Gout is a form of inflammatory arthritis characterized by sudden, severe attacks of pain, swelling, redness, and tenderness in one or more joints, most commonly seen in the big toe. Gout occurs when uric acid, a waste product circulating in the bloodstream, builds up and forms urate crystals in a joint or surrounding tissue. The essential cause of gout is hyperuricemia, or elevated levels of uric acid in the blood, which can result from the body producing too much uric acid or not excreting enough of it through the kidneys and intestines.
The way uric acid is handled in the body and how ultimately uric acid excess is manifested clinically is largely dependent on genetic factors.
Many believe diet and lifestyle factors are the main determinants of who develops high uric acid and gouty symptoms, but genetics plays a much greater role. The heritability of gout is 65% and it’s estimated that 20% of people with gout have a close relative with the condition (Reginato 1). The risk for developing gout is higher if it is a first degree relative, such as a sibling or a parent.
To understand the importance of genetics in gout, it is crucial to understand the role genes play in regulating the various processes of uric acid metabolism and elimination. Many genes are involved in uric acid production, metabolism, and excretion. Variations in these genes can lead to differences in uric acid levels among individuals and influence gout risk. These genetic factors are essential to understand how to identify individuals at risk for developing gout and creating targeted and personalized therapies.
Still, genetic predisposition and environmental factors such as diet, obesity, and medications are connected when analyzing the development and management of gout. For example, individuals with a genetic predisposition to gout may be more sensitive to the effects of high-purine foods. Genetic factors can also influence how individuals respond to certain gout medications, therefore affecting treatment efficacy and outcomes.
More specifically, a genotype named HLA-B5801 is strongly associated with severe cutaneous adverse reactions (SCAR) during treatment with allopurinol. Allopurinol, a drug used to lower high uric acid levels in the blood, produces adverse reactions to those with genotype HLA-B5801. This genotype is found most commonly in Asian subpopulations, notably in individuals of Korean, Han-Chinese, or Thai descent, making it harder for Asian subpopulations to manage their gout due to genetic qualities (Dean 1). In the U.S., African-Americans are four times more likely to carry this gene than white patients.
There is a clear interplay between genetics and gout diet and lifestyle, focusing on specific genes will demonstrate the interplay between gout and genetics.
Let’s dive deeper into the two key genes associated with gout.
SLC2A9
The SLC2A9 gene is significant in gout because it encodes a protein involved in uric acid transport. Variations in this gene can affect how efficiently uric acid is removed from the body, which influences gout risk. Certain variants of the SLC2A9 gene are associated with lower and varying serum uric acid levels and a reduced risk of gout. Other mutations of SLC2A9 have been associated with increased hyperuricemia and gout in white, Chinese, and Polynesian populations, as well as with low fractional excretion of urate in German, British and Croatian cohorts (Reginato 1).
ABCG2
Another important gene influencing gout is ABCG2, which plays an important role in uric acid excretion by the intestines. Mutations in the ABCG2 gene can lead to reduced efficiency in uric acid excretion, as well as interfering with the absorption of allopurinol. Common variants of this gene impact African and Southeast Asian populations disproportionately (Cleophas 1).
SLC22A12
Another significant gene is SLC22A12, which regulates the production of URAT-1 – the most important uric acid transporting protein. Mutations of SLC22A12 can lead to both increased and decreased uric acid levels.
After extensive research on genes associated with uric acid metabolism and gout, genetic testing and advancements have made it possible to identify individuals at increased risk for gout. Genetic testing allows information to be available for early intervention and management strategies. Understanding the limitations and benefits of genetic testing is crucial for its future application in predicting gout risk.
Current gout research efforts are focused on uncovering new genetic factors related to gout and for researchers, patients, and medical professionals to understand how these genes interact with environmental influences to affect disease risk and treatment responses. This research is paving the way for personalized medicine approaches to treating gout. Genetic profiles could better inform professionals to build more tailored and effective treatment and prevention strategies for those suffering with gout.
The connection between gout and genetics may not be as simple as someone may think. There are intrinsic factors at play with genetic history like diet, obesity, previous illness, kidney disease, cardiovascular health and so much more that all contribute to the way gout is identified, treated, and prevented.
