Caffeine inhibits both basal and insulin-activated urate transport.

We postulate that inhibition of urate transport activity of the reabsorptive transporters GLUT9, OAT10, and OAT4 by caffeine is a key mechanism in its urate-lowering effects. Additionally, the ability of caffeine to block insulin-activated urate transport by GLUT9a and OAT10 suggests greater relative inhibition of these transporters in hyperinsulinemia.