The role of soluble receptor for advanced glycation end-products (sRAGE) in the general population and patients with diabetes mellitus with a focus on renal function and overall outcome

The possible therapeutic role of advanced glycation end-product inhibitors in ischemic stroke

The advanced glycation end-products (AGEs) are toxic molecules result from non-enzymatic interactions of sugar with lipids or proteins. AGEs promote the generation of reactive oxygen species that induce the release of pro-inflammatory cytokines, and alter the intracellular signaling leading to progressive biochemical and metabolic derangements. AGEs-induced cellular aging is implicated in the development and progression of different neurological disorders such as dementia, neuropsychiatric disorders, and cerebrovascular diseases. Particularly, AGEs-induced microangiopathy and macroangiopathy trigger the induction of prothrombotic/thrombotic cascades with subsequent increase risk of acute ischemic stroke (AIS). Many studies highlighted that AGEs serum levels are correlated with the incidence, pathogenicity, and severity of AIS. However, the relationship between AGEs and AIS is not elucidated completely. Therefore, this review aims to discuss how AGEs promote the development and progression of AIS, and how AGEs inhibitors could be effective in the management of AIS.

The Role of P53 in Myocardial Ischemia-Reperfusion Injury

PURPOSE

P53 is one of the key tumor suppressors. In normal cells, p53 is maintained at low levels by the ubiquitination of the ubiquitinated ligase MDM2. In contrast, under stress conditions such as DNA damage and ischemia, the interaction between p53 and MDM2 is blocked and activated by phosphorylation and acetylation, thereby mediating the trans-activation of p53 through its target genes to regulate a variety of cellular responses. Previous studies have shown that the expression of p53 is negligible in normal myocardium, tends to increase in myocardial ischemia and is maximally induced in ischemia-reperfused myocardium, demonstrating a possible key role of p53 in the development of MIRI. In this review, we detail and summarize recent studies on the mechanism of action of p53 in MIRI and describe the therapeutic agents targeting the relevant targets to provide new strategies for the prevention and treatment of MIRI.

METHODS

We collected 161 relevant papers mainly from Pubmed and Web of Science (search terms "p53" and "myocardial ischemia-reperfusion injury"). After that, we selected pathway studies related to p53 and classified them according to their contents. We eventually analyzed and summarized them.

RESULTS AND CONCLUSION

In this review, we detail and summarize recent studies on the mechanism of action of p53 in MIRI and validate its status as an important intermediate affecting MIRI. On the one hand, p53 is regulated and modified by multiple factors, especially non-coding RNAs; on the other hand, p53 regulates apoptosis, programmed necrosis, autophagy, iron death and oxidative stress in MIRI through multiple pathways. More importantly, several studies have reported medications targeting p53-related therapeutic targets. These medications are expected to be effective options for the alleviation of MIRI, but further safety and clinical studies are needed to convert them into clinical applications.

Cardiovascular Risk Biomarkers in Women with and Without Polycystic Ovary Syndrome

OBJECTIVE

Polycystic ovary syndrome (PCOS) is a prevalent metabolic disorder with an increased risk for cardiovascular disease (CVD) that is enhanced by obesity. This study sought to determine whether a panel of cardiovascular risk proteins (CVRPs) would be dysregulated in overweight/obese PCOS patients, highlighting potential biomarkers for CVD in PCOS.

METHODS

In this exploratory cross-sectional study, plasma levels of 54 CVRPs were analyzed in women with PCOS (n = 147) and controls (n = 97). CVRPs were measured using the SOMAscan proteomic platform (version 3.1), with significant proteins identified through linear models, regression analysis, and receiver operating characteristic (ROC) analysis. Analysis on BMI-matched subsets of the cohort were undertaken. Functional enrichment and protein-protein interaction analyses elucidated the pathways involved.

RESULTS

Eleven CVRPs were dysregulated in PCOS (whole set, without matching for body mass index (BMI) or insulin resistance (IR)): leptin, Interleukin-1 receptor antagonist protein (IL-1Ra), polymeric immunoglobulin receptor (PIGR), interleukin-18 receptor (IL-18Ra), C-C motif chemokine 3 (MIP-1a), and angiopoietin-1 (ANGPT1) were upregulated whilst advanced glycosylation end product-specific receptor, soluble (sRAGE), bone morphogenetic protein 6 (BMP6); growth/differentiation factor 2 (GDF2), superoxide dismutase [Mn] mitochondrial (MnSOD), and SLAM family member 5 (SLAF5) were downregulated versus the controls. In BMI-matched (overweight/obese, BMI ≥ 26 kg/m2) subset analysis, six CVRPs were common to the whole set: ANGPT1 and IL-1Ra were upregulated; and sRAGE, BMP6, GDF2, and Mn-SOD were downregulated. In addition, lymphotactin (XCL1) was upregulated and placenta growth factor (PIGF), alpha-L-iduronidase (IDUA), angiopoietin-1 receptor, and soluble (sTie-2) and macrophage metalloelastase (MMP12) were downregulated. A subset analysis of BMI-matched plus insulin resistance (IR)-matched women revealed only upregulation of tissue factor (TF) and renin in PCOS, potentially serving as biomarkers for cardiovascular risk in overweight/obese women with PCOS.

