Yong-ho Lee

Association between polymorphisms in SLC30A8, HHEX, CDKN2A/B, IGF2BP2, FTO, WFS1, CDKAL1, KCNQ1 and type 2 diabetes in the Korean population

AbstractAccording to recent genome-wide association studies, a number of single nucleotide polymorphisms (SNPs) are reported to be associated with type 2 diabetes mellitus (T2DM). The aim of the present study was to investigate the association among the polymorphisms of SLC30A8, HHEX, CDKN2A/B, IGF2BP2, FTO, WFS1, CDKAL1 and KCNQ1 and the risk of T2DM in the Korean population. This study was based on a multicenter case-control study, including 908 patients with T2DM and 502 non-diabetic controls. We genotyped rs13266634, rs1111875, rs10811661, rs4402960, rs8050136, rs734312, rs7754840 and rs2237892 and measured the body weight, body mass index and fasting plasma glucose in all patients and controls. The strongest association was found in a variant of CDKAL1 [rs7754840, odds ratio (OR) = 1.77, 95% CI = 1.50–2.10, p = 5.0 × 10−11]. The G allele of rs1111875 (OR = 1.43, 95% CI = 1.18–1.72, p = 1.8 × 10−4) in HHEX), the T allele of rs10811661 (OR = 1.47, 95% CI = 1.23–1.75, p = 2.1 × 10−5) in CDKN2A/B) and the C allele of rs2237892 (OR = 1.31, 95% CI = 1.10–1.56, p = 0.003) in KCNQ1 showed significant associations with T2DM. Rs13266634 (OR = 1.19, 95% CI = 1.00–1.42, p = 0.045) in SLC30A8 showed a nominal association with the risk of T2DM, whereas SNPs in IGF2BP2, FTO and WFS1 were not associated. In conclusion, we have shown that SNPs in HHEX, CDKN2A/B, CDKAL1, KCNQ1 and SLC30A8 confer a risk of T2DM in the Korean population.

Effects of leptin and adiponectin on pancreatic β-cell function.

Leptin and adiponectin are hormones secreted from adipocytes that have important roles in metabolism and energy homeostasis. This review evaluates the effects of leptin and adiponectin on β-cell function by analyzing and compiling results from human clinical trials and epidemiologic studies as well as in vitro and in vivo experiments. Leptin has been shown to inhibit ectopic fat accumulation and thereby prevent β-cell dysfunction and protect the β-cell from cytokine- and fatty acid-induced apoptosis. However, leptin suppresses insulin gene expression and secretion as well as glucose transport into the β-cell. Adiponectin stimulates insulin secretion by enhancing exocytosis of insulin granules and upregulating the expression of the insulin gene; however, this effect depends on the prevailing glucose concentration and status of insulin resistance. In addition, adiponectin has antiapoptotic properties in β-cells. Available evidence concerning the role of these adipokines on insulin secretion, insulin gene expression, and apoptosis is not always entirely consistent; and many fundamental questions remain to be answered by future studies.

Korean red ginseng (Panax ginseng) improves insulin sensitivity and attenuates the development of diabetes in Otsuka Long-Evans Tokushima fatty rats.

Ginseng has been reported to ameliorate hyperglycemia in experimental and clinical studies; however, its mechanism of action remains unclear. In this study, we investigated the metabolic effects and putative molecular mechanisms of Korean red ginseng (KRG, Panax ginseng) in animal models for type 2 diabetes mellitus (T2DM) and peripheral insulin-responsive cell lines. Korean red ginseng was administered orally at a dose of 200 mg/(kg d) to Otsuka Long-Evans Tokushima fatty rats for 40 weeks. Initially, chronic administration of KRG reduced weight gain and visceral fat mass in the early period without altering food intake. The KRG-treated Otsuka Long-Evans Tokushima fatty rats showed improved insulin sensitivity and significantly preserved glucose tolerance compared with untreated control animals up to 50 weeks of age, implying that KRG attenuated the development of overt diabetes. KRG promoted fatty acid oxidation by the activation of adenosine monophosphate-activated protein kinase (AMPK) and phosphorylation of acetyl-coenzyme A carboxylase in skeletal muscle and cultured C2C12 muscle cells. Increased expression of peroxisome proliferator-activated receptor-gamma coactivator-1alpha, nuclear respiratory factor-1, cytochrome c, cytochrome c oxidase-4, and glucose transporter 4 by KRG treatment indicates that activated AMPK also enhanced mitochondrial biogenesis and glucose utilization in skeletal muscle. Although these findings suggest that KRG is likely to have beneficial effects on the amelioration of insulin resistance and the prevention of T2DM through the activation of AMPK, further clinical studies are required to evaluate the use of KRG as a supplementary agent for T2DM.

