Plasma resistin is associated with single nucleotide polymorphisms of a possible resistin receptor, the decorin gene, in the general Japanese population

[The rs7139228 polymorphism is located in the DCN gene and not in the RETN gene]

Introduction

Association of resistin (rs3138167) gene polymorphism with metabolic response after a hypocaloric Mediterranean diet

BACKGROUND

the single nucleotide polymorphism (SNP) (rs3138167) of resistin (RETN) gene is a polymorphism that has been associated with metabolic disorder in obese subjects and its effect on the metabolic response after a dietary intervention has not been evaluated.

OBJECTIVE

our aim was to analyze the effects of the rs3138167 RETN gene polymorphism on metabolic changes secondary to weight loss with a hypocaloric diet with a Mediterranean pattern.

METHOD

one thousand and eight Caucasian obese patients were evaluated. Before and after 12 weeks on a hypocaloric diet with Mediterranean pattern, an anthropometric evaluation and a biochemical analysis were performed. The statistical analysis was performed as a dominant model (CC vs CT + TT).

RESULTS

the values of insulin, HOMA-IR and resistin were higher in T allele carriers than non-T allele carriers in pre- and post-intervention time. In non-T allele carriers, resistin, insulin, HOMA-IR, triglycerides and C-reactive protein levels decreased. The improvement was statistically superior in non-T allele carriers; resistin (-1.2 ± 0.2 ng/dl; p = 0.02), triglycerides (-18.3 ± 4.3 mg/dl; p = 0.02), C-reactive protein (-2.6 ± 0.3 mg/dl; p = 0.02), insulin -4.4 ± 1.9 mUI/l; p = 0.02) and HOMA-IR (-2.1 ± 0.7; p = 0.03).

CONCLUSION

we report an association of rs3138167 with a worse metabolic response (insulin, HOMA-IR, triglyceride and C-reactive protein) in T allele carriers after weight loss with a hypocaloric diet with Mediterranean pattern.

Relationship of resistin gene polymorphism (rs7139228) with resistin levels and metabolic syndrome risk in obese subjects

Introduction

Background: despite the relationship of resistin with metabolic syndrome (MS), the relationship of the 5'UTR intron C/T variant SNP rs7139228 of the RETN gene with the presence of MS has not been evaluated. Objective: the objective of this study is to evaluate the influence of SNP rs7139228 of the RETN gene on circulating resistin levels, as well as on MS in obese subjects. Material and Methods: a Caucasian population of 1003 obese subjects was enrolled. An anthropometric evaluation (weight, waist circumference, fat mass), evaluation of nutritional intake, biochemical study (glucose, insulin, C-reactive protein, lipid profile, insulin, HOMA-IR, resistin) and rs7139228 genotype was carried out. Results: genotype distribution was: 852 subjects with GG (84.9 %), 147 subjects with GA (14.7 %) and 4 subjects with AA (0.4 %). The allelic frequency was G (0.92) and A (0.08). Serum levels of resistin (delta: 1.7 ± 0.2 ng/ml; p = 0.01), insulin (delta: 4.2 ± 0.4 IU/L; p = 0.01) and HOMA-IR (delta: 1.9 ± 0.2 units; p = 0.03) were higher in patients carrying the A allele than in non-carriers. The overall prevalence of MS was 48.1 %. A logistic regression analysis showed a high percentage of hyperglycemia (OR = 1.60, 95 % CI = 1.08-2.96; p = 0.02) and metabolic syndrome (OR = 1.33, 95 % CI = 1.07-3.39, p = 0.02) in carriers of the A allele after adjusting for resistin levels, sex, BMI and age. Conclusions: the A allele of the genetic variant rs7139228 is associated with higher levels of resistin, basal insulin, insulin resistance, and prevalence of metabolic syndrome in obese subjects.

Role of resistin (rs7139228) gene polymorphism with metabolic response after a hypocaloric mediterranean diet

BACKGROUND

The SNP (rs7139228) of the RETN gene is a polymorphism that has been associated with metabolic disorder in subjects with obesity, and its effect on metabolic response after dietary intervention has not been evaluated.

OBJECTIVE

Our objective was to analyse the effects of the polymorphism of the RETN gene rs7139228 on metabolic changes secondary to weight loss with a hypocaloric Mediterranean diet.

DESIGN

1000 obese Caucasian patients were evaluated. An anthropometric evaluation and a biochemical analysis were performed before and after 12 weeks of a hypocaloric Mediterranean diet. The statistical analysis was performed as a dominant model (GG vs GA+AA).

