Transformable Gel-to-Nanovaccine Enhances Cancer Immunotherapy via Metronomic-Like Immunomodulation and Collagen-Mediated Paracortex Delivery.

The generation of non-exhausted effector T-cells depends on vaccine's spatiotemporal profile, and untimely delivery and low targeting to lymph node (LN) paracortex by standard bolus immunization show limited efficacy. By recapitulating the dynamic processes of acute infection, a bioadhesive immune niche domain (BIND) is developed that facilitates the delivery of timely-activating conjugated nanovaccine (t-CNV) in a metronomic-like manner and increased the accumulation and retention of TANNylated t-CNV (tannic acid coated t-CNV) in LN by specifically binding to collagen in subcapsular sinus where they gradually transformed into TANNylated antigen-adjuvant conjugate by proteolysis, inducing their penetration into paracortex through the collagen-binding in LN conduit and evoking durable antigen-specific CD8+ T-cell responses. The BIND combined with t-CNV, mRNA vaccine, IL-2, and anti-PD-1 antibody also significantly enhanced cancer immunotherapy by the dynamic modulation of immunological landscape of tumor microenvironment. The results provide material design strategy for dynamic immunomodulation that can potentiate non-exhausted T-cell-based immunotherapy.

Trackable Liposomes for In Vivo Delivery Tracing toward Personalized Medicine Care under NIR Light on Skin Tumor.

We report an near-infrared (NIR)-trackable and therapeutic liposome with skin tumor specificity. Liposomes with a hydrodynamic diameter of ∼20 nm are tracked under the vein visualization imaging system in the presence of loaded paclitaxel and NIR-active agents. The ability to track liposome nanocarriers is recorded on the tissue-mimicking phantom model and in vivo mouse veins after intravenous administration. The trackable liposome delivery provides in vitro and in vivo photothermal heat (∼40 °C) for NIR-light-triggered area-specific chemotherapeutic release. This approach can be linked with a real-time vein-imaging system to track and apply area-specific local heat, which hitchhikes liposomes from the vein and finally releases them at the tumor site. We conducted studies on mice skin tumors that indicated the disappearance of tumors visibly and histologically (H&E stains). The ability of nanocarriers to monitor after administration is crucial for improving the effectiveness and specificity of cancer therapy, which could be achieved in the trackable delivery system.

Enhanced Postsurgical Cancer Treatment Using Methacrylated Glycol Chitosan Hydrogel for Sustained DNA/Doxorubicin Delivery and Immunotherapy.

Background: Cancer recurrence and metastasis are major contributors to treatment failure following tumor resection surgery. We developed a novel implantable drug delivery system utilizing glycol chitosan to address these issues. Glycol chitosan is a natural adjuvant, inducing dendritic cell activation to promote T helper 1 cell immune responses, macrophage activation, and cytokine production. Effective antigen production by dendritic cells initiates T-cell-mediated immune responses, aiding tumor growth control. Methods: In this study, we fabricated multifunctional methacrylated glycol chitosan (MGC) hydrogels with extended release of DNA/doxorubicin (DOX) complex for cancer immunotherapy. We constructed the resection model of breast cancer to verify the anticancer effects of MGC hydrogel with DNA/DOX complex. Results: This study demonstrated the potential of MGC hydrogel with extended release of DNA/DOX complex for local and efficient cancer therapy. The MGC hydrogel was implanted directly into the surgical site after tumor resection, activating tumor-related immune cells both locally and over a prolonged period of time through immune-reactive molecules. Conclusions: The MGC hydrogel effectively suppressed tumor recurrence and metastasis while enhancing immunotherapeutic efficacy and minimizing side effects. This biomaterial-based drug delivery system, combined with cancer immunotherapy, can substantial improve treatment outcomes and patient prognosis.

Pomegranate Polyphenol-Derived Injectable Therapeutic Hydrogels to Enhance Neuronal Regeneration.

Drug delivery for the treatment of neurological disorders has long been considered complex due to difficulties in ensuring the drug targeting on a specific site of the damaged neural tissues and its prolonged release. A syringe-injectable polymeric hydrogel with mechanical moduli matching those of brain tissues can provide a solution to deliver the drugs to the specific region through intracranial injections in a minimally invasive manner. In this study, an injectable therapeutic hydrogel with antioxidant pomegranate polyphenols, punicalagin, is reported for efficient neuronal repair. The hydrogels composed of tyramine-functionalized hyaluronic acid and collagen crosslinked by enzymatic reactions have great injectability with high shape fidelity and effectively encapsulate the polyphenol therapeutics. Furthermore, the punicalagin continuously released from the hydrogels over several days could enhance the growth and differentiation of the neurons. Our findings for efficacy of the polyphenol therapeutic-encapsulated injectable hydrogels on neuronal regeneration would be promising for designing a new type of antioxidative biomaterials in brain disorder therapy.

