Lipolysis, the breakdown of fats into glycerol and free fatty acids, is increased by several factors. Primarily, catecholamines, atrial natriuretic peptide, and insulin are the main physiological stimuli of exercise-induced lipolysis in humans.
Factors Influencing Lipolysis
While several factors can stimulate lipolysis in vitro (in isolated adipocytes), the key players in humans, particularly during exercise, are specific hormones.
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Catecholamines: These include adrenaline (epinephrine) and noradrenaline (norepinephrine). They bind to adrenergic receptors on fat cells, triggering a cascade that activates hormone-sensitive lipase (HSL), the enzyme responsible for breaking down triglycerides into free fatty acids and glycerol.
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Atrial Natriuretic Peptide (ANP): This hormone is released by the heart in response to increased blood volume. It promotes lipolysis by activating guanylate cyclase, leading to the production of cyclic GMP (cGMP), which stimulates HSL.
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Insulin: While often associated with promoting fat storage, insulin can also stimulate lipolysis under certain conditions. The reference highlights that insulin is a physiological stimulus of exercise-induced lipolysis.
Summary Table: Hormonal Influences on Lipolysis
| Hormone | Effect on Lipolysis | Mechanism |
|---|---|---|
| Catecholamines | Increases | Binds to adrenergic receptors, activating HSL. |
| Atrial Natriuretic Peptide | Increases | Activates guanylate cyclase, producing cGMP, stimulating HSL. |
| Insulin | Increases | Physiological stimulus of exercise-induced lipolysis. |
