Nutrition Lecture Week 7 - Advanced Exercise Physiology, Metabolism and Inflammation Flashcards
Cellular uptake of plasma CHO does not limit oxidation …
the major limiting step in oxidising ingestion CHO appears to be the transport across the intestinal mucosa
Role of insulin in glucose disposal …
Insulin stimulates a cascade of protein activity (phosphorylation) which causes GLUT-4 transport proteins to translocate to the plasma membrane
Muscle contraction can directly mediate cellular glucose disposal …
- AMPK mediated
- when both beta1 and beta2 subunits were genetically deleted, glucose uptake was reduced
- PGC-1aplha activity was incereased in the beta1/beta2 knockout
- Ca** mediated
- tetanic calcium (Ca**) release (muscle contraction) also activates AMPK
- Action of Ca2+/calmodulin dependant protein kinase
AMPK activity is reduced in AMPKalpha2 inactive mice when …
CaMKK is activated
Trained athletes use increased fat at same %VO2max …
at lower exercise intensity, fat oxidation increased further
Intramuscular triacylglycerol (IMTG) utilisation is …
fibre type dependant
- depletion of IMTG >60% in type 1 fibres
Increase in acetyl carnitine may inhibit CPT1 and down regulate FA entry into the mitochondria …
- Free carnitine reduced as increased actyl groups from acetyl CoA during high intensity exercise binds to carnitine, inhibiting CPT1
- free carnitine + acyl = acetylcarnitine = LCFA entry
- lower free carnitine = low carnitine = lower CPT 1 activitiy
=Effect of exercise intensity
Elevated plasma FA impairs…
impairs insulin signalling and intramuscular triacylglycerol oxidation
- inhibits the insulin cascade for GLUT4 translocation - IRS1, Akt, AS160 inactivation
- the metabolites PKC Ceramides and Fatty Acyl CoA impair the activation of insulin signalling intermediates
Why do people with obesity liberate IMTG at a lower rate …
-- Insulin resistant = ↓ adipose tissue FFA release -- Therefore ↑ lpl activity and FFA cellular availability -- Greater FA oxidation by products → direct inhibition IMTG liberation (adipose triglyceride lipase; agtl) -- Exacerbated by inactivity as IMTG turnover is reduced & FFA entry ↑ for energy storage (↑ FAT/CD36
Why do trained athletes have more IMTG ?
- Due to regular depletion and enzymatic up regulation
- CPT1 activity ↑
• ↑ type 1 fibre expression
with training
Niacin (vit b3)/ acipimox suppresses …
adipose tissue lipolysis
Acipimox increases IMTG utilisation during exercise and is associated with …
improved insulin sensitivity
Explain why Pdk 4 inhibitor reduces acetylcarnitine ?
• PDK 4: an enzyme responsible for converting pyruvate to acetyl-CoA • Remember ↑ acetylcarnitine inhibits CPT1 (and FA entry into mitochondria • It stands if we ↓ acetylcarnitine we can upregulate fat oxidation (and liberate IMTG) • Can this be achieved by dietary manipulation? • Increase fat oxidation and insulin sensitivity
Can diet/exercise increase fat oxidation ?
• ↓reliance on CHO • ↑ fat oxidation • ↑ circulatory ketone bodies • ↑ ketone oxidation? • Can fat provide enough energy to sustain higher intensity (% VO2max)? • What about performance?
Inflammation is …
The first physiological response to harmful stimuli which is required for the healing of injured
tissue
