Rachel Leproult

• PhD
• Cellule Europe at Université Libre de Bruxelles

Context The endocannabinoid (eCB) system partly controls hedonic eating, a major cause of obesity. While some studies suggested an over-activation of the eCB system in obesity, peripheral levels of eCBs across the 24-hr cycle have not been characterized in obese individuals despite the fact that in lean adults, levels of the eCB 2-arachidonoylglyce...

Aims: Chronic exposure to nocturnal transportation noise has been linked to cardiovascular disorders with sleep impairment as the main mediator. Here we examined whether nocturnal transportation noise affects the main stress pathways, and whether it relates to changes in the macro and micro structure of sleep. Methods and results: Twenty-six you...

Background: Slow-wave activity (SWA) in non-rapid eye movement (NREM) sleep, obtained by spectral analysis of the electroencephalogram, is a marker of the depth or intensity of NREM sleep. Higher levels of SWA are associated with lower arousability during NREM sleep and protect against sleep fragmentation. Multiple studies have documented that SWA...

Background: Epidemiological evidence indicates an association between transportation noise exposure and a higher risk of developing type 2 diabetes. Sleep disturbances are thought to be one of the mechanisms as it is well established that a few nights of short or poor sleep impair glucose tolerance and insulin sensitivity in healthy good sleepers....

Objectives: Obstructive sleep apnea (OSA) is more prevalent in men and is an independent risk factor for type 2 diabetes. We aimed to determine if there are sex differences in the impact of OSA on glucose metabolism in nondiabetic overweight and obese adults. Methods: One hundred and forty-five men and women (age 33.4 ± 0.6, BMI 37.2 ± 0.7, 70.3% b...

Study objectives This study investigates the impact of sleep deprivation (SD) on task-goal switching, a key component of cognitive flexibility. Methods Task-goal switching performance was tested after one night of regular sleep (n = 17 participants) or of total SD (n = 18). To understand the relationships between task-switching performance and oth...

Little is known about the regulation of temporal variations of progesterone over the 24-hr span in young cycling women as well as in postmenopausal women. The purpose of the present study was to investigate the relationships between diurnal variations of progesterone and diurnal variations of hormones of the gonadotropic and corticotropic axes, and...

Introduction Intermittency ratio (IR) has been proposed as a new metric to reflect the effects of transportation noise exposure on health. IR takes the frequency distribution of events into account. Since nocturnal transportation noise has been linked to higher risk of incident type 2 diabetes, we investigated the short-term effect of IR during sle...

Study Objectives Severe sleep restriction results in elevated evening cortisol levels. We examined whether this relative hypercortisolism is associated with alterations in the pituitary-adrenocortical response to evening corticotropin-releasing hormone (CRH) stimulation. Methods Eleven subjects participated in 2 sessions (2 nights of 10h versus 4h...

The present work investigates the effects of bright light exposure to prevent increased sleepiness and decreased alertness induced by a dual working memory task in which high cognitive demands (HCL) are adapted to the individual's maximal capacity. In a randomized cross-over study, twenty participants were exposed to two sessions that included 20 m...

Decreased neural plasticity is observed with healthy ageing in the primary sensorimotor (SM1) cortex thought to participate in motor learning and memory consolidation processes. In the present magnetoencephalography study, the post-training reorganization of resting-state functional connectivity (rsFC) and its relation with motor learning and early...

This magnetoencephalography study investigates how ageing modulates the relationship between pre-learning resting-state functional connectivity (rsFC) and subsequent learning. Neuromagnetic resting-state activity was recorded 5 min before motor sequence learning in 14 young (19–30 years) and 14 old (66–70 years) participants. We used a seed-based b...

Insufficient sleep and circadian rhythm disturbances have been each associated with adverse cardiovascular outcomes in epidemiological studies, but experimental evidence for a causal link is scarce. The present study compares the impact of circadian misalignment (CM) to circadian alignment (CA) on human autonomic function using a nonrandomized para...

Emerging evidence suggests that emotion and affect modulate the relation between sleep and cognition. In the present study, we investigated the role of rapid-eye movement (REM) sleep in mood regulation and memory consolidation for sad stories. In a counterbalanced design, participants (n = 24) listened to either a neutral or a sad story during two...

Study objectives: Increasing evidence from laboratory and epidemiologic studies indicates that insufficient sleep may be a risk factor for obesity. Sleep curtailment results in stimulation of hunger and food intake that exceeds the energy cost of extended wakefulness, suggesting the involvement of reward mechanisms. The current study tested the hy...