RESULTS

Improvements in anthropometric parameters, leptin levels and systolic blood pressure were similar in both genotype groups. In non- A allele carriers, levels of resistin, insulin, HOMA-IR, triglycerides and C-reactive protein decreased. The improvements were statistically significant in this group; resistin (-1.3+0.1ng/dL: p=0.02), triglycerides (-22.9+4.9mg/dl: p=0.02), CRP (-2.7+0 0.4mg/dl: p=0.02), insulin -6.5+1.8 mIU/L: p=0.02) and HOMA-IR (-2.2+0.8: p=0, 03). In addition, insulin, HOMA-IR and resistin levels were higher in A allele carriers than in non-carriers. Finally, the prevalence of metabolic syndrome and hyperglycaemia were higher in A allele carriers, and these percentages only decreased after intervention in non-A allele carriers.

CONCLUSION

The A rs7139228 allele is associated with a worse metabolic response (insulin, HOMA-IR, triglycerides and CRP) after weight loss with a hypocaloric Mediterranean diet. A non-significant decrease in the prevalence of metabolic syndrome and hyperglycaemia were detected in A allele carriers.

The Role of Leptin in the Association between Obesity and Psoriasis

Adipose tissue secretes many adipokines which contribute to various metabolic processes, such as blood pressure, glucose homeostasis, inflammation and angiogenesis. The biology of adipose tissue in an obese individual is abnormally altered in a manner that increases the body’s vulnerability to immune diseases, such as psoriasis. Psoriasis is considered a chronic inflammatory skin disease which is closely associated with being overweight and obese. Additionally, secretion of leptin, a type of adipokine, increases dependently on adipose cell size and adipose accumulation. Likewise, high leptin levels also aggravate obesity via development of leptin resistance, suggesting that leptin and obesity are closely related. Leptin induction in psoriatic patients is mainly driven by the interleukin (IL)-23/helper T (Th) 17 axis pathway. Furthermore, leptin can have an effect on various types of immune cells such as T cells and dendritic cells. Here, we discuss the relationship between obesity and leptin expression as well as the linkage between effect of leptin on immune cells and psoriasis progression.

An Overview of the Role of Adipokines in Cardiometabolic Diseases

Obesity as an independent risk factor for cardiovascular diseases (CVDs) leads to an increase in morbidity, mortality, and a shortening of life span. The changes in heart structure and function as well as metabolic profile are caused by obese people, including those free of metabolic disorders. Obesity alters heart function structure and affects lipid and glucose metabolism, blood pressure, and increase inflammatory cytokines. Adipokines, specific cytokines of adipocytes, are involved in the progression of obesity and the associated co-morbidities. In the current study, we review the scientific evidence on the effects of obesity on CVDs, focusing on the changes in adipokines. Several adipokines have anti-inflammatory and cardioprotective effects comprising omentin, apelin, adiponectin, and secreted frizzled-related protein (Sfrp-5). Other adipokines have pro-inflammatory impacts on the cardiovascular system and obesity including leptin, tumor necrosis factor (TNF), retinol-binding protein4 (RBP-4), visfatin, resistin, and osteopontin. We found that obesity is associated with multiple CVDs, but can only occur in unhealthy metabolic patients. However, more studies should be designed to clarify the association between obesity, adipokine changes, and the occurrence of CVDs.

Absence of the proteoglycan decorin reduces glucose tolerance in overfed male mice

Studies have implicated the extracellular matrix (ECM) of adipose tissue in insulin resistance. The proteoglycan decorin, a component of ECM, has been associated with glucose tolerance, but possible causal effects on metabolism remain to be explored. We here sought to determine metabolic consequences of loss of decorin in mice (DcnKO). DcnKO mice were fed a low-fat (LF) or high-fat (HF) diet for 10 weeks and body weight and food intake was recorded. An intraperitoneal glucose tolerance test was performed after eight weeks. Blood samples and adipose, liver and muscle tissues were collected at sacrifice. Global gene expression was measured in adipose tissue, and expression of decorin was also analyzed in human adipose samples. DcnKO mice showed increased feed efficiency during overfeeding and impaired glucose tolerance. Adipose leptin mRNA and circulating leptin levels were elevated in DcnKO mice, along with a downregulation of genes involved in ECM organization and triglyceride biosynthesis, and an upregulation of adipose genes involved in complement and coagulation cascades. Consistent with a protective metabolic role for decorin, in obese patients we found increased adipose decorin expression after profound fat loss, particularly in the stromal vascular fraction. Loss of decorin in mice caused impaired glucose tolerance in association with increased feed efficiency and altered gene expression in adipose tissue. Our data provide evidence that decorin is an important factor for maintaining glucose tolerance.

