Thiamin Deficiency and Wernicke-Korsakoff Syndrome
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Questions and Answers

What is the main reason why alcoholics suffer from many B vitamin deficiencies?

  • GI tract malfunctions
  • Inadequate energy intake
  • Inadequate levels of vitamins and other nutrients
  • Adequate energy intake but as 'empty calories' from alcohol (correct)

    • What is the function of Riboflavin (B2)?

  • Needed for vitamin D production
  • Essential for amino acid metabolism
  • Required for haem synthesis
  • Involved in redox reactions as FAD and FMN (correct)

    • What is the main source of niacin?

  • High protein diets
  • Cereals, with low bioavailability (correct)
  • Fruits and vegetables
  • Cereals, with high bioavailability

    • What is the active form of Pyridoxine (B6)?

    <p>Pyridoxal phosphate</p> Signup and view all the answers

    What is the commonest cause of Pyridoxine (B6) deficiency?

    <p>Presence of antagonistics</p> Signup and view all the answers

    What is the primary function of Niacin?

    <p>Involved in redox reactions as NAD and NADP</p> Signup and view all the answers

    What is the condition caused by Niacin deficiency?

    <p>Pellagra</p> Signup and view all the answers

    Why are patients given Pyridoxine (B6) supplements during Isoniazid treatment?

    <p>To prevent Pyridoxine deficiency</p> Signup and view all the answers

    What is the primary function of Vitamin B12 in mammalian metabolism?

    <p>Transfer of methyl groups</p> Signup and view all the answers

    What is the recommended daily intake of Vitamin B12?

    <p>1 μg/day</p> Signup and view all the answers

    What is the primary source of thiamin deficiency in the West?

    <p>Alcoholism</p> Signup and view all the answers

    What is the recommended daily intake of thiamin for a male?

    <p>1.4 mg / day</p> Signup and view all the answers

    What is the active form of Folate?

    <p>Tetrahydrofolate</p> Signup and view all the answers

    What is the consequence of thiamin deficiency in muscles?

    <p>Accumulation of lactate</p> Signup and view all the answers

    What is the primary source of Vitamin B12?

    <p>Animal tissues</p> Signup and view all the answers

    Which of the following is a characteristic of wet beri-beri?

    <p>Congestive heart failure, enlarged heart, and liver</p> Signup and view all the answers

    What is the role of Intrinsic Factor in B12 absorption?

    <p>Binding of B12 for absorption</p> Signup and view all the answers

    What is the recommended daily intake of Folate?

    <p>50 μg/day</p> Signup and view all the answers

    What is the principal feature of Korsakoff's psychosis?

    <p>Loss of memory of recent events</p> Signup and view all the answers

    What is the role of thiamin in the body?

    <p>Acts as a coenzyme</p> Signup and view all the answers

    What is the consequence of Vitamin B12 deficiency?

    <p>Pernicious anemia</p> Signup and view all the answers

    What is the relationship between thiamin requirement and carbohydrate intake?

    <p>Thiamin requirement increases with high carbohydrate intake</p> Signup and view all the answers

    What is the primary function of Folate in metabolism?

    <p>1-C transfer reactions</p> Signup and view all the answers

    What is the name of the complex involved in the biochemical role of thiamin?

    <p>Pyruvate dehydrogenase complex</p> Signup and view all the answers

    Which of the following conditions is most commonly associated with malabsorption of B12?

    <p>Crohn's disease</p> Signup and view all the answers

    What is the estimated reduction in the incidence of neural tube defects in women who take folic acid supplements around conception time?

    <p>72%</p> Signup and view all the answers

    What is the term used to describe elevated levels of homocysteine in the blood?

    <p>Hyperhomocysteinaemia</p> Signup and view all the answers

    What is the estimated rate of brain shrinkage per year in elderly people with mild memory problems who take high-dose B vitamin supplements?

    <p>0.76%</p> Signup and view all the answers

    Which of the following is a common cause of B12 deficiency?

    <p>All of the above</p> Signup and view all the answers

    What is the purpose of prescribing folic acid supplements to pregnant women in the UK?

    <p>To prevent neural tube defects</p> Signup and view all the answers

    Which of the following vitamins is NOT associated with a reduced risk of cardiovascular disease?

    <p>B1</p> Signup and view all the answers

    What is the term used to describe the birth defects that can be prevented by folic acid supplementation?

    <p>Neural tube defects</p> Signup and view all the answers

    Which of the following reactions is dependent on vitamin B12?

    <p>Conversion of homocysteine to methionine</p> Signup and view all the answers

    What is the consequence of a B12 deficiency on the folate pool?

    <p>'Trapping' of THF in the Me THF form</p> Signup and view all the answers

    What is the primary mechanism by which methotrexate acts as a chemotherapeutic agent?

