Abstract: Objective To explore the effect of Apelin-13 on epithelia-mesenchymal transition (EMT) of renal tubular epithelial cell line HK-2 cells induced by high glucose. Methods After pretreatment with Apelin-13 (10^-8, 10^-7 and 10^-6 mol/L) for 30 min, HK-2 cells were cultured in the medium containing 30 mmol/L Dglucose
for 48 h. Expression of mesenchymal cell markers alpha smooth muscle actin (α-SMA) in the HK-2 cells were tested by immunofluorescence assay. Ultrastructural changes of HK-2 cells were observed by transmission electron microscopy. Expressions of the epithelial marker E-cadherin, α-SMA, and autophagy related proteins were measured by western blot. Results Compared with the control group, HK-2 cells in the high glucose group showed long spindle shape and widened intercellular spaces, with down-regulated E-cadherin expression (t=4.751, P=0.011), up-regulated α-SMA expression (t=3.846, P=0.016), increased number of autophagy, increased expression of Beclin-1, LC3-II and LC3-II/LC3-I ratio (t=5.271, P=0.009 for Bectlin-1; t=4.695, P=0.012 for LC3- II; t=6.753, P=0.002 for LC3-II/LC3- I ratio), and decreased expression of p62 (t=4.562, P=0.012). Compared with the high glucose group, KH-2 cells in the Apelin-13 (10^-7 and 10^-6 mol/L) +high glucose group showed oval shape, with up-regulated E-cadherin expression (t=3.495, P=0.019 for 10^{- 7}mol/L Apelin-13; t=4.124, P=0.013 for 10^-6 mol/L Apelin-13), down-regulated α-SMA expression (t=4.014, P= 0.014 for 10^-7 mol/L Apelin-13; t=4.283, P=0.012 for 10^-6 mol/L Apelin-13), increased number of autophagy, increased expression of Beclin-1, and LC3-II and LC3-II/LC3-I ratio (t=3.487, P=0.018 for Beclin-1 and 10^-7mol/L Apelin-13; t=4.059, P=0.014 for Beclin-1 and 10^{- 6} mol/L Apelin-13; t=5.342, P=0.009 for LC3-II and10^{- 7} mol/L Apelin-13; t=4.271, P=0.011 for LC3-II and 10^{- 6} mol/L Apelin-13; t=5.360, P=0.005 for LC3-II/LC3-I ratio and 10^-7 mol/L Apelin-13; t=5.851, P=0.004 for LC3-II/LC3-I ratio and 10^-6 mol/L Apelin-13), and decreased expression of p62 (t=4.342, P=0.012 for 10^-7 mol/L Apelin-13; t=3.557, P=0.019 for 10^-6 mol/L Apelin-13). Conclusions Apelin-13 inhibits the EMT of renal tubular epithelial cell line HK-2 cells induced by high glucose. The increase of autophagy induced by Apelin-13 may relate to the inhibition of EMT in HK-2
cells.

Key words: Apelin-13, High glucose, Epithelia-mesenchymal transition, Autophagy, Autophagy related protein.