R01HL138932, RO1HL133100, RO1HL128970, AHACDA34700025

All experimental protocols have been approved by the Institutional Animal Care and Use Committee (MO18M211).
1. Leptin Infusion
NOTE: In order to examine the effect of leptin on breathing, we infused leptin subcutaneously in lean C57BL/6J mice by an osmotic pump to raise circulating leptin levels to those observed in obese mice.
<ol>
	<li>Osmotic pump preparation
	<ol>
		<li>Weigh the empty pump to check the net weight of the solu...

<ol>
	<li>O'donnell, C. P., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Leptin+prevents+respiratory+depression+in+obesity.">Leptin prevents respiratory depression in obesity.</a> American Journal of Respiratory and Critical Care Medicine. 159, 1477-1484 (1999).</li><li>Polotsky, V. Y., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Female+gender+exacerbates+respiratory+depression+in+leptin-deficient+obesity.">Female gender exacerbates respiratory depression in leptin-deficient obesity.</a> American Journal of Respiratory and Critical Care Medicine. 164, 1470-1475 (2001).</li><li>Bassi, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Central+leptin+replacement+enhances+chemorespiratory+responses+in+leptin-deficient+mice+independent+of+changes+in+body+weight.">Central leptin replacement enhances chemorespiratory responses in leptin-deficient mice independent of changes in body weight.</a> Pflu&#776;gers Archiv: European Journal of Physiology. 464, 145-153 (2012).</li><li>Inyushkina, E. M., Merkulova, N. A., Inyushkin, A. N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mechanisms+of+the+respiratory+activity+of+leptin+at+the+level+of+the+solitary+tract+nucleus.">Mechanisms of the respiratory activity of leptin at the level of the solitary tract nucleus.</a> Neuroscience and Behavioral Physiology. 40, 707-713 (2010).</li><li>Considine, R. V., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Serum+immunoreactive-leptin+concentrations+in+normal-weight+and+obese+humans.">Serum immunoreactive-leptin concentrations in normal-weight and obese humans.</a> New England Journal of Medicine. 334, 292-295 (1996).</li><li>Maffei, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Leptin+levels+in+human+and+rodent:+measurement+of+plasma+leptin+and+ob+RNA+in+obese+and+weight-reduced+subjects.">Leptin levels in human and rodent: measurement of plasma leptin and ob RNA in obese and weight-reduced subjects.</a> Nature Medicine. 1, 1155-1161 (1995).</li><li>Phipps, P. R., Starritt, E., Caterson, I., Grunstein, R. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Association+of+serum+leptin+with+hypoventilation+in+human+obesity.">Association of serum leptin with hypoventilation in human obesity.</a> Thorax. 57, 75-76 (2002).</li><li>Berger, S., Polotsky, V. Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Leptin+and+Leptin+Resistance+in+the+Pathogenesis+of+Obstructive+Sleep+Apnea:+A+Possible+Link+to+Oxidative+Stress+and+Cardiovascular+Complications.">Leptin and Leptin Resistance in the Pathogenesis of Obstructive Sleep Apnea: A Possible Link to Oxidative Stress and Cardiovascular Complications.</a> Oxidative Medicine and Cellular Longevity. 2018, 5137947 (2018).</li><li>Ribeiro, M. J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=High+fat+diet+blunts+the+effects+of+leptin+on+ventilation+and+on+carotid+body+activity.">High fat diet blunts the effects of leptin on ventilation and on carotid body activity.</a> The Journal of Physiology. 96, 3187-3199 (2018).</li><li>Yuan, F., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Leptin+signaling+in+the+carotid+body+regulates+a+hypoxic+ventilatory+response+through+altering+TASK+channel+expression.">Leptin signaling in the carotid body regulates a hypoxic ventilatory response through altering TASK channel expression.