•We describe mechanisms of formation of advanced glycation endproducts (AGE).•We critically examine analytical procedures and current intake assessments for AGE.•We highlight different biological ...actions of high- and low molecular weight AGEs.•We assess AGE toxicity based on ADME, receptor interactions and in vivo effects.•We recommend more AGE research at the analytical, molecular, and biological level.
Advanced glycation endproducts (AGEs) form by Maillard-reactions after initial binding of aldehydes with amines or amides in heated foods or in living organisms. The mechanisms of formation may include ionic as well as oxidative and radical pathways. The reactions may proceed within proteins to form high-molecular weight (HMW) AGEs or among small molecules to form low-molecular weight (LMW) AGEs. All free amino acids form AGEs, but lysine or arginine side chains dominate AGE formation within proteins. The analysis of AGEs in foods and body fluids is most often performed by ELISA or LC-MS; however, none of the methodologies cover all HMW and LMW AGEs. Most research is, therefore, carried out using ’representative’ AGE compounds, most often Nε-carboxymethyl-lysine (CML). Only LMW AGEs, including peptide-bound forms, and carbonyls may be absorbed from the gut and contribute to the body burden of AGEs. Some AGEs interact with specific pro- or anti-inflammatory receptors. Most studies on the biological effects of AGEs have been carried out by administering heated foods. The pro-inflammatory and deteriorating biological effects of AGEs in these studies, therefore, need further confirmation. The current review points out several research needs in order to address important questions on AGEs in foods and health.
Scope
Milk powder is commonly consumed throughout the world. However, advanced glycation end products (AGEs) will form in milk powder during thermal processing and long‐term storage. This study aimed ...to identify such compounds with potential as new urinary biomarkers of intake of heat‐treated skimmed milk powder (HSMP).
Methods and Results
A parallel study is performed with different dosages of HSMP as well as hydrolyzed HSMP and untreated skimmed milk powder (SMP) in 36 rats. The 24‐h urine samples on day 7 or 8 are collected and profiled by untargeted UPLC‐Qtof‐MS metabolomics. Statistical analysis revealed 25 metabolites differentiating SMP and HSMP; nineteen of these structures are proposed as lysine‐ and arginine‐derived AGEs, and heterocyclic compounds.
Conclusion
These metabolites may potentially serve as biomarkers of food intake pending further validation to assess intakes of heat‐processed dairy foods and thus help to elucidate the effects of HSMP consumption or dietary AGEs on human health.
The UPLC‐Qtof‐MS based untargeted metabolomics is applied for profiling 24‐h urine to discover new metabolites of heat‐treated skimmed milk powder. Twelve metabolites are found to be new advanced glycation end products; these could be useful in exploring the biochemical and physiological responses associated with consumption of heat‐processed dairy products, in the context of food processing, nutrition, and health.
Dietary advanced glycation end products (AGE) formed during heating of food have gained interest as potential nutritional toxins with adverse effects on inflammation and glucose metabolism. In the ...present study, we investigated the short-term effects of high and low molecular weight (HMW and LMW) dietary AGE on insulin sensitivity, expression of the receptor for AGE (RAGE), the AGE receptor 1 (AGER1) and TNF-α, F2-isoprostaglandins, body composition and food intake. For 2 weeks, thirty-six Sprague–Dawley rats were fed a diet containing 20 % milk powder with different proportions of this being given as heated milk powder (0, 40 or 100 %), either native (HMW) or hydrolysed (LMW). Gene expression of RAGE and AGER1 in whole blood increased in the group receiving a high AGE LMW diet, which also had the highest urinary excretion of the AGE, methylglyoxal-derived hydroimidazolone 1 (MG-H1). Urinary excretion of N
ε
-carboxymethyl-lysine increased with increasing proportion of heat-treated milk powder in the HMW and LMW diets but was unrelated to gene expression. There was no difference in insulin sensitivity, F2-isoprostaglandins, food intake, water intake, body weight or body composition between the groups. In conclusion, RAGE and AGER1 expression can be influenced by a high AGE diet after only 2 weeks in proportion to MG-H1 excretion. No other short-term effects were observed.
Advanced glycation end products (AGEs) have been implicated in the pathophysiology of type 2 diabetes and cardiovascular disease. We aimed to determine the associations of urinary ...carboxymethyl-lysine (CML) and methylglyoxal-hydroimidazolone (MG-H1) levels with cardiometabolic parameters in metabolically healthy obese women. Anthropometric, glycemic, cardiovascular, and urinary AGE parameters were measured in 58 metabolically healthy obese women (age: 39.98 ± 8.72 years; body mass index (BMI): 32.29 ± 4.05 kg/m
). Urinary CML levels were positively associated with BMI (
= 0.29,
= 0.02). After adjustment for age and BMI, there was a trend for positive associations between urinary CML levels and fasting (
= 0.06) and 2 h insulin (
= 0.05) levels, and insulin resistance measured by homeostatic model assessment (HOMA-IR) (
= 0.06). Urinary MG-H1 levels were positively associated with systolic and diastolic blood pressure, pulse pressure, mean arterial pressure, and total and low-density lipoprotein cholesterol after adjustment for age, BMI, and HOMA-IR (all
˂ 0.05). There were no associations between urinary CML levels and cardiovascular parameters, and between urinary MG-H1 levels and glycemic measurements. Our data support a role of urinary AGEs in the pathophysiology of insulin resistance and cardiovascular disease; however, future studies are highly warranted.
