Circulating adropin concentrations in pediatric obstructive sleep apnea: potential relevance to endothelial function

Hepatokines and their role in cardiohepatic interactions in heart failure

Heart failure is one of the leading causes of death and disease worldwide. It is a condition that affects multiple systems within the body. There is a large body of evidence supporting that the liver is a major organ involved in the pathogenesis of heart failure. Cardiac hepatopathy and cirrhotic cardiomyopathy are two conditions that are associated with poor clinical outcomes in patients with heart failure. Despite the extensive proposed explanations of the mechanisms entailing heart failure, there remains a gap in the role of proteins and metabolic regulators produced by hepatocytes and their effect on the development, progression, and prognosis of heart failure, including adverse cardiac remodeling, fibrosis, cardiac cachexia, and renal dysfunction associated with heart failure. The aim of this review is to identify the major hepatokines being studied (adropin, fetuin-A, fetuin-B, FGF-21, selenoprotein P and α1-microglobulin) as modulators of metabolic homeostasis and cardiac dysfunction in heart failure. Research suggests that these factors play a role in modulating oxidative stress, fibrosis, apoptosis, inflammatory responses, immune cell activation, mitochondrial dysfunction, and cellular migration. The exact role of each of these hepatokines is under on-going research and requires more investigations for future clinical use.

Role of the Unique Secreted Peptide Adropin in Various Physiological and Disease States

Adropin, a secreted peptide hormone identified in 2008, plays a significant role in regulating energy homeostasis, glucose metabolism, and lipid metabolism. Its expression is linked to dietary macronutrient intake and is influenced by metabolic syndrome, obesity, diabetes, and cardiovascular diseases. Emerging evidence suggests that adropin might be a biomarker for various conditions, including metabolic syndrome, coronary artery disease, and hypertensive disorders complicating pregnancy. In cerebrovascular diseases, adropin demonstrates protective effects by reducing blood-brain barrier permeability, brain edema, and infarct size while improving cognitive and sensorimotor functions in ischemic stroke models. The protective effects of adropin extend to preventing endothelial damage, promoting angiogenesis, and mitigating inflammation, making it a promising therapeutic target for cardiovascular and neurodegenerative diseases. This review provides a comprehensive overview of adropin's multifaceted roles in physiological and pathological conditions, as well as our recent work demonstrating adropin's role in subarachnoid hemorrhage-mediated neural injury and delayed cerebral infarction.

Epigenetics and aging: relevance for sleep medicine

PURPOSE OF REVIEW

Sleep disorders encompass a wide range of conditions with substantial individual variability. Epigenetics, the study of heritable changes beyond DNA sequence, offers a promising avenue for personalized medicine in this field.

RECENT FINDINGS

There is great potential of epigenetic markers for sleep disorder diagnosis and the development of epigenetic drugs for targeted treatment. Epigenetic age acceleration, a marker of biological aging, is linked to sleep disorders and comorbidities. Very importantly, this acceleration may be reversible with effective treatment.

SUMMARY

While the underlying mechanisms and assessment of clinical utility require further investigation, the potential of epigenetics in sleep medicine is recognized. Future research focused on closing knowledge gaps and clinical validation is crucial to translate these findings into practical applications, paving the way for more effective and personalized management of sleep disorders.

Impact of obstructive sleep apnea in cardiovascular risk in the pediatric population: A systematic review

While the association of obstructive sleep apnea (OSA) with an increased cardiovascular risk (CVR) in the adult population is well known, there is insufficient evidence to affirm something similar in the pediatric population. On the other hand, adenotonsillectomy has been shown to be an effective treatment. Our objective was to evaluate the association of sleep respiratory disorders in children with increased CVR and the impact of adenotonsillectomy in the literature. To this aim, a literature search was conducted, between 2002 to the present. After carrying out a systematic review, the following results were provided: thoracic echocardiography after surgery found improvements in terms of cardiac function and structure; blood pressure (BP) measurement, verified a tendency to higher BP values in the OSA pediatric population, which improved after surgery; different biomarkers of CVR, were increased in OSA patients and improved after treatment and finally; some studies found endothelial dysfunction in pediatric OSA, a measurement of vascular system function, was reversible with adenotonsillectomy. Increases in BP parameters, biological markers related to CVR and alterations in cardiac function structure, have been reported in pediatric patients with OSA. At least, some of these parameters would be reversible after adenotonsillectomy, reflecting a possible reduction in CVR.

Protective roles of adropin in neurological disease

Adropin is a highly conserved secreted peptide encoded by the Energy Homeostasis Associated gene (Enho). It is expressed in many tissues throughout the body, including the liver and brain, and plays a crucial role in maintaining lipid homeostasis and regulating insulin sensitivity. Adropin also participates in several other pathophysiological processes of multiple central nervous system (CNS) diseases. There is strong evidence of the protective effects of adropin in stroke, heart disease, aging, and other diseases. The peptide has been shown to reduce the risk of disease, attenuate histological alterations, and reduce cognitive decline associated with neurological disorders. Recent findings support its critical role in regulating endothelial cells and maintaining blood-brain barrier integrity through an endothelial nitric oxide synthase (eNOS)-dependent mechanism. Here we discuss current evidence of the protective effects of adropin in CNS diseases specifically involving the cerebrovasculature and highlight potential mechanisms through which the peptide exhibits these effects.

Expert Consensus Statement: Management of Pediatric Persistent Obstructive Sleep Apnea After Adenotonsillectomy

OBJECTIVE

To develop an expert consensus statement regarding persistent pediatric obstructive sleep apnea (OSA) focused on quality improvement and clarification of controversies. Persistent OSA was defined as OSA after adenotonsillectomy or OSA after tonsillectomy when adenoids are not enlarged.

METHODS

An expert panel of clinicians, nominated by stakeholder organizations, used the published consensus statement methodology from the American Academy of Otolaryngology-Head and Neck Surgery to develop statements for a target population of children aged 2-18 years. A medical librarian systematically searched the literature used as a basis for the clinical statements. A modified Delphi method was used to distill expert opinion and compose statements that met a standardized definition of consensus. Duplicate statements were combined prior to the final Delphi survey.

RESULTS

After 3 iterative Delphi surveys, 34 statements met the criteria for consensus, while 18 statements did not. The clinical statements were grouped into 7 categories: general, patient assessment, management of patients with obesity, medical management, drug-induced sleep endoscopy, surgical management, and postoperative care.

CONCLUSION

The panel reached a consensus for 34 statements related to the assessment, management and postoperative care of children with persistent OSA. These statements can be used to establish care algorithms, improve clinical care, and identify areas that would benefit from future research.

Adropin and MOTS-c as new peptides: Do levels change in neurodegenerative diseases and ischemic stroke?

BACKGROUND

Neurological diseases such as Alzheimer's disease and Parkinson's disease (AD, PD), acute ischemic stroke (AIS), and multiple sclerosis (MS) are thought to be deeply affected by changes in the pathophysiological processes of neurons. As new peptides, it was aimed to evaluate the level of adropin and MOTS-c (mitochondrial open reading frame of the 12S rRNA-c) and its possible relationship with NSE (neuron-specific enolase) and NF-L (neurofilament light chain) in terms of neuronal interaction.

METHODS

This study was conducted with 32 patients from each subgroup and group-appropriate controls. Disease identifiers and hemogram/biochemical parameters specific to the groups of participants were obtained. Additionally, plasma adropin, MOTS-c, NSE, and NF-L levels were evaluated by the ELISA method.

RESULTS

Plasma adropin levels were decreased in the AD group and decreased in MOTS-c, AIS, and AD groups compared to the control (p < 0.05). Similar values were found in the MS group compared to its control (p > 0.05). In correlation analysis of these markers with laboratory parameters, while platelet and cholesterol levels were negatively correlated with adropin levels; platelet, lymphocyte, and triglyceride levels were positively correlated with MOTS-c (p < 0.05).

CONCLUSION

This study provides new information about adropin may be potentially important markers in AD and MOTS-C in AIS and AD. Future studies are needed to examine the relationship between changes in metabolic profiles and these peptides.

