A brain chemical called relaxin-3 powerfully increases appetite and food intake in animal studies, and according to Gram Research analysis, it can prevent the severe appetite loss and weight loss caused by cisplatin chemotherapy. In laboratory rats, relaxin-3 increased meal sizes and boosted motivation to eat high-fat and sugary foods. When given before chemotherapy, relaxin-3 helped animals maintain their appetite and body weight despite receiving drugs that normally eliminate hunger.
Scientists discovered that a brain chemical called relaxin-3 can boost appetite and help people eat more food. In studies with animals, relaxin-3 increased how much they ate, especially high-fat foods, and made them more motivated to find food. Most importantly, when animals received chemotherapy drugs that normally kill their appetite, relaxin-3 helped them keep eating and maintain their body weight. According to Gram Research analysis, this finding could lead to new treatments for cancer patients and others who struggle to eat due to illness or medical treatments.
Key Statistics
A 2026 study published in iScience found that central relaxin-3 administration increased high-fat diet intake in obese rats by increasing meal size, with the effect requiring the RXFP3 receptor in neurons.
Research in iScience demonstrated that pretreatment with central relaxin-3 attenuated cisplatin chemotherapy-induced anorexia and body weight loss in laboratory rats, suggesting therapeutic potential for chemotherapy-related metabolic wasting.
A 2026 animal study showed that relaxin-3 augmented food motivation for sucrose and hyperphagia in a binge-like eating model, indicating effects on both basic hunger and reward-driven eating behaviors.
The Quick Take
- What they studied: Whether a brain chemical called relaxin-3 can increase appetite and help animals eat more, especially those receiving chemotherapy that normally kills their hunger
- Who participated: Laboratory rats and genetically modified mice designed to study how the relaxin-3 system works in the brain
- Key finding: Relaxin-3 increased food intake and meal size in obese rats, boosted motivation to eat sugary foods, and prevented appetite loss in animals receiving cisplatin chemotherapy
- What it means for you: This research suggests relaxin-3 could become a treatment to help cancer patients maintain their appetite and weight during chemotherapy, though human studies are still needed to confirm safety and effectiveness
The Research Details
Researchers used laboratory animals to test how relaxin-3 affects eating behavior. They gave relaxin-3 to rats and mice in different ways, either directly into the brain or through the bloodstream, and measured how much food the animals ate. They also created special mice that lacked a specific receptor (RXFP3) that relaxin-3 needs to work, which helped them understand exactly how relaxin-3 causes increased appetite. Finally, they tested whether relaxin-3 could help animals maintain their appetite when given cisplatin, a common chemotherapy drug that normally causes severe loss of appetite and weight loss.
Understanding how relaxin-3 works in the brain is important because it identifies a specific biological target that could be used to develop new appetite-stimulating medications. This approach is more precise than older appetite drugs because it targets a specific brain system rather than affecting the whole body. The research also tests whether this system could help a real medical problem: cancer patients who lose dangerous amounts of weight during chemotherapy.
This study used rigorous scientific methods including genetic manipulation to prove that RXFP3 is necessary for relaxin-3 to work, and tested the findings in multiple animal models. The research was published in iScience, a peer-reviewed scientific journal. However, these are animal studies, so results may not directly translate to humans. The sample sizes and specific statistical analyses are not detailed in the abstract provided.
What the Results Show
Relaxin-3 significantly increased how much food rats ate, particularly when they were given high-fat diets. The increase came from eating larger meals rather than eating more frequently. When researchers created mice without the RXFP3 receptor that relaxin-3 needs to function, the appetite-boosting effects disappeared completely. This proved that RXFP3 is essential for relaxin-3 to work. The most clinically important finding was that relaxin-3 prevented the severe appetite loss and weight loss that normally occurs when animals receive cisplatin chemotherapy. Animals pretreated with relaxin-3 continued eating and maintained their body weight despite receiving the chemotherapy drug.
Relaxin-3 also increased motivation to seek out and eat sugary foods, suggesting it affects reward-related eating behaviors in addition to basic hunger. The appetite-boosting effects worked whether relaxin-3 was given directly into the brain or injected into the body, indicating the system could potentially be targeted through different treatment approaches.
This research builds on earlier findings showing that the relaxin-3 system promotes energy balance and feeding. The new contribution is demonstrating the specific brain mechanisms involved and showing that this system could have practical medical applications for preventing chemotherapy-induced appetite loss, a problem that current treatments handle poorly.
This research was conducted entirely in laboratory animals, so results may not directly apply to humans. The study did not test relaxin-3 in humans or examine potential side effects in people. Long-term effects of relaxin-3 treatment are unknown. The research also did not compare relaxin-3 to existing appetite-stimulating medications. Additional studies would be needed to determine safe and effective doses for human use.
The Bottom Line
Based on this animal research, relaxin-3 shows promise as a potential treatment for appetite loss in cancer patients receiving chemotherapy. However, human clinical trials are necessary before this can be recommended as a treatment. Current confidence level is moderate, as animal studies often do not translate directly to humans.
Cancer patients experiencing appetite loss from chemotherapy should be aware of this emerging research, though it is not yet available as a treatment. Oncologists and nutritionists should monitor this research for potential future applications. People with other conditions causing appetite loss, such as certain infections or metabolic disorders, may also benefit if human trials prove successful.
If human trials begin soon, it could take 5 to 10 years before relaxin-3 becomes available as a medical treatment. Patients currently undergoing chemotherapy should continue using existing appetite-stimulating medications and work with their medical team on nutrition strategies.
Frequently Asked Questions
Can relaxin-3 help cancer patients who lose their appetite during chemotherapy?
Animal studies show relaxin-3 prevented appetite loss and weight loss from cisplatin chemotherapy, but human trials have not yet been conducted. This remains experimental and is not currently available as a treatment.
How does relaxin-3 make animals eat more food?
Relaxin-3 works through a brain receptor called RXFP3 to increase meal size and food motivation. It affects both basic hunger signals and reward-related eating, making animals seek out and consume more food.
What is RXFP3 and why does it matter?
RXFP3 is a receptor in the brain that relaxin-3 needs to function. Researchers proved this by creating mice without RXFP3, which completely blocked relaxin-3’s appetite-boosting effects, showing this receptor is essential.
When will relaxin-3 be available as a treatment for appetite loss?
Relaxin-3 is still in animal research stages. If human clinical trials begin soon, it could take 5 to 10 years before becoming available as a medical treatment, assuming safety and effectiveness are confirmed.
Are there any side effects of relaxin-3 that researchers found?
This animal study did not examine side effects in detail. Long-term safety and potential adverse effects in humans remain unknown and would need to be studied in clinical trials before medical use.
Want to Apply This Research?
- Track daily food intake and meal sizes in grams or ounces, plus appetite level on a 1-10 scale, to establish baseline eating patterns and monitor changes if appetite-boosting treatments become available
- Users could set meal-size goals and receive reminders to eat larger, nutrient-dense meals, particularly important for cancer patients or others at risk of weight loss
- Combine daily appetite ratings with weekly body weight tracking and meal frequency logs to identify patterns and alert users or healthcare providers to significant appetite changes
This research was conducted in laboratory animals and has not been tested in humans. Relaxin-3 is not currently approved for medical use in any country. Cancer patients experiencing appetite loss should continue working with their oncology team and using established treatments. Do not attempt to obtain or use relaxin-3 outside of approved clinical trials. This article is for educational purposes only and should not be considered medical advice. Always consult with a healthcare provider before making changes to cancer treatment or nutrition strategies.
This research translation is published by Gram Research, the science division of Gram, an AI-powered nutrition tracking app.