Differential influence of peripheral and systemic sex steroids on skeletal muscle quality in pre- and postmenopausal women

Expression of Estrogen Receptor Coactivator Proline-, Glutamic Acid- and Leucine-Rich Protein 1 within Paraspinal Muscles in Adolescents with Idiopathic Scoliosis

Purpose

The aim of this study was to detect and assess the estrogen receptor (ESR) coactivator PELP1 expression within human paraspinal skeletal muscles in patients suffering from idiopathic scoliosis.

Methods

During surgical correction of scoliosis the muscle biopsies harvested in 29 females. Presence of PELP1, ESR1 and ESR2 genes transcripts was studied using RT-qPCR technique while immunohistochemistry and western blot methods were used to detect the PEPL1 protein presence.

Results

PELP1 expression in deep paraspinal muscles revealed higher than in superficial back muscles (p = 0.005). Positive immunohistochemical staining for PELP1 was observed in the nuclei of the paraspinal muscle cells. Western blot revealed PELP1 protein in all samples. No significant difference in PELP1 expression between the convex and the concave scoliosis side (p>0.05) was found. In deep paraspinal back muscles, a significant correlation between the PELP1 expression level on the concave side and the Cobb angle (r = 0.4; p<0.05) was noted as well as between the PELP1 and ESR1 expression level (r = 0.7; p<0.05) while no correlation between PELP1 and ESR2 expression level was found.

Conclusion

To our knowledge, three techniques for the first time demonstrated the presence of the PELP1 in paraspinal muscles of patients with idiopathic scoliosis. The PELP1 potential regulatory impact on back muscle function is to be further investigated.

Influence of parity, type of delivery, and physical activity level on pelvic floor muscles in postmenopausal women

[Purpose] The aim of the present study was to assess the influence of parity, type of delivery, and physical activity level on pelvic floor muscles in postmenopausal women. [Subjects and Methods] This was an observational analytic cross-sectional study with a sample of 100 postmenopausal women, aged between 45 and 65 years, divided into three groups according to menopausal stage: hysterectomized and early and late postmenopause. Patients were assessed for sociodemographic and gyneco-obstetric factors and subjected to a muscle strength test and perineometry. Descriptive statistics, ANOVA, Kruskal-Wallis and multiple regression were applied. [Results] The results showed homogeneity in sociodemographic and anthropometric characteristics. There was no difference in pelvic floor muscle function among the three groups. Type of delivery, parity and physical activity level showed no influence on muscle function. [Conclusion] The findings demonstrate that parity, type of delivery, and physical activity level had no influence on pelvic floor muscle pressure in postmenopausal women. One hypothesis to explain these results is the fact that the decline in muscle function in postmenopausal women is related to the female aging process.

Intramuscular sex steroid hormones are associated with skeletal muscle strength and power in women with different hormonal status

Estrogen (E₂)-responsive peripheral tissues, such as skeletal muscle, may suffer from hormone deficiency after menopause potentially contributing to the aging of muscle. However, recently E₂ was shown to be synthesized by muscle and its systemic and intramuscular hormone levels are unequal. The objective of the study was to examine the association between intramuscular steroid hormones and muscle characteristics in premenopausal women (n = 8) and in postmenopausal monozygotic twin sister pairs (n = 16 co-twins from eight pairs) discordant for the use of E₂-based hormone replacement. Isometric skeletal muscle strength was assessed by measuring knee extension strength. Explosive lower body muscle power was assessed as vertical jump height. Due to sequential nature of enzymatic conversion of biologically inactive dehydroepiandrosterone (DHEA) to testosterone (T) and subsequently to E₂ or dihydrotestosterone (DHT), separate linear regression models were used to estimate the association of each hormone with muscle characteristics. Intramuscular E₂, T, DHT, and DHEA proved to be significant, independent predictors of strength and power explaining 59–64% of the variation in knee extension strength and 80–83% of the variation of vertical jumping height in women (P < 0.005 for all models). The models were adjusted for age, systemic E₂, and total body fat mass. The statistics used took into account the lack of statistical independence of twin sisters. Furthermore, muscle cells were shown to take up and actively synthesize hormones. Present study suggests intramuscular sex steroids to associate with strength and power regulation in female muscle providing novel insight to the field of muscle aging.

