Regulation of interleukin 8 production and gene expression in human adipose tissue in vitro

Examining the immunoepigenetic-gut microbiome axis in the context of self-esteem among Native Hawaiians and other Pacific Islanders

Introduction: Native Hawaiian and other Pacific Islander (NHPI) populations experience higher rates of immunometabolic diseases compared to other racial-ethnic groups in Hawaii. As annual NHPI mortality rates for suicide and type 2 diabetes mellitus (T2DM) exceed those of the state as a whole, understanding the social and biological mechanisms underlying these disparities are urgently needed to enable preventive strategies. Methods: A community-based approach was used to investigate the immunoepigenetic-gut microbiome axis in an NHPI-enriched cohort of Oahu residents (N = 68). Self-esteem (SE) data was collected using a modified Rosenberg self-esteem (SE) assessment as a proxy measure for mental wellbeing in consideration for cultural competency. T2DM status was evaluated using point-of-care A1c (%) tests. Stool samples were collected for 16s-based metagenomic sequencing analyses. Plasma from blood samples were isolated by density-gradient centrifugation. Peripheral blood mononuclear cells (PBMCs) were collected from the same samples and enriched for monocytes using negative selection techniques. Flow-cytometry was used for immunoprofiling assays. Monocyte DNA was extracted for Illumina EPIC array-based methylation analysis. Results: Compared to individuals with normal SE (NSE), those with low SE (LSE) exhibited significantly higher plasma concentrations (pg/ml) of proinflammatory cytokines IL-8 (p = 0.051) and TNF-α (p = 0.011). Metagenomic analysis revealed that the relative abundance (%) of specific gut bacteria significantly differed between SE groups - some of which directly correlated with SE scores. Gene ontology analysis revealed that 104 significantly differentially methylated loci (DML) between SE groups were preferentially located at genes involved in immunometabolic processes. Horvath clock analyses indicated epigenetic age (Epi-Age) deceleration in individuals with LSE and acceleration in individuals with NSE (p = 0.042), yet was not reproduced by other clocks. Discussion: These data reveal novel differences in the immunoepigenetic-gut microbiome axis with respect to SE, warranting further investigation into its relationship to brain activity and mental health in NHPI. Unexpected results from Epi-Age analyses warrant further investigation into the relationship between biological age and disparate health outcomes among the NHPI population. The modifiable component of epigenetic processes and the gut microbiome makes this axis an attractive target for potential therapeutics, biomarker discovery, and novel prevention strategies.

The serial changes of Neutrophile-Lymphocyte Ratio and correlation to weight loss after Laparoscopic Sleeve Gastrectomy

Purpose

This study aims to identify the pre- and postoperative changes in the neutrophil-lymphocyte ratio (NLR) and its correlations to clinical characteristics in obese patients who underwent laparoscopic sleeve gastrectomy (LSG).

Method

Retrospectively, we included patients who has undergone LSG in our institution between January 2019 and April 2021. A total of 100 patients whose body mass index over 32.5 and received primary laparoscopic sleeve gastrectomy without infectious condition were included.

Results

There was a significant decline in NLR (T0 vs. POM3 2.21 vs. 1.78, p = 0.005), neutrophil (T0 vs. POM3 5369 vs. 4050, p < 0.001) and lymphocyte count (T0 vs. POM3 2440: 2100, p < 0.001, respectively) at postoperative 3 months (POM3) compared to preoperative (T0) levels, but similar between POM3 and POM6. The declined counts (Neutrophile vs. Lymphocyte 1445.5/µl vs. 323.5/µl, p < 0.001) and percentage (Neutrophile vs. Lymphocyte 25.11% vs. 13.07%, p < 0.001) of neutrophile are higher than lymphocyte from T0 to POM3, but similar in POM3 and POM6. Preoperative NLR has a significant correlation with the preoperative body weight, preoperative insulin level, and excessive body weight loss (EBWL) at POM3. Preoperative NLR <2.36 had a sensitivity of 67.6% and a specificity of 62.5% in predicting successful weight loss (EBWL > 37.7%) at POM3 (AUC = 0.635, p = 0.032).

Conclusion

There was a significant decline in NLR, neutrophil, and lymphocyte count from T0 to POM3, but similar between POM3 and POM6. The declined counts and percentage of neutrophile are higher than lymphocyte. Preoperative NLR shows the potential to be used as a prognostic biomarker for predicting successful weight loss at POM3 after LSG. Further studies could be designed to evaluate the value of prediction in successful outcome after LSG and figure out the relationship between the changes of neutrophil function and oncogenesis.

Impact of Bariatric Surgery on Adipose Tissue Biology

Bariatric surgery (BS) procedures are actually the most effective intervention to help subjects with severe obesity achieve significant and sustained weight loss. White adipose tissue (WAT) is increasingly recognized as the largest endocrine organ. Unhealthy WAT expansion through adipocyte hypertrophy has pleiotropic effects on adipocyte function and promotes obesity-associated metabolic complications. WAT dysfunction in obesity encompasses an altered adipokine secretome, unresolved inflammation, dysregulated autophagy, inappropriate extracellular matrix remodeling and insufficient angiogenic potential. In the last 10 years, accumulating evidence suggests that BS can improve the WAT function beyond reducing the fat depot sizes. The causal relationships between improved WAT function and the health benefits of BS merits further investigation. This review summarizes the current knowledge on the short-, medium- and long-term outcomes of BS on the WAT composition and function.

ROS/TNF-α Crosstalk Triggers the Expression of IL-8 and MCP-1 in Human Monocytic THP-1 Cells via the NF-κB and ERK1/2 Mediated Signaling

IL-8/MCP-1 act as neutrophil/monocyte chemoattractants, respectively. Oxidative stress emerges as a key player in the pathophysiology of obesity. However, it remains unclear whether the TNF-α/oxidative stress interplay can trigger IL-8/MCP-1 expression and, if so, by which mechanism(s). IL-8/MCP-1 adipose expression was detected in lean, overweight, and obese individuals, 15 each, using immunohistochemistry. To detect the role of reactive oxygen species (ROS)/TNF-α synergy as a chemokine driver, THP-1 cells were stimulated with TNF-α, with/without H₂O₂ or hypoxia. Target gene expression was measured by qRT-PCR, proteins by flow cytometry/confocal microscopy, ROS by DCFH-DA assay, and signaling pathways by immunoblotting. IL-8/MCP-1 adipose expression was significantly higher in obese/overweight. Furthermore, IL-8/MCP-1 mRNA/protein was amplified in monocytic cells following stimulation with TNF-α in the presence of H₂O₂ or hypoxia (p ˂ 0.0001). Synergistic chemokine upregulation was related to the ROS levels, while pre-treatments with NAC suppressed this chemokine elevation (p ≤ 0.01). The ROS/TNF-α crosstalk involved upregulation of CHOP, ERN1, HIF1A, and NF-κB/ERK-1,2 mediated signaling. In conclusion, IL-8/MCP-1 adipose expression is elevated in obesity. Mechanistically, ROS/TNF-α crosstalk may drive expression of these chemokines in monocytic cells by inducing ER stress, HIF1A stabilization, and signaling via NF-κB/ERK-1,2. NAC had inhibitory effect on oxidative stress-driven IL-8/MCP-1 expression, which may have therapeutic significance regarding meta-inflammation.

