Le vieillissement de la peau est la résultante du chrono et du photo-vieillissement qui partagent des changements moléculaires incluant les modifications des protéines telles que la glycation. La glycation se produit lorsque le glucose ou ses dérivés dicarbonylés, le glyoxal et de méthylglyoxal, réagissent avec les protéines conduisant à la formation de produits de glycation avancée (AGE). Le but de ces travaux est de mieux comprendre le rôle des glyoxalases dans la détoxification des dicarbonyles et dans la protection des protéines au cours du vieillissement de la peau. Afin de comprendre la régulation du systeme dans la peau humaine pendant le chono et le photo-vieillissement, des coupes de peau de donneurs jeunes et âgées ont été analysées par immunohistochimie. Le système des glyoxalase, glyoxalase 1 (GLO1) et glyoxalase 2 (Glo2), et AGE ont été localisés et détectés dans les échantillons de peau. Pour comprendre le rôle des GLO en réponse au stress dicarbonyle, des kéartinocytes HaCaT ont été soumise à un stress dicarbonyle de 24h et l'expression et les activités des glyoxalases ont été déterminées. Enfin, des études protéomiques ont été réalisées sur des cellules HaCaT surexprimant Glo2 ou inhibant GLO1 et nous sommes en train d'identifier des protéines cibles des carboxymethyllysines. Nos résultats montrent que le système des glyoxalases est présent dans la peau en particulier dans les cellules basales et est capable de protéger les protéines cellulaires contre les dommages oxydatifs. Nous espérons que notre étude peut contribuer à comprendre le rôle des glyoxalases dans la maintenance protéique qui est un élément clé de l'homéostasie cellulaire au cours du vieillissement. / Skin aging is the result of intrinsic and photo-aging, due to UV exposure, that both share important molecular features including alterations of proteins such as glycation. Glycation occurs when glucose or its derivates the dicarbonyl compounds glyoxal and methylglyoxal react with proteins leading to the formation of advanced glycation endproducts (AGE). The aim of this work is to better understand the role of glyoxalases in the detoxification of dicarbonyls and in the protection of keratinocyte’s proteins during skin aging.In order to understand glyoxalases regulation in human skin during intrinsic and photo-aging, skin sections from young and old donors were analysed by immunohistochemistry. The glyoxalase system, glyoxalase 1 (Glo1) and glyoxalase 2 (Glo2), and AGE were localized and detected in the skin samples. To understand the role of glyoxalases in response to dicarbonyl stress, HaCaT keratinocytes were subjected to a 24h dicarbonyl stress and the expression and activities of glyoxalases were determined. HaCaT cells silenced for Glo1 or overexpressing Glo2 were developed and were used in proteomic studies to identify target proteins preferentially glycated by dicarbonyl compounds.Finally, proteomic studies were performed on cellular clones overexpressing Glo2 or inhibiting Glo1 and we are currently identifying proteins targets for carboxymethyllysine modifications.Our results show that glyoxalase system is present in skin especially in the basal cells and is able to protect cellular proteins against oxidative damages. We expect that our study may contribute to decipher the role of glyoxalases in protein maintenance, which is a key element of cellular homeostasis during aging.

