Keynote Speakers

Frank Scheer
Professor of Medicine, Harvard Medical School (HMS)
Director, Medical Chronobiology Program, Brigham and Women’s Hospital (BWH)
Senior Neuroscientist, Departments of Medicine and Neurology, BWH

Chrononutrition to Optimize Health

Abstract
Nutrition, sleep, physical activity, metabolism, and circadian rhythms are tightly intertwined and have an important impact on health and disease. There is convincing evidence that uncoupling their timing, e.g., during shift work, light at night, or inverted activity rhythms, has adverse health consequences. Recent findings indicate that normalizing the eating rhythm alone can reduce or prevent these effects. These insights have ignited interest in the power of chrononutrition to improve health.

In this keynote, I will present evidence for how the endogenous circadian system regulates metabolism, energy use, and appetite; show how circadian misalignment affects health markers; and discuss the promise of leveraging food timing to improve health, especially in shift workers.

Biography
Frank A.J.L. Scheer, PhD, MSc, is Professor of Medicine at Harvard Medical School and Director of the Medical Chronobiology Program at Brigham and Women’s Hospital. His interdisciplinary research explores how circadian rhythms and behaviors affect disease severity, food timing, and individual genetic responses.

His goal is to guide personalized, time-based interventions—like diet, sleep, and light exposure—to prevent or manage chronic disease.

Funded continuously by the NIH since 2005, Dr. Scheer has held leading roles in SRBR, EBRS, and SRS, and served on editorial boards of several journals including SLEEP and Frontiers in Sleep. His awards include the Neal Miller Award, Pillars of Excellence Award, and Mrosovsky Keynote Lecture Award.

Valérie Simonneaux
Co-directrice d'équipe Régulation et Perturbation des Rythmes Neuroendocriniens
Institut des Neurosciences Cellulaires et Intégratives
CNRS UPR-3212, Strasbourg

Neuroendocrine mechanisms of seasonal adaptation and maladaptation

Abstract
Annual changes in environmental factors had led organisms to develop adaptive biological and behavioural strategies. In mammals, the seasonal change in the nocturnal production of the pineal hormone melatonin is pivotal for metabolic and reproductive adaptations.

The discovery that melatonin acts on the pars tuberalis to control the synthesis of TSH, which in turn acts on the hypothalamic tanycytes to modulate local thyroid hormone metabolism, has been a breakthrough in our understanding of the neuroendocrine mechanisms underlying seasonal adaptation. In this lecture, I will discuss how this melatonin/thyroid hormone signal regulates hypothalamic circuits to synchronize physiological functions with the seasons. I will also report how exposure to environmental disruptors may affect seasonal adaptation.

Biography
Valérie Simonneaux is a CNRS director of research at the Institute of Cellular and Integrative Neurosciences in Strasbourg, France and leader of the team “Regulation and Disruption of Neuroendocrine Rhythms”. She also leads the Strasbourg’s Interdisciplinary Institute of Neuroscience of the University of Strasbourg.

She has a broad background in the neuroendocrinology of biological rhythms. She studies the mechanisms by which daily information (via neuroendocrine outputs of the circadian clock) and seasonal information (via melatonin) synchronize the cycles of reproduction and metabolic activity. In this respect, her work has demonstrated that hypothalamic peptides of the RF-amide family (kisspeptin and RFRP-3) are essential relays between temporal signals and the activity of GnRH neurons, and that hypothalamic tanycytes are involved in the long-term effect of thyroid control of seasonal functions (reproduction, maternal photoperiodic programming, hibernation). Currently, her work focuses more specifically on the study of environmental disturbances (light pollution, endocrine disruptors, metabolic diseases) on biological rhythms. These projects involve collaborations with national (Tours, Strasbourg) and international (Rabat, Tromso, South Africa) public research teams.

Besides her research activity, she teaches Chronobiology, Neuroendocrinology and Environmental Neurosciences to Master students, and she organizes an International ChronoSchool in Strasbourg.

Debra J. Skene
Professor of Neuroendocrinology
University of Surrey

Melatonin and Metabolomics: Tracking central and peripheral clock rhythms in humans

Abstract
The endogenous melatonin rhythm is routinely used as a phase marker of the light-entrainable circadian clock in the hypothalamic suprachiasmatic nuclei (SCN), providing important information about the human circadian timing system. For example, melatonin measurements have characterised the phase-shifting effects of light (phase response curve), the intrinsic human period (tau), spectral sensitivity of circadian photoreception and desynchrony between the environment, behaviour and circadian timing when working night shifts.

With the discovery of peripheral clocks, tracking their timing in humans has proved more challenging. Early work measured clock gene expression in human tissue that could easily be obtained such as white blood cells, buccal tissue, adipose tissue, hair, skin and muscle biopsies. More recently high-throughput transcriptomics of human tissue has significantly increased sensitivity and coverage of the transcriptome. However, tracking human peripheral clocks in organs involved in digestion and metabolism, such as the liver, pancreas and gut remains a challenge.

