Quantification of dicarbonyl compounds in commonly consumed foods and drinks; presentation of a food composition database for dicarbonyls

Dietary intake of dicarbonyl compounds and changes in body weight over time in a large cohort of European adults

Dicarbonyl compounds are highly reactive precursors of advanced glycation end products (AGE), produced endogenously, present in certain foods and formed during food processing. AGE contribute to the development of adverse metabolic outcomes, but health effects of dietary dicarbonyls are largely unexplored. We investigated associations between three dietary dicarbonyl compounds, methylglyoxal (MGO), glyoxal (GO) and 3-deoxyglucosone (3-DG), and body weight changes in European adults. Dicarbonyl intakes were estimated using food composition database from 263 095 European Prospective Investigation into Cancer and Nutrition-Physical Activity, Nutrition, Alcohol, Cessation of Smoking, Eating Out of Home in Relation to Anthropometry participants with two body weight assessments (median follow-up time = 5·4 years). Associations between dicarbonyls and 5-year body-weight changes were estimated using mixed linear regression models. Stratified analyses by sex, age and baseline BMI were performed. Risk of becoming overweight/obese was assessed using multivariable-adjusted logistic regression. MGO intake was associated with 5-year body-weight gain of 0·089 kg (per 1-sd increase, 95 % CI 0·072, 0·107). 3-DG was inversely associated with body-weight change (-0·076 kg, -0·094, -0·058). No significant association was observed for GO (0·018 kg, -0·002, 0·037). In stratified analyses, GO was associated with body-weight gain among women and older participants (above median of 52·4 years). MGO was associated with higher body-weight gain among older participants. 3-DG was inversely associated with body-weight gain among younger and normal-weight participants. MGO was associated with a higher risk of becoming overweight/obese, while inverse associations were observed for 3-DG. No associations were observed for GO with overweight/obesity. Dietary dicarbonyls are inconsistently associated with body weight change among European adults. Further research is needed to clarify the role of these food components in overweight and obesity, their underlying mechanisms and potential public health implications.

Determination of α-Dicarbonyl compounds in traditional Chinese herbal medicines

α-DCs (α-dicarbonyls) have been proven to be closely related to aging and the onset and development of many chronic diseases. The wide presence of this kind of components in various foods and beverages has been unambiguously determined, but their occurrence in various phytomedicines remains in obscurity. In this study, we established and evaluated an HPLC-UV method and used it to measure the contents of four α-DCs including 3-deoxyglucosone (3-DG), glyoxal (GO), methylglyoxal (MGO), and diacetyl (DA) in 35 Chinese herbs after they have been derivatized with 4-nitro-1,2-phenylenediamine. The results uncover that 3-DG is the major component among the α-DCs, being detectable in all the selected herbs in concentrations ranging from 22.80 μg/g in the seeds of Alpinia katsumadai to 7032.75 μg/g in the fruit of Siraitia grosuenorii. The contents of the other three compounds are much lower than those of 3-DG, with GO being up to 22.65 μg/g, MGO being up to 55.50 μg/g, and DA to 18.75 μg/g, respectively. The data show as well the contents of the total four α-DCs in the herbs are generally in a comparable level to those in various foods, implying that herb medicines may have potential risks on human heath in view of the α-DCs.

Changes in α-Dicarbonyl Compound Contents during Storage of Various Fruits and Juices

α-Dicarbonyl compounds (α-DCs) are commonly present in various foods. We conducted the investigation into concentration changes of α-DCs including 3-deoxyglucosone (3-DG), glyoxal (GO), and methylglyoxal (MGO) in fresh fruits and decapped commercial juices during storage at room temperature and 4 °C, as well as in homemade juices during storage at 4 °C. The studies indicate the presence of α-DCs in all samples. The initial contents of 3-DG in the commercial juices (6.74 to 65.61 μg/mL) are higher than those in the homemade ones (1.97 to 4.65 μg/mL) as well as fruits (1.58 to 3.33 μg/g). The initial concentrations of GO and MGO are normally less than 1 μg/mL in all samples. During storage, the α-DC levels in the fruits exhibit an initial increase followed by a subsequent decrease, whereas, in all juices, they tend to accumulate continuously over time. As expected, 4 °C storage reduces the increase rates of the α-DC concentrations in most samples. From the viewpoint of the α-DC contents, fruits and homemade juices should always be the first choice for daily intake of nutrients and commercial juices ought to be mostly avoided.

Exploring correlations between soy sauce components and the formation of thermal contaminants during low-salt solid-state fermentation

Soy sauce is a traditional seasoning in Asia and provides a unique flavor to food. However, some harmful Maillard reaction products (MRPs) were inevitably formed during the manufacturing process. Fermentation is a critical step of soy sauce manufacturing and has a significant impact on MRPs formation. Therefore, this study investigated the formation of some characteristic MRPs (e.g., furan, carboxymethyl lysine (CML), 5-hydroxymethylfurfural (5-HMF), α-dicarbonyl compounds) and their correlation with major quality indicators (e.g., free amino acids, reducing sugar, total acid, ammonia nitrogen, total nitrogen, non-salt soluble solids) in low-salt solid-state fermentation soy sauce (LSFSS). The result showed that the levels of furan, CML, and 5-HMF continue to increase during the fermentation process, reaching a maximum after sterilization. Further testing using Person correlation showed that the formation of furan, CML, and 5-HMF in LSFSS was positively correlated with glucose, fructose, α-dicarbonyl compounds, and most of the amino acids, while it was negatively correlated with sucrose and methionine. Among them, the contribution of lysine, valine, isoleucine, leucine, and arginine to furan formation has rarely been reported. Our results provide a good theoretical basis for the control of MRPs during LSFSS fermentation.

Scavenging Glyoxal and Methylglyoxal by Synephrine Alone or in Combination with Neohesperidin at High Temperatures

α-Dicarbonyl compounds, such as glyoxal (GO) and methylglyoxal (MGO), are a series of chemical hazards that exist in vivo and in vitro, posing a threat to human health. We aimed to explore the scavenging effects on GO/MGO by synephrine (SYN) alone or in combination with neohesperidin (NEO). First, through LC-MS/MS, we confirmed that both SYN and NEO could effectively remove GO and form GO adducts, while NEO could also clear MGO by forming MGO adducts, and its ability to clear MGO was stronger than that of GO. Second, a synergistic inhibitory effect on GO was found when SYN and NEO were used in combination by using the Chou-Talalay method; on the other hand, SYN could promote NEO to clear more MGO, although SYN could not capture MGO. Third, after synthesizing four GO/MGO-adducts (SYN-GO-1, SYN-GO-3, NEO-GO-7, and NEO-MGO-2) and identifying their structure through NMR, strict correlations between the GO/MGO-adducts and the GO/MGO-clearance rate were found when using SYN and NEO alone or in combination. Furthermore, it was inferred that the synergistic effect between SYN and NEO stems from their mutual promotion in capturing more GO by the quantitative analysis of the adducts in the combined model. Finally, a study was conducted on flowers of Citrus aurantium L. var. amara Engl. (FCAVA, an edible tea) rich in SYN and NEO, which could serve as an effective GO and MGO scavenger in the presence of both GO and MGO. Therefore, our study provided well-defined evidence that SYN and NEO, alone or in combination, could efficiently scavenge GO/MGO at high temperatures, whether in the pure form or located in FCAVA.

