Evaluation of the applicability of HRT as a preservative of muscle strength in women

Frailty in Rheumatic Diseases

Frailty is a syndrome characterized by the decline in the physiologic reserve and function of several systems, leading to increased vulnerability and adverse health outcomes. While common in the elderly, recent studies have underlined the higher prevalence of frailty in chronic diseases, independent of age. The pathophysiological mechanisms that contribute to frailty have not been completely understood, although significant progresses have recently been made. In this context, chronic inflammation is likely to play a pivotal role, both directly and indirectly through other systems, such as the musculoskeletal, endocrine, and neurological systems. Rheumatic diseases are characterized by chronic inflammation and accumulation of deficits during time. Therefore, studies have recently started to explore the link between frailty and rheumatic diseases, and in this review, we report what has been described so far. Frailty is dynamic and potentially reversible with 8.3%-17.9% of older adults spontaneously improving their frailty status over time. Muscle strength is likely the most significant influencing factor which could be improved with training thus pointing at the need to maintain physical activity. Not surprisingly, frailty is more prevalent in patients affected by rheumatic diseases than in healthy controls, regardless of age and is associated with high disease activity to affect the clinical outcomes, largely due to chronic inflammation. More importantly, the treatment of the underlying condition may prevent frailty. Scales to assess frailty in patients affected by rheumatic diseases have been proposed, but larger casuistries are needed to validate disease-specific indexes, which could allow more accurate prognostic estimates than demographic and disease-related variables alone. Frail patients can be more vulnerable and more difficult to treat, due to the risk of side effects, therefore frailty should be taken into account in clinical decisions. Clinical trials addressing frailty could identify patients who are less likely to tolerate potentially toxic medications and might benefit from more conservative regimens. In conclusion, the implementation of the concept of frailty in rheumatology will allow a better understanding of the patient global health, a finest risk stratification and a more individualized management strategy.

Aging of the musculoskeletal system: How the loss of estrogen impacts muscle strength

Skeletal muscle weakness occurs with aging and in females this is compounded by the loss of estrogen with ovarian failure. Estrogen deficiency mediates decrements in muscle strength from both inadequate preservation of skeletal muscle mass and decrements in the quality of the remaining skeletal muscle. Processes and components of skeletal muscle that are affected by estrogens are beginning to be identified. This review focuses on mechanisms that contribute to the loss of muscle force generation when estrogen is low in females, and conversely the maintenance of strength by estrogen. Evidence is accumulating that estrogen deficiency induces apoptosis in skeletal muscle contributing to loss of mass and thus strength. Estrogen sensitive processes that affect quality, i.e., force generating capacity of muscle, include myosin phosphorylation and satellite cell function. Further detailing these mechanisms and identifying additional mechanisms that underlie estrogenic effects on skeletal muscle is important foundation for the design of therapeutic strategies to minimize skeletal muscle pathologies, such as sarcopenia and dynapenia.

Lack of influence of estrogen on myosin phosphorylation and post-tetanic potentiation in muscles from young adult C57BL mice

Estrogen influences myosin phosphorylation and post-tetanic potentiation in murine fast muscle. We tested the hypothesis that this influence is mediated by estrogen effects on skeletal myosin light chain kinase (skMLCK) activity. To this end, extensor digitorum longus muscles from female wildtype and skMLCK-absent (skMLCK^-/-) mice were grouped as follows: ovariectomized with estrogen (E+), ovariectomized without estrogen (E-), sham surgery, and intact baseline. At 8 weeks of age, the ovariectomized groups were ovariectomized followed by implantation of either a 0.1 mg 17β-estradiol (E+) or placebo pellet (E-). Two weeks later, muscles were isolated and suspended in vitro (25° C) for determination of regulatory light chain phosphorylation and post-tetanic potentiation. Regulatory light chain phosphorylation was not different across conditions within either genotype although wildtype values were significantly greater than skMLCK^-/- values. Consistent with this, the potentiation of concentric twitch force was similar between E+ and E- groups within each genotype but wildtype values were greater than skMLCK^-/- values. However, unaltered estradiol levels following ovariectomy, likely due to previously underappreciated confounds of mouse age, development, and growth during estrogen supplementation, prevented direct testing of the hypothesis. Future studies should note the importance of estrous cycles and continuing physiological developments of young adult mice when working with ovarian hormones.

Estradiol modulates myosin regulatory light chain phosphorylation and contractility in skeletal muscle of female mice

Impairment of skeletal muscle function has been associated with changes in ovarian hormones, especially estradiol. To elucidate mechanisms of estradiol on skeletal muscle strength, the hormone's effects on phosphorylation of the myosin regulatory light chain (pRLC) and muscle contractility were investigated, hypothesizing an estradiol-specific beneficial impact. In a skeletal muscle cell line, C2C12, pRLC was increased by 17β-estradiol (E2) in a concentration-dependent manner. In skeletal muscles of C57BL/6 mice that were E2 deficient via ovariectomy (OVX), pRLC was lower than that from ovary-intact, sham-operated mice (Sham). The reduced pRLC in OVX muscle was reversed by in vivo E2 treatment. Posttetanic potentiation (PTP) of muscle from OVX mice was low compared with that from Sham mice, and this decrement was reversed by acute E2 treatment, demonstrating physiological consequence. Western blot of those muscles revealed that low PTP corresponded with low pRLC and higher PTP with greater pRLC. We aimed to elucidate signaling pathways affecting E2-mediated pRLC using a kinase inhibitor library and C2C12 cells as well as a specific myosin light chain kinase inhibitor in muscles. PI3K/Akt, MAPK, and CamKII were identified as candidate kinases sensitive to E2 in terms of phosphorylating RLC. Applying siRNA strategy in C2C12 cells, pRLC triggered by E2 was found to be mediated by estrogen receptor-β and the G protein-coupled estrogen receptor. Together, these results provide evidence that E2 modulates myosin pRLC in skeletal muscle and is one mechanism by which this hormone can affect muscle contractility in females.

