β2-AR Gene Research Articles

B2 adrenergic receptor gene polymorphism effect on childhood asthma severity and response to treatment.

BackgroundAlterations of B2 adrenergic receptor (β2AR) can modulate the severity of asthma and the response to treatment. Therefore, we aimed to evaluate β2AR gene polymorphism at codons 16 and 27 and their effect on asthma severity and response to treatment in asthmatic children.MethodsCase-control study was conducted on 156 children; 104 of them had bronchial asthma and 52 were healthy children (control group). Subjects of the study underwent history taking, clinical examination, pulmonary function tests, serum IgE level assessment, and identification of β2AR-16 A46G and β2AR-27 C79G polymorphism using PCR-Restriction Fragment length polymorphisms (RFLP) test.ResultsThere was a higher frequency of Arg-Gly genotypes (odds ratio (OR)=6.57; confidence interval (CI): 2.42-18.81, P<0.001) and lower frequency of Arg-Arg (OR=4.7; CI: 2.05-10.95, P<0.001) among asthmatic children compared with that among controls at codon 16. The presence or absence of Gly16 or Glu27 either homozygous or heterozygous for both correlated with the grade of asthma severity. The presence of heterozygous Arg-Gly and Gln-Glu gives a better response to drug therapy than the presence of Gly-Gly and Glu-Glu genotypes at codons 16 and 27.ConclusionPolymorphism of β2AR at codons 16 and 27 correlates with asthma severity and response to treatment in asthmatic children.

Profiling of Differential Expression of Genes in Mice Carrying Both Mutant Presenilin 1 and Amyloid Precursor Protein Transgenes with or without Knockout of B2 Adrenergic Receptor Gene.

Alzheimer's disease (AD) is a lifelong progressive neurodegenerativa disease related with accumulation of amyloid β peptide (Aβ) produced by processing of amyloid precursor protein (APP) in the brain. In spite of several-decades effort on AD, there is still no medicine used to intervene with its pathological processes. Our previous studies made in transgenic animal models harboring familial AD genes of mutant presenilin 1 and amyloid precursor protein (APP) showed that β2AR gene knock-out (β2AR-KO) is beneficial in senile AD animals. Consistently, an epidemiological study lasted for two decades showed that the sole usage of β blockers as antihypertensive medicines is associated with fewer brain lesions and less brain shrinkage seen in senile AD patients. In order to understand why senile β2AR-KO AD mice had better learning and memory, genomic effects of β2AR-KO in the double transgenic AD mice were investigated. In the analysis, major genomic significance of β2AR-KO was directed to influence protein-processing and presentation involving membrane structure and MHC class I and II protein complex, and lysosome and hydrolase activity for protein degradation, which are critical for accumulation of amyloid β peptide, the hallmark of AD.

The impact of apelin-36 on isolated rat hearts as a member of apelin family.

Apelinis an endogenousadipocytokine thatplays an important role in the regulation of cardiovascular function. Apelin-36 is a member of apelin family. However cardiac reports related to apelin-36 are very rare. The purpose of this study is to investigate the impact of apelin-36 onhemodynamic variables of the isolated rat hearts. Twenty-eight ratswere equally divided into four groups: control, apelin-36 at the following concentrations: 1 nM, 10 nM and 100 nM. Theisolatedhearts were perfused with modified Krebs-Henseleit solution (mK-Hs) by using theLangendorffmethod. Cardiac parameters, including left ventricular developed pressure (LVDP),maximal rate of pressure development (+dP/dtmax), heartrate (HR) and coronary flow (CF) were measured. Gene expressions relevant to cardiomyocyte contractility were determined by real-time PCR. 10 and 100 nM doses of apelin-36 perfusion led topositive inotropy with an increase of LVDP and +dP/dtmax, which are the indexes of cardiac contractility. Furthermore both doses of apelin-36 increased endothelial nitric oxide synthase (eNOS), sarco/endoplasmic reticulum Ca2+-ATPase (Serca2a) andβ2-Adrenergic receptors (β2-AR) mRNA. These results showed that apelin-36 had a positive inotropic effect on the isolated rat heart and can induceeNOS,Serca2aandβ2-ARgenes activation that enhancescontractilityof theheart (Tab. 1, Fig. 2, Ref. 23).