Estrogen influences on neuromuscular function in postmenopausal women

Exposure to ovarian sex steroids during different life phases has long-term effects on women's health and wellbeing. Menopause is characterized by rapid decline in ovarian sex steroids already during mid-life, between the ages of 46 and 52. Due to the menopause-related hormonal changes, women in most western countries live more than one-third of their lives in postmenopausal status. The role of ovarian steroids on neuromuscular function in middle-aged and older women has been investigated since the 1980s with increasing volume of research during the last decades. This review considers how different components of the neuromuscular system may be influenced by estrogens and so affects neuromuscular function in postmenopausal women. The main focus is on muscle strength and power, which are closely associated with mobility and functional capacity among older populations. In the end of the review, we summarize recent findings on the underlying biological mechanisms in skeletal muscle that could explain the association between hormone replacement therapy and neuromuscular function among postmenopausal women.

Exercise and sex steroid hormones in skeletal muscle

Sex steroid hormones are secreted mainly by the ovary and testis and regulate diverse physiological processes in target tissues. Recent studies have shown that sex steroidogenesis-related mRNA and protein expressions, such as for 17β-hydroxysteroid dehydrogenase (HSD), 3β-HSD, 5α-reductase and aromatase cytochrome P-450 (P450arom) enzymes, are detected in the skeletal muscle, while testosterone, estradiol, and 5α-dihydrotestosterone (DHT) were locally synthesized in skeletal muscle from dehydroepiandrosterone (DHEA). Moreover, in animal and human studies, the sex steroidogenesis enzymes and sex steroid hormone levels in skeletal muscle are upregulated by acute and chronic exercise stimulation. The enhanced muscle sex steroidgenesis is associated with glycemic control via upregulation of muscle glucose transporter-4 (GLUT-4) signaling in obese and diabetic rats and with muscle mass and strength in older men. Thus, an exercise-induced increase of sex steroid hormone in muscle may positively impact age-related concerns such as life-related diseases and sarcopenia.

Circulating miR-21, miR-146a and Fas ligand respond to postmenopausal estrogen-based hormone replacement therapy--a study with monozygotic twin pairs

Biological aging is associated with physiological deteriorations, which are partly due to changes in the hormonal profile. MicroRNAs regulate various processes associated with cell senescence; differentiation, replication and apoptosis. Serum microRNAs have potential to serve as noninvasive markers for diagnostics/prognostics and therapeutic targets. We analysed the association of estrogen-based hormone replacement therapy (HRT) with selected microRNAs and inflammation markers from the serum, leukocytes and muscle biopsy samples from 54 to 62 year-old postmenopausal monozygotic twins (n=11 pairs) discordant for HRT usage. Premenopausal 30-35 year-old women (n=8) were used as young controls. We focused on the hormonal aging and on the interaction between HRT use and the modulation of miR-21, miR-146a and classical inflammation markers. Fas-ligand was analysed since it functions in both apoptosis and inflammation. The inflammatory profile was healthier among the premenopausal women compared to the postmenopausal twins. Serum miR-21 and miR-146a levels and FasL concentrations were lower in HRT users compared to their non-using co-twins, demonstrating their responsiveness to HRT. Based on the pairwise FasL analysis, FasL concentration is likely to be genetically controlled. Overall, we suggest that postmenopausal estrogen deficiency sustains the development of "inflamm-aging". Estrogen sensitive, specific circulating microRNAs could be potential, early biomarkers for age-associated physiological deteriorations.