CONCLUSIONS

A combination of upregulated obesity-related CVRPs (ANGPT1/IL/1Ra/XCL1) and downregulated cardioprotective proteins (sRAGE/BMP6/Mn-SOD/GDF2) in overweight/obese PCOS women may contribute to the increased risk for CVD. TF and renin upregulation observed in the BMI- and IR-matched limited sample PCOS subgroup indicates their potential risk of CVD.

Receptor for advanced glycation end products polymorphisms in coronary artery ectasia

BACKGROUND

Although the implication of receptor of advanced glycation endproducts (RAGE) has been reported in coronary artery disease, its roles in coronary artery ectasia (CAE) have remained undetermined. Furthermore, the effect of RAGE polymorfisms were not well-defined in scope of soluble RAGE (sRAGE) levels. Thus, we aimed to investigate the influence of the functional polymorphisms of RAGE -374T > A (rs1800624) and G82S (rs2070600) in CAE development.

METHODS

This prospective observational study was conducted in 2 groups selected of 2452 patients who underwent elective coronary angiography (CAG) for evaluation after positive noninvasive heart tests. Group-I included 98 patients with non-obstructive coronary artery disease and CAE, and Group-II (control) included 100 patients with normal coronary arteries. SNPs were genotyped by real-time PCR using Taqman® genotyping assay. Serum sRAGE and soluble lectin-like oxidized receptor-1 (sOLR1) were assayed by ELISA and serum lipids were measured enzymatically.

RESULTS

The frequencies of the RAGE -374A allele and -374AA genotype were significantly higher in CAE patients compared to controls (p < 0.001). sRAGE levels were not different between study groups, while sOLR1 levels were elevated in CAE (p = 0.004). In controls without systemic disease, -374A allele was associated with low sRAGE levels (p < 0.05), but this association was not significant in controls with HT. Similarly, sRAGE levels of CAE patients with both HT and T2DM were higher than those no systemic disease (p = 0.02). The -374A allele was also associated with younger patient age and higher platelet count in the CAE group in both total and subgroup analyses. In the correlation analyses, the -374A allele was also negatively correlated with age and positively correlated with Plt in all of these CAE groups. In the total CAE group, sRAGE levels also showed a positive correlation with age and a negative correlation with HDL-cholesterol levels. On the other hand, a negative correlation was observed between sRAGE and Plt in the total, hypertensive and no systemic disease control subgroups. Multivariate logistic regression analysis confirmed that the -374A allele (p < 0.001), hyperlipidemia (p < 0.05), and high sOLR1 level (p < 0.05) are risk factors for CAE. ROC curve analysis shows that RAGE -374A allele has AUC of 0.713 (sensitivity: 83.7 %, specificity: 59.0 %), which is higher than HLD (sensitivity: 59.2 %, specificity: 69.0 %), HT (sensitivity: 62.4 %, specificity: 61.1 %) and high sOLR1 level (≥0.67 ng/ml)) (sensitivity: 59.8 %, specificity: 58.5 %).

CONCLUSION

Beside the demonstration of the relationship between -374A allele and increased risk of CAE for the first time, our results indicate that antihypertensive and antidiabetic treatment in CAE patients causes an increase in sRAGE levels. The lack of an association between the expected -374A allele and low sRAGE levels in total CAE group was attributed to the high proportion of hypertensive patients and hence to antihypertensive treatment. Moreover, the RAGE -374A allele is associated with younger age at CAE and higher Plt, suggesting that -374A may also be associated with platelet activation, which plays a role in the pathogenesis of CAE. However, our data need to be confirmed in a large study for definitive conclusions.

Correlation between circulating advanced glycation end products and thioredoxin-interacting protein levels and renal fat content in type 2 diabetes mellitus patients

BACKGROUND

This study sought to explore the clinical relevance of the associations of serum levels of advanced glycation end products (AGEs), soluble receptor for AGEs (sRAGE), and thioredoxin-interacting protein (TXNIP) with the renal fat fraction (RFF) in individuals with type 2 diabetes mellitus (T2DM).

METHODS

A total of 133 patients with T2DM were enrolled in the study. RFF, which represents the renal fat level, was determined utilizing Dixon magnetic resonance imaging (MRI). Serum levels of AGEs, sRAGE, TXNIP, and other biochemical parameters were measured in patients who fasted.

RESULTS

RFF in T2DM patients was positively correlated with the fasting levels of C-peptide (CP), triglycerides (TG), AGEs, TXNIP, and sRAGE (P < 0.05) and negatively correlated with the high-density lipoprotein cholesterol (HDL-c) level (P < 0.05). Pearson's correlation analysis indicated that the serum levels of AGEs, sRAGE, and TXNIP were interrelated and positively correlated (P < 0.05). Then, all patients were assigned to four groups according to the RFF quartile. The HC, CP, TG, AGEs, sRAGE, TXNIP, and DKD percentages tended to increase as the RFF quartiles increased, while the HDL-c level tended to decrease (p for trend < 0.05). Next, multiple linear regression analysis was performed using RFF as the dependent variable. After controlling for covariates related to RFF, the results showed that the serum levels of AGEs and TXNIP were still significantly correlated with RFF.

CONCLUSION

These results suggest that circulating AGEs and TXNIP levels may be associated with ectopic fat accumulation in the kidneys of T2DM patients and may serve as indicators of the severity of renal fat deposition.

