Number Of Adipose Tissue Macrophages Research Articles

Sex-specific association between adipose tissue inflammation and vascular and metabolic complications of obesity.

Adipose tissue (AT) inflammation predisposes to insulin resistance and metabolic syndrome in obesity. To investigate the association between adipocyte size, AT inflammation, systemic inflammation, and metabolic and atherosclerotic complications of obesity in a sex-specific manner. Cross-sectional cohort study. University hospital in the Netherlands. 302 adult subjects with a BMI ≥ 27 kg/m2. We obtained subcutaneous abdominal fat biopsies and systematically assessed, in a sex-specific manner, associations of several parameters of AT inflammation (including adipocyte size, macrophage content, crown like structures (CLS), and gene expression) to biomarkers of systemic inflammation, leukocyte number and function, and to the presence of metabolic syndrome, insulin resistance, and carotid atherosclerotic plaques, assessed with ultrasound. Adipocyte size was associated with metabolic syndrome and AT macrophage content with insulin resistance. In contrast, none of the AT parameters were associated with carotid atherosclerosis, although mRNA expression of the anti-inflammatory IL-37 was associated with a lower intima-media thickness. We revealed profound sex-specific differences, with an association between BMI and adipocyte size, and between adipocyte size and metabolic syndrome only in men. Also, only men showed an association between adipocyte size, AT expression of leptin and MCP-1, and AT macrophage numbers), and between AT inflammation (CLS number) and several circulating inflammatory proteins, including hsCRP, and IL-6. Inflammation in abdominal subcutaneous adipose tissue is more related to the metabolic than the atherosclerotic complications of obesity, and there are profound sex-specific differences in the association between BMI, adipocyte size, AT inflammation, and systemic inflammation, which are much stronger in men than women.

Dissociation between Corneal and Cardiometabolic Changes in Response to a Time-Restricted Feeding of a High Fat Diet.

Mice fed a high fat diet (HFD) ab libitum show corneal dysregulation, as evidenced by decreased sensitivity and impaired wound healing. Time-restricted (TR) feeding can effectively mitigate the cardiometabolic effects of an HFD. To determine if TR feeding attenuates HFD-induced corneal dysregulation, this study evaluated 6-week-old C57BL/6 mice fed an ad libitum normal diet (ND), an ad libitum HFD, or a time-restricted (TR) HFD for 10 days. Corneal sensitivity was measured using a Cochet-Bonnet aesthesiometer. A corneal epithelial abrasion wound was created, and wound closure was monitored for 30 h. Neutrophil and platelet recruitment were assessed by immunofluorescence microscopy. TR HFD fed mice gained less weight (p < 0.0001), had less visceral fat (p = 0.015), and had reduced numbers of adipose tissue macrophages and T cells (p < 0.05) compared to ad libitum HFD fed mice. Corneal sensitivity was reduced in ad libitum HFD and TR HFD fed mice compared to ad libitum ND fed mice (p < 0.0001). Following epithelial abrasion, corneal wound closure was delayed (~6 h), and neutrophil and platelet recruitment was dysregulated similarly in ad libitum and TR HFD fed mice. TR HFD feeding appears to mitigate adipose tissue inflammation and adiposity, while the cornea remains sensitive to the pathologic effects of HFD feeding.

Tracking macrophages in diabetic neuropathy with two-color nanoemulsions for near-infrared fluorescent imaging and microscopy