Resistin is a prognostic factor for death in type 2 diabetes

PURPOSE

To investigate the association of leptin, resistin, and tumour necrosis factor α (TNF-α) with prognosis in type 2 diabetes (T2D).

METHODS

Analysis included 284 T2D patients. Apart from routine laboratory parameters, baseline leptin, resistin, and TNF-α concentrations were measured. Patients were followed for a median of 5.4 years. The primary endpoint was all-cause death at follow-up. The secondary endpoint was a composite of death, acute coronary syndrome, and stroke or transient ischemic attack.

RESULTS

At baseline, median age was 68 years, and 48% of patients were female. Data on the primary endpoint were obtained for all patients: 32 (11%) died during follow-up. Data on the secondary endpoint were available for 230 patients, of whom 45 (20%) reached the secondary endpoint. In univariate analyses, older age, heart failure, lower-glomerular filtration rate, and higher resistin, TNF-α and NT-proBNP concentrations were predictors of the study endpoints. Of these variables, only resistin remained an independent predictor of both study endpoints in multivariate models. In receiver-operating characteristic analysis, area under the curve for resistin was 0.7. Resistin concentration of greater than or equal to 11.4 ng/mL had sensitivity of 41% and specificity of 91% for prediction of death at follow-up (Youden's index).

CONCLUSIONS

Higher resistin is associated with reduced survival in T2D, irrespectively of TNF-α. Resistin concentration of above 11 ng/mL indicates T2D patients at an increased risk of unfavourable outcomes. Leptin was not a prognostic factor. These results suggest that in T2D, association of resistin with unfavourable outcomes might, at least in part, result from its pro-inflammatory properties.

Resistin-Inhibited Neural Stem Cell-Derived Astrocyte Differentiation Contributes to Permeability Destruction of the Blood-Brain Barrier

Neuroinflammation is an important part of the development of neurodegenerative diseases such as Alzheimer's disease (AD), Parkinson's and amyotrophic lateral sclerosis. Inflammatory factors destroy the balance of the microenvironment, which results in changes in neural stem cell differentiation and proliferation behaviour. However, the mechanism underlying inflammatory factor-induced NSC behavioural changes is not clear. Resistin is a proinflammatory and adipogenic factor and is involved in several human pathology processes. The neural stem cell microenvironment changes when the concentration of resistin in the brain during an inflammatory response disease increases. In the present study, we explored the effect and mechanism of resistin on the proliferation and differentiation of neural stem cells. We found that intracerebroventricular injection of resistin induced a decrease in GFAP-positive cells in mice by influencing NSC differentiation. Resistin significantly decreased TEER and increased permeability in an in vitro blood-brain barrier model, which is consistent with the results of an HBMEC-astrocyte coculture system. Resistin-inhibited astrocyte differentiation is mediated through TLR4 on neural stem cells. To our knowledge, this is the first study reporting the effect of resistin on neural stem cells. Our findings shed light on resistin-involved neural stem cell degeneration mechanisms.

Resistin Is a Novel Marker for Postoperative Pain Intensity

BACKGROUND

Pro- and anti-inflammatory cytokines (adipokines) associated with adipose tissue can modulate inflammatory processes and lead to systemic inflammatory conditions such as metabolic syndrome. In the present pilot study, we investigated 3 major adipokines (leptin, adiponectin, and resistin) and 2 nonspecific proinflammatory cytokines (tumor necrosis factor α and interleukin-6) with regard to their association with postoperative pain intensity.

METHODS

We analyzed a total of 45 single-nucleotide polymorphisms of the adipokines in 57 patients with postlaparotomy pain. We adjusted for multiple testing to reduce the chance of false-positive results by controlling the false discovery rate. Serum levels of the adipokines and proinflammatory cytokines were measured in another 36 patients undergoing laparotomy. A stepwise multiple linear regression analysis using these measurements and opioid dosages as independent variables was performed to explore the factors associated with postoperative pain.

RESULTS

Only 1 variant of the resistin gene (rs3745367) demonstrated a significant association with postoperative pain (P < .002). Patients exhibiting homozygosity for the minor alleles (n = 7; numerical rating scale [NRS], 2.3 ± 1.3) demonstrated lower pain intensity compared with those exhibiting homozygosity for the major alleles (n = 29; NRS, 3.8 ± 1.0; P = .004) and heterozygosity for the minor alleles (n = 21; NRS, 4.2 ± 0.8; P < .001). Only serum resistin levels showed a positive association with postoperative pain.

