Oxidative Stress-Inducing Carbonyl Compounds From Common Foods: Novel Mediators of Cellular Dysfunction

A Mediterranean diet improves glycation markers in healthy people and in those with chronic diseases: a systematic review of clinical trials

CONTEXT

Consumption of the Mediterranean diet (MedDiet) has beneficial effects on cardiometabolic health and aging.

OBJECTIVE

This systematic review aimed to critically investigate the effect of the MedDiet on glycation markers in healthy or overweight individuals with type 2 diabetes or cardiovascular disease.

DATA SOURCES

MEDLINE, EMBASE, Web of Science, and the Cochrane Library were searched, using the terms "Mediterranean diet" AND "glycation end products, advanced".

DATA EXTRACTION

Three randomized and 3 nonrandomized clinical trials, containing data on 2935 adult and elderly individuals with normal weight or overweight, were included. All extracted data were compiled, compared, and critically analyzed.

DATA ANALYSIS

The authors of most of the studies demonstrated a reduction in serum concentrations of advanced glycation end products (AGEs), such as εN-carboxymethyllysine and methylglyoxal, and in skin autofluorescence levels after at least 4 weeks of adherence to the MedDiet. The MedDiet also led to positive effects on gene expression of receptors for AGEs, as RAGE and AGER1, and an enzyme involved in detoxification (glyoxalase I). There is no evidence that short-term adherence affects glycation markers.

CONCLUSIONS

Glycation markers improved in response to the MedDiet. The possible mechanisms involved may be related to the low AGE and refined sugars content of the diet, as well as its high monounsaturated fatty acid, phenolic compound, and dietary fiber contents.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO registration no. CRD42021284006.

The associations between dietary advanced glycation-end products intake and self-reported infertility in U.S. women: data from the NHANES 2013-2018

Evidence suggest that dietary advanced glycation end products (AGEs) might exert harmful effects on female reproductive function. However, population-based studies exploring the associations between dietary AGEs intake and female infertility remain lacking. This studyaimed to determine the relationship between dietary AGEs intake and female infertility based on National Health and Nutrition Examination Survey (NHANES). A cross-sectional analysis of 2863 participants in the NHANES 2013-2018 were included. The dietary AGEs, i.e. Nε-(carboxymethyl)lysine(CML), Nε-(1-carboxyethyl)lysine (CEL), and Nδ-(5-hydro-5-methyl-4-imidazolon-2-yl)-ornithine (MG-H1) were estimated using the combination of ultra-performance LC-tandem MS dietary AGEs database and two 24-h dietary recall interviews. Multivariate Logistic regression analyses were adopted to explore the relationships between dietary AGEs intake and self-reported infertility risk. Compared to the lowest tertile, total dietary AGEs (P-trend = 0.089) and CML (P-trend = 0.032) in the upper tertile were positively correlated with female infertility, and the corresponding odds radios (ORs) (95% confidence interval (CI)) were 1.44 (1.01, 2.06) and 1.64 (1.10, 2.45) respectively. Subgroups analysis found that in participants with overweight and obese, each 1-SD increment in dietary AGEs, CML and MG-H1 level was associated with 18% (95% CI: 1-38%), 21% (95% CI: 1-46%), and 16% (95% CI: 0-36%) elevated risk of infertility. Elevated dietary AGEs intake was associated with the higher risk of infertility for female subjects, this positive association was more pronounced in women with excess body weight.

Effect of low vs high dietary-advanced glycation end products on insulin-sensitivity and inflammatory- markers among overweight/obese Asian-Indian adults-A randomised controlled trial

The present study investigated the effect of low vs high-dietary-Advanced Glycation End products-based diets on oral disposition index-(DIo)-a marker of islet β-cell function and cardiometabolic risks factors in 38-overweight and obese Asian Indian-adults (aged 25-45 years with body-mass-index (BMI) ≥23kg/m2) through 12-week isocaloric crossover feeding trial. Biochemical-measures included-glucose tolerance test (GTT), Insulin assay (0,30 and 120 min), lipid-profile, serum-adiponectin, serum-AGE and serum-Thiobarbituric acid reactive substances-(TBARS) assessed both at baseline and end of each intervention. Generalised linear models showed that low-dAGE diet significantly improved in oral disposition index [Least Square Mean (SE), +0.3 (0.1); p = 0.03] compared to high-dAGE diet. The low-dAGE diet also showed a significant reduction in 30-minutes plasmapost-glucose-challenge-value:(-8.1[3.8] (mg/dl) vs 3.8 [3.8] (mg/dl); p = 0.01), serum-AGEs-(-3.2 [0.2] (μg/ml) vs -0.8 [0.2] (μg/ml); p = <0.0001) compared to high-dAGE diet. In summary, low-dAGE diets exhibited improvement in the insulin-sensitivity and reduction in the inflammatory levels compared to high-dAGE diets. Hence, study first time in India revealed that low dAGE diets could be a potential strategy to reduce diabetes risk.

Modulation of circulating levels of advanced glycation end products and its impact on intima-media thickness of both common carotid arteries: CORDIOPREV randomised controlled trial

BACKGROUND

Increasing evidence supports the role of advanced glycation end products (AGEs) in atherosclerosis in both diabetic and non-diabetic patients, suggesting that therapeutic strategies targeting AGEs may offer potential benefits in this population. The Mediterranean diet is associated with improved biomarkers and anthropometric measurements related with atherosclerosis in addition to its ability to modulate AGE metabolism. Our aim was to determine whether the reduction in atherosclerosis progression (measured by changes in intima-media thickness of both common carotid arteries (IMT-CC)), observed after consumption of a Mediterranean diet compared to a low-fat diet, is associated with a modulation of circulating AGE levels in patients with coronary heart disease (CHD).

METHODS

1002 CHD patients were divided in: (1) Non-increased IMT-CC patients, whose IMT-CC was reduced or not changed after dietary intervention and (2) Increased IMT-CC patients, whose IMT-CC was increased after dietary intervention. Serum AGE levels (methylglyoxal-MG and Nε-Carboxymethyllysine-CML) and parameters related to AGE metabolism (AGER1 and GloxI mRNA and sRAGE levels) and reduced glutathione (GSH) levels were measured before and after 5-years of dietary intervention.

RESULTS

The Mediterranean diet did not affect MG levels, whereas the low-fat diet significantly increased them compared to baseline (p = 0.029), leading to lower MG levels following the Mediterranean diet than the low-fat diet (p < 0.001). The Mediterranean diet, but not the low-fat diet, produced an upregulation of AGE metabolism, with increased AGER1 and GloxI gene expression as well as increased GSH and sRAGE levels in Non-increased IMT-CC patients (all p < 0.05). Although the Mediterranean diet increased MG levels in Increased IMT-CC patients, this increment was lower compared to the low-fat diet (all p < 0.05).

CONCLUSIONS

Our results suggest that an improvement in modulation of AGE metabolism, which facilitates better management of circulating AGE levels, may be one of the mechanisms through which the Mediterranean diet, compared to a low-fat diet, reduces the progression of atherosclerosis in patients with CHD. Trial registration https://clinicaltrials.gov/ct2/show/NCT00924937 , Clinicaltrials.gov number, NCT00924937.

