Role In Adipose Tissue Inflammation Research Articles

Low-grade systemic inflammation and the development of metabolic diseases: From the molecular evidence to the clinical practice

Abstract Background Systemic inflammation is characterised by high circulating levels of inflammatory cytokines and increased macrophage infiltration in peripheral tissues. Most importantly, this inflammatory state does not involve damage or loss of function of the infiltrated tissue, which is a distinctive feature of the low-grade systemic inflammation. The term “meta-inflammation” has also been used to refer to the low-grade systemic inflammation due to its strong relationship with the development of cardio-metabolic diseases in obesity. Objective A review is presented on the recent clinical and experimental evidence concerning the role of adipose tissue inflammation as a key mediator of low-grade systemic inflammation. Furthermore, the main molecular mechanisms involved in the inflammatory polarisation of macrophages with the ability to infiltrate both the adipose tissue and the vascular endothelium via activation of toll-like receptors by metabolic damage-associated molecular patterns, such as advanced glycation-end products and oxidised lipoproteins, is discussed. Finally, a review is made of the pathogenic mechanisms through which the low-grade systemic inflammation contributes to develop insulin resistance, dyslipidaemia, atherogenesis, type 2 diabetes, and hypertension in obese individuals. Conclusions A better understanding of the molecular mechanisms of low-grade systemic inflammation in promoting cardio-metabolic diseases is necessary, in order to further design novel anti-inflammatory therapies that take into consideration clinical data, as well as the circulating levels of cytokines, immune cells, and metabolic damage-associated molecular patterns in each patient.

Protein-Bound Plasma Nε-(Carboxymethyl)lysine Is Inversely Associated With Central Obesity and Inflammation and Significantly Explain a Part of the Central Obesity-Related Increase in Inflammation: The Hoorn and CODAM Studies.

Adipose tissue inflammation contributes to the development of complications, such as insulin resistance and type 2 diabetes mellitus. We previously reported that plasma levels of N(ε)-(carboxymethyl)lysine (CML) were decreased in obese subjects resulting from CML accumulation in adipose tissue and that this CML accumulation plays an important role in adipose tissue inflammation. The objective of this study is to investigate associations between obesity (body mass index, waist circumference, and trunk fat mass), plasma CML (as an inversely correlated marker of CML accumulation in adipose tissue), and low-grade inflammation (LGI) in a large sample of individuals whose weight status ranged from normal to morbid obesity. We studied 1270 individuals of the Cohort on Diabetes and Atherosclerosis Maastricht Study and Hoorn Study, in whom protein-bound CML levels were measured by UPLC-Tandem MS (ultra performance liquid chromatography-tandem mass spectrometry), and 6 inflammatory markers were measured with multiarrays. These inflammatory markers were compiled into an LGI score. Multiple linear regression, adjusted for covariates, showed that (1) waist circumference was inversely associated with protein-bound CML plasma levels (standardized regression coefficient [β]=-0.357 [95% confidence interval: -0.414; -0.301]); (2) protein-bound CML was inversely associated with LGI score (β=-0.073 [-0.130;-0.015]); and (3) the association between waist circumference and LGI (β=0.262 [0.203;0.321]) was attenuated after adjustment for protein-bound CML plasma levels and other potential mediators (to β=0.202 [0.138;0.266]), with CML explaining the greatest portion of the attenuation (≈12%). Further analysis with dual-energy X-ray absorptiometry measures of body composition confirmed a strong inverse association of fat mass preferentially accumulated in the trunk with protein-bound CML plasma levels, significantly explaining ≈21% of the trunk fat-LGI association. Obesity, in particular central obesity, is characterized by greater levels of LGI but by lower levels of circulating CML; the latter significantly explaining a portion of the positive association between central obesity and inflammation.

