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Some studies report that obesity is associated with more severe symptoms following SARS-CoV-2 infection and worse COVID-19 outcomes, however many other studies have not reproduced these findings. Therefore, it is uncertain whether obesity is in fact associated with worse COVID-19 outcomes compared to non-obese individuals. We conducted a systematic search of PubMed (including MEDLINE) and Google Scholar on May 18, 2020 to identify published studies on COVID-19 outcomes in non-obese and obese patients, covering studies published during the first 6 months of the pandemic. Meta-analyses with random effects modeling was used to determine unadjusted odds ratios (OR) and 95% confidence intervals (CI) for various COVID-19 outcomes in obese versus non-obese patients. By quantitative analyses of 22 studies from 7 countries in North America, Europe, and Asia, we found that obesity is associated with an increased likelihood of presenting with more severe COVID-19 symptoms (OR 3.03, 95% CI 1.45–6.28, P = 0.003; 4 studies, n = 974), developing acute respiratory distress syndrome (ARDS; OR 2.89, 95% CI 1.14–7.34, P = 0.025; 2 studies, n = 96), requiring hospitalization (OR 1.68, 95% CI 1.14–1.59, P P = 0.001; 9 studies, n = 5298), and undergoing invasive mechanical ventilation (IMV; OR 1.76, 95% CI 1.29–2.40, P P = 0.750; 9 studies, n = 20,597). Collectively, these data from the first 6 months of the pandemic suggested that obesity is associated with a more severe COVID-19 disease course but may not be associated with increased mortality.

The mechanisms underlying the association between obesity and coronavirus disease 2019 (COVID-19) severity remain unclear. After verifying that obesity was a correlate of severe COVID-19 in US Military Health System (MHS) beneficiaries, we compared immunological and virological phenotypes of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection in both obese and nonobese participants.COVID-19-infected MHS beneficiaries were enrolled, and anthropometric, clinical, and demographic data were collected. We compared the SARS-CoV-2 peak IgG humoral response and reverse-transcription polymerase chain reaction viral load in obese and nonobese patients, stratified by hospitalization, utilizing logistic regression models.Data from 511 COVID-19 patients were analyzed, among whom 24% were obese and 14% severely obese. Obesity was independently associated with hospitalization (adjusted odds ratio [aOR], 1.91; 95% confidence interval [CI], 1.15-3.18) and need for oxygen therapy (aOR, 3.39; 95% CI, 1.61-7.11). In outpatients, severely obese had a log10 (1.89) higher nucleocapsid (N1) genome equivalents (GE)/reaction and log10 (2.62) higher N2 GE/reaction than nonobese (P = 0.03 and P.001, respectively). We noted a correlation between body mass index and peak anti-spike protein IgG in inpatients and outpatients (coefficient = 5.48, P.001).Obesity is a strong correlate of COVID-19 severity in MHS beneficiaries. These findings offer new pathophysiological insights into the relationship between obesity and COVID-19 severity.

Obesity is a metabolic disease that promotes the development of a number of other pathologies. Despite its high disease burden, the underlying pathophysiology of obesity is poorly understood. Emerging research has indicated that adipocytes transfer their mitochondria to macrophages in white adipose tissue as a mechanism of cell-to-cell communication and that this process is impaired in obesity. However, the diversity of intercellular mitochondria transfer axes that occurs in adipose and its regulation in obesity are not known. Here, we utilized 31-color spectral flow cytometry of adipocyte-specific mitochondria reporter (MitoFat) mice to comprehensively analyze intercellular mitochondria transfer from adipocytes to other cell types in white, beige, and brown adipose tissues. Employing manifold machine learning, we generated reference clusters of cells in 5-month (young) and 20-month-old (aged) MitoFat mice fed a normal chow diet (low fat diet). Using the reference clusters and manifold, we then mapped differences in immune cell populations using nearest neighbor search approximations in MitoFat mice fed normal chow, high-fat diet (HFD), high-fat diet with low palmitate (LP-HFD). The degree of mitochondria transfer from adipocytes to each of the various cell clusters was determined for each tissue and for each condition. We observed that adipocytes transfer their mitochondria to a wide range of immune cell populations, most notably macrophages. Although aged mice develop obesity, surprisingly they do not exhibit decreased mitochondria transfer from adipocytes to macrophages in vivo in white, beige, or brown adipose tissue. In contrast, young mice fed a HFD highly enriched in palmitate exhibit obesity and markedly reduced mitochondria transfer from adipocytes to macrophages. The decrease in mitochondria transfer was largely ameliorated by the replacement of palmitate with medium chain fatty acids, suggesting a potential direct dietary mechanism in the alteration of mitochondria transfer. Overall, the 31-color quantification increased granularity, allowing us to quantify differences in immune populations and mitochondria transfer by tissue, age, and diet. Similar machine-learning approaches could be used to investigate both basic biological and clinical questions by effectively reducing dimensions, mitigating batch effect, and enabling comparisons across different tissues, timepoints, or conditions.

Summary Recent studies suggest that mitochondria can be transferred between cells to support the survival of metabolically compromised cells. However, whether intercellular mitochondria transfer occurs in white adipose tissue (WAT) or regulates metabolic homeostasis in vivo remains unknown. We found that macrophages acquire mitochondria from neighboring adipocytes in vivo and that this process defines a transcriptionally distinct macrophage subpopulation. A genome-wide CRISPR-Cas9 knockout screen revealed that mitochondria uptake depends on heparan sulfates (HS). High-fat diet (HFD)-induced obese mice exhibit lower HS levels on WAT macrophages and decreased intercellular mitochondria transfer from adipocytes to macrophages. Deletion of the HS biosynthetic gene Ext1 in myeloid cells decreases mitochondria uptake by WAT macrophages, increases WAT mass, lowers energy expenditure, and exacerbates HFD-induced obesity in vivo. Collectively, this study suggests that adipocytes and macrophages employ intercellular mitochondria transfer as a mechanism of immunometabolic crosstalk that regulates metabolic homeostasis and is impaired in obesity.

