B Vitamins

Presented by:Melissa Baranski Rebecca DixonDevon MyersNathan Wong

Focus on Niacin: Sources, Mechanism, and Deficiencies

PHM142 Fall 2012 Instructor: Dr. Jeffrey Henderson

IntroductionWater-soluble vitamins

Vitamin B1 (thiamine)Required coenzyme for mitochondrial enzymes involved in

critical roles in the production of energy from food.

Vitamin B2 (riboflavin) Integral component of flavoenzymes required for redox

reactions and metabolism of carbohydrates, fats, and proteins.

Introduction (cont.)Vitamin B3 (niacin)

Precursor in synthesis of NAD+

Required to produce hemoglobin and to increase its oxygen-carrying capacity. Helps maintain blood glucose levels in normal range.

Vitamin B5 (pantothenic acid)Component of coenzyme A which is required to produce

energy from food.

Introduction (cont.)Vitamin B6 (pyridoxine)

Has role in production of >100 enzymes required for chemical reactions, e.g., glycogen phosphorylation.

Vitamin B7 (biotin)Required for mammalian carboxylase enzymes.

Introduction (cont.)• Vitamin B9 (folic acid)

• Required for new cell growth formation and maintenance, especially during periods of rapid growth.

• Vitamin B12 (cyanocobalamin)

• Required for red blood cell formation, DNA synthesis and neurological function.

• The gaps in the numbers are due to the fact that these compounds (e.g. Vitamin B4) are no longer considered vitamins anymore.

Sources Health Canada recommends 16 mg/day Utilize salvage pathways (external

sources) Many foods fortified with different B

Vitamins Proteins

Liver, fish, poultry, meats Leafy green vegetables, beans, peas Nuts “Enriched Flours”

Bread, pasta, crackers, etc…

Also many supplementations available OTC Individual vitamins B-complex

Sources

Sources

Sources

B ComplexContain several B Vitamins

Thiamine (B1)Niacin (B3)Pantothenoic Acid (B5)Pyridoxidine (B6)Biotin (B7)Folic Acid (B9)Cobalamin (B12)

Niacin UtilizationVitamin B3 (niacin) is a precursor for the

coenzyme NAD+

Salvage pathway and de novo (tryptophan)NAD+ is an oxidizing agent that accepts

electrons from other molecules and can transfer substances from one compound to another

NAD+ plays a major role in many metabolic pathways where it can function in redox reactions e.g. Cellular respiration: glycolysis, citric

acid cycle

Niacin

Nicotinamide adenine dinucleotide

Niacin and Blood Cholesterol

Dietary niacin can help lower the concentration of low-density lipoprotein and tryglyceridesOxidized LDLs: can damage artery walls

Dietary niacin can help increase the concentration of high-density lipoprotein (good cholesterol); more efficient

Available over-the-counter in the forms: nicotinic acid (NA), nicotinamide, inositol hexanicotinate, others.

Metabolism of Tryptophan to Niacin and Nicotinamide Adenine

Dinucleotide

Niacin Deficiency Cornmeal in the 15th century First deficiency related disease to be discovered Also tryptophan deficient

Found mainly in developing countries Inadequate diet: alcoholism, anorexia

Hartnup disease, HIV Drug induced: isoniazid, 6-mercaptopurine, phenobarbital

Symptoms and Treatment Pellagra: diarrhea, dermatitis,

dementia, death (the 4D’s) Photosensitivity

Casal’s necklace Variety of mental conditions

Irritability, memory loss, confusion Treat with niacin, 50 - 150 mg/day

Summary All B vitamins (B1, B2, B3, B5, B6, B7, B9, B12) are water-soluble

Niacin requirements are 16mg/day and dietary sources include: Meat, poultry, fish Green vegetables, beans, nuts Enriched flours: pasta, breads, etc.

NAD+ can be derived from niacin via a salvage pathway, or synthesized de novo from AA-tryptophan

Niacin defiency manifests as pellagra which is characterized by the 4Ds: diarrhea, dermatitis, dementia, and death

Pellagra mainly develops in developing countries can occur with poor diet

Other causes of deficiency can be Hartnup’s disease, HIV infection, drug related

References Delgado-Sanchez L., Godkar D., and Niranjan S. (2008) Pellagra: Rekindling of an Old Flame. Am J Ther.

15(2):173-5.

Frank G.P., Voorend D.M., Chamdula A., van Oosterhout J.J., and Koop K. (2012) Pellagra: a non-communicable disease of poverty. Trop Doct. 42(3):182-4.

Gutschi, L. M. (2012). Appendices: Nutritional supplementation. In Canadian Pharmacists Association (Ed.), Therapeutic choices. Ottawa: Canadian Pharmacists Association.

Johnson L.E. (Aug 2007) Niacin. The Merck Manual Home Health Handbook. Sep 17, 2012. http://www.merckmanuals.com/home/print/disorders_of_nutrition/vitamins/niacin.html

Mackay D., Hathcock J., and Guarneri E (2012) Niacin: chemical forms, bioavailability, and health effects. Nutrition Reviews. 70 (6): 357-366

Nester E., Nester T., Anderson D., Roberts E., and Pearsall. (2004) Microbiology: A Human Perspective, 4 th Edition. McGraw-Hill, New York,NY

Saggini A, et al. (2011) Cholesterol and Vitamins: revisited study. Journal of Biological Regulators and Homeostatic Agents.25(4): 505-15

Wan P. Moat S., and Anstey A. (2011)Pellagra: a review with emphasis on photosensitivity. [Review]. Br J Dermatol. 164(6):1188-200.