High glucose impairs mitochondrial respiratory chain function in pancreatic beta cells / 南方医科大学学报

<p><b>OBJECTIVE</b>To investigate the effect of high glucose on mitochondrial respiratory chain function in INS-1 cells.</p><p><b>METHODS</b>The pancreatic beta cell line INS-1 was divided into the normal control (NC), high glucose (HG), and N-acetyl-L-cysteine (NAC) pretreatment groups, which were cultured for 72 h in the presence of 5.5 mmol/L glucose, 16.7 mmol/L glucose, and 16.7 mmol/L glucose with 1.0 mmol/L NAC, respectively. The activities of the enzyme complexes I and III of the respiratory chain in the cells were assessed with spectrophotometry, the ATP levels were examined using a luciferinluciferase kit, and insulin levels detected by radioimmunoassay.</p><p><b>RESULTS</b>The activities of the respiratory chain enzyme complexes I and III were 1.53-/+0.24 and 1.08-/+0.22 micromol.mg(-1).min(-1) in high glucose group, respectively, significantly lower than those in the normal control group (2.31-/+0.33 and 1.92-/+0.39 micromol.mg(-1).min(-1), P<0.01). ATP and insulin levels also decreased significantly in high glucose group as compared with those in the normal control group (P<0.01). The addition of NAC partially inhibited high glucose-induced decreases in the enzyme complex activities, ATP levels and insulin secretion (P<0.05).</p><p><b>CONCLUSION</b>The respiratory chain function is positively correlated to insulin secretion in INS-1 cells, and exposure to high glucose causes impairment of the two enzyme complexes activities through oxidative stress, resulting in the mitochondrial respiratory chain dysfunction. High glucose-induced damages of the mitochondrial respiratory chain function can be partially inhibited by NAC.</p>

Small interfering RNA-mediated islet neogenesis associated protein gene silencing inhibits the proliferation of INS-1 islet cells / 南方医科大学学报

<p><b>OBJECTIVE</b>To investigate the effect of small interfering RNA (siRNA)-mediated islet neogenesis associated protein (INGAP) gene silencing on the proliferation of islet cells.</p><p><b>METHODS</b>Different siRNAs targeting INGAP gene were designed and transfected into INS-1 islet cells, and the expression levels of INGAP mRNA and protein following the transfection were detected using RT-PCR, flow cytometry and Western blotting. The proliferation of the transfected INS-1 cells was evaluated using MTT assay.</p><p><b>RESULTS</b>Compared with those in the irrelevant siRNA, empty vector control, and un-transfected groups, the expression levels of INGAP mRNA and protein in the cells transfected with siRNA6 were reduced significantly. The cell proliferation rate significantly increased after transfection with siRNA6 (P<0.05).</p><p><b>CONCLUSION</b>siRNA targeting INGAP can effectively down-regulate INGAP expression and inhibit the proliferation of INS-1 cells.</p>