Predicting binding events in very flexible, allosteric, multi-domain proteins.

Knowledge of the structures formed by proteins and small ligands is of fundamental importance for understanding molecular principles of chemotherapy and for designing new and more effective drugs. Due to the still high costs and to the several limitations of experimental techniques, it is most often desirable to predict these ligand-protein complexes in silico, particularly when screening for new putative drugs from databases of millions of compounds. While virtual screening based on molecular docking is widely used for this purpose, it generally fails in mimicking binding events associated with large conformational changes in the protein, particularly when the latter involve multiple domains. In this work, we describe a new methodology aimed at generating bound-like conformations of very flexible and allosteric proteins bearing multiple binding sites. Validation was performed on the enzyme adenylate kinase (ADK), a paradigmatic example of proteins that undergo very large conformational changes upon ligand binding. By only exploiting the unbound structure and the putative binding sites of the protein, we generated a significant fraction of bound-like structures, which employed in ensemble-docking calculations allowed to find native-like poses of substrates, inhibitors, and catalytically incompetent binders. Our protocol provides a general framework for the generation of bound-like conformations of flexible proteins that are suitable to host different ligands, demonstrating high sensitivity to the fine chemical details that regulate protein's activity. We foresee applications in virtual screening for difficult targets, prediction of the impact of amino acid mutations on structure and dynamics, and protein engineering.

Angiogenic markers and maternal echocardiographic indices in women with hypertensive disorders of pregnancy.

OBJECTIVE: The maternal cardiovascular system of women with hypertensive disorders of pregnancy (HDP) can be impaired, with higher rates of left ventricular (LV) remodeling and diastolic dysfunction compared to those with normotensive pregnancy. The primary objective of this prospective study was to correlate cardiac indices obtained by transthoracic echocardiography (TTE) and circulating angiogenic markers, such as soluble fms-like tyrosine kinase-1 (sFlt-1) and placental growth factor (PlGF). METHODS: In this study, 95 women with a pregnancy complicated by HDP and a group of 25 with an uncomplicated pregnancy at term underwent TTE and blood tests to measure sFlt-1 and PlGF during the peripartum period (before delivery or within a week of giving birth). Spearman's rank correlation was used to derive correlation coefficients between biomarkers and cardiac indices in the HDP and control populations. RESULTS: The HDP group included 61 (64.2%) pre-eclamptic patients and, among them, 42 (68.9%) delivered before 37 weeks' gestation. Twelve women with HDP (12.6%) underwent blood sampling and TTE after delivery, and, as they showed significantly lower levels of angiogenic markers, they were excluded from the analysis. There was a correlation between sFlt-1 and LV mass index (LVMI) (r = 0.246; P = 0.026) and early diastolic mitral inflow velocity (E) and early diastolic mitral annular velocity (e') ratio (r = 0.272; P = 0.014) in the HDP group (n = 83), while in the controls, sFlt-1 showed a correlation with relative wall thickness (r = 0.409; P = 0.043), lateral e' (r = -0.562; P = 0.004) and E/e' ratio (r = 0.417; P = 0.042). PlGF correlated with LVMI (r = -0.238; P = 0.031) in HDP patients and with lateral e' (r = 0.466; P = 0.022) in controls. sFlt-1/PlGF ratio correlated with lateral e' (r = -0.568; P = 0.004) and E/e' ratio (r = 0.428; P = 0.037) in controls and with LVMI (r = 0.252; P = 0.022) and E/e' ratio (r = 0.269; P = 0.014) in HDP. CONCLUSIONS: Although the current data are not able to infer causality, they confirm the intimate relationship between the maternal cardiovascular system and angiogenic markers that are used both to diagnose and indicate the severity of HDP. © 2023 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.

Integrative Proteogenomics for Differential Expression and Splicing Variation in a DM1 Mouse Model.

