Rakesh Bhattacharjee

Adenotonsillectomy outcomes in treatment of obstructive sleep apnea in children: a multicenter retrospective study.

RATIONALE The overall efficacy of adenotonsillectomy (AT) in treatment of obstructive sleep apnea syndrome (OSAS) in children is unknown. Although success rates are likely lower than previously estimated, factors that promote incomplete resolution of OSAS after AT remain undefined. OBJECTIVES To quantify the effect of demographic and clinical confounders known to impact the success of AT in treating OSAS. METHODS A multicenter collaborative retrospective review of all nocturnal polysomnograms performed both preoperatively and postoperatively on otherwise healthy children undergoing AT for the diagnosis of OSAS was conducted at six pediatric sleep centers in the United States and two in Europe. Multivariate generalized linear modeling was used to assess contributions of specific demographic factors on the post-AT obstructive apnea-hypopnea index (AHI). MEASUREMENTS AND MAIN RESULTS Data from 578 children (mean age, 6.9 +/- 3.8 yr) were analyzed, of which approximately 50% of included children were obese. AT resulted in a significant AHI reduction from 18.2 +/- 21.4 to 4.1 +/- 6.4/hour total sleep time (P < 0.001). Of the 578 children, only 157 (27.2%) had complete resolution of OSAS (i.e., post-AT AHI <1/h total sleep time). Age and body mass index z-score emerged as the two principal factors contributing to post-AT AHI (P < 0.001), with modest contributions by the presence of asthma and magnitude of pre-AT AHI (P < 0.05) among nonobese children. CONCLUSIONS AT leads to significant improvements in indices of sleep-disordered breathing in children. However, residual disease is present in a large proportion of children after AT, particularly among older (>7 yr) or obese children. In addition, the presence of severe OSAS in nonobese children or of chronic asthma warrants post-AT nocturnal polysomnography, in view of the higher risk for residual OSAS.

Cardiovascular Complications of Obstructive Sleep Apnea Syndrome : Evidence from Children

Obstructive Sleep Apnea Syndrome (OSAS) is a common condition in children, and is characterized by intermittent partial or complete occlusion of the upper airway during sleep, leading to profound disturbances in homeostatic gas exchange, frequent arousals and disturbed sleep architecture. Pediatric OSAS is associated with a multitude of end-organ morbidities, most of which have been uncovered in the last decade. Of particular interest are the cardiovascular complications that may develop in children with OSAS, since they are posited to have not only an immediately significant impact on cardiovascular health during childhood, but may also affect cardiovascular outcomes later during adult life. In this review, we will present the specific cardiovascular complications that have thus far been described in children with OSAS, with reference to pertinent mechanisms, and potential implications.

Obesity and Obstructive Sleep Apnea Syndrome in Children: A Tale of Inflammatory Cascades

Obesity has emerged as one of the most prevalent diseases in the western hemisphere, and its prevalence continues to increase. Obese children are at increased risk for several disorders, particularly affecting the cardiovascular and metabolic systems. The mechanisms leading to obesity‐related morbidities are likely multifactorial, and include activation of inflammatory pathways ultimately leading to end‐organ injury. Furthermore, the concurrent presence of obesity and other diseases facilitated by increased fat deposition poses a theoretical risk of accentuating obesity‐related complications. One of the conditions whose prevalence is increased by obesity in childhood is the obstructive sleep apnea syndrome (OSAS). OSAS in non‐obese children may lead to co‐morbidities that are not only remarkably similar to those associated with obesity but recruit similar inflammatory mechanisms as those activated by obesity, suggesting that the two disorders may amplify each other and synergistically augment the magnitude of their respective adverse consequences. The objective of this review is to critically review the effects of both obesity and OSAS in inducing systemic inflammation in children and will examine the latest evidence pertaining to the up‐regulation of specific inflammatory mediators. Pediatr Pulmonol. 2011; 46:313–323.

