Inflammation, but not recruitment, of adipose tissue macrophages requires signalling through Mac-1 (CD11b/CD18) in diet-induced obesity (DIO)

SummaryCell accumulation is a prerequisite for adipose tissue inflammation. The leukocyte integrin Mac-1 (CD11b/CD18, αMβ2) is a classic adhesion receptor critically regulating inflammatory cell recruitment. Here, we tested the hypothesis that a genetic deficiency and a therapeutic modulation of Mac-1 regulate adipose tissue inflammation in a mouse model of diet-induced obesity (DIO). C57Bl6/J mice genetically deficient (Mac-1-/-) or competent for Mac-1 (WT) consumed a high fat diet for 20 weeks. Surprisingly, Mac-1-/- mice presented with increased diet-induced weight gain, decreased insulin sensitivity in skeletal muscle and in the liver in insulin-clamps, insulin secretion deficiency and elevated glucose levels in fasting animals, and dyslipidaemia. Unexpectedly, accumulation of adipose tissue macrophages (ATMs) was unaffected, while gene expression indicated less inflamed adipose tissue and macrophages in Mac-1-/- mice. In contrast, inflammatory gene expression at distant locations, such as in skeletal muscle, was not changed. Treatment of ATMs with an agonistic anti-Mac-1 antibody, M1/70, induced pro-inflammatory genes in cell culture. In vivo, treatment with M1/70 induced a hyper-inflammatory phenotype with increased expression of IL-6 and MCP-1, whereas accumulation of ATMs did not change. Finally, inhibition of Mac-1’s adhesive interaction to CD40L by the peptide inhibitor cM7 did not affect myeloid cell accumulation in adipose tissue. We present the surprising finding that adhesive properties of the leukocyte integrin Mac-1 are not required for macrophage accumulation in adipose tissue. Instead, Mac-1 modulates inflammatory gene expression in macrophages. These findings question the net effect of integrin blockade in cardio-metabolic disease.D. W., N. B., and D. E. equally contributed to this work.K. P., E. L., and A. Z. share senior authorship.Note: The review process for this manuscript was fully handled by Gregory Y. H. Lip, Editor in Chief.Supplementary Material to this article is available online at www.thrombosis-online.com.

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Autophagy Activity Is Up-Regulated in Adipose Tissue of Obese Individuals and Modulates Proinflammatory Cytokine Expression

Endocrinology ◽

10.1210/en.2012-1625 ◽

2012 ◽

Vol 153 (12) ◽

pp. 5866-5874 ◽

Cited By ~ 115

Author(s):

H. J. Jansen ◽

P. van Essen ◽

T. Koenen ◽

L. A. B. Joosten ◽

M. G. Netea ◽

...

Keyword(s):

Gene Expression ◽

Adipose Tissue ◽

Proinflammatory Cytokine ◽

Adipose Tissue Inflammation ◽

Inflammatory Gene Expression ◽

Tissue Inflammation ◽

Inflammatory Gene ◽

Tissue Explants ◽

Autophagy Activity ◽

Human And Mouse

Abstract Autophagy, an evolutionary conserved process aimed at recycling damaged organelles and protein aggregates in the cell, also modulates proinflammatory cytokine production in peripheral blood mononuclear cells. Because adipose tissue inflammation accompanied by elevated levels of proinflammatory cytokines is characteristic for the development of obesity, we hypothesized that modulation of autophagy alters adipose tissue inflammatory gene expression and secretion. We tested our hypothesis using ex vivo and in vivo studies of human and mouse adipose tissue. Levels of the autophagy marker LC3 were elevated in sc adipose tissue of obese vs. lean human subjects and positively correlated to both systemic insulin resistance and morphological characteristics of adipose tissue inflammation. Similarly, autophagic activity levels were increased in adipose tissue of obese and insulin resistant animals as compared with lean mice. Inhibition of autophagy by 3-methylalanine in human and mouse adipose tissue explants led to a significant increase in IL-1β, IL-6, and IL-8 mRNA expression and protein secretion. Noticeably, the enhancement in IL-1β, IL-6, and keratinocyte-derived chemoattractant (KC) by inhibition of autophagy was more robust in the presence of obesity. Similar results were obtained by blocking autophagy using small interfering RNA targeted to ATG7 in human Simpson-Golabi-Behmel syndrome adipocytes. Our results demonstrate that autophagy activity is up-regulated in the adipose tissue of obese individuals and inhibition of autophagy enhances proinflammatory gene expression both in adipocytes and adipose tissue explants. Autophagy may function to dampen inflammatory gene expression and thereby limit excessive inflammation in adipose tissue during obesity.

