Scoring system for poor limb perfusion after limb fracture in children

BACKGROUND

Assessment of the vascular status following limb fracture in children is important to evaluate the risk of compartment syndrome, which is an emergency condition.

AIM

To establish a simple and efficient grading scale of limb perfusion in children undergoing surgery for limb fracture.

METHODS

This retrospective study included pediatric patients with a limb fracture and postoperative plaster fixation who were admitted at The Department of Pediatric Orthopedics of Xinhua Hospital between February 2017 and August 2017. The outcome was poor limb perfusion, which is defined as the postoperative use of mannitol. The children were divided into two groups: The normal perfusion group and the poor perfusion group. Key risk factors have been selected by univariable analyses to establish the Grading Scale for Vascular Status.

RESULTS

A total of 161 patients were included in the study: 85 in the normal perfusion group and 76 in the poor perfusion group. There were no significant differences in age, sex, body mass index, ethnicity, cause of fracture, fixation, or site of fracture between the two groups. After surgery, the skin temperature (P = 0.048) and skin color (P < 0.001) of the affected limb were significantly different between the two groups. The relative risk and 95% confidence interval for skin temperature of the affected limb, skin color, and range of motion of the affected limb are 2.18 (1.84-2.59), 2.89 (2.28-3.66), and 2.16 (1.83-2.56), respectively. The grading scale was established based on those three factors (score range: 0-3 points). Forty-one patients (32.5%) with score 0 had poor limb perfusion; all patients with scores 1 (n = 32) and 2 (n = 3) had poor limb perfusion (both 100%).

CONCLUSION

In children undergoing surgery for limb fracture, a higher Grading Scale for Vascular Status score is associated with a higher occurrence of poor limb perfusion. A prospective study is required for validation.

Cobalt Nanoparticles-Catalyzed Widely Applicable Successive C-C Bond Cleavage in Alcohols to Access Esters

Selective cleavage and functionalization of C-C bonds have important applications in organic synthesis and biomass utilization. However, functionalization of C-C bonds by controlled cleavage remains difficult and challenging because they are inert. Herein, we describe an unprecedented efficient protocol for the breaking of successive C-C bonds in alcohols to form esters with one or multiple carbon atoms less using heterogeneous cobalt nanoparticles as catalyst with dioxygen as the oxidant. A wide range of alcohols including inactive long-chain alkyl aryl alcohols undergo smoothly successive cleavage of adjacent -(C-C)_n - bonds to afford the corresponding esters. The catalyst was used for seven times without any decrease in activity. Characterization and control experiments disclose that cobalt nanoparticles are responsible for the successive cleavage of C-C bonds to achieve excellent catalytic activity, while the presence of Co-N_x has just the opposite effect. Preliminary mechanistic studies reveal that a tandem sequence reaction is involved in this process.

Value of serum collagen triple helix repeat containing-1(CTHRC1) and 14-3-3η protein compared to anti-CCP antibodies and anti-MCV antibodies in the diagnosis of rheumatoid arthritis

INTRODUCTION

Serological markers are important in the diagnosis of rheumatoid arthritis (RA) and other connective tissues diseases This study explored the clinical value of collagen triple helix repeat containing-1 (CTHRC1) and 14-3-3η protein, compared to routine markers, in the diagnosis of RA.

METHODS

We recruited 103 RA patients, 105 non-RA patients (osteoarthritis, ankylosing spondylitis, systemic lupus erythematosus) and 59 healthy controls. CTHRC1, 14-3-3η, anti-cyclic citrullinated peptide antibody (anti-CCP), anti-mutated citrullinated vimentin antibody (anti-MCV), rheumatoid factor and erythrocyte sedimentation rate (ESR) levels were measured, and their diagnostic value for RA evaluated and compared.

