Summary: Study reveals the role the ventral tegmental area of the brain plays in craving protein-rich foods.
Source: University of Aberdeen
New research from scientists at the Universities of Aberdeen and Leicester in the UK and UiT The Arctic University of Norway has identified an area of the brain that may drive cravings for protein-rich food.
It is posited that a low protein diet contributes to obesity and this new finding could have implications for the development of targeted treatments for obesity.
The team found that when rats were given a low protein diet, a specific area of the brain known to play a central role in food-seeking behaviours called the ventral tegmental area (VTA), became more active when they were consuming protein-rich food.
The study led by Professor James McCutcheon at UiT The Arctic University of Norway was funded mainly by the BBSRC and the Leverhulme Trust and the Tromsø Research Foundation among other funding partners, is published in The Journal of Neuroscience.
The authors report that when protein had been restricted previously, the VTA responded more to protein than to other nutrients, which suggests that the animals’ brains had adapted to ensure protein levels are maintained.
Such an adaptation is meaningful as insufficient protein can have severe consequences for health and in extreme cases can lead to death. In addition, low levels of dietary protein has been proposed as a driver of obesity. Until now, it was not clear how the brain influenced protein intake.
Dr Fabien Naneix, Lecturer at the Rowett Institute at the University of Aberdeen, who co-led the study with Dr Giulia Chiacchierini, explains: “We found that protein restriction increased preference for protein enriched food over carbohydrate. This protein preference is associated with a greater VTA response and when animals are switched from a normal balanced diet to protein restriction, protein preference is rapidly induced but changes in VTA activity requires extensive learning processes. On the other hand, prior protein restriction induced slower changes in protein preference and maintained higher VTA responses for protein, suggesting long-lasting changes induced by protein appetite.
“Our findings are hugely significant as protein intake is essential for life. We need protein and amino acids for numerous biological processes and the only way is through food intake. So, it is important to understand how the brain drives our behaviours according to our current needs.
“Our study is the first linking changes in protein preference and specific brain activity. The VTA is known to play a central role in motivation processes for other nutrients and we show here it is also the case for protein.”
Dr Naneix completed this work at the University of Leicester prior to Dr Naneix joining the University of Aberdeen.
Funding: The project was funded by the European Commision the BBSRC, the Leverhulme Trust and the Tromsø Research Foundation. This work was funded by the Biotechnology and Biological Sciences Research Council [grant #BB/M007391/1 to J.E.M.], the European Commission [grant #GA 631404 to J.E.M.], The Leverhulme Trust [grant #RPG-2017-417 to J.E.M. and J.A-S.], and Tromsø Research Foundation [grant #19-SGJMcC to J.E.M)
NOTE: This article was amended with corrections provided by James McCutcheon, Principal Investigator and Corresponding Author of the study, on June 14, 2021.
About this neuroscience and food craving research news
Source: University of Aberdeen Contact: Press Office – University of Aberdeen Image: The image is in the public domain
Control of protein intake is essential for numerous biological processes as several amino acids cannot be synthesized de novo, however, its neurobiological substrates are still poorly understood. In the present study, we combined in vivo fiber photometry with nutrient-conditioned flavor in a rat model of protein appetite to record neuronal activity in the VTA, a central brain region for the control of food-related processes.
In adult male rats, protein restriction increased preference for casein (protein) over maltodextrin (carbohydrate). Moreover, protein consumption was associated with a greater VTA response, relative to carbohydrate.
After initial nutrient preference, a switch from a normal balanced diet to protein restriction induced rapid development of protein preference but required extensive exposure to macronutrient solutions to induce elevated VTA responses to casein. Furthermore, prior protein restriction induced long-lasting food preference and VTA responses.
This study reveals that VTA circuits are involved in protein appetite in times of need, a crucial process for animals to acquire an adequate amount of protein in their diet.
Acquiring insufficient protein in one’s diet has severe consequences for health and ultimately will lead to death. In addition, a low level of dietary protein has been proposed as a driver of obesity as it can leverage up intake of fat and carbohydrate.
However, much remains unknown about the role of the brain in ensuring adequate intake of protein.
Here, we show that in a state of protein restriction a key node in brain reward circuitry, the VTA, is activated more strongly during consumption of protein than carbohydrate.
Moreover, although rats’ behavior changed to reflect new protein status, patterns of neural activity were more persistent and only loosely linked to protein status.