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Basic Biochemistry: Purines in Food

Basic Biochemistry: Purines in Food. Dr Liz Carrey UCL Institute of Child Health. Gout. Primary gout: excess uric acid in circulation, from purines taken in the diet. DNA: genetic information. RNA: many roles. Nucleic acids. A mammalian cell. Mitochondria . Purines in the diet 1.

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Basic Biochemistry: Purines in Food

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  1. Basic Biochemistry:Purines in Food Dr Liz Carrey UCL Institute of Child Health

  2. Gout • Primary gout: excess uric acid in circulation, from purines taken in the diet

  3. DNA: genetic information RNA: many roles Nucleic acids

  4. A mammalian cell

  5. Mitochondria

  6. Purines in the diet 1 • DNA and RNA are highest in cells that are multiplying, tissues that are regenerating • Mitochondria are most numerous in energy-producing cells (e.g. muscle) • Mitochondria contain ATP and DNA

  7. NH2 N N N (phosphate)3 phosphate O O O O N IMP umami O OH OH OH OH N N N N ATP • energy • purinergic signalling • RNA, DNA • cofactors (NAD etc) • cAMP and AMP • phosphate donor

  8. Purines in the diet 2 • DNA, RNA, nucleotides and bases are digested in the gut • No purines are absorbed from the diet • Uric acid is excreted directly from the gut (1/3) or via kidneys, in the urine (2/3)

  9. NH2 N N N N H O H N H N O N O N H H O H N H N O H O N N H H Purines uric acid X allantoin

  10. O xanthine N N O N H N O H N H N O N O N H H uric acid Less soluble at acid pH Forms kidney stones if not excreted Excess may be deposited in joints and under the skin

  11. O xanthine N N O N H N O H N H N O N O N H H O H N H N O H O N N H H ALLOPURINOL uric acid URICASE allantoin

  12. High-purine foods • Red meat (mitochondria, ATP) • Organ meats (regenerating tissue: DNA) • Sea food (energy, growth) • Beer (yeast, rapidly multiplying: DNA) • Asparagus, cauliflower (multiplying: DNA) • Wheat germ, cereals, seeds (DNA)

  13. Purine-rich meat, seafood and beer increase the risk of gout in menChoi et al, 2004: NEJM & Lancet • Prospective 12-yr study of men aged 40 – 75, health professionals in USA • 5.6% already had gout symptoms • Of remaining 47,150 gout developed in 730, incidence of 1:1000 per year

  14. The risk of gout in men • Relative risk for meat-eaters 1.41; for high seafood consumption 1.51 • Beer: RR 1.49 per 12oz/day • No relationship to high-purine vegetables? • Highest dairy intake, RR 0.56

  15. ? ? ? ? Low-purine foods • White bread • Dairy products (milk, cheese, yogurt) • Sugar and confectionery • Most fruit and salad vegetables • Fruit juices • Water

  16. Giles Coren’s dinnerat Bond’s, 5 Threadneedle Street Salad of smoked eel Rooster’s testicles on a bed of sweetbreads and kidney Sea bass with frog leg aïoli and 2 fritters of bone marrowVegetables? Dessert? £100 for two without wine

  17. Purines in the diet 3 • Lower proportion of high-purine foods • More dairy products (low fat!) • Less fruit juice and fructose • Smaller portion sizes • More water – to dilute the urine

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