In 2008 the global prevalence of hypertension [high blood pressure (BP), systolic ≥140 mmHg and/or diastolic ≥90 mmHg] was around 40% in adults > 25 yrs of age, according to the 2013 WHO statistics. Hypertension is a major risk factor for myocardial infarction, heart failure and stroke. Currently, around 20% of the Canadian population is affected by hypertension. Hypertension is more closely associated with diabetes. More than two thirds of people with diabetes have hypertension, alongwith increased activity of the renin angiotensin aldosterone (RAAS) system. The RAAS plays a major role in maintaining fluid balance, vascular tone and BP. The components of the RAAS include the hormone renin, which cleaves angiotensinogen, a circulating inactive peptide into angiotensin I. Angiotensin converting enzyme (ACE) converts angiotensin I into the active peptide angiotensin II (Ang II). Ang II causes vasoconstriction, sodium reabsorption from the kidney tubules and also release of the hormone, aldosterone, from the adrenal cortex. The epidemic of hypertension, diabetes and obesity is widely attributed to a high carbohydrate diet, containing mainly high fructose corn syrup and sucrose. However, the underlying molecular mechanisms are far from clear. A high fructose diet increases BP in Sprague-Dawley (SD) rats; along with elevated plasma and aortic levels of methylglyoxal (MG). MG is a reactive dicarbonyl compound mainly formed as an intermediate during glycolysis. Small amounts of MG are also formed during amino acid (threonine) and fatty acid metabolism. MG reacts with certain proteins to form irreversible advanced glycation end products (AGEs). MG has high affinity for arginine, lysine and cysteine. Plasma MG levels are increased in hypertensive rats and diabetic patients. However, it is not yet clear whether MG is the cause or effect of hypertension. Moreover, safe and specific MG scavengers are not available. The aim of the project was to determine the effect of MG and a high fructose diet on the RAAS and the BP in male SD rats. The hypothesis that L-arginine, and its inactive isomer D-arginine, can efficiently scavenge MG in vitro, was also tested. Male SD rats were treated with a continuous infusion of MG with a subcutaneous minipump for 4 weeks, or with a high fructose diet (60% of total calories) for 16 weeks. We also used isolated aortic rings from 12 week old normal male SD rats to study endothelial function. Organs / tissues, cultured human umbilical vein endothelial cells (HUVECs) and vascular smooth muscle cells (VSMCs) were used for molecular studies. HPLC, Western blotting and Q-PCR were used to measure MG, reduced glutathione (GSH), proteins and mRNA, respectively. siRNA for angiotensinogen and the receptor for advanced glycation endproducts (RAGE) were used to study mechanisms. MG treated rats developed a significant increase in BP and plasma levels of aldosterone, renin, angiotensin and catecholamines. MG level, and protein and mRNA for angiotensin, AT1 receptor, adrenergic α1D receptor and renin were significantly increased in the aorta and/or kidney of MG treated rats, a novel finding. Alagebrium, a MG scavenger and AGEs breaker, attenuated the above effects of MG. Treatment of cultured VSMCs with MG or high glucose (25mM) significantly increased cellular MG, and protein and mRNA for nuclear factor kappa B (NF-κB), angiotensin, AT1 and α1D receptors, which were prevented by inhibition of NF-κB, and by alagebrium. Silencing of mRNA for RAGE prevented the increase in NF-kB induced by MG. Silencing of mRNA for angiotensinogen prevented the increase in NF-κB, angiotensin, AT1 and α1D receptors’ protein. Fructose treated rats developed a significant increase in BP. MG level and protein and mRNA for angiotensin II, AT1 receptor, adrenergic α1D receptor and renin were significantly increased, whereas GSH levels were decreased, in the aorta and/or kidney of fructose fed rats. The protein expression of the receptor for AGEs (RAGE) and NF-κB were also significantly increased in the aorta of fructose fed rats. MG treated VSMCs showed increased protein for angiotensin II, AT1 receptor, and α1D receptor. The effects of fructose and MG were attenuated by metformin, a MG scavenger and AGEs inhibitor. In experiments to test the MG scavenging action of arginine, both D-arginine and L-arginine prevented the attenuation of acetylcholine-induced endothelium-dependent vasorelaxation by MG and high glucose. However, the inhibitory effect of the NOS inhibitor, Nω-nitro-L-arginine methyl ester, on vasorelaxation was prevented only by L-arginine, but not by D-arginine. MG and high glucose increased protein expression of arginase, a novel finding, and also of NADPH oxidase 4 and NF-κB, and production of reactive oxygen species in HUVECs and VSMCs, which were attenuated by D- and L-arginine. However, D- and L-arginine did not attenuate MG and high glucose-induced increased arginase activity in VSMCs and the aorta. D- and L-arginine also attenuated the increased formation of the MG-specific AGE, Nε-carboxyethyl lysine, caused by MG and high glucose in VSMCs. In conclusion, MG activates NF-κB through RAGE and thereby increases renin angiotensin levels, a novel finding, and a probable mechanism of increase in BP. There is a strong association between elevated levels of MG, RAGE, NF-κB, mediators of the RAAS and BP in high fructose diet fed rats. Arginine attenuates the increased arginase expression, oxidative stress, endothelial dysfunction and AGEs formation induced by MG and high glucose, by an endothelial NOS independent mechanism.

