Effect of estrogen on tendon collagen synthesis, tendon structural characteristics, and biomechanical properties in postmenopausal women

Abstract

Flyvbjerg A, Langberg H, Kjaer M. Effect of estrogen on tendon collagen synthesis, tendon structural characteristics, and biomechanical properties in postmenopausal women. J Appl Physiol 106: 1385-1393, 2009. First published October 16, 2009 doi:10.1152/japplphysiol.90935.2008.-The knowledge about the effect of estradiol on tendon connective tissue is limited. Therefore, we studied the influence of estradiol on tendon synthesis, structure, and biomechanical properties in postmenopausal women. Nonusers (control, n ϭ 10) or habitual users of oral estradiol replacement therapy (ERT, n ϭ 10) were studied at rest and in response to one-legged resistance exercise. Synthesis of tendon collagen was determined by stable isotope incorporation [fractional synthesis rate (FSR)] and microdialysis technique (NH2-terminal propeptide of type I collagen synthesis). Tendon area and fibril characteristics were determined by MRI and transmission electron microscopy, whereas tendon biomechanical properties were measured during isometric maximal voluntary contraction by ultrasound recording. Tendon FSR was markedly higher in ERT users (P Ͻ 0.001), whereas no group difference was seen in tendon NH2-terminal propeptide of type I collagen synthesis (P ϭ 0.32). In ERT users, positive correlations between serum estradiol (sestradiol) and tendon synthesis were observed, whereas change in tendon synthesis from rest to exercise was negatively correlated to s-estradiol. Tendon area, fibril density, fibril volume fraction, and fibril mean area did not differ between groups. However, the percentage of medium-sized fibrils was higher in ERT users (P Ͻ 0.05), whereas the percentage of large fibrils tended to be greater in control (P ϭ 0.10). A lower Young's modulus (GPa/%) was found in ERT users (P Ͻ 0.05). In conclusion, estradiol administration was associated with higher tendon FSR and a higher relative number of smaller fibrils. Whereas this indicates stimulated collagen turnover in the resting state, collagen responses to exercise were negatively associated with s-estradiol. These results indicate a pivotal role for estradiol in maintaining homeostasis of female connective tissue. connective tissue; tendon fibrils; insulin-like growth factor-I; extracellular matrix; bone CROSS-SECTIONAL FINDINGS INDICATE that sex hormones influence tendon biomechanical properties (36), extracellular matrix adaptability in response to mechanical loading (11,21,36,41,59), and the risk of sustaining soft tissue injuries (11,24,25).Estrogen receptors have been localized in ligaments (32, 33), and tendons express transcripts for estrogen receptors (23). Nevertheless, the effect of estrogen on tendon and ligament turnover is not clarified. Thus an inhibiting effect (34, 60), no effect (51), and a stimulating effect (32) on collagen synthesis and fibroblast proliferation in vitro have been observed in anterior cruciate ligament (ACL) tissue samples. These contrasting findings are probably related to the variation between animal species and the applied methods. This ...

Contraction intensity and feeding affect collagen and myofibrillar protein synthesis rates differently in human skeletal muscle

“…For reasons that are unknown to us, the pool of matured and cross-linked collagen proteins has been isolated for determination of the muscle collagen protein FSR (5,23,47,68,70,71), despite the fact that the turnover rate is dependent on the maturation stage (4,6). The present data suggest that muscle collagen is synthesized at least as fast as collagen in tendon, ligament, and bone (5,46,47,69,70).…”

“…In relation to the muscle collagen synthesis measurement, it is relevant to address that we measured the synthesis rate of the total muscle collagen pool similar to methodologies used for other collagenous tissues (5,25,46,47,69,70). For reasons that are unknown to us, the pool of matured and cross-linked collagen proteins has been isolated for determination of the muscle collagen protein FSR (5,23,47,68,70,71), despite the fact that the turnover rate is dependent on the maturation stage (4,6).…”

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A Greater Reduction of Anterior Cruciate Ligament Elasticity in Women Compared to Men as a Result of Delayed Onset Muscle Soreness

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