The Gut-brain Axis: a Novel Target for Treating Behavioral Alterations in Obesity

In prior studies we have demonstrated an inverse relationship between body mass index and response in the dorsal striatum (DS) during consumption of a palatable milkshake (Stice et al. 2008). We have also shown that the magnitude of the reduced response predicts weight gain, especially in individuals who carry a copy of the A1 allele of the taq1A polymorphism (Stice et al. 2008). Since the A1 allele is associated with reduced striatal D2 receptors (Jonsson et al. 1999, Noble 2003, Noble et al. 1991, Pohjalainen et al. 1998, Ritchie et al. 1998, Thompson et al. 1997), this finding implicates the dopamine system in the reduced blood oxygen level dependent (BOLD) response. Our results also indicate that this reduced response is a consequence, rather than a cause of obesity, since gaining weight (Stice et al. 2010), but not risk for obesity (Stice et al. 2011) (by virtue of parental obesity), is associated with reduced DS response to palatable food. Taken together the results indicate that increased adiposity is associated with blunted DS response to palatable food that may reflect altered dopamine signaling. More recently we determined that reduced DS responses in overweight and obese subjects are associated with increased impulsivity measured with the Barratt Impulsiveness Scale and a go no/no-go task (Babbs et al, In Press).

Related to these findings in humans, preliminary work in rodents shows that exogenous administration of N-Acylethanolamines, such as oleoylethanolamine (OEA) can normalize high-fat diet induced dopamine decreases in DS and possibly induce a shift in preference (Tellez et al., In Press). Human testing of OEA supplementation is possible based on the availability of a dietary supplement containing the OEA precursor NOPE-EGCG ((PhosphoLEANtm, 100 mg NOPE+50mg EGCG per capsule). PhosphoLEAN has been shown to enhance adherence to dietary advice in overweight healthy subjects (Rondanelli et al. 2009, Mangine et al. 2012).

We therefore propose a double-blind cross-over study to test whether PhosphoLean will rescue striatal function, increase adherence to a diet, reduce weight-gain after a diet, improve performance on impulsivity, go/no-go tasks, and negative outcome learning, and shift fat and sweet preference in overweight/obese human subjects.