LECTURE 7 (Water-soluble vitamins) Flashcards

1
Q

Which vitamins are water-soluble?

A
  • The 8 B Vitamins (B1, B2, B3, B5, B6, B7, B9 & B12)
  • Vitamin C
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2
Q

What are the properties of Water soluble vitamins?

A
  • 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]
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3
Q

What are the common symptoms of B vitamin deficiency?

A
  • Dermatitis
  • Diarrhoea
  • Cheilitis (skin breakdown at corners of lips)
  • Glossitis (swelling/redness of tongue)
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4
Q

What are the properties of Vitamin B1?

A
  • Called “Thiamine”
  • Converted to active form -> THIAMINE PYROPHOSPHATE (TPP)
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5
Q

Vitamin B1 is a co-factor for which enzymes?

A
  • Pyruvate dehydrogenase
  • a-ketoglutarate dehydrogenase (TCA)
  • a-ketoacid dehydrogenase (branched-chain amino acids)
  • Transketolase
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6
Q

What are the Symptoms of Thiamine deficiency?

A
  • Loss of muscle coordination
  • Inability to form new memories
  • Memory loss
  • Double vision
  • Hallucinations
  • Confabulation (false memories)
  • Confusion
  • Abnormal eye movement
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7
Q

What are the two syndromes that Thiamine deficiency causes?

A
  • Beriberi
  • Wernicke-Korsakoff syndrome
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8
Q

Describe Beriberi syndrome

A

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

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9
Q

Describe Wernicke-Korsakoff syndrome

A

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)

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10
Q

What is the clinical correlation of Thiamine deficiency?

A

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

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11
Q

What are the properties of Vitamin B2?

A
  • also called “Riboflavin”
  • Component of flavins FAD & FMN (used as cofactors in redox reactions)
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12
Q

Describe Riboflavin deficiency

A

A very rare condition

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

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13
Q

What are the properties of Vitamin B3?

A
  • 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
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14
Q

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

A

Hyperlipidemia

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15
Q

Describe Niacin deficiency

A

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

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16
Q

Describe Niacin excess

A

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

17
Q

Describe Vitamin B5

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

NEUROLOGICAL SYMPTOMS:
PARESTHESIAS (burning feet) and numbness

18
Q

What is Vitamin B6 also called?

A

Pyridoxine or Pyridoxal phosphate

19
Q

Vitamin B6 is a Cofactor for which biochemical reactions?

A
  • Aminotransferases (ALT, AST)
  • Histamine synthesis
  • Niacin synthesis
  • Heme synthesis
  • Neurotransmitter synthesis
20
Q

Describe Pyridoxine deficiency

A
  • ISONIAZID (Tuberculosis medications) can induce pyridoxine deficiency
  • Forms an inactive form of vitamin B6
  • B6 should be supplemented when prescribing isoniazid
21
Q

Describe Vitamin B7

A
  • 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
22
Q

Which carboxylase enzymes is Vitamin B7 a cofactor for?

A
  • Pyruvate carboxylase
  • Acetyl-CoA carboxylase
  • Propionyl-CoA carboxylase
23
Q

Describe Vitamin C

A
  • 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)

24
Q

What is Scurvy?

A

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

25
Q

Describe Vitamin C excess

A

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)
26
Q
A