BackgroundThe incidence of diabetes and diabetic peripheral neuropathy continues to rise, and studies have shown that macrophages play an important role in their pathogenesis. To date, macrophage tracking has largely been achieved using genetically-encoded fluorescent proteins. Here we present a novel two-color fluorescently labeled perfluorocarbon nanoemulsion (PFC-NE) designed to monitor phagocytic macrophages in diabetic neuropathy in vitro and in vivo using non-invasive near-infrared fluorescent (NIRF) imaging and fluorescence microscopy.MethodsPresented PFC-NEs were formulated with perfluorocarbon oil surrounded by hydrocarbon shell carrying two fluorescent dyes and stabilized with non-ionic surfactants. In vitro assessment of nanoemulsions was performed by measuring fluorescent signal stability, colloidal stability, and macrophage uptake and subsequent viability. The two-color PFC-NE was administered to Leprdb/db and wild-type mice by tail vein injection, and in vivo tracking of the nanoemulsion was performed using both NIRF imaging and confocal microscopy to assess its biodistribution within phagocytic macrophages along the peripheral sensory apparatus of the hindlimb.ResultsIn vitro experiments show two-color PFC-NE demonstrated high fluorescent and colloidal stability, and that it was readily incorporated into RAW 264.7 macrophages. In vivo tracking revealed distribution of the two-color nanoemulsion to macrophages within most tissues of Leprdb/db and wild-type mice which persisted for several weeks, however it did not cross the blood brain barrier. Reduced fluorescence was seen in sciatic nerves of both Leprdb/db and wild-type mice, implying that the nanoemulsion may also have difficulty crossing an intact blood nerve barrier. Additionally, distribution of the nanoemulsion in Leprdb/db mice was reduced in several tissues as compared to wild-type mice. This reduction in biodistribution appears to be caused by the increased number of adipose tissue macrophages in Leprdb/db mice.ConclusionsThe nanoemulsion in this study has the ability to identify phagocytic macrophages in the Leprdb/db model using both NIRF imaging and fluorescence microscopy. Presented nanoemulsions have the potential for carrying lipophilic drugs and/or fluorescent dyes, and target inflammatory macrophages in diabetes. Therefore, we foresee these agents becoming a useful tool in both imaging inflammation and providing potential treatment in diabetic peripheral neuropathy.

Time-Restricted Feeding Restores Obesity-Induced Alteration in Adipose Tissue Immune Cell Phenotype.

Studies suggest that time-restricted feeding (TRF) may prevent obesity and its commodities. At present, little is known about how TRF impacts immune cells, and whether such an effect is linked to altered metabolic parameters under condition of a high-fat diet (HFD)-induced obesity. To address these issues, we conducted a study in which we determined whether TRF has therapeutic efficacy against weight gain, adiposity, as well as associated immune cell disturbance found in obese mice. Six-week-old male C57BL/6 mice were fed a low-fat diet (LFD) or HFD ad libitum for six weeks, after which time a subgroup of HFD mice was switched to the 10 h TRF paradigm (HFD-TRF) for additional eight weeks. We found that TRF intervention reduced HFD-induced weight gain. Even with comparable fat mass and mean adipocyte area, the HFD-TRF group had lower mRNA levels of proinflammatory cytokine Tnfα and chemokine Ccl8, along with reduced numbers of adipose tissue macrophages (ATM), CD11c+ ATM, and CD8+ T cell compared to the HFD group, while maintaining CD8+ to CD4+ ratio at levels similar to those in the LFD group. Furthermore, TRF intervention was effective in improving glucose tolerance and reducing HOMA-IR. Taken together, our findings suggest that TRF restores the obesity-induced alteration in immune cell composition, and this effect may in part contribute to health benefits (including insulin sensitivity) of practicing TRF.

Multinucleated Giant Cells in Adipose Tissue Are Specialized in Adipocyte Degradation.

Obesity is associated with chronic low-grade inflammation of visceral adipose tissue (AT) characterized by an increasing number of AT macrophages (ATMs) and linked to type 2 diabetes. AT inflammation is histologically indicated by the formation of so-called crown-like structures, as ATMs accumulate around dying adipocytes, and the occurrence of multinucleated giant cells (MGCs). However, to date, the function of MGCs in obesity is unknown. Therefore, the aim of this study was to characterize MGCs in AT and unravel the function of these cells. We demonstrated that MGCs occurred in obese patients and after 24 weeks of a high-fat diet in mice, accompanying signs of AT inflammation and then representing ∼3% of ATMs in mice. Mechanistically, we found evidence that adipocyte death triggered MGC formation. Most importantly, MGCs in obese AT had a higher capacity to phagocytize oversized particles, such as adipocytes, as shown by live imaging of AT, 45-µm bead uptake ex vivo, and higher lipid content in vivo. Finally, we showed that interleukin-4 treatment was sufficient to increase the number of MGCs in AT, whereas other factors may be more important for endogenous MGC formation in vivo. Most importantly, our data suggest that MGCs are specialized for clearance of dead adipocytes in obesity.