The effect of a combined lifestyle intervention with and without protein drink on inflammation in older adults with obesity and type 2 diabetes

BACKGROUND

Chronic low-grade inflammatory profile (CLIP) is one of the pathways involved in type 2 diabetes (T2D). Currently, there is limited evidence for ameliorating effects of combined lifestyle interventions on CLIP in type 2 diabetes. We investigated whether a 13-week combined lifestyle intervention, using hypocaloric diet and resistance exercise plus high-intensity interval training with or without consumption of a protein drink, affected CLIP in older adults with T2D.

METHODS

In this post-hoc analysis of the PROBE study 114 adults (≥55 years) with obesity and type 2 (pre-)diabetes had measurements of C-reactive protein (CRP), pro-inflammatory cytokines interleukin (IL)-6, tumor-necrosis-factor (TNF)-α, and monocyte chemoattractant protein (MCP)-1, anti-inflammatory cytokines IL-10, IL-1 receptor antagonist (RA), and soluble tumor-necrosis-factor receptor (sTNFR)1, adipokines leptin and adiponectin, and glycation biomarkers carboxymethyl-lysine (CML) and soluble receptor for advanced glycation end products (sRAGE) from fasting blood samples. A linear mixed model was used to evaluate change in inflammatory biomarkers after lifestyle intervention and effect of the protein drink. Linear regression analysis was performed with parameters of body composition (by dual-energy X-ray absorptiometry) and parameters of insulin resistance (by oral glucose tolerance test).

RESULTS

There were no significant differences in CLIP responses between the protein and the control groups. For all participants combined, IL-1RA, leptin and adiponectin decreased after 13 weeks (p = 0.002, p < 0.001 and p < 0.001), while ratios TNF-α/IL-10 and TNF-α/IL-1RA increased (p = 0.003 and p = 0.035). CRP increased by 12 % in participants with low to average CLIP (pre 1.91 ± 0.39 mg/L, post 2.13 ± 1.16 mg/L, p = 0.006) and decreased by 36 % in those with high CLIP (pre 5.14 mg/L ± 1.20, post 3.30 ± 2.29 mg/L, p < 0.001). Change in leptin and IL-1RA was positively associated with change in fat mass (β = 0.133, p < 0.001; β = 0.017, p < 0.001) and insulin resistance (β = 0.095, p = 0.024; β = 0.020, p = 0.001). Change in lean mass was not associated with any of the biomarkers.

CONCLUSION

13 weeks of combined lifestyle intervention, either with or without protein drink, reduced circulating adipokines and anti-inflammatory cytokine IL-1RA, and increased inflammatory ratios TNF-α/IL-10 and TNF-α/IL-1RA in older adults with obesity and T2D. Effect on CLIP was inversely related to baseline inflammatory status.

Inulin Reduces Kidney Damage in Type 2 Diabetic Mice by Decreasing Inflammation and Serum Metabolomics

This study is aimed at assessing the impact of soluble dietary fiber inulin on the treatment of diabetes-related chronic inflammation and kidney injury in mice with type 2 diabetes (T2DM). The T2DM model was created by feeding the Institute of Cancer Research (ICR) mice a high-fat diet and intraperitoneally injecting them with streptozotocin (50 mg/kg for 5 consecutive days). The thirty-six ICR mice were divided into three dietary groups: the normal control (NC) group, the T2DM (DM) group, and the DM + inulin diet (INU) group. The INU group mice were given inulin at the dose of 500 mg/kg gavage daily until the end of the 12th week. After 12 weeks, the administration of inulin resulted in decreased serum levels of fasting blood glucose (FBG), low-density lipoprotein cholesterol (LDL-C), blood urea nitrogen (BUN), and creatinine (CRE). The administration of inulin not only ameliorated renal injury but also resulted in a reduction in the mRNA expressions of inflammatory factors in the spleen and serum oxidative stress levels, when compared to the DM group. Additionally, inulin treatment in mice with a T2DM model led to a significant increase in the concentrations of three primary short-chain fatty acids (SCFAs) (acetic acid, propionic acid, and butyric acid), while the concentration of advanced glycation end products (AGEs), a prominent inflammatory factor in diabetes, exhibited a significant decrease. The results of untargeted metabolomics indicate that inulin has the potential to alleviate inflammatory response and kidney damage in diabetic mice. This beneficial effect is attributed to its impact on various metabolic pathways, including glycerophospholipid metabolism, taurine and hypotaurine metabolism, arginine biosynthesis, and tryptophan metabolism. Consequently, oral inulin emerges as a promising treatment option for diabetes and kidney injury.

Advanced glycation end products of dietary origin and their association with inflammation in diabetes - A minireview

Advanced glycation end products (AGEs) are a diverse group of compounds that are formed as a result of the non-enzymatic reaction between a reducing sugar such as glucose and the free NH2 groups of an amino acid in a protein or other biomolecule. The chemical reaction, by which these products are generated, is known as the Maillard reaction and occurs as a part of the body's normal metabolism. Such a reaction is enhanced during diabetes due to hyperglycemia, but it can also occur during the preparation, processing, and preservation of certain foods. Therefore, AGEs can also be obtained from the diet (d-AGE) and contribute to an increase of the total serum pool of these compounds. They have been implicated in a wide variety of pathological processes, mainly because of their ability to induce inflammatory responses and oxidative stress increase. They are extensively accumulated as a part of the normal aging, especially in tissues rich in long half-life proteins, which can compromise the physiology of these tissues. d-AGEs are abundant in diets rich in processed fats and sugars. This review is addressed to the current knowledge on these products and their impact on the immunomodulation of various mechanisms that may contribute to exacerbation of the diabetes pathophysiology.

