated hemoglobin (HbA1c, A1c) for fasting plasma glucose (FPG) of 126 mg/dL in the Korean adult population, using the 2011 Korea National Health and Nutrition Examination Survey. A total of 5,421 participants without a history of diabetes and over 19 years of age were included in the analysis. A point-wise area under the receiver operating characteristic curve was used to estimate the optimal A1c cutoff value. A1c threshold of 6.1% produced the highest sum of sensitivity (85.2%) and specificity (90.5%) for FPG of 126 mg/dL (area under the curve, 0.941, P<0.001). A1c of 6.5% produced a sensitivity of 67.7% and specificity of 98.0% for FPG of 126 mg/dL. Considering A1c as one of three criteria for the diagnosis of diabetes and the specificity of an A1c cutoff of 6.5%, the current diagnostic criteria of A1c≥6.5% might be acceptable in the Korean adult population.
PMCID: PMC4273035  PMID: 25541612
Diabetes mellitus; Diagnosis; Hemoglobin A, glycated
14.  Molecular Links between Caloric Restriction and Sir2/SIRT1 Activation 
Diabetes & Metabolism Journal  2014;38(5):321-329.
Ageing is the most significant risk factor for a range of prevalent diseases, including cancer, cardiovascular disease, and diabetes. Accordingly, interventions are needed for delaying or preventing disorders associated with the ageing process, i.e., promotion of healthy ageing. Calorie restriction is the only nongenetic and the most robust approach to slow the process of ageing in evolutionarily divergent species, ranging from yeasts, worms, and flies to mammals. Although it has been known for more than 80 years that calorie restriction increases lifespan, a mechanistic understanding of this phenomenon remains elusive. Yeast silent information regulator 2 (Sir2), the founding member of the sirtuin family of protein deacetylases, and its mammalian homologue Sir2-like protein 1 (SIRT1), have been suggested to promote survival and longevity of organisms. SIRT1 exerts protective effects against a number of age-associated disorders. Caloric restriction increases both Sir2 and SIRT1 activity. This review focuses on the mechanistic insights between caloric restriction and Sir2/SIRT1 activation. A number of molecular links, including nicotinamide adenine dinucleotide, nicotinamide, biotin, and related metabolites, are suggested to be the most important conduits mediating caloric restriction-induced Sir2/SIRT1 activation and lifespan extension.
PMCID: PMC4209345  PMID: 25349818
Biotin; Dietary restriction; NAD; Nicotinamide; Lifespan; Sirtuins
15.  Hyperglycemia as a Risk Factor for Cancer Progression 
Diabetes & Metabolism Journal  2014;38(5):330-336.
As the prevalence of diabetes mellitus is substantially increasing worldwide, associated diseases such as renal failure, cardiovascular diseases, fatty liver, and cancers have also increased. A number of cancers such as pancreatic, liver, breast, and female reproductive cancers have shown an increased prevalence and a higher mortality rate in diabetic patients compared to healthy subjects. Thus, this suggests an association between diabetes, especially type 2 diabetes and cancer incidence and progression. Recent studies have suggested that hyperinsulinemia, chronic inflammation and hyperglycemia, all frequently seen in diabetics, may lead to increased tumor growth; the underlying molecular mechanisms of this association are not fully understood. In particular, chronic hyperglycemic episodes could serve as a direct or indirect mediator of the increase in tumor cell growth. Here, we will discuss our current understanding how hyperglycemia and cancer risk may be linked, and what the implications are for the treatment of diabetic cancer patients.
PMCID: PMC4209346  PMID: 25349819
Cancer risk; Diabetes; Hyperglycemia; Therapeutics
16.  Diabetic Cardiomyopathy and Its Prevention by Nrf2: Current Status 
Diabetes & Metabolism Journal  2014;38(5):337-345.
Diabetic cardiomyopathy (DCM), as one of the major cardiac complications in diabetic patients, is known to related with oxidative stress that is due to a severe imbalance between reactive oxygen species (ROS) and/or reactive nitrogen species (RNS) generation and their clearance by antioxidant defense systems. Transcription factor nuclear factor NF-E2-related factor 2 (Nrf2) plays an important role in maintaining the oxidative homeostasis by regulating multiple downstream antioxidants. Diabetes may up-regulate several antioxidants in the heart as a compensative mechanism at early stage, but at late stage, diabetes not only generates extra ROS and/or RNS but also impairs antioxidant capacity in the heart, including Nrf2. In an early study, we have established that Nrf2 protect the cardiac cells and heart from high level of glucose in vitro and hyperglycemia in vivo, and in the following study demonstrated the significant down-regulation of cardiac Nrf2 expression in diabetic animals and patients. Using Nrf2-KO mice or Nrf2 inducers, blooming evidence has indicated the important protection by Nrf2 from cardiac pathogenesis in the diabetes. Therefore, this brief review summarizes the status of studies on Nrf2's role in preventing DCM and even other complications, the need for new and safe Nrf2 inducer screening and the precaution for the undesirable side of Nrf2 under certain conditions.