Circulating Concentrations of advanced Glycation end Products, Carboxymethyl Lysine and Methylglyoxal are Associated With Renal Function in Individuals With Diabetes

OBJECTIVE

Diabetic kidney disease (DKD) is one of the most severe chronic complications of diabetes and is associated with higher level of advanced glycation end products (AGEs). The aim of this study was to investigate the diagnostic potential of combined detection of multiple serum AGEs in diagnosing DKD.

METHODS

Serum AGEs, Nε-(carboxymethyl) lysine (CML), Nε-(carboxyethyl) lysine, and methylglyoxal (MGO) levels were measured by enzyme-linked immunosorbent assay in 176 individuals with type 2 diabetes. Participants were classified into normoalbuminuria, microalbuminuria, and macroalbuminuria group according to their urinary albumin to creatinine ratio (UACR).

RESULTS

Higher serum AGEs levels were found to be positively correlated with U-Alb, UACR, and blood urea nitrogen in the study of 176 individuals with type 2 diabetes. CML and MGO levels were positively correlated with U-Alb, UACR, blood urea nitrogen, Scr, and uric acid, and negatively correlated with estimated glomerular filtration rate (P < .05). Multivariate logistic regression analysis showed that elevated levels of AGEs, CML, and MGO were independent risk factors for the progression of DKD (odds ratio = 1.861, 1.016, 7.607, P < .01). The sensitivity, specificity, and area under receiver operating characteristic curve of combined detection of AGEs, MGO, and CML were higher than those of three individual detections (area under the curve = 0.952, 0.772, 0.868, 0905, respectively, P < .05).

CONCLUSION

The combined detection of AGEs, CML, and MGO may improve the reliability of early diagnosis of DKD.

Methylglyoxal scavenging capacity of fiber-bound polyphenols from highland barley during colonic fermentation and its modulation on methylglyoxal-interfered gut microbiota

Methylglyoxal (MGO) scavenging capacity of fiber-bound polyphenols from highland barley during colonic fermentation and its potential role in modulating MGO-induced detrimental effects on gut microbiota were studied. Results showed that only 25.3 % of polyphenols were released after 24 h of colonic fermentation. More than 45.5 % of MGO was scavenged by the residual fiber-bound polyphenols in the model system, showing a vital role in scavenging MGO in the colonic lumen compared to the released polyphenols. Moreover, MGO promoted the increase of gut pathogens (Escherichia-Shigella and Klebsiella) and inhibited the proliferation of Megasphaera, Bifidobacterium and Megamonas, as well as reduced short-chain fatty acids (SCFAs) concentration. The addition of fiber-bound polyphenols of highland barley could effectively counteract MGO-induced detrimental consequences on gut microbiota and SCFAs production. These results demonstrate that fiber-bound polyphenols from highland barley can exert beneficial role through scavenging MGO and promises to be a functional ingredient to maintain colon heath.

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

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

Contents of ɑ-dicarbonyl compounds in commercial black tea and affected by the processing

The species and contents of ɑ-dicarbonyls in commercial black tea were examined, along with the effects of the manufacturing process and drying temperature on the formation of ɑ-dicarbonyls. Ten ɑ-dicarbonyls were quantified in commercial and in-process black tea samples by using UPLC-MS/MS and their derived quinoxalines. The ɑ-dicarbonyls content in commercial black tea decreased significantly (p < 0.05) in the following order: 3-deoxyglucosone > glucosone > 3-deoxypentosone = threosone > galactosone ≥ methylglyoxal = glyoxal ≥ 3-deoxygalactosone = 3-deoxythreosone = diacetyl. Except for 3-deoxyglucosone and 3-deoxygalactosone, a further eight ɑ-dicarbonyls were identified in all manufacturing steps of black tea. Except for the drying step, the rolling and fermenting played important roles in the formation of ɑ-dicarbonyls. The total contents of ɑ-dicarbonyls in black tea infusion ranged from 16.48 to 75.32 μg/g based on our detected ten ɑ-dicarbonyls.

Contribution of Hydroxycinnamic Acids to Color Formation in Nonenzymatic Browning Reactions with Key Maillard Reaction Intermediates

The Maillard reaction is a vital part of food processing, involving a vast number of complex reaction pathways, resulting in high-molecular-weight colorants. So far, studies have been focused on the conversion of carbohydrates and amino compounds, but the literature elaborating the contribution of phenolic compounds to the formation of the colored end-products is still rare. The aim of this study was to characterize early reactions, underlying the formation of phenol-containing melanoidins. For this purpose, binary model systems of the prominent phenolic compounds caffeic acid and ferulic acid combined with α-dicarbonyl compounds typically formed in the Maillard reaction such as glyoxal, methylglyoxal, and diacetyl were analyzed after heat treatment. High-resolution mass spectrometry revealed that decarboxylation, aromatic electrophilic substitution, and nucleophilic addition are important reaction steps that lead to colored heterogeneous oligomers. Polymerization was favored for phenolic compounds with a high electron density in the aromatic system and for α-dicarbonyl compounds carrying aldehyde functions.

Study on the non-enzymatic browning of lotus rhizome juice during sterilization mediated by 1,2-dicarboxyl and heterocyclic compounds

BACKGROUND

Lotus rhizome juice (LRJ) is susceptible to the Maillard reaction (MR) and caramelization, which tend to cause a reduction in quality and lower consumer acceptance of the product. 1,2-Dicarbonyl compounds (DCs) and heterocyclic compounds have attracted increasing attention as key intermediates responsible for the formation of brown pigments during MR and caramelization. However, little is known about the effects of these two types of compounds on brown pigments in LRJ during sterilization. This study quantified the changes in brown intensity (A420), DCs, and heterocyclic compounds before and after spiking, and identified the precursors and intermediates for brown pigment formation as well as the formation pathways of the intermediates.