</a> Frontiers in Physiology. 9, 249 (2018).</li><li>Caballero-Eraso, C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Leptin+acts+in+the+carotid+bodies+to+increase+minute+ventilation+during+wakefulness+and+sleep+and+augment+the+hypoxic+ventilatory+response.">Leptin acts in the carotid bodies to increase minute ventilation during wakefulness and sleep and augment the hypoxic ventilatory response.</a> The Journal of Physiology. 591, 151-172 (2018).</li><li>Jun, J. C., Shin, M. K., Yao, Q., Devera, R., Fonti-Bevans, S., Polotsky, V. Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Thermoneutrality+modifies+the+impact+of+hypoxia+on+lipid+metabolism.">Thermoneutrality modifies the impact of hypoxia on lipid metabolism.</a> American Journal of Physiology Endocrinology and Metabolism. 304, 424-435 (2012).</li><li>Polotsky, V. Y., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Impact+of+interrupted+leptin+pathways+on+ventilatory+control.">Impact of interrupted leptin pathways on ventilatory control.</a> Journal of Applied Physiology. 96, 991-998 (2004).</li><li>Pho, H., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+effect+of+leptin+replacement+on+sleep-disordered+breathing+in+the+leptin-deficient+ob/ob+mouse.">The effect of leptin replacement on sleep-disordered breathing in the leptin-deficient ob/ob mouse.</a> Journal of Applied Physiology. 120, 78-86 (2016).</li><li>Hernandez, A. B., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Novel+whole+body+plethysmography+system+for+the+continuous+characterization+of+sleep+and+breathing+in+a+mouse.">Novel whole body plethysmography system for the continuous characterization of sleep and breathing in a mouse.</a> Journal of Applied Physiology. 112, 671-680 (2012).</li><li>Powell, F. L., Milsom, W. K., Mitchell, G. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Time+domains+of+the+hypoxic+ventilatory+response.">Time domains of the hypoxic ventilatory response.</a> Respiration Physiology. 112, 123-134 (1998).</li><li>Drorbaugh, J. E., Fenn, W. O. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+barometric+method+for+measuring+ventilation+in+newborn+infants.">A barometric method for measuring ventilation in newborn infants.</a> Pediatrics. 16, 81-87 (1955).</li><li>Duffin, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Measuring+the+ventilatory+response+to+hypoxia.">Measuring the ventilatory response to hypoxia.</a> The Journal of Physiology. 587, 285-293 (2007).</li><li>Teppema, L. J., Dahan, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+Ventilatory+Response+to+Hypoxia+in+Mammals:+Mechanisms,+Measurement,+and+Analysis.">The Ventilatory Response to Hypoxia in Mammals: Mechanisms, Measurement, and Analysis.</a> Physiological Reviews. 90, 675-754 (2010).</li><li>Nurse, C. A., Fearon, I. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Carotid+body+chemoreceptors+in+dissociated+cell+culture.">Carotid body chemoreceptors in dissociated cell culture.</a> Microscopy Research and Technique. 59, 249-255 (2002).</li><li>Kumar, P., Prabhakar, N. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Peripheral+chemoreceptors:+function+and+plasticity+of+the+carotid+body.">Peripheral chemoreceptors: function and plasticity of the carotid body.</a> Comprehensive Physiology. 2, 141-219 (2012).</li><li>Roux, J. C., Peyronnet, J., Pascual, O., Dalmaz, Y., Pequignot, J. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ventilatory+and+central+neurochemical+reorganisation+of+O2+chemoreflex+after+carotid+sinus+nerve+transection+in+rat.">Ventilatory and central neurochemical reorganisation of O2 chemoreflex after carotid sinus nerve transection in rat.</a> The Journal of Physiology. 522, 493-501 (2000).</li></ol>