Endothelial Progenitor Cells and Vascular Dysfunction in Children with Obstructive Sleep Apnea

RATIONALE Endothelial dysfunction is a potential complication of obstructive sleep apnea syndrome (OSAS) in children ascribed to systemic inflammatory changes. However, not all children with OSAS will manifest endothelial dysfunction. OBJECTIVES The variability in endothelial function in pediatric OSAS may be related to the ability to recruit repair mechanisms such as endothelial progenitor cells (EPCs). METHODS Prepubertal nonhypertensive children with or without polysomonographically confirmed OSAS had endothelial function assessed in a morning fasted state using a modified hyperemic test involving cuff-induced occlusion of the radial and ulnar arteries. Blood was drawn and EPCs were assessed by flow cytometry and triple staining using antibodies against CD133, CD34, and vascular endothelial growth factor receptor-2 after isolation of peripheral blood mononuclear cells. SDF-1 levels were measured by ELISA. MEASUREMENTS AND MAIN RESULTS Eighty children with OSAS (mean age 8.2 +/- 1.4 yr, mean body mass index [BMI] z-score, 1.43 +/- 0.3) and 20 controls (CO) matched for BMI, age, sex, and ethnicity were studied. Significant delays to peak capillary reperfusion after occlusion release (Tmax) occurred in OSAS children, but substantial variability was present. Despite similar OSAS severity, EPC counts, and stromal cell-derived factor-1 (SDF-1) levels were significantly lower among the 20 OSAS children with the longest Tmax, when compared with either the 20 children with normal Tmax values or to CO ( P < 0.01). Furthermore, Tmax was significantly and inversely correlated with EPCs (r(2), 0.51; P < 0.01), but neither EPCs nor Tmax were associated with apnea-hyponea index (AHI). CONCLUSIONS Endothelial dysfunction is frequently present in OSAS. Variance in endothelial functional phenotype may not only reside in the individual susceptibility but also in the ability to recruit endothelial repair mechanisms.

Two-Dimensional Differential In-Gel Electrophoresis Proteomic Approaches Reveal Urine Candidate Biomarkers in Pediatric Obstructive Sleep Apnea

RATIONALE Sleep studies are laborious, expensive, inaccessible, and inconvenient for diagnosing obstructive sleep apnea (OSA) in children. OBJECTIVES To examine whether the urinary proteome uncovers specific clusters that are differentially expressed in the urine of children with OSA. METHODS Two-dimensional differential in-gel electrophoresis (2D-DIGE) and mass spectrometry proteomics followed by validation with western blot of ELISA. MEASUREMENTS AND MAIN RESULTS Morning urine proteins from 60 children with polysomnographically confirmed OSA and from matched children with primary snoring (n = 30) and control subjects (n = 30) were assessed. A total of 16 proteins that are differentially expressed in OSA were identified, and 7 were confirmed by either immunoblots or ELISA. Among the latter, receiver-operator curve analyses of urinary concentrations of uromodulin, urocortin-3, orosomucoid-1, and kallikrein assigned favorable predictive properties to these proteins. Furthermore, combinatorial approaches indicated that the presence of values beyond the calculated cutoff concentrations for three or more of the proteins yielded a sensitivity of 95% and a specificity of 100%. CONCLUSIONS Proteomic approaches reveal that pediatric OSA is associated with specific and consistent alterations in urinary concentrations of specific protein clusters. Future studies aiming to validate this approach as a screening method of habitually snoring children appears warranted.

Endothelial Dysfunction in Children Without Hypertension: Potential Contributions of Obesity and Obstructive Sleep Apnea

BACKGROUND Endothelial dysfunction can develop in the context of both obesity and obstructive sleep apnea (OSA) in children. However, the potential interactions between OSA and obesity have not been defined. METHODS Children who were prepubertal and nonhypertensive were recruited. Endothelial function was assessed in a morning fasted state, using a modified hyperemic test involving cuff-induced occlusion of the radial and ulnar arteries, and blood was drawn for assessment of myeloid-related protein 8/14 (MRP8/14) levels using a commercial enzyme-linked immunosorbent assay. Overnight polysomnography defined the presence of OSA or absence of OSA (NOSA) in subjects investigated for sleep-disordered breathing. Anthropometric measurements were performed to assign subjects to obese (OB) and nonobese (NOB) categories. RESULTS Fifty-four children with OSA who were obese and nonobese (mean age, 7.90 ± 0.26 years; mean BMI z-score, 1.70 ± 0.3; obstructive apnea-hypopnea index [OAHI], 7.36 ± 1.09) were compared with 54 children without OSA who were obese and nonobese (mean age, 8.26 ± 0.24 years; mean BMI z-score, 1.41 ± 0.18; OAHI, 0.86 ± 0.07). Of those subjects, 62.5% of the OB-OSA category, 38.7% of the OB-NOSA category, and 20.0% of the NOB-OSA category had evidence of endothelial dysfunction, compared with 0.0% of the NOB-NOSA category (P < .01). The degree of endothelial dysfunction in all groups was associated with circulating MRP8/14 levels (r = 0.343, P < .001). CONCLUSIONS Both obesity and OSA can independently increase the risk for endothelial dysfunction, and the concurrent presence of both markedly increases such risk. Although the mechanisms underlying endothelial dysfunction remain unclear, a potential role for MRP8/14 as an inflammatory biomarker of endothelial dysfunction is suggested.

