Hung Tsung Wu

Endoplasmic Reticulum Stress Induces the Expression of Fetuin-A to Develop Insulin Resistance

Fetuin-A is a biomarker reported to be important in many metabolic disorders, including obesity, diabetes, and hepatic steatosis. Although it is well known that fetuin-A is increased in diabetes and nonalcoholic fatty liver disease (NAFLD), the levels of fetuin-A in diabetic patients with NAFLD are unknown. Furthermore, the regulation of fetuin-A expression is still obscure. In this study, a total of 180 age- and sex-matched subjects with normal glucose tolerance, NAFLD, newly diagnosed diabetes (NDD), and NDD with NAFLD were recruited. We found that the levels of fetuin-A were significantly increased in NDD with NAFLD as compared with NDD or NAFLD subjects. We further used HepG2 cells to investigate the regulation of fetuin-A. Treatment with endoplasmic reticulum (ER) stress activator, thapsigargin, increased the expression of fetuin-A mRNA and protein in a time- and dose-dependent manner. Pretreatment with ER stress inhibitor, 4-phenylbutyrate, reversed high glucose or palmitate-induced fetuin-A expression. Moreover, treatment with 4-phenylbutyrate in both streptozotocin-induced and high-fat diet-induced diabetic mice not only decreased hepatic fetuin-A levels but also improved hyperglycemia. Taken together, we found that fetuin-A levels were increased in diabetes patients with NAFLD. Moreover, ER stress induced by high glucose and palmitate increased the expression of fetuin-A and further contributed to the development of insulin resistance.

Serum fetuin-A concentrations are elevated in subjects with impaired glucose tolerance and newly diagnosed type 2 diabetes

Objectiveu2002 Hepatic steatosis is associated with an increased risk of diabetes. Although the levels of serum fetuin‐A, a liver‐derived glycoprotein that impairs insulin signalling, are positively correlated with hepatic steatosis, the levels of fetuin‐A in subjects with impaired fasting glucose (IFG), impaired glucose tolerance (IGT) and newly diagnosed type 2 diabetes (NDD) have not been established. The aim of this study is to investigate the relationship among serum fetuin‐A concentrations, IFG, IGT and NDD in Chinese subjects without nonalcoholic fatty liver disease (NAFLD).

Increased Fetuin-A Concentrations in Impaired Glucose Tolerance with or without Nonalcoholic Fatty Liver Disease, But Not Impaired Fasting Glucose

CONTEXTnFetuin-A, a liver-derived glycoprotein that impairs insulin signaling, is associated with nonalcoholic fatty liver disease (NAFLD), diabetes, and the risk of cardiovascular diseases. Both prediabetes and NAFLD are associated with increased cardiovascular risk, and their concurrence significantly impairs hepatic and adipose tissue insulin sensitivity.nnnOBJECTIVEnOur objective was to investigate the relationship between serum fetuin-A levels and prediabetes in subjects with or without NAFLD.nnnDESIGNnThis was a cross-sectional case-control study.nnnPATIENTSnA total of 510 age- and sex-matched subjects with normal glucose tolerance (NGT), impaired fasting glucose (IFG), and impaired glucose tolerance (IGT) with or without NAFLD were recruited. Each subject was assessed by abdominal ultrasound to diagnose NAFLD.nnnMAIN OUTCOME MEASURESnSerum fetuin-A concentrations were compared between groups. The association with clinico-metabolic parameters was examined.nnnRESULTSnThe presence of NAFLD significantly increases fetuin-A levels in subjects with NGT and prediabetes. As compared with NGT, IGT, but not IFG, significantly increases fetuin-A levels in subjects with or without NAFLD. Serum fetuin-A concentrations were positively related to postload 2-h glucose, body mass index, triglyceride, and homeostasis model assessment of insulin resistance but negatively associated with age, high-density lipoprotein cholesterol, and adiponectin. In multiple regression analysis, age, IGT vs. NGT, and IGT with NAFLD vs. NGT were independently associated with fetuin-A levels after adjustment for cardiovascular risk factors and adiponectin.nnnCONCLUSIONSnIGT with or without NAFLD was independently associated with fetuin-A levels after adjustment for cardiometabolic risk factors. The elevated fetuin-A levels could have a clinical implication in the increased cardiovascular risk and insulin resistance associated with NAFLD and IGT.