Adipocytes, Innate Immunity and Obesity: A Mini-Review

The role of adipose tissue (AT) inflammation in obesity and its multiple related-complications is a rapidly expanding area of scientific interest. Within the last 30 years, the role of the adipocyte as an endocrine and immunologic cell has been progressively established. Like the macrophage, the adipocyte is capable of linking the innate and adaptive immune system through the secretion of adipokines and cytokines; exosome release of lipids, hormones, and microRNAs; and contact interaction with other immune cells. Key innate immune cells in AT include adipocytes, macrophages, neutrophils, and innate lymphoid cells type 2 (ILC2s). The role of the innate immune system in promoting adipose tissue inflammation in obesity will be highlighted in this review. T cells and B cells also play important roles in contributing to AT inflammation and are discussed in this series in the chapter on adaptive immunity.

The association between leptin and inflammatory markers with obesity indices in Zanzibari children, adolescents, and adults

Background

Research from Western populations describes abdominal obesity as a low‐grade inflammatory disease; less is known from tropical areas with high pathogen burden.

Objectives

This cross‐sectional study investigated whether obesity contributes to low‐grade inflammation in 587 individuals from randomly selected households in Zanzibar.

Materials and Methods

The Association between obesity indices (body mass index [BMI], waist circumference [WC], and percentage body fat [%BF]), leptin, and inflammatory markers (C‐reactive protein [CRP], interleukin‐6 [IL‐6] and tumor‐necrosis factor‐α [TNF‐α]) was investigated using multinomial logistic regression analysis, accounting for ordinal outcome variables with four categories; 1st–4th quartile.

Results

Study participants were between 5 and 95 years; 49.6% were male. Mean serum levels were; leptin: 4.3 ± 5.2 ng/ml, CRP: 0.19 ± 0.42 µg/ml, IL‐6: 2.8 ± 5 pg/ml, and TNF‐α: 5.3 ± 5.2 pg/ml. Obesity indices were associated with leptin and CRP in the third and fourth quartiles in single models. In combined models, associations were observed between BMI (OR = 6.36 [95% CI, 1.09; 34.12]); WC (OR = 4.87 [95% CI, 1.59; 14.94]); and %BF (OR = 19.23 [95% CI, 4.70; 78.66]) and leptin in the fourth quartile; also between %BF and CRP in the third quartile (OR = 3.49 [95% CI 1.31; 9.31]).

Conclusion

Total body fat was associated with low‐grade inflammation in this tropical population rather than body fat distribution such as abdominal obesity. This may increase the risk of insulin resistance and other obesity‐related metabolic and cardiovascular health endpoints.

Gender dependent differences in lipid metabolism in individuals with type 2 diabetes mellitus

Aim

The present study investigates gender dependent effects of insulin resistance on lipid profile and adipocytokines in individuals with diabetes receiving oral antidiabetic drugs (OADs). The aim was also to reveal the changes in the expression of genes involved in lipid metabolism and inflammation.

Methods

Lipid profile, adipocytokine levels and homeostatic model assessment of insulin resistance (HOMA-IR) was assessed in 100 patients with diabetes (M = 43, F = 57) matched for age and gender with healthy individuals (M = 45, F = 55). The expression pattern of genes was analyzed by quantitative real time PCR.

Results

Males consuming metformin with other drugs exhibited a positive association between HOMA-IR and cholesterol, triglyceride and very low density lipoprotein (VLDL). Females consuming only metformin and metformin with other drugs, showed a positive association of HOMA-IR with cholesterol and a negative association with adiponectin. In males and females with diabetes, a comparable expression of peroxisome proliferator activated receptor γ (PPARγ) while higher expression of sterol regulatory element binding protein 1 (SREBP1) was observed. Expression of fatty acid synthase (FAS), long chain acyl CoA Synthetases (ACSL), malonyl-CoA-acyl carrier protein transacylase (MCAT) and nuclear factor kappa β (NFkβ) was higher in men with diabetes than healthy males. Expression of tumor necrosis factor α (TNF-α) was higher in males and females with diabetes than respective healthy genders.

Conclusion

Insulin resistance adversely affects lipid profile, adipocytokines in males with type 2 diabetes. Expression of genes involved in lipid metabolism and inflammation is found to be undesirably and differentially altered in both the genders.

Is There A Causal Relationship between Childhood Obesity and Acute Lymphoblastic Leukemia? A Review

Childhood obesity is a growing epidemic with numerous global health implications. Over the past few years, novel insights have emerged about the contribution of adult obesity to cancer risk, but the evidence base is far more limited in children. While pediatric patients with acute lymphoblastic leukemia (ALL) are at risk of obesity, it is unclear if there are potential causal mechanisms by which obesity leads to ALL development. This review explores the endocrine, metabolic and immune dysregulation triggered by obesity and its potential role in pediatric ALL's genesis. We describe possible mechanisms, including adipose tissue attraction and protection of lymphoblasts, and their impact on ALL chemotherapies' pharmacokinetics. We also explore the potential contribution of cytokines, growth factors, natural killer cells and adipose stem cells to ALL initiation and propagation. While there are no current definite causal links between obesity and ALL, critical questions persist as to whether the adipose tissue microenvironment and endocrine actions can play a causal role in childhood ALL, and there is a need for more research to address these questions.

Adipocytes: active facilitators in epithelial ovarian cancer progression?

There is growing evidence that adipocytes play important roles in the progression of multiple cancers. Moreover, in obesity, adipocytes alter their original functions and contribute to the metabolic and inflammatory changes of adipose tissue microenvironment, which can further enhance tumor development. At present, the roles of adipocytes in the pathogenesis of epithelial ovarian cancer (EOC) are far from being fully elucidated. Herein, we summarized the recent advances in understanding the roles of adipocytes in EOC progression. Adipocytes, close neighbors of EOC tissue, promote EOC growth, invasion, metastasis and angiogenesis through adipokine secretion, metabolic remodeling and immune microenvironment modulation. Moreover, adipocytes are important therapeutic targets and may work as useful anticancer drug delivery depot for EOC treatment. Furthermore, adipocytes also act as a therapeutic obstacle for their involvement in EOC treatment resistance. Hence, better characterization of the adipocytes in EOC microenvironment and the crosstalk between adipocytes and EOC cells may provide insights into EOC progression and suggest novel therapeutic opportunities.

