OBJECTIVE-We sought to determine the role of adipocyte death in obesity-induced adipose tissue (AT) inflammation and obesity complications.RESEARCH DESIGN AND METHODS-Male C57BL/6 mice were fed a high-fat diet for 20 weeks to induce obesity. Every 4 weeks, insulin resistance was assessed by intraperitoneal insulin tolerance tests, and epididymal (eAT) and inguinal subcutaneous AT (iAT) and livers were harvested for histological, immunohistochemical, and gene expression analyses.RESULTS-Frequency of adipocyte death in eAT increased from Ͻ0.1% at baseline to 16% at week 12, coincident with increases in 1) depot weight; 2) AT macrophages (ATM⌽s) expressing F4/80 and CD11c; 3) mRNA for tumor necrosis factor (TNF)-␣, monocyte chemotactic protein (MCP)-1, and interleukin (IL)-10; and 4) insulin resistance. ATM⌽s in crown-like structures surrounding dead adipocytes expressed TNF-␣ and IL-6 proteins. Adipocyte number began to decline at week 12. At week 16, adipocyte death reached ϳ80%, coincident with maximal expression of CD11c and inflammatory genes, loss (40%) of eAT mass, widespread collagen deposition, and accelerated hepatic macrosteatosis. By week 20, adipocyte number was restored with small adipocytes, coincident with reduced adipocyte death (fourfold), CD11c and MCP-1 gene expression (twofold), and insulin resistance (35%). eAT weight did not increase at week 20 and was inversely correlated with liver weight after week 12 (r ϭ Ϫ0. 85, P Ͻ 0.001). In iAT, adipocyte death was first detected at week 12 and remained Յ3%.CONCLUSIONS-These results implicate depot-selective adipocyte death and M⌽-mediated AT remodeling in inflammatory and metabolic complications of murine obesity. Diabetes

Patients with type 2 diabetes (T2D) have disease-associated changes in B-cell function, but the role these changes play in disease pathogenesis is not well established. Data herein show B cells from obese mice produce a proinflammatory cytokine profile compared with B cells from lean mice. Complementary in vivo studies show that obese B cell-null mice have decreased systemic inflammation, inflammatory B-and T-cell cytokines, adipose tissue inflammation, and insulin resistance (IR) compared with obese WT mice. Reduced inflammation in obese/insulin resistant B cell-null mice associates with an increased percentage of anti-inflammatory regulatory T cells (Tregs). This increase contrasts with the sharply decreased percentage of Tregs in obese compared with lean WT mice and suggests that B cells may be critical regulators of T-cell functions previously shown to play important roles in IR. We demonstrate that B cells from T2D (but not non-T2D) subjects support proinflammatory T-cell function in obesity/T2D through contact-dependent mechanisms. In contrast, human monocytes increase proinflammatory T-cell cytokines in both T2D and non-T2D analyses. These data support the conclusion that B cells are critical regulators of inflammation in T2D due to their direct ability to promote proinflammatory T-cell function and secrete a proinflammatory cytokine profile. Thus, B cells are potential therapeutic targets for T2D.immunometabolism | lymphocytes M ultiple studies support the concept that inflammation strongly associates with insulin resistance (IR), which, in addition to loss of islet function, defines type 2 diabetes (T2D) (1). Work implicating B cells in IR/T2D is limited. We showed B cells from T2D subjects secrete a proinflammatory cytokine profile, including an extraordinary inability to secrete the potent anti-inflammatory cytokine IL-10 and an elevated production of proinflammatory IL-8 compared with B cells from non-T2D subjects (2). Given the importance of B-cell IL-10 in preventing numerous inflammatory diseases (3, 4) and the links between IL-8 and T2D (5, 6), these data suggest that altered B-cell cytokine production plays an important role in initiating or promoting IR/T2D. Published analyses further support a role for B cells in IR and include studies of B cell-null New Zealand Obese (NZO) mice, which, in contrast to B cell-sufficient NZOs, fail to develop IR in response to obesity (7). These findings have been recently reproduced in studies showing obese B cell-null or B cell-depleted mice have less inflammation and IR than obese WT mice (8). Interestingly, T-cell cytokine production is decreased in obese B cell-null mouse adipose tissue (AT) (8), which raises the possibility that, in addition to production of a proinflammatory cytokine profile, B cells may function in IR by regulating the T cell-mediated inflammation known to drive disease pathogenesis (9, 10). We identified a proinflammatory T-cell ratio [defined by increased Th17 cells plus decreased regulatory T cells (Tregs)] in T2D patients that mirror...

