The diverse ligand repertoire of the receptor for advanced glycation endproducts and pathways to the complications of diabetes

Association of four differently processed diets with plasma and urine advanced glycation end products and serum soluble receptor for advanced glycation end products concentration in healthy dogs

Advanced glycation end products (AGEs), formed via the Maillard reaction (MR) during processing of foods, have been implicated in inflammatory and degenerative diseases in human beings. Cellular damage is primarily caused by AGE binding with the receptor for AGEs (RAGE) on cell membranes. An isoform of RAGE, soluble RAGE (sRAGE), acts as a decoy receptor binding circulating AGEs preventing cellular activation. Pet food manufacturing involves processing methods similar to human food processing that may increase dietary AGEs (dAGEs). We hypothesized that diet, plasma and urine AGEs, and serum sRAGE concentrations would differ between thermally processed diets. This study examined the association of four differently processed diets: ultra-processed canned wet food (WF); ultra-processed dry food (DF); moderately processed air-dried food (ADF) and minimally processed mildly cooked food (MF) on total plasma levels of the AGEs, carboxymethyllysine (CML), carboxyethyllysine (CEL), methylglyoxal hydroimidazolone-1, glyoxal hydroimidazolone-1, argpyrimidine, urine CML, CEL and lysinoalanine, and serum sRAGE concentration. Ultra-high-performance liquid chromatography-tandem mass spectrometry was used to measure AGEs. sRAGE concentration was measured using a commercial canine-specific enzyme-linked immunosorbent assay kit. Total dAGEs (mg/100 kcal as fed) were higher in WF than in other diets. Plasma total AGEs (nM/50 μL) were significantly higher with WF, with no difference found between DF, ADF, and MF; however, ADF was significantly higher than MF. Urine CML (nmol AGEs/mmol creatinine) was significantly higher with DF than with WF and MF. There were no significant differences in total urine AGEs or serum sRAGE concentration between diets. In conclusion, different methods of processing pet foods are associated with varied quantities of AGEs influencing total plasma AGE concentration in healthy dogs. Serum sRAGE concentration did not vary across diets but differences in total AGE/sRAGE ratio were observed between MF and WF and, ADF and DF.

Stem Cell-Based Tissue Engineering Approaches for Diabetic Foot Ulcer: a Review from Mechanism to Clinical Trial

Diabetic foot ulcer (DFU) is a complication from incomplete or prolonged wound healing, at times requires amputation, putting substantial health and socioeconomic burden. Wound healing is a dynamic overlapping process that can be regulated by arrays of molecular factors showing redundancy in function. However, dysregulation in the mechanism of angiogenesis, extra cellular matrix (ECM) formation and immune modulation are the major causes for impair wound healing in hyperglycaemic patients. Despite development of wound care research, there is a lack of well-accepted targeted therapy with multidisciplinary approach for DFU treatment. Stem cell therapy holds a promising outcome both in preclinical and clinical trials because of its ability to promote healing via regeneration and specialized tissue differentiation. Among different types of stem cells, regenerative potential of mesenchymal stem cell (MSC) is well demonstrated in both experimental and clinical trial. Still there is a huge knowledge gap among medical practitioners for deciding the best stem cell source, administration route, and safety. This review strengthens the fact that why stem cell therapy is a promising candidate to treat DFU and cited multiple tissue engineering and biomaterial-based approaches for delivering stem cells and their aftermath paracrine events. Based on the pre-clinical and clinical studies, the review tried to come up with optimum stem cell source and delivery route for the treatment of DFU. At last, the review glances on possible direction to enhance therapeutics strategy for the same, including different approaches like: phytocompounds, exosomes, scaffold geometry, cell preconditioning and licensing etc.

Soluble receptor for advanced glycation end products (sRAGE) is associated with obesity rates: a systematic review and meta-analysis of cross-sectional study

BACKGROUND

Several studies have highlighted the possible positive effects of soluble receptor for advanced glycation end products (sRAGE) against obesity. However, due to their inconsistent results, this systematic review and meta-analysis aimed to quantitatively evaluate and critically review the results of studies evaluating the relationship between sRAGE with obesity among adult population.

METHODS

In the systematic search, the eligibility criteria were as follows: studies conducted with a cross-sectional design, included apparently healthy adults, adults with obesity, or obesity-related disorders, aged over 18 years, and evaluated the association between general or central obesity indices with sRAGE.

RESULTS

Our systematic search in electronic databases, including PubMed, Scopus, and Embase up to 26 October, 2023 yielded a total of 21,612 articles. After removing duplicates, screening the titles and abstracts, and reading the full texts, 13 manuscripts were included in the final meta-analysis. According to our results, those at the highest category of circulating sRAGE concentration with median values of 934.92 pg/ml of sRAGE, had 1.9 kg/m2 lower body mass index (BMI) (WMD: -1.927; CI: -2.868, -0.986; P < 0.001) compared with those at the lowest category of sRAGE concentration with median values of 481.88 pg/ml. Also, being at the highest sRAGE category with the median values of 1302.3 pg/ml sRAGE, was accompanied with near 6 cm lower waist circumference (WC) (WMD: -5.602; CI: -8.820, -2.383; P < 0.001 with 86.4% heterogeneity of I2) compared with those at the lowest category of sRAGE concentration with median values of 500.525 pg/ml. Individuals with obesity had significantly lower circulating sRAGE concentrations (WMD: -135.105; CI: -256.491, -13.72; P = 0.029; with 79.5% heterogeneity of I2). According to the subgrouping and meta-regression results, country and baseline BMI were possible heterogeneity sources. According to Begg's and Egger's tests and funnel plots results, there was no publication bias.

CONCLUSION

According to our results, higher circulating sRAGE concentrations was associated with lower BMI and WC among apparently healthy adults. Further randomized clinical trials are warranted for possible identification of causal associations.

Prothrombotic status in COVID‑19 with diabetes mellitus (Review)

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection has caused an important social and health impact worldwide and the coronavirus disease-19 (COVID-19) has elicited devastating economy problems. The pathogenesis of SARS-CoV-2 infection is a complex mechanism and is considered to be the result of a challenging interaction, in which host and virus immune responses are the key elements. In this process, several inflammatory pathways are involved, and their initiation can have multiple consequences with a considerable impact on evolution, such as hyperinflammation and cytokine storm, thereby promoting activation of the coagulation system and fibrinolytic activity suppression. It is commonly recognized that COVID-19 severity involves multiple factors, including diabetes which increases the risk of developing different complications. This could be as a result of the low-grade inflammation as well as the innate and adaptive immune response dysfunction that is observed in patients with diabetes mellitus. In patients with diabetes, multiple metabolic disturbances which have a major impact in disturbing the balance between coagulation and fibrinolysis were discovered, thus the risk for thrombotic events is increased. Diabetes has been recognized as an important severity prognosis factor in COVID-19 cases and considering there is a significant association between diabetes and prothrombotic status, it could be responsible for the increased risk of thrombotic events with a worse prognosis.

Metformin may be a viable adjunctive therapeutic option to potentially enhance immune reconstitution in HIV-positive immunological non-responders

ABSTRACT

Incomplete immune reconstitution remains a global challenge for human immunodeficiency virus (HIV) treatment in the present era of potent antiretroviral therapy (ART), especially for those individuals referred to as immunological non-responders (INRs), who exhibit dramatically low CD4 + T-cell counts despite the use of effective antiretroviral therapy, with long-term inhibition of viral replication. In this review, we provide a critical overview of the concept of ART-treated HIV-positive immunological non-response, and also explain the known mechanisms which could potentially account for the emergence of immunological non-response in some HIV-infected individuals treated with appropriate and effective ART. We found that immune cell exhaustion, combined with chronic inflammation and the HIV-associated dysbiosis syndrome, may represent strategic aspects of the immune response that may be fundamental to incomplete immune recovery. Interestingly, we noted from the literature that metformin exhibits properties and characteristics that may potentially be useful to specifically target immune cell exhaustion, chronic inflammation, and HIV-associated gut dysbiosis syndrome, mechanisms which are now recognized for their critically important complicity in HIV disease-related incomplete immune recovery. In light of evidence discussed in this review, it can be seen that metformin may be of particularly favorable use if utilized as adjunctive treatment in INRs to potentially enhance immune reconstitution. The approach described herein may represent a promising area of therapeutic intervention, aiding in significantly reducing the risk of HIV disease progression and mortality in a particularly vulnerable subgroup of HIV-positive individuals.

