Circulating pathogen associated molecular pattern – Binding proteins and High Mobility Group Box protein 1 in nascent metabolic syndrome: Implications for cellular Toll-like receptor activity

doi:10.1016/j.atherosclerosis.2014.06.022

Atherosclerosis

Volume 236, Issue 1, September 2014, Pages 182-187

https://doi.org/10.1016/j.atherosclerosis.2014.06.022 Get rights and content

Highlights

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This study was aimed at elucidating the roles of monocytes and adipose tissue as cellular sources of Inflammation in nascent Metabolic Syndrome, uncomplicated by diabetes or CVD.
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In this paper, we make a novel observation that in patients with nascent MetS, soluble CD14 compared to LBP provides a better measure of increased TLR4 activity and cellular inflammation.
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We also show in-vitro that soluble CD14 is superior to LBP in activating TLR4 activity in human aortic endothelial cells.
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This could have implications to the increased CVD risk of MetS.
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Furthermore we make the additional novel observation, that the DAMP, HMGB1 also captures cellular inflammation although not specific for TLR activity in MetS.

Abstract

Objective

The Metabolic Syndrome, (MetS) a global epidemic, is a state of low grade chronic inflammation and confers an increased risk for diabetes and CVD. We have previously reported increased activity of the pathogen recognition receptors, Toll-like receptors (TLRs), TLR2 and TLR4 in MetS. We hypothesized that increased TLR activity in MetS is due in part to increased levels of circulating PAMP–binding proteins, soluble CD14 (sCD14), lipopolysaccharide binding protein (LBP) and the damage associated molecular pattern (DAMP), High Mobility Group Box protein 1 (HMGB-1).

Methods

We measured sCD14, LBP and HMGB-1 in fasting plasma from nascent MetS (n = 37) and healthy control subjects (n = 32) by ELISA. We also investigated the effects of sCD14 and LBP on TLR4 activity in human aortic endothelial cells (HAECs).

Results

Following adjustment for body mass index and waist circumference, sCD14, LBP and HMGB-1 levels remained significantly increased in MetS. Also their levels increased with increasing numbers of MetS risk factors. Only sCD14 correlated significantly with monocyte TLR4 protein and activity. None of these soluble biomarkers correlated with TLR2 protein. Both sCD14 and HMGB-1 correlated significantly with HOMA-IR.

In LPS primed HAECs, sCD14 compared to LBP, resulted in a greater increase in both TLR4 abundance and inflammatory biomediators (NF-κB, IL-1β, IL-8 and TNF-α).

Conclusion

Thus, we make the novel observation that sCD14 reflects increased monocyte TLR4 protein and activity in nascent MetS and by contributing to increased cellular inflammation could explain, in part, the increased risk for diabetes and CVD.

Section snippets

Study participants

All subjects were recruited from Sacramento County, California, through fliers and advertisements in the newspaper. Subjects (aged 21–69 years) with nascent MetS (n = 37) and control subjects (n = 32) were studied. MetS was defined using the criteria of the NCEP ATP III as described previously [2]. Subjects were classified as nascent MetS [29] since they did not have diabetes (Fasting plasma glucose <125 mg/dl and HbA_1C<6.5% (<47.5 mmol/mol) and/or clinical cardiovascular disease (Coronary

Results

As depicted in Table 1 patients with nascent MetS, whilst matched for gender and age, had significant abnormalities for all cardio-metabolic features of the MetS. In addition both hsCRP, the prototypic marker of inflammation and HOMA-IR were significantly increased.

In accord with our previous report for this entire cohort [5] both TLR2 (36 ± 22 vs 24 ± 11 MFI/10⁴ cells, p = 0.01) and TLR4 (38 ± 22 vs 22 ± 8 MFI/10⁴ cells, p = 0.0003) receptor abundance were significantly increased in nascent

Discussion

The paucity of data especially with respect to the PAMP-binding protein, sCD14 in MetS, prompted this study. In this report we show, even following adjustment for adiposity, that there are significant increases in plasma levels of sCD14 and LBP in MetS compared to controls. These data suggest that they are also features of MetS since levels remained significant following adjustment for adiposity. The more significant increase in sCD14 is not surprising given the strong correlation of LBP with

Funding

The study was supported by grant from American Diabetes Association (to I.J.).

Conflict of interest

There are no potential conflicts of interest related to this article and the authors have nothing to disclose.

Contribution statement

I.J. supervised the study and contributed to manuscript preparation. U.R. helped with performing assays and manuscript preparation. B.A-H. performed all statistical analyses. H.K. helped with performing assays and manuscript preparation.