Sex, eyes, and vision: male/female distinctions in ophthalmic disorders

There is growing recognition: (1) that sex (male and female) and sex hormones (androgens and estrogens) are important for physiologic functions outside those pertaining expressly to reproduction, and (2) that both classes of sex hormones are active in both sexes, and moreover are produced locally in non-gonadal tissues throughout the body. The visual system, in addition to being of tremendous inherent importance, is unique in a very distinctive way; it possesses an organ - the eye - having a window allowing its interior to be examined with exquisite precision and control in both laboratory and clinical settings. Plus, many diseases manifest in the eye or are exclusive to the eye. This special issue of Current Eye Research contains 12 review articles, each addressing a different topical area important for Sex, Eyes, and Vision: Male/Female Distinctions in Ophthalmic Disorders. Of course, the distinctions between topical areas are blurred, and the overlap between the various lines of knowledge and investigation likewise is substantial. Eye diseases can be both neurodegenerative and involve altered blood flow, for instance. In fact, the thematic overlap is greater yet, in that the articles for this special issue address matters of interest to clinicians and scientists who may identify more with women's health or sex & gender fields than with eye & vision fields. Nevertheless, because this special issue needs a home, the following 12 topical areas each have here their own dedicated review: age-related maculopathy, central nervous system function and cognition & perception, diabetic retinopathy, dry eye, glaucoma, inherited diseases, lens and cataract, neuro-ophthalmology, ocular blood flow, ocular inflammatory disorders, optical coherence tomography, and sex/gender eye care disparities. This overview article itself raises additional points expressly concerning: (1) the estrogen therapy timing hypothesis, and (2) breast cancer treatment with aromatase inhibitors.

Hormone replacement therapy enhances IGF-1 signaling in skeletal muscle by diminishing miR-182 and miR-223 expressions: a study on postmenopausal monozygotic twin pairs

MiRNAs are fine-tuning modifiers of skeletal muscle regulation, but knowledge of their hormonal control is lacking. We used a co-twin case–control study design, that is, monozygotic postmenopausal twin pairs discordant for estrogen-based hormone replacement therapy (HRT) to explore estrogen-dependent skeletal muscle regulation via miRNAs. MiRNA profiles were determined from vastus lateralis muscle of nine healthy 54–62-years-old monozygotic female twin pairs discordant for HRT (median 7 years). MCF-7 cells, human myoblast cultures and mouse muscle experiments were used to confirm estrogen’s causal role on the expression of specific miRNAs, their target mRNAs and proteins and finally the activation of related signaling pathway. Of the 230 miRNAs expressed at detectable levels in muscle samples, qPCR confirmed significantly lower miR-182, miR-223 and miR-142-3p expressions in HRT using than in their nonusing co-twins. Insulin/IGF-1 signaling emerged one common pathway targeted by these miRNAs. IGF-1R and FOXO3A mRNA and protein were more abundantly expressed in muscle samples of HRT users than nonusers. In vitro assays confirmed effective targeting of miR-182 and miR-223 on IGF-1R and FOXO3A mRNA as well as a dose-dependent miR-182 and miR-223 down-regulations concomitantly with up-regulation of FOXO3A and IGF-1R expression. Novel finding is the postmenopausal HRT-reduced miRs-182, miR-223 and miR-142-3p expression in female skeletal muscle. The observed miRNA-mediated enhancement of the target genes’ IGF-1R and FOXO3A expression as well as the activation of insulin/IGF-1 pathway signaling via phosphorylation of AKT and mTOR is an important mechanism for positive estrogen impact on skeletal muscle of postmenopausal women.

5α-reductase type 1 modulates insulin sensitivity in men

CONTEXT

5α-Reductase (5αR) types 1 and 2 catalyze the A-ring reduction of steroids, including androgens and glucocorticoids. 5α-R inhibitors lower dihydrotestosterone in benign prostatic hyperplasia; finasteride inhibits 5αR2, and dutasteride inhibits both 5αR2 and 5αR1. In rodents, loss of 5αR1 promotes fatty liver.

OBJECTIVE

Our objective was to test the hypothesis that inhibition of 5αR1 causes metabolic dysfunction in humans.

DESIGN, SETTING, AND PARTICIPANTS

This double-blind randomized controlled parallel group study at a clinical research facility included 46 men (20-85 years) studied before and after intervention.

INTERVENTION

Oral dutasteride (0.5 mg daily; n = 16), finasteride (5 mg daily; n = 16), or control (tamsulosin; 0.4 mg daily; n = 14) was administered for 3 months.

MAIN OUTCOME MEASURE

Glucose disposal was measured during a stepwise hyperinsulinemic-euglycemic clamp. Data are mean (SEM).

RESULTS

Dutasteride and finasteride had similar effects on steroid profiles, with reduced urinary androgen and glucocorticoid metabolites and reduced circulating DHT but no change in plasma or salivary cortisol. Dutasteride, but not finasteride, reduced stimulation of glucose disposal by high-dose insulin (dutasteride by -5.7 [3.2] μmol/kg fat-free mass/min, versus finasteride +7.2 [3.0], and tamsulosin +7.0 [2.0]). Dutasteride also reduced suppression of nonesterified fatty acids by insulin and increased body fat (by 1.6% [0.6%]). Glucose production and glycerol turnover were unchanged. Consistent with metabolic effects of dutasteride being mediated in peripheral tissues, mRNA for 5αR1 but not 5αR2 was detected in human adipose tissue.