Cell-Free Expression, Purification, and Characterization of the Functional β2-Adrenergic Receptor for Multianalyte Detection of β-Agonists.

Large-scale expression of β2-adrenergic receptor (β2-AR) in functional form is necessary for establishment of receptor assays for detecting illegally abused β-adrenergic agonists (β-agonists). Cell-based heterologous expression systems have manycritical difficulties in synthesizing this membrane protein, such as low protein yields and aberrant folding. To overcome these challenges, the main objective of the present work was to synthesize large amounts of functional β2-AR in a cell-free system based on Escherichia coli extracts. A codon-optimized porcine β2-AR gene (codon adaptation index: 0.96) suitable for high expression in E. coli was synthesized and transcribed to the cell-free system, which contributed to increase the expression up to 1.1mg/ml. After purification using Ni-affinity chromatography, the bioactivity of the purified receptor was measured by novel enzyme-linked receptor assays. It was determined that the relative affinities of the purified β2-AR for β-agonists in descending order were as follows: clenbuterol > salbutamol > ractopamine. Moreover, their IC50 values were 45.99, 60.38, and 78.02µg/liter, respectively. Although activity of the cell-free system was slightly lower than activity of systems based on insect and mammalian cells, this system should allow production of β2-AR in bulk amounts sufficient for the development of multianalyte screening methods for detecting β-agonist residues.

Trends in Severe Obesity Among 23 Million U.S. Children Aged 2–4 Years Who Enrolled in WIC — United States, 2000–2014

The aim of this study was to verify β2-AR expression in oral squamous cell carcinoma cell lines (SCC-9 and SCC-25), and to investigate the role of this receptor in migration and invasion of these neoplastic cells.SCC-9 and SCC-25 cells were investigated for gene and protein expression of β2-AR. Cell migration and invasion were analyzed by wound healing assay and transwell invasion camera system. Different concentrations (0.1, 1 and 10 μM) of norepinephrine were used to stimulate, and 1 μM propranolol was used to block the beta-adrenergic receptors on cancer cells. Differences in median values of SCC-9 and SCC-25 and β2-AR protein expression were analyzed by Friedman test and in case of significant differences; pairwise comparisons were performed using Bonferroni correction.The results showed that the β2-AR gene and protein expression were observed in both oral cancer cell lines. The concentration of 10 μM of norepinephrine significantly inhibited (p ≤ 0.05) migration of SCC-9 and SCC-25 cell lines. Furthermore, there was a significant reduction (p ≤ 0.05) in the effect of norepinephrine on cell migration when the β2-AR was inhibited by propranolol. The blockade by propranolol showed a tendency to reverse the effect of norepinephrine on the invasiveness of SCC-9 and SCC-25.The use of beta-adrenergic receptor agonists could become an adjuvant therapeutic target in the treatment of this malignancy.

Opposite effects of β2-adrenoceptor gene deletion on insulin signaling in liver and skeletal muscle

Background and aimβ2-Adrenoceptors (β2-ARs) are G protein-coupled receptors (GPCRs) expressed in the major insulin target tissues. The interplay between β2-AR and insulin pathways is involved in the maintenance of glucose homeostasis. The aim of this study was to explore the consequences of β2-ARs deletion on insulin sensitivity and insulin signaling cascade in metabolically active tissues. Methods and resultsWe evaluated glucose homeostasis in skeletal muscle and liver of β2-AR-null mice (β2-AR−/−) by performing in vivo (glucose tolerance test and insulin tolerance test) and ex vivo (glucose uptake and glycogen determination) experiments. β2-AR gene deletion is associated with hepatic insulin resistance and preserved skeletal muscle insulin sensitivity. Importantly, we demonstrate that hepatic β2-AR regulates insulin-induced AKT activation via Grb2-mediated SRC recruitment through a Gi-independent mechanism. Conclusionsβ-AR stimulation contributes to the development of early stages of insulin resistance progression in the liver. Our findings indicate that the cross-talk between β2-AR and insulin signaling represents a fundamental target towards the development of novel therapeutic approaches to treat type 2 diabetes and metabolic syndrome.

