Bridging advanced glycation end product, receptor for advanced glycation end product and nitric oxide with hormonal replacement/estrogen therapy in healthy versus diabetic postmenopausal women: A perspective

RAGE displays sex-specific differences in obesity-induced adipose tissue insulin resistance

Background

The receptor for advanced glycation end products (RAGE) plays an important role in obesity-associated insulin sensitivity. We have also previously reported that RAGE deficiency improved insulin resistance in obesity-induced adipose tissue. The current study was aimed to elucidate the sex-specific mechanism of RAGE deficiency in adipose tissue metabolic regulation and systemic glucose homeostasis.

Methods

RAGE-deficient (RAGE^−/−) mice were fed a high-fat diet (HFD) and subjected to glucose and insulin tolerance tests. Subcutaneous adipose tissue (sAT) was collected, and macrophage polarization was assessed by quantitative real-time PCR. Immunoblotting was performed to evaluate the insulin signaling in adipose tissues.

Results

Under HFD feeding conditions, body weight and adipocyte size of female RAGE deficient (RAGE^−/−) were markedly lower than that of male mice. Female RAGE^−/− mice showed significantly improved glucose and insulin tolerance compared to male RAGE^−/− mice, accompanied with increased M2 macrophages polarization. Expressions of genes involved in anti-oxidant and browning were up-regulated in adipose tissues of female RAGE^−/− mice. Moreover, insulin-induced AKT phosphorylation was significantly elevated in adipose tissue in female RAGE^−/− mice compared to male RAGE^−/− mice.

Conclusions

Our findings suggest that RAGE-mediated adipose tissue insulin resistance is sex-specific, which is associated with different expression of genes involved in anti-oxidant and browning and insulin-induced AKT phosphorylation.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13293-022-00476-6.

Female RAGE^−/− mice showed significantly improved glucose and insulin tolerance compared to male RAGE^−/− mice.

Female RAGE deficiency promotes M2 macrophage polarization in adipose tissues.

Female RAGE deficiency prevents oxidative stress in adipose tissues.

Female RAGE deficiency protects insulin-AKT signaling in adipose tissues.

Combination of LC-Q-TOF-MS/MS, network pharmacology, and nanoemulsion approaches identifies active compounds of two Artemisia species responsible for tackling early diabetes-related metabolic complications in the liver

INTRODUCTION

The chronicity of advanced glycation end-products (AGEs) imparts various damages resulting in metabolic dysfunction and diseases involving inflammation and oxidative stress. The use of plant extracts is of high interest in complementary medicine. Yet, extracts are multicomponent mixtures, and difficult to pinpoint their exact mechanism.

OBJECTIVES

We hypothesise that network pharmacology and bioinformatics can help experimental findings depict the exact active components and mechanism of action by which they induce their effects. Additionally, the toxicity and variability can be lowered and standardised with proper encapsulation methods.

METHODOLOGY

Here, we propose the formulation of phytoniosomes encapsulating two Artemisia species (Artemisia dracunculus and Artemisia absinthium) to mitigate AGEs and their induced cell redox dysregulation in the liver. Extracts from different solvents were identified via liquid chromatography quadrupole time-of-flight mass spectrometry (LC-Q-TOF-MS/MS). Phytoniosomes were explored for their anti-glycating effect and modulation of AGE-induced damages in THLE-2 liver cells. Network pharmacology tools were used to identify possible targets and signalling pathways implicated.

RESULTS

Data demonstrated that A. absinthium phytoniosomes had a significant anti-AGE effect comparable to reference molecules and higher than A. dracunculus. They were able to restore cell dysfunction through the restoration of tumour necrosis alpha (TNF-α), interleukin 6 (IL-6), nitric oxide, and total antioxidant capacity. Phytoniosomes were able to protect cells from apoptosis by decreasing caspase 3 activity. Network pharmacology and bioinformatic analysis confirmed the induction of the effect via Akt-PI3K-MAPK and AGE-RAGE signalling pathways through quercetin and luteolin actions.

CONCLUSION

The current report highlights the potential of Artemisia phytoniosomes as strong contenders in AGE-related disease therapy.

