Analysis of the effects of incretin-based peptides on human neuroblastoma SH-SY5Y cells

Abstract

Incretins are growth factors that have demonstrated neuroprotective properties in a range of studies. Here, we analyse the neuroprotective properties of the Glucagon likepeptide-1 (GLP-1) analogues in human neuroblastoma SH-SY5Y cells against methylglyoxal (MG) stress. The results demonstrate a range of growth factor-related cytoprotective processes induced by liraglutide (Victoza®), currently used to treat type2 diabetes. Further, we study the comparative long-term effects of three differentGLP-1 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-1 analogues in combination, but a 3-fold increase in cytoprotection observed when comparing 100nM 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 50nM 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 of MEK1/2 leads to the activation of Akt/PKB (p<0.001). A decrease in the survival (p<0.05) and an increase in the cytotoxicity (p<0.05) during inhibition ofMEK1/2 followed by liraglutide treatment, suggest a role of MEK1/2 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 MEK1/2withdraws this neuroprotective effect, suggesting the involvement of MAPK/ERK pathway in the neuroprotection conferred by liraglutide. Overall, incretins confer protection and have potential to be developed as possible drugs to treat neurodegenerative disorders.

Thesis is embargoed until 31st October 2015

Date of Award	Oct 2013
Original language	English
Sponsors	Vice Chancellor's Research Scholarship (VCRS)
Supervisor	Victor Gault (Supervisor) & Peter Flatt (Supervisor)