Molecular Mechanisms of P311 on White Adipogenesis

BackgroundThe obesity epidemic is a constant and chronic detriment to US as well as global health outcomes. Two‐thirds of the US population is either overweight or obese, and obesity can be linked to many chronic diseases, including diabetes mellitus, cardiovascular diseases, stroke and cancer. Diet and exercise remains the primary therapeutic approaches, but still obesity (40% of US adult population) incidence and prevalence continues to rise, prompting the development of new interventions. P311 is an 8 kDa protein shown to induce adipogenesis in an in vitro 3T3‐L1 cell culture model (Nunez et al. 2019). In the current study, we investigated the molecular mechanisms of P311 in white adipocyte biology.MethodsBoth male and female C57BL/6 control mice and P311 knockout (KO) mice were used for this study. Adipocytes were isolated from individual white adipose tissue depots and adipocyte number and size were quantified using LipidTox staining followed by Guava EasyCyte analysis. Additionally adipocyte cellular functions of P311 like apoptosis, lipophagy and adipose tissue macrophage numbers were verified in P311 KOs and compared with wild type control mice. Real‐time PCR, western blot and immunohistology studies were conducted as described by Badri et al. (2013) and Nunez et al. (2019)ResultsP311 was expressed in murine gonadal and subcutaneous white adipose tissue. White adipocytes isolated from 4‐month‐old mice had significantly higher levels of P311 compared to adipocytes isolated from the white subcutaneous adipose tissue of 1‐month‐old mice. However, progenitor cells (stromal vascular fraction) showed no (basal) expression of P311. P311 KO mice showed decreased PPARγ2 expression. P311 KO mice did not differ from wild type mice in subcutaneous or gonadal white adipose tissue weights, but they had fewer and enlarged adipocytes. Further, P311 KOs also showed decreased apoptosis and lipophagy along with decreased adipocyte macrophage numbers and browning of white adipose tissue. In addition, adult human visceral adipose tissue also showed the expression of P311 in adipocytes implicating a translational role for P311 in adipogenesis and obesity.ConclusionsP311 plays a key role in white adipogenesis and browning of WAT partly through modulating PPARγ2 and also by regulating adipocyte cellular processes including adipocyte apoptosis, lipophagy, browning and macrophage numbers.Support or Funding Information• 2019 Medical Student Summer Research and Public Health Experience (Morehouse School of Medicine)• NIMHD/NIH grant funding through S21MD000101 (to Morehouse School of Medicine)• U54MD008621 (Hampton University, Hampton, VA)

The Effects of Poncirus fructus on Insulin Resistance and the Macrophage-Mediated Inflammatory Response in High Fat Diet-Induced Obese Mice

Obesity is a chronic low-grade inflammatory condition in which hypertrophied adipocytes and adipose tissue immune cells, mainly macrophages, contribute to increased circulating levels of proinflammatory cytokines. Obesity-associated chronic low-grade systemic inflammation is considered a focal point and a therapeutic target in insulin resistance and metabolic diseases. We evaluate the effect of Poncirus fructus (PF) on insulin resistance and its mechanism based on inflammatory responses in high-fat diet (HFD)-induced obese mice. Mice were fed an HFD to induce obesity and then administered PF. Body weight, epididymal fat and liver weight, glucose, lipid, insulin, and histologic characteristics were evaluated to determine the effect of PF on insulin resistance by analyzing the proportion of macrophages in epididymal fat and liver and measured inflammatory gene expression. PF administration significantly decreased the fasting and postprandial glucose, fasting insulin, HOMA-IR, total-cholesterol, triglycerides, and low-density lipoprotein cholesterol levels. The epididymal fat tissue and liver showed a significant decrease of fat accumulation in histological analysis. PF significantly reduced the number of adipose tissue macrophages (ATMs), F4/80+ Kupffer cells, and CD68+ Kupffer cells, increased the proportion of M2 phenotype macrophages, and decreased the gene expression of inflammatory cytokines. These results suggest that PF could be used to improve insulin resistance through modulation of macrophage-mediated inflammation and enhance glucose and lipid metabolism.

Intermittent Fasting Improves Glucose Tolerance and Promotes Adipose Tissue Remodeling in Male Mice Fed a High-Fat Diet.

Obesity is associated with increased macrophage and extracellular matrix accumulation in adipose tissue, which can be partially reversed following weight loss by daily caloric restriction. This study examined the effects of 8 weeks of intermittent fasting (IF; 24-hour fast on 3 nonconsecutive days per week) in mice fed a chow or high-fat diet (HFD; 43% fat) on markers of adipose tissue inflammation and fibrosis. We found that IF decreased energy intake, body weight, and fat cell size in HFD-fed mice and decreased fat mass and improved glucose tolerance in chow- and HFD-fed mice. IF decreased mRNA levels of macrophage markers (Lgals3, Itgax, Ccl2, and Ccl3) in inguinal and gonadal fat, as well as adipose tissue macrophage numbers in HFD-fed mice only, and altered genes involved in NLRP3 inflammasome pathway in both diet groups. IF increased mRNA levels of matrix metallopeptidase 9, which is involved in extracellular matrix degradation, and reduced mRNA levels of collagen 6 α-1 and tissue inhibitor of matrix metallopeptidase 1, as well as fibrosis in gonadal fat in HFD-fed mice. In summary, our results show that intermittent fasting improved glucose tolerance in chow- and HFD-fed mice and ameliorated adipose tissue inflammation and fibrosis in HFD-fed mice.