An off switch for helminth immunity Group 2 innate lymphoid cells (ILC2s) are involved in responses to helminths, viruses, and allergens. Moriyama et al. found that ILC2s interact with the nervous system to modulate helminth immunity. ILC2s from the small intestine expressed the β 2 -adrenergic receptor (β 2 AR), which normally interacts with the neurotransmitter epinephrine. Inactivating β 2 AR resulted in lower helminth burden and more ILC2s, eosinophils, and type 2 cytokine production in mice. Conversely, treatment of helminth-infected mice with a β 2 AR agonist enhanced worm burden and reduced proliferation of ILC2s. Thus, β 2 AR negatively regulates ILC2-driven protective immunity. Science , this issue p. 1056

Obesity predisposes to cancer and a virtual universality of nonalcoholic fatty liver disease (NAFLD). However, the impact of hepatic steatosis on liver metastasis is enigmatic. We find that while control mice were relatively resistant to hepatic metastasis, those which were lipodystrophic or obese, with NAFLD, had a dramatic increase in breast cancer and melanoma liver metastases. NAFLD promotes liver metastasis by reciprocal activation initiated by tumor-induced triglyceride lipolysis in juxtaposed hepatocytes. The lipolytic products are transferred to cancer cells via fatty acid transporter protein 1, where they are metabolized by mitochondrial oxidation to promote tumor growth. The histology of human liver metastasis indicated the same occurs in humans. Furthermore, comparison of isolates of normal and fatty liver established that steatotic lipids had enhanced tumor-stimulating capacity. Normalization of glucose metabolism by metformin did not reduce steatosis-induced metastasis, establishing the process is not mediated by the metabolic syndrome. Alternatively, eradication of NAFLD in lipodystrophic mice by adipose tissue transplantation reduced breast cancer metastasis to that of control mice, indicating the steatosis-induced predisposition is reversible., Nonalcoholic fatty liver disease promotes liver metastasis in mice, likely due to lipid transfer to tumor cells.

Berardinelli-Seip congenital generalized lipodystrophy is associated with increased bone mass suggesting that fat tissue regulates the skeleton. Because there is little mechanistic information regarding this issue, we generated "fat-free" (FF) mice completely lacking visible visceral, subcutaneous and brown fat. Due to robust osteoblastic activity, trabecular and cortical bone volume is markedly enhanced in these animals. FF mice, like Berardinelli-Seip patients, are diabetic but normalization of glucose tolerance and significant reduction in circulating insulin fails to alter their skeletal phenotype. Importantly, the skeletal phenotype of FF mice is completely rescued by transplantation of adipocyte precursors or white or brown fat depots, indicating that adipocyte derived products regulate bone mass. Confirming such is the case, transplantation of fat derived from adiponectin and leptin double knockout mice, unlike that obtained from their WT counterparts, fails to normalize FF bone. These observations suggest a paucity of leptin and adiponectin may contribute to the increased bone mass of Berardinelli-Seip patients., Author summary Berardinelli-Seip congenital generalized lipodystrophy is a human disorder associated with increased bone mass suggesting that fat, per se, regulates the skeleton. To test this hypothesis we generated a murine model of congenital generalized lipodystrophy in which both brown and white adipose tissue are entirely depleted during embryogenesis. These “fat-free” (FF) exhibit a marked increase in bone mass throughout their body. The increased bone mass represents stimulation of bone formation and not retarded bone breakdown. Additionally, the increased bone mass of FF mice markedly increases skeletal strength and resistance to fracture. Like patients with congenital lipodystrophy, FF mice are diabetic but their metabolic state does not contribute to their increased bone mass. To identify the fat-produced molecules regulating bone mass we transplanted genetically modified adipose tissue into FF mice which established that absence of the fat-produced molecules, adiponectin and leptin, significantly enhances bone formation. These observations suggest that reducing the combined effect of adiponectin and leptin, on bone, will increase its abundance and fracture resistance.

We previously established that global deletion of the enhancer of trithorax and polycomb (ETP) gene, Asxl2, prevents weight gain. Because proinflammatory macrophages recruited to adipose tissue are central to the metabolic complications of obesity, we explored the role of ASXL2 in myeloid lineage cells. Unexpectedly, mice without Asxl2 only in myeloid cells (Asxl2(ΔLysM)) were completely resistant to diet-induced weight gain and metabolically normal despite increased food intake, comparable activity, and equivalent fecal fat. Asxl2(ΔLysM) mice resisted HFD-induced adipose tissue macrophage infiltration and inflammatory cytokine gene expression. Energy expenditure and brown adipose tissue metabolism in Asxl2(ΔLysM) mice were protected from the suppressive effects of HFD, a phenomenon associated with relatively increased catecholamines likely due to their suppressed degradation by macrophages. White adipose tissue of HFD-fed Asxl2(ΔLysM) mice also exhibited none of the pathological remodeling extant in their control counterparts. Suppression of macrophage Asxl2 expression, via nanoparticle-based siRNA delivery, prevented HFD-induced obesity. Thus, ASXL2 controlled the response of macrophages to dietary factors to regulate metabolic homeostasis, suggesting modulation of the cells’ inflammatory phenotype may impact obesity and its complications.

Objectives Bone marrow biopsies are essential for evaluating patients with suspected or confirmed hematopoietic disorders or malignancies, but little is known about how biopsy needle type affects biopsy length and/or quality. We sought to compare bone marrow biopsy quality in specimens obtained with two different needles. Methods A retrospective analysis was performed on bone marrow specimens obtained with manual single-bevel (n = 114) or triple-bevel (n = 166) needles. The lengths of evaluable marrow, core quality, and aspirate quality were assessed by blinded hematopathologists. Results The triple-bevel needle produced 1.33-mm shorter lengths of evaluable marrow than the single-bevel needle and was five times less likely to produce a specimen rated as "adequate" and 4.2 times more likely to produce crush artifact. The triple-bevel needle was also 2.4 times more likely to produce hemodilute aspirates. Conclusions Bone marrow biopsy needle type affects the length of evaluable marrow and quality of core and aspirate specimens.

