Orexin Plays a Role in Growth Impediment Induced by Obstructive Sleep Breathing in Rats

Candidate genes for obstructive sleep apnea in non-syndromic children with craniofacial dysmorphisms - a narrative review

Pediatric obstructive sleep apnea (POSA) is a complex disease with multifactorial etiopathogenesis. The presence of craniofacial dysmorphisms influencing the patency of the upper airway is considered a risk factor for POSA development. The craniofacial features associated with sleep-related breathing disorders (SRBD) - craniosynostosis, retrognathia and micrognathia, midface and maxillary hypoplasia - have high heritability and, in a less severe form, could be also found in non-syndromic children suffering from POSA. As genetic factors play a role in both POSA and craniofacial dysmorphisms, we hypothesize that some genes associated with specific craniofacial features that are involved in the development of the orofacial area may be also considered candidate genes for POSA. The genetic background of POSA in children is less explored than in adults; so far, only one genome-wide association study for POSA has been conducted; however, children with craniofacial disorders were excluded from that study. In this narrative review, we discuss syndromes that are commonly associated with severe craniofacial dysmorphisms and a high prevalence of sleep-related breathing disorders (SRBD), including POSA. We also summarized information about their genetic background and based on this, proposed 30 candidate genes for POSA affecting craniofacial development that may play a role in children with syndromes, and identified seven of these genes that were previously associated with craniofacial features risky for POSA development in non-syndromic children. The evidence-based approach supports the proposition that variants of these candidate genes could lead to POSA phenotype even in these children, and, thus, should be considered in future research in the general pediatric population.

Bone mineral density alteration in obstructive sleep apnea by derived computed tomography screening

The association between obstructive sleep apnea (OSA) and bone mineral density (BMD) is poorly elucidated and has contradictory findings. Abdominal computed tomography (CT) for other indications can provide a valuable opportunity for osteoporosis screening. Thus, we retrospectively explored the association between OSA and BMD by examining abdominal CT vertebrae images for a multitude of conditions and indications. We included 315 subjects (174 with OSA and 141 without OSA) who performed at least two CT scans (under similar settings). Both groups had a similar duration between the first and second CT scans of 3.6 years. BMD decreased in those with OSA and increased age. A multivariate linear regression indicated that OSA is associated with BMD alterations after controlling for age, gender, and cardiovascular diseases. Here, we report that OSA is associated with BMD alterations. Further studies are required to untangle the complex affect of OSA on BMD and the possible clinical implications of vertebra-depressed or femoral neck fractures.

A rare case of 46, XX (SRY positive) testicular disorder of sex development with growth hormone deficiency: Case report

RATIONALE

Chromosome karyotype analysis and SRY (sex determined region of Y chromosome) gene detection are routines for the diagnosis of growth hormone deficiency (GHD), but further whole exome gene sequencing occasionally leads to subversive results and unexpected conclusions.

PATIENT CONCERNS

We report a single case of a 7-year-old Chinese boy who had stunted growth since he was 1 year old. He was short in height (height Standard Deviation Score (SDS) was less than 2.9), bilateral scrotal dysplasia and delayed bone age.

DIAGNOSIS

His growth hormone (GH) stimulation tests showed GHD. His karyotype analysis and polymerase chain reaction (PCR) analyses indicated a 46, XX disorder of sex development (DSD) without the presence of the SRY gene. Nevertheless, considering that female gonad was not observed in the chest and abdominal magnetic resonance imaging, the whole exome gene sequencing was performed. Sequencing data confirmed the presence of SRY gene sequence and two copies of chromosome X. Later, using different primer sequences for PCR, it showed that the SRY gene was positive. The final diagnosis was a rare case of "46, XX (SRY positive) testicular DSD with GHD".

INTERVENTIONS

The boy's parents agreed to use recombinant human growth hormone (rhGH) for GHD treatment, the starting dose was 0.035 mg / kg / day. But they disagreed with molecular diagnostics and genomic analysis of the Y chromosome.

OUTCOMES

The boy was treated with rhGH for 3 months and his height increased by 2.2 cm. The patient will be followed-up until the end of his puberty.

LESSONS

In summary, whole exome gene sequencing overturned the preliminary diagnosis results of karyotype analysis and SRY gene detection, and found that there may be a certain correlation between testicular DSD and GHD.

