Papers by Oksana Gavrilova
PLOS ONE, Jan 17, 2014
Homeotherms have specific mechanisms to maintain a constant core body temperature despite changes... more Homeotherms have specific mechanisms to maintain a constant core body temperature despite changes in thermal environment, food supply, and metabolic demand. Brown adipose tissue, the principal thermogenic organ, quickly and efficiently increases heat production by dissipating the mitochondrial proton motive force. It has been suggested that activation of brown fat, via either environmental (i.e. cold exposure) or pharmacologic means, could be used to increase metabolic rate and thus reduce body weight. Here we assess the effects of intermittent cold exposure (4uC for one to eight hours three times a week) on C57BL/6J mice fed a high fat diet. Cold exposure increased metabolic rate approximately twofold during the challenge and activated brown fat. In response, food intake increased to compensate fully for the increased energy expenditure; thus, the mice showed no reduction in body weight or adiposity. Despite the unchanged adiposity, the cold-treated mice showed transient improvements in glucose homeostasis. Administration of the cannabinoid receptor-1 inverse agonist AM251 caused weight loss and improvements in glucose homeostasis, but showed no further improvements when combined with cold exposure. These data suggest that intermittent cold exposure causes transient, meaningful improvements in glucose homeostasis, but without synergy when combined with AM251. Since energy expenditure is significantly increased during cold exposure, a drug that dissociates food intake from metabolic demand during cold exposure may achieve weight loss and further metabolic improvements.
Journal of the Endocrine Society, Apr 1, 2019
Abstract The importance of multiple adenosine receptors (AR) and the role of adenosine signaling ... more Abstract The importance of multiple adenosine receptors (AR) and the role of adenosine signaling in normal physiology, as opposed to danger/damage situations, are unclear. We generated mice (QKO) lacking all four AR, Adora1-/-;Adora2a-/-;Adora2b-/-;Adora3-/-, to enable investigation of the AR-dependence of physiologic processes. The QKO mice bred normally and had similar body temperature regulation as controls, including diurnal variation, fasting-induced torpor, and response to environmental stimuli. Pharmacologic doses of adenosine agonists cause profound hypothermia via each of the four AR. We hypothesized that uptake and phosphorylation of adenosine might also trigger hypothermia by additional mechanisms, such as activation of adenosine monophosphate-activated protein kinase (AMPK). However, adenosine did not cause hypothermia (or bradycardia or hypotension) in QKO mice, indicating that AR-independent, ‘energy depletion’ signals do not cause adenosine-induced hypothermia. AMP-induced hypothermia was attenuated in QKO mice, demonstrating a role for both AR-dependent and AR-independent mechanisms in this process. In contrast, the hypothermias elicited by adenosine kinase inhibition (using A-134974), inosine, and uridine each require AR, as all were abolished in the QKO mice. The proposed mechanism for uridine-induced hypothermia is inhibition of adenosine transport, increasing local extracellular adenosine levels. The physiology of the QKO mice replicates that of the individual knockout mice, without evidence for synergy, suggesting that the actions of the four AR are generally complementary. The relatively mild phenotype of the QKO mice supports the hypothesis that extracellular adenosine has less of a contribution to baseline physiology and is more important as a local signal of stress, damage, and/or danger.
PLOS ONE, Dec 16, 2020
Extracellular adenosine, a danger signal, can cause hypothermia. We generated mice lacking neuron... more Extracellular adenosine, a danger signal, can cause hypothermia. We generated mice lacking neuronal adenosine A 1 receptors (A 1 AR, encoded by the Adora1 gene) to examine the contribution of these receptors to hypothermia. Intracerebroventricular injection of the selective A 1 AR agonist (Cl-ENBA, 5'-chloro-5'-deoxy-N 6-endo-norbornyladenosine) produced hypothermia, which was reduced in mice with deletion of A 1 AR in neurons. A non-brain penetrant A 1 AR agonist [SPA, N 6-(p-sulfophenyl) adenosine] also caused hypothermia, in wild type but not mice lacking neuronal A 1 AR, suggesting that peripheral neuronal A 1 AR can also cause hypothermia. Mice expressing Cre recombinase from the Adora1 locus were generated to investigate the role of specific cell populations in body temperature regulation. Chemogenetic activation of Adora1-Cre-expressing cells in the preoptic area did not change body temperature. In contrast, activation of Adora1-Cre-expressing dorsomedial hypothalamus cells increased core body temperature, concordant with agonism at the endogenous inhibitory A 1 AR causing hypothermia. These results suggest that A 1 AR agonism causes hypothermia via two distinct mechanisms: brain neuronal A 1 AR and A 1 AR on neurons outside the blood-brain barrier. The variety of mechanisms that adenosine can use to induce hypothermia underscores the importance of hypothermia in the mouse response to major metabolic stress or injury.