Altered Gonadal Fat Stromal Cell Populations in Adipocyte-Specific Oncostatin M Receptor Knockout Mice—A Possible Role for Local SDF1

The IL-6 family cytokine, oncostatin M (OSM), has several physiological roles, but its exact role in adipose tissue homeostasis is still unclear. We recently reported that high-fat diet-fed male mice with an adipocyte-specific deletion of the OSM-specific receptor (OSMR FKO mice) were insulin-resistant and had increased markers of inflammation in epididymal adipose tissue (eWAT). In the current study, we more closely examined eWAT stromal cell populations in high-fat fed OSMR FKO mice using flow cytometry. Results from flow cytometry studies revealed that, despite no differences in eWAT weights between genotypes, OSMR FKO mice had significantly fewer stromal cells per gram eWAT. Although there were fewer stromal cells overall, a significantly higher percentage of these cells were CD45+ leukocytes. Significant decreases in the numbers of adipose tissue macrophages (CD64+; CD11c+/-) and preadipocytes (CD45-; CD31-; Sca1+) were also observed in OSMR FKO eWAT. A cytokine array was performed on eWAT to assess differences in tissue cytokine profiles that may contribute to the alterations observed in stromal cell populations. Array results indicated a significant decrease in stromal cell-derived factor 1 (SDF1) protein expression in eWAT of OSMR FKO mice. Future studies will focus on the role of adipocyte OSM signaling as a regulator of adipose tissue SDF1 production and stromal cell homeostasis. Overall, our results suggest a homeostatic role for adipocyte OSM signaling in the maintenance of stromal cell populations in gonadal fat. Disclosure C.M. Elks: None.

Influence of adipocyte size and adipose depot on the number of adipose tissue macrophages and the expression of adipokines in dairy cows at the end of pregnancy

The aim of this study was to determine the number of adipose tissue macrophages (ATM) and the mRNA expression of adipokines [adiponectin (ADIPOQ), leptin (LEP), interleukin 6 (IL6), tumor necrosis factor (TNF), and interleukin 10 (IL10)] in different adipose depots from cows with a variable body condition score (BCS) at the end of the dry period. We hypothesized that the number of ATM and the expression of these adipokines depend on adipocyte size and the anatomical location of the adipose depot. Subcutaneous, omental, mesenteric, perirenal, and intrapelvic adipose tissue samples were taken immediately after euthanasia of 10 Holstein Friesian dairy cows (upcoming parity 2 to 5, age 3.9 ± 1.4 yr; mean ± standard deviation) at the end of pregnancy (actual days of pregnancy at the moment of euthanasia: 269 ± 5 d). During the dry period, all animals received similar diets to meet but not exceed requirements. Five animals were considered to have a normal BCS (2.5-3.5) and 5 animals were considered to be over-conditioned (BCS = 3.75-5). Body weight of the animals at the moment of euthanasia was 717 ± 77 kg. Expression of the different genes was determined by reverse transcription quantitative real-time PCR. Adipocyte size was determined by measuring the area of 100 adipocytes on histological sections. Average adipocyte area was 10,475 ± 1,019, 8,500 ± 780, 10,383 ± 1,227, 11,466 ± 1,039, and 11,087 ± 1,632 µm2 for the subcutaneous, mesenteric, omental, intrapelvic, and perirenal adipose depot, respectively. Immunohistochemistry using anti-bovine CD172a antibodies was performed to determine the proportion of ATM (the number of CD172a-positive cells per 100 adipocytes, given as a percentage). Expression of LEP, IL6, and TNF was positively associated with adipocyte size, whereas no association could be detected between ADIPOQ and IL10 with the size of the adipocytes. The omental adipose depot was especially infiltrated with ATM (1.92 ± 0.55, 1.10 ± 0.33, and 8.28 ± 2.24% for the subcutaneous, mesenteric, and omental adipose depot, respectively). The proportion of ATM was positively associated with the size of the adipocytes in the omental and mesenteric adipose depot. Expression of ADIPOQ, LEP, IL6, TNF, and IL10 differed among depots, which suggests differences in inflammatory characteristics depending on the anatomical location of depots. In conclusion, the results of the present study confirm the adipose tissue as a potential source of inflammatory mediators and demonstrate ATM infiltration, especially in the omental adipose depot.

