Intraoperative sRAGE kinetics

Association of Acute Systemic Inflammation with Patient-Centric Postoperative Pulmonary Complications After Elective Cardiac Surgery

BACKGROUND

Postoperative pulmonary complications (PPCs) occur frequently after cardiac surgery. Absolute postoperative values of biomarkers of inflammation (interleukin [IL]-6, IL-8, and tumor necrosis factor-alpha [TNF-α]) and alveolar epithelial injury (soluble receptor for advanced glycation end-products [sRAGE]) have been associated with hypoxia and prolonged ventilation. However, relationships between these biomarkers and PPCs, contextualized to preoperative inflammation and perioperative lung injury risk factors, are uncertain. We aimed to determine associations between perioperative increases in biomarkers of inflammation and alveolar epithelial injury with a patient-centric PPC definition in adult cardiac surgical patients, accounting for the influence of intraoperative risk factors for lung injury.

METHODS

Adults undergoing elective cardiac surgery were eligible for this observational cohort study. Blood concentrations of IL-6, IL-8, TNF-α, and sRAGE were collected after anesthesia induction (baseline) and on postoperative day 1 (POD 1). The primary outcome was the occurrence of moderate or severe PPCs, graded using a validated scale, in POD 0 to 7. We estimated the association between POD 1 IL-6, IL-8, TNF-α, and sRAGE concentrations and moderate/severe PPC presence using separate logistic regression models for each biomarker, adjusted for baseline biomarker values and risk factors for postoperative lung injury (age, baseline PaO 2 /F i O 2 , left ventricle ejection fraction [LVEF], procedural type, cardiopulmonary bypass duration, and transfusions). Covariables were chosen based on relevance to lung injury and unadjusted between-group differences among patients with versus without PPCs. The secondary outcome was postoperative ventilation duration, which was log-transformed and analyzed using linear regression, adjusted using the same variables as the primary outcome.

RESULTS

We enrolled 204 patients from 2016 to 2018. Biomarkers were analyzed in 2023 among 175 patients with complete data. In adjusted analyses, POD 1 IL-8 and IL-6 were significantly associated with moderate/severe PPCs. The odds ratio (OR) for developing a PPC for every 50 pg/mL increase in POD 1 IL-8 was 7.19 (95% confidence interval [CI], 2.13-28.53, P = .003) and 1.42 (95% CI, 1.13-1.93, P = .01) for every 50 pg/mL increase in POD 1 IL-6. In adjusted analyses, postoperative ventilation duration was significantly associated with POD 1 sRAGE; each 50 pg/mL increase in sRAGE was associated with a 25% (95% CI, 2%-52%, P = .03) multiplicative increase in hours of ventilation. TNF-α was not significantly associated with PPCs or ventilation duration.

CONCLUSIONS

Acute systemic inflammation is significantly associated with PPCs after elective cardiac surgery in adults when taking into consideration preoperative inflammatory burden and perioperative factors that may influence postoperative lung injury.

The role of sRAGE in cardiovascular diseases

Advanced glycation end products (AGEs), by-products of glucose metabolism, have been linked to the emergence of cardiovascular disorders (CVD). AGEs can cause tissue damage in four different ways: (1) by altering protein function, (2) by crosslinking proteins, which makes tissue stiffer, (3) by causing the generation of free radicals, and (4) by activating an inflammatory response after binding particular AGE receptors, such as the receptor for advanced glycation end products (RAGE). It is suggested that the soluble form of RAGE (sRAGE) blocks ligand-mediated pro-inflammatory and oxidant activities by serving as a decoy. Therefore, several studies have investigated the possible anti-inflammatory and anti-oxidant characteristics of sRAGE, which may help lower the risk of CVD. According to the results of various studies, the relationship between circulating sRAGE, cRAGE, and esRAGE and CVD is inconsistent. To establish the potential function of sRAGE as a therapeutic target in the treatment of cardiovascular illnesses, additional studies are required to better understand the relationship between sRAGE and CVD. In this review, we explored the potential function of sRAGE in different CVD, highlighting unanswered concerns and outlining the possibilities for further investigation.

Advanced Glycation End Product (AGE) and Soluble Receptor of AGE (sRAGE) Levels in Relation to Periodontitis Severity and as Putative 3-Year Outcome Predictors in Patients Undergoing Coronary Artery Bypass Grafting (CABG)