Sleep problems have been commonly reported in children with autism spectrum disorder (ASD). This review takes a lifespan perspective in discussing recent findings on sleep disturbances in ASD, including sparse but pivotal studies in toddlers and adults. Current evidence shows that more than a mere comorbidity, sleep disturbances can represent a key...

Epidemiological and laboratory studies, as well as clinical investigations in patients with sleep disorders, have provided strong evidence of a considerable impact of sleep restriction on endocrine–metabolic function. Both partial sleep deprivation (with a fairly good preservation of slow-wave sleep (SWS)) and SWS suppression or sleep fragmentation...

Beneficial effects of napping or bright light exposure on cognitive performance have been reported in participants exposed to sleep loss. Nonetheless, few studies investigated the effect of these potential countermeasures against the temporary drop in performance observed in mid-afternoon, and even less so on cognitive flexibility, a crucial compon...

Context: The endocannabinoid (eCB) system is involved in the regulation of food intake and of peripheral metabolism. Although the cross talk between energy metabolism and the circadian system is well documented, little is known about a potential circadian modulation of human eCB activity. Objective: The objective of the study was to define the 2...

Study objectives: A link between sleep loss and increased risk for the development of diabetes is now well recognized. The current study investigates whether sleep extension under real-life conditions is a feasible intervention with a beneficial impact on glucose metabolism in healthy adults who are chronically sleep restricted. Design: Interven...

Context: Insufficient sleep is associated with increased cardiometabolic risk. Alterations in hypothalamic-pituitary-adrenal axis may underlie this link. Objective: Our objective was to examine the impact of restricted sleep on daytime profiles of ACTH and cortisol concentrations. Methods: Thirteen subjects participated in 2 laboratory session...

Both reduction in total sleep duration with slow-wave sleep (SWS) largely preserved and alterations of sleep quality (especially marked reduction of SWS) with preservation of total sleep duration are associated with insulin resistance without compensatory increase in insulin secretion, resulting in impaired glucose tolerance and increased risk of t...

Shift workers, who are exposed to irregular sleep schedules resulting in sleep deprivation and misalignment of circadian rhythms, have an increased risk of diabetes relative to day workers. In healthy adults, sleep restriction without circadian misalignment promotes insulin resistance.To determine whether the misalignment of circadian rhythms that...

In the Stroop task, incongruent stimuli (e.g. “red” printed in blue) induce a robust interference effect. The impact of both the changes in the duration of the interval between the subject’s response and the next stimulus (RSI) and the development from childhood to adulthood on the size of the interference have not been systematically studied. We h...

To test the hypothesis that rapid eye movement (REM) sleep contributes to the consolidation of new memories, whereas non-rapid eye movement (NREM) sleep contributes to the prevention of retroactive interference. Randomized, crossover study. Two sessions of either a morning nap or wakefulness. Twenty-five healthy young adults. Declarative learning o...

Introduction Laboratory and epidemiological studies have evidenced an association between behavioral sleep restriction and an increased risk for the development of diabetes. The present study investigates the effects of bedtime extensions on fasting glucose and insulin levels in adults who are chronically sleep restricted during weekdays. Material...

Previous studies have shown that newly encoded memories are more resistant to retroactive interference when participants are allowed to sleep after learning the original material, suggesting a sleep-related strengthening of memories. In the present study, we investigated delayed, long-term effects of sleep vs. sleep deprivation (SD) on the first po...

Objective Dehydroepiandrosterone (DHEA) administration is widely evocated as a fountain of youth', but previous studies have provided inconsistent results. We aimed to investigate in healthy postmenopausal women the effects of a 3-week oral DHEA administration on individual steroid levels, multiple 24-h hormonal profiles and sleep architecture. Des...

Objectives: We previously reported that adult patients with GH deficiency (GHD) due to a confirmed or likely pituitary defect, compared with healthy controls individually matched for age, gender, and BMI, have more slow-wave sleep (SWS) and higher delta activity (a marker of SWS intensity). Here, we examined the impact of recombinant human GH (rhG...

Both circadian rhythmicity and sleep play significant roles in the regulation of plasma cortisol concentration by the hypothalamo-pituitary-adrenal (HPA) axis. Numerous studies have found links between sleep and changes in cortisol concentration, but the implications of these results have remained largely qualitative. In this paper, we present a qu...