Contrairement aux HDL de sujets sains, les HDL de patients diabétiques ont perdu leur capacité à contrecarrer les effets inhibiteurs des LDL oxydées sur la vasorelaxation endothélium dépendante. Les mécanismes en cause ne sont pas connus. Or la glycation et l’oxydation sont deux phénomènes majeurs au cours du diabète. Nous avons donc étudié in vitro, le rôle de la glycation (associée ou non à une oxydation spontanée), et de l’oxydation d’HDL issues de sujets sains, sur leurs capacités à contrecarrer les effets inhibiteurs des LDL oxydées sur la vasorelaxation endothélium dépendante. Chaque condition a conduit au même constat: les HDL modifiées perdent leur pouvoir vasorelaxant en présence de LDL oxydées. En revanche, en l’absence de LDL oxydées, elles n’altèrent pas la vasorelaxation induite par l’acétylcholine. Ainsi les modifications structurelles des HDL (glycation, oxydation, ou les deux) induisent une perte de leur capacité à protéger l’endothélium du stress oxydatif, plutôt qu’un effet délétère direct sur l’endothélium. Un des mécanismes majeur impliqué dans ce phénomène est probablement l’absence de fixation de ces HDL modifiées à leur récepteur SR-BI. Elles ne pourraient plus alors s’opposer au niveau des cavéoles aux effets délétères des LDL oxydées, et ne favoriseraient plus la production de NO. Mais si aussi bien la glycation que l’oxydation des HDL entraînent ces effets néfastes, il semblerait qu’en condition physiopathologique (oxydation spontanée des HDL glyquées), l’oxydation ne majore pas cette perte de capacité des HDL à contrecarrer les effets inhibiteurs des LDL oxydées sur la vasorelaxation. / Contrary to HDL from normolipidaemic and normoglycaemic subjects, HDL from diabetic patients have lost their capacity to reverse the inhibition of vasorelaxation induced by oxidized LDL. Mechanisms involved are unknown. The glycation and oxidation of HDL are two major phenomena in diabetes mellitus. The aim of this work was to study in vitro the role of glycation (with or without spontaneous oxidation) and oxidation of HDL, on their capacity to counteract the inhibitory effect of oxidized LDL on endothelium-dependent vasorelaxation. Each state showed the same result, modified HDL lost their vasorelaxing power in stress conditions (with oxidized LDL). Nevertheless, modified HDL alone (without oxidized LDL) did not alter vasorelaxation induced by acetylcholine, after noradrenaline-induced vasoconstriction. Thus, modifications of HDL induce a loss of the ability to protect vessels from oxidative stress rather than have a direct deleterious effect on the vessel. One of the major mechanisms involved in this phenomenon is probably the loss of SR-BI binding of these modified HDL, that could lead to the inability of HDL to protect caveolae from deleterious effects induced by oxidized LDL and could not preserve NO production. However, though glycation, like oxidation of HDL, leads to these deleterious effects, it would seem that during physiopathological conditions, with the spontaneous oxidation of glycated HDL, oxidation does not aggravate the loss of the capacity of diabetic HDL to counteract the inhibitory effect of oxidized LDL on endothelium-dependent vasorelaxation.

In der vorliegenden Arbeit wurde aneurysmatisches Aortengewebe von Patienten mit bikuspider oder trikuspider Aortenklappe untersucht. Im Laufe des Lebens ist die bikuspide Aortenklappe als häufigste angeborene Anomalie des Herzens mit zahlreichen, potentiell lebensbedrohlichen Komplikationen verbunden. Betroffene Patienten zeigen eine frühere Entwicklung und rapidere Progression von Dilatationen und – im schlimmsten Fall – Dissektionen der Aorta ascendens. Die Ätiologie dessen konnte bis dato nicht ausreichend geklärt werden. Hintergrund der Studie war eine Untersuchung von Branchetti et al., wobei eine Erhöhung von RAGE im Plasma bei Patienten mit bikuspider Klappe nachgewiesen werden konnte. Daraus wurde die Hypothese entwickelt, dass eine Expressionserhöhung von RAGE und dessen Liganden AGE im Aortengewebe selbst ursächlich mit der Aortendilatation verbunden sein könnte. In Proben von 93 Patienten wurde mittels Western Blot, ELISA und Immunhistochemie die Expression von RAGE und AGE untersucht. Hierbei zeigte sich eine signifikante Expressionserhöhung beider Proteine im Aortenaneurysma bei bikuspider Klappe im Vergleich zu Patienten mit trikuspider Aortenklappe. Auch die exemplarisch angefertigten Immunhistologien stützen diese Ergebnisse. Mögliche Folgen können Steifigkeitserhöhung der Aortenwand, Aktivierung von Matrixmetalloproteinasen sowie Erhöhung des oxidativen Stresses sein. Neben der Expression im aneurysmatischen Aortengewebe wurden auch Plasmaproben hinsichtlich AGE und RAGE analysiert, wobei sich keine Erhöhung feststellen ließ. Die Ergebnisse der Studie, die eine RAGE – Erhöhung im Plasma detektierten und ihn somit als potentiellen