How Can Diet Affect the Accumulation of Advanced Glycation End-Products in the Human Body?

The inhibitory effects of endophytic metabolites on glycated proteins under non-communicable disease conditions: A review

Protein glycation in human body is closely linked to the onset/progression of diabetes associated complications. These glycated proteins are commonly known as advanced glycation end products (AGEs). Recent literature has also highlighted the involvement of AGEs in other non-communicable diseases (NCDs) such as cardiovascular, cancer, and Alzheimer's diseases and explored the impact of plant metabolites on AGEs formation. However, the significance of endophytic metabolites against AGEs has recently garnered attention but has not been thoroughly summarized thus far. Therefore, the objective of this review is to provide a comprehensive overview of the importance of endophytic metabolites in combating AGEs under NCDs conditions. Additionally, this review aims to elucidate the processes of AGEs formation, absorption, metabolism, and their harmful effects. Collectively, endophytic metabolites play a crucial role in modulating signaling pathways and enhancing the digestibility properties of gut microbiota (GM) by targeting on AGEs/RAGE (receptor for AGEs) axis. Furthermore, these metabolites exhibit anti-AGEs activities similar to those derived from host plants, but at a lower cost and higher production rate. The use of endophytes as a source of such metabolites offers a risk-free and sustainable approach that holds substantial potential for the treatment and management of NCDs.

Glyoxal in Foods: Formation, Metabolism, Health Hazards, and Its Control Strategies

Glyoxal is a highly reactive aldehyde widely present in common diet and environment and inevitably generated through various metabolic pathways in vivo. Glyoxal is easily produced in diets high in carbohydrates and fats via the Maillard reaction, carbohydrate autoxidation, and lipid peroxidation, etc. This leads to dietary intake being a major source of exogenous exposure. Exposure to glyoxal has been positively associated with a number of metabolic diseases, such as diabetes mellitus, atherosclerosis, and Alzheimer's disease. It has been demonstrated that polyphenols, probiotics, hydrocolloids, and amino acids can reduce the content of glyoxal in foods via different mechanisms, thus reducing the risk of exogenous exposure to glyoxal and alleviating carbonyl stresses in the human body. This review discussed the formation and metabolism of glyoxal, its health hazards, and the strategies to reduce such health hazards. Future investigation of glyoxal from different perspectives is also discussed.

Advanced glycation end products are not associated with bone mineral density, trabecular bone score, and bone turnover markers in adults with and without type 1 diabetes: a cross-sectional study

It is unclear if AGEs are involved in the bone fragility of type 1 diabetes (T1D). We evaluated whether skin AGEs by skin autofluorescence and serum AGEs (pentosidine, carboxymethyl-lysine [CML]) are independently associated with BMD by DXA (lumbar spine, hip, distal radius), trabecular bone score (TBS), serum bone turnover markers (BTMs: CTX; P1NP; osteocalcin), and sclerostin in participants with and without T1D. Linear regression models were used, with interaction terms to test effect modification by T1D status. In participants with T1D, correlations between skin and serum AGEs as well as between AGEs and 3-year HbA1C were evaluated using Spearman's correlations. Data are mean ± SD or median (interquartile range). We included individuals who participated in a cross-sectional study and had BMD and TBS assessment (106 T1D/65 controls, 53.2% women, age 43 ± 15 yr, BMI 26.6 ± 5.5 kg/m2). Participants with T1D had diabetes for 27.6 ± 12.3 yr, a mean 3-yr HbA1C of 7.5 ± 0.9% and skin AGEs of 2.15 ± 0.54 arbitrary units. A subgroup of 65 T1D/57 controls had BTMs and sclerostin measurements, and those with T1D also had serum pentosidine (16.8[8.2-32.0] ng/mL) and CML [48.0 ± 16.8] ng/mL) measured. Femoral neck BMD, TBS, and BTMs were lower, while sclerostin levels were similar in participants with T1D vs controls. T1D status did not modify the associations between AGEs and bone outcomes. Skin AGEs were significantly associated with total hip and femoral neck BMD, TBS, BTMs, and sclerostin before, but not after, adjustment for confounders. Serum AGEs were not associated with any bone outcome. There were no significant correlations between skin and serum AGEs or between AGEs and 3-yr HbA1C. In conclusion, skin and serum AGEs are not independently associated with BMD, TBS, BTMs, and sclerostin in participants with relatively well-controlled T1D and participants without diabetes.

Blueberry anthocyanins extract inhibits advanced glycation end-products (AGEs) production and AGEs-stimulated inflammation in RAW264.7 cells

BACKGROUND

Pharmacological interference is considered to be a successful approach to inhibit advanced glycation end-products (AGEs) production and to block AGEs-induced diseases. Some synthetic medicines are effective for inhibiting the glycation reaction, but they cannot be widely applied in clinical as a result of their side effects and security concerns. The present study uses blueberry anthocyanins extract (BAE) to attenuate AGEs formation and AGEs-induced inflammatory response in vitro.

RESULTS

In a bovine serum albumin-glucose model, BAE showed similar inhibitory activity on AGEs compared to the synthetic anti-glycation agent (aminoguanidine). The results showed that BAE exhibit strong anti-glycative action by scavenging glycosylated intermediates (Schiff base, fructosamine and α-dicarbonyl compounds), attenuating the molecular aggregation and amyloid-like fibrils formation, and preventing conformational modification. Additionally, BAE was found to dose-dependently inhibit the AGEs-induced secretions of nitric oxide and pro-inflammatory cytokines (interleukin-6, monocyte chemoattractant protein-1 and tumor necrosis factor-α) in RAW264.7 cells. The anti-inflammation activity of BAE was mediated by down-regulating the expressions of critical inflammatory markers, inducible nitric oxide synthase and cyclooxygenase-2, through nuclear factor-kappa B signaling pathways inhibition.

CONCLUSION

BAE could serve as a natural inhibitor for controlling AGEs and AGEs-induced chronic inflammation. © 2023 Society of Chemical Industry.

Advanced glycation end products of dietary origin and their association with inflammation in diabetes - A minireview

Advanced glycation end products (AGEs) are a diverse group of compounds that are formed as a result of the non-enzymatic reaction between a reducing sugar such as glucose and the free NH2 groups of an amino acid in a protein or other biomolecule. The chemical reaction, by which these products are generated, is known as the Maillard reaction and occurs as a part of the body's normal metabolism. Such a reaction is enhanced during diabetes due to hyperglycemia, but it can also occur during the preparation, processing, and preservation of certain foods. Therefore, AGEs can also be obtained from the diet (d-AGE) and contribute to an increase of the total serum pool of these compounds. They have been implicated in a wide variety of pathological processes, mainly because of their ability to induce inflammatory responses and oxidative stress increase. They are extensively accumulated as a part of the normal aging, especially in tissues rich in long half-life proteins, which can compromise the physiology of these tissues. d-AGEs are abundant in diets rich in processed fats and sugars. This review is addressed to the current knowledge on these products and their impact on the immunomodulation of various mechanisms that may contribute to exacerbation of the diabetes pathophysiology.