Artemisia alleviates AGE-induced liver complications via MAPK and RAGE signaling pathways modulation: a combinatorial study

Artemisia herba-alba (AHA) is a traditionally used plant to treat various diseases, including diabetes and metabolic dysfunctions. Plant extracts are generally explored empirically without a deeper assessment of their mechanism of action. Here, we describe a combinatorial study of biochemical, molecular, and bioinformatic (metabolite-protein pharmacology network) analyses to elucidate the mechanism of action of AHA and shed light on its multilevel effects in the treatment of diabetes-related advanced glycation end-products (AGE)-induced liver damages. The extract's polyphenols and flavonoids content were measured and then identified via LC-Q-TOF-MS/MS. Active compounds were used to generate a metabolite-target interaction network via Swiss Target Prediction and other databases. The extract was tested for its antiglycation and aggregation properties. Next, THLE-2 liver cells were challenged with AGEs, and the mechanistic markers were measured [TNF-α, IL-6, nitric oxide, total antioxidant capacity, lipid peroxidation (LPO), and caspase 3]. Metabolite and network screening showed the involvement of AHA in diabetes, glycation, liver diseases, aging, and apoptosis. Experimental confirmation showed that AHA inhibited protein modification and AGE formation. Additionally, AHA reduced inflammatory mediators (IL-6, TNFα), oxidative stress markers (NO, LPO), and apoptosis (Caspase 3). On the other hand, cellular total antioxidant capacity was restored to normal levels. The combinatorial study showed that AHA regulates AGE-induced liver damages through MAPK-AKT and AGE-RAGE signaling pathways. This report highlights the combination of experimental and network pharmacology for the exact elucidation of AHA mechanism of action as a multitarget option in the therapy of diabetes and AGEs-related diseases.

Implication of RAGE Polymorphic Variants in COPD Complication and Anti-COPD Therapeutic Potential of sRAGE

Chronic obstructive pulmonary disease (COPD) is a slowly progressive and poorly reversible airway obstruction disease. It is caused either alone or in combination of emphysema, chronic bronchitis (CB), and small airways disease. COPD is thought to be a multi-factorial disorder in which genetic susceptibility, environmental factors and tobacco exposure could be doubly or simultaneously implicated. Available medicines against COPD include anti-inflammatory drugs, such as β2-agonists and anticholinergics, which efficiently reduce airflow limitation but are unable to avert disease progression and mortality. Advanced glycation end products (AGE) and their receptors i.e. receptor for advanced glycation end products (RAGE) are some molecules that have been implicated in the complication of COPD. Several RAGE single nucleotide polymorphic (SNP) variants are produced by the mammalian cells. Based on the ethnicity some SNPs aggravate the COPD severity. Mammalian cells produce several alternative RAGE splice variants including a soluble RAGE (sRAGE) and an endogenous soluble RAGE (esRAGE). Both of these act as decoy receptor and thus may help to arrest the COPD complications. Several lines of evidences indicate a decreased level of sRAGE in the COPD subjects. One of the new strategies to reduce COPD complication may be sRAGE therapeutic administration to the COPD subjects. This comprehensive discussion sheds light on the role of RAGE and its polymorphic variants in the COPD complication along with sRAGE therapeutic significance in the COPD prevention.

SARS-CoV-2 and the possible connection to ERs, ACE2, and RAGE: Focus on susceptibility factors

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic has provoked major stresses on the health-care systems of several countries, and caused the death of more than a quarter of a million people globally, mainly in the elderly population with preexisting pathologies. Previous studies with coronavirus (SARS-CoV) point to gender differences in infection and disease progression with increased susceptibility in male patients, indicating that estrogens may be associated with physiological protection against the coronavirus. Therefore, the objectives of this work are threefold. First, we aim to summarize the SARS-CoV-2 infection pathway and the roles both the virus and patient play in COVID-19 (Coronavirus disease 2019) progression, clinical symptomatology, and mortality. Second, we detail the effect estrogen has on viral infection and host infection response, including its role in both the regulation of key viral receptor expression and the mediation of inflammatory activity. Finally, we describe how ERs (estrogen receptors) and RAGE (receptor for advanced glycation end-products) play a critical role in metabolic pathways, which we envisage could maintain a close interplay with SARS-CoV and COVID-19 mortality rates, despite a current lack of research directly determining how. Taken together, we present the current state of the field regarding SARS-CoV-2 research and illuminate where research is needed to better define the role both estrogen and metabolic comorbidities have in the COVID-19 disease state, which can be key in screening potential therapeutic options as the search for effective treatments continue.