The effects and possible mechanism of β2AR gene expression in cardiocytes of canines with heart failure.

The objective of the present study was to observe the changes of β2-adrenergic receptor (β2AR) protein expression in a canine model of heart failure (HF), and the function of cardiocytes after transfection with Adv-β2AR. The canine model of chronic HF was induced by rapid right ventricular pacing and cardiocytes were isolated with collagenase II. Cardiocytes were transfected with Adv-β2AR to observe contractile function with a motion edge-detection system of single cells. Expression of β2AR protein in cardiocytes was measured by immunoblotting and the levels of intracellular cAMP were measured by ELISA. Compared with the control group (the sham group), the expression of β2AR protein in HF cardiocytes did not change, but the basal (1 mM Ca2+) contraction amplitude percentage (1.809±0.922 vs. 1.120±0.432%, P<0.05), the maximum contraction amplitude percentage (14.855±2.377 vs. 10.784±2.675%, P<0.01) and the basal levels of intracellular cAMP (9.39±2.54 vs. 5.26±0.95 pmol/ml, n=6, P<0.05) of HF cardiocytes were significantly decreased. However, when HF cardiocytes were transfected with Adv-β2AR and cultured for 48 h, compared with the non-transfected group, the basal contraction amplitude percentage (0.851±0.324 vs. 1.629±0.522%, P<0.05), the maximum contraction amplitude percentage (9.260±2.208% vs. 12.205±1.437%, P<0.01) and the basal levels of intracellular cAMP (5.26±0.95 vs. 9.03±1.03 pmol/ml, n=6, P<0.05) of cardiocytes in the transfected group were significantly increased. In conclusion, the expression of β2AR protein in HF cardiocytes did not change, but contraction function was impaired. The moderate overexpression of β2AR gene in the HF cardiocytes increased the levels of intracellular cAMP and improved contraction function.

Suppression of microRNA-16 protects against acute myocardial infarction by reversing beta2-adrenergic receptor down-regulation in rats.

microRNA-16 (miR-16) has been shown to be up-regulated in ischemic heart. Beta2-adrenoreceptor (β2-AR) exerts cardioprotective property in ischemic injury. This study aims to determine the effect of miR-16 in cardiac injury in rats and the possible involvement of β2-AR in this process. Acute myocardial infarction (AMI) model in rats was induced by ligation of left coronary artery. Neonatal rat ventricular cells (NRVCs) were cultured in vitro tests. The cardiomyocyte model of oxidative injury was mimicked by hydrogen peroxide. The expression of miR-16 was obviously up-regulated and β2-AR was remarkably down-regulated in both AMI rats and NRVCs under oxidative stress. miR-16 over-expression in NRVCs reduced cell viability and increased apoptosis. Conversely, inhibition of endogenous miR-16 with its specific inhibitor reversed these changes. Over-expression of miR-16 using an miR-16 lentivirus in AMI rats markedly increased cardiac infarct area, lactate dehydrogenase and creatine kinase activity, and exacerbated cardiac dysfunction. Lentivirus-mediated knockdown of miR-16 alleviated acute cardiac injury. Moreover, miR-16 over-expression significantly suppressed β2-AR protein expression in both cultured NRVCs and AMI rats, while inhibition of miR-16 displayed opposite effect on β2-AR protein expression. Luciferase assay confirmed that miR-16 could directly target the 3′untranslated region of β2-AR mRNA. miR-16 is detrimental to the infarct heart and suppression of miR-16 protects rat hearts from ischemic injury via up-regulating of β2-AR by binding to the 3′untranslated region of β2-AR gene. This study indicates that targeting miR-16/β2-AR axis may be a promising strategy for ischemic heart disease.