Neurocognitive and Endothelial Dysfunction in Children With Obstructive Sleep Apnea

OBJECTIVE: Pediatric obstructive sleep apnea syndrome (OSAS) is associated with neurocognitive and endothelial dysfunction. However, it is unclear whether these 2 frequent morbidities of OSAS in children represent similar or different underlying pathophysiological processes, because they have never been concurrently assessed in children. METHODS: Consecutive children (ages 5–8 years) with polysomnographically based OSAS underwent cognitive battery evaluation (Differential Ability Scales and the NeuroPsychological Assessment Battery) and cuff-occlusion hyperemic tests for assessment of endothelial function. The presence of neurocognitive deficits (NC+) was defined on the basis of the presence of ≥2 abnormal cognitive test results. Endothelial dysfunction (ED+) was defined as a time to maximal postocclusive hyperemic response of ≥45 seconds (Tmax). RESULTS: Twenty-one control children and 87 children with OSAS completed both cognitive and endothelial tests. Of these children, 48 were NC+ and 50 had a Tmax of ≥45 seconds, and at least 80% of these children were in both groups. Conversely, among children in whom there was no presence of neurocognitive deficits (NC−), only 25.6% were ED+, whereas among those without endothelial dysfunction (ED−) only 21.6% were NC+. Furthermore, approximately one-third of the children with OSAS was NC− and ED−. Thus, findings on hyperemic vascular responses were highly predictive of neurocognitive status. CONCLUSIONS: Endothelial dysfunction and neurocognitive deficits are more likely to coexist than otherwise predicted from the frequency of each of these morbidities alone in pediatric OSAS. Thus, both of these morbid consequences may share similar pathogenetic mechanisms. Furthermore, a simple test such as the postocclusive hyperemic vascular response may help detect at-risk patients for neuropsychological deficits.

DNA Methylation in Inflammatory Genes among Children with Obstructive Sleep Apnea

BACKGROUND Pediatric obstructive sleep apnea (OSA) leads to multiple end-organ morbidities that are mediated by the cumulative burden of oxidative stress and inflammation. Because not all children with OSA exhibit increased systemic inflammation, genetic and environmental factors may be affecting patterns of DNA methylation in genes subserving inflammatory functions. METHODS DNA from matched children with OSA with and without high levels of high-sensitivity C-reactive protein (hsCRP) were assessed for DNA methylation levels of 24 inflammatory-related genes. Primer-based polymerase chain reaction assays in a case-control setting involving 47 OSA cases and 31 control subjects were conducted to confirm the findings; hsCRP and myeloid-related protein (MRP) 8/14 levels were also assayed. MEASUREMENTS AND MAIN RESULTS Forkhead box P3 (FOXP3) and interferon regulatory factor 1 (IRF1) showed higher methylation in six children with OSA and high hsCRP levels compared with matched children with OSA and low hsCRP levels (P < 0.05). In the case-control cohort, children with OSA and high CRP levels had higher log FOXP3 DNA methylation levels compared with children with OSA and low CRP levels and control subjects. IRF1 did not exhibit significant differences. FOXP3 DNA methylation levels correlated with hsCRP and MRP 8/14 levels and with apnea-hypopnea index (AHI), BMI z score, and apolipoprotein B levels. A stepwise multiple regression model showed that AHI was independently associated with FOXP3 DNA methylation levels (P < 0.03). CONCLUSIONS The FOXP3 gene, which regulates expression of T regulatory lymphocytes, is more likely to display increased methylation among children with OSA who exhibit increased systemic inflammatory responses. Thus, epigenetic modifications may constitute an important determinant of inflammatory phenotype in OSA, and FOXP3 DNA methylation levels may provide a potential biomarker for end-organ vulnerability.

