Increased Toll-like receptor (TLR) mRNA expression in monocytes is a feature of metabolic syndrome in adolescents

Mechanisms and risk factors of metabolic syndrome in children and adolescents

Metabolic syndrome (MetS) is a complex disorder characterized by abdominal obesity, elevated blood pressure, hyperlipidemia, and elevated fasting blood glucose levels. The diagnostic criteria for MetS in adults are well-established, but there is currently no consensus on the definition in children and adolescents. The etiology of MetS is believed to involve a complex interplay between genetic predisposition and environmental factors. While genetic predisposition explains only a small part of MetS pathogenesis, modifiable environmental risk factors play a significant role. Factors such as maternal weight during pregnancy, children's lifestyle, sedentariness, high-fat diet, fructose and branched-chain amino acid consumption, vitamin D deficiency, and sleep disturbances contribute to the development of MetS. Early identification and treatment of MetS in children and adolescents is crucial to prevent the development of chronic diseases later in life. In this review we discuss the latest research on factors contributing to the pathogenesis of MetS in children, focusing on non-modifiable and modifiable risk factors, including genetics, dysbiosis and chronic low-grade inflammation.

Complex interplay of gut microbiota between obesity and asthma in children

Obesity is an important risk factor and common comorbidity of childhood asthma. Simultaneously, obesity-related asthma, a distinct asthma phenotype, has attracted significant attention owing to its association with more severe clinical manifestations, poorer disease control, and reduced quality of life. The establishment of the gut microbiota during early life is essential for maintaining metabolic balance and fostering the development of the immune system in children. Microbial dysbiosis influences host lipid metabolism, triggers chronic low-grade inflammation, and affects immune responses. It is intimately linked to the susceptibility to childhood obesity and asthma and plays a potentially crucial transitional role in the progression of obesity-related asthma. This review article summarizes the latest research on the interplay between asthma and obesity, with a particular focus on the mediating role of gut microbiota in the pathogenesis of obesity-related asthma. This study aims to provide valuable insight to enhance our understanding of this condition and offer preliminary evidence to support the development of therapeutic interventions.

Association between the expression of TLR4, TLR2, and MyD88 with low-grade chronic inflammation in individuals with metabolically healthy obesity

BACKGROUND

Among the Toll-like receptors (TLR) that are dependent of myeloid response protein (MyD88), the TLR4 and TLR2 are directly associated with low-grade chronic inflammation; however, they are not been investigated in subjects with metabolically healthy obesity (MHO). Thus, the objective of this study was to determine the association between the expression of TLR4, TLR2, and MyD88 with low-grade chronic inflammation in individuals with MHO.

METHODS AND RESULTS

Men and women with obesity aged 20 to 55 years were enrolled in a cross-sectional study. Individuals with MHO were allocated into the groups with and without low-grade chronic inflammation. Pregnancy, smoking, alcohol consumption, intense physical activity or sexual intercourse in the previous 72 h, diabetes, high blood pressure, cancer, thyroid disease, acute or chronic infections, renal impairment, and hepatic diseases, were exclusion criteria. The MHO phenotype was defined by a body mass index (BMI ≥ 30 kg/m²) plus one or none of the following cardiovascular risk factors: hyperglycemia, elevated blood pressure, hypertriglyceridemia, and low high-density lipoprotein cholesterol. A total of 64 individuals with MHO were enrolled and allocated into the groups with (n = 37) and without (n = 27) inflammation. The multiple logistic regression analysis indicated that TLR2 expression is significantly associated with inflammation in individuals with MHO. In the subsequent analysis adjusted by BMI, TLR2 expression remained associated with inflammation in individuals with MHO.

CONCLUSION

Our results suggest that overexpression of TLR2, but not TLR4 and MyD88, is associated with low-grade chronic inflammation in subjects with MHO.

Metabolic Syndrome: Updates on Pathophysiology and Management in 2021

Metabolic syndrome (MetS) forms a cluster of metabolic dysregulations including insulin resistance, atherogenic dyslipidemia, central obesity, and hypertension. The pathogenesis of MetS encompasses multiple genetic and acquired entities that fall under the umbrella of insulin resistance and chronic low-grade inflammation. If left untreated, MetS is significantly associated with an increased risk of developing diabetes and cardiovascular diseases (CVDs). Given that CVDs constitute by far the leading cause of morbidity and mortality worldwide, it has become essential to investigate the role played by MetS in this context to reduce the heavy burden of the disease. As such, and while MetS relatively constitutes a novel clinical entity, the extent of research about the disease has been exponentially growing in the past few decades. However, many aspects of this clinical entity are still not completely understood, and many questions remain unanswered to date. In this review, we provide a historical background and highlight the epidemiology of MetS. We also discuss the current and latest knowledge about the histopathology and pathophysiology of the disease. Finally, we summarize the most recent updates about the management and the prevention of this clinical syndrome.

