Diabetes & Metabolism Journal

Original Articles

The Effect of Chronic High Glucose Concentration on Endoplasmic Reticulum Stress in INS-1 Cells.: Mi Kyung Kim, Hye Young Seo, Tae Sung Yun, Nam Kyung Kim, Yu Jin Hah, Yun Jung Kim, Ho Chan Cho, Young Yun Jang, Hye Soon Kim, Seong Yeol Ryu, In Kyu Lee, Keun Gyu Park; Korean Diabetes J. 2008;32(2):112-120. Published online April 1, 2008; DOI: https://doi.org/10.4093/kdj.2008.32.2.112

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Abstract PDF: BACKGROUND
The highly developed endoplasmic reticulum (ER) structure is one of the characteristic features of pancreatic beta-cells. Recent study showed that ER stress causes beta-cell dysfunction. However, little is known about the effects of high glucose concentration on induction of ER stress in pancreatic beta-cells. Therefore, this study was designed to evaluate whether exposure of high glucose concentration in rat insulinoma cell line, INS-1 cell induces ER stress and whether ER stress decreases insulin gene expression. METHODS: The effect of 30 mM glucose on insulin expression and secretion in INS-1 cells was evaluated by Northern blot analysis and glucose-stimulated insulin secretion (GSIS). Cell viability was evaluated by XTT assay. The effect of 30 mM glucose on phosphorylation of eIF2alpha and CHOP expression, which are markers of ER stress were evaluated by Western blot analysis. RT-PCR analysis was performed to determine whether high glucose concentration induces XBP-1 splicing. To investigate whether ER stress decreases insulin gene expression, the effect of tunicamycin on insulin mRNA expression was evaluated by Northern blot analysis. RESULTS: The prolonged exposure of INS-1 cells with the 30 mM glucose concentration decreased insulin mRNA expression in a time dependent manner and impaired GSIS while did not influence on cell viability. 30 mM glucose increased phosphorylation of eIF2alpha, XBP-1 splicing and CHOP expression in INS-1 cells. Tunicamycin-treated INS-1 increased XBP-1 splicing and decreased insulin mRNA expression in a dose dependent manner. CONCLUSION: This study showed that prolonged exposure of INS-1 with high glucose concentration induces ER stress and ER stress decreases insulin gene expression. Further studies about underlying molecular mechanism by which ER stress induces beta-cell dysfunction are needed.

The Effects of Exendin-4 on IRS-2 Expression and Phosphorylation in INS-1 Cells.: Ji Hyun Kim, Ji Won Kim, Sung Yoon Jeon, Heon Seok Park, Dong Sik Ham, Young Hye You, Seung Hwan Lee, Jae Hyoung Cho, Mi Ja Kang, Kang Woo Lee, Hyuk Sang Kwon, Kun Ho Yoon, Bong Yun Cha, Kwang Woo Lee, Sung Koo Kang, Ho Young Son; Korean Diabetes J. 2008;32(2):102-111. Published online April 1, 2008; DOI: https://doi.org/10.4093/kdj.2008.32.2.102

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Abstract PDF: BACKGROUND
Insulin receptor substrate 2 (IRS-2) is a key regulator of beta cell proliferation and apoptosis. This study was aimed to investigate effect of the glucolipotoxicity on apoptosis in INS-1 cell, and the effect of Exendin-4, a GLP-1 receptor agonist, on IRS-2 expression in the glucolipotoxicity induced INS-1 cell. The goal was to discover the new action mechanism and function of Exendin-4 in beta cell apoptosis. METHOD: INS-1 cells were cultured in glucolipotoxic condition for 2, 4 or 6 days and were categorized as G groups. Another group in which 50 nM Exendin-4 was added to INS-1 cells, cultured in glucolipotoxic condition, were named as Ex-4 groups. We investigated the expression of IRS-2 by RT-PCR, phosphorylated IRS-2 and phosphorylated Akt protein levels by western blot. We measured the apoptosis ratio of INS-1 cell in glucolipotoxic condition by TUNEL staining in both groups. RESULT: IRS-2 expression of INS-1 cells decreased with correlation to the time of exposure to glucolipotoxic condition. pIRS-2 and pAkt protein levels decreased in the similar pattern in glucolipotoxicity group. However, this effect of glucolipotoxicity on INS-1 cell was inhibited by the Exendin-4 treatment. In the Ex-4 groups, IRS-2 expression, pIRS-2 and pAkt protein levels remained at the similar level to low glucose condition state. Also, apoptosis induced by glucolipotoxicity was suppressed by Exendin-4 treatment significantly. CONCLUSION: We showed that the long-term treatment of Exendin-4 inhibited the apoptosis of beta cells significantly in glucolipotoxic condition and that this effect of Exendin-4 was related with IRS-2 and Akt among the beta cell's intracellular signal transduction pathway.

