Gut-brain crosstalk regulates craving for fatty food

Patients undergoing Roux-en-Y gastric bypass (RYGB) surgery elicit striking loss of body weight. Anatomical re-structuring of the gastrointestinal (GI) tract, leading to reduced caloric intake and changes in food preference, are thought to be the primary drivers of weight loss in bariatric surgery patients. However, the mechanisms by which RYGB surgery causes a reduced preference for fatty foods remain elusive. In a recent report, Hankir et al described how RYGB surgery modulated lipid nutrient signals in the intestine of rats to blunt their craving for fatty food. The authors reported that RYGB surgery restored an endogenous fat-satiety signaling pathway, mediated via oleoylethanolamide (OEA), that was greatly blunted in obese animals. In RYGB rats, high fat diet (HFD) led to increased production of OEA that activated the intestinal peroxisome proliferation activator receptors-α (PPARα). In RYGB rats, activation of PPARα by OEA was accompanied by enhanced dopamine neurotransmission in the dorsal striatum and reduced preference for HFD. The authors showed that OEA-mediated signals to the midbrain were transmitted via the vagus nerve. Interfering with either the production of OEA in enterocytes, or blocking of vagal and striatal D1 receptors signals eliminated the decreased craving for fat in RYGB rats. These studies demonstrated that bariatric surgery led to alterations in the reward circuitry of the brain in RYGB rats and reduced their preference for HFD.