The authors have no conflicting interests or disclosures.

The main focus of our study was to examine respiratory effects of leptin signaling in the CB. Several protocols have been developed to assess the role of leptin in a mechanistic fashion. First, specific contribution of CB to the HVR was analyzed by careful quantification of the HVR during the first 2 min of hypoxic exposure. Second, the relevance of CB in leptin-mediated up-regulation of control of breathing was examined by two complementary approaches. In lean wild-type mice with low leptin levels, the HVR was measured ...

An adipocyte produced hormone leptin acts in the hypothalamus to suppress food intake and increase metabolic rate. Studies performed in our laboratory1,2 and by other investigators3,4 showed that leptin increases the hypercapnic ventilatory response (HVR) preventing obesity hypoventilation in leptin deficient obesity. However, a majority of obese individuals have high plasma leptin levels and demonstrate resistance to the metabolic and respiratory effects of the hormone5,6,7,8. Resistance to leptin is multifactorial, but limited permeability of the blood-brain barrier (BBB) to leptin plays a major role. We propose that leptin acts below BBB in a key organ of peripheral hypoxic sensitivity, the carotid bodies (CB), to defend breathing in obese individuals. CBs express the long functional isoform of leptin receptor, LepRb, but the role of CB in respiratory effects of leptin has not been sufficiently elucidated9,10.
The goal of our method was to examine the effect of leptin signaling in the CB on HVR. Our rationale was to perform (a) loss of function experiments infusing leptin in mice with intact carotid bodies and denervated carotid bodies followed by HVR measurements; (b) gain of function experiments in db/db mice lacking LepRb, in which we measured the HVR at baseline and after expression of LepRb exclusively in CB. The advantage of our techniques was that we performed all our experiments in unrestrained unanesthetized mice during sleep and wakefulness. Previous investigators either performed their experiments under anesthesia9 or did not measure effects of leptin during sleep10. In addition, our study is the first to utilize a unique gain of function approach with selective LepRb expression in CB described above.
In the broad context, our approach can be generalized to other receptors expressed in CB and their role in hypoxic sensitivity. Investigators can infuse a ligand to a receptor of interest and measure the HVR at baseline and after CB denervation. As a complementary approach, a receptor of interest can be overexpressed in CB and HVR measurements can be performed before and after overexpression using our technology described in this manuscript.

<table>
	<tbody>
		<tr>
			<td>1ml Insulin Syringes</td>
			<td>BD Biosciences</td>
			<td>309311</td>
			<td></td>
		</tr>
		<tr>
			<td>1x PBS (pH 7.4)</td>
			<td>Gibco</td>
			<td>10010-023</td>
			<td>500 ml</td>
		</tr>
		<tr>
			<td>Ad-Lacz</td>
			<td>Dr. Christopher Rhodes (University of Chicago)</td>
			<td></td>
			<td>1x1010 pfu/ml</td>
		</tr>
		<tr>
			<td>Ad-LepRb-GFP</td>
			<td>Vector Biolabs</td>
			<td>ADV-263380</td>
			<td>2-5x1010 pfu/ml</td>
		</tr>
		<tr>
			<td>Anesthetic cart</td>
			<td>Atlantic Biomedical</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Betadine</td>
			<td>Purdue Products Ltd.</td>
			<td>12496-0757-5</td>
			<td></td>
		</tr>
		<tr>
			<td>Buprenorphine (Buprenex)</td>
			<td>Reckitt Benckiser Healthcare Ltd.</td>
			<td>12496-0757-5</td>
			<td>0.3mg/ml</td>
		</tr>
		<tr>
			<td>C57Bl/6J</td>
			<td>Jackson laboratory</td>
			<td>000664</td>
			<td>Mice Strain</td>
		</tr>
		<tr>
			<td>Cotton Gauze Sponges</td>
			<td>Fisherbrand</td>
			<td>22-362-178</td>
			<td></td>
		</tr>
		<tr>
			<td>db/db</td>
			<td>Jackson laboratory</td>
			<td>000697</td>
			<td>Mice Strain</td>
		</tr>
		<tr>
			<td>Ethanol</td>
			<td>Pharmco-AAPER</td>
			<td>111000200</td>
			<td></td>
		</tr>
		<tr>
			<td>Isoflurane</td>
			<td>Vetone</td>
			<td>502017</td>
			<td></td>
		</tr>
		<tr>
			<td>Lab Chart</td>
			<td>Data Science International (DSI)</td>
			<td></td>
			<td>Software</td>
		</tr>
		<tr>
			<td>Matrigel Matrix</td>
			<td>BD Biosciences</td>
			<td>356234</td>
			<td></td>
		</tr>
		<tr>
			<td>Micro Spring Scissors</td>
			<td>World Precision Instruments (WPI)</td>
			<td>14124</td>
			<td></td>
		</tr>
		<tr>
			<td>Mouse Ox Plus</td>
			<td>STARR Life Sciences Corp.</td>
			<td></td>
			<td>Software</td>
		</tr>
		<tr>
			<td>Mouse Ox Plus Collar Sensor</td>
			<td>STARR Life Sciences Corp.</td>
			<td>015022-2</td>
			<td>Medium Collar Clip Special 7&#8221;</td>
		</tr>
		<tr>
			<td>Mouse Whole Body Plethysmography Chamber</td>
			<td>Data Science International (DSI)</td>
			<td>PLY3211</td>
			<td></td>
		</tr>
		<tr>
			<td>Ohio Care Plus Incubator</td>
			<td>Ohmeda</td>
			<td>HCHD000173</td>
			<td></td>
		</tr>
		<tr>
			<td>Operating Scissors</td>
			<td>World Precision Instruments (WPI)</td>
			<td>501753-G</td>
			<td>Straight</td>
		</tr>
		<tr>
			<td>Osmotic Pump</td>
			<td>Alzet</td>
			<td>1003D</td>
			<td>1ul per hour, 3 days</td>
		</tr>
		<tr>
			<td>Phenol</td>
			<td>Sigma-Aldrich</td>
			<td>P4557</td>
			<td></td>
		</tr>
		<tr>
			<td>Recombinant Mouse Leptin protein</td>
			<td>R&#38;D systems</td>
			<td>498-OB-05M</td>
			<td>5mg</td>
		</tr>
		<tr>
			<td>Saline</td>
			<td>RICCA Chemical</td>
			<td>7210-16</td>
			<td>0.9% Sodium Chloride</td>
		</tr>
		<tr>
			<td>Sterile Surgical Suture</td>
			<td>DemeTech</td>
			<td>DT-639-1</td>
			<td>Silk, size 6-0</td>
		</tr>
		<tr>
			<td>Thermometer</td>
			<td>Innovative Calibration Solutions (INNOCAL)</td>
			<td>EW 20250-91</td>
			<td></td>
		</tr>
	</tbody>
</table>