The Ephrin tyrosine kinase a3 (EphA3) is a novel mediator of RAGE-prompted motility of breast cancer cells

BACKGROUND

The receptor for advanced glycation-end products (RAGE) and its ligands have been implicated in obesity and associated inflammatory processes as well as in metabolic alterations like diabetes. In addition, RAGE-mediated signaling has been reported to contribute to the metastatic progression of breast cancer (BC), although mechanistic insights are still required. Here, we provide novel findings regarding the transcriptomic landscape and the molecular events through which RAGE may prompt aggressive features in estrogen receptor (ER)-positive BC.

METHODS

MCF7 and T47D BC cells stably overexpressing human RAGE were used as a model system to evaluate important changes like cell protrusions, migration, invasion and colony formation both in vitro through scanning electron microscopy, clonogenic, migration and invasion assays and in vivo through zebrafish xenografts experiments. The whole transcriptome of RAGE-overexpressing BC cells was screened by high-throughput RNA sequencing. Thereafter, Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses allowed the prediction of potential functions of differentially expressed genes (DEGs). Flow cytometry, real time-PCR, chromatin immunoprecipitation, immunofluorescence and western blot assays were performed to investigate the molecular network involved in the regulation of a novel RAGE target gene namely EphA3. The clinical significance of EphA3 was explored in the TCGA cohort of patients through the survivALL package, whereas the pro-migratory role of EphA3 signaling was ascertained in both BC cells and cancer-associated fibroblasts (CAFs). Statistical analysis was performed by t-tests.

RESULTS

RNA-seq findings and GSEA analysis revealed that RAGE overexpression leads to a motility-related gene signature in ER-positive BC cells. Accordingly, we found that RAGE-overexpressing BC cells exhibit long filopodia-like membrane protrusions as well as an enhanced dissemination potential, as determined by the diverse experimental assays. Mechanistically, we established for the first time that EphA3 signaling may act as a physical mediator of BC cells and CAFs motility through both homotypic and heterotypic interactions.

CONCLUSIONS

Our data demonstrate that RAGE up-regulation leads to migratory ability in ER-positive BC cells. Noteworthy, our findings suggest that EphA3 may be considered as a novel RAGE target gene facilitating BC invasion and scattering from the primary tumor mass. Overall, the current results may provide useful insights for more comprehensive therapeutic approaches in BC, particularly in obese and diabetic patients that are characterized by high RAGE levels.

Involvement of Intracellular TAGE and the TAGE-RAGE-ROS Axis in the Onset and Progression of NAFLD/NASH

The repeated excessive intake of sugar, a factor that contributes to the onset of nonalcoholic fatty liver disease (NAFLD) and its progression to the chronic form of nonalcoholic steatohepatitis (NASH), markedly increases the hepatocyte content of glyceraldehyde (GA), a glucose/fructose metabolic intermediate. Toxic advanced glycation end-products (toxic AGEs, TAGE) are synthesized by cross-linking reactions between the aldehyde group of GA and the amino group of proteins, and their accumulation has been implicated in the development of NAFLD/NASH and hepatocellular carcinoma (HCC). Our previous findings not only showed that hepatocyte disorders were induced by the intracellular accumulation of TAGE, but they also indicated that extracellular leakage resulted in elevated TAGE concentrations in circulating fluids. Interactions between extracellular TAGE and receptor for AGEs (RAGE) affect intracellular signaling and reactive oxygen species (ROS) production, which may, in turn, contribute to the pathological changes observed in NAFLD/NASH. RAGE plays a role in the effects of the extracellular leakage of TAGE on the surrounding cells, which ultimately promote the onset and progression of NAFLD/NASH. This review describes the relationships between intracellular TAGE levels and hepatocyte and hepatic stellate cell (HSC) damage as well as the TAGE-RAGE-ROS axis in hepatocytes, HSC, and HCC cells. The "TAGE theory" will provide novel insights for future research on NAFLD/NASH.

Blood-Borne Microparticles Are an Inflammatory Stimulus in Type 2 Diabetes Mellitus

The proinflammatory state associated with diabetes mellitus (DM) remains poorly understood. We found patients with DM have 3- to 14-fold elevations of blood-borne microparticles (MPs) that bind phalloidin (Ph; Ph positive [+] MPs), indicating the presence of F-actin on their surface. We hypothesized that F-actin-coated MPs were an unrecognized cause for DM-associated proinflammatory status. Ph+MPs, but not Ph-negative MPs, activate human and murine (Mus musculus) neutrophils through biophysical attributes of F-actin and membrane expression of phosphatidylserine (PS). Neutrophils respond to Ph+MPs via a linked membrane array, including the receptor for advanced glycation end products and CD36, PS-binding membrane receptors. These proteins in conjunction with TLR4 are coupled to NO synthase 1 adaptor protein (NOS1AP). Neutrophil activation occurs because of Ph+MPs causing elevations of NF-κB and Src kinase (SrcK) via a concurrent increased association of NO synthase 2 and SrcK with NOS1AP, resulting in SrcK S-nitrosylation. We conclude that NOS1AP links PS-binding receptors with intracellular regulatory proteins. Ph+MPs are alarmins present in normal human plasma and are increased in those with DM and especially those with DM and a lower-extremity ulcer.

The importance of caveolin as a target in the prevention and treatment of diabetic cardiomyopathy

The diabetic population has been increasing in the past decades and diabetic cardiomyopathy (DCM), a pathology that is defined by the presence of cardiac remodeling and dysfunction without conventional cardiac risk factors such as hypertension and coronary heart diseases, would eventually lead to fatal heart failure in the absence of effective treatment. Impaired insulin signaling, commonly known as insulin resistance, plays an important role in the development of DCM. A family of integral membrane proteins named caveolins (mainly caveolin-1 and caveolin-3 in the myocardium) and a protein hormone adiponectin (APN) have all been shown to be important for maintaining normal insulin signaling. Abnormalities in caveolins and APN have respectively been demonstrated to cause DCM. This review aims to summarize recent research findings of the roles and mechanisms of caveolins and APN in the development of DCM, and also explore the possible interplay between caveolins and APN.

Glycation and a Spark of ALEs (Advanced Lipoxidation End Products) - Igniting RAGE/Diaphanous-1 and Cardiometabolic Disease

Obesity and non-alcoholic fatty liver disease (NAFLD) are on the rise world-wide; despite fervent advocacy for healthier diets and enhanced physical activity, these disorders persist unabated and, long-term, are major causes of morbidity and mortality. Numerous fundamental biochemical and molecular pathways participate in these events at incipient, mid- and advanced stages during atherogenesis and impaired regression of established atherosclerosis. It is proposed that upon the consumption of high fat/high sugar diets, the production of receptor for advanced glycation end products (RAGE) ligands, advanced glycation end products (AGEs) and advanced lipoxidation end products (ALEs), contribute to the development of foam cells, endothelial injury, vascular inflammation, and, ultimately, atherosclerosis and its consequences. RAGE/Diaphanous-1 (DIAPH1) increases macrophage foam cell formation; decreases cholesterol efflux and causes foam cells to produce and release damage associated molecular patterns (DAMPs) molecules, which are also ligands of RAGE. DAMPs stimulate upregulation of Interferon Regulatory Factor 7 (IRF7) in macrophages, which exacerbates vascular inflammation and further perturbs cholesterol metabolism. Obesity and NAFLD, characterized by the upregulation of AGEs, ALEs and DAMPs in the target tissues, contribute to insulin resistance, hyperglycemia and type two diabetes. Once in motion, a vicious cycle of RAGE ligand production and exacerbation of RAGE/DIAPH1 signaling ensues, which, if left unchecked, augments cardiometabolic disease and its consequences. This Review focuses on RAGE/DIAPH1 and its role in perturbation of metabolism and processes that converge to augur cardiovascular disease.

