HUEC 3115 – Human Nutrition and Metabolism Water Soluble Vitamin Charts Vitamin CAscorbic AcidFunctionalFormL-isomer is the active form Humans are one of few mammals that cannot synthesizevitamin C because we lack gulonolactone oxidase. Absorption Occurs throughout the small intestines including the ileum, assisted via SVCT1 (high capacity) SVCT2 (low capacity). Both are sodium transporters. Absorption decreases with higher intakes. Maximal absorption 2g Dehydroascorbate (oxidized form of vitamin C) absorbedvia GLUT1 and GLUT3 and converted to ascorbic acid formTransportationTransported in the blood in the free form. Ascorbic acid uptake into body cells via SVCT1 and SVCT2. SVCT2 not present in skeletal muscle and lungs.FoodSourcesFruits and vegetables; citrus products Supplements: free ascorbic acidUsual intake 30-180mg/day and absorbed at 70-90% Functions Tyrosine synthesis and catabolism Neurotransmitter synthesis (Serotonin and Norepinephrine)Collagen synthesis Carnitine synthesis Microsomal metabolismAntioxidant activity by acting as a reducing agent Pro-oxidant activity (only at non-physiological conditions)Role inDiseasePrevention Cancer Cardiovascular Disease Eye Health – benefits against cataracts Interactionswith otherNutrients Enhances the absorption of nonheme iron RDA Men 90mgWomen 75mg Pregnancy 100mg Lactation 120mg Increased RDA for smokers Based on maximizing tissue concentration and minimizing urinary excretion Deficiency Scurvy – body pools below 300mg and plasma vitamin C below 0.2mg/dL Toxicity UL= 2g Excretion Excreted intact or oxidized to dehydroascorbic acid History Isolated in 1928 by Szent-Gyorgyi and King; Structure in 1HUEC 3115 – Human Nutrition and Metabolism Water Soluble Vitamin Charts 1932 by Haworth Vitamin B1Thiamin FunctionalForm Consists of a pyrimidine ring attached to a thiazole by a methylene bridge Found in plants in nonphosphorylated form (free form) Found in animals as thiamin diphosphate (TDP) aka thiamine pyrophosphate (TPP) Absorption Occurs in the jejunum as free thiamin. Absorption is bothactive and passive. Involves two carriers ThTr1 and ThTr2. Crosses the basolateral membrane into blood via hydrogen antiport TransportationTransported free, bound to albumin, or as TMP. Enters red blood cells via facilitated diffusion, but entering other cells requires energy. After absorption into portal blood it is taken up by the liver and converted to TDP inside of cells. FoodSources Widely available in foods, especially enriched grains. Sensitive to heat, oxygen, and low-acid conditions. Functions Energy transformation (oxidative decarboxylation of pyruvate) Synthesis of pentoses and NADPH Nerve conduction (noncoenzyme role) RDA 1.2mg Men 1.1 mg Women1.4 mg Pregnancy1.5 mg Lactation Deficiency Beriberi (impairment of the nerves and heart) Associated with alcoholism (decreased food consumption, liver damaged decreases TDP formation, and decreased absorption) Toxicity No UL High does used in treatment of maple syrup urine Excretion Excreted intact or catabolized History Isolated in 1912 by Funk; Structure by Williams in 1930. Discovered by chicken fed a diet of polished rice. Vitamin B2Riboflavin FunctionalForm FAD (Flavin adenine dinucleotide) is the coenzyme formFMN (Flavin mononucleotide) Riboflavin (free form) 2HUEC 3115 – Human Nutrition and Metabolism Water Soluble Vitamin Charts Absorption HCL in the stomach and enzymatic hydroloysis frees riboflavin. FAD FMN Riboflavin Absorption is by riboflavin transporter 2 (RFT2) in the proximal small intestines. Sodium independent. Absorbed riboflavin is converted to FMN in the intestinal cells then back to riboflavin to transport Alcohol impairs absorption TransportationTransported mainly by albumin Enters cells by riboflavin binding proteins. The liver, kidney, and heart has the greatest amount FAD predominates in tissues FoodSourcesAnimal origin foods are usually good sources. Milk and milk products contribute the most. In most foods riboflavin is in the free, FMN, or FAD state Functions Oxidation-reduction reactions Electron transport chain Oxidative decarboxylation of pyruvate Oxidative decarboxylation of alpha-ketoglutarate Fatty acyl CoA dehydrogenase Synthesis of 5-methyl tetrahydrofolate (THF)Interactionswith otherNutrients Pyridoxine phosphate oxidase converts PMP to PNP to PLP the coenzyme form of vitamin B6. RDA 1.3mg for Men1.1mg for Women 400mg is used to treat migraines Deficiency >1.4 serum level Ariboflavinosis Toxicity No UL Excretion Excreted in the urine intact History Discovered in 1917 by Paul Gyorgy. Following egg white injury in rats. Vitamin B3Niacin FunctionalFormNicotinic acid Nicotinamide (found in supplements) NAD and NADP (coenzyme forms) Absorption NAD and NADP converted to nicotinamide for absorption.Pyrophosphate removes phosphate off of NADP. Absorbed by sodium-dependent carriers by facilitated diffusion TransportationMovement into cells by simple diffusion, but carriers required for entrance into red blood cells. Nicotinamide converted to coenzyme forms NAD and NADP3HUEC 3115 – Human Nutrition and Metabolism Water Soluble Vitamin Charts FoodSourcesFish and other animal flesh. In animals found in coenzyme forms of NAD and NADP BodilySourcesProduction of NAD from tryptophan in the liver. 60mg of tryptophan required to produce 1mg NAD Interactionwith otherNutrients Riboflavin (FAD), vitamin B6 (PLP), and iron involved in conversion of tryptophan to NAD Functions Coenzyme forms used in glycolysis, oxidative decarboxylation of pyruvate to acetyl-CoA, oxidation of acetyl-CoA in TCA cycle, beta oxidation of fatty acids. Transfer of elections and hydrogen from metabolic intermediates in electron transport chain. Can be reduced into NADPH Nonredox roles RDA Recommendation given in niacin equivalents. Accounts for the 1mg of niacin that can be produced from 60mg oftryptophan 16mg for Men14mg for Women Deficiency Pellagra (Dermatisis, dementia, diarrhea, and death) Toxicity UL based on flushing is 35mg/day from supplements and fortified foodsLarge does 6g/day are used to treat hypercholesterolemia Excretion Converted in the liver to a variety of excretion products. NAD and NADP can be recycled. Used to assess niacin status. History Isolated in 1867. Goldberg did major research Vitamin B6FunctionalForm (PN) Pyridixine (PL) Pyridoxal (PM) Pyridoxamine (PNP) Pyridoxine phosphate (PLP) Pyridoxal phosphate (Coenzyme form) (PMP)