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

Effect of dietary intake of advanced glycation end products on biomarkers of type 2 diabetes: a systematic review and meta-analysis

Thermal treatment of food may undergo Maillard reactions and produce harmful substances, e.g., advanced glycation end products (AGEs). Current studies show different results about the effects of dietary AGE intake on the biomarkers of type 2 diabetes mellitus (T2DM). Therefore, this work conducted a systematic review and meta-analysis to explore the effect of dietary AGE intake on the biomarkers of T2DM, the available evidence, and the bias of this evidence. This meta-analysis focused on the association between high AGE intake and fasting plasma glucose, fasting plasma insulin, HbA1c, and HOMA-IR. Thirteen parallel studies and 4 randomized crossover studies were finally included. In the pooled analysis, fasting glucose (SMD: 0.98; 95% CI: 0.23, 1.73; p = .011), fasting insulin (SMD: 1.44; 95% CI: 0.63, 2.25; p < .01), and HOMA-IR (SMD: 1.47; 95% CI: 0.59, 2.34; p < .01) significantly increased after dietary intake with high AGEs. In the subgroup analyses, high-AGE diets and healthy participants were associated with changes in the biomarkers of T2DM. Taken together, the intake of high dietary AGE was related to the development of T2DM.

Thermal treatment under oxidative conditions increases the antioxidant and antiglycation activity of Chilean Tórtola beans (Phaseolus vulgaris)

The influence of oxygen on the thermal treatment (TT) of secondary metabolite-enriched extracts (SMEEs) from Tórtola beans and procyanidin C1 (PC1) on the inhibition of advanced glycation end products (AGEs) generation in proteins was investigated. SMEE was incubated at 4 °C (control) or thermally treated at 60 °C for 2 h, at either 0 % O2 (I) or 20 % O2 (II). Treatments I and II increased the content of procyanidin dimers B2. Treatment II was more effective than the control or treatment I in preventing homocysteine oxidation and AGEs generation. TT of PC1 at 0 % or 20 % O2 generated procyanidin dimers and tetramers. PC1 TT at 20 % O2 exhibited higher oxidation potentials and lower IC50 values of fluorescent AGEs than those of controls or TT at 0 % O2. These findings indicate that SMEE from Tórtola beans after treatment II changes the degree of polymerization and oxidation procyanidins, thereby increasing their antiglycation activity.

Dietary advanced glycation end-products and their associations with body weight on a Mediterranean diet and low-fat vegan diet: a randomized, cross-over trial

Objective

Evidence suggests that changes in dietary advanced glycation end-products (AGEs) may influence body weight, but the effects of different dietary patterns remain to be explored.The aim of this study was to compare the effects of a Mediterranean and a low-fat vegan diet on dietary AGEs and test their association with body weight.

Materials and methods

In this randomized cross-over trial, 62 overweight adults were assigned to a Mediterranean or a low-fat vegan diet for 16-week periods in random order, separated by a 4-week washout. Body weight was the primary outcome. Three-day diet records were analyzed using the Nutrition Data System for Research software and dietary AGEs were estimated, using an established database. Statistical approaches appropriate for crossover trials were implemented.

Results

Dietary AGEs decreased by 73%, that is, by 9,413 kilounits AGE/day (95% -10,869 to -7,957); p < 0.001, compared with no change on the Mediterranean diet (treatment effect -10,303 kilounits AGE/day [95% CI -13,090 to -7,516]; p < 0.001). The participants lost 6.0 kg on average on the vegan diet, compared with no change on the Mediterranean diet (treatment effect -6.0 kg [95% CI -7.5 to -4.5]; p < 0.001). Changes in dietary AGEs correlated with changes in body weight (r = +0.47; p < 0.001) and remained significant after adjustment for total energy intake (r = +0.39; p = 0.003).

Conclusion

Dietary AGEs did not change on the Mediterranean diet but decreased on a low-fat vegan diet, and this decrease was associated with changes in body weight, independent of energy intake.

Clinical trial registration

https://clinicaltrials.gov/, identifier NCT03698955.

An Intensive Culinary Intervention Programme to Promote Healthy Ageing: The SUKALMENA-InAge Feasibility Pilot Study

Dietary interventions are a key strategy to promote healthy ageing. Cooking skills training emerges as a promising approach to acquiring and maintaining healthy eating habits. The purpose was to evaluate the effectiveness of a culinary programme to improve healthy eating habits among overweight/obese adults (55-70 years old). A total of 62 volunteers were randomly (1:1) assigned to an culinary intervention group (CIG) or a nutritional intervention group (NIG). Dietary, cooking, and health-related outcomes, including body advanced glycation end product (AGE) levels, were evaluated at baseline and after four weeks. Mixed-effects linear models were used to assess the effects of the interventions within and between groups. Among the 56 participants who completed the trial, CIG participants achieved a significant improvement in Mediterranean diet adherence (1.2; 95%CI, 0.2 to 2.2) and a reduction in the use of culinary techniques associated with a higher AGE formation in foods (-2.8; 95%CI, -5.6 to -0.2), weight (-1.5; 95%CI, -2.5 to -0.5), body mass index (-0.5; 95%CI, -0.8 to -0.2), waist circumference (-1.4; 95%CI, -2.6 to -0.2), and hip circumference (-1.4; 95%CI, -2.4 to -0.4) compared with the NIG participants. Although a greater confidence in cooking in the CIG was found, attitudes and cooking habits did not improve. No significant differences in biochemical parameters or AGEs were found between groups. In conclusion, a culinary intervention could be successful in promoting healthy eating and cooking habits compared to a programme based on nutrition education alone. Nevertheless, further efforts are needed to strengthen attitudes and beliefs about home cooking, to address potential barriers and understand the impact of cooking interventions on biological parameters. Larger studies with longer follow-ups are needed to evaluate the relationship between cooking, diet, and health.

Consumption of red and processed meat during early pregnancy and risk of gestational diabetes: a prospective birth cohort study

To investigate the association of red and processed meat intake with the risk of gestational diabetes (GDM) in Iranian mothers. A total of 635 pregnant mothers were included. Dietary intake was assessed by a 90-item food frequency questionnaire during the first trimester of pregnancy. Intakes of total red meat, unprocessed red meat, and processed meat were calculated and then, Cox proportional hazard model was used to calculate the hazard ratios (HR) and 95%CIs of GDM across tertiles of red meat intake while controlling for age, occupation, pre-pregnancy body mass index, physical activities, history of cardiovascular disease, hypertension, hypothyroidism, hyperthyroidism, and pregnancy hypertension, order of pregnancy, nausea during current pregnancy, multivitamin use during current pregnancy, weight gain during current pregnancy and total energy intake. The average age of the mothers was 28.80 ± 5.09 years, the average pre-pregnancy body mass index was 25.13 ± 4.43 kg/m2, and the average weight gain during pregnancy was 13.50 ± 5.03 kg. The multivariable-adjusted HRs of GDM for the third tertiles of red and processed meat, red meat, and processed meat intake were, respectively, 1.92 (95% CI 1.06, 3.49), 1.52 (95% CI 0.85, 2.72) and 1.31 (95% CI 0.73, 2.34) when compared to the first tertiles. Our prospective cohort study suggested that there was a positive association between the consumption of red and processed meat and with risk of GDM in a small sample of Iranian mothers with low red meat intake. More large-scale cohort studies in the Iranian population are needed to present more robust evidence in this regard.