RESULTS

The spiking experiments suggested that spiking with fructose resulted in more 3-deoxyglucosone (3-DG) and 2,3-dihydro-3,5-dihydroxy-6-methyl-4(H)-pyran-4-one (DDMP), while that with lysine led to more glucosone (GS) and 2,3-butanedione (2,3-BD) in LRJ. The addition of glucose, asparagine, and glutamine promoted the formation of 5-hydroxymethylfurfural (HMF) significantly, whereas the addition of glucose, lysine, and asparagine resulted in more norfuraneol. Spiking with reducing sugars and amino acids promoted both glyoxal (GO) and methylglyoxal (MGO), and the effect of glucose on GO was particularly significant. Correlation analysis showed that A420 had the highest correlation with 3-DG in the fructose- and lysine-spiked group, and with HMF in the glucose-, asparagine-, and glutamine-spiked groups.

CONCLUSION

This study revealed that fructose, glucose, asparagine, glutamine, and lysine were essential precursors of MR and caramelization in LRJ during sterilization. 3-Deoxyglucosone and DDMP were mainly produced by caramelization with fructose as the primary precursor, whereas GS and 2,3-BD were primarily formed via MR with lysine catalysis. The MR and caramelization were the main formation pathways of HMF (catalyzed by asparagine and glutamine) and norfuraneol (catalyzed by lysine and asparagine), with glucose as the critical precursor. Methylglyoxal was mainly produced by MR or caramelization, and caramelization was the main formation pathway of GO, with glucose as the precursor. Dor brown pigment formation from fructose and lysine, 3-DG was identified as the most crucial intermediate, while for that from glucose, asparagine, and glutamine, HMF was found to be the most important intermediate. © 2023 Society of Chemical Industry.

Comparison of the methylglyoxal scavenging effects of kaempferol and glutathione and the consequences for the toxicity of methylglyoxal in SH-SY5Y cells

This study aimed to characterize the methylglyoxal (MGO) scavenging capacity of glutathione (GSH) and kaempferol in more detail with special emphasis on the possible reversible nature of the adduct formation and their competition for MGO, and the safety consequences of their MGO-scavenging effects. GSH showed immediate and concentration-dependent MGO-scavenging effects, while the scavenging effects by kaempferol appeared concentration- but also time-dependent, with stable adducts formed over time. The GSH adduct gradually disappeared in a competition reaction with kaempferol, and kaempferol became the preferred scavenger over time. Furthermore, the scavenging of MGO by kaempferol provided better protection than GSH against extracellular MGO in SH-SY5Y cells. It is concluded that flavonoids like kaempferol provide better scavengers for food-borne MGO than thiol-based scavengers such as GSH, while, given the endogenous concentrations of both scavengers and the detoxification of the GSH-MGO adduct by the glyoxalase system, GSH will be dominant for intracellular MGO protection.

Effect of Pretreatment Methods on the Formation of Advanced Glycation End Products in Fried Shrimp

Fried shrimp are popular for their attractive organoleptic and nutritional qualities. However, consumers are more concerned about the safety of fried foods. To investigate the formation of advanced glycation end products (AGEs) in fried shrimp and provide pretreatment guidance for producing low-AGEs fried pacific white shrimp were treated with seven pretreatment methods before frying. The AGEs contents, physicochemical indicators, and their correlations in the fried shrimps' interior, surface, and batter layer were analyzed. Results indicated that pretreatment methods influenced both Maillard and oxidation reactions by altering the basic compositions, which controlled the formation of AGEs. The highest and lowest AGEs contents were obtained in shelled shrimp with exscinded back and whole shrimp, respectively. The batter-coated treatment reduced the AGEs contents in samples but increased the oil content. Correlation analysis showed that lipid oxidation was the decisive chemical reaction to the formation of AGEs by promoting the generation of dicarbonyl compounds and their combination with free amino acids. Conclusively, the whole shrimp was suitable for producing fried shrimp with low AGEs, oil content, and desirable color.

Theanine in Tea: An Effective Scavenger of Single or Multiple Reactive Carbonyl Species at the Same Time

Reactive carbonyl species (RCS) are generated during thermal food processing, and their accumulation in the body increases the risk of various chronic diseases. Herein, the RCS-scavenging ability of theanine, a unique nonproteinogenic amino acid, was evaluated in terms of the scavenging rate, reaction kinetics, and reaction pathway using LC-MS/MS. Three major products of theanine conjugated with acrolein (ACR) and glyoxal (GO) were prepared and identified using nuclear magnetic resonance. Thereafter, the simultaneous reactions of four types of RCS (namely, ACR, crotonaldehyde, methylglyoxal, and GO) with theanine were discussed in RCS-theanine and RCS-tea models. Under different reaction ratios, theanine could nonspecifically scavenge the four coexisting RCS by forming adducts with them. The amount of theanine-RCS adducts in green and black tea was more than that of catechin (epigallocatechin gallate, epigallocatechin, epicatechin gallate, and epicatechin)-RCS adducts despite the lower content of theanine than catechins. Thus, theanine, as a food additive and dietary supplement, could demonstrate new bioactivity as a promising RCS scavenger in food processing.

Methylglyoxal, a highly reactive dicarbonyl compound, as a threat for blood brain barrier integrity

The brain is a highly metabolically active organ requiring a large amount of glucose. Methylglyoxal (MGO), a by-product of glucose metabolism, is known to be involved in microvascular dysfunction and is associated with reduced cognitive function. Maintenance of the blood-brain barrier (BBB) is essential to maintain optimal brain function and a large amount of evidence indicates negative effects of MGO on BBB integrity. In this review, we summarized the current literature on the effect of MGO on the different cell types forming the BBB. BBB damage by MGO most likely occurs in brain endothelial cells and mural cells, while astrocytes are most resistant to MGO. Microglia on the other hand appear to be not directly influenced by MGO but rather produce MGO upon activation. Although there is clear evidence that MGO affects components of the BBB, the impact of MGO on the BBB as a multicellular system warrants further investigation. Diminishing MGO stress can potentially form the basis for new treatment strategies for maintaining optimal brain function.

Simultaneous determination of six α-dicarbonyl compounds in traditional Chinese medicines using high-performance liquid chromatography-fluorescence detector with pre-column derivatization

A reliable method for determination of six α-dicarbonyl compounds in traditional Chinese medicines was first developed and validated by high-performance liquid chromatography-fluorescence detector with pre-column derivatization. α-Dicarbonyl compounds in traditional Chinese medicines were extracted and derivatized with 2,3-diaminaphthalene. The derivatization procedure of six α-dicarbonyl compounds was confirmed by high-resolution mass spectrometry. The limits of quantitation for six α-dicarbonyl compounds ranged from 3.70 × 10-3 to 2.21 × 10-2  μM. The established method showed good linearity (regression coefficient > 0.9990), precision (relative standard deviation < 3.37%), and high recovery (97.8%∼113.1%). The developed method was successfully applied to detect the six α-dicarbonyl compounds in traditional Chinese medicines. The result exhibited six α-dicarbonyl compounds was found in the 15 kinds of traditional Chinese medicines, which suggested us that the determination of α-dicarbonyl compounds should be paid more attention in the quality control of traditional Chinese medicines.

