Antiviral and Anti-Inflammatory Therapeutic Effect of RAGE-Ig Protein against Multiple SARS-CoV-2 Variants of Concern Demonstrated in K18-hACE2 Mouse and Syrian Golden Hamster Models

SARS-CoV-2 variants of concern (VOCs) continue to evolve and reemerge with chronic inflammatory long COVID sequelae, necessitating the development of anti-inflammatory therapeutic molecules. Therapeutic effects of the receptor for advanced glycation end products (RAGE) were reported in many inflammatory diseases. However, a therapeutic effect of RAGE in COVID-19 has not been reported. In the present study, we investigated whether and how the RAGE-Ig fusion protein would have an antiviral and anti-inflammatory therapeutic effect in the COVID-19 system. The protective therapeutic effect of RAGE-Ig was determined in vivo in K18-hACE2 transgenic mice and Syrian golden hamsters infected with six VOCs of SARS-CoV-2. The underlying antiviral mechanism of RAGE-Ig was determined in vitro in SARS-CoV-2-infected human lung epithelial cells (BEAS-2B). Following treatment of K18-hACE2 mice and hamsters infected with various SARS-CoV-2 VOCs with RAGE-Ig, we demonstrated (1) significant dose-dependent protection (i.e., greater survival, less weight loss, lower virus replication in the lungs); (2) a reduction of inflammatory macrophages (F4/80+/Ly6C+) and neutrophils (CD11b+/Ly6G+) infiltrating the infected lungs; (3) a RAGE-Ig dose-dependent increase in the expression of type I IFNs (IFN-α and IFN-β) and type III IFN (IFNλ2) and a decrease in the inflammatory cytokines (IL-6 and IL-8) in SARS-CoV-2-infected human lung epithelial cells; and (4) a dose-dependent decrease in the expression of CD64 (FcgR1) on monocytes and lung epithelial cells from symptomatic COVID-19 patients. Our preclinical findings revealed type I and III IFN-mediated antiviral and anti-inflammatory therapeutic effects of RAGE-Ig protein against COVID-19 caused by multiple SARS-CoV-2 VOCs.

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.

Association of Inflammatory and Oxidative Status Markers with Metabolic Syndrome and Its Components in 40-to-45-Year-Old Females: A Cross-Sectional Study

Oxidative stress and sterile inflammation play roles in the induction and maintenance of metabolic syndrome (MetS). This study cohort included 170 females aged 40 to 45 years who were categorized according to the presentation of MetS components (e.g., central obesity, insulin resistance, atherogenic dyslipidemia, and elevated systolic blood pressure) as controls not presenting a single component (n = 43), those with pre-MetS displaying one to two components (n = 70), and females manifesting MetS, e.g., ≥3 components (n = 53). We analyzed the trends of seventeen oxidative and nine inflammatory status markers across three clinical categories. A multivariate regression of selected oxidative status and inflammatory markers on the components of MetS was performed. Markers of oxidative damage (malondialdehyde and advanced-glycation-end-products-associated fluorescence of plasma) were similar across the groups. Healthy controls displayed lower uricemia and higher bilirubinemia than females with MetS; and lower leukocyte counts, concentrations of C-reactive protein, interleukine-6, and higher levels of carotenoids/lipids and soluble receptors for advanced glycation end-products than those with pre-MetS and MetS. In multivariate regression models, levels of C-reactive protein, uric acid, and interleukine-6 were consistently associated with MetS components, although the impacts of single markers differed. Our data suggest that a proinflammatory imbalance precedes the manifestation of MetS, while an imbalance of oxidative status accompanies overt MetS. Further studies are needed to elucidate whether determining markers beyond traditional ones could help improve the prognosis of subjects at an early stage of MetS.

The Remarkable Roles of the Receptor for Advanced Glycation End Products (RAGE) and Its Soluble Isoforms in COVID-19: The Importance of RAGE Pathway in the Lung Injuries

The respiratory symptoms of acute respiratory distress syndrome (ARDS) in the coronavirus disease 2019 (COVID-19) patients is associated with accumulation of pre-inflammatory molecules such as advanced glycation end-products (AGES), calprotectin, high mobility group box family-1 (HMGB1), cytokines, angiotensin converting enzyme 2 (ACE2), and other molecules in the alveolar space of lungs and plasma. The receptor for advanced glycation end products (RAGEs), which is mediated by the mitogen-activated protein kinase (MAPK), plays a critical role in the severity of chronic inflammatory diseases such as diabetes mellitus (DM) and ARDS. The RAGE gene is most expressed in the alveolar epithelial cells (AECs) of the pulmonary system. Several clinical trials are now being conducted to determine the possible association between the levels of soluble isoforms of RAGE (sRAGE and esRAGE) and the severity of the disease in patients with ARDS and acute lung injury (ALI). In the current article, we reviewed the most recent studies on the RAGE/ligands axis and sRAGE/esRAGE levels in acute respiratory illness, with a focus on COVID-19–associated ARDS (CARDS) patients. According to the research conducted so far, sRAGE/esRAGE measurements in patients with CARDS can be used as a powerful chemical indicator among other biomarkers for assessment of early pulmonary involvement. Furthermore, inhibiting RAGE/MAPK and Angiotensin II receptor type 1 (ATR1) in CARDS patients can be a powerful strategy for diminishing cytokine storm and severe respiratory symptoms.

Metabolic Syndrome and Male Fertility: Beyond Heart Consequences of a Complex Cardiometabolic Endocrinopathy

Metabolic syndrome (MetS) is a highly prevalent condition among adult males, affecting up to 41% of men in Europe. It is characterized by the association of obesity, hypertension, and atherogenic dyslipidemia, which lead to premature morbidity and mortality due to cardiovascular disease (CVD). Male infertility is another common condition which accounts for about 50% of cases of couple infertility worldwide. Interestingly, male infertility and MetS shares several risk factors (e.g., smoking, ageing, physical inactivity, and excessive alcohol consumption), leading to reactive oxygen species (ROS) production and increased oxidative stress (OS), and resulting in endothelial dysfunction and altered semen quality. Thus, the present narrative review aims to discuss the pathophysiological mechanisms which link male infertility and MetS and to investigate the latest available evidence on the reproductive consequences of MetS.