Evaluation of the effects of dietary advanced glycation end products on inflammation

Advanced glycation end products (AGEs) are a large number of heterogeneous compounds formed by the glycation of proteins, fats or nucleic acids. Endogenous AGEs have been associated with various health problems such as obesity, type 2 diabetes mellitus and cardiovascular disease. Inflammation is thought to be one of the main mechanisms in the development of these disorders. Although AGEs are produced endogenously in the body, exogenous sources such as smoking and diet also contribute to the body pool. Therefore, when the AGE pool in the body rises above physiological levels, different pathological conditions may occur through various mechanisms, especially inflammation. While the effects of endogenous AGEs on the development of inflammation have been studied relatively extensively, and current evidence indicates that dietary AGEs (dAGEs) contribute to the body's AGE pool, it is not yet known whether dAGEs have the same effect on the development of inflammation as endogenous AGEs. Therefore, this review aimed to evaluate the results of cross-sectional and intervention studies to understand whether dAGEs are associated with inflammation and, if there is an effect on inflammation, through which mechanisms this effect might occur.

Associations of dietary advanced glycation end products with liver steatosis via vibration controlled transient elastography in the United States: a nationwide cross-sectional study

PURPOSE

Large population-based studies for the associations between dietary advanced glycation end products (dAGEs) intake and liver steatosis remain lacking. It is necessary to clarify the relationship of dAGEsintake with liver steatosis through the National Health and Nutrition Survey (NHANES).

METHODS

A total of 5856 participants in the NHANES 2017-2018 were included. The dietary AGEs intake, including ε-(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. Liver steatosis was assessed by controlled attenuation parameter via transient elastography. Logistic regression model was adopted to explore the relationships between dAGEs intake and hepatic steatosis.

RESULTS

Compared with individuals of total dAGEs, CML, MG-H1 in the lowest tertile, those in the highest tertile had highest risk of hepatic steatosis, and the corresponding odds radios(ORs) (95% confidence interval(CI)) were 1.37 (1.01, 1.84), 1.36 (1.04,1.78) and 1.40 (1.06, 1.85), respectively. Subgroups analysis found that the positive association between dAGEs, CML, CEL and MG-H1 and hepatic steatosis appeared stronger in subjects with obesity and those with abnormal waist circumference (WC).

CONCLUSION

There was a positive correlation between dAGEs, CML, MG-H1, and hepatic steatosis, and this association mainly existed in subjects with obesity and those with abnormal WC. Dietary AGEs restriction might be of high priority for subjects with obesity for the prevention of fatty liver disease. Further longitudinal studies are required to confirm the causal associations and explore the potential mechanisms.

Dietary and serum advanced glycation end-products and clinical outcomes in breast cancer

One in five women with breast cancer will relapse despite ideal treatment. Body weight and physical activity are strongly associated with recurrence risk, thus lifestyle modification is an attractive strategy to improve prognosis. Trials of dietary modification in breast cancer are promising but the role of specific diets is unclear, as is whether high-quality diet without weight loss can impact prognosis. Advanced glycation end-products (AGEs) are compounds produced in the body during sugar metabolism. Exogenous AGEs, such as those found in food, combined with endogenous AGEs, make up the total body AGE load. AGEs deposit in tissues over time impacting cell signaling pathways and altering protein functions. AGEs can be measured or estimated in the diet and measured in blood through their metabolites. Studies demonstrate an association between AGEs and breast cancer risk and prognosis. Here, we review the clinical data on dietary and serum AGEs in breast cancer.

Causal associations between dietary habits and CVD: a Mendelian randomisation study

Over the years, numerous observational studies have substantiated that various dietary choices have opposing effects on CVD. However, the causal effect has not yet been established. Thus, we conducted a Mendelian randomisation (MR) analysis to reveal the causal impact of dietary habits on CVD. Genetic variants strongly associated with 20 dietary habits were selected from publicly available genome-wide association studies conducted on the UK Biobank cohort (n 449 210). Summary-level data on CVD were obtained from different consortia (n 159 836-977 323). The inverse-variance weighted method (IVW) was the primary outcome, while MR-Egger, weighted median and MR Pleiotropy RESidual Sum and Outlier were used to assess heterogeneity and pleiotropy. We found compelling evidence of a protective causal effect of genetic predisposition towards cheese consumption on myocardial infarction (IVW OR = 0·67; 95 % CI = 0·544, 0·826; P = 1·784 × 10-4) and heart failure (IVW OR = 0·646; 95 % CI = 0·513, 0·814; P = 2·135 × 10-4). Poultry intake was found to be a detrimental factor for hypertension (IVW OR = 4·306; 95 % CI = 2·158, 8·589; P = 3·416 × 10-5), while dried fruit intake was protective against hypertension (IVW OR = 0·473; 95 % CI = 0·348, 0·642; P = 1·683 × 10-6). Importantly, no evidence of pleiotropy was detected. MR estimates provide robust evidence for a causal relationship between genetic predisposition to 20 dietary habits and CVD risk, suggesting that well-planned diets may help prevent and reduce the risk of CVD.

Dietary Advanced Glycation End Products: Their Role in the Insulin Resistance of Aging

Insulin resistance (IR) is commonly observed during aging and is at the root of many of the chronic nontransmissible diseases experienced as people grow older. Many factors may play a role in causing IR, but diet is undoubtedly an important one. Whether it is total caloric intake or specific components of the diet, the factors responsible remain to be confirmed. Of the many dietary influences that may play a role in aging-related decreased insulin sensitivity, advanced glycation end products (AGEs) appear particularly important. Herein, we have reviewed in detail in vitro, animal, and human evidence linking dietary AGEs contributing to the bodily burden of AGEs with the development of IR. We conclude that numerous small clinical trials assessing the effect of dietary AGE intake in combination with strong evidence in many animal studies strongly suggest that reducing dietary AGE intake is associated with improved IR in a variety of disease conditions. Reducing AGE content of common foods by simple changes in culinary techniques is a feasible, safe, and easily applicable intervention in both health and disease. Large-scale clinical trials are still needed to provide broader evidence for the deleterious role of dietary AGEs in chronic disease.