Punicalagin-Loaded Alginate/Chitosan-Gallol Hydrogels for Efficient Wound Repair and Hemostasis.

For recently devised wound-healing materials, a variety of acute application systems with sustainable therapeutic effects on wound sites have been suggested. For example, hydrogel-type healing agents with porous structures and high drug encapsulation efficiencies have been developed for wound repair. However, challenges remain about the poor mechanical and adhesive properties of hydrogels. Herein, we propose a punicalagin (PC)-containing wound-healing hydrogel in adhesive form that is mechanically stable and has sustainable wound-healing therapeutic efficiency. The APC hydrogel, composed of alginate (ALG), PC, and chitosan-gallol (CHI-G), exhibits significant mechanical and self-healing properties, thus indicating that PC increases cross-linking in ALG/CHI-G as macromolecule. The PC-containing mechanically enhanced hydrogel demonstrates high tissue adhesiveness. Sustainable PC release for 192 h, which indicates high therapeutic effect of the released PC, and great blood compatibility are evaluated based on rapid blood coagulation and minimal hemolysis. The cytocompatibility and wound-healing abilities of the PC-containing APC hydrogel are greater than those of the non-PC hydrogel, as verified by cell compatibility and wound scratch assays. These results indicate that a suitable concentration of PC-containing hydrogel with sustainable moisture condition and PC release may inspire further polyphenol-agent-containing hydrogels as wound-healing agents with structural stability and therapeutic efficiency.

Plant-inspired Pluronic-gallol micelles with low critical micelle concentration, high colloidal stability, and protein affinity.

Polymeric micelles are the most common carriers used for hydrophobic drug delivery. However, they are vulnerable to physiological barriers, such as temperature changes and enzymatic degradation, and can be easily disassembled upon dilution below the critical micelle concentration (CMC) by body fluids after an intravenous injection. Here, we report that Pluronic® micelles with octyl gallate, which is a surfactant containing gallol moieties widely found in antioxidative plant polyphenols, have a low CMC, which improves their colloidal stability without the need for covalent crosslinking. Furthermore, the incorporated gallol moieties provide enzymatic degradation resistance to the micelles owing to their protein affinity, maintaining the hydrophobic cavity of unmodified Pluronic®. Thus, plant-inspired polymeric micelles with low CMC and bioavailability are promising multifunctional vehicles for drug delivery.

Addressing the Shortcomings of Polyphenol-Derived Adhesives: Achievement of Long Shelf Life for Effective Hemostasis.

For rapid and effective hemostasis of uncontrollable bleeding, versatile hemostatic agents have been emerging. Among them, polyphenol-derived adhesives have attracted those hemostatic materials due to instantaneous formation of sticky barriers by robust interactions between the material and the serum proteins from wound. However, a critical challenge in such phenolic materials lies in long-term storage due to spontaneous oxidation under humid environments, leading to changes in hemostatic capability and adhesive strength. Here, we report a transparent hemostatic film consisting of gallol-conjugated chitosan (CHI-G) for minimizing the phenolic oxidation even for 3 months and maintaining strong tissue adhesiveness and its hemostatic ability. The film undergoes a phase transition from solid to injectable hydrogels at physiological pH for efficiently stopping internal and external hemorrhage. Interestingly, the hemostatic capability of the CHI-G hydrogels after 3 month storage depends on (i) the folded microstructure of the polymer with optimal gallol modification and (ii) an initial phase of either a solution state or a solid film. When the hydrogels are originated from the dehydrated film, their successful hemostasis is observed in a liver bleeding model. Our finding would provide an insight for design rationale of hemostatic formulations with long shelf-life.

Polyphenol-modified nanovesicles for synergistically enhanced in vitro tumor cell targeting and apoptosis.

