Orally absorbed reactive glycation products (glycotoxins): an environmental risk factor in diabetic nephropathy

Role of RAGE in the Pathogenesis of Neurological Disorders

This review reflects upon our own as well as other investigators' studies on the role of receptor for advanced glycation end-products (RAGE), bringing up the latest information on RAGE in physiology and pathology of the nervous system. Over the last ten years, major progress has been made in uncovering many of RAGE-ligand interactions and signaling pathways in nervous tissue; however, the translation of these discoveries into clinical practice has not come to fruition yet. This is likely, in part to be the result of our incomplete understanding of this crucial signaling pathway. Clinical trials examining the therapeutic efficacy of blocking RAGE-external ligand interactions by genetically engineered soluble RAGE or an endogenous RAGE antagonist, has not stood up to its promise; however, other trials with different blocking agents are being considered with hope for therapeutic success in diseases of the nervous system.

Accumulation of Advanced Glycation End-Products in the Body and Dietary Habits

The formation of advanced glycation end-products (AGE) in tissues is a physiological process; however, excessive production and storage are pathological and lead to inflammation. A sedentary lifestyle, hypercaloric and high-fructose diet and increased intake of processed food elements contribute to excessive production of compounds, which are created in the non-enzymatic multi-stage glycation process. The AGE’s sources can be endogenous and exogenous, mainly due to processing food at high temperatures and low moisture, including grilling, roasting, and frying. Accumulation of AGE increases oxidative stress and initiates various disorders, leading to the progression of atherosclerosis, cardiovascular disease, diabetes and their complications. Inborn defensive mechanisms, recovery systems, and exogenous antioxidants (including polyphenols) protect from excessive AGE accumulation. Additionally, numerous products have anti-glycation properties, occurring mainly in fruits, vegetables, herbs, and spices. It confirms the role of diet in the prevention of civilization diseases.

High Molecular Weight Fucoidan Restores Intestinal Integrity by Regulating Inflammation and Tight Junction Loss Induced by Methylglyoxal-Derived Hydroimidazolone-1

Fucoidan from brown seaweeds has several biological effects, including preserving intestinal integrity. To investigate the intestinal protective properties of high molecular weight fucoidan (HMWF) from Undaria pinnatifida on intestinal integrity dysfunction caused by methylglyoxal-derived hydroimidazolone-1 (MG-H1), one of the dietary advanced-glycation end products (dAGEs) in the human-colon carcinoma-cell line (Caco-2) cells and ICR mice. According to research, dAGEs may damage the intestinal barrier by increasing gut permeability. The findings of the study showed that HMWF + MG-H1 treatment reduced by 16.8% the amount of reactive oxygen species generated by MG-H1 treatment alone. Furthermore, HMWF + MGH-1 treatment reduced MG-H1-induced monolayer integrity disruption, as measured by alterations in transepithelial electrical resistance (135% vs. 75.5%) and fluorescein isothiocyanate incorporation (1.40 × 10^-6 cm/s vs. 3.80 cm/s). HMWF treatment prevented the MG-H1-induced expression of tight junction markers, including zonula occludens-1, occludin, and claudin-1 in Caco-2 cells and mouse colon tissues at the mRNA and protein level. Also, in Caco-2 and MG-H1-treated mice, HMWF plays an important role in preventing receptor for AGEs (RAGE)-mediated intestinal damage. In addition, HMWF inhibited the nuclear factor kappa B activation and its target genes leading to intestinal inflammation. These findings suggest that HMWF with price competitiveness could play an important role in preventing AGEs-induced intestinal barrier dysfunction.

Advanced Glycation End Products in Health and Disease

Advanced glycation end products (AGEs), formed through the nonenzymatic reaction of reducing sugars with the side-chain amino groups of lysine or arginine of proteins, followed by further glycoxidation reactions under oxidative stress conditions, are involved in the onset and exacerbation of a variety of diseases, including diabetes, atherosclerosis, and Alzheimer’s disease (AD) as well as in the secondary stages of traumatic brain injury (TBI). AGEs, in the form of intra- and interprotein crosslinks, deactivate various enzymes, exacerbating disease progression. The interactions of AGEs with the receptors for the AGEs (RAGE) also result in further downstream inflammatory cascade events. The overexpression of RAGE and the AGE-RAGE interactions are especially involved in cases of Alzheimer’s disease and other neurodegenerative diseases, including TBI and amyotrophic lateral sclerosis (ALS). Maillard reactions are also observed in the gut bacterial species. The protein aggregates found in the bacterial species resemble those of AD and Parkinson’s disease (PD), and AGE inhibitors increase the life span of the bacteria. Dietary AGEs alter the gut microbiota composition and elevate plasma glycosylation, thereby leading to systemic proinflammatory effects and endothelial dysfunction. There is emerging interest in developing AGE inhibitor and AGE breaker compounds to treat AGE-mediated pathologies, including diabetes and neurodegenerative diseases. Gut-microbiota-derived enzymes may also function as AGE-breaker biocatalysts. Thus, AGEs have a prominent role in the pathogenesis of various diseases, and the AGE inhibitor and AGE breaker approach may lead to novel therapeutic candidates.

Bone matrix quality in a developing high-fat diet mouse model is altered by RAGE deletion

Overweightness and obesity in adolescents are epidemics linked to chronic low-grade inflammation and elevated fracture risk. The increased fracture risk observed in overweight/obese adolescence contrasts the traditional concept that high body mass is protective against fracture, and thus highlights the need to determine why weight gain becomes detrimental to fracture during growth and maturity. The Receptor for Advanced Glycation End products (RAGE) is a central inflammatory regulator that can influence bone metabolism. It remains unknown how RAGE removal impacts skeletal fragility in overweightness/obesity, and whether increased fracture risk in adolescents could result from low-grade inflammation deteriorating bone quality. We characterized the multiscale structural, mechanical, and chemical properties of tibiae extracted from adolescent C57BL/6J (WT) and RAGE null (KO) mice fed either low-fat (LF) or high-fat (HF) diet for 12 weeks starting at 6 weeks of age using micro-computed tomography, strength, Raman spectroscopy, and nanoindentation. Overweight/obese WT HF mice possessed degraded mineral-crystal quality and increased matrix glycoxidation in the form of pentosidine and carboxymethyl-lysine, with HF diet in females only showing reduced cortical surface expansion and TMD independently of RAGE ablation. Furthermore, in contrast to males, HF diet in females led to more material damage and plastic deformation. RAGE KO mitigated glycoxidative matrix accumulation, preserved mineral quantity, and led to increased E/H ratio in females. Taken together, these results highlight the complex, multi-scale and sex-dependent relationships between bone quality and function under overweightness, and identifies RAGE-controlled glycoxidation as a target to potentially preserve matrix quality and mechanical integrity.

5-Demethylnobiletin: Insights into its pharmacological activity, mechanisms, pharmacokinetics and toxicity

BACKGROUND

5-Demethylnobiletin (5DN) is a polymethoxyflavone (PMF) primarily found in citrus fruits. It has various health-promoting properties and hence has attracted significant attention from scholars worldwide.

PURPOSE

This review is the first to systematically summarize the recent research progress of 5DN, including its pharmacological activity, mechanism of action, pharmacokinetics, and toxicological effects. In addition, the pharmacological mechanism of action of 5DN has been discussed from a molecular biological perspective, and data from in vivo and in vitro animal studies have been compiled to provide a more thorough understanding of 5DN as a potential lead drug.

METHODS

Data were extracted from SciFinder, PubMed, ScienceDirect and China National Knowledge Infrastructure (CNKI) from database inception to January 2022.