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.

Blood and Tissue Advanced Glycation End Products as Determinants of Cardiometabolic Disorders Focusing on Human Studies

Cardiometabolic disorders are characterised by a cluster of interactive risk determinants such as increases in blood glucose, lipids and body weight, as well as elevated inflammation and oxidative stress and gut microbiome changes. These disorders are associated with onset of type 2 diabetes mellitus (T2DM) and cardiovascular disease (CVD). T2DM is strongly associated with CVD. Dietary advanced glycation end products (dAGEs) attributable from modern diets high in sugar and/or fat, highly processed foods and high heat-treated foods can contribute to metabolic etiologies of cardiometabolic disorders. This mini review aims to determine whether blood dAGEs levels and tissue dAGEs levels are determinants of the prevalence of cardiometabolic disorders through recent human studies. ELISA (enzyme-linked immunosorbent assay), high-performance liquid chromatography (HPLC), liquid chromatography-mass spectrometry (LC-MS) and gas chromatography-mass spectrometry (GC-MS) for blood dAGEs measurement and skin auto fluorescence (SAF) for skin AGEs measurement can be used. Recent human studies support that a diet high in AGEs can negatively influence glucose control, body weight, blood lipid levels and vascular health through the elevated oxidative stress, inflammation, blood pressure and endothelial dysfunction compared with a diet low in AGEs. Limited human studies suggested a diet high in AGEs could negatively alter gut microbiota. SAF could be considered as one of the predictors affecting risks for cardiometabolic disorders. More intervention studies are needed to determine how dAGEs are associated with the prevalence of cardiometabolic disorders through gut microbiota changes. Further human studies are conducted to find the association between CVD events, CVD mortality and total mortality through SAF measurement, and a consensus on whether tissue dAGEs act as a predictor of CVD is required.

Sex-specificities in offspring neurodevelopment and behaviour upon maternal glycation: Putative underlying neurometabolic and synaptic changes

AIM

Lactation is an important programming window for metabolic disease and neuronal alterations later in life. We aimed to study the effect of maternal glycation during lactation on offspring neurodevelopment and behaviour, assessing possible sex differences and underpinning molecular players.

METHODS

Female Wistar rats were treated with the Glyoxalase-1 inhibitor S-p-Bromobenzylguthione cyclopentyl diester (BBGC 5 mg/kg). A control and vehicle group treated with dimethyl sulfoxide were considered. Male and female offspring were tested at infancy for neurodevelopment hallmarks. After weaning, triglycerides and total antioxidant capacity were measured in breast milk. At adolescence, offspring were tested for locomotor ability, anxious-like behaviour, and recognition memory. Metabolic parameters were assessed, and the hippocampus and prefrontal cortex were collected for molecular analysis.

KEY FINDINGS

Maternal glycation reduced triglycerides and total antioxidant capacity levels in breast milk. At infancy, both male and female offspring presented an anticipation on the achievement of neurodevelopmental milestones. At adolescence, male offspring exposed to maternal glycation presented hyperlocomotion, whereas offspring of both sexes presented a risk-taking phenotype, accompanied by GABA_A receptor upregulation in the hippocampus. Females also demonstrated GABA_A and PSD-95 changes in prefrontal cortex. Furthermore, lower levels of GLO1 and consequently higher accumulation of AGES were also observed in both male and female offspring hippocampus.

SIGNIFICANCE

Early exposure to maternal glycation induces changes in milk composition leading to neurodevelopment changes at infancy, and sex-specific behavioural and neurometabolic changes at adolescence, further evidencing that lactation period is a critical metabolic programming window and in sculpting behaviour.

Dietary advanced glycation end-products and postmenopausal hot flashes: A post-hoc analysis of a 12-week randomized clinical trial

OBJECTIVE

Postmenopausal hot flashes are associated with an increased risk of cardiovascular disease and diabetes. Because dietary advanced glycation end-products (AGEs) may act as endocrine disruptors, this study examined the potential association of modifications to the intake of dietary AGEs with the frequency and severity of postmenopausal hot flashes.

METHODS

Postmenopausal women (n = 84) reporting ≥2 moderate-to-severe hot flashes daily were randomly assigned to either the intervention group or the control group. The former were asked to follow a low-fat, vegan diet, including cooked soybeans (1/2 cup [86 g]/day) for 12 weeks, and the latter continued their usual diets for 12 weeks. Frequency and severity of hot flashes were recorded with a mobile application. Three-day diet records were analyzed using the Nutrition Data System for Research software and dietary AGEs were estimated, using a database. Seventy-one participants completed the whole study and 63 provided complete hot flash and dietary data for the AGEs analysis (n = 31 in the intervention and n = 24 in the control group). Pearson correlations were used to assess the association between changes in hot flashes and dietary AGEs.

RESULTS

Dietary AGEs decreased in the intervention group by 73 %, that is by 5509 ku/day on average (95 % -7009 to -4009; p < 0.001), compared with the control group (+458; 95 % CI -835 to +1751; p = 0.47; treatment effect -5968 ku/day [95 % CI -7945 to -3991]; Gxt, p < 0.001). Severe hot flashes decreased by 92 % (p < 0.001) and moderate-to-severe hot flashes decreased by 88 % in the intervention group (p < 0.001). Changes in dietary AGEs correlated with changes in severe (r = +0.39; p = 0.002) and moderate hot flashes (r = +0.34; p = 0.009) and remained significant after adjustment for changes in energy intake (r = +0.45; p < 0.001; and r = +0.37; p = 0.004, respectively) and changes in body mass index (r = +0.37; p = 0.004; and r = +0.27; p = 0.04, respectively). The reduction in dietary AGEs required to achieve a predicted reduction in hot flashes by 1/day was 6933 ku/day for severe and 4366 ku/day for moderate-to-severe hot flashes.

CONCLUSIONS

The reduction in dietary AGEs with a low-fat plant-based diet was associated with a significant reduction in the frequency of severe and moderate-to-severe postmenopausal hot flashes, independent of changes in energy intake and weight loss. Plant-based diets could be used not only to alleviate vasomotor symptoms in postmenopausal women, but also to reduce other health risks associated with AGEs.

TRIAL REGISTRATION

ClinicalTrials.gov, NCT04587154.

