Flashcards
1 - Methods in Skeletal Muscle Physiology: Investigating Fuel Metabolism in Humans
Cards in this deck (36)
- 1What factors affect fuel metabolism in humans? (5)Intensity
Duration
Gender
Nutrition
Training Status - 2Why is it important to understand fuel utilisation?If we can quantify it we can apply this to optimise nutritional strategies and training interventions to improve health and performance
- 3Name 4 ways we can measure substrate oxidationIndirect Calorimetry
Douglas Bags
Metabolic Cart
Respiratory Chamber - 4What does indirect calorimetry do?Provides a measure of whole body fuel metabolism
- 5What do Douglas bags do?Measure the concentration of O2 and Co2
Measure the volume of expired air
Calculates VO2 and VCO2 - 6What do metabolic carts do?Has a fast response real time O2 and CO2 analyser
Can view data on a minute by minute basis
Is the most up to date - 7What does a respiratory chamber do?Is a sealed room which can be used for a long time
Is the most accurate IC method. - 8State the respiratory quotient (RQ)Co2/O2
- 9What does the RQ represent?The O2 and CO2 exchange, representative of combustion processes occurring in oxidative tissue (eg. muscle)
- 10State the glucose RQ formula
- 11What does an RQ = 1 indicate?All oxidation has been CHO fuelled not fat fuelled.
- 12State the fatty acid RQ formula.
- 13What does an RQ of 0.7 indicate?All oxidation has been fueled by fatty acids not CHO
- 14When does the RQ become invalid?Over 85% VO2 max
- 15Why does the RQ become invalid?Hyperventilation leads to excess CO2 being produced which was not derived metabolically.
Lactic acid accumulation occurs during high intensity exercise leading to increased buffering with bicarbonate, this leads to CO2 being produced. - 16How do you calculate whole body CHO oxidation?CHO oxidation (g/min) =
(4.21 x VCO2) - (2.962 x VO2) - 17How do you calculate whole body fat oxidation?Fat oxidation (g/min) =
(1.695 x VO2) - (1.701 x VCO2) - 18Where is Carbohydrate stored and in what form?
- 19Where are fatty acids stored and in what form?
- 20Where is blood glycerol in what form?
- 21What is the advantage of measuring blood metabolite concentration?It is easy to repeat sample and measure
- 22What are the disadvantages of measuring blood metabolite concentrations?Doesn't give information about flux or what happens within the muscles.
Only gives you a baseline measure.
eg. provides a measure of glucose in blood plasma but not how much is utilised by the muscle. - 23What is anterio-venous blood sampling?It measures the net glucose balance across the leg.
Net balance = (arterial concentration - venous concentration) x blood flow - 24What are the advantages of anterio-venous blood sampling?Provides information about net uptake or release across an organ/tissue
- 25What are the disadvantages of anterio-venous blood sampling?It is very invasive - requires a probe inserted in the femoral artery and femoral vein
The probe can move - difficult to measure blood flow
AV differences are difficult to detect
Provides NO information about what happens IN the tissue. - 26Name the three needles that can be used to take a muscle biopsy?Bergstrom needle
Micro-biopsy (gun) needle
Conchotome needle - 27What is the biochemical process to analyse muscle substrates?1) Immerse the sample in an isotonic homogenisation buffer
2) Grind the tissue
3) Centrifuge the sample
4) Intact cells, nuclei, membrane fragments and mitochondria will sink, supernatant will float. - 28What information does biochemical analysis of a muscle sample provide? What does it not take into account?Substrate concentrations within skeletal muscle (mmol/kg muscle)
Muscle fibre type differences - 29What is the Immunohistochemical analysis of muscle protocol?1) Muscle Biopsy
2) Freeze Sample
3) Cryosection Muscle
4) Stain Muscle Sections - 30How does muscle staining work?Apply primary antibody at saturating concentrations
Wash off excess antibody
Apply fluorescently labelled secondary antibodies. - 31What is GLUT 4? Where is it found?A protein encoded in humans that is responsible for transporting glucose.
Adipose tissue & striated muscle - 32During exercise what happens to GLUT 4?It moves towards the cell membrane to allow glucose into the muscle
- 33What does electron microscopy allow us to do?Consider the use of substrates from difference sub-cellular locations
- 34Where is glycogen stored?Distinct sub-cellular pods which are fibre type dependent.
Subsarcollemal 5-15%
Intramyofibrillar 5-15%
Intermyofibrillar 75% - 35What is the advantage of analysing muscle biopsies?Provides information about substrate/protein concentrations within skeletal muscle
- 36What are the disadvantages of analysing muscle biopsies?1) It is invasive
2) Only gives information about concentrations (snapshot in time)
3) Changes over time require repeated sampling
4) Only analyses a limited number of fibres.