Dysregulated mRNA splicing is involved in the pathogenesis of many diseases including cancer, neurodegenerative diseases, and muscular dystrophies such as myotonic dystrophy type 1 (DM1). Comprehensive assessment of dysregulated splicing on the transcriptome and proteome level has been methodologically challenging, and thus investigations have often been targeting only few genes. Here, we performed a large-scale coordinated transcriptomic and proteomic analysis to characterize a DM1 mouse model (HSALR) in comparison to wild type. Our integrative proteogenomics approach comprised gene- and splicing-level assessments for mRNAs and proteins. It recapitulated many known instances of aberrant mRNA splicing in DM1 and identified new ones. It enabled the design and targeting of splicing-specific peptides and confirmed the translation of known instances of aberrantly spliced disease-related genes (e.g., Atp2a1, Bin1, Ryr1), complemented by novel findings (Flnc and Ywhae). Comparative analysis of large-scale mRNA and protein expression data showed quantitative agreement of differentially expressed genes and splicing patterns between disease and wild type. We hence propose this work as a suitable blueprint for a robust and scalable integrative proteogenomic strategy geared toward advancing our understanding of splicing-based disorders. With such a strategy, splicing-based biomarker candidates emerge as an attractive and accessible option, as they can be efficiently asserted on the mRNA and protein level in coordinated fashion.

Ultrasonic Spray Coating to Optimize Performance of Bio-Electrochemical Systems.

This work investigates the optimization of carbon-based electrodes employed in bio-electrochemical systems (BES) through the deposition of nanostructured layers of poly(3,4-ethylene-dioxy-thiophene) poly(styrene-sulfonate) (PEDOT:PSS) on commercial carbon paper electrodes via ultrasonic spray coating (USC). This innovative application of USC demonstrated that uniform and controlled depositions of PEDOT:PSS can be successfully performed on carbon-based electrodes. To this end, the morphology and spatial uniformity of depositions were verified via scanning electron microscopy and Raman spectroscopy. Electrochemical characterizations of fabricated electrodes demonstrated a more than two-fold increase in the electrochemical active surface area with respect to bare carbon paper. A lab-scale experiment on BES was performed, selecting microbial fuel cells (MFCs) as the reference devices. Devices featuring USC-deposited PEDOT:PSS electrodes showed a three-fold-higher energy recovery with respect to control cells, reaching a maximum value of (13 ± 2) J·m-3. Furthermore, the amount of PEDOT:PSS required to optimize MFCs' performance is in line with values reported in the literature for other deposition methods. In conclusion, this work demonstrates that USC is a promising technique for application in BES.

First-trimester choroid-plexus-to-lateral-ventricle disproportion and prediction of subsequent ventriculomegaly.

OBJECTIVE: Ventriculomegaly can be associated with long-term neurodevelopmental impairment. Prenatal diagnosis of ventriculomegaly is most commonly made at the routine second-trimester anomaly scan. The value of first-trimester ultrasound has expanded to early diagnosis and screening of fetal abnormalities. The objective of this study was to assess the predictive accuracy of first-trimester choroid-plexus-to-lateral-ventricle-or-head ratios for development of ventriculomegaly at a later gestational age. METHODS: This was a case-control study of fetuses with isolated ventriculomegaly diagnosed after 16 weeks' gestation and a control group of normal fetuses (without ventriculomegaly). The exclusion criteria included aneuploidy, genetic syndrome and/or other brain abnormality. Stored two-dimensional first-trimester ultrasound images were analyzed blindly offline and fetal biometry was performed in the axial view of the fetal head. The ratios of choroid plexus area (PA) to lateral ventricular area (VA), choroid plexus length (PL) to lateral ventricular length (VL), choroid plexus diameter (PD) to lateral ventricular diameter (VD) and PA to biparietal diameter (BPD) were measured at 11 + 0 to 13 + 6 weeks' gestation. Intra- and interobserver variability of measurement of these fetal head biometric parameters at 11 + 0 to 13 + 6 weeks' gestation were assessed in 20 normal fetuses using intraclass correlation coefficients with 95% CI. The accuracy of first-trimester biometric measurements for prediction of ventriculomegaly was assessed using the area under the receiver-operating-characteristics curves (AUC). RESULTS: The analysis included 683 singleton pregnancies, of which 102 fetuses were diagnosed with ventriculomegaly. Ventriculomegaly was mild in 86 (84.3%) cases and severe in the other 16 (15.7%). All first-trimester fetal choroid-plexus-to-lateral-ventricle/head ratios were significantly lower in cases with ventriculomegaly compared with controls (P < 0.001), with good inter- and intraobserver agreement (≥ 0.95) for the majority of the fetal head biometric parameters assessed. On adjusting for crown-rump length, optimism-adjusted AUC values obtained after cross-validation showed that both PL/VL ratio (AUC, 0.87 (95% CI, 0.73-0.98)) and PA/VA ratio (AUC, 0.90 (95% CI, 0.82-0.98)) had good predictive accuracy for severe ventriculomegaly. The PA/BPD ratio (AUC, 0.73 (95% CI, 0.54-0.90)) had modest predictive ability, which was significantly lower compared with that of the PA/VA ratio and PL/VL ratio (P = 0.003 and P = 0.001, respectively). The predictive accuracy of PD/VD ratio was low with an AUC of 0.65 (95% CI, 0.47-0.84). Optimism-adjusted AUC values obtained after cross-validation showed that PA/VA ratio offered the highest predictive accuracy for mild ventriculomegaly with an AUC of 0.84 (95% CI, 0.79-0.89), followed by PL/VL ratio (AUC, 0.82 (95% CI, 0.76-0.88)), PA/BPD ratio (AUC, 0.76 (95% CI, 0.69-0.82)) and PD/VD ratio (AUC, 0.75 (95% CI, 0.67-0.81)). Calibration plots showed that both PA/VA and PL/VL ratios had good calibration. CONCLUSION: First-trimester prediction of ventriculomegaly using ratios of fetal choroid plexus to lateral ventricle/head appears promising. Future prospective studies are needed to validate the predictive accuracy of these ultrasound markers as a screening tool for ventriculomegaly. © 2023 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.

