Protein ingestion preserves proteasome activity during intense aseptic inflammation and facilitates skeletal muscle recovery in humans

Br J Nutr. 2017 Aug;118(3):189-200. doi: 10.1017/S0007114517001829.


The ubiquitin-proteasome system (UPS) is the main cellular proteolytic system responsible for the degradation of normal and abnormal (e.g. oxidised) proteins. Under catabolic conditions characterised by chronic inflammation, the UPS is activated resulting in proteolysis, muscle wasting and impaired muscle function. Milk proteins provide sulphur-containing amino acid and have been proposed to affect muscle inflammation. However, the response of the UPS to aseptic inflammation and protein supplementation is largely unknown. The aim of this study was to investigate how milk protein supplementation affects UPS activity and skeletal muscle function under conditions of aseptic injury induced by intense, eccentric exercise. In a double-blind, cross-over, repeated measures design, eleven men received either placebo (PLA) or milk protein concentrate (PRO, 4×20 g on exercise day and 20 g/d for the following 8 days), following an acute bout of eccentric exercise (twenty sets of fifteen eccentric contractions at 30°/s) on an isokinetic dynamometer. In each trial, muscle biopsies were obtained from the vastus lateralis muscle at baseline, as well as at 2 and 8 d post exercise, whereas blood samples were collected before exercise and at 6 h, 1 d, 2 d and 8 d post exercise. Muscle strength and soreness were assessed before exercise, 6 h post exercise and then daily for 8 consecutive days. PRO preserved chymotrypsin-like activity and attenuated the decrease of strength, facilitating its recovery. PRO also prevented the increase of NF-κB phosphorylation and HSP70 expression throughout recovery. We conclude that milk PRO supplementation following exercise-induced muscle trauma preserves proteasome activity and attenuates strength decline during the pro-inflammatory phase.

Keywords: CK creatine kinase activity; CT-L chymotrypsin-like; DOMS delayed onset of muscle soreness; ES effect size; PC protein carbonyls; PLA placebo; ROS reactive oxygen species; UPS ubiquitin–proteasome system; Aseptic inflammation; Muscle proteasome; Muscle strength performance; Protein supplementation; Skeletal muscle damage.

Publication types

  • Randomized Controlled Trial

MeSH terms

  • Adult
  • Cross-Over Studies
  • Dietary Supplements
  • Double-Blind Method
  • Exercise*
  • HSP70 Heat-Shock Proteins / genetics
  • HSP70 Heat-Shock Proteins / metabolism
  • Humans
  • Inflammation / metabolism*
  • Male
  • Milk Proteins / administration & dosage*
  • Muscle Strength / physiology
  • NF-kappa B / genetics
  • NF-kappa B / metabolism
  • Pain / prevention & control
  • Pain Measurement
  • Phosphorylation
  • Proteasome Endopeptidase Complex / metabolism*
  • Quadriceps Muscle / metabolism*
  • Sports Nutritional Physiological Phenomena
  • Young Adult


  • HSP70 Heat-Shock Proteins
  • Milk Proteins
  • NF-kappa B
  • Proteasome Endopeptidase Complex