PMCID: PMC4209347  PMID: 25349820
Antioxidant therapy; Diabetic cardiomyopathies; Nrf2; Oxidative stress
17.  Screening of Autonomic Neuropathy in Patients with Type 2 Diabetes 
Diabetes & Metabolism Journal  2014;38(5):346-348.
PMCID: PMC4209348  PMID: 25349821
18.  Relationship between the Korean Version Survey of the Autonomic Symptoms Score and Cardiac Autonomic Neuropathy Parameters in Patients with Diabetic Peripheral Neuropathy 
Diabetes & Metabolism Journal  2014;38(5):349-355.
The Survey of Autonomic Symptom (SAS) scale was reported as an easy instrument to assess the autonomic symptoms in patients with early diabetic neuropathy. In this study, we investigated the relationship between the SAS scale and the parameters of cardiac autonomic neuropathy (CAN) in Korean patients with diabetic peripheral neuropathy (DPN).
The SAS scale was tested in 30 healthy controls and 73 patients with DPN at Chonbuk National University Hospital, in Korea. The SAS score was compared to the parameters of the CAN test and the total symptom score (TSS) for DPN in patients with DPN.
The SAS symptom score and total impact score were increased in patients with DPN compared to the control group (P=0.01), particularly in sudomotor dysfunction (P=0.01), and vasomotor dysfunction (P=0.01). The SAS score was increased in patients with CAN compared to patients without CAN (P<0.05). Among the diverse CAN parameters, the valsalva ratio and postural hypotension were associated with the SAS score (P<0.05). However, there was no association between the SAS scale and TSS for DPN, and TSS for DPN did not differ between patients with and without CAN.
SAS is a simple instrument that can be used to assess autonomic symptoms in patients with diabetes and can be used as a screening tool for autonomic neuropathy, particularly for CAN.
PMCID: PMC4209349  PMID: 25349822
Autonomic neuropathy; Diabetes; Survey of autonomic symptom scale
19.  Adipose Gene Expression Profiles Related to Metabolic Syndrome Using Microarray Analyses in Two Different Models 
Diabetes & Metabolism Journal  2014;38(5):356-365.
Peroxisome proliferator-activated receptor-γ (PPAR-γ) agonist has a wide-ranging influence on multiple components of metabolic syndrome. The Otsuka Long-Evans Tokushima Fatty (OLETF) rat is a useful animal model of metabolic syndrome. To determine genes related to metabolic syndrome, we examined overlapping genes that are simultaneously decreased by PPAR-γ agonists and increased in OLETF rats using microarrays in two different models.
In the first microarray analysis, PPAR-γ agonist-treated db/db mice were compared to standard diet-fed db/db mice. In the second microarray analysis, OLETF rats were compared to Long-Evans Tokushima Otsuka (LETO) rats (control of OLETF rats).
Among the overlapping genes, in the present study, we validated that lipocalin-2 expression was significantly decreased in the visceral adipose tissue of PPAR-γ agonist-treated db/db mice compared to standard diet-fed db/db mice and increased in OLETF rats compared to LETO rats using real time reverse transcription polymerase chain reaction. Furthermore, we showed for the first time that lipocalin-2 expression was significantly increased in the visceral adipose tissues of obese humans compared with nonobese humans. In addition, the expression level of lipocalin-2 in human visceral adipose tissue had a significant positive correlation with body mass index, serum interleukin-6, adipocyte fatty acid binding protein levels, and white blood cell count.
Lipocalin-2 was confirmed to be a significant adipokine affected by PPAR-γ agonist and obesity in the present study. Also, for the first time in human visceral adipose tissue, it was determined that the expression of lipocalin-2 from obese humans was significantly increased and correlated with circulating inflammatory markers.
PMCID: PMC4209350  PMID: 25349823
Lipocalin-2; Microarray; PPAR gamma
20.  Effect of Livingstone Potato (Plectranthus esculenthus N.E.Br) on Diabetes and Its Complications in Streptozotocin Induced Diabetes in Rats 
Diabetes & Metabolism Journal  2014;38(5):366-374.
