B6-095 B Vitamins Flashcards
severe malnutrition, peripheral neuropathy, high output heart failure
cardiac “wet” beriberi
**B1 deficiency
polyneuropathy and symmetric muscle wasting caused by B1 deficiency
neuritic “dry” beriberi
cofactor for many enzymes, especially those involved in ATP, NADH, and ribose-5-phosphate production
thiamine (B1)
critical for generating cellular energy, amino acids, nucleic acids, and fatty acids
thiamine (B1)
4 most significant enzymes requiring B1 as a cofactor
Branched-chain ketoacid dehydrogenase
a-ketoglutarate dehydrogenase (TCA)
Pyruvate dehydrogenase (TCA)
Transketolase (HMP shunt)
B-APT
active form is FAD or FMN
B2 riboflavin
FAD and FMN are derived from riboFlavin
cofactor for methyltetrahydrofolate reductase
B2 riboflavin
B2=2 ATP
what medication can increase the breakdown of B2 riboflavin with long term use?
phenobarbital
Cheilosis
Corneal vascularization
“magenta” tongue
B2 riboflavin
2 Cs of B2
found as nicotinamide or nicotinic acid
B3 niacin
used in redox reactions as a cofactor for dehydrogenase
B3 Niacin
NAD derived from Niacin
B3= 3 ATP
derived from tryptophan
B3 Niacin
risk factors for B3 deficiency [5]
chronic alcoholism
low protein diet
drugs used for TB/leukemia isoniazid
Hartnup disease
carcinoid syndrome
increases conversion of tryptophan to serotonin causing B3 deficiency
carcinoid syndrome
(symptoms of carcinoid syndrome: skin flushing, diarrhea, dyspnea)
mutation in intestinal tryptophan transporter that causes B3 deficiency
Hartnup syndrome
3 D’s of vitamin B3 deficiency
diarrhea
dementia
dermatitis
(pellagra)
component of coenzyme A (cofactor for CoA, carbon transfers) and fatty acid synthase
B5 pantothenic acid
“pento”thenic acid
anytime you see CoA think B5
nitrous oxide can cause […] deficiency
B12
describe the absorption of vitamin B12 cobalamin
- food with B12 is ingested
- haptocorrin is secreted by salivary glands
- in stomach, parietal cells secrete HCl and intrinsic factor
- cobalamin is released from food by HCl or trypsin and binds haptocorrin
- in the small intestine, pancreatic proteases degrade haptocorrin and cobalamin binds IF
- cobalamin-IF complex is absorbed in the ileum via cubulin receptors
- cobalamin is released into blood. Can bind haptocorrin transporter for storage or transcobalamin II to go to cells/liver
causes of lack of intrinsic factor [2]
(leads to B12 deficiency)
pernicious anemia
gastric bypass surgery
some causes of malabsorption that can cause B12 deficiency
aging
enteritis
alcoholism
bacterial overgrowth
veganism
terminal ileum resection (such as in a Crohn’s patient) can increase the risk of […] deficiency
B12 cobalamin
most common cause of B12 cobalamin deficiency
pernicious anemia
auto-immune antibodies attack parietal cells, resulting in decreased HCl and IF
pernicious anemia
drugs that can cause B12 cobalamin deficiency
GERD: H2 blockers, PPIs
nitrous oxide
muscle weakness
sore tongue
neuropathy
neural-tube defects
megaloblastic anemia
B12 cobalamin deficiency
megaloblastic anemia
hypersegmented PMNs
parethesia due to abnormal myelin
B12 cobalamin deficiency
cofactor for methionine synthetase and methymalonyl CoA mutatase
important for DNA snythesis
B12 cobalamin
increased serum homocysteine and methylmalonic acid
B12 cobalamin deficiency
important enzyme in fatty acid metabolism in mitochondria
deficiency can cause abnormal myelination
B12 cobalamin
universal methyl donor for methylation of DNA, RNA, proteins
S-Adenosyl Methionine (SAM)
important in methionine cycle with B12, B9, and B6
converted to THF, a coenzyme for 1 carbon transfer/methylation
important to the synthesis of nitrogenous bases
B9 folate
required for regeneration of dTMP
B9 folate
**5 FU inhibits this pathway by inhibiting thymidylate synthase
diminished dTMP causes what?
