NF-κB-inducing kinase maintains T cell metabolic fitness in antitumor immunity.

Metabolic reprograming toward aerobic glycolysis is a pivotal mechanism shaping immune responses. Here we show that deficiency in NF-κB-inducing kinase (NIK) impairs glycolysis induction, rendering CD8+ effector T cells hypofunctional in the tumor microenvironment. Conversely, ectopic expression of NIK promotes CD8+ T cell metabolism and effector function, thereby profoundly enhancing antitumor immunity and improving the efficacy of T cell adoptive therapy. NIK regulates T cell metabolism via a NF-κB-independent mechanism that involves stabilization of hexokinase 2 (HK2), a rate-limiting enzyme of the glycolytic pathway. NIK prevents autophagic degradation of HK2 through controlling cellular reactive oxygen species levels, which in turn involves modulation of glucose-6-phosphate dehydrogenase (G6PD), an enzyme that mediates production of the antioxidant NADPH. We show that the G6PD-NADPH redox system is important for HK2 stability and metabolism in activated T cells. These findings establish NIK as a pivotal regulator of T cell metabolism and highlight a post-translational mechanism of metabolic regulation.

Activation of invariant natural killer T cells stimulates adipose tissue remodeling via adipocyte death and birth in obesity.

In obesity, adipose tissue undergoes dynamic remodeling processes such as adipocyte hypertrophy, hypoxia, immune responses, and adipocyte death. However, whether and how invariant natural killer T (iNKT) cells contribute to adipose tissue remodeling are elusive. In this study, we demonstrate that iNKT cells remove unhealthy adipocytes and stimulate the differentiation of healthy adipocytes. In obese adipose tissue, iNKT cells were abundantly found nearby dead adipocytes. FasL-positive adipose iNKT cells exerted cytotoxic effects to eliminate hypertrophic and pro-inflammatory Fas-positive adipocytes. Furthermore, in vivo adipocyte-lineage tracing mice model showed that activation of iNKT cells by alpha-galactosylceramide promoted adipocyte turnover, eventually leading to potentiation of the insulin-dependent glucose uptake ability in adipose tissue. Collectively, our data propose a novel role of adipose iNKT cells in the regulation of adipocyte turnover in obesity.

DNMT1 maintains metabolic fitness of adipocytes through acting as an epigenetic safeguard of mitochondrial dynamics.

White adipose tissue (WAT) is a key regulator of systemic energy metabolism, and impaired WAT plasticity characterized by enlargement of preexisting adipocytes associates with WAT dysfunction, obesity, and metabolic complications. However, the mechanisms that retain proper adipose tissue plasticity required for metabolic fitness are unclear. Here, we comprehensively showed that adipocyte-specific DNA methylation, manifested in enhancers and CTCF sites, directs distal enhancer-mediated transcriptomic features required to conserve metabolic functions of white adipocytes. Particularly, genetic ablation of adipocyte Dnmt1, the major methylation writer, led to increased adiposity characterized by increased adipocyte hypertrophy along with reduced expansion of adipocyte precursors (APs). These effects of Dnmt1 deficiency provoked systemic hyperlipidemia and impaired energy metabolism both in lean and obese mice. Mechanistically, Dnmt1 deficiency abrogated mitochondrial bioenergetics by inhibiting mitochondrial fission and promoted aberrant lipid metabolism in adipocytes, rendering adipocyte hypertrophy and WAT dysfunction. Dnmt1-dependent DNA methylation prevented aberrant CTCF binding and, in turn, sustained the proper chromosome architecture to permit interactions between enhancer and dynamin-1-like protein gene Dnm1l (Drp1) in adipocytes. Also, adipose DNMT1 expression inversely correlated with adiposity and markers of metabolic health but positively correlated with AP-specific markers in obese human subjects. Thus, these findings support strategies utilizing Dnmt1 action on mitochondrial bioenergetics in adipocytes to combat obesity and related metabolic pathology.

