The Role of Obesity in Obstructive Sleep Apnea (OSA)

Intermittent Hypoxia and Leptins

Scott Mesenger recently published a Master's Thesis that implicates compelling links between Leptin Signaling and OSA: http://ir.lib.uwo.ca/cgi/viewcontent.cgi?article=2487&context=etd. This work was done in the John Cirello Lab at University of Western Ontario. The study extensively uses our Ob-Rb Antibody to generate data.

There is a strong link between obesity and OSA. "Perhaps the single most important factor affecting OSA risk is body weight. Weight gain of 10% increases the risk of developing OSA by six-fold (Peppard et al., 2000a) and a 10% loss of body weight is estimated to decrease the apnea/hypopnea index (events/hour) by 26%  Within the obese population (BMI ≥ 30) (Wolk et al., 2003), approximately 40% experience significant OSA and approximately 70% of OSA patients are obese (Vgontzas et al., 1994), daunting numbers considering the obesity epidemic occurring in North America and estimates suggesting 41% of Americans will be obese by 2015 (Nejat et al., 2009)."

"Leptin can exert cardiovascular effects by acting centrally, as has been shown by studies introducing leptin directly into the CNS. Central administration serves to increase plasma catecholamines epinephrine and norepinephrine (Satoh et al., 1999). In other studies, leptin has been found to increase SNA, arterial pressure as well as heart rate and to inhibit the baroreflex (Arnold et al., 2009; Mark et al., 2009). Leptin may also have a role in modulating the peripheral chemoreflex at the level of the CNS as microinjection of leptin into caudal pressor areas of the NTS has been found to potentiate the sympathetic and blood pressure responses to chemoreflex activation (Ciriello & Moreau, 2012). These cardiovascular effects may not be debilitating under normal homeostatic conditions, however in conditions of increased circulating leptin, such as in OSA and obesity, the cardiovascular responses may be detrimental."

This study shows the increase in the expression of leptins like Ob-Rb in Carotid .

Images: Fluorescent (a-c) photomicrographs showing the effect of IH on Ob-Rb (a) and ERK 1/2 (b) expression in carotid body glomus cells. Note that Ob-Rb and ERK 1/2 are co-expressed in the same cells (c). Calibration mark in (a) represents 100 μm and applies to (a-c).

Images: Western blots showing the presence of Ob-Rb (a) and Ob-R100 (b) in carotid bodies after IH. Note that IH significantly (*) decreases the protein level of Ob-Rb (a), while significantly (*) increasing the protein level of Ob-R100 (b) compared to normoxic controls (b). p values are indicated. n=5-6.

This study will give the reader great insights on the molecular biology of OSA. Check it out: http://ir.lib.uwo.ca/cgi/viewcontent.cgi?article=2487&context=etd.

Leptins and Obesity

Our Leptin and Leptin Receptor Markers have proven effective for researchers studying root causes of obesity. In this reference the authors show an interesting twist regarding the impact of endothial vs neuronal leptin signaling: Weihong Pan, Hung Hsuchou, Germaine G. Cornelissen-Guillaume, Bhavvani Jayaram, Yuping Wang, Hong Tu, Franz Halberg, Xiaojun Wu, Streamson C. Chua Jr., and Abba J. Kastin. Endothelial leptin receptor mutation provides partial resistance to diet-induced obesity. Published online before print February 2012, doi: 10.​1152/​japplphysiol.​00590.​2011.
...chicken anti-ObRb (1:100, Neuromics)...

Highlights: Leptin, a polypeptide hormone produced mainly by adipocytes, has diverse effects in both the brain and peripheral organs, including suppression of feeding. Other than mediating leptin transport across the blood-brain barrier, the role of the endothelial leptin receptor remains unclear. We recently generated a mutant mouse strain lacking endothelial leptin receptor signaling, and showed that there is an increased uptake of leptin by brain parenchyma after its delivery by in-situ brain perfusion. Here, we tested the hypothesis that endothelial leptin receptor mutation confers partial resistance to diet-induced obesity. These ELKO mice had similar body weight and percent fat as their wildtype littermates when fed with rodent chow, but blood concentrations of leptin were significantly elevated. In response to a high fat diet, wildtype mice had a greater gain of body weight and fat than ELKO mice . As shown by metabolic chamber measurement, the ELKO mice had higher oxygen consumption, carbon dioxide production, and heat dissipation, although food intake was similar to that of the wildtype mice and locomotor activity was even reduced. This indicates that the partial resistance to diet-induced obesity was mediated by higher metabolic activity in the ELKO mice. Since neuronal leptin receptor knockout mice show obesity and diabetes, the results suggest that endothelial leptin signaling shows opposite effects from that of neuronal leptin signaling, with a facilitatory role in diet-induced obesity.


Obesity is a growing health problem and will continue to drive up costs. Research like this could help find effective and log term solutions for helping with weight loss.

LepRb-STAT3 Pathway and Obesity Research

Neuromics' Hypothalumus Neurons, Leptin Antibodies and Recombinant Proteins are being increasingly used by researchers studying root causes of diabetes and obesity. I am pleased to update you on an important study from our friends at Shanghai Jiaotong University School of Medicine. This publication references use of our LepRb/OBRb Antibody.