Tannic acid (TA) not only prevents drug carriers from sticking to the glycocalyx layer of vascular endothelial cells but also has anti-cancer properties, thereby improving drug delivery efficiency in cancer treatment. This study proposes a TANNylated nanovesicle-based cancer treatment approach by utilizing the aforementioned advantages of TA. We fabricated cancer cell-targeting BC71 peptide-conjugated TANNylated nanovesicles (TANVBC71) by covalently bonding the TA derivative and BC71 (cyclo[ßA-kRK(3-maleimidopropionyl)-D-(D-2-naphthyl)]) with thiol-modified phospholipids through the thiol-maleimide reaction. We demonstrated that TANVBC71 was absorbed faster in high amounts by cancer cells than nanovesicles owing to its high affinity for the epidermal growth factor receptor and extracellular matrix components that are driven by van der Waals attraction as well as hydrogen bonding and hydrophobic interactions in a complex manner. These complex attractions of TANVBC71 for cancer cells led to the effective induction of cancer cell apoptosis. The findings obtained in this study highlight that the TANVBC71 system has the potential for intelligent high-efficacy cancer cell drug delivery.

Molecular Rationale for the Design of Instantaneous, Strain-Tolerant Polymeric Adhesive in a Stretchable Underwater Human-Machine Interface.

Strain-tolerant reversible adhesion under harsh mechanical deformation is important for realizing long-lasting polymeric adhesives. Despite recent advances, cohesive failure within adhesives remains a critical problem that must be solved to achieve adhesion that is robust against humidity, heat, and mechanical stress. Here, we report a molecular rationale for designing an instantaneous polymeric adhesive with high strain tolerance (termed as iPASTE) even in a stretchable human-machine interface. The iPASTE consists of two biocompatible and eco-friendly polymers, linearly oligomerized green tea extracts, and poly(ethylene glycol) for densely assembled networks via dynamic and reversible hydrogen bonds. Other than the typical approach containing nanoclay or branched adhesive precursors, the linear configuration and conformation of such polymer chains within iPASTE lead to strong and moisture-resistant cohesion/adhesion. Based on the strain-tolerant adhesion of iPASTE, it was demonstrated that a subaqueous interactive human-machine interface integrated with a robot arm and a gold nanomembrane strain-sensitive electronic skin can precisely capture a slithery artificial fish by using finger gesture recognition.

Role of Free Catecholamine in Thiol-Ene Crosslinking for Hyaluronic Acid Hydrogels with High Loading Efficiency of Anticancer Drugs.

BACKGROUND: Hyaluronic acid (HA) is a widely used polysaccharide in biomedical field because of its excellent biocompatibility. Its chemical structure can be modified with various functional groups. Recently, dopamine has been tethered onto the polymeric backbone to ensure long-term stability and tissue adhesiveness of HA hydrogel. However, the radical scavenging effect of dopamine on typical photo-induced crosslinking for hydrogels has not been specifically studied. METHODS: Photo-crosslinkable norbornene-modified HA (NorHA) was synthesized and crosslinked by dithiothreitol containing dopamine at different concentrations. During in situ ultraviolet light-triggered crosslinking, storage moduli were monitored using an oscillatory rheometer. Additionally, the amount of thiol utilized for HA crosslinking was investigated under the presence and absence of dopamine. Finally, doxorubicin was encapsulated in the hydrogels, and the drug loading efficiency and release kinetics were measured. RESULTS: Adding dopamine into the NorHA pre-gel solution delayed the gelation time, yet the final storage modulus of the hydrogel remained constant. That is, dopamine might partially consume the energy required for thiol-ene reaction to generate semiquinone radicals. Furthermore, the residual thiols which were not involved in the crosslinking decreased when the hydrogel was formed at a high concentration of dopamine, indicating the formation of Michael adducts of semiquinone and thiols. Interestingly, the presence of dopamine in the hydrogel increased the loading efficiency of the hydrophobic drugs due to π-π stacking and hydrogen bonding between dopamine and drugs. CONCLUSION: The presence of free catecholamines in a photo-crosslinkable polymer can delay the gelation time but improve the drug loading efficiency.

Leptin Induces Epigenetic Regulation of Transient Receptor Potential Melastatin 7 in Rat Adrenal Pheochromocytoma Cells.

