Link found between sugary drinks, gene variant and gout

University of Otago and Auckland scientists have discovered a human gene variant that can ‘turn bad’ when affected by sugary drinks. This raises the risk of developing the arthritic disease gout - caused by high levels of uric acid in the blood, which crystallise in the joints and result in a painful inflammatory response.

The study shows that a variant of the gene SLC2A9, which exchanges uric acid for glucose and fructose, helps transport the uric acid out of the bloodstream and facilitates its excretion through the kidney.

“But when people with this gene variant consume sugary drinks, it takes on Jekyll and Hyde characteristics,” said Associate Professor Tony Merriman. “The apparent function of the gene variant reverses, such that we think uric acid is instead transported back into the bloodstream and the risk of gout is increased.

“So not only does sugar raise uric acid in the blood due to processing in the liver, but it also appears to directly interfere with excretion of uric acid from the kidney. This was a quite unpredictable interaction.”

US researchers studying gout have already shown that high-fructose corn syrup sweetened soft drinks increase the risk of gout for people of European ancestry. The Otago study examined blood samples of people of European, Maori and Pacific descent, and found that sugar-sweetened soft drinks also raised the risk of gout for the New Zealanders, independent of their weight.

“Each daily 300 mL serving of sugar-sweetened drink increases the chance of gout by 13%,” Associate Professor Merriman said. A survey of the participants found that 5% of European, 14.4% of Maori and 16.6% of Pacific Island people were drinking more than 1 L of sugar-sweetened soft drink and/or fruit juice drink per day.

Gout is the most common form of arthritis in New Zealand and has strong links with other ‘metabolic’ diseases such as diabetes, heart disease and kidney disease. Dr Merriman said gout attacks can be prevented by the prescribed daily use of the medicine allopurinol, which lowers the production of uric acid in the blood. He now recommends that people with gout should also not drink any sugary drinks.

“This study shows that sugary drinks reverse the benefits of a gene variant which would usually protect against gout,” he said.

The study was published online in the journal Annals of the Rheumatic Diseases.