Additional sex comb-like 1 (ASXL1) mutations are commonly associated with myeloid malignancies and are markers of aggressive disease. The fact that ASXL1 is necessary for myeloid differentiation raises the possibility it also regulates osteoclasts. We find deletion of ASXL1 in myeloid cells results in bone loss with increased abundance of osteoclasts. Because ASXL1 is an enhancer of trithorax and polycomb (ETP) protein, we asked if it modulates osteoclast differentiation by maintaining balance between positive and negative epigenetic regulators. In fact, loss of ASXL1 induces concordant loss of inhibitory H3K27me3 with gain of H3K4me3 at key osteoclast differentiation genes, including nuclear factor for activated T cells 1 (NFATc1) and itgb3. In the setting of ASXL1 deficiency, increased NFATc1 binds to the Blimp1 (Prdm1) promoter thereby enhancing expression of this pro-osteoclastogenic gene. The global reduction of K27 trimethylation in ASXL1-deficient osteoclasts is also attended by a 40-fold increase in expression of the histone demethylase Jumonji domain-containing 3 (Jmjd3). Jmjd3 knockdown in ASXL1-deficient osteoclast precursors increases H3K27me3 on the NFATc1 promoter and impairs osteoclast formation. Thus, in addition to promoting myeloid malignancies, ASXL1 controls epigenetic reprogramming of osteoclasts to regulate bone resorption and mass.

Obesity is an increasingly prevalent disease worldwide. While genetic and environmental factors are known to regulate the development of obesity and associated metabolic diseases, emerging studies indicate that innate and adaptive immune cell responses in adipose tissue have critical roles in the regulation of metabolic homeostasis. In the lean state, type 2 cytokine-associated immune cell responses predominate in white adipose tissue and protect against weight gain and insulin resistance through direct effects on adipocytes and elicitation of beige adipose. In obesity, these metabolically beneficial immune pathways become dysregulated, and adipocytes and other factors initiate metabolically deleterious type 1 inflammation that impairs glucose metabolism. This review discusses our current understanding of the functions of different types of adipose tissue and how immune cells regulate adipocyte function and metabolic homeostasis in the context of health and disease and highlights. We also highlight the potential of targeting immuno-metabolic pathways as a therapeutic strategy to treat obesity and associated diseases.

Obesity is associated with inflammatory arthritis (IA) but the mechanisms linking adipose tissue to joint inflammation are enigmatic. We explored this issue by selectively expressing diphtheria toxin in adipose tissue yielding “fat-free” (FF) mice completely lacking white and brown fat. FF mice exhibit systemic neutrophilia and elevated serum acute phase proteins, suggesting predisposition to severe IA. Surprisingly, however, FF mice are completely resistant to K/BxN serum-induced IA, maintaining normal ankle and paw thickness and no evidence of enhanced osteoclastogenesis or periarticular bone destruction. Despite their robust systemic basal neutrophilia, no neutrophil infiltration into joints of FF mice occurs when challenged with K/BxN serum. Absence of adiponectin, leptin or both has no effect on joint disease but deletion of the adipokine, adipsin (complement factor D) completely prevents serum-induced IA. Confirming fat-ex-pressed adipsin modulates the disorder, transplantation of WT adipose tissue into FF mice is sufficient to restore susceptibility to IA, whereas recipients of adipsin-deficient fat remain resistant. Our studies provide the first direct evi-dence that adipose tissue regulates development of IA and reveal a previously unrecognized pathway in which adipocytes modify neutrophil responses in distant tissues by producing adipsin.

Obesity is an increasingly prevalent disease regulated by genetic and environmental factors. Emerging studies indicate that immune cells, including monocytes, granulocytes and lymphocytes, regulate metabolic homeostasis and are dysregulated in obesity. Group 2 innate lymphoid cells (ILC2s) can regulate adaptive immunity and eosinophil and alternatively activated macrophage responses, and were recently identified in murine white adipose tissue (WAT) where they may act to limit the development of obesity. However, ILC2s have not been identified in human adipose tissue, and the mechanisms by which ILC2s regulate metabolic homeostasis remain unknown. Here we identify ILC2s in human WAT and demonstrate that decreased ILC2 responses in WAT are a conserved characteristic of obesity in humans and mice. Interleukin (IL)-33 was found to be critical for the maintenance of ILC2s in WAT and in limiting adiposity in mice by increasing caloric expenditure. This was associated with recruitment of uncoupling protein 1 (UCP1)(+) beige adipocytes in WAT, a process known as beiging or browning that regulates caloric expenditure. IL-33-induced beiging was dependent on ILC2s, and IL-33 treatment or transfer of IL-33-elicited ILC2s was sufficient to drive beiging independently of the adaptive immune system, eosinophils or IL-4 receptor signalling. We found that ILC2s produce methionine-enkephalin peptides that can act directly on adipocytes to upregulate Ucp1 expression in vitro and that promote beiging in vivo. Collectively, these studies indicate that, in addition to responding to infection or tissue damage, ILC2s can regulate adipose function and metabolic homeostasis in part via production of enkephalin peptides that elicit beiging.