Multiple mechanisms of GW-9508, a selective G protein-coupled receptor 40 agonist, in the regulation of glucose homeostasis and insulin sensitivity

Activation of G protein-coupled receptor 40 (GPR40) by agonists increases insulin release in isolated islets, whereas it is inconclusive whether GPR40 antagonists decrease blood glucose and increase insulin sensitivity. Although some clinical trials indicated that administration of a GPR40 agonist shows benefits in the regulation of blood glucose homeostasis, the pharmacological mechanisms of this receptor in the improvement of glycemic control remain unclear. Therefore, we used a selective GPR40 agonist, GW-9508, to clarify the role of GPR40 in the regulation of blood glucose. Bolus intraperitoneal injection of GW-9508 in mice showed a slight decrease in blood glucose, with an increase in plasma insulin levels under glucose stimuli. However, long-term treatment with low doses of GW-9508 in high-fat diet-induced (HFD) diabetic mice decreased blood glucose with decreased plasma insulin significantly and improved glucose intolerance and insulin resistance. Using small interfering ribonucleic acid to delete GPR40 in HepG2 cells, we demonstrated that GW-9508 reversed palmitate-induced insulin signaling impairment through a GPR40-dependent pathway. We also found that GW-9508 activates the Akt/GSK-3β pathway to increase glycogen levels in HepG2 cells. Furthermore, administration of GW-9508 decreased the hepatic expression of fetuin-A in HFD mice significantly and regulated high-glucose- or palmitate-induced fetuin-A expression to increase insulin sensitivity through a GPR40/PLC/PKC pathway in HepG2 cells. Taken together, GW-9508 exerts a partial agonist effect to regulate blood glucose through multiple mechanisms. Investigation of chemicals that act on GPR40 might be a new strategy for the treatment of diabetes.

The role of Hepassocin in the development of non-alcoholic fatty liver disease

BACKGROUND & AIMSnWhile non-alcoholic fatty liver disease (NAFLD) is the most common risk factor of chronic liver disease, the mechanisms that initiate its development are obscure. Hepassocin (HPS) is a hepatokine that has been reported to be involved in liver regeneration. In addition to the mitogenic activity of HPS, HPS expression is decreased in patients with hepatoma. However, the role of HPS in NAFLD is still unknown.nnnMETHODSnA total of 393 subjects with (n=194) or without (n=199) NAFLD were enrolled to evaluate the serum HPS concentration. In order to clarify the causal inference between HPS and NAFLD, we used experimental animal and cell models. Hepatic overexpression or silencing of HPS was achieved by lentiviral vector delivery in mice and lipofectamine transfection in HepG2 cells. Lipogenesis related proteins were detected by Western blots. The expression of inflammatory factors was determined by real-time polymerase chain reaction.nnnRESULTSnSubjects with NAFLD had a higher serum HPS concentration than those without it. Overexpression of HPS increased hepatic lipid accumulation and NAFLD activity scores (NAS), whereas deletion of HPS improved high fat diet-induced hepatic steatosis and decreased NAS in mice. Additionally, oleic acid, a steatogenic reagent, increased HPS expression in hepatocytes. Furthermore, overexpression of HPS in HepG2 cells induced lipid accumulation through an extracellular signal-regulated kinase 1/2 (ERK1/2)-dependent pathway, whereas deletion of HPS decreased oleic acid-induced lipid accumulation.nnnCONCLUSIONSnThe present study provides evidence that HPS plays an important role in NAFLD and induces hepatic lipid accumulation through an ERK1/2-dependent pathway.

A novel hepatokine, HFREP1, plays a crucial role in the development of insulin resistance and type 2 diabetes

Aims/hypothesisType 2 diabetes is highly correlated with nonalcoholic fatty liver disease (NAFLD). Hepatocyte-derived fibrinogen-related protein 1 (HFREP1) is a hepatokine that mediates NAFLD development; however, the role of HFREP1 in the development of insulin resistance and diabetes remains obscure.MethodsA total of 193 age- and sex-matched participants with normal glucose tolerance, impaired fasting glucose (IFG), impaired glucose tolerance (IGT) and newly diagnosed diabetes (NDD) were recruited for a cross-sectional study. Plasma HFREP1 levels were measured and multivariate linear regression analysis was used to evaluate the relationship between HFREP1, IFG, IGT and NDD. The causal relationship between HFREP1 and insulin resistance was then investigated in animal and cell models. Glucose and insulin tolerance tests, and euglycaemic–hyperinsulinaemic clamp, were used to evaluate insulin sensitivity in animals with Hfrep1 overexpression or knockdown in liver by lentiviral vectors. HepG2 cells were used to clarify the possible mechanism of HFREP1-induced insulin resistance.ResultsPlasma HFREP1 concentrations were significantly increased in participants with IFG, IGT and NDD. HFREP1 concentrations were independently associated with fasting plasma glucose levels, insulin resistance, IFG, IGT and NDD. Injection of recombinant HFREP1 or Hfrep1 overexpression induced insulin resistance in mice, and HFREP1 disrupted insulin signalling to induce insulin resistance through an extracellular signal-regulated kinase (ERK)1/2-dependent pathway. Moreover, hepatic knockdown of HFREP1 improved insulin resistance in both mice fed a high-fat diet and ob/ob mice.Conclusions/interpretationThese findings highlight the crucial role of HFREP1 in insulin resistance and diabetes, and provide a potential strategy and biomarker for developing therapeutic approaches to combat these diseases.