Adrenergic hormones induce extrapituitary prolactin gene expression in leukocytes-potential implications in obesity

The pituitary hormone prolactin (PRL), originally described for its role in lactation, has been implemented in over 300 functions and is produced by multiple cell types outside of the pituitary. Monocyte/macrophages in particular show robust expression of extra-pituitary prolactin (ePRL). While ePRL protein is identical to pituitary PRL and translated from the same gene, tissues outside the pituitary engage an alternative promoter to regulate expression. Many of the factors regulating this expression, however, remain unknown. Here we show that the adrenergic hormones epinephrine and norepinephrine induce PRL expression in the human monocytic cell line THP-1 at physiological concentrations. Furthermore, our experiments show the polarization state of differentiated macrophages can influence their response in vitro, with inflammatory M1 macrophages—common in obese adipose—showing the highest levels of PRL expression compared to other macrophage types. Adrenergic hormones have a clearly defined role in adipocyte lipid metabolism, stimulating lipolysis through hormone sensitive lipase (HSL) induction. Meanwhile, PRL has been shown to stimulate lipogenesis. This highlights ePRL production as a possible factor in obesity. The overall balance of these two signals could play a critical role in determining overall lipid turnover/accumulation in adipose depots where large numbers of adipose tissue macrophages (ATMs) reside.

PI3Kγ ablation does not promote diabetes in db/db mice, but improves insulin sensitivity and reduces pancreatic β-cell apoptosis.

PI3Kγ has emerged as a promising target for the treatment of obesity and insulin resistance; however, previous studies have indicated that PI3Kγ activity in pancreatic β cells is required for normal insulin secretion in response to glucose. Hence, a possible deterioration of insulin secretion capacity in patients who are predisposed to the failure of pancreatic β-cell function is a major concern for the pharmacologic inhibition of PI3Kγ. To address this issue, we investigated the effects of PI3Kγ ablation in db/db diabetic mice, a genetic model of obesity-driven β-cell failure and diabetes. Mice that lacked PI3Kγ were backcrossed into db/+ mice C57BL/KS (>10 generations) to obtain db/db-PI3Kγ-/- mice. db/db-PI3Kγ-/- mice and control db/db mice were phenotyped for glucose homeostasis, insulin sensitivity, insulin secretion, steatosis, metabolic inflammation, pancreatic islet morphometry, islet cellular composition, and inflammation. Pancreatic β-cell apoptosis and proliferation were also evaluated. db/db-PI3Kγ -/- mice and control db/db mice developed similar body weight, steatosis, glycemia, and insulin levels after a glucose load; however, db/db-PI3Kγ-/- mice displayed improved insulin tolerance, higher levels of fasting serum insulin, and lower pancreatic insulin content. In db/db-PI3Kγ-/- mice, the number of adipose tissue macrophages was similar to control, but displayed reduced adipose tissue neutrophils and M2-polarized adipose tissue gene expression. Finally, db/db-PI3Kγ-/- mice have more pancreatic β cells and larger islets than db/db mice, despite displaying similar islet inflammation. This phenotype could be explained by reduced β-cell apoptosis in db/db-PI3Kγ-/- mice compared with control db/db mice. Our results are consistent with the concept that the beneficial action of PI3Kγ ablation in obesity-driven glucose intolerance is largely a result of its leptin-dependent effects on adiposity and, to a lesser extent, the promotion of adipose tissue neutrophil recruitment and M1 polarization of gene expression. Of importance, our data challenge the concept that PI3Kγ is required for insulin secretion in response to glucose in vivo, and indicate that PI3Kγ ablation protects db/db mice from β-cell apoptosis and improves fasting insulin levels. We conclude that PI3Kγ inhibition in obese patients who are predisposed to β-cell failure is not expected to produce adverse effects on insulin secretion.-Breasson, L., Sardi, C., Becattini, B., Zani, F., Solinas, G. PI3Kγ ablation does not promote diabetes in db/db mice, but improves insulin sensitivity and reduces pancreatic β-cell apoptosis.

Circulating sex steroids coregulate adipose tissue immune cell populations in healthy men.