Neuropharmacology, Sep 1, 2018
Extracellular adenosine is a danger/injury signal that initiates protective physiology, such as h... more Extracellular adenosine is a danger/injury signal that initiates protective physiology, such as hypothermia. Adenosine has been shown to trigger hypothermia via agonism at A 1 and A 3 adenosine receptors (A 1 AR, A 3 AR). Here, we find that adenosine continues to elicit hypothermia in mice null for A 1 AR and A 3 AR and investigated the effect of agonism at A 2A AR or A 2B AR. The poorly brain penetrant A 2A AR agonists CGS-21680 and PSB-0777 caused hypothermia, which was not seen in mice lacking A 2A AR. MRS7352, a likely non-brain penetrant A 2A AR antagonist, inhibited PSB-0777 hypothermia. While vasodilation is probably a contributory mechanism, A 2A AR agonism also caused hypometabolism, indicating that vasodilation is not the sole mechanism. The A 2B AR agonist BAY60-6583 elicited hypothermia, which was lost in mice null
Cell Metabolism, Aug 1, 2014
The melanocortin system regulates metabolic homeostasis and inflammation. Melanocortin agonists h... more The melanocortin system regulates metabolic homeostasis and inflammation. Melanocortin agonists have contradictorily been reported to both increase and decrease metabolic rate and body temperature. We find two distinct physiologic responses occurring at similar doses. Intraperitoneal administration of the nonselective melanocortin agonist MTII causes a melanocortin-4 receptor (Mc4r)-mediated hypermetabolism/hyperthermia. This is preceded by a profound, transient hypometabolism/hypothermia that is preserved in mice lacking any one of Mc1r, Mc3r, Mc4r, or Mc5r. Three other melanocortin agonists also caused hypothermia, which is actively achieved via seeking a cool environment, vasodilation, and inhibition of brown adipose tissue thermogenesis. These results suggest that the hypometabolic/hypothermic effect of MTII is not due to a failure of thermoregulation. The hypometabolism/hypothermia was prevented by dopamine antagonists, and MTII selectively activated arcuate nucleus dopaminergic neurons, suggesting that these neurons may contribute to the hypometabolism/hypothermia. We propose that the hypometabolism/hypothermia is a regulated response, potentially beneficial during extreme physiologic stress.
PLOS Biology, Mar 1, 2019
Adenosine is a constituent of many molecules of life; increased free extracellular adenosine indi... more Adenosine is a constituent of many molecules of life; increased free extracellular adenosine indicates cell damage or metabolic stress. The importance of adenosine signaling in basal physiology, as opposed to adaptive responses to danger/damage situations, is unclear. We generated mice lacking all four adenosine receptors (ARs), Adora1 −/− ;Adora2a −/− ; Adora2b −/− ;Adora3 −/− (quad knockout [QKO]), to enable investigation of the AR dependence of physiologic processes, focusing on body temperature. The QKO mice demonstrate that ARs are not required for growth, metabolism, breeding, and body temperature regulation (diurnal variation, response to stress, and torpor). However, the mice showed decreased survival starting at about 15 weeks of age. While adenosine agonists cause profound hypothermia via each AR, adenosine did not cause hypothermia (or bradycardia or hypotension) in QKO mice, indicating that AR-independent signals do not contribute to adenosine-induced hypothermia. The hypothermia elicited by adenosine kinase inhibition (with A134974), inosine, or uridine also required ARs, as each was abolished in the QKO mice. The proposed mechanism for uridine-induced hypothermia is inhibition of adenosine transport by uridine, increasing local extracellular adenosine levels. In contrast, adenosine 5 0-monophosphate (AMP)-induced hypothermia was attenuated in QKO mice, demonstrating roles for both AR-dependent and AR-independent mechanisms in this process. The physiology of the QKO mice appears to be the sum of the individual knockout mice, without clear evidence for synergy, indicating that the actions of the four ARs are generally complementary. The phenotype of the QKO mice suggests that, while extracellular adenosine is a signal of stress, damage, and/or danger, it is less important for baseline regulation of body temperature.
