Effects of exenatide on circulating glucose, insulin, glucagon, cortisol and catecholamines in healthy volunteers during exercise

Conserved and convergent mechanisms underlying performance-life-history trade-offs

Phenotypic trade-offs are inevitable in nature, but the mechanisms driving them are poorly understood. Movement and oxygen are essential to all animals, and as such, the common ancestor to all living animals passed on mechanisms to acquire oxygen and contract muscle, sometimes at the expense of other activities or expression of traits. Nevertheless, convergent pathways have also evolved to deal with critical trade-offs that are necessary to survive ubiquitous environmental challenges. We discuss how whole-animal performance traits, such as locomotion, are important to fitness, yet costly, resulting in trade-offs with other aspects of the phenotype via specific conserved and convergent mechanistic pathways across all animals. Specifically, we discuss conserved pathways involved in muscle structure and signaling, insulin/insulin-like signaling, sirtuins, mitochondria and hypoxia-inducible factors, as well as convergent pathways involved in energy regulation, development, reproductive investment and energy storage. The details of these mechanisms are only known from a few model systems, and more comparative studies are needed. We make two main recommendations as a framework for future studies of animal form and function. First, studies of performance should consider the broader life-history context of the organism, and vice versa, as performance expression can require a large portion of acquired resources. Second, studies of life histories or mechanistic pathways that measure performance should do so in meaningful and standardized ways. Understanding proximate mechanisms of phenotypic trade-offs will not only better explain the phenotypes of the organisms we study, but also allow predictions about phenotypic variation at the evolutionary scale.

Effect of liraglutide on neural and peripheral markers of metabolic function during antipsychotic treatment in rats

BACKGROUND

Liraglutide is a glucagon-like peptide-1 (GLP-1) receptor agonist that prevents metabolic side effects of the antipsychotic drugs (APDs) olanzapine and clozapine through unknown mechanisms.

AIM

This study aimed to investigate the effect of chronic APD and liraglutide co-treatment on key neural and peripheral metabolic signals, and acute liraglutide co-treatment on clozapine-induced hyperglycaemia.

METHODS

In study 1, rats were administered olanzapine (2 mg/kg), clozapine (12 mg/kg), liraglutide (0.2 mg/kg), olanzapine + liraglutide co-treatment, clozapine + liraglutide co-treatment or vehicle for six weeks. Feeding efficiency was examined weekly. Examination of brain tissue (dorsal vagal complex (DVC) and mediobasal hypothalamus (MBH)), plasma metabolic hormones and peripheral (liver and kidney) cellular metabolism and oxidative stress was conducted. In study 2, rats were administered a single dose of clozapine (12 mg/kg), liraglutide (0.4 mg/kg), clozapine + liraglutide co-treatment or vehicle. Glucose tolerance and plasma hormone levels were assessed.

RESULTS

Liraglutide co-treatment prevented the time-dependent increase in feeding efficiency caused by olanzapine, which plateaued by six weeks. There was no effect of chronic treatment on melanocortinergic, GABAergic, glutamatergic or endocannabionoid markers in the MBH or DVC. Peripheral hormones and cellular metabolic markers were unaltered by chronic APD treatment. Acute liraglutide co-treatment was unable to prevent clozapine-induced hyperglycaemia, but it did alter catecholamine levels.

CONCLUSION

The unexpected lack of change to central and peripheral markers following chronic treatment, despite the presence of weight gain, may reflect adaptive mechanisms. Further studies examining alterations across different time points are required to continue to elucidate the mechanisms underlying the benefits of liraglutide on APD-induced metabolic side effects.

Identification and Functional Annotation of Genes Related to Horses' Performance: From GWAS to Post-GWAS

Simple Summary

It is assumed that the athletic performance of horses is influenced by a large number of genes; however, to date, not many genomic studies have been performed to identify candidate genes. In this study we performed a systematic review of genome-wide association studies followed by functional analyses aiming to identify the most candidate genes for horse performance. We were successful in identifying 669 candidate genes, from which we built biological process networks. Regulatory elements (transcription factors, TFs) of these genes were identified and used to build a gene–TF network. Genes and TFs presented in this study are suggested to play a role in the studied traits through biological processes related with exercise performance, for example, positive regulation of glucose metabolism, regulation of vascular endothelial growth factor production, skeletal system development, cellular response to fatty acids and cellular response to lipids. In general, this study may provide insights into the genetic architecture underlying horse performance in different breeds around the world.