Therapeutic Potential of Phlorotannin-Rich Ecklonia cava Extract on Methylglyoxal-Induced Diabetic Nephropathy in In Vitro Model

Advanced glycation end-products (AGEs) play a vital role in the pathogenesis of diabetic complications. Methylglyoxal (MGO), one of the major precursors of AGEs, is a highly reactive dicarbonyl compound that plays an important role in the pathogenesis of diabetic nephropathy. This study was designed to evaluate the therapeutic potential of phlorotannin-rich Ecklonia cava extract (ECE) on MGO-induced diabetic nephropathy in in vitro models using mouse glomerular mesangial cells. ECE showed anti-glycation activity via breaking of AGEs-collagen cross-links and inhibition of AGEs formation and AGE-collagen cross-linking formation. The renoprotective effects were determined by assessing intracellular reactive oxygen species (ROS) and MGO accumulation, cell apoptosis, and the Nrf-2/ARE signaling pathway. MGO-induced renal damage, intracellular ROS production level, and MGO-protein adduct accumulation were significantly decreased by pretreating ECE. Moreover, ECE pretreatment exhibited preventive properties against MGO-induced dicarbonyl stress via activation of the Nrf2/ARE signaling pathway and reduction of RAGE protein expression in mouse glomerular mesangial cells. Collectively, these results indicated potential anti-glycation properties and prominent preventive effects of ECE against MGO-induced renal damage. Additionally, ECE may be utilized for the management of AGE-related diabetic nephropathy.

Proteins in human body fluids contain in vivo antigen analog of the melibiose-derived glycation product: MAGE

Melibiose-derived AGE (MAGE) is an advanced glycation end-product formed in vitro in anhydrous conditions on proteins and protein-free amino acids during glycation with melibiose. Our previous studies revealed the presence of MAGE antigen in the human body and tissues of several other species, including muscles, fat, extracellular matrix, and blood. MAGE is also antigenic and induces generation of anti-MAGE antibody. The aim of this paper was to identify the proteins modified by MAGE present in human body fluids, such as serum, plasma, and peritoneal fluids. The protein-bound MAGE formed in vivo has been isolated from human blood using affinity chromatography on the resin with an immobilized anti-MAGE monoclonal antibody. Using mass spectrometry and immunochemistry it has been established that MAGE epitope is present on several human blood proteins including serum albumin, IgG, and IgA. In serum of diabetic patients, mainly the albumin and IgG were modified by MAGE, while in healthy subjects IgG and IgA carried this modification, suggesting the novel AGE can impact protein structure, contribute to auto-immunogenicity, and affect function of immunoglobulins. Some proteins in peritoneal fluid from cancer patients modified with MAGE were also observed and it indicates a potential role of MAGE in cancer.

Postnatal weaning to different diets leads to different reproductive phenotypes in female offspring following perinatal exposure to high levels of dietary advanced glycation end products

OBJECTIVE

To examine, following perinatal exposure to a diet high in advanced glycation end products (AGEs), whether the use of standard AGE-free mouse chow during the postweaning period alters metabolism and reproduction differently than exposure to a diet low in AGEs.

DESIGN

Experimental animal study.

SETTING

University-based research laboratory.

ANIMAL(S)

Female CD1 mice.

INTERVENTION(S)

Seven-week-old mice were placed on a diet either low or high in AGEs perinatally, before mating and then during pregnancy and lactation. All offspring were weaned onto an AGE-free normal chow.

MAIN OUTCOME MEASURE(S)

Growth curve, liver and abdominal fat weight, insulin and glucose tolerance tests, vaginal opening, estrous cyclicity, and serum levels of antimüllerian hormone, leptin, and adiponectin were assessed. Ovarian histologic examination for follicular count and gene expression was also performed.

RESULT(S)

Compared with the mice exposed to a diet low in AGEs, the mice exposed to a diet high in AGEs showed lower body weight in pups, lower liver weight, delayed vaginal opening, higher serum antimüllerian hormone levels, lower primordial and secondary follicle pools, and higher ovarian Fshr messenger RNA levels.

CONCLUSION(S)

Following weaning, perinatal AGEs can target puberty onset and folliculogenesis differently to standard mouse chow.

Impact of Low Humidity on Damage-associated Molecular Patterns at the Ocular Surface during Dry Eye Disease

SIGNIFICANCE

Dry eye is one of the leading causes for individuals to seek eye care, whereas the pathogenesis is poorly understood. One mechanism in which dry eye inflammation may ensue is by the release of damage-associated molecular patterns (DAMPs) by damaged cells to stimulate the production of cytokines and matrix metalloproteinases. Examining DAMP levels on the ocular surface during dry eye disease (DED) will increase our understanding of their potential involvement in the pathogenesis of DED.

PURPOSE

This study aimed to quantitate DAMPs, high-mobility group box 1 (HMGB1), and heat shock proteins on the ocular surface of normal and dry eye subjects and to examine the impact of low-humidity environment (LHE) on DAMPs and inflammation in dry eye subjects.

METHODS

Basal tears (10 to 20 μL) and conjunctival impression cytology samples were analyzed for HMGB1, HSP-27, HSP-60, HSP-70, and HSP-90α by ELISA or Luminex assays in normal (n = 15) and DED (n = 15) subjects. In addition, a subset of DED subjects were exposed to LHE for 2 hours. The level of DAMPs in the tear film was evaluated by ELISA or Luminex assay. Interleukin 6, interleukin 8, or metalloproteinase (MMP) 9 mRNA were quantitated by real-time polymerase chain reaction from conjunctival impression cytology samples.

RESULTS

Compared with age-matched normal subjects, HMGB1 was significantly elevated in the tear film of DED subjects (P = .03), whereas there was no significant difference in heat shock proteins. Conjunctival impression cytology samples revealed no significant difference in intracellular DAMP levels between both groups. After exposure to an LHE, there was an increase in corneal staining (P = .005), HSP-60 levels in the tear film (P = .01), and MMP-9 mRNA in the conjunctiva (P = .001).

CONCLUSIONS

Dry eye subjects had higher levels of HMGB1 in their tear film. Exposure to an LHE worsened corneal staining, increased conjunctival MMP-9 mRNA expression, and increased tear film HSP-60 levels. Larger studies are needed to understand the involvement of DAMPs in stimulating dry eye inflammation.

Possible Preventative/Rehabilitative Role of Gliflozins in OSA and T2DM. A Systematic Literature Review-Based Hypothesis

Obstructive sleep apnoea (OSA) is characterized by frequent apnoea episodes during sleep due to upper airway obstruction. The present review summarizes current knowledge on inter-relationships between OSA and type 2 diabetes mellitus (T2DM) and suggests the former as a possible target for sodium-glucose co-transporter-2 inhibitors (SGLT-2i). Based on pathophysiological mechanisms underlying OSA onset and renal SGLT-2 effects, we suggest that SGLT-2i indications might expand beyond current ones, including glucose, lipids, uric acid, blood pressure, and body weight control as well as chronic heart failure and kidney disease prevention.