CONCLUSIONS

A genetic variant of resistin and serum resistin levels were associated with postoperative pain intensity, while other adipokines and cytokines exhibit no such association. Resistin can alter the inflammatory responses in postoperative wounds, although it could be a determinant factor that is independent of inflammatory processes. Resistin may be a novel marker for postoperative pain intensity.

Association of RETN and CAP1 SNPs, Expression and Serum Resistin Levels with Breast Cancer in Mexican Women

BACKGROUND

Breast cancer is the most common cancer in women worldwide. Approximately 70% of female breast cancer patients have a body mass index (BMI) >25. In obesity, adipose tissue secretes additional resistin, which prompts a proinflammatory effect through its action on adenylate cyclase-associated protein 1 (CAP1). Several studies have associated the RETN gene single nucleotide polymorphism (SNP) rs1862513 (-420C<G) with serum resistin levels and breast cancer. The CAP1 gene SNP rs35749351 (missense, Arg294His), located in the extracellular domain, has not previously been studied in cancer. These two SNPs, the mRNA expression levels of the two alleles for each of the cognate genes, and the serum resistin levels were compared between patients and controls to determine their association with breast cancer in Mexican women in this study.

MATERIALS AND METHODS

This study included 308 controls and 100 female patients with breast cancer. SNPs were detected by PCR-RFLP from DNA isolated from peripheral blood. Gene expression was performed with hydrolysis probes in tumor tissue. Resistin levels were quantified from serum samples by ELISA.

RESULTS

The RETN rs1862513CG/GG and CAP1 rs35749351GA/AA genotypes were associated with 1.61 and 2.193-fold increased risks of breast cancer, respectively, compared with the CC and GG genotypes. Similarly, carriers of the G allele of rs1862513 and the A allele of rs35749351, had 1.51 and 2.217-fold increased risks of breast cancer compared with the C and G alleles, respectively. The rs1862513GG/rs35749351AA genotype combination increased breast cancer risk by twofold. Serum resistin levels in postmenopausal breast cancer women were higher compared with postmenopausal controls. Tissue CAP1 expression showed differences with regard to molecular subtypes and metastases.

CONCLUSION

The RETN and CAP1 polymorphisms and gene expression may be potential biomarkers for breast cancer risk.

Podocan Is Expressed in Blood and Adipose Tissue and Correlates Negatively With the Induction of Diabetic Nephropathy

Podocan, a member of the small leucine-rich repeat proteoglycans (SLRPs), is expressed in vascular endothelial cells with high levels of expression in the sclerotic glomerular lesions of experimental HIV-associated nephropathy. It is also found in vascular smooth muscle cells and is involved in atherosclerosis. Decorin, a protein similar to podocan, also belongs to the SLRP family and is highly expressed in adipose tissues. It is a secreted protein associated with obesity, type 2 diabetes, and diabetic nephropathy. Based on the similarity of podocan to decorin and its functions reported in the renal and cardiovascular systems, we hypothesized that podocan levels might correlate with the occurrence of metabolic syndromes such as obesity, diabetes, and diabetic nephropathy. We found that podocan was highly expressed in the adipose tissue of mice and humans and its expression was regulated by tumor necrosis factor-α in mouse 3T3-L1 adipocytes. In addition, podocan was detected in the plasma, and its levels tended to increase in diet-induced obese C57BL/6J mice and decrease in obese-diabetic KKA^y and db/db mice. Podocan messenger RNA (mRNA) levels in the renal cortex correlated negatively with the urinary albumin-to-creatinine ratio, a surrogate marker of glomerular injury in uninephrectomized db/db mice used as a model of diabetic nephropathy. Our results suggest that podocan is involved in kidney function and could be a unique therapeutic target for diabetic nephropathy.

