Understanding the neurological mechanisms that contribute to obesity

Obesity is increasingly an acute public health issue in industrialised countries. According to WHO, in 2022, 1 in 8 people in the world were living with obesity. Worldwide adult obesity has more than doubled since 1990, and adolescent obesity has quadrupled. Obesity can lead to increased risk of type 2 diabetes and heart disease, it can affect bone health and reproduction, it increases the risk of certain cancers and influences quality of life. Understanding the neurological mechanisms that contribute to obesity and the effectiveness  of existing treatments is therefore of high societal interest. This is why Marta Lapo Pais - a PhD student at the University of Coimbra - has designed and implemented a clinical neuroimaging multimodal study involving 48 participants. Her study mobilises  PET and MRI imaging approaches, supported by the Brain Imaging network (BIN) Node in Coimbra, to better understand the long-term effectiveness of one the most common obesity treatments, bariatric surgery.

Marta Lapo Pais is a PhD student in her last year at the University Coimbra, Faculty of Science & Technology. Her PhD project aims at understanding the relationship between the central dopamine receptors in the brain and the success of bariatric surgery in promoting a 50% weight-loss in obese subjects. 

Getting access to crucial imaging technologies

From the beginning, Marta knew she would need access to PET and MRI. During her PhD, she had taken advantage of the local ecosystem to learn as much as she could about imaging techniques and data analysis, but still she was missing the equipment and support from expert staff. Thus, she reached out to Professor Miguel Castelo Branco, the Head of the Portuguese Brain Imaging Network (BIN) Node in Coimbra. 

“I started joining informal weekly meetings with people on the campus who are working with PET & MRI. These meetings gave me a lot of insights into the technologies and I was also able to present my work there and get advice. I was really lucky to be surrounded by this ecosystem, ”

• Marta Lapo Pais

The proximity of the Node facility made it easier to manage the recruitment and management of participants, as well as the image acquisitions. Marta and the Node’s staff recruited 48 female participants divided into three groups: one including patients who underwent the bariatric surgery and presented a successful response, plus a group of  participants with obesity and a group of participants with normal weight. All the groups underwent clinical, anthropometrics and behavioural assessment, as well as PET and MRI scans to understand the gut brain axis, i.e. how the gut influences the brain. For that purpose, the central dopamine receptors were mapped through PET, and responses to food cues were analyzed by functional MRI. 

“In my first academic year, I was able to take some theoretical courses on PET and MRI. Then I started joining informal weekly meetings with people on the campus who are working with PET and MRI. These meetings gave me a lot of insights into the technologies and I was also able to present my work there and get advice. I was really lucky to be surrounded by this ecosystem, where it was possible for me to learn so much about imaging techniques and data analysis,” explains Marta. 

The experiment unfolds

Marta took care of the clinical, anthropometrics and behavioural assessment and was present during the image acquisition to support the subjects, while the Node staff performed most of the technical work including image reconstruction. Pre-processing and processing of the image data were then made by Marta, with support from the Node.

While control groups were recruited in Coimbra, the subjects in the surgery group came from all over Portugal. Thus, the study took quite some time to be completed, but in the end it nicely concluded that the obesity groups did have altered higher availability of central dopamine receptors in comparison with the control group. Even more interestingly, Marta found that bariatric surgery seems to restore the availability of these receptors, as levels within the treated group were closer to normal groups. 

Gaining new skills & perspectives for the future

Overall, accessing the BIN Node for her clinical study was very good for Marta’s career perspective. On the one hand, it contributed to the successful completion of her PhD project and the resulting data have been submitted for publication in Nature Communications. In addition, Marta learnt a lot about medical imaging data analysis, which is the field where she would like to work in the future. “It’s really wonderful to have gained knowledge in these technologies through the BIN Node,” she said.

Article written by Alessandra Viale