Malnutrition and cachexia Flashcards
The pathway of cysteine synthesis
The only part that goes from methionine to cysteine is sulphur group, carbons are totally different
serine gives the carbon skeleton
At first, from methionine we take off the methyl group
then, we add serine, resulting in homocysteine
Serine comes from glucose
Then cysteine can be converted to taurine
Cysteine can be converted to what ( apart beign utilized for protein synthesis)
Can be converted to glutathione, tripeptide, taurine
Functions of taurine
Beta- amino acid
Essential AA for cats
Involved in the development of retina for premature babies
Invovled in muscle metabolism
Not in DNA
Draw the cycle for cysteine synthesis
Critical control point here
Homocysteine- powerful prooxidant
Because the moment it is produced it should be converted back to methionine or converted to cysteine
If higher than very low, can cause oxidative stress
What compound is homocysteine
Technically an AAs , but it is not used in the protein
Enzyme involved in AA metabolism and thus in methione-cysteine circle is
B6-pyrodoxine
Enzymes invovled in transferring methyl groups
Folate and B12
If there is high homocysteine, does it mean that we have problems with high protein intake, because it is their intermediate?
No, problem is in coenzymes
Regulation of methione-cysteine pathway happens in
The liver
If you have not healthy liver-> no breaking down of methionine-> no synthesis of taurine and cysteine
When cysteine can be a conditional essential AAs
Premature infants ( not enough enzymes)
ill liver
Composition of glutathione
gamma-glutamate-cysteine-glycine
What happens with cysteine in solution
It is oxidized to cystine, which is 2 cysteine molecules together and it precipitates
Role of glutathione
Important intracellular redox agent
A substrate for another enzyme that conjugates with electrophiles (toxins, xenobiotics, drugs) and removal of reactive oxygen species
Protection of protein, lipid membranes and DNA (glutathione provides NADH)
Important for immune system function
Another name for tylenol and its metabolisma nd why you should be careful with dosage
acetaminophen or paracetomol
Painkiller and fever reducer
It is conjugated with glutathione to create an intermediate that can be excreted
If too much taken, potentially toxic to the liver, because uses all of glutathione, so no redox status control of liver cells
what drug is given in the case of paracetomol overdose
N-acetylcysteine-> by putting nitrogen cysteine becomes more stable and can be given in liquid form as a drug, so glutathione is saved for redox status
When glutathione status is decreased
During short term and long term fasting
Protein deficiency ->lower synthesis rate
Higher consumption is increased in inflamamtion/infection (burns, AIDS)
How creatine can be an exampel of inter organ colloboration for metabolism
In liver SAM to SAH, so methyl groups is added (can be conjugated with methione to cysteine pathway, because they have this step)
Synthesis of creatinine occurs how
Non-enzymatically from creatine and phosphocreatine
Creatinine levels in urine can be roughly estimated as
As an indicator of muscle mass
Should you consider taking glutathione and creatine
Glutathione-tripeptide-> will not survive in HCl
Increasing creatine pool is probably for power but not for endurance (here you are more limited in oxygen-myoglobin pool)
Increased creatine in muscles-> hydrophilic-> attraction of water-> increased lean body mass, but does not increase power
Can be useful for upregulating myosin synthesis, cytoskeleton, protein and glycogen-> so may be a little anabolic
But a reasonable ergogenic aid for atheletics
What is starvation
The physiological condition created in the body as a consequence of chronic insufficient food intake
2 types of starvation
Can be physiological (coordianted adaptation to reduce nutrient supply-> goal is to prolonging survival)
and pathological (metabolic scenario, where two many compromised functions has occured and now it is a pathology-> disease) will lead to protein-energy malnutrition
The most common aspect of starvation
Protein-energy malnutrition
What was diet of study for starvation
1500 kcal
50 g protein per day (close to RDA, but RDA for adequet energy intake), but if not enough kcal, some AAs are going to be used for energy
for 6 months
Due to what loss the adaptation to starvation occured
loss of a lot of fat (in the end only 1%), lean tissue mass, increased extracellular fluid mass ( because changes in protein metabolism and regulation of water)
Rate of weight change in the end was zero (no fat and muscle less in the end)
What is successul adaptation to starvation
No loss of body substance despite continued food deprivation
Stable body composition must mean cessation of fat loss and cessation of lean tissue loss
What happened to metabolism to reduce the energy expenditure
Reduced resting energy expenditure (reduced mass of metabolically active tissue (basal metabolic rate), reduced energy expenditure per unit active tissue (per kilo of muscle mass), reduced heart rate and muscle tone
Reduced non-resting energy expenditure (reduced work of moving and reduction of voluntary movements)
Why there is a reduced of protein requirement in starvation and what is nitrogen balance
Diminished lean tissue mass
More efficient retention of dietary protein
Lean tissue mass stabalizes despite continued low protein intake
Nitrogen balance at first is going to be negative and then after 6 month it is going to be zero
Benefit and cost of successful adaptation
Benefit: survival
Cost: lean tissue loss, fatigue and inactivity, immunodeficiency, reduced tolerance to stress
Clinical features of PEM
Reduced body weight
Muscle wasting and decreased strength
Reduced respiratory and cardiac muscular capacity
Skin thinning
Decreased metabolic rate
Hypothermia
Apathy
Edema
Immunodeficiency
Draw the scheme how the body is going to adapt to decreased protein and energy intake and how it can be successful and how it can fail
Hypoalbunemia- problems with electrolyte and fluid balance
What is unsuccessful adaptation to malnutrition
Add micronutrient deficient (iron, B1)
Stress (trauma,cancer, inflammation/infection)
And all adaptations before become catastrophic
What happens with resting metabolic rate with starvation and different diseases
what happens with nitrogen excretion starvation vs injury
the 6 causes of muscle atrophy
- Cachexia-cancer, systemic inflammation
- Hormone excess or deficiency
- Old age-sarcopenia
- Protein-energy malnutrition-starvation
- Inactivity-disuse atrophy
- Neuromuscular disease
What can we learn from famine in netherlands
Epigenetics of everyone was affected
But especially pregnant women
Intrauterine growth restricted (IUGR)
This infants had increased chronic disease and even their own babies were affected->Barker hypothesis