Male hypogonadism results in changes in body composition characterized by increases in fat mass. Resident immune cells influence energy metabolism in adipose tissue and could promote increased adiposity through paracrine effects. We hypothesized that manipulation of circulating sex steroid levels in healthy men would alter adipose tissue immune cell populations. Subjects (n = 44 men, 19-55 yr of age) received 4 wk of treatment with the gonadotropin-releasing hormone receptor antagonist acyline with daily administration of 1) placebo gel, 2) 1.25 g testosterone gel (1.62%), 3) 5 g testosterone gel, or 4) 5 g testosterone gel with an aromatase inhibitor. Subcutaneous adipose tissue biopsies were performed at baseline and end-of-treatment, and adipose tissue immune cells, gene expression, and intra-adipose estrogen levels were quantified. Change in serum total testosterone level correlated inversely with change in the number of CD3+ (β = -0.36, P = 0.04), CD4+ (β = -0.34, P = 0.04), and CD8+ (β = -0.33, P = 0.05) T cells within adipose tissue. Change in serum 17β-estradiol level correlated inversely with change in the number of adipose tissue macrophages (ATMs) (β = -0.34, P = 0.05). A negative association also was found between change in serum testosterone and change in CD11c+ ATMs (β = -0.41, P = 0.01). Overall, sex steroid deprivation was associated with increases in adipose tissue T cells and ATMs. No associations were found between changes in serum sex steroid levels and changes in adipose tissue gene expression. Circulating sex steroid levels may regulate adipose tissue immune cell populations. These exploratory findings highlight a possible novel mechanism that could contribute to increased metabolic risk in hypogonadal men.

Adipocyte-Macrophage Cross-Talk in Obesity.

Obesity is characterized by the chronic low-grade activation of the innate immune system. In this respect, macrophage-elicited metabolic inflammation and adipocyte-macrophage interaction has a primary importance in obesity. Large amounts of macrophages are accumulated by different mechanisms in obese adipose tissue. Hypertrophic adipocyte-derived chemotactic monocyte chemoattractant protein-1 (MCP-1)/C-C chemokine receptor 2 (CCR2) pathway also promotes more macrophage accumulation into the obese adipose tissue. However, increased local extracellular lipid concentrations is a final mechanism for adipose tissue macrophage accumulation. A paracrine loop involving free fatty acids and tumor necrosis factor-alpha (TNF-alpha) between adipocytes and macrophages establishes a vicious cycle that aggravates inflammatory changes in the adipose tissue. Adipocyte-specific caspase-1 and production of interleukin-1beta (IL-1beta) by macrophages; both adipocyte and macrophage induction by toll like receptor-4 (TLR4) through nuclear factor-kappaB (NF-kappaB) activation; free fatty acid-induced and TLR-mediated activation of c-Jun N-terminal kinase (JNK)-related pro-inflammatory pathways in CD11c+ immune cells; are effective in macrophage accumulation and in the development of adipose tissue inflammation. Old adipocytes are removed by macrophages through trogocytosis or sending an "eat me" signal. The obesity-induced changes in adipose tissue macrophage numbers are mainly due to increases in the triple-positive CD11b+ F4/80+ CD11c+ adipose tissue macrophage subpopulation. The ratio of M1-to-M2 macrophages is increased in obesity. Furthermore, hypoxia along with higher concentrations of free fatty acids exacerbates macrophage-mediated inflammation in obesity. The metabolic status of adipocytes is a major determinant of macrophage inflammatory output. Macrophage/adipocyte fatty-acid-binding proteins act at the interface of metabolic and inflammatory pathways. Both macrophages and adipocytes are the sites for active lipid metabolism and signaling.

The Effects of Mori folium on Insulin Resistance and Adipose Tissue Inflammation in an Experimental Mouse Model of Obesity

Objective: This study was undertaken to investigate the effects of Mori folium on insulin resistance and adipose tissue inflammation in an experimental mouse model of obesity. Methods: Obesity was induced in C57BL/6 mice by feeding them a high-fat diet. The mice were divided into four groups (n=6): a normal diet, high-fat diet, high-fat diet with 40 mg of Mori folium, and high-fat diet with 800 mg of Mori folium groups. After 13 wk, the body weights, fasting blood glucose and fasting serum insulin levels, insulin resistance (homeostatic model assessment) levels, oral glucose tolerance test levels, epididymal fat and liver weights, and gene expression of tumor necrosis factor-α, interleukin-6, and interferon-γ were measured. In addition, adipose tissue macrophages were analyzed by fluorescence- activated cell sorting. Results: Mori folium significantly reduced blood glucose levels, oral glucose tolerance levels, and liver weights. It also reduced adipose tissue macrophage numbers and tumor necrosis factor receptor-α gene expression. Conclusions: These results show that Mori folium has insulin resistance reduction and anti-inflammatory effects in an experimental mouse model of obesity. Keywords: Mori folium, obesity, blood glucose, insulin resistance, anti-inflammatory