Association between fingertip-measured advanced glycation end products and cardiovascular events in outpatients with cardiovascular disease

BACKGROUND

The accumulation of advanced glycation end products (AGEs) is associated with cardiovascular events in patients with cardiovascular disease (CVD). However, the relationship between the AGEs measured by an AGEs sensor noninvasively at the fingertip and prognosis in patients with CVD remains unclear. Therefore, this study aimed to determine the relationship between AGEs score and prognosis among patients with CVD.

METHODS

A total of 191 outpatients with CVD were included. AGEs score were measured using an AGEs sensor and the patients were classified into groups by the median value of AGEs score. The incidence of major adverse cardiovascular and cerebrovascular events (MACCE) at 30 months was compared between high- and low-AGEs score groups. In addition, receiver operating characteristic (ROC) curve analysis was used to calculate cutoff value for the AGEs score, which discriminates the occurrence of MACCE. Cox regression analysis was performed to identify the factors associated with the presence of MACCE. MACCE included cardiac death, myocardial infarction, percutaneous coronary intervention, heart failure, and stroke.

RESULTS

AGEs score was normally distributed, with a median value of 0.51. No significant intergroup differences were found in laboratory findings, physical functions, or medications. The high-AGEs score group had a significantly higher incidence of MACCE than the low-AGEs score group (27.1 vs. 10.5%, P = 0.007). A high-AGEs score was a risk factor for MACCE (hazard ratio, 2.638; 95% confidence interval, 1.271-5.471; P = 0.009). After the adjustment for confounders other than 6-min walking distance, the AGEs score remained a factor associated with the occurrence of MACCE. The best cutoff AGEs score for the detection of MACCE was 0.51 (area under the curve, 0.642; P = 0.008; sensitivity, 72.2%; specificity, 54.8%).

CONCLUSIONS

AGEs score measured at the fingertip in patients with CVD is associated with MACCE. AGEs score, which can be measured noninvasively and easily, may be useful as an assessment for the secondary prevention of CVD in patients with CVD.

Increased dietary intake of ultraprocessed foods and mitochondrial metabolism alterations in pediatric obesity

The increased intake of ultraprocessed foods (UPFs) in the pediatric age paralleled with the risen prevalence of childhood obesity. The Ultraprocessed Foods in Obesity (UFO) Project aimed at investigating the potential mechanisms for the effects of UPFs in facilitating pediatric obesity, focusing on the direct role of advanced glycation end-products (AGEs) on mitochondrial function, the key regulator of obesity pathophysiology. We comparatively investigated the daily dietary intake of UPFs, energy, nutrients, dietary AGEs [Nε -(carboxymethyl)lysine (CML), Nε -(1-carboxyethyl)lysine (CEL), and Nδ -(5-hydro-5- methyl-4-imidazolon-2-yl)-ornithine (MG-H1)] in 53 obese patients and in 100 healthy controls visiting the Tertiary Center for Pediatric Nutrition of the Department of Translational Medical Science at the University of Naples "Federico II". AGEs skin accumulation and mitochondrial function in peripheral blood mononuclear cells (PBMCs) were also assessed. A higher intake of UPFs and AGEs, energy, protein, fat, and saturated fatty acids was observed in obese patients. Obese children presented significantly higher skin AGEs accumulation and alterations in mitochondrial metabolism. PBMCs from healthy controls exposed to AGEs showed the same mitochondrial alterations observed in patients. These findings support the UPFs role in pediatric obesity, and the need for dietary strategies limiting UPFs exposure for obesity prevention and treatment.

Anti-Glucotoxicity Effect of Phytoconstituents via Inhibiting MGO-AGEs Formation and Breaking MGO-AGEs

The therapeutic benefits of phytochemicals in the treatment of various illnesses and disorders are well documented. They show significant promise for the discovery and creation of novel medications for treating a variety of human diseases. Numerous phytoconstituents have shown antibiotic, antioxidant, and wound-healing effects in the conventional system. Traditional medicines based on alkaloids, phenolics, tannins, saponins, terpenes, steroids, flavonoids, glycosides, and phytosterols have been in use for a long time and are crucial as alternative treatments. These phytochemical elements are crucial for scavenging free radicals, capturing reactive carbonyl species, changing protein glycation sites, inactivating carbohydrate hydrolases, fighting pathological conditions, and accelerating the healing of wounds. In this review, 221 research papers have been reviewed. This research sought to provide an update on the types and methods of formation of methylglyoxal-advanced glycation end products (MGO-AGEs) and molecular pathways induced by AGEs during the progression of the chronic complications of diabetes and associated diseases as well as to discuss the role of phytoconstituents in MGO scavenging and AGEs breaking. The development and commercialization of functional foods using these natural compounds can provide potential health benefits.

Contribution of Advanced Glycation End Products to PCOS Key Elements: A Narrative Review

In the last decade, data has suggested that dietary advanced glycation end products (AGEs) play an important role in both reproductive and metabolic dysfunctions associated with polycystic ovary syndrome (PCOS). AGEs are highly reactive molecules that are formed by the non-enzymatic glycation process between reducing sugars and proteins, lipids, or nucleic acids. They can be formed endogenously under normal metabolic conditions or under abnormal situations such as diabetes, renal disease, and other inflammatory disorders. Bodily AGEs can also accumulate from exogenous dietary sources particularly when ingested food is cooked and processed under high-temperature conditions, such as frying, baking, or grilling. Women with PCOS have elevated levels of serum AGEs that are associated with insulin resistance and obesity and that leads to a high deposition of AGEs in the ovarian tissue causing anovulation and hyperandrogenism. This review will describe new data relevant to the role of AGEs in several key elements of PCOS phenotype and pathophysiology. Those elements include ovarian dysfunction, hyperandrogenemia, insulin resistance, and obesity. The literature findings to date suggest that targeting AGEs and their cellular actions could represent a novel approach to treating PCOS symptoms.

An anti-inflammatory and low fermentable oligo, di, and monosaccharides and polyols diet improved patient reported outcomes in fibromyalgia: A randomized controlled trial

Background

Fibromyalgia (FM) has been associated with dysbiosis and low-grade inflammation. Studies have reported that diet influences clinical features in FM.

Objective

To evaluate the effect of an anti-inflammatory and low fermentable oligo, di, and monosaccharides and polyols (FODMAP) diet on clinical outcomes of patients with FM.

Methods

This two arms Randomized Controlled Trial (NCT04007705) included 46 female patients with FM. The intervention group (n = 22) adopted an anti-inflammatory diet for 3 months, excluding gluten, dairy, added sugar, and ultra-processed foods, along with a low FODMAPs diet in the first month. The control group (n = 24) followed general healthy eating recommendations. Both diets were applied by a certified dietitian. Before and after the intervention, participants were assessed regarding pain, fatigue, gastrointestinal symptoms, quality of sleep, and quality of life, through the Revised Fibromyalgia Impact Questionnaire (FIQR), Visual Analogue Pain Scale (VAS), Visual Analog Scale from gastrointestinal symptoms (VAS GI), Brief Pain Inventory (BPI), Pittsburg Sleep Quality Index (PSQI), Fatigue Severity Survey (FSS), and The Short Form Health Survey (SF-36). A blood sample was collected and high-sensitive C-Reactive Protein and Erythrocyte Sedimentation Rate were quantified. Paired Samples t-test/Wilcoxon and independent samples t-test/Mann−Whitney were used to compare variables between groups.