Objective Unrefined, complex carbohydrates and lean protein diets are used to combat obesity, although it's unknown whether more frequent meals may improve this response. The effects of consuming traditional (∼15%) versus higher (∼35%) protein intakes as three or six meals/day on abdominal fat, postprandial thermogenesis (TEM), and cardiometabolic biomarkers in overweight individuals during 28 days of energy balance (BAL) and deficit (NEG), respectively were compared. Design and Methods Overweight individuals (n = 30) were randomized into three groups: two high-protein groups (35% of energy) consumed as three (HP3) or six (HP6) meals/day and one group consumed three meals/day of a traditional intake (TD3). Following a 5-day baseline control (CON), subjects consumed their respective diets throughout a 56-day intervention consisting of two, 28 day phases: a BAL followed by a NEG phase (75% of energy needs). Total body fat (BF) and abdominal BF (ABF), body weight (BW), TEM, and fasting biomarkers were assessed at the end of CON, BAL, and NEG phases. Results BW remained stable throughout CON and BAL in all groups, whereas BF (P < 0.001) and ABF (P < 0.01) decreased in HP groups and lean body mass (LBM) and leptin increased in HP6. Following NEG, BW decreased in all groups. BF, ABF, and leptin decreased in HP groups; LBM remained higher (P < 0.05), and TEM was highest in HP6 (P < 0.05). Conclusions Consuming increased protein (∼35%) more frequently (6×) throughout the day decreases BF and ABF, increases LBM and TEM, and favorably affects adipokines more than current recommendations for macronutrients consumed over three meals/day in overweight individuals during both BAL and NEG.

Beige and brown adipocytes are thermogenic cells essential for maintaining metabolic homeostasis within white adipose tissue (WAT) and brown adipose tissue (BAT), respectively. Emerging studies indicate that various immune cell types such as alternatively activated macrophages (AAMacs), eosinophils, and group 2 innate lymphoid cells (ILC2s) critically regulate beige and/or brown adipocyte development and activation to protect against obesity and maintain core body temperature. These findings suggest that studies of beige and brown adipose tissue may benefit from traditional immunologic approaches such as flow cytometry of immune cells residing within WAT and BAT. The purpose of this article is to describe an efficient method to isolate immune cells from numerous adipose tissue samples in parallel. The composition, phenotype, and activation state of cells isolated with this protocol may then be assessed by multiple methods including but not limited to flow cytometry. As an example, this article briefly describes a method to identify AAMacs, eosinophils, and ILC2s in adipose tissues.

Red meat allergy is a tick-associated hypersensitivity reaction to galactose-α-1,3-galactose (α-gal) and is characterized by anaphylaxis, angioedema, urticaria and/or gastrointestinal symptoms occurring 3–6 hours after ingesting red meat such as beef, pork, or lamb. Diagnosis of red meat allergy is challenging due to the unusually long delay in symptom onset and poor sensitivity of skin prick tests with commercial meat extracts. The primary diagnostic tools available for this disease are quantification of α-gal-, beef-, pork-, and/or lamb-specific IgE in serum, however the diagnostic performance of these tests has not been reported. Using patient data for n=135 patients with red meat allergy and n=37 controls, we found that measurement of α-gal-specific IgE using the bovine thyroglobulin (bTG) ImmunoCAP method had the best overall sensitivity (100%) and specificity (92.3%) for diagnosis of red meat allergy. Measuring α-gal-specific IgE using the streptavidin (SA)-CAP technique or beef- or pork-specific IgE using ImmunoCAP were also effective tests with high sensitivities (89–92%) and variable specificities (65–82%). Lamb-specific IgE and total IgE had essentially no diagnostic value for red meat allergy. Positive and negative predictive values mirrored these trends. Taken together, these findings indicate that the α-gal-specific IgE test by bTG ImmunoCAP is the most useful for establishing a diagnosis of red meat allergy, although α-gal-specific IgE by SA-CAP and beef- and pork-specific IgE by ImmunoCAP are also effective tests.

OBJECTIVE Peripheral insulin resistance is linked to an increase in reactive oxygen species (ROS), leading in part to the production of reactive lipid aldehydes that modify the side chains of protein amino acids in a reaction termed protein carbonylation. The primary enzymatic method for lipid aldehyde detoxification is via glutathione S-transferase A4 (GSTA4) dependent glutathionylation. The objective of this study was to evaluate the expression of GSTA4 and the role(s) of protein carbonylation in adipocyte function. RESEARCH DESIGN AND METHODS GSTA4-silenced 3T3-L1 adipocytes and GSTA4-null mice were evaluated for metabolic processes, mitochondrial function, and reactive oxygen species production. GSTA4 expression in human obesity was evaluated using microarray analysis. RESULTS GSTA4 expression is selectively downregulated in adipose tissue of obese insulin-resistant C57BL/6J mice and in human obesity-linked insulin resistance. Tumor necrosis factor-α treatment of 3T3-L1 adipocytes decreased GSTA4 expression, and silencing GSTA4 mRNA in cultured adipocytes resulted in increased protein carbonylation, increased mitochondrial ROS, dysfunctional state 3 respiration, and altered glucose transport and lipolysis. Mitochondrial function in adipocytes of lean or obese GSTA4-null mice was significantly compromised compared with wild-type controls and was accompanied by an increase in superoxide anion. CONCLUSIONS These results indicate that downregulation of GSTA4 in adipose tissue leads to increased protein carbonylation, ROS production, and mitochondrial dysfunction and may contribute to the development of insulin resistance and type 2 diabetes.

Mammals have evolved neurophysiologic reflexes, such as coughing and scratching, to expel invading pathogens and noxious environmental stimuli. It is well established that these responses are also associated with chronic inflammatory diseases, including asthma and atopic dermatitis. However, the mechanisms by which inflammatory pathways promote sensations such as itch remain poorly understood. Here, we show that type 2 cytokines directly activate sensory neurons in both mice and humans. Further, we demonstrate that chronic itch is dependent on neuronal IL-4Rα and JAK1 signaling. We also observe that patients with recalcitrant chronic itch that failed other immunosuppressive therapies markedly improve when treated with JAK inhibitors. Thus, signaling mechanisms previously ascribed to the immune system may represent novel therapeutic targets within the nervous system. Collectively, this study reveals an evolutionarily conserved paradigm in which the sensory nervous system employs classical immune signaling pathways to influence mammalian behavior.