Nature Neuroscience, Oct 22, 2018
Bombesin-like receptor 3 (BRS3) is an orphan G protein-coupled receptor that regulates energy hom... more Bombesin-like receptor 3 (BRS3) is an orphan G protein-coupled receptor that regulates energy homeostasis and heart rate. We report that acute activation of Brs3-expressing neurons in the dorsomedial hypothalamus (DMH Brs3) increased body temperature (Tb), brown adipose tissue temperature, energy expenditure, heart rate and blood pressure, with no effect on food intake or physical activity. Conversely, activation of Brs3 neurons in the paraventricular nucleus of the hypothalamus (PVH Brs3) had no effect on Tb or energy expenditure, but suppressed food intake. Inhibition of DMH Brs3 neurons decreased Tb and energy expenditure, suggesting a necessary role in Tb regulation. We found that the preoptic area provides major input (excitatory and inhibitory) to DMH Brs3 neurons. Optogenetic stimulation of DMH Brs3 projections to the raphe pallidus (RPa) increased Tb. Thus, DMH Brs3 →RPa neurons regulate Tb, energy expenditure and heart rate, and PVH Brs3 neurons regulate food intake. Brs3 expression is a useful marker for delineating energy metabolism regulatory circuitry. <license-p>Users may view, print, copy, and download text and data-mine the content in such documents, for the purposes of academic research, subject always to the full Conditions of use:<uri xlink:href="
Neuropharmacology, Mar 1, 2017
Small mammals have the ability to enter torpor, a hypothermic, hypometabolic state, allowing impr... more Small mammals have the ability to enter torpor, a hypothermic, hypometabolic state, allowing impressive energy conservation. Administration of adenosine or adenosine 5'-monophosphate (AMP) can trigger a hypothermic, torpor-like state. We investigated the mechanisms for hypothermia using telemetric monitoring of body temperature in wild type and receptor knock out (Adora1 −/− , Adora3 −/−) mice. Confirming prior data, stimulation of the A 3 adenosine receptor (AR) induced hypothermia via peripheral mast cell degranulation, histamine release, and activation of central histamine H 1 receptors. In contrast, A 1 AR agonists and AMP both acted centrally to cause hypothermia. Commonly used, selective A 1 AR agonists, including N 6cyclopentyladenosine (CPA), N 6-cyclohexyladenosine (CHA), and MRS5474, caused hypothermia via both A 1 AR and A 3 AR when given intraperitoneally. Intracerebroventricular dosing, low peripheral doses of Cl-ENBA [(±)-5'-chloro-5'-deoxy-N 6-endo-norbornyladenosine], or using
Cell Reports, Apr 1, 2020
Human and mouse thermal physiology differ due to dissimilar body sizes. Unexpectedly, in mice we ... more Human and mouse thermal physiology differ due to dissimilar body sizes. Unexpectedly, in mice we found no ambient temperature zone where both metabolic rate and body temperature were constant. Body temperature began increasing once cold-induced thermogenesis was no longer required. This result reproduced in male, female, C57BL/6J, 129, chow-fed, diet-induced obese, and ob/ob mice as well as Trpv1 −/− ;Trpm8 −/− ;Trpa1 −/− mice lacking thermal sensory channels.
