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.

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.

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.

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.

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.

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.

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.

Adipose tissue quantification and primary graft dysfunction after lung transplantation: The Lung Transplant Body Composition study.

BACKGROUND: Obesity is associated with an increased risk of primary graft dysfunction (PGD) after lung transplantation. The contribution of specific adipose tissue depots is unknown. METHODS: We performed a prospective cohort study of adult lung transplant recipients at 4 U.S. transplant centers. We measured cross-sectional areas of subcutaneous adipose tissue (SAT) and visceral adipose tissue (VAT) on chest and abdominal computed tomography (CT) scans and indexed each measurement to height.2 We used logistic regression to examine the associations of adipose indices and adipose classes with grade 3 PGD at 48 or 72 hours, and Cox proportional hazards models to examine survival. We used latent class analyses to identify the patterns of adipose distribution. We examined the associations of adipose indices with plasma biomarkers of obesity and PGD. RESULTS: A total of 262 and 117 subjects had available chest CT scans and underwent protocol abdominal CT scans, respectively. In the adjusted models, a greater abdominal SAT index was associated with an increased risk of PGD (odds ratio 1.9, 95% CI 1.02-3.4, p = 0.04) but not with survival time. VAT indices were not associated with PGD risk or survival time. A greater abdominal SAT index correlated with greater pre- and post-transplant leptin (r = 0.61, p < 0.001, and r = 0.44, p < 0.001), pre-transplant IL-1RA (r = 0.25, p = 0.04), and post-transplant ICAM-1 (r = 0.25, p = 0.04). We identified 3 latent patterns of adiposity. The class defined by high thoracic and abdominal SAT had the greatest risk of PGD. CONCLUSIONS: Subcutaneous, but not visceral, adiposity is associated with an increased risk of PGD after lung transplantation.

A Subset of TREM2+ Dermal Macrophages Secretes Oncostatin M to Maintain Hair Follicle Stem Cell Quiescence and Inhibit Hair Growth.

Hair growth can be induced from resting mouse hair follicles by topical application of JAK inhibitors, suggesting that JAK-STAT signaling is required for maintaining hair follicle stem cells (HFSCs) in a quiescent state. Here, we show that Oncostatin M (OSM), an IL-6 family cytokine, negatively regulates hair growth by signaling through JAK-STAT5 to maintain HFSC quiescence. Genetic deletion of the OSM receptor or STAT5 can induce premature HFSC activation, suggesting that the resting telogen stage is actively maintained by the hair follicle niche. Single-cell RNA sequencing revealed that the OSM source is not intrinsic to the hair follicle itself and is instead a subset of TREM2+ macrophages that is enriched within the resting follicle and deceases immediately prior to HFSC activation. In vivo inhibition of macrophage function was sufficient to induce HFSC proliferation and hair cycle induction. Together these results clarify how JAK-STAT signaling actively inhibits hair growth.

A lipase-independent pathway of lipid release and immune modulation by adipocytes.

To meet systemic metabolic needs, adipocytes release fatty acids and glycerol through the action of neutral lipases. Here, we describe a secondary pathway of lipid release from adipocytes that is independent of canonical lipolysis. We found that adipocytes release exosome-sized, lipid-filled vesicles (AdExos) that become a source of lipid for local macrophages. Adipose tissue from lean mice released ~1% of its lipid content per day via exosomes ex vivo, a rate that more than doubles in obese animals. AdExos and associated factors were sufficient to induce in vitro differentiation of bone marrow precursors into adipose tissue macrophage-like cells. Thus, AdExos are both an alternative pathway of local lipid release and a mechanism by which parenchymal cells can modulate tissue macrophage differentiation and function.

Reduced plasma albumin predicts type 2 diabetes and is associated with greater adipose tissue macrophage content and activation.

BACKGROUND: Plasma albumin is reduced during inflammation. Obesity, a strong risk factor for type 2 diabetes (T2D), is associated with adipose tissue inflammation. However, whether albumin is associated with adipose tissue inflammation and whether it predicts T2D are unclear. METHODS: Adults (predominantly American Indian) from a longitudinal study were included. Macrophage content and gene expression related to recruitment/activation were measured from subcutaneous adipose tissue (n = 51). The relationship between plasma albumin and adiposity (dual-energy X-ray absorptiometry or hydrodensitometry), glucose (oral glucose tolerance test), insulin action (hyperinsulinemic-euglycemic clamp), and insulin secretion (intravenous glucose tolerance test) were evaluated (n = 422). Progression to T2D was evaluated by Cox regression (median follow-up 8.8 years; 102 progressors). RESULTS: Albumin was associated with macrophage markers including C1QB (r = - 0.30, p = 0.04), CSF1R (r = - 0.30, p = 0.03), and CD11b (r = - 0.36, p = 0.01). Albumin was inversely associated with body fat percentage (r = - 0.14, p = 0.003), fasting plasma glucose (r = - 0.17, p = 0.0003), and 2 h plasma glucose (r = - 0.11, p = 0.03), and was reduced in impaired glucose regulation compared with normal glucose regulation (mean ± SD: 39.4 ± 3.6 g/l and 40.1 ± 3.9 g/l, respectively; p = 0.049). Albumin predicted T2D, even after adjustment for confounders (HR, 0.75; 95% CI 0.58-0.96; p = 0.02; per one SD difference in albumin). CONCLUSIONS: Reduced albumin is associated with an unfavorable metabolic profile, characterized by increased adipose tissue inflammation, adiposity, and glucose, and with an increased risk for T2D.

Evidence for a Non-leptin System that Defends against Weight Gain in Overfeeding.

Weight is defended so that increases or decreases in body mass elicit responses that favor restoration of one's previous weight. While much is known about the signals that respond to weight loss and the central role that leptin plays, the lack of experimental systems studying the overfed state has meant little is known about pathways defending against weight gain. We developed a system to study this physiology and found that overfed mice defend against increased weight gain with graded anorexia but, unlike weight loss, this response is independent of circulating leptin concentration. In overfed mice that are unresponsive to orexigenic stimuli, adipose tissue is transcriptionally and immunologically distinct from fat of ad libitum-fed obese animals. These findings provide evidence that overfeeding-induced obesity alters adipose tissue and central responses in ways that are distinct from ad libitum obesity and activates a non-leptin system to defend against weight gain.

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.