RESULTS

5DN has broad pharmacological activities. It exerts anti-inflammatory effects, promotes apoptosis and autophagy, and induces melanogenesis mainly by regulating the JAK2/STAT3, caspase-dependent apoptosis, ROS-AKT/mTOR, MAPK and PKA-CREB signaling pathways. 5DN can be used for treating diseases such as cancer, inflammation-related diseases, rheumatoid arthritis, and neurodegenerative diseases. To date, there have been only a few toxicological studies on 5DN, and both in vitro and in vivo on 5DN have not revealed significant toxic side effects. Pharmacokinetic studies have revealed that the metabolites of 5DN are mainly 5,3'-didemethylnobiletin (M1); 5,4'-didemethylnobiletin (M2) and 5,3',4'-tridemethylnobiletin (M3), in either, glucuronide-conjugated or monomeric form. The pharmacokinetic products of 5DN, especially M1, possess better activity than 5DN for the treatment of cancer.

CONCLUSION

The anticancer effects of 5DN and its metabolites warrant further investigation as potential drug candidates, especially through in vivo studies. In addition, the therapeutic effects of 5DN in neurodegenerative diseases should be examined in more experimental models, and the absorption and metabolism of 5DN should be further investigated in vivo.

Advanced Glycation End Products (AGEs) and Chronic Kidney Disease: Does the Modern Diet AGE the Kidney?

Since the 1980s, chronic kidney disease (CKD) affecting all ages has increased by almost 25%. This increase may be partially attributable to lifestyle changes and increased global consumption of a “western” diet, which is typically energy dense, low in fruits and vegetables, and high in animal protein and ultra-processed foods. These modern food trends have led to an increase in the consumption of advanced glycation end products (AGEs) in conjunction with increased metabolic dysfunction, obesity and diabetes, which facilitates production of endogenous AGEs within the body. When in excess, AGEs can be pathological via both receptor-mediated and non-receptor-mediated pathways. The kidney, as a major site for AGE clearance, is particularly vulnerable to AGE-mediated damage and increases in circulating AGEs align with risk of CKD and all-cause mortality. Furthermore, individuals with significant loss of renal function show increased AGE burden, particularly with uraemia, and there is some evidence that AGE lowering via diet or pharmacological inhibition may be beneficial for CKD. This review discusses the pathways that drive AGE formation and regulation within the body. This includes AGE receptor interactions and pathways of AGE-mediated pathology with a focus on the contribution of diet on endogenous AGE production and dietary AGE consumption to these processes. We then analyse the contribution of AGEs to kidney disease, the evidence for dietary AGEs and endogenously produced AGEs in driving pathogenesis in diabetic and non-diabetic kidney disease and the potential for AGE targeted therapies in kidney disease.

Dietary advanced glycation end products and cancer risk in Japan: from the Takayama study

Few large epidemiological studies have evaluated the association between dietary advanced glycation end products (AGEs) and cancer risk. We evaluated the relationship between dietary AGE intake and the incidence of total cancer and site‐specific cancers in a population‐based prospective study in Japan. Participants were 14,173 men and 16,549 women who were 35 years of age or older in 1992. Dietary intake was assessed via a validated food frequency questionnaire. Intake of the AGE N^ε‐carboxymethyl‐lysine (CML) was estimated using databases of CML content in foods determined using ultraperformance liquid chromatography–tandem mass spectrometry. Cancer incidence was confirmed through regional population‐based cancer registries. During a mean follow‐up period of 13.3 years, 1954 men and 1477 women developed cancer. We did not observe a significant association between CML intake and the risk of total cancer in men or women. In men, compared with the lowest quartile of CML intake, the hazard ratios of liver cancer for the second, third, and highest quartiles were 1.69 (95% CI: 0.92–3.10), 1.48 (95% CI: 0.77–2.84), and 2.10 (95% CI: 1.10–3.98; trend p = 0.04). Conversely, a decreased relative risk of male stomach cancer was observed for the second and highest quartiles of CML intake versus the lowest quartile, with hazard ratios of 0.73 and 0.67, respectively (trend p = 0.08). Our finding on the potential harmfulness of consuming AGEs on liver cancer risk is intriguing and warrants further study.

Is dietary intake of advanced glycation end products associated with mortality among adults with diabetes?

BACKGROUND AND AIMS

Prior studies suggest a positive association between dietary AGEs and adverse health outcomes but have not well-characterized AGEs intake and its association with mortality in a general adult population in the United States.

METHODS AND RESULTS

We included 5474 adults with diabetes from the 2003 to 2018 National Health and Nutrition Examination Survey, a nationally representative sample of the non-institutionalized civilian population in the United States. Concordance to dietary guidelines (Healthy Eating Index 2015 [HEI-2015]) and intake of the AGE Nϵ-(carboxymethyl)lysine (CML) were estimated using an existing database and two 24-h food recalls. Multivariable Cox regression evaluated the association between AGEs intake and all-cause mortality. A secondary analysis measured CML, Nϵ-(1-carboxyethyl)lysine (CEL), and Nδ-(5-hydro-5-methyl-4-imidazolon-2-yl)-ornithine (MGH1) from an alternative database. Higher AGEs intake was associated with lower concordance to dietary guidelines (Means and standard errors of HEI-2015 score, by quartiles of AGEs intake: Q1 = 55.2 ± 0.6, Q2 = 54.1 ± 0.5, Q3 = 52.1 ± 0.5, Q4 = 49.0 ± 0.5; p < 0.001). There were 743 deaths among 3884 adults in the mortality analysis (mean follow-up = 3.8 years). AGEs intake was not significantly associated with all-cause mortality (Q2 vs. Q1: Hazard Ratio [HR] = 0.91 [0.69-1.21], Q3 vs. Q1: HR = 0.90 [0.63-1.27], Q4 vs. Q1: HR = 1.16 [0.84-1.60]). Results were similar in secondary analyses.

CONCLUSION

While dietary AGEs intake was associated with concordance to dietary guidelines, it was not significantly associated with all-cause mortality among adults with diabetes. Further research may consider other health outcomes as well as the evaluating specific contribution of dietary AGEs to overall AGEs burden.

A 4-Week Diet Low or High in Advanced Glycation Endproducts Has Limited Impact on Gut Microbial Composition in Abdominally Obese Individuals: The deAGEing Trial

Dietary advanced glycation endproducts (AGEs), abundantly present in Westernized diets, are linked to negative health outcomes, but their impact on the gut microbiota has not yet been well investigated in humans. We investigated the effects of a 4-week isocaloric and macronutrient-matched diet low or high in AGEs on the gut microbial composition of 70 abdominally obese individuals in a double-blind parallel-design randomized controlled trial (NCT03866343). Additionally, we investigated the cross-sectional associations between the habitual intake of dietary dicarbonyls, reactive precursors to AGEs, and the gut microbial composition, as assessed by 16S rRNA amplicon-based sequencing. Despite a marked percentage difference in AGE intake, we observed no differences in microbial richness and the general community structure. Only the Anaerostipes spp. had a relative abundance >0.5% and showed differential abundance (0.5 versus 1.11%; p = 0.028, after low- or high-AGE diet, respectively). While the habitual intake of dicarbonyls was not associated with microbial richness or a general community structure, the intake of 3-deoxyglucosone was especially associated with an abundance of several genera. Thus, a 4-week diet low or high in AGEs has a limited impact on the gut microbial composition of abdominally obese humans, paralleling its previously observed limited biological consequences. The effects of dietary dicarbonyls on the gut microbiota composition deserve further investigation.

The role of AGEs in pathogenesis of cartilage destruction in osteoarthritis

Osteoarthritis (OA) is a degenerative disease resulting from progressive joint destruction caused by many factors. Its pathogenesis is complex and has not been elucidated to date. Advanced glycation end products (AGEs) are a series of irreversible and stable macromolecular complexes formed by reducing sugar with protein, lipid, and nucleic acid through a non-enzymatic glycosylation reaction (Maillard reaction). They are an important indicator of the degree of ageing. Currently, it is considered that AGEs accumulation in vivo is a molecular basis of age-induced OA, and AGEs production and accumulation in vivo is one of the important reasons for the induction and acceleration of the pathological changes of OA. In recent years, it has been found that AGEs are involved in a variety of pathological processes of OA, including extracellular matrix degradation, chondrocyte apoptosis, and autophagy. Clearly, AGEs play an important role in regulating the expression of OA-related genes and maintaining the chondrocyte phenotype and the stability of the intra-articular environment. This article reviews the latest research results of AGEs in a variety of pathological processes of OA, to provide a new direction for the study of OA pathogenesis and a new target for prevention and treatment.