Lactiplantibacillus plantarum NKK20 Increases Intestinal Butyrate Production and Inhibits Type 2 Diabetic Kidney Injury through PI3K/Akt Pathway

Nephropathy injury is a prevalent complication observed in individuals with diabetes, serving as a prominent contributor to end-stage renal disease, and the advanced glycation products (AGEs) are important factors that induce kidney injury in patients with diabetes. Addressing this condition remains a challenging aspect in clinical practice. The aim of this study was to explore the effects of Lactiplantibacillus plantarum NKK20 strain (NKK20) which protects against diabetic kidney disease (DKD) based on animal and cell models. The results showed that the NKK20 can significantly reduce renal inflammatory response, serum oxidative stress response, and AGE concentration in diabetic mice. After treatment with NKK20, the kidney damage of diabetic mice was significantly improved, and more importantly, the concentration of butyrate, a specific anti-inflammatory metabolite of intestinal flora in the stool of diabetic mice, was significantly increased. In addition, nontargeted metabolomics analysis showed a significant difference between the metabolites in the mouse serum contents of the NKK20 administration group and those in the nephropathy injury group, in which a total of 24 different metabolites that were significantly affected by NKK20 were observed, and these metabolites were mainly involved in glycerophospholipid metabolism and arachidonic acid metabolism. Also, the administration of butyrate to human kidney- (HK-) 2 cells that were stimulated by AGEs resulted in a significant upregulation of ZO-1, Occludin, and E-cadherin gene expressions and downregulation of α-SMA gene expression. This means that butyrate can maintain the tight junction structure of HK-2 cells and inhibit fibrosis. Butyrate also significantly inhibited the activation of PI3K/Akt pathway. These results indicate that NKK20 can treat kidney injury in diabetic mice by reducing blood glucose and AGE concentration and increasing butyrate production in the intestine. By inhibiting PI3K pathway activation in HK-2 cells, butyrate maintains a tight junction structure of renal tubule epithelial cells and inhibits renal tissue fibrosis. These results suggest that NKK20 is helpful to prevent and treat the occurrence and aggravation of diabetic kidney injury.

Proteomic insights into the associations between obesity, lifestyle factors, and coronary artery disease

BACKGROUND

We aimed to investigate the protein pathways linking obesity and lifestyle factors to coronary artery disease (CAD).

METHODS

Summary-level genome-wide association statistics of CAD were obtained from the CARDIoGRAMplusC4D consortium (60,801 cases and 123,504 controls) and the FinnGen study (R8, 39,036 cases and 303,463 controls). Proteome-wide Mendelian randomization (MR) analysis was conducted to identify CAD-associated blood proteins, supplemented by colocalization analysis to minimize potential bias caused by linkage disequilibrium. Two-sample MR analyses were performed to assess the associations of genetically predicted four obesity measures and 13 lifestyle factors with CAD risk and CAD-associated proteins' levels. A two-step network MR analysis was conducted to explore the mediating effects of proteins in the associations between these modifiable factors and CAD.

RESULTS

Genetically predicted levels of 41 circulating proteins were associated with CAD, and 17 of them were supported by medium to high colocalization evidence. PTK7 (protein tyrosine kinase-7), RGMB (repulsive guidance molecule BMP co-receptor B), TAGLN2 (transgelin-2), TIMP3 (tissue inhibitor of metalloproteinases 3), and VIM (vimentin) were identified as promising therapeutic targets. Several proteins were found to mediate the associations between some modifiable factors and CAD, with PCSK9, C1S, AGER (advanced glycosylation end product-specific receptor), and MST1 (mammalian Ste20-like kinase 1) exhibiting highest frequency among the mediating networks.

CONCLUSIONS

This study suggests pathways explaining the associations of obesity and lifestyle factors with CAD from alterations in blood protein levels. These insights may be used to prioritize therapeutic intervention for further study.

Crosstalk between Aldosterone and Glycation through Rac-1 Induces Diabetic Nephropathy

Background: Advanced glycation end products (AGEs) interaction with its receptor (RAGE) and aldosterone (Aldo) through the mineralocorticoid receptor (MR) activates Rac-1 and NF-κB independently in diabetic nephropathy (DN). However, the crosstalk of Aldo with AGEs-RAGE is still unresolved. Our study examined the impact of the AGEs-Aldo complex on renal cells and its effect on the RAGE-MR interaction. Methods and results: Glycation of human serum albumin (HSA) (40 mg/mL) with methylglyoxal (10 mM) in the presence of Aldo (100 nM) and aminoguanidine (AG) (100 nM) was performed. Glycation markers such as fructosamine and carbonyl groups and fluorescence of AGEs, pentosidine, and tryptophan followed by protein modification were measured. Renal (HEK-293T) cells were treated with the glycated HSA-Aldo (200 μg/mL) along with FPS-ZM1 and spironolactone antagonists for RAGE and Aldo, respectively, for 24 h. Glycation markers and esRAGE levels were measured. Protein and mRNA levels of RAGE, MR, Rac-1, and NF-κB were estimated. Glycation markers were enhanced with Aldo when albumin was only 14-16% glycated. AGEs-Aldo complex upregulated RAGE, MR, Rac-1 and NF-κB expressions. However, FPS-ZM1 action might have activated the RAGE-independent pathway, further elevating MR, Rac-1, and NF-κB levels. Conclusion: Our study concluded that the presence of Aldo has a significant impact on glycation. In the presence of AGEs-Aldo, RAGE-MR crosstalk exerts inflammatory responses through Rac-1 in DN. Insights into this molecular interplay are crucial for developing novel therapeutic strategies to alleviate DN in the future.

