Tae Jung Oh

Differences in the HbA1c‐lowering efficacy of glucagon‐like peptide‐1 analogues between Asians and non‐Asians: a systematic review and meta‐analysis

To compare the HbA1c‐lowering efficacy of glucagon‐like peptide‐1 (GLP‐1) analogues between Asians and non‐Asians with type 2 diabetes.

Increasing Trend in the Number of Severe Hypoglycemia Patients in Korea

Background To investigate whether the number of subjects with severe hypoglycemia who are brought to a hospital emergency department is increasing and to identify whether there have been changes in the demographic and clinical characteristics of those subjects. Methods We analyzed data from the Emergency Departments of two general hospitals in Seoul, Korea. We included data from all adult subjects with type 2 diabetes who presented to an emergency department with severe hypoglycemia between January 1, 2004 and December 30, 2009. Results A total of 740 cases of severe hypoglycemia were identified. The mean subject age was 69±12 years, mean duration of diabetes was 13.8±9.3 years, and 53.2% of subjects were receiving insulin therapy. We observed a sharp rise in the number of cases between 2006 and 2007. Stages 3-5 chronic kidney disease was diagnosed in 31.5% of subjects, and low C-peptide levels (<0.6 ng/mL) were found in 25.5%. The mean subject age, duration of diabetes, HbA1c level, and renal and insulin secretory function values did not change significantly during the study period. The proportion of glimepiride use increased, while use of gliclazide decreased among sulfonylurea users. Use of insulin analogues increased, while use of NPH/RI decreased among insulin users. Conclusion We identified a sharp increase in the number of subjects with severe hypoglycemia presenting to an emergency room since 2006. The clinical characteristics of these subjects did not change markedly during the study period. Nationwide studies are warranted to further clarify this epidemic of severe hypoglycemia.

Long-term oral exposure to bisphenol A induces glucose intolerance and insulin resistance

Bisphenol A (BPA) is a widely used endocrine disruptor. Recent epidemiologic results have suggested an association between exposure to BPA and cardiovascular disease, type 2 diabetes, and obesity. We investigated the in vivo effects of long-term oral exposure to BPA on insulin resistance and glucose intolerance. In the present study, 4- to 6-week-old male mice on a high-fat diet (HFD) were treated with 50 μg/kg body weight per day of BPA orally for 12 weeks. Long-term oral exposure to BPA along with an HFD for 12 weeks induced glucose intolerance in growing male mice. Intraperitoneal glucose tolerance tests showed that the mice that received an HFD and BPA exhibited a significantly larger area under the curve than did those that received an HFD only (119.9±16.8 vs. 97.9±18.2 mM/min, P=0.027). Body weight, percentage of white adipose tissue, and percentage of body fat did not differ between the two groups of mice. However, treatment with BPA reduced Akt phosphorylation at position Thr308 and GSK3β phosphorylation at position Ser9 in skeletal muscle. BPA tended to decrease serum adiponectin levels and to increase serum interleukin 6 and tumor necrosis factor α, although these findings were not statistically significant. Treatment with BPA did not induce any detrimental changes in the islet area or morphology or the insulin content of β cells. In conclusion, long-term oral exposure to BPA induced glucose intolerance and insulin resistance in growing mice. Decreased Akt phosphorylation in skeletal muscle by way of altered serum adipocytokine levels might be one mechanism by which BPA induces glucose intolerance.

Mechanistic link between nonalcoholic fatty liver disease and cardiometabolic disorders

Nonalcoholic fatty liver disease (NAFLD) is a chronic condition characterized by fat accumulation combined with low-grade inflammation in the liver. A large body of clinical and experimental data shows that increased flux of free fatty acids from increased visceral adipose tissue can lead to NAFLD related with insulin resistance. Thus, individuals with obesity, insulin resistance, and dyslipidemia are at the greatest risk of developing NAFLD. Conversely, NAFLD is one of the phenotypes of insulin resistance or metabolic syndrome. Many researchers have discovered a close association between NAFLD and insulin resistance, and focused on the role of NAFLD in the development of type 2 diabetes. Further, substantial evidence has suggested the association between NAFLD and cardiovascular disease (CVD). In the current review, we provide a plausible mechanistic link between NAFLD and CVD and the potential of the former as a therapeutic target based on pathophysiology. We also discuss in detail about the role of insulin resistance, oxidative stress, low-grade inflammation, abnormal lipid metabolism, gut microbiota, changes of biomarkers, and genetic predisposition in the pathological linking between NAFLD and cardiometabolic disorders.

The incretin effect in Korean subjects with normal glucose tolerance or type 2 diabetes

The incretin effect is known to be decreased in type 2 diabetes. However, there are limited data on the incretin effect in non‐Caucasian subjects. Because Asian patients with type 2 diabetes are characterized by decreased insulin secretion, this study set out to examine the incretin effect in Korean subjects with normal glucose tolerance (NGT) or type 2 diabetes.

