Lecture 8- Thiamin

Question 1

food sources of thiamin

Answer 1

wholegrains,

pork (also other meats)

potatoes and their skin

Question 2

what is enrichment

Answer 2

when you add in the nutrient to make up for some kind of processing that removed the nutrient

Question 3

what is fortification

Answer 3

adding the nutrient to food that lots of people eat

Question 4

3 examples of food related thiamin losses

Answer 4

1- refining grains
2- thiamin antagonists
3- thiaminases = enzymes that act on thiamin

Question 5

how does refining grains result in thiamin losses

Answer 5

going from something like wholegrain down to brown down to white flour or bread etc

this removes thiamin, but improves shelf life as the embryo germ is removed

Question 6

what are 3 thiamin antagonists and what are they found in

Answer 6

sulfites (preserve the colour of meat)

cyanogenic glycosides (in cassava)

tannins (tea, coffee, betel nuts)

Question 7

how do tannins make thiamin less bioavailable

Answer 7

they will oxidise thiamin, making it less easy for your body to absorb

Question 8

what are thiaminases

Answer 8

enzymes that act on thiamin

Question 9

how can thiaminases cause thiamin losses

Answer 9

plants such as bracken fern

some kaimoana such as carp, mussels

some insects including African silk worm larvae

Question 10

where is betel nut chewing an important practice

Answer 10

in South and South-East Asia, Asia Pacific

Question 11

what is betel nut chewing considered

Answer 11

a stimulant drug, addictive

(one portion has the effect of about 6 cups of coffee)

Question 12

what are the long term impacts of betel nut chewing

Answer 12

discolouration of teeth and gums, mouth ulcers and oral cancers

Question 13

what is the chemical structure of thiamin

Answer 13

colourless organosulfur compound

Question 14

is thiamin water soluble or water insoluble

Answer 14

water soluble

Question 15

when is thiamin stable

Answer 15

when in acid solution and when frozen

Question 16

when is thiamin unstable

Answer 16

unstable to heat, UV light and alkali

Question 17

what are 3 of the 5 phosphorylated forms of thiamin (one of them has two names)

Answer 17

thiamin monophosphate (TMP)

thiamin diphosphate also known as thamin pyrophosphate (TPP)

thiamin triphosphate (TTP)

Question 18

all forms of thiamin can be interconverted in tissues but what is the distribution of these usually

Answer 18

80% is TPP

5-10% is TTP

remainder TMP, free thiamin

Question 19

how is thiamin converted to thiamin pyrophosphate

Answer 19

thiamin diphosphotransferase converted thiamin to its active form (TPP) via TMP

so converts it to thiamin monophosphate first and then thiamin pyrophosphate

Question 20

where is thiamin absorbed

Answer 20

mainly in the jejunum and ileum

Question 21

what are the two forms of thiamin absorption and when do they usually happen

Answer 21

active carried mediated process at low concentrations

passive diffusion at high concentrations (more at supplement level)

Question 22

what is the bioavailability of thiamin

Answer 22

little information

absorption can be inhibited by alcohol consumption

absorption will increase when intakes are low

Question 23

where is ~90% of the thiamin in your blood and why

Answer 23

in erythrocytes (red blood cells) in blood

because there is a TPP dependent enzyme that is on your red blood cells

Question 24

where is thiamin found in the plasma

Answer 24

majority bound to proteins, mainly albumin

Question 25

what is the average human storage of thiamin and how long does it take for this to be depleted

Answer 25

~25-30mg can be depleted within 2-3 weeks

Question 26

what are the highest tissue concentrations of thiamin

Answer 26

skeletal muscle heart brain liver kidneys

Question 27

where is thiamin also present in the body

Answer 27

plasma / serum, milk, cerebrospinal fluid

Question 28

what does thiamin have a critical role in

Answer 28

energy metabolism (key role in carbohydrate metabolism)

Question 29

what enzymes is thiamin required for (4)

Answer 29

transketolase a-ketoglutarate dehydrogenase pyruvate dehydrogenase branched chain a-keto acid dehydrogenase