Current Knowledge of Selected Cardiovascular Biomarkers in Pediatrics: Kidney Injury Molecule-1, Salusin-α and -β, Uromodulin, and Adropin

Cardiovascular diseases are the leading cause of morbidity and mortality in the modern world. Their common denominator is atherosclerosis, a process beginning in childhood. In pediatrics, the aim of preventive measures is to recognize children and adolescents at risk for accelerated atherosclerosis and possible premature cardiovascular events in adulthood. Several diagnostic procedures and biomarkers are available for cardiovascular risk assessment in adults. However, reliable markers in pediatrics are still insufficiently studied. In this contribution, we discuss five potential biomarkers of particular interest: kidney injury molecule-1, salusin-α and -β, uromodulin, and adropin. Studies regarding the pediatric population are scarce, but they support the evidence from studies in the adult population. These markers might entail both a prognostic and a therapeutic interest.

Role of Adropin in Cardiometabolic Disorders: From Pathophysiological Mechanisms to Therapeutic Target

Although a large amount of data supports the crucial role of endothelial dysfunction (ED) in cardiovascular diseases (CVDs), there is a large bench-to-bedside chasm between basic and clinical research of ED, limiting the implementation of these findings in everyday clinical settings. Hence, it is important to further investigate the pathophysiological mechanisms underlying ED and find modalities that will alleviate its clinical implementation. Adropin, a highly conserved peptide hormone secreted primarily by the liver, recently emerged as an important regulatory component of the vascular endothelium. Specifically, the vasoprotective role of adropin is achieved mainly by affecting endothelial NO synthesis. Thus, in this review, we aimed to summarize the current knowledge regarding the role of adropin in physiological processes and address the protective role of adropin in endothelium with consequent implications to CV pathologies. We focused on data regarding the role of adropin in the clinical setting, with concurrent implications to future clinical use of adropin. Studies suggest that plasma levels of adropin correlate with indices of ED in various pathologies and enhanced disease progression, implying that adropin may serve as a useful biomarker of ED in the upcoming future. On the other hand, despite notable results with respect to therapeutic potential of adropin in preliminary experiments, further well-designed studies are warranted in order to establish if adropin might be beneficial in this setting.

Investigation of blood leptin and adropin levels in patients with multiple sclerosis: A CONSORT-clinical study

BACKGROUND

The effects of adipokines have been investigated in multiple sclerosis (MS) in the literature. Results are uncertain, and subgroups like adropin have not been previously studied. We primarily aimed to determine leptin and adropin levels in MS and their potential use as a biomarker.

METHODS

This study was an experimental research. While 44 MS patients diagnosed according to McDonald criteria were included in the patient group, 40 people without MS diagnosis and risk factors took part in the control group. Demographic data, height, weight, body mass index, blood glucose, thyroid-stimulating hormone, alanine transaminase, aspartate transaminase, creatinine, low-density lipoprotein, leptin, adropin levels, presence of hypertension, diabetes mellitus, coronary artery disease were recorded. Expanded disability status scale and disease duration were also evaluated in the patient group. Our data were presented as mean ± standard deviations.

RESULTS

The mean blood leptin value of the patient group (6.12 ± 5.34 ng/mL) was significantly lower than the value of the control group (13.02 ± 8.25 ng/mL) (P < .001). The patient group had a mean adropin level of 504.12 ± 311.17 ng/mL, which was significantly lower than that of the control group (747.0 ± 309.42 ng/mL) (P < .001). Statistically insignificant differences were found between their body mass index, glucose, alanine transaminase, aspartate transaminase, thyroid-stimulating hormone, low-density lipoprotein levels (P > .001).

CONCLUSION

This is the first study that has evaluated adropin levels in patients with MS. The relationship between MS and leptin levels is still unclear. Therefore, our study might be helpful to elucidate MS pathogenesis and provide supportive criteria for diagnosis.

Association between adropin and coronary artery lesions in children with Kawasaki disease

Kawasaki disease (KD) is an acute systemic vasculitis in children. Coronary artery lesions (CALs) are the most serious complications in KD, but the pathogenesis is still unclear so far. Adropin, a new biopeptide, plays an important role in metabolism and cardiovascular function. The aim of this study was to explore the relationship between adropin and KD. 66 KD patients and 22 healthy controls (HCs) were included in the study. KD patients were divided into KD with coronary artery lesions (KD-CALs) group and KD without CALs (KD-NCALs) group. The levels of serum adropin were determined by enzyme-linked immunosorbent assay (ELISA). Compared with the HC group, adropin concentrations were significantly increased in the KD group (p < 0.05), and the KD-CAL group had higher levels of adropin than those in the KD-NCAL group (p < 0.05). Pct (Procalcitonin) and DD (D-dimer) were positively correlated with adropin in the KD group (p < 0.05). Moreover, adropin had positive correlations with CRP (C-reactive protein) and DD in the KD-NCAL group and positive correlations with Pct, PLR (platelet-to-lymphocyte ratio), and DD in the KD-CAL group (p < 0.05). The receiver operating characteristic (ROC) curve showed that the best threshold value of serum adropin level was more than 2.8 ng/mL, with 72.2% sensitivity and 71.4% specificity for predicting CALs in children with KD.Conclusion: Adropin might be involved in the pathogenesis of KD and CALs and can be used as an auxiliary diagnostic biomarker of KD. What is Known: • CALs in KD were mainly caused by inflammation, immune imbalance, and vascular endothelial dysfunction, and adropin is involved in metabolic diseases and cardiovascular diseases. What is New: • In this study, we have found the relationship between adropin and KD, and serum adropin level can be used as an auxiliary diagnostic biomarker to predict CALs in KD.

Serum adropin level is associated with endothelial dysfunction in patients with obstructive sleep apnea and hypopnea syndrome

OBJECTIVE

Adropin is a recently discovered peptide hormone that plays a vital role in metabolism and cardiovascular-cerebrovascular function. The purpose of this study is to investigate the role of circulating adropin levels in patients with obstructive sleep apnea-hypopnea syndrome (OSAHS) and further determine the relationship between serum adropin concentration and endothelial dysfunction in patients with OSAHS.

METHODS

Forty polysomnography-diagnosed patients with OSAHS and 21 age and sex-matched healthy controls were enrolled in the current study. Serum adropin level, endothelial function parameters including flow-mediated dilatation (FMD) of brachial artery, endothelin-1 (ET-1), and nitric oxide (NO) were measured in all participants.

RESULTS

Serum adropin levels were significantly lower in patients with OSAHS compared to the control subjects. FMD was lower and serum ET-1 levels were higher in patients with OSAHS compared to control subjects. No significant difference was seen in serum NO levels between the two groups. Multivariate linear regression analysis revealed that serum adropin level was positively associated with FMD and negatively correlated with AHI. Additionally, serum adropin levels were lower in patients with OSAHS who had endothelial dysfunction compared with those patients without endothelial dysfunction. The receiver operating characteristic (ROC) analysis showed that area under the curve (AUC) for serum adropin in predicting endothelial dysfunction status in patients with OSAHS was 0.815 (95% CI 0.680-0.951, p = 0.001). The cutoff value of serum adropin level was less than 235.0 pg/mL, which provided the sensitivity and specificity of 81% and 75%, respectively, for the detection of endothelial dysfunction in patients with OSAHS.

CONCLUSION

Lower circulating adropin levels are closely associated with endothelial dysfunction in patients with OSAHS. Circulating adropin level may serve as an early biomarker to predict the development of endothelial dysfunction before the emergence of clinical symptoms in patients with OSAHS.