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The Yin and Yang of toll-like receptors in endothelial dysfunction
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Not only does sCD14 increase TLR4 activity, but it also increases the TLR4 chief downstream mediators such as TNFa, IL-8, IL-1b, and NF-kB in developing metabolic syndrome. Also, HMGB-1 can emerge and capture cellular inflammation [263]. TLR4 signaling pathway in the epithelium of the intestine plays a crucial role in metabolic syndrome via the host metabolic and microbial signaling pathway [264].
Endothelial cells (ECs) play a critical role in health and disease due to their widespread distribution and unique location. Although ECs are not regarded as classical immune cells, they actively participate in innate immune and inflammatory responses. EC function is affected by exogenous activators (i.e., infectious agents) and endogenous triggers (i.e., damage-associated molecular pattern molecules (DAMPs) released by stressed or injured cells). Toll-like receptors (TLRs) can recognize both infectious agents and DAMPs and play a key role in activating innate mechanisms in ECs. Endothelial dysfunction (EDF) may lead to tissue damage in various inflammatory and autoimmune diseases through TLRs. This review summarizes the current knowledge about the role of TLRs in a variety of EDF-related conditions, including autoimmunity and graft rejection, cancer, cardiovascular diseases, diabetes and related complications, ischemia and related injuries, and sepsis.
HMGB1 signaling pathway in diabetes-related dementia: Blood-brain barrier breakdown, brain insulin resistance, and Aβ accumulation
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The activation of JNK suppresses insulin sensitivity and contributes to the phosphorylation of IRS-1 and IRS-2 on serine 307 and 310 residues, respectively [197,205]. Recent studies highlighted that the circulating levels of HMGB1 were increased in patients with type 2 diabetes and in obese patients compared to normal subjects based on a positive correlation with HOMA-IR [203,204]. More recently, the interaction of TREM-1, TLR4, and RAGE with HMGB1 was strongly linked to insulin resistance in patients with obesity [206].
Diabetes contributes to the onset of various diseases, including cancer and cardiovascular and neurodegenerative diseases. Recent studies have highlighted the similarities and relationship between diabetes and dementia as an important issue for treating diabetes-related cognitive deficits. Diabetes-related dementia exhibits several features, including blood-brain barrier disruption, brain insulin resistance, and Aβ over-accumulation. High-mobility group box1 (HMGB1) is a protein known to regulate gene transcription and cellular mechanisms by binding to DNA or chromatin via receptor for advanced glycation end-products (RAGE) and toll-like receptor 4 (TLR4). Recent studies have demonstrated that the interplay between HMGB1, RAGE, and TLR4 can impact both neuropathology and diabetic alterations. Herein, we review the recent research regarding the roles of HMGB1-RAGE-TLR4 axis in diabetes-related dementia from several perspectives and emphasize the importance of the influence of HMGB1 in diabetes-related dementia.
The effect of increasing tertiles of waist circumference on cardio-metabolic risk, adipokines and biomarkers of inflammation and oxidative stress in nascent metabolic syndrome
2018, Journal of Diabetes and its Complications
The effect of waist circumference (WC) on cardio-metabolic features and biomarkers of oxidative stress and inflammation and adipose tissue dysregulation is poorly defined in Metabolic Syndrome (MetS). Hence the aim of this study was to examine the effect of increasing tertiles of WC on the cardio metabolic risk profile, pro-oxidant state, pro-inflammatory state and adipose tissue dysregulation in nascent MetS patients (n = 59) without diabetes or CVD.
None of the main cardio-metabolic features including blood pressure, blood glucose, HDL-cholesterol, triglycerides, HOMA-IR, and free fatty acids increased with increasing WC tertiles except for hsCRP. In addition, none of the biomarkers of oxidative stress increased with increasing WC. Other circulating and cellular bio-mediators of inflammation and adipokines did not show significant increase with increasing WC. Using the waist to height ratio (WHtR) also did not reveal any major findings with increasing tertiles.
In conclusion, in a well-defined cohort of MetS we failed to show any superiority of either WC or WHtR compared to BMI in capturing the cardio-metabolic cluster, adipose tissue dysregulation and the increased burden of oxidative stress and inflammation in this pilot study. These observations need confirmation in larger studies.
The effect of increasing body mass index on cardio-metabolic risk and biomarkers of oxidative stress and inflammation in nascent metabolic syndrome
2017, Journal of Diabetes and its Complications
The effect of BMI defined obesity on cardio-metabolic features and biomarkers of oxidative stress and inflammation in patients with nascent metabolic Syndrome (MetS) is poorly defined. Hence the aim of this study was to examine the effect of increasing obesity on the cardio metabolic risk profile, pro-oxidant state and pro-inflammatory features in nascent MetS patients without Diabetes or CVD. MetS was diagnosed by ATPIII criteria using waist circumference (WC) as the measure of adiposity. Patients (n = 58) were stratified into overweight, obese and extreme obesity groups using BMI cut offs of 25–29.9, 30–39.9 kg/m² and ≥ 40 kg/m² and cardio-metabolic features, circulating and cellular biomarkers of oxidative stress and inflammation were determined and correlated with BMI. None of the main cardio-metabolic features including blood pressure, blood glucose, HDL-cholesterol, triglycerides, HOMA-IR, free fatty acids were increased with increasing BMI. Also none of the biomarkers of oxidative stress (ox-LDL, nitrotyrosine and monocyte superoxide anion release) were increased with increasing BMI. However, significant increase in hsCRP, the soluble TNFR1 and sTNFR2 and leptin, were observed with increasing adiposity. Other inflammatory bio-mediators (IL-1β, IL-6, IL-8, MCP-1, Toll-like receptors 2–4), endotoxin, LBP, sCD14 and HMGB1, adiponectin, and chemerin did not show significant increases with increasing BMI. Leptin, hsCRP, sTNFR1, and sTNFR2 correlated significantly with BMI. In conclusion, capturing the cardio-metabolic cluster of MetS that predisposed to both increased risk of diabetes and CVD, using waist circumference, as one of the 5 diagnostic criteria is sufficient and BMI does not appear to afford any major incremental benefit on the cardio-metabolic risk factors, increased oxidative stress and the majority of both cellular and circulating biomarkers of inflammation.
Factors that promote macrophage homing to adipose tissue in metabolic syndrome
2016, Journal of Diabetes and its Complications
Metabolic syndrome (MetS), a common cardio-metabolic cluster, predisposes to both increased cardiovascular disease and diabetes. Both adipose tissue and monocyte/macrophages contribute to the increased inflammation in MetS. However there are sparse data on factors that determine macrophage recruitment into adipose tissue (AT). In this preliminary report in patients with MetS, without the confounding of diabetes and cardiovascular diseases, we show that plasma resistin, soluble CD14 and monocyte p38 MAP kinase activity correlate significantly with AT macrophage density and hence could be important biomediators of macrophage homing to AT in MetS. However larger studies are required to confirm these novel findings and elucidate other important factors.
The role of the high-mobility group box1 protein–Toll like receptor pathway in diabetic vascular disease
2016, Journal of Diabetes and its Complications
Citation Excerpt :
There is a paucity of data on the direct role of HMGB-1 in MetS. In a recent study by Jialal, Rajamani, Adams-Huet, and Kaur (2014) in patients with MetS, they showed significantly increased levels of circulating HMGB-1 in patients after adjustment for adiposity and also the levels showed significant increase with increasing cardio-metabolic features of MetS. Although HMGB-1 correlated with HOMA-IR and NF-kB activity, they did not find significant correlations with TLR4 or TLR2.
Objectives: Increased Toll like receptors (TLRs) especially 2 and 4 have been demonstrated in obesity, metabolic syndrome (MetS) and diabetes resulting in increased cellular inflammation. Since we have shown increased TLR2 and 4 activities in both T1DM and T2DM and MetS, we wanted to elucidate the mechanisms of this sterile inflammation. In T1DM, T2DM and MetS we have shown that high mobility group box 1 protein (HMGB-1), a non-histone DNA binding protein is increased and could be a potential activator of TLRs since it has previously shown to activate TLR2, 4 and 9. We examined the role of HMGB-1 in patients and animal models of diabetes and MetS to determine how important it is as an activator of TLR mediated inflammation and its role in diabetic vascular complications. Methods: A Medline search was conducted using the terms HMGB-1, TLRs and diabetes. Results: HMGB-1 levels are increased in patients with diabetes and MetS, and associated with increased biomediators of inflammation. Furthermore data supported a role of HMGB-1 in both diabetic microvascular and macrovascular complications. Conclusions: HMGB-1 interaction with TLRs is implicated in diabetic complications and could be important therapeutic target.

