Ultradian hydrocortisone replacement alters neuronal processing, emotional ambiguity, affect and fatigue in adrenal insufficiency: The PULSES trial

Extended-release Hydrocortisone Formulations-Is There a Clinically Meaningful Benefit?

Despite best practice replacement therapy with corticosteroids, patients with adrenal insufficiency report diminished quality of life and face increased mortality and morbidity. Conventional formulations of hydrocortisone have short half-lives (about 90 minutes) requiring multiple dosing during the day. Since 2011, extended-release hydrocortisone (ER-HC) formulations have been available enabling once-, sometimes twice-daily dosing. Most studies comparing ER-HC formulations with conventional hydrocortisone therapy report reduction in body weight, blood pressure and glucose levels, and improved quality of life. However, it is still unclear if the reported beneficiary effects are due to differences in cortisol exposure or alterations in pharmacokinetics. Here, we review studies comparing conventional and ER-HC treatment in adrenal insufficiency and discuss whether these novel formulations are safe and offer clinically significant benefits.

Cortisol, Stress, and Disease-Bidirectional Associations; Role for Corticosteroid-Binding Globulin?

Selye described stress as a unified neurohormonal mechanism maintaining homeostasis. Acute stress system activation is adaptive through neurocognitive, catecholaminergic, and immunomodulation mechanisms, followed by a reset via cortisol. Stress system components, the sympathoadrenomedullary system, hypothalamic-pituitary-adrenal axis, and limbic structures are implicated in many chronic diseases by establishing an altered homeostatic state, allostasis. Consequent "primary stress system disorders" were popularly accepted, with phenotypes based on conditions such as Cushing syndrome, pheochromocytoma, and adrenal insufficiency. Cardiometabolic and major depressive disorders are candidates for hypercortisolemic etiology, contrasting the "hypocortisolemic symptom triad" of stress sensitivity, chronic fatigue, and pain. However, acceptance of chronic stress etiology requires cause-and-effect associations, and practical utility such as therapeutics altering stress system function. Inherent predispositions to stress system perturbations may be relevant. Glucocorticoid receptor (GR) variants have been associated with metabolic/neuropsychological states. The SERPINA6 gene encoding corticosteroid-binding globulin (CBG), was the sole genetic factor in a single-nucleotide variation-genome-wide association study linkage study of morning plasma cortisol, a risk factor for cardiovascular disease, with alterations in tissue-specific GR-related gene expression. Studies showed genetically predicted high cortisol concentrations are associated with hypertension and anxiety, and low CBG concentrations/binding affinity, with the hypocortisolemic triad. Acquired CBG deficiency in septic shock results in 3-fold higher mortality when hydrocortisone administration produces equivocal results, consistent with CBG's role in spatiotemporal cortisol delivery. We propose some stress system disorders result from constitutional stress system variants rather than stressors themselves. Altered CBG:cortisol buffering may influence interstitial cortisol ultradian surges leading to pathological tissue effects, an example of stress system variants contributing to stress-related disorders.

Circadian and ultradian rhythms: Clinical implications

The hypothalamic-pituitary-adrenal axis is an extremely dynamic system with a combination of both circadian and ultradian oscillations. This state of 'continuous dynamic equilibration' provides a platform that is able to anticipate events, is sensitive in its response to stressors, remains robust during perturbations of both the internal and external environments and shows plasticity to adapt to a changed environment. In this review, we describe these oscillations of glucocorticoid (GC) hormones and why they are so important for GC-dependent gene activation in the brain and liver, and their consequent effects on the regulation of synaptic and memory function as well as appetite control and metabolic regulation. Abnormalities of mood, appetite and metabolic regulation are well-known consequences of GC therapy, and we suggest that the pattern of GC treatment and hormone replacement should be a much higher priority for endocrinologists and the pharmaceutical industry. One of the major impediments to our research on the importance of these cortisol rhythms in our patients has been our inability to measure repeated levels of hormones across the day in patients in their home or work surroundings. We describe how new wearable methodologies now allow the measurement of 24-h cortisol profiles - including during sleep - and will enable us to define physiological normality and allow us both to develop better diagnostic tests and inform, at an individual patient level, how to improve replacement therapy.