The cardiovascular risk in paediatrics: the paradigm of the obstructive sleep apnoea syndrome

BACKGROUND

Obstructive sleep apnoea syndrome (OSAS) describes a spectrum of abnormal breathing patterns during sleep characterised by snoring, increased upper airway resistance and pharyngeal collapsibility, with alteration of normal oxygenation and ventilation. Intermittent desaturations during sleep have multi-organ implications. Adults with OSAS have an increased risk of developing a dysfunctional endothelium that is characterised by greater adherence of inflammatory mediators to endothelial cells and hypercoagulability. There is increasing evidence to show that risk factors for comorbid cardiovascular disease (CVD) can develop during childhood and adolescence and are likely to continue over time. Risk factors for CVD include both modifiable factors and factors that cannot be changed.

MATERIALS AND METHODS

Using the MEDLINE^® electronic database, we reviewed the scientific literature for published studies evaluating the association between sleep-disordered breathing and cardiovascular damage in children.

RESULTS

In this review, we show the role of blood markers in demonstrating the inflammation caused by intermitted oxygen desaturations during sleep in both healthy and obese children. Several instrumental techniques, in addition to serum biomarkers, can be used to assess vascular endothelial damage and its deterioration in the form of a pre-atherosclerotic condition. The confirmation of their role as markers of inflammation and vascular damage is supported by normalisation after resolution or improvement of the sleep-disordered breathing with surgery.

DISCUSSION

Great attention should be given to this condition in infants and children as it will significantly affect their present and future well-being as they grow into adulthood. Healthcare professionals, especially paediatricians, should be trained to recognise the signs and symptoms of the disease in order to send children forward for specialist care in centres dealing with sleep-disordered breathing.

Preoperative identification of children at high risk of obstructive sleep apnea

Obstructive sleep apnea is a common childhood disorder which can lead to serious health problems if left untreated. Enlarged adenoid and tonsils are the commonest causes, and adenotonsillectomy is the recommended first line of treatment. Obstructive sleep apnea poses as an anesthetic challenge, and it is a well-known risk factor for perioperative adverse events. The presence and severity of an obstructive sleep apnea diagnosis will influence anesthesia, pain management, and level of monitoring in recovery period. Preoperative obstructive sleep apnea assessment is necessary, and anesthetists are ideally placed to do so. Currently, there is no standardized approach to the best method of preoperative screening for obstructive sleep apnea. Focused history, clinical assessments, and knowledge regarding the strengths and limitations of available obstructive sleep apnea assessment tools will help recognize a child with obstructive sleep apnea in the preoperative setting.

Serum adropin as a predictive biomarker of erectile dysfunction in coronary artery disease patients

Introduction

Erectile dysfunction (ED) is associated with various comorbidities and an early diagnosis and treatment is necessary to avoid the development of these comorbidities. Unfortunately, there is no biochemical marker that can be used for early diagnosis of ED. Nitric oxide (NO) is released by nerve and endothelial cells in the corpora cavernosa of the penis and is believed to be the main vasoactive chemical mediator of penile erection. Adropin is a regulatory peptide which has effects on NO bioavailability and energy homeostasis. We hypothesized that adropin may contribute to the pathogenesis of ED because of the presence of both metabolic effects and the influence on NO bioavailability. To confirm this hypothesis, we investigated the relationship between ED and serum adropin and NO levels.

Material and methods

Seventy-five ED patients were enrolled for this study and the patients were divided into two groups according to angiographic scoring. Serum NO and adropin levels were measured by the Griess reaction and ELISA method, respectively.

Results

Serum adropin and NO levels were found to be lower in the group which has higher angiographic score and the difference in NO was statistically significant. Also, adropin has a significant correlation between IIEF scores in ED patients.

Conclusions

This is the first study in the literature investigating the levels of adropin in ED patients having coronary artery disease. The adropin molecule shows a promising future in clarifying the etiopathogenesis of ED. More comprehensive and multicenter studies are needed to reveal the role of adropin in ED and the effects of treatment on this molecule.

Negative association between serum adropin and hypertensive disorders complicating pregnancy

Objective: Study the association of adropin and hypertensive disorders complicating pregnancy (HDCP). Methods: Patients with HDCP were matched with normotensive women (47 pairs). Adropin concentrations were detected by enzyme-linked immunosorbent assay. Results: Compared with the controls, the serum adropin levels were lower in the HDCP group (P < 0.001) and in HDCP subgroups (gestational hypertension, mild preeclampisa, and severe preeclampsia, term, preterm, early onset, and late onset) (all P < 0.05). After adjustment for confounders, adropin remained negatively associated with HDCP (P = 0.027). Conclusion: Lower adropin concentration is significantly associated with HDCP, suggesting that higher or normal adropin levels may be protective against HDCP.

Related biomarkers of neurocognitive impairment in children with obstructive sleep apnea

OBJECTIVES

Different experiment approaches have demonstrated that children with obstructive sleep apnea (OSA) exhibit neurocognitive and behavioral deficits. This review summarized the potential biomarkers of OSA-associated neurocognitive impairment in children.

METHODS

A scoping review of studies on children with OSA that evaluated the potential value of different markers in identifying neurocognitive impairment was undertaken. Additionally, the biomarkers were categorized according to the different research methods, including brain imaging studies, serological indicators and urine markers.

RESULTS

Majority of the studies that evaluated blood biomarkers, plasma insulin growth factor-1 (IGF-1) and Alzheimer's disease (AD)-related biomarkers appeared to exhibit a favorable profile, and could discriminate between OSA children with or without neurocognitive impairments. Brain imaging studies and urinary neurotransmitters could also be helpful for screening OSA cognitive morbidity in children.

CONCLUSION

Due to limited research methods available in children, the cognitive susceptibility of children with OSA has been rarely studied. The main reason for this may be the limited research methods in children. Numerous study populations of children and complex psychological tests are required, which involve major labor and costs.Multi-center prospective studies are needed to identify suitable biomarkers for the timely prediction and effective intervention to prevent neurocognitive impairment in children with OSA and to explore further opportunities in this arena.

Polysomnographic correlates of endothelial function in children with obstructive sleep apnea

OBJECTIVES

To evaluate endothelial function in a large cohort of children clinically referred for suspected obstructive sleep apnea syndrome (OSAS), and to identify risk factors contributing to the presence of endothelial dysfunction (ED).

METHODS

Habitually snoring children (age range, 3-11 years) were recruited. All participants underwent overnight polysomnography (PSG). Endothelial function test used peripheral arterial tonometry (PAT) to derive the reactive hyperemia index (RHI). Subjects were then divided into mild OSA, moderate-severe OSA and primary snorers (PS), according to their obstructive apnea-hypopnea index (OAHI).

RESULTS

A total of 355 subjects were recruited. There were no differences in age, gender, or BMI z score among the three groups. Both mild and moderate-severe OSA groups had lower RHI than PS (P < 0.001, P = 0.001, respectively). Linear regression analysis revealed that RHI was positively correlated with age (r = 0.17, P = 0.002), BMI z score (r = 0.14, P = 0.008) and oxygen saturation nadir (r = 0.15, P = 0.006), but negatively correlated with oxygen desaturation index (ODI_3%; r = -0.19, P = 0.001) and respiratory-related arousal index (ArI-resp) (r = -0.24, P < 0.001). In stepwise regression analysis, age, BMI z score, and ArI-resp were independently associated with endothelial function (r = 0.34, P < 0.001).

CONCLUSION

Children with OSA are at increased risk for abnormal endothelial function than habitually snoring children. Furthermore, in addition to age and BMI, which are well-established factors affecting endothelial function, both intermittent hypoxia and sleep fragmentation during sleep also emerge as candidate risk factors contributing to endothelial dysfunction in snoring children.

CLINICAL TRIAL

Follow up of PS and OSAHS in Chinese children, https://clinicaltrials.gov/, Clinical number: NCT02447614.

Adropin and Inflammation Biomarker Levels in Male Patients With Obstructive Sleep Apnea: A Link With Glucose Metabolism and Sleep Parameters

STUDY OBJECTIVES

The main objectives of the study were to determine plasma adropin, systemic inflammation biomarker levels, and glucose metabolism parameters in patients with moderate and severe obstructive sleep apnea (OSA) compared to healthy controls.

METHODS

In this study, we included 50 male patients with OSA (25 moderate and 25 severe) and 25 age- and sex-matched control subjects. All subjects underwent fasting sampling of peripheral blood for laboratory analyses.

