Vitamins MUDr. Miroslava Hlaváčová, PhD. Department of Biochemistry, Faculty of Medicine, MU History •Casimir Funk – in 1912 first introduced the word "vitamine" derived from words vital and amine •later the final "e" was dropped • Definition •Vitamins are low molecular weight organic compounds with different chemical properties, that human body cannot synthetize and in low quantities are necessary for many biochemical and physiological functions. • •They belongs to essential nutrients together with nutrients of energetic metabolism (for example linoleic acid), essential amino acids, minerals and trace elements. Characteristics •solubility – basic dividing characteristic •stable when in crystal powder •less stable in water solutions (risk of oxidation) •pH (acidic pH OK, alkaline not - acidification) •temperature •oxygen (reducing agents) •UV radiation (vit. A, B2), light (flavonoids) •metal ions (chelating agents) Determination •microbiological tests – obsolent, incubation of sample extract with microbe dependent on vitamin •chemical methods without separation – mostly analyses of food and pharmaceutical samples, not biological ones (too many interferences), these methods use physical and chemical chracteristic of vitamins Determination II. •separative methods – most often used, mostly HPLC with different types of detection, or in combination with mass spectrometry; they enable also detection of isomers •enzymatic methods – activity of vitamin-dependent enzyme is determined Determination III. •immunochemical methods – they use specific antibodies; simple; main problem are cross reactions • • •preparation of sample – protection before and during transport (see p. 4), concentration and purification of a sample RDA* Recommended dietary allowance of vitamins Vitamin Unit Quantity B1 mg 1,1 B2 mg 1,4 B3 mg 16 B5 mg 6 B6 mg 1,4 B9 μg 200 B12 μg 2,5 Vitamin C mg 80 Biotin μg 50 A μg 800 D μg 10 (=400 IU) E mg 12 K μg 75 *valid for healthy people between 23-50 years, non-pregnant women, also sex-related charts exist Classes of vitamines water-soluble vitamins fat-soluble vitamins B1 thiamine A retinoids B2 riboflavin D1, 2, 3 B3 niacin (vitamin PP) E tocopherols B5 pantothenic acid K1, 2, 3, B6 pyridoxine B7 biotin (vitamin H) B9 folic acid/folate B12 cobalamin C ascorbic acid water-soluble vitamins fat-soluble vitamins Absorption easy* with lipids (+ bile salts) Transport proteins no* yes Storage no* yes Excretion yes no Deficit arise quickly* after depletion of reserves Toxicity rare possible hypervitaminosis Therapy of deficit regular intake single high dose possible Comparison of vitamin classes *except vitamin B12 Disorders •hypervitaminosis – especially vitamins A and D •hypovitaminosis – inappropriate intake –deficit in food –malabsorption –increased need •avitaminosis – severe stage of deficit Water-soluble vitamins Vitamin B1 - thiamine •active form is thiamine pyrophosphate (cofactor of enzymes) •functions: –oxidative decarboxylation of 2-oxoacids in citrate cycle (pyruvate, α-ketoglutarate) –cofactor of transketolase in pentose phosphate pathway (PNS, CNS, cardiomyocytes, erythrocytes) –stimulation of neutrophils a leukocytes •sources – yeast, bran, liver, oatmeal, natural rice, nuts, buckwheat, sprouted grains •alcohol inhibits active transport into enterocytes!!! (passive is functioning, but is able from dose 5mg/day, (RDA 1.1mg)) Deficit of thiamine •beriberi (means fatigue or weakness) –first signs: anorexia, dyspepsia, weakness, fatigue –"dry" form: affection of peripheral nerves, especially on lower limbs, paresthesia or anesthesia, paralysis –"wet" form: edema, dyspnea, hepatomegaly, tachycardia, heart failure, lactic acidosis (pyruvate is conversed to lactate) •Wernicke-Korsakoff syndrome –symptoms of beri beri + psychosis, ataxia, nystagmus, ophthalmoplegia •beware of parenteral nutrition!! (acidosis non-reacting on alkalization) Vitamin B2 - riboflavin •part of cofactors FAD and FMN •functions: –transport of electrons in respiratory chain –redox reactions of AA, saccharides, purines –integrity of cell membrane –cofactor of glutathione reductase (antioxidative effect) –detoxification of drugs and xenobiotics •sources – cheese, eggs, meat, broccoli, parsley, yeast, milk, whole wheat products Deficit of riboflavin •syndrome resulting from isolated deficit is not known, symptoms result mostly from malnutrition and deficit of all vitamin B complex •inflammation of conjunctiva and cornea, neural disorders, angular cheilitis, glossitis •possible influence on decreased immune function •avitaminosis – deprivation of growth http://healthh.com/cheilosis/ Vitamin B3 - niacin •part of cofactors NAD+ a NADP+, in humans partially synthetized from tryptophan (provitamin) •functions: –cofactor of at least 200 of enzymes involved in redox reactions, citric acid cycle, synthesis and β-oxidation of FA –vasodilatation –reduction of total cholesterol and LDL (inhibits flow of free FA from adipose tissue) –replication