Low Endogenous Secretory Receptor for Advanced Glycation End-Products Levels Are Associated With Inflammation and Carotid Atherosclerosis in Prediabetes

Receptor for advanced glycation end-products: Biological significance and imaging applications

The receptor for advanced glycation end-products (RAGE or AGER) is a transmembrane, immunoglobulin-like receptor that, due to its multiple isoform structures, binds to a diverse range of endo- and exogenous ligands. RAGE activation caused by the ligand binding initiates a cascade of complex pathways associated with producing free radicals, such as reactive nitric oxide and oxygen species, cell proliferation, and immunoinflammatory processes. The involvement of RAGE in the pathogenesis of disorders such as diabetes, inflammation, tumor progression, and endothelial dysfunction is dictated by the accumulation of advanced glycation end-products (AGEs) at pathologic states leading to sustained RAGE upregulation. The involvement of RAGE and its ligands in numerous pathologies and diseases makes RAGE an interesting target for therapy focused on the modulation of both RAGE expression or activation and the production or exogenous administration of AGEs. Despite the known role that the RAGE/AGE axis plays in multiple disease states, there remains an urgent need to develop noninvasive, molecular imaging approaches that can accurately quantify RAGE levels in vivo that will aid in the validation of RAGE and its ligands as biomarkers and therapeutic targets. This article is categorized under: Diagnostic Tools > In Vivo Nanodiagnostics and Imaging Diagnostic Tools > Biosensing.

Soluble RAGE and skeletal muscle tissue RAGE expression profiles in lean and obese young adults across differential aerobic exercise intensities

Nearly 40% of Americans have obesity and are at increased risk for developing type 2 diabetes. Skeletal muscle is responsible for >80% of insulin-stimulated glucose uptake that is attenuated by the inflammatory milieu of obesity and augmented by aerobic exercise. The receptor for advanced glycation endproducts (RAGE) is an inflammatory receptor directly linking metabolic dysfunction with inflammation. Circulating soluble isoforms of RAGE (sRAGE) formed either by proteolytic cleavage (cRAGE) or alternative splicing (esRAGE) act as decoys for RAGE ligands, thereby counteracting RAGE-mediated inflammation. We aimed to determine if RAGE expression or alternative splicing of RAGE is altered by obesity in muscle, and whether acute aerobic exercise (AE) modifies RAGE and sRAGE. Young (20-34 yr) participants without [n = 17; body mass index (BMI): 22.6 ± 2.6 kg/m2] and with obesity (n = 7; BMI: 32.8 ± 2.9 kg/m2) performed acute aerobic exercise (AE) at 40%, 65%, or 80% of maximal aerobic capacity (V̇o2max; mL/kg/min) on separate visits. Blood was taken before and 30 min after each AE bout. Muscle biopsy samples were taken before, 30 min, and 3 h after the 80% V̇o2max AE bout. Individuals with obesity had higher total RAGE and esRAGE mRNA and RAGE protein (P < 0.0001). In addition, RAGE and esRAGE transcripts correlated to transcripts of the NF-κB subunit P65 (P < 0.05). There was no effect of AE on total RAGE or esRAGE transcripts, or RAGE protein (P > 0.05), and AE tended to decrease circulating sRAGE in particular at lower intensities of exercise. RAGE expression is exacerbated in skeletal muscle with obesity, which may contribute to muscle inflammation via NF-κB. Future work should investigate the consequences of increased skeletal muscle RAGE on the development of obesity-related metabolic dysfunction and potential mitigating strategies.NEW & NOTEWORTHY This study is the first to investigate the effects of aerobic exercise intensity on circulating sRAGE isoforms, muscle RAGE protein, and muscle RAGE splicing. sRAGE isoforms tended to diminish with exercise, although this effect was attenuated with increasing exercise intensity. Muscle RAGE protein and gene expression were unaffected by exercise. However, individuals with obesity displayed nearly twofold higher muscle RAGE protein and gene expression, which positively correlated with expression of the P65 subunit of NF-κB.

RAGE/DIAPH1 and atherosclerosis through an evolving lens: Viewing the cell from the "Inside - Out"

BACKGROUND AND AIMS

In hyperglycemia, inflammation, oxidative stress and aging, Damage Associated Molecular Patterns (DAMPs) accumulate in conditions such as atherosclerosis. Binding of DAMPs to receptors such as the receptor for advanced glycation end products (RAGE) activates signal transduction cascades that contribute to cellular stress. The cytoplasmic domain (tail) of RAGE (ctRAGE) binds to the formin Diaphanous1 (DIAPH1), which is important for RAGE signaling. This Review will detail the evidence linking the RAGE/DIAPH1 signaling pathway to atherosclerosis and envisages future therapeutic opportunities from the "inside-out" point of view in affected cells.

METHODS

PubMed was searched using a variety of search terms, including "receptor for advanced glycation end products" along with various combinations including "and atherosclerosis," "soluble RAGE and atherosclerosis," "statins and RAGE," "PPAR and RAGE" and "SGLT2 inhibitor and RAGE."

RESULTS

In non-diabetic and diabetic mice, antagonism or global deletion of Ager (the gene encoding RAGE) retards progression and accelerates regression of atherosclerosis. Global deletion of Diaph1 in mice devoid of the low density lipoprotein receptor (Ldlr) significantly attenuates atherosclerosis; mice devoid of both Diaph1 and Ldlr display significantly lower plasma and liver concentrations of cholesterol and triglyceride compared to mice devoid of Ldlr. Associations between RAGE pathway and human atherosclerosis have been identified based on relationships between plasma/serum concentrations of RAGE ligands, soluble RAGEs and atherosclerosis.

CONCLUSIONS

Efforts to target RAGE/DIAPH1 signaling through a small molecule antagonist therapeutic strategy hold promise to quell accelerated atherosclerosis in diabetes and in other forms of cardiovascular disease.

Human intestine and placenta exhibit tissue-specific expression of RAGE isoforms

The receptor for advanced glycation end products (RAGE) is encoded by AGER, a gene that is subjected to tissue-specific alternative splicing. Splice variants of RAGE in intestine and placenta are unknown and contradictory data concerning RAGE protein expression in these tissues have been published. As a basis for future functional studies, we examined RAGE expression in small intestine, colon and placentas. PCR cloning revealed that full-length RAGE is the only RAGE transcript isoform expressed in placenta. In the small intestine, the major transcript isoform detected was RAGE_v1 encoding the C-terminally truncated soluble receptor. In the colon, both full-length RAGE as well as several splice variants were identified. Four antibodies were used to study protein expression by immunoblotting and were carefully validated. Appropriate controls were essential to avoid misinterpretation of bands caused by non-specific reactivity of antibodies. Only one of four antibodies tested detected full-length RAGE in placenta, whereas no RAGE-specific band was detected in intestinal tissues despite loading >30-fold more intestinal tissue than the positive control, human lung. RAGE expression levels in the placenta were 100-fold lower compared with human lung when analyzed by ELISA, and no significant differences in RAGE expression were detected between healthy placentas and placentas from women with preeclampsia, gestational diabetes mellitus, or fetal growth restriction. We conclude that healthy placental chorionic tissue expresses low levels of full-length RAGE, whereas expression of the tissue-specific intestinal isoforms is below the limit of detection. Low RAGE expression levels in combination with a lack of antibody validation may explain the conflicting published results on RAGE protein expression in intestine and placenta.