RESULTS

Adropin plasma levels were significantly lower in the severe OSA group in comparison with the moderate and control groups (4.50 ± 1.45 versus 6.55 ± 1.68 versus 8.15 ± 1.79 ng/mL, P < .001). Plasma biomarkers of systemic inflammation were significantly increased in patients with moderate OSA (interleukin [IL]-6 and tumor necrosis factor alpha [TNF-α]) and severe OSA (IL-6, TNF-α, high-sensitivity C-reactive protein) when compared with controls (P < .001). Adropin levels showed a significant negative correlation with IL-6 (r = -.419, P < .001), TNF-α (r = -.540, P < .001), fasting glucose (r = -.331, P = .004), hemoglobin A1c (r = -.438, P < .001), homeostatic model assessment insulin resistance index (r = -.213, P = .046), and polysomnographic parameters including apnea-hypopnea index (r = -.615, P < .001) and oxygen desaturation index (r = -.573, P < .001). A multivariate regression analysis showed that plasma adropin remained as a significant negative predictor of severe OSA status, when adjusted for age and body mass index and computed along with other inflammatory biomarkers in the regression model (odds ratio 0.069, 95% confidence interval 0.009-0.517, P = .009).

CONCLUSIONS

Plasma adropin concentrations significantly correlate with indices of disease severity in patients with OSA, suggesting that adropin potentially plays an important role in the complex pathophysiology of the disease.

Adropin: An endocrine link between the biological clock and cholesterol homeostasis

Objective

Identify determinants of plasma adropin concentrations, a secreted peptide translated from the Energy Homeostasis Associated (ENHO) gene linked to metabolic control and vascular function.

Methods

Associations between plasma adropin concentrations, demographics (sex, age, BMI) and circulating biomarkers of lipid and glucose metabolism were assessed in plasma obtained after an overnight fast in humans. The regulation of adropin expression was then assessed in silico, in cultured human cells, and in animal models.

Results

In humans, plasma adropin concentrations are inversely related to atherogenic LDL-cholesterol (LDL-C) levels in men (n = 349), but not in women (n = 401). Analysis of hepatic Enho expression in male mice suggests control by the biological clock. Expression is rhythmic, peaking during maximal food consumption in the dark correlating with transcriptional activation by RORα/γ. The nadir in the light phase coincides with the rest phase and repression by Rev-erb. Plasma adropin concentrations in nonhuman primates (rhesus monkeys) also exhibit peaks coinciding with feeding times (07:00 h, 15:00 h). The ROR inverse agonists SR1001 and the 7-oxygenated sterols 7-β-hydroxysterol and 7-ketocholesterol, or the Rev-erb agonist SR9009, suppress ENHO expression in cultured human HepG2 cells. Consumption of high-cholesterol diets suppress expression of the adropin transcript in mouse liver. However, adropin over expression does not prevent hypercholesterolemia resulting from a high cholesterol diet and/or LDL receptor mutations.

Conclusions

In humans, associations between plasma adropin concentrations and LDL-C suggest a link with hepatic lipid metabolism. Mouse studies suggest that the relationship between adropin and cholesterol metabolism is unidirectional, and predominantly involves suppression of adropin expression by cholesterol and 7-oxygenated sterols. Sensing of fatty acids, cholesterol and oxysterols by the RORα/γ ligand-binding domain suggests a plausible functional link between adropin expression and cellular lipid metabolism. Furthermore, the nuclear receptors RORα/γ and Rev-erb may couple adropin synthesis with circadian rhythms in carbohydrate and lipid metabolism.

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In male humans, plasma adropin concentrations are inversely related to low-density circulating cholesterol (LDL-C) levels.

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Adropin expression is regulated by core elements of the biological clock (RORA/G, Rev-Erb).

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Sterol-sensing by the ROR ligand-binding domain provides a plausible link between adropin expression and lipid metabolism.

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In mouse liver, adropin expression is rhythmic and suppressed by exogenous (dietary) cholesterol.

Aerobic exercise improves endothelial function and serum adropin levels in obese adolescents independent of body weight loss

Adropin is a secreted protein that regulates endothelial function. However, adropin levels in obese adolescent patients are currently uncertain. Therefore, we evaluated the association between plasma adropin levels and vascular endothelial function and investigated the effect of aerobic exercise in obese adolescents. A total of 45 obese adolescents and 20 controls (age 16-19 years) were included in our study. The obese adolescents received 12 weeks of aerobic exercise training. Serum adropin was detected using enzyme-linked immunosorbent assay. Vascular reactive hyperemia indexes (RHIs) were obtained using Endo-PAT2000. Adropin levels and RHI were significantly lower in obese adolescents than in normal-weight adolescents. Adropin levels and RHI increased significantly independently of changes in body weight after an exercise intervention (P < 0.01). Pearson correlation analysis revealed that adropin levels positively correlated with HDL-C levels (r = 0.389, P < 0.01) and RHI (r = 0.32, P < 0.01). Multiple linear stepwise regression analysis showed that the insulin resistance index (t = -3.301, P < 0.01) and HDL-C level (t = 2.620, P = 0.011) were independent risk factors of adropin levels. In addition, Δadropin (t = 3.261, P < 0.01) was an independent influencing factor of ΔRHI. Our findings suggest that adropin plays an important role in vascular endothelial function in obese adolescents.

The relationship between maternal and umbilical cord adropin levels with the presence and severity of preeclampsia

AIM

To investigate both maternal and umbilical cord adropin levels in patients with preeclampsia and the possible relations with its severity and perinatal outcomes.

MATERIALS AND METHODS

In this study, a total of 38 preeclamptic and 40 age-matched healthy pregnant women between January and June 2016 were included. Serum and cord adropin levels were measured using an enzyme-linked immunosorbent assay (ELISA).

RESULTS

The maternal and umbilical cord adropin levels were significantly lower in the preeclamptic group compared to controls [71.19±22.21 vs. 100.76±27.02 ng/L and 92.39 (59.77:129.89) vs. 106.20 (74.42:208.02) ng/L, P<0.001, respectively]. While maternal adropin levels were significantly lower in the severe preeclampsia group as compared to the mild preeclamptic group [66.45 (21.49:98.02) vs. 76.17 (58.06:109.58), P=0.007], umbilical cord adropin levels did not differ between each group [91.32 (59.77:113.34) vs. 92.87 (63.12:129.89), P=0.750]. Maternal adropin level was negatively correlated with systolic and diastolic blood pressures (r=-0.60, P<0.001 and r=-0.58, P<0.001, respectively) and positively correlated with platelet count (r=0.27, P=0.016). Moreover, umbilical cord adropin levels were weakly correlated with gestational age at delivery (r=0.28, P=0.012) and birth weight (r=0.28, P=0.014).

CONCLUSION

The present study is the first to demonstrate a significant association between maternal and umbilical adropin levels and the presence and severity of preeclampsia. Adropin might be a useful parameter for predicting the presence and severity of preeclampsia.

Longitudinal Cardiovascular Outcomes of Sleep Disordered Breathing in Children: A Meta-Analysis and Systematic Review

Objectives

The presence of sleep disordered breathing (SDB) is known to impact long-term cardiovascular morbidity in adults; however, the long-term effects in children are poorly understood. We aimed to systematically review and synthesize studies published to date on the long-term effects of SDB in children.

Study Design

Meta-analysis and systematic review using PubMed, CINAHL, Embase, and Scopus (all indexed years).

Methods

We searched for English-language articles containing original human data from prospective studies, with ≥7 participants, in children ≤18 years of age. Data regarding study design, demographics, clinical characteristics, outcomes, level of evidence, and risk of bias were obtained. Articles were independently reviewed by three investigators. Retrospective and cross-sectional studies were excluded.