In this lecture I will discuss the potential of metabolic profiling (metabolomics), using targeted UPLC-MS/MS technology, to track human peripheral clock timing in entrained and misaligned conditions. Experiments showing time-of-day and circadian variation in the human metabolome, the effects of sleep deprivation, mistimed food and simulated shift work on metabolite rhythms will be presented. After 3 nights of working shifts, endogenous circadian rhythms of many plasma metabolites were misaligned from the central SCN clock timing (melatonin and cortisol) by ~8–12 h (internal desynchrony), likely reflecting the peripheral clocks’ response to cues driven by mistimed behaviours. Melatonin measurement combined with metabolic profiling will thus be useful to measure circadian misalignment in shift work and test management strategies. The ambulatory U-RHYTHM device offers a novel and practical way of measuring high-resolution melatonin and metabolite rhythms in real life.

Biography
Debra J. Skene, PhD, FMedSci, is Professor of Neuroendocrinology in the Section of Chronobiology at the University of Surrey, UK. She has over 30 years of research experience studying the human circadian timing system and circadian rhythm sleep/wake disorders as experienced by blind people, shift workers and older people (>240 peer-reviewed publications).

Currently her main focus is studying the mechanisms linking circadian clocks, sleep and metabolism in health, circadian disorders and metabolic diseases using liquid chromatography/mass spectrometry (LC/MS) metabolomics. Currently Professor Skene's research team is studying the links between human circadian clocks, sleep/wake and feeding/fasting in health, circadian disorders and metabolic diseases (shift workers, Type 2 diabetes, liver disease). Investigating the effect of time of day, circadian clock, sleep and food influences on the human metabolome using targeted LC-MS metabolomics is currently a major focus.

Professor Skene is past President of the European Biological Rhythms Society (EBRS) and past Vice-President (Basic) of the European Sleep Research Society (ESRS). She is a Royal Society Wolfson Research Merit Awardee, an inventor on two granted patents and was a Co-Director of Stockgrand Ltd and Surrey Assays Ltd.

Anries Kalsbeek
Professor of Experimental Endocrinology
University of Amsterdam
Netherlands Institute for Neuroscience

Discovering the Ins and Outs of the SCN based on its Prototypical Neurotransmitter Vasopressin

Abstract
This lecture will concentrate on the significance of the vasopressin neurons in the SCN for the functional output of the biological clock that is contained within it. The vasopressin-containing subpopulation is a characteristic feature of the SCN in many species, including humans. The activity of the vasopressin neurons in the SCN shows a pronounced daily variation in its activity that has also been demonstrated in human post-mortem brains.

In the early years, animal experiments revealed an important role for SCN-derived vasopressin as an output signal in the control of neuroendocrine day/night rhythms, such as that of the hypothalamic-pituitary-adrenal (HPA) and hypothalamic-pituitary-gonadal (HPG) axes. More recently, studies using vasopressin receptor knockout animals highlighted its importance in the intrinsic synchrony of the SCN as well. Reducing vasopressin signaling within the SCN seems to reduce the robustness of the circadian clock and thereby facilitate resynchronization to a new L/D environment.

The remarkable correlation between a diminished presence of vasopressin in the SCN and a deterioration of sleep-wake rhythms during ageing and depression indicate that, also in humans, the vasopressin neurons contribute considerably to the rhythmic output of the SCN, but also highlight its potential as a target for therapeutic interventions.

Biography
Andries Kalsbeek is professor of Experimental Neuroendocrinology at the Department of Endocrinology and Metabolism at the Amsterdam UMC and leader of the Hypothalamic Integration Mechanisms group at the Netherlands Institute for Neuroscience (NIN), both in Amsterdam, The Netherlands.

He performed his Ph.D. work at the Netherlands Institute for Brain Research (NIBR, nowadays NIN) and received his Ph.D. in Neurobiology from the University of Amsterdam (supervisor Prof. D.F. Swaab). He completed postdoctoral training at the Université Louis Pasteur in Strasbourg (supervisor Prof. Paul Pevet) and the NIBR (supervisor Prof. Ruud Buijs).

Nowadays, his studies focus on the role of the hypothalamus in the control of energy metabolism, with an emphasis on glucose metabolism, hormonal rhythms, the central biological clock, and the autonomic nervous system. The most important scientific question throughout the years has been how circadian and metabolic (feedback) information is integrated in the hypothalamus and transferred onto the neuroendocrine and autonomic nervous system to modulate peripheral physiology.

His ultimate goal is to decipher the mechanisms involved in the circadian control of energy metabolism and understand how its perturbation results in pathologies like type 2 diabetes and obesity.