Advanced Glycation End-Products and Their Effects on Gut Health

Dietary advanced glycation end-products (AGEs) are a heterogeneous group of compounds formed when reducing sugars are heated with proteins, amino acids, or lipids at high temperatures for a prolonged period. The presence and accumulation of AGEs in numerous cell types and tissues are known to be prevalent in the pathology of many diseases. Modern diets, which contain a high proportion of processed foods and therefore a high level of AGE, cause deleterious effects leading to a multitude of unregulated intracellular and extracellular signalling and inflammatory pathways. Currently, many studies focus on investigating the chemical and structural aspects of AGEs and how they affect the metabolism and the cardiovascular and renal systems. Studies have also shown that AGEs affect the digestive system. However, there is no complete picture of the implication of AGEs in this area. The gastrointestinal tract is not only the first and principal site for the digestion and absorption of dietary AGEs but also one of the most susceptible organs to AGEs, which may exert many local and systemic effects. In this review, we summarise the current evidence of the association between a high-AGE diet and poor health outcomes, with a special focus on the relationship between dietary AGEs and alterations in the gastrointestinal structure, modifications in enteric neurons, and microbiota reshaping.

Can grape polyphenols affect glycation markers? A systematic review

Advanced glycation end-products (AGEs) favor inflammation and oxidative stress, playing a role in chronic diseases pathogenesis. Grape polyphenols exert antiglycative and antioxidant effects which may contribute to prevent chronic diseases. However, clinical evidence of grape polyphenols on chronic disease prevention and treatment by glycation markers modulation are limited. Therefore, we aimed to critically analyze studies about that topic to investigate the antiglycative power of dietary grape polyphenol, and to explore the molecular mechanism involved. This systematic review was conducted and reported according to PRISMA guidelines. The following search terms were used: "grape", "extract", "grape seed extract", "grape skin extract", "polyphenol extract", "grape polyphenol(s)", "grape juice", "resveratrol", "quercetin", "catechin", "epicatechin", "procyanidin(s)", and "anthocyanin(s)". Seven studies were included. Glycated hemoglobin was not affected. The interventions duration may not have been enough to detect changes. Grape polyphenols reduced fructosamine and methylglyoxal (MGO) concentrations, and increased endogenous secretory RAGE (esRAGE) gene expression but did not affect the serum concentration. Resveratrol antiglycative effects are mainly due its ability to trap MGO and downregulate RAGE. In conclusion, grape polyphenols may have a positive impact on early glycation products, AGEs and esRAGE. Future studies are needed to explore how they modulate AGEs and receptors in chronic diseases.

The sirtuin family in health and disease

Sirtuins (SIRTs) are nicotine adenine dinucleotide(+)-dependent histone deacetylases regulating critical signaling pathways in prokaryotes and eukaryotes, and are involved in numerous biological processes. Currently, seven mammalian homologs of yeast Sir2 named SIRT1 to SIRT7 have been identified. Increasing evidence has suggested the vital roles of seven members of the SIRT family in health and disease conditions. Notably, this protein family plays a variety of important roles in cellular biology such as inflammation, metabolism, oxidative stress, and apoptosis, etc., thus, it is considered a potential therapeutic target for different kinds of pathologies including cancer, cardiovascular disease, respiratory disease, and other conditions. Moreover, identification of SIRT modulators and exploring the functions of these different modulators have prompted increased efforts to discover new small molecules, which can modify SIRT activity. Furthermore, several randomized controlled trials have indicated that different interventions might affect the expression of SIRT protein in human samples, and supplementation of SIRT modulators might have diverse impact on physiological function in different participants. In this review, we introduce the history and structure of the SIRT protein family, discuss the molecular mechanisms and biological functions of seven members of the SIRT protein family, elaborate on the regulatory roles of SIRTs in human disease, summarize SIRT inhibitors and activators, and review related clinical studies.

Understanding the role of glycation in the pathology of various non-communicable diseases along with novel therapeutic strategies

Glycation refers to carbonyl group condensation of the reducing sugar with the free amino group of protein, which forms Amadori products and advanced glycation end products (AGEs). These AGEs alter protein structure and function by configuring a negative charge on the positively charged arginine and lysine residues. Glycation plays a vital role in the pathogenesis of metabolic diseases, brain disorders, aging, and gut microbiome dysregulation with the aid of 3 mechanisms: (i) formation of highly reactive metabolic pathway-derived intermediates, which directly affect protein function in cells, (ii) the interaction of AGEs with its associated receptors to create oxidative stress causing the activation of transcription factor NF-κB, and (iii) production of extracellular AGEs hinders interactions between cellular and matrix molecules affecting vascular and neural genesis. Therapeutic strategies are thus required to inhibit glycation at different steps, such as blocking amino and carbonyl groups, Amadori products, AGEs-RAGE interactions, chelating transition metals, scavenging free radicals, and breaking crosslinks formed by AGEs. The present review focused on explicitly elaborating the impact of glycation-influenced molecular mechanisms in developing and treating noncommunicable diseases.

Advanced Glycation End Products and Inflammation in Type 1 Diabetes Development

Type 1 diabetes (T1D) is an autoimmune disease in which the β-cells of the pancreas are attacked by the host's immune system, ultimately resulting in hyperglycemia. It is a complex multifactorial disease postulated to result from a combination of genetic and environmental factors. In parallel with increasing prevalence of T1D in genetically stable populations, highlighting an environmental component, consumption of advanced glycation end products (AGEs) commonly found in in Western diets has increased significantly over the past decades. AGEs can bind to cell surface receptors including the receptor for advanced glycation end products (RAGE). RAGE has proinflammatory roles including in host-pathogen defense, thereby influencing immune cell behavior and can activate and cause proliferation of immune cells such as islet infiltrating CD8+ and CD4+ T cells and suppress the activity of T regulatory cells, contributing to β-cell injury and hyperglycemia. Insights from studies of individuals at risk of T1D have demonstrated that progression to symptomatic onset and diagnosis can vary, ranging from months to years, providing a window of opportunity for prevention strategies. Interaction between AGEs and RAGE is believed to be a major environmental risk factor for T1D and targeting the AGE-RAGE axis may act as a potential therapeutic strategy for T1D prevention.

The association between dietary habits and metabolic syndrome: findings from the Shahedieh-cohort study

Objective

Metabolic syndrome (MetS) is a complex disorder with an increasing prevalence globally. Limited data are available about the association between dietary habits and the prevalence of MetS. The present cross-sectional study aimed to investigate the association between dietary habits and MetS in a large population sample from Iranians.

Methods

The study was conducted on 9261 adults aged 35–70 years who attended the baseline phase of Shahedieh cohort study, Yazd, Iran. Dietary habits including meal frequency, fried food consumption, adding salt to prepared meal, barbecued food consumption, used oil type and reuse oil number were assessed by a standard questionnaire. MetS was defined using the National Cholesterol Education Program Adult Treatment Panel III criteria. Logistic regression was used in different adjusted models to investigate the relationship between dietary habits and MetS: (Model I: adjusted for age, sex and energy. Model II: Model I + adjusted for wealth score index and physical activity. Model III: Model II + adjusted for cardiovascular diseases and liver diseases).

