Western Washington University Professor of Psychology Jeff Grimm has received a new grant from the National Institutes of Health furthering his research into the body’s craving for sugar, and he and his team of undergraduates recently published a paper showing how a certain protein, DARPP32, was related to sucrose craving and how that craving could be reduced through environmental enrichment. Western Today recently talked with Grimm about his work and the research of his team.
How did you get involved in the field of researching cravings and addictions?
JG: This happened by chance. My graduate school advisor at WSU made a course change from studying the neurobiology of antipsychotic drugs to the neurobiology of cocaine seeking. I went along for the adventure.
Your research has shown that sugar is an incredibly addicting substance. The nation is facing an obesity epidemic, which the American Association of Family Physicians recently stated is only getting worse. How related are these two items?
JG: Our studies have shown that rats will reliably respond for sugar and sugar-paired cues, and that response rates increase after weeks of abstinence from sugar. This is similar to what is seen with drugs of abuse. A couple of other labs have directly compared sucrose and drug abuse. For example, rats in withdrawal from sugar show physical and behavioral changes nearly identical to opiate withdrawal. In addition, rats will work harder for access to sugar than for access to cocaine.
The obesity epidemic is real and for some demographics, it continues to worsen. Why we have the epidemic is difficult to answer. However, there is consensus in the scientific community that the availability of refined sugar is a significant contributing factor in the “obesogenic” diet most available to consumers. Sugar intake has increased in the past couple of decades, in part due to changing preferences of consumers (e.g. avoiding fat? Have fat-free ice cream, loaded with sugar) and the availability of very cheap sources of fructose (sucrose = fructose + glucose).
Even the increased use of non-nutritive sweeteners may be contributing to the obesity epidemic, as our brains are tricked by the sweet taste; the sweetness may satisfy at that moment, but you may mindlessly consume those “missed” calories later in the day.
Your latest grant and most recent paper involved research mapping certain proteins in the brain that are altered in response to sucrose cues and environmental enrichment. What does this mapping project tell us in terms of how our brains respond to addictions and cravings?
JG: We published a paper a few years ago where we measured brain activation related to sucrose craving in our rat model. Activation was indicated by levels of the protein Fos. We found that increased sucrose craving was generally related to more activity in several brain regions, including regions typically associated with drug addiction. We also found that environmental enrichment reduced not only sucrose craving, but also levels of Fos.
In our most recent paper, we measured the state of activation of a protein involved in signaling of the neurotransmitter dopamine. Dopamine is a key neurotransmitter in motivation and addiction. We found that the activity state of this protein (DARPP32) in several brain regions was related to sucrose craving and its reduction by environmental enrichment. As with the Fos study, these brain regions were those typically associated with drug addiction.
The results of these studies support the theory that sugar and drugs of abuse affect similar brain pathways; this information informs strategies to prevent and treat addiction.
A team of undergraduates worked with you on this paper. What were their roles?
JG: Co-authors on the DARPP32 project are Edwin Glueck, Darren Ginder, Jeff Hyde, Katherine North, and Kyle Jiganti. These students have all graduated from WWU and are either in graduate or medical school, or work in the biomedical field. They were involved in all components of the project including the behavioral and molecular biology assays, data interpretation, and manuscript preparation. This project took about 3 years to complete.