thiamine

Question 1

structure of thiamine

Answer 1

Thiamine consists of a pyrimidine ring attached to a
thiazole ring by a methylene bridge.

Question 2

Active Form of Thiamine

Answer 2

Thiamine pyrophosphate (TPP) is an active coenzyme
form of vitamin thiamine

Question 3

Sources

Answer 3

• present in all natural foods but particularly good
  dietary sources are unrefined cereals, meat, nuts,
  green vegetables, eggs, etc.
• White bread and polished rice are very poor sources
  of the vitamin thiamine.

Question 4

Functions of thiamine

Answer 4

• carbohydrate
  metabolism
• Thiamine pyrophosphate (TPP) is a coenzyme
  involved in enzymatic reactions mainly for
  oxidative decarboxylation and transketolase
  reactions as follows:
  1. TPP is a coenzyme for pyruvate dehydrogenase
  complex which catalyzes the conversion of pyruvate into acetyl CoA by oxidative decarboxylation. Acetyl-CoA is a precursor for the synthesis of the neurotransmitter acetylcholine
  and also for the synthesis of myelin. Thus, thiamine
  is required for the normal functioning of the
  nervous system.
  2. TPP is a coenzyme for α-ketoglutarate dehydrogenase which catalyzes the conversion of α -ketoglutarate to succinyl-CoA in TCA cycle
  3. TPP is a coenzyme for the enzyme transketolase,
  in the pentose phosphate pathway of glucose
  oxidation.

Question 5

Nutritional Requirements

Answer 5

daily
intake of 1.0 to 1.5 mg of thiamine for adults which
is increased with increased muscular activity, dietary
carbohydrates and in pregnancy and lactation.

Question 6

Deficiency Manifestations

Answer 6

The deficiency of vitamin B1 results in a condition
called beriberi. Deficiency of thiamine occurs in
population who consume exclusively polished rice
as staple food. Polishing of rice removes thiamine.

Question 7

types of beriberi

Answer 7

1. Dry beriberi
2. Wet beriberi
3. Infantile beriberi
4. cerebral beriberi (Wernicke-Korsakoff Syndrome)

Question 8

Dry beriberi (neuritic beriberi)

Answer 8

• It develops when the diet chronically contains
  slightly less than the thiamine requirements.
• This form of beriberi is characterized primarily by
  peripheral neuritis, severe muscular weakness and
  fatigue. Other symptoms of dry beriberi include dry
  skin, mental confusion and poor appetite.

Question 9

Wet beriberi (cardiac beriberi)

Answer 9

• It develops when the deficiency is more severe in
  which cardiovascular system is affected in addition
  to neurological symptoms.
• Wet beriberi is characterized primarily by edema of
  extremities, heart enlargement and cardiac insufficiency. Other symptoms include tachycardia or
  bradycardia and palpitation.
• Both forms of beriberi may overlap to a varying
  degree and patients of beriberi may die due to heart
  failure, if not treated.

Question 10

Infantile beriberi

Answer 10

• Infantile beriberi is observed in breast fed infants
  born to mother suffering from thiamine deficiency.
  The breast milk of these mothers is deficient in
  thiamine.
• It is characterized by cardiac dilation (enlargement
  of heart), tachycardia, convulsions, edema and GI
  disturbances such as vomiting, abdominal colic, etc.
  In acute condition, the infant may die due to cardiac
  failure.

Question 11

Wernicke-Korsakoff Syndrome

Answer 11

• It is also known as cerebral beriberi and mostly seen
  in alcoholics.
• In chronic alcoholics, the nutritional deficiencies
  result from either poor intake of food or malabsorption of nutrients from intestine.
• Wernicke-Korsakoff syndrome is characterized by
  anorexia, nausea, vomiting, nystagmus, depression,
  ataxia, loss of memory, mental confusion, peripheral
  paralysis, muscular weakness, etc.

Question 12

Antimetabolites of thiamine

Answer 12

Thiamine can be destroyed if the diet contains thiaminase. Thiaminase is present in raw fish and
seafood.

Question 13

Thiamine Assay

Answer 13

Whole blood or Erythrocyte transketolase (requiring TPP
as a coenzyme) activity is used as a measure of thiamine
deficiency.