Results

The subjects who ate barbecued-food more than 3 times/ month had 1.18 times greater odds for MetS than individual who ate this less than once/ month (OR: 1.18, 95% CI: 1.01–1.38). After further adjustment for other confounding variables, the association remained significant. No significant association was found between other dietary habits and odds of MetS.

Conclusion

Higher intakes of barbecued-food consumption were related to the prevalence of MetS. Larger longitudinal studies in other population groups are needed to confirm these associations.

First trimester screening of serum advanced glycation end products levels of pregnant women who have risk factors for gestational diabetes and their obstetric outcomes: a preliminary case-control study

Advanced glycation end-products (AGE) are complex compounds formed by nonenzymatic glycosylation of proteins, nucleic acids, and lipids with glucose in the blood. We aimed to investigate whether there was a difference in first-trimester serum AGE levels of pregnant women with and without risk factors for gestational diabetes mellitus (GDM) and their obstetric outcomes. There were 44 women in study group who have risk factors for GDM and 44 as controls. Demographic features, serum AGE levels, adverse perinatal and neonatal outcomes were compared between groups. Five patients (11.4%) in the study group and one patient (2.3%) in the control group were diagnosed as GDM (p = .2). The serum AGE values were not statistically different between the study and control groups. There were no statistical differences between groups in terms of adverse perinatal and neonatal outcomes. However, in the group with adverse perinatal outcome (n = 25), AGE values were higher than the control group. The results of our preliminary study suggested that high-risk women for GDM did not have increased serum levels of AGE in the first trimester. Nevertheless, a high first-trimester serum AGE level was found to be associated with adverse perinatal outcomes. IMPACT STATEMENTWhat is already known on this subject? Advanced glycation end products (AGE) are markers that are associated with diabetes and its complications. For pregnant women, a high third trimester serum AGEs levels were found in women who had gestational diabetes.What do the results of this study add? The results of our study revealed that first trimester screening of serum AGE levels of women who had risk factors for gestational diabetes was not discriminate. Nevertheless, a high first trimester serum AGE levels was associated with adverse perinatal outcome.What are the implications of these findings for clinical practice and/or further research? Whether reducing exogenous sources of AGE (western-style diet, smoking) before pregnancy will be associated with better pregnancy outcomes should be investigated in future studies.

Sirtuins as novel pharmacological targets in podocyte injury and related glomerular diseases

Podocyte injury is a major cause of proteinuria in kidney diseases, and persistent loss of podocytes leads to rapid irreversible progression of kidney disease. Sirtuins, a class of nicotinamide adenine dinucleotide-dependent deacetylases, can promote DNA repair, modify transcription factors, and regulate the cell cycle. Additionally, sirtuins play a critical role in renoprotection, particularly against podocyte injury. They also have pleiotropic protective effects on podocyte injury-related glomerular diseases, such as improving the immune inflammatory status and oxidative stress levels, maintaining mitochondrial homeostasis, enhancing autophagy, and regulating lipid metabolism. Sirtuins deficiency causes podocyte injury in different glomerular diseases. Studies using podocyte sirtuin-specific knockout and transgenic models corroborate this conclusion. Of note, sirtuin activators have protective effects in different podocyte injury-related glomerular diseases, including diabetic kidney disease, focal segmental glomerulosclerosis, membranous nephropathy, IgA nephropathy, and lupus nephritis. These findings suggest that sirtuins are promising therapeutic targets for preventing podocyte injury. This review provides an overview of recent advances in the role of sirtuins in kidney diseases, especially their role in podocyte injury, and summarizes the possible rationale for sirtuins as targets for pharmacological intervention in podocyte injury-related glomerular diseases.

Advanced Glycation End Products and Their Effect on Vascular Complications in Type 2 Diabetes Mellitus

Diabetes is well established as a chronic disease with a high health burden due to mortality or morbidity from the final outcomes of vascular complications. An increased duration of hyperglycemia is associated with abnormal metabolism. Advanced glycation end products (AGEs) are nonenzymatic glycated forms of free amino acids that lead to abnormal crosslinking of extra-cellular and intracellular proteins by disrupting the normal structure. Furthermore, the interaction of AGEs and their receptors induces several pathways by promoting oxidative stress and inflammation. In this review, we discuss the role of AGEs in diabetic vascular complications, especially type 2 DM, based on recent clinical studies.

Ca2+/Calmodulin-Dependent Protein Kinase II Regulation by Inhibitor of Receptor Interacting Protein Kinase 3 Alleviates Necroptosis in Glycation End Products-Induced Cardiomyocytes Injury

Necroptosisis a regulatory programmed form of necrosis. Receptor interacting protein kinase 3 (RIPK3) is a robust indicator of necroptosis. RIPK3 mediates myocardial necroptosis through activation of calcium/calmodulin-dependent protein kinase II (CaMKII) in cardiac ischemia-reperfusion (I/R) injury and heart failure. However, the exact mechanism of RIPK3 in advanced glycation end products (AGEs)-induced cardiomyocytes necroptosis is not clear. In this study, cardiomyocytes were subjected to AGEs stimulation for 24 h. RIPK3 expression, CaMKII expression, and necroptosis were determined in cardiomyocytes after AGEs stimulation. Then, cardiomyocytes were transfected with RIPK3 siRNA to downregulate RIPK3 followed by AGEs stimulation for 24 h. CaMKIIδ alternative splicing, CaMKII activity, oxidative stress, necroptosis, and cell damage were detected again. Next, cardiomyocytes were pretreated with GSK′872, a specific RIPK3 inhibitor to assess whether it could protect cardiomyocytes against AGEs stimulation. We found that AGEs increased the expression of RIPK3, aggravated the disorder of CaMKII δ alternative splicing, promoted CaMKII activation, enhanced oxidative stress, induced necroptosis, and damaged cardiomyocytes. RIPK3 downregulation or RIPK3 inhibitor GSK′872 corrected CaMKIIδ alternative splicing disorder, inhibited CaMKII activation, reduced oxidative stress, attenuated necroptosis, and improved cell damage in cardiomyocytes.

Incorporation of Oxidized Phenylalanine Derivatives into Insulin Signaling Relevant Proteins May Link Oxidative Stress to Signaling Conditions Underlying Chronic Insulin Resistance

A link between oxidative stress and insulin resistance has been suggested. Hydroxyl free radicals are known to be able to convert phenylalanine (Phe) into the non-physiological tyrosine isoforms ortho- and meta-tyrosine (o-Tyr, m-Tyr). The aim of our study was to examine the role of o-Tyr and m-Tyr in the development of insulin resistance. We found that insulin-induced uptake of glucose was blunted in cultures of 3T3-L1 grown on media containing o- or m-Tyr. We show that these modified amino acids are incorporated into cellular proteins. We focused on insulin receptor substrate 1 (IRS-1), which plays a role in insulin signaling. The activating phosphorylation of IRS-1 was increased by insulin, the effect of which was abolished in cells grown in m-Tyr or o-Tyr media. We found that phosphorylation of m- or o-Tyr containing IRS-1 segments by insulin receptor (IR) kinase was greatly reduced, PTP-1B phosphatase was incapable of dephosphorylating phosphorylated m- or o-Tyr IRS-1 peptides, and the SH2 domains of phosphoinositide 3-kinase (PI3K) bound the o-Tyr IRS-1 peptides with greatly reduced affinity. According to our data, m- or o-Tyr incorporation into IRS-1 modifies its protein–protein interactions with regulating enzymes and effectors, thus IRS-1 eventually loses its capacity to play its role in insulin signaling, leading to insulin resistance.