Activation of angiotensin-converting enzyme 2 ameliorates metabolic syndrome-induced renal damage in rats by renal TLR4 and nuclear transcription factor κB downregulation

BACKGROUND

Metabolic syndrome (MetS) is an independent risk factor for chronic kidney disease (CKD) through many mechanisms, including activation of the renin-angiotensin system. The deleterious effects of angiotensin II (Ang II) can be counterbalanced by angiotensin-converting enzyme 2 (ACE2). Diminazene aceturate (DIZE), an anti-trypanosomal drug, can activate ACE2.

OBJECTIVE

This study aimed to investigate the possible reno-protective effects of DIZE in MetS rats with elucidation of related mechanisms.

MATERIALS AND METHODS

Thirty adult male Wistar albino rats were divided equally into control, MetS, and MetS + DIZE groups. Body weight, systolic blood pressure (SBP), and urinary albumin levels were measured. Serum levels of fasting blood glucose (FBG), insulin, uric acid, lipid profile, urea, and creatinine were measured. Homeostasis Model Assessment Index (HOMA-IR) was estimated. Subsequently, renal levels of ACE2, Ang II, malondialdehyde (MDA), reduced glutathione (GSH), and tumor necrosis factor-α (TNF-α) were measured with histopathological and immunohistochemical assessment of TLR4 and NF-κB in renal tissues.

RESULTS

MetS caused dyslipidemia with significant increases in body weight, SBP, FBG, serum insulin, HOMA-IR, uric acid, urea, creatinine, urinary albumin, and renal levels of Ang II, MDA, and TNF-α, whereas renal ACE2 and GSH were significantly decreased. Renal TLR4 and NF-κB immunoreactivity in MetS rats was upregulated. DIZE supplementation of MetS rats induced significant improvements in renal function parameters; this could be explained by the ability of DIZE to activate renal ACE2 and decrease renal Ang II levels with downregulation of renal TLR4 and NF-κB expression.

CONCLUSION

DIZE exerts a reno-protective effect in MetS, mainly by downregulating renal TLR4 and NF-κB levels.

Toll-like Receptor as a Molecular Link between Metabolic Syndrome and Inflammation: A Review

Metabolic Syndrome (MetS) involves a cluster of five conditions, i.e. obesity, hyperglycaemia, hypertension, hypertriglyceridemia and low High-Density Lipoprotein (HDL) cholesterol. All components of MetS share an underlying chronic inflammatory aetiology, manifested by increased levels of pro-inflammatory cytokines. The pathogenic role of inflammation in the development of MetS suggested that toll-like receptor (TLR) activation may trigger MetS. This review summarises the supporting evidence on the interactions between MetS and TLR activation, bridged by the elevation of TLR ligands during MetS. The regulatory circuits mediated by TLR activation, which modulates signal propagation, leading to the state of chronic inflammation, are also discussed. Taken together, TLR activation could be the molecular basis in the development of MetS-induced inflammation.

Anti-inflammatory effect of β2 adrenergic stimulation on circulating monocytes with a pro-inflammatory state in high-fat diet-induced obesity