and reparation of DNA, apoptosis •sources – meat, liver, tuna fish, sunflower seeds, peanuts, beans, yeast, lower amount in cereals Deficit of niacin •deficit occurs when the diet is deficient in niacin AND ALSO tryptophan •deficit of vitamins B1, B2, B6, copper, iron and magnesium worsen the conversion of tryptophan to niacin •pellagra – „three D disease“ –dermatitis (rush occurs predominantly on areas exposed to sun, typical is so called Casal‘s collar) –diarrhoe –dementia, irritability, later disorientation and hallucinations –others – smooth beefy red glossitis, neuritis, ataxia, convulsions Obsah obrázku košile Popis byl vytvořen automaticky from Color Atlas of Internal Medicine by Richard P. Usatine (Author), Gary Ferenchick (Author), Mindy Ann Smith (Author), E. J. Mayeux Jr. (Author), Heidi Chumley (Author) Hypervitaminosis of niacin? •it is possible after prolonged intake of higher doses than RDA (e.g. in diabetic patients is niacin used for increase in glucose tolerance and improving of metabolism of saccharides and lipids) •vasodilatation (headache, nausea, vomiting) •hepatitis, even fulminant liver failure •thrombocytopathy •myopathy Vitamin B5 – pantothenic acid •part of coenzyme A •functions: –essential for reactions in metabolism of lipids and saccharides, release of energy in lipids and saccharides –synthesis of hem, sterols and lipids –acetylation reactions, gluconeogenesis •sources – small quantities of pantothenic acid are found in nearly every food (pantos = everywhere), with high amounts in fortified whole-grain cereals, egg yolks, liver, partially synthetized by human microflora Deficit of pantothenic acid •very rare (famine, chronic alcoholics) •possible symptoms: –Burning Feet Syndrome (Grierson-Gopalan Syndrome) –impaired hearing, fatigue, depression, insomnia –impaired wound healing and transplant recovery –impaired immune system, disposition to infections • •despite the fact, that normal varied diet is rich in pantothenic acid, it‘s still favourite dietary supplement Vitamin B6 – pyridoxine •active form is cofactor pyridoxal phosphate •function: –cofactor of at least 100 of enzymes –decarboxylation, transamination, deamination of AA –metabolism of lipids, methionine and cysteine –gluconeogenesis, glycogenolysis –synthesis of DNA, hem, niacin, neurotransmitters, myelin, taurine •sources – yeast, sprouted grains, whole wheat bread, bananas, nuts and seeds, buckwheat, bran, meat Deficit of pyridoxine •neurological symptoms (lack of serotonin, adrenaline, noradrenaline, GABA), neuritis (disorders of myelin) •hypochromic sideroblastic anemia •hyperhomocysteinemia •inflammations of eye and mouth corners, follicular hyperkeratosis •developmental anomalies of apoenzymes coupled with pyridoxine leads in infants to mental retardation, bone deformations, osteoporosis, thrombosis and vision disorders http://www.medyouth.com/2015/04/the-treatment-methods-to-remove.html Vitamin B7/H – biotin •cofactor of carboxylases •function: –reactions of acetyl-CoA, propionyl-CoA, pyruvate –FA synthesis –metabolism of PUFA, leucin, cholesterol –gluconeogenesis, catabolism of branched chain AAs –cell growth •sources – synthetized by microflora, egg yolk, liver, soya beans, chocolate, cereals, yeast, sea fish Deficit of biotin •very rare •possible symptoms: nausea, anorexia, vomiting, pale skin, muscle pain, dry skin, hair loss, increased concentration of cholesterol, bile pigments, depression Vitamin B9 – folic acid/folate •active form is tetrahydrofolate •functions: –synthesis of methionine (together with vitamin B12) –normal function of erythrocytes and leukocytes –synthesis of purines, DNA –conversion of homocysteine to methionine, serine to glycine –key role in growth, division and differentiation of cells –antitumor effect (colon) –prevention of neural-tube defects in embryos •sources – yeast, green leafy vegetables, nuts, organ meats, orange juice Deficit of folate •neural-tube defects in embryos, •hyperhomocysteinemia, increased rick of cardiovascular disorders •macrocytic anemia, thrombocytopenia •gastrointestinal disorders (inflammation and ulceration of mucosa, diarrhea, nausea) •depression and psychical instability Vitamin B12 – cobalamins •active forms are methyl cobalamin and adenosyl cobalamin •functions: –maturation of erythrocytes –cofactor of DNA/RNA synthesis –cell proliferation, hematopoiesis –synthesis of myelin a nucleoproteins –recycling of folate coenzymes •sources – meat, eggs, milk Deficit of cobalamin •has several stages (decreased plasmatic concentrations, decreased intracellular concentration, metabolic aberration and clinical manifestation) •megaloblastic and pernicious anemia, disorders in methionine, purine and pyrimidine metabolism, homocystinuria •impaired myelin synthesis cause combined degeneration of sensory and motoric neurons → paresthesia, proprioception disorders, impaired body balance, confusion, impaired memory, depression •high doses of folate can cover the