Title:
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Analysis of the effects of incretin-based peptides on
human neuroblastoma SH-SY5Y cells.
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Incretins are growth factors that have demonstrated neuroprotective properties in a
range of studies. Here, we analyse the neuroprotective properties of the Glucagon like
peptide-l (GLP-l) analogues in human neuroblastoma SH-SY5Y cells against methyl
glyoxal (MG) stress. The results demonstrate a range of growth factor-related
cytoprotective processes induced by liraglutide (Victoza®), currently used to treat type
2 diabetes. FUl1her, we study the comparative long-term effects of three different
GLP-l analogues on cell viability, proliferation and cytotoxicity and demonstrate the
long-term exposure of liraglutide and lixisenatide (Lyxumia®) to be more protective
when compared to the exendin-4 (Byetta~ . We also report the absence of any
additive effect on cell viability and proliferation, when using GLP-l analogues in
combination, but a 3-fold increase in cytoprotection observed when comparing 100
nM doses of liraglutide and lixisenatide to exendin-4 (p<0.001). In addition, we
demonstrate that lixisenatide (10 and 50 nM) is neuroprotective when compared to 50
nM liraglutide (p<0.05) and 50 and 100 nM exendin-4 (p<0.001) against MG post
stress. Further, the most effective doses for native Glucose dependent insulinotropic
peptide (GIP), (D-Ala2)GIP and (Pro3)GIP were 200, 100 and 1 nM exhibiting a 43 ±
3% decrease in LDH levels (p<0.001). Lastly, we show a novel mechanism wherein
blockade ofMEK1I2 leads to the activation of AktIPKB (p<0.001). A decrease in the
survival (p<0.05) and an increase in the cytotoxicity (p<0.05) during inhibition of
MEK1I2 followed by liraglutide treatment, suggest a role ofMEK1I2 in protecting the
cells. Our studies show that the liraglutide pre-treatment confers neuroprotection by
increasing the cell survival and decreasing cytotoxicity but inhibition of MEK1I2
withdraws this neuroprotective effect, suggesting the involvement of MAPKIERK
pathway in the neuroprotection conferred by liraglutide. Overall, incretins confer
protection and have potential to be developed as possible drugs to treat
neurodegenerative disorders.
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