Implications of receptor for advanced glycation end products for progression from obesity to diabetes and from diabetes to cancer

Obesity and type 2 diabetes mellitus (T2DM) are chronic pathologies with a high incidence worldwide. They share some pathological mechanisms, including hyperinsulinemia, the production and release of hormones, and hyperglycemia. The above, over time, affects other systems of the human body by causing tissue hypoxia, low-grade inflammation, and oxidative stress, which lay the pathophysiological groundwork for cancer. The leading causes of death globally are T2DM and cancer. Other main alterations of this pathological triad include the accumulation of advanced glycation end products and the release of endogenous alarmins due to cell death (i.e., damage-associated molecular patterns) such as the intracellular proteins high-mobility group box protein 1 and protein S100 that bind to the receptor for advanced glycation products (RAGE) - a multiligand receptor involved in inflammatory and metabolic and neoplastic processes. This review analyzes the latest advanced reports on the role of RAGE in the development of obesity, T2DM, and cancer, with an aim to understand the intracellular signaling mechanisms linked with cancer initiation. This review also explores inflammation, oxidative stress, hypoxia, cellular senescence, RAGE ligands, tumor microenvironment changes, and the “cancer hallmarks” of the leading tumors associated with T2DM. The assimilation of this information could aid in the development of diagnostic and therapeutic approaches to lower the morbidity and mortality associated with these diseases.

Oleic Acid Status Positively Correlates with the Soluble Receptor for Advanced Glycation End-Products (sRAGE) in Healthy Adults Who Are Homozygous for G Allele of RAGE G82S Polymorphism

BACKGROUND

The soluble form of receptor for advanced glycation end products (sRAGE) have been implicated in the prevention of numerous pathologic states, and highlights as an attractive therapeutic target. Because diets rich in monounsaturated fatty acids (MUFA) reduce postprandial oxidative stress and inflammation that is related to better health during aging, we investigated the association between red blood cell (RBC) fatty acids with circulatory AGE biomarkers and further stratified this correlation based on GG and GA + AA genotype.

METHODS

A total of 172 healthy participants (median age = 53.74 ± 0.61 years) were recruited for the study. RBC fatty acid was analysed using gas chromatography and sRAGE was measured using a commercial ELISA kit.

RESULTS

The result showed a non-significant correlation between total MUFA with sRAGE however oleic acid (C18:1) exhibited a positive correlation (r = 0.178, p = 0.01) that remained statistically significant (β = 0.178, p = 0.02) after a stepwise multivariate regression analysis after adjusting for age, BMI and gender. In a univariate analysis, a positive significant correlation between C18:1 and sRAGE in GG genotype (r = 0.169, p = 0.02) and a non-significant correlation with GA + AA genotype (r = 0.192, p = 0.21) was evident. When C18:1 was stratified, a significant difference was observed for oleic acid and G82S polymorphism: low C18:1/GA + AA versus high C18:1/GG (p = 0.015) and high C18:1/GA + AA versus high C18:1/GG (p = 0.02).

CONCLUSION

Our study suggests that increased levels of C18:1 may be a potential therapeutic approach in increasing sRAGE in those with GG genotype and play a role in modulating AGE metabolism.

The AGE-RAGE Axis and the Pathophysiology of Multimorbidity in COPD

Chronic obstructive pulmonary disease (COPD) is a disease of the airways and lungs due to an enhanced inflammatory response, commonly caused by cigarette smoking. Patients with COPD are often multimorbid, as they commonly suffer from multiple chronic (inflammatory) conditions. This intensifies the burden of individual diseases, negatively affects quality of life, and complicates disease management. COPD and comorbidities share genetic and lifestyle-related risk factors and pathobiological mechanisms, including chronic inflammation and oxidative stress. The receptor for advanced glycation end products (RAGE) is an important driver of chronic inflammation. Advanced glycation end products (AGEs) are RAGE ligands that accumulate due to aging, inflammation, oxidative stress, and carbohydrate metabolism. AGEs cause further inflammation and oxidative stress through RAGE, but also through RAGE-independent mechanisms. This review describes the complexity of RAGE signaling and the causes of AGE accumulation, followed by a comprehensive overview of alterations reported on AGEs and RAGE in COPD and in important co-morbidities. Furthermore, it describes the mechanisms by which AGEs and RAGE contribute to the pathophysiology of individual disease conditions and how they execute crosstalk between organ systems. A section on therapeutic strategies that target AGEs and RAGE and could alleviate patients from multimorbid conditions using single therapeutics concludes this review.

The changes that occur in the immune system during immune activation in pre-diabetic patients of all ethnicities, from the age of 25- to 45-years: A systematic review and meta-analysis

BACKGROUND

Pre-diabetes is an intermediate state between normoglycaemia and type 2 diabetes (T2D). This condition has been shown to be asymptomatic thus making it hard to investigate the changes that occur in the body during this state. Recent findings stipulate that in this state, there are changes that are often associated with T2D. These include changes in concentration of immune cells and inflammatory markers. This systematic review will provide a synthesis of the data that is available reporting on the changes in the concentration of immune cells and selected markers during prediabetes. It will also give clarity of the variation of the complications of the condition among the various demographic groups.

METHODS

The assembly of this systematic review was through strict adherance to the PRISMA 2020 guidelines for reporting systematic reviews. This systematic review has been registered with the International Prospective Registry of Systematic Reviews (PROSPERO), registration number "CRD42020184828" dated 05-07-2020). In this systematic review, published clinical studies articles that involve observational reports, whether it is case-control, cross-sectional, and comparative cross-sectional will be used. Cohort study designs that involve normal/non-diabetic and pre-diabetes reports will be used in this systematic review and meta-analysis. Clinical MeSH headings to search on MEDLINE, COCHRANE library, EMBASE, and ICTRP and African Journal Online will be a tool used to achieve the required report. Reviewers (NCM, AMS, and AK) will screen all the results and select the studies that will be eligible by guidance according to eligibility criteria. Downs and Black Checklist will be used to check the risk of bias and then for meta-analysis Review Manager v5.4 Forrest plot will be used. Additionally, the Forrest plot will also be used for sensitivity analysis. The strength of evidence will then be assessed using the Grading of Recommendations Assessment, Development, and Evaluation approach.

RESULTS

Only 4 reports were eligible and risk of bias checked. The results indicated the outcomes even though there were only few reports.

DISCUSSION AND CONCLUSION

This systematic review will give an indication on the available data on this research area and lay a foundation for future studies.

Association of α-Dicarbonyls and Advanced Glycation End Products with Insulin Resistance in Non-Diabetic Young Subjects: A Case-Control Study

α-Dicarbonyls and advanced glycation end products (AGEs) may contribute to the pathogenesis of insulin resistance by a variety of mechanisms. To investigate whether young insulin-resistant subjects present markers of increased dicarbonyl stress, we determined serum α-dicarbonyls-methylglyoxal, glyoxal, 3-deoxyglucosone; their derived free- and protein-bound, and urinary AGEs using the UPLC/MS-MS method; soluble receptors for AGEs (sRAGE), and cardiometabolic risk markers in 142 (49% females) insulin resistant (Quantitative Insulin Sensitivity Check Index (QUICKI) ≤ 0.319) and 167 (47% females) age-, and waist-to-height ratio-matched insulin-sensitive controls aged 16-to-22 years. The between-group comparison was performed using the two-factor (sex, presence/absence of insulin resistance) analysis of variance; multiple regression via the orthogonal projection to latent structures model. In comparison with their insulin-sensitive peers, young healthy insulin-resistant individuals without diabetes manifest alterations throughout the α-dicarbonyls-AGEs-sRAGE axis, dominated by higher 3-deoxyglucosone levels. Variables of α-dicarbonyls-AGEs-sRAGE axis were associated with insulin sensitivity independently from cardiometabolic risk markers, and sex-specifically. Cleaved RAGE associates with QUICKI only in males; while multiple α-dicarbonyls and AGEs independently associate with QUICKI particularly in females, who displayed a more advantageous cardiometabolic profile compared with males. Further studies are needed to elucidate whether interventions alleviating dicarbonyl stress ameliorate insulin resistance.