Qidan Tiaozhi capsule attenuates metabolic syndrome via activating AMPK/PINK1-Parkin-mediated mitophagy

ETHNOPHARMACOLOGICAL RELEVANCE

Qidan Tiaozhi capsule (QD), a traditional Chinese medicine, has been used to treat metabolic syndrome for over a decade. However, the mechanism of QD in the treatment of metabolic syndrome is still unknown.

AIM OF THE STUDY

Growing studies demonstrate that impaired mitophagy is one of the important causes of metabolic syndrome. Thus, this research aims to investigate the mechanism of mitophagy in the QD treatment of metabolic syndrome.

MATERIALS AND METHODS

Network pharmacology and molecular docking were used to probe the mechanism of QD treatment of metabolic syndrome. In an oleic acid-induced cell model, glucose consumption and uptake capacity, triglyceride (TG), total cholesterol (TC), malonaldehyde (MDA), superoxide dismutase (SOD) and ROS levels, and mitochondrial membrane potential (MMP) were examined. mRFP-GFP-LC3 adenovirus and GFP-LC3 lentivirus were used to examine the effect of QD on mitophagy. The IRS2-PI3K and AMPK/PINK1-Parkin signal pathways were also determined. What's more, the PINK1 gene was silenced to verify the above findings. In a high-fat diet-fed mouse model, body weight, organ indexes, OGTT, ITT, HOMA-IR, insulin sensitivity, serum MDA, SOD, TC, TG, LDL-C and HDL-C, hepatic TC, TG, LDL-C and HDL-C levels, hepatic steatosis, and IRS2-PI3K and AMPK/PINK1-Parkin signal pathways were investigated.

RESULTS

Results from network pharmacology and molecular docking suggested that QD might suppress oxidative stress to improve metabolic syndrome. In an oleic acid-induced cell model, compared with the model group, enhanced glucose consumption and uptake ability, inhibited intracellular lipid accumulation, TC, TG, MDA and ROS levels, and increased SOD level and MMP were found in QD groups. And mitophagy levels, IRS2-PI3K and AMPK/PINK1-Parkin signal pathways were promoted. Interestingly, PINK1 silencing reversed the therapeutic action of QD on oleic acid-induced cells. In high-fat diet-fed mice, inhibited body weight, abdominal fat indexes, liver indexes, HOMA-IR, serum and hepatic TC, TG and LDL-C, serum MDA and hepatic steatosis, and increased insulin sensitivity, serum and hepatic HDL-C, serum SOD, and activated IRS2-PI3K and AMPK/PINK1-Parkin signal pathways were found in QD groups.

CONCLUSION

QD activates AMPK/PINK1-Parkin-mediated mitophagy to suppress oxidative stress to treat metabolic syndrome.

Blood and Tissue Advanced Glycation End Products as Determinants of Cardiometabolic Disorders Focusing on Human Studies

Cardiometabolic disorders are characterised by a cluster of interactive risk determinants such as increases in blood glucose, lipids and body weight, as well as elevated inflammation and oxidative stress and gut microbiome changes. These disorders are associated with onset of type 2 diabetes mellitus (T2DM) and cardiovascular disease (CVD). T2DM is strongly associated with CVD. Dietary advanced glycation end products (dAGEs) attributable from modern diets high in sugar and/or fat, highly processed foods and high heat-treated foods can contribute to metabolic etiologies of cardiometabolic disorders. This mini review aims to determine whether blood dAGEs levels and tissue dAGEs levels are determinants of the prevalence of cardiometabolic disorders through recent human studies. ELISA (enzyme-linked immunosorbent assay), high-performance liquid chromatography (HPLC), liquid chromatography-mass spectrometry (LC-MS) and gas chromatography-mass spectrometry (GC-MS) for blood dAGEs measurement and skin auto fluorescence (SAF) for skin AGEs measurement can be used. Recent human studies support that a diet high in AGEs can negatively influence glucose control, body weight, blood lipid levels and vascular health through the elevated oxidative stress, inflammation, blood pressure and endothelial dysfunction compared with a diet low in AGEs. Limited human studies suggested a diet high in AGEs could negatively alter gut microbiota. SAF could be considered as one of the predictors affecting risks for cardiometabolic disorders. More intervention studies are needed to determine how dAGEs are associated with the prevalence of cardiometabolic disorders through gut microbiota changes. Further human studies are conducted to find the association between CVD events, CVD mortality and total mortality through SAF measurement, and a consensus on whether tissue dAGEs act as a predictor of CVD is required.