Beta Adrenoceptor Polymorphism and Clinical Response to Sertraline in Major Depressive Patients.

The adrenoceptor family, as one of the main contributors in regulating the noradrenergic system, has been studied in involvement of depression and its treatment. A functional polymorphism of G1165C on beta adrenoceptor (βAR) enhances post receptor signalling and is assumed to be involved in pharmacotherapy of depression. The aim of the present study was to discern the influence of G1165C polymorphism in the β1AR gene on individual differences in response to sertraline. One hundred newly diagnosed patients completed 6 weeks of sertraline treatment. Response to treatment was defined as a 50% decrease in Hamilton Rating Scale for depression (HRSD). The patients who carried CC genotype responded five times more to sertraline comparing with other variants (P=0.005; OR=5.7; 95%CI=1.4-23.9). Moreover, carriers of C allele responded three times more to sertraline than patients with the G allele (P=0.001; OR= 3.3; 95%CI= 1.72-6.50). In conclusion, our results support the hypothesis that genetic variation of β1AR might influence clinical response to sertraline.This article is open to POST-PUBLICATION REVIEW. Registered readers (see "For Readers") may comment by clicking on ABSTRACT on the issue's contents page.

The role of genetic polymorphism of β3-adrenergic receptor in the susceptibility to diabetes and its related disorders: a case–control study on Egyptian population

Background The β3-adrenergic receptor (β3-AR) is mainly expressed in adipose tissue and plays an important role in lipid metabolism and metabolic rate by mediating lipolysis and thermogenesis. It has been suggested that the Trp64Arg (T→C) polymorphism in the β3-AR gene affects fat accumulation and/or impairment of lipid and carbohydrate metabolism. Objective The aim of this study was to investigate whether common polymorphism (Trp64Arg) of β3-AR gene has a role in the apparent susceptibility to type 2 diabetes mellitus (DM) and its related disorders in the Egyptian population. Patients and methods One hundred and thirty five healthy controls and 123 individuals with type 2 DM were enrolled in the study. The β3-AR Trp64Arg polymorphism was identified using restriction fragment length polymorphism PCR of peripheral blood DNA samples. Analysis of data was performed using SPSS program 11. Results Allele frequency for C was 23.2% in the diabetic group compared with 12.2% in the control group. The carriers of XC genotype (TC and CC) were at high risk of developing type 2 DM (odds ratio=2.8; 95% confidence interval=1.6–4.9) when compared with the carrier of TT genotype. Furthermore, they were at much higher risk of developing its related disorders such as central obesity, dyslipidemia, and hypertension (odds ratio=2.8; 1.8, 1.5, 2.2, and 2.7 for BMI, waist–hip ratio, triglycerides, high-density lipoprotein, and hypertension, respectively). Conclusion The prevalence of Arg64 allele of the Trp64Arg polymorphism in the β3-AR gene is a risk factor for type 2 DM and its related disorders in the Egyptian population.

Genetic background of aberrant thermogenin expression (UCP1) in obesity leading to metabolic syndrome.

Cardiovascular and metabolic disturbances individually and interdependently lead to chronic pathological conditions observed in cardio-metabolic diseases (CMDs). In Europe, the morbidity and mortality caused by cardiovascular disease are the highest among all diseases. Therefore, it seems important to search for new and alternative therapies for obesity, which is the main cause of type 2 diabetes (T2D) and cardiovascular disease (CD). Great attention has been paid to the role of brown adipose tissue in fat burning and the possibility of transformation of the white adipose tissue to cells with brown adipose tissue function as a potential form of treatment of obesity. The best-characterized marker of brown adipose tissue is uncoupling protein 1 (UCP1), which has the ability to dissipate energy as heat in the process called non-shivering thermogenesis. Numerous studies have shown that altered expression of this protein can lead to disturbances in fat metabolism. One possible reason for the aberrant expression of UCP1 may be inherited variations in the gene encoding that protein. Therefore, several studies investigating the role of polymorphisms in the gene encoding UCP1 in susceptibility to obesity or metabolic syndrome have been performed. Here we summarize the results of studies describing the associations between the UCP1 gene polymorphisms A-3826G, A-1766G, Met229Leu and Ala64Thr and polymorphism Trp64Arg in the β3-AR gene, their correlations and their associations with the occurrence of metabolic syndrome.

