PMID- 34610358 OWN - NLM STAT- MEDLINE DCOM- 20220330 LR - 20220330 IS - 1872-8057 (Electronic) IS - 0303-7207 (Linking) VI - 539 DP - 2022 Jan 1 TI - Low-grade elevation of palmitate and lipopolysaccharide synergistically induced beta-cell damage via inhibition of neutral ceramidase. PG - 111473 LID - S0303-7207(21)00317-8 [pii] LID - 10.1016/j.mce.2021.111473 [doi] AB - High concentrations of free fatty acids (FFAs) or lipopolysaccharide (LPS) could lead to beta-cell apoptosis and dysfunction, while low-grade elevation of FFAs or LPS, which are more common in people with type 2 diabetes mellitus (T2DM) or obesity, have no obvious toxic effect on beta-cells. Palmitate is a component closely related to metabolic disorders in FFAs. Recent studies have found that low-grade elevation of palmitate and LPS synergistically affects the sphingolipid signaling pathway by activating Toll-like receptor 4 (TLR4) and further enhances the expression of inflammatory cytokines in immune cells. Previous studies demonstrated that sphingolipids also played an important role in the occurrence and development of T2DM. This study aimed to investigate the synergistic effects of low-grade elevation of palmitate and LPS on viability, apoptosis and insulin secretion in the rat pancreatic beta-cell line INS-1 or islets and the role of sphingolipids in this process. We showed that low-grade elevation of palmitate or LPS alone did not affect the viability, apoptosis, glucose-stimulated insulin secretion (GSIS) or intracellular insulin content of INS-1 cells or islets, while the combination of the two synergistically inhibited cell viability, induced apoptosis and decreased basal insulin secretion in INS-1 cells or islets. Treatment with palmitate and LPS markedly upregulated TLR4 protein expression and downregulated neutral ceramidase (NCDase) activity and protein expression. Additionally, low-grade elevation of palmitate and LPS synergistically induced a significant increase in ceramide and a decrease in sphingosine-1-phosphate. Blocking TLR4 signaling or overexpressing NCDase remarkably attenuated INS-1 cell injury induced by the combination of palmitate and LPS. However, inhibition of ceramide synthase did not ameliorate injury induced by palmitate and LPS. Overall, we show for the first time that low-grade elevation of palmitate and LPS synergistically induced beta-cell damage by activating TLR4 signaling, inhibiting NCDase activity, and further modulating sphingolipid metabolism, which was different from a high concentration of palmitate-induced beta-cell injury by promoting ceramide synthesis. CI - Copyright (c) 2021 The Authors. Published by Elsevier B.V. All rights reserved. FAU - Xu, Ya-Nan AU - Xu YN AD - Department of Endocrinology, The Second Affiliated Hospital of Nanjing Medical University, Nanjing, 210011, China. FAU - Wang, Zheng AU - Wang Z AD - Department of Endocrinology, The Second Affiliated Hospital of Nanjing Medical University, Nanjing, 210011, China; Department of Nephrology, Jiangsu University Affiliated People's Hospital, Zhenjiang, 212002, China. FAU - Zhang, Shao-Kun AU - Zhang SK AD - Department of Endocrinology, The Second Affiliated Hospital of Nanjing Medical University, Nanjing, 210011, China. FAU - Xu, Jia-Rong AU - Xu JR AD - Department of Endocrinology, The Second Affiliated Hospital of Nanjing Medical University, Nanjing, 210011, China. FAU - Pan, Zhi-Xiong AU - Pan ZX AD - Guangxi Health Commission Key Laboratory of Basic Research in Sphingolipid Metabolism Related Diseases, Affiliated Hospital of Guilin Medical University, Guilin, 541001, China. FAU - Wei, Xiao AU - Wei X AD - Department of Endocrinology, Affiliated Hospital of Integrated Traditional Chinese and Western Medicine, Nanjing University of Chinese Medicine, Nanjing, 210028, China. FAU - Wen, Hong-Hua AU - Wen HH AD - Department of Endocrinology, The Second Affiliated Hospital of Nanjing Medical University, Nanjing, 210011, China. FAU - Luo, Yan-Shi AU - Luo YS AD - Department of Endocrinology, The Second Affiliated Hospital of Nanjing Medical University, Nanjing, 210011, China. FAU - Guo, Mao-Jun AU - Guo MJ AD - Department of Endocrinology, The Second Affiliated Hospital of Nanjing Medical University, Nanjing, 210011, China. FAU - Zhu, Qun AU - Zhu Q AD - Department of Endocrinology, The Second Affiliated Hospital of Nanjing Medical University, Nanjing, 210011, China. Electronic address: zhuqun@njmu.edu.cn. LA - eng PT - Journal Article PT - Research Support, Non-U.S. Gov't DEP - 20211002 PL - Ireland TA - Mol Cell Endocrinol JT - Molecular and cellular endocrinology JID - 7500844 RN - 0 (Lipopolysaccharides) RN - 0 (Palmitates) RN - 0 (Sphingolipids) RN - 0 (Tlr4 protein, rat) RN - 0 (Toll-Like Receptor 4) RN - EC 3.5.1.23 (Asah2 protein, rat) RN - EC 3.5.1.23 (Neutral Ceramidase) SB - IM MH - Animals MH - Apoptosis MH - Cell Line MH - Drug Synergism MH - Gene Expression Regulation/drug effects MH - Insulin-Secreting Cells/*cytology/drug effects/metabolism MH - Lipopolysaccharides/*adverse effects MH - Neutral Ceramidase/*metabolism MH - Palmitates/*adverse effects MH - Rats MH - Signal Transduction/drug effects MH - Sphingolipids/metabolism MH - Toll-Like Receptor 4/*metabolism OTO - NOTNLM OT - Lipopolysaccharide OT - Neutral ceramidase OT - Palmitate OT - Toll-like receptor 4 OT - beta-Cell EDAT- 2021/10/06 06:00 MHDA- 2022/03/31 06:00 CRDT- 2021/10/05 20:10 PHST- 2021/04/01 00:00 [received] PHST- 2021/09/28 00:00 [revised] PHST- 2021/09/30 00:00 [accepted] PHST- 2021/10/06 06:00 [pubmed] PHST- 2022/03/31 06:00 [medline] PHST- 2021/10/05 20:10 [entrez] AID - S0303-7207(21)00317-8 [pii] AID - 10.1016/j.mce.2021.111473 [doi] PST - ppublish SO - Mol Cell Endocrinol. 2022 Jan 1;539:111473. doi: 10.1016/j.mce.2021.111473. Epub 2021 Oct 2.