My cards Flashcards
Is glycation an enzyme-dependent process?
no, it’s a non-enzymatic process
Name non-enzymatic processes?
- Glycation
- conversion of creatine and creatine-p to creatinine for excretion
CHO-digesting enzymes in the SI
o Pancreatic amylase, glucoamylase
CHO-digesting enzymes on the brush-border of SI
o Sucrase‐isomaltase
o Lactase
What does histamine release in lactose intolerance lead to?
SWELLING of bronchi-> anaphylaxis
Gene that codes for GLUT1-5
SLC2A1-5
- Is glucose an energy demanding process?
Not directly, but Na/K ATPase does require ATP to set up the gradient
Galactose is preferentially converted to __; fructose is preferentially converted into __ and __
Galactose is preferentially converted to glycogen; fructose is preferentially converted into FA and TG
Normoglycemic range
between 4 and 6 mmol/L
What can pyruvate can be converted into/used for?
o lactate; o Acetyl-CoA for TCA; o amino acid synthesis o fatty acid synthesis o glycogen- via Acetyl-CoA in glycogenesis
What is the role of glucose-6-phosphatase
converts glucose-6-phosphate into glucose which allows it to be transported out of the cell
Possible fates of glucose 6-phosphate
- Go through glycolysis
o metabolic pathway that converts glucose C₆H₁₂O₆, into pyruvate - Be made into glycogen: phosphate group has to be moved from 6 to 1 Carbon by phosphoglucomutase
o It then has to be activated with UTP and incorporated into glycogen
What does Coenzyme A synthesis require?
Coenzyme A biosynthesis requires cysteine, pantothenate (vitamin B5), and adenosine triphosphate (ATP)
Can acetyl-CoA be converted into glucose?
no
When does gluconeogenesis begin?
4h after the meal
How do levels of FA in the circulation change? Levels of 3-hydroxybutyrate?
FA- steady after rapid increase in the first few days
3-HB- Rapidly increasing until day 20, then slower increase rate
Estimated BMR of males and females
o males: 1.0 kcal/kg/h ~~ 1700 kcal/d
o females: 0.9 kcal/kg/h ~~ 1200 kcal/d
o The longer the fast, the closer the RQ to __
o The longer the fast, the closer the RQ to 0.7
Does insulin have long or short half-life
short
Measure of insulin production
measure c-peptide levels in urine in 24h
Role of Carboxypeptidase E
• In vesicles there’s carboxypeptidase E which cleaves the c-peptide-> mature insulin, stored in the vesicle
Where is insulin stored? In which form
in vesicles in beta-cell
- Insulin is stored as a hexamer- 6 insulin molecules together- most stable form
Who discovered insulin?
Charles Best, Frederick Bantign have discovered insulin
Anaphylactic shock is a reaction to a __
Anaphylactic shock is a reaction to a protein
Which diabetes type has C-peptide present
T2 only
Urinlaysis tets
- Glucosuria/Ketonuria – urinalysis
* Dipstick with markers that change colour depending on glucose concentration
• Fasting plasma glucose concentration test values
7.0 mmol/L is suggestive of diabetes
normal 5 mmol/L
RBC lifespan
120 days
What is gliovascular disease
- Damage to small blood vessels
What is Macrovascular disease?
