Athena Vale
Glucocorticoids are highly conserved fundamental regulators of energy homeostasis. They are released from the adrenal gland in response to stress or acute inflammation, mobilizing energy from carbohydrates, fats, and proteins. While glucocorticoids are used to treat muscle weakness in patients with Duchenne muscular dystrophy, they can also cause muscle wasting and decreased bone formation. The effects of glucocorticoids on muscle wasting and osteoporosis are more pronounced when treatment exceeds 3 months or consists of 3-4 courses per year with an oral dose of at least 5 mg of prednisone per day. The mechanisms of muscle wasting related to glucocorticoids are not yet fully understood, but studies have shown that they can decrease intestinal calcium absorption, leading to secondary hyperparathyroidism.
| Characteristics | Values |
|---|---|
| Effect on muscle | Muscle wasting and decreased bone formation |
| Effect on calcium absorption | Decreased intestinal calcium absorption, leading to secondary hyperparathyroidism |
| Effect on muscle proteins | Muscle protein breakdown exceeds muscle protein synthesis |
| Effect on energy | Profound depletion of energy stores |
| Effect on serum glucose | Increase serum glucose |
| Effect on muscle strength | Reduced specific force (strength) of muscle fibres |
| Effect on muscle growth | Impaired formation of new myotubes and inhibited myogenesis |
| Effect on muscle wasting | Induces muscle wasting through JAK/STAT3 pathway inhibition |
| Effect on muscle atrophy | Induces bone and muscle atrophy by tissue-specific mechanisms upstream of E3 Ubiquitin Ligases |
| Effect on muscle performance | Improved muscle performance in both male and female mice |
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What You'll Learn
Glucocorticoids can cause muscle wasting
Glucocorticoids are highly conserved fundamental regulators of energy homeostasis. They are released from the adrenal gland in response to stress, perceived danger, or acute inflammation. While this response is adaptive in the case of infection, chronic mobilization can lead to a depletion of energy stores, particularly in skeletal muscle. This depletion of energy stores is further exacerbated by a decrease in appetite, resulting in an imbalance between energy intake and expenditure.
Glucocorticoids have been observed to cause muscle wasting, with the likelihood of this side effect increasing with longer durations of treatment or higher doses. The muscle atrophy induced by glucocorticoids is accompanied by suppression of protein synthesis and an increase in protein catabolism, leading to a reduced myotube diameter. Glucocorticoids also inhibit myogenesis by downregulating myogenin gene expression, impairing the formation of new myotubes. Furthermore, glucocorticoids reduce sarcolemmal excitability, decrease serum levels of creatine kinase and myoglobin, and reduce the cross-sectional area and specific force of muscle fibers.
However, the effects of glucocorticoids on muscle performance are complex and may vary depending on factors such as sex and dosage. Some studies have shown that short-term or pulse doses of glucocorticoid steroids can enhance muscle performance. For example, a study on mice found that administering the glucocorticoid steroid prednisone once a week improved overall muscle performance in both male and female mice. Nevertheless, long-term glucocorticoid use has been associated with side effects like obesity and osteoporosis, and further research is needed to fully understand the effects of glucocorticoids on muscle tissue in humans.
In summary, glucocorticoids can cause muscle wasting through a variety of mechanisms, including suppression of protein synthesis, increased protein catabolism, and impaired muscle growth. While short-term or pulse doses may enhance muscle performance, long-term use is associated with negative side effects. Further research is needed to fully understand the complex effects of glucocorticoids on muscle tissue, particularly in humans.
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Glucocorticoids can decrease bone formation
Glucocorticoids are highly conserved fundamental regulators of energy homeostasis. They are released from the adrenal gland in response to stress, perceived danger, or acute inflammation. While glucocorticoids are adaptive in response to infection, chronic mobilisation can lead to a depletion of energy stores. Glucocorticoids have important roles in modifying carbohydrate, fat, and protein metabolism, as well as numerous other physiologic functions.
Glucocorticoids have been found to decrease bone formation. They cause profound effects on bone cell replication, differentiation, and function. Glucocorticoids increase bone resorption by stimulating osteoclastogenesis, increasing the expression of the RANK ligand, and decreasing the expression of its decoy receptor, osteoprotegerin. This decrease in osteoblastic cell replication and differentiation, as well as an increase in the apoptosis of mature osteoblasts, leads to a decrease in bone formation. The likelihood of muscle wasting and steroid-induced osteoporosis increases if the duration of treatment exceeds 3 months or consists of 3-4 courses of treatment per year with an oral dose of at least 5 mg of prednisone per day.
Glucocorticoids have also been found to decrease intestinal calcium absorption, which results in secondary hyperparathyroidism. This further contributes to decreased bone formation. Additionally, there is a question as to whether glucocorticoids cause calcium malabsorption, which could also contribute to decreased bone formation.
However, it is important to note that the effects of glucocorticoids on bone formation may vary between males and females. In a study on male and female mice, it was found that overall performance improved in both sexes, but the genes that changed expression in the muscle demonstrated distinct responses. Specifically, myofibers from male mice showed an increased expression of genes in the IGF1/PI3K pathway, which promoted muscle growth, and genes important for calcium handling, which altered muscle contraction and function. In contrast, myofibers from female mice expressed genes to break down lipids and increase fatty acid oxidation.
