Obstructive sleep apnea (OSA) is common in pregnancy and may compromise fetal and even postnatal development. We developed an animal model to determine if maternal OSA could have lasting effects in offspring. Pregnant Sprague-Dawley rats were exposed to reduced ambient O₂ from 21 to 4–5%, approximately once per minute [chronic intermittent hypoxia (CIH)] for 8 h/day during gestation days 3–19. Similarly handled animals exposed to ambient air served as controls (HC). Offspring were studied for body growth and cardiovascular function for 8 postnatal weeks. Compared with HC, prenatal CIH led to growth restriction, indicated by smaller body weight and tibial length, and higher arterial blood pressure in both male and female offspring. Compared with same-sex HC, CIH males showed abdominal obesity (greater ratio of abdominal fat weight to body weight or tibial length), left ventricular (LV) hypertrophy (greater heart weight-to-tibial length ratio and LV posterior wall diastolic thickness), elevated LV contractility (increases in LV ejection fraction, end-systolic pressure-volume relations, and preload recruitable stroke work), elevated LV and arterial stiffness (increased end-diastolic pressure-volume relationship and arterial elasticity), and LV oxidative stress (greater lipid peroxide content). Compared with female CIH offspring, male CIH offspring had more profound changes in blood pressure (BP), cardiac function, myocardial lipid peroxidase (LPO) content, and abdominal adiposity. Rodent prenatal CIH exposure, mimicking human maternal OSA, exerts detrimental morphological and cardiovascular effects on developing offspring; the model may provide useful insights of OSA effects in humans. NEW & NOTEWORTHY Obstructive sleep apnea is common in human pregnancy. Following maternal exposure to chronic intermittent hypoxia, a hallmark of sleep apnea, both sexes of rat offspring showed growth retardation, with males being more vulnerable to hypertension and dysfunctional left ventricular changes. This model is useful to study detrimental effects of maternal obstructive sleep apnea on developing offspring in humans.

Without zinc, pancreatic beta cells cannot either assemble insulin molecules or precipitate insulin crystals; thus, a lack of zinc concentration in the beta cells would result in a decreased insulin production. ZIP8 is one of the zinc uptake transporters involved in zinc influx into the cytosol of beta cells. Thus, if ZIP8 is down-regulated, a decreased insulin production would result. We assumed that intermittent hypoxic exposure to the beta cells may result in a decreased production of insulin due to a lack of zinc. To test this hypothesis we harvested pancreatic islets from the rats conditioned under intermittent hypoxia (IH) (fluctuating between 20.5% and 10% every 4 min for 1 h) and compared the results with those from control animals and islets. We also compared their insulin and glucose homeostasis using glucose tolerance tests (GTT) after 3 weeks. GTT results show a significant delay (P<0.05) in recovery of the blood glucose level in IH treated pups. ZIP8 expression in the beta cell membrane was down-regulated. The zinc concentration in the cell as well as insulin production was significantly decreased in the islets harvested from IH animals. However, mRNA for insulin and C-peptide/insulin protein levels in the total cell lysates remained the same as those of controls. When we treated the beta cells using siRNA mediated ZIP8, we observed the commensurate results from the IH-treated islets. We conclude that a transient IH exposure could knockdown ZIP8 transporters at mRNA as well as protein levels in the beta cells, which would decrease the level of blood insulin. However, the transcriptional activity of insulin remains the same. We conclude that the precipitation process of insulin crystal may be disturbed by a lack of zinc in the cytosol that is modulated by mainly ZIP8 after IH exposure.

This initial report presents a neonatal rat model with exposure to a transient intermittent hypoxia (IH), which results in a persisting diabetes-like condition in the young rats. Twenty-five male pups were treated at postnatal day 1 with IH exposure by alternating the level of oxygen between 10.3% and 20.8% for 5h. The treated animals were then maintained in normal ambient oxygen condition for 3 week and compared to age-matched controls. The IH treated animals exhibited a significantly higher fasting glucose level than the control animals (237.00 ± 19.66 mg/dL vs. 167.25 ± 2.95 mg/dL; P=0.003); and a significantly lower insulin level than the control (807.0 ± 72.5 pg/mL vs. 1839.8 ± 377.6 pg/mL; P=0.023). There was no difference in the mass or the number of insulin producing beta cells as well as no indicative of inflammatory changes; however, glucose tolerance tests showed a significantly disturbed glucose homeostasis. In addition, the amount of C-peptide secreted from the islets harvested from the IH animals were decreased significantly (from 914 pM in control to 809 pM in IH; P=0.0006) as well. These observations demonstrate that the neonatal exposure to the IH regimen initiates the development of deregulation in glucose homeostasis without infiltration of inflammatory cells.