Enhanced Adipose Expression of Interferon Regulatory Factor (IRF)-5 Associates with the Signatures of Metabolic Inflammation in Diabetic Obese Patients

: Interferon regulatory factors (IRFs) are emerging as the metabolic transcriptional regulators in obesity/type-2 diabetes (T2D). IRF5 is implicated with macrophage polarization toward the inflammatory M1-phenotype, nonetheless, changes in the adipose expression of IRF5 in T2D and relationship of these changes with other markers of adipose inflammation remain unclear. Therefore, we determined the IRF5 gene expression in subcutaneous adipose tissue samples from 46 T2D patients including 35 obese (Body Mass Index/BMI 33.83 ± 0.42kg/m²) and 11 lean/overweight individuals (BMI 27.55 ± 0.46kg/m²) using real-time qRT-PCR. IRF5 protein expression was assessed using immunohistochemistry and confocal microscopy. Fasting plasma glucose, insulin, HbA1c, C-reactive protein, cholesterol, low- and high-density lipoproteins (LDL/HDL), and triglycerides were measured using commercial kits. IRF5 gene expression was compared with that of signature inflammatory markers and several clinico-metabolic indicators. The data (mean ± SEM) show the enhanced adipose IRF5 gene (p = 0.03) and protein (p = 0.05) expression in obese compared to lean/overweight diabetic patients. Adipose IRF5 transcripts in diabetic obese individuals associated positively with those of TNF-α, IL-18, IL-23A, CXCL8, CCL2, CCL7, CCR1/5, CD11c, CD68, CD86, TLR4/7/10, Dectin-1, FGL-2, MyD88, NF-κB, IRF3, and AML1 (p < 0.05). In diabetic lean/overweight subjects, IRF5 expression associated with BMI, body fat %age, glucose, insulin, homeostatic model assessment of insulin resistance (HOMA-IR, C-reactive protein (CRP), IL-5, and IL-1RL1 expression; while in all T2D patients, IRF5 expression correlated with that of IRF4, TLR2/8, and CD163. In conclusion, upregulated adipose tissue IRF5 expression in diabetic obese patients concurs with the inflammatory signatures and it may represent a potential marker for metabolic inflammation in obesity/T2D.

TNF-α in Combination with Palmitate Enhances IL-8 Production via The MyD88- Independent TLR4 Signaling Pathway: Potential Relevance to Metabolic Inflammation

Elevated levels of IL-8 (CXCL8) in obesity have been linked with insulin resistance and type 2 diabetes (T2D). The mechanisms that lead to the profound production of IL-8 in obesity remains to be understood. TNF-α and saturated free fatty acids (FFAs) are increased in obese humans and correlate with insulin resistance. Hence, we sought to investigate whether the cooccurrence of TNF-α and FFAs led to increase the production of IL-8 by human monocytes. We found that co-stimulation of human monocytes with palmitate and TNF-α led to increased IL-8 production as compared to those stimulated with palmitate or TNF-α alone. The synergistic production of IL-8 by TNF-α/palmitate was suppressed by neutralizing anti- Toll like receptor 4 (TLR4) antibody and by genetic silencing of TLR4. Both MyD88-deficient and MyD88-competent cells responded comparably to TNF-α/Palmitate. However, TIR-domain-containing adapter-inducing interferon (TRIF) inhibition or interferon regulatory transcription factor 3 (IRF3) knockdown partly blocked the synergistic production of IL-8. Our human data show that increased adipose tissue TNF-α expression correlated positively with IL-8 expression (r = 0.49, P = 0.001). IL-8 and TNF-α correlated positively with macrophage markers including CD68, CD163 and CD86 in adipose tissue. These findings suggest that the signaling cross-talk between saturated fatty acid palmitate and TNF-α may be a key driver in obesity-associated chronic inflammation via an excessive production of IL-8.

Micro-RNAs Are Related to Epicardial Adipose Tissue in Participants With Atrial Fibrillation: Data From the MiRhythm Study

Introduction: Epicardial adipose tissue (EAT) has been linked to incidence and recurrence of atrial fibrillation (AF), but the underlying mechanisms that mediate this association remain unclear. Circulating microRNAs (miRNAs) contribute to the regulation of gene expression in cardiovascular diseases, including AF. Thus, we sought to test the hypothesis that circulating miRNAs relate to burden of EAT.

Methods: We examined the plasma miRNA profiles of 91 participants from the miRhythm study, an ongoing study examining associations between miRNA and AF. We quantified plasma expression of 86 unique miRNAs commonly expressed in cardiomyocytes using quantitative reverse transcriptase polymerase chain reaction (qPCR). From computed tomography, we used validated methods to quantify the EAT area surrounding the left atrium (LA) and indexed it to body surface area (BSA) to calculate indexed LA EAT (iLAEAT). Participants were divided into tertiles of iLAEAT to identify associations with unique miRNAs. We performed logistic regression analyses adjusting for factors associated with AF to examine relations between iLAEAT and miRNA. We performed further bioinformatics analysis of miRNA predicted target genes to identify potential molecular pathways are regulated by the miRNAs.

Results: The mean age of the participants was 59 ± 9, 35% were women, and 97% were Caucasian. Participants in the highest tertile of iLAEAT were more likely to have hypertension, heart failure, and thick posterior walls. In regression analyses, we found that miRNAs 155-5p (p < 0.001) and 302a-3p (p < 0.001) were significantly associated with iLAEAT in patients with AF. The predicted targets of the miRNAs identified were implicated in the regulation of cardiac hypertrophy, adipogenesis, interleukin-8 (IL-8), and nerve growth factor (NGF) signaling.

Conclusion: miRNA as well as EAT have previously been linked to AF. Our finding that iLAEAT and miRNAs 155-5p and 302a-3p are associated suggest a possible direct link to between these entities in the development and maintenance of AF. Further research is needed to study causal relationships between these biomarkers.

Adipose Tissue T Cells in HIV/SIV Infection

Adipose tissue comprises one of the largest organs in the body and performs diverse functions including energy storage and release, regulation of appetite and other neuroendocrine signaling, and modulation of immuity, among others. Adipocytes reside in a complex compartment where antigen, antigen presenting cells, innate immune cells, and adaptive immune cells interact locally and exert systemic effects on inflammation, circulating immune cell profiles, and metabolic homeostasis. T lymphocytes are a major component of the adipose tissue milieu which are altered in disease states such as obesity and human immunodeficiency virus (HIV) infection. While obesity, HIV infection, and simian immunodeficiency virus (SIV; a non-human primate virus similar to HIV) infection are accompanied by enrichment of CD8⁺ T cells in the adipose tissue, major phenotypic differences in CD4⁺ T cells and other immune cell populations distinguish HIV/SIV infection from obesity. Furthermore, DNA and RNA species of HIV and SIV can be detected in the stromal vascular fraction of visceral and subcutaneous adipose tissue, and replication-competent HIV resides in local CD4⁺ T cells. Here, we review studies of adipose tissue CD4⁺ and CD8⁺ T cell populations in HIV and SIV, and contrast the findings with those reported in obesity.

Mineralocorticoid Receptor and Aldosterone-Related Biomarkers of End-Organ Damage in Cardiometabolic Disease

The mineralocorticoid receptor (MR) was first identified as a blood pressure regulator, modulating renal sodium handling in response to its principal ligand aldosterone. The mineralocorticoid receptor is also expressed in many tissues other than the kidney, such as adipose tissue, heart and vasculature. Recent studies have shown that MR plays a relevant role in the control of cardiovascular and metabolic function, as well as in adipogenesis. Dysregulation of aldosterone/MR signaling represents an important cause of disease as high plasma levels of aldosterone are associated with hypertension, obesity and increased cardiovascular risk. Aldosterone displays powerful vascular effects and acts as a potent pro-fibrotic agent in cardiovascular remodeling. Mineralocorticoid receptor activation regulates genes involved in vascular and cardiac fibrosis, calcification and inflammation. This review focuses on the role of novel potential biomarkers related to aldosterone/MR system that could help identify cardiovascular and metabolic detrimental conditions, as a result of altered MR activation. Specifically, we discuss: (1) how MR signaling regulates the number and function of different subpopulations of circulating and intra-tissue immune cells; (2) the role of aldosterone/MR system in mediating cardiometabolic diseases induced by obesity; and (3) the role of several MR downstream molecules as novel potential biomarkers of cardiometabolic diseases, end-organ damage and rehabilitation outcome.

