Androgen receptors and testosterone in men--effects of protein ingestion, resistance exercise and fiber type

J Steroid Biochem Mol Biol. 2008 May;110(1-2):130-7. doi: 10.1016/j.jsbmb.2008.03.030. Epub 2008 Mar 30.


The purpose of this study was to examine the impact of protein ingestion on circulating testosterone and muscle androgen receptor (AR) as well as on insulin-like growth factor-I (MGF and IGF-IEa) responses to a resistance exercise (RE) bout in (57-72 year) men. Protein (15 g whey) (n=9) or placebo (n=9) was consumed before and after a RE bout (5 sets of 10 repetition maximums), and vastus lateralis muscle biopsies were taken pre, 1 and 48 h post-RE. The protein ingestion blunted the RE-induced increase in serum free and total testosterone while the RE bout significantly increased muscle AR mRNA levels in older men (P<0.05). However, protein ingestion did not significantly affect AR mRNA or protein expression, or MGF and IGF-IEa mRNA expression at 1 and 48 h post-RE. Immunohistochemical staining of muscle cross-sections was done with antibodies specific to AR and MyHC I and II and showed that there seems to be within or near the type-I muscle fibers a greater staining of ARs than within or near the type-II fibres. In conclusion, the protein ingestion hinders RE-induced increase in serum testosterone in older men but may not significantly affect muscle AR, MGF or IGF-IEa gene expression. Furthermore, the present study shows that even older men are able to increase muscle AR mRNA expression in response to a RE bout.

Publication types

  • Randomized Controlled Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Age Factors
  • Blotting, Western
  • Dietary Proteins / administration & dosage
  • Dietary Proteins / pharmacology*
  • Double-Blind Method
  • Exercise / physiology*
  • Humans
  • Immunohistochemistry
  • Male
  • Middle Aged
  • Muscle Fibers, Skeletal / metabolism*
  • RNA, Messenger / genetics
  • RNA, Messenger / metabolism
  • Receptors, Androgen / genetics
  • Receptors, Androgen / metabolism*
  • Reverse Transcriptase Polymerase Chain Reaction
  • Testosterone / blood*


  • Dietary Proteins
  • RNA, Messenger
  • Receptors, Androgen
  • Testosterone