Mesolimbic lipid sensing and the regulation of feeding behaviour

In both developed and emerging countries, sedentary life style and over exposition to high energy dense foods has led to a thermodynamic imbalance and consequently obesity. Despite genetic predisposition, obesity often involves a behavioral component in which, similar to drugs of abuse, compulsive consumption of palatable food rich in lipids and sugar drives energy intake far beyond metabolic demands. Food intake is modulated by sensory inputs, such as tastes and odours, as well as by affective or emotional states. The mesolimbic pathway is well established as a main actor of the rewarding aspect of feeding. Particularly, the hedonic and motivational aspects of food are closely tied to the release of the neurotransmitter dopamine (DA) in striatal structure such as the Nucleus Accumbens (Nacc). In both rodent and humans several studies shows an attenuated activity of dopaminergic signal associated with obesity and there is evidence that consumption of palatable food per se leads to DA signalling alterations. Furthermore impaired cognition in obese mice is improved by selectively lowering triglycerides (TG) and intracerebroventricular administration of TG induces by itself acquisition impairment in several cognitive paradigms in normal body weight mice. Together, these observations raise the possibility that nutritional lipids, particularly TG, directly affect cognitive and reward processes by modulating the mesolimbic pathway and might contribute to the downward spiral of compulsive consumption of palatable and obesity. This review is an attempt to capture recent evolution in the field that might point toward a direct action of nutritional lipid in the mesolimbic pathway.