Cite this article: Bone Joint Res 2022;11(5):292–300.

Dietary Advanced Glycation End Products in an Elderly Population with Diabetic Nephropathy: An Exploratory Investigation

Advanced glycation end products (AGEs) are important in pathophysiology of type 2 diabetes mellitus (T2DM) and diabetic kidney disease (DKD). Dietary AGEs (dAGEs) contribute to the overall AGE pool in the body. Forty elderly T2DM patients with DKD were randomly allocated to a low-AGE (n = 20) or regular diabetic (n = 20) diet group. A three-day meal questionnaire was used to estimate average quantity of dAGEs. AGE accumulation was measured using skin autofluorescence and urine spectroscopy. sRAGE (soluble receptor AGE) was quantified using ELISA. After 8 weeks, the mean consumption of dAGEs was considerably reduced, both in the low-AGE diet (p = 0.004) and the control (p = 0.019) group. The expected urinary emission peak at 490 nm was shifted to 520 nm in some spectra. dAGEs did not correspond with urine AGE output. An AGE-limited diet for two months did not affect AGE content in skin and urine, or sRAGE concentration in the blood. The role of glycemia is likely to be greater than the impact of dAGE consumption. The unique observation of a fluorescence pattern at 520 nm warrants further examination, since it might point to genetic differences in AGE regulation, which could have clinical consequences, as AGE content depends on its formation and elimination.

Advanced Glycation End-Products (AGEs): Formation, Chemistry, Classification, Receptors, and Diseases Related to AGEs

Advanced glycation end-products (AGEs) constitute a non-homogenous, chemically diverse group of compounds formed either exogeneously or endogeneously on the course of various pathways in the human body. In general, they are formed non-enzymatically by condensation between carbonyl groups of reducing sugars and free amine groups of nucleic acids, proteins, or lipids, followed by further rearrangements yielding stable, irreversible end-products. In the last decades, AGEs have aroused the interest of the scientific community due to the increasing evidence of their involvement in many pathophysiological processes and diseases, such as diabetes, cancer, cardiovascular, neurodegenerative diseases, and even infection with the SARS-CoV-2 virus. They are recognized by several cellular receptors and trigger many signaling pathways related to inflammation and oxidative stress. Despite many experimental research outcomes published recently, the complexity of their engagement in human physiology and pathophysiological states requires further elucidation. This review focuses on the receptors of AGEs, especially on the structural aspects of receptor-ligand interaction, and the diseases in which AGEs are involved. It also aims to present AGE classification in subgroups and to describe the basic processes leading to both exogeneous and endogeneous AGE formation.

Differences in kinetics and dynamics of endogenous versus exogenous advanced glycation end products (AGEs) and their precursors

Advanced glycation end products (AGEs) and their precursors, referred to as glycation products, are a heterogenous group of compounds being associated with adverse health effects. They are formed endogenously and in exogenous sources including food. This review investigates the roles of endogenously versus exogenously formed glycation products in the potential induction of adverse health effects, focusing on differences in toxicokinetics and toxicodynamics, which appeared to differ depending on the molecular mass of the glycation product. Based on the available data, exogenous low molecular mass (LMM) glycation products seem to be bioavailable and to contribute to dicarbonyl stress and protein cross-linking resulting in formation of endogenous AGEs. Bioavailability of exogenous high molecular mass (HMM) glycation products appears limited, while these bind to the AGE receptor (RAGE), initiating adverse health effects. Together, this suggests that RAGE-binding in relevant tissues will more likely result from endogenously formed glycation products. Effects on gut microbiota induced by glycation products is proposed as a third mode of action. Overall, studies which better discriminate between LMM and HMM glycation products and between endogenous and exogenous formation are needed to further elucidate the contributions of these different types and sources of glycation products to the ultimate biological effects.

Revisiting Methodologies for In Vitro Preparations of Advanced Glycation End Products

Chronic elevation of sugar and oxidative stress generally results in development of advanced glycation end products (AGEs) in diabetic individuals. Accumulation of AGEs in an individual can give rise to the activation of several pathways that will ultimately lead to various complications. Such AGEs can also be prepared in an in vitro environment. For an in vitro preparation of advanced glycation end products (AGEs), proteins, lipids, or nucleic acids are generally required to be incubated with reducing sugars at a physiological temperature or higher depending upon the protocol optimized for its preparation. Certain other factors are also optimized and added to the buffer to hasten its preparation or alter the properties of prepared AGEs. Through this review, we intend to highlight the various studies related to the experimental procedures for the preparation of different types of AGEs. In addition, we present the comparative study of methodologies optimized for the preparation of AGEs.

Food-Related Carbonyl Stress in Cardiometabolic and Cancer Risk Linked to Unhealthy Modern Diet

Carbonyl stress is a condition characterized by an increase in the steady-state levels of reactive carbonyl species (RCS) that leads to accumulation of their irreversible covalent adducts with biological molecules. RCS are generated by the oxidative cleavage and cellular metabolism of lipids and sugars. In addition to causing damage directly, the RCS adducts, advanced glycation end-products (AGEs) and advanced lipoxidation end-products (ALEs), cause additional harm by eliciting chronic inflammation through receptor-mediated mechanisms. Hyperglycemia- and dyslipidemia-induced carbonyl stress plays a role in diabetic cardiovascular complications and diabetes-related cancer risk. Moreover, the increased dietary exposure to AGEs/ALEs could mediate the impact of the modern, highly processed diet on cardiometabolic and cancer risk. Finally, the transient carbonyl stress resulting from supraphysiological postprandial spikes in blood glucose and lipid levels may play a role in acute proinflammatory and proatherogenic changes occurring after a calorie dense meal. These findings underline the potential importance of carbonyl stress as a mediator of the cardiometabolic and cancer risk linked to today’s unhealthy diet. In this review, current knowledge in this field is discussed along with future research courses to offer new insights and open new avenues for therapeutic interventions to prevent diet-associated cardiometabolic disorders and cancer.

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

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

Dual Nature of RAGE in Host Reaction and Nurturing the Mother-Infant Bond

Non-enzymatic glycation is an unavoidable reaction that occurs across biological taxa. The final products of this irreversible reaction are called advanced glycation end-products (AGEs). The endogenously formed AGEs are known to be bioactive and detrimental to human health. Additionally, exogenous food-derived AGEs are debated to contribute to the development of aging and various diseases. Receptor for AGEs (RAGE) is widely known to elicit biological reactions. The binding of RAGE to other ligands (e.g., high mobility group box 1, S100 proteins, lipopolysaccharides, and amyloid-β) can result in pathological processes via the activation of intracellular RAGE signaling pathways, including inflammation, diabetes, aging, cancer growth, and metastasis. RAGE is now recognized as a pattern-recognition receptor. All mammals have RAGE homologs; however, other vertebrates, such as birds, amphibians, fish, and reptiles, do not have RAGE at the genomic level. This evidence from an evolutionary perspective allows us to understand why mammals require RAGE. In this review, we provide an overview of the scientific knowledge about the role of RAGE in physiological and pathological processes. In particular, we focus on (1) RAGE biology, (2) the role of RAGE in physiological and pathophysiological processes, (3) RAGE isoforms, including full-length membrane-bound RAGE (mRAGE), and the soluble forms of RAGE (sRAGE), which comprise endogenous secretory RAGE (esRAGE) and an ectodomain-shed form of RAGE, and (4) oxytocin transporters in the brain and intestine, which are important for maternal bonding and social behaviors.

