Thiamin (B1) Flashcards
TDP/ TPP Digestion
Main phosphorylated forms. Digested before absorbed.
Active and passive digestion depending on the amount present. Thiamin transporters ThTr 1 and 2.
Any free thiamin is taken up by the liver and phosphorylated into TDP form.
TMP
Unphosphorylated form found in plasma.
Bound to albumin.
Absorbed by reduced folate carrier RFC.
Excretion
Urine as thiamin or its metabolites.
Storage
30 mg pool
50% in muscle
80% TDP, 10% TTP
Coenzyme in Krebs cycle
Synthesizes NADPH.
Decarboxylates pyruvate to form acetyl CoA and eventually lead to production of ATP.
Maple syrup urine disease
Build up of BCAA because they were never decarboxylated and simply built up in blood.
Inborn metabolic error from insufficient dehydrogenase enzymes to oxidize BCAA.
RDA
- 2 mg men
1. 1 mg women
Deficiency
Dry: adults; chronic low thiamin intake characterized by muscle weakness, wasting, peripheral neuropathy.
Wet: cardiomegaly, tachycardia, peripheral edema.
Acute: common in infancy; vomiting, anorexia, lactic acidosis, cardiomegaly.
Lactic acidosis
Lack of thiamin to convert pyruvate to Acetyl CoA causes pyruvate to be converted into lactic acid instead.
Wernicke’s encephalopathy
TTP involved as a neural transmitter.
Thiamin deficiency found more in alcoholics.
Paralysis of eye muscles, involuntary eye twitch, ataxia, confusion, memory loss.
Synthesis of pentoses and NADPH
Pentose phosphate used in synthesis of nucleic acids for DNA. Needed by cells that replicate rapidly such as RBC.
Generates niacin (NADPH) used as a reducing agent and recycling of vitamin C.
Benefits of megadosing
Alzheimer’s
Alcoholism treatment
MSUD
ThTr1 mutation
Thiamin responsive megaloblastic anemia (Rogers syndrome).
Hearing loss, diabetes.
Assessment
Urine measure:
25% deficient
Antithiamin factors
Raw fish. Thiaminase.
Polyhydroxyphenols oxidize thiazole ring. Found in tea, coffee, blueberries, cabbage.
Made worse by magnesium and calcium.
Mad better by vitamin C.
