Rachel Leproult is a post-doc researcher working in the Neuropsychology and Functional Imaging Research Group (UR2NF) with Philippe Peigneux. After spending fifteen years at the University of Chicago, she returned to Brussels four years ago with the Brains Back to Brussels program. She is currently applying to obtain a Chaire Non Profilée with the ULB, which would give her a permanent position as a researcher in the CRCN, as well as the opportunity to teach a new course on sleep and health.
You have a slightly different educational background to most researchers here, can you tell me about it?
I obtained a bachelor in Mathematics and Statistics, here at the ULB, and then started to work with a researcher on sabbatical in Belgium, Eve Van Cauter from Chicago. I began to work on analysis of sleep and hormonal profiles. After a few months, Eve asked me to come to Chicago to continue working with her. At the beginning, I thought I would go for a year or two… I ended up staying seven years. During this time I was doing data analysis and was involved in many research projects – I was a researcher without knowing it. After a few years Eve advised me to do a PhD if I wanted to continue my career in research. After looking at different options, I realised a PhD in Biomedical Sciences was perfect for me. I came back to ULB and completed it in a speedy two years. After that Eve asked me to return to her lab in Chicago, and I stayed for another eight years. At that point I applied for a Brain Back to Brussels, a program which would allow me to be a post-doc at ULB. I had met Philippe Peigneux in a meeting and he had introduced me to MEG [magnetoencephalography]; I thought I might be able to do a project involving magnetic cerebral activity, so I was awarded the Brains Back to Brussels for three years and joined Philippe’s lab. I have been here for four years, having renewed the BBB after three years, for an extra two. In a year I will have finished with this program, which is one of the reasons why I am applying for the Chaire Non Profilée.
So you came from a very scientific background, with maths and stats – how did you transition to a more psychological background, studying sleep, physiology and metabolism as well as subjective and behavioural measures?
I’m studying new things every day! When I first started looking at hormonal profiles I was learning little by little. When we first spoke of circadian rhythms, Eve gave me papers to read and I had no idea what was going on. My English was also so-so, but luckily I worked with a lot of MDs who explained the physiology to me and I also read books, papers and used online resources to find information. Being self-taught gave me a very multidisciplinary approach. Now, in psychology, I’m still learning. It’s interesting because in the sleep field, vigilance is usually measured with simple tasks, especially the Psychomotor Vigilance Task, whereas psychology offers more complex cognitive tasks that can give a more in-depth portrayal of sleep. I can therefore incorporate all of these different perspectives in my research studies.
Why did you decide to come back to Belgium after these eight years?
I always had it in the back of my mind to come back to Europe, because I was born in France and had lived in Brussels. I loved Chicago, it’s a great city and the team I worked with was fantastic. While I was there, I actually came back to Brussels twice a year and now I find myself doing the opposite, traveling to Chicago twice a year to collaborate with my ex-team.
What is the overlap between metabolism and sleep in your studies? Do you study how sleep is modulated by hormones or how sleep modulates hormone profiles?
Mostly we looked at how sleep impacts hormonal profiles. These studies were pretty invasive because the subjects had a catheter from which blood samples were obtained every 20-30min. We tried to determine how hormonal profiles are affected with or without sleep. This allowed us to delineate the contribution of sleep to hormone secretion. We also asked our participants to sleep at different times of the day. For instance, after a night of sleep deprivation from 11pm to 7am, the participant is then made to sleep between 11am and 7pm. Some hormones are linked to the sleep period, like prolactin or growth hormone. Others, such as melatonin or cortisol, have reproducible patterns of expression each day, regardless of sleep; these hormones are mainly controlled by circadian processes. On the other hand, I didn’t personally look at how hormones affected sleep but I have participated in some studies where hormones were administered and their impact on sleep was measured. The interaction between sleep and hormones goes both ways, for sure.
So is your direct aim with these studies to produce treatments for people with sleep issues?
We began by studying the effects of one night of total sleep deprivation. Then, we moved on to more every-day life conditions, focusing on the fact that some people restrict their sleep during the week – this is semi-chronic sleep restriction. We started to study the impact of sleep restriction on health, more particularly on obesity and diabetic risk. This is how metabolism came into the picture. The aim then became to develop training and advice for people with these conditions. This is what I am doing currently: I am trying to study short sleepers – people who are sleep-restricted during the week and who recover during the weekend. We just conducted a study here at ULB, where we asked these subjects to sleep an extra hour per night. We observed that those who were able to do that could actually improve their insulin-sensitivity, meaning that the action of insulin was enhanced for them. I am now trying to do this study with diabetic patients. If this technique turns out to be effective, it would be an interesting treatment, or at least an additional factor that could improve traditional treatments.
What are the direct effects of sleep extension?
On average, people were able to achieve about 45min of additional sleep, as measured by self-timing, electroencephalographic recordings and actimeters. If you look at correlations, the participants who increased their sleep the most are also those who most improved their glucose metabolism. This was measured just from one fasting blood sample but it’s a promising start. It is already well known that sleep loss is bad for your health and a risk factor for diabetes, so now I have shown that the inverse intervention is also effective in improving glucose metabolism.
