This document discusses vitamin B1 (thiamine). It notes that thiamine is a water-soluble vitamin that acts as a coenzyme involved in carbohydrate metabolism. The key points are:
- Thiamine's coenzyme, thiamine pyrophosphate, facilitates the conversion of pyruvate to acetyl-CoA and links glycolysis to the TCA cycle.
- Deficiency can cause beriberi disease, characterized by neuropathy, edema, and heart failure.
- Good dietary sources include cereals, legumes, nuts and meat. Cooking can reduce thiamine levels in foods.
2. Vitamin B1- Thiamine
๏ Thiamine (anti-beri-beri or antineuritic vitamin) is
water soluble.
๏ It has a specific coenzyme, thiamine
pyrophosphate (TPP) which is mostly
associated with carbohydrate metabolism
๏ Thiamine contains a pyrimidine ring and a
thiazole ring held by a methylene bridge
๏ Thiamine is the only natural compound with
thiazole ring
3. ๏ The alcohol (OH) group of thiamine is esterfied
with phosphate (2 moles) to form the coenzyme,
thiamine pyrophosphate
๏ The pyrophosphate moiety is donated by ATP
and the reaction is catalysed by the enzyme
thiamine pyrophosphate transferasee (TPP or
cocarboxylase).
๏ Thiamine is a sulfur containing water soluble
vitamin
5. ๏ Thiamine: thiamine is carried by the portal blood
to the liver, present as free thiamine
๏ Storage:
๏ Mainly stored in skeletal muscle and also
present in the significant amount of liver , heart,
kidney, erythrocytes and nervous system.
๏ Co enzyme : TPP
6. BIOCHEMICAL FUNCTIONS
๏ The coenzyme , thiamine pyrophosphate or
cocarboxylase is intimately connected with the
energy releasing reactions in the carbohydrate
metabolism.
๏ Pyruvate dehydrogenase complex:
๏ Its catalyses the irreversible conversion of
pyruvate to acetyl coA.
๏ Its essential for complete oxidation of glucose
๏ Its links glycolysis and TCA cycle
8. RECOMMENDED DIETARY
ALLOWANCE
๏ The daily requirement of thiamine depends on
the intake of carbohydrate.
๏ A dietary supply of 1-1.5 mg/day is
recommended for adults (about 0.5 mg/1,000
Cals of energy ).
๏ For children RDA is 0.7-1.2 mg/day
๏ The requirement marginally increase in
pregnancy and lactation (2 mg/day ),old age and
alcoholism.
9. DIETARY SOURCES
๏ Cereals , pulses , oil seeds , nuts and yeast are
good sources
๏ Thamine is mostly concentrated in the outer layer
(bran) of cereals
๏ Polishing of rice removes about 80% of thiamine.
๏ Vitamin B1 is also present in animals food like
pork ,liver , heart, kidney, milk etc..
๏ In the parboiled (boiling of paddy with husk) and
milled rice ,thiamine is not lost in polishing
๏ Since thiamine is a water soluble vitamin, it is
extracted into the water during cooking process.
๏ Such water should not be discarded.
10. DEFICIENCY SYMPTOMS
๏ The deficiency of vitamin B1 results in a condition
called beri โberi
๏ Beri โberi is mostly seen in populations
consuming exclusively polished rice as staple
food .
๏ The early symptoms of thamine deficiency are
loss of appetite (anorexia)
weakness,conspitation,nausea,mental depression
,peripheral neuropathy, irritability etc..
๏ Numberness in the legs complaints of โ pins and
needles sensations are reported.
11.
12. BIOCHEMICAL CHANGES IN B1
DEFICIENCY
๏ Carbohydrate metabolism is impaired .Accumulation
of pyruvate occurs in the tissues which is harmful .
๏ Pyruvate concentration in plasma is elevated and it is
also excreted in urine.
๏ Normally pyruvate does not cross the blood-brain
barrier and enter the brain
๏ However , in thaimaine deficiency an alteration occurs
in the blood โbrain barrier permitting the pyruvate to
enter the brain directly
๏ It is believed that pyruvate accumulation in the brain
results in disturbed metabolism that may be
responsible for polyneuritis.
13.
14.
15. ๏ Thiamine deficiency leads to impairment in nerve
impulse transmission due to lack of TPP.
๏ The transketolase activity in erythrocytes is
decreased.
๏ Measurement of RBC transketolase activity or a
reliable diagnostic test to asses thiamaine
deficiency.
๏ In adults two types beri beri namely wet beri beri
and dry beri beri occur.
๏ Infantile beri-beri that differs from adult beri beri
is also seen
16. Wet beri -beri
๏ Breathlessness and palpitation and present
๏ The muscles are slightly swollen.
๏ The systolic blood pressure is elevated while
diastolic is decreased
๏ This is characterized by edema of legs ,face
,trunk ,and sources cavities
๏ Fast and bouncing pulse is observed
๏ The heart becomes weak and death may occur
due to heart failure.
17. Dry beri- beri
๏ This is associated with neurological
manifestations resulting in peripheral neuritis
๏ Edema is not commonly seen
๏ The muscles become progressively weak and
walking becomes difficult.
๏ The affected individuals depend on support to
walk and become bedridden, and may even die if
not treated.
๏ The symptoms of beri โberi are often mixed in
which case it is referred to as mixed beri-beri
18. INFANTILE BERI-BERI
๏ This is seen in infants born to mothers suffering
from thaimine deficiency.
๏ The breast milk of these mothers contains low
thaimine content .
๏ Infantile beri-beri is characterized by
sleeplessness ,restlessness ,vomiting
,convulsions and bouts of screaming that
resemble abdominal colic
๏ Most of these symptoms are due to cardiac
dilatation.
๏ Death may occur suddenly due to cardiac failure.
19.
20. WERNICKE-KORSAKOFF
SYNDROME
๏ This is a disorder mostly seen in chronic
alcoholics.
๏ The body demands of thiamine increase in
alcoholism.
๏ Insufficient intake or impaired intestinal
absorption of thiamine will lead to this syndrome.
๏ It is characterized by loss of memory ,apathy and
a rhythmical to and fro motion of the eye balls
21. THIAMINE DEFICIENCY DUE TO
THIAMINASE AND PYRITHAIMINE
๏ The enzyme thiaminase is present in certain sea
foods
๏ Their inclusion in the diet will destroy thiamine by
a cleavage action and lead to deficiency.
๏ Pyrithiamine, a structural analogue and an ant
metabolite of thiamine is found in certain plants
like ferns.
๏ Horses and cattle often develop thiamine
deficiency due to the overconsumption of the
plant fern.