Proceedings of the National Academy of Sciences of the United States of America, Dec 7, 1999
We tested the effect of chronic leptin treatment on fasting-induced torpor in leptin-deficient A-... more We tested the effect of chronic leptin treatment on fasting-induced torpor in leptin-deficient A-ZIP͞F-1 and ob͞ob mice. A-ZIP͞F-1 mice have virtually no white adipose tissue and low leptin levels, whereas ob͞ob mice have an abundance of fat but no leptin. These two models allowed us to examine the roles of adipose tissue and leptin in the regulation of entry into torpor. Torpor is a short-term hibernation-like state that allows conservation of metabolic fuels. We first characterized the A-ZIP͞F-1 animals, which have a 10-fold reduction in total body triglyceride stores. Upon fasting, A-ZIP͞F-1 mice develop a lower metabolic rate and decreased plasma glucose, insulin, and triglyceride levels, with no increase in free fatty acids or -hydroxybutyrate. Unlike control mice, by 24 hr of fasting, they have nearly exhausted their triglycerides and are catabolizing protein. To conserve energy supplies during fasting, A-ZIP͞F-1 (but not control) mice entered deep torpor, with a minimum core body temperature of 24°C, 2°C above ambient. In ob͞ob mice, fasting-induced torpor was completely reversed by leptin treatment. In contrast, neither leptin nor thyroid hormone prevented torpor in A-ZIP͞F-1 mice. These data suggest that there are at least two signals for entry into torpor in mice, a low leptin level and another signal that is independent of leptin and thyroid hormone levels. Studying rodent torpor provides insight into human torpor-like states such as near drowning in cold water and induced hypothermia for surgery. fasting ͉ lipoatrophic diabetes ͉ body temperature ͉ hypothermia ͉ A-ZIP͞F-1 mice
Journal of Biological Chemistry, Jul 1, 2014
Background: The chemical uncoupler 2,4-dinitrophenol was widely used as a treatment for obesity i... more Background: The chemical uncoupler 2,4-dinitrophenol was widely used as a treatment for obesity in the past. Results: In mice, 2,4-dinitrophenol generates heat and turns off brown fat heat production. It reduces weight gain at thermoneutrality but not at cooler ambient temperatures. Conclusion: Environmental temperature should be considered when assessing anti-obesity drugs in mice. Significance: Chemical uncouplers deserve further investigation for the treatment of obesity.
American Journal of Physiology-endocrinology and Metabolism, Sep 1, 2018
Intraperitoneal administration of the melanocortin agonist melanotan II (MTII) to mice causes a p... more Intraperitoneal administration of the melanocortin agonist melanotan II (MTII) to mice causes a profound, transient hypometabolism/hypothermia. It is preserved in mice lacking any one of melanocortin receptors 1, 3, 4, or 5, suggesting a mechanism independent of the canonical melanocortin receptors. Here we show that MTII-induced hypothermia was abolished in Kit W-sh/W-sh mice, which lack mast cells, demonstrating that mast cells are required. MRGPRB2 is a receptor that detects many cationic molecules and activates mast cells in an antigen-independent manner. In vitro, MTII stimulated mast cells by both MRGPRB2-dependent and-independent mechanisms, and MTII-induced hypothermia was intact in MRGPRB2-null mice. Confirming that MTII activated mast cells, MTII treatment increased plasma histamine levels in both wild-type and MRGPRB2null, but not in Kit W-sh/W-sh , mice. The released histamine produced hypothermia via histamine H 1 receptors because either a selective antagonist, pyrilamine, or ablation of H1 receptors greatly diminished the hypothermia. Other drugs, including compound 48/80, a commonly used mast cell activator, also produced hypothermia by both mast cell-dependent and-independent mechanisms. These results suggest that mast cell activation should be considered when investigating the mechanism of drug-induced hypothermia in mice.
Molecular metabolism, Nov 1, 2021
Objective To improve understanding of mouse energy homeostasis and its applicability to humans, w... more Objective To improve understanding of mouse energy homeostasis and its applicability to humans, we quantitated the effects of housing density on mouse thermal physiology in both sexes. Methods Littermate wild type and Brs3-null mice were single- or group- (three per cage) housed and studied by indirect calorimetry with continuous measurement of core body temperature, energy expenditure, physical activity, and food intake. Results At 23 °C, below thermoneutrality, single-housed males had a lower body temperature and unchanged metabolic rate compared to group-housed controls. In contrast, single-housed females maintained a similar body temperature to group-housed controls by increasing their metabolic rate. With decreasing ambient temperature below 27 °C, only group-housed mice decreased their heat conductance, likely due to huddling, thus interfering with the energy expenditure vs ambient temperature relationship described by Scholander. In a hot environment (35 °C), the single-housed mice were less heat stressed. Upon fasting, single-housed mice had larger reductions in body temperature, with male mice having more torpor episodes of similar duration and female mice having a similar number of torpor episodes that lasted longer. Qualitatively, the effects of housing density on thermal physiology of Brs3-null mice generally mimicked the effects in controls. Conclusions Single housing is more sensitive than group housing for detecting thermal physiology phenotypes. Single housing increases heat loss and amplifies the effects of fasting or a cold environment. Male and female mice utilize different thermoregulatory strategies to respond to single housing.