Periodontitis and implant complications in diabetes

Epidemiologic evidence indicates that periodontitis is more frequent in patients with uncontrolled diabetes mellitus than in healthy controls, suggesting that it could be considered the "sixth complication" of diabetes. Actually, diabetes mellitus and periodontitis are two extraordinarily prevalent chronic diseases that share a number of comorbidities all converging toward an increased risk of cardiovascular disease. Periodontal treatment has recently been shown to have the potential to improve the metabolic control of diabetes, although long-term studies are lacking. Uncontrolled diabetes also seems to affect the response to periodontal treatment, as well as the risk to develop peri-implant diseases. Mechanisms of associations between diabetes mellitus and periodontal disease include the release of advanced glycation end products as a result of hyperglycemia and a range of shared predisposing factors of genetic, microbial, and lifestyle nature. This review discusses the evidence for the risk of periodontal and peri-implant disease in diabetic patients and the potential role of the dental professional in the diabetes-periodontal interface.

Circulating levels of AGEs and soluble RAGE isoforms are associated with all-cause mortality and development of cardiovascular complications in type 2 diabetes: a retrospective cohort study

BACKGROUND

Advanced glycation end-products (AGEs) and their interaction with the receptor for advanced glycation end-products (RAGE) play a pivotal role in the development and progression of type 2 diabetes. In this retrospective cohort study, we explored the association of circulating levels of soluble RAGE (sRAGE) isoforms, i.e., endogenous secretory esRAGE and cleaved cRAGE, AGEs and their respective ratios with 15-year all-cause mortality in type 2 diabetes.

METHODS

Baseline AGEs and sRAGE isoforms concentration were measured by ELISA in 362 patients with type 2 diabetes and in 125 age- and gender-matched healthy control subjects (CTR). Independent predictors of mortality were determined using Cox proportional-hazards models and used to build and validate a nomogram for all-cause mortality prediction in type 2 diabetes.

RESULTS

AGEs, total sRAGE, cRAGE and the AGEs/sRAGE and AGEs/esRAGE ratios were significantly increased in patients with type 2 diabetes compared to CTR (p < 0.001). In CTR subjects, but not in type 2 diabetes patients, a significant negative correlation between cRAGE and age was confirmed (p = 0.003), whereas the AGEs/sRAGE (p = 0.032) and AGEs/cRAGE (p = 0.006) ratios were positively associated with age. At an average follow-up of 15 years (4,982 person-years), 130 deaths were observed. The increase in the AGEs/cRAGE ratio was accompanied by a higher risk of all-cause mortality in patients with type 2 diabetes (HR per each SD increment = 1.30, 95% CI 1.15-1.47; p < 0.001). Moreover, sRAGE was associated with the development of major adverse cardiovascular events (MACE) in type 2 diabetes patients without previous MACE (OR for each SD increase: 1.48, 95% CI 1.11-1.89). A nomogram based on age, sex, HbA1c, systolic blood pressure, and the AGEs/cRAGE ratio was built to predict 5-, 10- and 15-year survival in type 2 diabetes. Patients were categorized into quartiles of the monogram scores and Kaplan-Meier survival curves confirmed the prognostic accuracy of the model (log-rank p = 6.5 × 10- 13).

CONCLUSIONS

The ratio between AGEs and the cRAGE isoform is predictive of 15-year survival in patients with type 2 diabetes. Our data support the assessment of circulating AGEs and soluble RAGE isoforms in patients with type 2 diabetes as predictors of MACE and all-cause mortality.

Increased Platelet Reactivity and Proinflammatory Profile Are Associated with Intima-Media Thickness and Arterial Stiffness in Prediabetes

Alterations of glucose homeostasis are associated with subclinical vascular damage; however, the role of platelet reactivity in this process has not been fully investigated. In this cross-sectional study, we evaluated the correlation between markers of platelet reactivity and inflammation and markers of vascular disease in subjects with prediabetes. Markers of platelet reactivity such as 11-dehydro-thromboxane B2 urinary levels (11-dh-TXB2) and mean platelet volume (MPV) and inflammatory indexes such as platelet-to-lymphocyte ratio (PLR) were evaluated in subjects with prediabetes (n = 48), new-onset type 2 diabetes (NODM, n = 60) and controls (n = 62). Furthermore, we assessed the cardiovascular risk profile of the study population with arterial stiffness and quality intima–media thickness (qIMT). Subjects with prediabetes and NODM exhibited higher 11-dh-TXB2 urinary levels and MPV and a proinflammatory profile with an increased PLR, high-sensitivity C-reactive protein, ferritin and fibrinogen. Furthermore, after multiple regression analyses, we found that urinary 11-dh-TXB2 was one of the major determinants of IMT and arterial stiffness parameters. In conclusion, subjects with prediabetes exhibit increased platelet reactivity as well as a proinflammatory profile. Furthermore, this condition is associated with early markers of cardiovascular disease.

High glomerular filtration rate is associated with impaired arterial stiffness and subendocardial viability ratio in prediabetic subjects

BACKGROUND AND AIMS

High glomerular filtration rate (HGFR) is associated with cardiovascular damage in the setting of various conditions such as obesity and diabetes. Prediabetes was also associated with increased GFR, however, the association between prediabetes, HGFR and cardiovascular damage has not been investigated. In this study, we investigated the association between HGFR and early markers of cardiovascular disease in subjects with prediabetes.

METHODS AND RESULTS

Augmentation pressure (Aug), augmentation index (AIx), subendocardial viability ratio (SEVR), pulse wave velocity (PWV), intima-media thickness (IMT) and estimated GFR (eGFR) were evaluated in 230 subjects with prediabetes. The eGFR was assessed using the Chronic Kidney Disease Epidemiology Collaboration formula. HGFR was defined as an eGFR above the 75th percentile. Prediabetic subjects were divided into two groups according to presence/absence of HGFR: 61 subjects with HGFR and 169 subjects without HGFR. Subjects with HGFR showed higher Aug, AIx and lower SEVR compared with prediabetic subjects with lower eGFR (14.1 ± 7.2 vs 10.8 ± 6.2, 32.9 ± 12.7 vs 27.6 ± 11.7, 153.5 ± 27.8 vs 162 ± 30.2, p < 0.05). No differences were found in PWV and IMT values between the two groups. Then, we performed multiple regression analysis to test the relationship between Aug, SEVR and several cardiovascular risk factors. In multiple regression analysis Aug was associated with age, systolic blood pressure (BP), HOMA-IR and eGFR; the major determinants of SEVR were systolic BP, HOMA-IR and eGFR.

CONCLUSION

Subjects with prediabetes and HGFR exhibited an increased Aug, AIx and a reduced SEVR. These alterations are associated with eGFR, insulin resistance and systolic BP.

The relationship between endogenous secretory RAGE and cardiac autonomic function in prediabetes

AIMS

The putative protective role of esRAGE for cardiac autonomic function (CAF) remains unclear. To address this question, the present study has assessed the relationship of serum AGEs, sRAGE and esRAGE, and tissue AGEs with CAF in a high-risk population without diabetes.

MATERIAL AND METHODS

This study enrolled 48 subjects of mean age 52.7 ± 11.2 years and mean BMI 28.4 ± 6.3 kg/m² , divided into two groups according to glucose tolerance: 16 with normal glucose tolerance (NGT) and 24 with prediabetes. A standard oral glucose tolerance test (OGTT) was performed. The glucose tolerance was defined according to 2006 WHO criteria. Fasting, 120-minutes glucose, lipids, creatinine, and HbA1c were measured. eGFR was calculated (CKD-EPI). Fasting, 120-minutes insulin (ECLIA method), advanced glycation end products (AGEs), plasma-soluble receptor for AGE (sRAGE), and endogenous secreted isoform of the receptor for AGE (esRAGE), (ELISA method) were assessed. HOMA-IR was calculated. Tissue AGEs were assessed by skin autofluorescence (AGE-Reader, DiagnOpticsTM). CAF was evaluated with ANX 3.0 autonomic nervous-monitoring system (ANSAR), applying deep breathing, Valsalva, and standing.

