No effect of menstrual cycle on myofibrillar and connective tissue protein synthesis in contracting skeletal muscle

Abstract

-We tested the hypothesis that acute exercise would stimulate synthesis of myofibrillar protein and intramuscular collagen in women and that the phase of the menstrual cycle at which the exercise took place would influence the extent of the change. Fifteen young, healthy female subjects were studied in the follicular (FP, n ϭ 8) or the luteal phase (LP, n ϭ 7, n ϭ 1 out of phase) 24 h after an acute bout of one-legged exercise (60 min of kicking at 67% W max), samples being taken from the vastus lateralis in both the exercised and resting legs. Rates of synthesis of myofibrillar and muscle collagen proteins were measured by incorporation of [13 C]leucine. Myofibrillar protein synthesis (means Ϯ SD; rest FP: 0.053 Ϯ 0.009%/h, LP: 0.055 Ϯ 0.013%/h) was increased at 24-h postexercise (FP: 0.131 Ϯ 0.018%/h, P Ͻ 0.05, LP: 0.134 Ϯ 0.018%/h, P Ͻ 0.05) with no differences between phases. Similarly, muscle collagen synthesis (rest FP: 0.024 Ϯ 0.017%/h, LP: 0.021 Ϯ 0.006%/h) was elevated at 24-h postexercise (FP: 0.073 Ϯ 0.016%/h, P Ͻ 0.05, LP: 0.072 Ϯ 0.015%/h, P Ͻ 0.05), but the responses did not differ between menstrual phases. Therefore, there is no effect of menstrual cycle phase, at rest or in response to an acute bout of exercise, on myofibrillar protein synthesis and muscle collagen synthesis in women. stable isotopes; estrogen; exercise WE RECENTLY SHOWED THAT, in young healthy men, the rates of both myocellular proteins and intramuscular collagen (probably mostly peri-and epimysium) increased in response to an acute bout of exercise (24). Despite women having a smaller muscle mass than men (14), attempts to detect sex differences in protein metabolism have produced little evidence of their existence. There have been some reports of differences between the sexes in the rate of leucine oxidation at rest and during exercise (16,22,34) but there is no convincing evidence of major differences in whole body protein turnover and mixed-muscle protein synthesis (13,16,22,26,31,34) between the sexes, even after corrections for different sizes of fat-free mass (13,34). Furthermore, it is reported that men and women do not have different rates of muscle protein synthesis in response to exercise (31). The lower protein mass in women may therefore be the result of an accumulated sex-specific hormonal effect on synthesis or breakdown over a period of many years (32), or female sex hormones may influence protein synthesis in fractions of muscle, that are masked when measurements are made of mixed-muscle proteins in the whole body. Regarding the latter hypothesis, the synthetic rate of intramuscular connective tissue deserves scrutiny, because the frequency of several diseases linked to collagen-rich tissue, such as bone, connective tissue, and ligaments, seem to be sex specific (36). Women are at higher risk of suffering fibromyalgia, rheumatoid arthritis, and hypermobility and sustain more connective tissue injuries than men, and this may be related to exposure to different sex hormones. Estrogen and progesterone receptors hav...

Effect of administration of oral contraceptives in vivo on collagen synthesis in tendon and muscle connective tissue in young women

“…It cannot be excluded that the present findings are a result of secondary hormonal responses of the OC intake and not a direct effect of estradiol (synthetic or endogenous estradiol). In an earlier study, an ϳ3-fold increase in muscle collagen FSR was observed 24 h postexercise in eumenorrheic women in either the follicular phase or luteal phase of the menstrual cycle (45). This does not support a direct inhibiting effect of estradiol.…”

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

“…A 15-to 25 mg piece of muscle tissue was used for isolating the myofibrillar and collagen proteins using a solubility/centrifugation procedure used elsewhere (5,23,25,68,70,71). Briefly, muscle samples were homogenized in 1 ml ice-cold buffer containing 0.15 M NaCl, 5 mM EDTA, 0.1% Triton X-100, and 0.02 M Tris (pH 7.4) using an automatic homogenizer (FastPrep 120A-230; Thermo Savant, Holbrook, NY).…”

“…Data are means Ϯ SE. exercise on muscle collagen FSR has previously been shown (5,23,47,68,70,71), only the effect of contraction type (lengthening vs. shortening contractions) but not intensity has been investigated earlier. Contraction types induced slightly divergent improvements in the FSR of the mature human muscle collagen protein in the first hours after exercise (23,71).…”

A perspective on current research investigating the effects of hormonal contraceptives on determinants of female athlete performance

“…These findings suggests that exogenous hormones may in uence the anabolic response of muscle to resistance exercise. e myo brillar protein fractional synthetic rate (FSR) does not vary across the menstrual cycle 38 , however H et al 39 demonstrated that females using a third generation OC (30 µg EE and 0.0075 g Gestogen) had a lower FSR than second generation users (35 µg EE and 0.25 mg Norgestimate) and no hormone controls. is suggests that the exogenous synthetic component of contraceptives can a ect protein synthesis, unlike endogenous female reproductive hormones.…”