Biomarker für eine bikuspide Klappe diskutierten, ließen sich bei der vorliegenden Untersuchung einer kleineren Stichprobe nicht bestätigen. Ebenso stellt sich die Etablierung eines Biomarkers als anspruchsvolle Aufgabe dar. Eine Eignung von RAGE als Biomarker zur Identifikation von Patienten mit bikuspider Klappe ist kritisch zu betrachten.:Inhaltsverzeichnis Bibliographische Beschreibung Abkürzungsverzeichnis 1. Einleitung 1.1. Die bikuspide Aortenklappe (BAV) 1.1.1. Prävalenz 1.1.2. Klassifikation 1.1.3. Ätiologie 1.1.4. Assoziierte Pathologien 1.1.5. Hypothesen der Dilatationsentstehung 1.1.6. Diagnostik 1.1.7. Therapie 1.2. RAGE und AGE 1.2.1. Advanced Glycation End Products (AGE) 1.2.2. Receptor for Advanced Glycation End Products (RAGE) 1.2.3. Interaktion von AGE und RAGE 1.2.4. Bezug zum thorakalen Aortenaneurysma 2. Zielstellung 3. Material 3.1. Allgemeine Geräte 3.2. Allgemeine Materialien 3.3. Allgemeine Chemikalien 3.4. Proteinextraktion 3.5. Proteinkonzentrationsbestimmung 3.6. SDS – Gelelektrophorese 3.7. Antikörper (AK) 3.8. Western Blot Analyse 3.9. Enzyme – linked Immunosorbent Assay (ELISA) 3.10. Immunhistochemie (IHC) 3.11. Software 4. Methoden 4.1. Patientenpopulation und Probengewinnung 4.2. Isolation der Proteine aus Aortengewebe 4.3. Konzentrationsbestimmung nach BCA – Methode 4.4 Elektrophoretische Auftrennung der Proteine 4.5. Detektion von AGE und RAGE mittels Western Blot Analyse 4.6. Nachweis von AGE und RAGE mittels ELISA 4.7. Immunhistochemische Färbung von AGE und RAGE 4.8. Statistische Auswertung 5. Ergebnisse 5.1. Patientenpopulation 5.2. Expression von AGE in humanen aneurysmatischen Gewebeproben der Aorta ascendens 5.2.1. Analyse der AGE – Expression mittels Western Blot 5.2.2. Analyse der AGE – Expression mittels ELISA 5.2.3. Darstellung der Lokalisation von AGE in der Aortenwand mittels Immunhistochemie 5.3. Expression von RAGE im Aortengewebe 5.3.1. Analyse der Expression von RAGE mittels Western Blot 5.3.2. Analyse der RAGE – Expression mittels ELISA 5.3.3. Darstellung der Lokalisation von RAGE in der Aortenwand mittels Immunhistochemie 5.4. Bestimmung der Plasmaspiegel von AGE und RAGE in ausgewählten Plasmaproben 6. Diskussion 6.1. Expressionserhöhung von AGE in der Aortenwand von Patienten mit BAV 6.1.1. Mögliche Ursachen der Expressionserhöhung 6.1.2. Zusammenhang von AGE und Gefäßsteifigkeit 6.2. Expressionserhöhung von RAGE im Aortengewebe von Patienten mit BAV 6.2.1. Ätiologie der Expressionserhöhung unter Einbeziehung der Liganden 6.2.2. Folgen der RAGE – Erhöhung und ihr Einfluss auf die Gefäßwand 6.3. RAGE in seiner Rolle als Biomarker Schlussfolgerung Limitationen 7. Zusammenfassung 8. Literaturverzeichnis 9. Abbildungsverzeichnis 10. Tabellenverzeichnis Erklärung über die eigenständige Abfassung der Arbeit Lebenslauf Danksagung

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Background and Methods: The involvement of iron in the risk for, and complications of, type 2 diabetes has generated substantial interest over the past 15 years, initially sparked by an association with raised serum ferritin, and the observation that people with iron overload diseases frequently develop diabetes. Considerable advances have since been made in understanding the effect glucose has on molecules, cells, and tissues; and the role that oxidative stress plays in the development of the pathologies of long-term diabetes. Poorly liganded iron is potentially both a contributor to, and consequence of, these complications. In vitro experiments with glucose-incubated transferrin by earlier workers have demonstrated loss of function with increasing glycation, leading to the suggestion that the failure of this key iron-binding protein may contribute to diabetic pathology, via the presence of redox active non-transferrin-bound iron (NTBI). In vitro glycated transferrin is examined here by ultrafiltration, to assess loss of function and possible oxidative fragmentation. Mass spectrometry is used to identify a range of amino acid glycation sites on in vitro glycated transferrin for the first time. Finally, several groups have previously measured NTBI in people with diabetes, finding little agreement in results. NTBI is measured here in a cohort of people with type 2 diabetes, using a new adaptation of earlier NTBI assays. NTBI is also assessed in pre-dialysis chronic kidney disease (CKD) stages I to III for the first time. Results and Conclusions: Experiments with glycated transferrin in vitro demonstrate oxidative fragmentation, explaining the loss of function reported by earlier groups. In vitro glycated transferrin examined by mass spectrometry reveals a substantial number and range of amino acids subject to glycation. Comparison with in vivo glycated transferrin suggests that many of the in vitro glycation sites are not glycated in vivo, and that there are many oxidized methionine residues which are potential artefacts, or likely to be repaired by methionine sulphoxide reductases in vivo. A study of people with type 2 diabetes finds no direct association between NTBI and protein glycation. Unexpected correlations between NTBI and LDL, and LDL and haemoglobin with increasing protein glycation, are reported for the first time. NTBI is suggested to be iron sourced from haemoglobin or haem, from erythrocyte haemolysis prior to sample collection. In people with pre-dialysis CKD stages I to III no significant difference in NTBI level compared to controls is seen, or correlations with markers of renal function. No link between NTBI and kidney function at this stage of disease is indicated.