Results

After intervention, there was an improvement in intervention group scores of FIQR (p = 0.001), VAS (p = 0.002), BPI (p = 0.011), FSS (p = 0.042), VAS_GI (p = 0.002), PSQI (p = 0.048), and SF36 (p = 0.045) compared to control group. Inflammatory biomarkers (hs-CRP, ESR) did not change in both groups. The intervention was beneficial in the intervention group, regardless of age, disease duration, body mass index variation, and body fat change between baseline and post-intervention.

Conclusion

An anti-inflammatory and low-FODMAP diet improved clinical features in patients with FM and may be useful as a complement to pharmacological therapy.

Clinical Trial Registration

[https://clinicaltrials.gov/ct2/show/NCT04007705], identifier [NCT04007705].

Curcumin Prevents the Glycation of Tricarboxylic Acid Cycle and Cell Respiration Proteins in the Heart of Mice Fed with a High-Fructose Diet

BACKGROUND

A high fructose diet (HFD) induces protein glycation. The latter is related to a higher risk of cardiovascular disease. Curcumin is a natural pleiotropic compound that may possess antiglycant properties.

OBJECTIVE

To analyze the effect of curcumin on the content of glycated proteins in the hearts of 6-week-old mice fed with a HFD for 15 weeks.

METHODS

Mice were allocated in four groups (n = 6/group): a control group that received a standard diet (CT); a group that received 30% w/v fructose in water (F); a group that received 0.75% w/w curcumin supplemented in food (C); a group that received 30% w/v fructose in water and 0.75% w/w curcumin supplemented in food (F+C). The content of glycated proteins in the heart was determined by Western Blot (whereas the spots were detected by 2D-PAGE) using anti-AGE and anti-CML antibodies. A densitometric analysis was performed using the ImageLab software. Glycated proteins were identified by MALDI-TOF-MS, and an ontological analysis was performed in terms of biological processes and molecular function based on the STRING and DAVID databases.

RESULTS

Fourteen glycated protein spots were detected, two of them with anti-AGE and the other 12 with anti-CML. In total, eleven glycated proteins were identified, out of which three had decreased glycation levels due to curcumin exposure. The identified proteins participate in processes such as cellular respiration, oxidative phosphorylation, lipid metabolism, carbohydrate metabolism, the tricarboxylic acid cycle (TAC), and the organization of intermediate filaments.

CONCLUSIONS

Curcumin decreased the fructose-induced glycation level of the ACO2, NDUFS7, and DLAT proteins.

Natural Occurrence of Carbon Dots during In Vitro Nonenzymatic Glycosylation of Hemoglobin A0

Carbon dots, the nanostructures of carbon, have excellent optical and chemical properties and find a range of applications in various fields of biology and medicine. In the current study, carbon dots are synthesized using in vitro nonenzymatic glycosylation at 37 °C, which is the conventional method for the synthesis of Advanced Glycosylation End products. While comparing the physicochemical properties using a series of physical and chemical analyses including light absorption, fluorescence, photoluminescence, chemical composition, functional group analysis, and in vitro imaging, striking similarities are found among Carbon dots and Advanced Glycosylation End products. Based on the evident resemblance between the two, we propose either the presence of a common structural backbone or the coexistence of the two individual chemical entities. Thus, the formation of carbon dots at physiological temperatures raises health concerns as nonenzymatic glycosylation is a physiological process in humans and the rate of which is elevated during diabetes. The Advanced Glycosylation End products are known to have a detrimental effect in diabetic patients, and the chemical similarity between the two questions the widely studied biocompatibility of carbon dots.

Avenues for post-translational protein modification prevention and therapy

Non-enzymatic post-translational modifications (nPTMs) of proteins have emerged as novel risk factors for the genesis and progression of various diseases. We now have a variety of experimental and established therapeutic strategies to target harmful nPTMs and potentially improve clinical outcomes. Protein carbamylation and glycation are two common and representative nPTMs that have gained considerable attention lately as favorable therapeutic targets with emerging clinical evidence. Protein carbamylation is associated with the occurrence of cardiovascular disease (CVD) and mortality in patients with chronic kidney disease (CKD); and advanced glycation end products (AGEs), a heterogeneous group of molecules produced in a series of glycation reactions, have been linked to various diabetic complications. Therefore, reducing the burden of protein carbamylation and AGEs is an appealing and promising therapeutic approach. This review chapter summarizes potential anti-nPTM therapy options in CKD, CVD, and diabetes along with clinical implications. Using two prime examples-protein carbamylation and AGEs-we discuss the varied preventative and therapeutic options to mitigate these pathologic nPTMs in detail. We provide in-depth case studies on carbamylation in the setting of kidney disease and AGEs in metabolic disorders, with an emphasis on the relevance to reducing adverse clinical outcomes such as CKD progression, cardiovascular events, and mortality. Overall, whether specific efforts to lower carbamylation and AGE burden will yield definitive clinical improvement in humans remains largely to be seen. However, the scientific rationale for such pursuits is demonstrated herein.

Diabetes/Dementia in Sub-saharian Africa and Nigerian Women in the Eye of Storm

In the next few years, the prevalence of diabetes mellitus (DM) is projected to dramatically increase globally, but most of the cases will occur in low-to-middle-income countries. Some of the major risk factors for diabetes accelerate the development of dementia in African-Americans, thus leading to a higher prevalence of dementia than Caucasians. Sub-Saharan Africa women have a disproportionately two-to-eight fold increased prevalence of dementia. In the eye of this storm, Nigeria holds the highest number of diabetics on the African continent, and its prevalence is rising in parallel to obesity, hypertension, and the population's aging. The socio-economic impact of the rising prevalence of DM and dementia will be huge and unsustainable for the healthcare system in Nigeria, as has been recognized in developed economies. Here, we analyze the current situation of women's health in Nigeria and explore future perspectives and directions. The complex interplay of factors involved in diabetes and dementia in Nigerian women include key biological agents (metabolic syndrome, vascular damage, inflammation, oxidative stress, insulin resistance), nutritional habits, lifestyle, and anemia, that worsen with comorbidities. In addition, restricted resources, lack of visibility, and poor management result in a painful chain that increases the risk and burden of disease in Nigerian women from youth to elderly ages. Heath policies to increase the ra- tio of mental health professionals per number of patients, mostly in rural areas, foment of proactive primary care centers, and interventions targeting adolescents and adult women and other specific mothers-children pairs are strongly required for a sustainable development goal.

Dietary natural products as a potential inhibitor towards advanced glycation end products and hyperglycemic complications: A phytotherapy approaches

Natural products exist in various natural foods such as plants, herbs, fruits, and vegetables. Furthermore, marine life offers potential natural products with significant biological activity. The biochemical reaction is known as advanced glycation end products (AGEs) occurs in the human body. On the other hand, foods are capable of a wide range of processing conditions resulting in the generation of exogenous AGEs adducts. Protein glycation and the formation of advanced glycation end products both contribute to the pathogenesis of hyperglycemic complications. AGEs also play a pivotal role in microvascular and macrovascular complications progression by receptors for advanced glycation end products (RAGE). RAGE activate by AGEs leads to up-regulation of transcriptional factor NF-kB and inflammatory genes. Around the globe, researchers are working in various approaches for therapeutical implications on controlling AGEs mediated disease complications. In this regard, one of the potential promising agents observed with a wide range of AGEs inhibition by food-derived natural products. Current biotechnological tools have been turned to natural products or phytochemicals to manufacture the molecules without compromising their functionality. Metabolic engineering and bioinformatics perspectives have recently enabled the generation of a few potent metabolites with anti-diabetic activity. As the primary focus, this review article will also discuss multidisciplinary approaches that emphasize current advances in anti-diabetic therapeutic action and future perspectives of natural products.