Early Effects of Sleeve Gastrectomy on Obesity-Related Cytokines and Bile Acid Metabolism in Morbidly Obese Japanese Patients

BACKGROUND

Laparoscopic sleeve gastrectomy (LSG) has wide-ranging positive effects on adipocytokine metabolism, bile acid profile, and chronic low-grade inflammation related to obesity. However, the early temporal changes in these markers following LSG have not been well investigated. This study aimed to evaluate the early effects of LSG on adipocytokines, bile acid profile, and inflammatory markers.

METHODS

This was a nonrandomized prospective study examining morbidly obese Japanese patients undergoing LSG. Serial measurements of leptin, adiponectin, bile acids, fibroblast growth factor (FGF)-19, and inflammatory markers were performed preoperatively and 1 and 6 months after LSG.

RESULTS

The study included ten patients (five females) with a mean age of 48.8 years and BMI 40.9 kg/m². At baseline, 90% of the patients had T2DM, 70% had dyslipidemia, and 90% had hypertension. Patients lost 5.1 kg/m² BMI at 1 month and 10.1 kg/m² BMI at 6 months. The leptin levels sharply decreased, and FGF-19 increased significantly as early as 1 month postoperatively. Adiponectin levels showed an increasing trend at 1 month and a significant increase at 6 months. A significant decrease in high-sensitivity CRP and plasminogen activator inhibitor-1 was observed at 6 months. No significant changes were observed in interleukin (IL)-6, IL-8, tumor necrosis factor-α, serum amyloid A protein, or monocyte chemotactic protein-1 throughout the study.

CONCLUSIONS

LSG improved the secretion of adipocytokines, increased FGF-19 secretion soon after surgery, and slowly ameliorated inflammation related to obesity through significant weight loss.

Impact of Adrenal Steroids on Regulation of Adipose Tissue

Corticosteroids are secreted by the adrenal glands and control the functions of adipose tissue via the activation of mineralocorticoid receptor (MR) and glucocorticoid receptor (GR). In turn, adipocytes release a large variety of adipokines into the bloodstream, regulating the function of several organs and tissues, including the adrenal glands, hereby controlling corticosteroid production. In adipose tissue, the activation of the MR by glucocorticoids (GC) and aldosterone affects important processes such as adipocyte differentiation, oxidative stress, autophagic flux, adipokine expression as well as local production of GC through upregulation of the enzyme 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1). Notably, the proinflammatory responses induced by the MR are counteracted by activation of the GR, whose activity inhibits the expression of inflammatory adipokines. Both GR and MR are deeply involved in adipogenesis and adipose expansion; hence pharmacological blockade of these two receptors has proven effective against adipose tissue dysfunction in experimental models of obesity and metabolic syndrome (MetS), suggesting a potential use for MR and GR antagonists in these clinical settings. Importantly, obesity and Cushing's syndrome (CS) share metabolic similarities and are characterized by high levels of circulating corticosteroids, which in turn are able to deeply affect adipose tissue. In addition, pharmacological approaches aimed at reducing aldosterone and GC levels, by means of the inhibition of CYP11B2 (aldosterone synthase) or 11β-HSD1, represent alternative strategies to counter the detrimental effects of excessive levels of corticosteroids, which are often observed in obesity and, more general, in MetS. © 2017 American Physiological Society. Compr Physiol 7:1425-1447, 2017.

Acinetobacter baumannii Lipopolysaccharide Influences Adipokine Expression in 3T3-L1 Adipocytes

Acinetobacter baumannii is one of the most important nosocomial opportunistic pathogen worldwide. In addition, obesity has been associated with an increased risk of nosocomial infection, suggesting that there may be an association between A. baumannii and white adipose tissue. However, the effects of A. baumannii on adipocytes have not been well studied at the molecular level. Here, we investigated the potential role of A. baumannii-derived lipopolysaccharides (LPS) as signaling molecules that affect adipocyte functionality. We tested the effect of increasing concentrations of A. baumannii-derived LPS (10, 100, or 1000 ng/mL) on the 3T3-L1 adipocyte cell line. Exposure to LPS was found to increase the expression of several adipokines (e.g., MIP-2, MCP-1, TNF-α, IL-6, lipocalin-2, and FABP4) in 3T3-L1 adipocytes and significantly reduced the expression of leptin and adiponectin. The effects of A. baumannii-derived LPS on MIP-2 expression were similar in comparison with that of LPS prepared from Pseudomonas aeruginosa and Escherichia coli in our cell culture-based system. This study suggests that A. baumannii-derived LPS functions as a signaling molecule that impacts the inflammatory function of white adipose tissue on the level of gene expression.

Increased adipose tissue expression of TLR8 in obese individuals with or without type-2 diabetes: significance in metabolic inflammation

Background

The innate immune Toll-like receptors (TLRs) 2/4 are important players in chronic low-grade inflammation called metabolic inflammation in obesity and type-2 diabetes (T2D). While TLR2/4 expression changes associated with metabolic inflammation are known, the adipose tissue expression of endocytic TLR8, which is expressed by all major macrophage subsets, remain unclear. We, therefore, determined the TLR8 mRNA/protein expression in the adipose tissue samples from lean, overweight, and obese individuals with or without T2D.

Methods

Subcutaneous fat biopsy samples were collected from 49 non-diabetic (23 obese, 17 overweight, and nine lean) and 45 T2D (32 obese, ten overweight, and three lean) individuals. TLR8 gene expression was determined using real-time RT-PCR and TLR8 protein expression was assessed by both immunohistochemistry and confocal microscopy. The changes in TLR8 expression were compared with those of macrophage markers, proinflammatory cytokines/chemokines, and surface TLRs/adapter proteins. The data were analyzed using t-test/Mann-Whitney U-test, Pearson’s correlation, and multiple regression test.

Results

The data show that in obese non-diabetic/T2D individuals, TLR8 gene expression was significantly upregulated as compared with lean individuals which correlated with body mass index (BMI) and body fat percentage in non-diabetic population (P < 0.05). As expected, TLR8 adipose tissue protein expression in non-diabetic/T2D obese individuals was also higher than that of overweight/lean counterparts. In non-diabetic/T2D individuals, TLR8 gene expression associated (P < 0.05) with the expression of CD68, CD11c, CD86, and CD163 macrophage markers. Also, in these individuals, TLR8 gene expression correlated positively (P < 0.05) with adipose tissue expression of TNF-α, IL-18, and IL-8 as well as with systemic CRP levels (in non-diabetics). TLR8 expression was also associated with TLR4/TLR2 and MyD88 expression in the adipose tissue.

