- Chronic overconsumption of a western diet - foods consisting high levels of sugars and fats causes obesity.
- Peripheral endocannabinoid signaling seems to be the reason behind consuming more calories and adherence to a western diet in mice.
- Inhibiting peripheral endocannabinoid signaling with inhibitors like AM6545 completely normalized intake.
Hyperphagia or consuming significantly more calories, and significantly larger meals at a much higher rate of intake is closely related to western diet - foods consisting high levels of sugars and fats.
DiPatrizio and coauthor Donovan A. Argueta, a bioengineering Ph.D. student in his lab, used a mouse model of western diet-induced obesity (chronic exposure to high levels of sugars and fats).
They found that when compared to mice fed a standard low-fat/low-sugar diet, mice fed a western diet for 60 days rapidly gained body weight and became obese, and displayed hyperphagia.
Chronic consumption of a western diet leads to overeating and obesity due to elevations in "peripheral endocannabinoid signaling."
The endocannabinoid system is located throughout the mammalian body, including the brain and all peripheral organs, and participates in the control of many physiological functions in the body, including food intake, energy balance, and reward.
It is comprised of lipid signaling molecules called endocannabinoids which can be thought of as the body's own "natural cannabis" that bind to cannabinoid receptors located on cells throughout the body.
"Our research shows that targeting cannabinoid receptors in the periphery with pharmacological inhibitors that do not reach the brain holds promise as a safe therapeutic approach for the treatment of overeating and diet-induced obesity," said Nicholas V. DiPatrizio, an assistant professor of biomedical sciences in the School of Medicine, who led the research project.
"This therapeutic approach to targeting the periphery has substantial advantages over traditional drugs that interact with the brain and cause psychiatric side-effects."
The work describes for the first time that overeating associated with chronic consumption of a western diet is driven by an enhancement in endocannabinoid signals generated in peripheral organs.
To examine the role for endocannabinoids generated in peripheral organs in controlling the overeating of western diet. DiPatrizio and Argueta caution that further research is necessary to identify whether similar mechanisms drive obesity in humans.
"Importantly, however, other research groups have reported elevations in circulating levels of endocannabinoids in obese human subjects, which suggests that this system may also be overactive in human obesity," DiPatrizio said.
He explained that rimonabant, a drug which blocked endocannabinoid signaling at cannabinoid receptors, was on the market in Europe for the treatment of human obesity. "It worked quite well at reducing body weight and improving metabolic profiles; however, this drug was not restricted to the periphery and thus, led to severe psychiatric side effects and was not given FDA approval in the United States," DiPatrizio said.
"Peripherally restricted inhibitors of cannabinoid receptors, such as AM6545 used in our experiments, however, would be devoid of these side effects given that they do not reach the brain."
DiPatrizio and Argueta were surprised to find that inhibiting peripheral endocannabinoid signaling with inhibitors like AM6545 completely normalized intake to that found in lean mice maintained on a standard chow.
Next, the researchers plan to identify critical upstream and downstream mechanisms of endocannabinoid signaling in western diet-induced obesity, as well as the possible specific dietary constituents in western diet (e.g., sucrose) that drive overeating as a result of elevated peripheral endocannbinoid levels.
"In addition, we aim to translate our work in rodents to similar studies in humans," DiPatrizio said.
- Donovan A. Argueta and Nicholas V. DiPatrizio, Peripheral endocannabinoid signaling controls hyperphagia in western diet-induced obesity, Physiology & Behavior (2017) http:dx.doi.org/10.1016/j.physbeh.2016.12.044.