Adverse neonatal outcome in twin pregnancy complicated by small-for-gestational age: twin vs singleton reference charts.

OBJECTIVE: The use of twin-specific vs singleton growth charts in the assessment of twin pregnancy has been controversial. The aim of this study was to assess whether a diagnosis of small-for-gestational age (SGA) made using twin-specific estimated-fetal-weight (EFW) and birth-weight (BW) charts is associated more strongly with adverse neonatal outcomes in twin pregnancies, compared with when the diagnosis is made using singleton charts. METHODS: This was a cohort study of twin pregnancies delivered at St George's Hospital, London, between January 2007 and May 2020. Twin pregnancies complicated by intrauterine death of one or both twins, fetal aneuploidy or major abnormality, twin-twin transfusion syndrome or twin anemia-polycythemia sequence and those delivered before 32 weeks' gestation, were excluded. SGA was defined as EFW or BW below the 10th centile, and was assessed using both twin-specific and singleton EFW and BW charts. The main study outcome was composite adverse neonatal outcome. Mixed-effects logistic regression analysis with random pregnancy-level intercepts was used to test the association between SGA classified using the different charts and adverse neonatal outcome. RESULTS: A total of 1329 twin pregnancies were identified, of which 913 (1826 infants) were included in the analysis. Of these pregnancies, 723 (79.2%) were dichorionic and 190 (20.8%) were monochorionic. Using the singleton charts, 33.3% and 35.7% of pregnancies were classified as SGA based on EFW and BW, respectively. The corresponding values were 5.9% and 5.6% when using the twin-specific charts. Classification as SGA based on EFW using the twin charts was associated significantly with composite adverse neonatal outcome (odds ratio (OR), 4.78 (95% CI, 1.47-14.7); P = 0.007), as compared with classification as appropriate-for-gestational age (AGA). However, classification as SGA based on EFW using the singleton standard was not associated significantly with composite adverse neonatal outcome (OR, 1.36 (95% CI, 0.63-2.88); P = 0.424). Classification as SGA based on EFW using twin-specific standards provided a significantly better model fit than did using the singleton standard (likelihood ratio test, P < 0.001). When twin-specific charts were used, classification as SGA based on BW was associated significantly with a 9.3 times increased odds of composite adverse neonatal outcome (OR, 9.27 (95% CI, 2.86-30.0); P < 0.001). Neonates classified as SGA according to the singleton BW standard but not according to the twin-specific BW standards had a significantly lower rate of composite adverse neonatal outcome than did AGA twins (OR, 0.24 (95% CI, 0.07-0.66); P = 0.009). CONCLUSIONS: The singleton charts classified one-third of twins as SGA, both prenatally and postnatally. Infants classified as SGA according to the twin-specific charts, but not those classified as SGA according to the singleton charts, had a significantly increased risk of adverse neonatal outcome compared with infants classified as AGA. This study provides further evidence that twin-specific charts perform better than do singleton charts in the prediction of adverse neonatal outcome in twin pregnancies. The use of these charts may reduce misclassification of twins as SGA and improve identification of those that are truly growth restricted. © 2021 International Society of Ultrasound in Obstetrics and Gynecology.