Methylglyoxal (MG), a highly reactive dicarbonyl accumulates after myocardial infarction (MI), causing adverse remodelling and cardiac dysfunction. We hypothesized that therapy using bone marrow cells (BMCs) overexpressing glyoxalase1 (Glo1), the main enzyme that metabolizes MG, injected into mouse MI model would translate into better survival of transplanted cells and improve their therapeutic effect. We found that Glo1 expression is significantly reduced at 7 days post-MI. Glo1 BMCs exposed to MG in vitro displayed greater angiogenic potential and reduced reactive oxygen species production compared to wild type (WT) BMCs. However, in the mouse MI model, Glo1 BMCs did not improve cardiac function or vascularity or reduce scar formation compared to WT BMCs and saline treatments. In conclusion, Glo1 overexpression in BMCs does not confer superior therapeutic efficacy for treating MI under the conditions tested.

Myocardial infarction (MI) persists as one of the leading causes of death worldwide. Often patients whom survive the initial injury will develop heart failure characterized by a dilated and functionally incompetent heart. Heart failure (HF) carries a worse prognosis than most cancers, and the only curative therapy to date is heart transplantation. A better understanding of the repair and remodeling processes post-MI, and the development of novel therapies are required to combat this burgeoning medical challenge. This thesis research sought to identify a novel mediator of the impaired cardiac remodeling that often occurs post-MI, and to characterize a biomaterial hydrogel therapy as a novel treatment. We investigated the role of methylglyoxal (MG), an important precursor to advanced glycation end-products (AGE), using a transgenic mouse model to over-express glyoxalase 1 (GLO1). GLO1 is the primary enzyme involved in metabolizing MG and preventing its accumulation. The role for MG and AGEs in MI and HF had been alluded to in the literature, yet no study to date has causally linked them with the loss of function and impaired remodeling of the post-MI heart. We also assessed an injectable hydrogel for the treatment of MI using a mouse model and evaluated the impact of delivery timing on its therapeutic efficacy. In this thesis, we confirmed that MG derived AGEs accumulate post-MI (Chapter 3.1). We show that preventing their accumulation, through GLO1 over-expression, mitigates the loss of function post-MI and positively influences remodeling through reducing final infarct sizes and end-systolic volumes. We demonstrate that this may possibly occur through improving the bone marrow response post-MI by restoring ECM-cell signaling. In Chapter 3.2, we present results of a study assessing the efficacy of a collagen based injectable hydrogel for the treatment of MI, and assessing the role that timing plays into the benefits associated with this therapy by studying 3 separate timepoints including 3 hours, 7 days and 14 days post-MI. We found that the injectable hydrogel preserved cardiac function and reduced infarct sizes. It also positively interacted with the host repair response by reducing chronic inflammation and cell death. The benefits of the therapy depended on when the material was delivered, and we found that the earliest timepoint (3 hours post-MI) proved most beneficial. In Chapter 3.3, we combined the knowledge gained from Chapters 3.1 and 3.2 and functionalized our hydrogel with a flavonoid, Fisetin, that has been shown to scavenge MG and increase the activity of GLO1. We show that this novel functionalized material may be able to restore some function in MI, particularly in settings of low baseline cardiac function. Taken together, the results of this thesis demonstrate that MG accumulates as a result of the ischemia and contributes to the impaired repair resolution and remodeling processes post-MI. This identifies MG as a possible novel target for the treatment of MI. Indeed, we also confirm the role that delivery timing plays into injectable hydrogels post-MI, and present promising results for a functionalized material design to intervene on MG production.