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.

Can advanced glycation end-products and their receptors be affected by weight loss? A systematic review

Advanced glycation end products (AGEs) have been implicated in the pathogenesis of most chronic diseases. Therefore, identification of treatments that can attenuate the effects of these compounds and prevent cardiometabolic complications is of extreme public health interest. Recently, body weight management interventions showed positive results on reducing serum AGE concentrations. Moreover, the soluble receptor for advanced glycation end products (sRAGE) is considered to be a novel biomarker to identify patients with obesity most likely to benefit from weight management interventions. This systematic review aimed to critically analyze papers evaluating the effects of weight loss on serum AGEs and its receptors in adults with excess body weight. MEDLINE, Cochrane, Scopus, and Lilacs databases were searched. Three studies evaluating the response of AGEs to energy-restricted diets and six assessing sRAGE as the primary outcome were included. Energy-restricted diets and bariatric surgery reduced serum AGE concentrations, but effects on endogenous secretory RAGE (esRAGE) and sRAGE concentrations are conflicting. These results may be associated with mechanisms related to changes in dietary intake and limiting endogenous AGE formation. Therefore, the role of energy-restricted diets and bariatric surgery on lowering serum AGE concentrations, as well as its effects on AGEs receptors, deserves further investigation.

Sex Differences in Association of Elevated Blood Pressure with Variables Characterizing Cardiometabolic Risk in Young Subjects with or Without Metabolic Abnormalities

Males present higher blood pressure (BP) values, higher prevalence of elevated BP, and a different prevalence of cardiometabolic risk factors when compared with females. We assumed that the trends of risk markers across BP categories (normotension, high normal BP, and hypertension) differ in young males and females, and between subjects without metabolic abnormalities (without obesity, insulin resistance, atherogenic dyslipidemia, hyperuricemia, or microinflammation) and those presenting them. Data from 2543 subjects (48% males) aged from 16 to 23 years were analyzed. The findings showed that 15% of males and 4% of females presented high normal BP while 9% and 1%, respectively, had hypertension. In males, variables characterizing obesity status, insulin sensitivity, atherogenic dyslipidemia, uric acid, adiponectin, a soluble receptor for advanced glycation end-products, and leukocyte counts showed worsening trends across BP categories. Females presented significant trends only for obesity measures, LDL-cholesterol, and non-HDL-cholesterol. Across BP categories, trends of variables characterizing cardiometabolic risk differed among abnormalities-free and presenting males. The multivariate model selected measures of central obesity, atherogenic dyslipidemia, insulin resistance, and uric acid as significant predictors of BP in both genders, and C-reactive protein in females. Sex differences in measures of cardiovascular health in juveniles may remain undiscovered unless two sexes are analyzed separately. These differences may have implications for sex-specific disease risk in adulthood.

Associations of dicarbonyl stress with complement activation: the CODAM study

AIMS/HYPOTHESIS

Reactive α-dicarbonyl compounds are major precursors of AGEs and may lead to glycation of circulating and/or cell-associated complement regulators. Glycation of complement regulatory proteins can influence their capacity to inhibit complement activation. We investigated, in a human cohort, whether greater dicarbonyl stress was associated with more complement activation.

METHODS

Circulating concentrations of dicarbonyl stress markers, i.e. α-dicarbonyls (methylglyoxal [MGO], glyoxal [GO] and 3-deoxyglucosone [3-DG]), and free AGEs (N^ε-(carboxymethyl)lysine [CML], N^ε-(carboxyethyl)lysine [CEL] and N^δ-(5-hydro-5-methyl-4-imidazolon-2-yl)-ornithine [MG-H1]), and protein-bound AGEs (CML, CEL, pentosidine), as well as the complement activation products C3a and soluble C5b-9 (sC5b-9), were measured in 530 participants (59.5 ± 7.0 years [mean ± SD], 61% men) of the Cohort on Diabetes and Atherosclerosis Maastricht (CODAM) study. Multiple linear regression analyses were used to investigate the associations between dicarbonyl stress (standardised) and complement activation (standardised) with adjustment of potential confounders, including age, sex, lifestyle, use of medication and markers of obesity. In addition, the associations of two potentially functional polymorphisms (rs1049346, rs2736654) in the gene encoding glyoxalase 1 (GLO1), the rate-limiting detoxifying enzyme for MGO, with C3a and sC5b-9 (all standardized) were evaluated.

RESULTS

After adjustment for potential confounders, plasma concentration of the dicarbonyl GO was inversely associated with sC5b-9 (β -0.12 [95% CI -0.21, -0.02]) and the protein-bound AGE CEL was inversely associated with C3a (-0.17 [-0.25, -0.08]). In contrast, the protein-bound AGE pentosidine was positively associated with sC5b-9 (0.15 [0.05, 0.24]). No associations were observed for other α-dicarbonyls and other free or protein-bound AGEs with C3a or sC5b-9. Individuals with the AG and AA genotype of rs1049346 had, on average, 0.32 and 0.40 SD lower plasma concentrations of sC5b-9 than those with the GG genotype, while concentrations of C3a did not differ significantly between rs1049346 genotypes. GLO1 rs2736654 was not associated with either C3a or sC5b-9.

CONCLUSIONS/INTERPRETATION

Plasma concentrations of dicarbonyl stress markers showed distinct associations with complement activation products: some of them were inversely associated with either C3a or sC5b-9, while protein-bound pentosidine was consistently and positively associated with sC5b-9. This suggests different biological relationships of individual dicarbonyl stress markers with complement activation.