Metformin alleviates hepatosteatosis by restoring SIRT1-mediated autophagy induction via an AMP-activated protein kinase-independent pathway

Metformin activates both PRKA and SIRT1. Furthermore, autophagy is induced by either the PRKA-MTOR-ULK1 or SIRT1-FOXO signaling pathways. We aimed to elucidate the mechanism by which metformin alleviates hepatosteatosis by examining the molecular interplay between SIRT1, PRKA, and autophagy. ob/ob mice were divided into 3 groups: one with ad libitum feeding of a standard chow diet, one with 300 mg/kg intraperitoneal metformin injections, and one with 3 g/d caloric restriction (CR) for a period of 4 wk. Primary hepatocytes or HepG2 cells were treated with oleic acid (OA) plus high glucose in the absence or presence of metformin. Both CR and metformin significantly improved body weight and glucose homeostasis, along with hepatic steatosis, in ob/ob mice. Furthermore, CR and metformin both upregulated SIRT1 expression and also stimulated autophagy induction and flux in vivo. Metformin also prevented OA with high glucose-induced suppression of both SIRT1 expression and SIRT1-dependent activation of autophagy machinery, thereby alleviating intracellular lipid accumulation in vitro. Interestingly, metformin treatment upregulated SIRT1 expression and activated PRKA even after siRNA-mediated knockdown of PRKAA1/2 and SIRT1, respectively. Taken together, these results suggest that metformin alleviates hepatic steatosis through PRKA-independent, SIRT1-mediated effects on the autophagy machinery.

Sarcopaenia is associated with NAFLD independently of obesity and insulin resistance: Nationwide surveys (KNHANES 2008-2011).

BACKGROUND & AIMS Although sarcopaenia is associated with obesity-related comorbidities, its influence on non-alcoholic fatty liver disease (NAFLD) or steatohepatitis has not been fully determined. We aimed to investigate the direct relationship between sarcopaenia and NAFLD or steatohepatitis in the general population. METHODS We conducted a cross-sectional study using nationally representative samples of 15,132 subjects from the Korea National Health and Nutrition Examination Surveys 2008-2011. Subjects were defined as having NAFLD when they had higher scores from previously validated NAFLD prediction models such as the hepatic steatosis index, comprehensive NAFLD score and NAFLD liver fat score. BARD and FIB-4 scores were used to define advanced fibrosis in subjects with NAFLD. The skeletal muscle index (SMI) [SMI(%)=total appendicular skeletal muscle mass (kg)/weight (kg)×100] measured by dual-energy X-ray absorptiometry was used to diagnose sarcopaenia with cut points of 32.2% for men and 25.5% for women. RESULTS SMI was inversely correlated with all NAFLD predicting scores (Ps<0.001). After stratification, sarcopaenic subjects had an increased risk of NAFLD regardless of obesity (odds ratios [ORs]=1.55 to 3.02, depending on models; all Ps<0.001) or metabolic syndrome (ORs=1.63 to 4.00, all Ps<0.001). Multiple logistic regression analysis also demonstrated this independent association between sarcopaenia and NAFLD after adjusting for confounding factors related to obesity or insulin resistance (ORs=1.18 to 1.22, all Ps<0.001). Furthermore, among the NAFLD population, subjects with lower SMIs were likely to have advanced fibrosis compared with non-sarcopaenic individuals (BARD and FIB-4: ORs=1.83 and 1.69, respectively; both Ps<0.001). Compared with non-exercised subjects, individuals who exercised regularly had a lower risk of NAFLD (p<0.001), particularly among obese people with well-preserved muscle mass. CONCLUSIONS Sarcopaenia is associated with increased risks of NAFLD and advanced fibrosis, independent of obesity or metabolic control.

