Thiamin (Vitamin B1) Flashcards
(20 cards)
where do most products with Thiamin come from in the American diet?
products that have been enriched
what factors can lead to the loss of thiamin?
alkaline environment (pH of 8 or above), heat and anti-thiamin factors (thermolabile/polyhydroxy phenols)
what organ in the body can produce thiamin and TDP?
bacteria in the large intestine
where is free thiamin absorption thought to occur?
within the jejunum
which transporter has a higher capacity for thiamin?
ThTr1
which transporter has a higher specificity for thiamin?
ThTr2
where is ThTr1 found?
both on the brush border and basolateral membrane
where is ThTr2 found?
basolateral membrane
what allows the active transportation of thiamin into the intestinal cells?
exchange of H+ ions as part of an antiport carrier system
what inhibits the intestinal absorption of both ThTr1 and ThTr2?
alcohol
what causes rogers syndrome?
a defect in the SLC91A2 gene which codes for ThTr1
in what organs is ThTr1 found in?
skeletal muscles
in what organs is ThTr2 found in?
liver, kidneys, and heart
how is TMP formed?
the terminal phosphate on the TTP is hydrolyzed by thiamin triphosphatase to yield TDP and TDP can be converted to TMP by thiamin diphosphatase, which cleaves the terminal phosphate on TDP
how can TMP be converted to free thiamin?
by thiamin mono phosphatase
what is dry beriberi?
characterized by peripheral neuropathy and muscle weakness and cramping, especially in the lower extremities
what is wet beriberi?
characterized by more extensive cardiovascular system involvement (enlarged heart, tachycardia, right-sided heart failure and peripheral edema)
what is acute beriberi?
occurs mostly in infants, especially those who are breast fed by mothers having poor thiamin status
how does thiamin correct the lactic acidosis?
by increasing pyruvate dehydrogenase activity and enabling more pyruvate to be decarboxylated to acetyl-CoA for entry into the TCA cycle vs. being converted to lactic acid
how can thiamin status be assessed?
by measuring thiamin and/or TDP in the blood or urine and by measuring erythrocyte transketolase activity in hemolyzed whole blood