Contribution of Quadriceps Weakness to Fragility Fracture: A Prospective Study

The association between muscle weakness and fracture is not well understood. This study sought to examine the contribution of muscle strength at baseline and change in muscle strength to the observed risk of fragility fracture in older people. The study involved 595 men and 1066 women aged 60+ years (median 69 years) who had been followed for a median of 11 years (range, 4 to 22 years). Quadriceps isometric muscle strength (MS) measured at baseline and biennially was adjusted for height. Femoral neck bone mineral density (FNBMD) was measured by DXA. Low-trauma fracture was ascertained from X-ray reports and interview. The relationship between baseline MS and serial MS and fracture assessed by time-invariant and time-variant Cox's regression models was expressed as hazard ratio (HR) and 95% confidence interval (CI). During the follow-up period, 282 (26%) women and 89 (15%) men sustained a fragility fracture. From age 60 years, women lost 0.28 kg/m (1.6%) of MS per year, whereas men lost 0.39 kg/m (1.5%) of MS per year. In the time-variant model, using serial MS, each 1 SD (4.7 kg/m) lower MS was associated with a 27% increase in the risk of fracture in women (HR 1.27; 95% CI, 1.11 to 1.43); and 46% increase in men (HR 1.46; 95% CI, 1.22 to 1.75). After adjusting for FNBMD, age and prior fracture, history of fall and smoking, HR per SD of lower MS was 1.13 (95% CI, 0.99 to 1.28) for women and 1.35 (95% CI, 1.18 to 1.64) for men. These data indicate that muscle weakness is an independent determinant of fracture risk in men, but not in women. This sex difference suggests that apart from mechanical load effect of muscle on bone, there are other muscle-bone interactions that need to be investigated in future studies. The accuracy of fracture risk prediction for men may be improved by incorporating muscle strength.

Sex-based differences in skeletal muscle kinetics and fiber-type composition

Previous studies have identified over 3,000 genes that are differentially expressed in male and female skeletal muscle. Here, we review the sex-based differences in skeletal muscle fiber composition, myosin heavy chain expression, contractile function, and the regulation of these physiological differences by thyroid hormone, estrogen, and testosterone. The findings presented lay the basis for the continued work needed to fully understand the skeletal muscle differences between males and females.

Maximum Power During Vertical Jump and Isometric Knee Extension Torque Alter Mobility Performance: A Cross-Sectional Study of Healthy Individuals

OBJECTIVE

To provide reference values of muscle function (MF) and mobility performance (MP) and to clarify the effects of MF on MP.

DESIGN

A normative cross-sectional study.

SETTING

An urban area of Niigata, Japan.

PARTICIPANTS

A total of 401 individuals (210 men and 191 women) with a mean age of 41.8 years (range, 7-79 years) who lived in the community and did not have impairments in activities of daily living.

METHODS

Grip strength, isometric knee extension torque (IKET), and maximum ground reaction force (Fmax) and maximum power (Pmax) during a vertical jump were used as measurements of MF. The chair-rise test (CRT) and the timed "Up and Go" test (TUG) were used to assess MP.

MAIN OUTCOME MEASUREMENTS

Mean values of GS, IKET, CRT, TUG, Fmax, and Pmax were calculated according to age and gender. A stepwise multiple regression analysis was used to identify MF factors with an effect on CRT and TUG in participants ≥20 years of age.

RESULTS

Our results showed that all MF parameters were decreased in individuals ≥20 years of age compared to those <20 years old. Moreover, all of the MP parameters increasingly deteriorated with increasing age. CRT and TUG were affected by Pmax and IKET in men and by IKET in women according to logistic regression analysis.

CONCLUSION

The study findings suggest that muscle power affects MP more than the muscle strength in persons aged ≥20 years.

Role of G protein-coupled estrogen receptor-1, matrix metalloproteinases 2 and 9, and heparin binding epidermal growth factor-like growth factor in estradiol-17β-stimulated bovine satellite cell proliferation

In feedlot steers, estradiol-17β (E2) and combined E2 and trenbolone acetate (a testosterone analog) implants enhance rate and efficiency of muscle growth; and, consequently, these compounds are widely used as growth promoters. Although the positive effects of E2 on rate and efficiency of bovine muscle growth are well established, the mechanisms involved in these effects are not well understood. Combined E2 and trenbolone acetate implants result in significantly increased muscle satellite cell number in feedlot steers. Additionally, E2 treatment stimulates proliferation of cultured bovine satellite cells (BSC). Studies in nonmuscle cells have shown that binding of E2 to G protein-coupled estrogen receptor (GPER)-1 results in activation of matrix metalloproteinases 2 and 9 (MMP2/9) resulting in proteolytic release of heparin binding epidermal growth factor-like growth factor (hbEGF) from the cell surface. Released hbEGF binds to and activates the epidermal growth factor receptor resulting in increased proliferation. To assess if GPER-1, MMP2/9, and/or hbEGF are involved in the mechanism of E2-stimulated BSC proliferation, we have examined the effects of G36 (a specific inhibitor of GPER-1), CRM197 (a specific inhibitor of hbEGF), and MMP-2/MMP-9 Inhibitor II (an inhibitor of MMP2/9 activity) on E2-stimulated BSC proliferation. Inhibition of GPER-1, MMP2/9, or hbEGF suppresses E2-stimulated BSC proliferation (P < 0.001) suggesting that all these are required in order for E2 to stimulate BSC proliferation. These results strongly suggest that E2 may stimulate BSC proliferation by binding to GPER-1 resulting in MMP2/9-catalyzed release of cell membrane-bound hbEGF and subsequent activation of epidermal growth factor receptor by binding of released hbEGF.