Peripartum echocardiographic changes in women with hypertensive disorders of pregnancy.

OBJECTIVE: Hypertensive disorders of pregnancy (HDP) are associated with significant myocardial dysfunction on echocardiography. The impact of hemodynamic changes related to volume redistribution following delivery on myocardial function in women with HDP has not been evaluated systematically. The aim of this study was to compare echocardiographic findings immediately before and after delivery in women with HDP. METHODS: This was a prospective longitudinal study including 30 women with a diagnosis of HDP who underwent two consecutive transthoracic echocardiographic (TTE) examinations, before delivery and in the early postpartum period. Paired comparisons of the findings from the two assessments were performed. RESULTS: Left-ventricular (LV) concentric remodeling or hypertrophy was detected in 21 (70%) patients. There was no significant difference in cardiac morphology indices such as LV mass index (78.9 ± 16.3 g/m2 vs 77.9 ± 15.4 g/m2 ; P = 0.611) or relative wall thickness (0.45 ± 0.1 vs 0.44 ± 0.1; P = 0.453) before vs after delivery. LV diastolic function did not demonstrate any peripartum variation, with similar left-atrial volume (52.4 ± 15.3 mL vs 51.0 ± 15.6 mL; P = 0.433), lateral E' (0.12 ± 0.03 m/s vs 0.12 ± 0.03 m/s; P = 0.307) and E/E' ratio (7.9 ± 2.2 vs 7.9 ± 1.7; P = 0.934) before vs after delivery. Systolic function indices, such as LV ejection fraction (57.5 ± 3.4% vs 56.4 ± 2.1%; P = 0.295) and global longitudinal strain (-15.3 ± 2.6% vs -15.1 ± 3.1%; P = 0.582), also remained unchanged between before vs after delivery. CONCLUSIONS: Maternal hemodynamic changes associated with delivery did not influence significantly peripartum TTE indices in women with HDP. Suboptimal maternal echocardiographic findings in HDP are likely to be the consequence of chronic pregnancy cardiovascular load changes or pre-existing maternal cardiovascular impairment. Severity and persistence of myocardial dysfunction in the postpartum period may be related to the long-term maternal cardiovascular disease legacy of HDP. © 2021 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.

New insights into molecular changes in skeletal muscle aging and disease: Differential alternative splicing and senescence.

Progressive loss of muscle mass and function due to muscle fiber atrophy and loss in the elderly and chronically ill is now defined as sarcopenia. It is a major contributor to loss of independence, disability, need of long-term care as well as overall mortality. Sarcopenia is a heterogenous disease and underlying mechanisms are not completely understood. Here, we newly identified and used Tmem158, alongside Cdkn1a, as relevant senescence and denervation markers (SDMs), associated with muscle fiber atrophy. Subsequent application of laser capture microdissection (LCM) and RNA analyses revealed age- and disease-associated differences in gene expression and alternative splicing patterns in a rodent sarcopenia model. Of note, genes exhibiting such differential alternative splicing (DAS) are mainly involved in the contractile function of the muscle. Many of these splicing events are also found in a mouse model for myotonic dystrophy type 1 (DM1), underscoring the premature aging phenotype of this disease. We propose to add differential alternative splicing to the hallmarks of aging.

Peculiar clinical presentation of COVID-19 and predictors of mortality in the elderly: A multicentre retrospective cohort study.