The adaptor protein APPL2 controls glucose-stimulated insulin secretion via F-actin remodeling in pancreatic ß-cells.

Filamentous actin (F-actin) cytoskeletal remodeling is critical for glucose-stimulated insulin secretion (GSIS) in pancreatic ß-cells, and its dysregulation causes type 2 diabetes. The adaptor protein APPL1 promotes first-phase GSIS by up-regulating soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) protein expression. However, whether APPL2 (a close homology of APPL1 with the same domain organization) plays a role in ß-cell functions is unknown. Here, we show that APPL2 enhances GSIS by promoting F-actin remodeling via the small GTPase Rac1 in pancreatic ß-cells. ß-cell specific abrogation of APPL2 impaired GSIS, leading to glucose intolerance in mice. APPL2 deficiency largely abolished glucose-induced first- and second-phase insulin secretion in pancreatic islets. Real-time live-cell imaging and phalloidin staining revealed that APPL2 deficiency abolished glucose-induced F-actin depolymerization in pancreatic islets. Likewise, knockdown of APPL2 expression impaired glucose-stimulated F-actin depolymerization and subsequent insulin secretion in INS-1E cells, which were attributable to the impairment of Ras-related C3 botulinum toxin substrate 1 (Rac1) activation. Treatment with the F-actin depolymerization chemical compounds or overexpression of gelsolin (a F-actin remodeling protein) rescued APPL2 deficiency-induced defective GSIS. In addition, APPL2 interacted with Rac GTPase activating protein 1 (RacGAP1) in a glucose-dependent manner via the bin/amphiphysin/rvs-pleckstrin homology (BAR-PH) domain of APPL2 in INS-1E cells and HEK293 cells. Concomitant knockdown of RacGAP1 expression reverted APPL2 deficiency-induced defective GSIS, F-actin remodeling, and Rac1 activation in INS-1E cells. Our data indicate that APPL2 interacts with RacGAP1 and suppresses its negative action on Rac1 activity and F-actin depolymerization thereby enhancing GSIS in pancreatic ß-cells.

The Profile of Early Sedation Depth and Clinical Outcomes of Mechanically Ventilated Patients in Korea.

BACKGROUND: Current international guidelines recommend against deep sedation as it is associated with worse outcomes in the intensive care unit (ICU). However, in Korea the prevalence of deep sedation and its impact on patients in the ICU are not well known. METHODS: From April 2020 to July 2021, a multicenter, prospective, longitudinal, noninterventional cohort study was performed in 20 Korean ICUs. Sedation depth extent was divided into light and deep using a mean Richmond Agitation-Sedation Scale value within the first 48 hours. Propensity score matching was used to balance covariables; the outcomes were compared between the two groups. RESULTS: Overall, 631 patients (418 [66.2%] and 213 [33.8%] in the deep and light sedation groups, respectively) were included. Mortality rates were 14.1% and 8.4% in the deep and light sedation groups (P = 0.039), respectively. Kaplan-Meier estimates showed that time to extubation (P < 0.001), ICU length of stay (P = 0.005), and death (P = 0.041) differed between the groups. After adjusting for confounders, early deep sedation was only associated with delayed time to extubation (hazard ratio [HR], 0.66; 95% confidence interval [CI], 0.55-0.80; P < 0.001). In the matched cohort, deep sedation remained significantly associated with delayed time to extubation (HR, 0.68; 95% CI, 0.56-0.83; P < 0.001) but was not associated with ICU length of stay (HR, 0.94; 95% CI, 0.79-1.13; P = 0.500) and in-hospital mortality (HR, 1.19; 95% CI, 0.65-2.17; P = 0.582). CONCLUSION: In many Korean ICUs, early deep sedation was highly prevalent in mechanically ventilated patients and was associated with delayed extubation, but not prolonged ICU stay or in-hospital death.

Emerging roles of epigenetic regulation in obesity and metabolic disease.