Epidermal growth factor receptor is required for estradiol-stimulated bovine satellite cell proliferation

The objective of this study was to assess the role of the epidermal growth factor receptor (EGFR) in estradiol-17β (E2)-stimulated proliferation of cultured bovine satellite cells (BSCs). Treatment of BSC cultures with AG1478 (a specific inhibitor of EGFR tyrosine kinase activity) suppresses E2-stimulated BSC proliferation (P < 0.05). In addition, E2-stimulated proliferation is completely suppressed (P < 0.05) in BSCs in which EGFR expression is silenced by treatment with EGFR small interfering RNA (siRNA). These results indicate that EGFR is required for E2 to stimulate proliferation in BSC cultures. Both AG1478 treatment and EGFR silencing also suppress proliferation stimulated by LR3-IGF-1 (an IGF1 analogue that binds normally to the insulin-like growth factor receptor (IGFR)-1 but has little or no affinity for IGF binding proteins) in cultured BSCs (P < 0.05). Even though EGFR siRNA treatment has no effect on IGFR-1β mRNA expression in cultured BSCs, IGFR-1β protein level is substantially reduced in BSCs treated with EGFR siRNA. These data suggest that EGFR silencing results in post-transcriptional modifications that result in decreased IGFR-1β protein levels. Although it is clear that functional EGFR is necessary for E2-stimulated proliferation of BSCs, the role of EGFR is not clear. Transactivation of EGFR may directly stimulate proliferation, or EGFR may function to maintain the level of IGFR-1β which is necessary for E2-stimulated proliferation. It also is possible that the role of EGFR in E2-stimulated BSC proliferation may involve both of these mechanisms.

Hormone replacement therapy improves contractile function and myonuclear organization of single muscle fibres from postmenopausal monozygotic female twin pairs

Ageing is associated with a decline in muscle mass and strength leading to increased physical dependency in old age. Postmenopausal women experience a greater decline than men of similar age in parallel with the decrease in female sex steroid hormone production. We recruited six monozygous female twin pairs (55-59 years old) where only one twin pair was on hormone replacement therapy (HRT use = 7.8 ± 4.3 years) to investigate the association of HRT with the cytoplasmic volume supported by individual myonuclei (myonuclear domain (MND) size,) together with specific force at the single fibre level. HRT use was associated with a significantly smaller (∼27%; P < 0.05) mean MND size in muscle fibres expressing the type I but not the IIa myosin heavy chain (MyHC) isoform. In comparison to non-users, higher specific force was recorded in HRT users both in muscle fibres expressing type I (∼27%; P < 0.05) and type IIa (∼23%; P < 0.05) MyHC isoforms. These differences were fibre-type dependent, i.e. the higher specific force in fast-twitch muscle fibres was primarily caused by higher force per cross-bridge while slow-twitch fibres relied on both a higher number and force per cross-bridge. HRT use had no effect on fibre cross-sectional area (CSA), velocity of unloaded shortening (V0) and relative proportion of MyHC isoforms. In conclusion, HRT appears to have significant positive effects on both regulation of muscle contraction and myonuclei organization in postmenopausal women.

Role of estrogen receptor-α (ESR1) and the type 1 insulin-like growth factor receptor (IGFR1) in estradiol-stimulated proliferation of cultured bovine satellite cells

Although the exact mechanism(s) by which estradiol (E(2)) enhances muscle growth in a number of species, including humans and cattle, is not known, E(2) treatment has been shown to stimulate proliferation of cultured bovine satellite cells (BSCs). This is particularly significant because satellite cells are the source of nuclei needed to support postnatal muscle fiber hypertrophy and are thus crucial in determining the rate and extent of muscle growth. The objective of this study was to assess the role of estrogen receptor-α (ESR1) and the type 1 insulin-like growth factor receptor (IGFR1) in E(2)-stimulated proliferation of cultured BSCs. To accomplish this, we have used small interfering RNA (siRNA) to silence expression of ESR1 or IGFR1 and assessed the effects on E(2)-stimulated proliferation in BSC cultures. In BSCs treated with nonspecific siRNA, E(2) significantly (P < 0.05) stimulates proliferation under conditions in which neither IGF-1 nor IGF-2 expression is increased; however, treatment of ESR1- or IGFR1-silenced cells with E(2) does not significantly stimulate proliferation. These results indicate that both ESR1 and IGFR1 are required for E(2) to stimulate proliferation in BSC cultures. The fact that this occurs under culture conditions in which neither IGF-1 nor IGF-2 mRNA expression is increased strongly suggests that E(2) activates IGFR1 via a mechanism that does not involve increased IGF-1 or IGF-2 binding to the receptor.

Higher levels of endogenous estradiol are associated with frailty in postmenopausal women from the toledo study for healthy aging

BACKGROUND

Adverse effects of higher endogenous estradiol (E2) levels on various clinical outcomes and on determinants of the frailty syndrome have recently been reported. However, there are no data about the potential relationship between E2 and frailty. We aimed to study the association between E2 levels and frailty among older postmenopausal women not taking hormonal therapy.

METHODS

We used data from the Toledo Study for Healthy Aging, a Spanish population-based cohort study. Frailty was defined according to Fried's approach. Multivariate odds ratios (OR) and 95% confidence intervals (CI) associated with E2 levels were estimated using polytomous logistic regression.

RESULTS

E2 levels decreased significantly with age and educational level, whereas they increased with body mass index, high-sensitivity C-reactive protein (hs-CRP), and impairment in Katz activities of daily living. Higher E2 levels were associated with the prevalence of frailty among women younger than 79 yr, but not in the oldest group (p interaction = 0.047). After adjustment, OR of frailty associated with a 1 sd increase of E2 was 1.51 (95% CI, 1.04-2.20; P = 0.03). We identified an interaction between E2 and hs-CRP on the prevalence of frailty (P value = 0.042). Women with both higher E2 and hs-CRP (defined as values into the upper tertile) had an age-adjusted OR of 4.2 (95% CI, 1.7-10.5; P = 0.002), compared with women with low levels of both E2 and hs-CRP.

CONCLUSION

Higher E2 levels were associated with frailty in postmenopausal women. The synergism between higher E2 and hs-CRP levels suggests the existence of physiopathological mechanisms connecting inflammation and estrogen to frailty.

The role of androgens and estrogens on healthy aging and longevity

Aging is associated with a loss of sex hormone in both men (andropause) and women (menopause). In men, reductions in testosterone can trigger declines in muscle mass, bone mass, and in physical function. In women, the impact of the loss of sex hormones, such as estradiol, on bone is well elucidated, but evidence is limited on whether the loss of estradiol negatively affects muscle mass and physical function. However, deficiencies in multiple anabolic hormones have been shown to predict health status and longevity in older persons. Thus, consideration should be given as to whether targeted hormone replacement therapies may prove effective at treating clinical conditions, such as age-related sarcopenia, cancer cachexia, and/or acute or chronic illnesses. If initiated carefully in the appropriate clinical population, hormone replacement therapies in men and women may prevent and reverse muscle and bone loss and functional declines and perhaps promote healthy aging and longevity.