Peanut skin polyphenols inhibit toxicity induced by advanced glycation end-products in RAW264.7 macrophages

This is the first work to use a polyphenolic fraction derived from peanut skin to attenuate the toxicity induced by advanced glycation-end products (AGEs) in RAW264.7 macrophages. The RAW264.7 cells were stimulated by AGEs using the bovine serum albumin-fructose (BSA-FRU), bovine serum albumin-methylglyoxal (BSA-MGO) and arginine-methylglyoxal (ARG-MGO) models. The AGEs increased considerably the levels of reactive oxygen species and the gene expression of proinflammatory cytokines interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), and nitric oxide. Twenty-eight polyphenols, including catechin, phenolic acids, and resveratrol were annotated in peanut skin extract (PSE) with the use of ultra-performance liquid chromatography coupled to quadrupole time of flight mass spectrometry (UPLC-QTOF/MS^E) and to the UNIFI Scientific Information System. The administration of PSE at 100 and 150 μg/mL significantly inhibited oxidative stress, by suppressing the production of reactive oxygen species up to 70% and reducing the production of nitric oxide, IL-6 and TNF-α up to 1.7-, 10- and 107-fold, respectively.

Modulation of soluble receptor for advanced glycation end-products (RAGE) isoforms and their ligands in healthy aging

The receptor for advanced glycation end-products (RAGE) recognizes several ligands involved in inflammatory diseases. Two circulating soluble isoforms exist: esRAGE derived from alternative splicing and cRAGE generated by the membrane-bound RAGE (FL-RAGE) proteolysis. Together, esRAGE and cRAGE constitute sRAGE and function as decoy receptors preventing FL-RAGE/ligands binding.

We determined serum concentration of both, esRAGE and cRAGE, and their ligands AGEs, HMGB1 and S100A8/A9 in a healthy population of 169 subjects aged 20-90 years. cRAGE showed a negative (r=-0.375, P<0.0001) while AGEs (r=0.160, P=0.0384) and S100A8/A9 (r=0.207, P=0.0091) a positive correlation with age. esRAGE did not change during aging and inversely correlated with Hemoglobin, ALT, insulin, HOMA index, Waist-Hip ratio (W/H), Waist Circumference (WC) and positively with AGEs. cRAGE exhibited also an inverse correlation with WC, W/H, PAI-1, HMGB1, AGEs and S100A8/A9. Age, W/H, HMGB1, S100A8/A9 and AGEs are independent predictors of cRAGE, whereas W/H and AGEs associate with esRAGE. Treatment of cells with glycated albumin reduced cRAGE production and upregulated FL-RAGE.

These results indicate that in a healthy population cRAGE is a biomarker of aging while esRAGE represents a more reliable marker of obesity and insulin resistance. Hence, sRAGE isoforms levels could be differentially associated with age-related diseases risk factors.

The usefulness of soluble receptor for advanced glycation end-products in the identification of COPD frequent exacerbator phenotype

Introduction

Exacerbations of COPD (ECOPDs) are important events in the course of COPD, accelerating the rate of decline in lung function and increasing the mortality risk. A growing body of evidence suggests the significance of the “frequent exacerbator” phenotype. This phenotype seems to be associated with a more severe airflow limitation, symptoms, health-related quality of life impairment, and higher mortality. However, there is no described biomarker that would help to identify this group of patients.

Patients and methods

Patients with COPD in “D” GOLD category were monitored for 3 years according to events of ECOPD. Serum samples were collected from the patients. Circulating level of plasma soluble receptor for advanced glycation end-products (sRAGE) was measured using commercially available high sensitivity kits. The receiver operating characteristic (ROC) curve analysis was used to assess the usefulness of sRAGE to identify frequent exacerbator phenotype. Log-rank test was used in the analysis of time to the subsequent exacerbation. Pearson (R) or Spearman’s rank (R_S) correlation coefficients were used for correlation analysis.

Results

Nineteen patients were enrolled. The area under the ROC curve (AUROC) for sRAGE for the identification of frequent exacerbator phenotype was 0.81. Analysis identified the cutoff point as 850.407 pg/mL, characterized by a sensitivity of 0.80 (95% CI: 0.28–1.0) and specificity of 0.93 (95% CI: 0.66–1.0). Additionally, in the group with sRAGE ≤850.407 pg/mL, we observed significantly shorter time to the subsequent exacerbation: median of 32 vs 105.5 days (P=0.03). Correlation analysis revealed significant negative correlation between sRAGE and the number of exacerbations requiring hospitalization during the whole time of follow-up (R_S=−0.53; P=0.02) and significant positive correlation with FEV₁ expressed as the percentage of reference value (R=0.6; P=0.006).

Conclusion

sRAGE seems to be useful in the identification of frequent exacerbator phenotype. This parameter may also be used in the prediction of time to ECOPD. Our findings should be confirmed in a sufficiently powered larger sample.