CONCLUSION

Dual inhibition of 5αRs, but not inhibition of 5αR2 alone, modulates insulin sensitivity in human peripheral tissues rather than liver. This may have important implications for patients prescribed dutasteride for prostatic disease.

Estrogen replacement and skeletal muscle: mechanisms and population health

There is a growing body of information supporting the beneficial effects of estrogen and estrogen-based hormone therapy (HT) on maintenance and enhancement of muscle mass, strength, and connective tissue. These effects are also evident in enhanced recovery from muscle atrophy or damage and have significant implications particularly for the muscular health of postmenopausal women. Evidence suggests that HT will also help maintain or increase muscle mass, improve postatrophy muscle recovery, and enhance muscle strength in aged females. This is important because this population, in particular, is at risk for a rapid onset of frailty. The potential benefits of estrogen and HT relative to skeletal muscle function and composition combined with other health-related enhancements associated with reduced risk of cardiovascular events, overall mortality, and metabolic dysfunction, as well as enhanced cognition and bone health cumulate in a strong argument for more widespread and prolonged consideration of HT if started proximal to menopausal onset in most women. Earlier reports of increased health risks with HT use in postmenopausal women has led to a decline in HT use. However, recent reevaluation regarding the health effects of HT indicates a general lack of risks and a number of significant health benefits of HT use when initiated at the onset of menopause. Although further research is still needed to fully delineate its mechanisms of action, the general use of HT by postmenopausal women, to enhance muscle mass and strength, as well as overall health, with initiation soon after the onset of menopause should be considered.

Early inflammatory and myogenic responses to resistance exercise in the elderly

INTRODUCTION AND METHODS

This study compared changes in myokine and myogenic genes following resistance exercise (3 sets of 12 repetitions of maximal unilateral knee extension) in 20 elderly men (67.8 ± 1.0 years) and 15 elderly women (67.2 ± 1.5 years).

RESULTS

Monocyte chemotactic protein (MCP)-1, macrophage inhibitory protein (MIP)-1β, interleukin (IL)-6 and MyoD mRNA increased significantly (P < 0.05), whereas myogenin and myostatin mRNA decreased significantly after exercise in both groups. Macrophage-1 (Mac-1) and MCP-3 mRNA did not change significantly after exercise in either group. MIP-1β, Mac-1 and myostatin mRNA were significantly higher before and after exercise in men compared with women. In contrast, MCP-3 and myogenin mRNA were significantly higher before and after exercise in the women compared with the men.

CONCLUSIONS

In elderly individuals, gender influences the mRNA expression of certain myokines and growth factors, both at rest and after resistance exercise. These differences may influence muscle regeneration following muscle injury.

Age and estrogen-based hormone therapy affect systemic and local IL-6 and IGF-1 pathways in women

A thorough understanding of the role of estrogens on aging-related muscle weakness is lacking. To clarify the molecular mechanisms underlying the effects of hormone replacement therapy (HRT) on skeletal muscle, we analyzed systemic protein and local mRNA levels of factors related to interleukin 6 (IL-6) and insulin-like growth factor 1 (IGF-1) pathways in 30- to 35-year-old (n = 14) women (without hormonal contraceptives) and in 54- to 62-year-old monozygotic female twin pairs discordant for HRT (n = 11 pairs, mean duration of HRT 7.3 ± 3.7 years). Biopsies were taken from vastus lateralis muscle and from abdominal adipose tissue. We found, first, that the systemic levels of IL-6 receptors sIL-6R and sgp130 are sensitive to both age and HRT concomitant with the changes in body composition. The serum levels of sgp130 and sIL-6R were 16% and 52% (p ≤ 0.001 for both variables) higher in postmenopausal women than in premenopausal women, and 10% and 9% lower (p = 0.033 and p < 0.001, respectively) in the HRT using than in their non using co-twins. After adjustment for body fat amount, the differences were no more significant. Second, the transcript analyses emphasize the impact of adipose tissue on systemic levels of IL-6, sgp130 and sIL6R, both at pre- and postmenopausal age. In muscle, the most notable changes were 28% lower gene expression of IGF-1 splice variant Ea (IGF-1Ea) and 40% lower expression of splice variant Ec (IGF-1Ec) in the postmenopausal non-users than in premenopausal women (p = 0.016 and 0.019, respectively), and 28% higher expression of IGF1-receptor in HRT users than in non-users (p = 0.060). The results tend to demonstrate that HRT has positive anti-catabolic effect on aging skeletal muscle.