Question 30

what is a good measure of thiamin status

Answer 30

transketolase

Question 31

what kind of diets are risk factors for thiamin deficiency

Answer 31

monotonous diet with low thiamin staple regular consumption of thiamin antagonists (e.g betel nut) regular consumption of thiaminases (e,g raw fish)

Question 32

what are other factors that are risk factors for thiamin deficiency

Answer 32

breastfed infants from thiamin deficient mothers co-morbidities such as severe acute malnutrition with fever and shock, use of dextrose-based IV fluid disease states with low thiamin intakes, absorption, thiamin utilisation (e.g alcohol dependancy, bariatric surgery)

Question 33

what was the historical approach to Beriberi diagnosis

Answer 33

“wet” if it predominantly affects the cardiovascular system accompanied by oedema “dry” is predominantly affects the peripheral nervous system

Question 34

what was the historical symptoms that people then thought was Wernicke-Korsakoff encephalopathy

Answer 34

presents with neurological signs

Question 35

classic syndrome of thiamin deficiency is Beriberi, what is it characterised by

Answer 35

oedema and cardiac enlargement due to intense vasodilation from accumulation of pyruvate and lactate in tissues bradycardia (bounding pulse) cardiac failure

Question 36

what is the response of Beriberi to thiamin treatment

Answer 36

prompt response to thiamin treatment > recovery could be 1-3 days

Question 37

what does chronic Beriberi affect rather than the cardiovascular system

Answer 37

the peripheral nerves

Question 38

what are symptoms of chronic Beriberi

Answer 38

foot drop loss of sensation in feet absent ankle reflexes

Question 39

what are the non specific signs associated with infantile beriberi

Answer 39

irritability refusal to breastfeed vomiting incessant “piercing” cry that may become a “silent” cry

Question 40

what are the later signs of infantile beriberi

Answer 40

chronic heart failure

Question 41

in low income countries what often happens with infantile beriberi

Answer 41

death before diagnosis

Question 42

what is infantile beriberi often misdiagnosed as

Answer 42

viral infection, malaria, pneumonia

Question 43

in older infants and children what is beriberi often misiagnosed as

Answer 43

meningitis

Question 44

what are the more neurological symptoms associated with beriberi in older infants and children

Answer 44

loss of appetite, bulging frontanelle, loss of consciousness

Question 45

what is the most common form of thiamin deficiency in older children and adults

Answer 45

Wernikes encephalopathy

Question 46

what does Wernike’s encephalopathy affect in the brain and therefore what does this impact

Answer 46

cerebellum and brain stem = abnormal eye movement, gait ataxia, cognitive impairment

Question 47

what is the most severe form of Wernike-Korsakoff encephalopathy and what does this cause

Answer 47

Korsakoffs psychosis = amnesia, confusion, confabulation , little or no working memory

Question 48

who is Wernike-Korsakoff encephalopathy most common in and why

Answer 48

most common in people with alcohol dependancy because decreased intestinal thiamin absorption and increased thiamin requirements for metabolism

Question 49

what is possible if thiamin deficiency is corrected before development of significant brain damage in Wernike-Korsakoff encephalopathy

Answer 49

the neurological symptoms may be reversed

Question 50

mild thiamin deficiency is non specific and easily overlooked, especially in older adults, what are the symptoms

Answer 50

sleeplessness, depression, weight loss, malaise, anorexia, fatigue

Question 51

possible causes of mild thiamin deficiency

Answer 51

low intakes lowered absorption multiple medications

Question 52

what is thiamin deficiency disorders an umbrella term for

Answer 52

describe the spectrum of overlap of clinical presentations attributable to thiamin deficiency across the life course

Question 53

what are the 5 categories to the spectrum of thiamin deficiency disorders by the WHO

Answer 53

acute cardiologic form aphonic form pseudo meningitic form encephalopathy peripheral neuropathies

Question 54

what is the acute cardiologic form of thiamin deficiency associated with

Answer 54

heart

Question 55

what is the aphonic form of thiamin deficiency associated with

Answer 55

lack of sound - peak prevalence in 4-6 month old infants initially hoarse cry until no sound is produced while crying

Question 56

strategies to improve thiamin status

Answer 56

rice and wheat flour fortification programmes that include thiamin

Question 57

what is the upper level for intake of thiamin

Answer 57

no upper level, just pee it all out