L13 B-Vitamins and One-Carbon Metabolism Flashcards
What is B1?
Thiamin
What is B2?
Riboflavin
What is B3?
Niacin
What is B5?
Pantothenic Acid
What is B6?
Pyridoxine
What is B7?
Biotin
What is B9?
Folate
What is B12?
Cobalamin
What is the natural form of folate also known as?
Polyglutamate
What is the synthetic form of folate?
Folic acid/monoglutamate
What form is folate in to be absorbed in the intestine?
Polyglutamate is hydrolysed to monoglutamate
How much folate is stored in the body and where is most of it?
11-28mg with 50% in the liver
What are two active forms of Cobalamin called?
Methylcobalamin and Adensylcobalamin
How much B12 is stored in the body and where is most of it?
2-4mg with 50% in the liver and 50% in other tissues
How is folate absorbed and activated?
- Folate is eaten and broken into di- then monoglutamate
- Methyl group is added to make 5-methyltetrahydrofolate, then it can be absorbed
- Folate is trapped in an inactive form
- B12 removes the methyl group, making both folate and B12 active. Active folate is tetrahydrofolate (THF)
What is an important function of THF?
Acts as a coenzyme in the transfer of one-carbon compounds such as methyl groups
How is B12 digested and absorbed?
- Pepsin and HCL get B12 from food
- B12 binds to salivary (R) protein
- Carried to the small intestine where B12 is released from R protein and bound to intrinsic factor (IF)
- IF complex binds to receptors in the ileum where IF breaks down and B12 is bound to a transporter protein in the blood stream - Transcobalamin
What is a main complication from folate deficiency?
Neural tube defects
- Anencephaly - brain doesn’t form properly
- Spina bifida - incomplete development of the spine
What folate mandate did FSANZ implement in 2009?
Mandatory folate fortification of bread flour
What is a complication of folate and/or B12 deficiency? And what are its symptoms?
Megoblastic Macrocytic Anaemia - production of abnormally large blood cells and less RBCs in circulation
Symptoms include fatigue, weakness, headaches, palpitations
What are some causes of B12 deficiency? (3)
- Malabsorption
- Poor dietary intake
- Surgical/post op
What are some causes of folate deficiency? (4)
- Poor dietary intake
- Increased demand (e.g. pregnancy)
- Malabsorption
- Anti-folate drugs
What is epigenetics?
The study of how your behaviors and environment can cause changes that affect the way your genes work
What is the methyl-folate trap? What does this cause?
Without B12, 5-methyl THF cannot donate its methyl group to B12 which is how it becomes active
This causes a build up of homocysteine
What are some adverse effects of hyperhomocysteinaemia? (5)
- Damages blood vessels and degrades proteins
- Risk factor for CVD and thrombosis
- Role in Alzheimer’s disease
- Pregnancy complications
- Oxidative stress
What one-carbon nutrients are involved in pregnancy? (5)
- Folate (main)
- B12 (main)
- Methionine
- Choline
- B6
Why are one-carbon nutrients important in pregnancy? (3)
- Vital for epigenetic regulation of placenta and foetus
- Enabling DNA synthesis
- Required for optimal tissue growth and development
What is homocysteine (Hcy)?
A thiol containing amino acid
What are the two potential fates of homocysteine?
- Recycled into methionine
- Converted into cysteine
What are some factors that may cause hyperhomocysteinaemia? (8)
- Age
- Male gender
- Menopause
- Smoking
- High coffee consumption
- Low consumption of fruits and vegetables
- Diabetes
- Some drugs