Type 2 inflammation underlies allergic diseases such as atopic dermatitis, which is characterized by the accumulation of basophils and group 2 innate lymphoid cells (ILC2s) in inflamed skin lesions. Although murine studies have demonstrated that cutaneous basophil and ILC2 responses are dependent on thymic stromal lymphopoietin, whether these cell populations interact to regulate the development of cutaneous type 2 inflammation is poorly defined. In this study, we identify that basophils and ILC2s significantly accumulate in inflamed human and murine skin and form clusters not observed in control skin. We demonstrate that murine basophil responses precede ILC2 responses and that basophils are the dominant IL-4–enhanced GFP-expressing cell type in inflamed skin. Furthermore, basophils and IL-4 were necessary for the optimal accumulation of ILC2s and induction of atopic dermatitis–like disease. We show that ILC2s express IL-4Rα and proliferate in an IL-4–dependent manner. Additionally, basophil-derived IL-4 was required for cutaneous ILC2 responses in vivo and directly regulated ILC2 proliferation ex vivo. Collectively, these data reveal a previously unrecognized role for basophil-derived IL-4 in promoting ILC2 responses during cutaneous inflammation.

Manganese tetrakis benzoic acid porphyrin (MnTBAP) is a superoxide dismutase mimetic that has recently been shown to reduce visceral adiposity (Pires et al., 2013). In visceral fat of mice treated with MnTBAP, we have observed significant increases in hormone sensitive lipase activity and PGC-1α expression. These observations indicate that MnTBAP may activate the sympathetic nervous system, which is known to stimulate lipolysis and brown/beige adipocyte activity. To test whether the ability of MnTBAP to reduce adiposity is dependent on β-adrenergic receptor signaling, mice were fed a high fat diet (HFD) or a low fat diet (LFD) for six months. During the last six weeks of the dietary intervention mice were treated with MnTBAP alone or in combination with a β-adrenergic receptor antagonist cocktail (β-Blockers) containing propranolol and the β3-adrenergic receptor antagonist SR59230A. Prior to treatment, mice fed a HFD weighed significantly more than mice fed a LFD, but no significant differences in body we...

Interleukin-25 preferentially elicits multipotent progenitor type 2 cells, which are distinct from other populations of type 2 innate lymphoid cells., The predominantly epithelial cell–derived cytokines IL-25, IL-33, and thymic stromal lymphopoietin (TSLP) can promote CD4+ Th2 cell–dependent immunity, inflammation, and tissue repair at barrier surfaces through the induction of multiple innate immune cell populations. IL-25 and IL-33 were previously shown to elicit four innate cell populations, named natural helper cells, nuocytes, innate type 2 helper cells, and multipotent progenitor type 2 (MPPtype2) cells, now collectively termed group 2 innate lymphoid cells (ILC2). In contrast to other types of ILC2, MPPtype2 cells exhibit multipotent potential and do not express T1/ST2 or IL-7Rα, suggesting that MPPtype2 cells may be a distinct population. Here, we show that IL-33 elicits robust ILC2 responses, whereas IL-25 predominantly promotes MPPtype2 cell responses at multiple tissue sites with limited effects on ILC2 responses. MPPtype2 cells were distinguished from ILC2 by their differential developmental requirements for specific transcription factors, distinct genome-wide transcriptional profile, and functional potential. Furthermore, IL-25–induced MPPtype2 cells promoted Th2 cytokine–associated inflammation after depletion of ILC2. These findings indicate that IL-25 simultaneously elicits phenotypically and functionally distinct innate lymphoid– and nonlymphoid-associated cell populations and implicate IL-25–elicited MPPtype2 cells and extramedullary hematopoiesis in the promotion of Th2 cytokine responses at mucosal surfaces.

The first purpose of this chapter is to outline the roots of epidemiology as a metho­dological discipline, using a multiple-threads historical approach. We unravel what we see as the main historical threads relevant to the development of current health research methods involving human subjects, giving attention to the ethical, scientific-theoretical, and practical aspects. Roots of epidemiological concepts and methods go back a long time, to before epidemiology became a named discipline and before formal statistical comparisons of occurrence frequencies started being made. We take the stance that ancient thinkers, dating back at least as far back as Aristotle, formed early concepts that have been essential to the development of modern epidemiology as we know it. We therefore treat such critical developments as directly relevant to the history of epidemiology. As an introduction, we begin with a discussion of belief systems. We then discuss a series of historical threads, starting from health research topics, over ways of causal thinking about health, to the design of empirical information, research ethics and stakeholder participation. Other threads relevant to epidemiology such as history of data management, analysis, and study reporting, are not covered. Finally, we explore some possible and desirable future developments in epidemiological research.

Epidemiology is a methodological discipline offering principles and practical guidelines for the creation of new quantitative evidence about health-related phenomena. Its aim is to contribute to knowledge in support of clinical medicine and community medicine. Epidemiological research uses scientific methods, in which empirical evidence is obtained from a study population to make inferences about a target population. In this chapter we first establish a definition of epidemiology and describe the wide scope of epidemiology in terms of its subject domains, types of research topics, types of study designs, and range of research activities that occur from a study’s inception to its publication. Since epidemiology concerns both ‘scientific studies’ and ‘particularistic fact-finding investigations,’ we further orient the reader to the scope of epidemiology through a discussion of these. We then introduce general epidemiological principles that health researchers should continuously keep in mind during the planning, gathering and presentation of the empirical evidence. All of these topics are pursued in more depth in the chapters that follow.

Many clinical decisions, risk assessments, and public health policy decisions depend on the results of epidemiologic studies. Very rarely, however, do all studies on a particular subject reach the same conclusion. Consequently, there is a need in epidemiology to synthesize differing study findings objectively. Two related approaches to synthesizing findings from multiple studies are the systematic literature review and the meta-analysis. The purposes of this chapter are to introduce each of these useful approaches, to highlight their assumptions and limitations, and to illuminate practical aspects of conducting your own systematic literature reviews and meta-analyses.