Advanced glycation end product signaling and metabolic complications: Dietary approach

Advanced glycation end products (AGEs) are a heterogeneous collection of compounds formed during industrial processing and home cooking through a sequence of nonenzymatic glycation reactions. The modern western diet is full of heat-treated foods that contribute to AGE intake. Foods high in AGEs in the contemporary diet include processed cereal products. Due to industrialization and marketing strategies, restaurant meals are modified rather than being traditionally or conventionally cooked. Fried, grilled, baked, and boiled foods have the greatest AGE levels. Higher AGE-content foods include dry nuts, roasted walnuts, sunflower seeds, fried chicken, bacon, and beef. Animal proteins and processed plant foods contain furosine, acrylamide, heterocyclic amines, and 5-hydroxymethylfurfural. Furosine (2-furoil-methyl-lysine) is an amino acid found in cooked meat products and other processed foods. High concentrations of carboxymethyl-lysine, carboxyethyl-lysine, and methylglyoxal-O are found in heat-treated nonvegetarian foods, peanut butter, and cereal items. Increased plasma levels of AGEs, which are harmful chemicals that lead to age-related diseases and physiological aging, diabetes, and autoimmune/inflammatory rheumatic diseases such as systemic lupus erythematosus and rheumatoid arthritis. AGEs in the pathophysiology of metabolic diseases have been linked to individuals with diabetes mellitus who have peripheral nerves with high amounts of AGEs and diabetes has been linked to increased myelin glycation. Insulin resistance and hyperglycemia can impact numerous human tissues and organs, leading to long-term difficulties in a number of systems and organs, including the cardiovascular system. Plasma AGE levels are linked to all-cause mortality in individuals with diabetes who have fatal or nonfatal coronary artery disease, such as ventricular dysfunction. High levels of tissue AGEs are independently associated with cardiac systolic dysfunction in diabetic patients with heart failure compared with diabetic patients without heart failure. It is widely recognized that AGEs and oxidative stress play a key role in the cardiovascular complications of diabetes because they both influence and are impacted by oxidative stress. All chronic illnesses involve protein, lipid, or nucleic acid modifications including crosslinked and nondegradable aggregates known as AGEs. Endogenous AGE formation or dietary AGE uptake can result in additional protein modifications and stimulation of several inflammatory signaling pathways. Many of these systems, however, require additional explanation because they are not entirely obvious. This review summarizes the current evidence regarding dietary sources of AGEs and metabolism-related complications associated with AGEs.

Chaste honey in long term-storage: Occurrence and accumulation of Maillard reaction products, and safety assessment

Honey, a natural sweetener that can be stored long-term, is prone to Maillard reactions. Maillard reaction products (MRPs), such as 5-hydroxymethylfurfural (5-HMF), α-dicarbonyl compounds (α-DCs), and advanced glycation end products (AGEs), negatively affect human health. We analyzed MRP accumulation in chaste honey over four years. In the first year, α-DCs were dominant with total contents of 509.7 mg/kg. In the second year, Amadori compounds increased, accounting for the largest percentage. Their formation at the initial stage showed inhibition of the Maillard reaction over time. AGE contents were approximately 1.00 mg/kg over four years, which is negligible compared to other foods. Increased 5-HMF was significantly correlated with storage time (p < 0.01), making it a suitable indicator of honey quality. Due to the lack of MRP risk assessments, we compared our findings with daily intake of MRPs from other foods, and the levels of MRPs in honey over four years are acceptable.

Quantitation of α-Dicarbonyls, Lysine- and Arginine-Derived Advanced Glycation End Products, in Commercial Canned Meat and Seafood Products

Commercial sterilization is a thermal processing method commonly used in low-acid canned food products. Meanwhile, heat treatment can significantly promote advanced glycation end product (AGE) formation in foodstuffs. In this research, the validated analytical methods have been developed to quantitate both lysine- and arginine-derived AGEs and their precursors, α-dicarbonyls, in various types of commercial canned meat and seafood products. Methylglyoxal-hydroimidazolone 1 was the most abundant AGEs found in the canned food products, followed by Nε-(carboxyethyl)lysine, Nε-(carboxymethyl)lysine, and glyoxal-hydroimidazolone 1. Correlation analysis revealed that methylglyoxal and glyoxal were only positively associated with the corresponding arginine-derived AGEs, while their correlations with the corresponding lysine-derived AGEs were not significant. Importantly, we demonstrated for the first time that total sugar and carbohydrate contents might serve as the potential markers for the prediction of total AGEs in canned meats and seafoods. Altogether, this study provided a more complete view of AGEs' occurrence in commercial canned food products.

α-Dicarbonyl compounds in food products: Comprehensively understanding their occurrence, analysis, and control

α-Dicarbonyl compounds (α-DCs) are readily produced during the heating and storage of foods, mainly through the Maillard reaction, caramelization, lipid-peroxidation, and enzymatic reaction. They contribute to both the organoleptic properties (i.e., aroma, taste, and color) and deterioration of foods and are potential indicators of food quality. α-DCs are also important precursors to hazardous substances, such as acrylamide, furan, advanced lipoxidation end products, and advanced glycation end products, which are genotoxic, neurotoxic, and linked to several diseases. Recent studies have indicated that dietary α-DCs can elevate plasma α-DC levels and lead to "dicarbonyl stress." To accurately assess their health risks, quantifying α-DCs in food products is crucial. Considering their low volatility, inability to absorb ultraviolet light, and high reactivity, the analysis of α-DCs in complex food systems is a challenge. In this review, we comprehensively cover the development of scientific approaches, from extraction, enrichment, and derivatization, to sophisticated detection techniques, which are necessary for quantifying α-DCs in different foods. Exposure to α-DCs is inevitable because they exist in most foods. Recently, novel strategies for reducing α-DC levels in foods have become a hot research topic. These strategies include the use of new processing technologies, formula modification, and supplementation with α-DC scavengers (e.g., phenolic compounds). For each strategy, it is important to consider the potential mechanisms underlying the formation and removal of process contaminants. Future studies are needed to develop techniques to control α-DC formation during food processing, and standardized approaches are needed to quantify and compare α-DCs in different foods.

