Plasma glycation levels are associated with severity in sepsis

Effect of advanced glycation end-products in a wide range of medical problems including COVID-19

Glycation is a physiological process that determines the aging of the organism, while in states of metabolic disorders it is significantly intensified. High concentrations of compounds such as reducing sugars or reactive aldehydes derived from lipid oxidation, occurring for example in diabetes, atherosclerosis, dyslipidemia, obesity or metabolic syndrome, lead to increased glycation of proteins, lipids and nucleic acids. The level of advanced glycation end-products (AGEs) in the body depends on rapidity of their production and the rate of their removal by the urinary system. AGEs, accumulated in the extracellular matrix of the blood vessels and other organs, cause irreversible changes in the biochemical and biomechanical properties of tissues. As a consequence, micro- and macroangiopathies appear in the system, and may contribute to the organ failure, like kidneys and heart. Elevated levels of AGEs also increase the risk of Alzheimer's disease and various cancers. In this paper, we propose a new classification due to modified amino acid residues: arginyl-AGEs, monolysyl-AGEs and lysyl-arginyl-AGEs and dilysyl-AGEs. Furthermore, we describe in detail the effect of AGEs on the pathogenesis of metabolic and old age diseases, such as diabetic complications, atherosclerosis and neurodegenerative diseases. We summarize the currently available data on the diagnostic value of AGEs and present the AGEs as a therapeutic goal in a wide range of medical problems, including SARS-CoV-2 infection and so-called long COVID.

First-Days Reduction of Plasma and Skin Advanced Glycation End Products is Related to Outcome in Septic Patients

BACKGROUND

Advanced glycation end products (AGEs) are a result of nonenzymatic glycation of proteins and lipids, which can attach to either their cell surface receptor (RAGE) or its soluble form (sRAGE). Evidence exists for the implication of AGE-RAGE axis in sepsis, but data are still insufficient and conflicting. We aimed to analyze the kinetics of plasma and skin AGEs and sRAGE during sepsis, and their association with outcome in septic patients.

METHODS

We performed a prospective observational study. We enrolled 90 consecutive patients with severe sepsis or septic shock, within the first 24 h of Intensive Care Unit admission. During the first 5 days of sepsis, we measured plasma autofluorescence (PAF) and skin autofluorescence (SAF) as surrogates of circulating and skin AGEs, respectively. sRAGE was measured on days 1, 3, and 5. Delta values were defined as the difference between the PAF, SAF, or sRAGE on a specific day and the value on day 1.

RESULTS

28-day mortality was 18%. Bivariate analysis found that ΔPAF3-1, ΔPAF4-1, ΔPAF5-1, and ΔSAF5-1 were significantly associated with 28-day mortality. Additionally, sRAGE1 was inversely correlated to ΔPAF4-1 (r = -0.250, P = 0.019) and ΔPAF5-1 (r = -0.246, P = 0.024), and significantly associated with 28-day mortality. In an adjusted multivariate logistic regression analysis, ΔPAF2-1, ΔPAF3-1, ΔPAF4-1, ΔPAF5-1, and ΔSAF5-1 were associated with 28-day mortality.

CONCLUSIONS

Kinetics of plasma and skin AGEs during the first days of sepsis are independently associated with mortality, where a decrease of plasma and skin AGEs are related to higher mortality.

Targeting adaptor protein SLP76 of RAGE as a therapeutic approach for lethal sepsis

Accumulating evidence shows that RAGE has an important function in the pathogenesis of sepsis. However, the mechanisms by which RAGE transduces signals to downstream kinase cascades during septic shock are not clear. Here, we identify SLP76 as a binding partner for the cytosolic tail of RAGE both in vitro and in vivo and demonstrate that SLP76 binds RAGE through its sterile α motif (SAM) to mediate downstream signaling. Genetic deficiency of RAGE or SLP76 reduces AGE-induced phosphorylation of p38 MAPK, ERK1/2 and IKKα/β, as well as cytokine release. Delivery of the SAM domain into macrophages via the TAT cell-penetrating peptide blocks proinflammatory cytokine production. Furthermore, administration of TAT-SAM attenuates inflammatory cytokine release and tissue damage in mice subjected to cecal ligation and puncture (CLP) and protects these mice from the lethality of sepsis. These findings reveal an important function for SLP76 in RAGE-mediated pro-inflammatory signaling and shed light on the development of SLP76-targeted therapeutics for sepsis.

