Stress and food: investigating the neural connections
Comfort for the Troubled Mind Unraveling the neural circuits of stress eating
The vast majority of people nowadays experience stress in very different ways to our ancestors, but we often still respond in a similar way, namely by eating food. Dr Frank Meye tells us about his research into links between certain changes in the brain and stress-eating, work which could lead to new insights into several eating disorders. Many of us
react to a stressful day by treating ourselves to some sugary, fatty food, which often helps us to relax and unwind. This behaviour has deep historical roots, as it makes perfect sense from an evolutionary point of view, helping us to deal with stress efficiently. “Say you’re stressed because you’ve just been chased by a tiger, and you’ve used a lot of energy. When you’ve dealt with the stress, it makes sense to recover energy and probably even to consume more energy than you would have otherwise,” explains Dr Frank Meye. Tigers are not a common hazard nowadays, yet many of us still respond to modern forms of stress in a superficially similar way, a topic central to Dr Meye’s research. “The focus in my project is on stress-eating as a symptom not only of obesity, but also several eating disorders, for example bulimia nervosa,” he outlines.
Stress eating The wider goal in this research is to understand how stress-eating comes about, which holds importance for our understanding of not only obesity, but also several binge-eating disorders. Stress in this sense typically means the social and psychological stress that many of us experience on a daily basis, which can take several different forms. “Stress is not really a uniform concept – the kind of stress matters, and also the intensity of it. The effects can be different depending on if you have moderate or extremely high levels of stress, ” explains Dr Meye. A little bit of stress can be beneficial for an individual in some circumstances, making them feel involved in a task and driving them to
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perform well, but too much stress will have the opposite effect, which Dr Meye says may affect an individual’s attitude to food. “If stress becomes too intense, then you may become depressed, to the point where you lose interest in food,” he points out. This is not the main point of interest in the project, so researchers instead aim to mimic relatively moderate levels of stress in an animal model. In this model a mouse is paired with a larger, aggressive male. “The larger male asserts itself and shows who is the alpha male, and that leads to some fighting,” he says. The fighting is limited to a fairly short period, but for the rest of the time the
Project Objectives Neurons as viewed under a microscope. The green fluorescence in two cells identifies them as dopamine releasing. A thin glass patch pipette, coming in from the right, is placed on the top neuron to record its activity.
mice are co-habiting, separated by a semipermeable wall, so they are aware of each others’ presence. “There’s no actual physical stress at that point, nevertheless there is a looming stress,” continues Dr Meye. “We look at the response of the stressed mouse to this situation on the behavioural level in terms of food intake. We look at how much food the stressed mouse consumes, and we also give them a choice of food, to understand not only how much they eat and how many calories they consume, but also where they get their calories from.” The mouse is given a choice between bland but nutritious laboratory food,
We’re mainly focused on electrophysiological recordings from neurons embedded in identified brain circuits that we think are involved in stress-eating. typically referred to as chow, and a more fatty, tasty option. The data, both in terms of the amount of food consumed and the type, can then be compared to that from non-stressed mice, and Dr Meye has gained some interesting results. “The stressed mice show a greater preference for the tasty foods, and their overall calorie intake is increased as a consequence of that,” he outlines. Researchers are aiming to understand the neural circuits that are involved in this kind of behaviour. “We’re mainly focused on electrophysiological recordings from neurons embedded in identified brain circuits that we think are involved in stress-eating,” says Dr Meye.
EU Research
The goal of this study is to determine how stressors act on the function of specific neural circuits involving midbrain dopamine neurons, to enhance our proclivity for palatable food. To this end we use a mouse model of stress, and then use techniques that allow us to assess how such stress alters the function of midbrain dopamine neural circuitry, and what the consequence of this is for behaviors like intake of comfort food.
Project Funding
The funding for this particular project came from NWO (Veni Grant). https://www.nwo.nl/en/funding
Contact Details
A patch-clamp electrophysiology set-up allowing the recording of electrical activity of neurons identified as embedded in particular pathways in the brain.
A lot of attention here is focused on the dopamine system, which has been linked to reward processing. One hypothesis suggests that stress results in the dopamine system being primed in some way, so that both humans and animals are more inclined to seek out these highly-rewarding forms of food.“We make recordings of neurons, to see if they are indeed in a state where they’re more prone to firing,” outlines Dr Meye. Researchers are also using optogenetics to highlight specific pathways in the brain, from which more can be learned about their role in stress-eating. “Optogenetics has allowed us to make sure that only specific groups of neurons within a given piece of tissue become sensitive to the light. So we can stimulate neural circuits with much higher precision than previously possible,” explains Dr Meye. “We’re trying to understand exactly which pathways to, say, the dopamine system, are sensitive to stress.”
Preventative approaches This gives researchers a basis on which to investigate the changes in the brain that are involved in the stress-eating response in some way. From there, Dr Meye is also considering further steps, to actually prevent stress-eating from occurring. “We could take an approach where we try to silence a particular pathway to the dopamine neurons after stress, and see if that in itself is enough
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to prevent the stress-eating from occurring,” he explains. This would be a step towards proving a causal link between stress-induced changes in the brain and eating behaviour, which is a major priority in research. “That would be the goal – to show which changes are instrumental in driving that behaviour, and to identify strategies that can be employed with the mouse to prevent stress eating from occurrring,” continues Dr Meye. The mapping of which neural circuit changes are responsible for stress-eating in mice may not directly lead to translational approaches in humans, yet Dr Meye believes it could help researchers identify the areas in which attention should be focused. Over the short term, Dr Meye and his colleagues aim to build a clearer picture of which changes in the brain are associated with stress-eating. “We hope to have a thorough understanding of which parts of the brain that communicate with the dopamine system are actually altered by stress, and what the consequences of that are for stress-eating behaviour,” he says. Looking further ahead, Dr Meye has also gained funding from the ERC to look beyond the dopamine system. “This is kind of a more extended view of what really goes on during stress-eating,” he outlines. “With this ERC grant, we are also going to look at how cortical circuits may control the decisionmaking process in eating behaviour.”
Department of Translational Neuroscience Brain Center Rudolf Magnus Universiteitsweg 100; 3584 CG Utrecht The Netherlands Frank Meye T: +31 88 756 1234 E: f.j.meye-2@umcutrecht.nl W: www.meyelab.net W: https://www.researchgate.net/profile/Frank_Meye : @fjmeye
Frank Meye
Frank Meye has always been fascinated by the ways in which the function of specific neural circuits gives rise to reward seeking, and the ways in which this can become aberrant. During his PhD work (BRCM, Utrecht, The Netherlands) he demonstrated how the midbrain dopamine system (linked to reward seeking) is controlled by specific receptors implicated in feeding behavior. Afterwards, he pursued postdoctoral training at INSERM in Paris, France. There he used state-of-the-art approaches to decipher the neural basis for the aversive cocaine withdrawal state that emerges after abated use, and which is a key contributor to drug relapse. Currently as a young group leader he endeavors to unravel how stressful experiences drive us towards high-caloric unhealthy food choices.
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