Methylglyoxal (MG) is a reactive metabolite presents in all biological systems. The accumulation of MG in diabetic patients and animals has been long recognized. Recently, studies have shown that MG levels are elevated in hypertensive rats. However, the pathological effects of MG in diabetes and related insulin resistance syndrome such as obesity are currently unknown. In the present study, the role of MG in the pathogenesis of insulin resistance was investigated.<p> First, it was observed that MG induced structural and functional changes of insulin. Incubation of human insulin with MG in vitro yielded MG-insulin adducts, as evidenced by additional peaks observed upon mass spectrometric (MS) analysis. Tandem MS analysis of insulin B-chain adducts confirmed attachment of MG at an arginine residue. [3H]-2-deoxyglucose uptake ([3H]-2-DOG) by 3T3-L1 adipocytes was significantly and concentration-dependently decreased after treatment with MG-insulin adducts, in comparison with the effect of native insulin at the same concentration. A significant decrease of glucose uptake induced by MG-insulin adducts was also observed in L8 skeletal muscle cells. Unlike native insulin, MG-insulin adducts did not inhibit insulin release from pancreatic â-cells. The degradation of MG-insulin by cultured liver cells was also decreased. In conclusion, MG modifies insulin by attaching to internal arginine residue in the â-chain of insulin. The formation of this MG-insulin adduct decreases insulin-mediated glucose uptake, impairs autocrine control of insulin secretion, and decreases insulin clearance. These structural and functional abnormalities of the insulin molecule may contribute to the pathogenesis of insulin resistance.<p> Second, the effects of MG on the insulin signaling pathway were investigated. After 9 weeks of fructose treatment, an insulin resistant state was developed in Sprague-Dawley (SD) rats, demonstrated as increased triglyceride and insulin levels, elevated blood pressure, and decreased insulin-stimulated glucose uptake by adipose tissue. A close correlation between insulin resistance and the elevated MG accumulation in adipose and skeletal muscle tissues was observed. The insulin resistant state and the elevated MG level were reversed by the MG scavenger, N-acetyl cysteine (NAC) and metformin. In cultured adipose cells, MG treatment impaired insulin signaling as measured by decreased tyrosine phosphorylation of insulin-receptor substrate-1 (IRS-1) and the decreased kinase activity of phosphatidylinositol 3-kinase (PI3K). The ability of NAC to block MG-impairment of PI3K activity and IRS-1 phosphorylation further confirmed the role of MG in the development of insulin resistance. In cultured skeletal muscle cells, MG treatment significantly reduced the expression of IRS-1 and PI3K at the mRNA level. Similar to adipose cells, MG also decreased tyrosine phosphorylation of IRS-1 and PI3K activity. We also examined the mechanism of metformin to inhibit AGEs. Using mass spectrometry, stable metformin-MG adducts were identified.<p> In addition, we investigated the causative effect of MG in the pathogenesis of obesity, another form of insulin resistance. This study revealed a previously unrecognized effect of MG in stimulating adipogenesis by up-regulating Akt signaling. In Zucker fatty rats, dramatically increased MG accumulations in serum and different tissues were identified. The serum MG level increased age. In 10 and 12 week-old obese rats, MG was 144±50% and 171±15% of the age-matched control Zucker rats; this value increased to 241±7 % and 329±10% by 14 and 16 weeks (P<0.05, n=4). Further study suggested that MG accumulation stimulates the phosphorylation of Akt and its effectors p21 and p27. The activated Akt pathway then increased the activity of Cdk2 and accelerates the cell cycle progression and proliferation of pre-adipocytes. The effects of MG were efficiently reversed by both alagebrium, and Akt inhibitor SH-6.<p> Overall, the current study investigated the effect of MG during the pathogenesis of insulin resistance syndrome. MG, as the most potent precursor of AGEs, impairs the activity of insulin signaling pathway by glycating the insulin molecule and other insulin signaling proteins. Moreover, this study observed a previously unrecognized causative effect of MG in the proliferation of adipocytes by up-regulating the Akt signaling pathway. The results from this study offer new mechanisms to explain the development of insulin resistance and to prevent the related diseases.