Renal function in patients following a low carbohydrate diet for type 2 diabetes: a review of the literature and analysis of routine clinical data from a primary care service over 7 years

PURPOSE OF REVIEW

People with T2 Diabetes (T2D) who follow a low carbohydrate diet (LCD) may increase their dietary protein intake. Dietary protein can modulate renal function so there is debate about its role in renal disease. There is concern that higher protein intakes may promote renal damage, and that LCDs themselves may impact on cardiovascular risk. We review the evidence around LCDs, renal and cardiovascular risk factors and compare to results obtained in a real-world, primary care setting.

RECENT FINDINGS

Chronic kidney disease (CKD) is a well-recognised microvascular complication of T2D caused in part by; chronically increased glomerular pressure, hyperfiltration, increased blood pressure and advanced glycation end products. Hyperglycemia can be seen as central to all of these factors. A LCD is an effective first step in its correction as we demonstrate in our real-world cohort.

SUMMARY

We found evidence that LCDs for people with T2D may improve many renal and cardiovascular risk factors. In our own LCD cohort of 143 patients with normal renal function or only mild CKD, over an average of 30 months the serum creatinine improved by a significant mean of 4.7 (14.9) μmol/L. What remains to be shown is the effect of the approach on people with T2D and moderate/severe CKD.

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.

Incorporation of polyphenols in baked products

Bakery foods, including breads, cakes, cookies, muffins, rolls, buns, crumpets, pancakes, doughnuts, waffles, and bagels, etc., have been an important diet of humans for thousands of years. As the nutraceuticals with various biological activities, polyphenols, especially polyphenol-enriched products are widely used in bakery foods. The polyphenol-enriched products are mainly from fruits and vegetables, including fruits in whole, juice, puree, jam, and the powder of dried fruits, pomace, and peels. Incorporation of these products not only provide polyphenols, but also supply other nutrients, especially dietary fibers for bakery products. This chapter discussed the thermal stability of different types of polyphenols during baking, and the effect of polyphenols on the sensory attributes of baked foods. Moreover, their role in mitigation of reactive carbonyl species and the subsequent formation of advanced glycation end products, antioxidant and antimicrobial activities have been also discussed. Since polyphenols are subjected to high temperature for dozens of minutes during baking, future works need to focus on the chemical interactions of polyphenols and their oxidized products (quinones) with other food components, and the safety consequence of these interactions.

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).

Methylglyoxal-Lysine Dimer, an Advanced Glycation End Product, Induces Inflammation via Interaction with RAGE in Mesangial Cells

INTRODUCTION

Advanced glycation end products (AGEs) and receptor of advanced glycation end products (RAGE) mediate renal function during diabetic and non-diabetic nephropathy development. Methylglyoxal-lysine dimer (MOLD), a typical toxic advanced glycation end product (TAGE), contributes to inflammatory responses during renal diseases. This study determines the effect of MOLD on inflammatory responses in mouse mesangial cells.

METHODS AND RESULTS

The murine mesangial cell line SV40 MES 13 is used to assess nuclear factor-kappa B (NF-κB) expression, reactive oxygen species (ROS) production, and mitochondria labeling. The interaction model between RAGE and MOLD is also determined. MOLD treatment of mesangial cells markedly increases RAGE expression and the linkage with V-type Ig domain of RAGE. MOLD induces ROS production and mitochondrial dysfunction. MOLD activates phosphatidylinositol 3-kinase-protein kinase B (PI3KB) and NF-κB signaling pathways. It is confirmed that these changes are reversed when ROS is suppressed. These effects may be regulated through mitogen-activated protein kinases and pro-inflammatory cytokines in circulatory inflammation responses.

CONCLUSION

MOLD plays a major role in nephropathy via ROS production and mitochondrial dysfunction through direct association with RAGE. Further, the NF-kB and PI3K/AKT signaling pathways triggered by ROS mediate the inflammatory response to exacerbate MOLD-induced damages in inflammation-related diabetic and non-diabetic renal diseases.

Comprehensive Analyses of Carbohydrates, 1,2-Dicarbonyl Compounds, and Advanced Glycation End Products in Industrial Bread Making

The technology of bread making is characterized by three major steps: dough mixing, proofing, and baking. To follow the course of Maillard processes in an authentic food matrix, the complete manufacturing process of wheat bread rolls was assessed along all production steps with the quantitation of sugars, furfurals, 1,2-dicarbonyl compounds, and advanced glycation end products (AGEs). As a result, the AGE profile was significantly enlarged to more than 12 structures, and comprehensive mechanistic insights were provided. The analyses of five major German bread types including wheat, brown, rye bread, pumpernickel, and crispbreads led to AGE contents of 69-149 mg/kg bread or 984-1857 mg/kg protein. Major lysine protein modifications were carboxymethyl, carboxyethyl, and formyl lysine and pyrraline. Arginine was mainly modified by methylglyoxal (MGO) to give imidazolinones. A major part of MGO was confirmed to stem from microbial metabolism.

A study protocol for a randomized controlled trial of an anti-inflammatory nutritional intervention in patients with fibromyalgia

Background

This study aims to analyze the effects of a potentially anti-inflammatory nutritional intervention in disease assessment parameters, inflammatory markers, and quality of life of fibromyalgia (FM) patients.

Methods

A sample of 100 female patients diagnosed with FM, followed up at Portuguese Institute of Rheumatology (IPR) in Lisbon, is being randomly allocated in two groups. Patients in the intervention group are adopting an anti-inflammatory diet, characterized by the exemption of the intake of foods containing gluten, dairy, sugar, and ultra-processed foods, during 3 months. During the first month, a low fermentable oligo-, di-, and monosaccharides and polyols (FODMAPs) diet is implemented, along with the anti-inflammatory diet, followed by the reintroduction of all fruits and vegetables over a consecutive period of 2 months. Patients in the control group are adopting a diet based on general recommendations for healthy eating. The outcomes are pain, fatigue, quality of sleep, quality of life, gastrointestinal symptoms, and inflammation. Before and after the 3 months intervention, and also 1 month after beginning the intervention, the following questionnaires are applied: Revised Fibromyalgia Impact Questionnaire, visual analog pain scale, Brief Pain Inventory,visual analog scale from a list of common gastrointestinal and extraintestinal symptoms in FM, Short Form 36, Fatigue Severity Survey, and Pittsburg Sleep Quality Index. Ultra-sensitive serum C-reactive protein, eritrocyte sedimentation rate, and interleukin-8 are determined. Age, physical activity, anthropometric parameters, and body composition are being collected. Student’s t test will assess the association between the disease evaluation parameters, the inflammatory markers, and the dietary interventions.

Discussion

The results of this study are expected to determine whether a change in patient nutrition helps to alleviate symptoms, which would optimize medical intervention.

