Macrophage function in adipose tissue homeostasis and metabolic inflammation.

Obesity-related metabolic organ inflammation contributes to cardiometabolic disorders. In obese individuals, changes in lipid fluxes and storage elicit immune responses in the adipose tissue (AT), including expansion of immune cell populations and qualitative changes in the function of these cells. Although traditional models of metabolic inflammation posit that these immune responses disturb metabolic organ function, studies now suggest that immune cells, especially AT macrophages (ATMs), also have important adaptive functions in lipid homeostasis in states in which the metabolic function of adipocytes is taxed. Adverse consequences of AT metabolic inflammation might result from failure to maintain local lipid homeostasis and long-term effects on immune cells beyond the AT. Here we review the complex function of ATMs in AT homeostasis and metabolic inflammation. Additionally, we hypothesize that trained immunity, which involves long-term functional adaptations of myeloid cells and their bone marrow progenitors, can provide a model by which metabolic perturbations trigger chronic systemic inflammation.

Fighting for Fat: Gluttonous Tumors and Starved T Cells.

In this issue of Cell, Ringel et al. reveal a link between lipid utilization in the tumor microenvironment and anti-tumor immunity in obese mice. These findings provide one explanation for how obesity worsens cancer outcomes and may point to a new metabolic approach to treating some cancers.

Keeping Off the Weight with DCs.

Long studied as modulators of insulin sensitivity, adipose tissue immune cells have recently been implicated in regulating fat mass and weight gain. In this issue of Immunity, Reisner and colleagues (2015) report that ablation of perforin-expressing dendritic cells induces T cell expansion, worsening autoimmunity and surprisingly increasing adiposity.

Body Mass Index and Risk for Intubation or Death in SARS-CoV-2 Infection : A Retrospective Cohort Study.

BACKGROUND: Obesity is a risk factor for pneumonia and acute respiratory distress syndrome. OBJECTIVE: To determine whether obesity is associated with intubation or death, inflammation, cardiac injury, or fibrinolysis in coronavirus disease 2019 (COVID-19). DESIGN: Retrospective cohort study. SETTING: A quaternary academic medical center and community hospital in New York City. PARTICIPANTS: 2466 adults hospitalized with laboratory-confirmed severe acute respiratory syndrome coronavirus 2 infection over a 45-day period with at least 47 days of in-hospital observation. MEASUREMENTS: Body mass index (BMI), admission biomarkers of inflammation (C-reactive protein [CRP] level and erythrocyte sedimentation rate [ESR]), cardiac injury (troponin level), and fibrinolysis (D-dimer level). The primary end point was a composite of intubation or death in time-to-event analysis. RESULTS: Over a median hospital length of stay of 7 days (interquartile range, 3 to 14 days), 533 patients (22%) were intubated, 627 (25%) died, and 59 (2%) remained hospitalized. Compared with overweight patients, patients with obesity had higher risk for intubation or death, with the highest risk among those with class 3 obesity (hazard ratio, 1.6 [95% CI, 1.1 to 2.1]). This association was primarily observed among patients younger than 65 years and not in older patients (P for interaction by age = 0.042). Body mass index was not associated with admission levels of biomarkers of inflammation, cardiac injury, or fibrinolysis. LIMITATIONS: Body mass index was missing for 28% of patients. The primary analyses were conducted with multiple imputation for missing BMI. Upper bounding factor analysis suggested that the results are robust to possible selection bias. CONCLUSION: Obesity is associated with increased risk for intubation or death from COVID-19 in adults younger than 65 years, but not in adults aged 65 years or older. PRIMARY FUNDING SOURCE: National Institutes of Health.

Adipose Gene Expression Profile Changes With Lung Allograft Reperfusion.

