Vitamin/MineralB1 (Thiamin) B2 (Riboflavin) B3 (Niacin)RDA/FoodSourcesRDAMen: 1.2 mg/dayWomen: 1.1 mg/dayPregnancy: 1.4 mg/dayLactating: 1.5 mg/dayFood SourcesMeat, legumes, and whole, fortified, or enriched grain products; In supplements found mainly as thiamin hydrochloride or thiamin mononitrate saltBioavailabilityRDAMen: 1.3 mg/dayWomen: 1.1 mg/dayPregnancy: 1.4 mg/dayLactating: 1.6 mg/dayFood SourcesEspecially foods of animal origin; milk andmilk products main source; eggs, meat, and legumes alsoBioavailabilityUp to 95% of riboflavin is absorbed, up to maximum of 25 mgRDANiacin equivalent used to account for provision from tryptophan; average US diet usually contains about 900 mg tryptophan daily, so this equates to 15 mg niacinMen: 16 mg/dayWomen: 14 mg/dayPregnancy: 18 mg/dayLactating: 17 mg/dayUL35 mg/dayFood SourcesFish (tuna, halibut), meats (beef, chicken, turkey, pork), enriched and fortified cereals, seeds, legumes, bread products, whole grainsBioavailabilityFound as niacytin (high availability) or niacinogens (very low yield)May be synthesized in liver from tryptophan (only 3% of trp); 1mg niacin from 60 mg tryptophan; riboflavin, B6, and iron required in some reactions involved in conversionBody Forms/Storage FormsBody Content 30 mgBody FormsExists in free form in plants; 95% in animal exists in phosphorylated formStorage FormsHigh concentrations in liver, skeletal muscle, heart, kidney, and brain; skeletal muscle may contain half oftotal thiaminBody and Storage FormsRiboflavin, FMN, and FADBody FormsOccurs mainly as nicotinamide nucleotides (NAD and NADP)Storage FormsNAD and NADP trapped in cell; NAD concentration usually higher than NADP; excess NAD converted back to nicotinamide to transport to other tissues; NAD foundmainly as NAD and NADP found mainly as NADPHDigestionThiaminases catalyze cleavage of thiamin in raw fish Noncovalently attached riboflavin can be freed by HCl action; not all bound riboflavin is hydrolyzed and available for absorption; 7% of FAD attached to histidine or cysteineNAD and NADP may be hydrolyzed in GI tract by glycohydrolase to release free nicotinamideAbsorptionAbsorption thought to be highOccurs primarily in jejunum, with lesser amounts in the duodenum and ileum; free thiamin absorbed intointestinal mucosal cells; can be active or passive depending on amount presentHigh amounts = passive diffusionLow amounts = active and sodium-dependentAnimal sources better absorbed than plant sources; free riboflavin absorbed by saturable, energy-dependent carrier mechanism primarily in proximal small intestine; also through sodium-dependentcarriersCan be absorbed in stomach, but more so in small intestine; small concentrations absorbed by sodium-dependent, carrier-mediated diffusion; high concentrations absorbed almost completely by passive diffusionEnhancers/Inhibitors ofAbsorptionEnhancersCannot be foundInhibitorsCannot be foundEnhancersCannot be foundInhibitorsCannot be foundEnhancersCannot be foundInhibitorsCannot be foundTransportTransport either in free form bound to albumin or found as thiamine monophosphate; 90% found within blood cellsConverts to FMN on absorption into intestinal cells; riboflavin, FMN, and FAD transported by variety of proteins; albumin, fibrinogen, globulinsUp to 1/3 nicotinic acid in plasma bound to plasma proteins; transport into kidney tubules and red blood cells require a carrier; nicotinamide is primary precursor of NAD; nicotinic acid may also be used in liverInvolved inEnergy TransformationSynthesis of Pentoses and NADPHMembrane and Nerve ConductionFlavoproteins and oxidative energy system usageSuccinate dehydrogenase: FADH2 then electrons into ETC through ubiquitinFatty acyl CoA dehydrogenaseSphinganine oxidase requires FADCoenzyme for xanthine oxidaseAldehyde oxidasePyridoxine phosphate oxidase depends on FMN (converts PMP and PNP to PLP)Synthesize active form of folate Multiple dehydrogenases in choline catabolismSome neurotransmitters require monoamine oxidaseReduction of glutathioneErol and sulfhydryl oxidase (forms disulfide bridges)Thioredoxin reductase is involved in synthesis of deoxyribonucleotides200 enzymes require NAD and NADP; act as hydrogen donors or electron acceptorsAlso functions as substrate in non-redox roles as donor of ADP-riboseTightly bound to apoenzymes and can easily transport hydrogen from one part of cell to anotherNADH transfers its electrons from metabolic intermediates through electron transport chain making ATP: Glycolysis, Oxidative decarboxylation of pyruvate, Oxidation of acetyl CoA in TCA cycle, B-oxidation of fattyacids, Oxidation of ethanolNADPH acts as reducing agent in pathways such as fatty acid, cholesterol, steroid synthesis, Oxidation of glutamate, Regeneration of glutathione, vitamin C, and thioredoxin, Synthesis of deoxyribonucleotides- Generated in HMP shunt and by mitochondrial membrane malate-aspartate shuttleExcretion/AssessmentExcretionExcess is excreted intact, as well as catabolized for urinary excretionAssessmentErythrocyte transketolase activity or thiamin content in blood or urineExcretionExcreted primarily in urine, with small amounts in feces; riboflavin not bound to protein in plasma filtered by glomerulus and excreted; 60-70% excreted intact in urine; urinary excretion is noticeable, makes your pee yellow-orangeAssessmentActivity of erythrocyte glutathione reductase (high NADPH indicates deficiency)Cellular riboflavin concentrations and urinary excretionExcretionCan be degraded by glycohydrolase into nicotinamide and ADP-ribose; nicotinamide methylated and oxidized in liver into products excreted in urineAssessmentUrine metabolite amounts like N’ methyl nicotinamide test for deficiencyErythrocyte NAD concentrations or NAD/NADP ratiosToxicity/DeficiencyToxicityLittle danger of thiamin toxicity; excessive thiamin (100 times recommended amount all at once) associated with headaches, convulsions, cardiac arrhythmia, anaphylactic shockDeficiency (Beriberi)Loss of appetite; hypertrophy and altered heart rate; apathy, confusion, decreased short-term memory, and irritabilityDry- Predominantly in older adults- Chronic low intakeWet- More extensive cardiovascular system involvement- Cardiomegaly, tachycardia, right side heart failure, peripheral edemaAcute- Seen mostly in infants- Anorexia, vomiting, lactic acidosis, cardiomegalyCommonly associated with alcoholismWernicke-Korsakoff syndrome also commonly foundElder people also at risk (diseases that impair
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