Trial registration

www.ClinicalTrials.gov NCT04007705. Registered on July 5, 2019.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13063-021-05146-3.

A review on mechanism of inhibition of advanced glycation end products formation by plant derived polyphenolic compounds

Advanced glycation end products (AGEs) are naturally occurring biomolecules formed by interaction of reducing sugars with biomolecules such as protein and lipids etc., Long term high blood sugar level and glycation accelerate the formation of AGEs. Unchecked continuous formation and accumulation of AGEs are potential risks for pathogenesis of various chronic diseases. Current mode of antidiabetic therapy is based on synthetic drugs that are often linked with severe adverse effects. Polyphenolic compounds derived from plants are supposed to inhibit glycation and formation of AGEs at multiple levels. Some polyphenolic compounds regulate the blood glucose metabolism by amplification of cell insulin resistance and activation of insulin like growth factor binding protein signaling pathway. Their antioxidant nature and metal chelating activity, ability to trap intermediate dicarbonyl compounds could be possible mechanisms against glycation and AGEs formation and hence, against AGEs induced health complications. Although, few species of polyphenolic compounds are being used in in vitro trials and their in vivo study is still in progress, increasing the area of research in this field may produce a fruitful approach in management of overall diabetic complications.

The Possible Role of Saponin in Type-II Diabetes- A Review

BACKGROUND

The possible role of secondary metabolites in the management of diabetes is a great concern and constant discussion. This characteristic seems relevant and should be the subject of thorough discussion with respect to saponin.

OBJECTIVE

The current data mainly focus on the impact of saponin in the treatment of type-II diabetes. The majority of studies emphasize on other secondary metabolites such as alkaloids and flavonoids, but very few papers are there representing the possible role of saponin as these papers express the narrow perspective of saponin phytoconstituents but lacking in providing the complete information on various saponin plants. The aim of the study was to summarize all available data concerning the saponin containing plant in the management of type-II diabetes.

METHODS

All relevant papers on saponin were selected. This review summarizes the saponin isolation method, mechanism of action, clinical significance, medicinal plants and phytoconstituents responsible for producing a therapeutic effect in the management of diabetes.

RESULTS

The saponin is of high potential with structural diversity and inhibits diabetic complications along with reducing the hyperglycemia through different mechanisms thereby providing scope for improving the existing therapy and developing the novel medicinal agents for curing diabetes.

CONCLUSION

Saponins having potential therapeutic benefits and are theorized as an alternative medication in decreasing serum blood glucose levels in the patient suffering from diabetes.

The association between dietary and skin advanced glycation end products: the Rotterdam Study

BACKGROUND

Advanced glycation end products (AGEs) accumulate in tissues with age and in conditions such as diabetes mellitus and chronic kidney disease (CKD), and they may be involved in age-related diseases. Skin AGEs measured as skin autofluorescence (SAF) are a noninvasive reflection of long-term AGE accumulation in tissues. Whether AGEs present in the diet (dAGEs) contribute to tissue AGEs is unclear.

OBJECTIVES

Our aim was to investigate the association between dietary and skin AGEs in the Rotterdam Study, a population-based cohort of mainly European ancestry.

METHODS

In 2515 participants, intake of 3 dAGEs [carboxymethyl-lysine (CML), N-(5-hydro-5-methyl-4-imidazolon-2-yl)-ornithine (MGH1), and carboxyethyl-lysine (CEL)] was estimated using FFQs and the content of AGEs measured in commonly consumed foods. SAF was measured 5 y (median value) later using an AGE Reader. The association of dAGEs with SAF was analyzed in linear regression models and stratified for diabetes and chronic kidney disease (CKD, defined as estimated glomerular filtration rate ≤60 mL/min) status.

RESULTS

Mean ± SD intake was 3.40 ±0.89 mg/d for CML, 28.98 ±7.87 mg/d for MGH1, and 3.11 ±0.89 mg/d for CEL. None of them was associated with SAF in the total study population. However, in stratified analyses, CML was positively associated with SAF after excluding both individuals with diabetes and individuals with CKD: 1 SD higher daily CML intake was associated with a 0.03 (95% CI: 0.009, 0.05) arbitrary units higher SAF. MGH1 and CEL intake were not significantly associated with SAF. Nevertheless, the associations were stronger when the time difference between dAGEs and SAF measurements was shorter.

CONCLUSIONS

Higher dietary CML intake was associated with higher SAF only among participants with neither diabetes nor CKD, which may be explained by high AGE formation in diabetes and decreased excretion in CKD or by dietary modifications in these disease groups. The dAGE-SAF associations were also modified by the time difference between measurements. Our results suggest that dAGEs can influence tissue AGE accumulation and possibly thereby age-related diseases. This trial was registered at the Netherlands National Trial Register as NTR6831 (http://www.trialregister.nl/trialreg/admin/rctview.asp?TC=6831) and at the WHO International Clinical Trials Registry Platform as NTR6831 (http://www.who.int/ictrp/network/primary/en/).

Effects of Aging and Diet on Cardioprotection and Cardiometabolic Risk Markers

The prevalence of several diseases increases by age, including cardiovascular diseases, which are the leading cause of morbidity and mortality worldwide. Aging, as a complex process characterized by senescence, triggers various pathways, such as oxidative stress, systemic inflammation, metabolism dysfunction, telomere shortening, mitochondrial dysfunction and deregulated autophagy. A better understanding of the mechanisms underlying senescence may lead to the development of new therapeutic targets and strategies for age-related pathologies and extend the healthy lifespan. Modulating lifestyle risk factors and adopting healthy dietary patterns remain significant tools in delaying the aging process, decreasing age-associated comorbidities and mortality, increasing life expectancy and consequently, preventing the development of cardiovascular disease. Furthermore, such a strategy represents the most cost-effective approach, and the quality of life of the subjects may be significantly improved. An integrated, personalized approach targeting cardiometabolic aging and frailty is suggested in daily clinical practice. However, it should be initiated from an early age. Moreover, there is a need for further well designed and controlled studies in order to elucidate a link between the time of feeding, longevity and cardiovascular prevention. In the future, it is expected that the pharmacological treatment in cardioprotective management will be necessary, accompanied by equally important lifestyle interventions and adjunctive exercise.

Healthy eating recommendations: good for reducing dietary contribution to the body's advanced glycation/lipoxidation end products pool?

The present review aims to give dietary recommendations to reduce the occurrence of the Maillard reaction in foods and in vivo to reduce the body's advanced glycation/lipoxidation end products (AGE/ALE) pool. A healthy diet, food reformulation and good culinary practices may be feasible for achieving the goal. A varied diet rich in fresh vegetables and fruits, non-added sugar beverages containing inhibitors of the Maillard reaction, and foods prepared by steaming and poaching as culinary techniques is recommended. Intake of supplements and novel foods with low sugars, low fats, enriched in bioactive compounds from food and waste able to modulate carbohydrate metabolism and reduce body's AGE/ALE pool is also recommended. In conclusion, the recommendations made for healthy eating by the Spanish Society of Community Nutrition (SENC) and Harvard University seem to be adequate to reduce dietary AGE/ALE, the body's AGE/ALE pool and to achieve sustainable nutrition and health.

