Leptin impairs myogenesis in C2C12 cells through JAK/STAT and MEK signaling pathways

• Published in: Cytokine (Philadelphia, Pa.) Vol. 61; no. 2; pp. 445 - 454
• Main Authors: Pijet, Maja, Pijet, Barbara, Litwiniuk, Anna, Pajak, Beata, Gajkowska, Barbara, Orzechowski, Arkadiusz
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01.02.2013
• Subjects: 1-Phosphatidylinositol 3-kinase; Adipose tissue; AKT protein; Animals; C2C12 muscle cells; Cell Differentiation; Cell Differentiation - drug effects; Cell Line; Cell Survival; Cell Survival - drug effects; cell viability; Cytokines; cytology; Cytoprotection; Cytoprotection - drug effects; Differentiation; drug effects; enzymology; Flavonoids; Flavonoids - pharmacology; Glycogen Synthase Kinase 3; Glycogen Synthase Kinase 3 - metabolism; Glycogen Synthase Kinase 3 beta; Insulin; Insulin - pharmacology; Interferon-gamma; Interferon-gamma - pharmacology; Janus Kinases; Janus Kinases - metabolism; Lean body mass; Leptin; Leptin - pharmacology; MAP kinase; MAP Kinase Signaling System; MAP Kinase Signaling System - drug effects; metabolic inhibitors; metabolism; Mice; Mitogen-Activated Protein Kinase Kinases; Mitogen-Activated Protein Kinase Kinases - metabolism; mitogenesis; Mitogens; Mitogens - pharmacology; muscle development; Muscle Development - drug effects; muscle fibers; muscles; Myoblasts; Myoblasts - cytology; Myoblasts - drug effects; Myoblasts - enzymology; MyoD Protein; MyoD Protein - metabolism; Myogenesis; Myogenin; Myogenin - metabolism; Myotubes; Obesity; pharmacology; Phosphatidylinositol 3-Kinases; Phosphatidylinositol 3-Kinases - metabolism; Phosphorylation; Phosphorylation - drug effects; protein synthesis; Proteins; Signal transduction; Skeletal muscle; SOCS3/JAK/STAT3 pathway; Stat3 protein; STAT3 Transcription Factor; STAT3 Transcription Factor - metabolism; STAT5 Transcription Factor; STAT5 Transcription Factor - metabolism; Suppressor of Cytokine Signaling 3 Protein; Suppressor of Cytokine Signaling Proteins; Suppressor of Cytokine Signaling Proteins - metabolism; Sus scrofa; Transcription, Genetic; Transcription, Genetic - drug effects; white adipose tissue; SOCS3/JAK/STAT3 pathway; Insulin; Leptin; Myogenesis; C2C12 muscle cells
• DOI: 10.1016/j.cyto.2012.11.002
• ISSN: 1043-4666; 1096-0023

Schematic diagram showing the molecular mechanisms of leptin-dependent repression of myogenic differentiation. Leptin interacts with functional Ob-R to activate JAK/STAT and Ras/MEK but PI3-K/AKT signaling pathways. JAK/STAT stimulates proliferation/mitogenicity whereas MEK lowers both viability and myogenic differentiation through ERK1/2-dependent reduction in MRFs expression levels. GSK-3β activity inhibits viability (Y216-phospho-GSK-3β), while immobilization of SOCS3 breaks up the feedback control of JAK/STAT activity. [Display omitted] ► Leptin (100ng/mL) stimulates mitogenesis and raise T202/Y204P-ERK1/2 protein expression. ► Leptin impairs cell viability and muscle fiber formation. ► Both JAK/STAT3 and MEK/MAPK but not PI3-K/AKT/GSK-3β signaling pathways were activated by leptin. ► Insulin surpasses leptin effect through PI3-K/AKT-dependent inhibition of GSK-3beta. ► STAT3 (Y705P-STAT3) and MEK (T202/Y204P-ERK1/2) mediate leptin-dependent effects. Reduced lean body mass in genetically obese (ob/ob) or anorectic/cachectic subjects prompted us to verify the hypothesis whether leptin, white adipose tissue cytokine, might be a negative organizer of myogenesis. Recombinant leptin (100ng/mL) stimulated mitogenesis together with the raise in T202/Y204P-ERK1/2 protein expression. Concomitantly, it impaired cell viability and muscle fiber formation from C2C12 mouse myoblasts. Detailed acute and chronic studies with the use of metabolic inhibitors revealed that both JAK/STAT3 and MEK/MAPK but not PI3-K/AKT/GSK-3β signaling pathways were activated by leptin, and that STAT3 (Y705P-STAT3) and MEK (T202/Y204P-ERK1/2) mediate these effects. In contrary, insulin evoked PI3-K-dependent phosphorylation of AKT (S473) and GSK-3β (S9) and insulin surpassed leptin-dependent inhibition of myogenic differentiation in PI3-K-dependent manner. GSK-3β seems to play dual role in muscle development. Insulin-dependent effect on GSK-3β (S9P-GSK-3β) led to accelerated myotube construction. In contrary, leptin through MEK-dependent manner caused GSK-3β phosphorylation (Y216P-GSK-3β) with resultant drop in myoblast fusion. Summing up, partially opposite effects of insulin and leptin on skeletal muscle growth emphasize the importance of interplay between these cytokines. They determine how muscle mass is gained or lost.