Insulin plays a role in affecting the brain's "pleasure center": study

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Ever wonder why comfort food is literally so comforting? Researchers at the NYU Langone Medical Center have found the answer.

EurekAlert reports that a new study published in the journal Nature Communications shows that insulin, an essential blood-sugar-controlling, full-feeling-inducing hormone found in mammals plays a much stronger role in releasing dopamine, a neurotransmitter that helps control the reward and pleasure centers in the brain.

According to PR Newswire, researchers studied rodents and recorded a 20- to 55-percent increase in dopamine released in the striatal region of the brain, where the effects of dopamine are felt, and in the region that governs the body's response when getting a reward. The increase in dopamine occurred at about the same time that the rise in insulin activity required to process food sugars consumed by the rats and mice, despite the reuptake of dopamine in other brain regions that told the animal that its apetite had been satisfied.

The study's senior investigator and NYU Langone neuroscientist Margaret Rice explained, "We found that when there's more insulin in the brain, there will be more dopamine released, not less."

Medical Daily reports that Dr. Rice and Dr. Kenneth Carr conducted another set of experiments that revealed how rats with low-calorie diets had a 10 times greater sensitivity rising insulin compared to rats who were given a regular diet. This led researchers to conclude that it only required one 10 percent of the insulin lvels necessary to a rat that ate a normal diet to induce a dopamine release. On the contrary, high-calorie diet rats became unresponsive to insulin.

"Our work establishes what we believe is a new role for insulin as part of the brain's reward system and suggests that rodents, and presumably people, may choose to consume high-carb or low-fat meals that release more insulin—all to heighten dopamine release," Dr. Rice explained.

Dr. Rice also pointed out that chronically elevated insulin levels and lowered insulin sensitivity in the brain are linked to obesity and type 2 diabetes, which affect millions worldwide. She said, "If our future experiments prove successful, it could confirm our hypothesis that when people refer to an insulin-glucose rush, they may really be referring to a dopamine reward rush. And there are healthy ways to get that by making smart food choices."

According to the World Health Organization, about 9 percent of adults aged 18 and above had raised blood glucose in 2014. WHO also said that in 2012, diabetes claimed 1.5 million lives worldwide, with deaths occurring in low- and middle-income countries. The organization projects that diabetes will become the seventh leading cause of death by 2030.