Obesity is a chronic condition associated with low-grade inflammation, and it also involves alterations of the function of the hypothalamic-pituitaryadrenal axis and the sympathetic nervous system. Adrenergic agonists such as catecholamines are important immunoregulatory molecules that are involved in modulating both metabolism and most of the mechanisms of the immune response. The first objective of this study was to determine whether the systemic inflammatory state associated with obesity is also manifested in the inflammatory profile and phenotype of circulating monocytes; and the second objective was to evaluate the effects of β2 adrenergic stimulation on the inflammatory profile and phenotype of monocytes in obesity, and whether this response could be different from that in lean individuals. C57BL/6J mice were randomly allocated to one of two diets for 18 weeks: high-fat diet in order to obtain an experimental model of obesity, and standard diet in the control lean group. Circulating monocyte expression of inflammatory cytokines (MCP-1, TNF-α, IL-8, IL-6, IL-10, and TGF-β), surface membrane marker Ly6C, inducible nitric oxide synthase and arginase-1, and Toll-like receptor 4 were evaluated through flow cytometry in the presence or absence of selective β2 adrenergic receptor agonist terbutaline. Monocytes from high-fat diet-induced obese animals presented higher expression levels of all pro-inflammatory cytokines and a higher percentage of monocytes with a pro-inflammatory phenotype than those from lean animals. β2 adrenergic stimulation induced a shift towards an anti-inflammatory activity profile and phenotype in obese mice, whereas it induced a shift towards a pro-inflammatory activity profile and phenotype in lean mice. In conclusion, β2 adrenergic stimulation in monocytes was anti-inflammatory only in obese animals, which presented a pro-inflammatory state at baseline.

Metabolic syndrome is an inflammatory disorder: A conspiracy between adipose tissue and phagocytes

Metabolic syndrome (MetS) describes a cluster of cardio-metabolic factors that predispose to type 2 diabetes mellitus (T2DM) and atherosclerotic cardiovascular disease (ASCVD). While 35% of Americans suffer from this disorder, the specific pathways related to this disease are largely underexplored. The prevailing consensus is that inflammatory pathways contribute to the pathogenesis of this disease, and therefore new research has uncovered how inflammation plays a critical role in the development and progression of MetS. The purpose of this review is to understand the role of major inflammatory mechanisms and their role in MetS. Our review identifies that adipose tissue (AT) contributes to the inflammatory pathways through the release of pro-inflammatory adipokines such as leptin and chemerin and dysregulation of anti-inflammatory adiponectin. Chemokines and cytokines deriving from monocytes are also altered and promote inflammation and insulin resistance. Circulating inflammatory biomarkers including C-reactive protein (CRP), fibrinogen, Serum amyloid A (SAA), cytokines, and chemokines have also been linked to the pathogenesis of MetS. Researchers have identified the significance of CRP levels in predicting future sequelae of MetS such as ASCVD. Mast cells in subcutaneous adipose tissue (SAT) promote both inflammation and fibrosis. Thus, both AT and phagocyte activity define MetS as an inflammatory disorder.

Supplementation of Juçara Berry (Euterpe edulis Mart.) Modulates Epigenetic Markers in Monocytes from Obese Adults: A Double-Blind Randomized Trial

Nutrigenomics is an emerging field in obesity since epigenetic markers can be modified by environmental factors including diet. Considering juçara composition—rich in anthocyanins, monounsaturated fatty acids (MUFAs) and fibers—it has the potential for epigenetic modulation. We evaluated the juçara supplementation modulating the serum fatty acids profile and epigenetic markers in monocytes of adult obese humans. It was a randomized double-blind, controlled trial with 27 obese (Body mass index between 30.0 and 39.9 kg/m²) participants of both genders aged from 31 to 59 years, divided into juçara group (5 g juçara freeze-dried pulp) or placebo group (5 g of maltodextrin) for 6 weeks. Before and after supplementation, blood samples were collected. The serum and monocytes cells obtained were cultured and stimulated with lipopolysaccharides as proinflammatory stimulus. After 24 h of incubation, the cells and supernatants were collected and analyzed. Juçara improved the serum fatty acids profile on unsaturated fatty acids levels. The epigenetic markers evaluated were improved post-treatment. Also, the methylated DNA level was increased after treatment. We find that juçara supplementation is a predictor of methyl CpG binding proteins 2 (MeCP2) in monocytes. Concluding, juçara supplementation improved the serum fatty acids profile, modulating the epigenetic markers in monocytes from obese individuals.

Effects of endurance exercise training on inflammatory circulating progenitor cell content in lean and obese adults

KEY POINTS

Chronic inflammation underlies many of the health decrements associated with obesity. Circulating progenitor cells can sense and respond to inflammatory stimuli, increasing the local inflammatory response within tissues. Here we show that 6 weeks of endurance exercise training significantly decreases inflammatory circulating progenitor cells in obese adults. These findings provide novel cellular mechanisms for the beneficial effects of exercise in obese adults.

