Lecture 2-Flolate

Question 1

What are key sources of folate in the diet?

Answer 1

Dark green leafy vegetables, orange juice, legumes, liver,

Question 2

Folate is mediatory fortified into what ??

Answer 2

Bread
and cereals

Question 3

What is the difference between folate and folic acid, and what is their relationship to each other?

Answer 3

Folate is methyltetrahydrofolate and differs from folic acid by a methyl group and 4 extra
carbons.

Folic acid is a pre vitamin - needs to be reduced to active form of folate = Tetrahydrofolate

They
have different carriers to cross cell walls and carry in blood.

Question 4

What are the three main functions of folate in the body? For each, list at least three key
components of the relevant pathway

Answer 4

DNA synthesis
Purines
DNA methylation

Question 5

why is liver such an important source of folate

Answer 5

mammals store 50% of their folate in their liver, so consuming liver from animals is a useful source

Question 6

what part of the folate structure can we not make

Answer 6

• Humans can not make the middle bit
• We can also not combine all three so this is why it is an essential nutrient we get from our diet

Question 7

what is folic acid

Answer 7

being added when the food is fortified

Question 8

what is food folate

Answer 8

naturally present in food

Question 9

where is folic acid usually found

Answer 9

supplements and food fortification

Question 10

folic acid is in what form and why does this mean it is good to be used in fortification

Answer 10

fully oxidised form, it is quite stable and that is why it is used in fortification

Question 11

which one of food folate of Folic acid either a polyglutatmate or monoglutamate

Answer 11

Food folate =polyglutamate
Folic acid = monoglutamate

Question 12

absorption and cell retention order

Answer 12

Gut lumen
Enterocyte
Blood
Cell

Question 13

when are polyglutamates in absorption of folate

Answer 13

when it has entered the enterocyte

Question 14

what helps more food folate into the cell

Answer 14

reduced folate carrier

Question 15

what helps move folic acid into the cell

Answer 15

folate receptor

Question 16

what is DHFR (dihydrofolate reductase) do

Answer 16

add on hydrogens (reduction reaction) to get folate to the active form

Question 17

add on hydrogens (reduction reaction) to get folate to the active form

Answer 17

hydrogens have been added

Question 18

if converting from food folate to the active form what has changed

Answer 18

there has been removal of methyl group by enzymes

Question 19

how is folate involved in DNA synthesis

Answer 19

when there is sufficient folate, dUMP is converted to dTMP and its thymine (one of the four nucleotide bases) is incorporated into DNA

Question 20

what happens to DNA synthesis when there is insufficient folate

Answer 20

dUMP is not converted to dTMP, and uracil is misincorperated into DNA

Question 21

purines are what nucleotide bases

Answer 21

A and G bases for nucleotides

Question 22

purines are also what

Answer 22

part of AMP and GMP, which are converted to ATP and GTP to use as energy currencies

Question 23

what does folate provide for DNA methylation and what is this used for

Answer 23

a methyl group which is used for epigenetic modification

Question 24

what is epigenetic modification

Answer 24

a critical process in control of gene expression and stabilisation of the genome

Question 25

how is folate linked to DNA methylation

Answer 25

tetrahydrofolate has a methyl group added to it this gets converted to 5-methyltetrahydrofolate then conversion to methionine, then to SAM then number of steps to DNA methylation

Question 26

when is homocysteine formed

Answer 26

when the amino acid methionine is metabolised to cysteine

Question 27

what are the four possible fates of homocysteine

Answer 27

1. reform s-adenosyl homocysteine (SAH) 2. remethylation to form methionine 3. degradation through transulfuration pathway 4. leaks out of cell if intracellular concentration too high

Question 28

hyperhomocysteinemia is associated with increased risk of what

Answer 28

increased risk of CVD and thrombosis

Question 29

if there is not enough folic acid in the diet not enough what will be formed

Answer 29

not enough THF will be formed from folic acid

Question 30

if there is not enough 5-methyl THF then not enough what will be formed

Answer 30

not enough THF will be formed

Question 31

lacking 5-methyl THF means what for production of methionine

Answer 31

means you will not to be able to add on the methyl group to homocysteine to form methionine (stable compound)

Question 32

what is the stable compound that homocysteine is converted to

Answer 32

methionine

Question 33

if you are unable to form methionine because you are lacking in 5-methyl THF what will this mean

Answer 33

means you will have an increase in the homocysteine concentration and an increase in the SAH molecule as well

Question 34

why will homocysteine levels stay elevated if there is damage to the 5-methyl THF

Answer 34

you can not pump all of the homocysteine into SAH so will be left with higher levels of homocysteine

Question 35

a case study on 22 year old female student on a largely CHO diet but not vegetarian reported symptoms of tiredness and breathlessness on minimal exertion, what did she have and what was the reason

Answer 35

megaloblastic anaemia due to folate deficiency

Question 36

what are megaloblasts

Answer 36

really big compared to normal red blood cells, they are the immature form

Question 37

how is folate linked to meglaloblastic anaemia

Answer 37

you need folate to form the nucleotide bases to form DNA without enough folate proper cell devision does not occur and there for formation of the red blood cell does not happen properly and it enters the circulation still containing its nucleus

Question 38

what is another effect of folate deficiency

Answer 38

neural tube defects

Question 39

what are the complications that come with neural tube defects

Answer 39

below the defect you will get abnormal nerve conduction, so you will have issues with motor and sensory control / function

Question 40

what are the two main types of neural tube defects and what are they

Answer 40

spina bifida (lesion on the spine) anencephaly (not compatible with life)

Question 41

approximately how many cases of neural tube defects are there in NZ each year

Answer 41

approx 64

Question 42

what part of New Zealand has higher rates of neural tube defects

Answer 42

the north island

Question 43

what is the folate toxicity rates from naturally occurring folate in foods

Answer 43

no risk

Question 44

what is the upper limit of folate for fortified foods or supplements

Answer 44

1,000μg/day (adults)

Question 45

what is ministry of health recommendation of RDI and EAR of folate for adult men and women

Answer 45

EAR : 320μg/day RDI : 400μg/day

Question 46

Q what is ministry of health recommendation of RDI and EAR of folate during pregnancy

Answer 46

RDI : 600μg/day

Question 47

why is it important to have fortification of food with folate (pregnancy)

Answer 47

~53% of pregnancies are unplanned so they will not be taking a supplement which is why food sources need to be fortified