MCAT Content / Hormonal Regulation And Integration Of Metabolism / Hormonal Regulation Of Fuel Metabolism

Hormonal regulation of fuel metabolism

Topic: Hormonal Regulation And Integration Of Metabolism

Insulin and glucagon are the two regulatory hormones secreted by the pancreas that maintain a stable blood glucose level for fuel metabolism.

Essential hormones are secreted by the pancreas which monitors blood glucose levels. Insulin and glucagon are two hormones primarily responsible for maintaining homeostasis of blood glucose levels. An increase in blood glucose levels triggers the release of insulin which in turn promotes glycolysis, glycogen synthesis in liver and skeletal muscle, fatty acid synthesis in the liver, and fatty acid storage in adipose tissue. When blood glucose levels decrease, glucagon is released to promote beta-oxidation, glycogen breakdown in the liver and skeletal muscle, gluconeogenesis in the liver, and release of fatty acids from adipose tissue.

Other regulatory hormones that control fuel metabolism also function as stress hormones. These are epinephrine and cortisol. Epinephrine and cortisol are released from the adrenal glands mainly in response to stress. However, epinephrine also triggers glycogen breakdown, while cortisol promotes gluconeogenesis and increases blood sugar level.


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Key Points

• Insulin and glucagon are hormones secreted by the pancreas that play a key role in maintaining a stable blood glucose level.

• Glucagon acts to raise blood sugar levels, whereas insulin acts to lower blood sugar levels.

• Insulin promotes glycolysis, glycogen synthesis in liver and skeletal muscle, fatty acid synthesis in the liver, and fatty acid storage in adipose tissue.

• Glucagon promotes beta-oxidation, glycogen breakdown in the liver and skeletal muscle, gluconeogenesis in the liver, and release of fatty acids from adipose tissue.

• Epinephrine and cortisol are primarily released in response to stress but can also function as regulatory hormones that control fuel metabolism; epinephrine triggers glycogen breakdown, while cortisol promotes gluconeogenesis and increases blood sugar level.


Key Terms

insulin: a polypeptide hormone, produced by the pancreas, that regulates carbohydrate metabolism by lowering the sugar level in the blood

glucagon: a polypeptide hormone, produced by the pancreas, that opposes the action of insulin by stimulating the production of sugar

epinephrine: an amino acid-derived hormone secreted by the adrenal gland in response to stress

cortisol: a steroid hormone secreted by the adrenal gland in response to stress

homeostasis: the state of steady internal, physical, and chemical conditions maintained by living systems

adipose tissue: a term for loose connective tissue composed of adipocytes; its main role is to store energy in the form of fat

adrenal glands: hormonal glands located on the kidneys, secrete epinephrine 



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