Cytoprotective Effect by Antioxidant Activity of Quercetin in INS-1 Cell Line.: Min Jeong Kwon, Hye Sook Jung, Mi Kyung Kim, Seong Hoon Kang, Gwang Wook Seo, Jae Kwang Song, Tae Yeon Yoon, Min Kyeong Jeon, Tae Hwan Ha, Chang Shin Yoon, Mi Kyung Kim, Woo Je Lee, Jeong Hyun Noh, Soo Kyung Kwon, Dong Joon Kim, Kyung Soo Koh, Byung Doo Rhee, Kyung Ho Lim, Soon Hee Lee, Jeong Hyun Park; Korean Diabetes J. 2007;31(5):383-390. Published online September 1, 2007; DOI: https://doi.org/10.4093/jkda.2007.31.5.383

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Abstract PDF

BACKGROUND
Oxidative stress is induced under diabetic conditions and causes various forms of tissue damages in the patients with diabetes. Recently, pancreatic beta cells are regarded as a putative target of oxidative stress-induced tissue damage, and this seems to explain in part the progressive deterioration of beta cell function in type 2 diabetes. The aim of this study was to examine the potential of Quercetin (QE) to protect INS-1 cells from the H2O2-induced oxidative stress and the effects of QE on the glucose-stimulated insulin secretion in INS-1 cells. METHODS: To study the cell viability, cells were incubated with H2O2 and/or QE at the various concentrations. To confirm the protective effect by QE in response to H2O2, the levels of antioxidant enzymes were assessed by RT-PCR and Western blot, and glutathione peroxidase activities were quantified by spectrophotometrical method. Glucose-stimulated insulin secretion (GSIS) was measured by ELISA. RESULTS: Cell incubations were performed with 80 microM of H2O2 for 5 hours to induce 40 - 50% of cell death. QE gradually showed protective effect (IC50 = 50 microM) in dose-dependent manner. Superoxide dismutase (SOD) mRNA level in H2O2 + QE group was increased as compared to H2O2 group, but catalase did not changed. And the QE recruited glutathione peroxidase activity against H2O2-induced oxidative injuries in INS-1 cells. CONCLUSION: In conclusion, these findings suggest that QE might have protective effect on beta cells by ameliorating oxidative stress and preserving insulin secretory function.

Citations

Citations to this article as recorded by

Anti-diabetic effects of Allium tuberosum rottler extracts and lactic acid bacteria fermented extracts in type 2 diabetic mice model
Bae Jin Kim, Seung Kyeung Jo, Yoo Seok Jeong, Hee Kyoung Jung
Korean Journal of Food Preservation.2015; 22(1): 134. CrossRef
Protective Effects of Sasa Borealis Leaves Extract on High Glucose-Induced Oxidative Stress in Human Umbilical Vein Endothelial Cells
Ji-Young Hwang, Ji-Sook Han
Journal of the Korean Society of Food Science and Nutrition.2010; 39(12): 1753. CrossRef

gamma-glutamylcysteine Synthetase (gamma-GCS) mRNA Expression in INS-1 Cells and Patients with Type 2 Diabetes Mellitus.: Jae Hong Kim, Chan Hee Lee, Jun Sung Moon, Ji Sung Yoon, Kyu Chang Won, Hyoung Woo Lee; Korean Diabetes J. 2007;31(4):302-309. Published online July 1, 2007; DOI: https://doi.org/10.4093/jkda.2007.31.4.302