RESULTS

All laboratory indices were elevated in RA (P < 0.05). Of these, anti-MCV had the highest sensitivity (86.4%) and anti-CCP the highest specificity (94.5%). The areas under the curve (AUC) of CTHRC1, 14-3-3η, anti-CCP, anti-MCV, rheumatoid factor and ESR were 0.84, 0.81, 0.89, 0.91, 0.85 and 0.77 respectively (all P < 0.01). Anti-CCP and anti-MCV were the most valuable in the diagnosis of RA. The combination of anti-CCP and anti-MCV had the maximum Youden index, followed by the combination of anti-CCP and 14-3-3η. Binary logistic regression analysis showed that 14-3-3η had the largest odds ratio value (95% CI) at 5.1 (2.1-12.5) for RA.

CONCLUSION

CTHRC1 and 14-3-3η are promising serological indicators of RA, and when combined with anti-CCP, anti-MCV and ESR, can improve the diagnosis of this disease.

Comparison of Application Biological Variation and Patient Data for Selecting Delta Check Limits

BACKGROUND

This study aimed to evaluate delta check limits set by reference change value (RCV) and patient data.

METHODS

Patient data of 11 clinical chemistry analytes from June 2018 to May 2019 were collected. RCV with 95% or 99% levels of probability were calculated based on biological variation. The corresponding delta check limits for outpatients and inpatients were calculated by 95% or 99% central range of delta% which was the difference of two consecutive results within thirty days of the same patient for each analyte. Patient data in June 2019 were used to analyze the utility of delta check limits.

RESULTS

In total, 434,927 paired results for these 11 analytes were included. The delta check limits were different between outpatients and inpatients, but were wider than those established by RCV. The difference between Glu's outpatient and inpatient boundaries was the largest, 95% central range from the outpatient (inpatients) was from -32.29% (-56.97%) to 38.78% (106.00%) while 99% central range from the outpatient (inpatients) was from -56.86% (-90.56%) to 89.96% (262.54%). The RCV is mainly determined by within-individual biological variation so that the RCV of each analyte varied from each other. As for RCV, Na had the lowest value and BUN had the highest one. In addition, the main reason for delta% exceeding delta check limits was a clinically significant change.

CONCLUSIONS

Laboratories could use delta check procedure to find out errors in sample collection and monitor clinical significance. When delta% of patients exceed corresponding delta check limits in a short time, clinicians and personnel of clinical laboratory should pay more attention. Delta check limits should be reviewed regularly to check the utility of procedure.

Associations between the IL-6-neutralizing sIL-6R-sgp130 buffer system and coronary artery disease in postmenopausal women

Background

As a major inflammatory pathway in coronary artery disease (CAD), IL-6 trans-signaling is activated by the IL-6: sIL-6Rα binary complex (B) and inhibited by sgp130 through forming the IL-6: sIL-6Rα: sgp130 ternary complex (T). The aim of the present study was to examine the possible relationship between biomarkers mirroring the IL-6-neutralizing sIL-6R-sgp130 buffer system and CAD in postmenopausal women.

Methods

Our study recruited 155 CAD patients and 181 controls among postmenopausal women. Circulating levels of IL-6, sIL-6Rα and sgp130 were detected using an enzyme-linked immunosorbent assay, and the B/T ratio was calculated by the specific formulas.

Results

CAD patients showed significantly higher circulating levels of IL-6 and sIL-6Rα, significantly higher B/T ratio, and significantly lower sgp130 levels than controls (all P<0.05). Spearman’s correlation analysis indicated that IL-6 levels (r=0.185, P<0.01) and B/T ratio (r=0.319, P<0.01) were positively related to Gensini scores, while elevated sgp130 levels were significantly associated with decreased Gensini scores (r=−0.565, P<0.001). In addition, multiple regression analysis showed that Gensini scores were negatively associated with serum sgp130 levels (β-coefficient =−0.318, P<0.001) and had a positive association with IL-6 levels (β-coefficient =0.138, P<0.05). Multivariate logistic regression analysis identified that after adjusting for confounding factors, higher sgp130 remained an independent predictor of lower incidence of CAD in women after menopause (OR =0.904; 95% CI: 0.837–0.976, P=0.010). Moreover, sgp130 levels at 136.01 ng/mL (AUC =0.957, 95% CI: 0.928–0.986, P<0.001) and B/T ratio at 1.51 (AUC =0.765; 95% CI: 0.702–0.828, P<0.001) were effective cut-off points to determine the presence of CAD based on receiver operating characteristic curves.

