Insulin downregulates M2-muscarinic receptors in adult rat atrial cardiomyocytes: a link between obesity and cardiovascular complications

Pathak, Atul; Smih, Fatima; Galinier, Michel; Verwaerde, Patrick; Rouet, Philippe; Philip-Couderc, Pierre; Montastruc, Jean‐Louis; Senard, Jean‐Michel

doi:10.1038/sj.ijo.0802751

Cited by 17 publications

(10 citation statements)

References 42 publications

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“…Likewise, radioligand binding studies show increased M 2 receptors in the vas deferens of rats after depleting insulin with STZ (28), and again this effect was reversed by exogenous insulin. M 2 receptors are the dominant muscarinic receptor in the heart and expression of M 2 receptors in cultured rat atrial myocytes was also reduced by insulin (41). Our data show that insulin reduced M 2 receptor function rapidly; we were able to decrease M 2 receptor function after only 2 hours incubation with insulin.…”

Section: Discussionsupporting

confidence: 49%

Hyperinsulinemia Potentiates Airway Responsiveness to Parasympathetic Nerve Stimulation in Obese Rats

Nie

Jacoby

Fryer

2014

Am J Respir Cell Mol Biol

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Obesity is a substantial risk factor for developing asthma, but the molecular mechanisms underlying this relationship are unclear. We tested the role of insulin in airway responsiveness to nerve stimulation using rats genetically prone or resistant to diet-induced obesity. Airway response to vagus nerve stimulation and airway M 2 and M 3 muscarinic receptor function were measured in obeseprone and -resistant rats with high or low circulating insulin. The effects of insulin on nerve-mediated human airway smooth muscle contraction and human M 2 muscarinic receptor function were tested in vitro. Our data show that increased vagally mediated bronchoconstriction in obesity is associated with hyperinsulinemia and loss of inhibitory M 2 muscarinic receptor function on parasympathetic nerves. Obesity did not induce airway inflammation or increase airway wall thickness. Smooth muscle contraction to acetylcholine was not increased, indicating that hyperresponsiveness is mediated at the level of airway nerves. Reducing serum insulin with streptozotocin protected neuronal M 2 receptor function and prevented airway hyperresponsiveness to vagus nerve stimulation in obese rats. Replacing insulin restored dysfunction of neuronal M 2 receptors and airway hyperresponsiveness to vagus nerve stimulation in streptozotocintreated obese rats. Treatment with insulin caused loss of M 2 receptor function, resulting in airway hyperresponsiveness to vagus nerve stimulation in obese-resistant rats, and inhibited human neuronal M 2 receptor function in vitro. This study shows that it is not obesity per se but hyperinsulinemia accompanying obesity that potentiates vagally induced bronchoconstriction by inhibiting neuronal M 2 muscarinic receptors and increasing acetylcholine release from airway parasympathetic nerves.Keywords: hyperinsulinemia; obesity; asthma; airway responsiveness; neural M 2 muscarinic receptor Clinical RelevanceObesity-induced asthma does not respond well to traditional anti-inflammatory therapies, suggesting that it is a unique asthma phenotype. Here we show that hyperinsulinemia causes airway hyperresponsiveness to vagus nerve stimulation in obese rats. In human trachea and in rats, we demonstrate that insulin inhibits M 2 muscarinic receptors on airway parasympathetic nerves, resulting in increased acetylcholine release and increased airway contraction. Because hyperinsulinemia is greater and more prevalent in obese individuals, these data may explain why obese individuals are prone to asthma exacerbations and suggest that anticholinergic drugs may be effective in this specific phenotype of asthma.In the United States, 31% of adults and 15% of children are obese. In obese and overweight individuals, the prevalence of asthma (1-3) and the rate of new-onset asthma have increased (4-6). Obese patients with asthma also have increased severity of illness and reduced effectiveness of steroids compared with nonobese patients with asthma (1, 6, 7). The mechanisms by which obesity predisposes to asthma are unclear, limi...

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Section: Discussionsupporting

confidence: 49%

Hyperinsulinemia Potentiates Airway Responsiveness to Parasympathetic Nerve Stimulation in Obese Rats

Nie

Jacoby

Fryer

2014

Am J Respir Cell Mol Biol

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“…Furthermore, when CHRM2 is knocked out in mice, the adult mice weigh approximately 5% less then wild‐type littermates (53). Finally, it has been shown that insulin downregulates M 2 ‐muscarinic receptors in rat atrial cardiomyocytes (54). In our study, we genotyped 28 SNPs within the CHRM2 gene, and rs1824024 showed significant association ( P = 0.046, β‐estimate = −0.104) to BMI in linked families.…”