Inflamación sistémica de grado bajo y su relación con el desarrollo de enfermedades metabólicas: de la evidencia molecular a la aplicación clínica

BackgroundSystemic inflammation is characterised by high circulating levels of inflammatory cytokines and increased macrophage infiltration in peripheral tissues. Most importantly, this inflammatory state does not involve damage or loss of function of the infiltrated tissue, which is a distinctive feature of the low-grade systemic inflammation. The term “meta-inflammation” has also been used to refer to the low-grade systemic inflammation due to its strong relationship with the development of cardio-metabolic diseases in obesity. ObjectiveA review is presented on the recent clinical and experimental evidence concerning the role of adipose tissue inflammation as a key mediator of low-grade systemic inflammation. Furthermore, the main molecular mechanisms involved in the inflammatory polarization of macrophages with the ability to infiltrate both the adipose tissue and the vascular endothelium via activation of toll-like receptors by metabolic damage-associated molecular patterns, such as advanced glycation-end products and oxidized lipoproteins, is discussed. Finally, a review is made of the pathogenic mechanisms through which the low-grade systemic inflammation contributes to develop insulin resistance, dyslipidaemia, atherogenesis, type 2 diabetes, and hypertension in obese individuals. ConclusionsA better understanding of the molecular mechanisms of low-grade systemic inflammation in promoting cardio-metabolic diseases is necessary, in order to further design novel anti-inflammatory therapies that take into consideration clinical data, as well as the circulating levels of cytokines, immune cells, and metabolic damage-associated molecular patterns in each patient.

Deletion of TLR4 Attenuates Adipose Tissue Inflammation in Cancer Cachexia

Several studies have shown that syndrome of cachexia associated with cancer induces a drastic decrease in body weight and adipose tissue. Stimulation of TLR4 activates proinflammatory pathways and induces cytokine expression in a variety of cell types. Inflammatory pathways are activated in tissues of cachectic animals and play an important role in cancer‐cachexia syndrome. Loss of adipose tissue mass and inflammation occurred early considering the appearance of classical cachexia markers. In this study we evaluated cachexia development in TLR4 ‐/‐ mice. Male C57BL/6 mice, with 300µl (3,5 ×105) of LLC tumor cells or vehicle‐saline. Adipose tissue (SCAT, MEAT, RPAT) were collected on 27th day after cells injection. The SVF of AT was isolated and measured the infiltrated immune cells (macrophage and T lymphocytes) by Flow cytometry. SCAT (TWT 37,2% and TM 70,7%), MEAT (TWT 27,1% and TM 28,8%), RPAT (TWT 27,4% and TM 76,9%) showed an decrease of total mass on 27th. In flow cytometry using GR and MAC1 showed an accentuated decrease in MEAT of the TLR4 ‐/‐ mice when compared whit the Wild type mice, in both groups (CWT 77,5% and TWT 66,3%). We observed an accentuated body weight loss in both groups, WT and TLR4 ‐/‐. Therefore when we look at the MEAT, compared with the other depots of TLR4 ‐/‐ mice, presents an attenuated in tissue mass, besides occurring decreased of the most important inflammatory cells in to adipose tissue, characteristic during of the cachectic syndrome. Suggesting that deletion of TLR4 protein may play a role in adipose tissue inflammation.

Leucine-rich glioma inactivated 3 and tumor necrosis factor-α regulate mutually through NF-κB

Leucine-rich glioma inactivated 3 (LGI3) is a secreted protein member of LGI family. We previously reported that LGI3 increased in obese adipose tissues and suppressed adipogenesis through its receptor, ADAM23. We proposed that LGI3 may be a pro-inflammatory adipokine secreted predominantly by preadipocytes and macrophages. In this study, we showed that LGI3 and tumor necrosis factor-α (TNF-α) upregulated each other in 3T3-L1 cells. Treatment of 3T3-L1 preadipocytes with LGI3 protein increased TNF-α mRNA and protein. LGI3 treatment led to NF-κB activation and binding to an NF-κB binding site (−523 to −514) in TNF-α promoter. TNF-α treatment increased mRNA and protein expression of LGI3 and ADAM23. TNF-α increased NF-κB binding to a predicted binding site (−40 to −31) in LGI3 promoter. High fat diet-fed mice showed that LGI3 and TNF-α were increased and colocalized in adipose tissue inflammation. Taken together, these results suggested that mutual upregulation of LGI3 and TNF-α may play a role in adipose tissue inflammation in obesity.