Investigation on the Contents of Nε-carboxymethyllysine, Nε-carboxyethyllysine, and N-nitrosamines in Commercial Sausages on the Chinese Market

Sausages are among the most popular meat products worldwide. However, some harmful products, such as advanced glycation end-products (AGEs) and N-nitrosamines (NAs), can be formed simultaneously during sausage processing. In this study, the contents of AGEs, NAs, α-dicarbonyls and the proximate composition were investigated in two kinds of commercial sausages (fermented sausages and cooked sausages) in the Chinese market. The correlations among them were further analyzed. The results showed that the fermented and cooked sausages had different in protein/fat contents and pH/thiobarbituric acid reactive substance values due to their different processing technologies and added ingredients. The N^ε-carboxymethyllysine (CML) and N^ε-carboxyethyllysine (CEL) concentrations varied from 3.67 to 46.11 mg/kg and from 5.89 to 52.32 mg/kg, respectively, and the NAs concentrations ranged from 1.35 to 15.88 µg/kg. The contents of some hazardous compounds, such as CML, N-nitrosodimethylamine, and N-nitrosopiperidine, were observed to be higher in the fermented sausages than in the cooked sausages. Moreover, levels of NAs in some sausage samples exceeded the limit of 10 µg/kg issued by the United States Department of Agriculture, suggesting that particular attention should be paid to mitigating NAs, especially in fermented sausages. The correlation analysis suggested that the levels of AGEs and NAs were not significantly correlated in both kinds of sausages.

Reduction in Five Harmful Substances in Fried Potato Chips by Pre-Soaking Treatment with Different Tea Extracts

Thermally processed food always contains various types of harmful substances. Control of their levels in food is important for human health. This work used the extracts from green tea dust, old green tea, yellow tea, white tea, oolong tea, and black tea to simultaneously mitigate diverse harmful substances in fried potato chips. The six tea extracts (30 g/L) all showed considerable inhibitory effects on the formation of 5-hydroxymethylfurfural (reduced by 19.8%-53.2%), glyoxal (26.9%-36.6%), and methylglyoxal (16.1%-75.1%). Green tea and black tea extracts exhibited better inhibitory abilities than the other three teas and were further investigated for other harmful compounds by various concentration treatments. Finally, pre-soaking of fresh potato slices in 50 g/L extracts of green tea dust displayed, overall, the most promising inhibitory capacity of HMF (decreased by 73.3%), glyoxal (20.3%), methylglyoxal (69.7%), acrylamide (21.8%), and fluorescent AGEs (42.9%) in fried potato chips, while it exhibited the least impact on the color and texture. The high level of catechins in green tea dust may contribute most to its outstanding inhibitory effect, whereas the distinguished inhibitory effect of black tea extract was speculated to be attributable to the high levels of theaflavins and amino acids in the fully fermented tea. This study indicated that green tea dust, a predominant waste of the tea industry, had great potential to be exploited to improve food quality and safety.

Investigation on the contents of heat-induced hazards in commercial nuts

The purpose was to investigate the contents of heat-induced hazards by liquid chromatography-tandem mass spectrometry (LC-MS/MS) in 44 commercial nuts. Results showed that content ranges of Acrylamide (AA), 5-hydroxymethylfurfural (5-HMF), N^ε-carboxymethyl-lysine (CML), N^ε-carboxyethyl-lysine (CEL), 3-Deoxyglucosone (3-DG), Glyoxal (GO), and Methylglyoxal (MGO) were ND-123.57 µg/kg, 0.57-213.42 mg/kg, 3.18-18.67 mg/kg, 3.98-57.85 mg/kg, 1.5-133.86 mg/kg, 0.45-1.59 mg/kg and 0.29-13.84 mg/kg, respectively. Sunflower seeds contained more heat-induced hazards followed by pistachios, cashews, almonds, walnuts and hazelnuts. The content of 5-HMF was positively correlated with the content of 3-DG. CML exhibited positive correlation with content of GO while no correlation between CEL and MGO. Higher levels of 3-DG and 5-HMF were observed in nuts produced with sugar and honey. Deep processing had a stronger promoting effect on CML and CEL formation. These data could provide a crucial guide for consumers to select nut products which might reduce heat-induced hazards intake.

The Intake of Dicarbonyls and Advanced Glycation Endproducts as Part of the Habitual Diet Is Not Associated with Intestinal Inflammation in Inflammatory Bowel Disease and Irritable Bowel Syndrome Patients

A Western diet comprises high levels of dicarbonyls and advanced glycation endproducts (AGEs), which may contribute to flares and symptoms in inflammatory bowel disease (IBD) and irritable bowel syndrome (IBS). We therefore investigated the intake of dietary dicarbonyls and AGEs in IBD and IBS patients as part of the habitual diet, and their association with intestinal inflammation. Food frequency questionnaires from 238 IBD, 261 IBS as well as 195 healthy control (HC) subjects were used to calculate the intake of dicarbonyls methylglyoxal, glyoxal, and 3-deoxyglucosone, and of the AGEs Nε-(carboxymethyl)lysine, Nε-(1-carboxyethyl)lysine and methylglyoxal-derived hydroimidazolone-1. Intestinal inflammation was assessed using faecal calprotectin. The absolute dietary intake of all dicarbonyls and AGEs was higher in IBD and HC as compared to IBS (all p < 0.05). However, after energy-adjustment, only glyoxal was lower in IBD versus IBS and HC (p < 0.05). Faecal calprotectin was not significantly associated with dietary dicarbonyls and AGEs in either of the subgroups. The absolute intake of methylglyoxal was significantly higher in patients with low (<15 μg/g) compared to moderate calprotectin levels (15−<50 μg/g, p = 0.031). The concentrations of dietary dicarbonyls and AGEs generally present in the diet of Dutch patients with IBD or IBS are not associated with intestinal inflammation, although potential harmful effects might be counteracted by anti-inflammatory components in the food matrix.

Habitual intake of dietary methylglyoxal is associated with less low-grade inflammation: the Maastricht Study

BACKGROUND

Dicarbonyls are major reactive precursors of advanced glycation endproducts (AGEs). Dicarbonyls are formed endogenously and also during food processing. Circulating dicarbonyls and AGEs are associated with inflammation and microvascular complications of diabetes, but for dicarbonyls from the diet these associations are currently unknown.

OBJECTIVES

We sought to examine the associations of dietary dicarbonyl intake with low-grade inflammation and microvascular function.

METHODS

In 2792 participants (mean ± SD age: 60 ± 8 y; 50% men; 26% type 2 diabetes) of the population-based cohort the Maastricht Study, we estimated the habitual intake of the dicarbonyls methylglyoxal (MGO), glyoxal (GO), and 3-deoxyglucosone (3-DG) by linking FFQ outcome data to our food composition database of the MGO, GO, and 3-DG content of >200 foods. Low-grade inflammation was assessed as six plasma biomarkers, which were compiled in a z score. Microvascular function was assessed as four plasma biomarkers, compiled in a zscore; as diameters and flicker light-induced dilation in retinal microvessels; as heat-induced skin hyperemic response; and as urinary albumin excretion. Cross-sectional associations of dietary dicarbonyls with low-grade inflammation and microvascular function were investigated using linear regression with adjustments for age, sex, potential confounders related to cardiometabolic risk factors, and lifestyle and dietary factors.

