- 作者：G. Pujadas1 ; L. La Sala1 ; Antonio Ceriello1 ; 2
- 刊名：Diabetes Metabolism
- 出版年：2012
- 出版时间：November, 2012
- 年：2012
- 卷：38
- 期：supp_S5
- 页码：S100-S101
- 全文大小：58 K
Background and aims
We and others demonstrated that hyperglycemia induces endothelial dysfunction and the disruption of the endoplasmic reticulum (ER) function, activating intracellular signal transduction pathways, collectively termed the unfolded protein response (UPR). These conditions contribute to the development of cardiovascular disease (CVD) in diabetes. GLP-1 is interesting not only for its capacity in stimulating insulin secretion and in lowering blood glucose levels after nutrient ingestion, but also for its possible protective effects on cardiovascular system. Recently, Oeseburg et al. proposed GPL-1 as an antioxidant agent, because GLP-1 increases intracellular antioxidant enzyme gene expression. We have recently reported, in vivo, that hyperglycemia induces endothelial resistance to the action of GLP-1, in terms of reducing GLP-1 effects on endothelial function, inflammation and oxidative stress. In this study we plan to asses in human vein endothelial cells (HuVECs), if GLP-1 still improves antioxidant response in vitro, after HuVECs are exposed to hyperglycemic conditions or, conversely, if it loses its antioxidant capacity.Materials and Methods
HuVECs were incubated for 21 days in normal (NG) (5mmol/L) or high glucose (HG) (25mmol/L) conditions, and treated with 50¦ÌM GPL-1 for 1h before their harvesting. Differences in antioxidant genes, ER stress/UPR markers, and apoptosis/proliferation genes were assessed by qRT-PCR and immunoblotting.
Results
Chronic hyperglycemia induces the expression of the antioxidant genes HO-1 (NG vs HG P=0.01) and NQO-1 (NG vs HG P=0.07), as well as increases their protein levels. An equivalent activation of both genes was also found after GLP-1 addition in normal glucose concentration (NG vs NG+GLP-1 P=0.05 and P=0.07, HO-1 and NQO-1, respectively). GLP-1 loses this capacity when the HuVECs are exposed to high glucose (HG vs HG+GLP-1 P=1.00 and P=0.70, HO-1 and NQO-1, respectively). Furthermore, we confirm that hyperglycemia also induces gene expression of several ER stress markers in HuVECs, such as BIP, CHOP and PERK (NG vs HG P=0.01, P=0.05 and P=0.03, respectively), as well as eIF2a phosphorylation, and that GLP-1 activates some of them in normal glucose concentration. Consistently, we observe an attenuation or a complete loss of GLP-1 capacity in HuVECs after they are exposed to high glucose. Finally, as expected, hyperglycemia diminishes both gene (NG vs HG P=0.01) and protein expression of BCL-2, while the expression CDKN1a at mRNA level is increased (NG vs HG P=0.01). In both cases, GLP-1 does not exert its effects after chronic exposure to high glucose concentration (NG vs NG+GLP-1 P=0.02 and P=0.06, BCL-2 and CDKN1A, respectively. And HG vs HG+GLP-1 P=0.30 and P=0.74, BCL-2 and CDKN1A, respectively).
Conclusion
Our preliminary findings suggest that endothelial cells, after a long of exposure to high glucose, lose their ability to respond normally to the GLP-1 action, in terms of increasing their antioxidant capacity and regulating ER function and UPR response. This effect is probably due to the development of resistance to GLP-1 during high glucose chronic exposure.