Results

Of 1701 identified abstracts, 25 articles (combined n = 1418) were ultimately included. All studies reported longitudinal outcomes following treatment of SDB, 21 studies exclusively reporting outcomes after adenotonsillectomy. Therefore, studies were combined to objectively assess the effect of SDB treatment on cardiovascular outcomes. Although all cardiovascular parameters were within the normal range at baseline, at follow-up there was a significant decrease in mean pulmonary artery pressure, right ventricular end diastolic diameter, heart rate, mitral Em/Am ratio, and C-reactive protein. There was no significant change in interventricular septum thickness, left ventricular parameters (shortening fraction, systolic and end diastolic diameters, ejection fraction, posterior wall thickness, isovolumetric relaxation time), left atrial diameter, and aortic and pulmonary valve peak velocities.

Conclusions

Studies assessing the long-term cardiovascular effects of SDB in children are limited. The available literature indicates effects on autonomic function, right, and left heart function following treatment for SDB. However, well-designed, large-scale, prospective cohort studies (using standardized outcomes) are needed to better understand the relationship of cardiovascular morbidity in the context of pediatric SDB.

Adropin- A Novel Biomarker of Heart Disease: A Systematic Review Article

BACKGROUND

Heart disease is one of the most common chronic disease and leading cause of morbidity and mortality worldwide. Adropin, a newly identified protein, is important for energy homeostasis and maintaining insulin sensitivity, and has been referred to as a novel regulator of endothelial cells. Endothelial dysfunction is a key early event in atherogenesis and onset of HD. Therefore, this review gives a systematic overview of studies investigating plasma adropin level in patient with heart disease.

METHODS

Data carried out in PubMed, Scopus, Web of Science, Embase, Google scholar and MEDLINE, from the earliest available online indexing year through 2015. The search restricted to studies conducted in humans. The keyword search was adropin to apply in title, abstract and keywords. References lists of all original published articles were scanned to find additional eligible studies.

RESULTS

Heart failure (HF), coronary atherosclerosis acute myocardial infarction and Cardiac Syndrome X (CSX) were type of heart disease acknowledged in this study. Majority of evidences introduced low adropin as an independent risk factor of heart disease. In a case-control study, the plasma level of adropin increased with the severity of HF.

CONCLUSION

Adropinmay be a potential serum biomarker for early diagnosis of HD.

Pediatric OSA Syndrome Morbidity Biomarkers: The Hunt Is Finally On!

Since initial reports 40 years ago on pediatric OSA syndrome (OSAS) as a distinct and prevalent clinical entity, substantial advances have occurred in the delineation of diagnostic and treatment approaches. However, despite emerging and compelling evidence that OSAS increases the risk for cognitive, cardiovascular, and metabolic end-organ morbidities, routine assessment of such morbidities is seldom conducted in clinical practice. One of the major reasons for such discrepancies resides in the relatively labor-intensive and onerous steps that would be required to detect the presence of any of such morbidities, further adding to the already elevated cost of diagnosing the disorder. To circumvent these obstacles, the search for biomarker signatures of pediatric OSA and its cognitive and cardiometabolic consequences was launched, and considerable progress has occurred since then. Here, we review the current evidence for the presence of morbidity-related biomarkers among children with OSAS, and explore future opportunities in this promising arena.

Association between serum adropin level and burden of coronary artery disease in patients with non-ST elevation myocardial infarction

Objective:

Previous studies revealed the relationship between stable coronary artery disease (CAD) and serum adropin level, but this relationship has not been investigated in patients with non-ST segment elevation myocardial infarction (NSTEMI). The present study is an analysis of the relationship between adropin and severity of CAD assessed based on SYNTAX score in patients with NSTEMI.

Methods:

A total of 109 participants, 80 patients with NSTEMI and 29 healthy individuals, were prospectively enrolled in the study. Patients with NSTEMI were divided to 2 groups: high SYNTAX score (≥32) (35 patients) and low SYNTAX score (<32) (45 patients). Adropin level was measured from blood serum samples using enzyme-linked immunosorbent assay test.

Results:

Patients with NSTEMI and high SYNTAX score had significantly lower serum adropin level (2357.30 pg/mL±821.58) compared to NSTEMI patients with low SYNTAX score (3077.00 pg/mL±912.86) and control group (3688.00±956.65). Adropin cut-off value for predicting high SYNTAX score on receiver-operating characteristic curve analysis was determined to be 2759 pg/mL, with a sensitivity of 63% and a specificity of 57%. Adropin was an independent predictor for high SYNTAX score (odds ratio=0.999; 95% confidence interval: 0.998–1.000; p=0.007).

Conclusion:

Adropin could be an alternative blood sample value for predicting severity of CAD.

Inverse association between carbohydrate consumption and plasma adropin concentrations in humans

OBJECTIVE

The role of metabolic condition and diet in regulating circulating levels of adropin, a peptide hormone linked to cardiometabolic control, is not well understood. In this study, weight loss and diet effects on plasma adropin concentrations were examined.

METHODS

This report includes data from (1) a weight loss trial, (2) an evaluation of acute exercise effects on mixed-meal (60% kcal from carbohydrates) tolerance test responses, and (3) a meta-analysis to determine normal fasting adropin concentrations.

RESULTS

Distribution of plasma adropin concentrations exhibited positive skew and kurtosis. The effect of weight loss on plasma adropin concentrations was dependent on baseline plasma adropin concentrations, with an inverse association between baseline and a decline in concentrations after weight loss (Spearman's ρ = -0.575; P < 0.001). When ranked by baseline plasma adropin concentrations, only values in the upper quartile declined with weight loss. Plasma adropin concentrations under the main area of the bell curve correlated negatively with habitual carbohydrate intake and plasma lipids. There was a negative correlation between baseline values and a transient decline in plasma adropin during the mixed-meal tolerance test.

CONCLUSIONS

Plasma adropin concentrations in humans are sensitive to dietary macronutrients, perhaps due to habitual consumption of carbohydrate-rich diets suppressing circulating levels. Very high adropin levels may indicate cardiometabolic conditions sensitive to weight loss.

Adropin reduces paracellular permeability of rat brain endothelial cells exposed to ischemia-like conditions

Adropin is a peptide encoded by the energy homeostasis associated gene (Enho) and plays a critical role in the regulation of lipid metabolism, insulin sensitivity, and endothelial function. Little is known of the effects of adropin in the brain and whether this peptide modulates ischemia-induced blood-brain barrier (BBB) injury. Here, we used an in vitro BBB model of rat brain microvascular endothelial cells (RBE4) and hypothesized that adropin would reduce endothelial permeability during ischemic conditions. To mimic ischemic conditions in vitro, RBE4 cell monolayers were subjected to 16h hypoxia/low glucose (HLG). This resulted in a significant increase in paracellular permeability to FITC-labeled dextran (40kDa), a dramatic upregulation of vascular endothelial growth factor (VEGF), and the loss of junction proteins occludin and VE-cadherin. Notably, HLG also significantly decreased Enho expression and adropin levels. Treatment of RBE4 cells with synthetic adropin (1, 10 and 100ng/ml) concentration-dependently reduced endothelial permeability after HLG, but this was not mediated through protection to junction proteins or through reduced levels of VEGF. We found that HLG dramatically increased myosin light chain 2 (MLC2) phosphorylation in RBE4 cells, which was significantly reduced by adropin treatment. We also found that HLG significantly increased Rho-associated kinase (ROCK) activity, a critical upstream effector of MLC2 phosphorylation, and that adropin treatment attenuated that effect. These data indicate that treatment with adropin reduces endothelial cell permeability after HLG insult by inhibition of the ROCK-MLC2 signaling pathway. These promising findings suggest that adropin protects against endothelial barrier dysfunction during ischemic conditions.

Potential Roles of Adropin in Central Nervous System: Review of Current Literature

Adropin is a 4.9 kDa peptide that is important for maintenance of metabolic and non-metabolic homeostasis. It regulates glucose and fatty acid metabolism and is involved in endothelial cell function and endothelial nitric oxide (NO) synthase bioactivity as well as physical activity and motor coordination. Adropin is expressed in many tissues and organs including central nervous system (CNS). This peptide plays a crucial role in the development of various CNS disorders such as stroke, schizophrenia, bipolar disorder as well as Alzheimer's, Parkinson's, and Huntington's diseases. In this comprehensive review, the potential roles of adropin in cellular signaling pathways that lead to pathogenesis and/or treatment of CNS disorders will be discussed.

