Uric acid as a modulator of glucose and lipid metabolism

In humans, uric acid is the final oxidation product of purine catabolism. The serum uric acid level is based on the balance between the absorption, production and excretion of purine. Uric acid is similarly produced in the liver, adipose tissue and muscle and is primarily excreted through the urinary tract. Several factors, including a high-fructose diet and the use of xenobiotics and alcohol, contribute to hyperuricaemia. Hyperuricaemia belongs to a cluster of metabolic and haemodynamic abnormalities, called metabolic syndrome, characterised by abdominal obesity, glucose intolerance, insulin resistance, dyslipidaemia and hypertension. Hyperuricaemia reduction in the Pound mouse or fructose-fed rats, as well as hyperuricaemia induction by uricase inhibition in rodents and studies using cell culture have suggested that uric acid plays an important role in the development of metabolic syndrome. These studies have shown that high uric acid levels regulate the oxidative stress, inflammation and enzymes associated with glucose and lipid metabolism, suggesting a mechanism for the impairment of metabolic homeostasis. Humans lacking uricase, the enzyme responsible for uric acid degradation, are susceptible to these effects. In this review, we summarise the current knowledge of the effects of uric acid on the regulation of metabolism, primarily focusing on liver, adipose tissue and skeletal muscle.