Biacetilo (2,3-butanediona) é um contaminante de comida e cigarro, também implicado na hepatoxicidade do álcool e em doenças pulmonares. O metilglioxal (MG), um α-oxoaldeído reativo frequentemente associado ao diabetes e envelhecimento, é produto da fragmentação oxidativa de trioses fosfato, acetona e aminoacetona. Por sua vez, peroxinitrito - um potente oxidante, agente nitrante e nucleófilo formado in vivo pela reação controlada por difusão do ânion radical superóxido com o radical óxido nítrico (k ~1010 M-1s-1) é capaz de se adicionar a CO2 e compostos carbonílicos, gerando produtos potencialmente tóxicos ou sinalizadores celulares. Aminoácidos, peptídeos e nucleobases podem ser acetilados nos grupos amina e na porção desoxiribose. Relativamente ao tratamento com peroxinitrito isolado, níveis superiores de 3-nitrotirosina foram detectados quando tirosina foi tratada com peroxinitrito/biacetilo ou metilglioxal. Ambos os grupos amina de lisina (Lys) ou um deles de derivados de lisina bloqueados e um deles (Ac-Lys-OMe, Z-Lys-OMe) foram acetilados pelo sistema biacetilo ou metilglioxal/peroxinitrito. Em tetrapeptídeos sintéticos contendo lisina como aminoácido amino-terminal (H-KALA-OH, Ac-KALA-OH and H-K(Boc)ALA-OH), a lisina foi acetilada pelo sistemas dicarbonilico/peroxinitrito no grupo α-amina (em maior extensão) e/ou no ε-amina (em menor extensão). No conjunto, estes resultados podem ser interpretados à luz do mecanismo proposto para a reação de compostos α-dicarbonílicos com peroxinitrito, o qual envolve sequencialmente: (i) adição nucleofílica de peroxinitrito à carbonila; (ii) homólise do aduto peroxinitroso formado, liberando •NO2 e um radical oxila do reagente carbonílico; (iii) β-clivagem do radical oxila a um ácido carboxílico (ácido acético no caso de biacetilo e ácido fórmico, a partir de metilglioxal) e radical acetila; (iv) captação do radical acetila pelo oxigênio molecular dissolvido dando acetato, ou por aminoácido ou nucleobase, se presentes, gerando o produto acetilado. Tais resultados são interessantes ao levantar a hipótese de acetilação radicalar como mecanismo de modificação pós-traducional de proteínas, até então considerado um processo realizado apenas por acetilases. / Diacetyl (2,3-butanedione) is a food and cigarette contaminant recently implicated in alcohol hepatotoxicity and lung disease. In turn, methylglyoxal (MG) is an α-oxoaldehyde frequently associated with diabetes and aging that is putatively formed by the oxidative fragmentation of trioses phosphate, acetone and aminoacetone. Peroxynitrite - a potent oxidant, nitrating agent and nucleophile formed in vivo by the diffusion-controlled reaction of superoxide radical with nitric oxide (k ~1010 M-1s-1) - is able to form adducts with carbon dioxide and carbonyl compounds. When initially present in the reaction mixtures before addition of ONOO-, amino acids, peptides and nucleobases undergo acetylation at the amino group and purine moieties in the presence of biacetyl or methylglyoxal. Higher levels of 3-nitrotyrosine nitration were measured when peroxynitrite/biacetyl or metilglioxal was added to tyrosine, in comparison with peroxynitrite alone. Both amino groups of L-lysine or one of the amino groups of L-lysine derivatives (Z-Lys-OH and Ac-Lys-OH) were acetylated by biacetyl and methylglyoxal/peroxynitrite system. Using tetrapeptides containing lysine at the terminal amino acid (H-KALA-OH, Ac-KALA-OH and H-K(Boc)ALA-OH), the lysine residue was acetylated at both or either α-amino (major adduct) and ε-amino group (minor adduct). Altogether these data can be interpreted by the mechanism proposed to describe the reaction of α-dicarbonyls with peroxynitrite as follows: (i) nucleophilic addition of peroxynitrite to the carbonyl group of the reagent; (ii) homolysis of the formed peroxynitroso carbonyl adduct to •NO2 and a carbonyloxyl radical; (iii) β-cleavage of the oxyl radical to acetyl radical plus acetic acid (from diacetyl) or formic acid (from methylglyoxal); (iv) competitive scavenging of the acetyl radical by dissolved molecular oxygen and by added amino acid, peptide or nucleobase, ultimately yielding acetate or acetylated biomolecule. If occurring in vivo, these radical reactions may contribute to the post-translational modification of proteins catalyzed by transacetylases.