The RAGE/DIAPH1 Signaling Axis & Implications for the Pathogenesis of Diabetic Complications

Increasing evidence links the RAGE (receptor for advanced glycation end products)/DIAPH1 (Diaphanous 1) signaling axis to the pathogenesis of diabetic complications. RAGE is a multi-ligand receptor and through these ligand-receptor interactions, extensive maladaptive effects are exerted on cell types and tissues targeted for dysfunction in hyperglycemia observed in both type 1 and type 2 diabetes. Recent evidence indicates that RAGE ligands, acting as damage-associated molecular patterns molecules, or DAMPs, through RAGE may impact interferon signaling pathways, specifically through upregulation of IRF7 (interferon regulatory factor 7), thereby heralding and evoking pro-inflammatory effects on vulnerable tissues. Although successful targeting of RAGE in the clinical milieu has, to date, not been met with success, recent approaches to target RAGE intracellular signaling may hold promise to fill this critical gap. This review focuses on recent examples of highlights and updates to the pathobiology of RAGE and DIAPH1 in diabetic complications.

Advanced Glycation End Products and Diabetes Mellitus: Mechanisms and Perspectives

Persistent hyperglycemic state in type 2 diabetes mellitus leads to the initiation and progression of non-enzymatic glycation reaction with proteins and lipids and nucleic acids. Glycation reaction leads to the generation of a heterogeneous group of chemical moieties known as advanced glycated end products (AGEs), which play a central role in the pathophysiology of diabetic complications. The engagement of AGEs with its chief cellular receptor, RAGE, activates a myriad of signaling pathways such as MAPK/ERK, TGF-β, JNK, and NF-κB, leading to enhanced oxidative stress and inflammation. The downstream consequences of the AGEs/RAGE axis involve compromised insulin signaling, perturbation of metabolic homeostasis, RAGE-induced pancreatic beta cell toxicity, and epigenetic modifications. The AGEs/RAGE signaling instigated modulation of gene transcription is profoundly associated with the progression of type 2 diabetes mellitus and pathogenesis of diabetic complications. In this review, we will summarize the exogenous and endogenous sources of AGEs, their role in metabolic dysfunction, and current understandings of AGEs/RAGE signaling cascade. The focus of this review is to recapitulate the role of the AGEs/RAGE axis in the pathogenesis of type 2 diabetes mellitus and its associated complications. Furthermore, we present an overview of future perspectives to offer new therapeutic interventions to intervene with the AGEs/RAGE signaling pathway and to slow down the progression of diabetes-related complications.

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

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

A 4-week high-AGE diet does not impair glucose metabolism and vascular function in obese individuals

BACKGROUND

Accumulation of advanced glycation endproducts (AGEs) may contribute to the pathophysiology of type 2 diabetes and its vascular complications. AGEs are widely present in food, but whether restricting AGE intake improves risk factors for type 2 diabetes and vascular dysfunction is controversial.

METHODS

Abdominally obese but otherwise healthy individuals were randomly assigned to a specifically designed 4-week diet low or high in AGEs in a double-blind, parallel design. Insulin sensitivity, secretion, and clearance were assessed by a combined hyperinsulinemic-euglycemic and hyperglycemic clamp. Micro- and macrovascular function, inflammation, and lipid profiles were assessed by state-of-the-art in vivo measurements and biomarkers. Specific urinary and plasma AGEs N^ε-(carboxymethyl)lysine (CML), N^ε-(1-carboxyethyl)lysine (CEL), and N^δ-(5-hydro-5-methyl-4-imidazolon-2-yl)-ornithine (MG-H1) were assessed by mass spectrometry.

RESULTS

In 73 individuals (22 males, mean ± SD age and BMI 52 ± 14 years, 30.6 ± 4.0 kg/m²), intake of CML, CEL, and MG-H1 differed 2.7-, 5.3-, and 3.7-fold between the low- and high-AGE diets, leading to corresponding changes of these AGEs in urine and plasma. Despite this, there was no difference in insulin sensitivity, secretion, or clearance; micro- and macrovascular function; overall inflammation; or lipid profile between the low and high dietary AGE groups (for all treatment effects, P > 0.05).

CONCLUSION

This comprehensive RCT demonstrates very limited biological consequences of a 4-week diet low or high in AGEs in abdominally obese individuals.

TRIAL REGISTRATION

Clinicaltrials.gov, NCT03866343; trialregister.nl, NTR7594.

FUNDING

Diabetesfonds and ZonMw.

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSION

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

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.

Does dietary fat affect advanced glycation end products and their receptors? A systematic review of clinical trials

CONTEXT

Dietary fat seems to affect advanced glycation end products (AGEs) and their receptors. This systematic review assesses studies that evaluated the effect of dietary fat on markers of glycation.

OBJECTIVE

The aim of this systematic review was to analyze the effect of dietary fat on markers of glycation and to explore the mechanisms involved.

DATA SOURCES

This study was conducted according to PRISMA guidelines. PubMed, Cochrane, and Scopus databases were searched, using descriptors related to dietary fat, AGEs, and the receptors for AGEs.

STUDY SELECTION

Studies were selected independently by the 3 authors. Divergent decisions were resolved by consensus. All studies that evaluated the effects of the quantity and quality of dietary fat on circulating concentrations of AGEs and their receptors in adults and elderly adults with or without chronic diseases were included. Initially, 9 studies met the selection criteria.

DATA EXTRACTION

Three authors performed data extraction independently. Six studies were included.

RESULTS

Consumption of a Mediterranean diet rich in monounsaturated fatty acids (MUFAs) and low in dietary AGEs reduced serum concentrations of AGEs, reduced expression of the receptor for AGE (RAGE), and increased expression of the AGE receptor 1 (AGER1) when compared with consumption of a Western diet rich in saturated fatty acids and dietary AGEs. Supplementation with omega-3 polyunsaturated fatty acids (PUFAs) resulted in decreased concentrations of fluorescent AGEs and decreased expression of RAGE as well as increased expression of AGER1.