Obesity is a risk factor for primary graft dysfunction (PGD), a form of lung injury resulting from ischemia-reperfusion after lung transplantation, but the impact of ischemia-reperfusion on adipose tissue is unknown. We evaluated differential gene expression in thoracic visceral adipose tissue (VAT) before and after lung reperfusion. Total RNA was isolated from thoracic VAT sampled from six subjects enrolled in the Lung Transplant Body Composition study before and after allograft reperfusion and quantified using the Human Gene 2.0 ST array. Kyoto Encyclopedia of Genes and Genomes pathway analysis revealed enrichment for genes involved in complement and coagulation cascades and Jak-STAT signaling pathways. Overall, 72 genes were upregulated and 56 genes were downregulated in the postreperfusion time compared with baseline. Long pentraxin-3, a gene and plasma protein previously associated with PGD, was the most upregulated gene (19.5-fold increase, p = 0.04). Fibronectin leucine-rich transmembrane protein-3, a gene associated with cell adhesion and receptor signaling, was the most downregulated gene (4.3-fold decrease, p = 0.04). Ischemia-reperfusion has a demonstrable impact on gene expression in visceral adipose tissue in our pilot study of nonobese, non-PGD lung transplant recipients. Future evaluation will focus on differential adipose tissue gene expression and the development of PGD after transplant.

Expanded granulocyte/monocyte compartment in myeloid-specific triple FoxO knockout increases oxidative stress and accelerates atherosclerosis in mice.

RATIONALE: Increased neutrophil and monocyte counts are often associated with an increased risk of atherosclerosis, but their relationship to insulin sensitivity is unknown. OBJECTIVE: To investigate the contribution of forkhead transcription factors (FoxO) in myeloid cells to neutrophil and monocyte counts, atherosclerosis, and systemic insulin sensitivity. METHODS AND RESULTS: Genetic ablation of the 3 genes encoding FoxO isoforms 1, 3a, and 4, in myeloid cells resulted in an expansion of the granulocyte/monocyte progenitor compartment and was associated with increased atherosclerotic lesion formation in low-density lipoprotein receptor knockout mice. In vivo and ex vivo studies indicate that FoxO ablation in myeloid cells increased generation of reactive oxygen species. Accordingly, treatment with the antioxidant N-acetyl-l-cysteine reversed the phenotype, normalizing atherosclerosis. CONCLUSIONS: Our data indicate that myeloid cell proliferation and oxidative stress can be modulated via the FoxO branch of insulin receptor signaling, highlighting a heretofore-unknown link between insulin sensitivity and leukocytosis that can affect the predisposition to atherosclerosis.

Obesity accelerates Helicobacter felis-induced gastric carcinogenesis by enhancing immature myeloid cell trafficking and TH17 response.

OBJECTIVE: To investigate the role of obesity-associated inflammation and immune modulation in gastric carcinogenesis during Helicobacter-induced chronic gastric inflammation. DESIGN: C57BL/6 male mice were infected with H felis and placed on a high-fat diet (45% calories from fat). Study animals were analysed for gastric and adipose pathology, inflammatory markers in serum, stomach and adipose tissue, and immune responses in blood, spleen, stomach and adipose tissue. RESULTS: H felis-induced gastric carcinogenesis was accelerated in diet-induced obese mice compared with lean controls. Obesity increased bone marrow-derived immature myeloid cells in blood and gastric tissue of H felis-infected mice. Obesity also led to elevations in CD4 T cells, IL-17A, granulocyte macrophage colony-stimulating factor, phosphorylated STAT3 and prosurvival gene expression in gastric tissue of H felis-infected mice. Conversely, in adipose tissue of obese mice, H felis infection increased macrophage accumulation and expression of IL-6, C-C motif ligand 7 (CCL7) and leptin. Finally, the combination of obesity and gastric inflammation synergistically increased serum proinflammatory cytokines, including IL-6. CONCLUSIONS: Here, we have established a model to study the molecular mechanism by which obesity predisposes individuals to gastric cancer. In H felis-infected mice, obesity increased proinflammatory immune responses and accelerated gastric carcinogenesis. Interestingly, gastric inflammation augmented obesity-induced adipose inflammation and production of adipose-derived factors in obese, but not lean, mice. Our findings suggest that obesity accelerates Helicobacter-associated gastric cancer through cytokine-mediated cross-talk between inflamed gastric and adipose tissues, augmenting immune responses at both tissue sites, and thereby contributing to a protumorigenic gastric microenvironment.

Chemical screen identifies FDA-approved drugs and target pathways that induce precocious pancreatic endocrine differentiation.