Some damage to larger arteries, but it is very minor. More caused by T2DM
T2DM prevalence: men vs women
More prevalent in men
Hyperglycemic Hyperosmolar Nonketotic Syndrome
What is it? T2 vs T1DM
Hyperosmolar Hyperglycemic Nonketotic Syndrome (HHNK), s a dangerous condition resulting from very high blood glucose levels. HHNS can affect both types of diabetics, yet it usually occurs amongst people with type 2 diabetes
• More prevalent I Elderly
• Affects the brain lethargy, sleepiness
• Importance of adequate water intake
Possible mechanism of decreased insulin sensitivity in T2Dm
- Insulin receptor substrate 1 (IRS1) is a major signaling protein after insulin receptor
o In diabetes it becomes less effective in translating the signal caused by insulin binding
o The decreased effectiveness is caused by activation of cell’s coping mechanisms due to increased stress which starts in the cytoplasm and translates into ER
Increased stress is caused by increased obesity, excess fatty acids etc
o ER sends signals to IRS1 and inactivate it and prevents it from being activated by insulin - IRS1 is activated less efficiently by insulin -> less LGUT4 is released form vesicle
- Less GLUT4-> lower glucose absorption (but not cut off)
- This means that all the other anabolic response of the cells is decreased: less protein synthesis, less cell division
__ and __ is specific for T2
Atherosclerosis and increased VLDL is specific for T2
Microvascular diseases are related to increased levels of __
Microvascular diseases are related to increased levels of hexokinase (converts glucose to glucose-6-phosphate which cannot cross the membrane
Metformin effects
o Increases peripheral insulin sensitivity – increases removal
o Increases GLUT4 mediated glucose uptake- increases the output
o Increases fatty acid oxidation- increases the output
Metformin- principle of action
- Increases phosphorylation of AMPK which is a master regulation. That results in increase in
o Increase in GLUT4 and glucose intake
o Decreases SREBP1
-> Decreases hepatic fatty acid synthesis, VLDL synthesis-> decreases atherosclerosis; decreases fat all together, decreases TGs-> decreases fatty liver
-> Increases FA oxidation
o Decreases gluconeogenesis in the liver
o This results in decreased blood glucose and decreased plasma TGs
Sulfonylureas- mode of action
Target beta cells to increase insulin production and release (close K+ channels in beta cells)- assists b-cells to be more effective at releasing insulin
Close K channel, resultign in cell depolarization and opening of Ca2+ channels
What does opening of Ca2+ channels result in?
Ca2+ activates insulin gene expression via CREBP (Calcium Responsive Element Binding Protein)-> making more insulin
Ca2+ also causes exocytosis of stored insulin to the cell membrane
Are Sulfonylureas effective in all diabetic patients?
No, as their action is dependent upon the presence of functioning Beta cells, therefore, sulfonylureas do not work in people with type 1 diabetes.
What are incretins?
- Incretins are a group of endogenously made hormones that lower blood glucose by increasing or potentiating insulin and its effects
o A lot of them come from the gut
Gut hormones – GLP1 – (glucagon‐like peptide 1)
GIP (gastric inhibitory peptide)
Both increase insulin and decrease glucagon release- there are always both of them in circulation at any 1 time
Stimulate glucose uptake
How are incretins inactivated? What are the consequences?
Are inactivated by the enzyme DPP‐4 (diphenylpeptidease 4)
• Thus incretins have short half-life-> analogue drugs were created
What are incretin drugs? + and -
: exogenous analogues of GLP1 and GIP an inhibitors of DPP-4- 3 different drugs
o Expensive
o Proteins-> have to injected
o All 3 can be used at the same time
Catabolic response to surgery
- Surgery causes inflammatory response due to pro-inflammatory cytokines being released
o They promote protein breakdown and cause insulin resistance
o Result in decreased appetite and food intake
o Decreased GI function
o Decreased blood flow
Neuroendocrine response aka hypothalamic- pituitary axis
o Pain signals go into the brain causing release of cortisol stress hormones
o Causes release of glucagon
o They cause insulin resistance and counteract the effects of insulin
o That results in hyperglycemia and increases complication and causes breakdown of protein
Why shouldn’t we administer glucose via vein to patients?
If we feed glucose via a vein-> no secretion of incretins as they are gut hormones -> less insulin secretion for a given amount of glucose and a higher glucose level
at any time we have _g of plasma glucose
at any time we have 4g of plasma glucose
How to calculate NB?
Nitrogen Balance = N Intake – fecal N – urinary N (– misc losses)
How much protein is absorbed from the diet?