ABSTRACT

Circulating progenitor cells (CPCs) and subpopulations are normally found in the bone marrow, but can migrate to peripheral tissues to participate in local inflammation and/or remodelling. The purpose of this study was to compare the CPC response, particularly the inflammatory-primed haematopoietic stem and progenitor (HSPC) subpopulation, to a 6 week endurance exercise training (EET) intervention between lean and obese adults. Seventeen healthy weight (age: 23.9 ± 5.4 years, body mass index (BMI): 22.0 ± 2.6 kg m^-2 ) and 10 obese (age: 29.0 ± 8.0 years, BMI: 33.1 ± 6.0 kg m^-2 ) previously sedentary adults participated in an EET. Blood was collected before and after EET for quantification of CPCs and subpopulations via flow cytometry, colony forming unit assays and plasma concentrations of C-X-C motif chemokine 12 (CXCL12), granulocyte-colony stimulating factor (G-CSF), and chemokine (C-C motif) ligand 2 (CCL2). Exercise training reduced the number of circulating HSPCs and adipose tissue-derived mesenchymal stem cells (AT-MSCs). EET increased the colony forming potential of granulocytes and macrophages irrespective of BMI. EET reduced the number of HSPCs expressing the chemokine receptor CCR2 and the pro-inflammatory marker TLR4. EET-induced changes in adipose tissue-derived MSCs and bone marrow-derived MSCs were negatively related to changes in absolute fitness. Our results indicate that EET, regardless of BMI status, decreases CPCs and subpopulations, particularly those primed for contribution to tissue inflammation.

Intestinal epithelial Toll-like receptor 4 prevents metabolic syndrome by regulating interactions between microbes and intestinal epithelial cells in mice

Little is known about the pathogenesis of metabolic syndrome, although Toll-like receptor 4 (TLR4) has been implicated. We investigated whether TLR4 in the intestinal epithelium regulates metabolic syndrome by coordinating interactions between the luminal microbiota and host genes that regulate metabolism. Mice lacking TLR4 in the intestinal epithelium (TLR4^ΔIEC), but not mice lacking TLR4 in myeloid cells nor mice lacking TLR4 globally, developed metabolic syndrome; these features were not observed in TLR4^ΔIEC mice given antibiotics. Metagenomic analysis of the fecal microbiota revealed differences between TLR4^ΔIEC and wild-type mice, while meta-transcriptome analysis of the microbiota showed that intestinal TLR4 affected the expression of microbial genes involved in the metabolism of lipids, amino acids, and nucleotides. Genes regulated by peroxisome proliferator-activated receptors (PPARs) and the antimicrobial peptide lysozyme were significantly downregulated in TLR4^ΔIEC mice, suggesting a mechanism by which intestinal TLR4 could exert its effects on the microbiota and metabolic syndrome. Supportingly, antibiotics prevented both downregulation of PPAR genes and the development of metabolic syndrome, while PPAR agonists prevented development of metabolic syndrome in TLR4^ΔIEC mice. Thus, intestinal epithelial TLR4 regulates metabolic syndrome through altered host-bacterial signaling, suggesting that microbial or PPAR-based strategies might have therapeutic potential for this disease.

Toll-like receptor signaling and serum levels of interferon β and lipopolysaccharide binding protein are related to abdominal obesity: a case-control study between metabolically healthy and metabolically unhealthy obese individuals

It is still unclear whether toll-like receptor (TLR) signaling and serum levels of inflammatory markers in metabolically unhealthy abdominally obese (MUAO) are due to their obesity and/or their metabolic state. We hypothesized that abdominal obesity is an important mediator of the association of metabolic state with TLR signaling and serum inflammatory markers. Therefore, in this case-control study, we compared the expression levels of TLR4 and Toll/interleukin-1 receptor domain containing adaptor protein-inducing interferon β (TRIF) and serum concentrations of interferon β and lipoprotein-binding protein (LBP) in metabolically healthy abdominally obese (MHAO) and MUAO individuals. Basal blood samples from 65 abdominally obese subjects with waist circumference (WC) of at least 95 cm were collected to determine serum metabolic parameters, IFNβ, and LBP. Those with 3 or more metabolic alterations were defined as MUAO (n = 34), and those having 2 or less were classified as MHAO (n = 31). Furthermore, messenger RNA (mRNA) was isolated from peripheral blood mononuclear cells. TLR4 and TRIF gene expression assay was performed using quantitative real-time polymerase chain reaction. There were significant differences in serum fasting blood sugar (P = .017), triglyceride (P < .001), cholesterol (P = .002), and low-density lipoprotein cholesterol (P = .034) between the MUAO and MHAO groups, whereas no significant difference was observed in the expression ratio of TLR4 and TRIF mRNA and serum levels of IFNβ and LBP. However, a significant correlation was noticed between mRNA expression levels of TLR4 and TRIF (r = 0.50, P < .001) and serum IFNβ and LBP (r = 0.70, P < .001). It is concluded that the expression levels of TLR4 and TRIF as well as serum IFNβ and LBP are more related to abdominal obesity than to metabolic health.