Pancreatic ß-cells are an essential source of insulin and their destruction because of autoimmunity causes type I diabetes. We conducted a chemical screen to identify compounds that would induce the differentiation of insulin-producing ß-cells in vivo. To do this screen, we brought together the use of transgenic zebrafish as a model of ß-cell differentiation, a unique multiwell plate that allows easy visualization of lateral views of swimming larval fish and a library of clinical drugs. We identified six hits that can induce precocious differentiation of secondary islets in larval zebrafish. Three of these six hits were known drugs with a considerable background of published data on mechanism of action. Using pharmacological approaches, we have identified and characterized two unique pathways in ß-cell differentiation in the zebrafish, including down-regulation of GTP production and retinoic acid biosynthesis.

Macrophage-specific PPARgamma controls alternative activation and improves insulin resistance.

Obesity and insulin resistance, the cardinal features of metabolic syndrome, are closely associated with a state of low-grade inflammation. In adipose tissue chronic overnutrition leads to macrophage infiltration, resulting in local inflammation that potentiates insulin resistance. For instance, transgenic expression of Mcp1 (also known as chemokine ligand 2, Ccl2) in adipose tissue increases macrophage infiltration, inflammation and insulin resistance. Conversely, disruption of Mcp1 or its receptor Ccr2 impairs migration of macrophages into adipose tissue, thereby lowering adipose tissue inflammation and improving insulin sensitivity. These findings together suggest a correlation between macrophage content in adipose tissue and insulin resistance. However, resident macrophages in tissues display tremendous heterogeneity in their activities and functions, primarily reflecting their local metabolic and immune microenvironment. While Mcp1 directs recruitment of pro-inflammatory classically activated macrophages to sites of tissue damage, resident macrophages, such as those present in the adipose tissue of lean mice, display the alternatively activated phenotype. Despite their higher capacity to repair tissue, the precise role of alternatively activated macrophages in obesity-induced insulin resistance remains unknown. Using mice with macrophage-specific deletion of the peroxisome proliferator activated receptor-gamma (PPARgamma), we show here that PPARgamma is required for maturation of alternatively activated macrophages. Disruption of PPARgamma in myeloid cells impairs alternative macrophage activation, and predisposes these animals to development of diet-induced obesity, insulin resistance, and glucose intolerance. Furthermore, gene expression profiling revealed that downregulation of oxidative phosphorylation gene expression in skeletal muscle and liver leads to decreased insulin sensitivity in these tissues. Together, our findings suggest that resident alternatively activated macrophages have a beneficial role in regulating nutrient homeostasis and suggest that macrophage polarization towards the alternative state might be a useful strategy for treating type 2 diabetes.

Notch-mediated hepatocyte MCP-1 secretion causes liver fibrosis.

Patients with nonalcoholic steatohepatitis (NASH) have increased expression of liver monocyte chemoattractant protein-1 (MCP-1), but its cellular source and contribution to various aspects of NASH pathophysiology remain debated. We demonstrated increased liver CCL2 (which encodes MCP-1) expression in patients with NASH, and commensurately, a 100-fold increase in hepatocyte Ccl2 expression in a mouse model of NASH, accompanied by increased liver monocyte-derived macrophage (MoMF) infiltrate and liver fibrosis. To test repercussions of increased hepatocyte-derived MCP-1, we generated hepatocyte-specific Ccl2-knockout mice, which showed reduced liver MoMF infiltrate as well as decreased liver fibrosis. Forced hepatocyte MCP-1 expression provoked the opposite phenotype in chow-fed wild-type mice. Consistent with increased hepatocyte Notch signaling in NASH, we observed a close correlation between markers of Notch activation and CCL2 expression in patients with NASH. We found that an evolutionarily conserved Notch/recombination signal binding protein for immunoglobulin kappa J region binding site in the Ccl2 promoter mediated transactivation of the Ccl2 promoter in NASH diet-fed mice. Increased liver MoMF infiltrate and liver fibrosis seen in opposite gain-of-function mice was ameliorated with concomitant hepatocyte Ccl2 knockout or CCR2 inhibitor treatment. Hepatocyte Notch activation prompts MCP-1-dependent increase in liver MoMF infiltration and fibrosis.

Perception of the impact of maternal weight on pregnancy outcomes in overweight and obese women.

