Logan Steele
Skeletal muscle is an endocrine organ that secretes a variety of hormones, including interleukin-6 (IL-6), interleukin-8 (IL-8), interleukin-15 (IL-15), Brain-Derived Neurotrophic Factor (BDNF), Leukemia Inhibitory Factor (LIF), and musculin. These hormones have important roles in maintaining human health and improving physical condition. For example, BDNF is produced and secreted by skeletal muscles and is involved in autocrine and paracrine signaling to promote muscle fiber fat oxidation and muscle development. Exercise and resistance training increase the concentration of anabolic hormones in the blood, leading to greater increases in strength and muscle size. The secretion of these hormones by skeletal muscles has led to the suggestion that skeletal muscle may act as the body's largest endocrine gland.
| Characteristics | Values |
|---|---|
| Do muscles secrete hormones? | Yes, skeletal muscle acts as an endocrine organ by secreting interleukin-6 (IL-6) and an unidentified hormone into the systemic circulation. |
| What is the name of the hormone secreted by skeletal muscle? | Musculin |
| What other factors do skeletal muscles secrete? | Myokines, which have autocrine, paracrine, and/or endocrine effects; BDNF; Leukemia Inhibitory Factor (LIF); and Interleukin (IL)-8, IL-15 |
| What is the impact of muscle contraction on hormone secretion? | Muscle contraction increases the levels of circulating neurohypophyseal hormones, such as vasopressin and oxytocin, and their expression in various tissues. |
| How does testosterone affect muscle growth? | Testosterone binds to testosterone-specific receptors (androgen receptors) inside the muscle cell, signaling the cell's nucleus to increase protein synthesis and muscle fiber size. |
| How does exercise impact the secretion of hormones by skeletal muscle? | Exercise induces a five-fold increase in vasopressin levels and contributes to maintaining muscle homeostasis. |
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What You'll Learn
Skeletal muscle is an endocrine organ
Recent studies indicate that skeletal muscle may act as an endocrine organ by secreting interleukin-6 (IL-6) into the systemic circulation. Skeletal muscle has also been found to secrete an unidentified hormone, which has been named "musculin." Musculin may act on additional central nervous system sites, and it is suggested that analogues of this substance may be of therapeutic benefit in the treatment of diabetes and obesity.
The secretome of skeletal muscle comprises proteins, peptides, metabolites, lipids, and RNA molecules. These factors can act as muscle-derived paracrine or endocrine factors, termed "myokines" or "myometabokines." Myokines are proteins released by muscle cells in response to contractions and play a role in many exercise-induced adaptations, such as muscle hypertrophy and cancer protection. They also regulate the intramuscular cross-talk of myofibers, immune cells, fibroblasts, the vasculature, and the bone.
Understanding the mechanisms of production and secretion of myokines may lead to new pharmacological approaches for treating clinical disorders. For example, myokines have been found to mediate exercise-induced cognitive changes in older adults, and their role in muscle-fat cross-talk and the potential benefits of physical activity are well-established.
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Musculin is a hormone secreted by skeletal muscle
Skeletal muscle is an endocrine organ that synthesizes and secretes multiple factors, including interleukin-6 (IL-6) and other myokines. Recent studies indicate that skeletal muscle may secrete an unidentified hormone, which researchers have named "Musculin."
Musculin is a hormone that is hypothesized to be secreted by skeletal muscle, the body's largest endocrine organ. The name is derived from the Latin "musculus," meaning muscle. Musculin is thought to act on the endocrine pancreas to restrain beta-cell mass and inhibit insulin secretion and biosynthesis. Additionally, it may play a role in coordinating the neuroendocrine and appetite responses to exercise by acting on the hypothalamus (specifically the arcuate nucleus and dorsomedial hypothalamic nucleus). The amount of Musculin secreted is believed to be positively correlated with the prevailing insulin sensitivity of skeletal muscle, which could explain the hyperinsulinemia observed in insulin-resistant disorders such as type 2 diabetes mellitus, obesity, and polycystic ovary syndrome.
Furthermore, there is a possibility that Musculin acts on additional central nervous system sites and that other unidentified hormones may also be involved in these actions. The identification and understanding of Musculin and its potential analogues could lead to therapeutic benefits in treating global health issues such as diabetes and obesity.
The discovery of Musculin and its potential roles in the body highlights the complex interplay between skeletal muscle, hormones, and overall health. Further research is likely to provide valuable insights into the prevention and treatment of various metabolic disorders and age-related conditions, such as sarcopenia, which is characterized by a decline in muscle quantity and quality, leading to physical impairment and an increased risk of injuries.
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Exercise increases vasopressin levels
Skeletal muscle is an endocrine organ that secretes hormones, including interleukin-6 (IL-6) and an unidentified hormone, which has been named musculin. Muscles also produce and secrete myokines, which are molecules that act in an autocrine, paracrine, or endocrine hormone-like fashion. These myokines have beneficial effects on peripheral and remote organs and play a role in regulating the function of those organs and skeletal muscle itself.
