Does Chronic Cola Consumption Increase Urinary Stone Risk? Evidence from the Drosophila Model of Urolithiasis

There are rising public health concerns about the links between consumption of sugar-sweetened beverages and weight gain, obesity, and other metabolic problems. Sodium citrate (Na-citrate) is used as an additive in colas and various commercial drinks worldwide. Although potassium citrate (K-citrate) has been prescribed and well accepted by urologists for treating urinary stone disease (urolithiasis), the clinical role of Na-citrate has not been well established. We investigated the effects of Na-citrate and cola on the treatment of urolithiasis with an emerging translational model – Drosophila melanogaster. Drosophila medium containing 0.5% ethylene glycol (EG) was used as a lithogenic agent for calcium oxalate (CaOx) crystal formation in Drosophila Malpighian tubules. Cola (25%) and Na-citrate (2% and 4%) were added to the fly medium for urolithiasis treatment. Medium containing Kcitrate (2% and 4%) was used as a positive control. After 3 weeks of treatment, the Malpighian tubules were dissected, removed, and processed for polarized light microscopy examination; fly lifespan was also monitored in different groups. Cola failed to reduce CaOx crystal formation, whereas Na-citrate and the positive control K-citrate significantly reduced EG-induced CaOx crystal formation in Drosophila. Administration of either Na-citrate or cola did not inhibit Drosophila lifespan. Consumption of cola exerts no detectable change in the lithogenic agent associated with CaOx stone formation in the Drosophila model. By contrast, Na-citrate had an inhibitory effect on EG-induced CaOx crystal formation, albeit a lower inhibitory rate upon comparison with K-citrate.