Conclusions

Based on this small case-control study, sgp130 and B/T ratio in the IL-6-neutralizing sIL-6R-sgp130 buffer system may be promising biomarkers for CAD diagnosis and assessments of coronary stenosis severity in postmenopausal women.

Porphyromonas gingivalis Promotes Oral Squamous Cell Carcinoma Progression in an Immune Microenvironment

Increasing evidence has revealed a significant association between microorganisms and oral squamous cell carcinoma (OSCC). Porphyromonas gingivalis, the keystone pathogen in chronic periodontitis, is considered an important potential etiologic agent of OSCC, but the underlying immune mechanisms through which P. gingivalis mediates tumor progression of the oral cancer remain poorly understood. Our cohort study showed that the localization of P. gingivalis in tumor tissues was related to poor survival of patients with OSCC. Moreover, P. gingivalis infection increased oral lesion multiplicity and size and promoted tumor progression in a 4-nitroquinoline-1 oxide (4NQO)–induced carcinogenesis mouse model by invading the oral lesions. In addition, CD11b+ myeloid cells and myeloid-derived suppressor cells (MDSCs) showed increased infiltration of oral lesions. Furthermore, in vitro observations showed that MDSCs accumulated when human-derived dysplastic oral keratinocytes (DOKs) were exposed to P. gingivalis, and CXCL2, CCL2, interleukin (IL)–6, and IL-8 may be potential candidate genes that facilitate the recruitment of MDSCs. Taken together, our findings suggest that P. gingivalis promotes tumor progression by generating a cancer-promoting microenvironment, indicating a close relationship among P. gingivalis, tumor progression of the oral cancer, and immune responses.

Demonstration of Controlled-Phase Gates between Two Error-Correctable Photonic Qubits

To realize fault-tolerant quantum computing, it is necessary to store quantum information in logical qubits with error correction functions, realized by distributing a logical state among multiple physical qubits or by encoding it in the Hilbert space of a high-dimensional system. Quantum gate operations between these error-correctable logical qubits, which are essential for implementation of any practical quantum computational task, have not been experimentally demonstrated yet. Here we demonstrate a geometric method for realizing controlled-phase gates between two logical qubits encoded in photonic fields stored in cavities. The gates are realized by dispersively coupling an ancillary superconducting qubit to these cavities and driving it to make a cyclic evolution depending on the joint photonic state of the cavities, which produces a conditional geometric phase. We first realize phase gates for photonic qubits with the logical basis states encoded in two quasiorthogonal coherent states, which have important implications for continuous-variable-based quantum computation. Then we use this geometric method to implement a controlled-phase gate between two binomially encoded logical qubits, which have an error-correctable function.

1,4-Hydroboration Reactions of Electron-Poor Aromatic Rings by N-Heterocyclic Carbene Boranes

Reactions of N-heterocyclic carbene boranes (NHC-boranes) with electron-poor aromatic rings under photoredox conditions provide dearomatized 3-NHC-boryl-1,5-cycohexadienes, which are formally products of 1,4-hydroboration reactions. When regioisomers are possible, the more crowded (doubly ortho-substituted) product is formed preferably or exclusively. The mechanism may involve oxidation of the NHC-borane to an NHC-boryl radical, reduction of the electron-poor aromatic ring to a radical anion, coupling of the radical and the radical anion to give a cyclohexadienyl anion, and finally regioselective protonation.