Molecular metabolism, Nov 1, 2017
Objective: Bombesin-like receptor 3 (BRS-3) is an orphan G protein-coupled receptor. Brs3 null mi... more Objective: Bombesin-like receptor 3 (BRS-3) is an orphan G protein-coupled receptor. Brs3 null mice have reduced resting metabolic rate and body temperature, increased food intake, and obesity. Here we study the role of Brs3 in different neuron types. Methods: Mice able to undergo Cre recombinase-dependent inactivation or re-expression of Brs3 were generated, respectively Brs3 fl/y and Brs3 loxTB/y. We then studied four groups of mice with Brs3 selectively inactivated or re-expressed in cells expressing Vglut2-Cre or Vgat-Cre. Results: Deletion of Brs3 in glutamatergic neurons expressing Vglut2 reproduced the global null phenotype for regulation of food intake, metabolic rate, body temperature, adiposity, and insulin resistance. These mice also no longer responded to a BRS-3 agonist, MK-5046. In contrast, deletion of Brs3 in GABAergic neurons produced no detectable phenotype. Conversely, the wild type phenotype was restored by selective re-expression of Brs3 in glutamatergic neurons, with no normalization achieved by re-expressing Brs3 in GABAergic neurons. Conclusions: Brs3 expression in glutamatergic neurons is both necessary and sufficient for full Brs3 function in energy metabolism. In these experiments, no function was identified for Brs3 in GABAergic neurons. The data suggest that the anti-obesity pharmacologic actions of BRS-3 agonists occur via agonism of receptors on glutamatergic neurons.
Journal of Clinical Investigation, Feb 1, 2000
Molecular metabolism, May 1, 2023
Molecular metabolism, Jun 1, 2020
Objective: Bombesin-like receptor 3 (BRS3) is an orphan receptor and Brs3 knockout mice develop o... more Objective: Bombesin-like receptor 3 (BRS3) is an orphan receptor and Brs3 knockout mice develop obesity with increased food intake and reduced resting metabolic rate and body temperature. The neuronal populations contributing to these effects were examined. Methods: We studied energy metabolism in mice with Cre-mediated recombination causing 1) loss of BRS3 selectively in SIM1-or MC4Rexpressing neurons or 2) selective re-expression of BRS3 from a null background in these neurons. Results: The deletion of BRS3 in MC4R neurons increased body weight/adiposity, metabolic efficiency, and food intake, and reduced insulin sensitivity. BRS3 re-expression in these neurons caused partial or no reversal of these traits. However, these observations were confounded by an obesity phenotype caused by the Mc4r-Cre allele, independent of its recombinase activity. The deletion of BRS3 in SIM1 neurons increased body weight/adiposity and food intake, but not to the levels of the global null. The re-expression of BRS3 in SIM1 neurons reduced body weight/ adiposity and food intake, but not to wild type levels. The deletion of BRS3 in either MC4R-or SIM1-expressing neurons affected body temperature, with re-expression in either population reversing the null phenotype. MK-5046, a BRS3 agonist, increases light phase body temperature in wild type, but not Brs3 null, mice and BRS3 re-expression in either population restored response to MK-5046. Conclusions: BRS3 in both MC4R-and SIM1-expressing neurons contributes to regulation of body weight/adiposity, insulin sensitivity, food intake, and body temperature.