The role of ADH in high-intensity exercise is of particular interest to researchers. Studies have shown that high-intensity aerobic exercise significantly increases plasma ADH levels and endogenous glucose production rates. However, there is no significant association between changes in ADH levels and glucose production rates, possibly due to small sample sizes and varying exercise durations. Further investigations are warranted to understand the importance of the causal role that ADH may play in exercise-mediated hepatic glucose production.
Additionally, the duration of exercise and the hydration status of the individual can alter the observed increase in plasma vasopressin concentrations. Prolonged exercise and absolute submaximal exercise intensities result in lower increases in plasma vasopressin levels. Acute exercise and exercise training have also been shown to impact blood pressure, vasopressin, and plasma renin activity in spontaneously hypertensive rats.
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Interleukin-6 (IL-6) is a cytokine produced by skeletal muscle
Skeletal muscle is an endocrine organ that plays a key role in postural retention and locomotion, maintaining the physical activities of human life. It has a second role as an energy production and consumption system that influences the whole body's energy metabolism. Skeletal muscle is a specific organ that engenders a physical force, and exercise training has been known to bring about multiple benefits for human health maintenance and/or improvement.
Recent studies indicate that skeletal muscle may act as an endocrine organ by secreting interleukin-6 (IL-6) into the systemic circulation. Interleukin-6 (IL-6) is a cytokine produced by skeletal muscle. It is an interleukin that acts as both a pro-inflammatory cytokine and an anti-inflammatory myokine. In humans, it is encoded by the IL6 gene. IL-6 is probably the best-studied of the cytokines that use gp130, also known as IL-6 signal transducer (IL6ST), in their signalling complexes. It is significantly elevated with exercise and precedes the appearance of other cytokines in the circulation.
IL-6 is an important mediator of fever and of the acute phase response. It is responsible for stimulating acute-phase protein synthesis, as well as the production of neutrophils in the bone marrow. It supports the growth of B cells and is antagonistic to regulatory T cells. It is capable of crossing the blood-brain barrier and initiating synthesis in the hypothalamus, thereby changing the body's temperature setpoint. In muscle and fatty tissue, IL-6 stimulates energy mobilization, which leads to increased body temperature.
IL-6 has been identified as an essential regulator of satellite cell (muscle stem cell)-mediated hypertrophic muscle growth. It is locally and transiently produced by growing myofibers and associated satellite cells. IL-6 deficiency abrogated satellite cell proliferation and myonuclear accretion in the preexisting myofiber by impairing STAT3 activation and expression of its target gene cyclin D1. IL-6 is also produced by smooth muscle cells in the tunica media of many blood vessels as a pro-inflammatory cytokine.
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Testosterone increases muscle fibre size
Skeletal muscle has been identified as an endocrine organ, secreting a hormone called musculin. It is also believed that skeletal muscle secretes an unidentified hormone, in addition to interleukin-6 (IL-6) into the systemic circulation.
Testosterone is a hormone that has been shown to increase muscle fibre size. In a study, healthy young men were treated with a long-acting GnRH agonist to suppress their endogenous testosterone production and one of five different doses of testosterone enanthate to create different circulating testosterone concentrations. The results showed that testosterone administration was associated with a dose-dependent increase in muscle volume. The men receiving 300 and 600 mg of testosterone enanthate weekly experienced significant increases in the areas of type I muscle fibres. The men in the 600-mg group also had significant increments in the cross-sectional area of type II muscle fibres.
The study also found that testosterone-induced skeletal muscle hypertrophy was associated with increased satellite cell replication and activation. This was evident through the increase in the number of proliferating cell nuclear antigen+ satellite cells at the 125, 300, and 600 mg doses. Additionally, the expression of activated Notch and myogenin in satellite cells was examined, and both showed significant increases in the 300-mg group.
The findings of this study are consistent with previous research conducted on animals, which reported an increase in fibre diameter in the levator ani muscle of androgen-treated rats. Furthermore, the adaptive response of skeletal muscle varies with the type of stimulus, the fibre composition of the muscle, and the timing of biopsies taken. For example, muscle stretch in bird wing muscles results in an early increase in muscle fibre numbers, while hypertrophic and hyperplastic responses occur at different rates.
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Frequently asked questions
Yes, skeletal muscle has been shown to secrete hormones.
Skeletal muscle secretes a hormone called musculin. It also secretes interleukin-6 (IL-6) and other unidentified hormones. These hormones are known as myokines and have autocrine, paracrine, and/or endocrine effects.
Myokines have been shown to have a beneficial effect on peripheral and remote organs. They also play a role in regulating muscle homeostasis and muscle development.
Exercise has been shown to increase the levels of certain muscle-secreted hormones, such as vasopressin, oxytocin, and interleukin-6 (IL-6).
In addition to exercise, the secretion of muscle-derived hormones is affected by various factors such as mechanical and nervous stimuli, age, hormonal changes, and nutrient intake.
