The FNDC5 gene helps make a protein that is cut into irisin, a messenger linked to exercise that helps muscles communicate with fat and other tissues. If the FNDC5 gene does not work as expected, exercise related signaling and energy use in the body may be altered. What this gene does can influence how your body handles energy and may play a part in metabolism, muscle function, and brain health. Public interest in the FNDC5 gene grew when irisin was described in the media as an “exercise hormone.”
What is a gene?
A gene is a stretch of DNA that gives your cells instructions for making molecules or managing activities in the body. Some genes provide the directions for producing proteins, which do much of the cell’s work. Others mainly regulate when specific processes happen, where they take place, and how active they are. Taken together, genes affect how the body develops and works, and they can influence how you respond to food, stress, or medications. To explore this topic in more detail, you can learn more in the LearnHub.
Overview
FNDC5Gene function
What if the gene works
The FNDC5 gene helps muscle cells make a protein involved in energy use. During exercise, this protein can be cut into irisin, a messenger that helps muscles communicate with fat and other tissues.
Risk
What if the gene does not work
Changes in the FNDC5 gene can reduce how much FNDC5 protein cells make or how well it is released as irisin, a cell signal involved in exercise responses. Milder and more severe variants can reduce function to different degrees.
Treatment
What does that mean for your treatment
No FNDC5-specific treatment or management approach is currently established for pathogenic variants in the FNDC5 gene. FNDC5 and its hormone product irisin are being studied as possible biomarkers and drug targets in metabolic, brain, and cancer research, but this has not changed routine treatment choices.
Gene function
What if the gene works
Your body uses the FNDC5 gene as part of the link between movement and metabolism. It helps cells make a protein that can be processed into irisin, a small messenger released especially by muscle. This supports communication between tissues during exercise and everyday energy use.
The FNDC5 gene helps cells make a surface protein that can be cut to release irisin. Irisin acts as a messenger, carrying signals from muscle to other tissues.
During physical activity, signaling linked to the FNDC5 gene helps muscle and fat tissue coordinate energy use. This helps explain how the FNDC5 gene supports energy balance during exercise.
Signals from the FNDC5 gene and irisin can encourage some fat cells to behave more like cells that burn fuel to make heat. This helps the body adjust how it uses stored energy.
What is a variant?
A genetic variant is a minor change in the DNA sequence within a gene. These changes are common and are part of normal human diversity, including differences in appearance, metabolism, and the way the body responds to environmental influences. Many variants do not have any noticeable effect and are simply part of natural genetic variation. At times, though, a variant can change how a gene works to a greater extent and may contribute to or cause a genetic condition.
Genetic variants
What if the gene does not work
When looking at how variants in the FNDC5 gene affect protein function, DNA changes may alter how much FNDC5 is made, how stable the protein is, or how efficiently it is processed and released as irisin. Milder variants can slightly reduce expression or secretion, while more severe variants, including truncating variants, may markedly lower or stop protein production. Some variants may also change the protein’s shape, which can weaken its interactions with other cell components.
How variants are linked to conditions
Variants in the FNDC5 gene do not yet have a broadly confirmed link to a specific health condition, and research on FNDC5 gene variants and health conditions is still developing. If you have a confirmed finding in the FNDC5 gene, your doctor or genetic counselor can explain what it may mean for your health and family in the context of your personal history.
A variant is not necessarily a diagnosis
Genetic variants are common across the general population and are a normal feature of human biology. Most do not directly affect health and instead reflect natural variation among people. For many genes, having a variant associated with a condition points to a possible link rather than a certain diagnosis, particularly when several genes and environmental influences also play a role. In contrast, there are situations where one well-characterized variant in a particular gene is enough to confirm the diagnosis.
Are there things that can increase or change my risk?
There isn't yet broadly confirmed evidence on specific factors that increase or reduce health risk related to the FNDC5 gene. If a test finds a change in FNDC5, a doctor or genetic counselor can help put it in context with your personal and family health history.
Inheritance of FNDC5 variants
For people looking into the inheritance of FNDC5 gene variants, there is not yet a broadly confirmed disease specific Mendelian pattern tied to the FNDC5 gene. The FNDC5 gene is located on chromosome 1, which is an autosome, so you inherit one copy from each parent. This means a variant in the FNDC5 gene can be passed through either side of the family and can be inherited by sons and daughters alike.
What does my FNDC5 result mean for my family?
There is not yet a broadly confirmed, single-gene inheritance pattern tied to a specific health condition for FNDC5. If you have a FNDC5 result and want to understand what it could mean for relatives, a doctor or genetic counselor can review the exact finding in the context of your family history.
Genetic information
Genetic testing
How you find out about variants
To look for changes in the FNDC5 gene, a lab can analyze DNA from a saliva or blood sample. This type of testing for FNDC5 variants reads the gene's code and checks for differences from the usual sequence. Results may identify a variant or show no reportable change.
When should I consider getting a genetic test?
There isn't yet a broadly established, FNDC5-specific clinical reason for genetic testing in routine care. Decisions about testing are best made with a doctor or genetic counselor, based on your personal health, family history, and the reason testing is being considered.
A genetic result is only one part of your health story
A genetic finding can provide useful insight, but how much it reveals depends on the condition and on the kind of variant involved. Over time, factors such as age, lifestyle, environment, and medical history also shape how the body works. For some conditions, especially those influenced by many genes, genetic information provides context rather than certainty and is best understood alongside other parts of care. In other situations, a genetic result may offer a clear answer. In areas like medication response, genetic findings can also help put individual experiences into context.
Pharmacogenetics
How variants shape your response to medicine
Genetic variation can affect how people respond to medicines. Small differences in DNA can influence how the body breaks down a drug, how strongly it acts, or how sensitive someone is to side effects. This is common and helps explain why the same treatment may work well for one person, seem less effective for another, or feel harder to tolerate.
What is Pharmacogenetics?
Pharmacogenetics examines how differences in genes can affect the way people respond to medicines. By studying links between genes and medications, it helps explain why the same treatment may work differently in different people. For many drugs, genes influence both how strongly a medicine works and how the body handles it. This information can support treatment decisions that are better informed and more individualized. More detail on this topic is available in the LearnHub.
Drugs influenced by the FNDC5 gene
When should I seek medical advice?
There is not yet a broadly confirmed role for this gene in guiding medication response. If you have side effects, unexpected symptoms, or concerns about how a medicine is working, talk with your doctor.
History
The FNDC5 gene entered medical research more recently than many better known genes. In 2012, researchers brought it to wide attention when they reported that exercise could increase production of a protein fragment called irisin, which is made from FNDC5. From these first observations, research expanded steadily. Interest grew quickly because the finding linked muscle activity with broader body responses, but the early reports also sparked debate about how reliably irisin could be measured in humans. Over time, scientists refined laboratory methods and developed a clearer picture of FNDC5, making it a recognized part of research on exercise, metabolism, and energy balance.