Dissemination of scientific work to others is an essential component of the research process. The most common form of dissemination is to publish articles in academic journals (See: Chaps. 28 and 31); however, a researcher may wish to disseminate work directly to the public, policymakers, or other non-academic stakeholders to achieve desirablwe effects on public health and to enhance the profile of the research team. A general discussion around engaging with stakeholders is found in Chap. 8. The current chapter extends our discussion of engaging with stakeholders from the perspective of disseminating scientific work in forms other than academic journal articles. First, we will introduce principles of dissemination and diffusion of information. We will then provide practical advice on developing dissemination strategies and on communicating with selected types of stakeholders, such as news media reporters. Finally, we discuss some ethical aspects of influencing public health policy and summarize practical advice in this respect.

Background Cultural pressures to be thin and tall are postulated to cause people to misreport their body weight and height towards more socially normative (i.e., desirable) values, but a paucity of direct evidence supports this idea. We developed a novel non-linear approach to examining weight, height, and BMI misreporting biases and used this approach to examine the association between socially non-normative weight and misreporting biases in adults. Methods The Survey of Lifestyles, Attitudes, and Nutrition 2007 (SLÁN 2007), a nationally representative survey of the Republic of Ireland (N = 1942 analyzed) was used. Self-reported weight (height) was classified as under-reported by ≥2.0 kg (2.0 cm), over-reported by ≥2.0 kg (2.0 cm), or accurately reported within 2.0 kg (2.0 cm) to account for technical errors of measurement and short-term fluctuations in measured weight (height). A simulation strategy was used to define self-report-based BMI as under-estimated by more than 1.40 kg/m2, over-estimated by more than 1.40 kg/m2, or accurately estimated within 1.40 kg/m2. Patterns of biases in self-reported weight, height, and BMI were explored. Logistic regression was used to identify factors associated with mis-estimated BMI and to calculate adjusted odds ratios (AOR) and 99% confidence intervals (99%CI). Results The patterns of bias contributing the most to BMI mis-estimation were consistently, in decreasing order of influence, (1) under-reported weight combined with over-reported height, (2) under-reported weight with accurately reported height, and (3) accurately reported weight with over-reported height. Average bias in self-report-based BMI was -1.34 kg/m2 overall and -0.49, -1.33, and -2.66 kg/m2 in normal, overweight, and obese categories, respectively. Despite the increasing degree of bias with progressively higher BMI categories, persons describing themselves as too heavy were, within any given BMI category, less likely to have under-estimated BMI (AOR 0.5, 99%CI: 0.3-0.8, P < 0.001), to be misclassified in a lower BMI category (AOR 0.3, 99%CI: 0.2-0.5, P < 0.001), to under-report weight (AOR 0.5, 99%CI: 0.3-0.7, P < 0.001), and to over-report height (OR 0.7, 99%CI: 0.6-1.0, P = 0.007). Conclusions A novel non-linear approach to examining weight, height, and BMI misreporting biases was developed. Perceiving oneself as too heavy appears to reduce rather than exacerbate weight, height, and BMI misreporting biases.

An acute bout of endurance exercise (EE) enhances insulin sensitivity, but the effects of sprint interval exercise (SIE) have not yet been described. We sought to compare insulin sensitivity at baseline and after an acute bout of EE and SIE in healthy men (n = 8) and women (n = 5) (age, 20.7 ± 0.3 years; peak oxygen consumption (VO2 peak), 42.6 ± 1.7 mL·kg–1·min–1; –1 structured exercise; body fat, 21.1 ± 1.9%). Subjects underwent 3 oral glucose tolerance tests (OGTTs) the day after each of the following 3 conditions: no exercise, baseline (OGTTB); SIE at ~125% VO2 peak (OGTTSIE); and EE at ~75% VO2 peak (OGTTEE). SIE and EE sessions were randomized for each subject. Subjects consumed identical meals the day preceding each OGTT. Two insulin sensitivity indices — composite whole-body insulin sensitivity index (ISI-COMP) and ISI-hepatic insulin sensitivity (HOMA) — were calculated, using previously validated formulas (ISI-COMP = 10 000/√(glucosefasting × insulinfasting × glucosemean OGTT × insulinmean OGTT); ISI-HOMA = 22.5/(insulinfasting × glucosefasting)), and the plasma concentrations of cytokines interleukin-6 and tumor necrosis factor-α were measured. There were no differences by sex for any condition (men vs. women, p > 0.05). Pearson’s correlation coefficients between ISI-COMP and ISI-HOMA for each condition were highly correlated (p < 0.01), and followed similar patterns of response. ISI-COMPEE was 71.4% higher than ISI-COMPB (8.4 ± 1.4 vs. 4.9 ± 1.0; p < 0.01) and 40.0% higher than ISI-COMPSIE (8.4 ± 1.4 vs. 6.0 ± 1.5; p < 0.05), but there was no difference between ISI-COMPB and ISI-COMPSIE (p = 0.182). VO2 peak was highly correlated with both ISI-COMP and ISI-HOMA during baseline and SIE test conditions (p < 0.02). These findings demonstrate that an acute bout of EE, but not SIE, increases insulin sensitivity relative to a no-exercise control condition in healthy males and females. While these findings underscore the use of regular EE as an effective intervention strategy against insulin resistance, additional research examining repeated sessions of SIE on insulin sensitivity is warranted.

Studies of cultured cells have indicated that the mammalian target of rapamycin complex 1 (mTORC1) mediates the development of insulin resistance. Because a role for mTORC1 in the development of skeletal muscle insulin resistance has not been established, we studied mTORC1 activity in skeletal muscles of ob/ob (OB) mice and wild-type (WT) mice. In vivo insulin action was assessed in muscles of mice 15 min following an intraperitoneal injection of insulin or an equivalent volume of saline. In the basal state, the phosphorylation of S6K on Thr389, mTOR on Ser2448, and PRAS40 on Thr246were increased significantly in muscles from OB mice compared with WT mice. The increase in basal mTORC1 signaling was associated with an increase in basal PKB phosphorylation on Thr308and Ser473. In the insulin-stimulated state, no differences existed in the phosphorylation of S6K on Thr389, but PKB phosphorylation on Thr308and Ser473was significantly reduced in muscles of OB compared with WT mice. Despite elevated mTORC1 activity in OB mice, rapamycin treatment did not improve either glucose tolerance or insulin tolerance. These results indicate that the insulin resistance of OB mice is mediated, in part, by factors other than mTORC1.