Diabetes increases the susceptibility to acute kidney injury after myocardial infarction through augmented activation of renal Toll-like receptors in rats

Acute kidney injury (AKI) after acute myocardial infarction (MI) worsens the prognosis of MI patients. Although type 2 diabetes mellitus (DM) is a major risk factor of AKI after MI, the underlying mechanism remains unclear. Here, we examined the roles of renal Toll-like receptors (TLRs) in the impact of DM on AKI after MI. MI was induced by coronary artery ligation in Otsuka-Long-Evans-Tokushima fatty (OLETF) rats, a rat DM model, and Long-Evans-Tokushima-Otsuka (LETO) rats, nondiabetic controls. Sham-operated rats served as no-MI controls. Renal mRNA levels of TLR2 and myeloid differentiation factor 88 (MyD88) were significantly higher in sham-operated OLETF rats than in sham-operated LETO rats, although levels of TLR1, TLR3, and TLR4 were similar. At 12 h after MI, protein levels of kidney injury molecule-1 (KIM-1) and neutrophil gelatinase-associated lipocalin (NGAL) in the kidney were elevated by 5.3- and 4.0-fold, respectively, and their mRNA levels were increased in OLETF but not LETO rats. The increased KIM-1 and NGAL expression levels after MI in the OLETF kidney were associated with upregulated expression of TLR1, TLR2, TLR4, MyD88, IL-6, TNF-α, chemokine (C-C motif) ligand 2, and transforming growth factor-β₁ and also with activation of p38 MAPK, JNK, and NF-κB. Cu-CPT22, a TLR1/TLR2 antagonist, administered before MI significantly suppressed MI-induced upregulation of KIM-1, TLR2, TLR4, MyD88, and chemokine (C-C motif) ligand 2 levels and activation of NF-κB, whereas NGAL levels and IL-6 and TNF-α expression levels were unchanged. The results suggest that DM increases the susceptibility to AKI after acute MI by augmented activation of renal TLRs and that TLR1/TLR2-mediated signaling mediates KIM-1 upregulation after MI.NEW & NOTEWORTHY This is the first report to demonstrate the involvement of Toll-like recpetors (TLRs) in diabetes-induced susceptibility to acute kidney injury after acute myocardial infarction. We propose that the TLR1/TLR2 heterodimer may be a new therapeutic target for the prevention of acute kidney injury in diabetic patients.

Effects of a healthy Nordic diet on gene expression changes in peripheral blood mononuclear cells in response to an oral glucose tolerance test in subjects with metabolic syndrome: a SYSDIET sub-study

Background

Diet has a great impact on the risk of developing features of metabolic syndrome (MetS), type 2 diabetes mellitus (T2DM), and cardiovascular diseases (CVD). We evaluated whether a long-term healthy Nordic diet (ND) can modify the expression of inflammation and lipid metabolism-related genes in peripheral blood mononuclear cells (PBMCs) during a 2-h oral glucose tolerance test (OGTT) in individuals with MetS.

Methods

A Nordic multicenter randomized dietary study included subjects (n = 213) with MetS, randomized to a ND group or a control diet (CD) group applying an isocaloric study protocol. In this sub-study, we included subjects (n = 89) from three Nordic centers: Kuopio (n = 26), Lund (n = 30), and Oulu (n = 33) with a maximum weight change of ±4 kg, high-sensitivity C-reactive protein concentration ≤10 mg L⁻¹, and baseline body mass index <39 kg m⁻². PBMCs were isolated, and the mRNA gene expression analysis was measured by quantitative real-time polymerase chain reaction (qPCR). We analyzed the mRNA expression changes of 44 genes before and after a 2hOGTT at the beginning and the end of the intervention.

