Researchers from the University of California, Irvine report that oleic acid is converted to oleoylethanolamide (OEA), a lipid hormone, in the intestine. The study is reportedly the first time a food ingredient directly provides the raw materials for a hormone's production.
Previous studies reported that when OEA is administered as a drug it decreases meal frequency by engaging receptors called peroxisome proliferator-activated receptors alpha (PPAR-alpha).
If the results of the study, published in the journal Cell Metabolism, are repeated in further studies, particularly in humans, it could see oleic acid, or oleic acid-rich oils positioned in the weight management market.
With 50 per cent of Europeans and 62 per cent of Americans classed as overweight, the food industry is waking up to the potential of products for weight loss and management. The category is estimated to already be worth $7bn.
The researchers, led by Daniele Piomelli, report that an infusion of fat in the small intestine stimulated the mobilisation of OEA, while protein and carbohydrates did not.
Moreover, they found that OEA used oleic acid from the diet, and blood oleic acid had no effect.
“The results confirm that food-derived, rather than plasma-derived, oleic acid serves as substrate for OEA production,” wrote the researchers.
When they looked at animals genetically engineered to lack the membrane fatty-acid transporter CD36, no effect on satiety was observed, they said.
In general, the results indicated that CD36-mediated uptake of oleic acid from the diet enabled the activation of OEA release in the small intestine, and this serves as a molecular sensor linking fat consumption to satiety.
"Our studies identify OEA as a key physiological signal that specifically links dietary fat ingestion to across-meal satiety,” wrote the researchers. “Nutritional and pharmacological strategies aimed at magnifying this lipid-sensing mechanism, such as inhibitors of OEA degradation, might be useful in the treatment of obesity and other eating disorders," they concluded.
The researchers added that the findings in rats may ultimately produce a precise dietary makeup of fat and protein for optimal hunger control.
They also noted that diets high in processed foods with high saturated fat contents might disrupt this system of metabolic control.
"Eating is one of the most important things animals do," said Piomelli. "This is just one of many things that control it. That said, a system like this could be forced to inactivation by inappropriate feeding." Saturated fats generally lack in oleic acid.
Source: Cell Metabolism8 October 2008, Volume 8, Issue 4, Pages 281-288“The Lipid Messenger OEA Links Dietary Fat Intake to Satiety”Authors: G.J. Schwartz, J. Fu, G. Astarita, X. Li, S. Gaetani, P. Campolongo, V. Cuomo, D. Piomelli