Elevated blood pressure-associated cardiometabolic risk factors and biomarkers in 16-23 years old students with or without metabolic abnormalities

In obesity, cardiometabolic risk markers show worsening trends with increasing blood pressure (BP). We assumed that risk markers show similar trends across BP categories (normotension, high normal BP, hypertension) in metabolic abnormalities-free subjects (without obesity, insulin resistance, atherogenic dyslipidemia, hyperuricemia, microinflammation) and those presenting them. Data from 2547 (48.1% males) subjects aged 16-23 years were analyzed. The prevalence of males increased across BP categories. Forty-seven percent of individuals with elevated BP were metabolic abnormalities-free. Among 1461 metabolic abnormalities-free subjects, 9% had high normal BP, and 4% hypertension; among 1086 individuals presenting metabolic abnormalities, the prevalence reached 13% and 6%, respectively, (p < 0.001). Both groups displayed similar BP values in corresponding BP categories and significant trends in markers of adiposity, insulin resistance, HDL-cholesterol, atherogenic index of plasma, uric acid, adiponectinemia, and antioxidant capacity of plasma across BP categories. In metabolic abnormalities-free individuals, also significant trends in soluble receptors for advanced glycation end products were revealed. Continuous metabolic syndrome score, a measure of cardiometabolic risk, increased across BP categories regardless of presence or absence of metabolic abnormalities. Multivariate regression models selected male gender, fat-free mass, and uric acid as significant independent predictors for determining BP. Our data emphasize that having a BP outside the normal range significantly worsens risk for cardiometabolic disease in young individuals even if the thresholds for any of the risk factors are not exceeded. Longitudinal studies are needed to assess whether in patients with elevated BP the prognosis of adverse outcomes differs between those presenting and not presenting metabolic abnormalities.

Advanced Glycation End Products: Building on the Concept of the "Common Soil" in Metabolic Disease

The role of advanced glycation end products (AGEs) in promoting and/or exacerbating metabolic dysregulation is being increasingly recognized. AGEs are formed when reducing sugars nonenzymatically bind to proteins or lipids, a process that is enhanced by hyperglycemic and hyperlipidemic environments characteristic of numerous metabolic disorders including obesity, diabetes, and its complications. In this mini-review, we put forth the notion that AGEs span the spectrum from cause to consequence of insulin resistance and diabetes, and represent a "common soil" underlying the pathophysiology of these metabolic disorders. Collectively, the surveyed literature suggests that AGEs, both those that form endogenously as well as exogenous AGEs derived from environmental factors such as pollution, smoking, and "Western"-style diets, contribute to the pathogenesis of obesity and diabetes. Specifically, AGE accumulation in key metabolically relevant organs induces insulin resistance, inflammation, and oxidative stress, which in turn provide substrates for excess AGE formation, thus creating a feed-forward-fueled pathological loop mediating metabolic dysfunction.

Circulating Advanced Glycation Endproducts and Long-Term Risk of Cardiovascular Mortality in Kidney Transplant Recipients

BACKGROUND AND OBJECTIVES

In kidney transplant recipients, elevated circulating advanced glycation endproducts (AGEs) are the result of increased formation and decreased kidney clearance. AGEs trigger several intracellular mechanisms that ultimately yield excess cardiovascular disease. We hypothesized that, in stable kidney transplant recipients, circulating AGEs are associated with long-term risk of cardiovascular mortality, and that such a relationship is mediated by inflammatory, oxidative stress, and endothelial dysfunction biomarkers.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Prospective cohort study of stable kidney transplant recipients recruited between 2001 and 2003 in a university setting. We performed multivariable-adjusted Cox regression analyses to assess the association of AGEs (i.e., Nε-[Carboxymethyl]lysine (CML) and Nε-[Carboxyethyl]lysine (CEL), measured by tandem mass spectrometry) with cardiovascular mortality. Mediation analyses were performed according to Preacher and Hayes's procedure.

RESULTS

We included 555 kidney transplant recipients (age 51±12 years, 56% men). During a median follow-up of 6.9 years, 122 kidney transplant recipients died (52% deaths were due to cardiovascular causes). CML and CEL concentrations were directly associated with cardiovascular mortality (respectively, hazard ratio, 1.55; 95% confidence interval, 1.24 to 1.95; P<0.001; and hazard ratio, 1.53; 95% confidence interval 1.18 to 1.98; P=0.002), independent of age, diabetes, smoking status, body mass index, eGFR and proteinuria. Further adjustments, including cardiovascular history, did not materially change these findings. In mediation analyses, free thiol groups and soluble vascular cell adhesion molecule-1 consistently explained approximately 35% of the association of CML and CEL with cardiovascular mortality.

CONCLUSIONS

In stable kidney transplant recipients, circulating levels of AGEs are independently associated with long-term risk of cardiovascular mortality.

PODCAST

This article contains a podcast at https://www.asn-online.org/media/podcast/CJASN/2019_09_17_CJN00540119.mp3.

Vitamin D3 supplementation ameliorates ovariectomy-induced cardiac apoptotic and structural changes in adult albino rats

The effect of vitamin D on cardiac dysfunction after menopause is still under investigation. Therefore, we investigated the effect of vitamin D3 on cardiac apoptotic and structural changes in ovariectomized rats. Forty adult female albino rats were divided into 4 equal groups: sham rats, sham rats treated with vitamin D3, ovariectomized rats, and ovariectomized rats treated with vitamin D3 (500 IU/kg per day for 6 weeks, orally). Body mass, blood pressure, heart rate, and whole heart mass (WHM) were measured. Serum soluble receptors of advanced glycation end products (sRAGE), C-reactive protein, malondialdehyde, and total antioxidant capacity were estimated. Cardiac sections were stained with haematoxylin-eosin and Masson's trichrome stain. Fas and FasL apoptosis-related proteins were detected by immunohistochemistry. Vitamin D3 treatment significantly decreased ovariectomy-induced cardiac Fas and FasL apoptosis-related proteins, whole heart mass, body mass, C-reactive protein, and malondialdehyde accompanied by decreased inflammation and reduced collagen deposition between cardiac muscle fibres. However, vitamin D3 significantly increased total antioxidant capacity and sRAGE in ovariectomized and sham treated groups. Our findings suggest that vitamin D3 treatment can prevent ovariectomy-induced cardiac structural and apoptotic changes in rats via increasing sRAGE and antioxidant activity. Our results suggest that vitamin D3 has therapeutic effect against postmenopausal cardiovascular disease.

