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Macrophages, B cells, and adipocytes are among the adipose tissue (AT) APCs that differentiate and activate naive CD4+ T cells. Mice with adipocyte loss of MHC class II (MHC II) are more insulin sensitive. Because macrophages are professional APCs, mice with genetic myeloid MHC II depletion (myeloid MHC II knockout [mMHCII2/2]) were created and metabolically characterized. FITC+ glucan-coated particles (glucan-encapsulated small interfering RNA [siRNA] particles [GeRPs]) were also used to target MHC II knockout specifically in AT macrophages (ATMs). Mice with total body mMHCII-/- were generated by crossing LyzMCre with H2Ab1 floxed mice. For specific ATM depletion of H2Ab1, GeRPs containing H2Ab1 siRNA were administered to high-fat diet--fed C57BL/6 mice. Unexpectedly, mMHCII-/- mice had loss of both macrophage and adipocyte H2Ab1, one of only two Ag-presenting arms; thus, neither cell could present Ag and activate CD4+ T cells. This inability led to a reduction in AT immunosuppressive regulatory T cells, increased AT CD8+ T cells, and no improvement in systemic metabolism. Thus, with combined systemic myeloid and adipocyte MHC II loss, the impact of ATM-specific alterations in APC activity could not be delineated. Therefore, GeRPs containing H2Ab1 siRNA were administered to specifically reduce ATM H2Ab1 which, in contrast, revealed improved glucose tolerance. In conclusion, loss of either ATM or adipocyte APC function, but not both, improves systemic glucose metabolism because of maintenance of ATregulatory T cells. [ABSTRACT FROM AUTHOR]

Obesity is associated with a state of chronic low-grade inflammation both systemically and within specific tissues, including adipose tissue (AT). In murine models of obesity, there is a shift in the inflammatory profile of the AT immune cells, with an accumulation of proinflammatory M1 macrophages that surround the expanding adipocyte. However, much less is known about the immune cell composition and how to best define AT macrophages in humans. Objective. The goals of the current study were to determine the contribution of macrophages to the stromal vascular fraction (SVF) in lean versus obese human visceral AT (VAT); examine the expression of common M1, M2, and pan macrophage markers; and determine the association of specific macrophage types with known biomarkers of obesity-related cardiometabolic disease. Research Design and Methods. VAT biopsies were obtained from obese (n=50) and lean (n=8) patients during elective surgery. Adipocytes and SVF were isolated, and the SVF was subjected to flow cytometry analyses. Results. Our results indicate that VAT macrophages are increased in obesity and associate with biomarkers of CVD but that many macrophages do not fall into currently defined M1/M2 classification system based on CD206 receptor expression levels. Conclusions. VAT macrophages are increased in obese subjects, but the current markers used to define macrophage populations are inadequate to distinguish differences in human obesity. Further studies are needed to delineate the function of AT macrophages in the maintenance and progression of human AT inflammation in obesity. [ABSTRACT FROM AUTHOR]

For patients on multiple sequential systemic medications, the baseline for each was the laboratory value before medication start and the endpoint was 12 months or the cessation of medication. Since BMI has been linked with psoriasis severity[5], it is plausible that patients treated with systemic therapy had more severe disease at outset, although this cannot be confirmed since disease severity was not recorded. Patients utilizing systemic therapy were treated as follows: 7/26 patients with methotrexate, 13/26 with etanercept, 6/26 with adalimumab, 3/26 with infliximab, 4/26 with secukinumab, 4/26 with ustekinumab, 5/26 with apremilast, and 4/26 with acitretin. [Extracted from the article]

Background: AT Tregs are decreased in obese mice. We have previously shown that preventing this decline improves insulin sensitivity, despite persistent obesity, underscoring a key role for AT Tregs in systemic metabolism. Therefore, we sought to examine AT Treg changes in human subjects and elucidate potential mechanisms responsible for these changes. Methods: We obtained visceral (VAT) and subcutaneous adipose tissue (SAT) at elective surgery in 54 obese and 18 lean subjects, and SAT via liposuction in 15 lean subjects before and after 2 weeks high fat diet (HFD). Results: Obese individuals had 67% less Treg abundance in VAT (p<0.001) and 79% in SAT (p<0.001); Tregs as %CD4+ cells correlated with insulin sensitivity and inversely with BMI. Subjects ingesting a HFD experienced a 50% drop in SAT Tregs (p<0.001), which correlated with decreased insulin sensitivity by clamp. To understand this drop, we next performed gene expression analyses on isolated adipocytes, AT T cells, and VAT Tregs. Obese adipocytes had profound increases in major histocompatibility class II (MHCII) genes, but decreases in fatty acid oxidation and mitochondrial genes, suggesting a functional switch from a primary metabolic to an adaptive immune cell. These changes were associated with decreased AT Treg abundance, and increased insulin resistance and BMI. T cells revealed increased Tbet, a proinflammatory CD4+ Th1 cell marker, and decreased FOXP3, a Treg marker, consistent with our demonstration that human adipocytes can present antigen to activate CD4+ Th1 cells. Obese vs. lean VAT Tregs also had a 3-fold (p<0.05) increase in the T cell exhaustion marker, program cell death protein-1 (PD-1), and a 75% (p<0.05) decrease in CD127, which is attenuated in exhausted T cells. Discussion: Thus, human adipocyte immune cell activity, combined with Treg exhaustion, contributes to the drop in AT Tregs and strongly affects metabolism. Disclosure: D. Bradley: None. A.M. Blaszczak: None. A. Smith: None. A.D. Jalilvand: None. V.P. Wright: None. K. Wyne: Advisory Panel; Self; Novo Nordisk Inc. Research Support; Self; Sanofi. S. Noria: None. J. Joseph: None. J.Z. Liu: None. W. Hsueh: None. Funding: American Diabetes Association (1-16-ICTS-049 to W.H.); National Institutes of Health (KL2TR001068, R01HL135622) [ABSTRACT FROM AUTHOR]