RESULTS

Fully adjusted analyses revealed that higher intake of MGO was associated with a lower z score for inflammation [standardized β coefficient (STD β): -0.05; 95% CI: -0.09 to -0.01, with strongest inverse associations for hsCRP and TNF-α: both -0.05; -0.10 to -0.01]. In contrast, higher dietary MGO intake was associated with impaired retinal venular dilation after full adjustment (STD β: -0.07; 95% CI: -0.12 to -0.01), but not with the other features of microvascular function. GO and 3-DG intakes were not consistently associated with any of the outcomes.

CONCLUSION

Higher habitual intake of MGO was associated with less low-grade inflammation. This novel, presumably beneficial, association is the first observation of an association between MGO intake and health outcomes in humans and warrants further investigation.

Application of Aroma Precursors in Food Plant Raw Materials: Biotechnological Aspect

The article is devoted to the analysis of the main factors accompanying the use of aroma precursors, in particular, of a lipid nature, in food raw materials. The prerequisites for the impact on the precursors of aroma with the help of plant enzymes are given. The purpose of the article is to analyze the biotechnological aspect, which is based on enzymatic reactions with aroma precursors and enzymes of plant origin. Features of the mechanism of action of lipid precursors are highlighted, their diversity causing various characteristic reactions is analyzed, and possible end products of reactions with certain odors are noted. The attention is paid to the issue of the status of the naturalness of flavor precursors in food products, which varies in different countries. A scheme of factors influencing the formation of aroma from lipid precursors has been developed. The influence of pigments of carotenoid nature on the aroma is considered, namely: examples of instantaneous change of watermelon aroma to pumpkin one due to isomerization of carotenoids are given. The main factors of enzymatic formation of aroma from precursors of polyunsaturated fatty acids for their effective use by creating micromicelles are summarized. A way to overcome the barrier of interaction between lipid precursors of a hydrophobic nature and hydrophilic enzymes has been substantiated. It is proposed to accelerate enzymatic reactions under in vitro conditions and use the vacuum effect to overcome the barrier between enzymes and precursors. To explain the effect of vacuum in a system with enzymes, ideas about disjoining pressure and the reasonable expediency of its use are considered. A schematic process flow diagram for the restoration of aroma lost during the technological processing of raw materials is given; it demonstrates the factors for ensuring interfacial activation conditions for enzymes and aroma precursors.

Structural characterization of polar melanoidins deriving from Maillard reaction intermediates - A model approach

Chemical conversions of reducing sugars and amino compounds induce the formation of heterogenous, high-molecular-weight colorants ('melanoidins') with widely unknown chemical structures. Model experiments of reactive intermediates have proven to be suitable for unravelling the formation mechanisms of colored reaction products. Here, the active methylene norfuraneol was selected and incubated individually as well as in combination with glyoxal, glycolaldehyde, and acetaldehyde at elevated temperatures. Photometric and chromatographic methods as well as mass spectrometry were used to analyze the colored reaction products and reveal the reactivity of different carbonyls regarding the formation of heterogenous oligomers. Aqueous solutions of norfuraneol and glyoxal exceeded the color formation of all other model reaction systems and it could be shown that the initial reactants as well as their degradation products were incorporated into the colorants. The colored oligomers described herein were composed of carbohydrate-based intermediates of the Maillard reaction and defined as melanoidin precursors or pre-melanoidins.

Characterization of Colorants Formed by Non-Enzymatic Browning Reactions of Hydroxycinnamic Acid Derivatives

The browning of plant-based food is commonly understood to result from the enzymatic polymerization of phenolic compounds to pigments, called melanin. However, during the thermal treatment of food, enzymes are deactivated, and non-enzymatic reactions predominate. The extent of the contribution of phenolic compounds to these non-enzymatic reactions has been speculated (“melanin-like vs. melanoidin-like”), but the literature is limited. Therefore, the aim of the present study was to investigate the heat-induced reactions of caffeic acid (CA), para-coumaric acid (CS), ferulic acid (FA), hydrocaffeic acid (HC), and 5-O-caffeoylquinic acid (CGA) under dry conditions. The model systems were characterized by color formation, reactant conversion, and antioxidant properties. Reaction products were analyzed by high-resolution mass spectrometry (HRMS) and nuclear magnetic resonance (NMR) spectroscopy. Decarboxylation could be classified as the driving force for the observed color formation and was significantly impacted by the substitution of the aromatic system. Reaction products were found to contribute to an increase in the antioxidant properties of the model systems. The oligomers described in this study could be incorporated into food melanoidins, contributing to the color and antioxidant properties observed in roasted food rich in phenolic compounds, such as coffee or cocoa.

Studies on the Reaction of Dietary Methylglyoxal and Creatine during Simulated Gastrointestinal Digestion and in Human Volunteers

The reactive 1,2-dicarbonyl compound methylglyoxal (MGO) is consumed with food and its concentrations decrease during digestion. In the present paper, the reaction of MGO with creatine, arginine, and lysine during simulated digestion, and its reaction with creatine during the digestion in human volunteers, was studied. Therefore, simulated digestion experiments with a gastric and an intestinal phase were performed. Additionally, an intervention study with 12 subjects consuming MGO-containing Manuka honey and creatine simultaneously or separately was conducted. Derivatization with o-phenylenediamine and HPLC–UV was used to measure MGO, while creatine and glycated amino compounds were analyzed via HPLC–MS/MS. We show that MGO quickly reacts with creatine and arginine, but not lysine, during simulated digestion. Creatine reacts with 56% of MGO to form the hydroimidazolone MG-HCr, and arginine reacted with 4% of MGO to form the hydroimidazolone MG-H1. In the intervention study, urinary MG-HCr excretion is higher in subjects who consumed MGO and creatine simultaneously compared to subjects who ingested the substances separately. This demonstrates that the 1,2-dicarbonyl compound MGO reacts with amino compounds during human digestion, and glycated adducts are formed. These contribute to dietary glycation products consumed, and should be considered in studies investigating their physiological consequences.