Diabetes and Osteoporosis: Part I, Epidemiology and Pathophysiology

Both diabetes and osteoporosis are increasingly prevalent diseases, in part owing to aging populations worldwide. Epidemiologic data have shown that other organs may be adversely affected by diabetes, including the skeleton, in what has become known as diabetes-induced osteoporosis, which represents the combined impact of conventional osteoporosis with the additional fracture burden attributed to diabetes. There is an increased risk of fracture in patients with Type 1 and Type 2 diabetes, and some antidiabetic medications also may contribute to increased risk of fracture in diabetes.

Advanced-glycation end-products axis: A contributor to the risk of severe illness from COVID-19 in diabetes patients

Compelling pieces of evidence derived from both clinical and experimental research has demonstrated the crucial role of the receptor for advanced-glycation end-products (RAGE) in orchestrating a plethora of proinflammatory cellular responses leading to many of the complications and end-organ damages reported in patients with diabetes mellitus (DM). During the coronavirus disease 2019 (COVID-19) pandemic, many clinical reports have pointed out that DM increases the risk of COVID-19 complications, hospitalization requirements, as well as the overall severe acute respiratory syndrome coronavirus 2 case-fatality rate. In the present review, we intend to focus on how the basal activation state of the RAGE axis in common preexisting conditions in DM patients such as endothelial dysfunction and hyperglycemia-related prothrombotic phenotype, as well as the contribution of RAGE signaling in lung inflammation, may then lead to the increased mortality risk of COVID-19 in these patients. Additionally, the cross-talk between the RAGE axis with either another severe acute respiratory syndrome coronavirus 2 receptor molecule different of angiotensin-converting enzyme 2 or the renin-angiotensin system imbalance produced by viral infection, as well as the role of this multi-ligand receptor on the obesity-associated low-grade inflammation in the higher risk for severe illness reported in diabetes patients with COVID-19, are also discussed.

Biofilm-Innate Immune Interface: Contribution to Chronic Wound Formation

Delayed wound healing can cause significant issues for immobile and ageing individuals as well as those living with co-morbid conditions such as diabetes, cardiovascular disease, and cancer. These delays increase a patient’s risk for infection and, in severe cases, can result in the formation of chronic, non-healing ulcers (e.g., diabetic foot ulcers, surgical site infections, pressure ulcers and venous leg ulcers). Chronic wounds are very difficult and expensive to treat and there is an urgent need to develop more effective therapeutics that restore healing processes. Sustained innate immune activation and inflammation are common features observed across most chronic wound types. However, the factors driving this activation remain incompletely understood. Emerging evidence suggests that the composition and structure of the wound microbiome may play a central role in driving this dysregulated activation but the cellular and molecular mechanisms underlying these processes require further investigation. In this review, we will discuss the current literature on: 1) how bacterial populations and biofilms contribute to chronic wound formation, 2) the role of bacteria and biofilms in driving dysfunctional innate immune responses in chronic wounds, and 3) therapeutics currently available (or underdevelopment) that target bacteria-innate immune interactions to improve healing. We will also discuss potential issues in studying the complexity of immune-biofilm interactions in chronic wounds and explore future areas of investigation for the field.

Association of Follicular Fluid Advanced Glycation End-Products with Oocyte Response and Clinical Pregnancy in Assisted Reproduction Cycles

Context:

Advanced glycation end-products (AGEs) are toxic metabolic end-products of lipids, nucleic acids, and proteins. Their accumulation in the ovaries can alter the follicular microenvironment and affect stimulation response.

Aims:

We aimed to study the association of AGEs in follicular fluid (FF AGE) with oocyte response and clinical pregnancy in ART-Assisted Reproductive Technology cycles.

Settings and Design:

This prospective study involved 84 individuals undergoing ART.

Methods and Material:

FF was collected during oocyte retrieval, and the level of AGEs was measured by enzyme-linked immunosorbent assay. Oocyte response was grouped as below target (<7 MII oocytes) or above target response (≥7 MII).

Statistical Analysis Used:

The association of FF AGE with the oocyte response and clinical pregnancy rate was analyzed by Mann–Whitney U-test. The strength of association of FF AGE with the outcome variables was analyzed with receiver operating characteristic (ROC) curve.

Results:

The median FF AGE was 17.6 (8.5) μg/ml. It was significantly higher in the below target than the normal ovarian response group (18.5 [17.8] vs. 16.3 [7.8] μg/ml, P = 0.046). Similarly, it was significantly higher in those who did not conceive (19.9 [7.3] vs. 13.5 [5.9] μg/ml, P < 0.001). The cutoff of FF AGE obtained by ROC curve analysis was 16.5 μg/ml above which there were significantly lower oocyte response and clinical pregnancy.

Conclusions:

Elevated FF AGE can be a significant negative predictor of clinical pregnancy and ovarian response to stimulation in ART cycles. The FF AGE level above the cutoff value of 16.5 μg/ml was associated with significantly lower oocyte response and clinical pregnancy.

Circulating Ligands of the Receptor for Advanced Glycation End Products and the Soluble Form of the Receptor Modulate Cardiovascular Cell Apoptosis in Diabetes

We determined whether plasma concentrations of the receptor for advanced glycation end products (RAGE) and the soluble (s) form of RAGE (sRAGE) in healthy individuals and patients with type 2 diabetes (T2D) modulate vascular remodeling. Healthy individuals and patients with T2D were divided into two age groups: young = <35 years old or middle-aged (36-64 years old) and stratified based on normal glucose tolerance (NGT), impaired (IGT), and T2D. Plasma titers of sRAGE, the RAGE ligands, AGEs, S100B, S100A1, S100A6, and the apoptotic marker Fas ligand Fas(L) were measured by enzyme-linked immunosorbent assay (ELISA). The apoptotic potential of the above RAGE ligands and sRAGE were assessed in cultured adult rat aortic smooth muscle cells (ASMC). In NGT individuals, aging increased the circulating levels of AGEs and S100B and decreased sRAGE, S100A1 and S100A6. Middle-aged patients with T2D presented higher levels of circulating S100B, AGEs and FasL, but lower levels of sRAGE, S100A1 and S100A6 than individuals with NGT or IGT. Treatment of ASMC with either AGEs or S100B at concentrations detected in T2D patients increased markers of inflammation and apoptosis. Responses attenuated by concomitant administration of sRAGE. In middle-aged patients with T2D, lower circulating plasma levels of sRAGE may limit decoy and exogenous trapping of deleterious pro-apoptotic/pro-inflammatory RAGE ligands AGEs and S100B, increasing the risk for diabetic complications.

Dietary protein intake and circulating advanced glycation end product/receptor for advanced glycation end product concentrations in the Health, Aging, and Body Composition Study

BACKGROUND

Advanced glycation end products (AGEs) promote adverse health effects and may contribute to the multi-system functional decline observed in aging. Diet is a major source of AGEs, and foods high in protein may increase circulating AGE concentrations. However, epidemiological evidence that high-protein diets increase AGEs is lacking.

OBJECTIVES

We examined whether dietary protein intake was associated with serum concentrations of the major AGE carboxymethyl-lysine (CML) and the soluble receptor for AGEs (sRAGE) in 2439 participants from the Health, Aging, and Body Composition study (mean age, 73.6 ± 2.9 y; 52% female; 37% black).

METHODS

CML and sRAGE were measured by ELISA, and the CML/sRAGE ratio was calculated. Protein intake was estimated using an interviewer-administered FFQ and categorized based on current recommendations for older adults: <0.8 g/kg/d (n = 1077), 0.8 to <1.2 g/kg/d (n = 922), and ≥1.2 g/kg/d (n = 440). Associations between protein intake and AGE-RAGE biomarkers were examined using linear regression models adjusted for demographics, height, lifestyle behaviors, prevalent disease, cognitive function, inflammation, and other dietary factors.

