Endocrine System and Exercise

Glucose uptake increases during exercise  Release from kidneys, gut, and liver  Make new from 3-carbon molecules (LA, pyr., glycerol, and alanine, LA most important)  Deliver alternative substrates to the active tissue (FAs, triglycerides, lactate, aa leucine)

Increased glucose causes insulin levels to rise

Insulin Antagonists  Insulin stimulates glycogen storage, epi and glucagon stimulate glycogen breakdown  Insulin stimulates protein synthesis  Leptin is an anabolic hormone that promotes use of energy  Cortisol promotes catabolism and release of aa’s from muscle into blood

Insulin Leptin Energy Storage Energy Dissipation FFA Carbohydrates

Feed-forward control  When exercising, catacholamine-mediated stimulation of hepatic glucose production (why?)

Hormones  Chemical messengers  Generalized in action an circulate widely  Some specific, localized effect (ACH)  Norepi is both local and general

Two types of hormones:  Steroid: produced by the adrenal cortex and gonads, made from cholesterol  Polypeptides: aka small proteins, derived from aa’s in other endocrine glands

Action:  Usually bind on specific sites on target tissue, binding can:  Affect permeability  Activate an enzyme or enzyme system  Activate genetic apparatus to manufacture intracellular proteins or other substrates  Increase secretatory activity

cyclic AMP (cAMP)  Many hormones, when bind to a tissue form cAMP  cAMP activates many systems  Second messenger

Low intensity exercise  Little effect on hormone levels  >50% VO 2 max see elevation in catecholamines  Why?  With training, lower  Moderate exercise, the same or enhanced response  Why?

Insulin and glucagon: immediate control of blood glucose  Insulin stimulates uptake, glycogen and fat synthesis  Glucagon, secreted when blood levels are low, acting to raise those levels  Two effects: –Enhance glycogenolysis –Increase glycogenolysis (indirectly stimulating beta oxidation)

Liver’s role in stabilizing blood glucose levels  HGP is considered representative of glucose production  Critical for overall homeostasis  Levels are high, store  Levels are low, release