Thiamin Vitamin B 1 Beriberi Sara Parnell Thiamin
Thiamin (Vitamin B 1): Beriberi Sara Parnell
Thiamin • Discovered to be an important nutrient during the 1800 s when rice was being made with only the endosperm • people developed neurological problems (beri) • Water-soluble B vitamin • Structure consists of pyramidine ring and thiazole linked by a methylene bridge Source: http: //www. natuurlijkerwijs. com/english/vitamins. htm
Food Sources � RDA ◦ Men: 1. 2 mg ◦ Women: 1. 1 mg (up to 1. 5 mg if pregnant/lactating) � Meat (pork, beef, liver) � Salmon � Legumes � Whole, fortified, or enriched grains � In the American diet, majority comes from foods enriched with the vitamin.
Biochemistry • Thiamin is precursor to the coenzyme thiamin pyrophosphate (TPP) • Involved in carbohydrate metabolism catalyzes synthesis or cleavage of bonds between carbonyl carbons • Pyruvate Dehydrogenase Complex • Citric Acid Cycle • Pentose Phosphate Pathway Source: http: //www. chegg. com/homework-help/questions-and-answers/preeti-dhardepartmentchemistrysuny-new-paltz-people-malaysia-belong-communities-local-peo-q 4080231
Metabolic Pathways PDC • Oxidative decarboxylation of pyruvate (via pyruvate dehydrogenase, E 1) to form acetyl Co. A • Thiamin used as building block for TPP • The reaction also helps generate ATP Citric Acid Cycle • Decarboxylation of α-ketoglutarate • Reaction 4 Pentose Phosphate Pathway • TPP coenzyme for transketolase, which is needed for NADPH synthesis and pentoses
Thiamin Inhibition • If oxidative decarboxylation inhibited, ATP cannot be synthesized and acetyl Co. A cannot be formed. • If acetyl Co. A does not form, leads to accumulation of pyruvate, lactic acid, and αketoglutarate. Source: http: //www. stories-forchildren. ca/beri-good-discovery. php
Digestion & Absorption • Intestinal phosphatases responsible for digestion • Mediated by thiamin transporters (Th. Tr 1 and Th. Tr 2 in kidney and intestine) • Defects in the gene SLC 19 A 2 (codes for Th. Tr 1) shown to cause deficiency Source: http: //www. mikeblaber. org/oldwine/BCH 4053/Lecture 33. htm
Antithiamin Factors • Factors that contribute to decreased thiamin absorption • Polyhydroxyphenols in coffee, tea, blueberries, and brussel sprouts - inactivate thiamin by oxyreductive process that destroys the thiazole ring • Thiaminases in fish – catalyze cleavage of thiamin and decreases uptake of thiamin.
Beriberi • Beriberi – “beri” means weakness in Singhalese • Prevalence is high in Eastern Asian countries • Incidence rate unknown • Individuals with this disease have high levels of pyruvate and α-ketoglutarate in the blood • Can be life threatening, but effects are reversible – mortality is rare • Dry beri • Wet beri
Dry Beriberi • Chronic low thiamin intake • Affects nervous system • More prominent in adults • Muscle weakness • Difficulty walking • Mental confusion/speech difficulties • Strange eye movements • Vomiting • Acute beri : occurs predominantly in infants • Lactic acidosis
Wet Beriberi �Wet beri affects the cardiovascular system �Cardiomegaly �Tachycardia �Shortness of breath �Peripheral edema
Beriberi � Alcoholism in developed countries leads to Wernicke’s encephalopathy � Biggest cause of thiamin deficiency in the United States � Decreased thiamin absorption � Alcohol dependency leads to decreased food consumption, but also increased thiamin needs due to liver damage � GI cancers, liver disease, IBD can decrease ability to absorb thiamin
New Research and Treatments � Thiamin deficiency may occur following bariatric surgery � Decreased food intake in weeks following surgery � Thiamin half life = 20 days � Treatment requires 15 to 250 mg daily thiamin supplement for one month or more depending on the severity � Thiamin injections can also be given � With treatment, symptoms are reversible
References � (2012). Beriberi: Thiamine deficiency; vitamin b 1 deficiency. Pub. Med Health, http: //www. ncbi. nlm. nih. gov/pubmedhealth/PMH 0001379/ � Boyer, R. (2006). Biochemistry. (3 rd ed. ). Hoboken, NJ: John Wiley & Sons, Inc. � Gropper, S. , & Smith, J. (2013). Advanced nutrition and human metabolism. (6 th ed. ). Wadsworth Cengage Learning. � Jurgenson, C. T. , Begley, T. P. , & Ealick, S. E. (2009). The strctural and biochemical foundations of thiamin biosynthesis. Annu. Rev. Biochem. , � Rabinowitz, S. (2012, April 16). Pediatric beri. Retrieved from http: //emedicine. medscape. com/article/984721 -overview
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