The Effect of Chronic High Glucose Concentration on Endoplasmic Reticulum Stress in INS-1 Cells / 당뇨병

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.

Association of Polymorphism in beta3-Adrenergic Receptor Gene with Fat Distribution / 대한내분비학회지

BACKGROUND: Reasons for obesity include environmental factors and, more largely so, genetic factors. There have been many studies on these genetic factors. So far, genes related to obesity such as Leptin, Uncoupling Protein(UCP), Peroxisome proliferator activated receptor-gamma(PPAR-gamma), and Beta3-adrener-gic receptor(beta3-AR) gene have been discovered. Among these, beta3-AR is expressed in visceral adipose tissue and is thought to contribute to the regulation of resting metabolic rate and lipolysis. The missense mutation of beta3-AR gene, resulting in replacement of tryptophan by arginine at position 64(Trp64Arg), is associated with decreased resting metabolic rate and weightgain. We performed this study to determine if Trp64Arg polymorphism of beta3-AR gene is associatedwith obesity in Koreans. METHOD: We investigated the relationship between the beta3-AR gene mutation and body mass index (BMI), waist circumference, hip circumference, waist to hip ratio(WHR), area of subcutaneous fat, area of visceral fat, visceral to subcutaneous fat ratio(VSR), and lipid profile. 198 subjects were included in this study of which 97 were of normal weight and 101 were obese. Anthropometric data was obtained from physical examination and medical records. RESULT: In the cases of beta3-AR gene mutation of the obese group, the ratio of Trp/Arg and Arg/Arg are 43% and 5%, respectively, which were higher than the normal group(36%, 1%), although a statistical significant was not found. There was significant difference in the are of subcutaneous fat. Normal group(Trp/Trp) measured at 213.9+/-109.6cm2 versus 244.0+/-127.7cm2 (Trp/Arg) and 323.9+/-189.9cm2(Arg/Arg) for the mutation groups. Circumference of waist, circumference of hip, WHR, area of visceral fat, and VSR were higher in the mutation groups than in normal subject, but not significantly different. CONCLUSION: These results suggest that a genetic mutation in the beta3-AR gene can affect body fat composition, and is associated with obesity in Korean adults.