Leukotriene Pathways and In Vitro Adenotonsillar Cell Proliferation in Children With Obstructive Sleep Apnea

INTRODUCTION The abundant expression of leukotrienes (LTs) and their receptors in adenotonsillar tissues of children with obstructive sleep apnea (OSA) suggest that LT antagonists could be useful in treating OSA. METHODS The effects of LTD4 and of LT receptor antagonists zileuton, montelukast, and BAY u9773 were examined on mixed cell cultures prepared from dissociated tonsils or adenoids harvested intraoperatively from children with polysomnographically diagnosed OSA. Proliferation was assessed by (3)[H]-thymidine incorporation, and inflammatory cytokine production (tumor necrosis factor [TNF]-alpha, interleukin [IL]-6, IL-8, IL-10, and IL-12) was assessed in supernatants using enzyme-linked immunosorbent assay. RESULTS LTD4 elicited dose-dependent increases in adenotonsillar cell proliferation (p < 0.001; n = 12). All LT antagonists exhibited dose-dependent reductions in adenotonsillar cellular proliferation rates, with montelukast more than BAY u9773 more than zileuton (n = 14/group; p < 0.001). However, BAY u9773 showed partial agonist effects and increased cellular proliferation at higher concentrations (10(-4) mmol/L; p < 0.01; n = 12). LTD4 effects were partially blocked by montelukast and BAY u9773 but not by zileuton. All three antagonists reduced TNF-alpha, IL-6, and IL-12 concentrations, with selective changes in IL-8 and no effects on IL-10 levels. CONCLUSIONS LT pathways mediate intrinsic proliferative and inflammatory signaling pathways in adenotonsillar tissues from children with OSA, and targeted pharmacologic disruption of these pathways may provide nonsurgical alternatives for prevention and treatment of this disease.

Original ResearchSleep DisordersEndothelial Dysfunction in Children Without Hypertension: Potential Contributions of Obesity and Obstructive Sleep Apnea

BACKGROUND Endothelial dysfunction can develop in the context of both obesity and obstructive sleep apnea (OSA) in children. However, the potential interactions between OSA and obesity have not been defined. METHODS Children who were prepubertal and nonhypertensive were recruited. Endothelial function was assessed in a morning fasted state, using a modified hyperemic test involving cuff-induced occlusion of the radial and ulnar arteries, and blood was drawn for assessment of myeloid-related protein 8/14 (MRP8/14) levels using a commercial enzyme-linked immunosorbent assay. Overnight polysomnography defined the presence of OSA or absence of OSA (NOSA) in subjects investigated for sleep-disordered breathing. Anthropometric measurements were performed to assign subjects to obese (OB) and nonobese (NOB) categories. RESULTS Fifty-four children with OSA who were obese and nonobese (mean age, 7.90 ± 0.26 years; mean BMI z-score, 1.70 ± 0.3; obstructive apnea-hypopnea index [OAHI], 7.36 ± 1.09) were compared with 54 children without OSA who were obese and nonobese (mean age, 8.26 ± 0.24 years; mean BMI z-score, 1.41 ± 0.18; OAHI, 0.86 ± 0.07). Of those subjects, 62.5% of the OB-OSA category, 38.7% of the OB-NOSA category, and 20.0% of the NOB-OSA category had evidence of endothelial dysfunction, compared with 0.0% of the NOB-NOSA category (P < .01). The degree of endothelial dysfunction in all groups was associated with circulating MRP8/14 levels (r = 0.343, P < .001). CONCLUSIONS Both obesity and OSA can independently increase the risk for endothelial dysfunction, and the concurrent presence of both markedly increases such risk. Although the mechanisms underlying endothelial dysfunction remain unclear, a potential role for MRP8/14 as an inflammatory biomarker of endothelial dysfunction is suggested.