RESULTS

CML concentrations were higher in individuals with higher total protein intake (adjusted least squares mean ± SE: <0.8 g/kg/d, 829 ± 17 ng/ml; 0.8 to <1.2 g/kg/d, 860 ± 15 ng/ml; ≥1.2 g/kg/d, 919 ± 23 ng/ml; P for trend = 0.001), as were sRAGE concentrations (<0.8 g/kg/d, 1412 ± 34 pg/ml; 0.8 to <1.2 g/kg/d, 1479 ± 31 pg/ml; ≥1.2 g/kg/d, 1574 ± 47 pg/ml; P for trend < 0.0001). Every 0.1 g/kg/d increment in total protein intake was associated with a 13.3 ± 3.0 ng/ml increment in CML and a 22.1 ± 6.0 pg/ml increment in sRAGE (P < 0.0001 for both). Higher CML and sRAGE concentrations were also associated with higher intakes of both animal and vegetable protein (all P values ≤ 0.01). There were no significant associations with the CML/sRAGE ratio.

CONCLUSIONS

Higher dietary protein intake was associated with higher CML and sRAGE concentrations in older adults; however, the CML/sRAGE ratio remained similar across groups.

A Receptor of the Immunoglobulin Superfamily Regulates Adaptive Thermogenesis

Exquisite regulation of energy homeostasis protects from nutrient deprivation but causes metabolic dysfunction upon nutrient excess. In human and murine adipose tissue, the accumulation of ligands of the receptor for advanced glycation end products (RAGE) accompanies obesity, implicating this receptor in energy metabolism. Here, we demonstrate that mice bearing global- or adipocyte-specific deletion of Ager, the gene encoding RAGE, display superior metabolic recovery after fasting, a cold challenge, or high-fat feeding. The RAGE-dependent mechanisms were traced to suppression of protein kinase A (PKA)-mediated phosphorylation of its key targets, hormone-sensitive lipase and p38 mitogen-activated protein kinase, upon β-adrenergic receptor stimulation—processes that dampen the expression and activity of uncoupling protein 1 (UCP1) and thermogenic programs. This work identifies the innate role of RAGE as a key node in the immunometabolic networks that control responses to nutrient supply and cold challenges, and it unveils opportunities to harness energy expenditure in environmental and metabolic stress.

Hurtado del Pozo et al. show that the deletion of adipocyte RAGE, whose ligands accumulate in metabolic stress, protects from obesity and cold challenges through the modulation of protein kinase A activities. This work adds RAGE to the immunometabolic networks that regulate energy expenditure in environmental and metabolic stress.

Molecular complexities underlying the vascular complications of diabetes mellitus - A comprehensive review

Diabetes is a chronic disease, characterized by hyperglycemia, which refers to the elevated levels of glucose in the blood, due to the inability of the body to produce or use insulin effectively. Chronic hyperglycemia levels lead to macrovascular and microvascular complications. The macrovascular complications consist of peripheral artery disease (PAD), cardiovascular diseases (CVD) and cerebrovascular diseases, while the microvascular complications comprise of diabetic microangiopathy, diabetic nephropathy, diabetic retinopathy and diabetic neuropathy. Vascular endothelial dysfunction plays a crucial role in mediating both macrovascular and microvascular complications under hyperglycemic conditions. In diabetic microvasculature, the intracellular hyperglycemia causes damage to the vascular endothelium through - (i) activation of four biochemical pathways, namely the Polyol pathway, protein kinase C (PKC) pathway, advanced glycation end products (AGE) pathway and hexosamine pathway, all of which commutes glucose and its intermediates leading to overproduction of reactive oxygen species, (ii) dysregulation of growth factors and cytokines, (iii) epigenetic changes which concern the changes in DNA as a response to intracellular changes, and (iv) abnormalities in non-coding RNAs, specifically microRNAs. This review will focus on gaining an understanding of the molecular complexities underlying the vascular complications in diabetes mellitus, to increase our understanding towards the development of new mechanistic therapeutic strategies to prevent or treat diabetes-induced vascular complications.

Should we Try to Alleviate Immunosenescence and Inflammaging - Why, How and to What Extent?

With advancing age, immune responses of human beings to external pathogens, i.e., bacteria, viruses, fungi and parasites, and to internal pathogens - malignant neoplasm cells - become less effective. Two major features in the process of aging of the human immune system are immunosenescence and inflammaging. The immune systems of our predecessors co-evolved with pathogens, which led to the occurrence of effective immunity. However, the otherwise beneficial activity may pose problems to the organism of the host and so it has builtin brakes (regulatory immune cells) and - with age - it undergoes adaptations and modifications, examples of which are the mentioned inflammaging and immunosenescence. Here we describe the mechanisms that first created our immune systems, then the consequences of their changes associated with aging, and the mechanisms of inflammaging and immunosenescence. Finally, we discuss to what extent both processes are detrimental and to what extent they might be beneficial and propose some therapeutic approaches for their wise control.

Advanced glycation end products in diabetes, cancer and phytochemical therapy

The irreversible glycation and oxidation of proteins and lipids produces advanced glycation end products (AGEs). These modified AGEs are triggered to bind the receptor for AGE (RAGE), thereby activating its downstream signaling pathways, such as nuclear factor (NF)-κB and phosphoinositide 3-kinase (PI3K)/Akt, ultimately leading to diabetes and cancers. In this review, we focus on the interaction of AGE-RAGE and their associated pathways. We also consider the activity of phytochemicals, such as genistein and curcumin, that trap dicarbonyl compounds including methylglyoxal (MG) and glyoxalase that arise from multiple pathways to block AGE formation and prevent its interaction with RAGE.

Glycation of macrophages induces expression of pro-inflammatory cytokines and reduces phagocytic efficiency

Glycation and the accumulation of advanced glycation end products (AGEs) are known to occur during normal aging but also in the progression of several diseases, such as diabetes. Diabetes type II and aging both lead to impaired wound healing. It has been demonstrated that macrophages play an important role in impaired wound healing, however, the underlying causes remain unknown. Elevated blood glucose levels as well as elevated methylglyoxal (MGO) levels in diabetic patients result in glycation and increase of AGEs. We used MGO to investigate the influence of glycation and AGEs on macrophages. We could show that glycation, but not treatment with AGE-modified serum proteins, increased expression of pro-inflammatory cytokines interleukin 1β (IL-1β) and IL-8 but also affected IL-10 and TNF-α expression, resulting in increased inflammation. At the same time, glycation reduced phagocytic efficiency and led to impaired clearance rates of invading microbes and cellular debris. Our data suggest that glycation contributes to changes of macrophage activity and cytokine expression and therefore could support the understanding of disturbed wound healing during aging and diabetes.

Receptor for advanced glycation end products: a key molecule in the genesis of chronic kidney disease vascular calcification and a potential modulator of sodium phosphate co-transporter PIT-1 expression

BACKGROUND

Chronic kidney disease (CKD) is associated with increased cardiovascular mortality, frequent vascular calcification (VC) and accumulation of uraemic toxins. Advanced glycation end products and S100 proteins interact with the receptor for advanced glycation end products (RAGE). In the present work, we aimed to investigate the role(s) of RAGE in the CKD-VC process.

METHODS

Apoe-/- or Apoe-/-Ager (RAGE)-/- male mice were assigned to CKD or sham-operated groups. A high-phosphate diet was given to a subgroup of Apoe-/-and Apoe-/-Ager-/- CKD mice. Primary cultures of Ager+/+ and Ager-/- vascular smooth muscle cells (VSMCs) were established and stimulated with either vehicle, inorganic phosphate (Pi) or RAGE ligands (S100A12; 20 µM).

RESULTS

After 12 weeks of CKD we observed a significant increase in RAGE ligand (AGE and S100 proteins) concentrations in the serum of CKD Apoe-/- mice. Ager messenger RNA (mRNA) levels were 4-fold higher in CKD vessels of Apoe-/- mice. CKD Apoe-/- but not CKD Apoe-/- or Ager-/- mice displayed a marked increase in the VC surface area. Similar trends were found in the high-phosphate diet condition. mRNA levels of Runx2 significantly increased in the Apoe-/- CKD group. In vitro, stimulation of Ager+/+VSMCs with Pi or S100A12 induced mineralization and osteoblast transformation, and this was inhibited by phosphonoformic acid (Pi co-transporters inhibitor) and Ager deletion. In vivo and in vitro RAGE was necessary for regulation of the expression of Pit-1, at least in part through production of reactive oxygen species.