An update on cardiovascular effects of obstructive sleep apnoea syndrome

Obstructive sleep apnoea syndrome is an important health problem which may cause or worsen systemic diseases. Chronic intermittent hypoxia during repetitive airflow cessations may cause endothelial dysfunction. Sleep apnoea is also shown to be associated with hypercoagulability which may be due to decreased nitric oxide levels and impaired vasodilatation. Endothelial dysfunction, increased systemic inflammation, sympathetic nervous system activation, increased oxidative stress and dysglycaemia may all contribute to cardiovascular processes such as hypertension, arrhythmia, stroke, heart failure and coronary artery disease in patients with obstructive sleep apnoea. Treatment approaches in patients with obstructive sleep apnoea mainly focus on maintaining upper airway patency either with positive airway pressure devices or upper airway appliances. Strategies involving positive airway pressure therapy are associated with decreased morbidity and mortality. Obstructive sleep apnoea should be suspected as an underlying mechanism in patients with cardiovascular disease and warrants appropriate treatment.

Serum vascular endothelial growth factor receptor-2 and adropin levels in age-related macular degeneration

AIM

To investigate the serum levels of vascular endothelial growth factor receptor-2 (VEGFR-2) and adropin in age-related macular degeneration (AMD) patients.

METHODS

Ninety-eight AMD patients were included in the study. Seventy-eight age- and sex-matched healthy volunteers were recruited as the control group. Fundus florescein angiography and optical coherence tomography were performed to assess the posterior segment details. Serum VEGFR-2 and adropin levels were measured using enzyme-linked immunosorbent assays and compared between the study groups.

RESULTS

AMD group had significantly increased foveal retinal thickness, serum LDL and HDL levels and significantly decreased subfoveal choroidal thickness (P =0.01, 0.047, 0.025 and <0.001, respectively). Serum VEGFR-2 level revealed a significant decrease in AMD patients compared to controls (26.48±6.44 vs 30.42±7.92 ng/mL, P<0.001). There was an insignificant increase in serum adropin level in AMD patients (6.17±3.19 vs 5.79±2.71 ng/mL, P=0.4). Serum level of VEGFR-2 in AMD patients had a significant negative correlation with foveal retinal thickness (r=-0.226, P=0.025) and a significant positive correlation with subfoveal choroidal thickness (r=0.2, P=0.048).

CONCLUSION

The current study demonstrated that the decreased serum VEGFR-2 level may be considered in the development of AMD. Adropin does not seem to play a role in the pathogenesis of AMD.

Serum adropin level and ENHO gene expression in systemic sclerosis

Adropin, a secreted protein, is encoded by the energy homeostasis associated (ENHO) gene. It has been implicated in the several physiological and pathological processes such as angiogenesis and apoptosis. Therefore, the aim of present study was to investigate serum adropin levels and ENHO gene expressions in systemic sclerosis (SSc) characterized by vasculopathy, inflammation, and progressive fibrosis of the skin and internal organs. The study includes 27 patients with SSc, 39 patients with Behçet's disease (BD), and 20 healthy controls (HC). Serum adropin levels and ENHO gene expressions by peripheral blood mononuclear cells were analyzed by ELISA method and by real-time PCR, respectively. The serum adropin levels were higher in the SSc and BD groups than in the HC group (p = 0.023 and p < 0.001, respectively). However, there were no significant differences among the groups in terms of ENHO gene expressions (p ANOVA = 0.149). There was no significant difference between the limited and diffuse cutaneous subtypes of SSc in terms of serum adropin level and ENHO gene expression. Moreover, serum adropin level and ENHO gene expression were not associated with the disease activity and severity indexes. ENHO gene expression was correlated with the triglyceride levels in the BD group (r = -0.426, p = 0.027). The augmented serum adropin levels may be expected in the chronic inflammatory disease and seem not to be characteristic of only SSc. However, further studies are needed to explain the precise role of adropin in SSc.

Adropin acts in brain to inhibit water drinking: potential interaction with the orphan G protein-coupled receptor, GPR19

Adropin, a recently described peptide hormone produced in the brain and liver, has been reported to have physiologically relevant actions on glucose homeostasis and lipogenesis, and to exert significant effect on endothelial function. We describe a central nervous system action of adropin to inhibit water drinking and identify a potential adropin receptor, the orphan G protein-coupled receptor, GPR19. Reduction in GPR19 mRNA levels in medial basal hypothalamus of male rats resulted in the loss of the inhibitory effect of adropin on water deprivation-induced thirst. The identification of a novel brain action of adropin and a candidate receptor for the peptide should extend and accelerate the study of the potential therapeutic value of adropin or its mimetics for the treatment of metabolic disorders.

Molecular cloning, characterization and expression of the energy homeostasis-associated gene in piglet

The energy homeostasis-associated (Enho) gene encodes a secreted protein, adropin, which regulates the expression of hepatic lipogenic genes and adipose tissue peroxisome proliferator-activated receptor γ, a major regulator of lipogenesis. In the present study, the porcine (Sus scrofa) homologue of the Enho gene, which was named pEnho, was amplified by reverse transcriptase polymerase chain reaction (RT-PCR) using oligonucleotide primers derived from in silico sequences. The gene sequence was submitted into the GenBank of NCBI, and the access number is GQ414763. The pEnho encodes a protein of 76 amino acids which shows 75% similarity to Homo sapiens adropin. The expression profile of pEnho in tissues (liver, muscle, anterior jejunum, posterior jejunum, and ileum) was determined by quantitative real-time RT-PCR. pEnho was localized on porcine chromosome 10 and no introns were found. In conclusion, pEnho was cloned and analysed with the aim of increasing knowledge about glucose and lipid metabolism in piglets and helping to promote the health and growth of piglets through adropin regulation.

Tumor circulating DNA profiling in xenografted mice exposed to intermittent hypoxia

Intermittent hypoxia (IH) a hallmark characteristic of obstructive sleep apnea (OSA), is proposed as a major determinant of processes involving tumor growth, invasion and metastasis. To examine whether circulating DNA (cirDNA) in blood plasma reflects changes in tumor cells under IH conditions, we used a xenografted murine model. Mice engrafted with TC1 epithelial lung cancer cells and controls were exposed to IH or room air (RA) conditions. Plasma cirDNA amounts were significantly increased in mice exposed to IH (p<0.05). Significant associations between plasma cirDNA concentrations and tumor size, weight and invasiveness also emerged (p<0.05). Using a methylation microarray-based approach, we identified 2,094 regions showing significant differential cirDNA modifications. Systems biology analyses revealed an association with molecular pathways deregulated in cancer progression and with distal and TSS-associated transcription factor binding sites. We detected clusters of highly variable regions in chromosomes 7, 13, 14 and X, which may highlight hotspots for DNA deletions. Single locus displayed high intragroup variation, suggesting cellular heterogeneity within the tissue may be associated to cirDNA release. Thus, exposures to IH increase the shedding of cirDNA into circulation, which carries epigenetic modifications that may characterize cell populations within the tumor that preferentially release their DNA upon IH exposure.

Adropin concentrations in term pregnancies with normal, restricted and increased fetal growth

OBJECTIVE

To determine levels of adropin (implicated in insulin resistance and endothelial dysfunction) in intrauterine growth restricted (IUGR), large (LGA) and appropriate for gestational age (AGA) pregnancies.

METHODS

Cord-blood (UC) adropin and insulin concentrations were measured in 30 IUGR, 30 LGA and 20 AGA full-term infants and their mothers (MS).

