Lecture 1: Micronutrients Flashcards
What are the fat soluble vitamins? (learning outcome)
A
D
E
K
What are the water soluble vitamins? (learning outcome)
8 x B vitamins
C
How does the solubility of a vitamin influence its metabolism? (learning outcome)
Lipid soluble vitamins are absorbed efficiently with lipids and are transported in the blood via lipoproteins or specific binding proteins. They are also more likely to accumulate in the body and can more likely lead to toxicity.
Hydrophilic compounds are not readily stored and are excreted in the body more easily. They need to be taken in consistently. Many of these vitamins are synthesized by bacteria.
Which vitamins often act as transcriptional regulators? How?
Vitamin D (binds to vitamin D receptor) and Vitamin A (binds to retinoic X receptor). They bind to receptors that form a transcriptional regulatory complex that changes gene expression.
What does vitamin K do?
Modifies structure of proteins to activate their function. (post translational regulation)
What are the products of oxidative stress?
Mitochondria often produce *O2 (superoxide) *OH and H2O2. These are known as Reactive Oxygen Species.
*: indicates an additional electron
Why are ROS dangerous?
They react with lipids, proteins, and DNA causing damage to these molecules.
Which vitamins act as antioxidants?
E and C
Which vitamins act as antioxidants?
E and C
What is vitamin B1 also called?
Thiamin
What is vitamin B2 also called?
Riboflavin
What is vitamin B3 also called?
Niacin
What is vitamin B5 also called?
Pantothenic acid
What is vitamin B6 also called?
Pyridoxine and pyridoxamine
What is vitamin B7 also called?
Biotin
What is vitamin B9 also called?
Folic acid
What is vitamin B12 also called?
Cobalamin
What is vitamin C also called?
Ascorbic acid
Which vitamins function primarily as cofactors and coenzymes?
All the B vitamins.
What metabolic pathways is vitamin B1 involved in?
Thiamin is an active coenzyme (thiamin pyrophosphate, TPP):
Pyruvate dehydrogenase in CHO metabolism.
Alpha-ketoglutarate dehydrogenase -> TCA cycle
What is the role of vitamin B1?
Active coenzyme (TCA cycle, pyruvate dehydrogenase, and decarboxylation of alpha-ketoacids)
CHO, AA, DNA/RNA/neurotransmitter synthesis.
What does vitamin B1 deficiency do?
Causes problems with energy and neurotransmitter production.
What disease is caused by vitamin B1 deficiency?
Beri beri
Can vitamin B1 cause toxicity?
No, it is very water soluble
What are the clinical manifestations of beri beri?
CNS problems (memory loss, confusion, ataxia)
Peripheral neuropathy (muscle weakness, muscle wasting)
Wernicke-korsakoff syndrome (alcohol induced dementia)
What are the coenzymes formed from vitamin B2?
flavin mononucleotide (FMN)
flavin adenine dinucleotid (FAD)
What do FMN and FAD do?
They act as prosthetic groups in many redox enzymes.
Which enzymes use FAD and FMN?
Succinate dehydrogenase - TCA cycle
Succinyl CoA-dehydrogenase for the beta oxidation of fatty acids
NADH-dehydrogenase in the mitochondrial respiratory chain
Why is vitamin B2 deficiency rare?
riboflavin is rare due to ubiquity in food sources.
What happens if there is a deficiency in riboflavin?
Problems with proliferation in high cell turnover tissues such as lining of mouth/tongue and dry scaling skin
What is vitamin B2 also known as?
Riboflavin
What is another name for vitamin B3?
Niacin
What are the coenzyme forms of vitamin B3?
nicotinic acid and nicotinamide
Can vitamin B3 be synthesized by the body?
Yes, in the liver it is produced from tryptophan
What are the symptoms of B3 deficiency?
Affects tissue with high energy requirements and cellular turnover.
4 Ds: Diarrhea, dermatitis, dementia, death
What disease results from severe vitamin B3 deficiency?
Pellagra
Is vitamin B3 deficiency common?
No, it is seen in strict vegetarians, alcoholics, and people with poor nutrition.
What is vitamin B5 called?
Pantothenic acid
What coenzyme is produced by pantothenic acid?
Acetyl-CoA
What is the function of acetyl-CoA?
It is essential for TCA cycle
Fatty acid metabolism
Formation of sterols (cholesterol and 7-dehydrocholesterol)
Acetylcholine production
What are the symptoms of vitamin B5 deficiency?
THEY ARE EXTREMELY RARE:
General metabolic deficiencies
Parasthesia (pins and needles)
Disorders of synthesis of acetylcholine
which results in neurological symptoms
What coenzymes are produced by vitamin B6?
Pyridoxal phosphate - PLP
What is another name for vitamin B6?
Pyridoxine (PLP)
What is pyridoxal phosphate important for?