Parenchymal-stromal cell interaction in metabolic diseases

Chronic inflammation may involve sustained interaction between parenchymal and stromal cells in response to a variety of cellular stresses, thereby leading to tissue remodeling and organ malfunction. In obese adipose tissue, saturated fatty acids, which are released as a danger signal from hypertrophied adipocytes, stimulates a pathogen sensor TLR4 in the infiltrating macrophages, thus establishing a vicious cycle that aggravates inflammatory responses. Histologically, macrophages aggregate to constitute crown-like structures (CLS), where they are considered to scavenge the residual lipid droplets of dead adipocytes. Macrophage-inducible C-type lectin (Mincle), a pathogen sensor for Mycobacterium tuberculosis, is induced in adipose tissue macrophages constituting CLS, the number of which is correlated with the extent of interstitial fibrosis. Our data suggest that Mincle, when activated by an as-yet-unidentified danger signal released from dead or dying adipocytes, plays a key role in adipose tissue inflammation and fibrosis.

Increased GIP signaling induces adipose inflammation via a HIF-1α-dependent pathway and impairs insulin sensitivity in mice.

Glucose-dependent insulinotropic polypeptide (GIP) is a gut hormone secreted in response to dietary fat and glucose. The blood GIP level is elevated in obesity and diabetes. GIP stimulates proinflammatory gene expression and impairs insulin sensitivity in cultured adipocytes. In obesity, hypoxia within adipose tissue can induce inflammation. The aims of this study were 1) to examine the proinflammatory effect of increased GIP signaling in adipose tissues in vivo and 2) to clarify the association between GIP and hypoxic signaling in adipose tissue inflammation. We administered GIP intraperitoneally to misty (lean) and db/db (obese) mice and examined adipose tissue inflammation and insulin sensitivity. We also examined the effects of GIP and hypoxia on expression of the GIP receptor (GIPR) gene and proinflammatory genes in 3T3-L1 adipocytes. GIP administration increased monocyte chemoattractant protein-1 (MCP-1) expression and macrophage infiltration into adipose tissue and increased blood glucose in db/db mice. GIPR and hypoxia-inducible factor-1α (HIF-1α) expressions were positively correlated in the adipose tissue in mice. GIPR expression increased dramatically in differentiated adipocytes. GIP treatment of adipocytes increased MCP-1 and interleukin-6 (IL-6) production. Adipocytes cultured either with RAW 264 macrophages or under hypoxia expressed more GIPR and HIF-1α, and GIP treatment increased gene expression of plasminogen activator inhibitor 1 and IL-6. HIF-1α gene silencing diminished both macrophage- and hypoxia-induced GIPR expression and GIP-induced IL-6 expression in adipocytes. Thus, increased GIP signaling plays a significant role in adipose tissue inflammation and thereby insulin resistance in obese mice, and HIF-1α may contribute to this process.

High fat diet deviates PtC-specific B1 B cell phagocytosis in obese mice.

Phagocytosis had been attributed predominantly to “professional” phagocytes such as macrophages, which play critical roles in adipose tissue inflammation. However, recently, macrophage-like phagocytic activity has been reported in B1 B lymphocytes. Intrigued by the long-established correlation between high fat diet (HFD)-induced obesity and immune dysfunction, we investigated how HFD affects B1 B cell phagocytosis. A significant number of B1 B cells recognize phosphatidylcholine (PtC), a common phospholipid component of cell membrane. We report here that unlike macrophages, B1 B cells have a unique PtC-specific phagocytic function. In the presence of both PtC-coated and non-PtC control fluorescent nano-particles, B1 B cells from healthy lean mice selectively engulfed PtC-coated beads, whereas B1 B cells from HFD-fed obese mice non-discriminately phagocytosed both PtC-coated and control beads. Morphologically, B1 B cells from obese mice resembled macrophages, displaying enlarged cytosol and engulfed more beads. Our study suggests for the first time that HFD can affect B1 B cell phagocytosis, substantiating the link of HFD-induced obesity and immune deviation.