Mechanisms behind estrogen's beneficial effect on muscle strength in females

Muscle weakness ensues when serum testosterone declines with age in men. Testosterone's female counterpart, estrogen, also has been implicated in age-related strength loss, but these results are less conclusive. Our working hypothesis is that estrogens do benefit muscle strength, and that the underlying mechanism involves estrogen receptors to improve muscle quality more so than quantity.

Estradiol and genistein antagonize the ovariectomy effects on skeletal muscle myosin heavy chain expression via ER-beta mediated pathways

The age-related decline in ovarian sex hormone production following the onset of menopause alters skeletal muscle metabolic, structural and functional characteristics. The myosin heavy chain (MHC) expression pattern defines skeletal muscle contraction velocity and is therefore an important factor in skeletal muscle function. The present study was designed to examine the effects of 17beta estradiol (E2), estrogen receptor (ER) subtype selective agonists (ERalpha, ERbeta) or genistein (Gen) following ovary removal (OVX) in female Wistar rats in combination with a high intensity treadmill-based exercise protocol (Ex) or normal cage-based activity (NoEx) on MHC protein expression patterns in the slow fiber type m.Soleus (Sol) and the fast fiber type m.Gastrocnemius (Gas). Gen and E2 in the Sol significantly stimulated MHC-I expression relative to OVX only in the absence of exercise (NoEx). MHC-IIb expression in the Gas was significantly increased relative to OVX in Gen Ex and E2 Ex and NoEx groups. The estrogenic effects in the Sol and Gas were both predominantly mediated via ERbeta pathways, since the ERbeta agonist induced greater MHC increases than OVX or ERalpha. We therefore propose that high intensity exercise in combination with exposure to E2, Gen, ERalpha or ERbeta agonists in OVX rats exerts differential effects on MHC expression in skeletal muscles composed of mainly slow type I MHC (Sol) or fast type II MHC (Gas). In summary, the data shows that MHC composition is affected by estrogens and exercise in a fiber type specific manner and that these effects are mainly mediated by ER-beta. This is of great importance with respect to skeletal muscle health and potential treatment with ER selective agonists.

The influence of estrogen on skeletal muscle: sex matters

As women enter menopause, the concentration of estrogen and other female hormones declines. This hormonal decrease has been associated with a number of negative outcomes, including a greater incidence of injury as well as a delay in recovery from these injuries. Over the past two decades, our understanding of the protective effects of estrogen against various types of injury and disease states has grown immensely. In skeletal muscle, studies with animals have demonstrated that sex and estrogen may potentially influence muscle contractile properties and attenuate indices of post-exercise muscle damage, including the release of creatine kinase into the bloodstream and activity of the intramuscular lysosomal acid hydrolase, beta-glucuronidase. Furthermore, numerous studies have revealed an estrogen-mediated attenuation of infiltration of inflammatory cells such as neutrophils and macrophages into the skeletal muscles of rats following exercise or injury. Estrogen has also been shown to play a significant role in stimulating muscle repair and regenerative processes, including the activation and proliferation of satellite cells. Although the mechanisms by which estrogen exerts its influence upon indices of skeletal muscle damage, inflammation and repair have not been fully elucidated, it is thought that estrogen may potentially exert its protective effects by: (i) acting as an antioxidant, thus limiting oxidative damage; (ii) acting as a membrane stabilizer by intercalating within membrane phospholipids; and (iii) binding to estrogen receptors, thus governing the regulation of a number of downstream genes and molecular targets. In contrast to animal studies, studies with humans have not as clearly delineated an effect of estrogen on muscle contractile function or on indices of post-exercise muscle damage and inflammation. These inconsistencies have been attributed to a number of factors, including age and fitness level of subjects, the type and intensity of exercise protocols, and a focus on sex differences that typically involve factors and hormones in addition to estrogen. In recent years, hormone replacement therapy (HRT) or estrogen combined with exercise have been proposed as potentially therapeutic agents for postmenopausal women, as these agents may potentially limit muscle damage and inflammation and stimulate repair in this population. While the benefits and potential health risks of long-term HRT use have been widely debated, controlled studies using short-term HRT or other estrogen agonists may provide future new and valuable insights into understanding the effects of estrogen on skeletal muscle, and greatly benefit the aging female population. Recent studies with older females have begun to demonstrate their benefits.

17beta-Estradiol accentuates contractility of rat genioglossal muscle via regulation of estrogen receptor alpha

OBJECTIVE

This study in rat genioglossus muscle (GG) was designed to test the hypothesis that the effects of estrogen are at least in part, meditated directly by the estrogen receptors (ERs) of muscle.

DESIGN

Eighty-eight-week-old female Sprague-Dawley rats were randomly assigned to five groups: (1) normal animals (Normal); (2) sham operation animals (Sham); (3) ovariectomized animals without estrogen replacement (OVX); (4) ovariectomized animals with olive oil replacement (OVX+O); (5) ovariectomized animals with 17beta-estradiol replacement (OVX+E2). Six weeks later, GG was assessed in vivo for contractile properties and further analysis for ERs expression was carried out including real-time quantitative RT-PCR, immunohistochemistry and Western blotting.

RESULTS

The maximal twitch tension, 70%-decay time and fatigue index of GG decreased significantly in OVX group when compared with Normal group (P<0.05, P<0.05, P<0.05). However, all the three parameters reversed in OVX+E2 group especially fatigue index. Further analysis showed a clear expression of ERalpha and ERbeta in rat GG. The expression of both ERalpha protein and ERalpha mRNA was both significantly decreased in OVX group (P<0.05) and recovered back to previous level after receiving 17beta-estradiol replacement (P<0.05). But neither ERbeta protein nor ERbeta mRNA was regulated by estrogen deprivation and replacement.

CONCLUSION

The results demonstrated that the contractility of GG was accentuated by estrogen. Moreover, these effects were at least in part, meditated directly via regulation of the expression of ERalpha. It might contribute to the protective effects of estrogen on the patency of upper airway and the pathogenesis of obstructive sleep apnea hypopnoea syndrome.