Adipose tissue dysfunction is a hallmark of obesity and contributes to obesity-related sequelae such as metabolic complications and insulin resistance. Compelling evidence indicates that adipose-tissue-specific gene expression is influenced by gene interactions with proximal and distal cis-regulatory elements; the latter exert regulatory effects via three-dimensional (3D) chromosome conformation. Recent advances in determining the regulatory mechanisms reveal that compromised epigenomes are molecularly interlinked to altered cis-regulatory element activity and chromosome architecture in the adipose tissue. This review summarizes the roles of epigenomic components, particularly DNA methylation, in transcriptional rewiring in adipose tissue. In addition, we discuss the emerging roles of DNA methylation in the maintenance of 3D chromosome conformation and its pathophysiological significance concerning adipose tissue function.

Regulating Pseudo-Jahn-Teller Effect and Superstructure in Layered Cathode Materials for Reversible Alkali-Ion Intercalation.

The Jahn-Teller effect (JTE) is one of the most important determinators of how much stress layered cathode materials undergo during charge and discharge; however, many reports have shown that traces of superstructure exist in pristine layered materials and irreversible phase transitions occur even after eliminating the JTE. A careful consideration of the energy of cationic distortion using a Taylor expansion indicated that second-order JTE (pseudo-JTE) is more widespread than the aforementioned JTE because of the various bonding states that occur between bonding and antibonding molecular orbitals in transition-metal octahedra. As a model case, a P2-type Mn-rich cathode (Na3/4MnO2) was investigated in detail. MnO6 octahedra are well known to undergo either elongation or contraction in a specific direction due to JTE. Here, the substitution of Li for Mn (Na3/4(Li1/4Mn3/4)O2) helped to oxidize Mn3+ to Mn4+ suppressing JTE; however, the MnO6 octahedra remained asymmetric with a clear trace of the superstructure. With various advanced analyses, we disclose the pseudo-JTE as a general reason for the asymmetric distortions of the MnO6 octahedra. These distortions lead to the significant electrochemical degradation of Na3/4Li1/4Mn3/4O2. The suppression of the pseudo-JTE modulates phase transition behaviors during Na intercalation/deintercalation and thereby improves all of the electrochemical properties. The insight obtained by coupling a theoretical background for the pseudo-JTE with verified layered cathode material lattice changes implies that many previous approaches can be rationalized by regulating pseudo-JTE. This suggests that the pseudo-JTE should be thought more important than the well-known JTE for layered cathode materials.

GABA-stimulated adipose-derived stem cells suppress subcutaneous adipose inflammation in obesity.

Accumulating evidence suggests that subcutaneous and visceral adipose tissues are differentially associated with metabolic disorders. In obesity, subcutaneous adipose tissue is beneficial for metabolic homeostasis because of repressed inflammation. However, the underlying mechanism remains unclear. Here, we demonstrate that γ-aminobutyric acid (GABA) sensitivity is crucial in determining fat depot-selective adipose tissue macrophage (ATM) infiltration in obesity. In diet-induced obesity, GABA reduced monocyte migration in subcutaneous inguinal adipose tissue (IAT), but not in visceral epididymal adipose tissue (EAT). Pharmacological modulation of the GABAB receptor affected the levels of ATM infiltration and adipose tissue inflammation in IAT, but not in EAT, and GABA administration ameliorated systemic insulin resistance and enhanced insulin-dependent glucose uptake in IAT, accompanied by lower inflammatory responses. Intriguingly, compared with adipose-derived stem cells (ADSCs) from EAT, IAT-ADSCs played key roles in mediating GABA responses that repressed ATM infiltration in high-fat diet-fed mice. These data suggest that selective GABA responses in IAT contribute to fat depot-selective suppression of inflammatory responses and protection from insulin resistance in obesity.

Burnout of Faculty Members of Medical Schools in Korea.