A Macrophage NBR1-MEKK3 Complex Triggers JNK-Mediated Adipose Tissue Inflammation in Obesity

The c-Jun NH(2)-terminal kinase (JNK) is a critical determinant of obesity-associated inflammation and glucose intolerance. The upstream mechanisms controlling this pathway are still unknown. Here we report that the levels of the PB1 domain-containing adaptor NBR1 correlated with the expression of proinflammatory molecules in adipose tissue from human patients with metabolic syndrome, suggesting that NBR1 plays a key role in adipose-tissue inflammation. We also show that NBR1 inactivation in the myeloid compartment impairs the function, M1 polarization, and chemotactic activity of macrophages; prevents inflammation of adipose tissue; and improves glucose tolerance in obese mice. Furthermore, we demonstrate that an interaction between the PB1 domains of NBR1 and the mitogen-activated kinase kinase 3 (MEKK3) enables the formation of a signaling complex required for the activation of JNK. Together, these discoveries identify an NBR1-MEKK3 complex as a key regulator of JNK signaling and adipose tissue inflammation in obesity.

UEG Week Vienna 2014 cutting edge symposium: Today's Science, Tomorrow's Medicine session features the immune system - a driving force in digestive health and disease.

UEG Week Vienna 2014 cutting edge symposium: Today's Science, Tomorrow's Medicine session features the immune system - a driving force in digestive health and disease.

Essential Role of CD11a in CD8 + T-Cell Accumulation and Activation in Adipose Tissue

T cells, particularly CD8(+) T cells, are major participants in obesity-linked adipose tissue (AT) inflammation. We examined the mechanisms of CD8(+) T-cell accumulation and activation in AT and the role of CD11a, a β2 integrin. CD8(+) T cells in AT of obese mice showed activated phenotypes with increased proliferation and interferon-γ expression. In vitro, CD8(+) T cells from mouse AT displayed increased interferon-γ expression and proliferation to stimulation with interleukin-12 and interleukin-18, which were increased in obese AT. CD11a was upregulated in CD8(+) T cells in obese mice. Ablation of CD11a in obese mice dramatically reduced T-cell accumulation, activation, and proliferation in AT. Adoptive transfer showed that CD8(+) T cells from wild-type mice, but not from CD11a-deficient mice, infiltrated into AT of recipient obese wild-type mice. CD11a deficiency also reduced tumor necrosis factor-α-producing and interleukin-12-producing macrophages in AT and improved insulin resistance. Combined action of cytokines in obese AT induces proliferative response of CD8(+) T cells locally, which, along with increased infiltration, contributes to CD8(+) T-cell accumulation and activation in AT. CD11a plays a crucial role in AT inflammation by participating in T-cell infiltration and activation.

Inflammation triggers high mobility group box 1 (HMGB1) secretion in adipose tissue, a potential link to obesity