Collagen methionine sulfoxide and glucuronidine/LW-1 are markers of coronary artery disease in long-term survivors with type 1 diabetes. The Dialong study

Objectives

Type 1 diabetes is a risk factor for coronary heart disease. The underlying mechanism behind the accelerated atherosclerosis formation is not fully understood but may be related to the formation of oxidation products and advanced glycation end-products (AGEs). We aimed to examine the associations between the collagen oxidation product methionine sulfoxide; the collagen AGEs methylglyoxal hydroimidazolone (MG-H1), glucosepane, pentosidine, glucuronidine/LW-1; and serum receptors for AGE (RAGE) with measures of coronary artery disease in patients with long-term type 1 diabetes.

Methods

In this cross-sectional study, 99 participants with type 1 diabetes of ≥ 45-year duration and 63 controls without diabetes had either established coronary heart disease (CHD) or underwent Computed Tomography Coronary Angiography (CTCA) measuring total, calcified and soft/mixed plaque volume. Skin collagen methionine sulfoxide and AGEs were measured by liquid chromatography-mass spectrometry and serum sRAGE/esRAGE by ELISA.

Results

In the diabetes group, low levels of methionine sulfoxide (adjusted for age, sex and mean HbA_1c) were associated with normal coronary arteries, OR 0.48 (95% CI 0.27–0.88). Glucuronidine/LW-1 was associated with established CHD, OR 2.0 (1.16–3.49). MG-H1 and glucuronidine/LW-1 correlated with calcified plaque volume (r = 0.23–0.28, p<0.05), while pentosidine correlated with soft/mixed plaque volume (r = 0.29, p = 0.008), also in the adjusted analysis.

Conclusions

Low levels of collagen-bound methionine sulfoxide were associated with normal coronary arteries while glucuronidine/LW-1 was positively associated with established CHD in long-term type 1 diabetes, suggesting a role for metabolic and oxidative stress in the formation of atherosclerosis in diabetes.

Advanced Glycation End Products (AGEs) May Be a Striking Link Between Modern Diet and Health

The Maillard reaction is a simple but ubiquitous reaction that occurs both in vivo and ex vivo during the cooking or processing of foods under high-temperature conditions, such as baking, frying, or grilling. Glycation of proteins is a post-translational modification that forms temporary adducts, which, on further crosslinking and rearrangement, form permanent residues known as advanced glycation end products (AGEs). Cooking at high temperature results in various food products having high levels of AGEs. This review underlines the basis of AGE formation and their corresponding deleterious effects on the body. Glycated Maillard products have a direct association with the pathophysiology of some metabolic diseases, such as diabetes mellitus type 2 (DM2), acute renal failure (ARF), Alzheimer’s disease, dental health, allergies, and polycystic ovary syndrome (PCOS). The most glycated and structurally abundant protein is collagen, which acts as a marker for diabetes and aging, where decreased levels indicate reduced skin elasticity. In diabetes, high levels of AGEs are associated with carotid thickening, ischemic heart disease, uremic cardiomyopathy, and kidney failure. AGEs also mimic hormones or regulate/modify their receptor mechanisms at the DNA level. In women, a high AGE diet directly correlates with high levels of androgens, anti-Müllerian hormone, insulin, and androstenedione, promoting ovarian dysfunction and/or infertility. Vitamin D3 is well-associated with the pathogenesis of PCOS and modulates steroidogenesis. It also exhibits a protective mechanism against the harmful effects of AGEs. This review elucidates and summarizes the processing of infant formula milk and the associated health hazards. Formulated according to the nutritional requirements of the newborn as a substitute for mother’s milk, formula milk is a rich source of primary adducts, such as carboxy-methyl lysine, which render an infant prone to inflammation, dementia, food allergies, and other diseases. We therefore recommend that understanding this post-translational modification is the key to unlocking the mechanisms and physiology of various metabolic syndromes.

Potential effect of advanced glycation end products (AGEs) on spermatogenesis and sperm quality in rodents

The aim of the present study was to assess whether dietary advanced glycation end products (AGEs) induce testicular dysfunction. Using a BALB/c mouse model, AGE intake and serum levels were found to increase in AGE diet-treated mice relative to the controls. Histopathological damage was detected in the testes and epididymides of the AGE diet-induced mice. The total number of epididymal sperm decreased, and increased abnormal sperm rate was found in the mice. Moreover, the mice testes showed an increased level of the receptor for AGEs (RAGE) and malondialdehyde (MDA). Using a Sprague-Dawley rat model, AGE diet-induced rats showed 3- to 4-fold higher AGE intake than the controls. In these rats, higher serum and sperm MDA levels, decreased epididymal sperm numbers, and increased abnormal sperm rates were also observed. Silymarin, a natural AGE inhibitor, was found to restore these AGE-induced phenomena. Concluding from the above findings, dietary AGEs may promote testicular dysfunction.

The Importance of Lactose in the Human Diet: Outcomes of a Mexican Consensus Meeting

Lactose is a unique component of breast milk, many infant formulas and dairy products, and is widely used in pharmaceutical products. In spite of that, its role in human nutrition or lactose intolerance is generally not well-understood. For that reason, a 2-day-long lactose consensus meeting with health care professionals was organized in Mexico to come to a set of statements for which consensus could be gathered. Topics ranging from lactase expression to potential health benefits of lactose were introduced by experts, and that was followed by a discussion on concept statements. Interestingly, lactose does not seem to induce a neurological reward response when consumed. Although lactose digestion is optimal, it supplies galactose for liver glycogen synthesis. In infants, it cannot be ignored that lactose-derived galactose is needed for the synthesis of glycosylated macromolecules. At least beyond infancy, the low glycemic index of lactose might be metabolically beneficial. When lactase expression decreases, lactose maldigestion may lead to lactose intolerance symptoms. In infancy, the temporary replacing of lactose by other carbohydrates is only justified in case of severe intolerance symptoms. In those who show an (epi)genetic decrease or absence of lactase expression, a certain amount (for adults mostly up to 12 g per portion) of lactose can still be consumed. In these cases, lactose shows beneficial intestinal-microbiota-shaping effects. Avoiding lactose-containing products may imply a lower intake of other important nutrients, such as calcium and vitamin B12 from dairy products, as well as an increased intake of less beneficial carbohydrates.

[Hygieno-dietetic recommendations in the prevention of accumulation of advanced glycation products]

Advanced glycation products are proteins whose structural and functional properties have been modified by a process of oxidative glycation. The accumulation of advanced glycation products in most tissues and the oxidative stress and inflammatory reactions that accompany it, account for the multi-systemic impairment observed particularly in the elderly, diabetics and in chronic renal failure. The advanced glycation products endogenous production is continuous, related to oxidative stress, but the most important source of advanced glycation products is exogenous, mainly of food origin. Exogenous advanced glycation products are developed during the preparation of food and beverages. The advanced glycation products content is higher for animal foods, but it is mainly the preparation and cooking methods that play a decisive role. Dietary advice is based on the selection of foods and the choice of methods of preparation. Several randomized controlled studies have confirmed the favorable effect of these recommendations on serum advanced glycation products concentrations. In humans, as in animals, regular physical activity also results in a reduction of serum and tissue concentrations of advanced glycation products. There is a need for prospective clinical study to confirm the effects of hygienic and dietary recommendations that have only been appreciated, so far, on biological markers.