95%
How much of ingested protein is excreted in urine and in feces?
o 5% is excreted in feces
o 95% excreted in urine
- calculations take into account that protein is __% nitrogen
- calculations take into account that protein is 16% nitrogen
- Someone sick will have __ nitrogen balance
- Someone sick will have negative nitrogen balance
What does AA inflow include
inflow = input = Intake + Protein breakdown + De novo synthesis
What does AA outflow include
synthesis (AA incorporated into protein) + catabolism
__ = __ in people in nitrogen balance
- Rate of protein synthesis = rate of protein breakdown in people in nitrogen balance
How large is AA pool
300g
Why do we still need to consume AA if we recylce them?
no recycling program is perfect, there is a certain amount of obligatory losses, AAs that need to be metabolized for other functions (hormones, NTs)
- to keep cycle going need about about .8/ kg (0.6 is an average)
Can NB bes used to differentiate protein synthesis rates?
no
In what situation would increased protein intake stimulate protein syntheisis?
Only when we were initially under consuming protein
If we were consuming enough, increased intake wouldn’t drive protein synthesis
Steps of AA breakdown
remove amino group, transfer amino group ultimately to urea
o Carbon skeleton will remain, that will go to CO2 when oxidized
WHat is the period required to carry out NB test?
- NB takes 3 days to do and a person has to be on a diet for extra 7 days before the collection
On the graph, do we aim for NB of )
No, we aim for 5, due to misc losses and Curvilinear response as balance approaches zero
Precursor for cysteine
methionine
What is the flow equal to in terms of tracer
Flow = tracer infusion rate (rate of adding the dye) / tracer conc in pool (color of the water)
Name safe tracers
Carbon13
- Deuterium (H2)
- Nitrogen15
amino group is added to a _ acid and make a new amino acid- this process is impossible for__
amino group is added to a keto acid and make a new amino acid- this process is impossible for lysine, threonine and tryptophan
Nitrogen VS CO2 pool adaptations
o N: 7‐10 days for urea pool
o CO2: hours to a couple of days
How many C does phenylalanine have? WHat was Phe’s final mass after labellign with C13
9 carbons
m+9
What was noticed about labelled Phe? What was the conclusion?
What was noticed was there are no phenylalanine that contain 1-8 13C, there is only two types present, either no 13C containing phenylalanine amino acids or phenylalanine only containing 13C atoms from algae.
So, this clearly shows that there is no synthesis at all of phenylalanine in the body and it purely comes from the diet.
• Therefore, the conclusion that was made was that phenylalanine must be an essential amino acid in a normal healthy chicken.
What was concluded from the distribution of labeled Phe in tissues?
o Different tissues have different amounts of the algae phenylalanine in their proteins, where the liver has the highest amount and muscle has the lowest amount.
This means that since there were more algae phenylalanine in the proteins of the liver after 28 days, protein synthesis is the fastest in the liver and a lot faster than in muscles.
– visceral organs have rapid metabolism and rapid turnover of proteins.
What is GLX?
glutamine + glutamate
What is the glutamate used for the synthesis of?
o Glutamate is also required for the synthesis of Arginine/Citrulline and GSH
Mass of glutamate + C13?
M+5
Limitations of using growth as a marker of AA requirement
o Limited usefulness-> This method is good for measuring growth in agricultural animals or children, but not relevant to adults
o Gain of weight in not due to growth
Direct vs indirect oxidation: choice of test AA and AA label
Direct: test and label AA are the same, but the choice is limited; Only branched chain (isoleucine, leucine and valine) ,LYS, PHE can be tested
Indirect: any AA can be tested; PHE, LYS, LEU indicator AAs
Direct vs indirect oxidation: effect on AA pool
Direct: Free pool changes with changing test AA intake
Indirect: Tracer AA pool not perturbed with changing test AA intake
Low intake investigation: Direct vs indirect oxidation
Direct: can’t study very low intakes
Indirect: can study zero intake
Minimally invasive IAAO model
Tracer Administration
• Repeated oral “nibbling” of tracer solution after 4‐h feeding equilibration
Sampling
• Breath collection for CO2 enrichment
• Urine in place of blood for plasma AA enrichment
• Problem: D‐AA are efficiently excreted in the urine
• D and L AA can be differentiated by GCMS using a “chiral column”
Alternative way of AA pool testing via blood sample
Urine sample
__ mg of essential AA/g protein
285 mg of essential AA/g protein
Potentially limiting AAs-
Lys, Tyr, Thr, M+C
What was the effect of histidine absence on NB? Conclusion?
