Thiamin Flashcards
What is the active form of thiamin?
Thiamin pyrophosphate (TPP)
What is the function of the active form of thiamin?
(TPP) - functions as a coenzyme for a number of enzymes involved in CHO metabolism, thus making metabolites from this metabolism and keto analogs from amino and fatty acid metabolism available for the production of energy.
How is thiamin absorbed by the intestine?
Thiamine is absorbed by two transporters (THTR-1 & THTR-2)
thiamin is absorbed in the small intestine
most thiamin present in the intestinal mucosa in the phosphorylated form
thiamin on the serosal side of the intestine is largely in the free form (non-phosphorylated form)
What type of transport is required for thiamin absorption?
active transport AND passive diffusion
Active transport occurs at low concentrations
Passive diffusion occurs at high concentration
What are the two thiamin transporters?
THTR-1 => thiamin transporter 1
THTR-2 => thiamin transporter 2
What important element is present only in thiamin?
sulfur
thiamin is known as the sulfur-containing vitamin
Is thiamin synthesized in the body?
No, thiamin is NOT synthesized in the body and must be consumed in the diet
What are the daily requirements of thiamin for adults/children?
Adult: 1.0 - 1.5 mg
Children: 0.4 - 1.3 mg
What macronutrient can affect the amount of thiamin required?
CHO
excessive CHO intake can increase the amount of thiamin recommended
This is due to the role of CHO metabolism that thiamin has
What are the primary functions of thiamin?
- involved in the oxidative decarboxylation of alpha-keto acids - gives off CO2
- cofactor of thiamin pyrophosphate (TPP)
- essential for CHO utilization (requirement is related to CHO content of diet)
- cofactor for transketolase in HMP shunt
- essential for pyruvate dehydrogenase
The main signs of thiamine deficiency are neurologic. Describe the biochemical changes that may affect neurologic functions that occur in thiamine deficiency.
thiamine is important for glucose metabolism (glycolysis) which is in large part required by the brain and a deficiency in glucose metabolism would result in neurologic symptoms
TPP is a cofactor for which four mammalian enzymes?
pyruvate dehydrogenase
alpha-ketoglutarate dehydrogenase
transketolase
alpha-keto acid dehydrogenase
Where are THTR-1 and THTR-2 located on intestinal enterocytes?
THTR-1 = located on basal lateral membrane THTR-2 = located on the apical membrane
Who is at risk for thiamine deficiency?
alcoholics - the new term is alcohol-abuse disorder (AAD)
elderly population