Estimation of Advanced Glycation End Products in Selected Foods and Beverages by Spectrofluorimetry and ELISA

Advanced glycation end products (AGEs) are formed within the body as a part of normal metabolism and are also the by-products of cooking food. The elevated levels of AGEs in the body are considered pathogenic. The modern diets contain high levels of AGEs which are getting incorporated into the body AGEs pool and contribute to post-diabetic and age-related complications. The objective of the present study is to estimate the cross-linked AGEs (AGE-fluorescence) and the more stable carboxymethyl-lysine (CML) by spectrofluorimetry and ELISA in 58 kinds of foods in India. It was evident from the results that the foods cooked at higher temperatures showed high levels of AGEs. Among the studied foods, the highest fluorescence was observed in Biscuits 2 (362 AU), and the highest level of carboxymethyl lysine (CML) was found in Soya milk (659.3 ng/g). However, there was less correlation between the AGE-fluorescence and the CML content of the food samples. Processed food such as tomato sauce, chilli sauce, and cheese, along with western foods like chicken nuggets, pizza, and biscuits like Biscuits 2, are known to contain high levels of AGEs. In the present study a preliminary database of AGE-fluorescence and CML content of 58 foods was developed, which is the first attempt among Indian foods. Furthermore, elaborated database can be developed including maximum consumed foods in India which will help in suggesting a better diet for the diabetic population.

Associations of circulating advanced glycation end products and their soluble receptors with cancer risk: A systematic review and meta-analysis of observational studies

Advanced glycation end products (AGE) in complex with their receptors (RAGE) cause a chronic inflammatory state in the body, which is the major mechanism in cancer development. This study aimed to conduct a systematic review and meta-analysis on the observational studies investigating the association between AGEs / sRAGE and cancer incidence. The PubMed, Scopus, and Web of Science databases were comprehensively searched to identify papers focused on the associations of sRAGE and AGEs with cancer incidence up to May 2023. Eight studies with a total of 7690 participants were included in the analysis to evaluate the association between circulating sRAGE and cancer incidence. The results indicated that circulating sRAGE (per 100 ng/L) had a significant inverse association with cancer incidence (RR 0.977; 95% CI 0.956, 0.999; p = 0.036; I 2 = 73.3%). The association between AGEs and cancer incidence was evaluated in 8 studies with a total of 3718 individuals. Serum concentrations of AGEs (per 100 µg/L) were not associated with the risk of cancer incidence (RR 0.988; 95% CI 0.974, 1.002; p = 0.08; I2 = 78.8%). Our findings revealed that a higher circulating sRAGE may have a protective effect against cancer incidence.

Reduction of circulating methylglyoxal levels by a Mediterranean diet is associated with preserved kidney function in patients with type 2 diabetes and coronary heart disease: From the CORDIOPREV randomized controlled trial

AIM

Advanced glycation end products (AGEs) play a role in kidney disease in type 2 diabetes mellitus (T2DM). However, there have been no prior controlled clinical trials examining the effects of specific diets on AGE metabolism and their impact on kidney function. Our aim was to assess whether modulating AGE metabolism resulting in reduced AGEs levels, after consumption of two healthy diets, could delay kidney function decline in patients with T2DM and coronary heart disease (CHD).

METHODS

T2DM patients (540 out of 1002 patients from the CORDIOPREV study), with estimated glomerular filtration rate (eGFR) ≥ 30 ml/min/1.73 m2, were classified based on their baseline kidney function: normal eGFR (≥ 90 ml/min/1.73 m2), mildly decreased eGFR (60- < 90 ml/min/1.73 m2) and moderately decreased eGFR (<60 ml/min/1.73 m2). Serum AGE levels, methylglyoxal (MG) and N-carboximethyllysine (CML), and gene expression related to AGE metabolism (AGER1, RAGE, and GloxI mRNA) were measured before and after 5-years of dietary intervention (a Mediterranean diet or a low-fat diet).

RESULTS

Mediterranean diet produced a lower declined of eGFR compared to the low-fat diet only in patients with mildly decreased eGFR (P = 0.035). Moreover, Mediterranean diet was able to decrease MG levels and increase GloxI expression in normal and mildly decreased eGFR patients (all P < 0.05). One standard deviation increment of MG levels after dietary intervention resulted in a 6.8-fold (95 % CI 0.039;0.554) higher probability of eGFR decline.

CONCLUSION

Our study showed that lowering circulating AGE levels, specifically MG, after following a Mediterranean diet, might be linked to the preservation of kidney function, evidenced by a decreased decline of eGFR in T2DM patients with CHD. Patients with mildly decreased eGFR could potentially benefit more from AGE reduction in maintaining kidney function.

Sexual Dysfunction in Diabetic Patients: Τhe Role of Advanced Glycation End Products

Sexual dysfunction is a common but underestimated disorder of diabetic patients of both genders, entailing specific and complex pathogenesis and severely affecting reproductive health and quality of life. Hyperglycemia, dyslipidemia, hypertension, obesity, aging, and psychological factors underlie its pathogenesis. A large body of evidence indicates that advanced glycation end products and oxidative stress have a distinct impact on the pathogenesis of diabetes and its complications, including hypogonadism, which is closely related to sexual dysfunction. Advanced glycation end products seem to affect sexual function either directly by accumulation in various regions of the reproductive system and/or correlation or indirectly through oxidative stress induction via several mechanisms. They are also involved in the pathogenesis of diabetic complications, which are related to sexual dysfunction. Herein, we review the issue of sexual dysfunction in diabetic males and females, with special emphasis on the impact of advanced glycation end products in the pathogenesis of sexual dysfunction, the relationship of advanced glycation end products with low testosterone levels in diabetic subjects, which account for the proportion of disorder and the available therapeutic interventions.

Influence of Polycyclic Aromatic Compounds and Oxidation States of Soot Organics on the Metabolome of Human-Lung Cells (A549): Implications for Vehicle Fuel Selection

Decades of research have established the toxicity of soot particles resulting from incomplete combustion. However, the unique chemical compounds responsible for adverse health effects have remained uncertain. This study utilized mass spectrometry to analyze the chemical composition of extracted soot organics at three oxidation states, aiming to establish quantitative relationships between potentially toxic chemicals and their impact on human alveolar basal epithelial cells (A549) through metabolomics-based evaluations. Targeted analysis using MS/MS indicated that particles with a medium oxidation state contained the highest total abundance of compounds, particularly oxygen-containing polycyclic aromatic hydrocarbons (OPAHs) composed of fused benzene rings and unsaturated carbonyls, which may cause oxidative stress, characterized by the upregulation of three specific metabolites. Further investigation focused on three specific OPAH standards: 1,4-naphthoquinone, 9-fluorenone, and anthranone. Pathway analysis indicated that exposure to these compounds affected transcriptional functions, the tricarboxylic acid cycle, cell proliferation, and the oxidative stress response. Biodiesel combustion emissions had higher concentrations of PAHs, OPAHs, and nitrogen-containing PAHs (NPAHs) compared with other fuels. Quinones and 9,10-anthraquinone were identified as the dominant compounds within the OPAH category. This knowledge enhances our understanding of the compounds contributing to adverse health effects observed in epidemiological studies and highlights the role of aerosol composition in toxicity.

Dietary advanced glycation end products are associated with an increased risk of breast cancer in Iranian adults

BACKGROUND

Dietary advanced glycation end products (AGEs) can play an important role in increasing inflammatory factors and oxidative stress as risk factors for cancers. In the present study, we aimed to assess the relationship between dietary AGEs and the risk of breast cancer (BC) in Iranian adult women.

METHODS

This hospital-based case-control study includes 401 participants aged ≥ 30 years old. The cases group consisted of 134 women diagnosed with histologically confirmed BC. The control group included 267 women enrolled randomly from patients admitted to the same hospitals. Dietary intake information was determined using a validated food frequency questionnaire, and dietary AGEs intake was computed for all participants. Logistic regression models, adjusted for potential confounders, were used to determine the odds ratios (OR) and 95% confidence interval (CI) of BC across tertiles of dietary AGEs.