Advanced glycation end products and their receptors did not show any association with body mass parameters in metabolically healthy adolescents

AIM

We determined the relationship between circulating advanced glycation end products (AGEs), AGE receptors and homeostatic model assessment for insulin resistance (HOMA-IR) in metabolically healthy obese and normal weight adolescents.

METHODS

In 2015, we recruited 80 normal weight adolescents and 80 with obesity from schools Leon city, Mexico, and put them into metabolically healthy (HOMA-IR <3.0) and unhealthy (HOMA-IR >3.0) groups. We measured their body mass index (BMI) and carried out detailed blood analyses.

RESULTS

We found a higher triglycerides, triglycerides/high-density lipoproteins cholesterol (TG/HDL-C) index, HOMA-IR, tumour necrosis factor alpha (TNF-α) and interleukin-6 (IL-6) in the metabolically healthy group and found correlations between HOMA-IR with BMI, the TG/HDL-C index and IL-6 and the TG/HDL-C index and BMI and (TNF-α). There was no correlation between markers of obesity and circulating N-carboxymethyl-lysine (CML) or soluble receptor for advanced glycation end products (sRAGE). Some unhealthy adolescents had higher CML (15.5 ± 2.7 U/mL, p < 0.028) and sRAGE (3123 ± 1364 pg/mL, p < 0.001) than the healthy group.

CONCLUSION

HOMA-IR and the TG/HDL-C index were associated with BMI and inflammation markers. CML and sRAGE were not associated with obesity or inflammation. These parameters were higher in unhealthy obese adolescents.

Association of Dietary Advanced Glycation End Products with Metabolic Syndrome in Young Mexican Adults

Background: Consumption of dietary advanced glycation end products is linked to metabolic syndrome. The objective was to describe the association between dietary advanced glycation end products intake and metabolic syndrome in young Mexican adults. Methods: The present was a cross-sectional study in 126 Mexican adults 18–35 years old evaluating metabolic syndrome through the harmonized criteria. Macronutrients and dietary advanced glycation end products intake were estimated through three 24-hour dietary recalls and food composition tables. Association between metabolic syndrome and high advanced glycation end products intake (≥10,000 kU/day) was evaluated through three logistic regression models adjusted by sex, age, family history of cardiometabolic diseases and energy intake. Results: Subjects with a higher advanced glycation end products intake were more likely to have impaired fasting glucose (OR: 4.91, 95% CI 1.29–18.60, p < 0.05) and metabolic syndrome (OR: 2.67, 95% CI 0.96–7.44, p = 0.059) than those participants with low consumption of these products after adjustment of sex, age, family history of cardiovascular disease and energy intake. Conclusions: High intake of dietary advanced glycation end products was significantly associated with impaired fasting glucose and marginally with metabolic syndrome in young Mexican adults regardless of sex, age, family history of cardiovascular disease and energy intake.

Plasma markers of oxidative status were associated with increasing continuous cardiometabolic risk scores in healthy students aged 16-20 years without central obesity

AIM

We studied the association between increased cardiometabolic risk and markers of oxidative status and glycation in apparently healthy subjects who did not present with central obesity.

METHODS

From 2011 to 2012, we recruited 2064 students (53% girls) aged 16-20 years from Western Slovakia. Their continuous metabolic syndrome scores (MSS) were calculated as a mean of the sum of the z-scores of waist-to-height ratio, mean arterial pressure, triacylglycerols, high-density lipoprotein-cholesterol and quantitative insulin sensitivity check index. Plasma markers of protein glycation and oxidation, lipid peroxidation and total antioxidant status were analysed.

RESULTS

In both genders, advanced oxidation protein products (AOPPs) increased across the MSS quintiles (p < 0.001). AOPPs and fructosamines were significant predictors of the MSS in both genders. Moreover, high-sensitivity C-reactive protein, leukocyte counts and advanced glycation end-products (AGEs) contributed significantly in girls. Triacylglycerols, fructosamines, AGEs and total antioxidant capacity correlated significantly with AOPPs in both genders.

CONCLUSION

Advanced oxidation protein products may act as inflammatory mediators that contribute to the development of cardiometabolic afflictions. Determining these may provide information related to cardiometabolic risk and represent potential target to reduce or prevent irreversible oxidative stress-induced cellular damage.

Glycated proteins in nutrition: Friend or foe?

Advanced glycation end products (AGEs) are formed in in vivo, and accumulate in tissues and body fluids during ageing. Endogenous AGE-modified proteins show altered structure and function, and may interact with receptor for AGEs (RAGE) resulting in production of reactive oxygen species, inflammatory, atherogenic and diabetogenic responses. AGEs are also formed in thermally processed foods. Studies in rodents document that dietary AGEs are partially absorbed into circulation, and accumulate in different tissues. Knowledge on the health effects of high dietary intake of AGEs is incomplete and contradictory. In this overview we discuss the data from experimental and clinical studies, either those supporting the assumption that restriction of dietary AGEs associated with health benefits, or data suggesting that dietary intake of AGEs associates with positive health outcomes. We polemicize whether the effects of exaggerated intake or restriction of highly thermally processed foods might be straightforward interpreted as the effects of AGEs-rich vs. AGEs-restricted diets. We also underline the lack of studies, and thus a poor knowledge, on the effects of different single chemically defined AGEs administration, concurrent intake of different dietary AGEs, of load with dietary AGEs corresponding to the habitual diet in humans, and on those of dietary AGEs in vulnerable populations, such as infants and particularly elderly.