Upper Airway Obstruction Elicited Energy Imbalance Leads to Growth Retardation that Persists after the Obstruction Removal

Upper airway obstruction can lead to growth retardation by unclear mechanisms. We explored the effect of upper airway obstruction in juvenile rats on whole-body energy balance, growth plate metabolism, and growth. We show that after seven weeks, obstructed animals’ ventilation during room air breathing increased, and animals grew less due to abnormal growth plate metabolism. Increased caloric intake in upper airway-obstructed animals did not meet increased energy expenditure associated with increased work of breathing. Decreased whole-body energy balance induced hindrance of bone elongation following obstruction removal, and array pathways regulating growth plate development and marrow adiposity. This is the first study to show that rapidly growing animals cannot consume enough calories to maintain their energy homeostasis, leading to an impediment in growth in the effort to save energy.

Irreversible metabolic abnormalities following chronic upper airway loading

STUDY OBJECTIVES

Treatment of obstructive sleep apnea increases obesity risk by an unclear mechanism. Here, we explored the effects of upper airway obstruction and its removal on respiratory homeostasis, energy expenditure, and feeding hormones during the sleep/wake cycle from weaning to adulthood.

METHODS

The tracheas of 22-day-old rats were narrowed, and obstruction removal was performed on post-surgery day 14. Energy expenditure, ventilation, and hormone-regulated feeding were analyzed during 49 days before and after obstruction.

RESULTS

Energy expenditure increased and body temperature decreased in upper airway obstruction and was only partially recovered in obstruction removal despite normalization of airway resistance. Increased energy expenditure was associated with upregulation of ventilation. Decreased body temperature was associated with decreased brown adipose tissue uncoupling protein 1 level, suppressed energy expenditure response to norepinephrine, and decreased leptin level. Upper airway obstructed animals added less body weight, in spite of an increase in food intake, due to elevated hypothalamic orexin and neuropeptide Y and plasma ghrelin. Animals who underwent obstruction removal fed more due to an increase in hypothalamic neuropeptide Y and plasma ghrelin.

CONCLUSIONS

The need to maintain respiratory homeostasis is associated with persistent abnormal energy metabolism and hormonal regulation of feeding. Surgical treatment per se may not be sufficient to correct energy homeostasis, and endocrine regulation of feeding may have a larger effect on weight change.

Abnormal Growth and Feeding Behavior in Upper Airway Obstruction in Rats

Pediatric obstructive sleep apnea (OSA) is a syndrome manifesting with snoring and increased respiratory effort due to increased upper airway resistance. In addition to cause the abnormal sleep, this syndrome has been shown to elicit either growth retardation or metabolic syndrome and obesity. Treating OSA by adenotonsillectomy is usually associated with increased risk for obesity, despite near complete restoration of breathing and sleep. However, the underlying mechanism linking upper airways obstruction (AO) to persistent change in food intake, metabolism, and growth remains unclear. Rodent models have examined the impact of intermittent hypoxia on metabolism. However, an additional defining feature of OSA that is not related to intermittent hypoxia is enhanced respiratory loading leading to increased respiratory effort and abnormal sleep. The focus of this mini review is on recent evidence indicating the persistent abnormalities in endocrine regulation of feeding and growth that are not fully restored by the chronic upper AO removal in rats. Here, we highlight important aspects related to abnormal regulation of metabolism that are not related to intermittent hypoxia per se, in an animal model that mimics many of the clinical features of pediatric OSA. Our evidence from the AO model indicates that obstruction removal may not be sufficient to prevent the post-removal tendency for abnormal growth.

Abnormal Growth and Feeding Behavior Persist After Removal of Upper Airway Obstruction in Juvenile Rats

Pediatric obstructive sleep-disordered breathing is associated with growth retardation, but also with obesity that has a tendency to persist following treatment. We investigated the effect of upper airways obstruction (AO) and of obstruction removal (OR) in juvenile rats on gut-derived ghrelin and related hypothalamic factors, feeding, and growth hormone (GH) homeostasis. Here, we show that after seven weeks of AO, animals gained less weight compared to controls, despite an increase in food intake due to elevated ghrelin and hypothalamic feeding factors. OR rats who had complete restoration of tracheal diameter, consumed more food due to increased ghrelin and exhibited growth retardation due to deregulation of GH homeostasis. This study is the first to show dysregulation of the hormonal axes controlling feeding behavior and growth that are not fully restored following OR. Thus, surgical treatment by itself may not be sufficient to prevent post-surgical increased food intake and growth retardation.