BACKGROUND: There is no national survey on medical school faculty members' burnout in Korea. This study aimed to investigate burnout levels and explore possible factors related to burnout among faculty members of Korean medical schools. METHODS: An anonymous online questionnaire was distributed to 40 Korean medical schools from October 2020 to December 2020. Burnout was measured by a modified and revalidated version of the Maslach Burnout Inventory-Human Service Survey. RESULTS: A total of 996 faculty members participated in the survey. Of them, 855 answered the burnout questions, and 829 completed all the questions in the questionnaire. A significant number of faculty members showed a high level of burnout in each sub-dimension: 34% in emotional exhaustion, 66.3% in depersonalization, and 92.4% in reduced personal accomplishment. A total of 31.5% of faculty members revealed a high level of burnout in two sub-dimensions, while 30.5% revealed a high level of burnout in all three sub-dimensions. Woman faculty members or those younger than 40 reported significantly higher emotional exhaustion and depersonalization. Long working hours (≥ 80 hours/week) showed the highest reduced personal accomplishment scores (F = 4.023, P = 0.018). The most significant stressor or burnout source was "excessive regulation by the government or university." The research was the most exasperating task, but the education was the least stressful. CONCLUSION: This first nationwide study alerts that a significant number of faculty members in Korean medical schools seem to suffer from a high level of burnout. Further studies are necessary for identifying the burnout rate, related factors, and strategies to overcome physician burnout.

Perilipin 1 (Plin1) deficiency promotes inflammatory responses in lean adipose tissue through lipid dysregulation.

Lipid droplets are specialized cellular organelles that contain neutral lipid metabolites and play dynamic roles in energy homeostasis. Perilipin 1 (Plin1), one of the major lipid droplet-binding proteins, is highly expressed in adipocytes. In mice, Plin1 deficiency impairs peripheral insulin sensitivity, accompanied with reduced fat mass. However, the mechanisms underlying insulin resistance in lean Plin1 knockout (Plin1-/-) mice are largely unknown. The current study demonstrates that Plin1 deficiency promotes inflammatory responses and lipolysis in adipose tissue, resulting in insulin resistance. M1-type adipose tissue macrophages (ATMs) were higher in Plin1-/- than in Plin1+/+ mice on normal chow diet. Moreover, using lipidomics analysis, we discovered that Plin1-/- adipocytes promoted secretion of pro-inflammatory lipid metabolites such as prostaglandins, which potentiated monocyte migration. In lean Plin1-/- mice, insulin resistance was relieved by macrophage depletion with clodronate, implying that elevated pro-inflammatory ATMs might be attributable for insulin resistance under Plin1 deficiency. Together, these data suggest that Plin1 is required to restrain fat loss and pro-inflammatory responses in adipose tissue by reducing futile lipolysis to maintain metabolic homeostasis.

Brazing Characteristics and Bonding Strength of Pure Titanium Joints Brazed with Low-Melting Temperature Zi-17Ti-22Ni Filler Metal.

The brazing characteristics and bonding strengths of pure titanium joints are evaluated for joints brazed with Zr-17Ti-22Ni filler. Vacuum brazing was conducted at temperatures between the melting temperatures of the filler metals and the beta-transition temperature of pure titanium at 3 MPa of pressure for 5 min. Fracturing of the pure titanium joint brazed at 1,093 K occurred before yielding during the tensile tests owing to the presence of a serious segregation region containing harder and more brittle [Ti, Zr]2Ni intermetallic compounds. In contrast, in pure titanium joints brazed at and above 1,113 K, fracturing occurred at the base metal. The yield strengths of the samples brazed at 1,113 K-1,133 K were estimated to be in the range of 320-350 MPa and the ultimate tensile strengths likewise ranged from 350 to 380 MPa. The strength of pure titanium brazed at 1,153 K decreased rapidly. The results of this study show that the optimum temperature to ensure good performance after the brazing of pure titanium with Zr-17Ti-22Ni as a filler metal ranges from 1,113 K to 1,133 K.

Evaluation of the Hot Workability of Commercially Pure Ti Using Hot Torsion Tests.