Conclusions

The elevated adipose tissue expression of TLR8 in obesity/T2D has consensus with inflammatory signatures and may thus represent an immune marker of metabolic inflammation.

Electronic supplementary material

The online version of this article (doi:10.1186/s12950-016-0147-y) contains supplementary material, which is available to authorized users.

Interleukins 6 and 15 Levels Are Higher in Subcutaneous Adipose Tissue, but Obesity Is Associated with Their Increased Content in Visceral Fat Depots

Excess adiposity is associated with chronic inflammation, which takes part in the development of obesity-related complications. The aim of this study was to establish whether subcutaneous (SAT) or visceral (VAT) adipose tissue plays a major role in synthesis of pro-inflammatory cytokines. Concentrations of interleukins (IL): 1β, 6, 8 and 15 were measured at the protein level by an ELISA-based method and on the mRNA level by real-time PCR in VAT and SAT samples obtained from 49 obese (BMI > 40 kg/m²) and 16 normal-weight (BMI 20–24.9 kg/m²) controls. IL-6 and IL-15 protein concentrations were higher in SAT than in VAT for both obese (p = 0.003 and p < 0.0001, respectively) and control individuals (p = 0.004 and p = 0.001, respectively), while for IL-1β this was observed only in obese subjects (p = 0.047). What characterized obese individuals was the higher expression of IL-6 and IL-15 at the protein level in VAT compared to normal-weight controls (p = 0.047 and p = 0.016, respectively). Additionally, obese individuals with metabolic syndrome had higher IL-1β levels in VAT than did obese individuals without this syndrome (p = 0.003). In conclusion, concentrations of some pro-inflammatory cytokines were higher in SAT than in VAT, but it was the increased pro-inflammatory activity of VAT that was associated with obesity and metabolic syndrome.

Effects of Roux-en-Y gastric bypass on fasting and postprandial inflammation-related parameters in obese subjects with normal glucose tolerance and in obese subjects with type 2 diabetes

BACKGROUND

Obesity is characterized by low grade inflammation and an altered secretion of inflammatory cytokines from the adipose tissue. Weight loss has shown to reduce inflammation; however, changes in cytokine profiles during massive weight loss are not well described. The present study explored the hypothesis that Roux-en-Y gastric bypass (RYGB) reduces circulating levels of pro-inflammatory cytokines, while increasing anti-inflammatory cytokines in obese subjects with type 2 diabetes (T2D) and in obese normal glucose tolerant (NGT) subjects.

METHODS

Thirteen obese subjects with T2D [weight; 129 ± 14 kg, glycated hemoglobin (HbA1c); 7.0 ± 0.9%, body mass index (BMI); 43.2 ± 5.3 kg/m(2), mean ± SD] and twelve matched obese NGT subjects [weight; 127 ± 15 kg, HbA1c; 5.5 ± 0.4%, BMI; 41.5 ± 4.8 kg/m(2), mean ± SD] were examined before, one week, three months, and one year after surgery. Interleukin (IL)-6, leptin, adiponectin, IL-8, transforming growth factor beta (TGF-β), and the incretin hormone glucagon-like peptide-1 (GLP-1) were measured in the fasting state and during a liquid meal. Insulin resistance was evaluated by HOMA-IR.

RESULTS

Weight loss did not differ between the two groups. Before surgery, HbA1c was higher and HOMA-IR lower in T2D patients, however, converged to the values of NGT subjects one year after surgery. Circulating cytokine concentrations did not differ between the two groups at any time point. One week after surgery, circulating IL-6 and IL-8 were increased, while adiponectin and leptin were reduced compared with pre-surgical concentrations. Three months after surgery, IL-8 was increased, leptin was reduced, and no change was observed for IL-6, TGF-β, and adiponectin. One year after surgery, concentrations of IL-6, TGF-β, and leptin were significantly reduced compared to before surgery, while adiponectin was significantly increased.

CONCLUSIONS

One year after RYGB, fasting concentrations of IL-6 and leptin were reduced, while no changes were observed in IL-8. TGF-β was decreased and adiponectin increased in both T2D and NGT obese subjects. This study is the first to examine IL-8 and TGF-β in obese subject after RYGB. Resolution of inflammation could offer a potential explanation for the health improvement associated with major weight loss after bariatric surgery.

TRIAL REGISTRATION

http://www.clinicaltrials.gov (NCT01579981).

Biomarkers to improve diagnosis and monitoring of obstructive sleep apnea syndrome: current status and future perspectives

Obstructive sleep apnea syndrome (OSAS) is characterized by recurrent episodes of upper airway collapse associated with oxygen desaturation and sleep disruption. It is proposed that these periodic changes lead to molecular variations that can be detected by assessing serum biomarkers. Studies have identified inflammatory, oxidative, and metabolic perturbations attributable to sleep-disordered breathing. Given that OSAS is associated with increased cardiovascular and cerebrovascular morbidity, the ideal biomarker should enable timely recognition with the possibility of intervention. There is accumulating data on the utility of serum biomarkers for the evaluation of disease severity, prognosis, and response to treatment. However, current knowledge is limited by data collection techniques, disease complexity, and potential confounding factors. The current paper reviews the literature on the use of serum biomarkers in OSAS. It is concluded that the ideal serum biomarker still needs to be discovered, while caution is needed in the interpretation of hitherto available results.

Induction of cytosolic phospholipase a2α is required for adipose neutrophil infiltration and hepatic insulin resistance early in the course of high-fat feeding

In established obesity, inflammation and macrophage recruitment likely contribute to the development of insulin resistance. In the current study, we set out to explore whether adipose tissue infiltration by neutrophils that occurs early (3 days) after initiating a high-fat diet (HFD) could contribute to the early occurrence of hepatic insulin resistance and to determine the role of cytosolic phospholipase A2α (cPLA2α) in this process. The 3-day HFD caused a significant upregulation of cPLA2α in periepididymal fat and in the liver. A specific antisense oligonucleotide (AS) effectively prevented cPLA2α induction, neutrophil infiltration into adipose tissue (likely involving MIP-2), and protected against 3-day HFD-induced impairment in hepatic insulin signaling and glucose over-production from pyruvate. To sort out the role of adipose neutrophil infiltration independent of cPLA2α induction in the liver, mice were injected intraperitoneally with anti-intracellular adhesion molecule-1 (ICAM-1) antibodies. This effectively prevented neutrophil infiltration without affecting cPLA2α or MIP-2, but like AS, prevented impairment in hepatic insulin signaling, the enhanced pyruvate-to-glucose flux, and the impaired insulin-mediated suppression of hepatic glucose production (assessed by clamp), which were induced by the 3-day HFD. Adipose tissue secretion of tumor necrosis factor-α (TNF-α) was increased by the 3-day HFD, but not if mice were treated with AS or ICAM-1 antibodies. Moreover, systemic TNF-α neutralization prevented 3-day HFD-induced hepatic insulin resistance, suggesting its mediatory role. We propose that an acute, cPLA2α-dependent, neutrophil-dominated inflammatory response of adipose tissue contributes to hepatic insulin resistance and glucose overproduction in the early adaptation to high-fat feeding.