Metabolic Predictors of Change in Vascular Function: Prospective Associations From a Community-Based Cohort

Vascular function varies with age because of physiological and pathological factors. We examined relations of longitudinal change in vascular function with change in metabolic traits. Longitudinal changes in vascular function and metabolic traits were examined in 5779 participants (mean age, 49.8±14.5 years; 54% women) who attended sequential examinations of the Framingham Offspring, Third Generation, and Omni-1 and Omni-2 cohorts. Multivariable regression analysis related changes in vascular measures (dependent variables), including carotid-femoral pulse wave velocity (CFPWV), forward pressure wave amplitude, characteristic impedance, central pulse pressure, and mean arterial pressure (MAP), with change in body mass index, fasting total:high-density lipoprotein cholesterol ratio, serum triglycerides, and blood glucose. Analyses accounted for baseline value of each vascular and metabolic measure, MAP change, and multiple comparisons. On follow-up (mean, 5.9±0.6 years), aortic stiffness (CFPWV, 0.2±1.6 m/s), and pressure pulsatility (forward pressure wave, 1.2±12.4 mm Hg; characteristic impedance, 23±73 dyne×sec/cm⁵; central pulse pressure, 2.6±14.7 mm Hg; all P<0.0001) increased, whereas MAP fell (-3±10 mm Hg; P<0.0001). Worsening of each metabolic trait was associated with increases in CFPWV and MAP (P<0.0001 for all associations) and an increase in MAP was associated with an increase in CFPWV. Overall, worsening metabolic traits were associated with worsening aortic stiffness and MAP. Opposite net change in aortic stiffness and MAP suggests that factors other than distending pressure contributed to the observed increase in aortic stiffness. Change in metabolic traits explained a greater proportion of the change in CFPWV and MAP than baseline metabolic values.

Relationship between Advanced Glycation End Products and Steroidogenesis in PCOS

BACKGROUND

Women with PCOS have elevated levels of the harmful Advanced Glycation End Products (AGEs), which are highly reactive molecules formed after glycation of lipids and proteins. Additionally, AGEs accumulate in the ovaries of women with PCOS potentially contributing to the well-documented abnormal steroidogenesis and folliculogenesis.

MAIN BODY

A systematic review of articles and abstracts available in PubMed was conducted and presented in a systemic manner. This article reports changes in steroidogenic enzyme activity in granulosa and theca cells in PCOS and PCOS-models. It also described the changes in AGEs and their receptors in the ovaries of women with PCOS and presents the underlying mechanism(s) whereby AGEs could be responsible for the PCOS-related changes in granulosa and theca cell function thus adversely impacting steroidogenesis and follicular development. AGEs are associated with hyperandrogenism in PCOS possibly by altering the activity of various enzymes such as cholesterol side-chain cleavage enzyme cytochrome P450, steroidogenic acute regulatory protein, 17α-hydroxylase, and 3β-hydroxysteroid dehydrogenase. AGEs also affect luteinizing hormone receptor and anti-Mullerian hormone receptor expression as well as their signaling pathways in granulosa cells.

CONCLUSIONS

A better understanding of how AGEs alter granulosa and theca cell function is likely to contribute meaningfully to a conceptual framework whereby new interventions to prevent and/or treat ovarian dysfunction in PCOS can ultimately be developed.

Soluble RAGEs - Prospects for treating & tracking metabolic and inflammatory disease

Emerging evidence links the receptor for advanced glycation endproducts (RAGE) to the pathogenesis of tissue damage in chronic metabolic and inflammatory diseases. In human subjects, multiple reports suggest that in the plasma/serum, circulating levels of distinct forms of soluble RAGEs may be biomarkers of the presence or absence, and the extent of chronic disease. These considerations prompt us to consider in this review, what are soluble RAGEs; how are they formed; what might be their natural functions; and may they serve as biomarkers of inflammatory and metabolic disease activity? In this brief review, we seek to address what is known and suggest new areas for scientific investigation to uncover the biology of soluble RAGEs.

Glabridin, an isoflavan from licorice root, downregulates iNOS expression and activity under high-glucose stress and inflammation

SCOPE

In females, hyperglycemia abolishes estrogen-vascular protection, leading to inflammation and oxidative stress that are related to diabetes-associated cardiovascular complications. Such knowledge led us to examine the potential of glabridin, as a replacement of estrogen anti-inflammatory activity under high-glucose conditions.