2016 Lucian Award

Fifty years after it was established through a generous bequest to McGill University,1 the 2016 Louis and Artur Lucian Award for research in circulatory disease has been presented to Brian Kobilka, MD, of Stanford University. Kobilka is being honored for his enormous contributions to the understanding of G protein–coupled receptors (GPCRs), the versatile family of receptors that mediate the majority of cellular responses to hormones, neurotransmitters, and some types of sensory input. “Kobilka revealed the molecular configuration of the β2-adrenergic receptor (β2AR) through the use of crystallography, then doggedly pursued research in this area until he discovered how the receptor functions. He has now expanded his work to a whole range of GPCRs. Many of the other candidates for the 2016 Lucian award were extremely productive and highly cited, but his science was head and shoulders above the others. With a very long array of papers in high-impact and difficult-to-publish-in journals— Cell , Science , Nature , and PNAS —Kobilka’s contributions have been recognized by his peers as cutting-edge work that advances the field significantly, not as small incremental discoveries,” says James Martin, MD, chair of the McGill University Department of Medicine and new chair of the Lucian award committee. During his internship at Barnes Hospital, Kobilka often treated unstable patients with medications acting on GPCRs, including the adrenergic and muscarinic receptors regulating heart rate and blood pressure and opioid receptors controlling pain. His interest in intensive care medicine led Kobilka to apply for cardiology fellowships, and he was drawn to the program at Duke University because it encouraged fellows to pursue basic research. Kobilka joined the laboratory of Robert Lefkowitz, MD, where the β2AR had been identified and Jeff Benovic, a graduate student, had recently succeeded in purifying enough β2AR …

β2-Adrenergic receptor gene polymorphisms in the relapse of myasthenia gravis with thymus abnormality

Background. The role of β2-adrenergic receptor (β2-AR) in the relapse of myasthenia gravis (MG) associated with thymus abnormality has not been fully identified. Methods. Using polymerase chain reaction and gene sequencing method, we investigated the relationship of β2-AR gene polymorphisms with different thymus pathology in MG patients. The role of β2-AR gene polymorphisms in the relapse of MG was further investigated. Results. Age of onset (p = 0.034), the onset symptom of ocular MG (OMG; p = 0.023), the first symptom of OMG second generalization (p = 0.040) were different in MG with thymoma from those in MG with normal thymus or thymus hyperplasia. Gene polymorphisms of β2-AR on positions 16 and 27 showed no significant difference between relapsed and non-relapsed MG patients with thymus abnormality (thymus hyperplasia: position 16, p = 0.792; position 27, p = 0.664; thymoma: position 16, p = 0.226; position 27, p = 0.615). However, genotypes distribution on position 27 among MG patients with three thymus histology was significantly different (χ² = 8.153, p = 0.041). Furthermore, glucocorticoid can decrease relapse of MG with thymus hyperplasia (p = 0.021). Conclusions. MG patients with thymus abnormality differ from MG patients with normal thymus in age of onset, the onset symptom of OMG and the first symptom of OMG second generalization. β2-AR gene polymorphisms had no relationship with the relapse of MG with thymus abnormality. Gene polymorphism of β2-AR on position 27 was associated with different thymus histology of MG. Glucocorticoid was able to reduce the risk of relapse of MG with thymus hyperplasia.

Overexpression of the β2AR gene improves function and re-endothelialization capacity of EPCs after arterial injury in nude mice.

