LECTURE 7 (Water-soluble vitamins) Flashcards
Which vitamins are water-soluble?
- The 8 B Vitamins (B1, B2, B3, B5, B6, B7, B9 & B12)
- Vitamin C
What are the properties of Water soluble vitamins?
- Wash out easily -> deficiency can occur easily if insufficient diet (in weeks to months)
[EXCEPTION: B12 since is stored in LIVER -> requires years to develop deficiency symptoms] - Most absorbed in JEJENUM
[EXCEPTION: B12 -> terminal ileum]
What are the common symptoms of B vitamin deficiency?
- Dermatitis
- Diarrhoea
- Cheilitis (skin breakdown at corners of lips)
- Glossitis (swelling/redness of tongue)
What are the properties of Vitamin B1?
- Called “Thiamine”
- Converted to active form -> THIAMINE PYROPHOSPHATE (TPP)
Vitamin B1 is a co-factor for which enzymes?
- Pyruvate dehydrogenase
- a-ketoglutarate dehydrogenase (TCA)
- a-ketoacid dehydrogenase (branched-chain amino acids)
- Transketolase
What are the Symptoms of Thiamine deficiency?
- Loss of muscle coordination
- Inability to form new memories
- Memory loss
- Double vision
- Hallucinations
- Confabulation (false memories)
- Confusion
- Abnormal eye movement
What are the two syndromes that Thiamine deficiency causes?
- Beriberi
- Wernicke-Korsakoff syndrome
Describe Beriberi syndrome
Beriberi is a disease caused by vitamin B1 deficiency, also known as thiamine deficiency. There are two types: Dry type and Wet type.
SYMPTOMS:
- DRY TYPE: Polyneuritis (many nerves affected at the same time) and muscle weakness
- WET TYPE: Tachycardia, oedema and heart failure
Describe Wernicke-Korsakoff syndrome
Wernicke-Korsakoff syndrome (WKS) is a brain and memory disorder that requires immediate treatment. It happens due to a severe lack of thiamine (vitamin B1), which causes damage to your brain. It occurs in alcoholics.
Wernicke encephalopathy = acute, reversible, life-threatening neurologic condition
Korsakoff syndrome = amnestic disorder due to chronic alcohol overuse
SYMPTOMS:
- WERNICKE ENCEPHALOPATHY: Confusion, Ophthalmologia/Nystagmus, Ataxia
- KORSAKOFF SYNDROME: Confabulation, personality changes, memory loss (permanent)
What is the clinical correlation of Thiamine deficiency?
Thiamine deficiency = impaired glucose breakdown
When a patient presents to hospital in a malnourished state, he/she frequently has both THIAMINE and GLUCOSE deficiency -> Thiamine should always be given first because without thiamine, patient is unable to METABOLISE GLUCOSE -> ATP depletion is worsened by glucose infusion -> Can worsen Wernicke-Korsakoff syndrome
What are the properties of Vitamin B2?
- also called “Riboflavin”
- Component of flavins FAD & FMN (used as cofactors in redox reactions)
Describe Riboflavin deficiency
A very rare condition
SYMPTOMS:
- Dermatitis
- Glossitis (“magenta” tongue)
- Cheilitis (inflammation of lips)
- Corneal neovascularisation (rare & cause blindness)
What are the properties of Vitamin B3?
- also called “Niacin”
- Used for NADH and NADPH synthesis + required by dehydrogenase enzymes
- Can be synthesised from amino acid TRYPTOPHAN
- Conversion requires B6 vitamin as a COFACTOR
Vitamin B3 “Niacin” can be used as a treatment for which disease?
Hyperlipidemia
Describe Niacin deficiency
Niacin (vitamin B3) deficiency results in a condition known as pellagra. Pellagra includes the triad of dermatitis, dementia, and diarrhea and can result in death
CAUSES:
- Niacin is not found in corn -> corn-based diets can induce deficiency
- HARTNAP DISEASE (AR) -> increased levels of tryptophan lost in the intestine and urine
- MALIGNANT CARCINOID SYNDROME -> increases tryptophan metabolism -> increased serotonin synthesis + ISONIAZID (decreased B6)
SYMPTOMS:
deficiency causes a syndrome called “PALLAGRA” which manifests with 4 Ds:
- Dermatitis (lesions on sun-exposed areas)
- Diarrhoea
- Dementia
- Death
Describe Niacin excess
Niacin excess is seen with niacin treatment for hyperlipidemia
CAUSE:
- niacin stimulates the release of PROSTAGLANDINS in the skin
MANIFESTATIONS:
- Facial flushing (face turns red & warm)
- Can cause HYPERGLYCEMIA & HYPERURICEMIA (gout)
CHARACTERISTICS:
- Can blunt with ASPIRIN prior to niacin
- Fades with time
Describe Vitamin B5
- also called “Pantothenic acid”
- Used in COENZYME A synthesis
- Deficiency is very rare
NEUROLOGICAL SYMPTOMS:
PARESTHESIAS (burning feet) and numbness
What is Vitamin B6 also called?
Pyridoxine or Pyridoxal phosphate
Vitamin B6 is a Cofactor for which biochemical reactions?
- Aminotransferases (ALT, AST)
- Histamine synthesis
- Niacin synthesis
- Heme synthesis
- Neurotransmitter synthesis
Describe Pyridoxine deficiency
- ISONIAZID (Tuberculosis medications) can induce pyridoxine deficiency
- Forms an inactive form of vitamin B6
- B6 should be supplemented when prescribing isoniazid
Describe Vitamin B7
- also called “Biotin”
- Cofactor for carboxylase enzymes
- Deficiency is very rare
- Only occurs if massive consumption of raw egg whites happens -> contains AVIDINS -> molecules that inhibit the absorption of biotin from the GI tract
Which carboxylase enzymes is Vitamin B7 a cofactor for?
- Pyruvate carboxylase
- Acetyl-CoA carboxylase
- Propionyl-CoA carboxylase
Describe Vitamin C
- also called “Ascorbic acid”
- Antioxidant properties
- Found in fruits and vegetables
THREE MAIN ROLES:
- Absorption of iron (Fe3+ -> Fe2+)
- Collagen synthesis (Post-translational modification: hydroxylation of proline and lysine)
- Dopamine synthesis (Cofactor for Dopamine B-hydroxylase)
What is Scurvy?
Scurvy is a disease caused by a serious vitamin C deficiency. Not eating enough fruits and vegetables is the main cause of the disease.
CAUSES:
- Seen in “tea and toast” diet since no fruit & vegetables
MANIFESTATIONS:
- Common in sailors due to deficient diet on long voyages -> prevented by eating limes (high quantity of vitamin C)
- Defective collagen synthesis -> required in normal connective tissue synthesis
SYMPTOMS:
- Hemarthrosis (a condition of articular bleeding, that is into the joint cavity)
- Poor wound healing
- “corkscrew” hair
- Sore gums and loose teeth
- Fragile blood vessels -> easy bruising
Describe Vitamin C excess
Can lead to kidney stone formation -> CALCIUM OXALATE STONES -> Vitamin C excess is metabolised to oxalate -> combines with CALCIUM and forms stones
- Increased Vitamin C requirements in smokers
- Likely due to antioxidant properties
- Deficient levels common (scurvy or definite symptoms rare)