RESULTS

The mean ± SD age and body mass index of the study population were 47.92 ± 10.33 years and 29.43 ± 5.51 kg/m2, respectively. The median (interquartile) of dietary AGEs in all individuals was 9251(7450, 11,818) kU/day. After adjusting for age, first pregnancy age, and energy intake, participants in the highest tertile of dietary AGEs intakes had higher odds of BC compared to those in the lowest tertile of dietary AGEs (OR:2.29;95%CI:1.19-4.39, Ptrend:0.012). Additionally, in the multivariable model, after adjusting for age, age at first pregnancy, energy, menopausal status, family history of cancer, anti-inflammatory drug use, Vitamin D supplementation, physical activity, body mass index, number of childbirths, and history of abortion, breastfeeding, and oral contraceptive pills use, the odds of BC were increased across tertiles of dietary AGEs intake (OR: 2.33; 95%CI: 1.18-4.60, Ptrend: 0.017).

CONCLUSION

The present findings suggest that a diet with high AGEs is associated with a higher likelihood of BC in adult women.

Dietary Approach of Patients with Hormone-Related Cancer Based on the Glycemic Index and Glycemic Load Estimates

Hormone-related cancers, namely breast, endometrial, cervical, prostate, testicular, and thyroid, constitute a specific group of cancers dependent on hormone levels that play an essential role in cancer growth. In addition to the traditional risk factors, diet seems to be an important environmental factor that partially explains the steadily increased prevalence of this group of cancer. The composition of food, the dietary patterns, the endocrine-disrupting chemicals, and the way of food processing and preparation related to dietary advanced glycation end-product formation are all related to cancer. However, it remains unclear which specific dietary components mediate this relationship. Carbohydrates seem to be a risk factor for cancer in general and hormone-related cancers, in particular, with a difference between simple and complex carbohydrates. Glycemic index and glycemic load estimates reflect the effect of dietary carbohydrates on postprandial glucose concentrations. Several studies have investigated the relationship between the dietary glycemic index and glycemic load estimates with the natural course of cancer and, more specifically, hormone-related cancers. High glycemic index and glycemic load diets are associated with cancer development and worse prognosis, partially explained by the adverse effects on insulin metabolism, causing hyperinsulinemia and insulin resistance, and also by inflammation and oxidative stress induction. Herein, we review the existing data on the effect of diets focusing on the glycemic index and glycemic load estimates on hormone-related cancers.

Glycemic Index and Glycemic Load Estimates in the Dietary Approach of Polycystic Ovary Syndrome

Polycystic ovary syndrome is a common endocrine disorder characterized by hormonal imbalances and various metabolic abnormalities linked to insulin resistance via a vicious cycle. Genetic and environmental factors underlie its pathogenesis and evolution. Nutrition, in terms of nutrient composition, dietary patterns, endocrine-disrupting chemicals, and food processing and preparation, has gained significant attention in the pathogenesis and the therapeutic approach of polycystic ovary syndrome. Carbohydrate intake seems to be a critical point in the diet assignment. Glycemic index and glycemic load constitute indexes of the impacts of dietary carbohydrates on postprandial glucose levels. Numerous studies have indicated that a high glycemic index and glycemic load diet may exacerbate insulin resistance, a key feature of the syndrome, and offer a risk for its development and its complications. Conversely, low-glycemic index and low-glycemic load diets seem to improve insulin sensitivity, regulate menstrual cycles, and mitigate the risk of comorbidities associated with polycystic ovary syndrome, such as obesity, alterations in body composition, type 2 diabetes, cardiovascular disease, and quality of life. This comprehensive review aims to explore the relevance of nutrition and more specifically, the association of glycemic index and glycemic load with the various aspects of polycystic ovary syndrome, as well as to assess the potential benefits of manipulating those indexes in the dietary approach for the syndrome.

Dietary Patterns and Practices and Leucocyte Telomere Length: Findings from the UK Biobank

BACKGROUND

Shorter telomere length (TL) is associated with risk of several age-related diseases and decreased life span, but the extent to which dietary patterns and practices associate with TL is uncertain.

OBJECTIVE

This study aimed to investigate the association of dietary patterns and practices and leucocyte TL (LTL).

DESIGN

This was a cross-sectional study.

PARTICIPANTS AND SETTING

Data collected voluntarily from up to 422,797 UK Biobank participants, during 2006-2010.

MAIN OUTCOME MEASURES

LTL was measured as a ratio of the telomere repeat number to a single-copy gene and was loge-transformed and standardized (z-LTL).

STATISTICAL ANALYSES PERFORMED

Adherence a priori to a Mediterranean-style diet was assessed through the MedDietScore. Principal component analysis was used to a posteriori extract the "Meat" and "Prudent" dietary patterns. Additional dietary practices considered were the self-reported adherence to "Vegetarian" diet, "Eating 5-a-day of fruit and vegetables" and "Abstaining from eggs/dairy/wheat/sugar." Associations between quintiles of dietary patterns or adherence to dietary practices with z-LTL were investigated through multivariable linear regression models (adjusted for demographic, lifestyle, and clinical characteristics).

RESULTS

Adherence to the "Mediterranean" and the "Prudent" patterns, was positively associated with LTL, with an effect magnitude in z-LTL of 0.020 SD and 0.014 SD, respectively, for the highest vs the lowest quintile of adherence to the pattern (both P values < 0.05). Conversely, a reversed association between quintile of the "Meat" pattern and LTL was observed, with z-LTL being on average shorter by 0.025 SD (P = 6.12×10-05) for participants in the highest quintile of the pattern compared with the lowest quintile. For adherents to "5-a-day" z-LTL was on average longer by 0.027 SD (P = 5.36×10-09), and for "abstainers," LTL was shorter by 0.016 SD (P = 2.51×10-04). The association of LTL with a vegetarian diet was nonsignificant after adjustment for demographic, lifestyle, and clinical characteristics.

CONCLUSIONS

Several dietary patterns and practices associated with beneficial health effects are significantly associated with longer LTL. However, the magnitude of the association was small, and any clinical relevance is uncertain.

Prediagnostic serum glyceraldehyde-derived advanced glycation end products and mortality among colorectal cancer patients

Glyceraldehyde-derived advanced glycation end products (glycer-AGEs) could contribute to colorectal cancer development and progression due to their pro-oxidative and pro-inflammatory properties. However, the association of glycer-AGEs with mortality after colorectal cancer diagnosis has not been previously investigated. Circulating glycer-AGEs were measured by competitive ELISA. Multivariable Cox proportional hazards models were used to calculate hazard ratios (HRs) and corresponding 95% confidence intervals (CIs) for associations of circulating glycer-AGEs concentrations with CRC-specific and all-cause mortality among 1034 colorectal cancer (CRC) cases identified within the European Prospective Investigation into Cancer and Nutrition (EPIC) study between 1993 and 2013. During a mean of 48 months of follow-up, 529 participants died (409 from CRC). Glycer-AGEs were statistically significantly positively associated with CRC-specific (HRQ5 vs Q1  = 1.53, 95% CI: 1.04-2.25, Ptrend  = .002) and all-cause (HRQ5 vs Q1  = 1.62, 95% CI: 1.16-2.26, Ptrend  < .001) mortality among individuals with CRC. There was suggestion of a stronger association between glycer-AGEs and CRC-specific mortality among patients with distal colon cancer (per SD increment: HRproximal colon  = 1.02, 95% CI: 0.74-1.42; HRdistal colon  = 1.51, 95% CI: 1.20-1.91; Peffect modification  = .02). The highest HR was observed among CRC cases in the highest body mass index (BMI) and glycer-AGEs category relative to lowest BMI and glycer-AGEs category for both CRC-specific (HR = 1.78, 95% CI: 1.02-3.01) and all-cause mortality (HR = 2.15, 95% CI: 1.33-3.47), although no statistically significant effect modification was observed. Our study found that prediagnostic circulating glycer-AGEs are positively associated with CRC-specific and all-cause mortality among individuals with CRC. Further investigations in other populations and stratifying by tumor location and BMI are warranted.