In vivo and in vitro anti-tumor effects of fungal extracts

Fungal extracts are extensively used as nutritional supplements in Far-Eastern Asia. In this study, we aimed to evaluate the anti-cancer activities of some different fungal species against different cancer cell lines. The water or ethanol extracts of Fomitopsis pinicola (F. pinicola), Ganoderma sinense, Fomitopsis officinalis, Polyporus melanopus, and Taiwanofungus camphorates were used to evaluate the anti-cancer activities in various cancer cells. We found that all of the fungi ethanol extracts used in this study exert anti-cancer activities in vitro, whereas water extracts show lower inhibitory activities as determined by 3-(4,5-methylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assays. Among the tested fungi species, F. pinicola ethanol extract exerts the most significant anti-cancer activity (growth inhibitory ratio 82.8%, p < 0.001) by increasing cell apoptosis. Moreover, F. pinicola ethanol extract significantly decreased tumor size (tumor growth inhibitory ratio 54%, p < 0.05) and increased the lifespan in mice bearing sarcoma-180 tumors. Taken together, this is the first study indicating the anti-tumor effect of F. pinicola in vivo and in vitro. F. pinicola ethanol extract induces cell apoptosis to exert a significant anti-tumor activity, with potential to be a new alternative anti-tumor medicine.

Increased cardiotrophin-1 in subjects with impaired glucose tolerance and newly diagnosed diabetes

a Division of Endocrinology and Metabolism, Department of Internal Medicine, National Cheng Kung University Hospital, Tainan, Taiwan b Department of Family Medicine, National Cheng Kung University Hospital, Tainan, Taiwan c College of Medicine, National Cheng Kung University, Tainan, Taiwan d Research Center of Herbal Medicine, New Drugs, and Nutritional Supplements, National Cheng Kung University, Taiwan

Prothymosin-α overexpression contributes to the development of insulin resistance

CONTEXTnProthymosin-α (ProT) is involved in oxidative stress, inflammation, cell proliferation, and apoptosis. Increased oxidative stress and chronic inflammation participate in the pathogenesis of diabetes. A recent study found that ProT is a ligand of toll-like receptor 4, which plays an important role in the development of insulin resistance. However, its physiological role remains poorly understood.nnnOBJECTIVEnThe objective was to investigate whether ProT contributes to the development of insulin resistance.nnnDESIGN, SETTINGS, AND PATIENTSnA total of 185 subjects were recruited and classified into nondiabetes (n = 95) and newly diagnosed diabetes (n = 90) groups. Transgenic mice overexpressing ProT were used to investigate the role of ProT in the development of insulin resistance. Lentiviral vectors carrying short hairpin RNA specific for ProT were delivered via the portal vein to silence hepatic ProT expression in mice with high-fat diet-induced insulin resistance. Glucose uptake was determined in L6 myotubes.nnnRESULTSnWe show that the serum ProT levels of patients with type 2 diabetes were significantly higher than those of normal individuals (mean ± SEM, 419.8 ± 46.47 vs 246.4 ± 27.89 pg/mL; P < .001). Furthermore, ProT transgenic mice exhibited an insulin-resistant phenotype, whereas the silencing of hepatic ProT expression ameliorated high-fat diet-induced insulin resistance in C57BL/6 mice. In vitro studies reveal that ProT induced insulin resistance through a toll-like receptor 4-nuclear factor-κB-dependent pathway.nnnCONCLUSIONSnOur results support the role for ProT in the development of insulin resistance. Therefore, ProT is a potential novel therapeutic target for type 2 diabetes.

Elevated Retinol Binding Protein 4 Contributes to Insulin Resistance in Spontaneously Hypertensive Rats

Retinol binding protein 4 (RBP4) is an adipokine secreted by adipose tissue and liver and contributes to insulin resistance (IR) in animals. Although several human studies indicated that RBP4 is positively correlated with blood pressure and is elevated in untreated hypertensive subjects, the role of RBP4 in IR of hypertensive animals still remains obscure. In this study, spontaneously hypertensive rats (SHR) were used to investigate the relationship between RBP4 levels and IR. We found that at 7 weeks old, SHR had significantly increased plasma RBP4 levels and RBP4 expression in liver and epididymal adipose tissue accompanied by worsening of IR as compared with Wistar-Kyoto (WKY) control rats. Administration of fenretinide in SHR to increase urinary RBP4 excretion significantly decreased plasma RBP4 levels and improved IR. Moreover, treatment with valsartan markedly reduced blood pressure, circulating RBP4 and adiponectin levels, and IR in SHR. Valsartan also reversed the increase of hepatic gluconeogenic enzyme phosphoenolpyruvate carboxykinase (PEPCK) and the decrease of type 4 glucose transporter (GLUT4) in adipose tissue. In conclusion, these results suggest that RBP4 contributes, at least partly, to the pathogenesis of IR in SHR. Furthermore, the decrease of blood pressure caused by valsartan not only decreased RBP4 levels, but also improved IR in SHR.