Abstract

Integration of genomic data with gene network analysis can be a relevant strategy for unraveling genetic mechanisms. It can be used to explore shared biological processes between genes, as well as highlighting transcription factors (TFs) related to phenotypes of interest. Unlike other species, gene–TF network analyses have not yet been well applied to horse traits. We aimed to (1) identify candidate genes associated with horse performance via systematic review, and (2) build biological processes and gene–TF networks from the identified genes aiming to highlight the most candidate genes for horse performance. Our systematic review considered peer-reviewed articles using 20 combinations of keywords. Nine articles were selected and placed into groups for functional analysis via gene networks. A total of 669 candidate genes were identified. From that, gene networks of biological processes from each group were constructed, highlighting processes associated with horse performance (e.g., regulation of systemic arterial blood pressure by vasopressin and regulation of actin polymerization and depolymerization). Transcription factors associated with candidate genes were also identified. Based on their biological processes and evidence from the literature, we identified the main TFs related to horse performance traits, which allowed us to construct a gene–TF network highlighting TFs and the most candidate genes for horse performance.

Exendin-4 Exacerbates Burn-Induced Morbidity in Mice by Activation of the Sympathetic Nervous System

Background

Although glucagon-like peptide 1- (GLP-1-) based therapy of hyperglycemia in burn injury has shown great potential in clinical trials, its safety is seldom evaluated. We hypothesize that exendin-4, a GLP-1 analogue, might affect the immune response via the activation of the sympathetic nervous system in burn injury.

Methods

Male Balb/c mice were subjected to sham or thermal injury of 15% total body surface area. Exendin-4 on T cell function in vitro was examined in cultured splenocytes in the presence of β-adrenoceptor antagonist propranolol (1 nmol/L) or GLP-1R antagonist exendin (9-39) (1 μmol/L), whereas its in vivo effect was determined by i.p. injection of exendin-4 (2.4 nmol/kg) in mice. To further elucidate the sympathetic mechanism, propranolol (30 mg/kg) or vehicle was applied 30 min prior to injury.

Results

Although the exacerbated burn-induced mortality by exendin-4 was worsened by propranolol pretreatment, the inhibition of T cell proliferation by exendin-4 in vitro could be restored by propranolol instead of exendin (9-39). However, a Th2 switch by exendin-4 in vitro could only be reversed by exendin (9-39). Likewise, the inhibition of splenic T cell function and NFAT activity by exendin-4 in vivo was restored by propranolol. By contrast, the increased splenic NF-κB translocation by exendin-4 in vivo was potentiated by propranolol in sham mice but suppressed in burn mice. Accordingly, propranolol abrogated the heightened inflammatory response in the lung and the accelerated organ injuries by exendin-4 in burn mice. On the contrary, a Th2 switch and higher serum levels of inflammatory mediators by exendin-4 were potentiated by propranolol in burn mice. Lastly, exendin-4 raised serum stress hormones which could be remarkably augmented by propranolol.

Conclusions

Exendin-4 suppresses T cell function and promotes organ inflammation through the activation of the sympathetic nervous system, while elicits Th2 switch via GLP-1R in burn injury.

Can 24 weeks strength training reduce feelings of depression and increase neurotransmitter in elderly females?

BACKGROUND

Geriatric depression is common due to the high rate of chronic diseases suffered by the older population. There is a well-established effect of exercise on one's wellbeing, however, for the elderly females there is dearth in research addressing exercise and its effect on their neurotransmitters and depression score. Therefore, this study aimed to investigate the effects of 24 weeks of the Growing Stronger program on neurotransmitter and depression of older women.

METHODS

Twenty-one older women, aged between 67 and 81, participated in this study. The participants were randomly assigned into a strength exercise (n = 11) and control group (n = 10) (age 76.40 ± 3.27, height 152.77 ± 5.63 kg, Weight 52.35 ± 2.86Kg, BMI 22.50 ± 1.88). The strength exercise group (age 76.10 ± 3.85, height 151.14 ± 5.42 kg, Weight 54.74 ± 6.73Kg, BMI 23.96 ± 2.70) participated for 50-80 min a day three times per week for a total of 24 weeks. All participants had their height, weight, blood testing and depression score tested before and after the training program. Two-way ANOVA with effect sizes was used to identify differences between times in each group and the statistical significance was set at 0.05.

RESULTS

In neurotransmitter factor, serotonin, dopamine, epinephrine, and norepinephrine significantly decreased in the strength exercise group but not for the control group. Notably, one participant whose serotonin level was lower than normal range before the exercise program showed normal level in serotonin after the program. In depression factor, there were no significant differences for both the strength exercise group and control group.