METHODS AND RESULTS

In macrophage-like cells, chronic glucose stress (28 and 44 mM) upregulated inducible nitric oxide synthase (iNOS) mRNA expression by 42 and 189%, respectively. Pretreatment with glabridin, under chronic glucose stress, downregulated the LPS-induced nitric oxide secretion and nitrotyrosine formation, by 39 and 21%, respectively. Pretreatment with estradiol did not prevent the LPS-induced nitrotyrosine formation. Furthermore, glabridin, brought about a decrease in the LPS-induced iNOS mRNA expression by 48%, as compared to cells pretreated with estradiol. Glabridin decreased protein levels of liver iNOS by 69% in adult mouse offspring which developed hyperglycemia after early fetal exposure to a saturated fatty acid-enriched maternal diet. Glabridin also decreased liver nitrotyrosine levels in offspring of regular diet-fed mothers after further receiving high-fat diet.

CONCLUSION

Such results indicate that glabridin retains anti-inflammatory abilities to regulate the synthesis and activity of iNOS under high-glucose levels, implying that a glabridin supplement may serve as an anti-inflammatory agent in diabetes-related vascular dysfunction.

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.

Emerging role of advanced glycation-end products (AGEs) in the pathobiology of eye diseases

Advanced glycation end products (AGEs) have been implicated in vision loss associated with macula degeneration, cataract formation, diabetic retinopathy and glaucoma. This pathogenic potential is mainly attributed to their accumulation in ocular tissues where they mediate aberrant crosslinking of extracellular matrix proteins and disruption of endothelial junctional complexes that affects cell permeability, mediates angiogenesis and breakdown of the inner blood-retinal barrier. Furthermore, AGEs severely affect cellular metabolism by disrupting ATP production, enhancing oxidative stress and modulating gene expression of anti-angiogenic and anti-inflammatory genes. Elucidation of AGE-induced mechanisms of action in different eye compartments will help in the understanding of the complex cellular and molecular processes associated with eye diseases. Several pharmaceutical agents with anti-glycating and anti-oxidant properties as well as AGE crosslink 'breakers' have been currently applied to eye diseases. The role of diet and the beneficial effects of certain nutriceuticals provide an alternative way to manage chronic visual disorders that affect the quality of life of millions of people.

Estradiol reduces ferrous citrate complex-induced NOS2 up-regulation in cerebral endothelial cells by interfering the nuclear factor kappa B transactivation through an estrogen receptor β-mediated pathway

Hemorrhagic stroke caused leakage of red blood cells which converts to hemoglobin, heme, and iron accumulated at the lesions. High concentration of ferrous iron from subarachnoid hemorrhage (SAH) induced cerebral vasospasm. Using the two-hemorrhage SAH model in rats, we previously demonstrated that estradiol (E2) significantly attenuated the SAH-induced vasospasm by inhibiting the NOS2 expression. Adding ferrous citrate (FC) complexes to the primary cultured mouse cerebral endothelial cells (CEC) to mimic the SAH conditions, we also showed that FC up-regulates NOS2 through nuclear translocation of NFκB induced by free radicals generation. Here, we further studied the molecular mechanism underlying E2-mediated reduction of the FC-induced up-regulation of NOS2. Treatment with E2 (100 nM) reduced the FC (100 µM)-induced increases of free radical generation and the levels of NOS2 mRNA and protein in the CEC. Moreover, E2 also prevented the FC-induced increases of IκBα phosphorylation, NFκB nuclear translocation, NFκB binding onto the NOS2 promoter, and the NOS2 promoter luciferase activity. However, knock-down the estrogen receptor β (ERβ), but not ERα, abolished the E2-mediated prevention on the FC-induced increases of NOS2 mRNA and protein. The data from the present study suggest that E2 inhibited NOS2 gene expression by interfering with NFκB nuclear translocation and NFκB binding onto the NOS2 through an ERβ-mediated pathway. Our results provide the molecular basis for designing the applicable therapeutic or preventive strategies in the treatment SAH patients.

