title: Leukocyte IGF-1 receptor expression during muscle recovery.
abstract: BACKGROUND
  The insulin-like growth factor 1 (IGF-1) system plays a central role in anabolic cellular processes. Recently, a regulatory role of IGF-1 in the immune response for muscle repair has been suggested, but how it modulates the inflammatory process is largely unknown. We evaluated changes in leukocyte expression of IGF-1 receptors (IGF-1R) during recovery from resistance exercise to determine whether changes in the potential for IGF-1 interactions with leukocytes may mediate the role of IGF-1 in muscle repair.
  
  
  METHODS
  Twenty resistance-trained men (18-35 yr) performed resistance exercise followed by cold water immersion (CWI) or control treatment (CON) on three consecutive days. Blood was sampled at baseline (PRE), immediately (IP), 30 min (30P), 24 h (24H), and 48 h after (48H) exercise. Circulating IGF-1 was assayed, and IGF-1 receptor expression (CD221) on gated circulating leukocytes (monocytes, granulocytes, and lymphocytes) was measured by flow cytometry. Time and treatment effects were analyzed with ANCOVA.
  
  
  RESULTS
  Circulating IGF-1 significantly increased from PRE to IP as a result of resistance exercise, but no differences between CON and CWI were observed. Mean fluorescence intensity of CD221 on monocytes and granulocytes and percent of CD221+ granulocytes significantly increased at 30P (P < 0.000) and returned to preexercise levels by 24H. No treatment effects on monocytes or granulocytes were observed. On lymphocytes, mean fluorescence intensity of CD221+ significantly increased from PRE to 30P in CWI.
  
  
  CONCLUSIONS
  Changes in IGF-1 and its receptor on monocytes and granulocytes seem to be part of the mechanism that facilitates recovery from resistance exercise during earlier stages of muscle recovery. In addition, CWI seems to alter IGF-mediated responses on slower-acting lymphocytes, suggesting that its effects may be seen in later stages of muscle repair.
authors.affiliation: Department of Educational and Human Sciences, Institute of Exercise Physiology and Wellness, Sport and Exercise Science, University of Central Florida, Orlando, FL.
authors.forename: Maren S
authors.initials: MS
authors.lastname: Fragala
authors.forename: Adam R
authors.initials: AR
authors.lastname: Jajtner
authors.forename: Jeremy R
authors.initials: JR
authors.lastname: Townsend
authors.forename: Adam M
authors.initials: AM
authors.lastname: Gonzalez
authors.forename: Adam J
authors.initials: AJ
authors.lastname: Wells
authors.forename: Leonardo P
authors.initials: LP
authors.lastname: Oliveira
authors.forename: Jay R
authors.initials: JR
authors.lastname: Hoffman
authors.forename: Jeffrey R
authors.initials: JR
authors.lastname: Stout
authors.forename: David H
authors.initials: DH
authors.lastname: Fukuda
mesh_terms: D000293:Adolescent; D000328:Adult; D003080:Cold Temperature; D015444:Exercise / Q000502:physiology*; D006098:Granulocytes / Q000378:metabolism; D006801:Humans; D007101:Immersion; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D008214:Lymphocytes / Q000378:metabolism; D008297:Male; D009000:Monocytes / Q000378:metabolism; D018482:Muscle, Skeletal / Q000378:metabolism* / Q000473:pathology; D017526:Receptor, IGF Type 1 / Q000097:blood*; D020127:Recovery of Function / Q000502:physiology*; D055070:Resistance Training; D055815:Young Adult
chemical_list: D007334:Insulin-Like Growth Factor I; D017526:Receptor, IGF Type 1