Association of SARS-CoV-2 nucleocapsid viral antigen and the receptor for advanced glycation end products with development of severe disease in patients presenting to the emergency department with COVID-19

Introduction

There remains a need to better identify patients at highest risk for developing severe Coronavirus Disease 2019 (COVID-19) as additional waves of the pandemic continue to impact hospital systems. We sought to characterize the association of receptor for advanced glycation end products (RAGE), SARS-CoV-2 nucleocapsid viral antigen, and a panel of thromboinflammatory biomarkers with development of severe disease in patients presenting to the emergency department with symptomatic COVID-19.

Methods

Blood samples were collected on arrival from 77 patients with symptomatic COVID-19, and plasma levels of thromboinflammatory biomarkers were measured.

Results

Differences in biomarkers between those who did and did not develop severe disease or death 7 days after presentation were analyzed. After adjustment for multiple comparisons, RAGE, SARS-CoV-2 nucleocapsid viral antigen, interleukin (IL)-6, IL-10 and tumor necrosis factor receptor (TNFR)-1 were significantly elevated in the group who developed severe disease (all p<0.05). In a multivariable regression model, RAGE and SARS-CoV-2 nucleocapsid viral antigen remained significant risk factors for development of severe disease (both p<0.05), and each had sensitivity and specificity >80% on cut-point analysis.

Discussion

Elevated RAGE and SARS-CoV-2 nucleocapsid viral antigen on emergency department presentation are strongly associated with development of severe disease at 7 days. These findings are of clinical relevance for patient prognostication and triage as hospital systems continue to be overwhelmed. Further studies are warranted to determine the feasibility and utility of point-of care measurements of these biomarkers in the emergency department setting to improve patient prognostication and triage.

The Potential Influence of Advanced Glycation End Products and (s)RAGE in Rheumatic Diseases

Advanced glycation end products (AGEs) are a class of compounds formed by nonenzymatic interactions between reducing sugars and proteins, lipids, or nucleic acids. AGEs can alter the protein structure and activate one of their receptors, specifically the receptor for advanced glycation end products (RAGE). These phenomena impair the functions of cells, extracellular matrix, and tissues. RAGE is expressed by a variety of cells and has been linked to chronic inflammatory autoimmune disorders such as rheumatoid arthritis, systemic lupus erythematosus, and Sjögren's syndrome. The soluble (s)RAGE cleavage product is a positively charged 48-kDa cleavage product that retains the ligand binding site but loses the transmembrane and signaling domains. By acting as a decoy, this soluble receptor inhibits the pro-inflammatory processes mediated by RAGE and its ligands. In the present review, we will give an overview of the role of AGEs, sRAGE, and RAGE polymorphisms in several rheumatic diseases. AGE overproduction may play a role in the pathogenesis and is linked to accelerated atherosclerosis. Low serum sRAGE concentrations are linked to an increased cardiovascular risk profile and a poor prognosis. Some RAGE polymorphisms may be associated with increased disease susceptibility. Finally, sRAGE levels can be used to track disease progression.

Dietary Advanced Glycation End Products in an Elderly Population with Diabetic Nephropathy: An Exploratory Investigation

Advanced glycation end products (AGEs) are important in pathophysiology of type 2 diabetes mellitus (T2DM) and diabetic kidney disease (DKD). Dietary AGEs (dAGEs) contribute to the overall AGE pool in the body. Forty elderly T2DM patients with DKD were randomly allocated to a low-AGE (n = 20) or regular diabetic (n = 20) diet group. A three-day meal questionnaire was used to estimate average quantity of dAGEs. AGE accumulation was measured using skin autofluorescence and urine spectroscopy. sRAGE (soluble receptor AGE) was quantified using ELISA. After 8 weeks, the mean consumption of dAGEs was considerably reduced, both in the low-AGE diet (p = 0.004) and the control (p = 0.019) group. The expected urinary emission peak at 490 nm was shifted to 520 nm in some spectra. dAGEs did not correspond with urine AGE output. An AGE-limited diet for two months did not affect AGE content in skin and urine, or sRAGE concentration in the blood. The role of glycemia is likely to be greater than the impact of dAGE consumption. The unique observation of a fluorescence pattern at 520 nm warrants further examination, since it might point to genetic differences in AGE regulation, which could have clinical consequences, as AGE content depends on its formation and elimination.

The RAGE/DIAPH1 Signaling Axis & Implications for the Pathogenesis of Diabetic Complications

Increasing evidence links the RAGE (receptor for advanced glycation end products)/DIAPH1 (Diaphanous 1) signaling axis to the pathogenesis of diabetic complications. RAGE is a multi-ligand receptor and through these ligand-receptor interactions, extensive maladaptive effects are exerted on cell types and tissues targeted for dysfunction in hyperglycemia observed in both type 1 and type 2 diabetes. Recent evidence indicates that RAGE ligands, acting as damage-associated molecular patterns molecules, or DAMPs, through RAGE may impact interferon signaling pathways, specifically through upregulation of IRF7 (interferon regulatory factor 7), thereby heralding and evoking pro-inflammatory effects on vulnerable tissues. Although successful targeting of RAGE in the clinical milieu has, to date, not been met with success, recent approaches to target RAGE intracellular signaling may hold promise to fill this critical gap. This review focuses on recent examples of highlights and updates to the pathobiology of RAGE and DIAPH1 in diabetic complications.

