Li-Ping Gao1, Hai-Chao Chen2, Ze-Lin Ma1, An-Di Chen1, Hong-Li Du1, Jie Yin2, Yu-Hong Jing3. 1. Institute of Biochemistry and Molecular Biology, School of Basic Medical Sciences, Lanzhou University, Lanzhou City, Gansu province 730000, People's Republic of China. 2. Institute of Anatomy and Histology & Embryology, Neuroscience, School of Basic Medical Sciences, Lanzhou University, Lanzhou City, Gansu Province 730000, People's Republic of China. 3. Institute of Anatomy and Histology & Embryology, Neuroscience, School of Basic Medical Sciences, Lanzhou University, Lanzhou City, Gansu Province 730000, People's Republic of China; Key Laboratory of Preclinical Study for New Drugs of Gansu province, Lanzhou University, Lanzhou City, Gansu Province 730000, People's Republic of China. Electronic address: jingyh@lzu.edu.cn.
Abstract
BACKGROUND: Previous studies suggested that fibrillar human IAPP (hIAPP) is more likely to deposit in β-cells, resulting in β-cell injury. However, the changes in the conformation of hIAPP in lipid environment and the mechanism involved in β-cell damage are unclear. METHODS: Synthetic hIAPP was incubated with five types of free fatty acids and phospholipids 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) and 1-palmitoyl-2-oleoyl-sn-glycero-3-phospho-l-serine (POPS), which constitute the cell membrane. Thioflavin-T fluorescence assay was conducted to analyze the degree of hIAPP fibrosis, and circular dichroism spectroscopy was performed to detect the β-fold formation of hIAPP. Furthermore, INS-1 cells were infected with human IAPP delivered by a GV230-EGFP plasmid. The effects of endogenous hIAPP overexpression induced by sodium palmitate on the survival, endoplasmic reticulum (ER) stress, and apoptosis of INS-1 cells were evaluated. RESULTS: The five types of free fatty acids can accelerate the fibrosis of hIAPP. Sodium palmitate also maintained the stability of fibrillar hIAPP. POPS, not POPC, accelerated hIAPP fibrosis. Treatment of INS-1 cells with sodium palmitate increased the expression of hIAPP, activated ER stress and ER stress-dependent apoptosis signaling pathways, and increased the apoptotic rate. CONCLUSION: Free fatty acids and anionic phospholipid can promote β-fold formation and fibrosis in hIAPP. High lipid induced the overexpression of hIAPP and aggravated ER stress and apoptosis in INS-1 cells, which caused β-cell death in high lipid environment. GENERAL SIGNIFICANCE: Our study reveals free fatty acids and hIAPP synergistically implicated in endoplasmic reticulum stress and apoptosis of islet β-cells.
BACKGROUND: Previous studies suggested that fibrillar humanIAPP (hIAPP) is more likely to deposit in β-cells, resulting in β-cell injury. However, the changes in the conformation of hIAPP in lipid environment and the mechanism involved in β-cell damage are unclear. METHODS: Synthetic hIAPP was incubated with five types of free fatty acids and phospholipids1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) and 1-palmitoyl-2-oleoyl-sn-glycero-3-phospho-l-serine (POPS), which constitute the cell membrane. Thioflavin-T fluorescence assay was conducted to analyze the degree of hIAPP fibrosis, and circular dichroism spectroscopy was performed to detect the β-fold formation of hIAPP. Furthermore, INS-1 cells were infected with humanIAPP delivered by a GV230-EGFP plasmid. The effects of endogenous hIAPP overexpression induced by sodium palmitate on the survival, endoplasmic reticulum (ER) stress, and apoptosis of INS-1 cells were evaluated. RESULTS: The five types of free fatty acids can accelerate the fibrosis of hIAPP. Sodium palmitate also maintained the stability of fibrillar hIAPP. POPS, not POPC, accelerated hIAPP fibrosis. Treatment of INS-1 cells with sodium palmitate increased the expression of hIAPP, activated ER stress and ER stress-dependent apoptosis signaling pathways, and increased the apoptotic rate. CONCLUSION:Free fatty acids and anionic phospholipid can promote β-fold formation and fibrosis in hIAPP. High lipid induced the overexpression of hIAPP and aggravated ER stress and apoptosis in INS-1 cells, which caused β-cell death in high lipid environment. GENERAL SIGNIFICANCE: Our study reveals free fatty acids and hIAPP synergistically implicated in endoplasmic reticulum stress and apoptosis of islet β-cells.
Authors: Israel Martínez-Navarro; Raúl Díaz-Molina; Angel Pulido-Capiz; Jaime Mas-Oliva; Ismael Luna-Reyes; Eustolia Rodríguez-Velázquez; Ignacio A Rivero; Marco A Ramos-Ibarra; Manuel Alatorre-Meda; Victor García-González Journal: Biomolecules Date: 2020-08-19