BACKGROUND: The spectrum of COVID-19 clinical manifestations is not yet known. In the elderly, mortality and extrapulmonary involvement appears more frequent than expected. METHODS: A multicentre-retrospective-case-series study of COVID-19 patients, aged ≥65 years, hospitalised between March 1 and June 15, 2020. Patients were classified at admission into 3 groups based on their Clinical Frailty Scale (CFS) score: 1-3 (group A), 4-6 (group B) and 7-9 (group C). RESULTS: Of the 206 patients in the study, 60 (29%) were assigned to group A, 60 (29%) to B and 86 (42%) to C. Significantly more frequent in group C than in B or A were: mental confusion (respectively 65%, 33%, 7%; P < 0.001), kidney failure (39%, 22%, 20%; P = 0.019), dehydration syndrome (55%, 27%, 13%; P < 0.001), electrolyte imbalance (54%, 32%, 25%; P = 0.001), and diabetic decompensation (22%, 12%, 7%; P = 0.026). Crude mortality was 27%. By multivariate logistic regression model independent predictors of death were male sex (adjusted odds ratio (aOR) = 2.87,95%CI = 1.15-7.18), CFS 7-9 (aOR = 9.97,95%CI = 1.82-52.99), dehydration at admission (aOR = 4.27,95%CI = 1.72-10.57) and non-invasive/invasive ventilation (aOR = 4.88,95%CI = 1.94-12.26). CONCLUSIONS: Elderly patients with a high CFS showed frequent extrapulmonary signs at admission, even in the absence of lung involvement. These findings, along with a high CFS, predicted a significant risk of mortality.

Depletion of ASK1 blunts stress-induced senescence in adipocytes.

Increasing energy expenditure via induction of browning in white adipose tissue has emerged as a potential strategy to treat obesity and associated metabolic complications. We previously reported that ASK1 inhibition in adipocytes protected from high-fat diet (HFD) or lipopolysaccharide (LPS)-mediated downregulation of UCP1 both in vitro and in vivo. Conversely, adipocyte-specific ASK1 overexpression attenuated cold-induction of UCP-1 in inguinal fat. Herein, we provide evidence that both TNFα-mediated and HFD-induced activation of p38 MAPK in white adipocytes are ASK1-dependent. Moreover, expression of senescence markers was reduced in HFD-fed adipocyte-specific ASK1 knockout mice. Similarly, LPS-induced upregulation of senescence markers was blunted in ASK1-depleted adipocytes. Thus, our study identifies a previously unknown role for ASK1 in the induction of stress-induced senescence.

Obesity-Induced Increase in Cystatin C Alleviates Tissue Inflammation.

We recently demonstrated that removal of one kidney (uninephrectomy [UniNx]) in mice reduced high-fat diet (HFD)-induced adipose tissue inflammation, thereby improving adipose tissue and hepatic insulin sensitivity. Of note, circulating cystatin C (CysC) levels were increased in UniNx compared with sham-operated mice. Importantly, CysC may have anti-inflammatory properties, and circulating CysC levels were reported to positively correlate with obesity in humans and as shown here in HFD-fed mice. However, the causal relationship of such observation remains unclear. HFD feeding of CysC-deficient (CysC knockout [KO]) mice worsened obesity-associated adipose tissue inflammation and dysfunction, as assessed by proinflammatory macrophage accumulation. In addition, mRNA expression of proinflammatory mediators was increased, whereas markers of adipocyte differentiation were decreased. Similar to findings in adipose tissue, expression of proinflammatory cytokines was increased in liver and skeletal muscle of CysC KO mice. In line, HFD-induced hepatic insulin resistance and impairment of glucose tolerance were further aggravated in KO mice. Consistently, chow-fed CysC KO mice were more susceptible to lipopolysaccharide-induced adipose tissue inflammation. In people with obesity, circulating CysC levels correlated negatively with adipose tissue Hif1α as well as IL6 mRNA expression. Moreover, healthy (i.e., insulin-sensitive) subjects with obesity had significantly higher mRNA expression of CysC in white adipose tissue. In conclusion, CysC is upregulated under obesity conditions and thereby counteracts inflammation of peripheral insulin-sensitive tissues and, thus, obesity-associated deterioration of glucose metabolism.

ASK1 inhibits browning of white adipose tissue in obesity.