Cell division of ggeneflesmus quadricauda (Turp.) Breb. (Scenedesmaceae) is enhanced by methylglyoxal, a general inhibitor of cell division, at threshold concentration in conjunction with treatment timing related to growth stage of batch cultures. At 0.5 mM methylglyoxal concentration, cell division was significantly enhanced in algae treated in the logarithmic phase. Specific growth rates of methylglyoxal-treated cultures were rapidly increased at the beginning of logarithmic phase. Cultures inoculated with high cell numbers were less sensitive, but still showed high specific growth rates in logarithmic phase. Cell division in cultures which had low cell numbers was inhibited by 0.5 mM methylglyoxal treatment. Both specific activity of Glyoxalase I and the ratio of Glyoxalase I to Glyoxalase II of methylgloxal-treated cultures were higher than those of controls (1.3 and 2.1- fold, respectively). Pyruvate concentration in treated cultures was increased after methylglyoxal treatment.

Background: Glycation influences the ultrastructure and clot kinetics of fibrin clots due to the post-translational modifications in fibrinogen. Methylglyoxal (MG) is used to measure the level of glycation which has been associated with the pathogenesis of type 2 diabetes Melilites (T2DM) and coronary heart disease (CHD). The aim of the study was to determine the role of MG on clot kinetics and fibrin clot structure in CHD patients with and without T2DM to provide insight into the mechanism of pathogenesis of atherosclerosis in T2DM which results in the development of CHD. Methodology: Scanning electron microscopy (SEM) was used to evaluate the morphology of fibrin clots. Thromboelastography (TEG) was used to assess the physiological clot properties (kinetics). Enzyme-linked immunosorbent assay (ELISA) was used to determine the levels of methylglyoxal-adducts. Results: The morphology of clots from controls analysed using SEM showed thick and thin fibres which created an organised mesh of fibrin fibres. In T2DM, CHD with T2DM and CHD some alterations in the morphology were observed. The ultrastructure micrographs in CHD shows that some of the fibrin fibres formed have individual fibres with both thick and thin fibres as well as a thick mass of fibres with a net-like structure that forms dense-matted deposits. In addition, the fibrin fibres are not organised. The densitometry analysis between controls and patient groups’ (CHD: mean (standard deviation) 0.42±0.11; CHD+T2DM: 0.31±0.08 and T2DM: 0.29±0.08) was found to be significantly lower in all groups compared to the control which had a mean of 0.57±0.1, p<0.0001. There are no significant differences in the alpha angle between CHD, T2DM, CHD with T2DM and controls (60.88±2.321˚ vs. 60.81±2.385˚ vs. 59.09± 3.185˚ vs. 66.47±1.300˚, p=0.5279). There was no significant difference found in the K-value between T2DM, CHD with T2DM, CHD and control subjects (3.458±0.446mins vs. 5.118±1.589mins vs. 3.758±0.450mins vs. 2.839±0.2156mins, p=0.0102). The maximum amplitude was higher in T2DM patients compared to CHD, CHD with T2DM and controls (40.51±1.914mm vs. 34.10±2.127mm vs. 33.12±3.365mm vs. 33.60±1.525mm, p=0.0102). The MRTG was higher in CHD compared to T2DM, CHD 4 with T2DM and controls (10.74±3.335 dyn cm-2 s -1 vs. 4.268±0.690 dyn cm-2 s -1 vs. 5.046± 0.927 dyn cm-2 s -1 vs. 6.535±0.664 dyn cm-2 s -1 , p=0.0096). The reaction time was higher in CHD with T2DM patients compared to T2DM, CHD and controls (32.58±4.005min vs. 23.92±2.793min vs. 21.29± 2.383min vs. 8.322±0.886min, p<0.0001). There was no significant difference found in the TTG between T2DM, CHD with T2DM, CHD and control subjects (231.3±28.68 dyn cm-2 vs. 258.5±38.15 dyn cm2 vs. 343.7±71.92 