signs of deficit in cardiovascular system, but not in nervous system Vitamin C – ascorbic acid •function: –synthesis of collagen, formation of osteoid, synthesis of connective tissue‘s proteins –electron transporter in redox reactions –hydroxylation reactions (steroid hormones, adrenaline, 5-hydroxytryptophan) –antioxidant –metabolism of histamine, carnitine, cholesterol, bile acids –increase the resorption of iron (also part of iron dietary supplements) –phagocytosis of leukocytes, immunity •sources – citrus fruits, pepper, potatoes, rose hips, black currant, horseradish, strawberries, Deficit of ascorbic acid •fatigue, weakness, muscle pain •anorexia, increased disposition to infections, depression •impaired wound healing, anemia, hemorrhage, petechiae, hemarthrosis •fragile and swollen gums, teeth loss • • •beware of high doses!! (urolithiasis, interference with several biochemical urine tests, e.g. determination of glucose or blood in urine) Fat-soluble vitamins Vitamin A •terminology and conversions –active form of vitamin A is only in animal tissues, in plant tissue is as a provitamin A - β-carotene –vitamin A has several trans/cis isomers (A1, A2,...) –all molecules with vitamin A activity have common name retinoids: •retinol, retinal, retinoic acid –conversion between retinol and retinal is reversible, conversion of retinal to retinoic acid is irreversible Vitamin A •functions: –process of vision (retinal) –important factor in gene expression, reproduction and embryogenesis, proliferation, differentiation and apoptosis (RAR and RXR receptor, retinoic acid) –lipoprotein and immunologic integrity, stability of lysosomes –potential antioxidant function (carotenoids are probably more potent) –necessary for correct function of skin and epithelium •sources – liver, dairy products, oily fish, egg yolk (absorbed as a retinol) •sources of carotenoids – yellow and orange vegetables and fruit, green leafy vegetables •storage suffices under physiological conditions for 2 years Deficit of retinol •night blindness, xeropthalmia (inflammations of eyelid and conjunctiva, keratomalacia – softening of cornea with overgrowing of vessels – risk of loss of the vision) •xeroderma, follicular hyperkeratosis and keratinization of epithelium in respiratory, gastrointestinal and urinary system, increased risk of infections •disturbed immunity (potential antitumor effect) Hypervitaminosis •potential toxicity after administration of 20 times higher doses in kids or 100 times higher doses in adults •teratogenic effect (abortions, developmental anomalies) •high intake of carotenoids is not toxic •manifestation: alopecia, anemia, dermatitis, hepatomegaly, insomnia, hyperlipidemia, vomiting Vitamin D •D2 – ergocalciferol (plant origin) •D3 – cholecalciferol (formed in skin from precursor) •functions: –regulation of calcium and phosphate metabolism (more in following lecture) –not fully understood function in immune system – •sources – sunlight (15 min./day), oily fish, egg yolk, liver, milk, butter Deficit of vitamin D •tooth decay, bone deformities, rachitis, osteomalacia •substitution therapy –prophylaxis: 400 IU –deficit: 1000 IU –rachitis and osteomalacia: 5000 IU –involutional osteoporosis: thousands of IU Hypervitaminosis •cause is usually excessive substitution, not sunbathing (formation of D3 in skin is regulated) •manifestation: permanent thirst, skin itching, diarrhea and vomiting, calcification of vessels and kidneys Vitamin E – tocopherols •8 natural tocopherols, α-tocopherol has the highest biological activity •functions: –intracellular antioxidant, mostly of PUFA in membranes (nerves, erythrocytes, LDL) –synergic effect with selenium against lipoperoxidation –inhibits mutagens in digestive system –recently confirmed function in signaling pathways •sources – sprouted grains, poppy seeds, nuts, egg yolk, vegetable oils Deficit of vitamin E •decrease life span of erythrocytes, even hemolytic anemia •functional defects of peripheral nerves •increased cell death because of membrane damage (lipoperoxidation) •long term deficit – myopathies or muscle necrosis, retinopathies, liver necrosis Hypervitaminosis •dyspepsia, fatigue, headache, muscle fatigue •can cause developmental anomalies Vitamin K •functions: –vitamin K is essential factor of posttranslational carboxylation of glutamate to γ-carboyxyglutamate (coagulation factors II, VII, IX, X, protein C, osteocalcin) –antidote for warfarin overdose (administered with heparin) •sources – vegetables (especially green leafy vegetables), vegetable oils, cheese, yoghurts Deficit of vitamin K •rare, risk group are infants (vitamin K cannot pass through placenta and breast milk also contains low levels of it) and patients with lipid malabsorption •petechiae, disposition towards bleedings and hematomas Hypervitaminosis •risk group are premature babies (substitution needed, but dosing must be watched) •hemolysis, hyperbilirubinemia, kernicterus, brain damage Thank for your attention.