Maillard reaction products and amino acid cross-links in liquid infant formula: Effects of UHT treatment and storage

The formation of Maillard reaction products, including Amadori compounds (determined as furosine), advanced glycation end products (AGEs), α-dicarbonyl and furfural compounds, as well as amino acid cross-links (lysinoalanine and lanthionine) was investigated in direct (DI) and indirect (IN) UHT-treated experimental liquid infant formula (IF) during storage at 40 °C. IN-IF had higher concentrations of all investigated compounds compared to DI-IF and low pasteurized IF. IN UHT treatment induced significantly higher concentrations of α-dicarbonyl compounds (glyoxal, methylglyoxal, 3-deoxyglucosone and 3-deoxygalactosone) compared to DI, which facilitated increased formation of AGEs (N-Ɛ-(carboxymethyl)lysine, methylglyoxal- and glyoxal-derived hydroimidazolones) in unstored IFs. During storage for 6 months, concentrations of furosine and AGEs increased while α-dicarbonyl compounds decreased. Principal component analysis indicated that differences between IN-IF and DI-IF disappeared after 2 months of storage. IN-IF had higher concentrations of lysinoalanine and lanthionine and lower concentrations of available lysine and arginine than DI-IF indicating higher loss of protein quality in IN-IF.

Formation of melanoidins - Aldol reactions of heterocyclic and short-chain Maillard intermediates

In the course of the Maillard reaction, reducing sugars and amino compounds are converted to colorants, whose chemical structures are still mostly unknown. Active methylene compounds like norfuraneol that can initiate aldol condensation reactions are considered as key intermediates in this reaction. The aim of the present study was to characterize color formation of norfuraneol with different carbonyl compounds and to identify the underlying mechanisms of the reaction. Norfuraneol was incubated with methylglyoxal or diacetyl at elevated temperatures and the resulting reaction mixtures were analyzed by means of high-resolution mass spectrometry. It was demonstrated that aldol reactions lead to the formation of heterogeneous carbohydrate-based oligomers, which are likely to contribute to the elevated browning observed in the reaction mixtures. Furthermore, redox reactions were identified as another important part of the reaction, resulting in an increasing number of double bonds in the detected reaction products.

Formation of advanced glycation end products by novel food processing technologies: A review

Advanced glycation end products (AGEs) are a diverse group of compounds formed endogenously and exogenously due to non-enzymatic glycation of proteins and lipids. Although the effects of heating on AGE concentrations in foods are known, few studies have been published addressing the effects of new processing technologies on AGE formation. This work focuses on the current scientific knowledge about the impacts of novel technologies on AGE formation in food products. Most studies do not measure AGE content directly, evaluating only products of the Maillard reaction. Moreover, these studies do not compare distinct operational conditions associated with novel technologies. This lack of information impacts negatively the establishment of process-composition relationships for foods with safe AGE dietary intakes. Overall, the outcomes of this review suggest that the use of novel technologies is a promising alternative to produce food products with a lower AGE content.

Effects of Air Frying on French Fries: The Indication Role of Physicochemical Properties on the Formation of Maillard Hazards, and the Changes of Starch Digestibility

This study focused on the formation of Maillard hazards in air fried fries, highlighting the correlation between the resultant physical properties of the fries and the formation of Maillard hazards. In the meantime, the effects of air frying on the in vitro starch digestibility of fries were explored. Potato strips were fried at various temperatures (180-200°C) and time (12-24 min). Results indicated that the extent of browning, hardness, and the contents of Maillard hazards (acrylamide, 5-hydroxymethylfurfural, methylglyoxal, and glyoxal) all increased steadily with air frying temperature and time. Moisture content were negatively correlated (p < 0.001) with Maillard hazards content and physicochemical properties except for L^* with the correlation coefficients range from -0.53 to 0.94, and positively correlated with L^* value with correlation coefficient was 0.91, hence, reducing the Maillard hazard exposure while maintaining the desired product quality can be achieved by controlling the moisture content of the air fried French fries. Compared with deep frying (180°C-6 min), air frying decreased acrylamide and 5-hydroxymethylfurfural content with the maximum reduction rate were 47.31 and 57.04%, respectively. In addition, the in vitro digestion results suggested that air frying resulted in higher levels of slowly digestible starch (48.54-58.42%) and lower levels of resistant starch (20.08-29.34%) as compared to those from deep frying (45.59 ± 4.89 and 35.22 ± 0.65%, respectively), which might contribute to more balanced blood sugar levels after consumption. Based on the above results, it was concluded that air frying can reduce the formation of food hazards and was relatively healthier.

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

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

In Vitro Reactivity of the Glucose Degradation Product 3,4-Dideoxyglucosone-3-ene (3,4-DGE) towards Abundant Components of the Human Blood Circulatory System

3,4-Dideoxyglucosone-3-ene (3,4-DGE) is a glucose degradation product present in processed foods and medicinal products. Additionally, its constant formation from 3-deoxyglucosone in plasma has been suggested. Due to its α,β-unsaturated dicarbonyl moiety, 3,4-DGE is highly reactive and has shown harmful effects in vitro. Here, we investigated the impact of major components of the human blood circulatory system on 3,4-DGE in vitro. Under physiological conditions, plasma concentrations of human serum albumin (HSA) reacted efficiently with 3,4-DGE, resulting in only 8.5% of the initial 3,4-DGE concentration after seven hours (vs. 83.4% without HSA, p < 0.001). Thereby, accessible thiol groups were reduced from 0.121 to 0.064 mol/mol HSA, whereas ketoprofen binding and esterase-like activity of HSA were not affected. Plasma concentrations of glutathione (GSH) reacted immediately and completely with 3,4-DGE, leading to two stereoisomeric adducts. Plasma concentrations of immunoglobulin G (IgG) bound to 3,4-DGE to a lower extent, resulting in 62.6% 3,4-DGE after seven hours (vs. 82.2% in the control, p < 0.01). Immobilized human collagen type IV did not alter 3,4-DGE concentrations. The results indicated that particularly HSA, GSH, and IgG readily scavenge 3,4-DGE after its appearance in the blood stream, which may be associated with a reduced antioxidative and cytoprotective activity for the living cells and, thus, the human organism by blocking free thiol groups.

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

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

The role of endogenous versus exogenous sources in the exposome of putative genotoxins and consequences for risk assessment

The “totality” of the human exposure is conceived to encompass life-associated endogenous and exogenous aggregate exposures. Process-related contaminants (PRCs) are not only formed in foods by heat processing, but also occur endogenously in the organism as physiological components of energy metabolism, potentially also generated by the human microbiome. To arrive at a comprehensive risk assessment, it is necessary to understand the contribution of in vivo background occurrence as compared to the ingestion from exogenous sources. Hence, this review provides an overview of the knowledge on the contribution of endogenous exposure to the overall exposure to putative genotoxic food contaminants, namely ethanol, acetaldehyde, formaldehyde, acrylamide, acrolein, α,β-unsaturated alkenals, glycation compounds, N-nitroso compounds, ethylene oxide, furans, 2- and 3-MCPD, and glycidyl esters. The evidence discussed herein allows to conclude that endogenous formation of some contaminants appears to contribute substantially to the exposome. This is of critical importance for risk assessment in the cases where endogenous exposure is suspected to outweigh the exogenous one (e.g. formaldehyde and acrolein).

