Liraglutide prevents high glucose level induced insulinoma cells apoptosis by targeting autophagy / 中华医学杂志(英文版)

<p><b>BACKGROUND</b>The pathophysiology of type 2 diabetes is progressive pancreatic beta cell failure with consequential reduced insulin secretion. Glucotoxicity results in the reduction of beta cell mass in type 2 diabetes by inducing apoptosis. Autophagy is essential for the maintenance of normal islet architecture and plays a crucial role in maintaining the intracellular insulin content by accelerating the insulin degradation rate in beta cells. Recently more attention has been paid to the effect of autophagy in type 2 diabetes. The regulatory pathway of autophagy in controlling pancreatic beta cells is still not clear. The aim of our study was to evaluate whether liraglutide can inhibit apoptosis and modulate autophagy in vitro in insulinoma cells (INS-1 cells).</p><p><b>METHODS</b>INS-1 cells were incubated for 24 hours in the presence or absence of high levels of glucose, liraglutide (a long-acting human glucagon-like peptide-1 analogue), or 3-methyadenine (3-MA). Cell viability was measured using the Cell Counting Kit-8 (CCK8) viability assay. Autophagy of INS-1 cells was tested by monodansylcadaverine (MDC) staining, an autophagy fluorescent compound used for the labeling of autophagic vacuoles, and by Western blotting of microtubule-associated protein I light chain 3 (LC3), a biochemical markers of autophagic initiation.</p><p><b>RESULTS</b>The viability of INS-1 cells was reduced after treatment with high levels of glucose. The viability of INS-1 cells was reduced and apoptosis was increased when autophagy was inhibited. The viability of INS-1 cells was significantly increased by adding liraglutide to supplement high glucose level medium compared with the cells treated with high glucose levels alone.</p><p><b>CONCLUSIONS</b>Apoptosis and autophagy were increased in rat INS-1 cells when treated with high level of glucose, and the viability of INS-1 cells was significantly reduced by inhibiting autophagy. Liraglutide protected INS-1 cells from high glucose level-induced apoptosis that is accompanied by a significant increase of autophagy, suggesting that liraglutide plays a role in beta cell apoptosis by targeting autophagy. Thus, autophagy may be a new target for the prevention or treatment of diabetes.</p>

Role of PKC in regulation of CD73 by lysophosphatidylcholine in human endothelial cells / 中国应用生理学杂志

<p><b>OBJECTIVE</b>To discuss the effect of protein kinase C (PKC) on regulation of ecto-5'-nucleotidase activity by lysophosphatidylcholine(LPC) in human umbilical endothelial cells (HUVEC).</p><p><b>METHODS</b>Experiments were conducted in HUVEC grown on dishes which were divided into 4 groups (n=15): (1) Control group in which only eAMP (5 micromol/L) was added; (2) LPC group in which HUVEC were incubated with LPC (10 micromol/L) before eAMP was added; (3) Chelerythrine group in which cells were pre-incubated with the PKC inhibitor chelerythrine (100 micromol/L) before LPC and eAMP were added; (4) alpha, beta-Methyladenosine-5'-Diphosphate (AOPCP) group in which cells were incubated with AOPCP (10 micromol/L) before eAMP was added. Etheno-adenosine production was detected at 15th, 30th, 45th min with high performance liquid chromatography(HPLC) respectively.</p><p><b>RESULTS</b>Comparing to the control group LPC significantly increased etheno-adenosine production at three time points respectively (P < 0.05). Furthermore, PKC inhibitor chelerythrine abolished this effect of LPC and the ethenoadenosine production at three time points were at the same level of control group (P > 0.05). CD73 inhibitor AOPCP significantly decreased the etheno-adenosine production compared to the other three groups (P < 0.01).</p><p><b>CONCLUSION</b>Ecto-5'-nucleotidase can be modulated within minutes following exposure of HUVEC to LPC and this response may be mediated by PKC in HUVEC.</p>