In obesity, white adipose tissue (WAT) inflammation is linked to insulin resistance. Increased adipocyte chemokine (C-C motif) ligand 2 (CCL2) secretion may initiate adipose inflammation by attracting the migration of inflammatory cells into the tissue. Using an unbiased approach, we identified adipose microRNAs (miRNAs) that are dysregulated in human obesity and assessed their possible role in controlling CCL2 production. In subcutaneous WAT obtained from 56 subjects, 11 miRNAs were present in all subjects and downregulated in obesity. Of these, 10 affected adipocyte CCL2 secretion in vitro and for 2 miRNAs (miR-126 and miR-193b), regulatory circuits were defined. While miR-126 bound directly to the 3′-untranslated region of CCL2 mRNA, miR-193b regulated CCL2 production indirectly through a network of transcription factors, many of which have been identified in other inflammatory conditions. In addition, overexpression of miR-193b and miR-126 in a human monocyte/macrophage cell line attenuated CCL2 production. The levels of the two miRNAs in subcutaneous WAT were significantly associated with CCL2 secretion (miR-193b) and expression of integrin, α-X, an inflammatory macrophage marker (miR-193b and miR-126). Taken together, our data suggest that miRNAs may be important regulators of adipose inflammation through their effects on CCL2 release from human adipocytes and macrophages.

Loss of fat mass is a key feature of cancer cachexia and has been attributed to increased adipocyte lipolysis. The mechanism behind this alteration is unknown and was presently investigated. We studied mature s.c. fat cells and differentiated preadipocytes from 26 cancer patients with and without cachexia. Hormone-induced lipolysis and expression of lipolysis-regulating genes were determined together with body composition and in vivo lipolytic activity ( fasting plasma glycerol or fatty acids related to body fat). Body fat was reduced by 40% and in vivo lipolytic activity was 2-fold increased in cachexia (P = 0.001). In mature adipocytes, the lipolytic effects of catecholamines and natriuretic peptide were 2-to 3-fold increased in cachexia (P < 0.001). This was completely counteracted by inhibiting the rate-limiting lipolysis enzyme hormone-sensitive lipase (HSL). In cachexia, the expression levels of HSL mRNA and protein were increased by 50% and 100%, respectively (P = 0.005-0.03), which strongly correlated with in vitro lipolytic stimulation (r = 0.7-0.9). The antilipolytic effect of insulin in mature fat cells and the stimulated lipolytic effect in differentiated preadipocytes were unaltered in cachexia. Patients who lost weight due to other factors than cancer cachexia had no change in adipocyte lipolysis. In conclusion, adipocyte lipolysis is increased in cancer cachexia not due to nonepigenic factors or to weight loss per se, but most probably because of enhanced expression and function of adipocyte HSL. The selective inhibition of this enzyme may prevent fat loss in cancer patients. [Cancer Res 2007;67(11):5531-7]

OBJECTIVEChemerin is an adipokine that affects adipogenesis and glucose homeostasis in adipocytes and increases with BMI in humans. This study was aimed at investigating the regulation of chemerin release and its effects on glucose metabolism in skeletal muscle cells.RESEARCH DESIGN AND METHODSHuman skeletal muscle cells were treated with chemerin to study insulin signaling, glucose uptake, and activation of stress kinases. The release of chemerin was analyzed from in vitro differentiated human adipocytes and adipose tissue explants from 27 lean and 26 obese patients.RESULTSHuman adipocytes express chemerin and chemokine-like receptor 1 (CMKLR1) differentiation dependently and secrete chemerin (15 ng/ml from 106 cells). This process is slightly but significantly increased by tumor necrosis factor-α and markedly inhibited by >80% by peroxisome proliferator–activated receptor-γ activation. Adipose tissue explants from obese patients are characterized by significantly higher chemerin secretion compared with lean control subjects (21 and 8 ng from 107 cells, respectively). Chemerin release is correlated with BMI, waist-to-hip ratio, and adipocyte volume. Furthermore, higher chemerin release is associated with insulin resistance at the level of lipogenesis and insulin-induced antilipolysis in adipocytes. Chemerin induces insulin resistance in human skeletal muscle cells at the level of insulin receptor substrate 1, Akt and glycogen synthase kinase 3 phosphorylation, and glucose uptake. Furthermore, chemerin activates p38 mitogen-activated protein kinase, nuclear factor-κB, and extracellular signal–regulated kinase (ERK)-1/2. Inhibition of ERK prevents chemerin-induced insulin resistance, pointing to participation of this pathway in chemerin action.CONCLUSIONSAdipocyte-derived secretion of chemerin may be involved in the negative cross talk between adipose tissue and skeletal muscle contributing to the negative relationship between obesity and insulin sensitivity.