Obesity elevates the plasma level of leptin, which has been associated with hypertension. Our recent studies in mice demonstrated that leptin increases blood pressure by activating the carotid sinus nerve, which transmits the chemosensory input from carotid bodies (CBs) to the medullary centers, and that the effect of leptin is mediated via Trpm7 (TRP [transient receptor potential] melastatin 7) channels in CB glomus cells. We also found that Trpm7 overexpression and Trpm7 promoter demethylation in CBs correlate positively with the hyperleptinemia and leptin receptor overexpression in CBs. Hence, we postulated that leptin epigenetically regulates Trpm7 expression in CBs. We addressed our hypothesis by using rat adrenal pheochromocytoma (PC12) cells as a model of CB glomus cells. PC12 cells expressing LEPRb (long, active form of leptin receptor) showed dramatic induction of the promoter activity and expression of Trpm7 upon leptin treatment. The increased Trpm7 expression coincided with the reduction of CpG site-specific methylation and trimethylation of H3K27 (H3 [histone 3] K27 [lysine 27]) and the increase of acetylation of H3K27 and trimethylation of H3K4 (H3 lysine 4) at the Trpm7 promoter. The inhibitor of STAT3 (signal transducer and activator of transcription 3) signaling, SD1008, reversed the leptin-induced Trpm7 promoter activity via modulations of the binding of pSTAT3 (phosphorylated STAT3) and DNMT3B (DNA methyltransferase 3B) and modifications of H3K27 and H3K4 at the Trpm7 promoter. Our results suggest that leptin-activated pSTAT3 epigenetically regulates the transcription of Trpm7 through DNA methylation and histone modifications. Because epigenetic changes are reversible, targeting epigenetic modifications of Trpm7 may serve as a new therapeutic approach for the treatment of hypertension in obesity.

Safety and efficacy evaluations of an adeno-associated virus variant for preparing IL10-secreting human neural stem cell-based therapeutics.

Gene therapy technologies are inevitably required to boost the therapeutic performance of cell therapies; thus, validating the efficacy of gene carriers specifically used for preparing cellular therapeutics is a prerequisite for evaluating the therapeutic capabilities of gene and cell combinatorial therapies. Herein, the efficacy of a recombinant adeno-associated virus derivative (rAAVr3.45) was examined to evaluate its potential as a gene carrier for genetically manipulating interleukin-10 (IL10)-secreting human neural stem cells (hNSCs) that can potentially treat ischemic injuries or neurological disorders. Safety issues that could arise during the virus preparation or viral infection were investigated; no replication-competent AAVs were detected in the final cell suspensions, transgene expression was mostly transient, and no severe interference on endogenous gene expression by viral infection occurred. IL10 secretion from hNSCs infected by rAAVr3.45 encoding IL10 did not alter the transcriptional profile of any gene by more than threefold, but the exogenously boosted IL10 was sufficient to provoke immunomodulatory effects in an ischemic brain injury animal model, thereby accelerating the recovery of neurological deficits and the reduction of brain infarction volume. This study presents evidence that rAAVr3.45 can be potentially used as a gene carrier to prepare stem cell therapeutics.

Leptin acts in the carotid bodies to increase minute ventilation during wakefulness and sleep and augment the hypoxic ventilatory response.

KEY POINTS: Leptin is a potent respiratory stimulant. A long functional isoform of leptin receptor, LepRb , was detected in the carotid body (CB), a key peripheral hypoxia sensor. However, the effect of leptin on minute ventilation (VE ) and the hypoxic ventilatory response (HVR) has not been sufficiently studied. We report that LepRb is present in approximately 74% of the CB glomus cells. Leptin increased carotid sinus nerve activity at baseline and in response to hypoxia in vivo. Subcutaneous infusion of leptin increased VE and HVR in C57BL/6J mice and this effect was abolished by CB denervation. Expression of LepRb in the carotid bodies of LepRb deficient obese db/db mice increased VE during wakefulness and sleep and augmented the HVR. We conclude that leptin acts on LepRb in the CBs to stimulate breathing and HVR, which may protect against sleep disordered breathing in obesity. ABSTRACT: Leptin is a potent respiratory stimulant. The carotid bodies (CB) express the long functional isoform of leptin receptor, LepRb , but the role of leptin in CB has not been fully elucidated. The objectives of the current study were (1) to examine the effect of subcutaneous leptin infusion on minute ventilation (VE ) and the hypoxic ventilatory response to 10% O2 (HVR) in C57BL/6J mice before and after CB denervation; (2) to express LepRb in CB of LepRb -deficient obese db/db mice and examine its effects on breathing during sleep and wakefulness and on HVR. We found that leptin enhanced carotid sinus nerve activity at baseline and in response to 10% O2 in vivo. In C57BL/6J mice, leptin increased VE from 1.1 to 1.5 mL/min/g during normoxia (P < 0.01) and from 3.6 to 4.7 mL/min/g during hypoxia (P < 0.001), augmenting HVR from 0.23 to 0.31 mL/min/g/Δ FIO2 (P < 0.001). The effects of leptin on VE and HVR were abolished by CB denervation. In db/db mice, LepRb expression in CB increased VE from 1.1 to 1.3 mL/min/g during normoxia (P < 0.05) and from 2.8 to 3.2 mL/min/g during hypoxia (P < 0.02), increasing HVR. Compared to control db/db mice, LepRb transfected mice showed significantly higher VE throughout non-rapid eye movement (20.1 vs. -27.7 mL/min respectively, P < 0.05) and rapid eye movement sleep (16.5 vs 23.4 mL/min, P < 0.05). We conclude that leptin acts in CB to augment VE and HVR, which may protect against sleep disordered breathing in obesity.