Sepsis-Induced Adipokine Change with regard to Insulin Resistance

Background. Assessment of white adipose tissue has changed in recent years, with WAT now being considered as an active endocrine organ, secreting a large number of bioactive mediators, so-called adipokines. Besides other functions, these adipokines are involved in inflammatory response thereby exhibiting predominantly proinflammatory or anti-inflammatory properties and contribute to insulin resistance. Methods. Comprehensive review of the literature of the role of adipokines relevant to critical care medicine using PubMed search. Results. Adiponectin—the prototype of an anti-inflammatory and insulin-sensitizing adipokine—is diminished in sepsis, while resistin—a protein with proinflammatory properties—is elevated. Plasminogen activator inhibitor-1, interleukin (IL)-1, IL-6, IL-8, and IL-10, and tumor-necrosis-factor-alpha mediate insulin resistance and are elevated in sepsis, while retinol-binding protein-4 concentrations are significantly reduced in sepsis. Chemerin displays potent anti-inflammatory and insulin-resistance properties, while monocyte chemotactic protein-1—increased in sepsis—contributes to macrophage infiltration in adipose tissue and insulin resistance. Conclusions. The expression of adipokines in humans is altered as well in obese as in septic patients with elevated levels of proinflammatory adipokines. Changes in adipokine levels in acute sepsis could contribute to insulin resistance. Consequently, in critically ill patients, these alterations underline a possible contribution of adipokines in the development of hyperglycemia.

(n-3) Fatty acids alleviate adipose tissue inflammation and insulin resistance: mechanistic insights

Obesity is associated with the metabolic syndrome, a significant risk factor for developing type 2 diabetes and cardiovascular diseases. Chronic low-grade inflammation occurring in the adipose tissue of obese individuals is causally linked to the pathogenesis of insulin resistance and the metabolic syndrome. Although the exact trigger of this inflammatory process is unknown, adipose tissue hypoxia, endoplasmic reticular stress, and saturated fatty acid-mediated activation of innate immune processes have been identified as important processes in these disorders. Furthermore, macrophages and T lymphocytes have important roles in orchestrating this immune process. Although energy restriction leading to weight loss is the primary dietary intervention to reverse these obesity-associated metabolic disorders, other interventions targeted at alleviating adipose tissue inflammation have not been explored in detail. In this regard, (n-3) PUFA of marine origin both prevent and reverse high-fat-diet-induced adipose tissue inflammation and insulin resistance in rodents. We provide an update on the pathogenesis of adipose tissue inflammation and insulin resistance in obesity and discuss potential mechanisms by which (n-3) PUFA prevent and reverse these changes and the implications in human health.

IL-17 in obesity and adipogenesis

The pro-inflammatory cytokine interleukin (IL)-17 (also known as IL-17) has been associated with induction of tissue inflammation. Obese individuals exhibit many symptoms of chronic low-grade inflammation, suggesting that IL-17 may impact adipose tissue. However, the role of IL-17 in obesity is largely unexplored. Emerging studies indicate that obesity selectively promotes expansion of the Th17 T-cell lineage, exacerbating disease in murine models of autoimmunity such as EAE and colitis. Human studies support this concept, as new clinical studies suggest that IL-17 is expressed at elevated levels in obese individuals. Conversely, however, an anti-adipogenic role for IL-17 is becoming evident, and therefore the interconnections between IL-17 and fat metabolism may be quite complex. Here, we consolidate the potential implications of IL-17 in relation to obesity and describe the emerging data regarding the role of IL-17 in adipose tissue.

Genetic regulation of endothelial inflammatory responses in baboons

OBJECTIVE

To investigate the genetic contributions to the expression of cell surface adhesion molecules on endothelial cells (ECs) and to the release by ECs of chemokines, which are responsible for local inflammation.

METHODS AND RESULTS

Monocyte adhesion to ECs and transmigration across the endothelial barrier are the key steps in the formation of atherosclerotic plaques and the rupture of the existing plaques. Biopsy specimens were obtained from the femoral arteries of 131 pedigreed baboons (65 males and 66 females) aged 10.4+/-1.5 years (mean+/-SD); arterial ECs were harvested and cultured up to the second passage and then subjected to in vitro challenge with tumor necrosis factor (TNF) alpha, 10 ng/mL, or vehicle for 4 hours. Endothelial surface adhesion molecules were measured using flow cytometry, and chemokines released by the ECs were measured by immunoassay. In response to TNF-alpha treatment, interleukin 8 and monocyte chemoattractant protein-1 released by ECs were increased 3.4- and 26-fold, respectively (P<0.001). The expressions of E-selectin, intercellular adhesion molecule-1, and vascular cell adhesion molecule-1 were increased 12.2-, 41.4-, and 3.5-fold, respectively (P<0.001). The quantitative levels of several traits were heritable after TNF-alpha stimulation: h(2)=0.24 (P=0.02) for interleukin 8 and h(2)=0.28 (P=0.003) for E-selectin in culture medium; h(2)=0.21 (P=0.03) for intercellular adhesion molecule-1; and h(2)=0.37 (P<0.001) for vascular cell adhesion molecule-1 expression on EC surfaces. Furthermore, significant heritability was observed for lysate protein level, which is a measure of cell growth rate, with (h(2)=0.64, P<0.001) or without (h(2)=0.51, P<0.001) TNF-alpha stimulation.

CONCLUSIONS

This study reports on the heritability of adhesion molecules in ECs when activated by TNF-alpha. This finding suggests genetic regulation of key arterial wall inflammatory processes that are responsible for the initiation of atherosclerotic lesions and the plaque rupture of existing atheromas.

MicroRNA 132 regulates nutritional stress-induced chemokine production through repression of SirT1

Human adipose tissue secretes a number of proinflammatory mediators that may contribute to the pathophysiology of obesity-related disorders. Understanding the regulatory pathways that control their production is paramount to developing effective therapeutics to treat these diseases. Using primary human adipose-derived stem cells as a source of preadipocytes and in vitro differentiated adipocytes, we found IL-8 and monocyte chemoattractant protein-1 (MCP-1) are constitutively secreted by both cell types and induced in response to serum deprivation. MicroRNA profiling revealed the rapid induction of microRNA 132 (miR-132) in these cells when switched to serum-free medium. Furthermore, miR-132 overexpression was sufficient to induce nuclear factor-kappaB translocation, acetylation of p65, and production of IL-8 and MCP-1. Inhibitors of miR-132 decreased acetylated p65 and partially inhibited the production of IL-8 and MCP-1 induced by serum deprivation. MiR-132 was shown to inhibit silent information regulator 1 (SirT1) expression through a miR-132 binding site in the 3'-untranslated region of SirT1. Thus, in response to nutritional availability, induction of miR-132 decreases SirT1-mediated deacetylation of p65 leading to activation of nuclear factor-kappaB and transcription of IL-8 and MCP-1 in primary human preadipocytes and in vitro differentiated adipocytes.