No effect on nitrogen balance (thus histidine is non-essential)- didn’t trigger breakdown of other AA
What were the changes that occurred during histamine lacking diet?
Hematocrit went down substantially -> less RBC on circulation-> less oxygen delivery to tissues
Increased ferritin
Decreased Hb, albumin and transferrin
What are the 2 stages of adaptations?
short (no change in function) and longer and more severe (adaptation occurs due to compromised function)
Phe problem in infants
(cannot metabolize phenylalanine-> produce phenyl ketones in the urine and cannot produce tyrosine
Protein aim in ICU
2-2.5g/kg
Which vein is used in parenteral nutrition?
central line- vein that goes directly into the heart
WHat are the contents of 2 bags used in parenteral nutrition?
One bag contains fats
- Emulsify TGs in a water based solution-> add lecithin (a phospholipid)
The other bag contains water soluble nutrient- glucose, aa, vitamins and minerals
Concerns wiht a bag that contains water-soluble vitamins and nutrients?
- We need them to be stable
• many of vitamins get destroyed by light and solutions are put in transparent plastic bags
Which AA is not water soluble?
tyrosine
Which AA is not water-stable?
• cysteine will oxidize and that product s not soluble.
What are possible downsides of supplying high doses of AA?
. Someone who is critically ill, do not want metabolic burden of all excess AA on the liver and urea production that couldn’t be made into proteins.
Is growth supproted by vaminolact?
no
Is phe+ vaminolact a suitable approach?
- That resulted in increased in nitrogen retention and growth
- This supported that it was Phe that limited the growth in Vaminolact, however this produces really high concentration of Phe in the blood-> not great-> not advised to do in babies
Is n-acetyl-tyosine+ vaminolact a suitable approach?
It runs out that N-acetyl tyrosine is converted to tyrosine in adults and rat models, but not in human babies
Babies don’t have the enzyme to take the N group off-> NAT gets simply excreted
What was an effective approach of delivering sufficient tyrosine to babies?
Glycyl-tyrosine- a dipeptide is an effective way
- _% of protein made in gut mucosa is newly made everyday
- 75% of protein made in gut mucosa is newly made everyday
Is the breakpoint for protein higher in elderly?
Higher that current EAR, but the same as in adults
• In infants, we look at __ to analyze protein deficiency
• In infants, we look at growth to analyze protein deficiency
Pepsin- role and function
- Pepsin in stomach – activated by acid pH
* Cleaves peptide bonds
Role and specifics of proteases
- Proteases from pancreas in small intestine – luminal digestion
- Trypsin, chymotrypsin
- There are many different types of them due to different R groups
- Digestion is done in the lumen
What is the location and role of peptidases?
- Peptidases on brush border of intestinal epithelial cells
* Final cleavage of dipeptides
How do AA get into enterocytes?
• Active transporters transport AA across endothelial membrane
Amount of protein needed to max out in the protein synthesis rate?