Objectives: Sleep is regulated by circadian and homeostatic processes and is highly organized temporally. Our study was designed to determine whether this organization is preserved in patients receiving mechanical ventilation (MV) and intravenous sedation. Design: Observational study. Setting: Academic medical intensive care unit. Patients:...

Context A number of neuroactive progesterone metabolites produce sedative-like effects. However, the effects of progesterone administration on sleep are not well characterized. Objective To investigate the effects of a 3-wk progesterone administration on sleep architecture and multiple hormonal profiles. Subjects Eight healthy postmenopausal wome...

The acylation of ghrelin is essential for its stimulatory effects on GH release and appetite. Most of the physiology of ghrelin has been defined based on the assay of total ghrelin (TG), which mainly reflects levels of unacylated ghrelin. Whether levels of acylated ghrelin (AG) are influenced by circadian time and sleep and impact glucose regulatio...

Women with polycystic ovary syndrome (PCOS) are insulin resistant and have a high risk of early-onset diabetes and cardiovascular disease. Obstructive sleep apnea (OSA) has adverse cardiometabolic consequences and is highly prevalent in women with PCOS. We sought to determine whether continuous positive airway pressure (CPAP) treatment of OSA has b...

A number of neuroactive progesterone metabolites produce sedative-like effects. However, the effects of progesterone administration on sleep are not well characterized. To investigate the effects of a 3-wk progesterone administration on sleep architecture and multiple hormonal profiles. Eight healthy postmenopausal women, 48-74 yr old, without slee...

Sleep curtailment has become a common behavior in modern society. This review summarizes the current laboratory evidence indicating that sleep loss may contribute to the pathophysiology of diabetes mellitus and obesity. Experimentally induced sleep loss in healthy volunteers decreases insulin sensitivity without adequate compensation in beta-cell f...

Low energy and fatigue are frequent complaints in subjects with GH deficiency (GHD). Because interrelations between sleep and GH regulation are well documented, these complaints could partly reflect alterations of sleep quality. The objective of the study was to determine objective and subjective sleep quality and daytime sleepiness in adult GHD pa...

Compared to a few decades ago, adults, as well as children, sleep less. Sleeping as little as possible is often seen as an admirable behavior in contemporary society. However, sleep plays a major role in neuroendocrine function and glucose metabolism. Evidence that the curtailment of sleep duration may have adverse health effects has emerged in the...

The daily rhythm of cortisol secretion is relatively stable and primarily under the influence of the circadian clock. Nevertheless, several other factors affect hypothalamo-pituitary-adrenal (HPA) axis activity. Sleep has modest but clearly detectable modulatory effects on HPA axis activity. Sleep onset exerts an inhibitory effect on cortisol secre...

Introduction: the epidemic of diabesity The prevalence of obesity is increasing worldwide, particularly in the US. Obesity is a major risk factor for type 2 diabetes mellitus (T2DM), and it is estimated that more than 20 million Americans are currently diabetic and that one third of them remains undiagnosed (Diabetes statistics from the American Di...

The importance of sleep to hormones and glucose metabolism was first documented more than four decades ago. Since then, sleep curtailment has become an endemic behavior in modern society. In addition, the prevalence of sleep disorders, particularly obstructive sleep apnea (OSA), has increased. OSA is very common in endocrine and metabolic disorders...

Previous studies investigating the fluctuations of endocrine secretion across the menstrual cycle yielded inconsistent results. Our objective was to evaluate during the menstrual cycle the potential role of endogenous oestradiol and progesterone in the regulation of hormones primarily controlled by the circadian clock and/or the sleep-wake cycle. T...

Reduced sleep duration and quality appear to be endemic in modern society. Curtailment of the bedtime period to minimum tolerability is thought to be efficient and harmless by many. It has been known for several decades that sleep is a major modulator of hormonal release, glucose regulation and cardiovascular function. In particular, slow wave slee...

There is convincing evidence that, in humans, discrete sleep stages are important for daytime brain function, but whether any particular sleep stage has functional significance for the rest of the body is not known. Deep non-rapid eye movement (NREM) sleep, also known as slow-wave sleep (SWS), is thought to be the most “restorative” sleep stage, bu...

Sleep exerts important modulatory effects on neuroendocrine function and glucose regulation. During the past few decades, sleep curtailment has become a very common behavior in industrialized countries. This trend toward shorter sleep times has occurred over the same time period as the dramatic increases in the prevalence of obesity and diabetes. T...