OBJECTIVE: The purpose of this study was to assess and compare knowledge, self-awareness, and accuracy of perceived risks and weight status among overweight and obese women. METHODS: This study was a secondary analysis of a cross-sectional questionnaire study of overweight and obese pregnant women who sought a routine first-trimester screening ultrasound. Those with a pre-pregnancy body mass index (BMI) ≥25 kg/m2 (calculated using self-reported height and weight) were included. Perceived associations between estimated weight category and risk of pregnancy complications were assessed and compared in the overweight and obese groups. The perceived weight category was compared to an estimated weight category. A logistic regression identified the demographic and medical factors associated with correct identification of risk factors. RESULTS: A total of 169 participants (88 overweight; 81 obese) were included. Most participants believed their weight did not impact the ultrasound detection of a fetal malformation (92.1% overweight vs. 55.6% obese, p < .01). Few participants associated their weight with pregnancy-related problems (6.8% overweight vs. 24.7% obese, p < .01). Most participants did not associate their weight with specific maternal complications (72.7% overweight vs. 45.7% obese, p < .01) and fetal complications (83.0% overweight vs. 71.6% obese, p = .08). More obese than overweight women underestimated their weight category (64.4% vs 41.3% overweight, p = .01). Women who correctly estimated their weight status, non-Hispanic participants, and those with a history of depression or at least one maternal co-morbidity were more likely to associate their weight with increased risk for pregnancy-related problems. CONCLUSION: Although more obese than overweight women associated excess weight with pregnancy complications, both groups underestimated the impact on their pregnancies. Targeted educational programs are needed to improve the risk perception of these populations prior to pregnancy with the goal of improving their weight statuses and pregnancy outcomes.

An Overfeeding-Induced Obesity Mouse Model Reveals Necessity for Sin3a in Postnatal Peak ß-Cell Mass Acquisition.

The increase of functional ß-cell mass is paramount to maintaining glucose homeostasis in the setting of systemic insulin resistance and/or augmented metabolic load. Understanding compensatory mechanisms that allow ß-cell mass adaptation may allow for the discovery of therapeutically actionable control nodes. In this study, we report the rapid and robust ß-cell hyperplasic effect in a mouse model of overfeeding-induced obesity (OIO) based on direct gastric caloric infusion. By performing RNA sequencing in islets isolated from OIO mice, we identified Sin3a as a novel transcriptional regulator of ß-cell mass adaptation. ß-Cell-specific Sin3a knockout animals showed profound diabetes due to defective acquisition of postnatal ß-cell mass. These findings reveal a novel regulatory pathway in ß-cell proliferation and validate OIO as a model for discovery of other mechanistic determinants of ß-cell adaptation.

Physiology of Energy Expenditure in the Weight-Reduced State.

Although many individuals achieve weight loss of 10% or more, the ability to maintain a reduced body mass over months and years is much rarer. Unfortunately, our understanding of the adverse consequences of having overweight and obesity argues that long-term maintenance of a reduced weight provides the greatest health benefit. However, to achieve long-term weight reduction requires overcoming neuroendocrine systems that favor restoration of one's initial weight. Identifying and characterizing the components of these systems will be important if we are to develop therapies and strategies to reduce the rates of obesity and its complications in our modern society. During this session, Eric Ravussin and Steven R. Smith, respectively, discussed the physiology of the weight-reduced state that favors weight regain and a molecular component that contributes to this response.

Ethnic Disparities in Coronavirus Disease 2019 after the Implementation of Universal Screening in Hartford, Connecticut.

Objective The aim of this article was to estimate the prevalence of coronavirus disease 2019 (COVID-19) in Connecticut, examine racial/ethnic disparities, and assess pregnancy outcomes in pregnant women following the implementation of universal screening for the virus. Materials and methods This is a retrospective cohort study of all obstetric patients admitted to our labor and delivery unit during the first 4 weeks of implementation of universal screening of COVID-19. Viral studies were performed in all neonates born to mothers with severe acute respiratory syndrome coronavirus 2. We calculated the prevalence of COVID-19, compared the baseline characteristics and pregnancy outcomes between those who tested positive and negative for the virus, and determined the factors associated with COVID-19. Results A total of 10 (4.6%) of 220 women screened positive for the virus. All were asymptomatic. Week 1 had the highest prevalence of infection, nearing 8%. No neonates were infected. Hispanics were more likely to test positive (odds ratio: 10.23; confidence interval: [2.71-49.1], p = 0.001). Obstetric and neonatal outcomes were similar between the groups ( p > 0.05). Conclusion Although the rate of asymptomatic COVID-19 was low, ethnic disparities were present with Hispanics being more likely to have the infection. Key Points 4.6% of pregnant women in labor and delivery tested positive for COVID-19 while being asymptomatic.Hispanic women were more likely to test positive for severe acute respiratory syndrome coronavirus 2.Pregnancy outcomes were similar between COVID-19 positive and negative women.No vertical transmission was detected.