max is 30g/meal
Liver vs muscles BW BMR % of Body's Protein synthesis % newly made protein
Liver
- 3% BW
- 21% BMR
- 30% body’s protein synthesis
- 50% of proteins newly synthesized each day- small pool of AA, but the process is very rapid
Muscle
- 40% BW
- 21% BMR
- 30% body’s protein synthesis
- 3% of proteins newly synthesized each day – pool of aa is big, it’s slow
What are the 2 type of insulin clamp studies
1) Hyperglycemic clamp- infusing rate of glucose to keep blood glucose level at 11mmol/dL is indicative of how fast beta-cells respond to insulin-> measures insulin secretion capacity
2) Hyperinsulinemic clamp (euglycemic clamp)- High insulin dose is given; plasma glucose is maintained at a constant lecel. When steady state is achieved, the rate of glucose infusion is the rate of glucose uptake by the tissues-> tests how sensitive the tissues are to insulin
Describe AA infusion
o To maintain euAAemia or hyperAAemia
o Insulin increase protein synthesis and increases AA transport into cells and decreases protein breakdown – anabolic functions
o When insulin clamp study is done and you just clamp glucose, plasma AA go down as protein breakdown is decreased and there are no AA coming from the diet-> no AA to accommodate form increased AA synthesis
o Thus we need to clamp AA-> infuse AA at a rate to stimulate short term fasting (euAAnemia) or at a rate to stimulate what it’s like after a meal (hyperAAemia)
o This would allow to measure AA synthesis and breakdown
o This will allow to measure the effect of insulin on AA synthesis and breakdown
_- is always number 1 priority, no matter the nutrition status
Immune response is always number 1 priority, no matter the nutrition status
Components of body protein synthesis
50% visceral
30% muscle
10% plasma proteins
10% blood cells
Synthesis of dispensable AA accounts for _% of basal metabolic rate
Synthesis of dispensable AA accounts for 8% of basal metabolic rate
What are the parts that are similar between cysteine and methionine
For cysteine – only the S is from methionine. Only the S is transferred to cysteine
What is arginine used to produce?
Polyamines
Nitric oxide
Proteins
Also participates in ammonia detoxification
What are the precursors of arginine? Locations?
Glutamate and proline in the intestine are converted into citrulline
Citrulline is then transported to kidney to make arginine
Which demographic requires high levels of arginine?
Infants and patients with stress
Arginine absence in diet: adults vs babies
- Eliminate arginine from adult’s diet-> nothing will happen as we can make it
- Eliminate it from the diet of babies (pigs) -> tremor, vomiting, neuromuscular effect=> cannot make it
Where is serine made? What is it made of?
- Serine is made in the liver from 3 carbon intermediates of glycolysis
Is cysteine or methionine essential?
only methionine
How is methionine made
1) Methyl (CH3) group is removed from methionine, which gives us homocysteine
2) Serine (comes from glucose) is added to homocysteine and the methionine part that is after the Sulfur is cleaved off by alpha-ketobutyrate, such that sulfur is the only part that is left untouched from methionine -> Cysteine is formed
What are non-protein products that cysteine can be converted into?
glutathione, taurine
What kind of AA is taurine? What are it’s roles
Taurine is a beta AA
- Contains sulphur group form methionine
- Involved in development of retina in pre-mature babies, essential for muscle metabolism
- No T-RNA for taurine-> doesn’t get converted into protein
What is the difference between methionine and homocysteine
Homocysteine is methionine without the CH3 (methyl) group
Is there a net synthesis of methionine?
- There’s not NET synthesis of methionine, but it can get made in human bodies
Why is homocysteine bad?
- Homocysteine is a powerful pro-oxidant-> can damage arteries
What are the 2 pathways of getting rid off of homocysteine?
it should transfer sulfur atom to get transformed into cysteine or should be re-methylated back to methionine
What are the micronutrients essential for removal of homocysteine?
o Transfer of amino group-> B6 (pyridoxine) (needed to convert HCY to CYS)
o Transfer of methyl group-> folate and B12 (needed to convert HCY to MET)
What are the causes of high levels of homocysteine?
o High levels of homocysteine have nothing to do with protein intake, but it has to do with co-enzymes (vitamins)
What is required for the transfer of amino groupd
B6 pyrodoxine
What is required for the transfer of methyl group
folate and b12
What organ is important in the regulation of homocysteine levels?
Liver- it is the site of HCY/Met cycle
Problems with Cys in IVF?
Intravenous feeding – cysteine is oxidized in solution to Cystaine (Cys-Cys)-> precipitates in the solution and cannot be infused
Glutathione is a __peptide
Glutathione is a tripeptide
What is the role of glutathione?