Methylglyoxal (MG) is a reactive metabolite presents in all biological systems. The accumulation of MG in diabetic patients and animals has been long recognized. Recently, studies have shown that MG levels are elevated in hypertensive rats. However, the pathological effects of MG in diabetes and related insulin resistance syndrome such as obesity are currently unknown. In the present study, the role of MG in the pathogenesis of insulin resistance was investigated.<p> First, it was observed that MG induced structural and functional changes of insulin. Incubation of human insulin with MG in vitro yielded MG-insulin adducts, as evidenced by additional peaks observed upon mass spectrometric (MS) analysis. Tandem MS analysis of insulin B-chain adducts confirmed attachment of MG at an arginine residue. [3H]-2-deoxyglucose uptake ([3H]-2-DOG) by 3T3-L1 adipocytes was significantly and concentration-dependently decreased after treatment with MG-insulin adducts, in comparison with the effect of native insulin at the same concentration. A significant decrease of glucose uptake induced by MG-insulin adducts was also observed in L8 skeletal muscle cells. Unlike native insulin, MG-insulin adducts did not inhibit insulin release from pancreatic â-cells. The degradation of MG-insulin by cultured liver cells was also decreased. In conclusion, MG modifies insulin by attaching to internal arginine residue in the â-chain of insulin. The formation of this MG-insulin adduct decreases insulin-mediated glucose uptake, impairs autocrine control of insulin secretion, and decreases insulin clearance. These structural and functional abnormalities of the insulin molecule may contribute to the pathogenesis of insulin resistance.<p> Second, the effects of MG on the insulin signaling pathway were investigated. After 9 weeks of fructose treatment, an insulin resistant state was developed in Sprague-Dawley (SD) rats, demonstrated as increased triglyceride and insulin levels, elevated blood pressure, and decreased insulin-stimulated glucose uptake by adipose tissue. A close correlation between insulin resistance and the elevated MG accumulation in adipose and skeletal muscle tissues was observed. The insulin resistant state and the elevated MG level were reversed by the MG scavenger, N-acetyl cysteine (NAC) and metformin. In cultured adipose cells, MG treatment impaired insulin signaling as measured by decreased tyrosine phosphorylation of insulin-receptor substrate-1 (IRS-1) and the decreased kinase activity of phosphatidylinositol 3-kinase (PI3K). The ability of NAC to block MG-impairment of PI3K activity and IRS-1 phosphorylation further confirmed the role of MG in the development of insulin resistance. In cultured skeletal muscle cells, MG treatment significantly reduced the expression of IRS-1 and PI3K at the mRNA level. Similar to adipose cells, MG also decreased tyrosine phosphorylation of IRS-1 and PI3K activity. We also examined the mechanism of metformin to inhibit AGEs. Using mass spectrometry, stable metformin-MG adducts were identified.<p> In addition, we investigated the causative effect of MG in the pathogenesis of obesity, another form of insulin resistance. This study revealed a previously unrecognized effect of MG in stimulating adipogenesis by up-regulating Akt signaling. In Zucker fatty rats, dramatically increased MG accumulations in serum and different tissues were identified. The serum MG level increased age. In 10 and 12 week-old obese rats, MG was 144±50% and 171±15% of the age-matched control Zucker rats; this value increased to 241±7 % and 329±10% by 14 and 16 weeks (P<0.05, n=4). Further study suggested that MG accumulation stimulates the phosphorylation of Akt and its effectors p21 and p27. The activated Akt pathway then increased the activity of Cdk2 and accelerates the cell cycle progression and proliferation of pre-adipocytes. The effects of MG were efficiently reversed by both alagebrium, and Akt inhibitor SH-6.<p> Overall, the current study investigated the effect of MG during the pathogenesis of insulin resistance syndrome. MG, as the most potent precursor of AGEs, impairs the activity of insulin signaling pathway by glycating the insulin molecule and other insulin signaling proteins. Moreover, this study observed a previously unrecognized causative effect of MG in the proliferation of adipocytes by up-regulating the Akt signaling pathway. The results from this study offer new mechanisms to explain the development of insulin resistance and to prevent the related diseases.