Post-oral sensing of fat increases food intake and attenuates body weight defense.

In mammals, changes in weight elicit responses that favor a return to one's previous weight and promote weight stability. It has been hypothesized that palatable sweet and high-fat foods disturb the defense of body weight, leading to weight gain. We find that increasing sweetness or percent calories from fat increases diet palatability but that only increases in nutritive fat content increase caloric intake and body weight. In a mouse model of overfeeding that activates weight defense, high-fat diets, but not sweetened diets, attenuate the defense of body weight, leading to weight gain. The ability of a palatable, high-fat diet to increase food intake does not require tasting or smelling the food. Instead, the direct infusion of a high-fat diet into the stomach increases the ad libitum intake of less palatable, low-fat food. Post-oral sensing of percent calories from fat modulates feeding behavior to alter weight stability.

Nanoparticle Tracking Analysis for the Quantification and Size Determination of Extracellular Vesicles.

The physiological and pathophysiological roles of extracellular vesicles (EVs) have become increasingly recognized, making the EV field a quickly evolving area of research. There are many different methods for EV isolation, each with distinct advantages and disadvantages that affect the downstream yield and purity of EVs. Thus, characterizing the EV prep isolated from a given source by a chosen method is important for interpretation of downstream results and comparison of results across laboratories. Various methods exist for determining the size and quantity of EVs, which can be altered by disease states or in response to external conditions. Nanoparticle tracking analysis (NTA) is one of the prominent technologies used for high-throughput analysis of individual EVs. Here, we present a detailed protocol for quantification and size determination of EVs isolated from mouse perigonadal adipose tissue and human plasma using a breakthrough technology for NTA representing major advances in the field. The results demonstrate that this method can deliver reproducible and valid total particle concentration and size distribution data for EVs isolated from different sources using different methods, as confirmed by transmission electron microscopy. The adaptation of this instrument for NTA will address the need for standardization in NTA methods to increase rigor and reproducibility in EV research.

Antisense oligonucleotide treatment produces a type I interferon response that protects against diet-induced obesity.

OBJECTIVE: In mouse models, deficiency of TTC39B (T39) decreases hepatic lipogenic gene expression and protects against diet-induced steatohepatitis. While assessing the therapeutic potential of antisense oligonucleotides (ASOs) targeting T39, we discovered an unexpected weight loss phenotype. The objective of this study was to determine the mechanism of the resistance to diet-induced obesity. METHODS: To assess therapeutic potential, we used antisense oligonucleotides (ASO) to knock down T39 expression in a Western or high-fat, high-cholesterol, high-sucrose-diet-fed Ldlr-/- or wild-type mice. RESULTS: T39 ASO treatment led to decreased hepatic lipogenic gene expression and decreased hepatic triglycerides. Unexpectedly, T39 ASO treatment protected against diet-induced obesity. The reduced weight gain was seen with two different ASOs that decreased T39 mRNA in adipose tissue macrophages (ATMs), but not with a liver-targeted GalNac-ASO. Mice treated with the T39 ASO displayed increased browning of gonadal white adipose tissue (gWAT) and evidence of increased lipolysis. However, T39 knockout mice displayed a similar weight loss response when treated with T39 ASO, indicating an off-target effect. RNA-seq analysis of gWAT showed a widespread increase in type I interferon (IFN)-responsive genes, and knockout of the IFN receptor abolished the weight loss phenotype induced by the T39 ASO. Some human T39 ASOs and ASOs with different modifications targeting LDLR also induced a type I IFN response in THP1 macrophages. CONCLUSION: Our data suggest that extrahepatic targeting of T39 by ASOs in ATMs produced an off-target type 1 IFN response, leading to activation of lipolysis, browning of WAT, and weight loss. While our findings suggest that ASOs may induce off-target type 1 IFN response more commonly than previously thought, they also suggest that therapeutic induction of type 1 IFN selectively in ATMs could potentially represent a novel approach to the treatment of obesity.