A Simple Screening Score for Diabetes for the Korean Population Development, validation, and comparison with other scores

OBJECTIVE We developed and validated a self-assessment score for diabetes risk in Korean adults and compared it with other established screening models. RESEARCH DESIGN AND METHODS The Korea National Health and Nutrition Examination Survey (KNHANES) 2001 and 2005 data were used to develop a diabetes screening score. After excluding patients with known diabetes, 9,602 participants aged ≥20 years were selected. Undiagnosed diabetes was defined as a fasting plasma glucose ≥126 mg/dL and/or nonfasting plasma glucose ≥200 mg/dL. The SAS Survey Logistic Regression analysis was used to determine predictors of undiagnosed diabetes (n = 341). We validated our model and compared it with other existing methods using the KNHANES 2007–2008 data (n = 8,391). RESULTS Age, family history of diabetes, hypertension, waist circumference, smoking, and alcohol intake were independently associated with undiagnosed diabetes. We calculated a diabetes screening score (range 0–11), and a cut point of ≥5 defined 47% of adults as being at high risk for diabetes and yielded a sensitivity of 81%, specificity of 54%, positive predictive value of 6%, and positive likelihood ratio of 1.8 (area under the curve [AUC] = 0.73). Comparable results were obtained in validation datasets (sensitivity 80%, specificity 53%, and AUC = 0.73), showing better performance than other non-Asian models from the U.S. or European population. CONCLUSIONS This self-assessment score may be useful for identifying Korean adults at high risk for diabetes. Additional studies are needed to evaluate the utility and feasibility of this score in various settings.

Visceral adiposity and the severity of coronary artery disease in middle-aged subjects with normal waist circumference and its relation with lipocalin-2 and MCP-1

OBJECTIVE Visceral adipose tissue has emerged as a key organ contributing to the development of coronary artery disease (CAD). However, defining central obesity by waist circumference (WC) may underestimate visceral adiposity in lean patients. The aim of this study was to investigate the relationship between visceral adiposity and severity of CAD in subjects with normal WC. METHODS Among 365 patients with documented CAD, 90 male subjects with normal WC (<90 cm) were selected and their visceral fat areas (VFA) were examined using computed tomography. Lipid profiles and levels of adipokines including lipocalin-2, high molecular weight adiponectin, and monocyte chemoattractant protein (MCP)-1 were measured. Patients were divided into tertiles based on VFA at the L4 vertebra level. RESULTS Patients with single-vessel disease had significantly lower VFA than those with multi-vessel disease (P<0.05; 86.0 vs. 97.5 vs. 99.6 cm(2) for single- , double- , and triple-vessel diseases, respectively). Positive association between the extent of CAD and VFA was clearly demonstrated and logistic regression analysis showed that subjects in the upper tertile for VFA had a 4.5-fold higher risk of having multi-vessel disease compared with those in the lowest tertile (P<0.05; odds ratio=4.51; 95% confidence interval=1.10-18.45). Circulating levels of lipocalin-2 and MCP-1 were significantly higher in the upper tertiles of VFA. CONCLUSION Increased visceral adiposity is significantly associated with the severity of CAD, even in subjects without central obesity as determined by WC measurements. Abnormalities in adipokine regulation may provide a novel mechanistic connection between visceral adiposity and associated cardiovascular complications.

Sarcopenia is associated with significant liver fibrosis independently of obesity and insulin resistance in nonalcoholic fatty liver disease: Nationwide surveys (KNHANES 2008-2011)

Sarcopenia is associated with nonalcoholic fatty liver disease (NAFLD). This study investigated whether sarcopenia is associated with significant liver fibrosis in subjects with NAFLD. Data from the Korean National Health and Nutrition Examination Surveys 2008‐2011 database were analyzed. NALFD was defined by NAFLD liver fat score, comprehensive NAFLD score, or hepatic steatosis index. Degree of liver fibrosis was assessed by NAFLD fibrosis score (NFS), FIB‐4, and Forns index. Significant liver fibrosis was defined as FIB‐4 ≥2.67 and the highest quartile values of NFS and Forns index. Sarcopenia index (= total appendicular skeletal muscle mass [kg]/body mass index (kg/m2]) was calculated using dual‐energy X‐ray absorptiometry. Using the NAFLD liver fat score, NAFLD was identified in 2761 (28.5%) of 9676 subjects. Of subjects with NAFLD, sarcopenia was identified in 337 (12.2%). Sarcopenia was significantly associated with significant liver fibrosis assessed in fibrosis prediction models (all P < 0.05). In subgroups stratified according to body mass index and homeostasis model assessment of insulin resistance, a significant association between sarcopenia and significant liver fibrosis by NFS was consistently present (odds ratio = 1.76‐2.68 depending on the subgroup, all P < 0.05). Multivariate logistic regression analysis demonstrated an independent association between SI and significant liver fibrosis by NFS after adjusting for other confounders (odds ratio = 0.52‐0.67, all P < 0.01). Other NAFLD (comprehensive NAFLD score, hepatic steatosis index) and fibrosis prediction models (FIB‐4 and Forns index) produced similar results. Conclusion: Sarcopenia is associated with significant liver fibrosis in subjects with NAFLD, and the association is independent of obesity and insulin resistance. (Hepatology 2016;63:776–786)