The effect of five different sourdough on the formation of glyoxal and methylglyoxal in bread and influence of in vitro digestion

The aim of this study was to investigate sourdough impact on the in vitro bioaccessibility of Glyoxal (GO) and methylglyoxal (MGO). Five sourdough bread and one white bread (control bread) were prepared to observe sourdough influence on GO and MGO levels before and after in vitro digestion. GO and MGO levels increased in all breads after in vitro digestion. The highest increase in GO and MGO levels was realized in the control bread with bioaccessibility indexes (BIGO and BIMGO) of 8.67 and 4.14, respectively, whereas BIGO and BIMGO in sourdough breads were found in the range of 1.65 to 2.65 and 1.73 to 2.97, respectively. The extent of Maillard reaction (MR) in control bread was confirmed by FAST method. The lower increase in GO and MGO compounds after in vitro digestion thanks to sourdough addition may reduce bread's contribution of AGEs accumulation in the body.

Deciphering Changes in the Structure and IgE-Binding Ability of Ovalbumin Glycated by α-Dicarbonyl Compounds under Simulated Heating

As a complex reaction, biological consequences of the Maillard reaction (MR) on dietary proteins need to be deciphered. Despite previous studies on the structural and antigenic properties of ovalbumin (OVA) by MR, associated changes induced by specific MR intermediates and their downstream products are largely unknown. This study focused on the impacts of glycation by α-dicarbonyl compounds (α-DCs), intermediates of MR and precursors of advanced glycation end-products (AGEs), on the structural and IgE-binding properties of ovalbumin (OVA) under simulated heating. Methylglyoxal (MGO), glyoxal (GO), and butanedione (BU) were selected as typical α-DCs to generate glycated OVA with different AGE-modifications (AGE-Ms). The results showed that reactions between OVA and α-DCs generated OVA-AGE with various degrees of modification and conformational unfolding, and the reactivity of α-DCs followed the order GO > MGO > BU. Depending on the precursor type, the levels of 10 specific AGEs were verified, and the amounts of total AGEs increased with heating temperature and α-DC dosage. Compared to native OVA, glycated OVA showed reduced IgE-binding levels but with sRAGE-binding ligands, the extent of which was associated with the contents of total AGEs and Nε-carboxymethyllysine, and changes in certain protein conformational structures. High-resolution mass spectrometry further identified different AGE-Ms on the Lys and Arg residues of OVA, confirming variations in the glycation sites and their associations with the immunoreactive epitopes of OVA under different conditions.

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.

Higher habitual intake of dietary dicarbonyls is associated with higher corresponding plasma dicarbonyl concentrations and skin autofluorescence: the Maastricht Study

BACKGROUND

Dicarbonyls are highly reactive compounds and major precursors of advanced glycation end products (AGEs). Both dicarbonyls and AGEs are associated with development of age-related diseases. Dicarbonyls are formed endogenously but also during food processing. To what extent dicarbonyls from the diet contribute to circulating dicarbonyls and AGEs in tissues is unknown.

OBJECTIVES

To examine cross-sectional associations of dietary dicarbonyl intake with plasma dicarbonyl concentrations and skin AGEs.

METHODS

In 2566 individuals of the population-based Maastricht Study (age: 60 ± 8 y, 50% males, 26% with type 2 diabetes), we estimated habitual intake of the dicarbonyls methylglyoxal (MGO), glyoxal (GO), and 3-deoxyglucosone (3-DG) by combining FFQs with our dietary dicarbonyl database of MGO, GO, and 3-DG concentrations in > 200 commonly consumed food products. Fasting plasma concentrations of MGO, GO, and 3-DG were measured by ultra-performance liquid chromatography-tandem mass spectrometry. Skin AGEs were measured as skin autofluorescence (SAF), using the AGE Reader. Associations of dietary dicarbonyl intake with their respective plasma concentrations and SAF (all standardized) were examined using linear regression models, adjusted for age, sex, potential confounders related to cardiometabolic risk factors, and lifestyle.

RESULTS

Median intake of MGO, GO, and 3-DG was 3.6, 3.5, and 17 mg/d, respectively. Coffee was the main dietary source of MGO, whereas this was bread for GO and 3-DG. In the fully adjusted models, dietary MGO was associated with plasma MGO (β: 0.08; 95% CI: 0.02, 0.13) and SAF (β: 0.12; 95% CI: 0.07, 0.17). Dietary GO was associated with plasma GO (β: 0.10; 95% CI: 0.04, 0.16) but not with SAF. 3-DG was not significantly associated with either plasma 3-DG or SAF.

CONCLUSIONS

Higher habitual intake of dietary MGO and GO, but not 3-DG, was associated with higher corresponding plasma concentrations. Higher intake of MGO was also associated with higher SAF. These results suggest dietary absorption of MGO and GO. Biological implications of dietary absorption of MGO and GO need to be determined. The study has been approved by the institutional medical ethical committee (NL31329.068.10) and the Minister of Health, Welfare and Sports of the Netherlands (Permit 131088-105234-PG).

Analysis of Glyoxal- and Methylglyoxal-Derived Advanced Glycation End Products during Grilling of Porcine Meat

The reaction of the N⁶-amino group of lysine residues and 1,2-dicarbonyl compounds during Maillard processes leads to advanced glycation end products (AGEs). In the present work, we deliver a comprehensive analysis of changes of carbohydrates, dicarbonyl structures, and 11 AGEs during the grilling of porcine meat patties. While raw meat contained mainly glyoxal-derived N⁶-carboxymethyl lysine (CML), grilling led to an increase of predominantly methylglyoxal-derived AGEs N⁶-carboxyethyl lysine (CEL), N⁶-lactoyl lysine, methylglyoxal lysine dimer (MOLD), and methylglyoxal lysine amide (MOLA). Additionally, we identified and quantitated a novel methylglyoxal-derived amidine compound N¹,N²-di-(5-amino-5-carboxypentyl)-2-lactoylamidine (methylglyoxal lysine amide, MGLA) in heated meat. Analysis of carbohydrates suggested that approximately 50% of the methylglyoxal stemmed from the fragmentation of triosephosphates during the heat treatment. Surprisingly, N⁶-lactoyl lysine was the major AGE, and based on model incubations, we propose that approximately 90% must be explained by the nonenzymatic acylation of lysine through S-lactoylglutathione, which was quantitated for the first time in meat herein.