Hormone therapy and skeletal muscle strength: a meta-analysis

BACKGROUND

Our objective was to perform a systematic review and meta-analysis of the research literature that compared muscle strength in postmenopausal women who were and were not on estrogen-based hormone therapy (HT).

METHODS

Twenty-three relevant studies were found. Effect sizes (ESs) were calculated as the standardized mean difference, and meta-analyses were completed using a random effects model.

RESULTS

HT was found to result in a small beneficial effect on muscle strength in postmenopausal women (overall ES = 0.23; p = .003) that equated to an approximately 5% greater strength for women on HT. Among the 23 studies, various muscle groups were assessed for strength, and those that benefitted the most were the thumb adductors (ES = 1.14; p < .001). Ten studies that compared muscle strength in rodents that were and were not estradiol deficient were also analyzed. The ES for absolute strength was moderate but not statistically significant (ES = 0.44; p = .12), whereas estradiol had a large effect on strength normalized to muscle size (ES = 0.66; p = .03).

CONCLUSION

Overall, estrogen-based treatments were found to beneficially affect strength.

Potential role of G-protein-coupled receptor 30 (GPR30) in estradiol-17beta-stimulated IGF-I mRNA expression in bovine satellite cell cultures

Androgenic and estrogenic steroids enhance muscle growth in animals and humans. Estradiol-17beta (E2) and trenbolone acetate (TBA) (a synthetic testosterone analog) increased IGF-I mRNA expression in bovine muscle satellite cell (BSC) cultures. The goal of this study was to evaluate the mechanisms responsible for this increase by evaluating the effects of ICI 182 780 (an E2 receptor antagonist), flutamide (an androgen receptor inhibitor), G1 (a GPR30 agonist), and BSA-conjugated E2 on E2 and/or TBA-stimulated IGF-I mRNA expression in BSC cultures. Flutamide completely suppressed TBA-stimulated IGF-I mRNA expression in BSC cultures. ICI 182 780 did not suppress E2-stimulated IGF-I mRNA expression and 100 nM ICI 182 780 enhanced (93%, p<0.05) IGF-I mRNA levels in BSC cultures. G1 (100 nM) stimulated IGF-I mRNA expression (100%, p<0.05) but had no effect on proliferation in BSC cultures. E2-BSA, which cannot cross the cell membrane, stimulated IGF-I mRNA expression (approximately 100%, p<0.05) in BSC but even at extremely high concentrations had no effect on proliferation. In summary, our data indicate the E2-stimulation of proliferation and E2-stimulation of IGF-I mRNA expression in BSC cultures occur via different mechanisms. Our previous results showing that ICI 182 780 inhibited BSC proliferation and results of the current study showing lack of response to E2-BSA or G1 suggest that E2-stimulated proliferation in BSC cultures is mediated through classical estrogen receptors. Stimulation by ICI 182 780, G1 and E2-BSA suggests the E2-stimulated IGF-I mRNA expression in BSC cultures is mediated through the GPR30 receptor.

Skeletal muscle and bone: effect of sex steroids and aging

Both estrogen and testosterone are present in males and females. Both hormones contribute to the well being of skeletal muscle and bone in men and women, and there is evidence that the loss of sex hormones is associated with the age-related decline in bone and skeletal muscle mass. Hormonal supplementation of older adults to restore estrogen and testosterone levels to those of young men and women is not without penalty.

Sex differences in steroidogenesis in skeletal muscle following a single bout of exercise in rats

Sex steroid hormones, such as testosterone and estradiol, play important roles in developing both strength and mass of skeletal muscle. Recently, we demonstrated that skeletal muscle can synthesize sex steroid hormones. Whether there are sex differences in basal steroidogenesis or acute exercise-induced alterations of steroidogenesis in the skeletal muscle is unknown. We examined sex differences in the levels of testosterone, estradiol, and steroidogenesis-related enzymes, such as 17β-hydroxysteroid dehydrogenase (HSD), 3β-HSD, and aromatase cytochrome P-450 (P450arom), in the skeletal muscle at rest and after exercise. We studied the gastrocnemius muscles of resting rats (10 wk old) and exercised rats (10 wk old, treadmill running, 30 m/min, 30 min). Basal muscular testosterone levels were higher in males than females, whereas estradiol did not differ between sexes. Additionally, 17β-HSD, 3β-HSD, and P450arom transcript and protein expression were greater in females. After acute exercise, testosterone levels and 17β-HSD expression increased in muscle in both sexes. By comparison, muscular estradiol levels increased in males following exercise but were unchanged in females. Expression of P450arom, which regulates estrogen synthesis, increased after acute exercise in males but decreased after exercise in females. Thus a single bout of exercise can influence the steroidogenic system in skeletal muscle, and these alterations differ between sexes. The acute exercise-induced alteration of steroidogenic enzymes may enhance the local steroidogenesis in the skeletal muscle in both sexes.

The menstrual cycle and sport performance

The female sex steroid hormones estrogen and progesterone have potential effects on exercise capacity and performance through numerous mechanisms, such as substrate metabolism, cardiorespiratory function, thermoregulation, psychologic factors, and injuries. Consequently, hormone level changes may theoretically lead to either improved or decreased performance at various times throughout the menstrual cycle. Numerous methodological issues and a paucity of studies have precluded evidence-based conclusions in almost every area of research in this field. In addition, there appears to be a great degree of inter- and intraindividual variability in these hormonal responses. Using oral contraceptives may be advantageous for female athletes who are negatively affected by their menstrual cycle, as they may provide a stable yet controllable hormonal milieu for training and competition.

Soy isoflavones, body composition, and physical performance

OBJECTIVES

Physiologic changes, occurring during the process of aging, can have serious health consequences, such as increased risk of chronic disease and disability. Decline in estradiol levels after menopause is hypothesized to contribute to this risk. Thus, hormone therapy (HT) might prevent or delay those changes. However, HT has serious side effects and alternative approaches are needed.