CONCLUSION

The results suggest that the effect of strength exercise on neurotransmitter and depression score remain unclear, but highlight the need for future studies investigating the relationship between strength training and depression.

The autonomic nervous system and cardiac GLP-1 receptors control heart rate in mice

Objectives

Glucagon-like peptide-1 (GLP-1) is secreted from enteroendocrine cells and exerts a broad number of metabolic actions through activation of a single GLP-1 receptor (GLP-1R). The cardiovascular actions of GLP-1 have garnered increasing attention as GLP-1R agonists are used to treat human subjects with diabetes and obesity that may be at increased risk for development of heart disease. Here we studied mechanisms linking GLP-1R activation to control of heart rate (HR) in mice.

Methods

The actions of GLP-1R agonists were examined on the control of HR in wild type mice (WT) and in mice with cardiomyocyte-selective disruption of the GLP-1R (Glp1r^CM−/−). Complimentary studies examined the effects of GLP-1R agonists in mice co-administered propranolol or atropine. The direct effects of GLP-1R agonism on HR and ventricular developed pressure were examined in isolated perfused mouse hearts ex vivo, and atrial depolarization was quantified in mouse hearts following direct application of liraglutide to perfused atrial preparations ex vivo.

Results

Doses of liraglutide and lixisenatide that were equipotent for acute glucose control rapidly increased HR in WT and Glp1r^CM−/− mice in vivo. The actions of liraglutide to increase HR were more sustained relative to lixisenatide, and diminished in Glp1r^CM−/− mice. The acute chronotropic actions of GLP-1R agonists were attenuated by propranolol but not atropine. Neither native GLP-1 nor lixisenatide increased HR or developed pressure in perfused hearts ex vivo. Moreover, liraglutide had no direct effect on sinoatrial node firing rate in mouse atrial preparations ex vivo. Despite co-localization of HCN4 and GLP-1R in primate hearts, HCN4-directed Cre expression did not attenuate levels of Glp1r mRNA transcripts, but did reduce atrial Gcgr expression in the mouse heart.

Conclusions

GLP-1R agonists increase HR through multiple mechanisms, including regulation of autonomic nervous system function, and activation of the atrial GLP-1R. Surprisingly, the isolated atrial GLP-1R does not transduce a direct chronotropic effect following exposure to GLP-1R agonists in the intact heart, or isolated atrium, ex vivo. Hence, cardiac GLP-1R circuits controlling HR require neural inputs and do not function in a heart-autonomous manner.

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GLP-1 controls heart rate (HR) through the autonomic nervous system and the cardiac GLP-1R in mice.

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The acute induction of HR by GLP-1R agonists is sensitive to propranolol.

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GLP-1R agonists do not directly increase HR in isolated perfused mouse hearts ex vivo.

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The GLP-1R agonist liraglutide does not directly enhance sinoatrial activity ex vivo.

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GLP-1 does not increase heart rate in a heart autonomous manner.

GLP-1–Based Therapies Have No Microvascular Effects in Type 2 Diabetes Mellitus

Objective—

To assess the effects of glucagon-like peptide (GLP)-1–based therapies (ie, GLP-1 receptor agonists and dipeptidyl peptidase-4 inhibitors) on microvascular function in patients with type 2 diabetes mellitus.

Approach and Results—

We studied 57 patients with type 2 diabetes mellitus (mean±SD age: 62.8±6.9 years; body mass index: 31.8±4.1 kg/m 2 ; HbA 1c [glycated hemoglobin] 7.3±0.6%) in an acute and 12-week randomized, placebo-controlled, double-blind trial conducted at the Diabetes Center of the VU University Medical Center. In the acute study, the GLP-1 receptor agonist exenatide (therapeutic concentrations) or placebo (saline 0.9%) was administered intravenously. During the 12-week study, patients received the GLP-1 receptor agonist liraglutide (1.8 mg daily), the dipeptidyl peptidase-4 inhibitor sitagliptin (100 mg daily), or matching placebos. Capillary perfusion was assessed by nailfold skin capillary videomicroscopy and vasomotion by laser Doppler fluxmetry, in the fasting state and after a high-fat mixed meal. In neither study, treatment affected fasting or postprandial capillary perfusion compared with placebo ( P >0.05). In the fasting state, acute exenatide infusion increased neurogenic vasomotion domain power, while reducing myogenic domain power (both P <0.05). After the meal, exenatide increased endothelial domain power ( P <0.05). In the 12-week study, no effects on vasomotion were observed.

