Glucocorticoids increase skeletal muscle NF-κB inducing kinase (NIK): links to muscle atrophy

Physiol Rep. 2016 Nov;4(21):e13014. doi: 10.14814/phy2.13014. Epub 2016 Nov 14.

Abstract

Glucocorticoids (GC) are a frontline therapy for numerous acute and chronic diseases because of their demonstrated efficacy at reducing systemic inflammation. An unintended side effect of GC therapy is the stimulation of skeletal muscle atrophy. Pathophysiological mechanisms responsible for GC-induced skeletal muscle atrophy have been extensively investigated, and the ability to treat patients with GC without unintended muscle atrophy has yet to be realized. We have reported that a single, standard-of-care dose of Methylprednisolone increases in vivo expression of NF-κB-inducing kinase (NIK), an important upstream regulatory kinase controlling NF-κB activation, along with other key muscle catabolic regulators such as Atrogin-1 and MuRF1 that induce skeletal muscle proteolysis. Here, we provide experimental evidence that overexpressing NIK by intramuscular injection of recombinant human NIK via adenoviral vector in mouse tibialis anterior muscle induces a 30% decrease in the average fiber cross-sectional area that is associated with increases in mRNA expression of skeletal muscle atrophy biomarkers MuRF1, Atrogin-1, myostatin and Gadd45. A single injection of GC induced NIK mRNA and protein within 2 h, with the increased NIK localized to nuclear and sarcolemmal locations within muscle fibers. Daily GC injections induced skeletal muscle fore limb weakness as early as 3 days with similar atrophy of muscle fibers as observed with NIK overexpression. NIK overexpression in primary human skeletal muscle myotubes increased skeletal muscle atrophy biomarkers, while NIK knockdown significantly attenuated GC-induced increases in NIK and Atrogin-1. These results suggest that NIK may be a novel, previously unrecognized mediator of GC-induced skeletal muscle atrophy.

Keywords: Atrogin‐1; MuRF1; NF‐κB inducing kinase; catabolism; methylprednisolone.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, N.I.H., Extramural

MeSH terms

  • Animals
  • Glucocorticoids / administration & dosage
  • Glucocorticoids / pharmacology*
  • Humans
  • Male
  • Mice
  • Mice, Inbred C57BL
  • Muscle Fibers, Skeletal / drug effects
  • Muscle Proteins / metabolism
  • Muscle, Skeletal / enzymology*
  • Muscle, Skeletal / metabolism
  • Muscular Atrophy / chemically induced*
  • Muscular Atrophy / metabolism*
  • Muscular Atrophy / pathology
  • NF-kappa B / metabolism*
  • Protein-Serine-Threonine Kinases / administration & dosage
  • Protein-Serine-Threonine Kinases / metabolism*
  • RNA, Messenger / genetics
  • SKP Cullin F-Box Protein Ligases / metabolism
  • Tripartite Motif Proteins / metabolism
  • Ubiquitin-Protein Ligases / metabolism

Substances

  • Glucocorticoids
  • Muscle Proteins
  • NF-kappa B
  • RNA, Messenger
  • Tripartite Motif Proteins
  • FBXO32 protein, human
  • SKP Cullin F-Box Protein Ligases
  • TRIM63 protein, human
  • Ubiquitin-Protein Ligases
  • Protein-Serine-Threonine Kinases
  • NF-kappa B kinase