Over the last few decades, the importance of inflammation in the initiation and perpetuation of cardiovascular (CV) disease has become increasingly recognized. Patients with Rheumatoid Arthritis (RA) have been shown to have an increased risk of premature death, occurring predominantly due to an increased rate of premature CV disease. The presence of an adverse risk factor profile in RA is well established, but does not fully explain the excess risk. It is clear that chronic inflammation is a major pathogenic mechanism in atherosclerosis, and this is likely to explain at least some of the increased risk of CV disease in subjects with RA. Carotid intima-media thickness (cIMT) measured by ultrasound, is a good non-invasive approach to measurement of atherosclerotic burden, and is increased in preclinical atherosclerotic disease. cIMT is significantly higher in patients with RA than age and sex matched controls. The Receptor for Advanced Glycation End Products (RAGE) may be important for the perpetuation of chronic inflammation. This cell surface receptor molecule is upregulated at sites of chronic vascular inflammation, and can be signalled by a range of proinflammatory ligands as well as advanced glycation end-products. The gene has a number of polymorphisms, and the Glycine 82 Serine polymorphism has a prevalence of about 10% in Caucasians. Patients with RA are more likely to have this polymorphism than control subjects, as the gene is in linkage disequilibrium with DRB1*0401, one of the RA susceptibility alleles. There is evidence that ligation of RAGE in monocytes derived from donors with the Ser 82 allele signals an enhanced NF-kB and p38 MAP Kinase cellular response, associated with production of pro-inflammatory cytokines. In this study, I hypothesized an association between the RAGE 82 Ser polymorphism of this receptor, which is enriched in RA, and the risk of CV disease in subjects with RA. To investigate whether RAGE 82Ser is associated with CV disease in RA, I examined events, risk factors, features of RA and RAGE 82Ser, in 232 patients with RA attending a tertiary referral hospital. Carotid intima-media thickness was measured using carotid duplex scanning in 137 of those patients. CV events, duration and severity of RA, and CV disease risk factors were determined using patient questionnaires, chart review, laboratory analysis, and radiographs. DNA was typed for HLA-DRB1 genes and the RAGE 82Ser polymorphism. Twenty percent of patients carried the RAGE 82Ser allele. More than 20% of the cohort had suffered a vascular event. Increasing age, elevated fasting glucose, a history of hypercholesterolemia, and a shorter duration of RA were significantly associated with events. RAGE 82Ser was protective against CV events in this cohort. RA patients with RAGE 82Ser had lower LDL levels and LDL/HDL ratio. cIMT was independently and significantly associated with increasing age, male sex, hypertension, low BMI, and the number of pack years of smoking, but not RAGE genotype. Multiple factors, both CV and RA disease-related, contribute to atherosclerosis in established RA. These data suggest RAGE genotype may contribute to the risk of CV events in RA. The role of RAGE genotype requires further study in inception cohorts examining CV events to better understand its contribution to RA-associated CV disease.

