Utilizing PET scan images of the brain, researchers have been able to successfully identify a portion of the brain that functions in an abnormal way when basic individuals with an insulin-resistance ingest sugars. This insulin resistance is more often than not, a first indication of the development of type 2 diabetes.
For individuals with this metabolic syndrome, sugary drinks produced a lower-than-usual release of dopamine in a pivotal pleasure center of the brain. This interesting chemical reaction is indicative of a potentially deficient reward system, setting the stage for further insulin resistance.
This research, being presented at the Society of Nuclear Medicine and Molecular Imaging’s 2013 Annual Meeting, has the potential to change how the medical community understands and tests how food-reward signaling builds to obesity.
"Insulin resistance is a significant contributor to obesity and diabetes," commented Dr. Gene-Jack Wang, the study’s lead author. “A better understanding of the cerebral mechanisms underlying abnormal eating behaviors with insulin resistance would help in the development of interventions to counteract the deterioration caused by overeating and subsequent obesity. We suggest that insulin resistance and its association with less dopamine release in a central brain reward region might promote overeating to compensate for this deficit."
According to CDC estimations, currently around 1/3 of Americans are obese. The American Diabetes Association evaluates that 26,000,000 Americans are living with Diabetes and around 80 million are “pre-diabetic,” including individuals living with insulin resistance. While type 2 can be avoided and managed with exercise, diet, and reliance on diabetes support groups, any medical preventive measures to help identify causes are of immense value.
The disposition to overeat may actually be triggered by an intricate biochemical exchange, demonstrated by original research on rodent test subjects. Dr. Wang’s research is the first of its kind to focus on human subjects.
"Animal studies indicated that increased insulin resistance precedes the lack of control associated with pathological overeating," stated Wang. "They also showed that sugar ingestion releases dopamine in brain regions associated with reward. However, the central mechanism that contributes to insulin resistance, pathological eating and weight gain is unknown. "In this study we were able to confirm an abnormal dopamine response to glucose ingestion in the nucleus accumbens, where much of the brain's reward circuitry is located. This may be the link we have been looking for between insulin resistance and obesity. To test this, we gave a glucose drink to an insulin-sensitive control group and an insulin-resistant group of individuals and we compared the release of dopamine in the brain reward center using PET."
The study was made up of 19 volunteers, 10 healthy control subjects and 9 insulin-resistant. In the study, the 19 subjects each ingested a glucose drink, and then on a different day, an artificially sweetened drink which contained sucralose was administered. After each drink was ingested a PET scan was performed. The research team then mapped active areas of the brain and measured striatal dopamine receptor availability.
"This study could help develop interventions, i.e., medication and lifestyle modification, for early-stage insulin-resistant subjects to counteract the deterioration that leads to obesity and/or diabetes," stated Wang. "The findings set a path for future clinical studies using molecular imaging methods to assess the link of peripheral hormones with brain neurotransmitter systems and their association with eating behaviors."