dyn cm-2 vs. 287.7±21.37 dyn cm-2 , p=0.8421). The TMRTG was higher in T2DM patients compared to T2DM, CHD with T2DM, CHD and controls (23.91±2.409mins vs. 20.46±3.411mins vs. 14.14±1.287mins vs. 10.16±0.751mins, p<0.0001). To assess if an association between MG-adducts and clot kinetics exists, the Spearman r correlation was completed for each clot parameter. The reaction time (p=0.0047, 95% CI: 0.138 to 0.665) and time taken before maximum speed of the clot growth to be achieved (p=0.3958, 95% CI: 0.072 to 0.644) was significant. This indicates the relationship between the parameters i.e., the higher the level of MGadducts present, the longer it takes for clotting to begin and reach maximum speed of formation. Conclusion: This study showed that there are ultrastructural differences in fibrin fibres formed in CHD patients with T2DM. The viscoelastic parameters indicated that haemostasis was irregular in CHD and T2DM. The levels of MG-adducts were much higher in T2DM, CHD with T2DM and CHD and may be a contributing factor to the pathogenesis associated with altered coagulation in these patients. / Dissertation (MSc (Physiology))--University of Pretoria, 2020. / NRF / Physiology / MSc (Physiology) / Unrestricted

No description available.

Glyoxalase-I (Glo-I) and glyoxalase-II (Glo-II) comprise the glyoxalase system and are responsible for the detoxification of methylglyoxal (MGO). MGO is formed non-enzymatically as a by-product, mainly in glycolysis, and leads to the formation of advanced glycation endproducts (AGEs). AGEs bind to their receptor, RAGE, and activate intracellular transcription factors, resulting in the production of pro-inflammatory cytokines, oxidative stress, and inflammation. This review will focus on the implication of the Glo-I/AGE/RAGE system in liver injury and hepatocellular carcinoma (HCC). AGEs and RAGE are upregulated in liver fibrosis, and the silencing of RAGE reduced collagen deposition and the tumor growth of HCC. Nevertheless, data relating to Glo-I in fibrosis and cirrhosis are preliminary. Glo-I expression was found to be reduced in early and advanced cirrhosis with a subsequent increase of MGO-levels. On the other hand, pharmacological modulation of Glo-I resulted in the reduced activation of hepatic stellate cells and therefore reduced fibrosis in the CCl4-model of cirrhosis. Thus, current research highlighted the Glo-I/AGE/RAGE system as an interesting therapeutic target in chronic liver diseases. These findings need further elucidation in preclinical and clinical studies.

Methylglyoxal is a highly reactive dicarbonyl compound, which is widely distributed in food products and beverages, and is particularly high in Manuka honey. In addition to its antibacterial effects, methylglyoxal is also known as a major precursor of advanced glycation end products (AGEs), that produces altered macromolecules (such as proteins and DNA), leading to abnormal physiological changes. However, the effects of methylglyoxal on development is unclear. Thus, this study aimed to determine the role of methylglyoxal in this aspect using Caenorhabditis elegans (C. elegans). Treatment of methylglyoxal at 0.1 mM and 1 mM for 48 h significantly inhibited development of C. elegans and reduced pumping rate. Activity, measured by moving speed, was increased with 0.1 mM methylglyoxal, but reduced with 1 mM methylglyoxal. Lifespan of C. elegans was not influenced by methylglyoxal at 0.1 mM, but was shortened at 1 mM. Treatment methylglyoxal on the mutant, lin-41, which has a precocious phenotype, could alleviate the implication on wild-type worms. These results suggested that methylglyoxal significantly influenced the development of C. elegans through the heterochronic pathway.