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Published by Elsevier Ltd.

Circulating pathogen associated molecular pattern – Binding proteins and High Mobility Group Box protein 1 in nascent metabolic syndrome: Implications for cellular Toll-like receptor activity

Highlights

Abstract

Objective

Methods

Results

Conclusion

Section snippets

Study participants

Results

Discussion

Funding

Conflict of interest

Contribution statement

J Hepatol

J Biol Chem

J Biol Chem

J Biol Chem

J Biol Chem

Atherosclerosis

J Biol Chem

Life Sci

Diagnosis and management of the metabolic syndrome: an American Heart Association/National Heart, Lung, and Blood Institute Scientific Statement

Circulation

Circulation

Nonalcoholic fatty liver disease: a manifestation of the metabolic syndrome

Cleve Clin J Med

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

Pediatr Obes

Increased Toll-like receptor activity in patients with metabolic syndrome

Diabetes Care

Toll-like receptor status in obesity and metabolic syndrome: a translational perspective

J Clin Endocrinol Metab

Modulatory effects of sCD14 and LBP on LPS-host cell interactions

J Endotoxin Res

Lipopolysaccharide activation of human endothelial and epithelial cells is mediated by lipopolysaccharide-binding protein and soluble CD14

Proc Natl Acad Sci U S A

Cell-free pool of CD14 mediates activation of transcription factor NF-kappa B by lipopolysaccharide in human endothelial cells

Proc Natl Acad Sci U S A

Metabolic endotoxemia initiates obesity and insulin resistance

Diabetes

CD14 modulates inflammation-driven insulin resistance

Diabetes

A genetic basis for the “Adonis” phenotype of low adiposity and strong bones

FASEB J