The role of insulin, corticosterone and other factors in the acute recovery of muscle protein synthesis on refeeding food-deprived rats.

Persistently high insulin levels lead to impaired metabolism and increased fat storage, while short-term increases in insulin stimulate the building of muscle protein.

In rats that have been starved and then fed again, the return of muscle protein synthesis cannot be fully explained by known hormones insulin and corticosterone, meaning another unknown factor must also be involved.

In rats that have been deprived of food, blocking insulin stops the increase in skeletal muscle protein synthesis that normally occurs when food is reintroduced.

In rats that have been deprived of food, muscle protein synthesis increases rapidly during refeeding, and this increase occurs alongside higher insulin and lower corticosterone levels; both hormonal changes are required for this effect, and corticosterone reduces the ability of insulin to stimulate protein synthesis.

In food-deprived rats, high levels of the hormone corticosterone reduce the rate of muscle protein synthesis when food is reintroduced, and this reduction occurs through disruption of insulin's signaling pathway that promotes muscle growth.

When food-deprived rats are fed again, their muscle protein synthesis rises sharply within 20 to 40 minutes, and this response does not require sustained nutrient intake or changes in growth hormone.