CONCLUSION

RAGE, through the modulation of Pit-1 expression, is a key molecule in the genesis of VC.

Soluble Receptor for Advanced Glycation End Products and Its Correlation with Vascular Damage in Adolescents with Obesity

OBJECTIVE

The aim of this study was to evaluate soluble receptor for advanced glycation end products (sRAGE) and advanced glycation end products (AGEs) in adolescents with and without obesity (OB) and their correlation with vascular damage.

METHODS

This is a cross-sectional study with 15-19 years old adolescents: 33 with OB and 33 with normal weight (NW), each group included 17 male and 16 female. Lipid profile, insulin, carboxymethylysine (CML), sRAGE, total AGEs, and dietary AGEs intake (dAGEs) were evaluated. Vascular damage was measured by flow-mediated vasodilation (FMD) and arterial stiffness index (Iβ). Homeostatic model assessment-insulin (HOMA-IR) and atherogenic index (AI) were calculated.

RESULTS

The group with OB had higher triglycerides (TG; p < 0.0001), AI (p < 0.001), HOMA-IR (p < 0.0001), dAGEs intake (p < 0.0001), lower CML (p = 0.05), total AGEs (p < 0.01), sRAGE (p < 0.001), and FMD (p < 0.002). In the total group, sRAGE correlated with AI (r = -0.26 p = 0.037); in the NW group, CML correlated with Iβ (r = -0.36; p = 0.037); and in the group of adolescents with OB, sRAGE correlated with FMD (r = -0.37; p = 0.037) and Iβ (r = 0.47; p = 0.006), while CML and total AGEs correlated with AI, p = 0.007 and p < 0.01, respectively).

CONCLUSIONS

The group of adolescents with OB showed higher cardiometabolic risk as shown by higher TG, AI, HOMA-IR, and lower sRAGE and FMD. sRAGE correlated negatively with FMD and positively with Iβ, so it could be suggested as a biochemical marker of impaired endothelial function.

Advanced glycation end products (AGEs), protein aggregation and their cross talk: new insight in tumorigenesis

Protein glycation and protein aggregation are two distinct phenomena being observed in cancer cells as factors promoting cancer cell viability. Protein aggregation is an abnormal interaction between proteins caused as a result of structural changes in them after any mutation or environmental assault. Protein aggregation is usually associated with neurodegenerative diseases like Alzheimer's and Parkinson's, but of late, research findings have shown its association with the development of different cancers like lung, breast and ovarian cancer. On the contrary, protein glycation is a cascade of irreversible nonenzymatic reaction of reducing sugar with the amino group of the protein resulting in the modification of protein structure and formation of advanced glycation end products (AGEs). These AGEs are reported to obstruct the normal function of proteins. Lately, it has been reported that protein aggregation occurs as a result of AGEs. This aggregation of protein promotes the transformation of healthy cells to neoplasia leading to tumorigenesis. In this review, we underline the current knowledge of protein aggregation and glycation along with the cross talk between the two, which may eventually lead to the development of cancer.

An overlooked danger of ketogenic diets: Making the case that ketone bodies induce vascular damage by the same mechanisms as glucose

Intense debate surrounds the use of low-carbohydrate, ketogenic diets for the promotion of weight loss and avoidance of cardiovascular disease. The rationale behind these diets is that they promote fat oxidation and minimize the addition of glucose to proteins in the formation of adducts that trigger inflammation. Although nutritional ketosis is widely assumed to be a safe metabolic condition, proper consideration has not been given to the fact that ketones are reactive toward proteins through the same mechanisms as glucose. Here, the case is made that ketone bodies are more potent than glucose in bringing about the protein modifications to which the harmful effects of glucose have been attributed. It is suggested, therefore, that attempts to minimize such protein modifications through nutritional ketosis are futile and may lead to adverse health outcomes.

The Role of Nonenzymatic Post-translational Protein Modifications in Uremic Vascular Calcification

Considerable technological advances have enabled the identification and linkage of nonenzymatic post-translationally modified proteins to the pathogenesis of cardiovascular disease (CVD) in patients with kidney failure. Through processes such as the nonenzymatic carbamylation reaction as well as the formation of advanced glycation end products, we now know that protein modifications are invariably associated with the development of CVD beyond a mere epiphenomenon and this has become an important focus of nephrology research in recent years. Although the specific mechanisms by which protein modifications occurring in kidney failure that may contribute to CVD are diverse and include pathways such as inflammation and fibrosis, vascular calcification has emerged as a distinct pathological sequelae of protein modifications. In this review, we consider the biological mechanisms and clinical relevance of protein carbamylation and advanced glycation end products in CVD development with a focus on vascular calcification.

Novel potential biomarkers for the diagnosis and monitoring of patients with ulcerative colitis

Unambiguously, great progress has been achieved in the unraveling of more pathological pathways implicated in the development and progression of ulcerative colitis during the last decades. Novel effective drugs that have augmented the management armamentarium have been developed alongside this growing comprehension of the disease, rendering mucosal healing not only a feasible but the optimal goal of every therapy. Clinical evaluation, colonoscopy and biomarkers are the tools used by practitioners for the diagnosis and assessment of the status of the disease in order to achieve clinical remission and mucosal healing for their patients. Among these tools, colonoscopy is the gold method for the cause but is still an invasive, high-cost procedure with possible adverse events such as perforation. While clinical evaluation entails much subjectivity, biomarkers are objective, easily reproducible, non-invasive, cheap and potent surrogate tools of mucosal inflammation. Unfortunately, the well-established, currently in use serum biomarkers, such as C-reactive protein, erythrocyte sedimentation rate and others, do not display sufficiently acceptable sensitivity and specificity rates for the diagnosis of ulcerative colitis and, most importantly, do not represent precisely the mucosal inflammation status of the disease. Therefore, the discovery of new serum biomarkers has been the cause of several studies attempting to discover an "optimal" serum biomarker during the recent years. After thorough research, collection and examination of current data, this review focuses on and selectively presents promising, potential, novel serum biomarkers of ulcerative colitis as they are indicated by studies on the patient over the last years.

Advanced glycation end products (AGEs) and their soluble receptors (sRAGE) as early predictors of reno-vascular complications in patients with uncontrolled type 2 diabetes mellitus

AIM

To evaluate the role of advanced glycation end-products (AGEs) and their soluble receptors (sRAGE) expression levels as predictors of vascular complications in uncontrolled type 2 diabetes mellitus (T2DM).

METHODS

Cross-sectional study was conducted on T2DM adults of both sexes who attended the outpatient service of Al-Karak Teaching Hospital, Jordan during the period from June 2017 to August 2018. Participants were categorized in two groups according to their glycemic control and the presence of reno-vascular complications. Twenty healthy subjects were recruited as control group. Blood sample was obtained from all participants and used for the assessment of FBG, HbA1c, serum AGEs and sRAGE, serum urea and creatinine; 24 h urine was also collected for the determination of urinary albumin.

RESULTS

Diabetic subjects with vascular complication had a significantly higher serum AGEs 50.3 ± 13 vs. 28.9 ± 8 pg/ml) and AGEs/sRAGE ratio (0.058 ± 0.02 vs. 0.037 ± 0.02) associated with significantly lower serum sRAGE (868.7 ± 50.8 vs. 912.8 ± 294.3) compared to those with no complications. Serum AGEs and sRAGE showed weak negative and non-significant association in both groups of patients. However, the AGEs/sRAGE ration was inversely and significantly associated with the urinary albumin/creatinine ratio (r = - 0.51, P = 0.009) only in DM patients with reno-vascular complications.