EPR Studies on the Addition of Ligated Boryl Radicals to Carbonyl Compounds

The boron-centered radicals derived from alkenyl N-heterocyclic carbene (NHC)-boranes bearing ester substituents were recently found to ring close in 5-endo mode by addition to the oxygen atoms of the ester substituents. The inference from this was that NHC-boryl radicals might add intermolecularly to carbonyl-containing substrates. Several different NHC-boryl radicals were generated by H-atom abstraction from NHC-ligated trihydroborates. Electron paramagnetic resonance (EPR) spectroscopy proved that these did indeed add to the oxygen atoms of diaryl ketones with production of the corresponding bora-ketyl radicals. The same unusual regioselectivity of addition was observed with monoaryl ketones, but no bora-ketyls were observed with dialkyl ketones. Similarly, no bora-ketyl adduct radicals were observed with esters, even esters of benzoic acid. EPR spectroscopic evidence suggested that NHC-boryl radicals were also added to the O-atoms of aromatic aldehydes. Amine-boryl and phosphine-boryl radicals were also observed to add to the O-atom of benzophenone with production of the corresponding ketyl radicals.

Multifunctional nanocomposites MGO/FU-MI inhibit the proliferation of tumor cells and enhance the effect of chemoradiotherapy in vivo and in vitro

PURPOSE

The limitation of surgery, radiotherapy and chemotherapy in the treatment of cancer and the rise of the application of nanomaterials in the field of biomedicine have promoted the application of various nanomaterials in the combination of radiotherapy and chemotherapy in the treatment of cancer. To improve the efficiency of cancer treatment, the multifunctional nanocomposites MGO/FU-MI (MGO/FU-MI NCs) were used for combination chemotherapy and radiotherapy to verify its effectiveness in treating tumors.

METHODS

The proliferation activity of MGO/FU-MI NCs on MC-38 and B16 cells was detected by CCK-8, and the level of apoptosis and reactive oxygen species were detected by flow cytometry. To verify its efficacy in the combination of chemoradiotherapy, different treatment regimens were developed for several groups of tumor-bearing mice.

RESULTS

The MGO/FU-MI NCs can induce apoptosis, stimulate ROS production, and inhibit cell proliferation. In vivo experiments, when MGO/FU-MI NCs are used alone for chemotherapy, have a certain therapeutic effect on mouse tumors. When MGO/FU-MI NCs are combined with radiation, the tumor volume can be significantly reduced and the survival time of mice is significantly prolonged.

CONCLUSION

The MGO/FU-MI NCs are very effective in the treatment of tumors when combined with radiotherapy and chemotherapy, and have the potential to be a combination of radiotherapy and chemotherapy.

[Spatio-temporal distribution of Oncomelania hupensis snails along the Danyang section of the Beijing-Hangzhou Grand Canal and the Danyang-Jintan-Liyang Canal]

OBJECTIVE

To explore the spatio-temporal characteristics of Oncomelania hupensis snails along the Danyang section of the Beijing-Hangzhou Grand Canal and the Danyang-Jintan-Liyang Canal, so as to provide scientific evidence for the dynamic assessment of the risk of snail spread in this region.

METHODS

O. hupensis snail status was collected in the plain regions with waterway networks in the study area from 2012 to 2017. The spatio-temporal variations of snail distribution were investigated along the Danyang section of the Beijing-Hangzhou Grand Canal and the Danyang-Jintan-Liyang Canal using buffer zone analysis, spatial autocorrelation, hotspot analysis and standard deviational ellipse with the geographical information system (GIS) tools.

RESULTS

The number of snail habitats showed a tendency towards a rise in the study area from 2012 to 2017, and snail habitats were predominantly distributed in the 1 000 m long buffer zone of the Danyang-Jintan-Liyang Canal, notably along the Jiuqu River at the junction between the Beijing-Hangzhou Grand Canal and the Danyang-Jintan-Liyang Canal. The distribution of snail habitats appeared spatial autocorrelations in 2014, 2016 and 2017, and the hotspot areas were mainly identified at the junction between the Danyang-Jintan-Liyang Canal and the Beijing-Hangzhou Grand Canal. In addition, the overall distribution of snail habitats was located in the northeastern-southwestern part of the study aera, and gradually shifted to the southern and northern parts with the time.

CONCLUSIONS

The spatial distribution of O. hupensis snails is complex along the Danyang section of the Beijing-Hangzhou Grand Canal and the Danyang-Jintan-Liyang Canal, and there is a risk of snail spread from the upper reaches to the lower reaches, where snail control needs to be intensified.