Increasing energy expenditure via induction of adipose tissue browning has become an appealing strategy to treat obesity and associated metabolic complications. Herein, we identify adipocyte-expressed apoptosis signal-regulating kinase 1 (ASK1) as regulator of adipose tissue browning. High fat diet-fed adipocyte-specific ASK1 knockout mice reveal increased UCP1 protein levels in inguinal adipose tissue concomitant with elevated energy expenditure, reduced obesity and ameliorated glucose tolerance compared to control littermates. In addition, ASK1-depletion blunts LPS-mediated downregulation of isoproterenol-induced UCP1 in subcutaneous fat both in vitro and in vivo. Conversely, adipocyte-specific ASK1 overexpression in chow-fed mice attenuates cold-induced UCP1 protein levels in inguinal fat. Mechanistically, ASK1 phosphorylates interferon regulatory factor 3 (IRF3) resulting in reduced Ucp1 expression. Taken together, our studies unravel a role of ASK1 in mediating the inhibitory effect of caloric surplus or LPS-treatment on adipose tissue browning. Adipocyte ASK1 might be a pharmacological target to combat obesity and associated morbidities.

Liver ASK1 protects from non-alcoholic fatty liver disease and fibrosis.

Non-alcoholic fatty liver disease (NAFLD) is strongly associated with obesity and may progress to non-alcoholic steatohepatitis (NASH) and liver fibrosis. The deficit of pharmacological therapies for the latter mainly results from an incomplete understanding of involved pathological mechanisms. Herein, we identify apoptosis signal-regulating kinase 1 (ASK1) as a suppressor of NASH and fibrosis formation. High-fat diet-fed and aged chow-fed liver-specific ASK1-knockout mice develop a higher degree of hepatic steatosis, inflammation, and fibrosis compared to controls. In addition, pharmacological inhibition of ASK1 increased hepatic lipid accumulation in wild-type mice. In line, liver-specific ASK1 overexpression protected mice from the development of high-fat diet-induced hepatic steatosis and carbon tetrachloride-induced fibrosis. Mechanistically, ASK1 depletion blunts autophagy, thereby enhancing lipid droplet accumulation and liver fibrosis. In human livers of lean and obese subjects, ASK1 expression correlated negatively with liver fat content and NASH scores, but positively with markers for autophagy. Taken together, ASK1 may be a novel therapeutic target to tackle NAFLD and liver fibrosis.

Cerebrospinal fluid compartmentalization of HIV-1 and correlation with plasma viral load and blood-brain barrier damage.

PURPOSE: We aimed to evaluate HIV-1 compartmentalization between the cerebrospinal fluid (CSF) and plasma and investigate as to which extent HIV-1 strains in CSF differ from those in blood and whether a correlation with either plasma viral load (pVL) or an altered blood-brain barrier (BBB) does exist. STUDY DESIGN: We retrospectively evaluated paired CSF/blood samples collected from 86 HIV+ patients. HIV-RNA quantification, pol (PR/RT), and V3 sequencing were performed. HIV coreceptor tropism (CRT) was inferred (g2p, false-positive rate 10%, FPR). Data of standard CSF analysis were also reviewed; an altered CSF/plasma albumin ratio signified BBB damage. Neurological abnormalities (NA) were recorded. RESULTS: Overall, 32% of patients had a CSF/plasma HIV-RNA ratio > 1 (discordance); 3% of patients had detectable CSF HIV-RNA despite suppressed pVL (escape). Discordance was more frequent in ART-treated patients (p < 0.001) and in patients with NA (p = 0.016), but was independent of BBB damage (p = 0.65) and AIDS diagnosis (p = 0.96). Finally, CSF/plasma discordance was significantly more frequent (p < 0.0001) in patients with lower pVL values (< 10.000 copies/ml). Env divergence > 10% was found in 44% of sequences and was associated with ART (p = 0.008) and NA (p = 0.037). Overall, 24% of patients had a discordant CSF/blood CRT. A 100% nucleotide identity was observed in only 7.3% of pol sequences; notably, 10% of patients had resistance-associated mutations in CSF, but not in blood. CONCLUSIONS: Our data confirm an independent replication and evolution of HIV within the CSF. A number of factors either hinder or contribute to the compartmentalization of HIV.

