title: Local administration of insulin-like growth factor-I (IGF-I) stimulates tendon collagen synthesis in humans.
abstract: Collagen is the predominant structural protein in tendons and ligaments, and can be controlled by hormonal changes. In animals, injections of insulin-like growth factor I (IGF-I) has been shown to increase collagen synthesis in tendons and ligaments and to improve structural tissue healing, but the effect of local IGF-I administration on tendon collagen synthesis in human has not been studied. The purpose of this study was to study whether local injections of IGF-I would have a stimulating effect on tendon collagen synthesis. Twelve healthy nonsmoking men [age 62 ± 1 years (mean ± SEM), BMI 27 ± 1] participated. Two injections of either human recombinant IGF-I (0.1 mL Increlex©) or saline (control) into each patellar tendon were performed 24-h apart, respectively. Tendon collagen fractional synthesis rate (FSR) was measured by stable isotope technique in the hours after the second injection. Simultaneously, interstitial peritendinous (IGF-I) and [procollagen type I N-terminal propeptide (PINP)], as a marker for type I collagen synthesis, were determined by microdialysis technique. Tendon collagen FSR and PINP were significantly higher in the IGF-I leg compared with the control leg (P < 0.05). In conclusion, local IGF-I administration can directly enhance tendon collagen synthesis both within and around the human tendon tissue.
authors.affiliation: Institute of Sports Medicine, Department of Orthopedic Surgery M81, Bispebjerg Hospital and Center for Healthy Aging, Faculty of Health Sciences, University of Copenhagen, Copenhagen, Denmark; Department of Endocrinology and Internal Medicine, Aarhus University Hospital and The Medical Research Laboratories, Institute of Clinical Medicine, Faculty of Health Sciences, Aarhus University, Aarhus, Denmark.
authors.forename: M
authors.initials: M
authors.lastname: Hansen
authors.forename: A
authors.initials: A
authors.lastname: Boesen
authors.forename: L
authors.initials: L
authors.lastname: Holm
authors.forename: A
authors.initials: A
authors.lastname: Flyvbjerg
authors.forename: H
authors.initials: H
authors.lastname: Langberg
authors.forename: M
authors.initials: M
authors.lastname: Kjaer
mesh_terms: D000368:Aged; D015415:Biomarkers / Q000097:blood; D003094:Collagen / Q000096:biosynthesis* / Q000097:blood / Q000187:drug effects; D024042:Collagen Type I / Q000378:metabolism / Q000494:pharmacology; D003718:Denmark; D004311:Double-Blind Method; D006801:Humans; D007267:Injections; D007334:Insulin-Like Growth Factor I / Q000378:metabolism / Q000494:pharmacology*; D008297:Male; D017551:Microdialysis / Q000379:methods; D008875:Middle Aged; D017847:Patellar Ligament / Q000187:drug effects*; D012965:Sodium Chloride / Q000008:administration & dosage
chemical_list: D015415:Biomarkers; D024042:Collagen Type I; D012965:Sodium Chloride; D007334:Insulin-Like Growth Factor I; D003094:Collagen