The effect of livingstone potato (Plectranthus esculenthus N.E.Br) on diabetes and its complications in Streptozotocin induced diabetic rats was investigated. The duration of the experiment was 4 weeks.
The blood glucose level of the rats was measured with a glucometer, the protein and glucose and specific gravity in the urine samples of the rats were measured using urine assay strips and urinometer respectively. The liver and kidney function parameters in the serum of the rats were determined using Biosystem Kits.
The diabetic rats given livingstonepotato incorporated feeds, had 129.7% decrease in their hyperglycemia with corresponding amelioration of their elevated urinary protein, sugars, specific gravity, renal growth, liver growth as well as 15.64% decrease in body weights compared with the nondiabetic rats that had 5.54% decrease in blood glucose and 20.39% increase in body weight unlike the diabetic control rats that had 18.34% decrease in blood glucose and 52.68% decrease in body weight. There were significant differences (P<0.05) in the relative liver, pancreas, and kidney weights of the diabetic rats given livingstone potato feeds compared with the diabetic control while there were no significant differences (P>0.05) in the relative heart weights of all the rats in the three different groups. In terms of liver and kidney function parameters, values obtained for the diabetic rats given livingstone potato incorporated feeds were not significantly different from that of the nondiabetic rats except for total bilurubin, aspartate transaminase, and creatinine (P>0.05) while they were significantly different from the values obtained for the diabetic control rats (P<0.05). In addition, the serum amylase of the diabetic control rats were significantly higher (P<0.05) than that of the nondiabetic and diabetic rats treated with livingstone potato incorporated feeds.
Results show the antidiabetic actions of livingstone potato and its ability to ameliorate glomerular complication and liver hypertrophy in diabetics.
PMCID: PMC4209351  PMID: 25349824
Diabetic complications; Incorporated feeds; Livingstonepotato; Rats; Streptozotocin
21.  Clinical Characteristics of Diabetic Patients Transferred to Korean Referral Hospitals 
Diabetes & Metabolism Journal  2014;38(5):388-394.
We evaluated the disease profile and clinical management, including the status of both glycemic control and complications, in patients with diabetes who were transferred to referral hospitals in Korea.
Patients referred to 20 referral hospitals in Gyeongsangnam/Gyeongsangbuk-do and Jeollanam/Jeollabuk-do with at least a 1-year history of diabetes between January and June 2011 were retrospectively reviewed using medical records, laboratory tests, and questionnaires.
A total of 654 patients were enrolled in the study. In total, 437 patients (67%) were transferred from clinics and 197 (30%) patients were transferred from hospitals. A total of 279 patients (43%) visited higher medical institutions without a written medical request. The main reason for the referral was glycemic control in 433 patients (66%). Seventy-three patients (11%) had received more than one session of diabetic education. Only 177 patients (27%) had been routinely self-monitoring blood glucose, and 146 patients (22%) were monitoring hemoglobin A1c. In addition, proper evaluations for diabetic complications were performed for 74 patients (11%). The most common complication was neuropathy (32%) followed by nephropathy (31%). In total, 538 patients (82%) had been taking oral hypoglycemic agents. A relatively large number of patients (44%) had been taking antihypertensive medications.
We investigated the clinical characteristics of diabetic patients and identified specific problems in diabetic management prior to the transfer. We also found several problems in the medical system, which were divided into three medical institutions having different roles in Korea. Our findings suggested that the relationships among medical institutions have to be improved, particularly for diabetes.
PMCID: PMC4209353  PMID: 25349826
Diabetes mellitus; Korea; Referral and consultation
22.  Background and Data Configuration Process of a Nationwide Population-Based Study Using the Korean National Health Insurance System 
Diabetes & Metabolism Journal  2014;38(5):395-403.
The National Health Insurance Service (NHIS) recently signed an agreement to provide limited open access to the databases within the Korean Diabetes Association for the benefit of Korean subjects with diabetes. Here, we present the history, structure, contents, and way to use data procurement in the Korean National Health Insurance (NHI) system for the benefit of Korean researchers.
The NHIS in Korea is a single-payer program and is mandatory for all residents in Korea. The three main healthcare programs of the NHI, Medical Aid, and long-term care insurance (LTCI) provide 100% coverage for the Korean population. The NHIS in Korea has adopted a fee-for-service system to pay health providers. Researchers can obtain health information from the four databases of the insured that contain data on health insurance claims, health check-ups and LTCI.
Metabolic disease as chronic disease is increasing with aging society. NHIS data is based on mandatory, serial population data, so, this might show the time course of disease and predict some disease progress, and also be used in primary and secondary prevention of disease after data mining.