Serum levels of advanced glycation end-products (AGEs) and the decoy soluble receptor for AGEs (sRAGE) can identify non-alcoholic fatty liver disease in age-, sex- and BMI-matched normo-glycemic adults

BACKGROUND

Non-alcoholic fatty liver disease (NAFLD) is a serious health problem affecting ~25% of the global population. While NAFLD pathogenesis is still unclear, multiple NAFLD parameters, including reduced insulin sensitivity, impaired glucose metabolism and increased oxidative stress are hypothesised to foster the formation of advanced glycation end-products (AGEs). Given the link of AGEs with end organ damage, there is scope to examine the role of the AGE/RAGE axis activation in liver injury and NAFLD.

METHODS

Age, sex and body mass index matched normo-glycemic NAFLD adults (n = 58) and healthy controls (n = 58) were enrolled in the study. AGEs were analysed by liquid chromatography-mass spectrometry (CML, CEL), fluorescence (pentosidine, AGE fluorescence), colorimetry (fructosamine) and ELISA (sRAGE). Their association with liver function, inflammation, fibrosis and stage of NAFLD was examined.

RESULTS

Early and advanced glycation end-products, except N^ε-carboxymethyl-L-lysine (CML), were 10-30% higher, sRAGE levels 1.7-fold lower, and glycation/sRAGE ratios 4-fold higher in the NAFLD cases compared to controls. While AGEs presented weak to moderate correlations with indices of liver function and damage (AST/ALT, HOMA-IR, TNF-α and TGF-β1), including sRAGE to characterize the AGEs/sRAGE axis strengthened the associations observed. High glycation/sRAGE ratios were associated with 1.3 to 14-fold likelihood of lower AST/ALT ratios. The sum of AGEs/sRAGE ratios accurately distinguished between healthy controls and NAFLD patients (area under the curve of 0.85). Elevated AGEs/sRAGE (>7.8 mmol/pmol) was associated with a 12-fold likelihood of the presence of NAFLD.

CONCLUSION

These findings strengthen the involvement of AGEs-RAGE axis in liver injury and the pathogenesis of NAFLD.

The AGE-RAGE axis in an Arab population: The United Arab Emirates Healthy Futures (UAEHFS) pilot study

AIMS

The transformation of the United Arab Emirates (UAE) from a semi-nomadic to a high income society has been accompanied by increasing rates of obesity and Type 2 diabetes mellitus. We examined if the AGE-RAGE (receptor for advanced glycation endproducts) axis is associated with obesity and diabetes mellitus in the pilot phase of the UAE Healthy Futures Study (UAEHFS).

METHODS

517 Emirati subjects were enrolled and plasma/serum levels of AGE, carboxy methyl lysine (CML)-AGE, soluble (s)RAGE and endogenous secretory (es)RAGE were measured along with weight, height, waist and hip circumference (WC/HC), blood pressure, HbA1c, Vitamin D levels and routine chemistries. The relationship between the AGE-RAGE axis and obesity and diabetes mellitus was tested using proportional odds models and linear regression.

RESULTS

After covariate adjustment, AGE levels were significantly associated with diabetes status. Levels of sRAGE and esRAGE were associated with BMI and levels of sRAGE were associated with WC/HC.

CONCLUSIONS

The AGE-RAGE axis is associated with diabetes status and obesity in this Arab population. Prospective serial analysis of this axis may identify predictive biomarkers of obesity and cardiometabolic dysfunction in the UAEHFS.

Association between metabolically healthy central obesity in women and levels of soluble receptor for advanced glycation end products, soluble vascular adhesion protein-1, and the activity of semicarbazide-sensitive amine oxidase

AIM

To determine the levels of circulating soluble receptor for advanced glycation end products (sRAGE), as a biomarker of risk of metabolic syndrome and cardiovascular disease development in centrally obese (CO) women considered metabolically healthy (COH) in comparison with those metabolically unhealthy (COU).

METHODS

47 lean healthy, 17 COH (presenting waist-to-height ratio ≥0.5 but not elevated blood pressure, atherogenic lipid profile, and insulin resistance), and 50 COU (CO presenting ≥2 risk factors) women aged 40-45 years were included. Anthropometric characteristics, blood chemistry and hematology data, adipokines, markers of inflammation, sRAGE, soluble vascular adhesion protein-1 (sVAP-1), and the activity of semicarbazide sensitive amine oxidase (SSAO) were determined.

RESULTS

Central obesity associated with low sRAGE levels (lean healthy: 1503±633 pg/mL; COH: 1103±339 pg/mL, P<0.05; COU: 1106±367 ng/mL, P<0.0.1), hyperleptinemia, and elevated markers of inflammation irrespective of the presence or absence of cardiometabolic risk factors. COU women presented high adiponectin levels. SVAP-1 concentrations and the activity of SSAO were similar in all 3 groups.

CONCLUSION

COH women present abnormalities in non-standard markers of cardiometabolic risk (sRAGE, leptin, high sensitive C-reactive protein), supporting the view that there is no healthy pattern of obesity. The clinical impact of our findings for future prognosis of metabolically healthy obese subjects remains to be elucidated in longitudinal studies.

A Comparative Study on Skin and Plasma Advanced Glycation End Products and Their Associations with Arterial Stiffness

BACKGROUND

We compared skin and plasma measurements of advanced glycation end products (AGEs), with particular focus on their levels in the presence of hypertension or diabetes and prediabetes and their associations with arterial stiffness in outpatients with suspected or diagnosed hypertension.

