Exercise-dependent IGF-I, IGFBPs, and type I collagen changes in human peritendinous connective tissue determined by microdialysis

TY - JOUR

T1 - Exercise-dependent IGF-I, IGFBPs, and type I collagen changes in human peritendinous connective tissue determined by microdialysis

AU - Olesen, Jens L

AU - Heinemeier, Katja M

AU - Gemmer, Carsten

AU - Kjaer, Michael

AU - Flyvbjerg, Allan

AU - Langberg, Henning

PY - 2007

Y1 - 2007

N2 - Microdialysis studies indicate that mechanical loading of human tendon during exercise elevates type I collagen production in tendon. However, the possibility that the insertion of microdialysis fibers per se may increase the local collagen production due to trauma has not been explored. Insulin-like growth factor I (IGF-I) and its binding proteins (IGFBPs), which are known to stimulate collagen production in animal tendons, may regulate the translation of mechanical loading to collagen synthesis. Systemic and tissue levels of IGF-I, IGFBP, and type I collagen metabolism markers [procollagen I COOH-terminal propeptide (PICP) and COOH-terminal telopeptide of type I collagen] were measured by microdialysis in peritendinous tissue of the human Achilles tendon in an exercise group (performing a 36-km run, n = 6) and a control group (no intervention, n = 6). An increase in local PICP concentration was seen in both groups after 72 h and stayed elevated in the exercise group at 96 h (P <0.05). IGFBP-1 in both serum and dialysate increased in the exercise group immediately after exercise (P <0.05), whereas IGFBP-3 decreased systemically (P <0.05). Elevation of local IGFBP-4 was observed in both the control and exercise groups after 48 h (P <0.05). Total IGF-I did not change in locally or systemically in either group. Our results indicate an increased local production of PICP in human peritendinous tissue in response to prolonged mechanical loading with part of the increase due to trauma from the sampling technique. Care must therefore be emphasized to minimize the numbers of insertions with microdialysis. We demonstrated an elevation of IGFBP-1 both systemically and peritendinously in response to prolonged acute exercise. The local increased collagen synthesis was preceded by an elevation of local concentration of IGFBP-4, suggesting that IGFBP-4 may have a key role in the IGF-axis effect on the human collagen synthesis in vivo.

AB - Microdialysis studies indicate that mechanical loading of human tendon during exercise elevates type I collagen production in tendon. However, the possibility that the insertion of microdialysis fibers per se may increase the local collagen production due to trauma has not been explored. Insulin-like growth factor I (IGF-I) and its binding proteins (IGFBPs), which are known to stimulate collagen production in animal tendons, may regulate the translation of mechanical loading to collagen synthesis. Systemic and tissue levels of IGF-I, IGFBP, and type I collagen metabolism markers [procollagen I COOH-terminal propeptide (PICP) and COOH-terminal telopeptide of type I collagen] were measured by microdialysis in peritendinous tissue of the human Achilles tendon in an exercise group (performing a 36-km run, n = 6) and a control group (no intervention, n = 6). An increase in local PICP concentration was seen in both groups after 72 h and stayed elevated in the exercise group at 96 h (P <0.05). IGFBP-1 in both serum and dialysate increased in the exercise group immediately after exercise (P <0.05), whereas IGFBP-3 decreased systemically (P <0.05). Elevation of local IGFBP-4 was observed in both the control and exercise groups after 48 h (P <0.05). Total IGF-I did not change in locally or systemically in either group. Our results indicate an increased local production of PICP in human peritendinous tissue in response to prolonged mechanical loading with part of the increase due to trauma from the sampling technique. Care must therefore be emphasized to minimize the numbers of insertions with microdialysis. We demonstrated an elevation of IGFBP-1 both systemically and peritendinously in response to prolonged acute exercise. The local increased collagen synthesis was preceded by an elevation of local concentration of IGFBP-4, suggesting that IGFBP-4 may have a key role in the IGF-axis effect on the human collagen synthesis in vivo.

KW - Adult

KW - Biomechanics

KW - Collagen Type I

KW - Connective Tissue

KW - Exercise

KW - Gene Expression Regulation

KW - Humans

KW - Insulin-Like Growth Factor Binding Protein 1

KW - Insulin-Like Growth Factor Binding Protein 4

KW - Insulin-Like Growth Factor Binding Proteins

KW - Insulin-Like Growth Factor I

KW - Male

KW - Microdialysis

KW - Middle Aged

KW - Peptide Fragments

KW - Procollagen

KW - Tendons

KW - Time Factors

U2 - 10.1152/japplphysiol.01205.2005

DO - 10.1152/japplphysiol.01205.2005

M3 - Journal article

C2 - 16973813

SN - 8750-7587

VL - 102

SP - 214

EP - 220

JO - Journal of Applied Physiology

JF - Journal of Applied Physiology

IS - 1

ER -