Adipose tissue (AT) inflammation promotes insulin resistance (IR) and other obesity complications. AT inflammation and IR are associated with oxidative stress, adipocyte death, and the scavenging of dead adipocytes by proinflammatory CD11c+ AT macrophages (ATMPhi). We tested the hypothesis that supplementation of an obesitogenic (high-fat) diet with whole blueberry (BB) powder protects against AT inflammation and IR. Male C57Bl/6j mice were maintained for 8 wk on 1 of 3 diets: low-fat (10% of energy) diet (LFD), high-fat (60% of energy) diet (HFD) or the HFD containing 4% (wt:wt) whole BB powder (1:1 Vaccinium ashei and V. corymbosum) (HFD+B). BB supplementation (2.7% of total energy) did not affect HFD-associated alterations in energy intake, metabolic rate, body weight, or adiposity. We observed an emerging pattern of gene expression in AT of HFD mice indicating a shift toward global upregulation of inflammatory genes (tumor necrosis factor-alpha, interleukin-6, monocyte chemoattractant protein 1, inducible nitric oxide synthase), increased M1-polarized ATMPhi (CD11c+), and increased oxidative stress (reduced glutathione peroxidase 3). This shift was attenuated or nonexistent in HFD+B-fed mice. Furthermore, mice fed the HFD+B were protected from IR and hyperglycemia coincident with reductions in adipocyte death. Salutary effects of BB on adipocyte physiology and ATMPhi gene expression may reflect the ability of BB anthocyanins to alter mitogen-activated protein kinase and nuclear factor-kappaB stress signaling pathways, which regulate cell fate and inflammatory genes. These results suggest that cytoprotective and antiinflammatory actions of dietary BB can provide metabolic benefits to combat obesity-associated pathology.

The role of adaptive immunity in obesity-associated adipose tissue (AT) inflammation and insulin resistance (IR) is controversial. We employed flow cytometry and quantitative PCR to assess T-cell recruitment and activation in epididymal AT (eAT) of C57BL/6 mice during 4-22 weeks of a high (60% energy) fat diet (HFD). By week 6, eAT mass and stromal vascular cell (SVC) number increased 3-fold in mice fed HFD, coincident with onset of IR. We observed no increase in the proportion of CD3+ SVCs or in gene expression of CD3, IFNγ, or regulated upon activation, normal T-cell expressed and secreted (RANTES) during the first 16 weeks of HFD. In contrast, CD11c+ macrophages (Mφ) were enriched 6-fold by week 8 (p < 0.01). SVC enrichment for T cells (predominantly CD4+ and CD8+) and elevated IFNγ and RANTES gene expression were detected by 20-22 weeks of HFD (p < 0.01), coincident with the resolution of eAT remodeling. HFD-induced T cell priming earlier in the obesity time course is suggested by (1) elevated (5-fold) IL-12p40 gene expression in eAT by week 12 (p ≤ 0.01) and (2) greater IFNγ secretion from PMA/ionophorestimulated eAT explants at week 6 (1 fold, p = 0.08) and week 12 (5 fold, p < 0.001). In summary, T cell enrichment and IFNγ gene induction occur subsequent to ATMφ recruitment, onset of IR and resolution of eAT remodeling. However, enhanced priming for IFNγ production suggests the contribution of CD4+ and/or CD8+ effectors to cell-mediated immune responses promoting HFDinduced AT inflammation and IR.

Objective T cell inflammation plays pivotal roles in obesity-associated type 2 diabetes (T2DM). The identification of dominant sources of T cell inflammation in humans remains a significant gap in understanding disease pathogenesis. We hypothesized that cytokine profiles from circulating T cells identify T cell subsets and T cell cytokines that define T2DM-associated inflammation. Methods We used multiplex analyses to quantify T cell-associated cytokines in αCD3/αCD28-stimulated PBMCs, or B cell-depleted PBMCs, from subjects with T2DM or BMI-matched controls. We subjected cytokine measurements to multivariate (principal component and partial least squares) analyses. Flow cytometry detected intracellular TNFα in multiple immune cells subsets in the presence/absence of antibodies that neutralize T cell cytokines. Results T cell cytokines were generally higher in T2DM samples, but Th17 cytokines are specifically important for classifying individuals correctly as T2DM. Multivariate analyses indicated that B cells support Th17 inflammation in T2DM but not control samples, while monocytes supported Th17 inflammation regardless of T2DM status. Partial least squares regression analysis indicated that both Th17 and Th1 cytokines impact %HbA1c. Conclusions Among various T cell subsets, Th17 cells are major contributors to inflammation and hyperglycemia, and are uniquely supported by B cells in obesity-associated T2DM.