Conclusions—

Despite modest changes in vasomotion, suggestive of sympathetic nervous system activation and improved endothelial function, acute exenatide infusion does not affect skin capillary perfusion in type 2 diabetes mellitus. Twelve-week treatment with liraglutide or sitagliptin has no effect on capillary perfusion or vasomotion in these patients. Our data suggest that the effects of GLP-1–based therapies on glucose are not mediated through microvascular responses.

The Insulin:Glucagon Ratio and the Choice of Glucose-Lowering Drugs

The influence of alpha and beta cells, through glucagon and insulin, on energy metabolism is well known. The insulin:glucagon ratio (IGR) is a frequently discussed entity in the medical literature. However, in recent years, focus has shifted to other pathways and markers of health and disease. This communication revisits the insulin:glucagon bipolar axis and describes the significance of the IGR. It reviews the effects of various glucose-lowering drugs on this ratio, and hypothesizes that the ratio can be used to predict the appropriate choice of drugs for managing diabetes. Drugs which increase the IGR may be beneficial in insulinopenic conditions, while those which decrease IGR may be of help in the setting of hyperinsulinemia or insulin resistance.

Effect of the GLP-1 Receptor Agonist Lixisenatide on Counterregulatory Responses to Hypoglycemia in Subjects With Insulin-Treated Type 2 Diabetes

OBJECTIVE

Counterregulatory responses are critical to prevent hypoglycemia in subjects with type 2 diabetes. This is particularly important in insulin-treated patients. This study explored the effect of the glucagon-like peptide 1 receptor agonist lixisenatide on the hormonal counterregulatory responses to insulin-induced hypoglycemia when added to basal insulin therapy in subjects with type 2 diabetes.

RESEARCH DESIGN AND METHODS

The study was a single-center, double-blind, randomized, placebo-controlled crossover study involving 18 subjects with type 2 diabetes (11 males) with a mean age of 55 years, diabetes duration of 12 years, HbA1c level of 7.7%, fasting blood glucose (FBG) concentration of 9.7 mmol/L, and a BMI of 33 kg/m(2), who were treated with basal insulin (mean duration 7 years, daily dose 39 units/day) and metformin (mean daily dose 2.1 g). Subjects received treatment with lixisenatide or placebo for 6 weeks in random order, with a 4-week washout period in between. After 6 weeks of treatment, subjects underwent a two-step hyperinsulinemic hypoglycemic clamp at 3.5 and 2.8 mmol/L.

RESULTS

After 6 weeks of treatment, HbA1c and FBG levels were lower after lixisenatide therapy than after placebo therapy. At the hypoglycemic level of 3.5 mmol/L, glucagon and epinephrine levels were significantly lower during lixisenatide treatment than during placebo treatment, whereas at 2.8 mmol/L glucagon and epinephrine levels did not differ between the subjects. Cortisol, pancreatic polypeptide, and norepinephrine levels did not differ significantly between the treatments.

CONCLUSIONS

Glucagon and epinephrine levels are reduced by lixisenatide at a concentration of 3.5 mmol/L, but their counterregulatory responses to deep hypoglycemia at a concentration of 2.8 mmol/L are sustained during treatment with lixisenatide in combination with basal insulin.

GLP-1 Receptor Agonist Exenatide Increases Capillary Perfusion Independent of Nitric Oxide in Healthy Overweight Men

Objective—

The insulinotropic gut–derived hormone glucagon-like peptide-1 (GLP-1) increases capillary perfusion via a nitric oxide–dependent mechanism in rodents. This improves skeletal muscle glucose use and cardiac function. In humans, the effect of clinically used GLP-1 receptor agonists (GLP-1RAs) on capillary density is unknown. We aimed to assess the effects of the GLP-1RA exenatide on capillary density as well as the involvement of nitric oxide in humans.

