Palmitate induces autophagy in pancreatic β-cells via endoplasmic reticulum stress and its downstream JNK pathway

Chen,Ying-Ying; Sun,Lian-Qing; Wang,Bao-An; Zou,Xiao-Man; Mu,Yi-Ming; Lu,Ju-Ming

doi:10.3892/ijmm.2013.1530

Palmitate induces autophagy in pancreatic β-cells via endoplasmic reticulum stress and its downstream JNK pathway

Authors:
- Ying-Ying Chen
- Lian-Qing Sun
- Bao-An Wang
- Xiao-Man Zou
- Yi-Ming Mu
- Ju-Ming Lu
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Affiliations: Department of Endocrinology, Chinese PLA General Hospital, Beijing 100853, P.R. China, Department of Traditional Chinese Medicine, First Affiliated Hospital of Medical College of Xi'an Jiaotong University, Xi'an 710061, P.R. China
Published online on: October 18, 2013 https://doi.org/10.3892/ijmm.2013.1530
Pages: 1401-1406

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Abstract

Endoplasmic reticulum (ER) stress and autophagy have both been reported to be associated with lipotoxicity in β-cells, yet the relationship between them has not been fully clarified. In the present study, we tested the hypothesis that the ER stress-autophagic pathway in β-cells is a downstream pathway activated following saturated fatty acid treatment. Mouse insulinoma (MIN6) β-cells were treated with either palmitate or thapsigargin (TG) with or without various inhibitors. The results indicated that palmitate strongly enhanced the protein expression of microtubule-associated protein 1 light chain 3 (LC3)-II. Furthermore, the expression levels of ER stress markers, BiP and CHOP, and phosphorylation levels of JNK were increased after palmitate treatment. In addition, palmitate-induced autophagy was blocked by 500 µM of the ER stress inhibitor tauroursodeoxycholic acid (TUDCA) or 20 µM JNK inhibitor SP600125. In turn, the phosphorylation of Akt (Ser473) was also downregulated by palmitate, while the levels of insulin receptor β (IRβ) were not reduced. A further increase in LC3-II levels was observed in cells treated with both palmitate and 50 µM PI3K/Akt inhibitor LY294002 compared with cells treated with palmitate alone. Palmitate-induced phospho-Akt (Ser473) downregulation was also inhibited by TUDCA or SP600125. Pretreatment with the autophagy inhibitor 3-methyladenine (3-MA, 5 mM) for 1 h increased the expression of ER stress markers, and enhanced cell injuries caused by 0.1 µM TG, including decreased cell viability and insulin secretion. Palmitate induces autophagy in pancreatic β-cells possibly through activation of ER stress and its downstream JNK pathway. Palmitate-induced autophagy may protect β-cells against cell injuries caused by ER stress.

