Hormonal Responses to Exercise Dr. Kyle Coffey

1. Hormonal Responses to ExerciseDr. Kyle Coffey Week 4&5

2. Blood Hormone Concentration • Hormones only affect tissue with specific receptors and trigger events at the cell • Concentrationdetermines the magnitude of the effect at the tissue level • Determinant Factors • Rate of secretion of hormone from endocrine gland • Rate of metabolism or excretion of hormone • Quantity of transport protein • Changes in plasma volume • With exercise: concentration changes!

3. Mechanism of Hormone Reaction • Hormones modify cellular activity by: • Alteration of membrane transport • Activate carrier molecules in or near membrane to increase movement of substrates or ions from outside to inside cell • Insulin • Altering activity of DNA to increase protein synthesis • Lipids diffuse across membrane easily, bind in cytoplasm • Steroid hormones • Activation of “second messengers” via G-Protein • Do not cross membrane (not permeable) • Use Cyclic AMP, Ca++,Inositol triphosphate, Diacylglycerol • Insulin is the odd ball: does not utilize second messengers

4. Hormones: Regulation & Action • Hormones are secreted from endocrine glands • Hypothalamus and pituitary glands • Thyroid and parathyroid glands • Adrenal glands • Pancreas • Testes and ovaries

5. Hypothalamus and Pituitary Gland • Hypothalamus • Controls secretions from pituitary gland • Anterior Pituitary Gland • Adrenocorticotropic hormone (ACTH) • Follicle-stimulating hormone (FSH) • Luteinizing hormone (LH) • Melanocyte-stimulating hormone (MSH) • Thyroid-stimulating hormone (TSH) • Growth hormone (GH) • Prolactin • Posterior Pituitary Gland • Oxytocin • Antidiuretic hormone (ADH)

6. Growth Hormone • Stimulates release of insulin-like growth factors (IGFs) • Essential for growth of all tissues • Amino acid uptake and stimulates protein synthesis • Long bone growth • Used to treat childhood dwarfism • Also used by athletes and elderly • Spares plasma glucose (supports Cortisol) • Opposes insulin: maintains plasma glucose • Increases gluconeogenesis (new glucose in liver) • Mobilizes fatty acids from adipose tissue • What happens with exercise?

7. Growth Hormone

8. Changes in Plasma Growth Hormone during Exercise

9. Growth Hormone Supplementation • No evidence that GH promotes strength gains • Protein synthesis is collagen, not contractile protein • 2010: Associations of exercise-induced hormone profiles and gains in strength and hypertrophy in a large cohort after weight training • 2010: Elevations in ostensibly anabolic hormones with resistance exercise enhance neither training-induced muscle hypertrophy nor strength of the elbow flexors • Improve healing capacity? • 2009: Growth hormone stimulates the collagen synthesis in human tendon and skeletal muscle without affecting myofibrillar protein synthesis

10. Growth Hormone Discussion • Commonly utilized substance – difficult to obtain? • What is the impact for us as EPs? • Is this performance enhancing or solely a healing benefit? • Impact with young children or adolescents? Not skeletally mature? • Video: HGH on the rise

11. Posterior Pituitary Gland • Antidiuretic hormone (ADH) • Reduces water loss from the body to maintain plasma volume • Favors reabsorption of water from kidney tubules to capillaries • Release stimulated by high plasma osmolality and low plasma volume • Exercise • Increases during exercise >60% VO2 max • To maintain plasma volume • Normal exercise: osmolality increases, plasma volume decreases • WHY?!

13. Adrenal Medulla • Secretes the catecholamines • Epinephrine (E) and norepinephrine (NE) • Fast-acting hormones • Part of “fight or flight”response • Increase HR, and maintenance of BP • Maintenance of plasma glucose concentration

14. Epinephrine and Norepinephrine • Increase linearly during exercise • Favor the mobilization of FFA and maintenance of plasma glucose • Decreased plasma levels in response to exercise bout • Parallels reduction in glucose mobilization What does linear increase mean?!

15. Effects of E and NE

16. Change in Catecholamine with Exercise

17. Role of Catecholamines (E and NE) in Substrate Mobilization

18. Plasma Epinephrine with Exercise

19. Catecholamines Following Exercise

20. Plasma Catecholamines Responses to Exercise Following Training

21. Adrenal Cortex • Mineralcorticoids • Aldosterone • Regulation of blood pressure • Glucocorticoids • Cortisol • Regulation of plasma glucose (supported by GH) through protein breakdown and use of FFAs as fuel

22. Aldosterone • Control of Na+ reabsorption and K+ secretion • Na+/H2O balance • Regulation of blood volume and blood pressure • Part of renin-angiotensin-aldosterone system • All three hormones increase during exercise • Stimulated by: • Increased K+concentration • Where does this occur with exercise? • Decreased plasma volume • When does this occur with exercise?

24. Why should EPs care about this? • Angiotensin II • Powerful vasoconstrictor stimulated by increased SNS activity • When does this occur? • Effect? • ACE inhibitors • Reduce production of angiotensin • Common medication class used to treat HTN • Medications end in –pril (i.e. Lisinopril) • Impact on exercise performance? • Signs and symptoms?

25. Cortisol • Maintenance of plasma glucose • Promotes protein breakdown for gluconeogenesis • Stimulates FFA mobilization • Stimulates glucose synthesis • Blocks uptake of glucose into cells (opposes insulin) • Promotes the use of free fatty acids as fuel • Stimulated by: • Stress • Exercise • Decrease during low-intensity exercise • Why? • Increase during high-intensity exercise • Above ~60% VO2 max

27. Changes in Plasma Cortisol during Exercise

28. Pancreas • Secretes: • Insulin (from cells in islets of Langerhans) • Promotes the storage of glucose, amino acids, and fats • Glucagon (from cells in islets of Langerhans) • Promotes the mobilization of fatty acids and glucose • Somatostatin(from cells in islets of Langerhans) • Controls rate of entry of nutrients into the circulation

29. Effects of Insulin and Glucagon

30. Factors in Secretion of Insulin

31. Changes in Plasma Insulin During Exercise

32. Changes in Plasma Glucagon during Exercise

33. Training Effects • Trained subjects during exercise • More rapid decrease in plasma insulin • Increase in plasma glucagon

34. Effect of Epinephrine and Norepinephrine on Insulin and Glucagon Secretion

35. Effect of the SNS on Substrate Mobilization

36. Testosterone • Released from testes • Anabolic steroid • Promotes tissue (muscle) building • Exercise performance enhancement

37. Muscle: Endocrine Gland • Skeletal muscle produces myokines (signaling molecules) when it contracts • Stimulate glucose uptake and fatty acid oxidation • Promote blood vessel growth in muscle (training adaptation) • Promote liver glucose production and triglyceride breakdown • Regular exercise promotes anti-inflammatory environment through myokine release • Reduction in chronic inflammation and reduced risk of heart disease, type 2 diabetes, and certain cancers

38. Hormonal Control of Substrate Mobilization During Exercise • Muscle glycogen utilization • Related to exercise intensity • High-intensity exercise results in greater and more rapid glycogen depletion • Muscle then liver • Plasma epinephrine is a powerful simulator of glycogenolysis • High-intensity exercise results in greater increases in plasma epinephrine

39. Glycogen Depletion during Exercise

40. Summary of Hormonal Responses to Exercise

41. Link • Interval Training and Blood Glucose