title: Androgen receptors and testosterone in men--effects of protein ingestion, resistance exercise and fiber type.
abstract: 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.
authors.affiliation: Department of Biology of Physical Activity, University of Jyväskylä, Jyväskylä, Finland. juha.hulmi@sport.jyu.fi
authors.forename: Juha J
authors.initials: JJ
authors.lastname: Hulmi
authors.forename: Juha P
authors.initials: JP
authors.lastname: Ahtiainen
authors.forename: Harri
authors.initials: H
authors.lastname: Selänne
authors.forename: Jeff S
authors.initials: JS
authors.lastname: Volek
authors.forename: Keijo
authors.initials: K
authors.lastname: Häkkinen
authors.forename: Vuokko
authors.initials: V
authors.lastname: Kovanen
authors.forename: Antti A
authors.initials: AA
authors.lastname: Mero
mesh_terms: D000328:Adult; D000367:Age Factors; D015153:Blotting, Western; D004044:Dietary Proteins / Q000008:administration & dosage / Q000494:pharmacology*; D004311:Double-Blind Method; D015444:Exercise / Q000502:physiology*; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D008875:Middle Aged; D018485:Muscle Fibers, Skeletal / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D011944:Receptors, Androgen / Q000235:genetics / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013739:Testosterone / Q000097:blood*
chemical_list: D004044:Dietary Proteins; D012333:RNA, Messenger; D011944:Receptors, Androgen; D013739:Testosterone