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1	Fujitani Y, Ebato C, Uchida T, Kawamori R and Watada H: β-cell autophagy: a novel mechanism regulating β-cell function and mass: lessons from β-cell-specific Atg7-deficient mice. Islets. 1:151–153. 2009.
2	Ebato C, Uchida T, Arakawa M, Komatsu M, Ueno T, Komiya K, Azuma K, et al: Autophagy is important in islet homeostasis and compensatory increase of beta cell mass in response to high-fat diet. Cell Metab. 8:325–332. 2008. View Article : Google Scholar : PubMed/NCBI
3	Jung HS, Chung KW, Won Kim J, Kim J, Komatsu M, Tanaka K, Nguyen YH, et al: Loss of autophagy diminishes pancreatic beta cell mass and function with resultant hyperglycemia. Cell Metab. 8:318–324. 2008. View Article : Google Scholar : PubMed/NCBI
4	Choi SE, Lee SM, Lee YJ, Li LJ, Lee SJ, Lee JH, Kim Y, et al: Protective role of autophagy in palmitate-induced INS-1 beta-cell death. Endocrinology. 150:126–134. 2009. View Article : Google Scholar : PubMed/NCBI
5	Fujimoto K, Hanson PT, Tran H, Ford EL, Han Z, Johnson JD, Schmidt RE, et al: Autophagy regulates pancreatic beta cell death in response to Pdx1 deficiency and nutrient deprivation. J Biol Chem. 284:27664–27673. 2009. View Article : Google Scholar : PubMed/NCBI
6	Masini M, Bugliani M, Lupi R, del Guerra S, Boggi U, Filipponi F, Marselli L, et al: Autophagy in human type 2 diabetes pancreatic beta cells. Diabetologia. 52:1083–1086. 2009. View Article : Google Scholar : PubMed/NCBI
7	Levine B and Klionsky DJ: Development by self-digestion: molecular mechanisms and biological functions of autophagy. Dev Cell. 6:463–477. 2004. View Article : Google Scholar : PubMed/NCBI
8	Kuma A, Hatano M, Matsui M, Yamamoto A, Nakaya H, Yoshimori T, Ohsumi Y, et al: The role of autophagy during the early neonatal starvation period. Nature. 432:1032–1036. 2004. View Article : Google Scholar : PubMed/NCBI
9	Komiya K, Uchida T, Ueno T, Koike M, Abe H, Hirose T, Kawamori R, et al: Free fatty acids stimulate autophagy in pancreatic β-cells via JNK pathway. Biochem Biophys Res Commun. 401:561–567. 2010.PubMed/NCBI
10	Karaskov E, Scott C, Zhang L, Teodoro T, Ravazzola M and Volchuk A: Chronic palmitate but not oleate exposure induces endoplasmic reticulum stress, which may contribute to INS-1 pancreatic beta-cell apoptosis. Endocrinology. 147:3398–3407. 2006. View Article : Google Scholar
11	Cnop M, Igoillo-Esteve M, Cunha DA, Ladrière L and Eizirik DL: An update on lipotoxic endoplasmic reticulum stress in pancreatic beta-cells. Biochem Soc Trans. 36:909–915. 2008. View Article : Google Scholar : PubMed/NCBI
12	Lai E, Bikopoulos G, Wheeler MB, Rozakis-Adcock M and Volchuk A: Differential activation of ER stress and apoptosis in response to chronically elevated free fatty acids in pancreatic beta-cells. Am J Physiol Endocrinol Metab. 294:E540–E550. 2008. View Article : Google Scholar : PubMed/NCBI
13	Cnop M, Ladrière L, Igoillo-Esteve M, Moura RF and Cunha DA: Causes and cures for endoplasmic reticulum stress in lipotoxic β-cell dysfunction. Diabetes Obes Metab. 12:76–82. 2010.PubMed/NCBI
14	Ogata M, Hino S, Saito A, Morikawa K, Kondo S, Kanemoto S, Murakami T, et al: Autophagy is activated for cell survival after endoplasmic reticulum stress. Mol Cell Biol. 26:9220–9231. 2006. View Article : Google Scholar : PubMed/NCBI
15	Qin L, Wang Z, Tao L and Wang Y: ER stress negatively regulates AKT/TSC/mTOR pathway to enhance autophagy. Autophagy. 6:239–247. 2010. View Article : Google Scholar : PubMed/NCBI
16	Mizushima N and Yoshimori T: How to interpret LC3 immunoblotting. Autophagy. 3:542–545. 2007. View Article : Google Scholar : PubMed/NCBI
17	Klionsky DJ, Elazar Z, Seglen PO and Rubinsztein DC: Does bafilomycin A1 block the fusion of autophagosomes with lysosomes? Autophagy. 4:849–950. 2008. View Article : Google Scholar : PubMed/NCBI
18	Ozcan U, Yilmaz E, Ozcan L, Furuhashi M, Vaillancourt E, Smith RO, Görgün CZ, et al: Chemical chaperones reduce ER stress and restore glucose homeostasis in a mouse model of type 2 diabetes. Science. 313:1137–1140. 2006. View Article : Google Scholar : PubMed/NCBI
19	Urano F, Wang X, Bertolotti A, Zhang Y, Chung P, Harding HP and Ron D: Coupling of stress in the ER to activation of JNK protein kinases by transmembrane protein kinase IRE1. Science. 287:664–666. 2000. View Article : Google Scholar : PubMed/NCBI
20	Hirosumi J, Tuncman G, Chang L, Görgün CZ, Uysal KT, Maeda K, Karin M, et al: A central role for JNK in obesity and insulin resistance. Nature. 420:333–336. 2002. View Article : Google Scholar : PubMed/NCBI
21	Leibiger IB, Leibiger B and Berggren PO: Insulin signaling in the pancreatic beta-cell. Annu Rev Nutr. 28:233–251. 2008. View Article : Google Scholar : PubMed/NCBI
22	Kahn CR, Brüning JC, Michael MD and Kulkarni RN: Knockout mice challenge our concepts of glucose homeostasis and the pathogenesis of diabetes mellitus. J Pediatr Endocrinol Metab. 13:1377–1384. 2000.PubMed/NCBI
23	Wu YT, Tan HL, Huang Q, Ong CN and Shen HM: Activation of the PI3K-Akt-mTOR signaling pathway promotes necrotic cell death via suppression of autophagy. Autophagy. 5:824–834. 2009. View Article : Google Scholar : PubMed/NCBI
24	Scarlatti F, Bauvy C, Ventruti A, Sala G, Cluzeaud F, Vandewalle A, Ghidoni R, et al: Ceramide-mediated macroautophagy involves inhibition of protein kinase B and up-regulation of beclin 1. J Biol Chem. 279:18384–18391. 2004. View Article : Google Scholar : PubMed/NCBI
25	Meijer AJ and Codogno P: Macroautophagy: protector in the diabetes drama? Autophagy. 3:523–526. 2007. View Article : Google Scholar : PubMed/NCBI
26	Leibowitz G, Cerasi E and Ketzinel-Gilad M: The role of mTOR in the adaptation and failure of beta-cells in type 2 diabetes. Diabetes Obes Metab. 10:157–169. 2008. View Article : Google Scholar : PubMed/NCBI
27	Matsuda T, Kido Y, Uchida T and Kasuga M: Reduced insulin signaling and endoplasmic reticulum stress act synergistically to deteriorate pancreatic beta cell function. Kobe J Med Sci. 54:E114–E121. 2008.PubMed/NCBI
28	Ozcan U, Cao Q, Yilmaz E, Lee AH, Iwakoshi NN, Ozdelen E, Tuncman G, et al: Endoplasmic reticulum stress links obesity, insulin action, and type 2 diabetes. Science. 306:457–461. 2004. View Article : Google Scholar : PubMed/NCBI