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Abstract PDF: BACKGROUND
Hyperglycemia is a well-recognized pathogenic factor of long term complications in diabetes mellitus and hyperglycemia also generates reactive oxygen species (ROS) in beta cells when ROS accumulate in excess for prolonged periods of time, they cause chronic oxidative stress and adverse effects. Unfortunately, the islet contacts low capacity of endogenous antioxidant effects. But, gamma-glutamylcysteine synthetase (gamma-GCS), the rate-limiting enzyme for glutathione synthesis, is well represented in islets. METHODS: This study is to evaluate the changes in the activity of gamma-GCS, glutathione in beta-cells exposed to high glucose, in pancreatic tissue of OLETF (Otsuka Long Evans Tokushima Fatty) and LETO (Long-Evans Tokushima Otsuka) rats, in leukocytes from patients with Korean type 2 DM (T2DM) and to disclose the effects of high blood glucose on this impairment in patients with T2DM. We divided our patients into 3 groups by HbA1c (controls: n = 20, well controls diabetes: n=24, poorly controlled diabetes: n = 36). RESULTS: We observed that decreased glutathione level, gamma-GCS expression, glucose-stimulated (GSIS) and increased intracellular peroxide level in the INS-1 cells exposed to 30 mM glucose condition. Also decreased glutathione level at erythrocytes, gamma-GCS expression at leukocytes and increased oxidized LDL, MDA (malondialdehyde) level at plasma from patients with T2DM compared to controls (esp, poorly controlled patients). CONCLUSION: These results suggest that insufficient antioxidant defenses by the glutathione pathway may be one of the factors responsible for development of complications in T2DM.

Microarray Analysis of Short Heterodimer Partner (SHP)-induced Changes in Gene Expression in INS-1 Cells.: Eui Dal Jung, Ji Hyun Lee, Won Gu Jang, Jung Guk Kim, Bo Wan Kim, In Kyu Lee; Korean Diabetes J. 2007;31(3):193-199. Published online May 1, 2007; DOI: https://doi.org/10.4093/jkda.2007.31.3.193

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Abstract PDF: BACKGROUND
Nuclear receptors are involved in the cell growth, development, differentiation, and metabolism. The orphan nuclear receptor SHP which lacks a DNA-binding domain is a negative regulator of nuclear receptor signaling pathways. In pancreas, SHP regulate transcriptional activity of HNF3 and HNF4 through binding them and BETA2 which is involved in beta cell differentiation and insulin production. Here, we examined transcriptional activity changes of genes expressed in beta cell when SHP was overexpressed. METHOD: INS-1 cells of passage number 24 - 30 were prepared. Affimetrix DNA chip was used to examine gene expression in INS-1 cell when SHP was overexpressed. INS-1 cells were infected with adenovirus-SHP to overexpress SHP. To confirm the result of DNA chip, we used real time RT-PCR. RESULT: When SHP was overexpressed by adenovirus-SHP transfection, FXR, Transforming growth factor, beta 2, fructose-1,6-bisphosphatase 2, bone morphogenetic protein 4 genes expression were increased. Contrarily, Activating transcription factor 2, Glycogen synthase kinase 3 alpha, Nur 77, fibroblast growth factor 14 genes expression were decreased. We confirmed DNA microarray analysis by real time RT-PCR. FXR, tribbles homolog 3 (Drosophila), fructose-1,6-bisphosphatase 2, CD36 genes expression were increased in real time RT-PCR. Nur 77 and cAMP response element modulator genes expression were decreased in real time RT-PCR. CONCLUSION: we identified several genes which expression are regulated by SHP in pancreas beta cell. These results help to explain how SHP act in the various metabolism of pancreas beta cell.

