HEALTH NEWS

Study Title:

Dietary Fat Helps Memory

Study Abstract

The ability to remember contexts associated with aversive and rewarding experiences provides a clear adaptive advantage to animals foraging in the wild. The present experiments investigated whether hormonal signals released during feeding might enhance memory of recently experienced contextual information. Oleoylethanolamide (OEA) is an endogenous lipid mediator that is released when dietary fat enters the small intestine. OEA mediates fat-induced satiety by engaging type-α peroxisome proliferator-activated receptors (PPAR-α) in the gut and recruiting local afferents of the vagus nerve. Here we show that post-training administration of OEA in rats improves retention in the inhibitory avoidance and Morris water maze tasks. These effects are blocked by infusions of lidocaine into the nucleus tractus solitarii (NTS) and by propranolol infused into the basolateral complex of the amygdala (BLA). These findings suggest that the memory-enhancing signal generated by OEA activates the brain via afferent autonomic fibers and stimulates noradrenergic transmission in the BLA. The actions of OEA are mimicked by PPAR-α agonists and abolished in mutant mice lacking PPAR-α. The results indicate that OEA, acting as a PPAR-α agonist, facilitates memory consolidation through noradrenergic activation of the BLA, a mechanism that is also critically involved in memory enhancement induced by emotional arousal.


From press release:

Having strong memories of that rich, delicious dessert you ate last night? If so, you shouldn't feel like a glutton. It's only natural.


UC Irvine researchers have found that eating fat-rich foods triggers the formation of long-term memories of that activity. The study adds to their recent work linking dietary fats to appetite control and may herald new approaches for treating obesity and other eating disorders.

Study results appear this week in the early online edition of the Proceedings of the National Academy of Sciences.

Daniele Piomelli, the Louise Turner Arnold Chair in Neurosciences, teamed with UCI's James McGaugh, one of the world's leading learning and memory researchers, to examine how dietary fats facilitate memory retention.

Piomelli's previous studies identified how oleic acids from fats are transformed into a compound called oleoylethanolamide (OEA) in the upper region of the small intestine. OEA sends hunger-curbing messages to the brain to increase feelings of fullness. In elevated levels, OEA can reduce appetite, produce weight loss and lower blood cholesterol and triglyceride levels.

Piomelli and McGaugh discovered that OEA also causes memory consolidation, the process by which superficial, short-term memories are transformed into meaningful, long-term ones. It does this, Piomelli said, by activating memory-enhancing signals in the amygdala, part of the brain involved in the consolidation of memories of emotional events.

The researchers found that administering OEA to rodents improved memory retention in two different tests. When cell receptors activated by OEA were blocked, memory retention effects decreased.

"OEA is part of the molecular glue that makes memories stick," Piomelli said. "By helping mammals remember where and when they have eaten a fatty meal, OEA's memory-enhancing activity seems to have been an important evolutionary tool for early humans and other mammals."

Dietary fats are important for overall health, helping with the absorption of vitamins and the protection of vital organs. While the human diet is now rich in fats, this was not the case for early humans. In fact, fat-rich foods in nature are quite rare.

"Remembering the location and context of a fatty meal was probably an important survival mechanism for early humans," Piomelli said. "It makes sense that mammals have this capability."

Today, he noted, such memory enhancement may not be so beneficial. While OEA contributes to feelings of fullness after a meal, it could also engender long-term cravings for fatty foods that, when eaten in excess, can cause obesity.

Currently, Piomelli said, drugs that mimic OEA are in clinical trials for triglyceride control. He is interested in learning whether they could improve consolidation in people with memory problems.

Patrizia Campolongo, Jin Fu, Giuseppe Astarita and Benno Roozendaal of UCI and Viviana Trezza and Vincenzo Cuomo of the University of Rome participated in the study, which was supported by grants from the National Institutes of Health.

Study Information

Patrizia Campolongo, Benno Roozendaal, Viviana Trezza, Vincenzo Cuomo, Giuseppe Astarita, Jin Fu, James L. McGaugh, and Daniele Piomelli.
Fat-induced satiety factor oleoylethanolamide enhances memory consolidation.
Proceedings of the National Academy of Sciences
2009 April
UC Irvine