BackgroundProliferation and migration of endothelial progenitor cells (EPCs) play important roles in restoring vascular injuries. β2 adrenergic receptors (β2ARs) are widely expressed in many tissues and have a beneficial impact on EPCs regulating neoangiogenesis. The aim of the present study was to determine the effect of overexpressing β2ARs in infused peripheral blood (PB)-derived EPCs on the re-endothelialization in injured vessels.MethodsInduction of endothelial injury was performed in male nude mice that were subjected to wire-mediated injury to the carotid artery. Human PB-derived EPCs were transfected with an adenovirus serotype 5 vector expressing β2AR (Ad5/β2AR-EPCs) and were examined 48 h later. β2AR gene expression in EPCs was detected by real-time polymerase chain reaction and Western blot analysis. In vitro, the proliferation, migration, adhesion, and nitric oxide production of Ad5/β2AR-EPCs were measured. Meanwhile, phosphorylated Akt and endothelial nitric oxide synthase (eNOS), which are downstream of β2AR signaling, were also elevated. In an in vivo study, CM-DiI-labeled EPCs were injected intravenously into mice subjected to carotid injury. After 3 days, cells recruited to the injury sites were detected by fluorescent microscopy, and the re-endothelialization was assessed by Evans blue dye.ResultsIn vitro, β2AR overexpression augmented EPC proliferation, migration, and nitric oxide production and enhanced EPC adhesion to endothelial cell monolayers. In vivo, when cell tracking was used, the number of recruited CM-DiI-labeled EPCs was significantly higher in the injured zone in mice transfused with Ad5/β2AR-EPCs compared with non-transfected EPCs. The degree of re-endothelialization was also higher in the mice transfused with Ad5/β2AR-EPCs compared with non-transfected EPCs. We also found that the phosphorylation of Akt and eNOS was increased in Ad5/β2AR-EPCs. Preincubation with β2AR inhibitor (ICI118,551), Akt inhibitor (ly294002), or eNOS inhibitor (L-NAME) significantly attenuated the enhanced in vitro function and in vivo re-endothelialization capacity of EPCs induced by β2AR overexpression.ConclusionsThe present study demonstrates that β2AR overexpression enhances EPC functions in vitro and enhances the vascular repair abilities of EPCs in vivo via the β2AR/Akt/eNOS pathway. Upregulation of β2AR gene expression through gene transfer may be a novel therapeutic target for endothelial repair.

Influence of CYP2D6 and β2-adrenergic receptor gene polymorphisms on the hemodynamic response to propranolol in Chinese Han patients with cirrhosis.

Propranolol is widely used to prevent gastroesophageal variceal bleeding; however, some patients could not benefit from propranolol. This study is to evaluate the relationship between CYP2D6 and β2-adrenergic receptor (β2-AR) gene polymorphisms and the hemodynamic response to propranolol in Chinese Han patients. The clinical data of patients with gastroesophageal varices undergoing hepatic venous pressure gradient (HVPG) measurement before and 7 days after oral propranolol administration in our department were collected. Four single nucleotide polymorphisms of CYP2D6 and β2-AR genes were detected. The relationship was identified by logistic regression model. Thirty patients were involved in the analysis. Sixty milligram propranolol twice each day was well tolerated by all the patients. The initial and secondary average of HVPG was 17.4 ± 5.8 mmHg vs. 13.2 ± 4.8 mmHg, respectively (t = 5.726, P < 0.001). Twenty patients responded to propranolol. The mean reduction value of HVPG was 6.6 ± 3.6 mmHg (range from 3 to 19). Genotype analysis showed: 20 homozygotes for C/C188 and 10 for heterozygous C/T188, 8 homozygotes for G/G4268 and 22 heterozygotes for G/C4268, 14 homozygotes for Gly16 and 10 heterozygotes, and 6 homozygotes for Arg16, 27 homozygotes for Gln27 and 3 heterozygotes. The multivariate logistic regression analysis indicated that CYP2D6 (188C>T) genotype was an independent predicting factor for HVPG response to propranolol (P = 0.033). CYP2D6 (188C>T) gene polymorphisms influence the hemodynamic response to propranolol in this population of Chinese Han patients with gastroesophageal varices. However, HVPG response cannot be completely predicted from CYP2D6 and β2-AR gene polymorphisms.

