Thiamine (Vitamin B1) Flashcards
How can the Vitamin B group be divided?
Energy releasing: Thiamin, Riboflavin, Niacin, Pantothenic acid & Biotin
Hematopoietic: Folic Acid and B12
Vitamin with both & other functions: Pyridoxine
What is the coenzyme form of Thiamine?
Thiamine Pyrophosphate (TPP)
What are the roles of Thiamine?
- Coenzyme in carbohydrate metabolism: Required in (1) Conversion pyruvate to Acetyl CoA, (2) TCA cycle, (3) Pentose phosphate pathway
- Required for transmission of nerve impulse & normal functioning of nerves
- Involved in production of acetylcholine (neurotransmitter) and for myelin synthesis
Thiamine requirement is directly proportion to carbohydrate intake
Pyruvate & lactate will accumulate in case of Thiamine deficiency causing life threatening lactic acidosis in subjects with high carbohydrate diet
Thiamine sources
Aleurone layer of cereals
Whole grains, yeast, seeds, vegetables, egg and milk
What factors may cause thiamine to be destroyed?
Excessive cooking
RDA of thiamine
1 mg/day
What are the symptoms of thiamine deficiency?
Mild deficiency:
Irritability
Depression
Fatigue
Peripheral neuropathy
Anorexia
Dyspepsia
Weight loss
Severe deficiency:
Beri-beri
Wernicke-Korsakoff syndrome
What are the types of Beri-beri?
Dry Beri-beri
Wet Beri-beri
Infantile Beri-beri
What are the characteristics of dry beri-beri?
CNS manifestations are the major features
Atrophy of the muscles
Initial peripheral neuritis (loss of sensation in the feet) which may progress into complete paralysis
What are the characteristics of wet beri-beri?
Cardiovascular symptoms are prominent: (edema of face, legs, palpitation and if untreated, lead to heart failure)
Caused by intense vasodilatation from accumulation of pyruvate & lactate in blood and tissues
What are the characteristics of infantile beri-beri?
Seen in nursing infants whose mothers are deficient in thiamine
Characterised by tachycardia, vomiting, convulsions and death
Which group is predisposed to Wernicke-Korsakoff syndrome?
Alcoholics
Why are alcoholics predisposed to Wernicke-Korsakoff syndrome?
Alcohol requires thiamine for its metabolism
Some alcoholics may have thiamine deficiency due to inadequate intake and decreased thiamine absorption from the GIT due to alcohol
What are the signs and symptoms of Wernicke-Korsakoff syndrome?
Mental confusion
Memory loss
Ataxia (shaky movements & unsteady gait)
Uncoordinated eye movements
Lower level of consciousness
When do deficiency symtoms begin to arise?
More than 3 weeks of starvation
No real stores of thiamine in the body