Abstract 608: Induction of Lysosomal Biogenesis in Adipose Tissue Macrophages Attenuates Inflammation and Cardiometabolic Disease

Adipose tissue inflammation is a fundamental feature of obesity and is strongly implicated in progression to overt cardiometabolic disease. In situ, this response is defined by a notable increase in number of adipose tissue macrophages (ATM’s) surrounding dying adipocytes and a phenotypic switch towards pro-inflammatory “M1” polarization. However, recent data suggest an equally notable upregulation of lysosomal catabolic pathways in these cells, and that inflammatory phenotypes may regulated by these processes. We and others speculate ATM lysosomal biogenesis is an adaptive response that can be harnessed for therapeutic benefit in treating cardiometabolic disease. To this end, we examined the effects of macrophage-specific overexpression of TFEB (mϕ-TFEB), a transcription factor master regulator of lysosomal biogenesis, in a murine model of diet induced obesity. We show broad physiological metabolic benefits including attenuated weight gain, improved body composition, and increased metabolic rate. Further, mϕ-TFEB mice demonstrate increased insulin sensitivity and glucose tolerance (Insulin and Glucose Tolerance Tests). These phenotypes are linked to profound changes in cellular, tissue, and systemic inflammation. mϕ-TFEB overexpression greatly reduces circulating interleukin 1β, and polarizes adipose tissue macrophages isolated from epididymal fat to an anti-inflammatory “M2” state in a manner that is dependent on lysosomal lipolysis. In cultured primary macrophages, TFEB overexpression attenuates LPS-induced proinflammatory M1 activation, and predisposes to IL-4 induced M2 polarization. Thus, harnessing the lysosomal biogenesis response in macrophages abrogates diet induced metabolic pathophysiology, potentially through regulation of inflammatory phenotypes. We postulate that ATM lysosomal biogenesis is a crucial, adaptive cellular response to obesity that can be preemptively induced to slow progression of cardiometabolic disease.

IL-37 protects against obesity-induced inflammation and insulin resistance.

Cytokines of the IL-1 family are important modulators of obesity-induced inflammation and the development of systemic insulin resistance. Here we show that IL-1 family member IL-37, recently characterized as an anti-inflammatory cytokine, ameliorates obesity-induced inflammation and insulin resistance. Mice transgenic for human IL-37 (IL-37tg) exhibit reduced numbers of adipose tissue macrophages, increased circulating levels of adiponectin and preserved glucose tolerance and insulin sensitivity after 16 weeks of HFD. In vitro treatment of adipocytes with recombinant IL-37 reduces adipogenesis and activates AMPK signalling. In humans, elevated steady-state IL-37 adipose tissue mRNA levels are positively correlated with insulin sensitivity and a lower inflammatory status of the adipose tissue. These findings reveal IL-37 as an important anti-inflammatory modulator during obesity-induced inflammation and insulin resistance in both mice and humans, and suggest that IL-37 is a potential target for the treatment of obesity-induced insulin resistance and type 2 diabetes.

Abstract 18139: Genetic Deficiency of Traf-1 Attenuates Diet-Induced Adipose Tissue Inflammation by Limiting the Pool of Circulating and Splenic Monocytes in Mice

