BIOD43H3 Lecture Notes - Lecture 18: Monosaccharide, Lipid Peroxidation, Blood Sugar
Lecture 18: Variation in Aerobic Capacity and Fuel Use part 2
Mammalian model of fuel use during exercise:
• Did experiments where they flux substrate into blood of these animals and looked at
ho uikl the disappea, ho uik the’e eig used muscles
• Found this general pattern
o Oxidation rate µmol O2/kg/min analogous to mass specific O2 consumption rate
o Total value the dog can get to at 85%-100% exercise intensity is much greater
than goat
• Then they broke down where that energy is coming from, what substrates are oxidized
at each intensity
o Start at moderate intensity, dogs going at 40% max
o Note that circulatory glucose at low exercise intensity is minority, minority player
for O2 consumption
o Muscle glycogen is even more a minority player
o At low exercise intensity,
most of oxidation is from
lipids
o Same pattern seen in goat,
with some contribution of
circulatory glucose
• As we increase exercise intensity,
contribution of circulatory glucose
does’t hage at all → stas the
same
o Proportion of metabolism
accounted for by lipids
decreases, absolute total
ate of lipid oidatio deeases a little ut it’s a peetage of total aout of
fuel that’s eig oidized (-20% rather than ~60-70%)
o Same pattern seen in goat: no big changes in circulatory glucose oxidation rates,
delie i asolute ate of lipid oidatio → delie i popotio otiutio to
total energy turnover
o Intramuscular glycogen make difference
• Aials ae uig a itue of fuels → soe fat soe as → depeds o hat
proportions are
• Intramuscular fuels dominate at high intensity (mostly intramuscular lipids)
o Rel o this eause iulato sste a’t suppl iulatig gluose/lipids at
a fast-enough rate to meet high turnover demands
• Evolutionary conserved phenomenon, we all show similar patterns of fuel use
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The Crossover Coept:
• Percent of O2 consumption due to oxidation of lipids as
function of percent of VO2max → exercise intensity
o The harder you exercise, the less important lipids
are to explain total energy turnover
o Going from sedentary to increasing levels of
physical activity
• Carbohydrates show opposite pattern
o Increase in exercise intensity, importance of
carbohydrates as fuel goes up and up such that
when going flat out, most important fuel being
used is intramuscular glycogen
• Symbols represent different species
• Highly conserved phenomena known as crossover concept
o Thee’s a poit hee elatie otiutio of aohdates switches, from
being mostly lipid to being mostly carbohydrates
Fuel use during migration:
• Dogs have comparatively large stores of intramuscular glycogen in locomotor muscles,
eause the’e usig it up at faste ate
o They should also have greater fuel reserve
• Crossover concept might not apply to birds, because of importance of intramuscular
glycogen which is energy sparse compared to lipid
• Birds have to generate lift to offset/support weight
o Red knot has long migratory journey
o Energy density for wet mass is way lower in glycogen than it is for lipids
o Can also talk about amount of water produced per g H2O per g wet tissue →
better in lipids
Enhanced fat usage during migration:
• Birds should be fat-burning specialists, even at high exercise intensity
o Look at fatty-acid binding protein or beta oxidation enzyme, we find that in
migrants these things are increased
o In red knots, during migration they are enhancing lipid oxidation capabilities
o Conclude that they are fat oxidation specialists
Protein usage in migrating salmon:
• Fo salo’s pespetie, suial past laig eggs ot goal
• What are they burning in one-way journey → look at percent activity and percent
protein concentration compared to distance travelled through different stops in BC
• Burning of protein, fish metabolizing lean muscle mass to sustain long journey → birds
do that to some extent as well
find more resources at oneclass.com
find more resources at oneclass.com