The Course of Skin and Serum Biomarkers of Advanced Glycation Endproducts and Its Association with Oxidative Stress, Inflammation, Disease Severity, and Mortality during ICU Admission in Critically Ill Patients: Results from a Prospective Pilot Study

Background

Advanced glycation end products (AGEs) have been implicated in multiple organ failure, predominantly via their cellular receptor (RAGE) in preclinical studies. Little is known about the time course and prognostic relevance of AGEs in critically ill human patients, including those with severe sepsis.

Objective

1) To explore the reliability of Skin Autofluorescence (AF) as an index of tissue AGEs in ICU patients, 2) to compare its levels to healthy controls, 3) to describe the time course of AGEs and influencing factors during ICU admission, and 4) to explore their association with disease severity, outcome, and markers of oxidative stress and inflammation.

Methods

Skin AF, serum N"-(carboxyethyl)lysine (CEL), N"-(carboxymethyl)lysine (CML), and soluble RAGE (sRAGE) were serially measured for a maximum of 7 days in critically ill ICU patients with multiple organ failure and compared to age-matched healthy controls. Correlations with (changes in) clinical parameters of disease severity, LDL dienes, and CRP were studied and survival analysis for in-hospital mortality was performed.

Results

Forty-five ICU patients (age: 59±15 years; 60% male), and 37 healthy controls (59±14; 68%) were included. Skin AF measurements in ICU patients were reproducible (CV right-left arm: 13%, day-to-day: 10%), with confounding effects of skin reflectance and plasma bilirubin levels. Skin AF was higher in ICU patients vs healthy controls (2.7±0.7 vs 1.8±0.3 au; p<0.001). Serum CEL (23±10 vs, 16±3 nmol/gr protein; p<0.001), LDL dienes (19 (15–23) vs. 9 (8–11) μmol/mmol cholesterol; <0.001), and sRAGE (1547 (998–2496) vs. 1042 (824–1388) pg/ml; p = 0.003) were significantly higher in ICU patients compared to healthy controls, while CML was not different (27 (20–39) vs 29 (25–33) nmol/gr protein). While CRP and LDL dienes decreased significantly, Skin AF and serum AGEs and sRAGE did not change significantly during the first 7 days of ICU admission. CML and CEL were strongly correlated with SOFA scores and CML above the median at baseline was associated with increased risk for mortality (Hazard ratio 3.3 (1.3–8.3); p = 0.01). All other markers did not correlate with disease severity and did not predict mortality.

Conclusions

This study demonstrates that markers for the AGE-RAGE axis are elevated in critically ill patients compared to healthy controls but remain stable for at least 7 days despite clearly fading inflammation and oxidative stress. Circulating AGEs may be associated with disease severity and outcome. Further research should be conducted to elucidate the role of the AGE-RAGE axis in the exaggerated inflammatory response leading to multiple organ failure and death, and whether or not this may be a target for treatment.

Increased circulating advanced glycation endproducts (AGEs) in acute trauma patients

BACKGROUND

Circulating levels of pro-inflammatory advanced glycation end products (AGEs) are increased in diabetes and other conditions characterized by chronically elevated oxidant stress (OS). OS also increases after acute trauma and is implicated in the development of complications such as multiple organ failure. Herein, we assess the effect of acute OS on circulating levels of AGEs in a cohort of acute trauma victims.

METHODS

An observational study was performed at a large Level 1 Trauma Center. Blood samples for measurement of two AGEs, carboxymethyllysine (CML) and methylglyoxal (MG), were obtained at admission, and serially afterwards in patients admitted to the ICU. Demographics, dietary history, markers of injury severity and ICU morbidity and mortality data were collected.

RESULTS

One hundred and fifty-six trauma patients (TP) (age: 39±17 years, 83% males, injury severity score: 18±14) were included in the study. TP had significantly higher serum AGE levels than normal healthy controls (CML, TP 12.4±8.2 U/mL vs. controls 8.9±5.3 U/mL, p<0.001; MG, TP 2.1±1.4 nmol/mL vs. controls 0.79±0.3 nmol/mL, p<0.001). Admission serum AGE levels in 49 severe TP admitted to the ICU were lower than those who were not. However, among the ICU patients, serum AGEs increased further for about 7 days in patients with an uncomplicated course, and remained markedly elevated in those with a complicated course.

CONCLUSIONS

Circulating AGEs are transiently increased after acute trauma and persistently elevated AGE levels are associated with greater severity of injury.