LECTURE 7 (Water-soluble vitamins)

Question 1

Which vitamins are water-soluble?

Answer 1

• The 8 B Vitamins (B1, B2, B3, B5, B6, B7, B9 & B12)
• Vitamin C

Question 2

What are the properties of Water soluble vitamins?

Answer 2

• 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]

Question 3

What are the common symptoms of B vitamin deficiency?

Answer 3

• Dermatitis
• Diarrhoea
• Cheilitis (skin breakdown at corners of lips)
• Glossitis (swelling/redness of tongue)

Question 4

What are the properties of Vitamin B1?

Answer 4

• Called “Thiamine”
• Converted to active form -> THIAMINE PYROPHOSPHATE (TPP)

Question 5

Vitamin B1 is a co-factor for which enzymes?

Answer 5

• Pyruvate dehydrogenase
• a-ketoglutarate dehydrogenase (TCA)
• a-ketoacid dehydrogenase (branched-chain amino acids)
• Transketolase

Question 6

What are the Symptoms of Thiamine deficiency?

Answer 6

• Loss of muscle coordination
• Inability to form new memories
• Memory loss
• Double vision
• Hallucinations
• Confabulation (false memories)
• Confusion
• Abnormal eye movement

Question 7

What are the two syndromes that Thiamine deficiency causes?

Answer 7

• Beriberi
• Wernicke-Korsakoff syndrome

Question 8

Describe Beriberi syndrome

Answer 8

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

Question 9

Describe Wernicke-Korsakoff syndrome

Answer 9

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)

Question 10

What is the clinical correlation of Thiamine deficiency?

Answer 10

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

Question 11

What are the properties of Vitamin B2?

Answer 11

• also called “Riboflavin”
• Component of flavins FAD & FMN (used as cofactors in redox reactions)

Question 12

Describe Riboflavin deficiency

Answer 12

A very rare condition

SYMPTOMS:
- Dermatitis
- Glossitis (“magenta” tongue)
- Cheilitis (inflammation of lips)
- Corneal neovascularisation (rare & cause blindness)

Question 13

What are the properties of Vitamin B3?

Answer 13

• 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

Question 14

Vitamin B3 “Niacin” can be used as a treatment for which disease?

Answer 14

Hyperlipidemia

Question 15

Describe Niacin deficiency

Answer 15

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

Question 16

Describe Niacin excess

Answer 16

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

Question 17

Describe Vitamin B5

Answer 17

• also called “Pantothenic acid”
• Used in COENZYME A synthesis
• Deficiency is very rare

NEUROLOGICAL SYMPTOMS:
PARESTHESIAS (burning feet) and numbness

Question 18

What is Vitamin B6 also called?

Answer 18

Pyridoxine or Pyridoxal phosphate

Question 19

Vitamin B6 is a Cofactor for which biochemical reactions?

Answer 19

• Aminotransferases (ALT, AST)
• Histamine synthesis
• Niacin synthesis
• Heme synthesis
• Neurotransmitter synthesis

Question 20

Describe Pyridoxine deficiency

Answer 20

• ISONIAZID (Tuberculosis medications) can induce pyridoxine deficiency
• Forms an inactive form of vitamin B6
• B6 should be supplemented when prescribing isoniazid

Question 21

Describe Vitamin B7

Answer 21

• 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

Question 22

Which carboxylase enzymes is Vitamin B7 a cofactor for?

Answer 22

• Pyruvate carboxylase
• Acetyl-CoA carboxylase
• Propionyl-CoA carboxylase

Question 23

Describe Vitamin C

Answer 23

• 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)

Question 24

What is Scurvy?

Answer 24

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

Question 25

Describe Vitamin C excess

Answer 25

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)