The superoxide dismutase mimetic manganese [III] tetrakis [5,10,15,20]-benzoic acid porphyrin (MnTBAP) is a potent antioxidant compound that has been shown to limit weight gain during short-term high fat feeding without preventing insulin resistance. However, whether MnTBAP has therapeutic potential to treat pre-existing obesity and insulin resistance remains unknown. To investigate this, mice were treated with MnTBAP or vehicle during the last five weeks of a 24-week high fat diet (HFD) regimen. MnTBAP treatment significantly decreased body weight and reduced white adipose tissue (WAT) mass in mice fed a HFD and a low fat diet (LFD). The reduction in adiposity was associated with decreased caloric intake without significantly altering energy expenditure, indicating that MnTBAP decreases adiposity in part by modulating energy balance. MnTBAP treatment also improved insulin action in HFD-fed mice, a physiologic response that was associated with increased protein kinase B (PKB) phosphorylation and expression in muscle and WAT. Since MnTBAP is a metalloporphyrin molecule, we hypothesized that its ability to promote weight loss and improve insulin sensitivity was regulated by heme oxygenase-1 (HO-1), in a similar fashion as cobalt protoporphyrins. Despite MnTBAP treatment increasing HO-1 expression, administration of the potent HO-1 inhibitor tin mesoporphyrin (SnMP) did not block the ability of MnTBAP to alter caloric intake, adiposity, or insulin action, suggesting that MnTBAP influences these metabolic processes independent of HO-1. These data demonstrate that MnTBAP can ameliorate pre-existing obesity and improve insulin action by reducing caloric intake and increasing PKB phosphorylation and expression.

In a logical sequence of progressively deduced propositions and principles, Dr. Miettinen attempts to re-orient medical academia to the theories underlying clinical research in his recent book Up from Clinical Epidemiology & EBM (Evidence Based Medicine) [1]. This ambitious avant-garde text first examines the role of medical academia and criticizes—perhaps too harshly at times—the current ways of achieving knowledge about diagnosis, etiognosis, and prognosis in clinical medicine. Currently lacking for clinicians is an immediately applicable scientific knowledge base of clinical practice. Instead, in the current clinical epidemiology culture, practitioners are advised to spend lengths of time critically appraising literature on particular topics, form their own opinions on it, and use their uncodified experiences and varying opinions to make clinical decisions. The aim of EBM to standardize clinical practice is stymied by the process currently required to employ EBM. Exacerbating the problem are widespread imperfections in designs of clinical studies. For these reasons and others, Miettinen argues that EBM is a fallacy, “a cult movement…at variance with the essence of science and the imperatives of professionalism in medicine.” In place of current EBM, Miettinen suggests different approaches to diagnosis, etiognosis, and prognosis—ones that are arguably more valid and objective and that may have the potential to bring major improvements to clinical medicine. To construct a proper knowledge base for clinical practice and offer it in a more directly usable form, Miettinen proposes the construction and use of ‘gnostic probability functions.’ These address the probability of an illness being present, a risk factor having played a causal role, or an untoward event happening in the course of an illness as a function of diagnostic, etiognostic, or prognostic indicators, respectively. Miettinen develops in his book many new ideas about diagnosis, so we focus our review mainly to these. In support of diagnosis, Miettinen proposes that diagnostic probability functions (DPF) be used instead of ‘reverse probabilities’ (i.e., probabilities derived from comparing past signs and symptoms in series of patients and non-patients) and Bayes factors now commonly used in clinical epidemiology. Miettinen describes a strategy of constructing DPF using codified tacit knowledge of experts. We agree with Lubsen [2] that the description of this strategy is one of the major contributions of the book. Basically, panels of experts are presented with hypothetical patient presentations and asked to attach a probability to each scenario that a particular illness is present. Using the responses from many experts, multiple logistic regression analysis is then employed to model the probability of an illness as a function of diagnostic indicators, which include components of the risk profile (e.g., socio-demographic factors) and manifestation profile (e.g., symptoms, signs, and test results). The resulting model is incorporated into software that allows users to estimate diagnostic probabilities for real presenting patients. A derived method provides for the evaluation of diagnostic tests as well. As Miettinen states, “In this Information Age, the implication is that the availability of user-friendly gnostic expert systems would enhance the efficiency of healthcare by inherently contributing to both quality assurance and cost containment in it.” Assuming that valid DPF are defined for a wide enough range of clinical scenarios, we too see the approach of codifying experts’ tacit knowledge and the e-implementation of DPF as having great promise in supporting clinical diagnosis, especially in settings where clinical expertise is limited or inaccessible. However, a probability function will be only as good as the data used to fit such a model. We note that those data will be limited by the ability of experts to recognize and accurately describe all aspects of an illness process or presentation, and must be regularly updated to accommodate evolving perspectives of disease and continuous biomedical innovation. There may be a role here for cloud-based artificial intelligence. The scale of research efforts needed to construct such detailed descriptions of diagnostic profiles and the challenges of implementing DPF seem so daunting that we are sceptical about the practical nature of this great idea. Moreover, it is unclear to us how well such models can incorporate local effect-modifying circumstances as part of the risk profile, or how useful they will be for atypical clinical presentations. Yet even if the use of DPF is not feasible for making refined diagnoses, we wonder about the value of their application for the specific purpose of triage. A major theme in Up from Clinical Epidemiology & EBM is that several currently popular general study designs—examples of which include the cohort, case–control, and traditional diagnostic performance studies—are fallacies. This theme has also dominated many of Miettinen’s previous writings. We agree with him that classical cohort studies fail to see etiologic time as inherently negative; that classical case–control approaches fail to define the reference series from the study base; and that traditional diagnostic studies are limited by their reverse orientation and inability to clearly define a study domain. For Miettinen these imperfections, together with his view that particularistic studies are not scientific and not even research, seem to imply the need for a tabula rasa approach, a blank slate. Consequently, the range of general study designs considered in this book is narrower than what many readers will expect. Readers should be advised that reading this book is a serious undertaking, and we recommend using Miettinen’s other recent book Epidemiological Research: Terms and Concepts [3–5] in support. By questioning widely held assumptions and using logical deductive reasoning, Miettinen invokes his Socratic nature and confirms his great strength as a theoretical epidemiologist. We highly recommend this fascinating book to all epidemiologists and look forward to the much-needed discourse on its content.

