Part 1.1 Flashcards
Original word for vitamins
Vital amines (used to think they all had amine groups)
Vitamins: identifiable function, when removed from the diet a deficiency disease presents
We know all the vitamins have been identified because parenteral nutrition can sustain someone for a long time
Who discovered the structure of B12?
X-ray crystallographer Dorothy Crowfoot Hodgkin in 1964 discovered the structure of B12 and insulin
after Lord Alexander Todd discovered it in 1957
SGLT2i in heart failure, chronic kidney disease and type II diabetes patients
Flozin is a SGLT2 inhibitor
Normally glucose spill over into urine only occurs above 10 mM [glucose], inhibiting SGLT2 in the kidneys reduces the amount of glucose being reabsorbed and increases spill over into urine
Definition of metabolic homeostasis
Metabolic condition that is the result of dynamic processes to maintain a constant internal environment despite changing external environment
Why is measuring plasma concentrations of metabolites a poor measure?
What is the plasma pool?
Flow and response is a better measure than plasma levels of a metabolite
Ex. In diabetes there is excess glucose in the plasma and cells expressing GLUT4 transporters and deficiency of glucose in cells that don’t express GLUT4 (AKA different concentrations depending on where you look) - different concentrations in different fluids
The pool is the collection of a metabolite in various plasma concentrations in different parts of the body
ex. interstitial fluid concentrations might be different from cerebral fluid concentrations
Glucose flow
Glucose comes from: diet, glycogenolysis and gluconeogenesis
flux/flow of [glucose] in blood to maintain 5 mM concentrations
Glucose goes to: glycolysis, TCA, lipogenesis, PPP, glycogenesis, AA synthesis, glycosylation of proteins
Clinical use of indirect calorimetry
As a tool to measure energy expenditure and give more specific nutritional recommendation and track which fuels are being used by the body
RER: VCO2/VO2
How to calculate the g of glucose in the blood?
If fasting glucose is 5mM
5mmol/L= .005 mol/L x 5 L of blood in the body x 180g/1 mol = 4.5g of glucose in the body homeostasis
1 cubic cm or ~4g (requires disposal mechanisms)
Flux of amino acids
AA come from: diet, proteolysis, and glucose
AA go to: protein synthesis, catabolism, neurotransmitters, adrenaline, melatonin, carnitine, creatinine, heme, histamine
AA pool is highly regulated
Catabolism modulates AA intake - excess will always be catabolized
All protein synthesized has a function
Review of DRIs (EAR and RDA)
Old and new recommendations
Usual intake
Dietary Reference Intake - refers to healthy individuals
EAR - estimated average requirement - covers 50% of the population’s needs
- Old EAR: .66g/kg/day
- New EAR: .8g/kg/day
RDA - recommended dietary allowance - EAR + 2 standard deviations or 97.5% of the population’s needs
- Old RDA: .8g/kg/day
- New RDA: 1.2g/kg/day based on flux analysis
Usual intake is 80-100g per day
Principles of protein metabolism
AAs are not saved, excess AA are catabolized
All proteins synthesized have a function
Each AA pool is regulated to achieve metabolic homeostasis
Nitrogen balance equation
Nitrogen excretion with 100g N intake
Nitrogen balance (AA are 99% source of N) =
N (intake) - N (fecal) - N (urinary) - N (misc)
Homeostasis is when nitrogen balance = 0
Positive N balance = growth
Negative N balance = loss/disease
Misc: skin, fingernails, hair, sweat ~ .5g N loss
100g N intake –> 5g feces, 95g urinary + CO2 + H2O
What contributes to and feeds off free AA pool?
Dietary, de novo synthesis and protein breakdown (300g) feed into free AA pool
Special products are made and protein is synthesized (300g)
Grams of protein per 1g of N?
16g of protein per 1g of N (protein is 16% by weight)
Protein turnover equation
Why do we need to continually consume protein?
Q (flux) = I (rate of intake) + B rate of breakdown/proteolysis) = S (synthesis) + O (oxidation/catabolism)
AA are recycled but no recycling is 100% so we need to consume protein to replace losses