Protective effects of magnesium lithospermate B against diabetic atherosclerosis via Nrf2-ARE-NQO1 transcriptional pathway

Hyperglycemia-induced oxidative stress is known to play an important role in the development of several diabetic complications, including atherosclerosis. Although a number of antioxidants are available, none have been found to be suitable for regulating the oxidative stress response and enhancing antioxidative defense mechanisms. In this study, we evaluated the effects of magnesium lithospermate B (LAB) against oxidative stress. We also endeavored to identify the target molecule of LAB in vascular smooth muscle cells (VSMCs) and the underlying biochemical pathways related to diabetic atherosclerosis. Modified MTT and transwell assays showed that the increased proliferation and migration of rat aortic VSMCs in culture with high glucose was significantly inhibited by LAB. LAB also attenuated neointimal hyperplasia after balloon catheter injury in diabetic rat carotid arteries. To determine molecular targets of LAB, we studied the effects of LAB on aldose reductase (AR) activity, O-GlcNAcylation, and protein kinase C (PKC) activity in VSMCs under normoglycemic or hyperglycemic conditions and showed the improvement of major biochemical pathways by LAB. Potential involvement of the nuclear factor erythroid 2-related factor-2 (Nrf2)--antioxidant responsive element (ARE)-NAD(P)H: quinone oxidoreductase-1 (NQO1) pathway was assessed using siRNA methods. We found that LAB activates the NQO1 via the Nrf2-ARE pathway, which plays an important role in inhibition of the major molecular mechanisms that lead to vascular damage and the proliferation and migration of VSMCs. Together, these findings demonstrate that the induction of the Nrf2-ARE-NQO1 pathway by LAB could be a new therapeutic strategy to prevent diabetic atherosclerosis.

Natural therapeutic magnesium lithospermate B potently protects the endothelium from hyperglycaemia-induced dysfunction

AIMS We have investigated the effects of magnesium lithospermate B (MLB), the active compound of the Oriental herbal remedy, Salvia miltiorrhizae, on endothelial dysfunction associated with diabetes mellitus using cultured endothelial cells and an animal model of type 2 diabetes mellitus. METHODS AND RESULTS The effect of MLB on vasodilatory function in Otsuka Long-Evans Tokushima Fatty (OLETF) rats was assessed. MLB treatment for 20 weeks starting at 12 weeks attenuated the decrease in endothelium-dependent vasodilation in OLETF rats. MLB treatment also increased serum nitrite level and reduced serum advanced glycation end products concentration. The effect of MLB was greater than an equivalent dose of alpha-lipoic acid (alphaLA), a popular antioxidant treatment. MLB rescued the inhibition of endothelial nitric oxide synthase (eNOS) activity and eNOS phosphorylation in endothelial cells cultured in hyperglycaemia. This effect was dependent on Akt phosphorylation and associated with decreased O-linked N-acetylglucosamine protein modification of eNOS. MLB also increased nuclear factor erythroid 2-related factor-2 (Nrf-2) activation in a phosphoinositide 3-kinase/Akt pathway dependent manner. MLB treatment induced the expression of the Nrf-2-regulated antioxidant enzyme, heme oxygenase-1. The antioxidant alphaLA could not produce this effect. Moreover, MLB decreased oxidative stress and endothelial cell apoptosis caused by hyperglycaemia. CONCLUSION MLB is a naturally occurring, new generation antioxidant that activates eNOS and ameliorates endothelial dysfunction in diabetes by enhancing vasodilation in addition to reducing oxidative stress. The relative strong performance of MLB makes it an ideal candidate for further, expanded trials as a new generation of antioxidant to treat diabetes-related complications.