Skeletal muscle mitochondrial uncoupling drives endocrine cross-talk through induction of FGF21 as a myokine

S. Keipert, M. Ost, K. Johann, F. Imber, M. Jastroch, E.M. van Schothorst, J. Keijer, S. Klaus

Research output: Contribution to journalArticleAcademicpeer-review

133 Citations (Scopus)

Abstract

UCP1-Tg mice with ectopic expression of uncoupling protein 1 (UCP1) in skeletal muscle (SM) are a model of improved substrate metabolism and increased longevity. Analysis of myokine expression showed an induction of fibroblast growth factor 21 (FGF21) in SM, resulting in approximately fivefold elevated circulating FGF21 in UCP1-Tg mice. Despite a reduced muscle mass, UCP1-Tg mice showed no evidence for a myopathy or muscle autophagy deficiency but an activation of integrated stress response (ISR; eIF2a/ATF4) in SM. Targeting mitochondrial function in vitro by treating C2C12 myoblasts with the uncoupler FCCP resulted in a dose-dependent activation of ISR, which was associated with increased expression of FGF21, which was also observed by treatment with respiratory chain inhibitors antimycin A and myxothiazol. The cofactor required for FGF21 action, ß-klotho, was expressed in white adipose tissue (WAT) of UCP1-Tg mice, which showed an increased browning of WAT similar to what occurred in altered adipocyte morphology, increased brown adipocyte markers (UCP1, CIDEA), lipolysis (HSL phosphorylation), and respiratory capacity. Importantly, treatment of primary white adipocytes with serum of transgenic mice resulted in increased UCP1 expression. Additionally, UCP1-Tg mice showed reduced body length through the suppressed IGF-I-GH axis and decreased bone mass. We conclude that the induction of FGF21 as a myokine is coupled to disturbance of mitochondrial function and ISR activation in SM. FGF21 released from SM has endocrine effects leading to increased browning of WAT and can explain the healthy metabolic phenotype of UCP1-Tg mice. These results confirm muscle as an important endocrine regulator of whole body metabolism.
Original languageEnglish
Pages (from-to)E469-E482
JournalAmerican Journal of Physiology. Endocrinology and Metabolism
Volume306
Issue number5
DOIs
Publication statusPublished - 2014

Keywords

  • growth-factor 21
  • activated-receptor-gamma
  • white adipose-tissues
  • ppar-alpha
  • adaptive thermogenesis
  • protein-1 expression
  • glucose-homeostasis
  • insulin sensitivity
  • respiratory-chain
  • lipid-metabolism

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