Genetic variants in the folate metabolic pathway genes predict cutaneous melanoma-specific survival

BACKGROUND

Folate metabolism plays an important role in DNA methylation and nucleic acid synthesis and thus may function as a regulatory factor in cancer development. Genome-wide association studies (GWASs) have identified some single-nucleotide polymorphisms (SNPs) associated with cutaneous melanoma-specific survival (CMSS), but no SNPs were found in genes involved in the folate metabolic pathway.

OBJECTIVES

To examine associations between SNPs in folate metabolic pathway genes and CMSS.

METHODS

We comprehensively evaluated 2645 (422 genotyped and 2223 imputed) common SNPs in folate metabolic pathway genes from a published GWAS of 858 patients from The University of Texas MD Anderson Cancer Center and performed the validation in another GWAS of 409 patients from the Nurses' Health Study and Health Professionals Follow-up Study, in which 95/858 (11·1%) and 48/409 (11·7%) patients died of cutaneous melanoma, respectively.

RESULTS

We identified two independent SNPs (MTHFD1 rs1950902 G>A and ALPL rs10917006 C>T) to be associated with CMSS in both datasets, and their meta-analysis yielded an allelic hazards ratio of 1·75 (95% confidence interval 1·32-2·32, P = 9·96 × 10^-5 ) and 2·05 (1·39-3·01, P = 2·84 × 10^-4 ), respectively. The genotype-phenotype correlation analyses provided additional support for the biological plausibility of these two variants' roles in tumour progression, suggesting that variation in SNP-related mRNA expression levels is likely to be the mechanism underlying the observed associations with CMSS.

CONCLUSIONS

Two possibly functional genetic variants, MTHFD1 rs1950902 and ALPL rs10917006, were likely to be independently or jointly associated with CMSS, which may add to personalized treatment in the future, once further validated. What is already known about this topic? Existing data show that survival rates vary among patients with melanoma with similar clinical characteristics; therefore, it is necessary to identify additional complementary biomarkers for melanoma-specific prognosis. A hypothesis-driven approach, by pooling the effects of single-nucleotide polymorphisms (SNPs) in a specific biological pathway as genetic risk scores, may provide a prognostic utility, and genetic variants of genes in folate metabolism have been reported to be associated with cancer risk. What does this study add? Two genetic variants in the folate metabolic pathway genes, MTHFD1 rs1950902 and ALPL rs10917006, are significantly associated with cutaneous melanoma-specific survival (CMSS). What is the translational message? The identification of genetic variants will make a risk-prediction model possible for CMSS. The SNPs in the folate metabolic pathway genes, once validated in larger studies, may be useful in the personalized management and treatment of patients with cutaneous melanoma.

Next-generation sequencing of cerebrospinal fluid for the diagnosis of neurocysticercosis

OBJECTIVE

Neurocysticercosis (NCC) is the most common parasitic disease of the human central nervous system (CNS). However, a diagnosis of NCC may be hard to make if the specific clinical and routine neuroimaging manifestations are lacking, which hinders physicians from considering further immunodiagnostic tests.

PATIENTS AND METHODS

Seven patients presented with fever, headache, nausea, cognitive decline, confusion, or progressive leg weakness. There were no pathogens found in the cerebrospinal fluid (CSF); patients were clinically suspected of meningoencephalitis or cerebrovascular disease. To clearly determine the etiology, next generation sequencing (NGS) of the CSF was used to detect pathogens in these seven patients.

RESULTS

Taenia solium DNA sequences were detected in the seven patients, but not in the non-template controls (NTCs) or the other patients with clinically suspected CNS infections. Based on the patients' medical data and the diagnostic criteria for NCC, seven patients were diagnosed with probable NCC. The unique reads aligning to Taenia solium ranged from 6 to 261064, with genomic coverage ranging from 0.0003% to 14.8079%. The number of unique reads and genomic coverage dropped in three of the seven patients after antiparasitic treatment, consistent with the relief of symptoms.

