2. Glucose Homeostasis  brain has high consumption of glucose –uses ~20% of RMR –1° fuel for energy  during exercise, working muscle competes with brain for glucose  many redundant systems for maintaining glucose homeostasis –hepatic glucose production (glycogen, lactate, pyruvate, glycerol, alanine) –pancreatic hormones (insulin, glucagon) –sympathoadrenal stimulation (epinephrine)

3. Claude Bernard (1813-1878)  Discovery of new function of liver-- glucose secretion into blood (1848) –Previously thought that only plants could produce sugar –Sugar must be taken in by diet

4. Glucose Production During Exercise

5. Maintenance of Blood Glucose  glucose needed for CNS, ATP synthesis, Kreb’s cycle intermediates   muscle glucose uptake (Rd) matched by  liver glucose release (Ra) –glucose pool = ~5 g (~20 kcal) –dependent upon exercise intensity and duration  endurance exercise may need CHO ingestion to maintain blood [glucose]

6. Cori Cycle

7. Liver Gluconeogenesis  uses pyruvate & lactate (Cori cycle), glycerol, and alanine (glucose- alanine cycle) as substrates  liver contains glucose 6-phosphatase and other enzymes that allow reversal of glycolysis and release of glucose

8. Gluconeogenic amino acids  urea formation from excreted N in amino acid degradation  C skeletons are degraded into: –glucose –ketone acetoacetate or acetyl Co-A  during fasting, starvation, and prolonged exercise, AA supply most of C used in gluconeogenesis –glucose-alanine cycle  AA metabolism contributes 10-15% of total substrates used during exercise

9. Glucose- alanine cycle Leucine is 1° BCAA that provides N for alanine formation. This model may not operate when glucose & glycogen is low leucine

10. Interrelationship of leucine catabolism and alanine formation Rate of appearance (Ra) of alanine (a) and leucine N transfer to alanine (b) at rest and during exercise Wolf et al., 1982, 1984

11. Regulation of liver glucose output  glucose threshold stimulates liver glucose output –hypoglycemia stimulates hormonal response (EPI, glucagon, cortisol, GH) –glucose threshold is dynamic  like blood, glucose uptake is shunted to active tissue –skeletal muscle GLUT transporters GLUT1 is 1º transporter at rest GLUT4 is 1º transporter during exercise

12. Endocrine Regulation of Glucose Homeostasis  Insulin—secreted from pancreatic islet ß cells –released regulated by blood [glucose] (glycemic threshold) –stimulates glucose oxidation & storage and inhibits glucose production stimulates glycogen synthase inhibits phosphorylase inhibits gluconeogenesis stimulates glucose transport into adipocytes, which is then converted into TG inhibits hormone-sensitive lipase (HPL) (  cAMP) and lipoprotein lipase activates GLUT1 –release inhibited by EPI and NE –obesity increases and training decreases insulin secretion

13. Endocrine Regulation of Glucose Homeostasis  Glucagon—secreted from pancreatic islet  cells –promotes liver mobilization of fuels –stimulates cAMP –released regulated by blood [glucose] (glycemic threshold) –Activates phosphorylase –Stimulates gluconeogenesis

14. Endocrine Regulation of Glucose Homeostasis  Epinephrine—secreted from adrenal medulla –released in response to exercise and decreased blood [glucose] stimulates liver and muscle phosphorylase a and PFK increases liver glucose output and muscle glucose metabolism

15. Glucose Homeostasis During Exercise Effect of CHO feeding during exercise on glucose homeostasis

16. CHO metabolism during prolonged exercise (~72% VO 2max ) to exhaustion w/ and w/out CHO feedings (every 20 min) Coyle et al., JAP, 1986 1 hr2 hr3 hr4 hr Placebo.85.84.80-- CHO.85.86.85 RER results

17. Substrate use during exercise to exhaustion w/ and w/out CHO feeding Decreased muscle glycogen caused increased glucose utilization Coyle et al., JAP, 1986

18. Hepatic glucose output (HGP) and glucose uptake (Rd) w/ and w/out CHO feedings during prolonged exercise (~70% of VO 2max ) McConell et al., JAP, 1994

19. CHO Feeding during Prolonged Exercise   blood glucose  maintains CHO oxidation rate   time to exhaustion/performance  conserves liver glycogen   muscle glucose uptake  no effect on muscle glycogen utilization

20. Effects of Prolonged Exercise on Blood Glucose

28. Liver glucose output from gluconeogenesis (GNG) and glycogenolysis (GLY) during prolonged exercise at 30% of VO 2max Effect of exercise intensity on liver glucose output

29. Effects of Incremental Exercise on Blood Glucose

33. Liver glucose output from gluconeogenesis (GNG) and glycogenolysis (GLY) during prolonged exercise at 30% of VO 2max Effect of exercise intensity on liver glucose output

34. And now a contest: Why women live longer than men.

35. 6 th place

37. 5 th place

39. 4th place

41. 3rd place

43. 2nd place

45. And the winner is:

47. ...and now, a close runner up

49. EUROPEAN HUSBAND OF THE YEAR AWARDS

50. 3rd Place goes to : Greece

51. 2nd Place goes to : Serbia

52. and the winner of the husband of the year is: Ireland...........

53. Focus on Research

54. Scientific Process  What is truth? How is truth determined?  Scientific process –research question & hypothesis –experimental design –data analysis, interpretation, & conclusion –communication of results peer-reviewed paper presentation