Cortisol, a glucocorticoid hormone produced by the adrenal cortex, plays a significant role in protein metabolism, especially under stress. Its influence on protein breakdown (proteolysis) is crucial for providing substrates for gluconeogenesis, the process of generating glucose from non-carbohydrate sources.
Mechanism of Cortisol in Protein Breakdown
1. Catabolic Effect: Cortisol has a catabolic effect on skeletal muscle protein, which is the body’s largest reservoir of amino acids. During periods of high cortisol secretion (e.g., stress, fasting, illness), cortisol promotes the breakdown of proteins in muscle cells, releasing amino acids into the bloodstream.
2. Amino Acid Mobilization: The amino acids from protein breakdown are transported to the liver, where they are used for gluconeogenesis. This process is particularly essential in maintaining blood glucose levels during stress or fasting, as it provides an energy source for the brain and other vital organs.
3. Inhibition of Protein Synthesis: Cortisol decreases protein synthesis in muscle cells and other tissues by downregulating certain cellular processes involved in building proteins. This contributes to a net loss of muscle protein, which can lead to muscle wasting if cortisol levels remain chronically high.
4. Impact on Other Tissues: Cortisol-induced protein breakdown also affects other tissues like skin and connective tissue, potentially leading to skin thinning, delayed wound healing, and other structural changes, especially in cases of prolonged corticosteroid use or chronic stress.
Clinical Implications of Cortisol-Induced Proteolysis
Muscle Wasting: Chronically elevated cortisol levels, as seen in conditions like Cushing’s syndrome or prolonged stress, lead to muscle atrophy and weakness due to the sustained catabolic effect on muscle proteins.
Hyperglycemia: The amino acids released during proteolysis are converted to glucose, contributing to elevated blood glucose levels, which can worsen conditions like diabetes.
Immune Suppression: Since some proteins involved in immune responses are affected by cortisol, excessive protein breakdown can suppress immune function, making the body more susceptible to infections.
Summary
Cortisol’s role in protein breakdown is a double-edged sword: while it provides necessary substrates for glucose production during stress, prolonged elevation can lead to muscle wasting, immune suppression, and metabolic disturbances.