RESULTS

There was a significant decline in CAF in prediabetes in comparison with NGT. Serum and tissue AGEs, sRAGE, and esRAGE levels were similar between groups. On the matrix analysis, both sympathetic and parasympathetic activities at baseline and after standing and sympathetic tone during Valsalva were positively related to esRAGE in prediabetes. Multivariate regression analysis showed that esRAGE is an independent contributor to sympathetic, parasympathetic, and total autonomic tone in prediabetes accounting for about 28%, 34%, and 35% of their variances, respectively.

CONCLUSION

Our results have demonstrated that CAF is decreased in prediabetes. esRAGE, but not sRAGE, is reciprocally related to CAF, probably opposing the negative effects of glycation.

Diabetes Mellitus, Arterial Stiffness and Cardiovascular Disease: Clinical Implications and the Influence of SGLT2i

Type 2 diabetes mellitus (T2DM) is a rapidly evolving global health issue associated with a markedly increased risk of cardiovascular (CV) morbidity and mortality. The hyperglycaemic milieu contributes to the development of CV complications via several pathological pathways, leading to increased arterial stiffness (AS), that can be considered as a predictor of CV events in patients with diabetes. The measurement of AS is increasingly used for the clinical assessment of patients. Several methodologies were used in extensive population studies to assess AS; the most commonly used is the pulse wave velocity (PWV). The cardio-ankle vascular index (CAVI) was developed to measure AS; it is not affected by blood pressure at the time of measurement and shows stable values in healthy persons for years. There are several potential pharmacological and non-pharmacological interventions aiming to reduce AS. Recent evidence from clinical trials suggests that newer antidiabetic drugs do not only exert glycaemic-lowering properties but also decrease CV risk. In this context, sodium glucose cotransporter- 2 inhibitors (SGLT2i) ( empagliflozin, canagliflozin and dapagliflozin) significantly reduced the risk of CV and all-cause mortality (only EMPA-REG OUTCOME study) and hospitalization for heart failure in patients with T2DM with established CV disease and/or with CV risk factors. Improved endothelial function and AS probably represents one of the mechanisms by which these drugs exert their beneficial effects. The present review aimed both to describe the association between AS and T2DM and to discuss the effectiveness of SGLT2i on vascular endothelial dysfunction and AS.

The Mechanisms of the Development of Atherosclerosis in Prediabetes

Lifestyle changes, such as overeating and underexercising, can increase the risk of prediabetes. Diabetes is one of the leading causes of atherosclerosis, and recently it became clear that the pathophysiology of atherosclerosis progresses even before the onset of diabetic symptoms. In addition to changes in platelets and leukocytes in the hyperglycemic state and damage to vascular endothelial cells, extracellular vesicles and microRNAs were found to be involved in the progression of prediabetes atherosclerosis. This review discusses the cellular and molecular mechanisms of these processes, with an intention to enable a comprehensive understanding of the pathophysiology of prediabetes and atherosclerosis.

Association Between Soluble Receptor for Advanced Glycation End Product and Endogenous Secretory Soluble Receptor for Advanced Glycation End Product Levels and Carotid Atherosclerosis in Diabetes: A Systematic Review and Meta-analysis

BACKGROUND

The soluble receptor for advanced glycation end product (sRAGE) and endogenous secretory RAGE (esRAGE) are novel biomarkers that are associated with vascular disease. We carried out a systematic review to provide a more complete picture of sRAGE, esRAGE, carotid atherosclerosis and cardiovascular disease (CVD) in patients with diabetes.

METHODS

We searched the Cochrane Library, PubMed and Embase databases. Systematic review best practices were followed, and study quality was assessed.

RESULTS

Ultimately, 11 studies met all the inclusion criteria. Meta-analysis indicated that esRAGE was not significantly lower in patients with type 1 diabetes (T1D) (standardized mean difference [SMD], -0.76; 95% confidence interval [CI], -1.57 to 0.05; I²=90%; p=0.002), whereas it was significantly lower in patients with type 2 diabetes (T2D) (SMD, -1.08; 95% CI, -1.53 to -0.62; I²=80%; p=0.006). Meta-analysis suggested that sRAGE levels were not significantly lower or higher in T1D (SMD, 0.06; 95% CI, -0.14 to 0.26; I²=38%; p=0.20) or T2D (SMD, 0.00; 95% CI, -0.26 to 0.26; I²=0.00%; p=1.00) patients. The level of esRAGE was inversely correlated with carotid intima-media thickness (IMT) in T2D patients, whereas there was a contrasting relationship between sRAGE and carotid IMT in T1D patients. Higher sRAGE was associated with cardiovascular events.

CONCLUSION

Our meta-analysis showed that circulating esRAGE was lower and inversely correlated with IMT in T2D patients.

RAGE Mediates Cholesterol Efflux Impairment in Macrophages Caused by Human Advanced Glycated Albumin

We addressed the involvement of the receptor for advanced glycation end products (RAGE) in the impairment of the cellular cholesterol efflux elicited by glycated albumin. Albumin was isolated from type 1 (DM1) and type 2 (DM2) diabetes mellitus (HbA1c > 9%) and non-DM subjects (C). Moreover, albumin was glycated in vitro (AGE-albumin). Macrophages from Ager null and wild-type (WT) mice, or THP-1 transfected with siRNA-AGER, were treated with C, DM1, DM2, non-glycated or AGE-albumin. The cholesterol efflux was reduced in WT cells exposed to DM1 or DM2 albumin as compared to C, and the intracellular lipid content was increased. These events were not observed in Ager null cells, in which the cholesterol efflux and lipid staining were, respectively, higher and lower when compared to WT cells. In WT, Ager, Nox4 and Nfkb1, mRNA increased and Scd1 and Abcg1 diminished after treatment with DM1 and DM2 albumin. In Ager null cells treated with DM-albumin, Nox4, Scd1 and Nfkb1 were reduced and Jak2 and Abcg1 increased. In AGER-silenced THP-1, NOX4 and SCD1 mRNA were reduced and JAK2 and ABCG1 were increased even after treatment with AGE or DM-albumin. RAGE mediates the deleterious effects of AGE-albumin in macrophage cholesterol efflux.

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

Isoforms of the receptor for advanced glycation end-product (RAGE) protein, which lack the transmembrane and the signaling (soluble RAGE or sRAGE) domains are hypothesized to counteract the detrimental action of the full-length receptor by acting as a decoy, and they provide a potential tool to treat RAGE-associated diseases. Multiple studies have explored the relationship between sRAGE and endogenous secretory RAGE and its polymorphism and obesity, metabolic syndrome, atherosclerosis, kidney function, and increased mortality in the general population. In addition, sRAGE may be a key player in the pathogenesis of diabetes mellitus and its microvascular (e.g. kidney disease) as well as macrovascular (e.g. cardiovascular disease) complications. In this review, we focus on the role of sRAGE as a biomarker in these specific areas. As there is a lack of an underlying unifying hypothesis about how sRAGE changes according to the disease condition or risk factor, there is a call to incorporate all three players of the AGE-RAGE axis into a new universal biomarker/risk marker: (AGE + RAGE)/sRAGE. However, the measurement of RAGE in humans is not practical as it is a cell-bound receptor for which tissue is required for analysis. A high AGE/sRAGE ratio may be a valuable alternative and practical universal biomarker/risk marker for diseases associated with the AGE-RAGE axis, irrespective of low or high serum sRAGE concentrations.