CONCLUSION

This study showed that NGS of the CSF might be an auxiliary diagnostic method for NCC patients. Larger studies are required.

The association of serum total bile acid with non-alcoholic fatty liver disease in Chinese adults: a cross sectional study

Background

Non-alcoholic fatty liver disease (NAFLD) is currently the major cause of chronic liver disease globally. Bile acids (BAs) have emerged as relevant signaling molecules that are associated with NAFLD development. This study was aimed to examine the association of serum total bile acids (TBAs) with NAFLD in a large population of Chinese subjects.

Methods

This cross sectional study recruited 152,336 participants from the Second Xiangya Hospital, China. NAFLD was diagnosed based on the presence of hepatic steatosis on ultrasonography, without significant alcohol consumption and other known causes for chronic liver disease. A multivariate logistic regression model was used to test for the association of serum TBAs with NAFLD, adjusting for conventional risk factors of NAFLD.

Results

A total of 27.4% of the participants had NAFLD. Patients with NAFLD had slightly higher TBA levels than those without, 3.4 vs. 3.0 μmol/L (p < 0.001). However, TBA levels were not associated with NAFLD in the multivariate logistic regression model, which adjusted for age, gender and other acknowledged risk factors for NAFLD (OR = 1.00. 95% CI: 1.00–1.00, p = 0.797).

Conclusions

We found that the serum TBA levels were not associated with NAFLD. Future studies in a large population, focusing on serum BA composition may improve the understating of the role of BAs in NAFLD.

Theoretical screening of efficient single-atom catalysts for nitrogen fixation based on a defective BN monolayer

The electrocatalytic reduction of naturally abundant N2 to NH3 is an attractive approach to replace the Haber-Bosch nitrogen-fixation process that causes enormous energy consumption and greenhouse gas emissions. However, designing high-performance catalysts toward the electrocatalytic N2 reduction reaction (eNRR) remains one of the greatest challenges in this area. Herein, high-throughput screening of catalysts for the NRR among a series of transition metal atoms supported on a defective hexagonal boron nitride (h-BN) nanosheet is performed through spin-polarized density functional theory (DFT) computations. Strikingly, among the 18 candidates, the V/Tc atom anchored on a defective h-BN monolayer (V@BN and Tc@BN) showed good NRR activity with relatively low onset potentials. Particularly, V@BN was found to exhibit outstanding catalytic activity for the NRR via an enzymatic pathway with an extremely low overpotential of 0.25 V. The value is significantly lower than that on the Ru (0001) stepped surface that has the best NRR catalytic performance among bulk metal catalysts. The novel NRR activity of V@BN is attributed to the enhanced electrical conductivity due to V-doping, the "donation-backdonation" process for N2 activation, and the highly centralized spin-polarization on the V atom. This work not only provides a quite promising catalyst for the NRR but also provides new insights for the rational design of single-atom NRR catalysts.

Estrogen downregulates gp130 expression in HUVECs by regulating ADAM10 and ADAM17 via the estrogen receptor

Glycoprotein130 (gp130) is an important signal transducer in the interleukin-6 (IL-6) trans-signaling pathway, which plays a crucial role in chronic inflammation in atherosclerosis. Studies suggest that estrogen can inhibit IL-6/gp130 signaling and reduce the risk of coronary artery disease, but the precise mechanism is unclear. The aim of this study was to investigate whether and how estrogen regulates gp130 in human umbilical vein endothelial cells (HUVECs). HUVECs were first treated with IL-6 and soluble IL-6 receptor (sIL-6R) to induce inflammation, then treated with estradiol. We then measured the expression of gp130, a disintegrin and metalloproteinase 10 (ADAM10) and 17 (ADAM17) by RT-PCR and western blot. Levels of soluble gp130 (sgp130) in the culture supernatant were measured by ELISA. We found that IL-6 and sIL-6R increased expression of gp130 protein and decreased levels of sgp130 protein, without affecting gp130 mRNA levels. Estradiol treatment reversed these effects in a concentration- and time-dependent manner. These effects were regulated by ADAM10 and ADAM17 via an estrogen receptor α/β-dependent mechanism. These results shed further light on the mechanism underlying the clinical effects of estrogen therapy in atherosclerosis and coronary artery disease.