METHODS

We performed a 12-month double-blind randomized trial comparing soy protein containing 99mg isoflavones (aglycone weights) with milk protein (placebo) daily in 202 postmenopausal women aged 60-75 years. Endpoints were body composition, and physical performance. Randomization resulted in reasonable well-balanced groups, 153 (76%) women completed the trial. Compliance was good (plasma genistein levels 55 +/- 101 and 1259 +/- 1610 nmol/L for placebo and soy group, respectively). The changes in the endpoints during the intervention period among the two intervention groups were analyzed.

RESULTS

Body mass index (BMI) and waist-to-hip ratio did not change during intervention. Handgrip strength at the final visit was slightly worse in the soy group compared to the placebo group (-0.45 kg (95% C.I.: -2.5, 1.6 kg; p = 0.7), but this difference was not statistically significant. Self-reported functional status, mobility and physical performance, all slightly improved during intervention but there were no differences between the groups.

CONCLUSIONS

The results of the present trial do not support the view that soy isoflavones have favorable effects on body composition and physical performance in postmenopausal women.

Soleus and EDL muscle contractility across the lifespan of female C57BL/6 mice

All previous aging research on the contractility of rodent skeletal muscle has been conducted on male rodents. Because males and females age differently, we undertook this study to determine if and when age-related decrements in skeletal muscle contractility occur in female mice. Soleus and extensor digitorum longus (EDL) muscles from female C57BL/6 mice aged approximately 4, 8, 16, 24 and 28 mo were assessed in vitro for contractility and subsequently contractile protein content. EDL muscle was resistant to age-related changes in force generation but displayed characteristics of becoming more slow-twitch like. Maximal isometric tetanic force (Po) generated by soleus muscle declined with age. Soleus muscle size and contractile protein contents were not affected by age and thus could not explain the age-related force decrements. Soleus muscle specific Po declined with age being approximately 26% lower in muscles of 16-28 mo-old mice indicating that a deterioration in soleus muscle quality of female mice occurred beginning around the age of ovarian failure. Thus this study provides essential, comprehensive baseline data for future studies on age-related muscle dysfunction in the female mouse.

A TA-repeat polymorphism in the gene for the estrogen receptor alpha does not correlate with muscle strength or body composition in young adult Swedish women

OBJECTIVES

There are conflicting data in the literature whether estrogens affect muscle strength. Prospective studies with hormone replacement therapy have not been able to convincingly demonstrate a muscular effect and the putative role of estrogen in the development of lean body mass is not established. Both lean mass and fat mass are known to be under strong genetic control and therefore we have investigated the relation between a TA-repeat in the gene for the estrogen receptor alpha (ERalpha) and muscle strength and body composition.

METHODS

175 healthy Swedish women, aged 20-39 were randomly selected from the population registry and included in the study. Body mass measurements (lean mass, fat mass, body weight and BMI) and muscle strength (quadriceps, hamstring and grip strength) were evaluated. The TA-repeat in the ERalpha gene was amplified by polymerase chain reaction.

RESULTS

Alleles with a TA-repeat length of 16 repeats or shorter were denoted short (e), and repeat length of 17 repeats or longer were denoted long (E). Women homozygous for the short and long genotype were denoted ee (31%) and EE (21%), respectively, while heterozygous individuals were denoted Ee (48%). The frequencies were in Hardy-Weinberg equilibrium. No associations were found between ERalpha genotypes and muscle strength or body composition.

CONCLUSION

The TA-repeat in the human ERalpha gene does not correlate with muscle strength or body mass measurements, indicating that body composition is not as sensitive to genetic variation in this receptor as other target organs for estrogen.

Osteoarthritis and the postmenopausal woman: Epidemiological, magnetic resonance imaging, and radiological findings

BACKGROUND

There is some observational evidence to suggest an effect of hormones on osteoarthritis (OA), especially in perimenopausal women.

OBJECTIVES

To review the epidemiological evidence for an effect of estrogen replacement therapy (ERT) on the incidence and prevalence of OA, especially radiological OA, and the effect of ERT on articular cartilage in women.

METHODS

The literature relating to these questions was reviewed using OVID Medline (1966 to March 2003).

RESULTS

Some studies which have suggested a protective effect of ERT on the incidence and prevalence of OA. However, many of the confidence intervals include unity. Although a protective effect also was seen on articular knee cartilage in long-term users of ERT compared with never users, no difference in change in cartilage was seen over 2 years.

CONCLUSIONS

There is weak epidemiological evidence suggesting a role for estrogen therapy in joint health in postmenopausal women. The data are more suggestive of an effect on large joint OA than small joint OA.

Effect of HRT on hormone responses to resistance exercise in post-menopausal women

PURPOSE

The purpose of this study was to evaluate the effect of hormone replacement therapy (HRT) on the acute and chronic hormonal responses to resistance exercise in post-menopausal women.

METHODS

Thirty-two post-menopausal women were recruited for this study; 16 who were currently using HRT and 16 who were not using HRT. Subjects in both the HRT and NHRT groups were randomly assigned to either a resistance training group (N = 16; 8 HRT and 8 NHRT) or a control group (N = 16; 8 HRT and 8 NHRT). The training group completed a supervised resistance training program three times a week for 12 weeks. To evaluate changes in hormone levels, resting blood samples were drawn at weeks 0, 4, and 13 of the program. In addition, at weeks 0 and 13, post-exercise blood samples were drawn in order to examine the hormone response to an acute bout of resistance exercise. Samples were analyzed for serum growth hormone (GH), insulin-like growth factor-1 (IGF-1), testosterone, estradiol, dehydroepiandrosterone (DHEA), and cortisol.

RESULTS

There were no significant changes in resting hormone levels between weeks 0, 4, and 13 of the training program. There was a significant week-by-group interaction for DHEA (P < 0.05 ) and cortisol (P < 0.05 ) with the NHRT-training group having a greater post-exercise increase in DHEA and cortisol after training. Overall, the post-exercise GH levels were significantly greater than pre-exercise (P < 0.05 ) or recovery levels (P < 0.01). There were no significant differences between HRT and NHRT groups in the acute hormone response to exercise.

CONCLUSION

These results indicate that HRT will not have an effect on the acute or chronic hormone response to a recreational resistance training program in post-menopausal women.