Relationship of brown adipose tissue perfusion and function: a study through β2-adrenoreceptor stimulation.

Brown adipose tissue (BAT) activation increases glucose and lipid consumption; as such, it is been considered as a potential therapy to decrease obesity. BAT is highly vascularized and its activation is associated with a necessary increase in blood flow. However, whether increasing BAT blood flow per se increases BAT activity is unknown. To examine this hypothesis, we investigated whether an isolated increase in BAT blood flow obtained by β2-adrenoreceptor (β2-AR) stimulation with salbutamol increased BAT activity. BAT blood flow was estimated in vivo in mice using contrast-enhanced ultrasound. The absence of direct effect of salbutamol on the function of isolated brown adipocytes was assessed by measuring oxygen consumption. The effect of salbutamol on BAT activity was investigated by measuring BAT glucose uptake in vivo. BAT blood flow increased by 2.3 ± 0.6-fold during β2-AR stimulation using salbutamol infusion in mice (P= 0.003). β2-AR gene expression was detectable in BAT but was extremely low in isolated brown adipocytes. Oxygen consumption of isolated brown adipocytes did not change with salbutamol exposure, confirming the absence of a direct effect of β2-AR agonist on brown adipocytes. Finally, β2-AR stimulation by salbutamol increased BAT glucose uptake in vivo (991 ± 358 vs. 135 ± 49 ng glucose/mg tissue/45 min in salbutamol vs. saline injected mice, respectively,P= 0.046). In conclusion, an increase in BAT blood flow without direct stimulation of the brown adipocytes is associated with increased BAT metabolic activity. Increasing BAT blood flow might represent a new therapeutic target in obesity.

Abstract 16113: Upregulation of Cardiac β3-Adrenergic Signaling Promotes Heart Failure Progression

Background. The negative inotrope and upregulation of β 3 -adrenergic receptors (AR) in failing human and animal hearts suggest a direct and contributing role of cardiac β 3 -AR activation on heart failure (HF) progression. However, its precise role is still being debated. We hypothesize that up-regulation of β 3 -AR is detrimental and chronic β 3 -AR blockade may limit or prevent the progression of HF. Methods. We determined Left ventricular (LV) and myocyte functional response and β 1 - and β 3 -AR expressions in 3 groups of rats (6/group) for a period of 4 months: 1) Isoproterenol (ISO)-treated, 4 months after receiving ISO (170 mg/kg, sq, for 2 days); 2) ISO/β 3 -ANT, two months after receiving ISO, L-748,337, a selective β 3 -AR antagonist (β 3 -ANT) (10 -7 M/kg/day by implanted osmotic mini pump) was initiated after established HF and was given for 2 months; and 3) sham controls. Results. Compared with controls, ISO-treated rats had HF onset at one month after ISO and progressed to severe HF at 4 months. Plasma norepinephrine (NE, 1482 vs 247 pg/ml) increased 6 fold. Both stroke volume (SV) and ejection fraction (EF, 32% vs 61%) decreased more than 48%, and LV end-diastolic pressure (P ED , 15.4 vs 6.0 mmHg) doubled, parallel with 48% reductions in cell contraction (dL/dt max, 78 vs 149 μm/s) and relaxation (dR/dt max , 66 vs 128 μm/s) and a much less increase in dL/dt max (30% vs 74%) in response to superfusion of ISO (10 -8 M). These changes were associated with significantly decreased β 1 -AR mRNA (0.30 vs 0.64) and protein levels (0.36 vs 0.62), but increased β 3 -AR mRNA (1.29 vs 0.52) and protein levels (0.35 vs 0.18). Treatment with β 3 -ANT significantly decreased P ED and plasma NE (191 pg/ml). Both SV and EF (59%) increased to more than 76% from ISO-treated values. The signal ratios of β 1 -AR mRNA (0.61) and β 3 -AR mRNA (0.59) remained close to control levels. ISO-induced increase in dL/dt max (75%) was also significantly augmented. Conclusion. Chronic β 3 -ANT prevented plasma norepinephrine elevations and causes normalization of β 1 - and β 3 -AR gene expression, restores normal responsiveness of myocyte to β-AR stimulation, and leads to regression of LV and myocyte dysfunction in a rat model of progressive HF. Thus, β 3 -AR blocker may provide a new therapeutic strategy for the treatment of HF.