Menopause promotes central obesity, adipose tissue (AT) inflammation, and insulin resistance (IR). Both obesity and the loss of estrogen can activate innate and adaptive immune cells (macrophages, T cells). The respective impacts of weight gain and loss of ovarian hormones on AT inflammation and IR are poorly understood. Here we determined the temporal kinetics of fat accretion, AT inflammation, and IR over a 26-wk time course in ovariectomized (OVX) mice, a model of menopause. OVX and sham-operated (SHM) C57BL6 mice were fed a normal chow diet. Weight, body composition (magnetic resonance imaging), total and regional adiposity, activity, food intake, AT crown-like structures, biohumoral measures, and insulin sensitivity (insulin tolerance testing and homeostatic model assessment) were determined at wk 12, 20, and 26. Macrophages and T cells from perigonadal AT were immunophenotyped by fluorescence-associated cell sorting, and perigonadal adipose tissue (PGAT) gene expression was quantified by quantitative PCR. OVX mice (ϳ31 g) became fatter than SHM mice (ϳ26 g) by wk 12, but mice were equally insulin sensitive. PGAT of OVX mice contained more T cells but expressed higher levels of M2-M⌽ (arginase-1) and T cell-regulatory (cytotoxic T-lymphocyte antigen 4) genes. At wk 20, both OVX and SHM mice weighed approximately 35 g and were equally insulin sensitive with comparable amounts of PGAT and total body fat. OVX mice became less insulin sensitive than SHM mice by wk 26, coincident with the down-regulation of PGAT arginase-1 (Ϫ20-fold) and cytotoxic T-lymphocyte antigen 4 (2-fold) and up-regulation of M1/Th1 genes CD11c (ϩ2-fold), IL12p40 (ϩ2-fold), and interferon-␥ (ϩ78-fold). Ovarian hormone loss in mice induces PGAT inflammation and IR by mechanisms that can be uncoupled from OVX-induced obesity. (Endocrinology 153: 4266 -4277, 2012) C ompared with premenopausal women, postmenopausal women are at a much greater risk of developing metabolic diseases, such as cardiovascular disease and type 2 diabetes (1). Although the mechanism(s) linking the loss of ovarian hormone production to metabolic disturbances are not fully understood, weight gain and a redistribution of body fat toward a more android (i.e. central) distribution pattern are thought to play major roles (2).However, recent evidence suggests that the loss of ovarian hormone production is associated with symptoms of the metabolic syndrome, even in the absence of body weight changes (3), signifying that the loss of ovarian hormone production per se may disturb metabolic function. The aging process itself is associated with a decline in metabolic functioning; for example, insulin sensitivity declines with age in rodents and humans (4, 5). Although the mech-

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The HLA-F adjacent transcript 10 (FAT10) is a member of the ubiquitinlike gene family that alters protein function/stability through covalent ligation. Although FAT10 is induced by inflammatory mediators and implicated in immunity, the physiological functions of FAT10 are poorly defined. We report the discovery that FAT10 regulates lifespan through pleiotropic actions on metabolism and inflammation. Median and overall lifespan are increased 20% in FAT10ko mice, coincident with elevated metabolic rate, preferential use of fat as fuel, and dramatically reduced adiposity. This phenotype is associated with metabolic reprogramming of skeletal muscle (i.e., increased AMP kinase activity, β-oxidation and -uncoupling, and decreased triglyceride content). Moreover, knockout mice have reduced circulating glucose and insulin levels and enhanced insulin sensitivity in metabolic tissues, consistent with elevated IL-10 in skeletal muscle and serum. These observations suggest novel roles of FAT10 in immune metabolic regulation that impact aging and chronic disease.longevity | obesity | mammals