IGF-I mRNA levels in bovine satellite cell cultures: effects of fusion and anabolic steroid treatment

Androgenic and estrogenic steroids enhance muscle growth in a number of species; however, the mechanism by which anabolic steroids enhance muscle growth is not known. Castrated male cattle (steers) provide a particularly good model system in which to study the effects of anabolic steroids on muscle growth because they respond dramatically to treatment with both estrogens and androgens. The goal of this study was to determine if treatment of bovine satellite cell (BSC) cultures with 17beta-estradiol (E(2)) or trenbolone (a synthetic androgen) directly affects proliferation rate or level of mRNA for estrogen receptor (ER)-alpha, androgen receptor, and growth factors that have been shown to affect muscle growth (insulin-like growth factor (IGF)-I, IGF binding protein (IGFBP)-3, and myostatin). BSC cultures were established from the semimembranosus muscles of steers and then treated for 48 h with various concentrations of E(2) or trenbolone ranging from 0.001 to 10 nM. IGF-I mRNA levels in proliferating BSC cultures were significantly increased at 0.01 (1.9-times control values, P < 0.02) and at 0.1, 1, and 10 nM E(2) (2.9-, 3.5-, and 3.5-times control values, respectively, P < 0.0001). Additionally both 1 and 10 nM trenbolone increased IGF-I mRNA levels to 1.7-times control values (P < 0.02). ER-alpha mRNA was detectable in BSC cultures, and levels were increased (2.3-times control levels, P < 0.001) in cultures treated with 0.001 nM E(2) but not in cultures treated with higher concentrations of E(2). Androgen receptor mRNA levels also were increased (1.5-times control levels, P < 0.02) in cultures treated with 0.001 nM trenbolone but not by treatment with higher concentrations of trenbolone. Levels of IGFBP-3 were increased (1.4-times control values, P < 0.02) by treatment with 0.001 nM E(2) but not by treatment with high concentrations of E(2). Myostatin mRNA levels were not affected by any concentration of either of the steroids. Although, levels of IGF-I mRNA were 10-times greater (P < 0.02) in fused BSC cultures than in proliferating cultures, treatment of fused cultures for 48 h with 10 nM E(2) increased IGF-I mRNA levels (2.5-times control levels, P < 0.02). Both E(2) and trenbolone increased (3)H-thymidine incorporation rate (1.5-times control levels, P < 0.001) in BSC cultures in media containing serum from which IGFBP-3 had been removed by anti-IGFBP-3 affinity chromatography. In summary, treatment of BSC cultures with either E(2) or trenbolone increased IGF-I mRNA level and proliferation rate, thus, establishing that these steroids have direct anabolic effects on cells present in the BSC culture.

The effects of physical activity and estrogen treatment on rat fast and slow skeletal muscles following ovariectomy

Decreased estrogen production is associated with changes in the skeletal, cardiovascular and muscular systems. At the level of skeletal muscles, it has been shown that a reduction in force production occurs at menopause but the underlying mechanisms are still unknown. The aim of the study was to investigate the effects of ovariectomy on myosin heavy chain (MyHC) composition. Additionally, we studied the effects of physical activity and the combined effects of physical activity and estrogen treatment on MyHC content in ovariectomised (OX) animals. Twenty-five rats were randomly assigned to five different groups: controls, runners, OX, ovariectomised runners and ovariectomised runners receiving estrogen. Exercise consisted of voluntary running for 5 weeks. Two muscles were analysed: m. extensor digitorum longus, EDL, (fast muscle) and m. soleus (slow muscle). MyHC content was analysed on 8% gel electrophoresis. The level of running activity is reduced in OX animals and estrogen administration is associated with the normalisation of the level of physical activity. Ovariectomy induces a shift from fast to slow MyHC isoforms in both the soleus and EDL. When OX animals are allowed to run, alterations in MyHC isoforms are still observed in the EDL but not in the soleus. When physical activity is combined with estrogen treatment no alterations are observed in both muscles. In conclusion, this study shows that ovariectomy induces alterations in the contractile properties of skeletal muscles and that physical activity in combination with estrogen treatment are associated with the maintenance of slow and fast muscle characteristics.

Resistance training in postmenopausal women with and without hormone therapy

PURPOSE

The main purpose of this study was to analyze the impact of a 1-yr resistance-training program on body composition and muscle strength in postmenopausal women, and to describe the impact of hormone replacement therapy (HRT) on body composition changes, with and without exercise. Secondarily, we wanted to study dose-response relationships between measures of program compliance and changes in primary outcomes.

METHODS

Subjects were postmenopausal women (40-66 yr) randomly assigned to an exercise (EX) group (N = 117) and a nonexercise group (N = 116). The EX group participated in a 1 yr trainer-supervised resistance-training program, 60-75 min.d-1, 3 d.wk-1. Lean soft tissue (LST) and fat tissue (FT) changes were measured by dual-energy x-ray absorptiometry and strength by one-repetition maximum testing.

RESULTS

Significant (P < 0.001) gains in LST were observed for women who exercised, regardless of HRT status, whereas women who did not exercise lost LST (P < 0.05) if they were not taking HRT, and gained LST (P = 0.08) if they were on HRT. The only significant FT losses were observed for women who exercised while on HRT (P < 0.05). Strength increases were observed at all sites (P < 0.001). Total weight lifted by subjects in their training sessions was a significant predictor of changes in LST (P < 0.001) and strength (P < 0.01).

CONCLUSIONS

Resistance and weight-bearing exercise significantly changed total and regional body composition in postmenopausal women by increasing LST in all women and decreasing FT in women on HRT. Hormone therapy showed no independent effects on body composition, but it protected nonexercising women from losses in LST. The lean and muscle strength changes observed were partially dependent on the volume of training, as expressed by attendance and total weight lifted in 1 yr of training.

Six months of hormone replacement therapy does not influence muscle strength in postmenopausal women

OBJECTIVES

Postmenopausal hormone replacement therapy (HRT) has positive effects on fracture incidence before any effects on bone mineral density can be demonstrated. This has been attributed to increased muscle strength by HRT. This study was designed to evaluate the effect of 6 months of HRT on muscle strength in postmenopausal women.