Pei Wang, Feng-Jiao Yang, Hui Du, Yun-Feng Guan, Tian-Ying Xu, Xue-Wen Xu, Ding-Feng Su, and Chao-Yu Miao. Involvement of Leptin Receptor Long Isoform (LepRb)-STAT3 Signaling Pathway in Brain Fat Mass– and Obesity-Associated(FTO) Downregulation during Energy Restriction. © 2011 The Feinstein Institute for Medical Research, www.feinsteininstitute.org.Online address: http://www.molmed.org. doi: 10.2119/molmed.2010.00013.
Abstract: Obesity is an important risk factor for cardiovascular disease, diabetes and certain cancers. The fat mass– and obesity associated (FTO) gene is tightly associated with the pathophysiology of obesity, whereas the exact role of FTO remains poorly understood. Here, we investigated the alternations of FTO mRNA and protein expression in the peripheral metabolic tissues and the brain upon energy restriction (ER) and explored the involvement of the leptin signaling pathway in FTO regulation under ER status. ER decreased the FTO mRNA and protein expression in hypothalamus and brainstem but not in periphery. Using doubleimmunofluorescence staining, FTO was found to be colocalized with the leptin receptor long isoform (LepRb) in arcuate nucleus of hypothalamus and the nucleus of the solitary tract. In LepRb mutant db/db mice, the FTO downregulation in brain and body weight reduction induced by ER were completely abolished. The enhanced phosphorylation of signal transducer and activator of transcription 3 (STAT3) induced by ER was also impaired in db/db mice. Moreover, leptin directly activated the STAT3 signaling pathway and downregulated FTO in in vitro arcuate nucleus of hypothalamus cultures and in vivo wild-type mice but not db/db mice. Thus, our results provide the first evidence that the LepRb-STAT3 signaling pathway is involved in the brain FTO downregulation during ER.

LepRB (CH14104) staining of rat brain sections

Images: Frozen brain sections were incubated with LepRb (clone number CH14014; chicken antirat) and FTO (rabbit antirat) antibodies and then incubated with Cy3-conjugated secondary antibody (goat antichicken, red) or FITC-conjugated secondary (goat antirabbit, red). Nuclei were stained by 4′,6-diamidino-2-phenylindole dihydrochloride (DAPI). NTS, nucleus of the solitary tract.

I will continue to track these kind of studies closely. They build the foundation for potential Obesity resduction therapies. This would have a major impact on growing burden of world wide Health Costs.

TRHR1 and LepRb receptors and Thermogenesis

I would like to thank Montina Van Meter, Lab Manager, Autonomic Neuroscience at Pennington Biomedical Research Center, for alerting me to this just published study. Included are excellent images of stained LepRb (OB-Rb) and GAD1 expressing neurons localized in loose clusters of cells in the DMN, NST, and the VLM.

This study focus on identifying loci in the hindbrain where leptin and TRH act synergistically to increase thermogenesis. Since thermogenic processes are at the root of how our bodies regulate energy, understanding the related expression and signaling pathways could be key to finding therapies for obesity.

Maria J. Barnes, Richard C. Rogers, Montina J. Van Meter and Gerlinda E. Hermann. Co-localization of TRHR1 and LepRb receptors on neurons in the hindbrain of the rat. doi:10.1016/j.brainres.2010.07.094

Example images: Distribution of LepRb+ fibers in hindbrain. LepRb-ir (red) fibers and varicosities are seen among TRHR1-ir (green) cells and fibers. These red and green fibers are adjacent and co-mingle but do not show co-localization of receptors. This pattern is seen in (A) fascicles of the solitary tract (ST); (B) raphe pallidus (RP), and (C) raphe obscurrus (RO). (D) Border between the medial solitary nucleus (NST) and the area postrema (AP; white dashed line) showing an abundance of LepRb-ir (red) fibers and
 neurons (white arrows for selected neurons) in the NST but not the AP. (E) LepRb-ir staining is suppressed by pretreatment of tissue with LepRb epitope blocking peptide. (F) TRHR1-ir staining is suppressed by treatment with excess TRHR1. Scale bar A–D=100 microns; E, F=300 microns. cc=central canal.

Abstract: We have reported a highly cooperative interaction between leptin and thyrotropin releasing hormone (TRH) in the hindbrain to generate thermogenic responses (Hermann et al., 2006) (Rogers et al., 2009). Identifying the locus in the hindbrain where leptin and TRH act synergistically to increase thermogenesis will be necessary before we can determine the mechanism(s) by which this interaction occurs. Here, we performed heat-induced epitope recovery techniques and in situ hybridization to determine if neurons or afferent fibers in the hindbrain possess both TRH type 1 receptor and long-form leptin receptor [TRHR1; LepRb, respectively]. LepRb receptors were highly expressed in the solitary nucleus [NST], dorsal motor nucleus of the vagus [DMN] and catecholaminergic neurons of the ventrolateral medulla [VLM]. All neurons that contained LepRb also contained TRHR1. Fibers in the NST and the raphe pallidus [RP] and obscurrus [RO] that possess LepRb receptors were phenotypically identified as glutamatergic type 2 fibers (vglut2). Fibers in the NST and RP that possess TRHR1 receptors were phenotypically identified as serotonergic [i.e., immunopositive for the serotonin transporter; SERT]. Co-localization of LepRb and TRHR1 was not observed on individual fibers in the hindbrain but these two fiber types co-mingle in these nuclei. These anatomical arrangements may provide a basis for the synergy between leptin and TRH to increase thermogenesis.

Related Reagents:
Leptin and Leptin Receptor Antibodies

Leptin Proteins

Diabetes and Obesity Research

Antibodies

Diabetes and Obesity Proteins