1,2-Dicarbonylverbindungen spielen aufgrund ihrer Reaktivität gegenüber Aminosäureseitenketten von Proteinen eine Schlüsselrolle bei der Bildung von Maillard Reaktionsprodukten (MRP) und werden auch im Zusammenhang mit der Entstehung pathophysiologischer Konsequenzen bei metabolischen Erkrankungen diskutiert. Vor diesem Hintergrund stellt sich die Frage nach der physiologischen Relevanz alimentär aufgenommener 1,2 Dicarbonylverbindungen. Das Ziel der vorliegenden Arbeit war zunächst eine Bestandsaufnahme zum Vorkommen von 1,2-Dicarbonylverbindungen in einem Spektrum von Lebensmitteln, gefolgt von Untersuchungen zum metabolischen Transit von 3 Desoxyglucoson (3-DG) und Methylglyoxal (MGO) bzw. spezifischer Metabolite in Abhängigkeit der alimentären Aufnahme und zur Stabilität der Verbindungen während einer simulierten gastrointestinalen Verdauung. 1a Die 1,2-Dicarbonylverbindungen 3-DG, 3 Desoxygalactoson (3-DGal), MGO und Glyoxal (GO) sowie das Zuckerabbauprodukt 5-Hydroxymethylfurfural (HMF) als ein wichtiger Indikator für Erhitzungsprozesse in Lebensmitteln wurden in 173 Lebensmittelproben mittels einer optimierten RP-HPLC-Methode mit UV-Detektion bestimmt. Darunter waren neben alkoholfreien und alkoholischen Getränken auch süße Aufstriche, Brot- und Backwaren. In allen untersuchten Lebensmittelproben war 3 DG die quantitativ bedeutendste 1,2 Dicarbonylverbindung. Hohe 3-DG-Gehalte wurden in Bonbons, Honig und süßen Aufstrichen (Mediane: 165–626 mg/kg) und in Essig (Aceto balsamico bis 2622 mg/L) analysiert. Lebensmittel wie Fruchtsäfte, Bier, Brot- und Backwaren wiesen geringere 3 DG-Gehalte auf (Median: 27–129 mg/L bzw. mg/kg). In allen untersuchten Lebensmitteln lagen die Gehalte des 3-DG höher als die des HMF. 3-DGal konnte erstmals in nahezu allen Lebensmittel detektiert werden, mit einem Maximalwert von 162 mg/L in Aceto balsamico. In dieser Probe wurde auch ein hoher MGO-Gehalt (53 mg/L) gemessen. GO kommt in etwa gleichen Konzentrationsbereichen wie MGO vor. Generell lagen die Gehalte für 3-DGal höher als die für MGO. Eine Ausnahme stellt der untersuchte Manuka-Honig dar (463 mg MGO/kg). 1b Auf Basis der quantitativen Daten wurden Gehalte von 1,2-Dicarbonylverbindungen in verzehrüblichen Portionsgrößen verschiedener Lebensmittel berechnet und eine tägliche alimentäre Aufnahme von 20–160 mg (0,1–1,0 mmol) 3-DG und 5–20 mg (0,1–0,3 mmol) MGO abgeschätzt. 2a Der metabolische Transit von 3-DG und MGO wurde jeweils in einer dreitägigen Ernährungsstudie untersucht. Während der 3 Tage hatten die Probanden eine Dicarbonyl- und MRP-freie Diät (Rohkosternährung) einzuhalten. Am Morgen des zweiten Tages erhielten die Probanden eine definierte Menge 3-DG bzw. MGO (je 500 µmol), enthalten in Waldhonig bzw. Manuka-Honig. In den 24 h Urinproben der 3-DG-Interventionsstudie wurde 3-DG und dessen Metabolit 3-Desoxyfructose (3-DF) analysiert, außerdem Pyrralin und 3 DG-Hydroimidazolon (3-DG-H) als 3-DG-spezifisches MRP. In den 24 h Urinproben der MGO-Interventionsstudie wurde MGO und dessen Metabolit D-Lactat analysiert, außerdem MGO-Hydroimidazolon 1 (MG-H1) als charakteristisches MRP des MGO. Alle Verbindungen waren in den Urinproben nachweisbar. 