Genome-wide association study of plasma resistin levels identified rs1423096 and rs10401670 as possible functional variants in the Japanese population

Resistin is a cytokine inducing insulin resistance in mice. We previously identified single nucleotide polymorphisms (SNPs) at -420 (rs1862513) and -358 (rs3219175) located in the human resistin gene (RETN) promoter as strong determinants for circulating resistin in the Japanese population. The objective was to identify additional functional variants for circulating resistin. We conducted a genome-wide association study in 448 Japanese subjects. A peak association signal was found on chromosome 19 where RETN is located. The top-hit SNP was SNP -358 G>A, followed by rs1423096 C>T, SNP -420 C>G, and rs10401670 C>T (P = 5.39×10^-47, 1.81×10^-22, 2.09×10^-16, and 9.25×10^-15, respectively). Meta-analysis including another two independent general Japanese populations showed that circulating resistin was most strongly associated with SNP-358, followed by SNP-420, rs1423096, and rs10401670. Rs1423096 and rs10401670 were located in the 3'-region of RETN and were in strong linkage disequilibrium. Although these SNPs were also in linkage disequilibrium with the promoter SNPs, conditional and haplotype association analyses identified rs1423096 and rs10401670 as independent determinants for circulating resistin. Functionally, nuclear proteins specifically recognized T but not C at rs10401670 as evidenced by an electrophoretic mobility shift assay. The promoter activity of a luciferase reporter with T at either rs1423096 or rs10401670 was lower than that with C in THP-1 human monocytes. Therefore, rs1423096 and rs10401670, in addition to SNP-420 and SNP-358, were identified as possible functional variants affecting circulating resistin by the genome-wide search in the Japanese population.

Resistin's, obesity and insulin resistance: the continuing disconnect between rodents and humans

PURPOSE

This review aimed to discuss the conflicting findings from resistin research in rodents and humans as well as recent advances in our understanding of resistin's role in obesity and insulin resistance.

METHODS

A comprehensive review and synthesis of resistin's role in obesity and insulin resistance as well as conflicting findings from resistin research in rodents and humans.

RESULTS

In rodents, resistin is increased in high-fat/high-carbohydrate-fed, obese states characterized by impaired glucose uptake and insulin sensitivity. Resistin plays a causative role in the development of insulin resistance in rodents via 5' AMP-activated protein kinase (AMPK)-dependent and AMPK-independent suppressor of cytokine signaling-3 (SOCS-3) signaling. In contrast to rodents, human resistin is primarily secreted by peripheral-blood mononuclear cells (PBMCs) as opposed to white adipocytes. Circulating resistin levels have been positively associated with central/visceral obesity (but not BMI) as well as insulin resistance, while other studies show no such association. Human resistin has a role in pro-inflammatory processes that have been conclusively associated with obesity and insulin resistance. PBMCs, as well as vascular cells, have been identified as the primary targets of resistin's pro-inflammatory activity via nuclear factor-κB (NF-κB, p50/p65) and other signaling pathways.

CONCLUSION

Mounting evidence reveals a continuing disconnect between resistin's role in rodents and humans due to significant differences between these two species with respect to resistin's gene and protein structure, differential gene regulation, tissue-specific distribution, and insulin resistance induction as well as a paucity of evidence regarding the resistin receptor and downstream signaling mechanisms of action.

Epigenome-wide association study suggests that SNPs in the promoter region of RETN influence plasma resistin level via effects on DNA methylation at neighbouring sites

AIMS/HYPOTHESIS

To investigate epigenetic regulation of the plasma concentration of resistin, we performed an epigenome-wide association study for this variable and DNA methylation (DNAm) in an elderly Japanese cohort and then assessed the relation of single nucleotide polymorphisms (SNPs) associated with the plasma resistin concentration to DNAm level at identified sites.

METHODS

The association of plasma resistin level with DNAm status was examined in 191 nondiabetic elderly men with the Illumina Infinium HumanMethylation450 BeadChip array. The association between DNAm status at specific sites in the flanking region of the resistin gene (RETN) and RETN mRNA abundance was then evaluated with a public data set for 1202 monocyte samples from a multi-ethnic cohort. Finally, the association of DNAm status and SNPs in the promoter region of RETN was assessed in two cohorts comprising a total of 478 Japanese individuals.

RESULTS

DNAm status at cg02346997 located in the RETN promoter region showed a negative genome-wide significant association with the plasma resistin level (p = 6.02 × 10(-10)). Four DNAm sites in the RETN promoter region including cg02346997 (p = 4.23 × 10(-70)) showed a negative genome-wide significant association with RETN mRNA abundance in monocytes. Furthermore, the number of minor alleles of the RETN promoter SNPs rs34861192 and rs3219175 was negatively associated with DNAm level at cg02346997 (p = 4.43 × 10(-17)).

CONCLUSIONS/INTERPRETATION

Our results suggest that RETN promoter SNPs might influence the circulating resistin level through an effect on DNAm at cg02346997 and on RETN mRNA abundance in monocytes.