Background: In the absence of a gold-standard diagnostic modality for cellulitis, sterile inflammatory disorders may be misdiagnosed as cellulitis. Objective: To determine the utility of skin biopsy and tissue culture for the diagnosis and management of patients admitted with a diagnosis of presumed cellulitis. Design: Pilot single-blind parallel group randomized controlled clinical trial in 56 patients with a primary diagnosis of presumed cellulitis. In the intervention group only, skin biopsy and tissue culture results were made available to the primary care team to guide diagnosis and management. Length of hospital stay and antibiotic use were evaluated as outcome measures. Results: Length of stay showed the greatest opportunity for further study as a primary outcome (intervention: 4, IQR (2–6) vs. control: 5 IQR (3–8) days; p = 0.124). Limitations: The COVID-19 pandemic placed limitations on participant enrollment and study duration; in addition, data was collected from a single medical center. Conclusion: This study demonstrates that length of stay and anti-pseudomonal antibiotic de-escalation are endpoints that may be influenced by biopsy and tissue culture results in presumed cellulitis patients; these outcomes warrant further study. [ABSTRACT FROM AUTHOR]

Background: In the absence of a gold-standard diagnostic modality for cellulitis, sterile inflammatory disorders may be misdiagnosed as cellulitis. Objective: To determine the utility of skin biopsy and tissue culture for the diagnosis and management of patients admitted with a diagnosis of presumed cellulitis. Design: Pilot single-blind parallel group randomized controlled clinical trial in 56 patients with a primary diagnosis of presumed cellulitis. In the intervention group only, skin biopsy and tissue culture results were made available to the primary care team to guide diagnosis and management. Length of hospital stay and antibiotic use were evaluated as outcome measures. Results: Length of stay showed the greatest opportunity for further study as a primary outcome (intervention: 4, IQR (2–6) vs. control: 5 IQR (3–8) days; p = 0.124). Limitations: The COVID-19 pandemic placed limitations on participant enrollment and study duration; in addition, data was collected from a single medical center. Conclusion: This study demonstrates that length of stay and anti-pseudomonal antibiotic de-escalation are endpoints that may be influenced by biopsy and tissue culture results in presumed cellulitis patients; these outcomes warrant further study. [ABSTRACT FROM AUTHOR]

Background: The obese adipose tissue (AT) immune cell microenvironment contributes to low-grade inflammation increasing the risk of multiple metabolic complications. Type 2 innate lymphoid cells (ILC2s) were recently discovered in mice to regulate metabolic health, but the clinical relevance of ILC2s in human AT is unknown. Rationale: Our goals were to characterize changes human AT ILC2s in obesity, insulin resistance, and aging. We further examined changes in AT ILC2s with aging, high fat diet (HFD), and weight loss in mice. Methods: We collected visceral AT (VAT) biopsies from 50 obese and 9 lean patients during elective surgery, isolated the adipocytes from the stromal vascular fraction, and performed flow cytometry. Results: Human VAT %ILC2s were not different between lean and obese subjects (p=0.896), but were negatively associated with insulin sensitivity (r=-0.449, p=0.005), beta-cell function (r=-0.364, p=0.024), and increasing age (r=-0.337, p=0.012). ILC2s were also positively associated with T helper type 2 cells (Th2s). All of these relationships were independent of BMI and gender, suggesting that ILC2s play a weight-independent role in human glucose homeostasis and age-related insulin resistance, possibly through an interaction with Th2s. When placed on HFD for 6 and 12 weeks, mice demonstrated a depletion in VAT ILC2s, and 12- vs. 3-month old mice had decreased VAT ILC2s, which did not recover after 12 weeks of weight loss despite normalization of body weight. Conclusions: In humans and mice, VAT ILC2s decrease with HFD and age. In humans ILC2s may be a weight-independent determinant of hyperinsulinemia and insulin resistance, provide a potential link to reduced insulin sensitivity in aging, and offer a novel therapeutic target in insulin resistance and T2D. Disclosure: D. Bradley: None. A.M. Blaszczak: None. J.Z. Liu: None. A.D. Jalilvand: None. V.P. Wright: None. S. Noria: None. J. Joseph: None. W. Hsueh: None. Funding: American Diabetes Association (1-16-ICTS-049 to W.H.); National Institutes of Health (KL2TR001068, HL135622) [ABSTRACT FROM AUTHOR]