2b Am ersten Tag der 3-DG-Interventionsstudie betrug der Median der renalen 3-DG- und 3 DF-Exkretion aller 9 Probanden 4,6 bzw. 77 µmol/d. Am Tag der definierten 3-DG-Aufnahme (Tag 2) stieg der Median der renalen 3-DG- und 3-DF-Exkretion signifikant auf 7,5 bzw. 147 µmol/d an. An Tag 3 unterschieden sich die täglichen renalen Ausscheidungen von 3-DG und 3-DF nicht signifikant von denen an Tag 1 (P > 0,05). Der Median der renalen Wiederfindung des an Tag 2 alimentär aufgenommenen 3-DG wurde mit 14 % abgeschätzt (Spannweite: 6–25 %). Der Median der renalen Exkretion von Pyrralin und 3-DG-H sank im Verlauf der dreitägigen Studie von 2,5 bzw. 1,0 auf 1,2 µmol/d bzw. 0,5 µmol/d. Diese Ergebnisse deuten erstmalig darauf hin, dass 3-DG aus der Nahrung resorbiert, resorbiertes 3 DG zu 3-DF metabolisiert und resorbiertes 3-DG hauptsächlich als 3-DF renal eliminiert wird. Die Exkretion der untersuchten MRP erwies sich in dieser Studie als nicht abhängig von der alimentären Aufnahme des 3 DG. 2c Die renale MGO- sowie D-Lactat-Ausscheidung wies keinen Zusammenhang mit der oralen Aufnahme einer hohen MGO-Menge auf. An allen 3 Tagen der MGO-Interventionsstudie lag die renale MGO-Exkretion aller 4 Probanden zwischen 0,11 und 0,30 µmol/d und die D-Lactat-Ausscheidung zwischen 52 und 224 µmol/d. Der Median der renalen MG-H1-Ausscheidung sank im Verlauf der dreitägigen Studie von 3,8 auf 1,2 µmol/d an Tag 3. Diese Ergebnisse deuten darauf hin, dass keine Resorption des MGO in die Zirkulation erfolgte. 3a Zur Beurteilung der Stabilität von 3-DG und MGO während der gastrointestinalen Verdauung wurde ein zweistufiges System von Hellwig et al. (2013b) adaptiert, bestehend aus einer zweistündigen „Magenstufe“ (Pepsin, pH = 2) und einer sechsstündigen „Darmstufe“ (Pankreatin/Trypsin, pH = 7,5). Für die Verdauungssimulation wurden jeweils wässrige 3 DG- und MGO-Standardlösungen mit Konzentrationen im lebensmittelrelevanten Bereich eingesetzt. Weiterhin wurde die simulierte Verdauung in Anwesenheit von Casein als Modellprotein, durchgeführt. 3b Nach achtstündiger simulierter Verdauung war im Verdauungsansatz noch 70 ± 10 % der initialen 3-DG-Menge bestimmbar. Die Anwesenheit des Caseins zeigte keinen Effekt auf die 3-DG-Konzentration. Damit dürfte nach gastrointestinaler Verdauung ein Großteil des alimentär aufgenommenen 3-DG zur Resorption zur Verfügung stehen. 3c Im Gegensatz zum 3-DG sank die MGO-Konzentration im Verlauf der achtstündigen simulierten Verdauung auf 15 ± 4 % der Ausgangskonzentration. In Anwesenheit von Casein verstärkte sich die Abnahme der MGO-Konzentration auf 9 ± 1 %. Es konnte gezeigt werden, dass die Abnahme der MGO-Konzentration auf Reaktionen mit den in den Verdauungsansätzen enthaltenen Enzymen und Proteinen zurückzuführen ist. MGO wird damit nach gastrointestinaler Verdauung nur noch in begrenztem Maße zur Resorption zur Verfügung. Die in der vorliegenden Arbeit gewonnenen Resultate lassen den Schluss zu, dass die biologische Verfügbarkeit alimentärer 1,2-Dicarbonylverbindungen gering (3-DG) bis vernachlässigbar (MGO) ist und selbst stark erhitzte Lebensmittel damit keinen maßgeblichen Beitrag zum „Gesamtpool“ an Dicarbonylverbindungen in vivo und den damit möglicherweise einhergehenden physiologischen Konsequenzen leisten.