METHODS

Forty postmenopausal women, aged 60-78 were included in the study. They were randomly divided in two groups with 20 women in each group. One group received Menorest 50 microg/24 h (estradiol 4.3 mg) and Gestapuran 2.5 mg (medroxyprogesteron) daily and the other group received placebo treatment. The study was conducted as a double blinded, prospective and placebo controlled trial. Hand grip strength, isokinetic knee flexion and extention, and physical activity were measured before treatment, after 3 and 6 months. Physical activity was estimated using a classification system of physical activity. A JAMAR hydraulic hand dynamometer and a Cybex II dynamometer were used to evaluate muscle strength.

RESULTS

Hand grip strength in the right hand, increased significantly in both groups (HRT P<0.001 and placebo P<0.01) and in the left hand in the HRT group (P<0.01). However, there were no differences in muscle strength between the two groups. There was no significant change in isokinetic knee flexion or extension after 6 months in either of the groups. The estimated physical activity increased slightly in the placebo group, but there was no significant difference compared to the treatment group.

CONCLUSIONS

Our data suggest that 6 months of HRT does not influence muscle strength in postmenopausal women.

Relationship between estrogen use and musculoskeletal function in postmenopausal women

OBJECTIVES

The purpose of this study was to examine the relationship between estrogen use and muscle strength, bone mineral density (BMD), and body composition variables in postmenopausal women. Forty healthy, untrained women participated in this study. Subjects (53-65 years) were > or =5 years postmenopausal and were categorized into either estrogen replacement therapy (ERT n=20) or non-estrogen replacement therapy (Non-ERT n=20) groups.

METHODS

Muscular strength was measured by 1-RM testing using Cybex isotonic weight machines. Handgrip strength was measured using a handgrip dynamometer. Diagnostic Ultrasound was used to determine cross-sectional areas of the biceps brachii and rectus femoris muscle groups. BMD of the lumbar spine, proximal femur, and total body was assessed by Dual Energy X-Ray Absorptiometry (Lunar DPX-IQ). Body composition variables were obtained from the total body scan. Serum osteocalcin was measured as an indicator of bone remodeling.

RESULTS

There were no significant differences (P>0.05) for isotonic muscular strength, muscle cross-sectional areas, handgrip strength, or percent fat between ERT and Non-ERT groups. ERT had significantly higher (P<0.05) BMD for the total body, femoral neck and Ward's Area. There were moderate positive relationships between lean body mass and the hip sites (r=0.61-0.70, P<0.05). Regression analyses determined that lean body mass was the strongest predictor of the hip BMD sites. Estrogen use also was a significant predictor for the femoral neck and Ward's Area sites.

CONCLUSION

Women taking estrogen exhibited similar muscular strength, muscle size, and body composition as their estrogen-deficient counterparts. Estrogen use was also associated with higher BMD for the total body and hip sites. Generally, body composition, specifically lean body mass, influenced hip BMD more than muscular strength or estrogen use.

The effect of hormone replacement therapy on appendicular lean tissue mass in early postmenopausal women

OBJECTIVE

The impact of hormone replacement therapy (HRT) on skeletal muscle mass is still a controversial issue in women's health. Some authors hypothesize anabolic effects, others catabolic. These hypotheses, however, await confirmation by longitudinal observations based on more direct measurements of muscle mass. The aim of the present preliminary study was to evaluate the effect of a 3-year HRT program on appendicular lean tissue mass (LTM(A)) in early postmenopausal women aged 45-54 years.

DESIGN

This was a randomized, double-blind and placebo-controlled trial. Women received HRT with 2 mg estradiol valerate combined either continuously with 1 mg cyproterone acetate (days 1-28; n = 15) or sequentially with 75 mug levonorgestrel (days 17-28; n = 15), or placebo (n = 18). Serum estradiol was measured by radioimmunoassay. LTM(A) was measured by dual photon absorptiometry (baseline) and dual energy X-ray absorptiometry (years 2 and 3).

RESULTS

Baseline serum estradiol did not show significant correlation with the respective LTM(A) (r = 0.018, p = 0.88, n = 75). Cross-sectional analysis found no significant differences between the intervention groups at any time points. The longitudinal changes between years 2 and 3 showed a trend toward decreasing LTM(A) in those receiving HRT (-0.08 +/- 0.12 kg, n = 30) compared to those receiving placebo (0.12 +/- 0.25 kg, n = 18, p = 0.44).

CONCLUSIONS

The present preliminary study did not find significant effects on LTM(A) caused by HRT. The trends toward decreasing LTM(A) in the HRT groups might suggest catabolic rather than anabolic effects. These trends, however, await confirmation by larger clinical trials.

Muscle strength and tibolone: a randomised, double-blind, placebo-controlled trial

OBJECTIVE

To investigate the effects of tibolone, a tissue-specific compound with a mixed (estrogenic, progestogenic and androgenic) hormonal profile, on skeletal muscle strength in a group of healthy postmenopausal women.

DESIGN

Randomised, parallel group, double-blind, placebo-controlled, single-centre trial conducted between August 1997 and July 1999.

PARTICIPANTS

Eighty-five healthy women, between one and 15 years postmenopausal, (mean [SD] age, 54.2 [4.7] years) recruited from local paper advertisements. Participants were randomly assigned to 2.5 mg tibolone or to identically appearing placebo pills daily for 12 months, taken orally in the morning.

METHODS

Both maximal handgrip strength, representing upper body strength, and maximal quadriceps strength, representing lower body strength, were measured isometrically.

MAIN OUTCOME MEASURES

Treatment effect estimates (between group differences) in handgrip strength and isometric knee extension at last visit.

RESULTS

Tibolone significantly (P = 0.04) increased handgrip strength compared with placebo (difference 0.99 kg, [95% CI 0.1-1.9]). No significant treatment effect (P = 0.61) was observed in isometric knee extension strength. Isometric strength adjusted for body mass index resulted in a trend favouring tibolone (P = 0.06). Individual trend analysis showed a significant difference in rate of change throughout the year (6.8% [95% CI 2.1-10.7]) favouring tibolone.

CONCLUSIONS

Administration of tibolone increased handgrip strength in postmenopausal women compared with placebo. A trend indicating a positive effect in isometric knee extension strength adjusted for body mass index was observed. Tibolone seems to mitigate the menopause-related decline in muscle strength.