CONCLUSION

We found an association between AGEs/sRAGE ratio and urinary albumin/serum creatinine ratio in T2DM patients with reno-vascular complications; providing evidence that serum AGEs and sRAGE can be considered as predictors of vascular complications in uncontrolled T2DM patients.

Soluble Forms of the Receptor for Advanced Glycation Endproducts (RAGE) in Periodontitis

The receptor for advanced glycation endproducts (RAGE) is critically involved in the pathobiology of chronic inflammatory diseases. Soluble forms of RAGE have been proposed as biomarkers of severity in inflammatory and metabolic conditions, and in monitoring therapeutic responses. The aim of the present study was to determine circulating levels of the soluble forms of RAGE in periodontitis and to evaluate the expression of cell-bound, full-length RAGE and its antagonist AGER1 locally, in gingival tissues. Periodontitis patients and periodontally healthy, sex- and age-matched controls (50 per group) were included. Serum levels of total soluble RAGE and cleaved RAGE (cRAGE) were significantly lower in periodontitis patients. Levels of the endogenous secretory esRAGE were similar in the two groups. cRAGE remained significantly lower in the periodontitis group following multiple adjustments, and had a statistically significant inverse correlation with body mass index and all periodontal parameters. In periodontitis patients, gene expression of full-length RAGE and of AGER1 were significantly higher in periodontitis-affected gingival tissues compared to healthy gingiva. Soluble forms of RAGE, particularly cRAGE, may serve as biomarkers for the presence and severity/extent of periodontitis, and may be implicated in its pathogenesis and its role as a systemic inflammatory stressor.

AGE-RAGE stress: a changing landscape in pathology and treatment of Alzheimer's disease

Numerous hypotheses including amyloid cascade, cholinergic, and oxidative have been proposed for pathogenesis of Alzheimer's disease (AD). The data suggest that advanced glycation end products (AGEs) and its receptor RAGE (receptor for AGE) are involved in the pathogenesis of AD. AGE-RAGE stress, defined as a balance between stressors (AGE, RAGE) and anti-stressors (sRAGE, AGE degraders) in favor of stressors, has been implicated in pathogenesis of diseases. AGE and its interaction with RAGE-mediated increase in the reactive oxygen species (ROS) damage brain because of its increased vulnerability to ROS. AGE and ROS increase the synthesis of amyloid β (Aβ) leading to deposition of Aβ and phosphorylation of tau, culminating in formation of plaques and neurofibrillary tangles. ROS increase the synthesis of Aβ, high-mobility group box 1(HMGB1), and S100 that interacts with RAGE to produce additional ROS resulting in enhancement of AD pathology. Elevation of ROS precedes the Aβ plaques formation. Because of involvement of AGE and RAGE in AD pathology, the treatment should be targeted at lowering AGE levels through reduction in consumption and formation of AGE, and lowering expression of RAGE, blocking of RAGE ligand binding, increasing levels of soluble RAGE (sRAGE), and use of antioxidants. The above treatment aspect of AD is lacking. In conclusion, AGE-RAGE stress initiates, and Aβ, HMGB1, and S100 enhance the progression of AD. Reduction of levels of AGE and RAGE, elevation of sRAGE, and antioxidants would be beneficial therapeutic modalities in the prevention, regression, and slowing of progression of AD.

FoxO1 inhibits autophagosome-lysosome fusion leading to endothelial autophagic-apoptosis in diabetes

Aims

Inadequate autophagy contributed to endothelial dysfunction in diabetic patients. We aimed to investigate the relationship between inadequate autophagy and endothelial cells (ECs) apoptosis in diabetes and its underlying mechanism.

Methods and results

Aortic intima and ECs were isolated from diabetic patients. Cultured human aortic endothelial cells (HAECs) were stimulated with advanced glycation end products (AGEs). The expression of autophagy and apoptosis-related proteins were determined by western blotting. Autophagosomes were observed by electron microscopy. The fusion of autophagosome and lysosomes was detected by immunofluorescence. Compared with non-diabetic subjects, the levels of LC3-II, p62, FoxO1, and Ac-FoxO1 were increased in ECs from diabetic patients, accompanied by the decreased expressions of Atg14, STX17, and co-localization of LC3-II/LAMP2 and Atg14/STX17. Long-term stimulation with AGEs up-regulated LC3-II and p62 expression and the number of autophagosomes with decreased level of Atg14, STX17, Ras-related protein 7 (Rab7), and co-localization of LC3-II/LAMP2 and Atg14/STX17 in HAECs. The apoptosis rates were increased with elevated cleaved-caspase-3 and declined Bcl-2 expression. Inhibition of autophagy with 3-methyladenine could reduce long-term AGEs-induced apoptosis. Higher levels of FoxO1, Ac-FoxO1, and Ac-FoxO1 binding to Atg7 were detected in AGEs-treated HAECs. AGEs-induced FoxO1 enhanced Akt activity, decreased SIRT1-deacetylase activity by phosphorylation and elevated Ac-FoxO1. Knockout of FoxO1 reduced AGEs-induced autophagy and promoted the expression of Atg14 and the co-localization of LC3-II/LAMP 2 and Atg14/STX17.

Conclusion

Inadequate autophagy with impaired autophagosome-lysosomal fusion exists in aortic intima and ECs from diabetic patients. FoxO1 mediates AGEs-induced ECs autophagic apoptosis through impairing autophagosome-lysosomes fusion by inhibiting Atg14 expression.

Crosstalk between advanced glycation end products and vitamin D: A compelling paradigm for the treatment of ovarian dysfunction in PCOS

Women with PCOS have elevated levels of the harmful advanced glycation end products (AGEs) and low serum levels of vitamin D. AGEs and their receptors may contribute to the pathogenesis of PCOS and its metabolic and reproductive consequences. On the other hand, vitamin D might improve PCOS phenotype and could alleviate the detrimental effects of AGEs. A literature review using PubMed was performed. Critical analysis was carried out for articles pertaining to: 1) the role of AGEs and their receptors in the pathophysiology of PCOS, in particular ovarian dysfunction, and 2) the action of vitamin D in attenuating the adverse effects of AGEs in women with PCOS at both the serum and the cellular levels. Data from in vitro experiments, animal models, and human studies provide compelling evidence that AGEs and their receptors may contribute to the pathogenesis of ovarian dysfunction in PCOS. The actions of AGEs in PCOS might be attenuated and/or reversed by the presence or supplementation of vitamin D. Once a mechanistic understanding of the relationship between AGEs and vitamin D is established, this knowledge might contribute to the subsequent development of new-targeted pharmacological therapies for improving ovarian health in women with PCOS.

Vitamin D attenuates the effect of advanced glycation end products on anti-Mullerian hormone signaling

Vitamin D3 (1,25-dihydroxyvitamin D3, VD3) in vitro attenuates the effect of the pro-inflammatory advanced glycation end products (AGEs) on steroidogenesis in human granulosa cells (GCs) by downregulating the receptor for AGEs (RAGE). It has been shown that VD3 alone downregulates anti-Mullerian hormone (AMH) type 2 receptor (AMHR-2) gene expression and suppresses AMH-induced SMAD 1/5/8 phosphorylation in granulosa cells. However, the effect of AGEs, in the absence or presence of VD3, on AMH action in GCs has not been studied. Using human GCs, this study showed that human glycated albumin (HGA), an in vitro representative for AGEs, upregulated AMHR-2 mRNA but did not alter AMH mRNA expression levels. VD3 inhibited the HGA-induced increase in AMHR-2 mRNA expression levels. In KGN granulosa cell line, recombinant AMH induced SMAD 1/5/8 phosphorylation. HGA augmented the recombinant AMH-induced SMAD 1/5/8 phosphorylation while the addition of VD3 to HGA attenuated the recombinant AMH-induced SMAD 1/5/8 phosphorylation. Thus, AGEs could potentially affect folliculogenesis as reflected by changes in AMH signaling. These findings have significant implications for women with polycystic ovary syndrome who have significantly elevated serum and ovarian AGEs.