Adipose resident T lymphocytes (ARTs) are known metabolic mediators in mice. In particular, immunosuppressive regulatory T cells (Tregs) protect against insulin resistance. However, little is known about ARTs in humans or the effect of human weight gain on the AT immunoenvironment. We obtained visceral AT (VAT) and subcutaneous AT (SAT) biopsies from obese (n=83, BMI 48.9±8.5 kg/m2) and lean (n=15, BMI 23.6±1.9 kg/m2) patients undergoing elective surgery. A separate group of lean metabolically healthy patients (n=15, BMI 22.4 ± 1.8 kg/m2) underwent baseline and repeat SAT biopsies and hyperinsulinemic clamps before and after 2 weeks of a high-fat diet (HFD) overfeeding protocol (additional 1,320 kcal/day:>50% total fat:>10% saturated fat). Adipocytes were isolated for gene expression and flow analysis. Tregs (CD4+CD25+FOXP3+) as percent (%) of CD4+ cells were substantially increased in lean compared to obese SAT (22.1±15.0% vs. 7.3±3.8%; p<0.001) and VAT (18.9±16.8% vs. 3.9±2.7%; p<0.001) and negatively correlated with BMI and insulin sensitivity. After HFD, there was a significant increase in BMI (p<0.001) and fasting glucose (p<0.001), but no change in fasting insulin or HOMA-IR. We noted a dramatic overall decline in SAT Tregs after HFD (7.5 ± 1.0% to 3.3 ± 0.5%, p<0.001), with all participants experiencing a decrease. The post-surgical change in SAT %Tregs positively correlated with the change in insulin sensitivity (M value) by hyperinsulinemic-euglycemic clamp (p=0.003, r=+0.797), so that those subjects with the greatest decline in Tregs had the largest decline in insulin sensitivity. This relationship persisted despite adjusting for, age, gender, pre-intervention BMI, and the change in weight from pre to post intervention (p=0.012). Our data thus demonstrates that Tregs decline in response to acute overfeeding, potentially contributing to development of insulin resistance. These results highlight a role for adipose tissue Tregs in human metabolism. Disclosure: D. Bradley: None. A.M. Blaszczak: None. A.D. Jalilvand: None. V.P. Wright: None. S. Noria: None. J. Joseph: None. J.Z. Liu: None. W. Hsueh: None. Funding: American Diabetes Association (1-16-ICTS-049 to W.H.); National Institutes of Health (KL2TR001068, HL135622) [ABSTRACT FROM AUTHOR]

Background: Obesity heightens the risk for both cardiometabolic complications and Alzheimer's disease (AD). Although the reasons have yet to be fully elucidated, weight loss improves cognition. Given this link, factors overproduced by obese adipose tissue are ideal candidates for novel investigation into AD pathogenesis. We have recently shown that clusterin from the adipocyte is related to multiple factors of the metabolic syndrome (insulin resistance, dyslipidemia, NAFLD, and atherosclerosis). Clusterin is also involved in CNS lipid trafficking and has been proposed as an AD biomarker. Rationale: Our goals were to characterize the effect of high-fat diet (HFD) feeding on CNS clusterin and neuronal insulin signaling in an AD mouse model (5XFAD); and furthermore, determine the relationship of adipocyte clusterin with neurocognition and insulin sensitivity in obese humans at baseline and following bariatric surgery. Methods: We treated 5XFAD and WT mice with normal chow and HFD for 4 mo., measured CNS clusterin, and determined its effect on neuronal insulin signaling. We next measured subcutaneous adipocyte (SAd) clusterin expression, and performed neuropsychological evaluation and a hyperinsulinemic-euglycemic clamp procedure in obese human subjects (n=11) before and after sleeve gastrectomy. Results: In the 5XFAD mice, HFD increases brain clusterin levels compared to WT, and in primary cortical neurons clusterin attenuates insulin signaling in a dose-dependent manner. In humans, SAd clusterin is related to hepatic insulin resistance, higher fasting glucose, and reduced working memory/attention. After sleeve gastrectomy SAd clusterin expression is reduced, with a significant inverse association between clusterin and working memory/attention and hepatic insulin sensitivity. Conclusions: Our data suggests that SAd clusterin is a potential player in AD pathology, providing a critical link between excess adiposity, T2D, insulin resistance, and heightened AD risk. Disclosure: D. Bradley: None. J.Z. Liu: None. A.M. Blaszczak: None. V.P. Wright: None. R. Tarawneh: None. Y. Liu: None. J. Ryu: None. S. Yoon: None. W. Hsueh: None. Funding: American Diabetes Association (1-16-ICTS-049 to W.H.); National Institutes of Health (KL2TR001068, R01HL135622) [ABSTRACT FROM AUTHOR]