Thermoregulation and nausea

Migraine inhibitor olcegepant reduces weight loss and IL-6 release in SARS-CoV-2-infected older mice with neurological signs

COVID-19 can cause neurological symptoms such as fever, dizziness, and nausea. However, such neurological symptoms of SARS-CoV-2 infection have been hardly assessed in mouse models. In this study, we infected two commonly used wild-type mouse lines (C57BL/6J and 129/SvEv) and a 129S calcitonin gene-related peptide (αCGRP) null-line with mouse-adapted SARS-CoV-2 and demonstrated neurological signs including fever, dizziness, and nausea. We then evaluated whether a CGRP receptor antagonist, olcegepant, a "gepant" antagonist used in migraine treatment, could mitigate acute neuroinflammatory and neurological signs of SARS-COV-2 infection. First, we determined whether CGRP receptor antagonism provided protection from permanent weight loss in older (>18 m) C57BL/6J and 129/SvEv mice. We also observed acute fever, dizziness, and nausea in all older mice, regardless of treatment. In both wild-type mouse lines, CGRP antagonism reduced acute interleukin 6 (IL-6) levels with virtually no IL-6 release in mice lacking αCGRP. These findings suggest that migraine inhibitors such as those blocking CGRP receptor signaling protect against acute IL-6 release and subsequent inflammatory events after SARS-CoV-2 infection, which may have repercussions for related pandemic or endemic coronavirus outbreaks.IMPORTANCECoronavirus disease (COVID-19) can cause neurological symptoms such as fever, headache, dizziness, and nausea. However, such neurological symptoms of severe acute respiratory syndrome CoV-2 (SARS-CoV-2) infection have been hardly assessed in mouse models. In this study, we first infected two commonly used wild-type mouse lines (C57BL/6J and 129S) with mouse-adapted SARS-CoV-2 and demonstrated neurological symptoms including fever and nausea. Furthermore, we showed that the migraine treatment drug olcegepant could reduce long-term weight loss and IL-6 release associated with SARS-CoV-2 infection. These findings suggest that a migraine blocker can be protective for at least some acute SARS-CoV-2 infection signs and raise the possibility that it may also impact long-term outcomes.

Activation of GFRAL+ neurons induces hypothermia and glucoregulatory responses associated with nausea and torpor

GFRAL-expressing neurons actuate aversion and nausea, are targets for obesity treatment, and may mediate metformin effects by long-term GDF15-GFRAL agonism. Whether GFRAL+ neurons acutely regulate glucose and energy homeostasis is, however, underexplored. Here, we report that cell-specific activation of GFRAL+ neurons using a variety of techniques causes a torpor-like state, including hypothermia, the release of stress hormones, a shift from glucose to lipid oxidation, and impaired insulin sensitivity, glucose tolerance, and skeletal muscle glucose uptake but augmented glucose uptake in visceral fat. Metabolomic analysis of blood and transcriptomics of muscle and fat indicate alterations in ketogenesis, insulin signaling, adipose tissue differentiation and mitogenesis, and energy fluxes. Our findings indicate that acute GFRAL+ neuron activation induces endocrine and gluco- and thermoregulatory responses associated with nausea and torpor. While chronic activation of GFRAL signaling promotes weight loss in obesity, these results show that acute activation of GFRAL+ neurons causes hypothermia and hyperglycemia.

A natural sustained-intestinal release formulation of red chili pepper extracted capsaicinoids (Capsifen®) safely modulates energy balance and endurance performance: a randomized, double-blind, placebo-controlled study

Introduction

Overweight and obesity are major public health concerns, with a sharp increase in prevalence over the last few decades. The primary cause is an imbalance between calorie intake and expenditure due to a rise in calorie-rich processed food and reduced physical activity. Energy balance in humans involves complex processes including thermogenesis, a crucial factor in regulating energy expenditure.

Methods

In this randomized, double-blinded, placebo-controlled three-arm three-sequence study, we investigated the efficacy of Capsifen® (CapF), a pungency-masked sustained-intestinal release formulation of red chili extract, on energy expenditure, fat oxidation, and endurance using the Quark C-PET system in healthy overweight participants, with and without exercise. In the study, 105 healthy participants were randomized to receive either placebo, CapF 100 mg/day, or CapF 200 mg/day for 28 days.

Results

CapF demonstrated a dose-dependent response to increased energy expenditure and fatty acid oxidation with a concomitant reduction in body weight. Both CapF 100 and CapF 200 also increased the time to exhaustion.

Discussion

These results demonstrate the plausible efficacy of CapF in energy expenditure and physical performance in otherwise healthy adults who have a high body mass index.

Clinical trial registration

https://ctri.nic.in/Clinicaltrials/pmaindet2.php?EncHid=MjQzNTg=&Enc=&userName=CTRI/2018/04/013157 dated 04 October 2018.