Is there a large part of sleep research which is dedicated to this simultaneous study of the hormonal and cognitive properties of sleep?
The field of sleep is very small and the section dedicated to study of sleep conjunct with hormones and cognition is even smaller. However, at the last sleep meeting I attended, there were many presentations about metabolism, whereas a few years ago, all we knew was that sleep loss negatively impacted vigilance but that health was fine overall. Eve Van Cauter directs the lab that first showed the actual impact of sleep loss on physiology. Now many people are interested in studying metabolism because it’s a hot topic, and there are very obvious implications for society.
So you study circadian rhythms as well as sleep?
Yes. The last protocol I worked on in Chicago included both sleep loss and circadian misalignment, which is what occurs in shift work or jet lag for example. It occurs when your internal clock is not synchronized with your environment and/or your sleep-wake cycle. We found that when you are desynchronized, the effects of sleep loss on metabolism are actually worse than with sleep loss alone. This paper was published in January in Diabetes and had a big impact because it was the first demonstration that circadian misalignment per se is harmful. So I have always studied sleep and circadian rhythms together, because they both influence hormonal profiles.
You look at the overlap of sleep and circadian rhythms and how they affect metabolism. Is there any way of using your knowledge of hormonal profiles to look at other cognitive processes like memory or cognitive control for example?
It’s true that some of the hormones related to sleep are also related to cognitive processes. In sleep deprivation studies, it is possible to test the subjects on cognitive functions every hour and observe their fluctuations in capacities and how they are linked to hormonal profiles. I look at this from a slightly different perspective, investigating how sleep loss could affect hormone secretion and cognitive functions and not exactly how these hormones affect cognitive functions. I published the findings of one study with total sleep deprivation where I looked at hormonal profiles, relative to sleepiness and vigilance profiles.
During sleep extension and sleep deprivation, what are the actual tests that you use on subjects?
In Chicago, the participants wore an actimeter to measure wrist activity from which we could derive both their active and resting periods. We also placed some electrodes on their scalp to measure sleep more accurately (polysomnography). We used a catheter to obtain 24-hour hormonal profiles. During the night, the catheter went through a little closed window to avoid disturbing the subject. To measure metabolism, we used what is called an IVGTT [intravenous glucose tolerance test] and obtained glucose and insulin profiles. We also used questionnaires to measure sleepiness, hunger, appetite, mood, global vigour, and global affect. Finally, we used some performance tasks such as PVT [psychomotor vigilance task], and a battery of tasks to measure logical reasoning, vigilance, response time, divided attention… Currently, I am using actimeters and performing polysomnographies to measure sleep. I cannot obtain hormonal profiles yet so we use one fasting blood sample instead. The cognitive tasks used in my current research include word-pair tasks to test memory, N-Back tasks to test working memory (numbers flash and you are asked to detect two identical consecutive numbers, for example), inhibitory tasks like Stroop and task switching, to name a few.
What are your future prospects in research?
As I mentioned, my main project is to study sleep extension in diabetics, and it is the one I would most like to pursue. I am also planning another project in collaboration with Karine Spiegel in Lyon which aims to look at the effect of sleep on people in weight loss programs. We want to investigate whether sleep extension would help the efficiency of the weight loss programs – either to influence the amount or quality of weight loss. In other projects, I want to look at the beneficial effects of light on cognitive tasks. We acquired what are called ‘Luminettes’ which are visors that project light to the bottom of the retina. We want to investigate if we could improve performances on different tasks with these visors. We already began one such project with Gaétane Deliens and Hichem Slama and light was effective in improving performance on task-switching. So we submitted one paper and we are now working on the revisions. We would like to pursue these studies by looking at the effects of light using the visors on word-pair memory task and N-back tasks with high cognitive load.
What is the importance of conducting research with a social outreach?
I believe that the main responsibility of a researcher consists in increasing knowledge about specific topics, a knowledge which should eventually lead to practical applications. Some types of research do not directly result in social outreach but are also important because they add pieces to the puzzle. These seemingly opposite types of research should be complementary. I have the privilege of working in areas of research that are immediately applicable to real life situations and I find this very rewarding.
Could you tell me more about your interest in teaching, and why you think it is important for researchers to teach and talk about their research?
I have always been interested in sharing my knowledge. I have never taught an entire course but I have contributed to several courses and lectures. Thus far, my audience has mainly been composed of my colleagues and the students I work with on research projects. I also find it important to be actively involved in meetings, in order to present my research data to various audiences. I believe the exchange of knowledge and ideas is of the utmost importance, more specifically, in my case, to stress the importance of sleep for health. Our current understanding of the implications of sleep on physiology suggests that endocrinologists, dieticians, psychologists, and generalist doctors alike, should integrate sleep into their clinical assessment and potentially their suggested treatment. As the fields of sleep research and sleep medicine are expanding, I am eager to teach a course on sleep, circadian rhythms and their impact on health. Such a course could be of great interest to students and offer potential ideas for job opportunities in these areas.
Research highlight by Lua Koenig