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Abstract 417: Control of Adipose Tissue Macrophage Metabolism by Oxidized Phospholipids

Arteriosclerosis Thrombosis and Vascular Biology ◽

10.1161/atvb.36.suppl_1.417 ◽

2016 ◽

Vol 36 (suppl_1) ◽

Author(s):

Vlad Serbulea ◽

Akshaya K Meher ◽

Samantha Adamson ◽

Norbert Leitinger

Keyword(s):

Gene Expression ◽

Mass Spectrometry ◽

Insulin Resistance ◽

Adipose Tissue ◽

Stromal Vascular Fraction ◽

Adipose Tissue Inflammation ◽

Oxidized Phospholipids ◽

Inflammatory Gene Expression ◽

Tissue Inflammation ◽

Inflammatory Gene

Our group has previously shown that oxidized phospholipids (OxPL) induce a unique macrophage (MΦ) phenotype known as “Mox,” distinct from pro- and anti-inflammatory M1 and M2 phenotypes. We have also shown that Mox make up 30% of the MΦs found in atherosclerotic lesions. OxPL induce TLR2-dependent inflammatory gene expression in MΦs. TLR2 activation by peptidoglycan was shown to induce accumulation of ceramides, which can alter bioenergetics by inhibiting the mitochondria. Recently, it has been shown that spleen tyrosine kinase (Syk) is phosphorylated upon TLR2 agonist Pam3CSK stimulation in MΦs. The effect of OxPL on bioenergetics has never before been studied. Here we test the hypothesis that OxPL change MΦ bioenergetics and inflammatory capacity via a TLR2-Syk-Ceramide pathway. Using flow cytometry, we found that in mice fed a high-fat diet, more than 20% of all adipose tissue MΦs can be described as Mox. Concomitantly, using immunohistochemistry and liquid-chromatography mass spectrometry, we measured increased levels of OxPL in the stromal vascular fraction of obese murine adipose tissue, as compared to lean controls. We treated bone marrow-derived MΦs (BMDMs) from WT, TLR2-KO, and Syk-KO mice with OxPL and measured bioenergetics using a Seahorse Flux Analyzer. Our results show that OxPL decrease oxygen consumption rate (OCR), a measure of oxidative phosphorylation, and decrease extracellular acidification rate (ECAR), a measure of glycolytic capacity. These MΦs can be described as quiescent, but they still engage in low-level cytokine production. Moreover, OxPL result in the accumulation of ceramides, as quantified by mass spectrometry. Finally, using Syk-KO MΦs and Syk inhibitors, we show that OxPL-induced inflammatory gene expression and ceramide accumulation are dependent on Syk. In summary, our results demonstrate that OxPL accumulate in obese adipose tissue and induce a change in the inflammatory and metabolic profiles of MΦs, involving a TLR2-ceramide-Syk dependent pathway. These results suggest that OxPL are triggers of adipose tissue inflammation and subsequent development of insulin resistance. Furthermore, we identify Syk as a therapeutic target for inhibiting diet-induced adipose tissue inflammation and insulin resistance.

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Effects of Endurance Exercise Training on Adipose Tissue Inflammatory Gene Expression in Elderly Rats with Diet-Induced Obesity

The Asian Journal of Kinesiology ◽

10.15758/ajk.2019.21.1.37 ◽

2019 ◽

Vol 21 (1) ◽

pp. 37-45

Author(s):

Kijin Kim

Keyword(s):

Gene Expression ◽

Adipose Tissue ◽

Exercise Training ◽

Endurance Exercise ◽

Inflammatory Gene Expression ◽

Inflammatory Gene ◽

Diet Induced Obesity ◽

Endurance Exercise Training

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Abstract 597: Diet-induced Obesity Requires Signalling Through Tumor Necrosis Factor Receptor-associated Factor 1 (TRAF-1) in Adipocytes

Arteriosclerosis Thrombosis and Vascular Biology ◽

10.1161/atvb.36.suppl_1.597 ◽

2016 ◽

Vol 36 (suppl_1) ◽

Author(s):

Dennis Wolf ◽

Nathaly Anto Michel ◽

Ingo Hilgendorf ◽

Christoph Bode ◽

Andreas Zirlik

Keyword(s):