Dietary glycotoxins affect scavenger receptor expression and the hormonal profile of female rats

The levels of advanced glycation end products (AGEs) are increased under conditions of impaired glucose metabolism and/or oxidative stress, promoting insulin resistance and other endocrine abnormalities. AGEs play a major role in the pathogenesis of several diseases such as diabetes, atherosclerosis, polycystic ovary syndrome and Alzheimer's disease, contributing to progressive ageing. Receptor-based clearance of AGEs by the receptor for AGE (RAGE) and/or the macrophage scavenger receptor A (SR-A) is considered as a main factor for the regulation of the concentration of AGEs under these conditions. This study aimed to investigate the expression of RAGE (AGER) and SR-A (MSR1) under high/low-dietary AGE conditions in vivo and their potential contribution to the metabolic and sex hormonal profile of female rats. Female Wistar rats were fed a low-AGE or high-AGE diet for 3 months. Serum samples were collected at baseline and at the completion of the 3-month period for the measurements of metabolic and hormonal parameters. Peripheral blood mononuclear cells (PBMCs) were isolated for the determination of the expression of RAGE and SR-A. The high-AGE diet-fed rats exhibited increased glucose, insulin and testosterone levels as well as decreased oestradiol and progesterone levels compared with the low-AGE diet-fed ones, thus indicating a metabolic and hormonal dysregulation attributed to high-AGE dietary exposure. The expression of RAGE was significantly down-regulated in the PBMCs of the high-AGE diet-fed rats (P=0.041), and it was correlated negatively with insulin and testosterone levels and positively with progesterone levels. The expression of SR-A was also decreased in the high-AGE diet-fed rats to marginal significance. Decreased monocytic expression of scavenger receptors such as RAGE and SR-A may result in a higher deposition of AGEs in peripheral endocrine tissues, thus promoting endocrine-related abnormalities and diseases.

Reduced ovarian glyoxalase-I activity by dietary glycotoxins and androgen excess: a causative link to polycystic ovarian syndrome

Glyoxalase detoxification system composed of glyoxalase (GLO)-I and GLO-II is ubiquitously expressed and implicated in the protection against cellular damage because of cytotoxic metabolites such as advanced glycation end products (AGEs). Recently, ovarian tissue has emerged as a new target of excessive AGE deposition and has been associated with either a high AGE diet in experimental animals or hyperandrogenic disorders such as polycystic ovarian syndrome (PCOS) in humans. This study was designed to investigate the impact of dietary AGEs and androgens in rat ovarian GLO-I activity of normal nonandrogenized (NAN, group A, n = 18) and androgenized prepubertal (AN) rats (group B, n = 29). Both groups were further randomly assigned, either to a high-AGE (HA) or low-AGE (LA) diet for 3 months. The activity of ovarian GLO-I was significantly reduced in normal NAN animals fed an HA diet compared with an LA diet (p = 0.006). Furthermore, GLO-I activity was markedly reduced in AN animals compared with NAN (p ≤ 0.001) when fed with the corresponding diet type. In addition, ovarian GLO-I activity was positively correlated with the body weight gain (r(s) = 0.533, p < 0.001), estradiol (r(s) = 0.326, p = 0.033) and progesterone levels (r(s) = 0.500, p < 0.001). A negative correlation was observed between GLO-I activity and AGE expression in the ovarian granulosa cell layer of all groups with marginal statistical significance (r(s) = -0.263, p = 0.07). The present data demonstrate that ovarian GLO-I activity may be regulated by dietary composition and androgen levels. Modification of ovarian GLO-I activity, observed for the first time in this androgenized prepubertal rat model, may present a contributing factor to the reproductive dysfunction characterizing PCOS.

Intrafollicular soluble receptor for advanced glycation end products (sRAGE) and embryo quality in assisted reproduction

The developmental potential of human embryos has important implications in assisted reproduction and depends, among other factors, on oocyte competency. The receptor for advanced glycation end products (RAGE) is a member of the superfamily of immunoglobulin cell-surface molecules that are constitutively expressed during embryonic development. RAGE is down-regulated in homeostasis in adult life. This study measured the concentration of soluble RAGE (sRAGE) in follicular fluid obtained from the leading follicle after ovarian stimulation of 54 women undergoing intracytoplasmic sperm injection. Corresponding embryos and sRAGE concentrations in follicular fluid were evaluated and correlations were investigated by multi-adjusted regression analysis. High intrafollicular sRAGE concentrations predicted poor-quality embryos (n=45, OR=0.986; P=0.026), adjusted for patient age, body mass index and oocyte quality, showing an inverse association between intrafollicular sRAGE concentrations and embryo development. The developmental potential of human embryos has important implications in assisted reproduction, and it depends, among other factors, on oocyte competency. The receptor for advanced glycation end products (RAGE) is a molecule constitutively expressed during embryonic development, but it is down-regulated in adult life. RAGE is frequently associated with pro-inflammatory responses, and it is implicated as an underlying condition in immune disorders, cardiovascular diseases, diabetes, Alzheimer's disease and cancer. In addition to activating the pro-inflammatory responses, RAGE down-regulates cellular defence mechanisms. The present study measured the concentrations of soluble RAGE (sRAGE) in follicular fluid samples obtained from leading follicles of women undergoing intracytoplasmic sperm injection (ICSI). This prospective cohort study included 54 patients undergoing ICSI, and follicular fluid samples were obtained from the leading follicle after ovarian stimulation. The corresponding embryos were evaluated and correlations with intrafollicular sRAGE concentrations were investigated using multi-adjusted regression analysis. We observed that high intrafollicular concentrations of sRAGE predicted poor embryo quality. Our findings suggest an association between high concentrations of intrafollicular sRAGE and poor embryo development following ovarian stimulation for ICSI.