Inflammation: A New Look at an Old Problem

Pro-inflammatory stress is inherent in any cells that are subject to damage or threat of damage. It is defined by a number of universal components, including oxidative stress, cellular response to DNA damage, unfolded protein response to mitochondrial and endoplasmic reticulum stress, changes in autophagy, inflammasome formation, non-coding RNA response, formation of an inducible network of signaling pathways, and epigenetic changes. The presence of an inducible receptor and secretory phenotype in many cells is the cause of tissue pro-inflammatory stress. The key phenomenon determining the occurrence of a classical inflammatory focus is the microvascular inflammatory response (exudation, leukocyte migration to the alteration zone). This same reaction at the systemic level leads to the development of life-critical systemic inflammation. From this standpoint, we can characterize the common mechanisms of pathologies that differ in their clinical appearance. The division of inflammation into alternative variants has deep evolutionary roots. Evolutionary aspects of inflammation are also described in the review. The aim of the review is to provide theoretical arguments for the need for an up-to-date theory of the relationship between key human pathological processes based on the integrative role of the molecular mechanisms of cellular and tissue pro-inflammatory stress.

Differences in kinetics and dynamics of endogenous versus exogenous advanced glycation end products (AGEs) and their precursors

Advanced glycation end products (AGEs) and their precursors, referred to as glycation products, are a heterogenous group of compounds being associated with adverse health effects. They are formed endogenously and in exogenous sources including food. This review investigates the roles of endogenously versus exogenously formed glycation products in the potential induction of adverse health effects, focusing on differences in toxicokinetics and toxicodynamics, which appeared to differ depending on the molecular mass of the glycation product. Based on the available data, exogenous low molecular mass (LMM) glycation products seem to be bioavailable and to contribute to dicarbonyl stress and protein cross-linking resulting in formation of endogenous AGEs. Bioavailability of exogenous high molecular mass (HMM) glycation products appears limited, while these bind to the AGE receptor (RAGE), initiating adverse health effects. Together, this suggests that RAGE-binding in relevant tissues will more likely result from endogenously formed glycation products. Effects on gut microbiota induced by glycation products is proposed as a third mode of action. Overall, studies which better discriminate between LMM and HMM glycation products and between endogenous and exogenous formation are needed to further elucidate the contributions of these different types and sources of glycation products to the ultimate biological effects.

Angiogenesis, Metabolism, Endothelial and Platelet Markers in Diabetes and Cardiovascular Disease

Introduction: Diabetes is a leading risk factor for cardiovascular disease (CVD), the pathophysiology of both being linked to metabolic, endothelial, renal, angiogenic and platelet abnormalities. We hypothesised that abnormalities in these systems are more adverse in those whose CVD is compounded by diabetes, compared to those with diabetes or CVD alone.

Materials and methods: Serum or plasma from 66 patients with diabetes alone, 76 with CVD alone, and 70 with both diabetes and CVD i.e. diabetic cardiovascular disease, was probed for markers of angiogenesis [angiopoietin 1 and 2, vascular endothelial growth factor (VEGF) and endoglin], metabolic [soluble receptor for advanced glycation products (sRAGE), leptin, lipocalin-2, interleukin-8, and cystatin-C], the endothelium (von Willebrand factor, endothelial microparticles and soluble E selectin)], and the platelet (platelet microparticles and soluble P selectin) by ELISA, Luminex or flow cytometry.

Results: VEGF (p = 0.04), von Willebrand factor (p = 0.001) and endothelial microparticles (p = 0.042) were all higher in diabetic cardiovascular disease than in diabetes alone and cardiovascular disease alone. Soluble E selectin was higher in diabetic cardiovascular disease than in diabetes alone (p = 0.045), whilst cystatin-C (p = 0.004) and soluble P selectin (p < 0.001) were higher in diabetes and diabetic cardiovascular disease than in cardiovascular disease alone. There were no differences in angiopoietin 1 or 2, endoglin, sRAGE, leptin, lipocalin-2, or interleukin-8.

Conclusion: Angiopoietin 1 or 2, endoglin, sRAGE, leptin, lipocalin-2, interleukin-8, and cystatin-c cannot differentiate diabetes from cardiovascular disease, or both conditions combined. Our data point to a more adverse endothelial (von Willebrand factor, endothelial microparticles), and angiogenic profile (VEGF) in those with diabetic cardiovascular disease, supporting the view that this group should be targeted more aggressively.