Gallol-derived ECM-mimetic adhesive bioinks exhibiting temporal shear-thinning and stabilization behavior.

3D bioprinting is an attractive technique to fabricate well-organized, cell-laden constructs for tissue repair and disease modeling. Although numerous hydrogel bioinks have been developed, materials are still needed that mimic the cellular microenvironment, have the appropriate viscosity and stabilization for printing, and are cytocompatible. Here, we present a unique gallol-modified extracellular matrix (ECM) hydrogel ink that is inspired by rapid fruit browning phenomena. The gallol-modification of ECM components (e.g., hyaluronic acid, gelatin) allowed (i) immediate gelation and shear-thinning properties by dynamic hydrogen bonds on short time-scales and (ii) further auto-oxidation and covalent crosslinking for stabilization on longer time-scales. The gallol ECM hydrogel ink was printable using an extrusion-based 3D printer by exploiting temporal shear-thinning properties, and further showed cytocompatibility (∼95% viability) and on-tissue printability due to adhesiveness of gallol moieties. Printed cell-laden filaments degraded and swelled with culture over 6 days, corresponding to increases in cell density and spreading. Ultimately, this strategy is useful for designing hydrogel inks with tunable properties for 3D bioprinting. STATEMENT OF SIGNIFICANCE: 3D bioprinting is a promising technique for the fabrication of cell-laden constructs for applications as in vitro models or for therapeutic applications. Despite the previous development of numerous hydrogel bioinks, there still remain challenging considerations in the design of bioinks. In this study, we present a unique cytocompatible hydrogel ink with gallol modification that is inspired by rapid fruit browning phenomena. The gallol hydrogel ink has three important properties: i) it shows immediate gelation by dynamic, reversible bonds for shear-thinning extrusion, ii) it allows spontaneous stabilization by subsequent covalent crosslinking after printing, and iii) it is printable on tissues by adhesive properties of gallol moieties. As such, this work presents a new approach in the design of hydrogel inks.

Effect of adrenal medullectomy on metabolic responses to chronic intermittent hypoxia in the frequently sampled intravenous glucose tolerance test.

Obstructive sleep apnea is associated with type 2 diabetes. We have previously developed a mouse model of intermittent hypoxia (IH) mimicking oxyhemoglobin desaturations in patients with sleep apnea and have shown that IH increases fasting glucose, hepatic glucose output, and plasma catecholamines. We hypothesize that adrenal medulla modulates glucose responses to IH and that such responses can be prevented by adrenal medullectomy. We performed adrenal medullectomy or sham surgery in lean C57BL/6J mice, which were exposed to IH or intermittent air (control) for 4 wk followed by the frequently sampled intravenous glucose tolerance test (FSIVGTT) in unanesthetized unrestrained animals. IH was administered during the 12-h light phase (9 AM to 9 PM) by decreasing inspired oxygen from 21 to 6.5% 60 cycles/h. Insulin sensitivity (SI), insulin independent glucose disposal [glucose effectiveness (SG)], and the insulin response to glucose (AIRG) were determined using the minimal model method. In contrast to our previous data obtained in restrained mice, IH did not affect fasting blood glucose and plasma insulin levels in sham-operated mice. IH significantly decreased SG but did not affect SI and AIRG Adrenal medullectomy decreased fasting blood glucose and plasma insulin levels and increased glycogen synthesis in the liver in hypoxic mice but did not have a significant effect on the FSIVGTT metrics. We conclude that, in the absence of restraints, IH has no effect on glucose metabolism in lean mice with exception of decreased SG, whereas adrenal medullectomy decreases fasting glucose and insulin levels in the IH environment.NEW & NOTEWORTHY To our knowledge, this is the first study examining the role of adrenal catecholamines in glucose metabolism during intermittent hypoxia (IH) in unanesthetized unrestrained C57BL/6J mice. We report that IH did not affect fasting glucose and insulin levels nor insulin sensitivity and insulin secretion during, whereas glucose effectiveness was decreased. Adrenal medullectomy decreased fasting blood glucose and insulin levels in mice exposed to IH but had no effect on glucose metabolism, insulin secretion, and insulin sensitivity.