METHODS

Skin AGE accumulation was measured as autofluorescence on the left forearm using the skin autofluorescence Reader and expressed in arbitrary units in the range from 0 to 25. Plasma AGE concentration was measured by the enzyme-linked immunosorbent assay method and logarithmically transformed for statistical analysis. Arterial stiffness was assessed by carotid-femoral pulse wave velocity (cfPWV) using the SphygmoCor system (Sydney, Australia).

RESULTS

The 218 participants (96 [44.0%] men, mean age 51.9 years) had a mean skin autofluorescence of 1.89 arbitrary units, plasma AGE concentration of 4.47 μg/ml, and cfPWV of 8.0 m/s. Skin autofluorescence was significantly correlated with plasma AGEs in diabetic or prediabetic patients (n = 31, r = 0.37, p = 0.04) but not in subjects with normoglycemia (n = 187, r = -0.05, p = 0.48). Nonetheless, both measurements were significantly (p ≤ 0.001) higher in men (2.00 arbitrary units and 6.73 μg/ml, respectively) than women (1.81 arbitrary units and 3.60 μg/ml, respectively) and in diabetic or prediabetic (2.03 arbitrary units and 6.61 μg/ml, respectively) than normoglycemia subjects (1.87 arbitrary units and 4.17 μg/ml, respectively), but similar in hypertensive (n = 105) and normotensive subjects (n = 113, p ≥ 0.35). In adjusted multiple regression analyses, plasma AGE concentration, but not skin autofluorescence (p ≥ 0.37), was significantly associated with cfPWV in all subjects (β 0.44 m/s for each 10-fold increase; p = 0.04) and in subgroups of men and diabetes and prediabetes (β 0.12-0.55 m/s for each 10-fold increase; p ≤ 0.02).

CONCLUSIONS

Although skin and plasma AGEs were similarly associated with gender and diabetes or prediabetes, they might measure something different and have different clinical relevance, such as for arterial stiffness.

Correlation among soluble receptors for advanced glycation end-products, soluble vascular adhesion protein-1/semicarbazide-sensitive amine oxidase (sVAP-1) and cardiometabolic risk markers in apparently healthy adolescents: a cross-sectional study

In non-diabetics, low levels of soluble receptor for advanced glycations end products (sRAGE) associate with an increased risk of development of diabetes, cardiovascular afflictions, or death. The majority of studies in non-diabetics report an inverse relationship between measures of obesity, cardiometabolic risk factors and sRAGE and/or endogenous secretory RAGE (esRAGE) levels. To elucidate whether this inconsistency is related to the metabolically healthy obese phenotype, or a different impact of the risk factors in presence and absence of obesity, we analyzed data from 2206 apparently healthy adolescents (51 % girls) aged 15-to-19 years. The association of sRAGE levels with soluble vascular adhesion protein-1/semicarbazide sensitive amine oxidase (sVAP-1/SSAO) was also investigated. Centrally obese, including metabolically healthy, adolescents present significantly lower sRAGE and esRAGE, but not sVAP-1, levels in comparison with their lean counterparts. An increasing number of cardiometabolic risk factors did not associate with significant changes in sRAGE, esRAGE or sVAP-1 levels either in lean or in obese subjects. In multivariate analyses, WHtR, hsCRP, markers of glucose homeostasis, renal function, adiponectin, and sVAP-1 associated significantly with sRAGE and esRAGE. SVAP-1 correlated significantly with glycemia, adiponectin, hsCRP, and sRAGE. Thus, in adolescents, a decline in sRAGE and esRAGE precedes the development of metabolic syndrome. When combined, standard and non-standard cardiometabolic risk factors explain only minor proportion in a variability of sRAGE and esRAGE (8 %-11 %); or sVAP-1 (12 %-20 %). Elucidation of pathogenetic mechanisms underlying early decline in sRAGE and esRAGE levels in obese adolescents and their clinical impact with regard to future cardiometabolic health requires further studies.

Diet low in advanced glycation end products increases insulin sensitivity in healthy overweight individuals: a double-blind, randomized, crossover trial

BACKGROUND

The consumption of advanced glycation end products (AGEs) has increased because of modern food processing and has been linked to the development of type 2 diabetes in rodents.

OBJECTIVE

We determined whether changing dietary AGE intake could modulate insulin sensitivity and secretion in healthy, overweight individuals.

DESIGN

We performed a double-blind, randomized, crossover trial of diets in 20 participants [6 women and 14 men; mean ± SD body mass index (in kg/m(2)): 29.8 ± 3.7]. Isoenergetic- and macronutrient-matched diets that were high or low in AGE content were alternately consumed for 2 wk and separated by a 4-wk washout period. At the beginning and end of each dietary period, a hyperinsulinemic-euglycemic clamp and an intravenous glucose tolerance test were performed. Dietary, plasma and urinary AGEs N(€)-(carboxymethyl)lysine (CML), N(€)-(carboxyethyl)lysin (CEL), and methylglyoxal-derived hydroimadazolidine (MG-H1) were measured with the use of mass spectrometry.

RESULTS

Participants consumed less CML, CEL, and MG-H1 during the low-AGE dietary period than during the high-AGE period (all P < 0.05), which was confirmed by changes in urinary AGE excretion. There was an overall difference in insulin sensitivity of -2.1 mg · kg(-1) · min(-1) between diets (P = 0.001). Insulin sensitivity increased by 1.3 mg · kg(-1) · min(-1) after the low-AGE diet (P = 0.004), whereas it showed a tendency to decrease by 0.8 mg · kg(-1) · min(-1) after the high-AGE diet (P = 0.086). There was no difference in body weight or insulin secretion between diets (P = NS).

CONCLUSIONS

A diet that is low in AGEs may reduce the risk of type 2 diabetes by increasing insulin sensitivity. Hence, a restriction in dietary AGE content may be an effective strategy to decrease diabetes and cardiovascular disease risks in overweight individuals. This trial was registered at clinicaltrials.gov as NCT00422253.

Elevated serum advanced glycation endproducts in obese indicate risk for the metabolic syndrome: a link between healthy and unhealthy obesity?