Lipolysis is the catabolic pathway by which triglycerides are hydrolyzed into fatty acids. Adipose triglyceride lipase (ATGL) and hormone-sensitive lipase (HSL) have the capacity to hydrolyze in vitro the first ester bond of triglycerides, but their respective contributions to whole cell lipolysis in human adipocytes is unclear. Here, we have investigated the roles of HSL, ATGL, and its coactivator CGI-58 in basal and forskolin-stimulated lipolysis in a human white adipocyte model, the hMADS cells. The hMADS adipocytes express the various components of fatty acid metabolism and show lipolytic capacity similar to primary cultured adipocytes. We show that lipolysis and fatty acid esterification are tightly coupled except in conditions of stimulated lipolysis. Immunocytochemistry experiments revealed that acute forskolin treatment promotes HSL translocation from the cytosol to small lipid droplets and redistribution of ATGL from the cytosol and large lipid droplets to small lipid droplets, resulting in enriched colocalization of the two lipases. HSL or ATGL overexpression resulted in increased triglyceride-specific hydrolase capacity, but only ATGL overexpression increased whole cell lipolysis. HSL silencing had no effect on basal lipolysis and only partially reduced forskolin-stimulated lipolysis. Conversely, silencing of ATGL or CGI-58 significantly reduced basal lipolysis and essentially abolished forskolin-stimulated lipolysis. Altogether, these results suggest that ATGL/CGI-58 acts independently of HSL and precedes its action in the sequential hydrolysis of triglycerides in human hMADS adipocytes.Adipose tissue fat stores in humans are mainly dependent upon fatty acid (FA) 2 supply, FA esterification to triglycerides (TG), and TG breakdown, or lipolysis. Adipose tissue lipolysis is governed by three lipases. Adipose triglyceride lipase (ATGL) and hormone-sensitive lipase (HSL) both have the capacity to initiate TG degradation by cleaving the first ester bond, but HSL is unique in its capacity to break down the second ester bond, converting diglycerides (DG) to monoglycerides (1-3). The non-rate-limiting monoglyceride lipase completes lipolysis by cleaving the last ester bond from a monoglyceride molecule, leading to glycerol release (4). Adipose tissue lipolysis has received much attention over the past 10 years because of its altered regulation in obesity (5).HSL resides freely in the cytosol and can associate with lipid droplets (LD). It is regulated by hormones such as catecholamines, insulin, and natriuretic peptides. Catecholamines bind to ␤-adrenoceptors on adipocyte cell membranes and activate cyclic AMP-dependent protein kinase. Similarly, natriuretic peptides bind to type A receptors and activate cyclic GMPdependent protein kinase (6). The protein kinase action in stimulated lipolysis is 2-fold: 1) phosphorylation of HSL, leading to its translocation from the cytosol to LD (7,8), and 2) phosphorylation of perilipin A (6, 9, 10), the predominant perilipin isoform in adipocytes, enhancing interaction be...