The NHIS database represents the entire Korean population and can be used as a population-based database. The integrated information technology of the NHIS database makes it a world-leading population-based epidemiology and disease research platform.
PMCID: PMC4209354  PMID: 25349827
National Health Insurance; National Health Insurance Service; Population-based data; Korea
23.  Genome-Wide Association Study Identifies Two Novel Loci with Sex-Specific Effects for Type 2 Diabetes Mellitus and Glycemic Traits in a Korean Population 
Diabetes & Metabolism Journal  2014;38(5):375-387.
Until recently, genome-wide association study (GWAS)-based findings have provided a substantial genetic contribution to type 2 diabetes mellitus (T2DM) or related glycemic traits. However, identification of allelic heterogeneity and population-specific genetic variants under consideration of potential confounding factors will be very valuable for clinical applicability. To identify novel susceptibility loci for T2DM and glycemic traits, we performed a two-stage genetic association study in a Korean population.
We performed a logistic analysis for T2DM, and the first discovery GWAS was analyzed for 1,042 cases and 2,943 controls recruited from a population-based cohort (KARE, n=8,842). The second stage, de novo replication analysis, was performed in 1,216 cases and 1,352 controls selected from an independent population-based cohort (Health 2, n=8,500). A multiple linear regression analysis for glycemic traits was further performed in a total of 14,232 nondiabetic individuals consisting of 7,696 GWAS and 6,536 replication study participants. A meta-analysis was performed on the combined results using effect size and standard errors estimated for stage 1 and 2, respectively.
A combined meta-analysis for T2DM identified two new (rs11065756 and rs2074356) loci reaching genome-wide significance in CCDC63 and C12orf51 on the 12q24 region. In addition, these variants were significantly associated with fasting plasma glucose and homeostasis model assessment of β-cell function. Interestingly, two independent single nucleotide polymorphisms were associated with sex-specific stratification in this study.
Our study showed a strong association between T2DM and glycemic traits. We further observed that two novel loci with multiple diverse effects were highly specific to males. Taken together, these findings may provide additional insights into the clinical assessment or subclassification of disease risk in a Korean population.
PMCID: PMC4209352  PMID: 25349825
Genome-wide association study; Glycemic trait; Sex-specific; Type 2 diabetes
24.  FGF21 as a Stress Hormone: The Roles of FGF21 in Stress Adaptation and the Treatment of Metabolic Diseases 
Diabetes & Metabolism Journal  2014;38(4):245-251.
Fibroblast growth factor 21 (FGF21) is an endocrine hormone that is primarily expressed in the liver and exerts beneficial effects on obesity and related metabolic diseases. In addition to its remarkable pharmacologic actions, the physiological roles of FGF21 include the maintenance of energy homeostasis in the body in conditions of metabolic or environmental stress. The expression of FGF21 is induced in multiple organs in response to diverse physiological or pathological stressors, such as starvation, nutrient excess, autophagy deficiency, mitochondrial stress, exercise, and cold exposure. Thus, the FGF21 induction caused by stress plays an important role in adaptive response to these stimuli. Here, we highlight our current understanding of the functional importance of the induction of FGF21 by diverse stressors as a feedback mechanism that prevents excessive stress.
PMCID: PMC4160577  PMID: 25215270
Fibroblast growth factor 21; Insulin resistance; Mitochondria; Obesity; Stress
25.  Diabetic Kidney Disease: From Epidemiology to Clinical Perspectives 
Diabetes & Metabolism Journal  2014;38(4):252-260.
With worldwide epidemic of diabetes mellitus, diabetic nephropathy which is one of the major causes of microvascular complication has become a serious concern in Korea as well as the rest of the world. In view of its significance, there is an urgent and paramount need for proper managements that could either deter or slow the progression of diabetic nephropathy. Despite advances in care, ever increasing number of patients suffering from diabetic kidney disease and from end-stage renal disease implies that the current management is not adequate in many aspects. The reasons for these inadequacies compromise lack of early diagnosis, failure to intervene with timely and aggressive manner, and lack of understanding on the kind of interventions required. Another issue equally important for the adequate care of patients with diabetic nephropathy is an understanding of past, present and future epidemiology of diabetic nephropathy which serves, especially in Korea, as a material determining standard diagnosis and treatment and a national health-policy decision.
PMCID: PMC4160578  PMID: 25215271
Cardiovascular disorder; Diabetic nephropathies; Renal insufficiency, chronic; Renal replacement therapy

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