The brain directly senses the presence of triacylglycerols.
In a recently published study, Cansell and co-workers show very clearly that the presence of triglycerides in the blood affects dopamine-signalling from the brain. This is part of the so called “reward-system”, which is very important in controlling preferences for palatable food. In the study, they show that infusing small amounts of triglycerides in the brain, this reduced the preference for palatable (sweet and fat) food and reduced their feed-seeking behaviour. This is might be an important finding, since it indicates that the triglyceride-peaks in the blood occurring after a meal is important in regulating appetite and preferences for energy-dense foodstuffs, and that increased strive after sugar and fat might be due to dysfunctions in this system.
Reference: Cansell C, Castel J, Denis RG, Rouch C, Delbes AS, Martinez S, Mestivier D, et al. Dietary triglycerides act on mesolimbic structures to regulate the rewarding and motivational aspects of feeding. Mol Psychiatry 2014.