Advanced Glycation End-Products (AGEs) of Lysine and Effects of Anti-TCR/Anti-TNF-α Antibody-Based Therapy in the LEW.1AR1-iddm Rat, an Animal Model of Human Type 1 Diabetes

The LEW.1AR1-iddm rat is an animal model of human type 1 diabetes (T1D). Previously, we have shown that combination with anti-TCR/anti-TNF-α antibody-based therapy re-established normoglycemia and increased proteinic arginine-dimethylation in the spleen, yet not in the pancreas. High blood glucose is often associated with elevated formation of advanced glycation end-products (AGEs) which act via their receptor (RAGE). Both anti-TCR and anti-TNF-α are inhibitors of RAGE. The aim of the present work was to investigate potential biochemical changes of anti-TCR/anti-TNF-α therapy in the LEW.1AR1-iddm rat. We determined by stable-isotope dilution gas chromatography-mass spectrometry (GC-MS) the content of free and proteinic AGEs and the N^ε-monomethylation of lysine (Lys) residues in proteins of pancreas, kidney, liver, spleen and lymph nodes of normoglycemic control (ngCo, n = 6), acute diabetic (acT1D, n = 6), chronic diabetic (chT1D, n = 4), and cured (cuT1D, n = 4) rats after anti-TCR/anti-TNF-α therapy. Analyzed biomarkers included Lys and its metabolites N^ε-carboxymethyl lysine (CML), furosine and N^ε-monomethyl lysine (MML). Other amino acids were also determined. Statistical methods including ANOVA, principal component analysis (PCA) and orthogonal partial least squares discriminant analysis (OPLS-DA) were used to evaluate the effects. Most statistical differences between the study groups were observed for spleen, pancreas and kidney, with liver and lymph nodes showing no such differences. In the pancreas, the groups differed with respect to proteinic furosine (p = 0.0289) and free CML (p = 0.0023). In the kidneys, the groups differed with respect to proteinic furosine (p = 0.0076) and CML (p = 0.0270). In the spleen, group differences were found for proteinic furosine (p = 0.0114) and free furosine (p = 0.0368), as well as for proteinic CML (p = 0.0502) and proteinic MML (p = 0.0191). The acT1D rats had lower furosine, CML and MML levels in the spleen than the rats in all other groups. This observation corresponds to the lower citrullination levels previously measured in these rats. PCA revealed diametric associations between PC1 and PC2 for spleen (r = −0.8271, p < 0.0001) compared to pancreas (r = 0.5805, p = 0.0073) and kidney (r = 0.8692, p < 0.0001). These findings underscore the importance of the spleen in this animal model of human T1D. OPLS-DA showed that in total sixteen amino acids differed in the experimental groups.

Soluble Receptor for Advanced Glycation End Products (sRAGE) Is a Sensitive Biomarker in Human Pulmonary Arterial Hypertension

Pulmonary arterial hypertension (PAH) is a progressive condition with an unmet need for early diagnosis, better monitoring, and risk stratification. The receptor for advanced glycation end products (RAGE) is activated in response to hypoxia and vascular injury, and is associated with inflammation, cell proliferation and migration in PAH. For the adult cohort, we recruited 120 patients with PAH, 83 with idiopathic PAH (IPAH) and 37 with connective tissue disease-associated PAH (CTD-PAH), and 48 controls, and determined potential plasma biomarkers by enzyme-linked immunoassay. The established heart failure marker NTproBNP and IL-6 plasma levels were several-fold higher in both adult IPAH and CTD-PAH patients versus controls. Plasma soluble RAGE (sRAGE) was elevated in IPAH patients (3044 ± 215.2 pg/mL) and was even higher in CTD-PAH patients (3332 ± 321.6 pg/mL) versus controls (1766 ± 121.9 pg/mL; p < 0.01). All three markers were increased in WHO functional class II+III PAH versus controls (p < 0.001). Receiver-operating characteristic analysis revealed that sRAGE has diagnostic accuracy comparable to prognostic NTproBNP, and even outperforms NTproBNP in the distinction of PAH FC I from controls. Lung tissue RAGE expression was increased in IPAH versus controls (mRNA) and was located predominantly in the PA intima, media, and inflammatory cells in the perivascular space (immunohistochemistry). In the pediatric cohort, plasma sRAGE concentrations were higher than in adults, but were similar in PH (n = 10) and non-PH controls (n = 10). Taken together, in the largest adult sRAGE PAH study to date, we identify plasma sRAGE as a sensitive and accurate PAH biomarker with better performance than NTproBNP in the distinction of mild PAH from controls.

Inflammation Meets Metabolism: Roles for the Receptor for Advanced Glycation End Products Axis in Cardiovascular Disease

Fundamental modulation of energy metabolism in immune cells is increasingly being recognized for the ability to impart important changes in cellular properties. In homeostasis, cells of the innate immune system, such as monocytes, macrophages and dendritic cells (DCs), are enabled to respond rapidly to various forms of acute cellular and environmental stress, such as pathogens. In chronic stress milieus, these cells may undergo a re-programming, thereby triggering processes that may instigate tissue damage and failure of resolution. In settings of metabolic dysfunction, moieties such as excess sugars (glucose, fructose and sucrose) accumulate in the tissues and may form advanced glycation end products (AGEs), which are signaling ligands for the receptor for advanced glycation end products (RAGE). In addition, cellular accumulation of cholesterol species such as that occurring upon macrophage engulfment of dead/dying cells, presents these cells with a major challenge to metabolize/efflux excess cholesterol. RAGE contributes to reduced expression and activities of molecules mediating cholesterol efflux. This Review chronicles examples of the roles that sugars and cholesterol, via RAGE, play in immune cells in instigation of maladaptive cellular signaling and the mediation of chronic cellular stress. At this time, emerging roles for the ligand-RAGE axis in metabolism-mediated modulation of inflammatory signaling in immune cells are being unearthed and add to the growing body of factors underlying pathological immunometabolism.