Time-restricted feeding reveals a role for neural respiratory clocks in optimizing daily ventilatory-metabolic coupling in mice.

The master circadian clock, located in the suprachiasmatic nuclei (SCN), organizes the daily rhythm in minute ventilation (V̇e). However, the extent that the daily rhythm in V̇e is secondary to SCN-imposed O2 and CO2 cycles (i.e., metabolic rate) or driven by other clock mechanisms remains unknown. Here, we experimentally shifted metabolic rate using time-restricted feeding (without affecting light-induced synchronization of the SCN) to determine the influence of metabolic rate in orchestrating the daily V̇e rhythm. Mice eating predominantly at night exhibited robust daily rhythms in O2 consumption (V̇o2), CO2 production (V̇co2), and V̇e with similar peak times (approximately ZT18) that were consistent with SCN organization. However, feeding mice exclusively during the day separated the relative timing of metabolic and ventilatory rhythms, resulting in an approximately 8.5-h advance in V̇co2 and a disruption of the V̇e rhythm, suggesting opposing circadian and metabolic influences on V̇e. To determine if the molecular clock of cells involved in the neural control of breathing contributes to the daily V̇e rhythm, we examined V̇e in mice lacking BMAL1 in Phox2b-expressing respiratory cells (i.e., BKOP mice). The ventilatory and metabolic rhythms of predominantly night-fed BKOP mice did not differ from wild-type mice. However, in contrast to wild-type mice, exclusive day feeding of BKOP mice led to an unfettered daily V̇e rhythm with a peak time aligning closely with the daily V̇co2 rhythm. Taken together, these results indicate that both daily V̇co2 changes and intrinsic circadian time-keeping within Phox2b respiratory cells are predominant orchestrators of the daily rhythm in ventilation.NEW & NOTEWORTHY The master circadian clock organizes the daily rhythm in ventilation; however, the extent that this rhythm is driven by SCN regulation of metabolic rate versus other clock mechanisms remains unknown. We report that metabolic rate alone is insufficient to explain the daily oscillation in ventilation and that neural respiratory clocks within Phox2b-expressing cells additionally optimize breathing. Collectively, these findings advance our mechanistic understanding of the circadian rhythm in ventilatory control.

Utility, acceptability and applicability of a nucleic acid amplification test in comparison with a syndromic approach in the management of sexually transmitted diseases at Mulago National Referral Hospital in Uganda (ASTRHA): protocol for an open-label, randomised controlled trial.

INTRODUCTION: Sexually transmitted diseases (STDs) are a major cause of long-term disability. Urethral discharge syndrome (UDS), abnormal vaginal discharge (AVD) and genital ulcer disease (GUD) are very common in low-income and middle-income countries (LMICs), where, due to lack of resources, these infections are managed according to a syndromic approach. Although microbiological diagnosis using nuclear acid amplification tests (NAAT) is already a standard to prescribe targeted treatments in industrialised countries, no randomised clinical trials have been conducted to evaluate clinical usefulness and acceptability of NAAT in comparison with syndromic approach in LMICs. The results of this study could inform diagnostic guidelines since they may suggest an update of the current recommendation if microbiological diagnosis using NAAT in the management of STD is demonstrated to be both useful and acceptable in an LMIC context. METHODS AND ANALYSIS: The primary objective of this randomised, open-label trial is to evaluate the clinical usefulness of a NAAT and its acceptability in comparison with a clinical syndromic approach and to explore whether this test could replace the syndromic approach in the management of STDs at a national referral hospital in Uganda. 220 patients presenting to the STD clinic at Mulago Hospital in Kampala, Uganda with AVD, UDS or GUD will be randomised to either standard of care (syndromic management) or NAAT-based treatment with a 1:1 ratio. All the patients will be asked to return after 2 or 3 weeks for a control visit. Primary outcome will be therapeutic appropriateness. ETHICS AND DISSEMINATION: This trial was approved by the Mulago Hospital Research and Ethical Committee (MHREC2023-97) and the Uganda National Council for Science and Technology (HS31000ES). Patients will give informed consent to participate before taking part in the study. Results will be published in peer-reviewed journals in open-access formats and data made available in anonymised form. TRIAL REGISTRATION NUMBER: NCT05994495.

Peripheral clock disruption and metabolic disease: moving beyond the anatomy to a functional approach.