Quantitative imaging of the receptor for advanced glycation end-products in prostate cancer

PURPOSE

Current screening and monitoring of prostate cancer (PCa) is insufficient, producing inaccurate diagnoses. Presence of the receptor for advanced glycation end-products (RAGE) is associated with signature characteristics of PCa development such as cell proliferation, anchorage-independent growth, angiogenesis, migration, invasion, and poor patient survival. Therefore, we developed a preclinical multimodal imaging strategy targeted at RAGE to diagnose and monitor PCa.

METHODS

In this work, RAGE-targeted multimodal nanoparticles (64Cu-Cy5-G4-CML) were synthesized and rendered functional for nuclear and optical imaging using previously established methods. The probe's binding affinity and targeting specificity was assessed in androgen-dependent (LNCaP) and androgen-independent (DU145) prostate cancer cells using flow cytometry and confocal microscopy. In vivo PET-CT imaging was used to evaluate RAGE levels in DU145 and LNCaP xenograft models in mice. Then, tumors were excised post-imaging for histological staining and autoradiography to further assess RAGE levels and targeting efficiency of the tracer. Finally, RAGE levels from human PCa samples of varying Gleason Scores were evaluated using Western blot and immunohistochemical staining.

RESULTS

PCa cell culture studies confirmed adequate RAGE-targeting with 64Cu-Cy5-G4-CML with K_D between 360 and 540 nM as measured by flow cytometry. In vivo PET-CT images of PCa xenografts revealed favorable kinetics, rapid blood clearance, and a non-homogenous, enhanced uptake in tumors, which varied based on cell type and tumor size with mean uptake between 0.5 and 1.4%ID/g. RAGE quantification of human samples confirmed increased RAGE uptake corresponding to increased Gleason scoring.

CONCLUSIONS

Our study has shown that RAGE-targeted cancer imaging is feasible and could significantly impact PCa management.

Receptor for Advanced Glycation End Products (RAGE) and Mechanisms and Therapeutic Opportunities in Diabetes and Cardiovascular Disease: Insights From Human Subjects and Animal Models

Obesity and diabetes are leading causes of cardiovascular morbidity and mortality. Although extensive strides have been made in the treatments for non-diabetic atherosclerosis and its complications, for patients with diabetes, these therapies provide less benefit for protection from cardiovascular disease (CVD). These considerations spur the concept that diabetes-specific, disease-modifying therapies are essential to identify, especially as the epidemics of obesity and diabetes continue to expand. Hence, as hyperglycemia is a defining feature of diabetes, it is logical to probe the impact of the specific consequences of hyperglycemia on the vessel wall, immune cell perturbation, and endothelial dysfunction-all harbingers to the development of CVD. In this context, high levels of blood glucose stimulate the formation of the irreversible advanced glycation end products, the products of non-enzymatic glycation and oxidation of proteins and lipids. AGEs accumulate in diabetic circulation and tissues and the interaction of AGEs with their chief cellular receptor, receptor for AGE or RAGE, contributes to vascular and immune cell perturbation. The cytoplasmic domain of RAGE lacks endogenous kinase activity; the discovery that this intracellular domain of RAGE binds to the formin, DIAPH1, and that DIAPH1 is essential for RAGE ligand-mediated signal transduction, identifies the specific cellular means by which RAGE functions and highlights a new target for therapeutic interruption of RAGE signaling. In human subjects, prominent signals for RAGE activity include the presence and levels of two forms of soluble RAGE, sRAGE, and endogenous secretory (es) RAGE. Further, genetic studies have revealed single nucleotide polymorphisms (SNPs) of the AGER gene (AGER is the gene encoding RAGE) and DIAPH1, which display associations with CVD. This Review presents current knowledge regarding the roles for RAGE and DIAPH1 in the causes and consequences of diabetes, from obesity to CVD. Studies both from human subjects and animal models are presented to highlight the breadth of evidence linking RAGE and DIAPH1 to the cardiovascular consequences of these metabolic disorders.

Circulating Irisin and esRAGE as Early Biomarkers of Decline of Metabolic Health

A decline in metabolic health may take place before observing any alteration in the levels of the traditional metabolic markers. New indicators of metabolic derangement are therefore compelling. Irisin is a myokine with important metabolic functions. The role of irisin as a metabolic biomarker in humans has not been fully established yet. We quantified plasma irisin and esRAGE in 106 apparently healthy individuals and we performed a cluster analysis to evaluate their associations with metabolic profile. Plasma levels of various traditional markers of metabolic risk (i.e., glucose and lipid levels) were all within the ranges of normality. We identified two clusters of individuals. Compared to cluster 2, individuals in cluster 1 had higher irisin levels, a metabolic profile shifted toward the limits of the reference ranges and lower esRAGE levels. The traditional metabolic blood tests seem not to be enough to identify a metabolic decline early. Irisin increase and esRAGE decrease may reflect a metabolic derangement at the beginning of its development. The role of these molecules as early biomarkers of decline of metabolic health seems an interesting topic to be further explored.

Insulin Resistance and Atherosclerosis: Implications for Insulin-Sensitizing Agents

Patients with type 2 diabetes mellitus (T2DM) are at high risk for macrovascular complications, which represent the major cause of mortality. Despite effective treatment of established cardiovascular (CV) risk factors (dyslipidemia, hypertension, procoagulant state), there remains a significant amount of unexplained CV risk. Insulin resistance is associated with a cluster of cardiometabolic risk factors known collectively as the insulin resistance (metabolic) syndrome (IRS). Considerable evidence, reviewed herein, suggests that insulin resistance and the IRS contribute to this unexplained CV risk in patients with T2DM. Accordingly, CV outcome trials with pioglitazone have demonstrated that this insulin-sensitizing thiazolidinedione reduces CV events in high-risk patients with T2DM. In this review the roles of insulin resistance and the IRS in the development of atherosclerotic CV disease and the impact of the insulin-sensitizing agents and of other antihyperglycemic medications on CV outcomes are discussed.

Lung function measurements in the prediabetes stage: data from the ILERVAS Project

AIMS

Patients with type 2 diabetes have been considered a susceptible group for pulmonary dysfunction. Our aim was to assess pulmonary function on the prediabetes stage.

METHODS

Pulmonary function was assessed in 4,459 non-diabetic subjects, aged between 45 and 70 years, without cardiovascular disease or chronic pulmonary obstructive disease from the ongoing study ILERVAS. A "restrictive spirometric pattern", an "abnormal FEV1" and an "obstructive ventilatory defect" were assessed. Prediabetes was defined by glycosylated hemoglobin (HbA1c) between 5.7 and 6.4% according to the American Diabetes Association criteria.

RESULTS

Population was composed of 52.1% women, aged 57 [53;63] years, a BMI of 28.6 [25.8;31.8] kg/m², and with a prevalence of prediabetes of 29.9% (n = 1392). Subjects with prediabetes had lower forced vital capacity (FVC: 93 [82;105] vs. 96 [84;106], p < 0.001) and lower forced expired volume in the first second (FEV1: 94 [82;107] vs. 96 [84;108], p = 0.011), as well as a higher percentage of the restrictive spirometric pattern (16.5% vs. 13.6%, p = 0.015) and FEV1 < 80% (20.3% vs. 17.2%, p = 0.017) compared to non-prediabetes group. In the prediabetes group, HbA1c was negatively correlated with both pulmonary parameters (FVC: r = - 0.113, p < 0.001; FEV1: r = - 0.079, p = 0.003). The multivariable logistic regression model in the whole population showed that there was a significant and independent association between HbA1c with both restrictive spirometric pattern [OR = 1.42 (1.10-1.83), p = 0.008] and FEV1 < 80% [OR = 1.50 (1.19-1.90), p = 0.001].

CONCLUSIONS

The deleterious effect of type 2 diabetes on pulmonary function appears to be initiated in prediabetes, and it is related to metabolic control. TRIAL REGISTRATION CLINICALTRIALS.GOV: NCT03228459.