experimental approach to examine leptin signaling in the carotid bodies and its effects on control of breathing

An adipocyte-produced hormone leptin is a potent respiratory stimulant, which may play an important role in defending respiratory function in obesity. The carotid bodies (CB), a key organ of peripheral hypoxic sensitivity, express the long functional isoform of leptin receptor (LepRb) but the role of leptin signaling in control of breathing has not been fully elucidated. We examined the hypoxic ventilatory response (HVR) (1) in C57BL/6J mice before and after leptin infusion at baseline and after CB denervation; (2) in LepRb-deficient obese db/db mice at baseline and after LepRb overexpression in CBs. In C57BL/6J mice, leptin increased HVR and effects of leptin on HVR were abolished by CB denervation. In db/db mice, LepRb expression in CB augmented the HVR. Therefore, we conclude that leptin acts in CB to augment responses to hypoxia.

Continuous infusion of leptin significantly increased HVR in lean C57BL/6J mice from 0.23 to 0.31 mL/min/g/&#916;FiO2 (P &#60; 0.001, Figure 2)11. CSND abolished the leptin-induced increase in HVR (Figure 2), while no attenuating effects of CSND on HVR were observed in sham surgery group after leptin infusion.
LepRb expression in the CB of LepRb-deficient obese...

Watch this Scientific Journal Video about Experimental Approach to Examine Leptin Signaling in the Carotid Bodies and its Effects on Control of Breathing at JoVE.com

Experimental Approach to Examine Leptin Signaling in the Carotid Bodies and its Effects on Control of Breathing

Our study focuses on the effects of leptin signaling in carotid body (CB) on the hypoxic ventilatory response (HVR). We performed &#39;loss of function&#39; experiments measuring the effect of leptin on HVR after CB denervation and &#39;gain of function&#39; experiments measuring HVR after overexpression of the leptin receptor in CB.

An adipocyte-produced hormone leptin is a potent respiratory stimulant, which may play an important role in defending respiratory function in obesity. The ...

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5.8K vistas.  Johns Hopkins University. Nuestro protocolo se puede utilizar para examinar los efectos respiratorios de la leptina en el cuerpo carótido en el control respiratorio quimiorrestos periférico, y las respuestas fisiológicas a la hipoxia. También podemos evaluar los efectos de la pérdida y ganancia de la función corporal carótida utilizando la denervación quirúrgica y química y la transfección de adenovirus respectivamente. Antes de comenzar el procedimiento, mida la temperatura dentro de una cámara de plastem...