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HUNT241 > Nutrition Lecture 8: Thiamin > Flashcards

Nutrition Lecture 8: Thiamin Flashcards

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1
Q

What are rich sources of thiamin?

A

Whole grains, pork, potato skin, fortified wheat-bix and soy milk

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2
Q

What foods cause thiamin losses?

A

Refining grains (e.g. rice, wheat)

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3
Q

What does a ‘thiamin antagonist’ mean?

A

Substances that interfere with the absorption of thiamin

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4
Q

What are examples of thiamin antagonists?

A
  • Sulfites (to preserve colour of meat)
  • Cyanogenic glycosides (in cassava)
  • Tannins (tea, coffee, betel nuts)
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5
Q

What does thiaminases mean?

A

Enzymes that break down thiamin

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6
Q

What are examples of thiaminases?

A
  • Plants such as bracken fern
  • Some kaimoana including carp, mussels
  • Insects including african silk worm larvae
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7
Q

What is betel nut chewing?

A

An important cultural practice in south and south-east Asia, Asia pacific

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8
Q

What are the effects of betel nut chewing?

A

Stimulant drug, addictive

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9
Q

What are the long term affects of betel nut chewing?

A

Discolouration of teeth and gums, mouth ulcers and oral cancers

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10
Q

Is thiamin water soluble?

A

Yes, water soluble, stable in acid solution and when frozen

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11
Q

What is thiamin unstable to?

A

Heat, UV light and alkali

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12
Q

What type of compound is thiamin?

A

Colourless organosulfur compound

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13
Q

What is the chemical structure of thiamin?

A

2 rings and a bridge in-between

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14
Q

What are the names of the two rings that make up thiamin?

A

Aminopyrimidine ring and Thiazolium ring

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15
Q

What is the name of the bridge that connects the two rings that make up thiamin?

A

Methylene bridge

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16
Q

How many phosphorylated forms of thiamin are there?

A

3

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17
Q

What are the three phosphorylated forms of thiamin

A

TMP, TPP, TTP

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18
Q

What does TMP stand for?

A

Thiamin monophosphate

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19
Q

What does TPP stand for?

A

Thiamin diphosphate

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20
Q

What does TTP stand for?

A

Thiamin triphosphate

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21
Q

What can all three forms of thiamin do?

A

All can be interconverted in tissues

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22
Q

What percent of total tissue thiamin is TMP, TPP and TTP?

A
  • 80% is TPP
  • 5-10% is TTP
  • Remainder is TMP
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23
Q

What is the active form of Thiamin?

A

Thiamin pyrophosphate (TPP)

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24
Q

How is thiamin turned into its active form TPP?

A

By the enzyme thiamin diphosphotransferase
- This conversion involves the addition of two phosphate groups to thiamin, utilizing ATP in the process

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25
Where does absorption of thiamin happen?
Mainly in the jejunum and ileum
26
What are the two main mechanisms of absorption of thiamin?
- Active carrier-mediated - Passive diffusion
27
When does active-carrier mediated process happen?
When thiamin is at low concentrations
28
When does passive diffusion occur?
When thiamin is at high concentrations
29
What is thiamin released by in the upper small intestine?
By phosphatase and pyrophosphatase
30
What is bioavailability of thiamin affected by?
Little information, alcohol consumption, absorption increases when intakes are low
31
Where is approximately 90% of thiamin in blood found?
In erthrocytes
32
Where is majority of thiamin in plasma found?
Mainly bound to proteins, mainly albumin
33
How much thiamin can humans store?
approx. 25 to 30mg - can be depleted within 2-3 weeks
34
Where are the highest tissue concentrations of thiamin?
Skeletal muscle, heart, brain, liver and kidneys
35
What metabolisms are thiamin important for?
Energy metabolism and CHO metabolism (as TPP)
36
What is thiamin required for the activity of?
- Transketolase - a-ketoglutarate dehydrogenase - pyruvate dehydrogenase - branched chain a-keto acid dehydrogenase
37
What is Transketolase?
Transketolase is an enzyme that plays a crucial role in the pentose phosphate pathway (PPP)
38
What is the pentose phosphate pathway (PPP)?
an alternative glucose metabolic pathway parallel to glycolysis, primarily involved in the production of NADPH and ribose-5-phosphate
39
What is a-ketoglutarate dehydrogenase?
an enzyme complex involved in the citric acid cycle
40
What is a-ketoglutarate dehydrogenase responsible for?
is responsible for the conversion of α-ketoglutarate to succinyl-CoA
41
What is pyruvate dehydrogenase?
pyruvate dehydrogenase is a crucial enzyme complex in cellular respiration
42
What is pyruvate dehydrogenase responsible for?
the conversion of pyruvate to acetyl-CoA to enter the CAC
43
What is the branched chain a-keto acid dehydrogenase?
complex that helps break down certain types of protein building blocks called branched-chain amino acids (BCAAs)
44
What is branched chain a-keto acid dehydrogenase responsible for?
forming Acetyl-CoA derivatives to enter the CAC
45
Consuming what causes risk factors for thiamin deficiency?
Thiamin antagonists, thiaminases
46
What disease states are risks for thiamin deficiency?
Alcoholism, bariatric surgery
47
What conditions does thiamin deficiency cause?
Beriberi, wernickes encephalopathy
48
What is beriberi?
"WET" Oedema and cardiac enlargement due to intense vasodilation from accumulation of pyruvate and lactate in blood and tissues
49
What is chronic beriberi?
"DRY" Affects peripheral nerves rather than the CV system
50
What is infantile beriberi?
Infants < 4 months with non-specific signs
51
What are the symptoms of infantile beriberi?
Irritability, refusal to breastfeed, vomiting, piercing cry, then signs of chronic heart failure
52
What is the most common form of thiamin deficiency in adults and older children?
Wernickes encephalopathy
53
What does wernickes encephalopathy affect?
Cerebellum and brain stem
54
What is the most severe form of wernickes encephalopathy?
Korsakoff's psychosis
55
What is Korsakoff's psychosis?
amnesia, confusion, confabulation, little working memory
56
What are symptoms of milk thiamin deficiency?
Sleeplessness, depression, weight loss, fatigue and irritability
57
What are stratagies to improve thiamin status?
Rice and wheat flour fortification with thiamin
58
What is the EAR for thiamin?
Men = 1.0mg/day Women = 0.9mg/day
59
What is the RDI for thiamin?
Men = 1.0mg/day Women = 1.1mg/day
60
What is the upper level of intake for thiamin?
No upper level of intake set

HUNT241 (22 decks)

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