Cell Signaling in the Circadian Pacemaker: New Insights from in vivo Imaging

BACKGROUND

"One for all, and all for one," the famous rallying cry of the Three Musketeers, in Alexandre Dumas's popular novel, certainly applies to the 20,000 cells composing the suprachiasmatic nuclei (SCN). These cells work together to form the central clock that coordinates body rhythms in tune with the day-night cycle. Like virtually every body cell, individual SCN cells exhibit autonomous circadian oscillations, but this rhythmicity only reaches a high level of precision and robustness when the cells are coupled with their neighbors. Therefore, understanding the functional network organization of SCN cells beyond their core rhythmicity is an important issue in circadian biology.

SUMMARY

The present review summarizes the main results from our recent study demonstrating the feasibility of recording SCN cells in freely moving mice and the significance of variations in intracellular calcium over several timescales.

KEY MESSAGE

We discuss how in vivo imaging at the cell level will be pivotal to interrogate the mammalian master clock, in an integrated context that preserves the SCN network organization, with intact inputs and outputs.

Recent advances in the crosstalk between the brain-derived neurotrophic factor and glucocorticoids

Brain-derived neurotrophic factor (BDNF), a key neurotrophin within the brain, by selectively activating the TrkB receptor, exerts multimodal effects on neurodevelopment, synaptic plasticity, cellular integrity and neural network dynamics. In parallel, glucocorticoids (GCs), vital steroid hormones, which are secreted by adrenal glands and rapidly diffused across the mammalian body (including the brain), activate two different groups of intracellular receptors, the mineralocorticoid and the glucocorticoid receptors, modulating a wide range of genomic, epigenomic and postgenomic events, also expressed in the neural tissue and implicated in neurodevelopment, synaptic plasticity, cellular homeostasis, cognitive and emotional processing. Recent research evidences indicate that these two major regulatory systems interact at various levels: they share common intracellular downstream pathways, GCs differentially regulate BDNF expression, under certain conditions BDNF antagonises the GC-induced effects on long-term potentiation, neuritic outgrowth and cellular death, while GCs regulate the intraneuronal transportation and the lysosomal degradation of BDNF. Currently, the BDNF-GC crosstalk features have been mainly studied in neurons, although initial findings show that this crosstalk could be equally important for other brain cell types, such as astrocytes. Elucidating the precise neurobiological significance of BDNF-GC interactions in a tempospatial manner, is crucial for understanding the subtleties of brain function and dysfunction, with implications for neurodegenerative and neuroinflammatory diseases, mood disorders and cognitive enhancement strategies.

Clinical Endocrinology-Time for a Reset?

Measurement of blood levels of circulating hormones has always been the cornerstone of the biochemical diagnosis of endocrine diseases, with the objective of detecting hormone excess or insufficiency. Unfortunately, the dynamic nature of hormone secretion means single-point measurements of many hormones often lack diagnostic validity. Endocrinologists have devised complex dynamic tests as indirect assessments of the functioning of the hormone system under investigation. Recent advances in the measurement of dynamic hormone changes across the day now offer an opportunity to reconsider whether there might be better ways both to diagnose and to monitor the therapy of endocrine conditions.

How an appreciation of dynamics has altered our understanding of the HPA axis

Rhythmicity is a intrinsic feature of biological systems, including the hypothalamic-pituitary-adrenal axis, a mammalian neurohormonal system crucial both in daily life and as a network that responds to stressful stimuli. Circadian and ultradian rhythmicity underlie HPA activity in rodents and in humans, regulating gene expression, metabolism and behavior, and adverse consequences occur when rhythms are disturbed. In the assessment of human disease, the complexity of HPA rhythmicity is rarely acknowledged or understood, and is currently a limitation to better diagnosis and treatment. However, the recent emergence of ambulatory, high frequency and blood-free hormone sampling techniques has the promise to substantially change our understanding of the function of HPA axis in healthy normal life, and provide new opportunities for the diagnosis and treatment of disease.