1 h Postload Glycemia Is Associated with Low Endogenous Secretory Receptor for Advanced Glycation End Product Levels and Early Markers of Cardiovascular Disease

We investigated the correlation of the soluble receptor for advanced glycation end products (sRAGE) and endogenous secretory RAGE (esRAGE) with markers of cardiovascular disease in subjects with normal glucose tolerance (NGT) and 1 h postload glucose ≥155 mg/dL after an oral glucose tolerance test. We stratified 282 subjects without a previous diagnosis of diabetes into three groups: 123 controls (NGT and 1 h postload glycemia <155 mg/dL), 84 NGT and 1 h postload glycemia ≥155 mg/dL (NGT 1 h high), and 75 subjects with impaired fasting glucose and/or impaired glucose tolerance (IFG/IGT). NGT 1 h high subjects exhibited lower esRAGE (0.36 ± 0.18 vs. 0.4 5 ± 0.2, p < 0.05) and higher S100A12 levels than controls (5684 (3193.2–8295.6) vs. 3960.1 (2101.8–7419), p < 0.05). Furthermore, they showed an increased pulse wave velocity (PWV) and intima–media thickness (IMT). No differences were found between the NGT 1 h high group and the IFG/IGT group regarding cardiometabolic profiles. After multiple regression analyses, esRAGE was associated with glycated hemoglobin (HbA_1c) and high-sensitivity C-reactive protein (hs-CRP). Age, HbA_1c, and esRAGE were the determinants of IMT, whereas S100A12 and systolic pressure were the determinants of PWV. The NGT 1 h high group exhibited low esRAGE levels and an altered cardiometabolic profile. HbA_1c, S100A12, and hs-CRP were associated with these alterations. In conclusion, subjects with NGT are not a homogeneous population, and they present different cardiovascular and glycometabolic risks.

Analysis of S100A12 plasma levels in hyperlipidemic subjects with or without familial hypercholesterolemia

AIMS

Inflammation is a key regulatory process that links hypercholesterolemia and immune mechanisms promoting atherosclerosis. Inflammatory biomarkers may be helpful to better define the atherosclerotic burden in patients with high cholesterol levels such as familial hypercholesterolemia (FH). Our aim was to evaluate the concentration of S100A12 protein in FH patients and its association with pulse wave velocity (PWV).

METHODS

We measured glucose and lipid profile, S100A12, sRAGE, esRAGE and PWV in 39 patients with a genetically confirmed diagnosis of FH and 39 hypercholesterolemic subjects without a clinical diagnosis of FH (Dutch score ≤ 3). All subjects were on statin treatment at the time of the enrollment.

RESULTS

No difference of glucose and lipid profile was found in the two groups. FH patients had higher S100A12 plasma levels than non-FH subjects (12.87 ± 4.82 vs. 8.57 ± 4.87 ng/mL, p < 0.01). No difference of hs-CRP, sRAGE and esRAGE was found between the two groups. Also, PWV was higher in FH patients than non-FH subjects (8.63 ± 0.92 vs. 6.68 ± 0.73 m/s, p < 0.05). Finally, S100A12 was independently correlated with age (p < 0.01), genetic mutation (p < 0.01) and PWV (p < 0.001).

CONCLUSIONS

FH patients exhibited higher S100A12 levels than non-FH subjects. A novel vascular inflammation pathway, other than hs-CRP, might be useful to better characterize cardiovascular risk profile.

The role of damage-associated molecular pattern for pathogenesis and biomarkers in adult-onset Still's disease

Introduction: Adult-onset Still's disease (AOSD) is a systemic inflammatory disease, which presents itself as an adult form of systemic juvenile idiopathic arthritis. Innate immune activation driven by a combination of genetic and environmental factors is the primary mechanism underlying disease pathogenesis in AOSD patients. Few biomarkers have been identified for AOSD diagnosis or for the assessment of disease activity or prediction of clinical outcomes. Damage-associated molecular patterns (DAMPs) can activate innate immunity, resulting in tissue damage. Changes in several DAMPs are associated with disease pathogenesis in AOSD patients. Areas covered: This review describes the role of DAMPs in AOSD pathogenesis and discusses their potential for use as disease biomarkers. Together with overall pathogenesis of AOSD, high-mobility group box-1, advanced glycation end products, S100 proteins, and neutrophil extracellular traps are introduced and discussed in detail. Expert opinion: The activation of macrophages and neutrophils is associated with several DAMPs, causing high concentrations of proinflammatory cytokines in AOSD patients. Involvement of certain DAMPs in AOSD patients is well documented due to the presence of sterile inflammation; however, direct evidence for some DAMPs is lacking. Further research into the role of DAMP molecules in AOSD patients may reveal new biomarkers and provide targets for disease intervention.

Increased Arterial Stiffness in Prediabetic Subjects Recognized by Hemoglobin A1c with Postprandial Glucose but Not Fasting Glucose Levels

Previous studies exploring the association between arterial stiffness and prediabetes remain controversial. This study aimed to investigate the association of the different domains of prediabetes categorized by glycated hemoglobin A1c (A1c) 5.7–6.4%, impaired fasting glucose (IFG), fasting plasma glucose of 5.6–6.9 mmol/L, and impaired glucose tolerance (IGT), two-hour post-load glucose of 7.8–11.0 mmol/L, on arterial stiffness. These were measured by brachial–ankle pulse-wave velocity (baPWV). We enrolled 4938 eligible subjects and divided them into the following nine groups: (1) normoglycemic; (2) isolated A1c 5.7–6.4%; (3) isolated IFG; (4) IFG with A1c 5.7–6.4%; (5) isolated IGT; (6) combined IGT and IFG with A1c <5.7%; (7) IGT with A1c 5.7–6.4%; (8) combined IGT and IFG with A1c 5.7–6.4%; and (9) newly diagnosed diabetes (NDD). The baPWV values were significantly high in subjects with NDD (β = 47.69, 95% confidence interval (CI) = 29.02–66.37, p < 0.001), those with IGT with A1c 5.7–6.4% (β = 36.02, 95% CI = 19.08–52.95, p < 0.001), and those with combined IGT and IFG with A1c 5.7–6.4% (β = 27.72, 95% CI = 0.68–54.76, p = 0.044), but not in the other subgroups. These findings suggest that increased arterial stiffness was found in prediabetes individuals having an A1c 5.7–6.4% with IGT, but not IFG. Isolated A1c 5.7–6.4% and isolated IGT were not associated with elevated arterial stiffness.

Gene Expression of Sirtuin-1 and Endogenous Secretory Receptor for Advanced Glycation End Products in Healthy and Slightly Overweight Subjects after Caloric Restriction and Resveratrol Administration

Sirtuin-1 (Sirt-1) and an endogenous secretory receptor for an advanced glycation end product (esRAGE) are associated with vascular protection. The purpose of this study was to examine the effects of resveratrol (RSV) and caloric restriction (CR) on gene expression of Sirt-1 and esRAGE on serum levels of Sirt1 and esRAGE in healthy and slightly overweight subjects. The study included 48 healthy subjects randomized to 30 days of RSV (500 mg/day) or CR (1000 cal/day). Waist circumference (p = 0.011), TC (p = 0.007), HDL (p = 0.031), non-HDL (p = 0.025), ApoA1 (p = 0.011), and ApoB (p = 0.037) decreased in the CR group. However, TC (p = 0.030), non-HDL (p = 0.010), ApoB (p = 0.034), and HOMA-IR (p = 0.038) increased in the RSV group. RSV and CR increased serum levels of Sirt-1, respectively, from 1.06 ± 0.71 ng/mL to 5.75 ± 2.98 ng/mL (p < 0.0001) and from 1.65 ± 1.81 ng/mL to 5.80 ± 2.23 ng/mL (p < 0.0001). esRAGE serum levels were similar in RSV (p = NS) and CR (p = NS) groups. Significant positive correlation was observed between gene expression changes of Sirt-1 and esRAGE in RSV (r = 0.86; p < 0.0001) and in CR (r = 0.71; p < 0.0001) groups, but not for the changes in serum concentrations. CR promoted increases in the gene expression of esRAGE (post/pre). Future long-term studies are needed to evaluate the impact of these outcomes on vascular health.