Could high heat cooking and food processing promoting neo-formed contaminants partially explain the high prevalence of chronic kidney disease in South Asian populations? A hypothesis

BACKGROUND AND AIMS

The occurrence of chronic heart and kidney diseases among the South Asian populations has been rising exponentially over the years. Research has been carried out in the past to explain the increased susceptibility with no resultant strong evidence. Various possible causes have been suggested with a previous hypothesis suggestive of high heat cooking techniques being responsible for increased production of neo-formed contaminants such as advanced glycation end products (AGEs) and trans-fatty acids (TFAs) leading to increased chronic heart diseases among the South Asian diaspora (India, Pakistan, Bangladesh, Sri Lanka in South Asia and overseas). The aim of this study proposes the high-heating cooking techniques and subsequent NFCs also to be responsible for the development of chronic kidney ailments among the South Asians.

METHODS

Review of the literature was conducted to ascertain the burden of accumulation and actions of AGEs and TFAs on kidney structure and functions. The varied high-heat cooking techniques including reheating of oils, food processing and kinds of food sources and their association with increased NFCs production and kidney damage were explored.

RESULTS

Higher NFCs content of AGEs/TFAs in reheated oils at elevated temperatures and TFAs among processed and fast foods of South Asians was associated with elevated diabetic complications and CKDs progression in few animal and human studies but the research on the actual burden of NFCs in the renal tissues of South Asians was lacking.

CONCLUSION

We hypothesize the high heat cooked foods generating increased levels of NFCs to be responsible for the preponderance of higher risk of CKDs among South Asians. Scientific exploration of the hypothesis to obtain quantifiable evidence of NFCs is suggested.

In Vitro Methodologies to Study the Role of Advanced Glycation End Products (AGEs) in Neurodegeneration

Advanced glycation end products (AGEs) can be present in food or be endogenously produced in biological systems. Their formation has been associated with chronic neurodegenerative diseases such as Alzheimer’s disease, Parkinson’s disease, multiple sclerosis, and amyotrophic lateral sclerosis. The implication of AGEs in neurodegeneration is related to their ability to bind to AGE-specific receptors and the ability of their precursors to induce the so-called “dicarbonyl stress”, resulting in cross-linking and protein damage. However, the mode of action underlying their role in neurodegeneration remains unclear. While some research has been carried out in observational clinical studies, further in vitro studies may help elucidate these underlying modes of action. This review presents and discusses in vitro methodologies used in research on the potential role of AGEs in neuroinflammation and neurodegeneration. The overview reveals the main concepts linking AGEs to neurodegeneration, the current findings, and the available and advisable in vitro models to study their role. Moreover, the major questions regarding the role of AGEs in neurodegenerative diseases and the challenges and discrepancies in the research field are discussed.

Receptor Mediated Effects of Advanced Glycation End Products (AGEs) on Innate and Adaptative Immunity: Relevance for Food Allergy

As of late, evidence has been emerging that the Maillard reaction (MR, also referred to as glycation) affects the structure and function of food proteins. MR induces the conformational and chemical modification of food proteins, not only on the level of IgG/IgE recognition, but also by increasing the interaction and recognition of these modified proteins by antigen-presenting cells (APCs). This affects their biological properties, including digestibility, bioavailability, immunogenicity, and ultimately their allergenicity. APCs possess various receptors that recognize glycation structures, which include receptor for advanced glycation end products (RAGE), scavenger receptors (SRs), galectin-3 and CD36. Through these receptors, glycation structures may influence the recognition, uptake and antigen-processing of food allergens by dendritic cells (DCs) and monocytes. This may lead to enhanced cytokine production and maturation of DCs, and may also induce adaptive immune responses to the antigens/allergens as a result of antigen uptake, processing and presentation to T cells. Here, we aim to review the current literature on the immunogenicity of AGEs originating from food (exogenous or dietary AGEs) in relation to AGEs that are formed within the body (endogenous AGEs), their interactions with receptors present on immune cells, and their effects on the activation of the innate as well as the adaptive immune system. Finally, we review the clinical relevance of AGEs in food allergies.

Dietary Advanced Glycation End Products Shift the Gut Microbiota Composition and Induce Insulin Resistance in Mice

OBJECTIVE

This study aimed to explore the associations between gut microbiota characteristics and glycometabolic profiles in mice fed diets high in advanced glycation end products (AGEs).

METHODS

C57BL/6 mice were exposed to a heat-treated diet or exogenous AGEs for 24 weeks, and glucose metabolism was assessed via the intraperitoneal glucose-tolerance test (IPGTT). Serum AGE and lipopolysaccharide-binding protein (LBP) levels were quantified using ELISA kits. 16S rDNA sequencing was performed to analyze the changes in gut microbiota according to α- and β-diversity. Key operational taxonomic units (OTUs) were evaluated, and co-abundance groups (CAGs) were delineated using weighted correlation network analysis. Associations between CAGs and clinical parameters were analyzed using Spearman correlation; predictive functional analysis of gut microbiota was performed using Kyoto Encyclopedia of Genes and Genomes data.

RESULTS

We identified significant increases in fasting blood glucose (FBG) and fasting insulin levels, as well as homeostatic model assessment insulin resistance (HOMA-IR) and glucose area under the receiver operating characteristic curve from IPGTT, in the high-AGE diet groups relative to controls at week 24. Serum AGE and LBP levels were elevated, and the α- and β-diversity of gut microbiota reduced in high-AGE diet groups. We identified 92 key OTUs that clustered into six CAGs, revealing positive correlations between CAG2/3/5 and insulin levels and mice weight and negative correlations between CAG1/3/4/5 and AGE, FBG, and LBP levels and HOMA-IR in mice fed high-AGE diets. We observed a reduced abundance of butyrate-producing bacteria, including Bacteroidales_S24-7, Ruminococcaceae, and Lachnospiraceae, in mice fed high-AGE diets, with pathway analysis of gut microbiota revealing significantly enriched fructose and mannose metabolism.

CONCLUSION

High-AGE diets altered the gut microbiota composition and structure, and induced insulin resistance in mice. In the pathogenesis of insulin resistance, the loss of butyrate-producing bacteria might impair the colonic epithelial barrier, thereby triggering chronic low-grade inflammation.

Fisetin, potential flavonoid with multifarious targets for treating neurological disorders: An updated review

Neurodegenerative disorders pose a significant health burden and imprint a debilitative impact on the quality of life. Importantly, aging is intricately intertwined with the progression of these disorders, and their prevalence increases with a rise in the aging population worldwide. In recent times, fisetin emerged as one of the potential miracle molecules to address neurobehavioral and cognitive abnormalities. These effects were attributed to its actions on several macromolecules and multiple molecular mechanisms. Fisetin belongs to a class of flavonoids, which is found abundantly in several fruits and vegetables. Fisetin has manifested several health benefits in preclinical models of neurodegenerative diseases such as Alzheimer's disease, Vascular dementia, and Schizophrenia. Parkinson's disease, Amyotrophic Lateral Sclerosis, Huntington's disease, Stroke, Traumatic Brain Injury (TBI), and age-associated changes. This review aimed to evaluate the potential mechanisms and pharmacological effects of fisetin in treating several neurological diseases. This review also provides comprehensive data on up-to-date recent literature and highlights the various mechanistic pathways pertaining to fisetin's neuroprotective role.