Amino acid synthesis and gluconeogenesis
What is vitamin B6 important for besides what PLP does?
RBC metabolism
Haemoglobin formation
Neurotransmitter biosynthesis
What results from vitamin B6 deficiency?
Anaemia
Neurological problems (Seizures, confusion, and depression)
Inflammation of GI tract and skin
How much vitamin B6 causes toxicity?
> 200 mg/day
What is another name for vitamin B7?
Biotin
When is deficiency seen in vitamin B7?
People with inflammation of GI and skin (Biotin is produced by gut bacteria)
People who consume lots of raw eggs (due to avidin from egg albumin)
What coenzymes are produced from vitamin B7?
pyruvate carboxylase, acetyl CoA carboxylase
What is another name for vitamin B9?
Folic acid (folate)
Where does vitamin B9 come from?
Leafy vegetables (folic refers to foliage)
What is the function of vitamin B9?
Essential for the production of purines and pyrimidines (DNA and RNA synthesis)
Where is vitamin B9 important to know about?
In pregnant women. It is more common in pregnant women and causes neural tube defects (spina bifida)
What is another name for vitamin B12?
Cobalamin
What enzymes does vitamin B12 assist with?
Methionine synthase (DNA synthesis)
Methylmalonyl-CoA mutase (MMCoA -> succinylCoA)
What is the function of vitamin B12?
Essentially the same as vitamin B9. It is essential for energy metabolism as well as purine + pyrimidine synthesis.
RBC maturation and cell growth as well as nervous system maturation.
What are the deficiency symptoms of vitamin B9 and B12?
Macrocytic anaemia
Nervous system weakness resulting in fatigue, aranesia, depression, delirium
How common is vitamin B12 deficiency?
It is common in vegans and vegetarians and people with receptor mediated uptake with intrinsic factor.
Which vitamins are the antioxidant vitamins?
Vitamin E (lipid peroxidation, membranes, and membrane bound proteins)
Vitamin C (free radicals in solution)
What enzyme reduces vitamin C and E?
Glutathione reduces vitamin C
Vitamin C reduces vitamin E
What is another name for vitamin C deficiency?
Ascorbic acid
What are the functions of vitamin C besides clearing of free radicals?
It is a cofacter for synthesis of noradrenaline from dopamine
Leukocyte mobility
Synthesis of collagen
What is the result of vitamin C deficiency?
Scurvy (over 3 - 5 months)
Neuronal problems (Fatigue, decline in psychomotor performance, motivation and dyspneoa)
Collagen problems such as spongy gums and bleeding from mucous membranes and loss of teeth
What results from vitamin E deficiency?
Impairment of fertility in men
Peripheral neuropathy
Anaemia, and diminished RBC life span
symptoms associated with problems in membranes and fatty parts of the body
What is another name for vitamin E?
E - tocopherol (alpha-tocopherol is the most common one)
What do both vitamin A and D do?
Both are important regulators of transcription
What are the acute toxicity symptoms of vitamin A?
Acute symptoms include headache, vomiting, and impaired consciousness
What are the chronic toxicity symptoms of vitamin A?
Chronic intoxication causes weight loss, vomiting, joint pain, blurred vision, hair loss, and excessive bone growth
What happens in pregnant women when too much or too little vitamin A is taken?
Both are teratogenic (monster forming)
What is vitamin D synthesized from?
Cholesterol
How is vitamin D metabolised into its active form?
7-dehydrocholesterol is converted into cholecalciferol (vitamin D3) in the skin.
Cholecalciferol is converted into 1,25-dihydroxyvitamin D3 (which is the active form and is also known as calcitrol) in the kidneys
Summary of vitD metabolism:
7-dehydrocholesterol + sunlight / dietary vitD3 -> calcitrol (in the liver) -> 1,25 dihydroxy D3 (in the kidneys)
What does vitamin D do?
Important transcription factor for Ca2+ level regulation. Its binding increases calcium absorption in the gut, switches on genes for calcium transporters (TRPV6), and calcium binding proteins
What happens when deficient in vitamin D?
Rickets (low calcium levels causing bones to be soft and pliable)
Osteomalacia in adults (after closure of epiphyseal plates)
What is another name for vitamin K?
Koagulationsvitamin
What are the 2 forms of vitamin K?
K1 (phylloquinon) - plants
K2 (menaquinon) - converted from K1 by animals/bacteria, synthesized by bacteria
What does vitamin K do?
Vitamin K acts as a switch to activate certain molecules in coagulation, most importantly converts prothrombin to thrombin
It is also important for bone metabolism
What are deficiency symptoms of vitamin K?
Rare but causes:
Fat malabsorption
Blood clotting disorders
Osteoporosis (important for osteoblast activity)
Is vitamin K toxicity possible?
No, vitamin K is water soluble