To examine sex differences in nocturnal growth hormone and prolactin release in older adults. Sleep was polygraphically recorded for 2 consecutive nights, and blood was sampled at frequent intervals during the last 24 hours. The University of Chicago Clinical Research Center. Two groups of healthy nonobese older subjects: 10 men (59 +/- 2 years, me...

To examine sex effects on sleep stages and electroencephalogram (EEG) spectral power in older adults. Sleep was polygraphically recorded for 2 consecutive nights, and blood was sampled during the last 24 hours. The University of Chicago Clinical Research Center. Two groups of healthy nonobese older subjects: 10 men (59 +/- 2 years), and 10 postmeno...

Chronic sleep loss as a consequence of voluntary bedtime restriction is an endemic condition in modern society. Although sleep exerts marked modulatory effects on glucose metabolism, and molecular mechanisms for the interaction between sleeping and feeding have been documented, the potential impact of recurrent sleep curtailment on the risk for dia...

Older adults are less responsive to the phase-shifting effects of light than younger subjects and may have difficulties adapting to abrupt time shifts. This study aims to determine whether the potent melatonin agonist agomelatine (S-20098) is capable of phase-shifting overt circadian rhythms in older adults. Eight healthy elderly men participated i...

When energy intake is restricted in mammals, there are neuroendocrine adjustments in the secretion of reproductive and metabolic hormones to reallocate energy for vital functions. In the present study, we investigated whether there were differences in the luteinising hormone (LH), growth hormone (GH) and cortisol responses to a 48-h fast in adult g...

Sleep plays an important role in energy homeostasis. The present study tests the hypothesis that circulating levels of leptin, a hormone that signals energy balance to the brain, are influenced by sleep duration. We also analyzed associations between leptin and sympathovagal balance, cortisol, TSH, glucose, and insulin under different bedtime condi...

For more than 30 years, growth hormone (GH) has been observed to be preferentially secreted during deep, slow-wave sleep (SWS). However, the mechanisms that underlie this robust relationship that links anabolic processes in the body with behavioral rest and decreased cerebral metabolism remain to be elucidated. Current evidence indicates that GH se...

Sleep loss due to voluntary bedtime curtailment has become a hallmark of modern society. Even though sleep deprivation in rodents has been shown to result in death, it was until a few years ago thought that sleep loss results in increased sleepiness and decreased cognitive performance but has little or no adverse effects on human health. We measure...

This study examines the individual reproducibility of alterations of subjective, objective, and EEG measures of alertness during 27 h of continuous wakefulness and analyzes their interrelationships. Eight subjects were studied twice under similar constant-routine conditions. Scales and performance tasks were administered at hourly intervals to defi...

most of us have had the remarkable experience of performing several mental tasks very well during slight fever or while body temperature rises unexpectedly during jet lag. This may not simply be a misperception related to the fever process or desynchrony, as pointed out by Wright and colleagues ([13

Sleep loss due to voluntary bedtime curtailment has become a hallmark of modern society. Even though sleep deprivation in rodents has been shown to result in death, it was until a few years ago thought that sleep loss results in increased sleepiness and decreased cognitive performance but has little or no adverse effects on human health. We measure...

To investigate the adaptation of plasma cortisol profiles to an abrupt phase advance of the rest-activity cycle, eight normal young subjects were submitted in a sleep laboratory to an 8-h advance shift of their sleep-wake and dark-light cycles. The shift was achieved by advancing bedtimes from 2300-0700 to 1500-2300. Blood samples were obtained at...

In humans and mammals, reproducible, behavioral, as well as physiological changes happen over a period of 24 hr cycle. Sleep in humans is under the dual control of circadian rhythmicity and homeostatic process, which is in turn related to the depth of sleep and duration of prior wakefulness. In the normal aging process, profound variations have bee...

The only well documented effect of light exposure on endocrine function is the suppression of nocturnal melatonin. Bright light exposure has behavioral effects, including the alleviation of sleepiness during nocturnal sleep deprivation. The present study examines the effects of bright light on the profiles of hormones known to be affected by sleep...

In normal men, the majority of GH secretion occurs in a single large postsleep onset pulse that is suppressed during total sleep deprivation. We examined the impact of semichronic partial sleep loss, a highly prevalent condition, on the 24-h growth hormone profile. Eleven young men were studied after six nights of restricted bedtimes (0100-0500) an...

In young adults, sleep affects the regulation of growth hormone (GH) and cortisol. The relationship between decreased sleep quality in older adults and age-related changes in the regulation of GH and cortisol is unknown. To determine the chronology of age-related changes in sleep duration and quality (sleep stages) in healthy men and whether concom...