The Role of cAMP/PKA Activation on Exendin-4-Induced Cyclin D1 Expression in INS-1 Cell.: Gyeong Ryul Ryu, Jung Hoon Kang, Hwa In Jang, Seung Hyun Ko, In Kyung Jeong, Duck Joo Rhie, Shin Hee Yoon, Sang June Hahn, Yang Hyeok Jo, Myung Suk Kim, Myung Jun Kim; Korean Diabetes J. 2005;29(4):295-303. Published online July 1, 2005

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Abstract PDF: BACKGROUND
Glucagon-like peptide-1(GLP-1) and exendin-4(EX-4) have been known to induce pancreatic islet proliferation and increases in the betacell mass. Cyclin D1 is a key protein responsible for the entry of the G into the S phase, thereby contributing to cell proliferation. Therefore, the effect of EX-4 on the expression of cyclin D1 in INS-1 cells, a rat pancreatic betacell line, was investigated. The involvement of either mitogen-activated protein kinases(MAPKs) or cyclic adenosine 5'-monophosphate/protein kinase A(cAMP/ PKA) in the EX-4-induced cyclin D1 expression was also examined. METHODS: INS-1 cells were treated with EX-4 (10 nM), and the cyclin D1 protein levels then determined by Western blot. To investigate the involvement of MAPKs in the EX-4- induced cyclin D1 expression, either a combined treatment of MAPKs inhibitors or transient transfection of extracellular signal-regulated kinase-1 (ERK1) was performed. The effect of cAMP on the EX-4-induced cyclin D1 expression was also examined by treatments with forskolin, an adenylyl cyclase activator, and H-89, a PKA inhibitor. RESULTS: EX-4 increased the expression of cyclin D1 protein in a dose-dependent manner. Although EX-4 induced phosphorylation of ERK1/2, the treatment with PD 98059 or the overexpression of ERK1 had no effect on the EX-4-induced cyclin D1 expression. However, forskolin significantly induced the expression of cyclin D1, whereas the pretreatment of H-89 inhibited the EX-4-induced cyclin D1 expression. CONCLUSION: These results suggest that EX-4 induce cyclin D1 expression in INS-1 cells via cAMP/PKA pathway, but this is not due to ERK activation.

Mitogenic Effects and Signaling Pathway of Insulin-Like Growth Factor-I (IGF-I) in the Rat Beta Cell Line (INS-1).: In Kyung Jeong, Ja Young Kim, Hyung Joon Yoo, Myung Shik Lee, Moon Kyu Lee, Kwang Won Kim; Korean Diabetes J. 2004;28(6):478-489. Published online December 1, 2004

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Abstract PDF: BACKGROUND
Nutrients and growth factors are known to stimulate pancreatic beta cell mitogenesis. IGF-I acts as a survival factor by limiting apoptosis and stimulating proliferation in many cell types. However, the appropriate mitogenic signaling pathways have not been defined. The aim of this study is to elucidate the mitogenic effect and signaling pathways of IGF-I in the rat beta cell line (INS-I). METHODS: The studies were performed using the rat pancreatic beta cell line, INS-1. INS-1 cells were cultured in RPMI 1640 containing serum-free, 0.2% BSA and 11.1 mmol/L glucose media for 24 hours, and the cells were then treated with IGF-I and different concentrations of glucose or tyrosine phosphorylation inhibitors, or insulin. The cell proliferation was measured by the [3H]thymidine uptake and MTT assay. The cell cycle was analyzed by a flow cytometer by using propidium iodide staining. Western blot analyses were performed using antibodies against PY20 and phospho-MAPK. RESULTS: 1) MTT assay and the [3H]thymidine uptake showed that IGF-I stimulated the INS-1 cell proliferation in a dose dependent manner. Glucose was noted to independently increase the INS-1 cell proliferation. A combination of IGF-I and glucose has a synergistic effect on the proliferation of INS-I cells. Insulin did not influence on the mitogenic effect of IGF-I. 2) The S fraction of INS-1 cells treated with IGF-I was increased in a dose dependent manner. IGF-I stimulated the exit from G1 into the S phase of the cell cycle. 3) Investigation of the role of the PI3K and MAPK, by using of the inhibitors LY294002, wortmannin, and PD98059, demonstrated that the activation of MAPK, but not PI3K, required to stimulate the proliferation of INS-1 cells. 4) IGF-I stimulated the phosphorylation activation of pp60 and phospho-MAPK in the INS-1 cells. IGF-I induced the beta cell proliferation, and this was mediated via a signaling mechanism that was facilitated by MAPK. CONCLUSION: The proliferative effect of IGF-I on pancreatic beta cell seems to be mediated through MAPK signaling pathway.

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