Results

The healthy ND significantly down-regulated the expression of toll-like receptor 4 (TLR4), interleukin 18 (IL18), and thrombospondin receptor (CD36) mRNA transcripts and significantly up-regulated the expression of peroxisome proliferator-activated receptor delta (PPARD) mRNA transcript after the 2hOGTT compared to the CD.

Conclusions

A healthy ND is able to modify the gene expression in PBMCs after a 2hOGTT. However, more studies are needed to clarify the biological and clinical relevance of these findings.

Electronic supplementary material

The online version of this article (doi:10.1186/s12263-016-0521-4) contains supplementary material, which is available to authorized users.

Perspectives for Monocyte/Macrophage-Based Diagnostics of Chronic Inflammation

Low-grade chronic inflammation underlies the development of the most dangerous cardiometabolic disorders including type 2 diabetes and its vascular complications. In contrast to acute inflammation induced by bacteria and viruses, chronic inflammation can be driven by abnormal reaction to endogenous factors, including Th2 cytokines, metabolic factors like advanced glycation end products (AGEs), modified lipoproteins, or hyperglycemia. The key innate immune cells that recognize these factors in blood circulation are monocytes. Inflammatory programming of monocytes which migrate into tissues can, in turn, result into generation of tissue macrophages with pathological functions. Therefore, determination of the molecular and functional phenotype of circulating monocytes is a very promising diagnostic tool for the identification of hidden inflammation, which can precede the development of the pathology. Here we propose a new test system for the identification of inflammatory programming of monocytes: surface biomarkers and ex vivo functional system. We summarize the current knowledge about surface biomarkers for monocyte subsets, including CD16, CCR2, CX3CR1, CD64, stabilin-1 and CD36, and their association with inflammatory human disorders. Furthermore, we present the design of an ex vivo monocyte-based test system with minimal set of parameters as a potential diagnostic tool for the identification of personalized inflammatory responses.

Innate immunity in diabetes and diabetic nephropathy

The innate immune system includes several classes of pattern recognition receptors (PRRs), including membrane-bound Toll-like receptors (TLRs) and nucleotide-binding oligomerization domain (NOD)-like receptors (NLRs). These receptors detect pathogen-associated molecular patterns (PAMPs) and danger-associated molecular patterns (DAMPs) in the extracellular and intracellular space. Intracellular NLRs constitute inflammasomes, which activate and release caspase-1, IL-1β, and IL-18 thereby initiating an inflammatory response. Systemic and local low-grade inflammation and release of proinflammatory cytokines are implicated in the development and progression of diabetes mellitus and diabetic nephropathy. TLR2, TLR4, and the NLRP3 inflammasome can induce the production of various proinflammatory cytokines and are critically involved in inflammatory responses in pancreatic islets, and in adipose, liver and kidney tissues. This Review describes how innate immune system-driven inflammatory processes can lead to apoptosis, tissue fibrosis, and organ dysfunction resulting in insulin resistance, impaired insulin secretion, and renal failure. We propose that careful targeting of TLR2, TLR4, and NLRP3 signalling pathways could be beneficial for the treatment of diabetes mellitus and diabetic nephropathy.

Gene expression profiling and association of circulating lactoferrin level with obesity-related phenotypes in Latino youth

BACKGROUND/OBJECTIVES

Low-grade inflammation is an underlying feature of obesity and identifying inflammatory markers is crucial to understanding this disease. Therefore, the purpose of this study was twofold: (i) to perform a global microarray analysis and (ii) to investigate the role of lactoferrin (LTF), one of the most altered genes, in relation to obesity in Latino youth.

METHODS

Non-diabetic Latino youth (71 males/92 females; 15.6 ± 3.2 years) were studied. A subset of 39 participants was randomly selected for global microarray analysis profiling from the whole blood sample. Serum LTF was compared between lean (n = 78) and overweight/obese (n = 85) participants.

RESULTS

Microarray analysis revealed that a total of 1870 probes were altered in expression ≥1.2-fold and P < 0.05 in overweight/obese participants compared with lean. KEGG (Kyoto Encyclopedia of Genes and Genomes) analysis revealed significant enrichment for pathways including toll-like receptor (TLR) and B cell receptor signalling pathways. LTF and TLR5 were increased in expression by 2.2 and 1.5 fold, respectively, in the overweight/obese participants. Increased LTF concentrations were significantly associated with high risk of obesity-related phenotypes (all P < 0.05).