Approach and Results—

We included 10 healthy overweight men (age, 20–27 years; body mass index, 26–31 kg/m 2 ). Measurements were performed during intravenous infusion of placebo (saline 0.9%), exenatide, and a combination of exenatide and the nonselective nitric oxide–synthase inhibitor l - N G -monomethyl arginine. Capillary videomicroscopy was performed, and baseline and postocclusive (peak) capillary densities were counted. Compared with placebo, exenatide increased baseline and peak capillary density by 20.1% and 8.3%, respectively (both P =0.016). Concomitant l - N G -monomethyl arginine infusion did not alter the effects of exenatide. Vasomotion was assessed using laser Doppler fluxmetry. Exenatide nonsignificantly reduced the neurogenic domain of vasomotion measurements ( R =−5.6%; P =0.092), which was strongly and inversely associated with capillary perfusion ( R =−0.928; P =0.036). Glucose levels were reduced during exenatide infusion, whereas levels of insulin were unchanged.

Conclusions—

Acute exenatide infusion increases capillary perfusion via nitric oxide–independent pathways in healthy overweight men, suggesting direct actions of this GLP-1RA on microvascular perfusion or interaction with vasoactive factors.

Basal insulin combined incretin mimetic therapy with glucagon-like protein 1 receptor agonists as an upcoming option in the treatment of type 2 diabetes: a practical guide to decision making

The combination of basal insulin and glucagon-like protein 1 receptor agonists (GLP-1 RAs) is a new intriguing therapeutic option for patients with type 2 diabetes. In our daily practice we abbreviate this therapeutic concept with the term BIT (basal insulin combined incretin mimetic therapy) in a certain analogy to BOT (basal insulin supported oral therapy). In most cases BIT is indeed an extension of BOT, if fasting, prandial or postprandial blood glucose values have not reached the target range. In our paper we discuss special features of combinations of short- or prandial-acting and long- or continuous-acting GLP-1 RAs like exenatide, lixisenatide and liraglutide with basal insulin in relation to different glycemic targets. Overall it seems appropriate to use a short-acting GLP-1 RA if, after the near normalization of fasting blood glucose with BOT, the prandial or postprandial values are elevated. A long-acting GLP-1 RA might well be given, if fasting blood glucose values are the problem. Based on pathophysiological findings, recent clinical studies and our experience with BIT and BOT as well as BOTplus we developed chart-supported algorithms for decision making, including features and conditions of patients. The development of these practical tools was guided by the need for a more individualized antidiabetic therapy and the availability of the new BIT principle.

Corticotropin-releasing hormone and the sympathoadrenal system are major mediators in the effects of peripherally administered exendin-4 on the hypothalamic-pituitary-adrenal axis of male rats

Glucagon-like peptide-1 (GLP-1) and the GLP-1 receptor agonist, exendin-4 (Ex-4), potently stimulate hypothalamic-pituitary-adrenal (HPA) axis activity after either central or peripheral administration. Because several GLP-1 derivative drugs, including synthetic Ex-4, are currently in use to treat patients with type II diabetes mellitus, the characterization of Ex-4 effects on the HPA axis is highly relevant. Herein, the roles of CRH and AVP on these effects were investigated by administering the antagonists astressin and d(CH2)5Tyr(Me)AVP, respectively. The role of the sympathoadrenal system (SAS) was explored in bilateral adrenal enucleated and guanethidine-treated rats, whereas primary pituitary cell cultures were used to study direct effects on the corticotropes. Astressin completely abrogated (P < .05) the effects of Ex-4 central administration on ACTH secretion but only slightly reduced (by 35%) the ACTH response to Ex-4 peripheral administration. Moreover, astressin significantly (P < .05) decreased the corticosterone response to centrally but not peripherally administered Ex-4, suggesting different mechanisms depending on the route of administration. Pretreatment with d(CH2)5Tyr(Me)AVP failed to diminish either the ACTH or corticosterone response to Ex-4 and no direct effect of Ex-4 or GLP-1 was observed on pituitary cell cultures. In contrast, a significant (P < .05) reduction in the corticosterone response elicited by Ex-4 peripheral administration was observed in enucleated and guanethidine-treated rats, indicating a role of the SAS in the glucocorticoid stimulatory effects of Ex-4. Our data demonstrate that the effects of Ex-4 on the HPA axis are partially mediated by CRH and the sympathoadrenal system, and stress the relevance of Ex-4 as a corticosterone secretagogue.

GLP-1-Based Strategies: A Physiological Analysis of Differential Mode of Action

DPP4 inhibitors and GLP-1 receptor agonists used in incretin-based strategies treat Type 2 diabetes with different modes of action. The pharmacological blood GLP-1R agonist concentration targets pancreatic and some extrapancreatic GLP-1R, whereas DPP4i favors the physiological activation of the gut-brain-periphery axis that could allow clinicians to adapt the management of Type 2 diabetes, according to the patient's pathophysiological characteristics.

