2. THIAMINE (Vitamin B1)
• Also called as Antiberiberi factor, antineuritic
vitamin.
• It is involved in carbohydrate, fat , aminoacid
and alcohol metabolism.
• Free thiamine is a basic substance and
contains
(a) a pyrimidine, and
(b)a thiazole ring.
• It contains sulphur(sulphur containing
vitamin).
3. • The active coenzyme form of thiamin, vitamin
B1, is thiamin pyrophosphate (TPP) . It is
formed by addition of two phosphate groups,
by thiamine pyrophosphate transferase.
4.
5. THIAMINE (Vitamin B1)
Sources
• Aleurone layer of cereals (food grains) is a rich
source of thiamine. Therefore, whole wheat
flour and unpolished hand pound rice have
better nutritive value than completely polished
refined foods.
• Liver, meat and eggs supply considerable
amounts. Ham/pork meats are particularly rich.
6. Biosynthesis :
• Synthesized by plants, yeasts and bacteria.
• Not synthesized by human beings, hence
should be supplied in diet.
• Intestinal bacterial flora can synthesize the
vitamin.
• There can be a substantial loss of thiamine in
cooking above 100degrees.
7. Absorption
• Free thiamine is absorbed readily from the
small intestine.
• Bulk of the dietary vegetable thiamine is in the
“free” form. In tissues, it is actively
phosphorylated to form Thiamine
pyrophosphate (TPP) in Liver, and to a lesser
extent in other tissues like muscle, brain and
RBC Cells.
8. Storage
• Capacity to store is limited.
• It is present in both free and combined forms
in heart (highest concentration), Liver and
kidneys.
• In lower concentration in skeletal muscle and
brain.
• Total amount of Thiamine in body is approx.
25 mg.
9. Recommended Daily Allowance of
Thiamine
• It depends on calorie intake (0.5 mg/1,000
calories).
• Requirement is 1.5–2 mg/day.
• Actual requirement is related more directly to
carbohydrates content of diet than to calorie
value of diet.
10. Requirements Increases in
• Anoxia-shock and hemorrhage, Serious illness
and injury, During prolonged administration of
broad-spectrum oral antibiotics, Increased
calorie expenditure like fever,
hyperthyroidism, Increased carbohydrate
intake, Increased alcohol intake, and
pregnancy and in lactation.
11. Metabolic Role of Thiamine
• Pyruvate dehydrogenase: The coenzyme form
is thiamine pyrophosphate (TPP). It is used in
oxidative decarboxylation of alpha-keto acids,
e.g. pyruvate dehydrogenase catalyzes the
breakdown of pyruvate, to acetyl-CoA, and
carbon dioxide.
12. • Alpha-ketoglutarate dehydrogenase: requires
TPP is the oxidative decarboxylation of alpha-
ketoglutarate to succinyl- CoA and CO2.
α-ketoglutarate succinyl- CoA + CO2
14. • B1 is also required in amino acid Tryptophan
metabolism for the activity of the enzyme
Tryptophan pyrrolase.
• Also acts as a coenzyme for mitochondrial
branched-chain α-ketoacid decarboxylase which
catalyzes oxidative decarboxylations of branched-
chain α-ketoacids formed in the catabolism of
valine, Leucine and Iso-leucine.
• The main role of thiamine (TPP) is in carbohydrate
metabolism. So, the requirement of thiamine is
increased along with higher intake of carbohydrates
15. Deficiency Manifestations of Thiamine
• The deficiency of thiamine produces a
condition called beriberi. It is characterized by
the following manifestations
• CV manifestations: These include palpitation,
dyspnea, cardiac hypertrophy and dilatation,
which may progress to congestive cardiac
failure.
16. • Neurological manifestations: These are
predominantly those of ascending,
symmetrical, peripheral polyneuritis.
• These neurological features may be
accompanied occasionally by an acute
polyencephalitis which is then called as
Wernicke’s encephalopathy. Carl Wernicke in
1894 and Sergiei Sergievich Korsakoff in 1887
described the condition.
17.
18. • Clinical features are those of encephalopathy
(ophthalmoplegia, nystagmus, cerebellar
ataxia) plus psychosis. It is seen only when the
nutritional status is severely affected.
• GI symptoms: Amongst these, anorexia is an
early symptom. There may be gastric atony,
with diminished gastric motility and nausea;
fever and vomiting occur in advanced stages.
19. Types of beri beri
• Dry beriberi: Central nervous system (CNS)
manifestations are the major features.
Peripheral neuritis with sensory disturbance
leads to complete paralysis. It is not
associated with edema.
• Wet beriberi: Here cardiovascular
manifestations are prominent. Edema of legs,
face, trunk and serous cavities are the main
features.
20.
21. • Infantile beriberi: It occurs in infants born to
mothers suffering from thiamine deficiency.
Restlessness and sleeplessness are observed.
Absence of deep tendon reflexes.
• Thiamine deficiency is manifested as
horizontal ridges in nails.
22. • Polyneuritis: It is common in chronic
alcoholics.
• Alcohol inhibits intestinal absorption of
thiamine, leading to thiamine deficiency.
• Thiamine deficiency in alcoholism may cause
impairment of conversion of pyruvate to
acetyl CoA. The result is increased plasma
concentration of pyruvate and lactate, leading
to lactic acidosis.
23. Causes for Thiamine deficiency
Due to Increased consumption
• Carbohydrate rich diet
• Pregnancy
• Fever
• Hyperthyroidsm
• Lactation
24. Due to Increased depletion
• Diarrhoea
• Diuretics therapy
• Dialysis
• Hyperemesis gravidarum
25. Due to decreased absorption
• Chronic gastric inflammation
• Alcoholism
• Malabsorption syndrome
• Gastric bypass surgery
26. Biochemical features in thiamine
deficiency
• Decreased level of thiamine and carboxylase
TPP in blood and urine.
• Accumulation of pentose sugars in RB cells
due to retardation of transketolation reaction.
• Increased level of pyruvic acid and lactic acid
in blood,due to retardation of oxidative
decarboxylation of pyruvic acid.
28. Treatment of thiamine deficiency
• Supplemental thiamine
• Mild neuropathy – 10-20mg/day for 2 weeks.
• Moderate /severe neuropathy – 20-30mg/day
treatment should be continued after few
weeks of disappearance of symptoms.
• In cases of edema and congestion in cardiac
beri beri – 100 mg iv OD.
29. Prognosis of Beri beri
• Usually good unless in cases progressed to
koroskoff syndrome. In such cases damage is
minimally irreversible.