Comparison of metabolic fate, target organs, and microbiota interactions of free and bound dietary advanced glycation end products

Increased intake of Western diets and ultra-processed foods is accompanied by increased intake of advanced glycation end products (AGEs). AGEs can be generated exogenously in the thermal processing of food and endogenously in the human body, which associated with various chronic diseases. In food, AGEs can be divided into free and bound forms, which differ in their bioavailability, digestion, absorption, gut microbial interactions and untargeted metabolites. We summarized the measurements and contents of free and bound AGE in foods. Moreover, the ingestion, digestion, absorption, excretion, gut microbiota interactions, and metabolites and metabolic pathways between free and bound AGEs based on animal and human studies were compared. Bound AGEs were predominant in most of the selected foods, while beer and soy sauce were rich in free AGEs. Only 10%-30% of AGEs were absorbed into the systemic circulation when orally administered. The excretion of ingested free and bound AGEs was approximately 90% and 60%, respectively. Dietary free CML has a detrimental effect on gut microbiota composition, while bound AGEs have both detrimental and beneficial impacts. Free and bound dietary AGEs changed amino acid metabolism, energy metabolism and carbohydrate metabolism. And besides, bound dietary AGEs altered vitamin metabolism, and glycerolipid metabolism.

Persistent Effect of Advanced Glycated Albumin Driving Inflammation and Disturbances in Cholesterol Efflux in Macrophages

Advanced glycated albumin (AGE-albumin) impairs cholesterol efflux and contributes to inflammation in macrophages. The current study evaluated: (1) the persistence of the deleterious effect of AGE-albumin in cholesterol efflux and in inflammation, and (2) how metabolic control in diabetes mellitus (DM) contributes to attenuate the deleterious role of AGE-albumin in macrophage cholesterol homeostasis. Methods: AGE-albumin was produced in vitro or isolated from uncontrolled DM subjects' serum before (bGC) and after improved glycemic control (aGC). Albumin samples were incubated with bone marrow-derived macrophages and ¹⁴C-cholesterol efflux or LPS- induced cytokine secretion were determined immediately, or after cell resting in culture media alone. The ABCA-1 degradation rate was determined after cell incubation with cycloheximide, and ABCA1 protein level by immunoblot. Oil Red O staining was used to assess intracellular lipid accumulation. Results: A persistent effect of AGE-albumin was observed in macrophages in terms of the secretion of inflammatory cytokines and reduced cholesterol efflux. HDL-mediated ¹⁴C-cholesterol efflux was at least two times higher in macrophages treated with aCG-albumin as compared to bGC-albumin, and intracellular lipid content was significantly reduced in aGC-albumin-treated cells. As compared to bGC-albumin, the ABCA-1 protein content in whole cell bulk was 94% higher in aCG-albumin. A 20% increased ABCA-1 decay rate was observed in macrophages treated with albumin from poorly controlled DM. AGE-albumin has a persistent deleterious effect on macrophage lipid homeostasis and inflammation. The reduction of AGEs in albumin ameliorates cholesterol efflux.

Diet-Derived Advanced Glycation End Products (dAGEs) Induce Proinflammatory Cytokine Expression in Cardiac and Renal Tissues of Experimental Mice: Protective Effect of Curcumin

The beneficial effect of curcumin (CU) on dietary AGEs (dAGEs) involves blocking the overexpression of proinflammatory cytokine genes in the heart and kidney tissues of experimental mice. The animals were divided into six groups (n = 6/group) and were fed a heat-exposed diet (dAGEs) with or without CU for 6 months. Their blood pressure (BP) was monitored by a computerized tail-cuff BP-monitoring system. The mRNA and protein expression levels of proinflammatory genes were analyzed by RT-PCR and western blot, respectively. A marked increase in BP (108 ± 12 mmHg vs 149 ± 15 mmHg) accompanied by a marked increase in the heart and kidney weight ratio was noted in the dAGE-fed mice. Furthermore, the plasma levels of proinflammatory molecules (C5a, ICAM-1, IL-6, MCP-1, IL-1β and TNF-α) were found to be elevated (3-fold) in dAGE-fed mice. mRNA expression analysis revealed a significant increase in the expression levels of inflammatory markers (Cox-2, iNOS, and NF-κB) (3-fold) in cardiac and renal tissues of dAGE-fed mice. Moreover, increased expression of RAGE and downregulation of AGER-1 (p < 0.001) were noticed in the heart and kidney tissues of dAGE-fed mice. Interestingly, the dAGE-induced proinflammatory genes and inflammatory responses were neutralized upon cotreatment with CU. The present study demonstrates that dietary supplementation with CU has the ability to neutralize dAGE-induced adverse effects and alleviate proinflammatory gene expression in the heart and kidney tissues of experimental mice.

Restriction of Dietary Advanced Glycation End Products Induces a Differential Plasma Metabolome and Lipidome Profile

SCOPE

Diets with low content in advanced glycation end products (AGEs) lead to beneficial properties in highly prevalent age-related diseases. To shed light on the mechanisms behind, the changes induced by a low AGE dietary intervention in the circulating metabolome are analyzed.

METHODS AND RESULTS

To this end, 20 non-diabetic patients undergoing peritoneal dialysis are randomized to continue their usual diet or to one with a low content of AGEs for 1 month. Then, plasmatic metabolome and lipidomes are analyzed by liquid-chromatography coupled to mass spectrometry. The levels of defined AGE structures are also quantified by ELISA and by mass-spectrometry. The results show that the low AGE diet impinged significant changes in circulating metabolomes (166 molecules) and lipidomes (91 lipids). Metabolic targets of low-AGE intake include sphingolipid, ether-lipids, and glycerophospholipid metabolism. Further, it reproduces some of the plasma characteristics of healthy aging.

CONCLUSION

The finding of common pathways induced by low-AGE diets with previous metabolic traits implicated in aging, insulin resistance, and obesity suggest the usefulness of the chosen approach and supports the potential extension of this study to other populations.

Demonstration of advanced glycation end product (AGE) expression in bladder cancer tissue in type-2 diabetic and non-diabetic patients and the relationship between AGE accumulation and endoplasmic reticulum stress with bladder cancer

PURPOSE

This study aimed to investigate the relationship between advanced glycation end product (AGE) expression and accumulation in transurethral resection (TUR-B) material taken from type-2 diabetes mellitus (DM) and non-DM bladder cancer patients and endoplasmic reticulum stress (ERS) with bladder cancer.

METHOD

The patients who had TUR-B between May 2016 and September 2018 were included in the study. After the tissue samples had been taken and frozen at -80°C, they were homogenised to be used in enzyme-linked immunosorbent assay (ELISA) experiments. The patients were grouped as DM and non-DM. In both groups, mean AGE, IRE1, PERK and ATF6 expression amounts were evaluated through ELISA method in the pathological material.

RESULTS

The expression amounts in tissue samples were AGE 0.59 ± 0.03 µg/mL, ATF6 1.08 ± 0.11 µg/mL, IRE1 30.71 ± 1.68 ng/mL, PERK 0.28 ± 0.02 ng. It was /mL. While there was no significant difference amongst AGE µg/mL (P = .146), ATF6 µg/mL (P = .175), IRE1 ng/mL (P = NA) and PERK ng/mL (P = .125) (P > .05) in the presence of DM, a positive correlation was observed between AGE values and PERK ng/mL values (r = .629; P < .05).

CONCLUSION

Bladder cancer may develop as a result of accumulation of AGEs and ERS. Demonstration of the expression of proteins resulting from AGEs and ERS may be useful biomarkers for the diagnosis, prognosis, prevention and development of treatment alternatives for bladder cancer.

Skin autofluorescence is associated with higher risk of cardiovascular events in Chinese adults with type 2 diabetes: A prospective cohort study from the Hong Kong Diabetes Biobank

AIMS

To investigate association between skin autofluorescence (SAF) and cardiovascular events (CVE) and assess its predictive value in Chinese adults with type 2 diabetes (T2D).

MATERIALS AND METHODS

SAF was measured non-invasively in 3806 Chinese adults with T2D between 2016 and 2019 with CVE as primary endpoint and individual components as secondary endpoints. Cox proportional hazard models were used to examine associations between SAF and endpoints with adjustment for conventional risk factors. C-statistic, integrated discrimination improvement (IDI), and net reclassification improvement (NRI) were performed to evaluate SAF's predictive value.