    <p>Inhibition of DHF reductase</p> Signup and view all the answers

    What is the characteristic feature of megaloblastosis in terms of DNA synthesis?

    <p>Decreased thymidylate synthesis</p> Signup and view all the answers

    What is the primary neurological symptom of B12 deficiency?

    <p>Numbness and tingling in the hands and feet</p> Signup and view all the answers

    Which of the following is a consequence of B12 deficiency on the haematopoietic system?

    <p>Haemopoietic cells die in the bone marrow without completing the cell cycle</p> Signup and view all the answers

    What is the role of tetrahydrofolate in cellular metabolism?

    <p>Donor of a methyl group in the synthesis of thymidylate</p> Signup and view all the answers

    What is the primary function of methionine synthetase in the context of B12 deficiency?

    <p>Conversion of homocysteine to methionine</p> Signup and view all the answers

    Study Notes

    Thiamin (Vitamin B1)

    • Deficiency still present in Thailand, the Philippines, India, and some areas in Japan, particularly in infantile beri-beri.
    • In the West, the main manifestation of thiamin deficiency is Wernicke-Korsakoff syndrome, mainly associated with alcoholism.
    • In the USA, alcohol-related thiamin deficiency is the 5th commonest cause of dementia.
    • Good sources of thiamin: whole grain, pork, poultry, fish, vegetables, and dairy produce.
    • Foodstuffs deficient in thiamin: polished rice, sugar, fat, and refined and processed foods.
    • Recommended daily intake: 1.4 mg/day (male) and 1.0 mg/day (female).
    • Requirement increases with high carbohydrate intake.
    • Thiaminases (raw fish) and anti-thiamin factors (coffee, tea) can reduce thiamin availability.

    Biochemical Role of Thiamin

    • Thiamin is converted to thiamin pyrophosphate (TPP), which acts as a coenzyme in pyruvate dehydrogenase complex.
    • Deficiency leads to lactate accumulation in muscles.

    Presentation of Thiamin Deficiency

    • Beri-beri:
      • Infantile beri-beri: sudden onset, cardiovascular symptoms.
      • Acute cardiac beri-beri: congestive heart failure, enlarged heart, liver, and engorged neck veins.
      • Chronic dry beri-beri: symmetrical ascending peripheral neuropathy, weakness, numbness, ataxic gait, and painful extremities.
    • Wernicke-Korsakoff syndrome:
      • Wernicke's encephalopathy: confusion, ataxia, polyneuropathy, and disorientation in space and time.
      • Korsakoff's psychosis: loss of memory of recent events.

    Other B Vitamins

    Riboflavin (B2)

    • UV sensitive, mainly found in milk, and associated with protein.
    • Function: as FAD and FMN in redox reactions.
    • Deficiency: rare, except in alcoholics, with symptoms of cheilosis, angular stomatitis, and cataracts.
    • Not toxic in excess.

    Niacin (Vitamin B3)

    • Viatmers: nicotinic acid and nicotinamide.
    • Function: as NAD and NADP in redox reactions.
    • Sources: cereals, with low bioavailability, and high protein diets that can form niacin from tryptophan.
    • Deficiency: Pellagra, with symptoms of dermatitis, diarrhoea, and dementia.

    Pyridoxine (Vitamin B6)

    • Viatmers: pyridoxine, pyridoxamine, and pyridoxal.
    • Function: as pyridoxal phosphate, essential for amino acid metabolism and haem synthesis.
    • Deficiency: common, secondary, caused by the presence of antagonists, and can be treated with supplements.

    Folate and Vitamin B12

    • Function: as carriers of 1C units and methyl groups in mammalian metabolism.
    • Active forms: tetrahydrofolate and pyridoxal phosphate.
    • Deficiency: megaloblastosis, with symptoms of anaemia, numbness, tingling, and loss of position sense.
    • Causes of deficiency: inadequate intake, inadequate absorption, and certain diseases or medications.

    Methotrexate

    • Used in chemotherapy, as an immunosuppressant in autoimmune diseases, and in ectopic pregnancies.
    • Mechanism: inhibits dihydrofolate reductase, reducing folate availability.

    Folate and Neural Tube Defects

    • Supplementation with folic acid around conception time can prevent neural tube defects in women who have had a previous affected pregnancy.
    • In the UK, all pregnant women attending ante-natal clinics are prescribed folate supplements.

    Folate, B6, and B12 and Cardiovascular Mortality

    • Hyperhomocysteinaemia may be linked to cardiovascular disease, but it is unclear whether it is a cause or a link.

    Folate, B6, and B12 and Alzheimer's Disease

    • High doses of B vitamins may halve the rate of brain shrinkage in elderly people with mild memory problems.

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    Description

    This quiz covers the manifestations of thiamin deficiency, including Wernicke-Korsakoff syndrome, its prevalence in different countries, and good sources of thiamin. It also explores its association with alcoholism and dementia.

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