Lipid peroxides, superoxide dismutase and circulating IL-8 and GCP-2 in patients with severe obstructive sleep apnea: a pilot study

Obstructive sleep apnea (OSA) is associated with cardiovascular morbidity and mortality and many other physiological and immunological disorders. An increase in hypoxia due to OSA may cause generation of reactive oxygen species (ROS). ROS are toxic to biomembranes and may lead to peroxidation of lipids. An increase in systemic biomarkers of inflammation and oxidative stress has been found in patients with OSA. The first aim of this study was to test the hypothesis that OSA is linked to increased oxidative stress (lipid peroxidation) and decreased antioxidant defense [superoxide dismutase (SOD)]. The second aim was to measure the serum levels of neutrophil chemokines [interleukin-8 (IL-8)], and granulocyte chemotactic protein-2 (GCP-2) in OSA patients. Twenty five patients with severe OSA and 17 healthy subjects were recruited. IL-8 and GCP-2 were measured in the serum by a specific enzyme immunoassay kit. Oxidative stress level was quantitated by measurement of thiobarbituric acid reactive substances. SOD enzymatic activity was measured by purely chemical system based on NAD(P)H oxidation. Mean SOD and lipid peroxidation concentrations of patients were not significantly different from those of control subjects (0.29+/-0.015 vs 0.31+/-0.01 U/ml and 4.64+/-0.57 vs 4.62+/-0.54 mmol/ml, respectively). Higher concentrations of IL-8 and GCP-2 were found in OSA patients (198.8+/-4.76 vs 180.83+/-3.38 and 383.34+/-46.19 vs 218+/-13.16 pg/ml, respectively, p<0.005). The present study does not support the hypothesis that OSA is linked to increased oxidative stress and decreased antioxidant defense. On the other hand, it suggests that systemic inflammation characterizes OSA patients.

The usefulness of circulating adipokine levels for the assessment of obesity-related health problems

Because the prevalence of obesity has increased dramatically in recent years, one of the key targets of public health is obesity and its associated pathological conditions. Obesity occurs as a result of white adipose tissue enlargement, caused by adipocyte hyperplasia and/or hypertrophy. Recently, endocrine aspects of adipose tissue have become an active research area and these adipose tissue-derived factors are referred to as adipokines. These adipokines interact with a range of processes in many different organ systems and influence a various systemic phenomena. Therefore, dysregulated production of adipokines has been found to participate in the development of metabolic and vascular diseases related to obesity. The obese state is also known to be associated with increased local and systemic inflammation. Adipokines influence not only systemic insulin resistance and have pathophysiological roles in the metabolic syndrome and cardiovascular disease, but also contribute toward an increase in local and systemic inflammation. Thus, circulating levels of adipokines can be used as high-throughput biomarkers to assess the obesity-related health problems, including low grade inflammation. This review focuses on the usefulness of measuring circulating adipokine levels for the assessment of obesity-related health problems.

Eggs modulate the inflammatory response to carbohydrate restricted diets in overweight men

Background

Carbohydrate restricted diets (CRD) consistently lower glucose and insulin levels and improve atherogenic dyslipidemia [decreasing triglycerides and increasing HDL cholesterol (HDL-C)]. We have previously shown that male subjects following a CRD experienced significant increases in HDL-C only if they were consuming a higher intake of cholesterol provided by eggs compared to those individuals who were taking lower concentrations of dietary cholesterol. Here, as a follow up of our previous study, we examined the effects of eggs (a source of both dietary cholesterol and lutein) on adiponectin, a marker of insulin sensitivity, and on inflammatory markers in the context of a CRD.

Methods

Twenty eight overweight men [body mass index (BMI) 26–37 kg/m²] aged 40–70 y consumed an ad libitum CRD (% energy from CHO:fat:protein = 17:57:26) for 12 wk. Subjects were matched by age and BMI and randomly assigned to consume eggs (EGG, n = 15) (640 mg additional cholesterol/day provided by eggs) or placebo (SUB, n = 13) (no additional dietary cholesterol). Fasting blood samples were drawn before and after the intervention to assess plasma lipids, insulin, adiponectin and markers of inflammation including C-reactive protein (CRP), tumor necrosis factor-alpha (TNF-α), interleukin-8 (IL-8), monocyte chemoattractant protein-1 (MCP-1), intercellular adhesion molecule-1 (ICAM-1), and vascular cell adhesion molecule-1(VCAM-1).

Results

Body weight, percent total body fat and trunk fat were reduced for all subjects after 12 wk (P < 0.0001). Increases in adiponectin were also observed (P < 0.01). Subjects in the EGG group had a 21% increase in this adipokine compared to a 7% increase in the SUB group (P < 0.05). Plasma CRP was significantly decreased only in the EGG group (P < 0.05). MCP-1 levels were decreased for the SUB group (P < 0.001), but unchanged in the EGG group. VCAM-1, ICAM-1, TNF-α, and IL-8 were not modified by CRD or eggs.

Conclusion

A CRD with daily intake of eggs decreased plasma CRP and increased plasma adiponectin compared to a CRD without eggs. These findings indicate that eggs make a significant contribution to the anti-inflammatory effects of CRD, possibly due to the presence of cholesterol, which increases HDL-C and to the antioxidant lutein which modulates certain inflammatory responses.

Whole-body proteolysis rate is elevated in HIV-associated insulin resistance

Type 2 diabetes is characterized by impaired glucose tolerance (IGT) and insulin resistance with respect to glucose metabolism but not amino acid metabolism. We examined whether whole-body leucine and protein metabolism are dysregulated in HIV-infected individuals with IGT. Glucose and leucine kinetics were measured under fasting insulin conditions and during euglycemic hyperinsulinemia using primed-constant infusions of 2H2-glucose and 13C-leucine in 10 HIV-seronegative control subjects, 16 HIV+ subjects with normal glucose tolerance, and 21 HIV+IGT subjects. Glucose disposal rate during hyperinsulinemia was lower in HIV+IGT than the other two groups. Absolute plasma leucine levels and rate of appearance (whole-body proteolysis) were higher in HIV+IGT at all insulin levels but declined in response to hyperinsulinemia in parallel to those in the other two groups. HIV+IGT had greater visceral adiposity, fasting serum interleukin (IL)-8 and free fatty acid levels, and higher lipid oxidation rates during the clamp than the other two groups. These findings implicate several factors in the insulin signaling pathway, which may be further dysregulated in HIV+IGT, and support the notion that insulin signaling pathways for glucose and leucine metabolism may be disrupted by increased proinflammatory adipocytokines (IL-8) and increased lipid oxidation. Increased proteolysis may provide amino acids for gluconeogenesis, exacerbating hyperglycemia in HIV.

Chemokines as risk factors for type 2 diabetes: results from the MONICA/KORA Augsburg study, 1984-2002

AIMS/HYPOTHESIS

The chemokines monocyte chemoattractant protein-1 (MCP-1), IL-8 and interferon-gamma-inducible protein-10 (IP-10) are released by adipocytes and appear to be involved in atherosclerosis. We hypothesised that these chemokines may be risk factors for the development of type 2 diabetes.

SUBJECTS AND METHODS

Using a case-cohort design based on data from the population-based Monitoring of Trends and Determinants in Cardiovascular Disease (MONICA)/Kooperative Gesundheitsforschung in der Region Augsburg/Cooperative Health Research in the Region of Augsburg (KORA Augsburg) study, chemokine levels at baseline were analysed in 526 individuals with and 1,695 individuals without incident type 2 diabetes. The mean follow-up time was 10.8 years.