CONCLUSIONS

Our data suggest that increased LTF is associated with obesity risk among Latino youth. This finding is discordant to what has been shown in adults and suggests that age may modulate the association between LTF and obesity-related health.

TLR4 at the Crossroads of Nutrients, Gut Microbiota, and Metabolic Inflammation

Obesity is accompanied by the activation of low-grade inflammatory activity in metabolically relevant tissues. Studies have shown that obesity-associated insulin resistance results from the inflammatory targeting and inhibition of key proteins of the insulin-signaling pathway. At least three apparently distinct mechanisms-endoplasmic reticulum stress, toll-like receptor (TLR) 4 activation, and changes in gut microbiota-have been identified as triggers of obesity-associated metabolic inflammation; thus, they are expected to represent potential targets for the treatment of obesity and its comorbidities. Here, we review the data that place TLR4 in the center of the events that connect the consumption of dietary fats with metabolic inflammation and insulin resistance. Changes in the gut microbiota can lead to reduced integrity of the intestinal barrier, leading to increased leakage of lipopolysaccharides and fatty acids, which can act upon TLR4 to activate systemic inflammation. Fatty acids can also trigger endoplasmic reticulum stress, which can be further stimulated by cross talk with active TLR4. Thus, the current data support a connection among the three main triggers of metabolic inflammation, and TLR4 emerges as a link among all of these mechanisms.

Increased adipose tissue secretion of Fetuin-A, lipopolysaccharide-binding protein and high-mobility group box protein 1 in metabolic syndrome

OBJECTIVE

Adipose Tissue (AT) dysregulation contributes to the pro-inflammatory state and insulin resistance of Metabolic Syndrome (MetS). We examined AT secretion of the hepatokine, Fetuin-A, LBP, sCD14 and HMGB-1, and toll-like receptor 2 and 4 protein levels in MetS and controls.

DESIGN AND METHODS

Secreted levels of Fetuin-A, LBP, HMGB-1 and sCD14 and TLR2 and TLR4 protein in AT of controls and MetS patients were assayed. Also mRNA and protein for Fetuin-A, LBP, sCD14 and HMGB-1 were studied in subcutaneous fat depot of mice and during adipocyte differentiation.

RESULTS

Secretion of Fetuin-A, LBP and HMGB-1 from AT were significantly increased in MetS (n = 28) compared to controls (n = 25), even after adjustment for adiposity. There were no significant differences in sCD14. Both LBP and Fetuin-A correlated significantly with HOMA-IR and increased significantly with increasing features of MetS. There was a significant increase in AT TLR2 and TLR4 protein in MetS compared to controls. Expression of Fetuin-A and LBP were significantly higher in subcutaneous white adipose tissue of HFD fed mice as well as in ob/ob mice compared to C57BL6/J control mice (n = 6 per group). Additionally mRNA and protein levels of FetA, LBP and HMGB-1 increased during differentiation of 3T3-L1 adipocytes.

CONCLUSIONS

We make the novel observation of increased secretion of Fetuin A, LBP and HMGB-1 from AT and hypothesize that these engage TLRs in AT and other tissues contributing to the pro-inflammatory state and insulin resistance of MetS.

A blueberry-enriched diet improves renal function and reduces oxidative stress in metabolic syndrome animals: potential mechanism of TLR4-MAPK signaling pathway

Background

Metabolic syndrome (MetS) is characterized by a cluster of health factors that indicate a higher risk for cardio-renal diseases. Recent evidence indicates that antioxidants from berries are alternative to attenuate oxidative stress and inflammation. We tested the hypothesis that inflammation-induced renal damage is triggered by the activation of TLR4, and subsequent modulation of redox-sensitive molecules and mitogen-activated protein kinase (MAPK) pathway.

Methods

Five-week old lean and obese Zucker rats (LZR and OZR) were fed a blueberry-enriched diet or an isocaloric control diet for 15 weeks. A glucose tolerance test and acute renal clearance experiments were performed. Gene and protein expression levels for TLR4, cytokines and phosphorylation of ERK and p38MAPK were measured. Kidney redox status and urinary albumin levels were quantified. Renal pathology was evaluated histologically.