Dietary modulation of advanced glycation end products metabolism on carotid intima-media thickness in type 2 diabetes patients: From the CORDIOPREV study

BACKGROUND

Advanced glycation end products (AGEs) are pro-oxidant and cytotoxic compounds involved in the progression of chronic diseases as cardiovascular disease (CVD) and type 2 diabetes mellitus (T2DM). The total body burden of AGEs also depend of those consume through the diet. Our aim was to analyze whether the reduction of AGE levels, after the consumption of two-healthy diets were associated with a greater decrease of intima-media thickness of both common carotid arteries (IMT-CC) in patients with T2DM and coronary heart disease (CHD).

METHODS

540 CHD patients with T2DM, at baseline, from the CORDIOPREV study, were divided into two groups: (1) Responders, patients whose IMT-CC was reduced or not changed after dietary intervention and (2) Non-responders, patients whose IMT-CC was increased after dietary intervention. A total of 423 completed baseline and the 5-year follow-up carotid ultrasounds were analyzed in this study.

RESULTS

Our data showed that Responders, despite had a higher baseline IMT-CC and serum methylglyoxal (MG) levels than Non-responders, showed a reduction of serum levels of this glycotoxin after dietary intervention. Conversely, in patients whose IMT-CC was increased after dietary intervention (Non-responders), serum MG levels were increased. Moreover, an increase of circulating level of AGEs (and in particular, MG), after dietary intervention, could be considered a risk factor for the progression of atherosclerosis in patients with T2DM and CHD.

CONCLUSION

These results support the importance of identifying underlying mechanisms in the context of secondary prevention of CVD that would provide therapeutic targets to reduce the high risk of cardiovascular events of these patients.

CLINICAL TRIAL REGISTRATION-URL

https://clinicaltrials.gov/ct2/show/NCT00924937. Unique Identifier: NCT00924937.

Linkage between a plant-based diet and age-related eye diseases: a systematic review and meta-analysis

CONTEXT

An increased risk of age-related eye disease has been observed in individuals lacking a balanced diet. Following a plant-based diet may result in nutritional insufficiencies and negatively affect health if an effort is not made to ensure the consumption of fortified foods or specific supplements.

OBJECTIVE

The purpose of this article is to characterize the relationship between plant-based diets and age-related ocular outcomes among adults.

DATA SOURCES

A comprehensive literature review was performed using the MEDLINE, Embase, Cochrane, and PubMed databases up until December 19, 2021.

STUDY SELECTION

Studies that focused on observed visual changes due to a reduced intake of animal products and that included a minimum of 50 eyes were eligible for inclusion.

DATA EXTRACTION

Two levels of screening, quality assessment, and data extraction were conducted by 2 reviewers independently. The 21 studies identified from 814 unique studies progressed to data extraction and 15 were included in the quantitative analysis using STATA 15.0 fixed-effect and random-effect models computed on the basis of heterogeneity.

RESULTS

The 15 (n = 51 695 participants) assessed the impact of fish consumption, 8 studies (n = 28 753 participants) analyzed the effect of red meat intake, and 3 studies (n = 7723 participants) assessed the impact of omission of skim milk, poultry, and non-meat animal products and the presence of disease incidence as indicated by age-related macular degeneration or cataract development. Meta-analysis indicated regular consumption of fish (odds ratio [OR], 0.70; 95%CI, 0.62-0.79) and skim milk, poultry, and non-meat animal products (OR, 0.70; 95%CI, 0.61-0.79) reduced the risk of age-related eye disease development among adults. Consumption of red meat (OR, 1.41; 95%CI, 1.07-1.86) may increase the risk of age-related eye disease development.

CONCLUSION

A pescatarian diet is associated with the most favorable visual outcomes among adults, whereas consumption of red meat negatively affects ocular health. Results suggest a need for more initiatives promoting a healthy and balanced diet.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO registration no. CRD42021269925.

Reactivity of Vitamin E as an Antioxidant in Red Meat and the Stomach Medium

The stomach is a bioreactor and an important intersection of biochemical reactions that affect human health. Lipid peroxidation of meat in the stomach medium generates malondialdehyde (MDA), which is absorbed from the gut into human plasma and modifies low-density lipoprotein (LDL) to MDA-LDL. We found in the stomach medium (pH 3.0) a high antioxidant activity of vitamin E against meat lipid peroxidation, almost 35-fold higher than at pH 6.3. In the stomach medium, the antioxidant activity of vitamin E on meat lipid peroxidation was 20-fold higher than that of catechin. Vitamin E, at pH 3.0, acts synergistically with metmyoglobin (MbFe⁺³), as a peroxidase/antioxidant couple. The synergistic effect of MbFe⁺³/vitamin E was almost 150-fold higher than the antioxidant effect achieved by MbFe⁺³/catechin. The meat antioxidant activity was maintained continuously by addition of a low concentration of vitamin E, catechin, and vitamin C, preventing the propagation of lipid oxidation, reactive aldehyde generation, and the loss of vitamin E.

Involvement of AMP-activated Protein Kinase α/Nuclear Factor (Erythroid-derived 2) Like 2-iniatived Signaling Pathway in Cytoprotective Effects of Wasabi 6-(Methylsulfinyl) Hexyl Isothiocyanate

6-(Methylsulfinyl) hexyl isothiocyanate (6-MSITC) is an active ingredient present in Wasabi, which is a popular pungent spice used in Japanese cuisine. Our previous studies suggested that the primary antioxidant activity of 6-MSITC may link to other biological activity. This study aimed to clarify how the antioxidant activity of 6-MSITC contributes to preventing overloaded lipid stress in hepatic cell model. HepG2 cells were treated with 6-MSITC at defined concentrations and times in normal medium or in combined fatty acids (CFA) medium, and the targeted proteins were detected by Western blotting. The kinetic data revealed that 6-MSITC activated AMP-activated protein kinase α (AMPKα) and nuclear factor (erythroid-derived 2) like 2 (Nrf2), and then enhanced the protein expression of Forkhead box protein O1 (FOXO1) and Sirtuin1 as well as that of the Nrf2 target proteins, NAD(P)H:quinone oxidoreductase 1 (NQO1) and heme oxygenase (HO-1). Furthermore, lipid metabolic stress was mimicked in HepG2 cells by overloading CFA. 6-MSITC significantly alleviated CFA-induced formation of thiobarbituric acid reactive substances and fat accumulation. Signaling analysis data revealed that 6-MSITC enhanced phosphorylation of AMPKα, upregulated the expression of Nrf2, NQO1, heme oxygenase 1, FOXO1, and Siruin1, and downregulated the expression of PPARα. Taken together, our results suggested that the AMPKα/Nrf2-mediated signaling pathways might be involved in the cytoprotective effects of Wasabi 6-MSITC against metabolic lipid stress.

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).

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.