Exercise improves cardiac autonomic function in obesity and diabetes

Physical activity is a key element in the prevention and management of obesity and diabetes. Regular physical activity efficiently supports diet-induced weight loss, improves glycemic control, and can prevent or delay type 2 diabetes diagnosis. Furthermore, physical activity positively affects lipid profile, blood pressure, reduces the rate of cardiovascular events and associated mortality, and restores the quality of life in type 2 diabetes. However, recent studies have documented that a high percentage of the cardiovascular benefits of exercise cannot be attributed solely to enhanced cardiovascular risk factor modulation. Obesity in concert with diabetes is characterized by sympathetic overactivity and the progressive loss of cardiac parasympathetic influx. These are manifested via different pathogenetic mechanisms, including hyperinsulinemia, visceral obesity, subclinical inflammation and increased thrombosis. Cardiac autonomic neuropathy is an underestimated risk factor for the increased cardiovascular morbidity and mortality associated with obesity and diabetes. The same is true for the role of physical exercise in the restoration of the heart cardioprotective autonomic modulation in these individuals. This review addresses the interplay of cardiac autonomic function in obesity and diabetes, and focuses on the importance of exercise in improving cardiac autonomic dysfunction.

Investigation of the haemodynamic effects of exenatide in healthy male subjects

AIMS

In clinical studies of glucagon-like peptide-1 (GLP-1) agonists used in the management of patients with type 2 diabetes, there is often a small accompanying fall in blood pressure. The mechanism underlying this effect is not known, although exenatide, a GLP-1 mimetic, has acute regional vasodilator properties in rats. We have therefore studied the haemodynamic effects of exenatide in healthy male volunteers.

METHODS

We compared the effects of a single 10 µg subcutaneous injection of exenatide with placebo in a double-blind, randomized, crossover study. For 2 h after dosing, haemodynamic measurements were made using a Finometer, venous occlusion plethysmography and Doppler ultrasound. The urine sodium : creatinine excretion ratio was determined.

RESULTS

At the end of the study when exenatide was compared with placebo, heart rate had risen by a mean of 8.2 (95% CI 4.2, 12.2, P < 0.01) beats min(-1) , cardiac output by a mean of 1.2 (95% CI 0.42, 20.3, P < 0.05) l min(-1) and total peripheral resistance had fallen by 120 (95% CI -8, -233, P < 0.05) dyn s cm(-5) .There were no differences in blood pressure. The urinary sodium : creatinine ratio was increased by mean 12.4 (95% CI 4.6, 20.2, P < 0.05) mmol mmol(-1) when exenatide was compared with placebo.

CONCLUSIONS

Exenatide has significant haemodynamic effects in healthy volunteers. The results of this study are consistent with exenatide having both vasodilator and natriuretic properties. The vascular changes may contribute to the hypotensive effect of exenatide when used chronically in patients with diabetes.

Exercise protects against myocardial ischemia-reperfusion injury via stimulation of β(3)-adrenergic receptors and increased nitric oxide signaling: role of nitrite and nitrosothiols

RATIONALE

Exercise training confers sustainable protection against ischemia-reperfusion injury in animal models and has been associated with improved survival following a heart attack in humans. It is still unclear how exercise protects the heart, but it is apparent that endothelial nitric oxide synthase (eNOS) and nitric oxide (NO) play a role.

OBJECTIVE

To determine the role of β(3)-adrenergic receptors (β(3)-ARs), eNOS activation, and NO metabolites (nitrite and nitrosothiols) in the sustained cardioprotective effects of exercise.

METHODS AND RESULTS

Here we show that voluntary exercise reduces myocardial injury in mice following a 4-week training period and that these protective effects can be sustained for at least 1 week following the cessation of the training. The sustained cardioprotective effects of exercise are mediated by alterations in the phosphorylation status of eNOS (increase in serine 1177 and decrease in threonine 495), leading to an increase in NO generation and storage of NO metabolites (nitrite and nitrosothiols) in the heart. Further evidence revealed that the alterations in eNOS phosphorylation status and NO generation were mediated by β(3)-AR stimulation and that in response to exercise a deficiency of β(3)-ARs leads to an exacerbation of myocardial infarction following ischemia-reperfusion injury.

CONCLUSIONS

Our findings clearly demonstrate that exercise protects the heart against myocardial ischemia-reperfusion injury by stimulation of β(3)-ARs and increased cardiac storage of nitric oxide metabolites (ie, nitrite and nitrosothiols).