Curcumin promotes browning of white adipose tissue in a norepinephrine-dependent way

Brown adipose tissue converts energy from food into heat via the mitochondrial uncoupling protein UCP1, defending against cold. In some conditions, inducible 'brown-like' adipocytes, also known as beige adipocytes, can develop within white adipose tissue (WAT). These beige adipocytes have characteristics similar to classical brown adipocytes and thus can burn lipids to produce heat. In the current study, we demonstrated that curcumin (50 or 100 mg/kg/day) decreased bodyweight and fat mass without affecting food intake in mice. We further demonstrated that curcumin improves cold tolerance in mice. This effect was possibly mediated by the emergence of beige adipocytes and the increase of thermogenic gene expression and mitochondrial biogenesis in inguinal WAT. In addition, curcumin promotes β3AR gene expression in inguinal WAT and elevates the levels of plasma norepinephrine, a hormone that can induce WAT browning. Taken together, our data suggest that curcumin can potentially prevent obesity by inducing browning of inguinal WAT via the norepinephrine-β3AR pathway.

Abstract 122: Hyperinsulinmia Promotes Cardiac Dysfunction via Upregulation of Phosphodiesterase in Heart

Accumulating evidence suggests that hyperinsulinemia contributes to heart dysfunction. Here we show that insulin signaling is responsible for high fat diet (HFD) feeding-induced expression of phosphodiesterase 4D (PDE4D) in the myocardium of mice. The increased expression of PDE4D, in concert with reduced phosphorylation of phospholamban (PLB), promotes systolic and diastolic heart dysfunction. We revealed that insulin-mediated induction of PDE4D was dependent on β2AR-mediaed β-arrestin2-ERK pathway, which is transactivated in a GRK2-dependent fashion. Deletion of β2AR gene significantly attenuated insulin-induced phosphorylation of extracellular signal-regulated kinase (ERK) and Akt, as well as the upregulation of PDE4D expression, which prevented the heart dysfunction. β-arrestin2 KO mice did not display increased PDE4D expression and did not develop systolic or diastolic dysfunction following HFD. In brief, these data indicate that chronic hyperinsulinimia leads to heart dysfunction by increasing PDE4D expression via β2AR-GRK2-β-arrestin2 -ERK pathway, which suggests that β2AR signaling could be an attractive therapeutic target for preserving or improving cardiac function in subjects with insulin resistance.

β-2 Adrenergic receptor gene polymorphism and response to propranolol in cirrhosis.

To evaluate the association of β-2 adrenergic receptor (β2-AR) gene polymorphism with response of variceal pressure to propranolol in cirrhosis. Sixty-four non-related cirrhotic patients participated in this study and accepted variceal pressure measurement before and after propranolol administration. Polymorphism of the β2-AR gene was determined by directly sequencing of the polymerase chain reaction products from the DNA samples that were prepared from the patients. The prevalence of Gly16-Glu/Gln27 and Arg16-Gln27 homozygotes, and compound heterozygotes was 29.7%, 10.9%, and 59.4%, respectively. Patients with cirrhosis with Gly16-Glu/Gln27 homozygotes had a greater decrease of variceal pressure after propranolol administration than those with Arg16-Gln27 homozygotes or with compound heterozygotes (22.4% ± 2.1%, 13.1% ± 2.7% and 12.5% ± 3.1%, respectively, P < 0.01). The variceal pressure response to propranolol was associated with polymorphism of β2-AR gene. Patients with the Gly(16)-Glu/Gln(27) homozygotes probably benefit from propranolol therapy.