Metal-Level Thermally Conductive yet Soft Graphene Thermal Interface Materials

Along with the technology evolution for dense integration of high-power, high-frequency devices in electronics, the accompanying interfacial heat transfer problem leads to urgent demands for advanced thermal interface materials (TIMs) with both high through-plane thermal conductivity and good compressibility. Most metals have satisfactory thermal conductivity but relatively high compressive modulus, and soft silicones are typically thermal insulators (0.3 W m^-1 K^-1). Currently, it is a great challenge to develop a soft material with the thermal conductivity up to metal level for TIM application. This study solves this problem by constructing a graphene-based microstructure composed of mainly vertical graphene and a thin cap of horizontal graphene layers on both the top and bottom sides through a mechanical machining process to manipulate the stacked architecture of conventional graphene paper. The resultant graphene monolith has an ultrahigh through-plane thermal conductivity of 143 W m^-1 K^-1, exceeding that of many metals, and a low compressive modulus of 0.87 MPa, comparable to that of silicones. In the actual TIM performance measurement, the system cooling efficiency with our graphene monolith as TIM is 3 times as high as that of the state-of-the-art commercial TIM, demonstrating the superior ability to solve the interfacial heat transfer issues in electronic systems.

Hepatic Glucagon Signaling Regulates PCSK9 and Low-Density Lipoprotein Cholesterol

RATIONALE

Glucagon is a key hormone that regulates the adaptive metabolic responses to fasting. In addition to maintaining glucose homeostasis, glucagon participates in the regulation of cholesterol metabolism; however, the molecular pathways underlying this effect are incompletely understood.

OBJECTIVE

We sought to determine the role of hepatic Gcgr (glucagon receptor) signaling in plasma cholesterol regulation and identify its underlying molecular mechanisms.

METHODS AND RESULTS

We show that Gcgr signaling plays an essential role in LDL-C (low-density lipoprotein cholesterol) homeostasis through regulating the PCSK9 (proprotein convertase subtilisin/kexin type 9) levels. Silencing of hepatic Gcgr or inhibition of glucagon action increased hepatic and plasma PCSK9 and resulted in lower LDLR (LDL receptor) protein and increased plasma LDL-C. Conversely, treatment of wild-type (WT) mice with glucagon lowered LDL-C levels, whereas this response was abrogated in Pcsk9^-/- and Ldlr^-/- mice. Our gain- and loss-of-function studies identified Epac2 (exchange protein activated by cAMP-2) and Rap1 (Ras-related protein-1) as the downstream mediators of glucagon's action on PCSK9 homeostasis. Moreover, mechanistic studies revealed that glucagon affected the half-life of PCSK9 protein without changing the level of its mRNA, indicating that Gcgr signaling regulates PCSK9 degradation.

CONCLUSIONS

These findings provide novel insights into the molecular interplay between hepatic glucagon signaling and lipid metabolism and describe a new posttranscriptional mechanism of PCSK9 regulation.

Graphene foam-embedded epoxy composites with significant thermal conductivity enhancement

High thermal conductivity polymer composites at low filler loading are of considerable interest because of their wide range of applications. The construction of three-dimensional (3D) interconnected networks can offer a high-efficiency increase for the thermal conductivity of polymer composites. In this work, a facile and scalable method to prepare graphene foam (GF) via sacrificial commercial polyurethane (PU) sponge templates was developed. Highly thermally conductive composites were then prepared by impregnating epoxy resin into the GF structure. An ultrahigh thermal conductivity of 8.04 W m-1 K-1 was obtained at a low graphene loading of 6.8 wt%, which corresponds to a thermal conductivity enhancement of about 4473% compared to neat epoxy. This strategy provides a facile, low-cost and scalable method to construct a 3D filler network for high-performance composites with potential to be used in advanced electronic packaging.