Tissue concentrations of advanced glycation end product (AGE) and peripheral soluble receptor of AGE (sRAGE) levels may be associated with periodontitis severity. Both parameters and periodontitis might serve as outcome predictors for patients undergoing coronary artery bypass grafting (CABG). This study aimed to investigate possible associations between periodontitis and AGE/sRAGE. Ultimately, we wanted to examine whether AGE, sRAGE, and severe periodontitis are associated with the incidence of new cardiovascular events within 3 years of follow-up after CABG. Ninety-five patients with coronary vascular disease (CVD) (age 69 years, 88.3% males) needing CABG surgery were included. Periodontal diagnosis was made according to the guidelines of the “Centers for Disease Control and Prevention (CDC)” (2007) and staged according to the new classification of periodontal diseases (2018). AGE tissue concentrations were assessed as skin autofluorescence (sAF). sRAGE levels were determined by using a commercially available enzyme-linked immunoabsorbance assay (ELISA) kit. Univariate and multivariate baseline and survival analyses were carried out with Mann–Whitney U test, Chi² test, Kaplan–Meier curves with Log-Rank test, and logistic and Cox regression. sAF was identified as an independent risk indicator for severe periodontitis with respect to the cofactors age, gender, plaque index, and diabetes (adjusted odds ratio [OR] = 2.9, p = 0.028). The degree of subgingival inflammation assessed as a percentage of sites with bleeding on probing (BOP) was inversely correlated with sRAGE concentration (r = −0.189, p = 0.034). Both sAF (Hazard Ratio [HR] = 2.4, p = 0.004) and sRAGE (HR = 1.9, p = 0.031) increased the crude risk for new adverse events after CABG. The occurrence of severe periodontitis trends towards a higher risk for new cardiovascular events (HR = 1.8, p = 0.115). Applying multivariate Cox regression, only peripheral arterial disease (adjusted HR = 2.7, p = 0.006) and history of myocardial infarction (adjusted HR = 2.8, p = 0.010) proved to be independent risk factors for cardiovascular outcome. We conclude that sAF may represent a new, independent risk indicator for severe periodontitis. In contrast, sAF, sRAGE, and severe periodontitis were not independent prognostic factors for postoperative outcome in patients undergoing CABG.

Advanced Glycation End Products: A Sweet Flavor That Embitters Cardiovascular Disease

Epidemiological studies demonstrate the role of early and intensive glycemic control in the prevention of micro and macrovascular disease in both type 1 and type 2 diabetes mellitus (DM). Hyperglycemia elicits several pathways related to the etiopathogenesis of cardiovascular disease (CVD), including the generation of advanced glycation end products (AGEs). In this review, we revisit the role played by AGEs in CVD based in clinical trials and experimental evidence. Mechanistic aspects concerning the recognition of AGEs by the advanced glycosylation end product-specific receptor (AGER) and its counterpart, the dolichyl-diphosphooligosaccharide-protein glycosyltransferase (DDOST) and soluble AGER are discussed. A special focus is offered to the AGE-elicited pathways that promote cholesterol accumulation in the arterial wall by enhanced oxidative stress, inflammation, endoplasmic reticulum stress and impairment in the reverse cholesterol transport (RCT).

Circulating antibodies against age-modified proteins in patients with coronary atherosclerosis

Advanced glycation endproducts (AGEs) are formed in a series of non-enzymatic reactions between reducing sugars and the amino groups of proteins and accumulate during aging, diabetes mellitus, chronic kidney disease and other chronic diseases. Accumulation of AGE-modifications alters protein structure and function, transforming these molecules into potential targets of the immune system, presumably triggering the production of autoantibodies against AGEs. In this study, we detected autoantibodies against AGE-modified proteins with ELISA in plasma samples of 91 patients with documented coronary artery disease (CAD), who underwent coronary artery bypass grafting (CABG) surgery. Patients with high levels of autoantibodies had a higher body mass index (BMI 28.6 vs 27.1 kg/m²; p = 0.046), were more likely to suffer from chronic obstructive pulmonary disease (COPD 30% vs 9.8%; p = 0.018), and more likely to need dialysis after the surgery (10% vs 0%; p = 0.037). Our findings show a weak link between the levels of autoantibodies against AGEs and diabetes mellitus (DM 44% vs 24.4%; p = 0.05). In a small subpopulation of patients, antibodies against native bovine serum albumin (BSA) were detected. A growing body of research explores the potential role of antibodies against AGE-modified proteins in pathogenesis of different chronic diseases; our data confirms the presence of AGE-autoantibodies in patients with CAD and that in parallel to the AGEs themselves, they may have a potential role in concomitant clinical conditions in patients undergoing CABG surgery. Further research is necessary to verify the molecular role of these antibodies in different pathological conditions.

Association between advanced glycation end products, their soluble receptor, and mortality in the general population: Results from the CARLA study

BACKGROUND

Advanced glycation end products (AGEs) in the plasma are associated with a number of age-related diseases that possibly lead to reduced longevity. However, previous studies showed large inconsistencies in the association between AGEs or their soluble receptor (sRAGE) and mortality. We studied this association in a cohort study of general population and assessed the potential changes in this association over time.

METHODS

We used data of 958 men and 802 women from the general population in Halle, Germany with a follow up of 12 years. The associations were assessed by means of Kaplan-Meyer survival curves and multivariable and time-varying Cox-regression.

RESULTS

AGEs and sRAGE were either not or only weakly (and in the other direction than expected) associated with all-cause mortality after 12 years follow-up in men and women (AGEs: Hazard ratio (HR) = 0.93, 95% confidence interval (95%CI) = 0.83-1.05 for men; HR = 0.88, 95%CI = 0.74-1.05 for women; sRAGE: HR = 1.08, 95%CI = 0.95-1.23 for men; HR = 1.10, 95%CI = 0.92-1.30 for women). There was no change of the predictive values over the follow up time. Sub-analyses with participants with and without AGEs-related conditions (diabetes mellitus and decreased renal function), with age stratified groups (younger (<65 years) and older (≥65 years) participants), with cardiovascular disease mortality as the outcome and the AGE/sRAGE ratio as predictor provided similar results.

CONCLUSIONS

Our findings suggest a lack of the expected association with mortality and contribute to the inconsistent findings for plasma-measured AGEs, sRAGE, and AGE/sRAGE ratio.