title: Melatonin inhibits tunicamycin-induced endoplasmic reticulum stress and insulin resistance in skeletal muscle cells.
abstract: The prevalence of type 2 diabetes mellitus (T2D) is increasing worldwide. Melatonin possesses various beneficial metabolic actions, decreased levels of which may accelerate T2D. Endoplasmic reticulum stress (ERS) has been linked to insulin resistance in multiple tissues, but the role of melatonin on ERS and insulin resistance in skeletal muscle has not yet been investigated. In this study, the results showed that tunicamycin decreased insulin-stimulated Akt phosphorylation, but promoted the phosphorylation of protein kinase R-like ER protein kinase (PERK) time-dependently in C2C12 cells. Consistently, ERS gene markers, including binding immunoglobulin protein (BIP)/glucose regulated protein 78 (GRP78) expression and the splicing of X box binding protein 1 (XBP-1), were activated by tunicamycin time-dependently. Interestingly, melatonin pretreatment reversed the elevated PERK phosphorylation, as well as the activation of Bip expression and XBP-1 splicing, and prevented the inhibitory effect of tunicamycin on Akt phosphorylation. In addition, the insulin-provoked glucose transport was reduced by tunicamycin, and then promoted by melatonin pretreatment. A strong phosphorylation of inositol-requiring enzyme 1 (IRE-1), c-JUN NH2-terminal kinase (JNK), and insulin receptor substrate 1 (IRS-1) serine, and simultaneously, a dramatic decrease of IRS-1 tyrosine phosphorylation were observed in the presence of tunicamycin, leading to a blockade of insulin signaling, which was reversed by melatonin pretreatment. Furthermore, luzindole pretreatment acted inversely with melatonin action on glucose uptake and insulin signaling. Therefore, these results demonstrated that melatonin pretreatment inhibited the activated role of tunicamycin on ERS and insulin resistance through melatonin receptor-mediated IRE-1/JNK/IRS-1 insulin signaling in skeletal muscle cells.
authors.affiliation: Department of Geriatrics, the Second Affiliated Hospital, Medical School of Xi'an Jiaotong University, Xi'an, 710004, Shaanxi, PR China. Electronic address: xiaojuanquan@163.com.
authors.forename: Xiaojuan
authors.initials: X
authors.lastname: Quan
authors.affiliation: Department of Pediatrics, Shaanxi Provincial People's Hospital, Xi'an, 710068, Shaanxi, PR China.
authors.forename: Juyan
authors.initials: J
authors.lastname: Wang
authors.affiliation: Department of Geriatrics, the Second Affiliated Hospital, Medical School of Xi'an Jiaotong University, Xi'an, 710004, Shaanxi, PR China.
authors.forename: Chunlian
authors.initials: C
authors.lastname: Liang
authors.affiliation: Department of Geriatrics, the Second Affiliated Hospital, Medical School of Xi'an Jiaotong University, Xi'an, 710004, Shaanxi, PR China.
authors.forename: Huadong
authors.initials: H
authors.lastname: Zheng
authors.affiliation: Department of Geriatrics, the Second Affiliated Hospital, Medical School of Xi'an Jiaotong University, Xi'an, 710004, Shaanxi, PR China.
authors.forename: Lin
authors.initials: L
authors.lastname: Zhang
mesh_terms: D000818:Animals; D002460:Cell Line; D004721:Endoplasmic Reticulum / Q000187:drug effects* / Q000378:metabolism; D000091342:Endoplasmic Reticulum Chaperone BiP; D008550:Melatonin / Q000494:pharmacology*; D051379:Mice; D018482:Muscle, Skeletal / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D010766:Phosphorylation; D015398:Signal Transduction; D013312:Stress, Physiological; D014415:Tunicamycin / Q000037:antagonists & inhibitors* / Q000494:pharmacology
chemical_list: D000091342:Endoplasmic Reticulum Chaperone BiP; C000717248:Hspa5 protein, mouse; D014415:Tunicamycin; D008550:Melatonin
keywords: ERS; Insulin resistance; Melatonin; Skeletal muscle cells; Tunicamycin