Metabolic Syndrome ◽

Adipose Tissue ◽

Hormone Sensitive Lipase ◽

Obese Mouse ◽

Adipose Tissue Inflammation ◽

Tissue Inflammation ◽

Diet Induced Obesity ◽

The Metabolic Syndrome ◽

Adipose Tissue Macrophages ◽

Genetic Deficiency

Background: Accumulation of inflammatory leukocytes is a prerequisite of adipose tissue inflammation during cardio-metabolic disease. We recently reported that a genetic deficiency of the intracellular signalling adaptor TRAF-1 attenuates inflammatory cell recruitment and vascular inflammation in atherosclerosis. Here, we tested the contribution of TRAF-1 to diet-induced obesity (DIO) in mice. Methods and Results: To test the association of TRAFs and obesity we screened for expression of different TRAFs in adipose tissue. We found an up-regulation of TRAF-1 mRNA in obese mouse and human adipose tissue, resulting from higher gene expression in adipocytes, but not in adipose tissue macrophages. To test a functional relevance of TRAF-1 signalling in obesity, WT or TRAF-1 -/- mice consumed a high fat diet HFD for 20 weeks. Surprisingly, genetic deficiency of TRAF-1 abolished diet-induced weight gain by supressing peripheral fat depositions. Consequently, TRAF-1 -/- mice demonstrated ameliorated glucose levels after glucose and insulin tolerance tests and dampened insulin signalling. Consistently, we also found reduced accumulation of adipose tissue macrophages. Mechanistically, TRAF-1 -/- mice demonstrated no differences in basic energy metabolism, such as in energy expenditure. However, TRAF-1 -/- adipocytes had higher expression of Adipose Triglyceride Lipase (ATGL) and Hormone-sensitive Lipase (HSL), suggesting increased lipid breakdown in adipocytes. In accord, plasma levels of free fatty acids were higher, while leptin levels were reduced in TRAF-1 -/- mice. Finally, in a collective of patients with a high prevalence of the metabolic syndrome, TRAF-1 expression correlated with the metabolic syndrome, suggesting clinical relevance of our findings. Conclusion: We present the novel finding that the signalling adapter TRAF-1 correlates with obesity in mice and humans. Genetic deficiency of TRAF-1 attenuates diet-induced obesity by increasing lipolysis in adipocytes. These findings identify TRAF-1 as a novel therapeutic target in obesity and adipose-tissue inflammation.

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Erythropoietin Signaling: A Novel Regulator of White Adipose Tissue Inflammation During Diet-Induced Obesity

Diabetes ◽

10.2337/db13-0883 ◽

2014 ◽

Vol 63 (7) ◽

pp. 2415-2431 ◽

Cited By ~ 28

Author(s):

M. Alnaeeli ◽

B. M. Raaka ◽

O. Gavrilova ◽

R. Teng ◽

T. Chanturiya ◽

...

Keyword(s):

Adipose Tissue ◽

White Adipose Tissue ◽

Adipose Tissue Inflammation ◽

Tissue Inflammation ◽

Diet Induced Obesity

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The role of uncoupling protein 2 in macrophages and its impact on obesity-induced adipose tissue inflammation and insulin resistance

Journal of Biological Chemistry ◽

10.1074/jbc.ra120.014868 ◽

2020 ◽

Vol 295 (51) ◽

pp. 17535-17548

Author(s):

Xanthe A. M. H. van Dierendonck ◽

Tiphaine Sancerni ◽

Marie-Clotilde Alves-Guerra ◽

Rinke Stienstra

Keyword(s):

Insulin Resistance ◽

Adipose Tissue ◽

Macrophage Activation ◽

Uncoupling Protein ◽

Uncoupling Protein 2 ◽

Adipose Tissue Inflammation ◽

Tissue Inflammation ◽

Obesity And Diabetes ◽

Adipose Tissue Macrophages

The development of a chronic, low-grade inflammation originating from adipose tissue in obese subjects is widely recognized to induce insulin resistance, leading to the development of type 2 diabetes. The adipose tissue microenvironment drives specific metabolic reprogramming of adipose tissue macrophages, contributing to the induction of tissue inflammation. Uncoupling protein 2 (UCP2), a mitochondrial anion carrier, is thought to separately modulate inflammatory and metabolic processes in macrophages and is up-regulated in macrophages in the context of obesity and diabetes. Here, we investigate the role of UCP2 in macrophage activation in the context of obesity-induced adipose tissue inflammation and insulin resistance. Using a myeloid-specific knockout of UCP2 (Ucp2ΔLysM), we found that UCP2 deficiency significantly increases glycolysis and oxidative respiration, both unstimulated and after inflammatory conditions. Strikingly, fatty acid loading abolished the metabolic differences between Ucp2ΔLysM macrophages and their floxed controls. Furthermore, Ucp2ΔLysM macrophages show attenuated pro-inflammatory responses toward Toll-like receptor-2 and -4 stimulation. To test the relevance of macrophage-specific Ucp2 deletion in vivo, Ucp2ΔLysM and Ucp2fl/fl mice were rendered obese and insulin resistant through high-fat feeding. Although no differences in adipose tissue inflammation or insulin resistance was found between the two genotypes, adipose tissue macrophages isolated from diet-induced obese Ucp2ΔLysM mice showed decreased TNFα secretion after ex vivo lipopolysaccharide stimulation compared with their Ucp2fl/fl littermates. Together, these results demonstrate that although UCP2 regulates both metabolism and the inflammatory response of macrophages, its activity is not crucial in shaping macrophage activation in the adipose tissue during obesity-induced insulin resistance.

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