Development and Progression of Non-Alcoholic Fatty Liver Disease: The Role of Advanced Glycation End Products

Non-alcoholic fatty liver disease (NAFLD) affects up to 30% of the adult population and is now a major cause of liver disease-related premature illness and deaths in the world. Treatment is largely based on lifestyle modification, which is difficult to achieve in most patients. Progression of simple fatty liver or steatosis to its severe form non-alcoholic steatohepatitis (NASH) and liver fibrosis has been explained by a 'two-hit hypothesis'. Whilst simple steatosis is considered the first hit, its transformation to NASH may be driven by a second hit. Of several factors that constitute the second hit, advanced glycation end products (AGEs), which are formed when reducing-sugars react with proteins or lipids, have been implicated as major candidates that drive steatosis to NASH via the receptor for AGEs (RAGE). Both endogenous and processed food-derived (exogenous) AGEs can activate RAGE, mainly present on Kupffer cells and hepatic stellate cells, thus propagating NAFLD progression. This review focuses on the pathophysiology of NAFLD with special emphasis on the role of food-derived AGEs in NAFLD progression to NASH and liver fibrosis. Moreover, the effect of dietary manipulation to reduce AGE content in food or the therapies targeting AGE/RAGE pathway on disease progression is also discussed.

The Modern Western Diet Rich in Advanced Glycation End-Products (AGEs): An Overview of Its Impact on Obesity and Early Progression of Renal Pathology

Advanced glycation end-products (AGEs) are an assorted group of molecules formed through covalent bonds between a reduced sugar and a free amino group of proteins, lipids, and nucleic acids. Glycation alters their structure and function, leading to impaired cell function. They can be originated by physiological processes, when not counterbalanced by detoxification mechanisms, or derive from exogenous sources such as food, cigarette smoke, and air pollution. Their accumulation increases inflammation and oxidative stress through the activation of various mechanisms mainly triggered by binding to their receptors (RAGE). So far, the pathogenic role of AGEs has been evidenced in inflammatory and chronic diseases such as chronic kidney disease, cardiovascular disease, and diabetic nephropathy. This review focuses on the AGE-induced kidney damage, by describing the molecular players involved and investigating its link to the excess of body weight and visceral fat, hallmarks of obesity. Research regarding interventions to reduce AGE accumulation has been of great interest and a nutraceutical approach that would help fighting chronic diseases could be a very useful tool for patients’ everyday lives.

Advanced glycation end products as biomarkers in systemic diseases: premises and perspectives of salivary advanced glycation end products

Advanced glycation end products (AGEs) are glycated proteins associated with high dry temperature food processing, coloring and flavor modification of food products. Previous studies on diet-related disease support the role of the glycation products as biomarkers in local and general proinflammatory response. Exogenous and endogenous AGEs are involved in chronic low-level inflammation, which underlies the onset of metabolic syndrome influenced by food intake, there by demonstrating their implication in diet-related pathologies. Although studies have revealed a strong association between the accumulation of AGEs and the occurrence/worsening of metabolic diseases, their routine use for the diagnosis or monitoring of local and general disease has not yet been reported.

The LepRdb/db mice model for studying glycation in the context of diabetes

BACKGROUND

Early (furosine) and advanced (carboxymethyllysine, CML) products of glycation (AGEs) have been reported as increased in plasma, tissues, and organs of diabetic people, indicating a direct link between glycation and type 2 diabetes (T2D). While murine models present some of the characteristics observed in diabetic humans, their pertinence as models of glycation, particularly for T2D, remains poorly described. The aim of this study was to characterize and compare glycation in several organs of two commonly studied murine models of T2D using stable isotope dilution liquid chromatography tandem mass spectrometry (LC-MS/MS).

METHODS

Defining parameters of type 2 diabetes including body weight, fasting glycaemia, and glucose intolerance were measured in three different C57BL6 mouse models of T2D-the genetic LepR^db/db (db/db) model and two diet-induced obesity (DIO) models-and their respective controls. Furosine, free, and protein-bound CML were quantified in kidneys, lungs, heart, and liver by LC-MS/MS.

RESULTS

The obesity, hyperglycaemia, and glucose intolerance in db/db mice was accompanied by an increase of furosine and protein-bound CML levels in all organs relative to controls. The DIO models took several months to become obese, exhibited less severe hyperglycaemia and glucose intolerance, while glycation products were not significantly different between these groups (with the exception of furosine in liver and CML in lungs).

CONCLUSIONS

The db/db model better reflected the characteristics of human T2D compared with the DIO models and exhibited greater formation and accumulation of both furosine and protein-bound CML in all of the organs tested here.

Dietary Advanced Glycation End Products: Digestion, Metabolism and Modulation of Gut Microbial Ecology

The formation of advanced glycation end products (AGEs) in foods is accelerated with heat treatment, particularly within foods that are cooked at high temperatures for long periods of time using dry heat. The modern processed diet is replete with AGEs, and excessive AGE consumption is thought to be associated with a number of negative health effects. Many dietary AGEs have high molecular weight and are not absorbed in the intestine, and instead pass through to the colon, where they are available for metabolism by the colonic bacteria. Recent studies have been conducted to explore the effects of AGEs on the composition of the gut microbiota as well as the production of beneficial microbial metabolites, in particular, short-chain fatty acids. However, there is conflicting evidence regarding the impact of dietary AGEs on gut microbiota reshaping, which may be due, in part, to the formation of alternate compounds during the thermal treatment of foods. This review summarises the current evidence regarding dietary sources of AGEs, their gastrointestinal absorption and role in gut microbiota reshaping, provides a brief overview of the health implications of dietary AGEs and highlights knowledge gaps and avenues for future study.

Characterization of advanced glycation end products and their receptor (RAGE) in an animal model of myocardial infarction

Circulating advanced glycation end products (AGE) and their receptor, RAGE, are increased after a myocardial infarction (MI) episode and seem to be associated with worse prognosis in patients. Despite the increasing importance of these molecules in the course of cardiac diseases, they have never been characterized in an animal model of MI. Thus, the aim of this study was to characterize AGE formation and RAGE expression in plasma and cardiac tissue during cardiac remodeling after MI in rats. Adult male Wistar rats were randomized to receive sham surgery (n = 15) or MI induction (n = 14) by left anterior descending coronary artery ligation. The MI group was stratified into two subgroups based on postoperative left ventricular ejection fraction: low (MIlowEF) and intermediate (MIintermEF). Echocardiography findings and plasma levels of AGEs, protein carbonyl, and free amines were assessed at baseline and 2, 30, and 120 days postoperatively. At the end of follow-up, the heart was harvested for AGE and RAGE evaluation. No differences were observed in AGE formation in plasma, except for a decrease in absorbance in MIlowEF at the end of follow-up. A decrease in yellowish-brown AGEs in heart homogenate was found, which was confirmed by immunodetection of N-ε-carboxymethyl-lysine. No differences could be seen in plasma RAGE levels among the groups, despite an increase in MI groups over the time. However, MI animals presented an increase of 50% in heart RAGE at the end of the follow-up. Despite the inflammatory and oxidative profile of experimental MI in rats, there was no increase in plasma AGE or RAGE levels. However, AGE levels in cardiac tissue declined. Thus, we suggest that the rat MI model should be employed with caution when studying the AGE-RAGE signaling axis or anti-AGE drugs for not reflecting previous clinical findings.

