Vitamins

1
Vitamins

• Frantiek Duka

2
Nomenclature

• Definition compound indispensable for metabolism
  (usually co-enzyme), which cannot be synthetized
  in the body
• Nomenclature
• is historical and therefore confusing
• according to order of discovery
• a letter covers whole group of compounds

3
Vitamins

• Water soluble
• indispensible for the intermediary metabolism
• anemia preventing
• vitamin C
• Lipid soluble A, D, E, K

4
Lipid-Soluble Vitamins

• Resorption from the gut is coupled with the
  absorption of fat
• Fat malabsorption (e.g. pancreatic insuficiency,
  xenical) can lead to vitamin deficiency
• Hypervitaminosis is possible due to poor
  water-solubility and slow renal excretion

5
Water-Soluble Vitamins

• Deficiencies can occure relatively quickly
  (except B12)
• Readily exreted by the kidney when surpassing the
  renal threshold - toxicity is rare

6
Vitamin A - Retinol

• ?-caroten yellow and green vegetable
• cleavage (6mg to 1mg)
• Retinol/-al/-ic acid liver, yolk, milk

7
(No Transcript)
8
Vitamin A - Functions

• Both ?-caroten and retinol are antioxidants
• Retinol-P as a glycosyl donor for the synthesis
  of glycoproteins and proteoglycans
• Steroid-hormone-like action
• Vision

9
Vitamin A - Deficiency and Toxicity

• Deficiency
• hyperkeratosis due to impaired epithelial
  regeneration and mucus sercetion
• imunity disturbancies and anemia
• night-blindness
• Toxicity !!! teratogenic!!!
• polar-bear liver eaters, otherwise uncommon

10
Vitamin D

• Is rather a hormone than a vitamin can be
  synthetized in the body from 7-dehydrocholesterol
  (UV light is recquired)
• Cholecalciferol - saltwater fish, liver, egg
• (liver)
• 25-hydroxycholecalciferol
• (kidney - PTH)
• 1,25-dihydroxycholecalciferol calcitriol

11
(No Transcript)
12
Vitamin D - Action

• Increase calcium absorbtion (calbinden expression
  in the enterocyte)
• Promotes bone resorbtion (with PTH)
• Inhibits Ca excretion by the kidney

13
Vitamin D - Deficiency and Toxicity

• Deficiency
• fat malabsorption, vegans, the eldery, renal
  failure (impaired 25-hydroxylation)
• rickets in children and osteomalacia in adults
  (soft bones due to impaierd mineralization of
  normal organic matrix)
• Toxicity
• hypercalcemia with hypercalciuria (!stones), bone
  demineralization

14
Vitamin E

• a mixture of tocopherols
• Function
• antioxidant O. scavenger
• possible role in the respiratory chain or heme
  synthesis
• helps to prevent atherosclerosis
• Deficiency and toxicity unknown

15
Tocopherol
16
Vitamin K
Frantiek Duka carboxylation of Glu residues to
gama-carboxyglutamic acid form a chelat-like
comp., indispensable for Ca binding

• A group of quinone derivates
• K1(phytylmetaquinone) from green veg.
• K2(multiprenylmenaquinone) syntethized by the
  intestinal bacteria
• Function
• recquired for the synthesis of clotting factors
  II., VII, IX and X.
• indispensable for osteocalcin synthesis (
  Ca-binding protein of the bone matrix)

17
Vitamin K
18
Vitamin K (cont.)

• Deficiency
• increase coagulation time (Quick test), i.e.
  increase the risk of hemorhage and decrease th
  risk of thrombosis
• newborns or long-term antibiotic treatment, fat
  malabsorbtion
• Vitamin K antagonists (Warfarine) are widely used
  as an anticoagulant drug.

19
Water-Soluble Vitamins

• Its useful to learn features common for whole
  group of vitamins!

20
Water-Soluble Vitamins

• 1. For energy metabolism
• B1, B2, B6 and niacin
• pantothenic acid and biotine
• 2. Hematopoetic vitamins
• Folic acid and B12
• 3. Vitamin C

21
Energy-Releasing Vitamins

• Are turned to co-enzymes of key reactions of
  energy metabolism
• Sources whole-grain cereals, meat, yolk, yeasts
• For B1, B2 and B6 is recommended daily dose 1 to
  2 mg for the normal adult.

22
Energy-Releasing Vitamins

• Deficiencies can appear in alcoholics
• otherwise rare extreme diets, the eldery,
  increased recquirements (pregnancy)
• Symptoms are derived from impaired energy
  metabolism
• rapidly growing tissues (cheilitis, dermatitis,
  diarhoea)
• peripheral and central nervous system
• malaise

23
Vitamin B1 (Thiamine)

• is a precursor for TDP co-enzyme of
• PDH and ?KG-DH (Krebs cycle)
• transketolase (pentose-P pathway)
• ? possible role in nerve transmission
• Recomended daily dose is dependent oncarbohydrate
  and alcohol intake
• Sources whole-grain cereals (incl. flour), yeast
  etc.
  

24
(No Transcript)
25
Thiamine deficiency

• In whom?
• alcoholics
• polished rice as a major source of energy
• Beri-beri impairment of nervous tissue, heart
  failure, muscle weakness

26
(No Transcript)
27
Vitamin B2 Riboflavine

• As a part of FMN and FAD
• Important for respiratory chain and various
  red-ox reactions
• Deficiency in alcoholics, impairment of the skin
  and mucous membranes

28
(No Transcript)
29
Niacin Nicotinic Acid

• a part of NADH NADPH molecules in the form of
  nicotinamid
• can be synthetized from tryptophan
• Deficiency pelagra 3Ds
• dermatitis
• diarhoea
• dementia

30
Vitamin B6 (Pyridoxin)

• Pyridoxin, pyridoxal, pyridoxamin are all turned
  to pyridoxalphosphate (PLP)
• Recquired for
• transamination
• other reactions (e.g. serotonin and catecholamine
  synthesis, ?-ALA synthesis, homocystein
  breakdown)
• Deficiency causes neurologic symtoms

31
(No Transcript)
32
Panthotenic Acid ? Biotin

• Panthotenic acid is a part of CoA
• used by more than 70 enzymes
• widespread in all food, deficiency not described
• Biotin is a co-enzyme of carboxylation
• pyruvatecarboxylase anaplerotic for Krebs cycle
  and gluconeogenesis
• AcCoA carboxylase FA syntesis

33
Hematopoetic vitamins

• The lack of B12 and/or folate causes macrocytic
  anemia.

34
Hematopoetic vitamins

• Both co-operate in one-carbon metabolism,
  recquired for
• purines and dTMP (i.e. nucleic acids)
• conversion of homocystein to Met
• other choline, Ser, Gly
• Deficiency leads to
• macrocytic anemia (impaired DNA synthesis)
• hyperhomocysteinemia (risk factor of
  atherosclerosis)

35
Folic Acid

• Absorbed and stored as polyglutamate
• reductase
• dihydroholate (FH2)
• reductase
• tetrahydrofolate (FH4)
• active form

36
(No Transcript)
37
Vitamin B12

• Cyanocobalamin