CONTEXT

Although obesity can predispose to the metabolic syndrome (MS), diabetes, and cardiovascular disease, not all obese subjects develop MS, hence the need for new indicators of risk for this syndrome. Advanced glycation end products (AGEs) correlate with factors involved in the MS, including inflammation and insulin resistance (IR). Because AGEs can be derived from food and are modifiable, it is important to determine whether they are a risk factor for MS.

OBJECTIVE

The objective of this study was to assess the association of endogenous and exogenous AGEs with MS criteria.

DESIGN

The following data were collected in a cross-sectional study of subjects with and without the MS: serum AGEs (sAGEs) and mononuclear cell AGEs, metabolites, pro- and antiinflammatory markers, body fat mass measures, including abdominal magnetic resonance imaging, and caloric and dietary AGE (dAGE) consumption.

SETTING

The study was conducted in the general community.

PARTICIPANTS

Participants included 130 MS and 139 non-MS subjects of both sexes, older than 50 years.

RESULTS

sAGEs ((ϵ)N-carboxymethyllysine, methylglyoxal) were markedly elevated in obese persons with more than one other MS criteria but not in obese without MS criteria. sAGEs directly correlated with markers of IR (HOMA) and inflammation (leptin, TNFα, RAGE) and inversely with innate defenses (SIRT1, AGE receptor 1 [AGER1], glyoxalase-I, adiponectin). sAGEs correlated with dAGEs but not with calories, nutrient consumption, or fat mass measures. Consumption of dAGE, but not of calories, was markedly higher in MS than in non-MS.

CONCLUSION

High sAGEs, a modifiable risk factor for IR, may indicate risk for the MS, type 2 diabetes, and cardiovascular disease. High dietary AGE consumption and serum AGE levels may link healthy obesity to at-risk obesity.

Relationship of Advanced Glycation End Products With Cardiovascular Disease in Menopausal Women

Cardiovascular disease (CVD) represents the most significant cause of death in postmenopausal women. Advanced glycation end products (AGEs) are formed by nonenzymatic modification of proteins, lipids, and nucleic acids by glucose. This review focuses on the contribution of AGEs and their receptors to the development of CVD in menopause. Advanced glycation end products circulate and activate the proinflammatory endothelial cell surface receptor called RAGE, bind to the extracellular matrix of the cardiovascular system, or bind to the circulating anti-inflammatory soluble form of RAGE (sRAGE). Data emerging from human and animal studies suggest that AGEs and both receptors (RAGE and sRAGE) are implicated in the pathophysiology of CVD. Particular emphasis has been given to the role of AGE-RAGE axis in oxidative stress, inflammation, endothelial cell toxicity, and progression of atherosclerosis in menopause. Data accruing from human and animal studies suggest that RAGE expression level and circulating sRAGE level are associated with estradiol and are correlated with CVD risk factors, such as adiposity, dyslipidemia, insulin resistance, diabetes, and metabolic syndrome. By recognizing the impact of AGEs on atherosclerosis, pharmacological strategies targeting the AGE-RAGE pathway hold therapeutic potential for CVD in menopausal women.

Serum levels of soluble receptor for advanced glycation end-products and metabolic syndrome: the Northern Manhattan Study

OBJECTIVE

Recent studies have shown a strong link between serum soluble receptor for advanced glycation end-products (sRAGE) levels and cardiovascular risk factors and disease. What is less clear is the relationship between metabolic risk factors and sRAGE levels. Here, we tested the hypothesis that lower sRAGE levels may be associated with the metabolic syndrome (MetS) in an urban multi ethnic population.

MATERIALS/METHODS

From the Northern Manhattan Study (NOMAS), we included 1101 stroke-free participants (mean age: 71 ± 9 years, 60% women, 64% Hispanic, 18% black, 16% white). Serum sRAGE was measured by ELISA. Quantile regression analysis was performed to evaluate the association between sRAGE and MetS components and MetS, after adjusting for sociodemographics, smoking status and kidney function.

RESULTS

The median (interquartile) sRAGE was 899 pg/ml (647-1248 pg/ml), 42% had metabolic syndrome. The prevalence of unfavorable metabolic factors was 50% for waist circumference (WC), 81% for blood pressure, 39% for fasting glucose, 35% for reduced high density lipoproteins (HDL), and 23% for triglycerides. After adjustment, the median sRAGE levels were at least 120 pg/ml lower in those who had elevated WC (p<0.0001), blood pressure (p=0.0014), and fasting glucose (p<0.0001), and those who had 2 or more unfavorable metabolic factors. No relationship was seen between sRAGE levels and elevated triglycerides or reduced HDL levels. Interaction and stratified analyses revealed that the association of sRAGE with MetS was more prominent in Hispanics compared to whites, and displaying no association with components of MetS in blacks.

CONCLUSIONS

sRAGE levels were mainly associated with MetS factors related to obesity, diabetes and hypertension, and displayed variation with ethnicity in a multi-ethnic population. Further studies of sRAGE, MetS and their relationship to cardiovascular disease are warranted.

Reference values of skin autofluorescence as an estimation of tissue accumulation of advanced glycation end products in a general Slovak population

AIMS

For decades, Slovakia has maintained a prominent place in mortality rates from cardiovascular diseases among European Union (EU-27) countries. Determination of skin autofluorescence serves as an estimate of tissue accumulation of advanced glycation end products--substances accumulating in tissues and body fluids that play a pathophysiological role in age-related diseases and their complications, such as diabetes.

METHODS

In 1385 apparently healthy Slovakian subjects aged from a few days old to 77 years, skin autofluorescence was determined using an advanced glycation end product reader and compared with reference data from Dutch Caucasians. The impact of the weekly frequency of recreational physical exercise on skin autofluorescence was investigated in the adults, and the impact of feeding regimen in the infants.