Endogenous Secretory Receptor for Advanced Glycation End Products Protects Endothelial Cells from AGEs Induced Apoptosis

Endogenous secretory receptor for advanced glycation end products (esRAGE) binds extracellular RAGE ligands and blocks RAGE activation on the cell surface, protecting endothelial cell function. However, the underlying mechanism remains unclear. Endothelial cells overexpressing the esRAGE gene were generated using a lentiviral vector. Then, quantitative real-time polymerase chain reaction (qRT-PCR) and enzyme-linked immunosorbent assay (ELISA) were used to assess esRAGE mRNA and protein levels, respectively. Hoechst-PI double staining was used to assess apoptosis. Western blot and qRT-PCR were used to assess the expression levels of apoptosis-related factors and the proinflammatory cytokine NF-кB. Compared with the control group, AGEs significantly induced endothelial cell apoptosis, which was significantly reduced by esRAGE overexpression. Incubation with AGEs upregulated the proapoptotic factor Bax and downregulated the antiapoptotic factor Bcl-2. Overexpression of esRAGE reduced Bax expression induced by AGEs and increased Bcl-2 levels. Furthermore, AGEs increased the expression levels of proinflammatory cytokine NF-кB, which were reduced after esRAGE overexpression. esRAGE protects endothelial cells from AGEs associated apoptosis, by downregulating proapoptotic (Bax) and inflammatory (NF-кB) factors and upregulating the antiapoptotic factor Bcl-2.

Circulating soluble RAGE isoforms are attenuated in obese, impaired-glucose-tolerant individuals and are associated with the development of type 2 diabetes

The soluble receptor for advanced glycation end products (sRAGE) may be protective against inflammation associated with obesity and type 2 diabetes (T2DM). The aim of this study was to determine the distribution of sRAGE isoforms and whether sRAGE isoforms are associated with risk of T2DM development in subjects spanning the glucose tolerance continuum. In this retrospective analysis, circulating total sRAGE and endogenous secretory RAGE (esRAGE) were quantified via ELISA, and cleaved RAGE (cRAGE) was calculated in 274 individuals stratified by glucose tolerance status (GTS) and obesity. Group differences were probed by ANOVA, and multivariate ordinal logistic regression was used to test the association between sRAGE isoform concentrations and the proportional odds of developing diabetes, vs. normal glucose tolerance (NGT) or impaired glucose tolerance (IGT). When stratified by GTS, total sRAGE, cRAGE, and esRAGE were all lower with IGT and T2DM, while the ratio of cRAGE to esRAGE (cRAGE:esRAGE) was only lower (P < 0.01) with T2DM compared with NGT. When stratified by GTS and obesity, cRAGE:esRAGE was higher with obesity and lower with IGT (P < 0.0001) compared with lean, NGT. In ordinal logistic regression models, greater total sRAGE (odds ratio, 0.91; P < 0.01) and cRAGE (odds ratio, 0.84; P < 0.01) were associated with lower proportional odds of developing T2DM. Reduced values of sRAGE isoforms observed with both obesity and IGT are independently associated with greater proportional odds of developing T2DM. The mechanisms by which each respective isoform contributes to obesity and insulin resistance may reveal novel treatment strategies for diabetes.

High intake of dietary advanced glycation end-products is associated with increased arterial stiffness and inflammation in subjects with type 2 diabetes

BACKGROUND AND AIMS

Modern diets are high in advanced glycation end-products (dAGEs), derived from processing methods, exerting a pivotal role in promoting atherosclerotic risk. In this cross-sectional study we investigate the relationship between dAGE intake, arterial stiffness, inflammatory profile and macronutrient composition, in subjects with type 2 diabetes without overt cardiovascular disease.

METHODS AND RESULTS

Arterial stiffness, carboxy-methyl-lysine, endogenous secretory receptor for AGEs (esRAGE), high sensitivity C reactive protein (hs-CRP), S100A12 and macronutrient intake were evaluated in 85 subjects with type 2 diabetes. The subjects were stratified into two groups according to dAGE consumption: high and low dAGE intake (≥ or <15.000 kU/day, respectively). Subjects with high dAGE intake (n = 45) showed a higher augmentation, augmentation index and pulse wave velocity (PWV) compared with those subjects with low dAGE intake (18 ± 5.4 vs 12.2 ± 6.3 mmHg, P < 0.05; 38.3 ± 5.4 vs 29.3 ± 10%; 9.2 ± 1.4 m/sec vs 7.9 ± 1.7, P < 0.05, respectively). hs-CRP were higher in subjects with high dAGE intake [0.42 (0.18-0.54) vs 0.21 (0.14-0.52) mg/dL, P < 0.05] whereas esRAGE plasma levels were lower [0.16 (0.23-0.81) vs 0.2 (0.14-0.54) ng/dL, P < 0.05]. Simple regression analysis showed a correlation between dAGEs and fat intake. Multivariate analysis showed an independent association between augmentation, systolic blood pressure (BP) and dAGE consumption; BMI and esRAGE were the major determinants of PWV.

CONCLUSIONS

Our data suggests that a chronic high dAGE diet could lead to a vascular dysfunction and inflammatory activation, contributing to the development of vascular complications in subjects with type 2 diabetes. Testing this hypothesis may represent a direction of future research.

HbA1c Identifies Subjects With Prediabetes and Subclinical Left Ventricular Diastolic Dysfunction

CONTEXT

Prediabetes is associated with subclinical cardiac changes associated with heart failure development.

OBJECTIVE

We investigated diastolic function and its association with markers of glycation and inflammation related to cardiovascular disease in patients with prediabetes. We focused on individuals with prediabetes identified only by glycated hemoglobin A1c [HbA1c; 5.7% to 6.4% and normal fasting glucose (NFG) and normal glucose tolerance (NGT) after an oral glucose tolerance test (OGTT)].

DESIGN

Cross-sectional study.

SETTING

Departments of Clinical and Experimental Medicine and Cardiology, University of Catania, Catania, Italy.

MAIN OUTCOME MEASURES

HbA1c, OGTT, Doppler echocardiography, soluble receptor for advanced glycation end products (sRAGEs), and endogenous secretory RAGE (esRAGE) were evaluated.

PATIENTS

We recruited 167 subjects with NFG/NGT who were stratified according to HbA1c level: controls (HbA1c <5.7%) and HbA1c prediabetes (HbA1c 5.7% to 6.4%).

RESULTS

Patients with HbA1c prediabetes (n = 106) showed a lower peak mitral inflow in early diastole (E wave) to late diastolic atrial filling velocity (A wave) ratio (E/A ratio) than controls (n = 61) (1.10 ± 0.24 vs 1.18 ± 0.23; P < 0.05). They showed a higher left atrium volume (LAV) (28.4 ± 5 vs 22.1 ± 3; P < 0.05) and sphericity index (SI) (0.6 ± 0.06 vs 0.5 ± 0.05; P < 0.05). After multiple regression analyses, HbA1c, sRAGE, and esRAGE were the major determinants of E/A ratio, LAV, and SI.

CONCLUSIONS

Subjects with HbA1c prediabetes exhibited subclinical cardiac alterations associated with sRAGE, esRAGE, and HbA1c. These subjects would not have been classified as having prediabetes on the basis of fasting glycemia or post-OGTT values.

Signs of subclinical atherosclerosis in asymptomatic patients at increased risk of type 2 diabetes mellitus

AIMS

We aimed to study carotid intima media thickness (CIMT) in asymptomatic patients with an increased risk of type 2 diabetes mellitus (T2DM) and in a pre-diabetic state.