Martha Merrow
Visiting Professor in Circadian Medicine, University of Oxford
Professor emerita, Institute of Medical Psychology, LMU Munich

On assumptions and hypotheses: two unlikely chronobiology stories, Bacillus and the Stonechat

Abstract
In 1990, Ebo Gwinner published (with John Dittami) experiments on annual rhythms in the Stonechat that spanned at least 7.5 years. In 2021, my group and collaborators published experiments on circadian rhythms in Bacillus subtilis that had started over a decade earlier. In addition to describing both of these (disparate) stories, I will discuss the justification for such experimental work and how the foundations of chronobiology drive us forward whilst the structures of modern research might hold us back.

Biography
Martha Merrow is a professor of medical psychology and former head of the Institute of Medical Psychology at LMU Munich, one of Europe’s leading institutions for research and education. She is currently a visiting professor in Circadian Medicine at Oxford University.

Merrow studied and trained at Middlebury College, Tufts University School of Medicine, Dartmouth Medical School, and LMU Munich. She attained her first professorship at the University of Groningen in 2004 and returned to LMU Munich in 2012 until her mandatory retirement in 2023.

The research of the Merrow group has focused on entrainment of the circadian clock including in humans, as well as the discovery of new model systems in which to study circadian rhythms. Her most recent work in this direction describes circadian properties in Bacillus subtilis, a non-photosynthetic prokaryote representative of a category that includes 12% of life on earth.

Martha Merrow has served as secretary and member-at-large of the Society for Research on Biological Rhythms, and as President-elect and President of the European Biological Rhythms Society. She developed a new conferencing model (CArbon-REduced or CARE Conferencing) prior to the pandemic (link 1 and link 2). She has organized ‘Clock Clubs’ in the Netherlands and Germany, and faculty networks such as The Women’s Table (Groningen) and Frauentisch (Munich). She was elected as a member of the European Academy of Science and Arts in 2015 and has taught medical chronobiology students for decades.

Ralf Stanewsky
Institute of Neuro- and Behavioral Biology
University of Münster

Circadian temporal organization of behaviour and its benefits in insects

Abstract
Circadian rhythms are prevalent on Earth and temporally organize behaviour and physiology of organisms to occur in species specific ‘temporal niches’. However, species differ in how strictly individuals are controlled by their circadian clock, suggesting that it may offer advantages to extend the temporal niche under certain circumstances, for example during stressful environmental conditions. In this lecture, I will discuss two insect species (the fruit fly Drosophila melanogaster and the red flour beetle Tribolium castaneum) as examples for tight and relaxed temporal niche control, respectively. A potential mechanism controlling temporal niche adherence involves the evolutionary capacitor and chaperon protein HSP90. Within a small subset of clock neurons in the fly brain, HSP90 mitigates inter-individual behavioural variation by regulating expression of the circadian neuropeptide Pigment Dispersing Factor (PDF), presumably restricting temporal niche extension to stressful environmental conditions.

Even though such temporal organization and circadian clocks in general are not essential for survival of an individual (at least under laboratory conditions), it is assumed that they contribute to the overall fitness of organisms. By applying a novel behavioural choice assay we could show that the fruit fly D. melanogaster actively chooses environmental conditions allowing it to live in a temporally organized manner. Flies become arrhythmic in constant light, and offering them the possibility to enter a dark area restored circadian rhythms. We show that this self-generated behavioural rhythmicity is correlated with an improvement of sleep quality, demonstrating a direct benefit for circadian clocks and temporal organisation.

Biography
Ralf Stanewsky is a Professor of Molecular Behavioural Genetics at the Institute of Neuro- and Behavioural Biology at the University of Münster, Germany. He graduated from the University of Cologne (Germany) where he also obtained his PhD. His subjects were genetics and the study of nuclear proteins, which led him to a gene influencing vision and courtship song behaviours in the fruit fly Drosophila melanogaster.

For his Postdoc he went to the lab of Jeffrey C Hall (Nobel Laureate 2017), at Brandeis University in Waltham, MA (USA) to study the fruit fly circadian clock. In collaboration with Patrick Emery (at the time postdoc with Michael Rosbash) he identified Cryptochrome as a key protein for light-synchronisation of the circadian clock in fruit flies.

He set up his own lab at the University of Regensburg in Bavaria (Germany) before obtaining a Full Professorship at Queen Mary College, University of London and later on moved to UCL. Since 2016 he is a Professor at the University of Münster, Germany, where he continues his studies on the circadian clock.

His research focuses on how the circadian clock is synchronized to natural light:dark and temperature cycles, and how clocks can maintain constant clock speed, despite increasing temperatures, a phenomenon known as temperature compensation. Recently he also developed an interest to investigate the ecological importance of circadian clocks, for example to which extent individuals are confined to their temporal niche.