The Microbiotic Highway to Health-New Perspective on Food Structure, Gut Microbiota, and Host Inflammation

This review provides evidence that not only the content of nutrients but indeed the structural organization of nutrients is a major determinant of human health. The gut microbiota provides nutrients for the host by digesting food structures otherwise indigestible by human enzymes, thereby simultaneously harvesting energy and delivering nutrients and metabolites for the nutritional and biological benefit of the host. Microbiota-derived nutrients, metabolites, and antigens promote the development and function of the host immune system both directly by activating cells of the adaptive and innate immune system and indirectly by sustaining release of monosaccharides, stimulating intestinal receptors and secreting gut hormones. Multiple indirect microbiota-dependent biological responses contribute to glucose homeostasis, which prevents hyperglycemia-induced inflammatory conditions. The composition and function of the gut microbiota vary between individuals and whereas dietary habits influence the gut microbiota, the gut microbiota influences both the nutritional and biological homeostasis of the host. A healthy gut microbiota requires the presence of beneficial microbiotic species as well as vital food structures to ensure appropriate feeding of the microbiota. This review focuses on the impact of plant-based food structures, the "fiber-encapsulated nutrient formulation", and on the direct and indirect mechanisms by which the gut microbiota participate in host immune function.

Polymorphisms in the receptor for advanced glycation end-products (RAGE) gene and circulating RAGE levels as a susceptibility factor for non-alcoholic steatohepatitis (NASH)

Non-alcoholic fatty liver disease (NAFLD) is a hepatic manifestation of metabolic syndrome and major cause of chronic liver disease in developed countries. Its prevalence is increasing in parallel with the prevalence of obesity and other components of the metabolic syndrome. As the liver is central to the clearance and catabolism of circulating advanced glycosylation end-products (AGEs), AGEs and their cognate receptors—RAGE (receptor for AGEs) system might be involved in NAFLD in obese patients. To examine this, we investigated four common polymorphisms of RAGE gene: 1704G/T (rs184003), G82S (rs2070600), -374T/A (rs1800624) and −429T/C (rs1800625) in 340 obese patients with metabolic syndrome. and protein levels of AGE and RAGE. This is the first study to describe association of 4 common polymorphisms with non-alcoholic steatohepatitis (NASH) as well as to examine protein levels of RAGE and AGE. Univariate analysis showed patients carrying the rs1800624 heterozygote genotype (AT) exhibited 2.36-fold increased risk of NASH (odds ratio (OR) = 2.36; 95% confidence interval (95% CI): 1.35–4.19) after adjusting for confounders. The minor allele -374 A has been shown to suppress the expression of RAGE protein. The protein levels of esRAGE, total sRAGE and AGE protein levels did not correlate with each other in obese patients with no liver disease, indicative of RAGE signaling playing an independent role in liver injury. In obese patients with non-NASH NAFLD and NASH respectively, esRAGE protein showed strong positive correlation with total sRAGE protein. Further, haplotype analysis of the 4 SNPs, indicated that haplotype G-A-T-G was significantly associated with 2-fold increased risk for NASH (OR = 2.08; 95% CI: 1.21–3.5; P = 0.006) after adjusting for confounders. In conclusion, the presented data indicate that the G-A-T-G haplotype containing minor allele at position −374 A and major allele at position −429T, 1704G, and G82S G could be regarded as a marker for NASH.

Advanced glycation end products alter steroidogenic gene expression by granulosa cells: an effect partially reversible by vitamin D

STUDY QUESTION

Does vitamin D attenuate the adverse effects of advanced glycation end products (AGEs) on steroidogenesis by human granulosa cells (GCs)?

SUMMARY ANSWER

AGEs alter the expression of genes important in steroidogenesis while 1,25-dihydroxyvitamin D3 (vit D3) in vitro attenuates some of the actions of AGEs on steroidogenic gene expression, possibly by downregulating the expression of the pro-inflammatory cell membrane receptor for AGEs (RAGE).

WHAT IS KNOWN ALREADY

Vitamin D attenuates the pro-inflammatory effects of AGEs in non-ovarian tissues.

STUDY DESIGN, SIZE, DURATION

Women who were undergoing IVF were enrolled. Follicular fluid samples (n = 71) were collected and cumulus GCs (n = 12) were treated in culture.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Follicular fluid levels of the anti-inflammatory soluble RAGE (sRAGE), AGEs and 25-hydroxyvitamin D (25-OHD) were quantified for possible correlations. GCs of each participant were split equally and treated with either media alone (control) or with human glycated albumin (HGA as a precursor for AGEs) with or without vit D3 after which RT-PCR and immunofluorescence were performed and cell culture media estradiol (E2) levels were compared.

MAIN RESULTS AND THE ROLE OF CHANCE

In follicular fluid, sRAGE levels were positively correlated with 25-OHD levels. HGA treatment (i) increased CYP11A1 (by 48%), 3β-HSD (by 38%), StAR (by 42%), CYP17A1 (by 30%) and LHR (by 37%) mRNA expression levels (P < 0.05 for all) but did not alter CYP19A1 or FSHR mRNA expression levels; and (ii) increased E2 release in cell culture media (P = 0.02). Vit D3 treatment (i) downregulated RAGE mRNA expression by 33% and RAGE protein levels by 44% (P < 0.05); (ii) inhibited the HGA-induced increase in CYP11A1, StAR, CYP17A1 and LHR mRNA levels, but not the increase in 3β-HSD mRNA levels; and (iii) did not inhibit the HGA-induced E2 release in cell culture media.

LIMITATIONS REASONS FOR CAUTION

This study used luteinized GCs that were collected from women who received gonadotropins thus the results obtained may not fully extrapolate to non-luteinized GCs in vivo.

WIDER IMPLICATIONS OF THE FINDINGS

This study suggests that there is a relationship between AGEs and their receptors (RAGE and sRAGE) with vitamin D. Understanding the interaction between AGEs and vitamin D in ovarian physiology could lead to a more targeted therapy for the treatment of ovarian dysfunction.

STUDY FUNDING/COMPETING INTEREST(S)

Funding was received from NIH (R01 NS045940), American Society for Reproductive Medicine, Ferring Pharmaceuticals Inc., and University of Vermont College of Medicine Bridge Funds. All authors have nothing to disclose.

Deficiency of S100B confers resistance to experimental diabetes in mice

The calcium binding protein S100B has been implicated in diabetic neuronal and vascular complications but has not been examined in the development of diabetes. S100B knock out (S100B KO) and wild-type (WT) mice were injected with 40 mg/kg body weight streptozotocin (STZ) for 5 days. Blood and pancreatic tissue samples were obtained to examine islet structure and function, the profile of glucose and insulin and expression of glucose transporter 2 (Glut2), S100B and its receptor, the receptor for advanced glycation end products (RAGE). Primary islet β-cells cultures from WT mice were used to test the apoptotic potential of S100B. S100B KO mice were resistant to STZ induced-diabetes with lower urine volume, food and water intake compared to WT mice. S100B increased in the WT islet following diabetes but did not co-localize with beta or peri-islet Schwann cells but with CD3 + T lymphocytes. S100B KO mice exhibited enhanced glucose tolerance, insulin sensitivity, prevented β-cell destruction and functional impairment in response to STZ treatment. S100B deficiency was associated with decreased Glut2 and RAGE. In primary β-cell cultures from WT mice, S100B induced reactive oxygen species (ROS) and RAGE-dependent apoptosis. In the STZ diabetic animal model, abrogation of S100B enhances insulin sensitivity and reduces pancreatic islet, and β-cell destruction. S100B may be a promising target for pharmacological interventions aimed at repressing diabetes.