Background: Accumulation of inflammatory leukocytes, such as of macrophages, is a prerequisite of adipose tissue inflammation during the metabolic syndrome. We recently reported that genetic deficiency of Tumor necrosis factor receptor-associated factor (TRAF) -1 attenuated inflammatory cell recruitment in atherosclerosis. Here, we tested the hypothesis that TRAF-1 deficiency modulates adipose tissue inflammation in a model of diet-induced obesity (DIO) in mice. Methods and Results: To test the association of TRAFs and adipose tissue inflammation we screened for expression of different TRAFs in mouse adipose tissue after 20 weeks of feeding with a high fat (HFD) or a control diet. HFD induced up-regulation of TRAF-1, -3, -5, -6, and -7 mRNA. Interestingly, the amplitude of gene regulation was highest for TRAF-1 (4.9-fold, n=8 per group, p=0.002). Also, in human subcutaneous tissue TRAF-1 gene expression correlated with body mass index of donors (r=0.94, p=0.019). To test functional relevance of our findings, WT or TRAF-1-/- mice consumed HFD for 12 weeks (n ≥ 10 mice per group). Interestingly, TRAF-1-/- mice gained less weight during DIO (119 ± 7.5 % vs. 41 ± 3.7 % of starting body weight for WT and TRAF-1-/-, respectively). Accordingly, total body weight, weight of visceral and cardiac fat pads was decreased in TRAF-1-/- mice. Moreover, TRAF-1-/- mice demonstrated lower glucose levels after starving and during weight-adapted intraperitoneal glucose and insulin tolerance tests, suggesting functional involvement of TRAF-1 in insulin and glucose signaling. Finally, inflammatory cell recruitment was impaired in TRAF-1-/- mice with reduced numbers of adipose tissue macrophages. Functionally, circulating and splenic, but not bone marrow monocytes were lowered in TRAF-1-/- mice, proposing that TRAF-1 modulates monocyte mobilization during inflammation. Conclusion: We present the novel finding that TRAF-1 is regulated in obese murine and human adipose tissue. Genetic deficiency of TRAF-1 attenuates adipose tissue inflammation in mice by limiting monocyte recruitment. These findings identify TRAF-1 as a potent mediator at the interface of cardiovascular and metabolic disease.

Obesity phenotype is related to NLRP3 inflammasome activity and immunological profile of visceral adipose tissue

Obesity is a heterogeneous condition comprising both individuals who remain metabolically healthy (MHO) and those who develop metabolic disorders (metabolically unhealthy, MUO). Adipose tissue is also heterogeneous in that its visceral component is more frequently associated with metabolic dysfunction than its subcutaneous component. The development of metabolic disorders is partly mediated by the NLR family pyrin domain containing-3 (NLRP3) inflammasome, which increases the secretion of inflammatory cytokines via activation of caspase-1. We compared the immunological profile and NLRP3 activity in adipose tissue between MUO and MHO individuals. MHO and MUO phenotypes were defined, respectively, as the absence and the presence of the metabolic syndrome. Cellular composition and intrinsic inflammasome activity were investigated by flow cytometry, quantitative RT-PCR and tissue culture studies in subcutaneous and visceral adipose tissue from 23 MUO, 21 MHO and nine lean individuals. We found significant differences between the three study groups, including an increased secretion of IL-1β, increased expression of IL1B and NLRP3, increased number of adipose tissue macrophages and decreased number of regulatory T cells in the visceral adipose tissue of MUO patients compared with MHO and lean participants. In macrophages derived from visceral adipose tissue, both caspase-1 activity and IL-1β levels were higher in MUO patients than in MHO patients. Furthermore, caspase-1 activity was higher in CD11c(+)CD206(+) adipose tissue macrophages than in CD11c(-)CD206(+) cells. The MUO phenotype seems to be associated with an increased activation of the NLPR3 inflammasome in macrophages infiltrating visceral adipose tissue, and a less favourable inflammatory profile compared with the MHO phenotype.

Human Adipose Tissue Macrophages Display Activation of Cancer-related Pathways

Obesity is associated with a significantly increased risk for cancer suggesting that adipose tissue dysfunctions might play a crucial role therein. Macrophages play important roles in adipose tissue as well as in cancers. Here, we studied whether human adipose tissue macrophages (ATM) modulate cancer cell function. Therefore, ATM were isolated and compared with monocyte-derived macrophages (MDM) from the same obese patients. ATM, but not MDM, were found to secrete factors inducing inflammation and lipid accumulation in human T47D and HT-29 cancer cells. Gene expression profile comparison of ATM and MDM revealed overexpression of functional clusters, such as cytokine-cytokine receptor interaction (especially CXC-chemokine) signaling as well as cancer-related pathways, in ATM. Comparison with gene expression profiles of human tumor-associated macrophages showed that ATM, but not MDM resemble tumor-associated macrophages. Indirect co-culture experiments demonstrated that factors secreted by preadipocytes, but not mature adipocytes, confer an ATM-like phenotype to MDM. Finally, the concentrations of ATM-secreted factors related to cancer are elevated in serum of obese subjects. In conclusion, ATM may thus modulate the cancer cell phenotype.