FA/AMBOSS Vit B1 12/27 Flashcards
Vit B1 name?
thiamine
active form of B1?
Active form: thiamine pyrophosphate (TPP)
how is activated B1?
activation via intracellular phosphorylation of thiamine
source of B1?
Sources: whole-grain cereals (e.g., whole wheat, brown rice), yeast, pork, legumes
vit B1 transport in blood?
Transport in blood: mainly via blood cells; only ∼10% is free or bound to albumin
General function of B1 (tiksliau TPP)?
Cofactor for 4 dehydrogenase enzymes involved in carbohydrate and amino acid metabolism
what are 4 enzymes?
Pyruvate dehydrogenase
Alpha-ketoglutarate acid dehydrogenase
Branched-chain ketoacid dehydrogenase
Transketolase
what are 4 enzymes? ........... Alpha-ketoglutarate acid dehydrogenase Branched-chain ketoacid dehydrogenase Transketolase
Pyruvate dehydrogenase
what are 4 enzymes? Pyruvate dehydrogenase ............. Branched-chain ketoacid dehydrogenase Transketolase
Alpha-ketoglutarate acid dehydrogenase
what are 4 enzymes? Pyruvate dehydrogenase Alpha-ketoglutarate acid dehydrogenase ............. Transketolase
Branched-chain ketoacid dehydrogenase
what are 4 enzymes? Pyruvate dehydrogenase Alpha-ketoglutarate acid dehydrogenase Branched-chain ketoacid dehydrogenase .............
Transketolase
what does pyruvate dehydrogenase?
(connects glycolysis to citric acid cycle): pyruvate → acetyl-CoA
what does alpha-ketoglutarate dehydrogenase?
(TCA cycle): α-Ketoglutarate → succinyl-CoA
where participates transketolase?
HMP shunt
what does Branched-chain ketoacid dehydrogenase?
Valine/isoleucine → Propionyl-CoA
Leucine → Acetyl-CoA
B1 deficiency causes?
Heavy drinking
Malnutrition, starvation
Malabsorption
Malignancy
Diarrhea, prolonged vomiting
Diuretics, hemodialysis
Bariatric surgery
pathophysiology of B1 def?
Thiamine deficiency → impaired glucose breakdown → ATP depletion → tissue damage that primarily affects highly aerobic tissues (e.g., brain, heart)
what happens if give glucose before restoration of thiamine?
High-dose glucose infusions lead to increased ATP depletion, which can trigger Wernicke encephalopathy
In malnourished individuals and chronic alcohol users/heavy drinkers, thiamine should be administered before glucose infusions.
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why manifest beriberi in b1 def?
inadequate thiamine uptake due to malnutrition, heavy drinking, or increased demand (e.g., hyperthyroidism, pregnancy)
what is dry beriberi? manifestation
NEURO!! !!Symmetrical peripheral neuropathy (sensory and motor) Progressive muscle wasting Paralysis Confusion
what is wet beriberi?
Cardiomegaly
Edema
!!High-output cardiac failure (dilated cardiomyopathy)
diagnosis of b1 def?
vitamin B1 administration → ↑ RBC transketolase activity
wernicke encephalopathy manifestation?
An acute neurological syndrome caused by thiamine deficiency that is characterized by a triad of confusion, ophthalmoplegia, and ataxia. Requires emergency treatment with thiamine repletion. Typically occurs in alcoholics.
