Genetic Mapping Study Identifies Liver Enzyme Ces1 as Key Driver of Cocaine Addiction, Opening New Therapeutic Avenues
Key Insights
A large-scale genetic study in nearly 900 heterogeneous stock rats identified Ces1 (search), a liver-based enzyme that metabolizes cocaine, as a critical determinant of compulsive drug-taking behavior.
Researchers at UC San Diego found six major genetic regions linked to addiction-like behaviors, including escalation of drug intake and time between doses.
The findings replicated a known human genetic link (Trak2 (search)), providing a translational bridge between animal research and potential human therapies.
A decade-long genetic mapping effort led by researchers at the University of California San Diego has uncovered a surprising driver of cocaine addiction: a liver-based enzyme rather than a brain-based mechanism. The study, published in Nature Communications, identified the Ces1 (search) gene family—responsible for producing the enzyme that metabolizes cocaine—as a key factor in determining how frequently and compulsively rats self-administer the drug.
"Finding a liver-based enzyme that shapes cocaine-taking behavior was a real 'aha' moment for us," said co-corresponding author Olivier George, PhD, professor of psychiatry at UC San Diego School of Medicine. "It reminds us that addiction isn't only in the brain. It's a complex puzzle involving how the entire body processes the drug."
The research team utilized nearly 900 heterogeneous stock rats, a model system specifically designed to mimic the vast genetic diversity found in human populations. This approach enabled the researchers to capture critical differences between individuals genetically susceptible to addiction and those naturally more resistant.
Mapping the Genetic Landscape of Addiction
By analyzing millions of genetic markers in each animal, the team identified six major genetic regions linked to addiction-like behaviors, including the escalation of drug intake and the time elapsed between doses. The Ces1 (search) gene family emerged as a central finding, validating a hypothesis that has circulated in the field for decades.
"Seeing the Ces1 (search) signal validate a hypothesis that has been circulating for decades is incredibly exciting," said first author Montana Kay Lara, PhD, a postdoctoral researcher at UC San Diego School of Medicine. "It gives us a concrete target to test whether changing how cocaine is metabolized can blunt the drive toward compulsive use."
The study also replicated a known genetic link found in humans—Trak2 (search)—providing a vital translational bridge between animal research and human medicine. This replication strengthens the argument that the biological pathways identified in the laboratory could eventually lead to real-world therapies.
From Brain-Centric to Whole-Body Understanding
Current research on cocaine use disorder (search) has often focused on the brain, but the UC San Diego team's findings suggest that how the body breaks down cocaine may be just as critical in determining whether someone develops an addiction. While cocaine use disorder has a strong genetic component, scientists have struggled to pinpoint the specific genes that make certain individuals more vulnerable.
"Identifying those genes is an important goal, because drugs could then be developed to target those genes, shifting genetically susceptible people to become more like genetically resistant people," said co-corresponding author Abraham A. Palmer, PhD, professor of psychiatry at UC San Diego School of Medicine, who led the project's genetic modeling and analysis.
The findings suggest that by targeting the enzymes that metabolize cocaine with medicines, scientists might be able to alter how the drug affects the body, potentially reducing its addictive impact.
A Collaborative Scientific Achievement
"This work showcases the power of long-term, team-science collaboration that pairs experts in rodent behavior with quantitative geneticists," said Palmer. "A decade of coordinated effort across multiple cohorts and federal partners made possible a discovery that no single lab could achieve alone."
The study was funded by the National Institute on Drug Abuse within the National Institutes of Health through multiple grants (P50DA037844, P30DA060810, U01DA051234, U01DA043799, and U01DA060810).
Next Steps and Clinical Implications
The research team is now moving into the next phase of the project, investigating exactly how these genetic mutations change the function of the Ces1 (search) enzyme. They also plan to leverage the study's extensive Preclinical Addiction Biobanks—collections of blood, urine, brain, and other tissue samples—to identify biological markers that could one day help predict an individual's risk of developing a substance use disorder.
The researchers hope that by translating these genetic discoveries into diagnostic tools and new treatments, they can help stabilize individuals struggling with addiction. The authors declared no competing interests.