Vestibular CCK signaling drives motion sickness-like behavior in mice

Travel can induce motion sickness (MS) in susceptible individuals. MS is an evolutionary conserved mechanism caused by mismatches between motion-related sensory information and past visual and motion memory, triggering a malaise accompanied by hypolocomotion, hypothermia, hypophagia, and nausea. Vestibular nuclei (VN) are critical for the processing of movement input from the inner ear. Motion-induced activation of VN neurons recapitulates MS-related signs. However, the genetic identity of VN neurons mediating MS-related autonomic and aversive responses remains unknown. Here, we identify a central role of cholecystokinin (CCK)-expressing VN neurons in motion-induced malaise. Moreover, we show that CCK VN inputs onto the parabrachial nucleus activate Calca-expressing neurons and are sufficient to establish avoidance to novel food, which is prevented by CCK-A receptor antagonism. These observations provide greater insight into the neurobiological regulation of MS by identifying the neural substrates of MS and providing potential targets for treatment.

Assessment of PDE4 Inhibitor-Induced Hypothermia as a Correlate of Nausea in Mice

Simple Summary

Type 4 cAMP-phosphodiesterases (PDE4s) comprise a family of four isoenzymes, PDE4A to D, that hydrolyze and inactivate the second messenger cAMP. Non/PAN-selective PDE4 inhibitors, which inhibit all four PDE4 subtypes simultaneously, produce many promising therapeutic benefits, such as anti-inflammatory or cognition- and memory-enhancing effects. However, unwanted side effects, principally, nausea, diarrhea, and emesis, have long hampered their clinical and commercial success. Targeting individual PDE4 subtypes has been proposed for developing drugs with an improved safety profile, but which PDE4 subtype(s) is/are actually responsible for nausea and emesis remains ill-defined. Based on the observation that nausea is often accompanied by hypothermia in humans and other mammals, we used the measurement of core body temperatures of mice as a potential correlate of nausea induced by PDE4 inhibitors in humans. We find that selective inactivation of any of the four PDE4 subtypes did not change the body temperature of mice, suggesting that PAN-PDE4 inhibitor-induced hypothermia (and hence nausea in humans) requires the simultaneous inhibition of multiple PDE4 subtypes. This finding contrasts with prior reports that proposed PDE4D as the subtype mediating these side effects of PDE4 inhibitors and suggests that subtype-selective inhibitors that target any individual PDE4 subtype, including PDE4D, may not cause nausea.

Abstract

Treatment with PAN-PDE4 inhibitors has been shown to produce hypothermia in multiple species. Given the growing body of evidence that links nausea and emesis to disturbances in thermoregulation in mammals, we explored PDE4 inhibitor-induced hypothermia as a novel correlate of nausea in mice. Using knockout mice for each of the four PDE4 subtypes, we show that selective inactivation of individual PDE4 subtypes per se does not produce hypothermia, which must instead require the concurrent inactivation of multiple (at least two) PDE4 subtypes. These findings contrast with the role of PDE4s in shortening the duration of α₂-adrenoceptor-dependent anesthesia, a behavioral surrogate previously used to assess the emetic potential of PDE4 inhibitors, which is exclusively affected by inactivation of PDE4D. These different outcomes are rooted in the distinct molecular mechanisms that drive these two paradigms; acting as a physiologic α₂-adrenoceptor antagonist produces the effect of PDE4/PDE4D inactivation on the duration of α₂-adrenoceptor-dependent anesthesia, but does not mediate the effect of PDE4 inhibitors on body temperature in mice. Taken together, our findings suggest that selective inhibition of any individual PDE4 subtype, including inhibition of PDE4D, may be free of nausea and emesis.

Prevalence of Inadvertent Perioperative Hypothermia and Associated Factors: A Cross-Sectional Study

Inadvertent perioperative hypothermia, defined as a body temperature <36.0°C, is a common outcome of anesthesia that can cause serious consequences to patients. The aim of this study is to determine the prevalence of inadvertent hypothermia among surgical procedures from two referral centers in Brazil and to identify sociodemographic, clinical, or surgery-related predictors of hypothermia. This is a cross-sectional study, conducted at two public hospitals in Brasília, Brazil. After the exclusion of 109 patients, 312 subjects (American Society of Anesthesiologists [ASA] physical status I-III) were enrolled from July 2016 through July 2018. The main outcome measures were the prevalence of hypothermia and its predictors. The mean age of the 312 patients was 43.2 (18.2) years (range 18-85 years), and 186 (59.6%) were female. The prevalence of inadvertent hypothermia was 56.7%. Predictors of hypothermia were perioperative chills (p = 0.026), patient's body temperature on arrival in the operating room (p < 0.001), diabetes (p < 0.001), ASA status III (p < 0.001), systolic blood pressure (p < 0.001), general anesthesia (p < 0.001), medical specialty (p < 0.001), fentanyl-based anesthesia (p = 0.002), and surgery time (p < 0.001). The multivariable model prediction model for hypothermia showed fairly good discrimination (area under the receiver operating characteristic: 79.0%, 95% confidence interval 68.0 to 80.1). Approximately 6 in 10 patients undergoing surgery developed inadvertent perioperative hypothermia. The risk of hypothermia is influenced by a myriad of factors that can be used in simple and low-cost predictive models with adequate discriminatory power.