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Dendritic cells (DCs) are the sentinels of the immune system. They mature at the encounter of the appropriate stimuli or danger signals, which induce them to perform pro-inflammatory antigen presentation to naïve and memory T cells, resulting in inflammation. Remaining in an immature state however, DCs acquire a tolerogenic phenotype. When activated by TLR ligands, DCs undergo metabolic re-programming and switch to TBK1/IKKe/AKT-induced glycolysis at the early activation phase, which is sustained due to nitric oxide (NO)-mediated inhibition of mitochondrial metabolism at the later activation phase. Targeting DC activation in the view of promoting less activated or tolerogenic DCs could be an approach to reduce or abrogate inflammation in settings such as solid organ transplant rejection or in autoimmune diseases such as systemic lupus erythematosus (SLE). In this thesis, we present data pertaining to three different approaches for targeting DC activation including 1) the use of ethyl p / Microbiology and Immunology

[ES] El cáncer de mama es el cáncer más común en mujeres en todo el mundo y la principal causa de muerte por cáncer en mujeres junto al cáncer de pulmón. Este cáncer tiene muy buen pronóstico en general, con una supervivencia del 80%. Sin embargo, el pronóstico del cáncer de mama triple negativo es mucho peor, al no conocerse ninguna diana farmacológica y tratarse de forma inespecífica. La metformina, fármaco prescrito para la diabetes, ha mostrado algunos buenos resultados preliminares como potencial terapia. Por otro lado, el principal tratamiento dirigido de las pacientes HER2+ es el trastuzumab, que neutraliza al receptor HER2 amplificado; sin embargo, un elevado número de pacientes desarrollan resistencias al tratamiento. Los microRNAs son pequeños RNAs no codificantes capaces de regular la expresión génica epigenéticamente, y pueden ser secretados de la célula en vesículas llamadas exosomas. El objetivo de este trabajo es abordar estas dos problemáticas en cáncer de mama. Son necesarios estudios de los mecanismos de acción o resistencia de estos fármacos a través de la regulación epigenética por microRNAs. Queremos determinar la relación del miR-26a y sus dianas con el efecto de la metformina en cáncer de mama triple negativo y estudiar las diferencias de expresión de microRNAs que generan resistencias a trastuzumab en cáncer de mama HER2+, así como estudiar su modo de transmisión entre células. Se realizaron ensayos celulares tratando con metformina las líneas MDA-MB-231, MDA-MB-468 y MCF-7 así como sobreexpresando o inhibiendo miR-26a y se midieron sus dianas teóricas por qPCR. Para las líneas HER2+ se realizó un Affymetrix Genechip miRNA 4.0 microarray comparando líneas SKBR-3wt y BT-474wt con sus respectivas líneas con resistencia generada a trastuzumab y HCC-1954 como resistente innata. Se estudiaron los microRNAs más relevantes del array en las líneas celulares y en pacientes y se comprobó su presencia en exosomas, así como el efecto de los exosomas en la transmisión de la resistencia. La sobreexpresión de miR-26a resultó en una reducción en la viabilidad celular que se recuperó parcialmente al inhibirla. E2F3, MCL-1, EZH2, MTDH y PTEN fueron regulados negativamente por miR-26a y la proteína PTEN también se redujo tras la sobreexpresión de miR-26a. El tratamiento con metformina redujo la viabilidad de las células de cáncer de mama, aumentó la expresión de miR-26a y condujo a una reducción en la expresión de BCL-2, EZH2 y PTEN. La inhibición de miR-26a previene parte del efecto en viabilidad de la metformina y la reducción de la expresión de PTEN y EZH2. En las líneas HER2+, miR-23b-3p y miR-146a-5p fueron los principales candidatos extraídos del array. miR-23b-3p inhibió PTEN significativamente en la línea BT-474. miR-146a-5p aumentó la resistencia de las células SKBR-3 al trastuzumab y su inhibición redujo la resistencia de las SKBR-3r. El aumento de miR-146a-5p en SKBR-3wt tuvo un efecto en ciclo celular aumentando la fase S y la G2/M, inhibiendo la expresión de CDKN1A y aumentando la de CCNB1. Los exosomas de las SKBR-3 contenían miR-146a-5p, con mayores niveles en los de las resistentes (exoR). Los exoR aumentaron la resistencia a trastuzumab, la transición epitelio-mesenquimal y la migración al co-cultivarse con SKBR-3wt, y la angiogénesis en las HUVEC. Nuestros resultados sugieren que el efecto de la metformina está mediado por una mayor expresión de miR-26a y reducción de sus dianas, PTEN y EHZ2. Por tanto, el uso de metformina en el tratamiento del cáncer de mama constituye una prometedora potencial terapia. En HER2+, miR-23b parece provocar resistencia a trastuzumab vía PTEN y miR-146a a