An explorative analysis of secretory receptor for advanced glycation endproducts in primary focal segmental glomerulosclerosis

BACKGROUND

Despite remarkable medical progress, the main pathogenetic mechanisms of focal segmental glomerulosclerosis (FSGS) have not been fully delineated and its prognosis is poor at present. Recently, it was revealed that the receptor for advanced glycation endproducts (RAGE) was highly expressed at the base of podocytes with an up-regulation mainly in diabetic nephropathy. However, there is no report about the association between glomerulonephritis and RAGE. The aims of the current study were to explore the relationships between several clinical parameters and circulating soluble RAGE in primary FSGS and compare serum levels in primary FSGS with immunoglobulin A nephropathy (IgAN) and controls.

METHODS

A total of 35 subjects aged >18 years were enrolled. Thirty-five subjects consisted of three groups: primary FSGS (N = 15), IgAN (N = 10), and normal controls (N = 10). Laboratory measurements of serum carboxymethyl-lysin (CML), soluble RAGE (sRAGE), and endogenous secretory RAGE (esRAGE) were performed.

RESULTS

Serum esRAGE level in the FSGS group was higher than that in the IgAN group (0.55 ± 0.32 ng/mL vs. 0.27 ± 0.11 ng/mL, p = 0.013). There was no statistical difference between sRAGE and CML among the three groups. Within the FSGS group, esRAGE, but not sRAGE, was positively correlated with 24-h urinary protein (r = 0.553, p = 0.033) and negatively correlated with body mass index (r = -0.623, p = 0.013). In stepwise multiple regression analysis, body mass index and 24-h urinary protein were significant contributors to esRAGE within the FSGS group.

CONCLUSION

This study showed that only the serum level of esRAGE, not sRAGE, was higher in the FSGS group than in the IgAN and control groups. The amount of 24-h proteinuria was also related to the serum level of esRAGE in the FSGS group.

Calycosin protects HUVECs from advanced glycation end products-induced macrophage infiltration

ETHNOPHARMACOLOGICAL RELEVANCE

Astragali radix is a traditional Chinese medicine that has long been used for treatment of diabetes and diabetes-associated disease, but its active component and mechanism on the disease is not well defined.

AIM OF THE STUDY

Infiltration of leukocytes within the glomeruli and vasculature is one of the early and characteristic features of diabetic nephropathy. Advanced glycation end products (AGEs) play pivotal role in the progression of diabetic-associated diseases. The present study was designed to explore the therapeutic effect of calycosin, an active component from A. radix, on AGEs-induced macrophages infiltration in HUVECs.

MATERIALS AND METHODS

Transwell HUVEC-macrophage co-culture system was established to evaluate macrophage migration and adhesion. Immunocytochemistry was applied to examine TGF-beta1, ICAM-1 and RAGE protein expressions; real-time PCR was carried out to determine mRNA expression of TGF-beta1, ICAM-1 and RAGE. Immunofluorescence was carried out to observe estrogen receptor-alpha, ICAM-1, RAGE expression and the phosphorylation status of ERK1/2 and NF-κB.

RESULTS

Calycosin significantly reduced AGEs-induced macrophage migration and adhesion to HUVEC. Pre-treatment with calycosin strikingly down-regulated HUVEC TGF-beta1, ICAM-1 and RAGE expressions in both protein and mRNA levels. Furthermore, calycosin incubation significantly increased estrogen receptor expression and reversed AGEs-induced ERK1/2 and NF-κB phosphorylation and nuclear translocation in HUVEC, and this effect of calycosin could be inhibited by estrogen receptor inhibitor, ICI182780.

CONCLUSIONS

These findings suggest that calycosin can reduce AGEs-induced macrophage migration and adhesion to endothelial cells and relieve the local inflammation; furthermore, this effect was via estrogen receptor-ERK1/2-NF-κB pathway.