METHODS

Diabetes risk assessment was performed in 2420 participants in a voluntary screening program between 2011 and 2013. The risk of T2DM was estimated by the Findrisc scoring system (FR). A FR≥12 was considered as increased risk. HbA1c% between 5.7 and 6.4% signified a pre-diabetic state. Carotid duplex scan was performed and CIMT above 0.9 mm was regarded as pathological. Patients with T2DM or a history of cardiovascular disease were excluded.

RESULTS

Overall 1475 subjects were included. Four groups were compared: "control" (normal HbA1c, FR<12), "HbA1c only" (HbA1c: 5.7-6.4%, FR<12), "Findrisc only" (normal HbA1c, FR≥12) and "combined" (HbA1c: 5.7-6.4%, FR≥12). Frequency of pathological maximal CIMT was 9.4%, 19.7%, 27.4% and 36.4% in the groups, respectively (p<0.001). Logistic regression analysis revealed that compared to control subjects, sex and risk factor-adjusted Odds Ratios for the presence of pathological maximal CIMT were 2.2 (p<0.001), 3.4 (p<0.001) and 5.1 (p<0.001) for the groups, respectively.

CONCLUSIONS

Evaluation of Findrisc score and HbA1c at population level may facilitate early recognition of subclinical vascular complications even in the pre-diabetic state.

Do Advanced Glycation End Products and Its Receptor Play a Role in Pathophysiology of Hypertension?

There is a close relationship between arterial stiffness and blood pressure. The studies suggest that the advanced glycation end products (AGEs) and its cell receptor (RAGE) are involved in the arterial stiffness in two ways: changes in arterial structure and vascular function. Plasma levels of AGEs and expression of RAGE are elevated, while the levels of soluble RAGE (sRAGE) and endogenous secretory RAGE (esRAGE) are lowered in patients with hypertension (HTN). There is a positive correlation between plasma levels of AGEs and arterial stiffness, and an inverse association between arterial stiffness/HTN, and serum levels of sRAGE and esRAGE. Various measures can reduce the levels of AGEs and expression of RAGE, and elevate sRAGE. Arterial stiffness and blood pressure could be reduced by lowering the serum levels of AGEs, and increasing the levels of sRAGE. Levels of AGEs can be lowered by reducing the consumption of AGE-rich diet, short duration of cooking in moist heat at low temperature, and cessation of cigarette smoking. Drugs such as aminoguanidine, vitamins, angiotensin-converting enzyme (ACE) inhibitors, angiotensin-II receptor blockers, statins, and metformin inhibit AGE formation. Alagebrium, an AGE breakers reduces levels of AGEs. Clinical trials with some drugs tend to reduce stiffness. Systemic administration of sRAGE has beneficial effect in animal studies. In conclusion, AGE-RAGE axis is involved in arterial stiffness and HTN. The studies suggest that inhibition of AGEs formation, reduction of AGE consumption, blockade of AGE-RAGE interaction, suppression of RAGE expression, and exogenous administration of sRAGE may be novel therapeutic strategies for treatment of arterial stiffness and HTN.

Pioglitazone and cardiovascular outcomes in patients with insulin resistance, pre-diabetes and type 2 diabetes: a systematic review and meta-analysis

OBJECTIVES

To evaluate the effect of pioglitazone in people with insulin resistance, pre-diabetes and type 2 diabetes.

DESIGN AND SETTING

Systematic review and meta-analysis of randomised, controlled trials.

DATA SOURCES

Literature searches were performed across PubMed, EMBASE, MEDLINE and Cochrane Central Register of Controlled Trials from 1966 to May 2016 to identify randomised, controlled trials with more than 1 year follow-up.

OUTCOME MEASURES

Relative risk (RR) with 95% CI was used to evaluate the association between pioglitazone and the risk of major adverse cardiovascular events (MACE: composite of non-fatal myocardial infarction, non-fatal stroke and cardiovascular death) and safety outcomes, after pooling data across trials in a fixed-effects model.

RESULTS

Nine trials with 12 026 participants were enrolled in the current meta-analysis. Pioglitazone therapy was associated with a lower risk of MACE in patients with pre-diabetes or insulin resistance (RR 0.77, 95% CI 0.64 to 0.93), and diabetes (RR 0.83, 95% CI 0.72 to 0.97). Risks of heart failure (RR 1.32; CI 1.14 to 1.54), bone fracture (RR 1.52, 95% CI 1.17 to 1.99), oedema (RR, 1.63; CI 1.52 to 1.75) and weight gain (RR 1.60; CI 1.50 to 1.72) increased in pioglitazone group.

CONCLUSIONS

Pioglitazone was associated with reduced risk of MACE in people with insulin resistance, pre-diabetes and diabetes mellitus. However, the risks of heart failure, bone fracture, oedema and weight gain were increased.

Elevated endogenous secretory receptor for advanced glycation end products (esRAGE) levels are associated with circulating soluble RAGE levels in diabetic children

BACKGROUND

Advanced glycation end products (AGEs) and the receptor for AGE (RAGE) play an important role in the development of diabetic vascular complications. This study aimed at investigating the relationship between the soluble form of RAGE (sRAGE), endogenous secretory RAGE (esRAGE), and pentosidine in childhood diabetes.

METHODS

The study included 18 children with type 1 diabetes mellitus (T1DM), 10 with type 2 DM (T2DM), and 22 age-matched, non-diabetic children (control).

RESULTS

Serum sRAGE levels in the T1DM (2557.7 pg/mL) were significantly higher than both T2DM (1956.4 pg/mL) and control (1658.5 pg/mL). The circulating levels of esRAGE in T1DM and T2DM children were similar, but significantly higher than those of control. Serum pentosidine levels in the T1DM group were positively correlated with serum sRAGE and esRAGE levels, but not with anthropometric or biochemical measurements. The duration of diabetes and esRAGE levels were independent predictors of the circulating sRAGE levels.

CONCLUSIONS

Unlike adults, children with diabetes exhibit high circulating esRAGE levels, and both sRAGE and esRAGE levels are correlated with pentosidine levels. These results suggest that circulating sRAGE and esRAGE in children may be surrogate markers for progressive glucose toxicity in pediatric patients with childhood-onset diabetes.

Update on pre-diabetes: Focus on diagnostic criteria and cardiovascular risk

Pre-diabetes, which is typically defined as blood glucose concentrations higher than normal but lower than the diabetes threshold, is a high-risk state for diabetes and cardiovascular disease development. As such, it represents three groups of individuals: Those with impaired fasting glucose (IFG), those with impaired glucose tolerance (IGT) and those with a glycated haemoglobin (HbA_1c) between 39-46 mmol/mol. Several clinical trials have shown the important role of IFG, IGT and HbA_1c-pre-diabetes as predictive tools for the risk of developing type 2 diabetes. Moreover, with regard to cardiovascular disease, pre-diabetes is associated with more advanced vascular damage compared with normoglycaemia, independently of confounding factors. In view of these observations, diagnosis of pre-diabetes is mandatory to prevent or delay the development of the disease and its complications; however, a number of previous studies reported that the concordance between pre-diabetes diagnoses made by IFG, IGT or HbA_1c is scarce and there are conflicting data as to which of these methods best predicts cardiovascular disease. This review highlights recent studies and current controversies in the field. In consideration of the expected increased use of HbA_1c as a screening tool to identify individuals with alteration of glycaemic homeostasis, we focused on the evidence regarding the ability of HbA_1c as a diagnostic tool for pre-diabetes and as a useful marker in identifying patients who have an increased risk for cardiovascular disease. Finally, we reviewed the current evidence regarding non-traditional glycaemic biomarkers and their use as alternatives to or additions to traditional ones.