Too low uric acid, is it a disease?

Mr. Hirotaka Matsuo Lecturer, National Defense Medical College

A woman in her sixties. Her blood uric acid level is 0.5 milligrams per deciliter. When I was in my thirties, it was pointed out at a health checkup that my blood pressure was too low, and I received a detailed examination, but I still don't know the cause. I've been told that it's okay if it's just low, but I'm worried about what kind of impact it will have. (Kyoto Prefecture, T)

[Answer] Mr. Hirotaka Matsuo, lecturer at the National Defense Medical College (gout, uric acid-related diseases) = Tokorozawa City, Saitama Prefecture

What is uric acid?

Uric acid, which is produced by the metabolism of purines contained in the nucleus of cells, has the effect of reducing active oxygen. When the concentration becomes too high to be dissolved in the blood, it accumulates in the joints, causing inflammation and gout. In adults, 700 milligrams are produced daily in the liver. When urine is made, most of it is reabsorbed in the kidneys and returned to the blood.

Is it a problem if my uric acid is low?

Women are originally lower than men due to the influence of hormones, but it goes up after menopause. It used to be thought that there was no problem with low levels, but it has become clear that there is a disease called "renal hypouricemia." There is a mutation in the gene of the protein that carries uric acid, and it cannot be reabsorbed and stored in the blood. It is common in Japanese, with a prevalence of 0.2% in men and 0.4% in women.

What kind of illness do you have?

There are no subjective symptoms, but in some people complications such as urinary tract stones and acute kidney injury after strenuous exercise occur. According to the clinical practice guidelines published in April, the disease is positively suspected when the uric acid level in the blood is less than 2 milligrams per deciliter. In addition, it is diagnosed by examining whether the uric acid level in the urine is high.

What is the cure?

If there are no symptoms, no treatment is needed. If you do strenuous exercise, drink plenty of water before doing so. Exercise should be avoided after taking anti-inflammatory drugs that predispose to acute kidney injury. If you experience back or hip pain after sprinting, you may have acute kidney injury. Seek medical attention. Measures such as taking drugs to prevent acute kidney injury may be taken.

Renal hypouricemia found in a health survey of Self-Defense Force personnel

Professor Shigeyoshi Shinomiya (center) and other research members involved in the development of guidelines for renal hypouricemia = Tokorozawa, Saitama Prefecture City Defense Medical College

For "renal hypouricemia," which has low uric acid levels in the blood, a clinical practice guideline was created for the first time in April this year. A team from the Department of Molecular Bioregulation at the National Defense Medical College played a central role in coordinating the findings.

According to Professor Shigeyoshi Shinomiya of the course, he noticed renal hypouricemia while examining the uric acid levels of Self-Defense Forces personnel engaged in intense exercise and training. A volunteer with low blood uric acid levels was taking anti-inflammatory drugs (painkillers) to relieve pain such as muscle pain. Some of these members developed acute kidney injury.

When we examined the genes of the members with low uric acid levels, we found that the cause was a gene related to a protein that carries uric acid. Mutations in either one of the two types impair the function of the uric acid reabsorption. While searching for the cause of low uric acid, research on the causative gene of "high uric acid" such as gout has progressed.

Lecturer Hirotaka Matsuo said, "Some athletes suffer from low uric acid. When exercising vigorously, it is necessary to stay well hydrated and avoid medication. Seek medical attention. I want you to," he said.

Guidelines for renal hypouricemia can be found on the website of the Japanese Society of Gout and Nucleic Acid Metabolism (http://www.tukaku.jp/guideline/1445.html). (Azusa Mizuno)

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