RESULTS

No significant differences in adropin concentrations were observed between the three groups. In the IUGR group MS adropin was significantly decreased when neonates had higher birth weights [b = -0.003, 95% CI -0.006 to 0.0, p = 0.043]. In all groups, MS adropin levels were positively correlated with UC ones (r = 0.282, p = 0.011) and were significantly increased in female neonates [b = 0.977, 95% CI 0.122-1.832, p = 0.026]. In the LGA group, MS insulin was negatively correlated with UC adropin (r =  -0.362 p = 0.049).

CONCLUSIONS

Increased maternal adropin levels in severe IUGR cases might represent a regulatory feedback mechanism against endothelial placental dysfunction. The positive correlation between maternal and umbilical cord adropin levels implies its transplacental transfer. Increased maternal adropin levels in female neonates could be attributed to interaction of adropin with fetal estrogens through vascular endothelial growth factor (VEGF). The negative correlation between maternal insulin and fetal adropin levels in the LGA group is probably attributed to their respective insulin resistance.

Inverse Correlation Between Plasma Adropin and ET-1 Levels in Essential Hypertension: A Cross-Sectional Study

Adropin is a recently identified bioactive protein that promotes energy homeostasis by affecting glucose and lipid metabolism. Recently, adropin has also been reported to be associated with endothelial dysfunction. Also, ET-1, as a biomarker for endothelial dysfunction, is a key regulator in hypertension. Accordingly, the aim of the present study was to detect the relationship between plasma adropin and ET-1 levels in hypertension. A total of 123 participants, diagnosed with primary hypertension on the basis of World Health Organization criteria (systolic blood pressure [SBP] ≥ 140 mmHg and/or diastolic blood pressure (DBP) ≥ 90 mmHg), and 58 normotensive subjects were enrolled in the cross-sectional study from October 2011 to December 2013. All study participants were older than 18 years of age. Adropin and ET-1 levels were measured by enzyme-linked immunosorbent assay (ELISA). We found that plasma adropin levels were significantly lower in hypertensives compared with controls (3.18 ± 1.00 vs 4.21 ± 1.14 ng/mL, P < 0.001). Plasma ET-1 levels were higher in hypertensives than controls (2.60 ± 1.14 vs 1.54 ± 0.66 pg/mL, P < 0.001). Adropin had a negative correlation with DBP (r = -0.40, P < 0.001), SBP (r = -0.49, P < 0.001), and adjusted for age, body mass index, SBP, DBP, glucose, TC, TG, LDL, and Cr, there was a negative correlation between ET-1 and adropin (r = -0.20, P = 0.04). In multivariate logistic regression analysis of the variables, ET-1 (odds ratio [OR], 3.84; 95% CI, 2.16-6.81; P < 0.001) and adropin (OR, 0.99; 95% CI, 0.99 -1.0; P <  .001) were found to be independent predictors for hypertension.In conclusion, decreased plasma adropin levels are associated with increased blood pressure in hypertension. Adropin is an independent predictor for hypertension, and may influence blood pressure by protecting endothelial function.

Biomarkers associated with obstructive sleep apnea: A scoping review

The overall validity of biomarkers in the diagnosis of obstructive sleep apnea (OSA) remains unclear. We conducted a scoping review to provide assessments of biomarkers characteristics in the context of obstructive sleep apnea (OSA) and to identify gaps in the literature. A scoping review of studies in humans without age restriction that evaluated the potential diagnostic value of biological markers (blood, exhaled breath condensate, salivary, and urinary) in the OSA diagnosis was undertaken. Retained articles were those focused on the identification of biomarkers in subjects with OSA, the latter being confirmed with a full overnight or home-based polysomnography (PSG). Search strategies for six different databases were developed. The methodology of selected studies was classified using an adaptation of the evidence quality criteria from the American Academy of Pediatrics. Additionally the biomarkers were classified according to their potential clinical application. We identified 572 relevant studies, of which 117 met the inclusion criteria. Eighty-two studies were conducted in adults, 34 studies involved children, and one study had a sample composed of both adults and children. Most of the studies evaluated blood biomarkers. Potential diagnostic biomarkers were found in nine pediatric studies and in 58 adults studies. Only nine studies reported sensitivity and specificity, which varied substantially from 43% to 100%, and from 45% to 100%, respectively. Studies in adults have focused on the investigation of IL-6, TNF-α and hsCRP. There was no specific biomarker that was tested by a majority of authors in pediatric studies, and combinatorial urine biomarker approaches have shown preliminary promising results. In adults IL-6 and IL-10 seem to have a favorable potential to become a good biomarker to identify OSA.

Aerobic exercise training-induced changes in serum adropin level are associated with reduced arterial stiffness in middle-aged and older adults

Aging-induced arterial stiffening is reduced by aerobic exercise training, and elevated production of nitric oxide (NO) participates in this effect. Adropin is a regulator of endothelial NO synthase and NO release, and circulating adropin level decreases with age. However, the effect of habitual aerobic exercise on circulating adropin levels in healthy middle-aged and older adults remains unclear. We sought to determine whether serum adropin level is associated with exercise training-induced changes in arterial stiffness. First, in a cross-sectional study, we investigated the association between serum adropin level and both arterial stiffness and cardiorespiratory fitness in 80 healthy middle-aged and older subjects (65.6 ± 0.9 yr). Second, in an intervention study, we examined the effects of 8-wk aerobic exercise training on serum adropin level and arterial stiffness in 40 healthy middle-aged and older subjects (67.3 ± 1.0 yr) divided into two groups: aerobic exercise training and sedentary controls. In the cross-sectional study, serum adropin level was negatively correlated with carotid β-stiffness (r = -0.437, P < 0.001) and positively correlated with plasma NOx level (r = 0.493, P < 0.001) and cardiorespiratory fitness (r = 0.457, P < 0.001). Serum adropin levels were elevated after the 8-wk aerobic exercise training intervention, and training-induced changes in serum adropin level were correlated with training-induced changes in carotid β-stiffness (r = -0.399, P < 0.05) and plasma NOx level (r = 0.623, P < 0.001). Thus the increase in adropin may participate in the exercise-induced reduction of arterial stiffness.

Evaluation of the relationship between serum adropin levels and blood pressure in obese children

BACKGROUND

The prevalence of obesity and related cardiovascular comorbodities is increasing rapidly. Adipokines play a major role in the pathogenesis of obesity-related inflammation and hypertension.

AIM

The aim of this study was to evaluate the serum adropin levels in obese children and to determine the relationship between adropin levels and blood pressure (BP) in the pediatric age group.

METHODS

Forty obese children (mean age: 12.5 ± 2.5 years; male/female ratio: 18/22) and 15 healthy controls (mean age: 15 ± 3.14 years; male/female ratio: 5/15) were included in the study. Serum adropin levels, and a number of laboratory and clinical variables were compared. Ambulatory blood pressure monitoring was performed on obese subjects. Relationship between adropin levels and BP variables was examined.

RESULTS

Serum adropin levels were significantly lower in obese subjects than in healthy controls (193.56 ± 94 vs. 289 ± 187 pg/mL, p = 0.03). Adropin levels were correlated negatively with body mass index z-score (r = -0.56; p = 0.034). There was no correlation between serum adropin levels and laboratory variables in obese subjects. Five of the patients (12.5%) were nondipper, and nine of the patients (22.5%) had hypertension. There was no significant correlation between serum adropin levels and BP variables.

CONCLUSION

Serum adropin levels were significantly lower in obese children; however, there was no correlation between serum adropin levels and BP variables. Further studies are needed to determine the role of adipokines on BP.

Effects of adenotonsillectomy on plasma inflammatory biomarkers in obese children with obstructive sleep apnea: A community-based study

Background

Obesity and obstructive sleep apnea syndrome (OSA) are highly prevalent and frequently overlapping conditions in children that lead to systemic inflammation, the latter being implicated in the various end-organ morbidities associated with these conditions.

Aim

To examine the effects of adenotonsillectomy (T&A) on plasma levels of inflammatory markers in obese children with polysomnographically diagnosed OSA who were prospectively recruited from the community.