RESULTS

During a median 1.8 (interquartile range, 1.2-3.1) years of follow-up, 172 individuals experienced CVE. Multivariate Cox model showed that SAF was independently associated with CVE (HR 1.18 per SD, 95% CI [1.02, 1.37]), coronary heart disease (HR 1.29 per SD, 95% CI [1.02, 1.63]), and congestive heart failure (HR 1.53 per SD, 95% CI [1.14, 2.05]). SAF yielded additional value on CVE risk stratification with enhanced IDI (95% CI) (0.023 [0.001, 0.057]) and continuous NRI (0.377 [0.002, 0.558]) over traditional risk factors.

CONCLUSIONS

Higher SAF was independently associated with CVE in Chinese adults with T2D and yielded incremental predictive information for CVE. SAF has potential as a prognostic maker for CVE.

Experimental Animal Studies Support the Role of Dietary Advanced Glycation End Products in Health and Disease

The increased incidence of obesity, diabetes mellitus, aging, and associated comorbidities indicates the interplay between genetic and environmental influences. Several dietary components have been identified to play a role in the pathogenesis of the so-called "modern diseases", and their complications including advanced glycation end products (AGEs), which are generated during the food preparation and processing. Diet-derived advanced glycation end products (dAGEs) can be absorbed in the gastrointestinal system and contribute to the total body AGEs' homeostasis, partially excreted in the urine, while a significant amount accumulates to various tissues. Various in vitro, in vivo, and clinical studies support that dAGEs play an important role in health and disease, in a similar way to those endogenously formed. Animal studies using wild type, as well as experimental, animal models have shown that dAGEs contribute significantly to the pathogenesis of various diseases and their complications, and are involved in the changes related to the aging process. In addition, they support that dAGEs' restriction reduces insulin resistance, oxidative stress, and inflammation; restores immune alterations; and prevents or delays the progression of aging, obesity, diabetes mellitus, and their complications. These data can be extrapolated in humans and strongly support that dAGEs' restriction should be considered as an alternative therapeutic intervention.

Advanced Glycation End-Products in Common Non-Infectious Liver Diseases: Systematic Review and Meta-Analysis

BACKGROUND

Excessive intake of fructose, glucose and alcohol is associated with the development of non-alcoholic fatty liver disease (NAFLD) and alcoholic liver disease (ALD). At the same time, these dietetic factors create an environment favorable for the generation of advanced glycation end-products. For this reason, advanced glycation end-products (AGEs) are hypothesized to play role in the development of NAFLD and ALD. In this systematic review and meta-analysis, we explore the relationship between NAFLD and ALD with AGE levels, including their diagnostic accuracy.

METHODS

The systematic review and meta-analysis has been pre-registered with PROSPERO (CRD42021240954) and was performed in accordance with the PRISMA guidelines. Meta-analyses were performed using the meta R package.

RESULTS

We have obtained 11 studies meeting our inclusion criteria, reporting data on 1844 participants (909 with NAFLD, 169 with ALD and 766 healthy controls). NAFLD was associated with significantly higher AGE fluorescence and serum N-(carboxyethyl)lysine (CEL) levels. Patients with alcoholic cirrhosis had significantly higher levels of N-(carboxymethyl)lysine (CML). Only individual studies examined AGEs in the context of their diagnostic accuracy. AGE fluorescence distinguished low and moderate steatosis with an AUC of 0.76. The ratio of CML, CEL and pentosidine to a soluble variant of the AGE receptor differentiated patients with NAFLD from healthy controls with high AUC (0.83-0.85). Glyceraldehyde-derived AGE separated non-alcoholic fatty liver (NAFL) from non-alcoholic steatohepatitis (NASH) with acceptable performance (AUC 0.78).

CONCLUSIONS

In conclusion, NAFLD and ALD are associated with significantly higher levels of several AGEs. More research is needed to examine the diagnostic accuracy of AGEs, however individual studies show that AGEs perform well in distinguishing NAFL from NASH.

Dietary Advanced Glycation End-Products and Colorectal Cancer Risk in the European Prospective Investigation into Cancer and Nutrition (EPIC) Study

Dietary advanced glycation end-products (dAGEs) have been hypothesized to be associated with a higher risk of colorectal cancer (CRC) by promoting inflammation, metabolic dysfunction, and oxidative stress in the colonic epithelium. However, evidence from prospective cohort studies is scarce and inconclusive. We evaluated CRC risk associated with the intake of dAGEs in the European Prospective Investigation into Cancer and Nutrition (EPIC) study. Dietary intakes of three major dAGEs: Nε-carboxy-methyllysine (CML), Nε-carboxyethyllysine (CEL), and Nδ-(5-hydro-5-methyl-4-imidazolon-2-yl)-ornithine (MG-H1) were estimated in 450,111 participants (median follow-up = 13 years, with 6162 CRC cases) by matching to a detailed published European food composition database. Hazard ratios (HRs) and 95% confidence intervals (CIs) for the associations of dAGEs with CRC were computed using multivariable-adjusted Cox regression models. Inverse CRC risk associations were observed for CML (HR comparing extreme quintiles: HRQ5vs.Q1 = 0.92, 95% CI = 0.85-1.00) and MG-H1 (HRQ5vs.Q1 = 0.92, 95% CI = 0.85-1.00), but not for CEL (HRQ5vs.Q1 = 0.97, 95% CI = 0.89-1.05). The associations did not differ by sex or anatomical location of the tumor. Contrary to the initial hypothesis, our findings suggest an inverse association between dAGEs and CRC risk. More research is required to verify these findings and better differentiate the role of dAGEs from that of endogenously produced AGEs and their precursor compounds in CRC development.

Dietary AGEs as Exogenous Boosters of Inflammation

Most chronic modern non-transmissible diseases seem to begin as the result of low-grade inflammation extending over prolonged periods of time. The importance of diet as a source of many pro-inflammatory compounds that could create and sustain such a low-grade inflammatory state cannot be ignored, particularly since we are constantly exposed to them during the day. The focus of this review is on specific components of the diet associated with inflammation, specifically advanced glycation end products (AGEs) that form during thermal processing of food. AGEs are also generated in the body in normal physiology and are widely recognized as increased in diabetes, but many people are unaware of the potential importance of exogenous AGEs ingested in food. We review experimental models, epidemiologic data, and small clinical trials that suggest an important association between dietary intake of these compounds and development of an inflammatory and pro-oxidative state that is conducive to chronic diseases. We compare dietary intake of AGEs with other widely known dietary patterns, such as the Mediterranean and the Dietary Approaches to Stop Hypertension (DASH) diets, as well as the Dietary Inflammation Index (DII). Finally, we delineate in detail the pathophysiological mechanisms induced by dietary AGEs, both direct (i.e., non-receptor-mediated) and indirect (receptor-mediated).

Dietary advanced glycation end-products elicit toxicological effects by disrupting gut microbiome and immune homeostasis

The aging immune system is characterized by a low-grade chronic systemic inflammatory state ("inflammaging") marked by elevated serum levels of inflammatory molecules such as interleukin (IL)-6 and C-reactive protein (CRP). These inflammatory markers were also reported to be strong predictors for the development/severity of Type 2 diabetes, obesity, and COVID-19. The levels of these markers have been positively associated with those of advanced glycation end-products (AGEs) generated via non-enzymatic glycation and oxidation of proteins and lipids during normal aging and metabolism. Based on the above observations, it is clinically important to elucidate how dietary AGEs modulate inflammation and might thus increase the risk for aging-exacerbated diseases. The present narrative review discusses the potential pro-inflammatory properties of dietary AGEs with a focus on the inflammatory mediators CRP, IL-6 and ferritin, and their relations to aging in general and Type 2 diabetes in particular. In addition, underlying mechanisms - including those related to gut microbiota and the receptors for AGEs, and the roles AGEs might play in affecting physiologies of the healthy elderly, obese individuals, and diabetics are discussed in regard to any greater susceptibility to COVID-19.