Tannic Acid as a Degradable Mucoadhesive Compound.

To achieve site-specific delivery of pharmaceuticals, the development of effective mucoadhesive polymers is essential. Thus far, only a few polymers, such as thiolated ones and related variants, have been studied. However, their mucoadhesiveness varies depending on the type of polymer and the degree of chemical functionalization. Furthermore, the chemistry of tethering often requires harsh reaction conditions. Recently, pyrogallol-containing molecules have emerged as good tissue and hemostatic adhesives, but their in vivo mucoadhesive properties have not been demonstrated. Herein, we found that pyrogallol-rich tannic acid (TA) formulated with poly(ethylene glycol) (PEG), named TAPE, exhibits superior mucoadhesive properties. TAPE is prepared by a simple physical mixture of TA and PEG. It remained on esophageal mucus layers for at least several hours (<8 h) after oral feeding. The mucoadhesion originated from intermolecular interaction between the polyphenols of TA and mucin, exhibiting pH dependency. TAPE adhered strongly to mucin in neutral conditions but bound weakly in acidic conditions due to different hydrolysis rates of the ester linkages in TA. Thus, TAPE might be useful as a long-lasting esophageal mucoadhesive composite.

Lysyl Oxidase as a Serum Biomarker of Liver Fibrosis in Patients with Severe Obesity and Obstructive Sleep Apnea.

STUDY OBJECTIVES: Obstructive sleep apnea (OSA) is associated with the progression of nonalcoholic fatty liver disease (NAFLD). We hypothesized that the hypoxia of OSA increases hepatic production of lysyl oxidase (LOX), an enzyme that cross-links collagen, and that LOX may serve as a biomarker of hepatic fibrosis. DESIGN: Thirty-five patients with severe obesity underwent liver biopsy, polysomnography, and serum LOX testing. A separate group with severe OSA had serum LOX measured before and after 3 mo of CPAP or no therapy, as did age-matched controls. LOX expression and secretion were measured in mouse hepatocytes following exposure to hypoxia. SETTING: The Johns Hopkins Bayview Sleep Disorders Center, and the Hypertension Unit of the Heart Institute at the University of São Paulo Medical School. MEASUREMENTS AND RESULTS: In the bariatric cohort, the apnea-hypopnea index was higher in patients with hepatic fibrosis than in those without fibrosis (42.7 ± 30.2 events/h, versus 16.2 ± 15.5 events/h; P = 0.002), as was serum LOX (84.64 ± 29.71 ng/mL, versus 45.46 ± 17.16 ng/mL; P < 0.001). In the sleep clinic sample, patients with severe OSA had higher baseline LOX than healthy controls (70.75 ng/mL versus 52.36 ng/mL, P = 0.046), and serum LOX decreased in patients with OSA on CPAP (mean decrease 20.49 ng/mL) but not in untreated patients (mean decrease 0.19 ng/mL). Hypoxic mouse hepatocytes demonstrated 5.9-fold increased LOX transcription (P = 0.046), and enhanced LOX protein secretion. CONCLUSIONS: The hypoxic stress of obstructive sleep apnea may increase circulating lysyl oxidase (LOX) levels. LOX may serve as a biomarker of liver fibrosis in patients with severe obesity and nonalcoholic fatty liver disease.

The effect of adrenal medullectomy on metabolic responses to chronic intermittent hypoxia.