BackgroundLow grade inflammation is one of the major metabolic disorders in case of obesity due to variable secretion of adipose derived cytokines called adipokines. Recently the nuclear protein HMGB1 was identified as an inflammatory alarmin in obesity associated diseases. However HMGB1 role in adipose tissue inflammation is not yet studied. ObjectivesThe aim of this study was to prove the expression of HMGB1 in human adipose tissue and to assess the levels of expression between normo-weight and obese individuals. Furthermore we determined which type of cells within adipose tissue is involved in HMGB1 production under inflammatory signal. MethodsWestern-blot was performed on protein lysates from human normo-weight and obese adipose tissue to study the differential HMGB1 expression. Human normo-weight adipose tissue, adipose-derived stromal cells (ASCs) and adipocytes were cultured and stimulated with LPS to induce inflammation. HMGB1, IL-6 and MCP-1 secretion and gene expression were quantified by ELISA and Q-PCR respectively, as well as cell death by LDH assay. HMGB1 translocation during inflammation was tracked down by immunofluorescence in ASCs. ResultsHMGB1 was expressed 2-fold more in adipose tissue from obese compared to normo-weight individuals. LPS led to an up-regulation in HMGB1 secretion and gene expression in ASCs, while no change was noticed in adipocytes. Moreover, this HMGB1 release was not attributable to any cell death. In LPS-stimulated ASCs, HMGB1 translocation from nucleus to cytoplasm was detectable at 12h and the nuclear HMGB1 was completely drained out after 24h of treatment. ConclusionThe expression level studies between adipose tissue from normo-weight and obese individuals together with in vitro results strongly suggest that adipose tissue secretes HMGB1 in response to inflammatory signals which characterized obesity.

Adipocyte hypertrophy is associated with lysosomal permeability both in vivo and in vitro: role in adipose tissue inflammation.

Obesity in both humans and rodents is characterized by adipocyte hypertrophy and the presence of death adipocytes surrounded by macrophages forming "crown-like structures." However, the biochemical pathways involved in triggering adipocyte death as well as the role of death adipocytes in adipose tissue remodeling and macrophage infiltration remain poorly understood. We now show that induction of adipocyte hypertrophy by incubation of mature adipocytes with saturated fatty acids results in lysosomal destabilization and cathepsin B (ctsb), a key lysosomal cysteine protease, activation and redistribution into the cytosol. ctsb activation was required for the lysosomal permeabilization, and its inhibition protected cells against mitochondrial dysfunction. With the use of a dietary murine model of obesity, ctsb activation was detected in adipose tissue of these mice. This is an early event during weight gain that correlates with the presence of death adipocytes, and precedes macrophage infiltration of adipose tissue. Moreover, ctsb-deficient mice showed decreased lysosomal permeabilization in adipocytes and were protected against adipocyte cell death and macrophage infiltration to adipose tissue independent of body weight. These data strongly suggest that ctsb activation and lysosomal permeabilization in adipocytes are key initial events that contribute to the adipocyte cell death and macrophage infiltration into adipose tissue associated with obesity. Inhibition of ctsb activation may be a new therapeutic strategy for the treatment of obesity-associated metabolic complications.

Adipose tissue biglycan as a potential anti-inflammatory target of sodium salicylate in mice fed a high fat diet

BackgroundInflammation in adipose tissue (AT) during obesity causes impaired AT function. Although multiple extracellular matrix (ECM) proteins are expressed in AT their potential role in adipose tissue inflammation is unclear. Biglycan, a pro-inflammatory ECM gene, is highly enriched in adipose tissue. However, whether it is correlated with adipose tissue inflammation is unknown. We provide evidence in support of a strong association between biglycan expression and inflammatory status of adipose tissue.MethodsC57BL6 mice were fed either a control (10% fat calories) or a high fat diet (HFD) (60% fat calories) for 8 weeks. Adipose tissue was analyzed for the expression of biglycan, IL-6 and TNFα. Biglycan knockout or wild type were also fed a high fat diet for 8 weeks and the expression of inflammatory genes in the mesenteric adipose tissue was examined. To test anti-inflammatory treatment on biglycan expression, a group of mice were fed either the low fat or high fat diet for eight weeks supplemented with either saline or sodium salicylate @ 25mg/100ml in their drinking water.ResultsMice on HFD had an increase in ECM genes (BGN and COL1A1), inflammatory genes (IL-6 and TNFα) in both the subcutaneous and epididymal depots. However, correlation analysis only shows a positive correlation between biglycan, IL-6 and TNFα expression. In addition, lower expression of IL-6 and CD68 was found in the mesenteric adipose tissue of biglycan knockout mice compared to the wild type. Sodium salicylate treatment reduced subcutaneous adipose tissue expression of BGN, COL1A1, and COL6A1 and a concurrent downregulation of TNFα and IL-6 and TLR4 expression. Salicylate also lowered the serum TGFβ1 levels.ConclusionBiglycan expression correlates with adipose tissue inflammation, especially in the subcutaneous depot compared to the epididymal depot. This is supported by the greater effect of sodium salicylate in attenuating both inflammatory and ECM gene expression the subcutaneous adipose depot compared to the epididymal depot. These results show that inflammatory state may explain the induction of biglycan, and perhaps, other ECM genes in adipose tissue.