Dietary Intake of Advanced Glycation End Products (AGEs) and Mortality among Individuals with Colorectal Cancer

Advanced glycation end-products (AGEs) may promote oxidative stress and inflammation and have been linked to multiple chronic diseases, including cancer. However, the association of AGEs with mortality after colorectal cancer (CRC) diagnosis has not been previously investigated. Multivariable Cox proportional hazards models were used to calculate hazard ratios and corresponding 95% confidence intervals for associations between dietary intake of AGEs with CRC-specific and all-cause mortality among 5801 participant cases diagnosed with CRC in the European Prospective Investigation into Cancer and Nutrition study between 1993 and 2013. Dietary intakes of AGEs were estimated using country-specific dietary questionnaires, linked to an AGE database, that accounted for food preparation and processing. During a median of 58 months of follow-up, 2421 cases died (1841 from CRC). Individually or combined, dietary intakes of AGEs were not associated with all-cause and CRC-specific mortality among cases. However, there was a suggestion for a positive association between AGEs and all-cause or CRC-specific mortality among CRC cases without type II diabetes (all-cause, Pinteraction = 0.05) and CRC cases with the longest follow-up between recruitment and cancer diagnosis (CRC-specific, Pinteraction = 0.003; all-cause, Pinteraction = 0.01). Our study suggests that pre-diagnostic dietary intakes of AGEs were not associated with CRC-specific or all-cause mortality among CRC patients. Further investigations using biomarkers of AGEs and stratifying by sex, diabetes status, and timing of exposure to AGEs are warranted.

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.

High Dietary Advanced Glycation End Products Impair Mitochondrial and Cognitive Function

BACKGROUND

Advanced glycation end products (AGEs) are an important risk factor for the development of cognitive decline in aging and late-onset neurodegenerative diseases including Alzheimer's disease. However, whether and how dietary AGEs exacerbate cognitive impairment and brain mitochondrial dysfunction in the aging process remains largely unknown.

OBJECTIVE

We investigated the direct effects of dietary AGEs on AGE adducts accumulation, mitochondrial function, and cognitive performance in mice.

METHODS

Mice were fed the AGE+ diet or AGE- diet. We examined levels of AGE adducts in serum and cerebral cortexes by immunodetection and immunohistochemistry, determined levels of reactive oxygen species by biochemical analysis, detected enzyme activity associated with mitochondrial respiratory chain complexes I & IV and ATP levels, and assessed learning and memory ability by Morris Water Maze and nesting behavior.

RESULTS

Levels of AGE adducts (MG-H1 and CEL) were robustly increased in the serum and brain of AGE+ diet fed mice compared to the AGE- group. Furthermore, greatly elevated levels of reactive oxygen species, decreased activities of mitochondrial respiratory chain complexes I & IV, reduced ATP levels, and impaired learning and memory were evident in AGE+ diet fed mice compared to the AGE- group.

CONCLUSION

These results indicate that dietary AGEs are important sources of AGE accumulation in vivo, resulting in mitochondrial dysfunction, impairment of energy metabolism, and subsequent cognitive impairment. Thus, reducing AGEs intake to lower accumulation of AGEs could hold therapeutic potential for the prevention and treatment of AGEs-induced mitochondrial dysfunction linked to cognitive decline.

Dietary intake of advanced glycation endproducts and risk of hepatobiliary cancers: A multinational cohort study

Advanced glycation endproducts (AGEs) may contribute to liver carcinogenesis because of their proinflammatory and prooxidative properties. Diet is a major source of AGEs, but there is sparse human evidence on the role of AGEs intake in liver cancer etiology. We examined the association between dietary AGEs and the risk of hepatobiliary cancers in the European Prospective Investigation into Cancer and Nutrition prospective cohort (n = 450 111). Dietary intake of three AGEs, Nε -[carboxymethyl]lysine (CML), Nε -[1-carboxyethyl]lysine (CEL) and Nδ -[5-hydro-5-methyl-4-imidazolon-2-yl]-ornithine (MG-H1), was estimated using country-specific dietary questionnaires linked to an AGEs database. Cause-specific hazard ratios (HR) and their 95% confidence intervals (CI) for associations between dietary AGEs and risk of hepatocellular carcinoma (HCC), gallbladder and biliary tract cancers were estimated using multivariable Cox proportional hazard regression. After a median follow-up time of 14.9 years, 255 cases of HCC, 100 cases of gallbladder cancer and 173 biliary tract cancers were ascertained. Higher intakes of dietary AGEs were inversely associated with the risk of HCC (per 1 SD increment, HR-CML  = 0.87, 95% CI: 0.76-0.99, HR-CEL  = 0.84, 95% CI: 0.74-0.96 and HR-MH-G1  = 0.84, 95% CI: 0.74-0.97). In contrast, positive associations were observed with risk of gallbladder cancer (per 1 SD, HR-CML  = 1.28, 95% CI: 1.05-1.56, HR-CEL  = 1.17; 95% CI: 0.96-1.40, HR-MH-G1  = 1.27, 95% CI: 1.06-1.54). No associations were observed for cancers of the intra and extrahepatic bile ducts. Our findings suggest that higher intakes of dietary AGEs are inversely associated with the risk of HCC and positively associated with the risk of gallbladder cancer.

Contribution of RAGE axis activation to the association between metabolic syndrome and cancer

Far beyond the compelling proofs supporting that the metabolic syndrome represents a risk factor for diabetes and cardiovascular diseases, a growing body of evidence suggests that it is also a risk factor for different types of cancer. However, the involved molecular mechanisms underlying this association are not fully understood, and they have been mainly focused on the individual contributions of each component of the metabolic syndrome such as obesity, hyperglycemia, and high blood pressure to the development of cancer. The Receptor for Advanced Glycation End-products (RAGE) axis activation has emerged as an important contributor to the pathophysiology of many clinical entities, by fueling a chronic inflammatory milieu, and thus supporting an optimal microenvironment to promote tumor growth and progression. In the present review, we intend to highlight that RAGE axis activation is a crosswise element on the potential mechanistic contributions of some relevant components of metabolic syndrome into the association with cancer.

Perspectives on signaling for biological- and processed food-related advanced glycation end-products and its role in cancer progression

Receptor for advanced glycation end-products (RAGE) is a multifunctional receptor binds a broad spectrum of ligands and mediates responses to cell damage and stress conditions. It also activates programs leading to acute and chronic inflammation and implicated in several pathological diseases, including cancer. In this review, we presented the non-enzymatic reaction of reducing sugar with the amino groups of proteins, lipids, and nucleic acids. This reaction initiates a complex series of rearrangements and dehydrations, and then produces a class of irreversibly cross-linked heterogeneous fluorescent moieties, termed advanced glycation end products (AGEs). There is a growing body of evidence that interaction of processes food-related AGEs with a cell surface receptor RAGE brings out the generation of oxidative stress and subsequently evokes proliferative, angiogenic and inflammatory reactions, thereby being involved in the development and progression of various types of cancers. This review is an insightful assessment of molecular mechanisms through which RAGE signaling contributes to the enhancement and survival of the tumorigenic cell. Here we summarize the procurement of individual ligands of RAGE like amphoterin, calcium-binding proteins, and resultant mediation of RAGE signaling pathway, which partially can elucidate the elevated risk of several cancers. Besides, we summarize many factors or conditions including APE1 (apurinic/apyrimidinic endonuclease 1), retinol mutations, retinoblastoma (Rb), proteinase 3 (PR3) hypoxia and so on through which RAGE signaling presents an establishment of cancerous environment. Additionally, we also reviewed some recent findings that give shreds of evidence for presenting the role of RAGE and its ligands in the advanced stage of cancers.

Dietary Advanced Glycation Endproducts and the Gastrointestinal Tract

The prevalence of inflammatory bowel diseases (IBD) is increasing in the world. The introduction of the Western diet has been suggested as a potential explanation of increased prevalence. The Western diet includes highly processed food products, and often include thermal treatment. During thermal treatment, the Maillard reaction can occur, leading to the formation of dietary advanced glycation endproducts (dAGEs). In this review, different biological effects of dAGEs are discussed, including their digestion, absorption, formation, and degradation in the gastrointestinal tract, with an emphasis on their pro-inflammatory effects. In addition, potential mechanisms in the inflammatory effects of dAGEs are discussed. This review also specifically elaborates on the involvement of the effects of dAGEs in IBD and focuses on evidence regarding the involvement of dAGEs in the symptoms of IBD. Finally, knowledge gaps that still need to be filled are identified.