Intracrine and myotrophic roles of 5α-reductase and androgens: a review

Historically, the circulation was thought to be the primary source of androgens influencing skeletal muscle. However, a growing body of research indicates that skeletal muscle expresses several androgen-synthesizing enzymes, including 5α-reductase. The intramuscular expression of these enzymes suggests that skeletal muscle is capable of synthesizing bioactive androgens, which could induce myotrophic effects via intracrine action.

PURPOSE

The aim of this brief review is to discuss recent research related to the intracrine and myotrophic roles of androgens, with particular focus on 5α-reductase as a myotrophic mediator.

METHODS

Included in the review are 17 reviews and 58 original studies that were identified by a systematic review from MEDLINE and deemed particularly relevant to our purpose. Results are summarized to provide an overview of 5α-reductase as a mediator of the myotrophic effects of androgens. In particular, discussions are included regarding androgen biosynthesis and androgen signaling within skeletal muscle, the effects of exercise on intramuscular androgen biosynthesis, and clinical applications of androgens and of a new class of myotrophic agonists termed selective androgen receptor modulator.

RESULTS

The ability of several peripheral tissues to synthesize bioactive androgens is well documented in the literature. Herein, we summarize newer studies that demonstrate that 1) skeletal muscle has the capability to synthesize both testosterone and dihydrotestosterone from dehydroepiandrosterone, which is present in abundance within the circulation, and 2) that exercise increases the expression of certain androgen-biosynthesizing enzymes within muscle.

CONCLUSIONS

Intramuscularly synthesized androgens have the potential to influence skeletal muscle via intracrine action; however, their exact role in skeletal muscle development and maintenance requires further elucidation.

Tissue-Specific Effects of Loss of Estrogen during Menopause and Aging

The roles of estrogens have been best studied in the breast, breast cancers, and in the female reproductive tract. However, estrogens have important functions in almost every tissue in the body. Recent clinical trials such as the Women's Health Initiative have highlighted both the importance of estrogens and how little we know about the molecular mechanism of estrogens in these other tissues. In this review, we illustrate the diverse functions of estrogens in the bone, adipose tissue, skin, hair, brain, skeletal muscle and cardiovascular system, and how the loss of estrogens during aging affects these tissues. Early transcriptional targets of estrogen are reviewed in each tissue. We also describe the tissue-specific effects of selective estrogen receptor modulators (SERMs) used for the treatment of breast cancers and postmenopausal symptoms.

The G-protein-coupled estrogen receptor GPER in health and disease

Estrogens mediate profound effects throughout the body and regulate physiological and pathological processes in both women and men. The low prevalence of many diseases in premenopausal women is attributed to the presence of 17β-estradiol, the predominant and most potent endogenous estrogen. In addition to endogenous estrogens, several man-made and plant-derived molecules, such as bisphenol A and genistein, also exhibit estrogenic activity. Traditionally, the actions of 17β-estradiol are ascribed to two nuclear estrogen receptors (ERs), ERα and ERβ, which function as ligand-activated transcription factors. However, 17β-estradiol also mediates rapid signaling events via pathways that involve transmembrane ERs, such as G-protein-coupled ER 1 (GPER; formerly known as GPR30). In the past 10 years, GPER has been implicated in both rapid signaling and transcriptional regulation. With the discovery of GPER-selective ligands that can selectively modulate GPER function in vitro and in preclinical studies and with the use of Gper knockout mice, many more potential roles for GPER are being elucidated. This Review highlights the physiological roles of GPER in the reproductive, nervous, endocrine, immune and cardiovascular systems, as well as its pathological roles in a diverse array of disorders including cancer, for which GPER is emerging as a novel therapeutic target and prognostic indicator.