The AGE receptor, OST48 drives podocyte foot process effacement and basement membrane expansion (alters structural composition)

AIMS

The accumulation of advanced glycation end products is implicated in the development and progression of diabetic kidney disease. No study has examined whether stimulating advanced glycation clearance via receptor manipulation is reno-protective in diabetes. Podocytes, which are early contributors to diabetic kidney disease and could be a target for reno-protection.

MATERIALS AND METHODS

To examine the effects of increased podocyte oligosaccharyltransferase-48 on kidney function, glomerular sclerosis, tubulointerstitial fibrosis and proteome (PXD011434), we generated a mouse with increased oligosaccharyltransferase-48kDa subunit abundance in podocytes driven by the podocin promoter.

RESULTS

Despite increased urinary clearance of advanced glycation end products, we observed a decline in renal function, significant glomerular damage including glomerulosclerosis, collagen IV deposition, glomerular basement membrane thickening and foot process effacement and tubulointerstitial fibrosis. Analysis of isolated glomeruli identified enrichment in proteins associated with collagen deposition, endoplasmic reticulum stress and oxidative stress. Ultra-resolution microscopy of podocytes revealed denudation of foot processes where there was co-localization of oligosaccharyltransferase-48kDa subunit and advanced glycation end-products.

CONCLUSIONS

These studies indicate that increased podocyte expression of oligosaccharyltransferase-48 kDa subunit results in glomerular endoplasmic reticulum stress and a decline in kidney function.

Circulating Advanced Glycation End Products and Their Soluble Receptors in Relation to All-Cause and Cardiovascular Mortality: A Systematic Review and Meta-analysis of Prospective Observational Studies

Advanced glycation end products (AGEs) are involved in the development of several age-related complications. The protective role of soluble receptors for AGEs (sRAGE) against deleterious effects of AGEs has been indicated in several studies. However, findings on the association of AGEs or sRAGE with mortality are equivocal. In this meta-analysis we aimed to present a quantitative estimation of the association between circulating AGEs or sRAGE and all-cause or cardiovascular disease (CVD) mortality. A comprehensive literature search was performed to determine relevant publications through the online databases including PubMed, Scopus, and Web of Science up to 29 November 2020. Prospective observational studies assessing the association between circulating AGEs or sRAGE and all-cause or CVD mortality were included. Seven studies with a total of 3718 participants and 733 mortality cases (345 CVD deaths) were included in the meta-analysis for assessing the association between circulating AGEs and mortality. Our results showed that higher circulating AGEs were associated with increased risk of all-cause (pooled effect measure: 1.05; 95% CI: 1.01, 1.09; P = 0.018, I2 = 77.7%) and CVD mortality (pooled effect measure: 1.08; 95% CI: 1.01, 1.14; P = 0.015, I2 = 80.2%), respectively. The association between sRAGE and mortality was assessed in 14 studies with a total of 16,335 participants and 2844 mortality cases (419 CVD deaths). Serum concentrations of sRAGE were not associated with the risk of all-cause mortality (pooled effect measure: 1.01; 95% CI: 1.00, 1.01; P = 0.205, I2 = 75.5%), whereas there was a significant link between sRAGE and the risk of CVD mortality (pooled effect measure: 1.02; 95% CI: 1.00, 1.04; P = 0.02, I2 = 78.9%). Our findings showed that a higher serum AGE concentration was associated with increased risk of all-cause and CVD mortality. In addition, higher circulating sRAGE was related to increased risk of CVD mortality. This review was registered at PROSPERO as CRD42021236559.

Inflammation Meets Metabolism: Roles for the Receptor for Advanced Glycation End Products Axis in Cardiovascular Disease

Fundamental modulation of energy metabolism in immune cells is increasingly being recognized for the ability to impart important changes in cellular properties. In homeostasis, cells of the innate immune system, such as monocytes, macrophages and dendritic cells (DCs), are enabled to respond rapidly to various forms of acute cellular and environmental stress, such as pathogens. In chronic stress milieus, these cells may undergo a re-programming, thereby triggering processes that may instigate tissue damage and failure of resolution. In settings of metabolic dysfunction, moieties such as excess sugars (glucose, fructose and sucrose) accumulate in the tissues and may form advanced glycation end products (AGEs), which are signaling ligands for the receptor for advanced glycation end products (RAGE). In addition, cellular accumulation of cholesterol species such as that occurring upon macrophage engulfment of dead/dying cells, presents these cells with a major challenge to metabolize/efflux excess cholesterol. RAGE contributes to reduced expression and activities of molecules mediating cholesterol efflux. This Review chronicles examples of the roles that sugars and cholesterol, via RAGE, play in immune cells in instigation of maladaptive cellular signaling and the mediation of chronic cellular stress. At this time, emerging roles for the ligand-RAGE axis in metabolism-mediated modulation of inflammatory signaling in immune cells are being unearthed and add to the growing body of factors underlying pathological immunometabolism.

Aspects of high hydrostatic pressure food processing: Perspectives on technology and food safety

The last two decades saw a steady increase of high hydrostatic pressure (HHP) used for treatment of foods. Although the science of biomaterials exposed to high pressure started more than a century ago, there still seem to be a number of unanswered questions regarding safety of foods processed using HHP. This review gives an overview on historical development and fundamental aspects of HHP, as well as on potential risks associated with HHP food applications based on available literature. Beside the combination of pressure and temperature, as major factors impacting inactivation of vegetative bacterial cells, bacterial endospores, viruses, and parasites, factors, such as food matrix, water content, presence of dissolved substances, and pH value, also have significant influence on their inactivation by pressure. As a result, pressure treatment of foods should be considered for specific food groups and in accordance with their specific chemical and physical properties. The pressure necessary for inactivation of viruses is in many instances slightly lower than that for vegetative bacterial cells; however, data for food relevant human virus types are missing due to the lack of methods for determining their infectivity. Parasites can be inactivated by comparatively lower pressure than vegetative bacterial cells. The degrees to which chemical reactions progress under pressure treatments are different to those of conventional thermal processes, for example, HHP leads to lower amounts of acrylamide and furan. Additionally, the formation of new unknown or unexpected substances has not yet been observed. To date, no safety-relevant chemical changes have been described for foods treated by HHP. Based on existing sensitization to non-HHP-treated food, the allergenic potential of HHP-treated food is more likely to be equivalent to untreated food. Initial findings on changes in packaging materials under HHP have not yet been adequately supported by scientific data.

Dysbiosis-Related Advanced Glycation Endproducts and Trimethylamine N-Oxide in Chronic Kidney Disease

Chronic kidney disease (CKD) is a public health concern that affects approximately 10% of the global population. CKD is associated with poor outcomes due to high frequencies of comorbidities such as heart failure and cardiovascular disease. Uremic toxins are compounds that are usually filtered and excreted by the kidneys. With the decline of renal function, uremic toxins are accumulated in the systemic circulation and tissues, which hastens the progression of CKD and concomitant comorbidities. Gut microbial dysbiosis, defined as an imbalance of the gut microbial community, is one of the comorbidities of CKD. Meanwhile, gut dysbiosis plays a pathological role in accelerating CKD progression through the production of further uremic toxins in the gastrointestinal tracts. Therefore, the gut-kidney axis has been attracting attention in recent years as a potential therapeutic target for stopping CKD. Trimethylamine N-oxide (TMAO) generated by gut microbiota is linked to the progression of cardiovascular disease and CKD. Also, advanced glycation endproducts (AGEs) not only promote CKD but also cause gut dysbiosis with disruption of the intestinal barrier. This review summarizes the underlying mechanism for how gut microbial dysbiosis promotes kidney injury and highlights the wide-ranging interventions to counter dysbiosis for CKD patients from the view of uremic toxins such as TMAO and AGEs.