Adipose Tissue Remodeling as Homeostatic Inflammation

Evidence has accumulated indicating that obesity is associated with a state of chronic, low-grade inflammation. Obese adipose tissue is characterized by dynamic changes in cellular composition and function, which may be referred to as “adipose tissue remodeling”. Among stromal cells in the adipose tissue, infiltrated macrophages play an important role in adipose tissue inflammation and systemic insulin resistance. We have demonstrated that a paracrine loop involving saturated fatty acids and tumor necrosis factor-α derived from adipocytes and macrophages, respectively, aggravates obesity-induced adipose tissue inflammation. Notably, saturated fatty acids, which are released from hypertrophied adipocytes via the macrophage-induced lipolysis, serve as a naturally occurring ligand for Toll-like receptor 4 complex, thereby activating macrophages. Such a sustained interaction between endogenous ligands derived from parenchymal cells and pathogen sensors expressed in stromal immune cells should lead to chronic inflammatory responses ranging from the basal homeostatic state to diseased tissue remodeling, which may be referred to as “homeostatic inflammation”. We, therefore, postulate that adipose tissue remodeling may represent a prototypic example of homeostatic inflammation. Understanding the molecular mechanism underlying homeostatic inflammation may lead to the identification of novel therapeutic strategies to prevent or treat obesity-related complications.

Interleukin-33 Induces Protective Effects in Adipose Tissue Inflammation During Obesity in Mice

Chronic low-grade inflammation involving adipose tissue likely contributes to the metabolic consequences of obesity. The cytokine interleukin (IL)-33 and its receptor ST2 are expressed in adipose tissue, but their role in adipose tissue inflammation during obesity is unclear. To examine the functional role of IL-33 in adipose tissues and investigate the effects on adipose tissue inflammation and obesity in vivo. We demonstrate that treatment of adipose tissue cultures in vitro with IL-33 induced production of Th2 cytokines (IL-5, IL-13, IL-10) and reduced expression of adipogenic and metabolic genes. Administration of recombinant IL-33 to genetically obese diabetic (ob/ob) mice led to reduced adiposity, reduced fasting glucose and improved glucose and insulin tolerance. IL-33 also induced accumulation of Th2 cells in adipose tissue and polarization of adipose tissue macrophages toward an M2 alternatively activated phenotype (CD206(+)), a lineage associated with protection against obesity-related metabolic events. Furthermore, mice lacking endogenous ST2 fed high-fat diet had increased body weight and fat mass and impaired insulin secretion and glucose regulation compared to WT controls fed high-fat diet. In conclusion, IL-33 may play a protective role in the development of adipose tissue inflammation during obesity.

Newly identified adipose tissue macrophage populations in obesity with distinct chemokine and chemokine receptor expression