Concepts and terms are the building blocks of our reasoning and communication, respectively, and are therefore crucial in epidemiology. Unfortunately, many epidemiologists today would agree that there is confusion about many concepts and terms within our discipline. Serious theoretical work on this issue, like the work presented in Dr Miettinen's latest book, Epidemiological Research: Terms and Concepts,1 should therefore be very welcome. This book contains a selection of concepts and terms that he sees as crucial for epidemiological research; some of these concepts and terms are not yet familiar to all epidemiologists, nor are all of his definitions in line with received ideas, and it is partly for these reasons that the book is particularly interesting. This book is the condensation of many decennia of serious reflection and has the potential to advance considerably our understanding of the theoretical dimensions of epidemiology. One of the striking features of the book is its unusual structure: the concepts and terms are grouped in chapters based on whether they pertain to medicine, science and statistics in Part I, or to epidemiological or clinical (meta-epidemiological) research in Part II. Consequently, looking up terms is not as straightforward as in traditionally formatted dictionaries or glossaries; instead, the use of the index is necessary if one wants to find a term. Alternative definitions of that term are then distributed in different chapters rather than being grouped together. For example, ‘study’ appears under both ‘Terms and Concepts of Medicine’ and ‘Terms and Concepts of Science.’ Miettinen’s intention with this structure is obviously didactical: to encourage users to make the proper distinctions between categories of concepts. Miettinen’s highly laudable passion is to challenge epidemiologists to think and re-think. The chosen structure of the book constitutes such a challenge. It offers a unique and exciting opportunity for learning but may also seem a little daunting. The book is thus much more than just a dictionary. It is also an important book for studying and gaining deeper insight into the theory of epidemiology. Indeed, studying definitions in this book and comparing them with those found in the International Epidemiology Association (IEA) dictionary2 is a very interesting and instructive exercise. Some of the terms will be new for those unfamiliar with Miettinen’s corpus, and it is helpful to have this book at hand when reading Miettinen’s other works, such as his other recent book Up from Clinical Epidemiology and EBM (Evidence Based Medicine)3,4. The definitions express and clarify Miettinen’s particular views on science and epidemiological research. The definition of ‘study’ under the category of Terms and Concepts of Science is an example that illustrates this point. The definition starts with ‘Study - A piece of research; that is, a project to produce evidence (for inductive judgments) about the abstract truth (unknown) at issue … ’ When reading this definition, one must keep in mind the category of concepts for this particular definition and Miettinen’s framework of thinking to understand that, in this particular definition, ‘study’ only concerns the search for abstract scientific truths and excludes surveys, outbreak investigations or other particularistic investigations. To understand Miettinen’s framework of thinking, it is sufficient usually to read the chapter introductions and accompanying annotations. These explain and clarify Miettinen’s views of the chosen concepts and, especially, how his views are different from mainstream views and commonly held assumptions, mainly as reflected in the IEA dictionary. Worth mentioning is the rather limited overlap of entries with the IEA dictionary, and this is a supplementary reason why this book is useful. Miettinen has, on multiple occasions, scholarly criticized definitions in the IEA dictionary, leaving many in the field to expect that Miettinen would produce an alternative dictionary or glossary. This book is his response. Although we think this book advances the theory of epidemiology, we note that two dimensions of epidemiological research are receiving comparatively less attention than the theoretical-scientific dimension covered in Miettinen’s book: these are the practical and ethical dimensions of research, although ethical aspects have received some attention. This book will be particularly helpful for those interested in theoretical epidemiology and concerned with proper usage of concepts and terms. We therefore warmly recommend it to all students of epidemiology and all practitioners of epidemiological research.

Received 26 February 2009. Accepted 26 February 2009. Published on the NRC Research Press Web site at apnm.nrc.ca on 1 April 2009. J.R. Brestoff, B. Clippinger, T. Spinella, and P.J. Arciero.1 Department of Exercise Science, Skidmore College, Saratoga Springs, NY 12866, USA. S.P. vonDuvillard. Department of Sport Science and Kinesiology, University of Salzburg, Austria. B.C. Nindl. United States Army Research Institute of Environmental Medicine, Military Performance Division, Natick, MA 01760, USA. 1Corresponding author (e-mail: parciero@skidmore.edu). 306

Atopic dermatitis (AD) is a widespread, chronic skin disease associated with aberrant allergic inflammation. Current treatments involve either broad or targeted immunosuppression strategies. However, enhancing the immune system to control disease remains untested. We demonstrate that patients with AD harbor a blood natural killer (NK) cell deficiency that both has diagnostic value and improves with therapy. Multidimensional protein and RNA profiling revealed subset-level changes associated with enhanced NK cell death. Murine NK cell deficiency was associated with enhanced type 2 inflammation in the skin, suggesting that NK cells play a critical immunoregulatory role in this context. On the basis of these findings, we used an NK cell-boosting interleukin-15 (IL-15) superagonist and observed marked improvement in AD-like disease in mice. These findings reveal a previously unrecognized application of IL-15 superagonism, currently in development for cancer immunotherapy, as an immunotherapeutic strategy for AD.