Effect of dietary advanced glycation end-products restriction on type 2 diabetes mellitus control: a systematic review

CONTEXT

Reducing dietary advanced glycation end-products (AGEs) may favor diabetes control.

OBJECTIVE

Critically analyze studies about the effect of dietary AGEs restriction on inflammation, oxidative stress, and glycemic control in patients with type 2 diabetes mellitus (DM2).

DATA SOURCE

This systematic review was conducted according to PRISMA methodology. The PubMed, Web of Science, LILACS, and Cochrane Library databases were searched, using the terms "type 2 diabetes," "advanced glycation end products" and "diet."

DATA EXTRACTION

Seven original studies were included in this review. The duration of the studies ranged from 1 day to 16 weeks. All extracted data were compiled, compared, and critically analyzed.

DATA ANALYSIS

Glycemic variables were considered the primary outcomes. The secondary outcomes were glycation, inflammatory, and oxidative stress markers.

CONCLUSION

Although serum insulin, homeostasis model assessment of insulin resistance, and glycated hemoglobin values were lower after the consumption of AGEs restricted diets in most studies, there was a lack of unanimity regarding dietary AGEs' positive effect on inflammation, oxidative stress, and blood glucose.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO registration no. CRD42020152640.

Early AGEing and metabolic diseases: is perinatal exposure to glycotoxins programming for adult-life metabolic syndrome?

Perinatal early nutritional disorders are critical for the developmental origins of health and disease. Glycotoxins, or advanced glycation end-products, and their precursors such as the methylglyoxal, which are formed endogenously and commonly found in processed foods and infant formulas, may be associated with acute and long-term metabolic disorders. Besides general aspects of glycotoxins, such as their endogenous production, exogenous sources, and their role in the development of metabolic syndrome, we discuss in this review the sources of perinatal exposure to glycotoxins and their involvement in metabolic programming mechanisms. The role of perinatal glycotoxin exposure in the onset of insulin resistance, central nervous system development, cardiovascular diseases, and early aging also are discussed, as are possible interventions that may prevent or reduce such effects.

Antiglycating Effect of Phenolics from the Chilean Currant Ribes cucullatum under Thermal Treatment

Numerous dietary polyphenols possess antiglicating activity, but the effects of thermal treatment on this activity are mostly unknown. The effect of thermal treatment in the antiglycating activity of polyphenolic enriched extracts (PEEs) from Ribes cucullatum towards glyoxal-induced glycation of sarcoplasmic proteins was assessed. Sarcoplasmic proteins from chicken, beef, salmon, and turkey, were incubated 2 h at 60 °C with and without glyoxal and different concentrations of PEEs (0.25, 0.5, 1, and 5 mg/mL). The antiglycating activity was evaluated by: (1) Lys and Arg consumption, (2) Carboxymethyl lysine (CML) generation, and (3) lipid-derived electrophiles inhibition in a gastric digestion model. Protective effects were observed against CML generation in proteins and a decrease of electrophiles in the gastric digestion model. A dose-dependent consumption of Lys and Arg in proteins/PEEs samples, indicated the possible occurrence of quinoproteins generation from the phenolics. Protein/PEEs incubations were assessed by: (1) High pressure liquid chromatography analysis, (2) Gel electrophoresis (SDS-PAGE), and (3) Redox cycling staining of quinoproteins. Protein/PEEs incubations produced: (1) Decrease in phenolics, (2) increase of protein crosslinking, and (3) dose-dependent generation of quinoproteins. We demonstrate that phenolic compounds from R. cucullatum under thermal treatment act as antiglycating agents, but oxidative reactions occurs at high concentrations, generating protein crosslinking and quinoproteins.

An oral absorbent, AST-120, restores vascular growth and blood flow in ischemic muscles in diabetic mice via modulation of macrophage transition

Background Diabetes has a pronounced effect on the peripheral vasculature. The accumulation of advanced glycation end products (AGEs) is regarded as the crucial mechanism responsible for vascular damage in diabetes, but it is not easy to be avoided from food. In this study, we aimed to investigate the effects of an oral absorbent, AST-120, on the accumulation of AGEs and changes in blood flow recovery in diabetic mice. Methods The mice were divided into four groups, wild-type (WT) mice without treatment, WT mice treated with 5% AST-120 mixed into pulverized chow, streptozotocin-induced diabetes mellitus (DM) mice, and DM mice treated with 5% AST-120. Six weeks after hind-limb ischemia surgery, blood flow reperfusion, histology, plasma AGE, and cytokine were examined. Bone marrow cells were cultured and derived into macrophages to evaluate the effects of AGEs on macrophage polarization. Results Plasma AGEs were significantly increased in diabetic mice. AST-120 could bind to AGEs and reduced their plasma concentrations. Histological analysis revealed fewer collateral vessels with corresponding impairment of blood flow recovery in diabetic mice. In these mice, AGE-positive and AGE receptor-positive macrophages were numerous in ischemic limbs compared with non- diabetic mice. In diabetic mice, macrophages in ischemic tissues demonstrated greater M1 polarization than M2 polarization; this pattern was reversed in the AST-120 treatment group. The change in macrophage polarization was associated with the corresponding expression of pro-inflammatory cytokines in the ischemic tissues. In cell cultures, AGEs triggered the transformation of bone marrow-derived macrophages into the M1 phenotype. The alterations in the polarization of macrophages were reversed after treatment with AST-120. Conclusions Oral administration of AST-120 decreased the serum levels of AGEs in diabetic mice and improved neovascularization of ischemic limbs. This benefit may be due to, at least partially, the alterations in macrophage polarization and the associated changes in inflammatory cytokines.

A negative association of dietary advanced glycation end products with obesity and body composition in Iranian adults

Obesity caused by excessive deposited fat is generally classified as BMI ≥ 30 kg/m2. Research regarding the association between dietary advanced glycation end products (dAGE) and obesity is limited. The aim of the present study was to investigate the association between dAGE and obesity and body composition in Iranian adults. This cross-sectional study included 265 adults aged 18-75 years from Tehran, Iran. dAGE were estimated using a validated semi-quantitative FFQ, according to the published food carboxymethyl lysine-AGE database for 549 routinely consumed food items for the Northeastern American multiethnic urban population, and were reported by dividing total energy intake. Dietary intake, sociodemographic data and physical activity status were collected using validated questionnaires, and anthropometric characteristics were measured. Body composition was assessed by bioelectrical impedance analysis, and obesity was defined based on WHO guidelines. The intake of fat and meat was significantly increased in higher tertiles, compared with the first tertile of dAGE (P < 0·001). No association between dAGE and body composition measures and obesity was observed; however, there was a significant negative association between dAGE and BMI (BMI; P = 0·01), waist circumference (P = 0·01), waist:hip ratio (P = 0·03), fat-free mass (P = 0·02) and muscle mass index (P = 0·01) in non-linear models. In conclusion, higher consumption of dAGE was associated with increased intake of fat and meat and was negatively related to changes in body composition measurements. Therefore, dAGE may connect obesity to diet by energy imbalance.

Advanced glycation end products and their adverse effects: The role of autophagy

The critical roles played by advanced glycation endproducts (AGEs) accumulation in diabetes and diabetic complications have gained intense recognition. AGEs interfere with the normal functioning of almost every organ with multiple actions like apoptosis, inflammation, protein dysfunction, mitochondrial dysfunction, and oxidative stress. However, the development of a potential treatment strategy is yet to be established. Autophagy is an evolutionarily conserved cellular process that maintains cellular homeostasis with the degradation and recycling systems. AGEs can activate autophagy signaling, which could be targeted as a therapeutic strategy against AGEs induced problems. In this review, we have provided an overview of the adverse effects of AGEs, and we put forth the notion that autophagy could be a promising targetable strategy against AGEs.