Reduction in Circulating Advanced Glycation End Products by Mediterranean Diet Is Associated with Increased Likelihood of Type 2 Diabetes Remission in Patients with Coronary Heart Disease: From the Cordioprev Study

SCOPE

It is hypothesized that decreased advanced glycation end products (AGEs) levels could affect type 2 diabetes mellitus (T2DM) remission in newly diagnosed patients through the consumption of two healthy diets.

METHODS AND RESULTS

Patients from CORDIOPREV study, all with previous cardiovascular events, with T2DM at the beginning of the study are included. Patients are randomized to a Mediterranean or a low-fat diet for five years. No different diabetes remission rates are found among diets. Serum methylglioxal (MG) and carboximethyllysine (CML), levels dietary AGE, as well as gene expression of AGER1 and RAGE are measured. Serum MG decreases only after the consumption of the Mediterranean diet. Moreover, a COX regression analysis shows that each SD decrease in the MG, occurring after the Mediterranean diet, increases the probability of T2DM remission with HR:2.56(1.02-6.25) and p = 0.046 and each SD increase in disposition index at baseline increases the probability of remission with HR:1.94(1.32-2.87) and p = 0.001.

CONCLUSIONS

It is demonstrated that the reduction of serum AGEs levels and the modulation of its metabolism, occurring after the consumption of a Mediterranean diet, might be involved in the molecular mechanism underlying the T2DM remission of newly diagnosed patients with coronary heart disease.

Hypoxia-Induced Degenerative Protein Modifications Associated with Aging and Age-Associated Disorders

Aging is an inevitable time-dependent decline of various physiological functions that finally leads to death. Progressive protein damage and aggregation have been proposed as the root cause of imbalance in regulatory processes and risk factors for aging and neurodegenerative diseases. Oxygen is a modulator of aging. The oxygen-deprived conditions (hypoxia) leads to oxidative stress, cellular damage and protein modifications. Despite unambiguous evidence of the critical role of spontaneous non-enzymatic Degenerative Protein Modifications (DPMs) such as oxidation, glycation, carbonylation, carbamylation, and deamidation, that impart deleterious structural and functional protein alterations during aging and age-associated disorders, the mechanism that mediates these modifications is poorly understood. This review summarizes up-to-date information and recent developments that correlate DPMs, aging, hypoxia, and age-associated neurodegenerative diseases. Despite numerous advances in the study of the molecular hallmark of aging, hypoxia, and degenerative protein modifications during aging and age-associated pathologies, a major challenge remains there to dissect the relative contribution of different DPMs in aging (either natural or hypoxia-induced) and age-associated neurodegeneration.

Prooxidant modifications in the cryptome of beef jerky, the deleterious post-digestion composition of processed meat snacks

Snacking has traditionally been associated with consumption of foods rich in fats and carbohydrates. However, new dietary trends switched to consumption of protein-rich foods. This study investigates the impact of food processing on the cryptome of one of the most widely consumed meat snacks, beef jerky. We have performed discovery-driven proteome-wide analyses, which identified a significantly elevated presence of reactive prooxidant post-translational modifications in jerky. We also found that these protein decorations impact an important subset of in-silico predicted DNA binding cryptides. Furthermore, we observed cell-dependent reduction in cell viability after prolonged treatments with endogenous-like jerky digests. Collectively these findings uncover the presence of prooxidant modifications in processed dried beef snacks and associate their presence with cytotoxicity. Thus, the findings reported here can pave the way for future studies aimed to establish appropriate dietary recommendations on snacking trends.

Implications and Future Perspectives of AGEs in PCOS Pathophysiology

Human, animal, and in vitro studies provide evidence that advanced glycation end-products (AGEs) may contribute to the pathogenesis of polycystic ovary syndrome (PCOS) and its metabolic and reproductive consequences. AGEs are able to induce, via activation of key intracellular signaling pathways, the generation of oxidative stress and proinflammatory cytokines, thus contributing to the adverse health impact of PCOS. This review presents the implications of AGEs in several disease pathophysiologies, including PCOS, as well as the cellular and systemic effects of AGEs on insulin resistance (IR), hyperandrogenemia, endoplasmic reticulum (ER) stress, hypoxia, and ovarian function. The gaps in our knowledge will serve as launching pad for future developments ranging from dietary and lifestyle changes to pharmaceutical interventions aiming at potential applications in women with PCOS.

Dietary Advanced Glycation Endproducts Induce an Inflammatory Response in Human Macrophages in Vitro

Advanced glycation endproducts (AGEs) can be found in protein- and sugar-rich food products processed at high temperatures, which make up a vast amount of the Western diet. The effect of AGE-rich food products on human health is not yet clear and controversy still exists due to possible contamination of samples with endotoxin and the use of endogenous formed AGEs. AGEs occur in food products, both as protein-bound and individual molecules. Which form exactly induces a pro-inflammatory effect is also unknown. In this study, we exposed human macrophage-like cells to dietary AGEs, both in a protein matrix and individual AGEs. It was ensured that all samples did not contain endotoxin concentrations > 0.06 EU/mL. The dietary AGEs induced TNF-alpha secretion of human macrophage-like cells. This effect was decreased by the addition of N(ε)-carboxymethyllysine (CML)-antibodies or a receptor for advanced glycation endproducts (RAGE) antagonist. None of the individual AGEs induce any TNF-alpha, indicating that AGEs should be bound to proteins to exert an inflammatory reaction. These findings show that dietary AGEs directly stimulate the inflammatory response of human innate immune cells and help us define the risk of regular consumption of AGE-rich food products on human health.

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

AIM

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

METHODS

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

RESULTS

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

CONCLUSION

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

Role of advanced glycation end products in mobility and considerations in possible dietary and nutritional intervention strategies

Advanced glycation end products (AGEs), a group of compounds that are formed by non-enzymatic reactions between carbonyl groups of reducing sugars and free amino groups of proteins, lipids or nucleic acids, can be obtained exogenously from diet or formed endogenously within the body. AGEs accumulate intracellularly and extracellularly in all tissues and body fluids and can cross-link with other proteins and thus affect their normal functions. Furthermore, AGEs can interact with specific cell surface receptors and hence alter cell intracellular signaling, gene expression, the production of reactive oxygen species and the activation of several inflammatory pathways. High levels of AGEs in diet as well as in tissues and the circulation are pathogenic to a wide range of diseases. With respect to mobility, AGEs accumulate in bones, joints and skeletal muscles, playing important roles in the development of osteoporosis, osteoarthritis, and sarcopenia with aging. This report covered the related pathological mechanisms and the potential pharmaceutical and dietary intervention strategies in reducing systemic AGEs. More prospective studies are needed to determine whether elevated serum AGEs and/or skin autofluorescence predict a decline in measures of mobility. In addition, human intervention studies are required to investigate the beneficial effects of exogenous AGEs inhibitors on mobility outcomes.

Complexity of Advanced Glycation End Products in Foods: Where Are We Now?

Recent clinical trials indicate that consumption of dietary advanced glycation end products (AGEs) may promote the development of major chronic diseases. However, the outcomes of human studies have proven inconclusive as a result of estimates of the total AGE intake being taken with a single AGE in most of the studies. In this perspective, we summarized the major types of AGEs derived from proteins, nucleic acids, and phospholipids during food processing and suggested a panel of AGEs as markers to better measure the intake of total dietary AGEs in human studies.