Prevalence and Clinical Characteristics of Recently Diagnosed Type 2 Diabetes Patients with Positive Anti-Glutamic Acid Decarboxylase Antibody

Background Latent autoimmune diabetes in adults (LADA) refers to a specific type of diabetes characterized by adult onset, presence of islet auto-antibodies, insulin independence at the time of diagnosis, and rapid decline in β-cell function. The prevalence of LADA among patients with type 2 diabetes varies from 2% to 20% according to the study population. Since most studies on the prevalence of LADA performed in Korea were conducted in patients who had been tested for anti-glutamic acid decarboxylase antibody (GADAb), a selection bias could not be excluded. In this study, we examined the prevalence and clinical characteristics of LADA among adult patients recently diagnosed with type 2 diabetes. Methods We included 462 patients who were diagnosed with type 2 diabetes within 5 years from the time this study was performed. We measured GADAb, fasting insulin level, fasting C-peptide level, fasting plasma glucose level, HbA1c, and serum lipid profiles and collected data on clinical characteristics. Results The prevalence of LADA was 4.3% (20/462) among adult patients with newly diagnosed type 2 diabetes. Compared with the GADAb-negative patients, the GADAb-positive patients had lower fasting C-peptide levels (1.2±0.8 ng/mL vs. 2.0±1.2 ng/mL, P=0.004). Other metabolic features were not significantly different between the two groups. Conclusion The prevalence of LADA is 4.3% among Korean adult patients with recently diagnosed type 2 diabetes. The Korean LADA patients exhibited decreased insulin secretory capacity as reflected by lower C-peptide levels.

Glucagon-Like Peptide-1 Increases Mitochondrial Biogenesis and Function in INS-1 Rat Insulinoma Cells.

Glucagon-like peptide-1 (GLP-1) is a gut-derived incretin hormone that increases glucose-stimulated insulin secretion in pancreatic β-cells. Since mitochondrial function is crucial to insulin secretion, we hypothesized that GLP-1 may increase mitochondrial biogenesis in pancreatic β-cells. We treated INS-1 rat insulinoma cells with GLP-1 or exendin-4 for 48 hours and measured mitochondrial mass and function. Both GLP-1 and exendin-4 increased mitochondrial mass by approximately 20%. The mitochondria/cytosol ratio was increased from 7.60±3.12% to 10.53±2.70% by exendin-4. In addition, GLP-1 increased the mitochondrial membrane potential and oxygen consumption. Proliferator-activated receptor-gamma coactivator 1α expression was increased approximately 2-fold by GLP-1 treatment. In conclusion, the present study presents evidence for a new mechanism of action by which GLP-1 improves pancreatic β-cell function via enhanced mitochondrial mass and performance.

Efficacy and safety of the addition of a dipeptidyl peptidase-4 inhibitor to insulin therapy in patients with type 2 diabetes: A systematic review and meta-analysis

AIMS To compare the efficacy and safety of the addition of a dipeptidyl peptidase-4 (DPP-4) inhibitor or a placebo in patients with type 2 diabetes inadequately controlled with insulin. METHODS We searched randomised controlled trials (RCTs) from MEDLINE, EMBASE, LILACS, the Cochrane Central Register of Controlled Trials and the ClinicalTrials.gov online registry. Studies of at least 12week treatment duration were eligible if they were RCTs in patients with type 2 diabetes comparing addition of a DPP-4 inhibitor to insulin therapy (INS/DPP4i) with addition of a placebo to insulin therapy (INS/PCB) and contained information on the change in glycated haemoglobin (HbA1c) from baseline. RESULTS Of 3105 potentially relevant published articles and 206 registered trials, 9 studies were included for meta-analysis. Compared to INS/PCB, INS/DPP4i exhibited a greater reduction in HbA1c (weighted mean difference [WMD] -0.58%; 95% CI -0.70, -0.46) and fasting plasma glucose (WMD -0.59mmol/L; 95% CI -0.79, -0.40) with less daily insulin doses (WMD -1.86IU; 95% CI -3.27, -0.45) and with no difference in weight gain (WMD -0.04kg; 95% CI -0.25, 0.16). The risk of hypoglycaemia was similar between INS/DPP-4i and INS/PCB (the RR in favour of INS/PCB was 0.94; 95% CI 0.84, 1.05). CONCLUSIONS Compared to placebo, DPP-4 inhibitors exhibit a better glycaemic control without further increasing the risk of weight gain and hypoglycaemia in patients with type 2 diabetes inadequately controlled with insulin.

One-hour postload plasma glucose concentration in people with normal glucose homeostasis predicts future diabetes mellitus: a 12-year community-based cohort study

In Caucasians, plasma glucose concentration at 1 h during an oral glucose tolerance test (OGTT) may be a better predictor of future diabetes mellitus than the fasting or 2‐h postload glucose concentration. We investigated whether the 1‐h glucose concentration could be used to predict future diabetes mellitus in Asian ethnicity.

Clinical Characteristics of the Responders to Dipeptidyl Peptidase-4 Inhibitors in Korean Subjects with Type 2 Diabetes

We investigated characteristics associated with the efficacy of dipeptidyl peptidase-4 inhibitors (DPP4i) in Korean patients with type 2 diabetes. We reviewed medical records of 477 patients who had taken sitagliptin or vildagliptin longer than 40 weeks. Response to DPP4i was evaluated with HbA1c change after therapy (ΔHbA1c). The Students t-test between good responders (GR: ΔHbA1c > 1.0%) and poor responders (PR: ΔHbA1c < 0.5%), a correlation analysis among clinical parameters, and a linear multivariate regression analysis were performed. The mean age was 60 yr, duration of diabetes 11 yr and HbA1c was 8.1%. Baseline fasting plasma glucose (FPG), HbA1c, C-peptide, and creatinine were significantly higher in the GR compared to the PR. Duration of diabetes, FPG, HbA1c, C-peptide and creatinine were significantly correlated with ΔHbA1c. In the multivariate analysis, age (r2 = 0.006), duration of diabetes (r2 = 0.019), HbA1c (r2 = 0.296), and creatinine levels (r2 = 0.024) were independent predictors for the response to DPP4i. Body mass index and insulin resistance were not associated with the response to DPP4i. In conclusion, better response to DPP4i would be expected in Korean patients with type 2 diabetes who have higher baseline HbA1c and creatinine levels with shorter duration of diabetes.