Results

Control OZR exhibited lower glucose tolerance; exacerbated renal function parameters; increased oxidative stress. Gene and protein expression levels of TLR4 were higher and this was accompanied by increased renal pathology with extensive albuminuria and deterioration in antioxidant levels in OZR. In addition, OZR had increased phosphorylation of ERK and p38MAPK. Blueberry-fed OZR exhibited significant improvements in all these parameters compared to OZR.

Conclusion

TLR4-MAPK signaling pathway is a key to the renal structural injury and dysfunction in MetS and blueberry (BB) protect against this damage by inhibiting TLR4.

Significance

This is the first study to put forth a potential mechanism of TLR4-induced kidney damage in a model of MetS and to elucidate a downstream mechanism by which blueberry exert their reno-protective effects.

Suppressor of cytokine signalling (SOCS) proteins as guardians of inflammatory responses critical for regulating insulin sensitivity

Overactivation of immune pathways in obesity is an important cause of insulin resistance and thus new approaches aimed to limit inflammation or its consequences may be effective for treating Type 2 diabetes. The SOCS (suppressors of cytokine signalling) are a family of proteins that play an essential role in mediating inflammatory responses in both immune cells and metabolic organs such as the liver, adipose tissue and skeletal muscle. In the present review we discuss the role of SOCS1 and SOCS3 in controlling immune cells such as macrophages and T-cells and the impact this can have on systemic inflammation and insulin resistance. We also dissect the mechanisms by which SOCS (1-7) regulate insulin signalling in different tissues including their impact on the insulin receptor and insulin receptor substrates. Lastly, we discuss the important findings from SOCS whole-body and tissue-specific null mice, which implicate an important role for these proteins in controlling insulin action and glucose homoeostasis in obesity.

Dysregulation of monocyte biology in metabolic syndrome

Metabolic syndrome (MetS), which constitutes a cardio-metabolic risk cluster, is becoming a global epidemic. It is a pro-inflammatory and pro-oxidant state that confers an increased risk of cardiovascular disease and diabetes. MetS is not only characterized by increased circulating biomarkers of inflammation and oxidative stress but also by dysregulation of a pivotal phagocyte, the circulating monocyte. Pertubations manifesting in monocytes of patients with MetS include increased Toll-like receptors, CD40-CD40L dyad, increased ER stress, increased CCR5 and Fc-γ receptors (CD32 and CD64). Additionally, the monocytes demonstrate increase in NADPH oxidase activity and decreased Nrf2, resulting in oxidative damage to biomolecules. Thus the dysregulated monocyte in MetS appears to be a critical cell in the predisposition of MetS patients to diabetes and CVD. Therapeutic strategies targeting monocytes can attenuate this risk and the most compelling data derives from studies with statin therapy.

Adipocytes as immune regulatory cells

Obesity is a chronic inflammatory state and adipocytes are capable of contributing to this inflammation by their production of inflammatory mediators. The present study used fibroblast-derived adipocytes and normal spleen cells as a model to determine if adipocytes can also serve as immune regulatory cells by modulating the functions of conventional immune cells. Media conditioned by the adipocytes stimulated release of the Th1-type cytokines IL-2, IFN-γ and GM-CSF from cultures of normal spleen cells. The adipocytes also stimulated spleen cell release of inhibitory cytokines, although to varying degrees. This included IL-10, IL-13 and, to a lesser extent, IL-4. Spleen cell production of the inflammatory cytokines IL-6, TNF-α and IL-9 was stimulated by adipocytes, although production of the Th17-derived cytokine, IL-17, was not stimulated. The adipocyte-conditioned medium did not stimulate production of predominantly monocytes-derived chemokines CXCL9, CCL2, CCL3, CCL4, but stimulated production of the predominantly T-cell-derived chemokine CCL5. In all cases where cytokine/chemokine production from spleen cells was stimulated by adipocytes, it was to a far greater level than was produced by the adipocytes themselves. Studies initiated to determine the identity of the adipocyte-derived mediators showed that the spleen cell modulation could not be attributed to solely adiponectin or leptin. Studies to determine the source of some of the cytokines whose production was stimulated by adipocytes showed that expression of the inflammatory cytokine IL-6 was not increased in either CD4(+) or CD8(+) T-cell. When the splenic T-cells were examined for IFN-γ, the adipocyte stimulation of IFN-γ was within CD8(+) T-cells, not CD4(+) T-cells. These studies show that adipocytes may be able to serve as immune regulatory cells to stimulate conventional immune cells to release a spectrum of immune mediators.