Predominant intracellular redox agent. Affects redox status of the cell
What is the makeup of GSH?
- γ‐glutamyl‐cysteinyl‐glycine
What is special about bonding in glutathione?
- γ‐glutamyl‐cysteinyl‐glycine- unusual peptide bond, glutamate R group has a carboxylic acid, so instead of the regular carboxylic acid group, the peptide bond is with the carboxylic acid on the R group called gamma carbon, unusual bond not hydrolyzed the same way-> requires special enzymes
What is the role of GSH?
reduce oxidative stress by conjugating electrophyles
Provides NADH
- immune system function- creates free radicles to kill invading organisms
Tylenol and GSH
Tylenol Conjugates with GSH to create an intermediate that will get excreted
o Excess of Tylenol -> toxic as glutathione gets used up-> no GSH to fix redox status
How to replenish GSH deficeincy?
o N-acetyl cysteine is more stable and can be given as the drug to fix γ‐glutamyl‐cysteinyl‐glycine deficiency
o By putting an acetyl group on nitrogen, we make it more stable and can give it as a drug to conjugate excess of Tylenol and save GSH to save the health of the liver
Glutathione depletion and nutritional status
- Affected by nutritional status-> Decreased in fasting-> Cells are more susceptive to oxidative stress
- Its rate of synthesis is compromised during malnutrition
- Its synthesis will increase in states of inflammation, infection, burns
o Thus, any events that affects nutritional status will affect GSH synthesis and will in particular affect liver health
Creatine-phosphate production pathway
1) In kidney, arginine donates an amino group to glycine to form guanidinoacetic acid
2) Guanidinoacetic acid is then transported to the liver, where it is methylated (CH3 comes from methionine-homocysteine conversion) to form creatine
3) Creatine is transported into muscles, where Pi is added to it, usign ATP, creating phosphocreatine
How is creatine and phosphocreatine excreted?
Both get non-enzymatically converted into creatinine to be excreted in urine
__ can be used as an indicator of muscle mass
Creatinine can be used as an indicator of muscle mass
Can GSH supplements be consumed
- Eat a GSH pill-> it is a tri-peptide-> will get broken down
Can creatine supplements be taken?
- Creatine supplements can be taken-> creatine pool will be increased in the muscle-
What is the effect of creatine supplements?
• Probably power, but not endurance
- In endurance, oxygen is the limiting factor
- Myoglobin pool is the factor that need to be looked at in endurance
• May be useful in upregulating myosin synthesis
• Increased lean body mass: water, osmoregulation
• Genes in muscle upregulating myosin, cytoskeleton, protein and glycogen synthesis
What is successful adaptation?
Successful adaptation- reaching homeostasis and no longer losing weight
What are the factors that contribute to reduced energy expenditure in starvation
Reduced resting energy expenditure
- Reduced mass of metabolically active tissue (slow, weeks)
- Reduced energy expenditure per unit active tissue (fast, days) – occurred right from the begging in
- Reduced heart rate, muscle tone, less RBC
- Lower body temperature
- Less muscle and tissue to transport-> less energy is needed for activity
• Reduced non-resting energy expenditure
- reduced work of moving
- reduction of voluntary movements
Why is there a reduced protein requirement in starvation?
• Diminished lean tissue mass
• More efficient retention of dietary protein
- NB balance will be really negative, then it will be becoming less and less negative. At the end it will be 0
• Lean tissue mass stabilizes despite continued low protein intake
What is successful adaptation to starvation mostly due to?
o Mostly due to reduced muscle mass, but some is due to decreased number of tissue cells
What is the cost of successful adaptation to starvation mostly due to?
o Lean tissue loss
o Fatigue and inactivity
o Immunodeficiency
o Reduced tolerance to stress
Physiological vs pathological stavation?
physiological - consequence of chronic insufficient food intake
- Pathological starvation is a disease
When would unsuccessful adaptation occur?
when starvation is too severe
B1 deficiency associated conditions
Beri Beri edema, heart disfunction