Section: Discussionmentioning

confidence: 99%

Multiple Genes Influence BMI on Chromosome 7q31–34: The NHLBI Family Heart Study

Laramie

Wilk

Williamson

et al. 2009

Obesity

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The National Heart, Lung, and Blood Institute Family Heart Study (FHS) genome‐wide linkage scan identified a region of chromosome 7q31–34 with a lod score of 4.9 for BMI at D7S1804 (131.9 Mb). We report the results of linkage and association to BMI in this region for two independent FHS samples. The first sample includes 225 FHS pedigrees with evidence of linkage to 7q31–34, using 1,132 single‐nucleotide polymorphisms (SNPs) and 7 microsatellites. The second represents a case–control sample (318 cases; BMI >25 and 325 controls; BMI <25) derived from unrelated FHS participants who were not part of the genome scan. The latter set was genotyped for 606 SNPs, including 37 SNPs with prior evidence for association in the linked families. Although variance components linkage analysis using only SNPs generated a peak lod score that coincided with the original linkage scan at 131.9 Mb, a conditional linkage analysis showed evidence of a second quantitative trait locus (QTL) near 143 cM influencing BMI. Three SNPs (rs161339, rs12673281, and rs1993068) located near the three genes pleiotrophin (PTN), diacylglycerol (DAG) kinase iota (DGKι), and cholinergic receptor, muscarinic 2 (CHRM2) demonstrated significant association in both linked families (P = 0.0005, 0.002, and 0.03, respectively) and the case–control sample (P = 0.01, 0.0003, and 0.03, respectively), regardless of the genetic model tested. These findings suggest that several genes may be associated with BMI in the 7q31–34 region.

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“…The estimated density of 0.88 ϫ 10 6 receptors per cell is about onehalf of the density reported for intact cardiomyocytes from rat atria. The latter value is 1.7 ϫ 10 6 receptors per cell (47), which may be an underestimate. It was determined from the binding of N- [ 3 H]methylscopolamine, which presumably labeled only those receptors that were located at the plasma membrane.…”

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confidence: 89%

Oligomeric Size of the M2 Muscarinic Receptor in Live Cells as Determined by Quantitative Fluorescence Resonance Energy Transfer

Pisterzi

Jansma

Georgiou

et al. 2010

Journal of Biological Chemistry

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Fluorescence resonance energy transfer (FRET), measured by fluorescence intensity-based microscopy and fluorescence lifetime imaging, has been used to estimate the size of oligomers formed by the M 2 muscarinic cholinergic receptor. The approach is based on the relationship between the apparent FRET efficiency within an oligomer of specified size (n) and the pairwise FRET efficiency between a single donor and a single acceptor (E). The M 2 receptor was fused at the N terminus to enhanced green or yellow fluorescent protein and expressed in Chinese hamster ovary cells. Emission spectra were analyzed by spectral deconvolution, and apparent efficiencies were estimated by donor-dequenching and acceptor-sensitized emission at different ratios of enhanced yellow fluorescent protein-M 2 receptor to enhanced green fluorescent protein-M 2 receptor. The data were interpreted in terms of a model that considers all combinations of donor and acceptor within a specified oligomer to obtain fitted values of E as follows: n ‫؍‬ 2, 0.495 ؎ 0.019; n ‫؍‬ 4, 0.202 ؎ 0.010; n ‫؍‬ 6, 0.128 ؎ 0.006; n ‫؍‬ 8, 0.093 ؎ 0.005. The pairwise FRET efficiency determined independently by fluorescence lifetime imaging was 0.20 -0.24, identifying the M 2 receptor as a tetramer. The strategy described here yields an explicit estimate of oligomeric size on the basis of fluorescence properties alone. Its broader application could resolve the general question of whether G protein-coupled receptors exist as dimers or larger oligomers. The size of an oligomer has functional implications, and such information can be expected to contribute to an understanding of the signaling process.Much evidence now indicates that G protein-coupled receptors can exist as oligomers (1, 2), a development that has implications for all aspects of GPCR 4 -mediated signaling. Among the many questions prompted by the emergence of such structures is that of oligomeric size. Although commonly referred to as dimers, oligomers of GPCRs have been detected most often by means of coimmunoprecipitation or resonance energy transfer (3). As typically applied, neither technique can distinguish dimers from larger oligomers. The latter have been identified on the basis of their electrophoretic mobility (reviewed in Ref. 4), but the composition of the bands may be unclear, and the size under the conditions of electrophoresis may have little in common with that in the membrane. Larger oligomers also have been identified by approaches in which detection requires the colocalization of three or four proteins, each bearing a different tag (5-11), but such procedures place only a lower limit on the possible size of the array.There have been comparatively few attempts to examine the oligomeric status of a GPCR in a more quantitative and explicit manner. Measurements of BRET at different ratios of acceptor to donor have pointed to dimers of the melatonin receptor (12), the ␤ 1 -and ␤ 2 -adrenergic receptors (13), the M 1 , M 2 , and M 3 muscarinic receptors (14), and the neurotensin receptor (15)....

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Insulin downregulates M2-muscarinic receptors in adult rat atrial cardiomyocytes: a link between obesity and cardiovascular complications

Cited by 17 publications

References 42 publications

Hyperinsulinemia Potentiates Airway Responsiveness to Parasympathetic Nerve Stimulation in Obese Rats

Hyperinsulinemia Potentiates Airway Responsiveness to Parasympathetic Nerve Stimulation in Obese Rats

Multiple Genes Influence BMI on Chromosome 7q31–34: The NHLBI Family Heart Study

Oligomeric Size of the M2 Muscarinic Receptor in Live Cells as Determined by Quantitative Fluorescence Resonance Energy Transfer

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