Optimum processing conditions were obtained by evaluating the hot working behavior of commercially pure Ti using hot torsion tests. Hot torsion tests were conducted at temperatures ranging from 800 °C-1000 °C and strain rates ranging from 0.1-10 s-1. The flow curves show that the peak stress increases as the temperature decreases and the strain rate increases. The optimum processing conditions were derived by comparing the processing and activation energy maps. The microstructure was characterized based on various regions of the processing map. The activation energy for plastic deformation was obtained using the constitutive equation. The activation energy differs depending on the constituent phases.

Protein Kinase A Subunit Balance Regulates Lipid Metabolism in Caenorhabditis elegans and Mammalian Adipocytes.

Protein kinase A (PKA) is a cyclic AMP (cAMP)-dependent protein kinase composed of catalytic and regulatory subunits and involved in various physiological phenomena, including lipid metabolism. Here we demonstrated that the stoichiometric balance between catalytic and regulatory subunits is crucial for maintaining basal PKA activity and lipid homeostasis. To uncover the potential roles of each PKA subunit, Caenorhabditis elegans was used to investigate the effects of PKA subunit deficiency. In worms, suppression of PKA via RNAi resulted in severe phenotypes, including shortened life span, decreased egg laying, reduced locomotion, and altered lipid distribution. Similarly, in mammalian adipocytes, suppression of PKA regulatory subunits RIα and RIIß via siRNAs potently stimulated PKA activity, leading to potentiated lipolysis without increasing cAMP levels. Nevertheless, insulin exerted anti-lipolytic effects and restored lipid droplet integrity by antagonizing PKA action. Together, these data implicate the importance of subunit stoichiometry as another regulatory mechanism of PKA activity and lipid metabolism.

Alteration of gut microbiota by vancomycin and bacitracin improves insulin resistance via glucagon-like peptide 1 in diet-induced obesity.

Firmicutes and Bacteroidetes, 2 major phyla of gut microbiota, are involved in lipid and bile acid metabolism to maintain systemic energy homeostasis in host. Recently, accumulating evidence has suggested that dietary changes promptly induce the alteration of abundance of both Firmicutes and Bacteroidetes in obesity and its related metabolic diseases. Nevertheless, the metabolic roles of Firmicutes and Bacteroidetes on such disease states remain unclear. The aim of this study was to determine the effects of antibiotic-induced depletion of Firmicutes and Bacteroidetes on dysregulation of energy homeostasis in obesity. Treatment of C57BL/6J mice with the antibiotics (vancomycin [V] and bacitracin [B]), in the drinking water, before diet-induced obesity (DIO) greatly decreased both Firmicutes and Bacteroidetes in the gut as revealed by pyrosequencing of the microbial 16S rRNA gene. Concomitantly, systemic glucose intolerance, hyperinsulinemia, and insulin resistance in DIO were ameliorated via augmentation of GLP-1 secretion (active form; 2.03-fold, total form; 5.09-fold) independently of obesity as compared with untreated DIO controls. Furthermore, there were increases in metabolically beneficial metabolites derived from the gut. Together, our data suggest that Firmicutes and Bacteroidetes potentially mediate insulin resistance through modulation of GLP-1 secretion in obesity.

Ring finger protein20 regulates hepatic lipid metabolism through protein kinase A-dependent sterol regulatory element binding protein1c degradation.