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Glucocorticoids are released in response to stress
Glucocorticoids are highly conserved fundamental regulators of energy homeostasis. In response to stress, glucocorticoids are released from the adrenal gland, rapidly mobilizing energy from carbohydrate, fat, and protein stores. This mobilization of energy is critical for an efficient immune response to infection. However, chronic mobilization can lead to a profound depletion of energy stores.
The secretion of glucocorticoids is a classic endocrine response to stress. While the purpose of this release is still debated, one view posits that glucocorticoids help mediate the ongoing or pending stress response. In contrast, a revisionist viewpoint suggests that glucocorticoids suppress the stress response, preventing it from being overactivated.
The surge in glucocorticoid secretion after stress must be tightly controlled. The characteristics of this surge, such as peak height, curvature, and duration, depend on the nature and severity of the stressor. Proper glucocorticoid responses to stress are critical for adaptation, and their dysregulation can increase the risk for developing stress-related mental disorders.
Glucocorticoids have also been observed to enhance muscle performance through sex-specific mechanisms. In a study, male and female mice administered glucocorticoid steroids showed improved overall performance. However, the genes that changed expression in the muscles demonstrated distinct responses between the sexes. While male mice showed increased expression of genes promoting muscle growth, female mice expressed genes for breaking down lipids and increasing fatty acid oxidation.
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Glucocorticoids can cause osteoporosis
Glucocorticoids are synthetic hormones, also known as steroids, that are released from the adrenal gland in response to stress or acute inflammation. They are highly conserved fundamental regulators of energy homeostasis. However, despite their beneficial effects, glucocorticoids can cause muscle wasting and decreased bone formation. This is where the topic of glucocorticoids causing osteoporosis comes into play.
Glucocorticoid-induced osteoporosis (GIO or GIOP or GCOP) is a condition in which people who take glucocorticoids develop osteoporosis, which is the weakening of bones. The association between glucocorticoid excess and osteoporosis was first described nearly 80 years ago, but its importance in clinical practice has only recently been recognized. GIO is the most common cause of secondary osteoporosis, especially before the age of 50, and it is the most common iatrogenic cause of the disease.
The use of glucocorticoids increases the risk of fracture and bone loss. The increase in fracture risk is not fully assessed by bone mineral density measurements, as it is also related to an increased risk of falls and alteration in bone quality. The risk of fracture may occur in 30-50% of patients on chronic GC therapy. The likelihood of osteoporosis increases if the duration of treatment exceeds 3 months or consists of 3-4 courses of treatment per year with an oral dose of at least 5 mg of prednisone per day. Glucocorticoids given by mouth, vein, or skin injection are most likely to cause osteoporosis.
To prevent glucocorticoid-induced osteoporosis, experts recommend considering bone-protective medicine for certain groups who are taking glucocorticoids for at least 3 months. Additionally, even if one is taking glucocorticoids for less than 3 months, it is suggested to take calcium (1000-1200 mg daily) and vitamin D (1000-2000 IU or more daily) through supplements if dietary intake is insufficient.
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Glucocorticoids can improve muscle strength
Glucocorticoids are highly conserved fundamental regulators of energy homeostasis. They are released from the adrenal gland in response to stress or acute inflammation. While glucocorticoids are adaptive in response to infection, chronic mobilization can lead to a depletion of energy stores. Glucocorticoids have been shown to cause muscle wasting and decreased bone formation, with muscle wasting occurring as early as 7 days after the start of administration. This is due to the suppression of protein synthesis and a simultaneous increase in protein catabolism, leading to reduced muscle diameter.
However, glucocorticoids can improve muscle strength in certain contexts. For example, patients with Duchenne muscular dystrophy, a genetic disorder that causes progressive muscle weakness, are prescribed glucocorticoids to improve muscle strength. Short-term dosing of glucocorticoids has been found to result in modest improvements in athletic performance in both humans and mice. In mice, a chronic once-weekly dosing regimen improved muscle strength and endurance in models of Duchenne muscular dystrophy and limb girdle muscular dystrophies.
The mechanisms behind the improvement in muscle strength with glucocorticoid use are not yet fully understood. One study found that male and female mice exhibited similar improvements in muscle strength with weekly glucocorticoid treatment, but the mechanisms behind this improvement differed. Male mice showed an increased expression of genes in the IGF1/PI3K pathway, which promoted muscle growth, while female mice expressed genes to break down lipids and increase fatty acid oxidation.
In summary, while glucocorticoids are generally associated with muscle wasting and weakness, particularly with chronic daily use, short-term or intermittent use may improve muscle strength through sex-specific mechanisms. Further research is needed to fully understand the molecular mechanisms behind this improvement and to determine the optimal dosing regimens for different patient populations.
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Frequently asked questions
Glucocorticoids are fundamental regulators of energy homeostasis, which are released from the adrenal gland in response to stress or acute inflammation.
Glucocorticoids can cause muscle wasting and muscle atrophy. They reduce the cross-sectional area of myofibers and reduce the specific force of muscle fibres.
Glucocorticoids cause muscle wasting by decreasing intestinal calcium absorption, which results in secondary hyperparathyroidism.
Long-term glucocorticoid use can lead to side effects such as obesity and osteoporosis.
Glucocorticoids can improve muscle strength in patients with Duchenne muscular dystrophy, a genetic disorder that causes progressive muscle weakness.