A brief intermittent hypoxia (IH, ambient O₂ levels alternating between room air and 12% O₂) for 1 h immediately after birth resulted in pancreatic islet dysfunction associated with zinc deficiency as previously reported. We hypothesized that IH exposure modulates zinc homeostasis in bone as well, which leads to increased bone fragility. To test this hypothesis, we used neonatal rats and human osteoblasts (HObs). To examine IH influences on osteoblasts devoid of neural influences, we quantified amounts of alkaline phosphatase and mineralization in IH-treated HObs. Bones harvested from IH-treated animals showed significantly reduced hardness and elasticity. The IH group also showed discretely decreased levels of alkaline phosphatase and mineralization amounts. The IH group showed a decreased expression of ZIP8 or Zrt and Irt-like protein 8 (a zinc uptake transporter), Runx2 (or Runt-related transcription factor 2, a master protein in bone formation), Collagen-1 (a major protein comprising the extracellular matrix of the bone), osteocalcin, and zinc content. When zinc was eliminated from the media containing HObs using a zinc chelate and added later with zinc sulfate, Runx2, ZIP8, and osteocalcin expression decreased first, and recovered with zinc supplementation. Adenovirus-mediated ZIP8 over-expression in osteoblasts increased mineralization significantly as well. We conclude that IH impairs zinc homeostasis in bones and osteoblasts, and that such disturbances decrease bone strength, which can be recovered by zinc supplementation.

Mesenchymal stem cells (MSCs) are multipotent cells, which can give rise to variety of cell types, including adipocytes and osteoblasts. Previously, we have shown that cysteine dioxygenase type 1 (Cdo1) promoted adipogenesis of primary mouse bone marrow stromal cells (BMSCs) and 3T3-L1 pre-adipocytes via interaction with Pparγ. However, the role of Cdo1 in osteogenesis remains unclear. Here, we demonstrated that expression of Cdo1 was elevated during osteoblastic differentiation of BMSCs in vitro. Interestingly, knockdown of Cdo1 by siRNA led to an increased expression of osteogenic related genes, elevated alkaline phosphatase (ALP) activity, and enhanced mineralization. Overexpression of Cdo1 in BMSCs inversely suppressed the osteogenesis. Furthermore, we found that overexpression of Cdo1 impaired Wnt signaling and restricted the Wnt3a induced expression of osteogenic transcriptional factors, such as Runx2 and Dlx5. Collectively, our findings indicate Cdo1 suppresses osteogenic differentiation of BMSCs, through a potential mechanism which involves in Wnt signaling reduction concomitantly.

The objective was to determine whether hyoid bone elevation induced by an anterior mandibular positioning appliance (AMP) predicts the effectiveness of the AMP in patients with obstructive sleep apnea (OSA). Fifteen patients (12 males and 3 females) underwent polysomnographic recordings and lateral cephalograms before and after AMP use of at least 6 months. Measurements of sleep variables and upper airway morphology were compared between pre-AMP and with-AMP states. The AMP appliance reduced apnea-hypopnea indices (AHI) ~53% (33.77 ± 3.29 vs. 15.85 ± 3.78, P = 0.0013). Cephalograms of the oropharyngeal airway showed that the hyoid bone moved superiorly toward the inferior mandibular border (Δ H-MP) ~5 mm (23.4 ± 1.44 vs. 18.27 ± 1.86, P = 0.0377), with the AMP inserted in the oral cavity; no airway measurement other than hyoid bone position changed. No significant correlations emerged between AHI improvement (Δ AHI) and amounts of hyoid elevation (Δ H-MP) when all patients were pooled. However, when the samples were subcategorized, the correlation coefficients increased significantly (P < 0.01) in both subgroups. This outcome suggests the presence of two distinct types among the “Good-Responders” to AMP appliance use. Overall use of the AMP appliance is effective; however, the effectiveness of the appliance appears to depend on the mode of hyoid elevations, likely resulting from muscle responsiveness in patients with AMP use. The results suggest that Δ H-MP measurements may be a useful marker to segregate patients with tongue and hyoid muscles responsive to AMP from those not-so-responsive.