PURPOSE: Advanced glycation end products (AGEs) formed in food during high-heat cooking may induce overeating and inflammation. We investigated whether AGE contents in a single meal affect ...postprandial appetite and markers of inflammation, endothelial activation, and oxidative stress. METHODS: In total, 19 healthy overweight individuals completed a crossover meal test with two meals of identical ingredients prepared by roasting (H-AGE) or steaming (L-AGE), respectively. Postprandial blood samples were analysed for Nᵋ-carboxymethyl-lysine (CML), appetite-regulating gut hormones, glucose, insulin, triacylglycerol, and markers of inflammation and endothelial activation. Subjective appetite ratings and subsequent food intake were also assessed, and urine was analysed for CML, methylglyoxal-derived hydroimidazolone (MG-H1), and F2-isoprostanes. RESULTS: CML content of the H- and L-AGE meals was 5.0 and 2.8 mg, respectively. Plasma CML and urinary CML and MG-H1 tended to be higher after the H-AGE meal. There was no change in subsequent food intake, appetite sensations, or appetite hormone responses between meals, except for the overall ghrelin response, which was higher after the H-AGE meal compared with the L-AGE meal (p = 0.016). There was an increased glycaemic response to the H-AGE meal (p = 0.027) compared with the L-AGE meal. Inflammatory and endothelial activation markers did not differ between meals, but there was an overall effect on endothelial activation (p = 0.021) and on the oxidative marker, F2-isoprostanes, in urine (p = 0.013). CONCLUSION: The present study did not show any pronounced effects of AGEs on appetite and markers of inflammation, but did indicate that AGEs may affect postprandial ghrelin, oxidative stress, and glucose responses.
Insights into the evolution of plant cell walls have important implications for comprehending these diverse and abundant biological structures. In order to understand the evolving structure–function ...relationships of the plant cell wall, it is imperative to trace the origin of its different components.
The present study is focused on plant 1,4-β-xylan, tracing its evolutionary origin by genome and transcriptome mining followed by phylogenetic analysis, utilizing a large selection of plants and algae. It substantiates the findings by heterologous expression and biochemical characterization of a charophyte alga xylan synthase.
Of the 12 known gene classes involved in 1,4-β-xylan formation, XYS1/IRX10 in plants, IRX7, IRX8, IRX9, IRX14 and GUX occurred for the first time in charophyte algae. An XYS1/IRX10 ortholog from Klebsormidium flaccidum, designated K. flaccidum XYLAN SYNTHASE-1 (KfXYS1), possesses 1,4-β-xylan synthase activity, and 1,4-β-xylan occurs in the K. flaccidum cell wall.
These data suggest that plant 1,4-β-xylan originated in charophytes and shed light on the origin of one of the key cell wall innovations to occur in charophyte algae, facilitating terrestrialization and emergence of polysaccharide-based plant cell walls.
Short-term effects of dietary advanced glycation end products in rats Poulsen, Malene W; Jeanette M. AndersenauthorDepartment of Nutrition, Exercise and Sports, University of Copenhagen, Rolighedsvej 30, 1958 Frederiksberg C, DenmarkDepartment of Drug Design and Pharmacology, University of Copenhagen, Universitetsparken 2, 2100 Copenhagen Ã, Denmark; Rikke V. HedegaardauthorDepartment of Food Science, University of Copenhagen, Rolighedsvej 26, 1958 Frederiksberg C, Denmark ...
2015
Journal Article
Intensive sampling at the coastal waters of the central Red Sea during a period of thermal stratification, prior to the main seasonal bloom during winter, showed that vertical patches of prokaryotes ...and microplankton developed and persisted for several days within the apparently density uniform upper layer. These vertical structures were most likely the result of in situ growth and mortality (e.g., grazing) rather than physical or behavioural aggregation. Simulating a mixing event by adding nutrient-rich deep water abruptly triggered dense phytoplankton blooms in the nutrient-poor environment of the upper layer. These findings suggest that vertical structures within the mixed layer provide critical seeding stocks that can rapidly exploit nutrient influx during mixing, leading to winter bloom formation.
Summary
<list list-type='bullet'>
Insights into the evolution of plant cell walls have important implications for comprehending these diverse and abundant biological structures. In order to ...understand the evolving structure–function relationships of the plant cell wall, it is imperative to trace the origin of its different components.
The present study is focused on plant 1,4‐β‐xylan, tracing its evolutionary origin by genome and transcriptome mining followed by phylogenetic analysis, utilizing a large selection of plants and algae. It substantiates the findings by heterologous expression and biochemical characterization of a charophyte alga xylan synthase.
Of the 12 known gene classes involved in 1,4‐β‐xylan formation,
<styled-content style='fixed-case'>XYS</styled-content>
1/
<styled-content style='fixed-case'>IRX</styled-content>
10 in plants,
<styled-content style='fixed-case'>IRX</styled-content>
7,
<styled-content style='fixed-case'>IRX</styled-content>
8,
<styled-content style='fixed-case'>IRX</styled-content>
9,
<styled-content style='fixed-case'>IRX</styled-content>
14 and
<styled-content style='fixed-case'>GUX</styled-content>
occurred for the first time in charophyte algae. An
<styled-content style='fixed-case'>XYS</styled-content>
1/
<styled-content style='fixed-case'>IRX</styled-content>
10 ortholog from
Klebsormidium flaccidum
, designated
K. flaccidum
<styled-content style='fixed-case'>XYLAN SYNTHASE</styled-content>
‐1 (
Kf
<styled-content style='fixed-case'>XYS</styled-content>
1), possesses 1,4‐β‐xylan synthase activity, and 1,4‐β‐xylan occurs in the
K. flaccidum
cell wall.
These data suggest that plant 1,4‐β‐xylan originated in charophytes and shed light on the origin of one of the key cell wall innovations to occur in charophyte algae, facilitating terrestrialization and emergence of polysaccharide‐based plant cell walls.
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