Obstructive sleep apnea causes intermittent hypoxia (IH) and is associated with insulin resistance and type 2 diabetes. IH increases plasma catecholamine levels, which may increase insulin resistance and suppress insulin secretion. The objective of this study was to determine if adrenal medullectomy (MED) prevents metabolic dysfunction in IH. MED or sham surgery was performed in 60 male C57BL/6J mice, which were then exposed to IH or control conditions (intermittent air) for 6 weeks. IH increased plasma epinephrine and norepinephrine levels, increased fasting blood glucose and lowered basal and glucose-stimulated insulin secretion. MED decreased baseline epinephrine and prevented the IH induced increase in epinephrine, whereas the norepinephrine response remained intact. MED improved glucose tolerance in mice exposed to IH, attenuated the impairment in basal and glucose-stimulated insulin secretion, but did not prevent IH-induced fasting hyperglycemia or insulin resistance. We conclude that the epinephrine release from the adrenal medulla during IH suppresses insulin secretion causing hyperglycemia.

Carotid body denervation prevents fasting hyperglycemia during chronic intermittent hypoxia.

Obstructive sleep apnea causes chronic intermittent hypoxia (IH) and is associated with impaired glucose metabolism, but mechanisms are unknown. Carotid bodies orchestrate physiological responses to hypoxemia by activating the sympathetic nervous system. Therefore, we hypothesized that carotid body denervation would abolish glucose intolerance and insulin resistance induced by chronic IH. Male C57BL/6J mice underwent carotid sinus nerve dissection (CSND) or sham surgery and then were exposed to IH or intermittent air (IA) for 4 or 6 wk. Hypoxia was administered by decreasing a fraction of inspired oxygen from 20.9% to 6.5% once per minute, during the 12-h light phase (9 a.m.-9 p.m.). As expected, denervated mice exhibited blunted hypoxic ventilatory responses. In sham-operated mice, IH increased fasting blood glucose, baseline hepatic glucose output (HGO), and expression of a rate-liming hepatic enzyme of gluconeogenesis phosphoenolpyruvate carboxykinase (PEPCK), whereas the whole body glucose flux during hyperinsulinemic euglycemic clamp was not changed. IH did not affect glucose tolerance after adjustment for fasting hyperglycemia in the intraperitoneal glucose tolerance test. CSND prevented IH-induced fasting hyperglycemia and increases in baseline HGO and liver PEPCK expression. CSND trended to augment the insulin-stimulated glucose flux and enhanced liver Akt phosphorylation at both hypoxic and normoxic conditions. IH increased serum epinephrine levels and liver sympathetic innervation, and both increases were abolished by CSND. We conclude that chronic IH induces fasting hyperglycemia increasing baseline HGO via the CSN sympathetic output from carotid body chemoreceptors, but does not significantly impair whole body insulin sensitivity.

Chronic intermittent hypoxia induces atherosclerosis via activation of adipose angiopoietin-like 4.

RATIONALE: Obstructive sleep apnea is a risk factor for dyslipidemia and atherosclerosis, which have been attributed to chronic intermittent hypoxia (CIH). Intermittent hypoxia inhibits a key enzyme of lipoprotein clearance, lipoprotein lipase, and up-regulates a lipoprotein lipase inhibitor, angiopoietin-like 4 (Angptl4), in adipose tissue. The effects and mechanisms of Angptl4 up-regulation in sleep apnea are unknown. OBJECTIVES: To examine whether CIH induces dyslipidemia and atherosclerosis by increasing adipose Angptl4 via hypoxia-inducible factor-1 (HIF-1). METHODS: ApoE(-/-) mice were exposed to intermittent hypoxia or air for 4 weeks while being treated with Angptl4-neutralizing antibody or vehicle. MEASUREMENTS AND MAIN RESULTS: In vehicle-treated mice, hypoxia increased adipose Angptl4 levels, inhibited adipose lipoprotein lipase, increased fasting levels of plasma triglycerides and very low density lipoprotein cholesterol, and increased the size of atherosclerotic plaques. The effects of CIH were abolished by the antibody. Hypoxia-induced increases in plasma fasting triglycerides and adipose Angptl4 were not observed in mice with germline heterozygosity for a HIF-1α knockout allele. Transgenic overexpression of HIF-1α in adipose tissue led to dyslipidemia and increased levels of adipose Angptl4. In cultured adipocytes, constitutive expression of HIF-1α increased Angptl4 levels, which was abolished by siRNA. Finally, in obese patients undergoing bariatric surgery, the severity of nocturnal hypoxemia predicted Angptl4 levels in subcutaneous adipose tissue. CONCLUSIONS: HIF-1-mediated increase in adipose Angptl4 and the ensuing lipoprotein lipase inactivation may contribute to atherosclerosis in patients with sleep apnea.