IL-6-Type Cytokine Signaling in Adipocytes Induces Intestinal GLP-1 Secretion.

We recently showed that interleukin (IL)-6-type cytokine signaling in adipocytes induces free fatty acid release from visceral adipocytes, thereby promoting obesity-induced hepatic insulin resistance and steatosis. In addition, IL-6-type cytokines may increase the release of leptin from adipocytes and by those means induce glucagon-like peptide 1 (GLP-1) secretion. We thus hypothesized that IL-6-type cytokine signaling in adipocytes may regulate insulin secretion. To this end, mice with adipocyte-specific knockout of gp130, the signal transducer protein of IL-6, were fed a high-fat diet for 12 weeks. Compared with control littermates, knockout mice showed impaired glucose tolerance and circulating leptin, GLP-1, and insulin levels were reduced. In line, leptin release from isolated adipocytes was reduced, and intestinal proprotein convertase subtilisin/kexin type 1 (Pcsk1) expression, the gene encoding PC1/3, which controls GLP-1 production, was decreased in knockout mice. Importantly, treatment with the GLP-1 receptor antagonist exendin 9-39 abolished the observed difference in glucose tolerance between control and knockout mice. Ex vivo, supernatant collected from isolated adipocytes of gp130 knockout mice blunted Pcsk1 expression and GLP-1 release from GLUTag cells. In contrast, glucose- and GLP-1-stimulated insulin secretion was not affected in islets of knockout mice. In conclusion, adipocyte-specific IL-6 signaling induces intestinal GLP-1 release to enhance insulin secretion, thereby counteracting insulin resistance in obesity.

Interleukin-33-Activated Islet-Resident Innate Lymphoid Cells Promote Insulin Secretion through Myeloid Cell Retinoic Acid Production.

Pancreatic-islet inflammation contributes to the failure of ß cell insulin secretion during obesity and type 2 diabetes. However, little is known about the nature and function of resident immune cells in this context or in homeostasis. Here we show that interleukin (IL)-33 was produced by islet mesenchymal cells and enhanced by a diabetes milieu (glucose, IL-1ß, and palmitate). IL-33 promoted ß cell function through islet-resident group 2 innate lymphoid cells (ILC2s) that elicited retinoic acid (RA)-producing capacities in macrophages and dendritic cells via the secretion of IL-13 and colony-stimulating factor 2. In turn, local RA signaled to the ß cells to increase insulin secretion. This IL-33-ILC2 axis was activated after acute ß cell stress but was defective during chronic obesity. Accordingly, IL-33 injections rescued islet function in obese mice. Our findings provide evidence that an immunometabolic crosstalk between islet-derived IL-33, ILC2s, and myeloid cells fosters insulin secretion.

Fas cell surface death receptor controls hepatic lipid metabolism by regulating mitochondrial function.

Nonalcoholic fatty liver disease is one of the most prevalent metabolic disorders and it tightly associates with obesity, type 2 diabetes, and cardiovascular disease. Reduced mitochondrial lipid oxidation contributes to hepatic fatty acid accumulation. Here, we show that the Fas cell surface death receptor (Fas/CD95/Apo-1) regulates hepatic mitochondrial metabolism. Hepatic Fas overexpression in chow-fed mice compromises fatty acid oxidation, mitochondrial respiration, and the abundance of mitochondrial respiratory complexes promoting hepatic lipid accumulation and insulin resistance. In line, hepatocyte-specific ablation of Fas improves mitochondrial function and ameliorates high-fat-diet-induced hepatic steatosis, glucose tolerance, and insulin resistance. Mechanistically, Fas impairs fatty acid oxidation via the BH3 interacting-domain death agonist (BID). Mice with genetic or pharmacological inhibition of BID are protected from Fas-mediated impairment of mitochondrial oxidation and hepatic steatosis. We suggest Fas as a potential novel therapeutic target to treat obesity-associated fatty liver and insulin resistance.Hepatic steatosis is a common disease closely associated with metabolic syndrome and insulin resistance. Here Item et al. show that Fas, a member of the TNF receptor superfamily, contributes to mitochondrial dysfunction, steatosis development, and insulin resistance under high fat diet.