cell cycle arrest of hemopoietic cells –> megaloblastic anemia
drugs that can cause B9 folate deficiency
methotrexate (inhibits DHFR)
trimethoprim (DHFR antagonist)
phenytoin
only coenzyme as pyridoxal-5-phosphate (PLP)
B6 pyroxidine
serves as a cofactor in transamination, decarboxylation reactions, and glycogen phosphorylase
B6 pyroxidine
serves as a cofactor in the synthesis of glutathione, cystathionine, heme, niacin, histamine, and neurotrasmitters
B6 pyroxidine
required as a cofactor in the alanine cycle for the removal of ammonium
B6 pyroxidine
can cause an anemia with normal number of RBCs but low hemoglobin content
B6 pyroxidine deficiency
(sideroblastic anemia)
convulsions
hyper irritability
peripheral neuropathy
sideroblastic anemia
B6 pyroxidine deficiency
cofactor found in pyruvate carboxylase and acetyl CoA carboxylase
key cofactor to enzymes that perform gluconeogenesis, fatty acid metabolism, and amino acid metabolism
B7 biotin
inhibition of […] has been considered for obesity drugs as it would stimulate fat oxidation
acetyl-CoA carboxylase
**B7 biotin pathway
enzyme that is first step in fatty acid synthesis and highly regulated
acetyl-CoA carboxylase
**B7 biotin pathway
enzyme that produces oxaloactetate, key to gluconeogenesis and keeping TCA replenished via anaplerotic reactions
pyruvate carboxylase
**B7 biotin pathway
excessive ingestion of raw egg whites can cause
B7 biotin deficiency
avidin in eggs binds biotin
assists in glucose metabolism, RNA, DNA, and ATP synthesis
B1 thiamine
deficiency causes fatigue, confusion, movement impairment, swelling, heart failure
B1 thiamine
assists in glucose, fat, and carbohydrate metabolism
electron carrier
other B vitamins dependent on
B2 riboflavin
deficiency causes dry scaly skin, mouth inflammation and sore, sore throat, itchy eyes, light sensitivity
B2 riboflavin
assists in glucose, fat, and protein metabolism
electron carrier
B3 niacin
deficiency causes pellagra: diarrhea, dermatitis, dementia, death
B3 niacin
assists in glucose, fat, and protein metabolism
assists in cholesterol and neurotransmitter synthesis
B5 pantothenic acid
deficiency causes muscle numbness and pain, fatigue, irritability
B5 pantothenic acid
assists in amino-acid synthesis, glycogenolysis
assists in hemoglobin and neurotransmitter synthesis
B6 pyroxidine
deficiency causes muscle weakness, dermatitis, mouth sores, fatigue, confusion
B6 pyroxidine
assists in glucose, fat, and protein metabolism
assists in amino acid synthesis
B7 biotin
deficiency causes muscle weakness, dermatitis, fatigue, hair loss
B7 biotin
assist in amino acid synthesis, RNA, DNA, and RBC synthesis
B9 folate
deficiency causes diarrhea, mouth sores, confusion, anemia, neural tube defects
B9 folate
assists in fat and protein catabolism
folate function
RBC synthesis
B12 cobalamin
deficiency causes muscle weakness, sore tongue, anemia, nerve damage, neural tube defects
B12 cobalamin
how do PPIs cause B12 deficiency?
increase the pH of the stomach, resulting in reduction of release of cobalamin from food
malabsorption causes of B12 deficiency can be treated with
IM B12 injection
methotrexate can cause a […] deficiency
B9 folate
[…] deficiency can cause seizures or dystonic movement due to its role in the neurotransmitter synthesis pathway
B6 pyrodoxine
amino acid transaminases require […] in the catabolism of amino acids
B6 pyrodoxine