CDH13 genotype-dependent association of high-molecular weight adiponectin with all-cause mortality: the J-SHIPP study

OBJECTIVE

Despite its anti-inflammatory and antiatherogenic effects, adiponectin is potentially associated with adverse clinical outcomes, such as all-cause mortality. As plasma adiponectin levels are strongly influenced by single nucleotide polymorphisms in the gene encoding T-cadherin (CDH13), we conducted a longitudinal study to investigate the possible link between the CDH13 genotype, plasma adiponectin levels, and all-cause mortality.

RESEARCH DESIGN AND METHODS

This longitudinal study evaluated 2,020 Japanese subjects. Baseline clinical parameters were obtained from subjects' personal health records as evaluated at annual medical check-ups. Plasma high-molecular weight adiponectin (HMWA) levels were measured by an ELISA assay, and genotyping was performed by a TaqMan probe assay.

RESULTS

Mean follow-up duration was 6.5 years. Kaplan-Meier analysis showed that HMWA levels were positively associated with mortality (P < 0.001). HMWA levels were associated with older age, lower body weight, lower plasma triglyceride and glucose levels, and higher plasma HDL cholesterol. However, the Cox regression analysis showed that the positive association between HMWA and all-cause mortality was independent of these covariates (hazard ratio [HR] 1.92, P = 0.006). The CDH13 rs4783244 genotype was strongly associated with baseline HMWA levels (per-allele effect size 1.65 μg/mL, P < 0.001). In a separate analysis by the CDH13 genotype, the HR for all-cause mortality was linearly increased with the number of G alleles (P value for HMWA-CDH13 genotype interaction = 0.023).

CONCLUSIONS

Higher plasma HMWA level was an independent prognostic factor for all-cause mortality in a general population. The CDH13 genotype may be a factor that affects not only the plasma level of HMWA but also the prognostic significance of HMWA.

Rapid cloning and comparative sequence analysis of full-length cDNA of Rhesus monkey (Macaca mulatta) resistin

Resistin protein is thought to link insulin resistance in murine models of obesity and type-2 diabetes, but the role of resistin in human studies of inflammatory metabolic disorders have generated conflicting data. Here, we describe the structure of the resistin gene using adipose tissue from non-human primates (NHPs), which have been used extensively to model a host of human diseases. Full-length cDNA from rhesus macaque resistin obtained by rapid amplification of cDNA ends (RACE) is comprised of 526 nucleotides covering an open-reading frame (ORF) that encodes a 108-amino-acid protein that is 92% homologous with the human counterpart but only 60% homologous with the murine counterpart. Using a modified polymerase chain reaction technique, we identified single nucleotide polymorphisms and a 78-bp deletion within resistin cDNA of nine rhesus macaques. Comparisons of the full-length cDNA sequence and an amplified 569-bp genomic DNA sequence revealed an error in published predictions arising from genomic studies about the gene's exon 3 region. Our data show, for the first time, the full-length macaque resistin cDNA sequence (GenBank: JF740676.1). These findings will illuminate future studies into the role of resistin in NHP models of inflammatory metabolic diseases.

Biological interplay between proteoglycans and their innate immune receptors in inflammation

An emerging body of evidence indicates that secreted proteoglycans act as signaling molecules, in addition to their canonical function in maintaining and regulating the architecture of various extracellular matrices. Proteoglycans interact with a number of receptors that regulate growth, motility and immune response. In part, as a consequence of their complex structure, proteoglycans can induce crosstalk among various families of receptors and can also interact with natural receptor ligands, often blocking and sequestering their bioactivity. In their soluble form, originating from either partial proteolytic processing or through de novo synthesis by activated cells, some proteoglycans can become potent danger signals, denoting tissue stress and injury. Recently, it has been shown that proteoglycans, especially those belonging to the small leucine-rich and hyaluronan-binding gene families as well as the glycosaminoglycan hyaluronan, act as endogenous ligands of the toll-like receptors, a group of central receptors regulating innate immunity. Furthermore, proteoglycans can activate intracellular inflammasomes and trigger sterile inflammation. In this review, we critically assess the signaling events induced by the proteoglycans biglycan, decorin, lumican and versican as well as hyaluronan during inflammation. We discuss the intriguing emerging notion that, in spite of structural diversity of biglycan, decorin, versican and hyaluronan, all of them signal through the same toll-like receptors, albeit triggering differential responses and biological outcomes. Finally, we review the modes of action of these endogenous ligands of toll-like receptors and their ability to specifically modify the final signaling events and the inflammatory response.