Uric acid is a natural waste product of normal metabolism. It is the end product of purine degradation, and is typically removed by the kidneys from the body through urine. Levels of uric acid in the blood should be kept within a normal range, because excessive amounts can lead to diseases.
Uric acid comes from the normal metabolism of DNA constituents. Imagine DNA as a ladder that is twisted to form a double helix. The rungs of the DNA ladder are occupied by any of four nitrogenous bases: adenine, guanine, cytosine and thymine. Adenine and guanine comprise the purines, while cytosine and thymine comprise the pyrimidines.
The two purines are sequentially degraded by a series of enzymes to form xanthine and hypoxanthine. Both compounds are then oxidized by a final enzyme, called xanthine oxidase, to produce uric acid. In most mammals, uric acid is further oxidized to allantoin via the enzyme uricase. Humans, however, lack uricase, and thus uric acid is already the final product of purine metabolism.
Factors that Cause High Uric Acid
You can get high levels of uric acid by consuming a diet high in purines. If you already have gout or stones, it is best to avoid foods high in purines such as meat (beef, pork and lamb), animal innards (liver and kidneys, including gravy), seafood such as anchovies and sardines, beans and legumes, as well as alcoholic beverages. A high uric acid may also be expected if you have impaired kidney functions or if you have a deficiency in enzymes normally involved in purine metabolism.
The normal range for uric acid concentration in blood is generally between 3.0 and 8.0 mg/dL, although there are very slight variations depending on the standards used by the testing laboratory. Any measurement greater than this is known as hyperuricemia, while excess uric acid spilling into urine is known as hyperuricosuria. Both hyperuricemia and hyperuricosuria are associated with diseases.
Excessive uric acid can crystallize in joints, where the needlelike crystals trigger an inflammatory reaction and a type of arthritis called gout. Affected joints are red, warm, swollen and extremely tender to touch. The big toe is the most commonly involved joint, a condition known as podagra, although other joints like the ankles, knees, wrists and elbows are not spared. Gout may be treated with medications that lower uric acid production (such as allopurinol) or ease the inflammation (such as colchicine).
2. Uric Acid Stones
Uric acid also crystallizes in the kidney and urinary tract to form stones. Scant and acidic urine promotes the precipitation of uric acid into stones by increasing the concentration and reducing the solubility of the acid in urine. Prevention of stone formation involves intake of plenty of fluids and medications that make urine alkaline.
3. Lesch-Nyhan Syndrome
Lesch-Nyhan Syndrome is a rare hereditary condition caused by a deficiency in the enzyme hypoxanthine:guanine phosphoribosyl transferase (HGPRT). The condition is characterized by very high levels of uric acid in the blood, accompanied by mental retardation and bouts of self-mutilation.
4. Cardiovascular Diseases and Diabetes
Some studies have implicated hyperuricemia as a risk factor for both cardiovascular diseases and diabetes.