Metabolism in exercise

Question 1

Changes during exercise

Answer 1

• in skeletal m: O2 + fuel molecule consumption + production of lactic acid and alanine
• change in consumption -> change in redistribution of nutrients through entire body
• change in muscle waste production -> change in liver metabolism

Question 2

Metabolic balance in muscle during exercise

Answer 2

1. recruitment of different types of fibers
2. shifts in energy sources for contraction during exercise
3. shift in pathway of glucose metabolism

Question 3

Shifts in energy sources of contraction during exercise

Answer 3

• first seconds: ATP
• rest of 30 seconds: CREATINE PHOSPHATE
• rest of exercise: GLYCOGEN/FA + glucose
• takes >45min of jogging to deplete glycogen storage + start burn fat
• heavy exercise - O2 supply not enough - glucose used as fuel - glycogen depletion faster
• in starvation: liver synthesizes ketone bodies

Question 4

Glycogen phosphorylase activators

Answer 4

• increased Ca2+
• increased AMP
• increased NE/E - cAMP - PKA

Question 5

Shift in pathway of glucose metabolism

Answer 5

• start of exercise - metabolism anaerobic (takes time to adapt to O2 demand)
• first triggers of vasodilation:
  
  • Ca2+ - activate NO synthase
  • lactate/ alanine
  • red muscle switches to anaerobic glycolysis
  • increased blood supply removes lactate, alanine, CO2
  • after 30 min: adrenaline -> B2R -> vessels can’t dilate much more
  • lactic threshold: after which muscle produces more lactate than can be eliminated by liver

Question 6

Glucose transport into skeletal muscle

Answer 6

• dependent on GLUT1 and GLUT4
• GLUT1: insulin independent, always present
• GLUT4: insulin dependent, no insulin-less GLUT4s

Question 7

GLUT4 in exercise

Answer 7

• insulin not produced, yet many GLUT4s
• Ach stimulates muscle + Ca2+ increase - NO, AMP, aPKC- translocate GLUT4 from vesicle to membrane
• neurons secrete neuroregulin- translocation
• glycogen content: when high inhibits translocation
• trained persons: less GLUT4 on membrane, more in storage -> longer/ heavier exercise

Question 8

Insulin sensitivity

Answer 8

• after exercise-> rebuild glycogen storage -> sensitivity to insulin stays high for hours
• type1 DM: #GLUT4 same as in healthy
• type2 DM: #GLUT4 decreased by half
• exercise help reduce blood glucose -> insulin sensitivity elevated -> receptors less resistant

Question 9

Fatty acids

Answer 9

• used as fuel in low intensity training- bigger O2 need
• broken down fast after exercise
• during some hours after exercise: increased insulin sensitivity, HSL more active
• more FA release to blood, taken up by muscle, used for ATP
• after training- fat used up directly from food

Question 10

Interrelationship between working muscle and liver

Answer 10

• liver breaks down glycogen + synthesizes glucose -> secreted to blood -> taken up by brain, RBCs, muscle
• exercising muscle huge consumer of glucose, but also FAs

Question 11

Liver uses FAs for gluconeogenesis

Answer 11

• lactate + alaning produces in muscle by pyruvate -> secreted to bood -> picked up by liver -> use for gluconeogenesis -> glucose secreted to blood -> used by muscle
• in starvation: liver synthetizes ketone bodies from FAs -> secreted to blood -> muscle converts to FAs

Question 12

Fatigue

Answer 12

• in long lasting exercise usually due to glycogen depletion + lactate accumulation
• in short exercise due to depletion of creating-P + lactate accumulation
• mental retardation due to decreased blood glucose + increased tryptophan

Question 13

Tryptophan in exercise

Answer 13

• usually travels bound to albumin but now albumin occupied with FAs-> more free tryptophan
• tryptophan transported across blood-brain barrier with BCAA but in exercise BCAAs used as fuel leading to increased conc of free tryptophan and decreased BCAA tryptophan -> faster transport to brain
• tryptophan used to synthesize seratonin in brain - overproduction during exercise leads to tiredness and depression