UNLABELLED: Sterol regulatory element binding protein1c (SREBP1c) is a key transcription factor for de novo lipogenesis during the postprandial state. During nutritional deprivation, hepatic SREBP1c is rapidly suppressed by fasting signals to prevent lipogenic pathways. However, the molecular mechanisms that control SREBP1c turnover in response to fasting status are not thoroughly understood. To elucidate which factors are involved in the inactivation of SREBP1c, we attempted to identify SREBP1c-interacting proteins by mass spectrometry analysis. Since we observed that ring finger protein20 (RNF20) ubiquitin ligase was identified as one of SREBP1c-interacting proteins, we hypothesized that fasting signaling would promote SREBP1c degradation in an RNF20-dependent manner. In this work, we demonstrate that RNF20 physically interacts with SREBP1c, leading to degradation of SREBP1c via ubiquitination. In accordance with these findings, RNF20 represses the transcriptional activity of SREBP1c and turns off the expression of lipogenic genes that are targets of SREBP1c. In contrast, knockdown of RNF20 stimulates the expression of SREBP1c and lipogenic genes and induces lipogenic activity in primary hepatocytes. Furthermore, activation of protein kinase A (PKA) with glucagon or forskolin enhances the expression of RNF20 and potentiates the ubiquitination of SREBP1c via RNF20. In wild-type and db/db mice, adenoviral overexpression of RNF20 markedly suppresses FASN promoter activity and reduces the level of hepatic triglycerides, accompanied by a decrease in the hepatic lipogenic program. Here, we reveal that RNF20-induced SREBP1c ubiquitination down-regulates hepatic lipogenic activity upon PKA activation. CONCLUSION: RNF20 acts as a negative regulator of hepatic fatty acid metabolism through degradation of SREBP1c upon PKA activation. Knowledge regarding this process enhances our understanding of how SREBP1c is able to turn off hepatic lipid metabolism during nutritional deprivation.

Arp2/3 complex regulates adipogenesis by controlling cortical actin remodelling.

Extensive actin cytoskeleton remodelling occurs during adipocyte development. We have previously shown that disruption of stress fibres by the actin-severing protein cofilin is a requisite step in adipogenesis. However, it remains unclear whether actin nucleation and assembly into the cortical structure are essential for adipocyte development. In the present study we investigated the role of cortical actin assembly and of actin nucleation by the actin-related protein 2/3 (Arp2/3) complex in adipogenesis. Cortical actin structure formation started with accumulation of filamentous actin (F-actin) patches near the plasma membrane during adipogenesis. Depletion of Arp2/3 by knockdown of its subunits Arp3 or ARPC3 strongly impaired adipocyte differentiation, although adipogenesis-initiating factors were unaffected. Moreover, the assembly of F-actin-rich structures at the plasma membrane was suppressed and the cortical actin structure poorly developed after adipogenic induction in Arp2/3-deficient cells. Finally, we provide evidence that the cortical actin cytoskeleton is essential for efficient glucose transporter 4 (GLUT4) vesicle exocytosis and insulin signal transduction. These results show that the Arp2/3 complex is an essential regulator of adipocyte development through control of the formation of cortical actin structures, which may facilitate nutrient uptake and signalling events.

Endoplasmic reticulum stress induces hepatic steatosis via increased expression of the hepatic very low-density lipoprotein receptor.

UNLABELLED: Recent evidence suggests that obese animals exhibit increased endoplasmic reticulum (ER) stress in the liver and adipose tissue. Although ER stress is closely associated with lipid homeostasis, it is largely unknown how ER stress contributes to hepatic steatosis. In this study, we demonstrate that the induction of ER stress stimulates hepatic steatosis through increased expression of the hepatic very low-density lipoprotein receptor (VLDLR). Among the unfolded protein response sensors, the protein kinase RNA-like ER kinase-activating transcription factor 4 signaling pathway was required for hepatic VLDLR up-regulation. In primary hepatocytes, ER stress-dependent VLDLR expression induced intracellular triglyceride accumulation in the presence of very low-density lipoprotein. Moreover, ER stress-dependent hepatic steatosis was diminished in the livers of VLDLR-deficient and apolipoprotein E-deficient mice compared with wild-type mice. In addition, the VLDLR-deficient mice exhibited decreased hepatic steatosis upon high-fat diet feeding. CONCLUSION: These data suggest that ER stress-dependent expression of hepatic VLDLR leads to hepatic steatosis by increasing lipoprotein delivery to the liver, which might be a novel mechanism explaining ER stress-induced hepatic steatosis.