Dietary Advanced Glycosylation End-Products (dAGEs) and Melanoidins Formed through the Maillard Reaction: Physiological Consequences of their Intake

The main purpose of this review is to clarify whether the consumption of food rich in melanoidins and dietary advanced glycosylation end-products (dAGEs) is harmful or beneficial for human health. There are conflicting results on their harmful effects in the literature, partly due to a methodological issue in how dAGEs are determined in food. Melanoidins have positive functions particularly within the gastrointestinal tract, whereas the intake of dAGEs has controversial physiological consequences. Most of the in vivo intervention trials were done comparing boiled versus roasted diet (low and high dAGE, respectively). However, these studies can be biased by different lipid oxidation and by different calorie density of foods in the two conditions. The attraction that humans have to cooked foods is linked to the benefits they have had during mankind's evolution. The goal for food technologists is to design low-energy-dense products that can satisfy humans' attraction to rewarding cooked foods.

The AGE-RAGE Axis: Implications for Age-Associated Arterial Diseases

The process of advanced glycation leads to the generation and accumulation of an heterogeneous class of molecules called advanced glycation endproducts, or AGEs. AGEs are produced to accelerated degrees in disorders such as diabetes, renal failure, inflammation, neurodegeneration, and in aging. Further, AGEs are present in foods and in tobacco products. Hence, through both endogenous production and exogenous consumption, AGEs perturb vascular homeostasis by a number of means; in the first case, AGEs can cause cross-linking of long-lived molecules in the basement membranes such as collagens, thereby leading to “vascular stiffening” and processes that lead to hyperpermeability and loss of structural integrity. Second, AGEs interaction with their major cell surface signal transduction receptor for AGE or RAGE sets off a cascade of events leading to modulation of gene expression and loss of vascular and tissue homeostasis, processes that contribute to cardiovascular disease. In addition, it has been shown that an enzyme, which plays key roles in the detoxification of pre-AGE species, glyoxalase 1 (GLO1), is reduced in aged and diabetic tissues. In the diabetic kidney devoid of Ager (gene encoding RAGE), higher levels of Glo1 mRNA and GLO1 protein and activity were observed, suggesting that in conditions of high AGE accumulation, natural defenses may be mitigated, at least in part through RAGE. AGEs are a marker of arterial aging and may be detected by both biochemical means, as well as measurement of “skin autofluorescence.” In this review, we will detail the pathobiology of the AGE-RAGE axis and the consequences of its activation in the vasculature and conclude with potential avenues for therapeutic interruption of the AGE-RAGE ligand-RAGE pathways as means to forestall the deleterious consequences of AGE accumulation and signaling via RAGE.

Probing Protein Glycation by Chromatography and Mass Spectrometry: Analysis of Glycation Adducts

Glycation is a non-enzymatic post-translational modification of proteins, formed by the reaction of reducing sugars and α-dicarbonyl products of their degradation with amino and guanidino groups of proteins. Resulted early glycation products are readily involved in further transformation, yielding a heterogeneous group of advanced glycation end products (AGEs). Their formation is associated with ageing, metabolic diseases, and thermal processing of foods. Therefore, individual glycation adducts are often considered as the markers of related pathologies and food quality. In this context, their quantification in biological and food matrices is required for diagnostics and establishment of food preparation technologies. For this, exhaustive protein hydrolysis with subsequent amino acid analysis is the strategy of choice. Thereby, multi-step enzymatic digestion procedures ensure good recoveries for the most of AGEs, whereas tandem mass spectrometry (MS/MS) in the multiple reaction monitoring (MRM) mode with stable isotope dilution or standard addition represents “a gold standard” for their quantification. Although the spectrum of quantitatively assessed AGE structures is continuously increases, application of untargeted profiling techniques for identification of new products is desired, especially for in vivo characterization of anti-glycative systems. Thereby, due to a high glycative potential of plant metabolites, more attention needs to be paid on plant-derived AGEs.

Comparative evaluation of three different ELISA assays and HPLC-ESI-ITMS/MS for the analysis of Nε-carboxymethyl lysine in food samples

N^ε-carboxymethyl-lysine (CML) is measured in food, but there is a controversy concerning the most convenient yet reliable method(s) for this task. This work compares three different ELISA assays and HPLC-ESI-ITMS/MS for the analysis of CML in several food items. The four methods showed the same decreasing order of CML concentration: beef, bacon>chicken > fish>dairy products>grain products>fruits/vegetables. HPLC-ESI-ITMS/MS results highly correlated with those obtained by ELISA performed with monoclonal CML-antibody (β=0.98, p<0.0001) whereas My Bio Source® kit results were not correlated with those provided by Lamider®. Small differences of CML concentrations in food items prepared by different culinary treatment were clearly distinguished by HPLC-ESI-ITMS/MS, but could not always be detected by ELISA. This work demonstrates a reasonable relationship between CM determined by ELISA and HPLC-ESI-ITMS/MS and therefore supports the implementation of ELISA in food CML/AGEs screening.

Advanced Glycation End Products and Risks for Chronic Diseases: Intervening Through Lifestyle Modification

Advanced glycation end products (AGEs) are a family of compounds of diverse chemical nature that are the products of nonenzymatic reactions between reducing sugars and proteins, lipids, or nucleic acids. AGEs bind to one or more of their multiple receptors (RAGE) found on a variety of cell types and elicit an array of biologic responses. In this review, we have summarized the data on the nature of AGEs and issues associated with their measurements, their receptors, and changes in their expression under different physiologic and disease states. Last, we have used this information to prescribe lifestyle choices to modulate AGE-RAGE cycle for better health.

Dietary fat quantity and quality modifies advanced glycation end products metabolism in patients with metabolic syndrome

SCOPE

Advanced glycation end products (AGEs) increase in dysmetabolic conditions. Lifestyle, including diet, has shown be effective in preventing the development of metabolic syndrome (MetS). We investigated whether AGE metabolism is affected by diets with different fat quantity and quality in MetS patients.

METHODS AND RESULTS

A randomized, controlled trial assigned 75 MetS patients to one of four diets: high SFA (HSFA), high MUFA (HMUFA), and two low-fat, high-complex carbohydrate diets (LFHCC) supplemented with long-chain n-3 PUFA or placebo for 12-weeks each. Dietary and serum AGE [methylglyoxal (MG: lysine-MG-H1) and N-carboxymethyllysine] levels and gene expression related to AGE metabolism in peripheral blood mononuclear cells (AGER1, RAGE, GloxI, and Sirt1 mRNA) were determined. HMUFA diet reduced serum AGE (sAGE) and RAGE mRNA, increased AGER1 and GloxI mRNA levels compared to the other diets. LFHCC n-3 diet reduced sAGE levels and increased AGER1 mRNA levels compared to LFHCC and HSFA diets. Multiple regression analyses showed that sMG and AGER1 mRNA appeared as significant predictors of oxidative stress/inflammation-related parameters.

CONCLUSIONS

Low AGE content in HMUFA diet reduces sAGEs and modulates the gene expression related to AGE metabolism in MetS patients, which may be used as a therapeutic approach to reduce the incidence of MetS and related chronic diseases.

Advanced Glycation End Products, Inflammation, and Chronic Metabolic Diseases: Links in a Chain?