Methods

Obese children prospectively diagnosed with OSA, underwent T&A and a second overnight polysomnogram (PSG) after surgery. Plasma fasting morning samples obtained after each of the 2 PSG were assayed for multiple inflammatory and metabolic markers including interleukin-6 (IL-6), IL-18, plasminogen activator inhibitor-1 (PAI-1), monocyte chemoattractant protein-1 (MCP-1), matrix metalloproteinase- (MMP-9), adiponectin, apelin C, leptin and osteocrin.

Results

Out of 122 potential candidates, 100 obese children with OSA completed the study with only 1/3 exhibiting normalization of their PSG after T&A (i.e., AHI≤1/hrTST). However, overall significant decreases in MCP-1, PAI-1, MMP-9, IL-18 and IL-6, and increases in adropin and osteocrin plasma concentrations occurred after T&A. Several of the T&A responsive biomarkers exhibited excellent sensitivity and moderate specificity to predict residual OSA (i.e., AHI≥/hrTST).

Conclusions

A defined subset of systemic inflammatory and metabolic biomarkers is reversibly altered in the context of OSA among community-based obese children, further reinforcing the concept on the interactive pro-inflammatory effects of sleep disorders such as OSA and obesity contributing to downstream end-organ morbidities.

Therapeutic effects of adropin on glucose tolerance and substrate utilization in diet-induced obese mice with insulin resistance

Objective

The peptide hormone adropin regulates fuel selection preferences in skeletal muscle under fed and fasted conditions. Here, we investigated whether adropin treatment can ameliorate the dysregulation of fuel substrate metabolism, and improve aspects of glucose homeostasis in diet-induced obesity (DIO) with insulin resistance.

Methods

DIO C57BL/6 mice maintained on a 60% kcal fat diet received five intraperitoneal (i.p.) injections of the bioactive peptide adropin^34-76 (450 nmol/kg/i.p.). Following treatment, glucose tolerance and whole body insulin sensitivity were assessed and indirect calorimetry was employed to analyze whole body substrate oxidation preferences. Biochemical assays performed in skeletal muscle samples analyzed insulin signaling action and substrate oxidation.

Results

Adropin treatment improved glucose tolerance, enhanced insulin action and augmented metabolic flexibility towards glucose utilization. In muscle, adropin treatment increased insulin-induced Akt phosphorylation and cell-surface expression of GLUT4 suggesting sensitization of insulin signaling pathways. Reduced incomplete fatty acid oxidation and increased CoA/acetyl-CoA ratio suggested improved mitochondrial function. The underlying mechanisms appear to involve suppressions of carnitine palmitoyltransferase-1B (CPT-1B) and CD36, two key enzymes in fatty acid utilization. Adropin treatment activated pyruvate dehydrogenase (PDH), a rate-limiting enzyme in glucose oxidation, and downregulated PDH kinase-4 (PDK-4) that inhibits PDH. Along with these changes, adropin treatment downregulated peroxisome proliferator-activated receptor-gamma coactivator-1α that regulates expression of Cpt1b, Cd36 and Pdk4.

Conclusions

Adropin treatment of DIO mice enhances glucose tolerance, ameliorates insulin resistance and promotes preferential use of carbohydrate over fat in fuel selection. Skeletal muscle is a key organ in mediating adropin's whole-body effects, sensitizing insulin signaling pathways and altering fuel selection preference to favor glucose while suppressing fat oxidation.

Diagnostic capability of biological markers in assessment of obstructive sleep apnea: a systematic review and meta-analysis

OBJECTIVE

The purpose of this systematic review is to evaluate the diagnostic value of biological markers (exhaled breath condensate, blood, salivary and urinary) in the diagnosis of OSA in comparison to the gold standard of nocturnal PSG.

METHODS

Studies that differentiated OSA from controls based on PSG results, without age restriction, were eligible for inclusion. The sample of selected studies could include studies in obese patients and with known cardiac disease. A detailed individual search strategy for each of the following bibliographic databases was developed: Cochrane, EMBASE, MEDLINE, PubMed, and LILACS. The references cited in these articles were also crosschecked and a partial grey literature search was undertaken using Google Scholar. The methodology of selected studies was evaluated using the 14-item Quality Assessment Tool for Diagnostic Accuracy Studies.

RESULTS

After a two-step selection process, nine articles were identified and subjected to qualitative and quantitative analyses. Among them, only one study conducted in children and one in adults found biomarkers that exhibit sufficiently satisfactory diagnostic accuracy that enables application as a diagnostic method for OSA.

CONCLUSION

Kallikrein-1, uromodulin, urocotin-3, and orosomucoid-1 when combined have enough accuracy to be an OSA diagnostic test in children. IL-6 and IL-10 plasma levels have potential to be good biomarkers in identifying or excluding the presence of OSA in adults.

Hemoglobinopathies and sleep--The road less traveled

Sickle cell disease and thalassemia are common hereditary blood disorders associated with increased systemic inflammation, tissue hypoxia, endothelial dysfunction and end-organ damage, the latter accounting for the substantial morbidity and abbreviated lifespan associated with these conditions. Sleep perturbations in general, and sleep-disordered breathing in particular are also highly prevalent conditions and the mechanisms underlying their widespread end-organ morbidities markedly and intriguingly overlap with the very same pathways implicated in the hemoglobinopathies. However, little attention has been given to date to the potential contributing role of sleep disorders to sickle cell disease manifestations. Here, we comprehensively review the pathophysiological mechanisms and clinical manifestations linking disturbed sleep and hemoglobinopathies, with special emphasis on sickle cell disease. In addition to a broad summary of the available evidence, we identify many of the research gaps that require attention and future investigation, and provide the scientific contextual setting that should enable opportunities to investigate the intertwined pathophysiological mechanisms and clinical outcomes of sleep disorders and hemoglobinopathies.

Association between serum adropin levels and gestational diabetes mellitus; a case-control study

Gestational diabetes mellitus (GDM) is increasing worldwide. The aim of this study was to investigate the association between serum adropin concentration and GDM. In a case-control study, conducted in 2013, 40 pregnant women with GDM and 40 healthy pregnant women (controls) were evaluated. Fasting serum adropin and lipid concentration were measured during 24th-28th weeks of gestation for both groups. These factors were compared between the two groups using independent sample t-test. There was a significant difference in adropin levels between the two groups and mean adropin levels were lower in GDM group (p: 0.016). There was no significant correlation between serum adropin levels and body mass index as well as fasting blood glucose (FBS) or serum lipid profile including high-density lipoprotein, low-density lipoprotein, cholesterol and triglyceride concentration (p > 0.05). There was a significant association between adropin concentration and GDM even after using regression model for removing confounding factors (odds ratio = 0.681). Low serum adropin concentration is associated with GDM in Iranian pregnant women.

Circulating adropin levels in patients with endometrium cancer

AIM

Adropin is a recently identified protein in liver, brain and many peripheral tissues, which is important in energy homeostasis. The purpose of this study is to determine adropin levels in patients with endometrium cancer (EC).

MATERIAL AND METHODS

A total of 74 patients (47 EC patients and 27 healthy controls) were included in the study. Fasting venous blood samples were collected from all patients. Serum adropin levels were measured by an enzyme-linked immunosorbent assay (ELISA). The correlations between serum adropin levels and clinicopathologic variables were determined.

RESULTS

In body mass index and age-matched groups of patients, adropin levels were determined lower in patients with EC than control group (p < 0.01). Adropin levels were negatively correlated with age (r = -0.265, p = 0.023), homeostasis model-resistance index (HOMA-IR) (r = -0.294, p = 0.005) and fasting insulin levels (r = -0.292, p = 0.001). It was shown that in receiver operator characteristic (ROC) analysis, at cut-off value ≤ 1.055 (ng/ml), adropin had 92.7% sensitivity, 91.5% specificity and had AUC = 0.948, CI; 0.894-1.000 for diagnosis of EC (p < 0.001).

CONCLUSION

Adropin seems to be an important protein in pathogenesis of EC. Clearly, there are largely unknown aspects of adropin in EC pathophysiology and require further multi-centered, molecular and genetic studies including high number of cases.