abstract: Birds have shown promise as models of diabetes due to health and longevity despite naturally high plasma glucose concentrations, a condition which in diabetic humans leads to protein glycation and various complications. Research into mechanisms that protect birds from high plasma glucose have shown that some species of birds have naturally low levels of protein glycation. Some hypothesize a diet rich in carotenoids and other antioxidants protects birds from protein glycation and oxidative damage. There is little research, however, into the amount of protein glycation in birds of prey, which consume a high protein, high fat diet. No studies have examined the potential link between the diet of carnivorous birds and protein glycation. The overall purpose of this study was to evaluate whether birds of prey have higher protein glycation given their high protein, high fat diet in comparison to chickens, which consume a diet higher in carbohydrates. This was accomplished through analyses of serum samples from select birds of prey (bald eagle, red-tailed hawk, barred owl, great horned owl). Serum samples were obtained from The Raptor Center at the University of Minnesota where the birds of prey consumed high protein, high fat, non-supplemented diets that consisted of small animals and very little to no carbohydrate. Serum was also obtained from one chicken for a control, which consumed a higher carbohydrate and antioxidant-rich diet. Glucose, native albumin glycation and antioxidant concentrations (uric acid, vitamin E, retinol and several carotenoids) of each sample was measured. Statistical analyses showed significant between group differences in percent protein glycation amongst the birds of prey species. Glycation was significantly higher (p < 0.001) in bald eagles (23.67 ± 1.90%) and barred owls (24.28 ± 1.43%) compared to red-tailed hawks (14.31 ± 0.63%). Percent glycation was higher in all birds of prey compared to the chicken sample and literature values for chicken albumin glycation. Levels of the carotenoid lutein were significantly higher in bald eagles and barred owls compared to great horned owls and red-tailed hawks and the carotenoids beta-cryptoxanthin and beta-carotene were significantly greater in bald eagles compared to red-tailed hawks and great horned owls. / Dissertation/Thesis / Masters Thesis Nutrition 2017

Advanced glycation end products (AGEs) are molecules formed through the nonenzymaticglycation of proteins and are central to the development of cardiovascularcomplications of diabetes including heart failure. AGEs influence cellular function throughthe cross-linking of cellular proteins as well as through actions on cell surface receptors,the most common of which is (RAGE). However, it is still unclear whether AGEs contributeto myocardial abnormalities observed in diabetes through direct myocardial actionsmediated through the RAGE receptor and if so, their underlying mechanisms of action. Wehave therefore investigated the effects of AGEs on calcium handling in isolated adultmouse cardiomyocytes and cultured neonatal rat cardiomyocytes (NRCM) andcharacterised their underlying mechanisms of action in NRCM.Standard molecular techniques were used. Western blot showed expression of RAGEreceptor in mouse whole heart tissue and in both NRCM and adult mouse cardiomyocytes. Incubation of NRCM for 24 hours with AGEs showed a dose dependant reduction ofcalcium transient amplitude with a maximum of 50% at 1 g/l (P<0.01) accompanied with32% reduction in SR calcium content with no detectable changes in calcium handlingproteins expression. We demonstrated a 24% increase (P<0.01) in the production ofreactive oxygen species (ROS) in AGE treated cardiomyocytes induced by enhancedNADPH oxidase activity (P<0.05) with subsequent activation and translocation of NF-kB, atranscriptional factor from the cytoplasm to the nucleus. Activation of NF-kB induced a56% increase in iNOS gene protein expression (P<0.01), a downstream target of NF-kBwhich was accompanied by a significant increase in NO production (P<0.05). Wedemonstrated nitrosylation of several key cellular proteins involved in excitationcontractioncoupling including the Ryanodine receptor and SERCA2a as detected byimmunofluorescence. In conclusion, our work provides insights into novel pathophysiological mechanisms thatunderlie the development of heart failure in diabetes. We demonstrate the presence andfunctionality of AGE receptors in myocardium and show that AGEs inhibit excitationcontractioncoupling through increased ROS production leading to activation andtranslocation of NF-kB from the cytoplasm to the nucleus resulting in increase in NOproduction. Concomitant increases in intracellular levels of ROS and NO favours theproduction of peroxynitrite with subsequent nitrosylation of key cellular proteins involved inthe process of excitation-contraction coupling such as the Ryanodine receptor andSERCA2a. This study provides novel insights into the role of AGEs in inducing myocardialdamage in diabetes mediated through RAGE receptor and independent from the vascular effects.