RESULTS

MCP-1 was associated with type 2 diabetes, largely independently of classic risk factors, whereas various clinical and metabolic parameters as well as lifestyle factors were major confounders of the association of IL-8 and IP-10 with type 2 diabetes. Further adjustment for C-reactive protein (CRP) and IL-6 had no impact on the observed associations. The hazard ratio (HR) for subjects with systemic concentrations of all three chemokines (MCP-1, IL-8 and IP-10) above the respective median compared with those with all chemokines below or equal to the median was 1.79 (95% CI 1.18-2.72) and was comparable with the HR for elevated CRP and IL-6 together (adjusted for age, sex, survey, BMI, systolic blood pressure, total cholesterol:HDL cholesterol ratio, physical activity, alcohol intake, smoking and parental history of diabetes).

CONCLUSIONS/INTERPRETATION

Elevated concentrations of MCP-1, IL-8 and IP-10 are associated with incident type 2 diabetes. Whereas the association of IL-8 and IP-10 with diabetes was attenuated by multivariable adjustment, high MCP-1 levels contributed to diabetes risk independently of previously described clinical, metabolic and immunological risk factors.

Increased expression of inflammation-related genes in cultured preadipocytes/stromal vascular cells from obese compared with non-obese Pima Indians

AIMS/HYPOTHESIS

The specific contributions made by the various cell types in adipose tissue to obesity, particularly obesity-related inflammation, need to be clarified. The aim of this study was to elucidate the potential role of adipocyte precursor cells (preadipocytes/stromal vascular cells [SVC]).

METHODS

We performed Affymetrix oligonucleotide microarray expression profiling of cultured abdominal subcutaneous preadipocytes/SVC isolated from the adipose tissue of 14 non-obese (BMI 25+/-4 kg/m2) and 14 obese (55+/-8 kg/m2) non-diabetic Pima Indian subjects. Quantitative real-time PCR (RT-PCR) was used to verify the differential expression of several genes in an independent group of subjects.

RESULTS

We identified 218 differentially expressed genes with p values less than 0.01. Microarray expression profiling revealed that the expression of inflammation-related genes was significantly upregulated in preadipocytes/SVC of obese individuals. Quantitative RT-PCR confirmed the upregulation of IL8, CTSS, ITGB2, HLA-DRA, CD53, PLA2G7 and MMP9 in preadipocytes/SVC of obese subjects.

CONCLUSIONS/INTERPRETATION

The upregulation of inflammation-related genes in preadipocytes/SVC of obese subjects may increase the recruitment of immune cells into adipose tissue and may also result in changes in the extracellular matrix (tissue remodelling) to accommodate adipose tissue expansion in obesity.

Conjugated linoleic acid induces human adipocyte delipidation: autocrine/paracrine regulation of MEK/ERK signaling by adipocytokines

Dietary conjugated linoleic acid (CLA) reduces body fat in animals and some humans. Here we show that trans-10, cis-12 CLA, but not cis-9, trans-11 CLA, when added to cultures of stromal vascular cells containing newly differentiated human adipocytes, caused a time-dependent decrease in triglyceride content, insulin-stimulated glucose and fatty acid uptake, incorporation into lipid, and oxidation compared with controls. In parallel, gene expression of peroxisome proliferator-activated receptor-gamma and many of its downstream targets were diminished by trans-10, cis-12 CLA, whereas leptin gene expression was increased. Prior to changes in gene expression and metabolism, trans-10, cis-12 CLA caused a robust and sustained activation of mitogen-activated protein kinase kinase/extracellular signal-related kinase (MEK/ERK) signaling. Furthermore, the trans-10, cis-12 CLA-mediated activation of MEK/ERK could be attenuated by pretreatment with U0126 and pertussis toxin. In parallel, pretreatment with U0126 blocked the ability of trans-10, cis-12 CLA to alter gene expression and attenuate glucose and fatty acid uptake of the cultures. Intriguingly, the induction by CLA of MEK/ERK signaling was linked to hypersecretion of adipocytokines interleukin-6 and interleukin-8. Collectively, these data demonstrate for the first time that trans-10, cis-12 CLA decreases the triglyceride content of newly differentiated human adipocytes by inducing MEK/ERK signaling through the autocrine/paracrine actions of interleukins-6 and 8.

Plasma interleukin 8 concentrations in obese subjects with impaired glucose tolerance

BACKGROUND

Interleukin 8 (IL-8) is a cytokine with atherogenic properties. In vitro studies revealed that it is produced and secreted by human adipocytes. We recently reported that plasma IL-8 is increased in obese subjects with normal glucose tolerance (NGT). The aim of the present study was to measure plasma IL-8 concentrations in subjects with impaired glucose tolerance (IGT).

METHODS

A total of 44 subjects with marked overweight or obesity (BMI > 27.8 kg/m2), 27 with NGT and 17 with IGT, were recruited for the present study. Plasma IL-8 levels were measured in fasting state, after an oral glucose tolerance test (OGTT) and after euglycemic hyperinsulinemic clamp.

RESULTS

The studied groups did not differ in fasting IL-8 concentrations. Both OGTT and clamp resulted in a significant increase in plasma IL-8. The change in IL-8 after clamp was similar in both groups. In contrast, after OGTT plasma IL-8 levels (IL-8OGTT) were markedly higher in IGT individuals. In IGT, but not NGT group, IL-8OGTT was positively related to postload glucose and negatively to insulin sensitivity.

CONCLUSION

Plasma IL-8 concentrations after glucose load are increased in obese IGT subjects in comparison to normoglycemic weight-matched individuals. Increase in plasma IL-8 might be both insulin-mediated (during clamp) and glucose-mediated (during OGTT).

Interleukin-6 production in human subcutaneous abdominal adipose tissue: the effect of exercise

The interleukin-6 (IL-6) output from subcutaneous, abdominal adipose tissue was studied in nine healthy subjects before, during and for 3 h after 1 h two-legged bicycle exercise at 60 % maximal oxygen consumption. Seven subjects were studied in control experiments without exercise. The adipose tissue IL-6 output was measured by direct Fick technique. An artery and a subcutaneous vein on the anterior abdominal wall were catheterized. Adipose tissue blood flow was measured using the 133Xe-washout method. In both studies there was a significant IL-6 output in the basal state and no significant change was observed during exercise. Post-exercise the IL-6 output began to increase after 30 min. Three hours post-exercise it was 58.6 +/- 22.2 pg (100 g)(-1) min(-1). In the control experiments the IL-6 output also increased, but it only reached a level of 3.5 +/- 0.8 pg (100 g)(-1) min(-1). The temporal profile of the post-exercise change in the IL-6 output closely resembles the changes in the outputs of glycerol and fatty acids, which we have described previously in the same adipose tissue depot. The difference is that it begins to increase ~30 min before the glycerol and fatty acid outputs begin to increase. Thus, we suggest that the enhanced IL-6 production post-exercise in abdominal, subcutaneous adipose tissue may act locally via autocrine/paracrine mechanisms influencing lipolysis and fatty acid mobilization rate from this lipid depot.