Sepsis attenuates the anabolic response to skeletal muscle contraction

Shock. 2015 Apr;43(4):344-51. doi: 10.1097/SHK.0000000000000304.

Abstract

Electrically stimulated muscle contraction is a potential clinical therapy to treat sepsis-induced myopathy; however, whether sepsis alters contraction-induced anabolic signaling is unknown. Polymicrobial peritonitis was produced by cecal ligation and puncture (CLP) in male C57BL/6 mice and time-matched, pair-fed controls (CON). At ∼24 h post-CLP, the right hindlimb was electrically stimulated via the sciatic nerve to evoke maximal muscle contractions, and the gastrocnemius was collected 2 h later. Protein synthesis was increased by muscle contraction in CON mice. Sepsis suppressed the rate of synthesis in both the nonstimulated (31%) and stimulated (57%) muscle versus CON. Contraction of muscle in CON mice increased the phosphorylation of mTORC1 (mammalian target of rapamycin [mTOR] complex 1) substrates S6K1 (70-kd ribosomal protein S6 kinase 1) Thr (8-fold), S6K1 ThrSer (7-fold) and 4E-BP1 Ser (11-fold). Sepsis blunted the contraction-induced phosphorylation of S6K1 Thr (67%), S6K1 ThrSer (46%), and 4E-BP1 Ser (85%). Conversely, sepsis did not appear to modulate protein elongation as eEF2 Thr phosphorylation was decreased similarly by muscle contraction in both groups. Mitogen-activated protein kinase signaling was discordant following contraction in septic muscle; phosphorylation of extracellular signal-regulated kinase ThrTyr and p38 ThrTyr was increased similarly in both CON and CLP mice, while sepsis prevented the contraction-induced phosphorylation of JNK ThrTyr and c-JUN Ser. The expression of interleukin 6 and tumor necrosis factor α (TNF-α) mRNA in muscle was increased by sepsis, and contraction increased TNF-α to a greater extent in muscle from septic than CON mice. Injection of the mTOR inhibitor Torin2 in separate mice confirmed that contraction-induced increases in S6K1 and 4E-BP1 were mTOR mediated. These findings demonstrate that resistance to contraction-induced anabolic signaling occurs during sepsis and is predominantly mTORC1-dependent.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Adaptor Proteins, Signal Transducing
  • Anabolic Agents
  • Animals
  • Carrier Proteins / metabolism
  • Cell Cycle Proteins
  • Electric Stimulation
  • Eukaryotic Initiation Factors
  • Hindlimb / pathology
  • Inflammation / metabolism
  • Interleukin-6 / metabolism
  • Male
  • Mechanistic Target of Rapamycin Complex 1
  • Mice
  • Mice, Inbred C57BL
  • Multiprotein Complexes / metabolism
  • Muscle Contraction*
  • Muscle, Skeletal / metabolism
  • Muscle, Skeletal / microbiology*
  • Muscle, Skeletal / physiology*
  • Naphthyridines / chemistry
  • Peritonitis / physiopathology
  • Phosphoproteins / metabolism
  • Phosphorylation
  • Ribosomal Protein S6 Kinases, 90-kDa / metabolism
  • Sciatic Nerve / pathology
  • Sepsis / physiopathology*
  • Signal Transduction
  • TOR Serine-Threonine Kinases / metabolism
  • Tumor Necrosis Factor-alpha / metabolism

Substances

  • 9-(6-aminopyridin-3-yl)-1-(3-(trifluoromethyl)phenyl)benzo(h)(1,6)naphthyridin-2(1H)-one
  • Adaptor Proteins, Signal Transducing
  • Anabolic Agents
  • Carrier Proteins
  • Cell Cycle Proteins
  • Eif4ebp1 protein, mouse
  • Eukaryotic Initiation Factors
  • Interleukin-6
  • Multiprotein Complexes
  • Naphthyridines
  • Phosphoproteins
  • Tumor Necrosis Factor-alpha
  • Mechanistic Target of Rapamycin Complex 1
  • Ribosomal Protein S6 Kinases, 90-kDa
  • Rps6ka1 protein, mouse
  • TOR Serine-Threonine Kinases