Sleep and circadian disruption are associated with an increased risk of metabolic disease, including obesity and diabetes. Mounting evidence indicates that misaligned and/or non-functional clock proteins in peripheral tissues critically contribute to the presentation of metabolic disease. Many of the foundational studies which led to this conclusion have focused on specific tissues such as the adipose, pancreas, muscle, and liver. While these studies have greatly advanced the field, the use of anatomical markers to manipulate tissue-specific molecular clocks may not be representative of the circadian disruption that occurs within the clinical population. In this manuscript, we argue that investigators can gain a better understanding of the consequences of sleep and circadian disruption by targeting groups of cells with a functional relationship, even if those cells go beyond anatomical boundaries. This approach is especially important when considering metabolic outcomes which rely on endocrine signaling molecules, such as leptin, that have multiple sites of action. Through the review of several studies, as well as our own work, this article reframes peripheral clock disruption from a functional approach. We additionally present new evidence that disruption of the molecular clock within all cells expressing the leptin receptor affects leptin sensitivity in a time-dependent manner. Taken together, this perspective aims to provide new insight into the mechanisms leading to metabolic disease associated with circadian disruption and various sleep disorders.

The Molecular Circadian Clock of Phox2b-expressing Cells Drives Daily Variation of the Hypoxic but Not Hypercapnic Ventilatory Response in Mice.

While the suprachiasmatic nucleus (SCN) controls 24-h rhythms in breathing, including minute ventilation (VE), the mechanisms by which the SCN drives these daily changes are not well understood. Moreover, the extent to which the circadian clock regulates hypercapnic and hypoxic ventilatory chemoreflexes is unknown. We hypothesized that the SCN regulates daily breathing and chemoreflex rhythms by synchronizing the molecular circadian clock of cells. We used whole-body plethysmography to assess ventilatory function in transgenic BMAL1 knockout (KO) mice to determine the role of the molecular clock in regulating daily rhythms in ventilation and chemoreflex. Unlike their wild-type littermates, BMAL1 KO mice exhibited a blunted daily rhythm in VE and failed to demonstrate daily variation in the hypoxic ventilatory response (HVR) or hypercapnic ventilatory response (HCVR). To determine if the observed phenotype was mediated by the molecular clock of key respiratory cells, we then assessed ventilatory rhythms in BMAL1fl/fl; Phox2bCre/+ mice, which lack BMAL1 in all Phox2b-expressing chemoreceptor cells (hereafter called BKOP). BKOP mice lacked daily variation in HVR, similar to BMAL1 KO mice. However, unlike BMAL1 KO mice, BKOP mice exhibited circadian variations in VE and HCVR comparable to controls. These data indicate that the SCN regulates daily rhythms in VE, HVR, and HCVR, in part, through the synchronization of the molecular clock. Moreover, the molecular clock of Phox2b-expressing cells is specifically necessary for daily variation in the hypoxic chemoreflex. These findings suggest that disruption of circadian biology may undermine respiratory homeostasis, which, in turn, may have clinical implications for respiratory disease.

Touching Base with Some Mediterranean Diseases of Interest from Paradigmatic Cases at the "Magna Graecia" University Unit of Infectious Diseases: A Didascalic Review.

Among infectious diseases, zoonoses are increasing in importance worldwide, especially in the Mediterranean region. We report herein some clinical cases from a third-level hospital in Calabria region (Southern Italy) and provide a narrative review of the most relevant features of these diseases from epidemiological and clinical perspectives. Further, the pathogenic mechanisms involved in zoonotic diseases are reviewed, focusing on the mechanisms used by pathogens to elude the immune system of the host. These topics are of particular concern for individuals with primary or acquired immunodeficiency (e.g., people living with HIV, transplant recipients, patients taking immunosuppressive drugs). From the present review, it appears that diagnostic innovations and the availability of more accurate methods, together with better monitoring of the incidence and prevalence of these infections, are urgently needed to improve interventions for better preparedness and response.

Photoperiod Manipulation Reveals a Light-Driven Component to Daily Patterns of Ventilation in Male C57Bl/6J Mice.

Obstructive sleep apnea is a common sleep disorder that increases risk for cardiovascular disease and mortality. The severity of sleep-disordered breathing in obstructive sleep apnea patients fluctuates with the seasons, opening the possibility that seasonal changes in light duration, or photoperiod, can influence mechanisms of breathing. Photoperiod can have profound effects on internal timekeeping and can reshape metabolic rhythms in mammals. While the daily rhythm in ventilation is largely shaped by the metabolic rate, less is known about whether ventilatory rhythms are altered in accordance with metabolism under different photoperiods. Here, we investigate the relationship between ventilation and metabolism under different photoperiods using whole-body plethysmography and indirect calorimetry. We find that the daily timing of ventilation is chiefly synchronized to dark onset and that light cues are important for maintaining daily ventilatory rhythms. Moreover, changes in ventilatory patterns are not paralleled by changes in oxygen consumption, energy expenditure, or respiratory exchange rate under different photoperiods. We conclude that ventilatory patterns are not only shaped by the metabolic rate and circadian timing but are also influenced by other light-driven factors. Collectively, these findings have clinical implications for the seasonal variations in sleep-disordered breathing found in individuals with obstructive sleep apnea.