Summary: Fruit flies use the neurotransmitter octopamine to decide whether food memories are stored long-term or short-term. This process, influenced by energy reserves, affects future eating behavior.
High glycogen levels lead to stable food memories, leading to increased food consumption even after fasting. Research suggests that similar mechanisms could influence overeating in humans.
Highlights:
- Octopamine in fruit flies decides the storage of food-related memories based on energy reserves.
- High glycogen levels lead to lasting food memories and increased food consumption.
- The study provides potential insights into overeating and obesity in humans.
Source: University of Cologne
In behavioral experiments using the fruit fly Drosophila melanogaster, a research team from the Institute of Zoology at the University of Cologne studied the control of food intake in the brain.
Similar to humans, insulin-like molecules regulate food intake in fruit flies. Among other things, this is influenced by a system of neurotransmitters that mediates decisions.
The system uses the neurotransmitter octopamine, a molecule related to norepinephrine. The neurotransmitter determines whether memories of carbohydrate consumption are stored in long-term or short-term memory.
This decision is made based on the level of internal energy reserves, which in turn will have a decisive influence on future dietary behavior.
The study, led by Professor Dr Henrike Scholz, was published in the journal eLife under the title “Octopamine integrates the state of internal energy supply in the formation of food-related memories”.
Researchers studied how light fasting and reduced glycogen levels in fat and muscle tissue affect carbohydrate perception in fruit flies. Glycogen, the storage form of glucose, is stored in fatty tissues and is widely used for energy in muscles.
Information about the energy reserves of these tissues is integrated into the decision-making system by octopamine and influences the biomechanics of the brain.
Previous studies have shown that overeating can lead to increased glycogen levels in animals and humans. In the experiment, fruit flies were genetically modified to have a higher glycogen level.
During fasting, the increase in energy reserves leads to the formation of a very stable memory that does not disappear when eating again. This is also the case if the nutritional value of the next meal is indeed sufficient to compensate for the deficits caused by fasting. Memory triggers an increase in food consumption.
If the glycogen level was very high, the consumption of carbohydrates in the experiment resulted in only a small rewarding effect in the brain. This diminished effect fueled the desire to continue eating.
If food intake was sufficient or there was sufficient energy in the animal, the decision-making system in turn suppressed the formation of such a more lasting memory regarding the food source.
This was independent of the carbohydrate content of the food or whether it was protein enriched. In general, glycogen level had no influence on how fruit flies evaluated protein-enriched foods.
Carbohydrate Memories: Once Helpful, Now Harmful
Depending on the energy level, octopamine is responsible for the type of memory that is formed in response to food intake: foods that normally offer sufficient nutritional value are no longer perceived as sufficiently rewarding. The result can be overeating, regardless of the nutritional value or type of food.
“In ancient times, when food was a limited or rare resource, this mechanism could be used to build up energy reserves when food was available. In times of food surplus, long-lasting memory of a carbohydrate source may promote excessive food consumption and thus contribute to the development of obesity,” said lead author Henrike Scholz.
No studies prove a similar mechanism in humans, but because the molecules involved are very similar in fruit flies and humans, the research team suggests that the mechanism works similarly.
The results could therefore explain why it is difficult to lose weight: if the memory of the rewarding effect of food lasts longer than the rewarding and satiating effect of the actual food intake, this may lead to an increase in consumption eating.
Scholz concluded: “In the future, it might be important to figure out how to erase this lasting memory so that losing weight becomes easier. »
About this research news in neuroscience and food memory
Author: Eva Schüssler
Source: University of Cologne
Contact: Eva Schissler – University of Cologne
Picture: Image is credited to Neuroscience News
Original research: Free access.
“Octopamine integrates the state of internal energy supply into the formation of food-related memories” by Henrike Scholz et al. eLife
Abstract
Octopamine integrates the state of internal energy supply into the formation of food-related memories
The brain regulates food consumption in response to internal energy demands and food availability. However, can internal energy storage influence the type of memory formed?
We show that the duration of famine determines whether Drosophila melanogaster forms intermediate appetitive memories in the short term or longer term.
Internal storage of glycogen in muscle and adipose tissue influences the intensity of information storage associated with sucrose. Insulin-like signaling in octopaminergic reward neurons integrates internal energy storage into memory formation. Octopamine, in turn, suppresses long-term memory formation.
Octopamine is not required for short-term memory, because octopamine-deficient mutants can form appetitive short-term memory for sucrose and other nutrients depending on internal energy state.
The reduced positive reinforcement effect of sucrose at high internal glycogen levels, combined with the increased stability of food-related memories due to prolonged periods of starvation, could lead to increased food consumption.
News Source : neurosciencenews.com
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