CONCLUSIONS

Increased consumption of MUFAs and omega-3 PUFAs and reduced consumption of saturated fatty acids seem to be effective strategies to beneficially affect glycation markers, which in turn may prevent and control chronic diseases.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO registration number CRD42021220489.

High hydrostatic pressure processing of human milk preserves milk oligosaccharides and avoids formation of Maillard reaction products

BACKGROUND & AIMS

High hydrostatic pressure (HHP) processing is a non-thermal method proposed as an alternative to Holder pasteurization (HoP) for the treatment of human milk. HHP preserves numerous milk bioactive components that are degraded by HoP, but no data are available for milk oligosaccharides (HMOs) or the formation of Maillard reaction products, which may be deleterious for preterm newborns.

METHODS

We evaluated the impact of HHP processing of human milk on 22 HMOs measured by liquid chromatography with fluorescence detection and on furosine, lactuloselysine, carboxymethyllysine (CML) and carboxyethyllysine (CEL) measured by liquid chromatography with tandem mass spectrometric detection (LC-MS/MS), four established indicators of the Maillard reaction. Human raw milk was sterilized by HoP (62.5 °C for 30 min) or processed by HHP (350 MPa at 38 °C).

RESULTS

Neither HHP nor HoP processing affected the concentration of HMOs, but HoP significantly increased furosine, lactuloselysine, CML and CEL levels in milk.

CONCLUSIONS

Our findings demonstrate that HPP treatment preserves HMOs and avoids formation of Maillard reaction products. Our study confirms and extends previous findings that HHP treatment of human milk provides safe milk, with fewer detrimental effects on the biochemically active milk components than HoP.

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

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

Habitual intake of dietary advanced glycation end products is not associated with generalized microvascular function-the Maastricht Study

BACKGROUND

Endogenously formed advanced glycation end products (AGEs) may be important drivers of microvascular dysfunction and the microvascular complications of diabetes. AGEs are also formed in food products, especially during preparation methods involving dry heat.

OBJECTIVES

We aimed to assess cross-sectional associations between dietary AGE intake and generalized microvascular function in a population-based cohort.

METHODS

In 3144 participants of the Maastricht Study (mean ± SD age: 60 ± 8 y, 51% men) the dietary AGEs 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 our ultra-performance LC-tandem MS dietary AGE database and an FFQ. Microvascular function was determined in the retina as flicker light-induced arteriolar and venular dilation and as central retinal arteriolar and venular equivalents, in plasma as a z score of endothelial dysfunction biomarkers (soluble vascular adhesion molecule 1 and soluble intracellular adhesion molecule 1, soluble E-selectin, and von Willebrand factor), in skin as the heat-induced skin hyperemic response, and in urine as 24-h albuminuria. Associations were evaluated using multiple linear regression adjusting for demographic, cardiovascular, lifestyle, and dietary factors.

RESULTS

Overall, intakes of CML, CEL, and MG-H1 were not associated with the microvascular outcomes. Although higher intake of CEL was associated with higher flicker light-induced venular dilation (β percentage change over baseline: 0.14; 95% CI: 0.02, 0.26) and lower plasma biomarker z score (β: -0.04 SD; 95% CI: -0.08, -0.00 SD), the effect sizes were small and their biological relevance can be questioned.

CONCLUSIONS

We did not show any strong association between habitual intake of dietary AGEs and generalized microvascular function. The contribution of dietary AGEs to generalized microvascular function should be further assessed in randomized controlled trials using specifically designed dietary interventions.

Effect of Advanced Glycation End Products on Cognition in Older Adults with Type 2 Diabetes: Results from a Pilot Clinical Trial

BACKGROUND

Dietary advanced glycation end-products (AGEs) are linked to cognitive decline. However, clinical trials have not tested the effect of AGEs on cognition in older adults.

OBJECTIVE

The aim of the current pilot trial was to examine the feasibility of an intervention to reduce dietary AGEs on cognition and on cerebral blood flow (CBF).

METHODS

The design is a pilot randomized controlled trial of dietary AGEs reduction in older adults with type 2 diabetes. Seventy-five participants were randomized to two arms. The control arm received standard of care (SOC) guidelines for good glycemic control; the intervention arm, in addition to SOC guidelines, were instructed to reduce their dietary AGEs intake. Global cognition and CBF were assessed at baseline and after 6 months of intervention.

RESULTS

At baseline, we found a reverse association between AGEs and cognitive functioning, possibly reflecting the long-term toxicity of AGEs on the brain. There was a significant improvement in global cognition at 6 months in both the intervention and SOC groups which was more prominent in participants with mild cognitive impairment. We also found that at baseline, higher AGEs were associated with increased CBF in the left inferior parietal cortex; however, 6 months of the AGEs lowering intervention did not affect CBF levels, despite lowering AGEs exposure in blood.

CONCLUSION

The current pilot trial focused on the feasibility and methodology of intervening through diet to reduce AGEs in older adults with type 2 diabetes. Our results suggest that participants with mild cognitive impairment may benefit from an intensive dietary intervention.

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).

Measurement of Advanced Glycation End Products Could Be Used as an Indicator of Unhealthy Nutrition for Colorectal Cancer Risk

The main culprit behind most cancers is the accumulation of reactive oxygen species. Glyoxal (GO) and methylglyoxal (MGO) are reactive intermediates created by food processing and they are precursors of advanced glycation end products (AGE) that cause glycative stress. We aimed to evaluate the relationship between AGE levels of healthy volunteers and treatment-naive patients diagnosed with colorectal cancer. The study consisted of patients diagnosed with colorectal cancer and healthy volunteers who underwent routine colonoscopy. The study was conducted with a total of 42 cases, 47.6% (n = 20) female. The ages of the participants in the study ranged from 41 to 82 years, and the mean was 60.57 ± 10.78 years. The GO and MGO values of the patient group were found to be significantly higher than those of the control group (p = 0.007, p = 0.001, respectively). The risk of colorectal cancer was 22 and 57 times higher in individuals with GO and MGO values above 1.25 μg/mL and 0.0095 μg/mL, respectively. The blood AGE level is closely related to diet, and it can be decreased through the appropriate improvement of diet. Thus, the measurement of AGE can be used to predict whether a person's nutrition is healthy or unhealthy and prevent increased risk of colorectal cancer.