Infiltration by macrophages is a hallmark of obesity-related adipose tissue (AT) inflammation that is tightly linked to insulin resistance. Although CD11c+ AT macrophages (ATMs) have recently been shown to promote inflammation in obese mice, the knowledge on phenotype and function of different ATM populations is still very limited. This study aimed at identifying and characterizing ATM populations in obesity. Isolation of ATM populations defined by CD11c and mannose receptor (MR) expression and analysis of gene expression in high-fat diet-induced obese mice. Obesity provoked a shift from a predominant MR+CD11c⁻ population ('MR-ATM') to two MR⁻ populations, namely MR⁻CD11c+ ('CD11c-ATM') and MR⁻CD11c⁻ (double negative, 'DN-ATM'). Although CD11c-ATMs were of a clear inflammatory M1 phenotype, DN-ATMs expressed few inflammatory mediators and highly expressed genes for alternative activation (M2) markers involved in tissue repair, such as arginase and YM1. In contrast, MR-ATMs marginally expressed M1 and M2 markers but highly expressed chemokines, including Mcp-1 (Ccl2) and Mcp-3 (Ccl7). Both CD11c-ATMs and DN-ATMs, but not MR-ATM, highly expressed a panel of chemokine receptors (namely Ccr2, Ccr5, Ccr3 and Cx3cr1), whereas the expression of Ccr7 and Ccr9 was selective for CD11c-ATMs and DN-ATMs, respectively. Notably, stressed adipocytes upregulated various chemokines capable of attracting CD11c-ATM and DN-ATM. This study identifies a novel ATM population with a putatively beneficial role in AT inflammation. This DN-ATM population could be attracted to the obese AT by similar chemokines such as inflammatory CD11c-ATM, on which only Ccr7 is uniquely expressed.

Inflammation of adipose tissue. Part 2. Pathogenetic role in type 2 diabetes mellitus

This review deals with the role of adipose tissue inflammation (ATI) in the development of type 2 diabetes mellitus (DM2). ATI is regarded as a link between obesity and DM2. The review illustrates the involvement of main adipokines in pathogenesis of DM2 and provides a detailed description of such factors as impaired adiponectin and stimulation of cytokine production responsible for metabolic disorders, activation of lipolysis, in adipocytes, increased fatty acid and triglyceride levels, suppression of insulin activity at the receptor and intracellular levels. Adipokines, in the first place cytokines, act on the insulin signal pathway and affect the intracellular inflammatory kinase cascade. At the intercellular level, ATI stimulates JNK and IKK-beta/kB responsible for the development of insulin resistance via such mechanisms as activation of cytokine secretion in the adipose tissue, oxidative stress, and induction of endoplasmic reticulum enzymes. The key role of JNK and IKK-beta/kB in the inhibition of the insulin signal pathway is mediated through inactivation of insulin receptor substrate 1. Also, it is shown that ATI modulates B-cell function and promotes progressive reduction of insulin secretion.

Adipocyte metabolism and obesity

Adipose tissue metabolism exerts a profound impact on whole-body metabolism. We review how fuel partitioning between adipocytes and other tissues affects insulin signaling pathways. We discuss the role of adipose tissue inflammation in adipocyte metabolism and whole-body insulin sensitivity. Finally, we mention the role of adipokines in autocrine and paracrine signaling.

Circulating concentrations of monocyte chemoattractant protein-1 are associated with menopause status in Korean women

Background Monocyte chemoattractant protein-1 (MCP-1) plays a role in adipose tissue inflammation and insulin resistance. Human circulating MCP-1 concentrations reportedly increase or remain unchanged according to obesity or insulin resistance in various ethnic populations; whether or not circulating MCP-1 concentrations increase after menopause has remained unclear. Methods We investigated the relationship between circulating MCP-1 concentrations and obesity or insulin resistance, and the relationship between circulating MCP-1 and menopause status in premenopausal ( n = 111) and postmenopausal ( n = 64) Korean women. Results Circulating MCP-1 concentrations were significantly higher in postmenopausal women than in obesity-matched premenopausal women; they did not differ between non-obese and obese subgroups of pre- and postmenopausal women. Circulating MCP-1 concentrations had a relationship with menopause status ( ρ = 0.500, p = 0.000), irrespective of obesity, but no relationship with obesity or insulin resistance. Circulating MCP-1 concentrations correlated with serum triglycerides ( r = 0.4, p = 0.001) and also correlated with serum triglyceride concentrations, after adjusting for age and obesity, in postmenopausal women. Conclusions Circulating MCP-1 concentrations are associated with menopause status itself, irrespective of obesity; they do not correlate with obesity or insulin resistance in Korean women, most of whom are not severely obese.