RESULTS

With the exception of 10- to 19-year-olds, Slovaks had lower skin autofluorescence values in comparison with the Dutch Caucasians. In healthy non-smokers, physical exercise for > 30 min/day performed ≥ 3 times/week was associated with lower skin autofluorescence levels. In infants, breastfeeding (advanced glycation end product-poor diet) was associated with lower skin autofluorescence levels in comparison with consumption of infant formulas (advanced glycation end product-rich diet).

CONCLUSIONS

Reference ranges of skin autofluorescence in Slovak Caucasians, detailed for paediatric age groups, are provided. Our data show that, in healthy adults, regular physical exercise associates with lower skin autofluorescence. Infants fed or weaned from infant formulas (advanced glycation end product-rich diet) have higher skin autofluorescence than their breast milk-consuming counterparts. It is unclear why Slovaks have lower skin autofluorescence compared with a Dutch population with lower cardiovascular mortality rates. Reference data on skin autofluorescence from diverse populations are needed for the precise clinical interpretation of skin autofluorescence measurements.

Higher serum soluble receptor for advanced glycation end product levels and lower prevalence of metabolic syndrome among Japanese adult men: a cross-sectional study

BACKGROUND

Although several studies showed that decreased soluble receptor for advanced glycation end products (sRAGE) is associated with metabolic syndrome (MetS), inflammation level has not been considered, even though ligand-RAGE interaction induces inflammation. The objective of the study was to determine the association between sRAGE and MetS among Japanese adult in a cross-sectional survey, taking the level of low grade inflammation into consideration.

METHODS

Serum soluble RAGE (sRAGE) were measured in 712 men and 176 women aged 30-83 years with serum C-reactive protein (hsCRP) concentration below 3 mg/L. MetS was defined using the criteria of the American Heart Association Scientific Statements of 2009.

RESULTS

After multivariable adjustment, among men, higher sRAGE levels were associated with lower odds of MetS as well as central obesity and elevated blood pressure. Comparing the extreme tertiles of sRAGE, odds ratios (95% confidence interval) were 0.58 (0.36-0.95; P for trend = 0.001) for MetS; 0.41 (0.25-0.52; P for trend < 0.001) for central obesity; and 0.45 (0.29-0.70; P for trend < 0.001) for elevated blood pressure. Moreover, participants were categorized according to their median hsCRP and sRAGE values. Men in the higher hsCRP/higher sRAGE category had a 40% lower odds ratio for MetS than those in the higher hsCRP/lower sRAGE category (P = 0.031). Among women, there was no association between sRAGE levels and the prevalence of MetS.

CONCLUSIONS

Higher circulating RAGE concentrations were associated with lower prevalence of MetS and its components among Japanese men.

Soluble form of receptor for advanced glycation end products is associated with obesity and metabolic syndrome in adolescents

The aim of this cross-sectional study was to investigate the relationship between soluble form of receptor for advanced glycation end products (sRAGE), obesity, and metabolic syndrome (MetS) in adolescents. A total of 522 male and 561 female adolescents were enrolled into the final analyses. Anthropometric parameters, blood pressure, blood biochemistry, fasting insulin, and plasma sRAGE levels were measured. In males, sRAGE was significantly and inversely correlated with waist circumference (WC), body mass index (BMI), systolic blood pressure, triglyceride (TG), low density lipoprotein cholesterol (LDL-C), and homeostasis model assessment-insulin resistance (HOMA-IR). Only WC and BMI were significantly and inversely correlated with sRAGE in females. Using linear regression analysis adjusting for age and gender, significant association was found between sRAGE and WC, BMI, TG, LDL-C, and HOMA-IR in adolescents of either gender (P < 0.05). This association was abolished when further adjusting BMI. In addition, sRAGE was significantly and inversely correlated with the increasing number of components of MetS in males (P for trend = 0.006) but not in females (P for trend = 0.422). In conclusion, plasma sRAGE is associated with obesity and MetS among adolescents. BMI may be the most important determinant of sRAGE levels in adolescents.

Effects of high-amount-high-intensity exercise on in vivo platelet activation: modulation by lipid peroxidation and AGE/RAGE axis

Physical activity is associated with cardiovascular risk reduction, but the effects of exercise on platelet activation remain controversial. We investigated the effects of regular high-amount, high intensity aerobic exercise on in vivo thromboxane (TX)-dependent platelet activation and plasma levels of platelet-derived proteins, CD40L and P-selectin, and whether platelet variables changes may be related to changes in high-density lipoprotein (HDL) and in the extent of oxidative stress and oxidative stress-related inflammation, as reflected by urinary isoprostane excretion and endogenous soluble receptor for advanced glycation end-products (esRAGE), respectively. Urinary excretion of 11-dehydro-TXB₂ and 8-iso-prostaglandin (PG)F(2α) and plasma levels of P-selectin, CD40L and esRAGE were measured before and after a eight-week standardised aerobic high-amount-high-intensity training program in 22 sedentary subjects with low-to-intermediate risk. Exercise training had a clear beneficial effect on HDL cholesterol (+10%, p=0.027) and triglyceride (-27%, p=0.008) concentration. In addition, a significant (p<0.0001) decrease in urinary 11-dehydro-TXB₂ (26%), 8-iso-PGF(2α) (21%), plasma P-selectin (27%), CD40L (35%) and a 61% increase in esRAGE were observed. Multiple regression analysis revealed that urinary 8-iso-PGF(2α) [beta=0.33, SEM=0.116, p=0.027] and esRAGE (beta=-0.30, SEM=31.3, p=0.046) were the only significant predictors of urinary 11-dehydro-TXB₂ excretion rate over the training period. In conclusion, regular high-amount-high-intensity exercise training has broad beneficial effects on platelet activation markers, paralleled and possibly associated with changes in the lipoprotein profile and in markers of lipid peroxidation and AGE/RAGE axis. Our findings may help explaining why a similar amount of exercise exerts significant benefits in preventing cardiovascular events.