Caloric restriction and redox homeostasis in various regions of aging male rat brain: Is caloric restriction still worth trying even after early-adulthood?: Redox homeostasis and caloric restriction in brain

Despite recent studies have shown that caloric restriction (CR) could improve some functional loss associated with brain aging, the biochemical effects of CR on brain aging are still not well understood on a quantifiable biochemical basis, including whether CR could be protective when started around middle adulthood, when age-related neurodegenerative diseases are thought to set in. Therefore, in the light of more than ever aging societies and increasing neurodegenerative diseases, we aimed to test the biochemical effects of CR on redox homeostasis in different parts of male Sprague-Dawley rat brain by using the biomarkers we consistently validated in our previous work (TOS, PCO, AOPP, AGEs, sRAGE, P-SH, LHPs, 4-HNE, TAS, Cu, Zn-SOD). Our results indicate that oxidative stress biomarkers are lower in CR group, implying a more favorable redox status that has been previously shown to be correlated with better neural function. PRACTICAL APPLICATIONS: We report that the beneficial effects of caloric restriction (CR) on various brain tissues result in significant improvements in biochemical markers, even though CR is not started in early adulthood. Hence, our select age group provides a sound redox status-related neurochemical understanding for many recent CR studies, where a functional loss was detected at this age.

Caenorhabditis elegans, un modèle d’étude du vieillissement

Le vieillissement est un processus physiologique complexe qui accompagne l’avancée en âge de tout organisme vivant. L’utilisation d’organismes modèles considérés comme simples a été fondamentale pour la compréhension des mécanismes impliqués dans ce processus. Caenorhabditis elegans, nématode utilisé initialement pour établir les bases génétiques et moléculaires du développement, est devenu un des modèles d’étude du vieillissement. L’utilisation de cet invertébré a permis de détecter un lien direct entre l’activation de voies de signalisation cellulaire et la longévité. Si C. elegans ne permet pas d’analyser le processus complet du vieillissement humain, il reste un modèle de choix pour étudier des mécanismes et phénotypes particuliers du vieillissement.

Analysis and Chemistry of Novel Protein Oxidation Markers in Vivo

Proteins continually undergo spontaneous oxidation reactions, which lead to changes in structure and function. The quantitative assessment of protein oxidation adducts provides information on the level of exposure to reactive precursor compounds with a high oxidizing potential and reactive oxygen species (ROS). In the present work, we introduce N⁶-(2-hydroxyethyl)lysine as a novel marker based on the ratio of glycolaldehyde and its oxidized form glyoxal. The high analytical potential was proven with a first set of patients undergoing hemodialysis versus healthy controls, in comparison with well-established parameters for oxidative stress. In vitro experiments with N¹- t-BOC-lysine and N¹- t-BOC-arginine enlightened the mechanistic relationship of glycolaldehyde and glyoxal. Oxidation was strongly dependent on the catalytic action of the ε-amino moiety of lysine. Investigations on the formation of N⁶-carboxymethyl lysine revealed glycolaldehyde-imine as the more reactive precursor, even though an additional oxidative step is required. As a result, a novel and very effective alternative mechanism was unraveled.

Food-derived 1,2-dicarbonyl compounds and their role in diseases

Reactive 1,2-dicarbonyl compounds (DCs) are generated from carbohydrates during food processing and storage and under physiological conditions. In the recent decades, much knowledge has been gained concerning the chemical formation pathways and the role of DCs in food and physiological systems. DCs are formed mainly by dehydration and redox reactions and have a strong impact on the palatability of food, because they participate in aroma and color formation. However, they are precursors of advanced glycation end products (AGEs), and cytotoxic effects of several DCs have been reported. The most abundant DCs in food are 3-deoxyglucosone, 3-deoxygalactosone, and glucosone, predominating over methylglyoxal, glyoxal, and 3,4-dideoxyglucosone-3-ene. The availability for absorption of individual DCs is influenced by the release from the food matrix during digestion and by their reactivity towards constituents of intestinal fluids. Some recent works suggest formation of DCs from dietary sugars after their absorption, and others indicate that certain food constituents may scavenge endogenously formed DCs. First works on the interplay between dietary DCs and diseases reveal an ambiguous role of the compounds. Cancer-promoting but also anticancer effects were ascribed to methylglyoxal. Further work is still needed to elucidate the reactions of DCs during intestinal digestion and pathophysiological effects of dietary DCs at doses taken up with food and in "real" food matrices in disease states such as diabetes, uremia, and cancer.

Hand, shoulder and back stiffness in long-term type 1 diabetes; cross-sectional association with skin collagen advanced glycation end-products. The Dialong study

AIMS

We aimed to: (i) estimate the prevalence of Dupuytren's disease, trigger finger, carpal tunnel syndrome and frozen shoulder; (ii) assess stiffness of the hand, shoulder and back; and (iii) explore the association of joint stiffness with both long-term HbA_1c and collagen advanced glycation end-products (AGEs) in long-term type 1 diabetes mellitus (T1DM).

METHODS

Patients with T1DM from 1970 or earlier attending a specialized diabetes center were included in this cross-sectional controlled study. We collected HbA₁/HbA_1c measurements from 1980 to 2015 and data on hand and shoulder diagnoses and joint stiffness through interviews, charts, and standardized examination. Skin biopsies were analyzed for collagen AGEs by liquid chromatography-mass spectrometry.

RESULTS

Lifetime prevalence of hand and shoulder diagnoses in the diabetes group (n=102) ranged from 37%-76% (frozen shoulder) versus 11%-15% in controls (n=73) (p<0.001). There was an association between joint stiffness and long-term HbA_1c (odds ratio 2.01 [95% CI 1.10-3.7]) and the AGEs methyl-glyoxal-lysine-dimer (odds ratio 1.68 [95% CI 1.03-2.73]) and pentosidine (odds ratio 1.81 [95% CI 1.04-3.16]).

CONCLUSIONS

Patients with T1DM >45years had a very high prevalence of hand and shoulder diagnoses versus controls. Joint stiffness was associated with collagen AGEs. However, joint biopsies and prospective studies must explore this association further.

Fructose Intake, Serum Uric Acid, and Cardiometabolic Disorders: A Critical Review

There is a direct relationship between fructose intake and serum levels of uric acid (UA), which is the final product of purine metabolism. Recent preclinical and clinical evidence suggests that chronic hyperuricemia is an independent risk factor for hypertension, metabolic syndrome, and cardiovascular disease. It is probably also an independent risk factor for chronic kidney disease, Type 2 diabetes, and cognitive decline. These relationships have been observed for high serum UA levels (>5.5 mg/dL in women and >6 mg/dL in men), but also for normal to high serum UA levels (5-6 mg/dL). In this regard, blood UA levels are much higher in industrialized countries than in the rest of the world. Xanthine-oxidase inhibitors can reduce UA and seem to minimize its negative effects on vascular health. Other dietary and pathophysiological factors are also related to UA production. However, the role of fructose-derived UA in the pathogenesis of cardiometabolic disorders has not yet been fully clarified. Here, we critically review recent research on the biochemistry of UA production, the relationship between fructose intake and UA production, and how this relationship is linked to cardiometabolic disorders.