basic biochemistry: purines in food dr liz carrey ucl institute of child health
TRANSCRIPT
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
Nucleic acids
DNA: genetic information
RNA: many roles
A mammalian cell
Mitochondria
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
NN
NN
NH2
O O (phosphate)3
OH OH
ATP
• energy
• purinergic signalling
• RNA, DNA
• cofactors (NAD etc)
• cAMP and AMP
• phosphate donor
O O phosphate
OH OH
NN
NN
OIMP
umami
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)
Purines
uric acid
allantoin
N N
NH
N
NH2
N
NN
O
H
H
H
O
O
H N
NH
O
N
NH
H
OHN
O
H
X
uric acid
N
NN
O
H
H
H
O
O
H N
xanthine N N
NHNO
O
Less soluble at acid pH
Forms kidney stones if not excreted
Excess may be deposited in joints and under the skin
uric acid
allantoin
N
NN
O
H
H
H
O
O
H N
NH
O
N
NH
H
OHN
O
H
xanthine N N
NHNO
O
ALLOPURINOL
URICASE
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)
Purine-rich meat, seafood and beer increase the risk of gout in men
Choi 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
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
Low-purine foods
• White bread
• Dairy products (milk, cheese, yogurt)
• Sugar and confectionery
• Most fruit and salad vegetables
• Fruit juices
• Water
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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
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