High plasma uric acid concentration: causes and consequences

High plasma uric acid (UA) is a prerequisite for gout and is also associated with the Metabolic Syndrome and risk factors for cardiovascular diseases [1-4]. Hyperuricemia increase in 16% all causes of mortality and 39% of total cardiovascular disease [5].The hyperuricemia is defined as ≥7 mg/dL for men and ≥6.0 mg/dL for women [6], and is found mainly in postmenopausal women, African American, patients with renal disease and alcohol intake [7]. Furthermore, many factors can influence the concentrations of UA, eg. diet, obesity, and Metabolic Syndrome [1,8-10]. However, we still don't know if UA is a protective factor for the moderate oxidative stress in these situations or if it's a risk factor.The aim of this review was to discuss the function of the UA in our organism and the main causes and consequences of the higher concentration of UA.Uric acid (2,6,8 trioxypurine-C5H4N4O3) is an organic compound that is endogenously produced by animals as a purine metabolite. It is formed by the liver and mainly excreted by the kidneys (65-75%) and intestines (25-35%). UA is the end product of purine metabolism in humans due to the loss of uricase activity, which led to humans having higher UA levels than other mammals [11,12].Due to its double bonds, uric acid has excellent antioxidant capacity, and it can be responsible for 2/3 of total plasma antioxidant capacity [13,14].Because it is a weak acid that have a high dissociation constant, uric acid circulates in plasma (pH 7.4) predominantly (98%) in the form of a monovalent sodium salt (urate) [15]. It shows low solubility in water (as well as in plasma), and it would theoretically reach plasma saturation in the concentration of 6.4 mg/dL, which may not occur because solubility increase is provided by its binding to proteins, namely albumin, which is its main transporter. Protein-bound uric acid shows plasma solubility that is 70% higher than in its free state [16]. Uric acid pathogenesis is usually associated with gouty arth