Advanced glycation end products (AGEs) are a diverse group of compounds produced when reducing sugars react with proteins or other compounds to form glycosylated molecules. AGEs may form endogenously, and glycation of molecules may negatively affect their function. AGEs may also be consumed in food form with dietary AGEs reported to be particularly high in foods treated with high heat: baked, broiled, grilled, and fried foods. Whether dietary AGEs are absorbed in significant quantities and whether they are harmful if absorbed is a question under current debate. The American Diabetes Association makes no recommendation regarding avoidance of these foods, but many researchers are concerned that they may be pro-inflammatory and way worsen cardiac function, kidney function, diabetes and its complications and may even contribute to obesity.

Skin advanced glycation end-products evaluation in infants according to the type of feeding and mother's smoking habits

OBJECTIVES

This study was conducted to assess whether formula-fed infants had increased skin advanced glycation end-products compared with breastfed ones. We also evaluated the effect of maternal smoke during pregnancy and lactation on infant skin advanced glycation end-products accumulation.

METHODS

Advanced glycation end-product-linked skin autofluorescence was measured in 101 infants.

RESULTS

In infants born from non-smoking mothers, advanced glycation end-products were higher in formula-fed subjects than in breastfed subjects (0.80 (0.65-0.90) vs 1.00 (0.85-1.05), p < 0.001). Advanced glycation end-products in breastfed infants from smoking mothers were higher than in those from non-smoking mothers (0.80 (0.65-0.90) vs 1.00 (0.90-1.17), p = 0.009).

CONCLUSION

Formula-fed infants had increased amounts of advanced glycation end-products compared with the breastfed ones, confirming that breast milk represents the best food for infants. Breastfed infants from mothers smoking during pregnancy and lactation had increased skin advanced glycation end-products, suggesting that smoke-related advanced glycation end-products transfer throughout breast milk. Moreover, advanced glycation end-products may already increase during gestation, possibly affecting fetal development. Thus, we reinforced that smoking must be stopped during pregnancy and lactation.

Processed Meat, but Not Unprocessed Red Meat, Is Inversely Associated with Leukocyte Telomere Length in the Strong Heart Family Study

BACKGROUND

Telomeres are repetitive nucleotide sequences (TTAGGG) and their associated proteins at the end of eukaryote chromosomes. Telomere length shortens throughout the lifespan with each cell division, and leukocyte telomere length (LTL) is often used as a biomarker of cellular aging. LTL is related to many chronic diseases, including cardiovascular disease and diabetes. However, to our knowledge, the relation between LTL and risk factors for cardiovascular disease and diabetes, such as dietary intake of processed meat and unprocessed red meat, is largely unknown.

OBJECTIVE

We examined the associations of processed meat intake and unprocessed red meat intake with LTL.

METHODS

This cross-sectional study comprised 2846 American Indians from the Strong Heart Family Study who participated in the 2001-2003 examination. Dietary factors, including past-year consumption of processed meat and unprocessed red meat, were assessed with the use of a 119-item Block Food-Frequency Questionnaire. LTL was measured with the use of quantitative polymerase chain reaction. Generalized estimating equations were used to examine the associations of intake of processed meat and unprocessed red meat with LTL.

RESULTS

Consumption of processed meat was negatively associated with LTL after adjustment for age, sex, site, education, smoking, alcohol use, physical activity, and other dietary factors. For every additional daily serving of processed meat, LTL was 0.021 units (telomeric product-to-single-copy gene ratio) shorter (β ± SE = -0.021 ± 0.008, P = 0.009). No association was observed between the intake of unprocessed red meat and LTL (β ± SE = 0.008 ± 0.011, P = 0.46).

CONCLUSIONS

In the Strong Heart Family Study, consumption of processed meat, but not unprocessed red meat, was associated with shorter LTL, a potential mediator for several age-related diseases. Further studies are needed to better understand the biological mechanism by which processed meat intake influences cellular aging.

Oral AGE restriction ameliorates insulin resistance in obese individuals with the metabolic syndrome: a randomised controlled trial

AIMS/HYPOTHESIS

We previously reported that obese individuals with the metabolic syndrome (at risk), compared with obese individuals without the metabolic syndrome (healthy obese), have elevated serum AGEs that strongly correlate with insulin resistance, oxidative stress and inflammation. We hypothesised that a diet low in AGEs (L-AGE) would improve components of the metabolic syndrome in obese individuals, confirming high AGEs as a new risk factor for the metabolic syndrome.

METHODS

A randomised 1 year trial was conducted in obese individuals with the metabolic syndrome in two parallel groups: L-AGE diet vs a regular diet, habitually high in AGEs (Reg-AGE). Participants were allocated to each group by randomisation using random permuted blocks. At baseline and at the end of the trial, we obtained anthropometric variables, blood and urine samples, and performed OGTTs and MRI measurements of visceral and subcutaneous abdominal tissue and carotid artery. Only investigators involved in laboratory determinations were blinded to dietary assignment. Effects on insulin resistance (HOMA-IR) were the primary outcome.

RESULTS

Sixty-one individuals were randomised to a Reg-AGE diet and 77 to an L-AGE diet; the data of 49 and 51, respectively, were analysed at the study end in 2014. The L-AGE diet markedly improved insulin resistance; modestly decreased body weight; lowered AGEs, oxidative stress and inflammation; and enhanced the protective factors sirtuin 1, AGE receptor 1 and glyoxalase I. The Reg-AGE diet raised AGEs and markers of insulin resistance, oxidative stress and inflammation. There were no effects on MRI-assessed measurements. No side effects from the intervention were identified. HOMA-IR came down from 3.1 ± 1.8 to 1.9 ± 1.3 (p < 0.001) in the L-AGE group, while it increased from 2.9 ± 1.2 to 3.6 ± 1.7 (p < 0.002) in the Reg-AGE group.

CONCLUSIONS/INTERPRETATION

L-AGE ameliorates insulin resistance in obese people with the metabolic syndrome, and may reduce the risk of type 2 diabetes, without necessitating a major reduction in adiposity. Elevated serum AGEs may be used to diagnose and treat 'at-risk' obesity.

TRIAL REGISTRATION

ClinicalTrials.gov NCT01363141 FUNDING: The study was funded by the National Institute of Diabetes and Digestive and Kidney Diseases (DK091231).

Carboxymethyl lysine, an advanced glycation end product, and incident diabetes: a case-cohort analysis of the ARIC Study

AIMS

To verify whether elevated fasting levels of circulating carboxymethyl lysine (CML), an advanced glycation end product, predict the development of diabetes in middle-age adults.

METHODS

Using a stratified case-cohort design, we followed 543 middle-aged individuals who developed diabetes and 514 who did not over a median 9 years in the Atherosclerosis Risk in Communities Study. Weighted Cox proportional hazards analyses were used to account for the design.

RESULTS

In weighted analyses, correlation between CML levels and anthropometric, inflammatory or metabolic variables was minimal (Pearson correlations usually < 0.10). CML, when modelled as a continuous variable and after adjustment for age, sex, race, centre, parental history of diabetes, BMI, waist-to-hip ratio, non-esterified fatty acids, oxidized LDL-cholesterol, GFR, smoking, an inflammation score, adiponectin, leptin, insulin and glucose levels, was associated with an increased risk of diabetes [Hazard ratio (HR) = 1.35; 95% confidence interval (CI) 1.09-1.67, for each 100 ng/ml CML increment]. Baseline glucose level and race each modified the association (P < 0.05 for interaction), which was present only among those with impaired fasting glucose (≥ 5.6 mmol/l, HR = 1.61, 95% CI 1.26-2.05) and among white participants (HR = 1.50, 95% CI 1.13-1.99).

CONCLUSIONS

Elevated fasting CML, after adjustment for multiple risk factors for diabetes, predicts the development of incident diabetes, the association being present among those with impaired fasting glucose and in white participants. These prospective findings suggest that advanced glycation end products might play a role in the development of diabetes.