Background: Cardiovascular risk in diabetes remains elevated despite glucose lowering therapies. We hypothesised that hyperglycaemia induces trained immunity in macrophages, promoting persistent pro-atherogenic characteristics. Methods: Bone marrow derived macrophages from control and mice with diabetes were grown in physiological glucose (5 mM) and subject to RNA-sequencing (n=6), ATAC-sequencing (n=6) and ChIP-sequencing (n=6) for determination of hyperglycaemia-induced trained immunity. Bone marrow transplantation from mice with (n=9) or without (n=6) diabetes into [normoglycaemic] Ldlr -/- mice was used to assess its functional significance in vivo . Evidence of hyperglycaemia-induced trained immunity was sought in human peripheral blood mononuclear cells (PBMCs) from patients with diabetes (n=8) compared with case controls (n=16) and in human atherosclerotic plaque macrophages excised by laser capture microdissection. Results: In macrophages, high extracellular glucose promoted pro-inflammatory gene expression and pro-atherogenic functional characteristics, through glycolysis-dependent mechanisms. Bone marrow-derived macrophages (BMDM) from diabetic mice, retained these characteristics, even when cultured in physiological glucose, indicating hyperglycaemia-induced trained immunity. Bone marrow transplantation from diabetic mice into [normoglycaemic] Ldlr -/- mice increased aortic root atherosclerosis, confirming a disease-relevant and persistent form of trained innate immunity. Integrated ATAC-seq, ChIP-seq and RNA-seq analyses of haematopoietic stem cells and BMDM revealed a pro-inflammatory "priming effect" in diabetes. The pattern of open chromatin implicated transcription factor, RUNX1, while transcriptomes of atherosclerotic plaque macrophages and peripheral leukocytes in patients with type 2 diabetes were enriched for RUNX1 targets, consistent with a potential role in human disease. Pharmacological inhibition of RUNX1 in vitro inhibited the trained phenotype. Conclusions: Hyperglycaemia-induced trained immunity may explain why targeting elevated glucose is ineffective in reducing macrovascular risk in diabetes and suggests new targets for disease prevention and therapy.

Aims/hypothesis We aimed to elucidate the impact of fat cell size and inflammatory status of adipose tissue on the development of type 2 diabetes in non-obese individuals. Methods We characterised subcutaneous abdominal adipose tissue by examining stromal cell populations by 13 colour flow cytometry, measuring expression of adipogenesis genes in the progenitor cell fraction and determining lipolysis and adipose secretion of inflammatory proteins in 14 non-obese men with type 2 diabetes and 13 healthy controls matched for age, sex, body weight and total fat mass. Results Individuals with diabetes had larger fat cells than the healthy controls but stromal cell population frequencies, adipose lipolysis and secretion of inflammatory proteins did not differ between the two groups. However, in the entire cohort fat cell size correlated positively with the ratio of M1/M2 macrophages, TNF-α secretion, lipolysis and insulin resistance. Expression of genes encoding regulators of adipogenesis and adipose morphology (BMP4, CEBPα [also known as CEBPA], PPARγ [also known as PPARG] and EBF1) correlated negatively with fat cell size. Conclusions/interpretation We show that a major phenotype of white adipose tissue in non-obese individuals with type 2 diabetes is adipocyte hypertrophy, which may be mediated by an impaired adipogenic capacity in progenitor cells. Consequently, this could have an impact on adipose tissue inflammation, release of fatty acids, ectopic fat deposition and insulin sensitivity.

BACKGROUND.Cancer cachexia is an important, negative prognostic marker that has been linked to systemic inflammation and cell death through unclear mechanisms. A key feature of cancer cachexia is loss of white adipose tissue (WAT) because of increased adipocyte lipolysis and possibly reduced lipid synthesis (lipogenesis). In this study, the authors investigated whether alterations in fat cell numbers, lipogenesis, or cytokine and/or leukocyte infiltration could account for some of the functional changes observed in WAT in cancer cachexia.METHODS.Blood and subcutaneous WAT samples were obtained from a 10 weight‐stable patients, from 13 weight losing (cachexia) patients with cancer, and from 5 patients without cancer (noncancer patients) who initially were classified with cancer.RESULTS.Systemic inflammation (increased circulating levels of interleukin 6 [IL‐6]) and enhanced lipolysis were confirmed in the cachectic patients compared with the other patients. However, the messenger RNA expression of IL‐6 and other cytokine or leukocyte markers, as well as WAT secretion of IL‐6, were not altered in the patients with cachexia. Thus, the elevated serum levels of IL‐6 that were observed in cachexia were not derived from WAT. Insulin‐induced lipogenesis in adipocytes from patients with cachexia was the same as that in adipocytes from patients with weight‐stable cancer and from noncancer patients (2.5‐fold maximal stimulation; half‐maximum effective concentration, ∼0.03 nmol/L). Fat cell size was decreased but adipocyte numbers were normal in cancer patients with cachexia, suggesting that there was no major fat cell death.CONCLUSIONS.The current findings indicated that subcutaneous WAT does not contribute to the systemic inflammatory reaction and does not induce adipocyte insulin resistance in cancer cachexia. Moreover, increased fat cell lipolysis, not reduced lipogenesis or adipocyte cell death, appeared to be the primary cause of fat loss in this condition. Cancer 2008. © 2008 American Cancer Society.

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