Circulating soluble receptor for advanced glycation end products is inversely associated with body mass index and waist/hip ratio in the general population

Advanced glycation end products, AGEs, and its specific receptor, RAGE, are involved in vascular complications. A role for the soluble form of RAGE (sRAGE), which acts as a decoy for AGE, has been documented in patients with diabetes but no information is available in non-diabetic subjects. The aim of this study was to investigate the association of plasma levels of sRAGE with cardiometabolic risk factors in the general population. In addition we evaluated the relation of the common -374A/T polymorphism of RAGE with plasma levels of sRAGE. One hundred and seventy-six healthy subjects free of diabetes or coronary artery disease untreated for hypertension, dyslipidemia or cardiometabolic related diseases were randomly selected for this study from the general population. Plasma sRAGE were negatively and significantly correlated with BMI, waist/hip circumference ratio and fasting glycemia, while a positive correlation was observed with apolipoprotein A-I. These correlations were observed mainly in women who showed significantly higher sRAGE levels (1744+/-660 pg/mL vs 1414+/-649 pg/mL; P<0.05). In a stepwise regression analysis waist circumference was independently associated with sRAGE and, when waist circumference was excluded, BMI was independently associated with sRAGE. Finally in overweight subjects (BMI>25 kg/m(2)) plasma sRAGE was significantly lower compared to lean subjects (1460+/-640 pg/mL vs 1710+/-693 pg/mL; P<0.05). In healthy subjects plasma levels of sRAGE were negatively correlated with BMI and waist/hip ratio supporting a possible protective role for these proteins before any evidence of diabetic or vascular complications.

Ovariectomy increases neuronal amyloid-beta binding alcohol dehydrogenase level in the mouse hippocampus

Ovarian hormone decline after menopause may influence cognitive performance and increase the risk for Alzheimer's disease (AD) in women. Amyloid-beta peptide (Abeta) has been proposed to be the primary cause of AD. In this study, we examined whether ovariectomy (OVX) could affect the levels of cofactors Abeta-binding alcohol dehydrogenase (ABAD) and receptor for advanced glycation endproducts (RAGE), which have been reported to potentiate Abeta-mediated neuronal perturbation, in mouse hippocampus, correlating with estrogen and Abeta levels. Female ICR mice were randomly divided into ovariectomized or sham-operated groups, and biochemical analyses were carried out at 5 weeks after the operation. OVX for 5 weeks significantly decreased hippocampal 17beta-estradiol level, while it tended to reduce the hormone level in serum, compared with the sham-operated control. In contrast, OVX did not affect hippocampal Abeta(1-40) level, although it significantly increased serum Abeta(1-40) level. Furthermore, we demonstrated that OVX increased hippocampal ABAD level in neurons, but not astrocytes, while it did not affect RAGE level. These findings suggest that the expression of neuronal ABAD depends on estrogen level in the hippocampus and the increase in serum Abeta and hippocampal ABAD induced by ovarian hormone decline may be associated with pre-stage of memory deficit in postmenopausal women and Abeta-mediated AD pathology.

Soluble RAGE in type 2 diabetes: association with oxidative stress

Advanced glycation end products (AGEs) contribute to diabetic vascular complications by engaging the AGE receptor (RAGE). A soluble RAGE form (sRAGE) acts as a decoy domain receptor, thus decreasing AGE cellular binding. A cross-sectional comparison of sRAGE, asymmetric dimethylarginine (ADMA) plasma levels (index of endothelial dysfunction), and urinary 8-iso-prostaglandin (PG)F(2alpha) (marker of oxidative stress) was performed between 86 diabetic patients and 43 controls. Plasma sRAGE levels were significantly lower and ADMA levels were significantly higher in diabetic patients as compared to controls (P<0.0001). HbA1c and urinary 8-iso-PGF(2alpha) were correlated inversely with sRAGE and directly with ADMA. On multivariate analysis HbA1c was independently related to sRAGE levels in diabetic patients. Twenty-four of 86 patients with newly diagnosed diabetes and 12 patients in poor metabolic control were reevaluated after treatment with a hypoglycemic agent or insulin, respectively. Improvement in metabolic control by oral agents or insulin resulted in a significant increase in sRAGE and decrease in ADMA levels (P<0.0001). Thus, poor glycemic control reduces sRAGE levels, in association with enhanced oxidative stress and endothelial dysfunction in diabetes. These abnormalities are susceptible to modulation by improvement in metabolic control.