Beyond the Paradigm of Weight Loss in Non-Alcoholic Fatty Liver Disease: From Pathophysiology to Novel Dietary Approaches

Current treatment recommendations for non-alcoholic fatty liver disease (NAFLD) rely heavily on lifestyle interventions. The Mediterranean diet and physical activity, aiming at weight loss, have shown good results in achieving an improvement of this liver disease. However, concerns related to compliance and food accessibility limit the feasibility of this approach, and data on the long-term effects on liver-related outcomes are lacking. Insulin resistance is a central aspect in the pathophysiology of NAFLD; therefore, interventions aiming at the improvement of insulin sensitivity may be preferable. In this literature review, we provide a comprehensive summary of the available evidence on nutritional approaches in the management of NAFLD, involving low-calorie diets, isocaloric diets, and the novel schemes of intermittent fasting. In addition, we explore the harmful role of single nutrients on liver-specific key metabolic pathways, the role of gene susceptibility and microbiota, and behavioral aspects that may impact liver disease and are often underreported in clinical setting. At present, the high variability in terms of study populations and liver-specific outcomes within nutritional studies limits the generalizability of the results and highlights the urgent need of a tailored and standardized approach, as seen in regulatory trials in Non-Alcoholic Steatohepatitis (NASH).

The Disorders of Endometrial Receptivity in PCOS and Its Mechanisms

Polycystic ovary syndrome (PCOS) is a mysterious and complicated endocrine disease with the combination of metabolic, reproductive, psychological dysfunctions. Impaired endometrial receptivity and ovulation disorders/anovulation are both important causes of PCOS-related infertility. However, change in endometrium has never received the same attention as ovulatory dysfunction. Besides, putting emphasis on endometrial function may be more realistic for PCOS-related infertility, given the wide use of assisted reproductive technology. The present review focuses on the disorders of endometrial receptivity of patients with PCOS, summarizes the changes of the indicators of endometrial receptivity including leukemia inhibitory factor, homeobox genes A, pinopodes, αvβ3-integrin, and intercellular junctions and also analyzes the possible mechanisms of decreased endometrial receptivity and its relationship with the main endocrine and metabolic disorders of PCOS such as hyperandrogenism, inflammation, insulin resistance, and obesity. Despite several biomarkers have been found to be associated with decreased endometrial receptivity in PCOS, the clinical relevance of these findings still awaits future clarification.

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

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

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

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

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.

Oxidized Pork Induces Disorders of Glucose Metabolism in Mice

SCOPE

Consumption of red meat, particularly processed red meat, has been reported to be associated with type 2 diabetes risk, and oxidized proteins and amino acids may be involved in this process. This study explores the effects of pork with varying degrees of oxidative injury caused by cooking on glucose metabolism in mice.

METHODS AND RESULTS

Cooked pork is freeze-dried to prepare animal feed. Mice are fed either a control diet (CON), a low- (LOP), or a high-oxidative injury pork diet (HOP) for 12 weeks. Intake of HOP causes hyperglycemia, hypoinsulinemia, and impaired glucose tolerance, indicating a glucose metabolism disorder. Accumulation of oxidation products increases oxidative stress and inflammatory response, which impairs pancreatic islet β cells function and reduces insulin secretion. Moreover, HOP-mediated hyperglycemia can be partly attributed to elevated hepatic glucose output, as indicated by increased gluconeogenesis and glycogenolysis, and decreased glycolysis and glycogen content. Changes in these processes may be regulated by reduced insulin levels and suppression of the insulin receptor substrate-1 (IRS-1)/phosphoinositide 3-kinase (PI3K)/protein kinase B (Akt) signaling pathway and its downstream signaling molecules.

CONCLUSION

HOP intake induces disorders of glucose metabolism by impairing pancreatic insulin secretion and increasing hepatic glucose output. Protein oxidation plays a key role in abnormal glucose metabolism induced by HOP.

Design and Feasibility of a Randomized Controlled Pilot Trial to Reduce Exposure and Cognitive Risk Associated With Advanced Glycation End Products in Older Adults With Type 2 Diabetes

Introduction: Advanced glycation end products (AGEs) in diet and serum are positively correlated with chronic conditions such as type 2 diabetes and cognitive decline. Dietary reduction of AGEs was shown to reduce their level in serum and to have a beneficial effect on metabolic biomarkers. However, in part due to limitations of feasibility, clinical trials have not tested its effect on cognition in elderly. The current pilot study examines the feasibility of AGE reduction in elderly with diabetes in terms of recruitment and retention.

Methods: The design is a randomized controlled pilot trial of dietary AGEs in elderly with type 2 diabetes (clinicaltrials.gov NCT02739971). Recruitment followed two stages: we first recruited participants with mild cognitive impairment (MCI), and after expanding inclusion criteria, we later recruited cognitively normal participants with subjective memory complaints (SMCs). Participants were randomized to two arms. Participants in the control arm received standard of care (SOC) guidelines for good glycemic control; those in the experimental arm, in addition to SOC guidelines, were instructed to lower their dietary AGE intake, primarily by changing their cooking methods. Participants were closely followed for dietary adherence over 6 months and evaluated before and after the intervention for adherence to the assigned diet, blood tests, cognitive performance, and brain MRI.

Results: Seventy-five participants (52 with MCI and 23 cognitively normal with SMCs) were recruited primarily through mass mailing and advertising in social media websites. Seventy participants finished the study, and dropout was similar in both groups (7.5% in control vs. 5.7% in intervention, p = 0.757). The majority (57.5%) of participants in the AGEs-lowering arm showed very high adherence with the dietary guidelines.

Discussion: Targeting feasible lifestyle modifications in high-risk populations could prevent substantial cases of cognitive decline. Observational evidence supports that AGEs may contribute to cognitive decline; however, the cognitive effect of reducing AGEs exposure has yet to be evaluated in a randomized controlled trial (RCT). The results of our pilot trial delineate a methodology including effective recruitment strategies, population of choice, and ways to assure high adherence during lifestyle modifications, and significantly advance progress toward a definitive and well-powered future RCT.

Low advanced Glycation end product diet improves the central obesity, insulin resistance and inflammatory profiles in Iranian patients with metabolic syndrome: a randomized clinical trial

The study aimed to investigate the effects of 8-weeks AGEs restricted diet on glycemic control as well as lipid profile, inflammatory and oxidative stress biomarkers and IR in overweight patients with Mets. In this randomized, controlled clinical trial 40 clients were randomly assigned to take either a low AGE (L-AGE) or a regular AGE (Reg-AGE) diet. Also, both groups were advised to follow an energy-restricted diet. At baseline and after 8-weeks of intervention, anthropometric parameters, dietary intake, plasma concentrations of malondialdehyde, carboxymethyllysine, TNF-α, hs-CRP and levels of serum glucose, lipid and insulin were assessed. AGEs restriction resulted in significant changes in mean differences levels of CML (p < 0.004), FBG (p < 0.01), HOMA-IR (p < 0.04), TNF-α (p < 0.01) and MDA (p < 0.02) in comparison to Reg-AGE. Moreover, weight (p < 0.0001) and WC (p < 0.001) significantly declined in the intervention group. Our results indicate that dAGEs restriction plus a low-calorie diet is superior to a low-calorie diet in amelioration of central obesity and IR at least partially through reduction of OS and inflammation in Mets subjects.