bioRxiv (Cold Spring Harbor Laboratory), Mar 5, 2021
The preoptic area (POA) is a key region controlling body temperature (Tb), dictating thermogenic,... more The preoptic area (POA) is a key region controlling body temperature (Tb), dictating thermogenic, cardiovascular, and behavioral responses to regulate Tb. Known POA neuronal populations reduce Tb when activated; a population that increases Tb upon activation has not yet been reported. We now identify bombesin-like receptor 3 (BRS3)-expressing POA (POA BRS3) neurons as having this missing functionality. BRS3 is an orphan receptor that regulates energy and cardiovascular homeostasis, but the relevant neural circuits are incompletely understood. In mice, we demonstrate that POA BRS3 neuronal activation increases Tb, heart rate, and blood pressure sympathetically, via projections to the paraventricular nucleus of the hypothalamus and dorsomedial hypothalamus. Acute POA BRS3 inhibition reduces Tb. Long-term inactivation of POA BRS3 neurons increased Tb variability with exaggerated Tb changes, overshooting both increases and decreases in Tb set point. BRS3 marks preoptic populations that regulate Tb and heart rate, contribute to cold-defense and fine-tune feedback control of Tb. These findings advance understanding of homeothermy, a defining feature of mammalian biology.
Molecular metabolism, Mar 1, 2018
ENeuro, Jul 1, 2021
Bombesin receptor subtype-3 (BRS3) is an orphan receptor that regulates energy homeostasis. We co... more Bombesin receptor subtype-3 (BRS3) is an orphan receptor that regulates energy homeostasis. We compared Brs3 driver mice with constitutive or inducible Cre recombinase activity. The constitutive BRS3-Cre mice show reporter signal (Cre-dependent tdTomato) in the adult brain due to lineage tracing in the dentate gyrus, striatal patches, and indusium griseum, in addition to sites previously identified in the inducible BRS3-Cre mice (including hypothalamic and amygdala subregions, and parabrachial nucleus). We detected Brs3 reporter expression in the dentate gyrus at day 23 but not at postnatal day one or five months of age. Hypothalamic sites expressed reporter at all three time points, and striatal patches expressed Brs3 reporter at one day but not five months. Parabrachial nucleus Brs3 neurons project to the preoptic area, hypothalamus, amygdala, and thalamus. Both Cre recombinase insertions reduced Brs3 mRNA levels and BRS3 function, causing obesity phenotypes of different severity. These results demonstrate that driver mice should be characterized phenotypically and illustrate the need for knock-in strategies with less effect on the endogenous gene. Significance Statement Bombesin receptor subtype-3 (BRS3) expression is a marker for selected neurons that regulate body temperature and energy metabolism, among other functions. BRS3-Cre recombinase driver mice allow investigation of these neurons, demonstrating discrete populations with stable (including hypothalamic and amygdala subregions, parabrachial nucleus) and with developmentally transient expression (dentate gyrus, striatal patches). These mice also illustrate the need for knock-in strategies having less effect proper expression of the endogenous gene. Introduction Bombesin receptor subtype-3 (BRS3, Bombesin-like receptor 3, BB3) is a G protein-coupled receptor critical for the maintenance of energy balance (Jensen et al., 2008; Gonzalez et al., 2015; Xiao and Reitman, 2016). BRS3 is considered an orphan receptor as its endogenous ligand is not known; specifically, it does not bind the natural ligands (gastrin-releasing peptide and neuromedin B) for the most closely related receptors (Mantey et al., 1997), nor does it bind bombesin, which is the frog ortholog of neuromedin B (Hirooka et al., 2021). Mice lacking BRS3 are hyperphagic, have a reduced resting metabolic rate and body temperature, and consequently become obese (Ohki-Hamazaki et al., 1997b). Brs3 knockout (KO) mice are also reported to exhibit reduced social responses, heightened preference for sweetness, and increased aversion to bitterness (Yamada et al., 1999; Yamada et al., 2000). Although Brs3 is also expressed outside the CNS (Jensen et al., 2008), the metabolic phenotypes of Brs3 KO mice are predominantly mediated by glutamatergic Brs3 neurons, with contributions from neurons expressing MC4R and SIM1, demonstrating the necessity of brain BRS3 (Xiao et al., 2017; Xiao et al., 2020). Consistent with the phenotypes of BRS3-null mice, administration of a BRS3 agonist reduces food intake and body weight and increases brown adipose tissue (BAT)-induced thermogenesis, heart rate, and blood pressure, while BRS3 antagonists increase food intake and body weight (
Uploads
Papers by Oksana Gavrilova