través del ciclo celular. Además, miR-146a se transmite en exosomas, que son capaces de reducir la sensibilidad al trastuzumab de las células sensibles y aumentar la TEM, migración y angiogénesis. / [EN] Breast cancer is the most common cancer in women worldwide and the leading cause of cancer death in women along with lung cancer. This cancer has a very good general prognosis, with a survival of 80%. However, the prognosis for triple negative breast cancer is much worse, as it has no pharmacological target and treats it nonspecifically. Metformin, a prescribed diabetes drug, has shown some good preliminary results as potential therapy. On the other hand, the main targeted treatment for HER2 + patients is trastuzumab, which neutralizes the amplified HER2 receptor, but a large number of patients experienced resistance to treatment. MicroRNAs are small non-coding RNAs that are part of epigenetics and are capable of regulating gene expression, and which can be secreted from the cell into vesicles called exosomes. The objective of this work is to address these two problems in breast cancer, which need to study the mechanism of action or resistance of these drugs, through the epigenetics of microRNAs. We want to determine the relationship of miR-26a and its targets with the effect of metformin in triple negative breast cancer and to study the differences in the expression of microRNAs that process resistance to trastuzumab in HER2 + breast cancer, as well as to study its mode of transmission between cells. Cellular assays were performed treating the MDA-MB-231, MDA-MB-468 and MCF-7 lines with metformin as well as overexpressing or inhibiting miR-26a, and their theoretical targets were measured by qPCR. For the HER2+ cell lines, an Affymetrix Genechip miRNA 4.0 microarray was performed comparing SKBR-3wt and BT-474wt lines with their respective cell lines with generated resistance to trastuzumab and HCC-1954 as innate resistance. The most relevant microRNAs of the array in cell lines and in patients were studied and their presence in exosomes was verified, as well as the effect of exosomes in the transmission of resistance. The overexpression of miR-26a resulted in a reduction in cell viability that was partially recovered by inhibiting it. E2F3, MCL-1, EZH2, MTDH, and PTEN were down-regulated by miR-26a, and the PTEN protein was also reduced after overexpression of miR-26a. Metformin treatment reduced the viability of breast cancer cells, increased miR-26a expression, and led to a reduction in BCL-2, EZH2, and PTEN expression. Inhibition of miR-26a partly prevents the effect of metformin in viability and the reduction of the expression of PTEN and EZH2. In the HER2+ lines, miR-23b-3p and miR-146a-5p were the main candidates extracted from the array. miR-23b-3p was shown to significantly inhibit PTEN in the BT-474 cell line. miR-146a-5p increased resistance of SKBR-3wt cells to trastuzumab and its inhibition reduced resistance of SKBR-3r. The increase of miR-146a-5p in SKBR-3wt had effect on the cell cycle by increasing the S phase and the G2/M, inhibiting the expression of CDKN1A and increasing CCNB1 levels. Exosomes isolated from SKBR-3 cell lines contained miR-146a-5p, with higher levels in exosomes from the resistant cell line (exoR). The exoR were shown to increase trastuzumab resistance, EMT, and migration when co-cultivated with SKBR-3wt, and angiogenesis when in culture with HUVEC. Our results indicate that metformin effectively reduces breast cancer cell viability and suggests that the effects of the drug are mediated by an increase in miR-26a expression and a reduction of its targets, PTEN and EHZ2. Thus, the use of metformin constitutes a promising potential triple negative breast cancer therapy. In HER2+ breast cancer, miR-23b appears to elicit resistance to trastuzumab via PTEN and miR-146a throughout the cell cycle. Furthermore, miR-146a is transmitted in exosomes, which have been shown to reduce the sensitivity to trastuzumab of sensitive cells and increase EMT, migration, and angiogenesis. / [CA] El càncer de mama és el càncer més comú en dones arreu del món i la principal causa de mort per càncer en dones junt amb el càncer de pulmó. Aquest càncer té molt bon pronòstic en general, amb una supervivència del 80%. No obstant això, el pronòstic del càncer de mama triple negatiu és molt pitjor, al no conèixer-se'n cap diana farmacològica i tractar-se de forma inespecífica. La metformina, fàrmac prescrit per a la diabetis, ha mostrat alguns bons resultats preliminars com a potencial teràpia. D'altra banda, el principal tractament dirigit de les pacients HER2+ és el trastuzumab, que neutralitza el receptor HER2 amplificat; tanmateix, un elevat nombre de pacients desenvolupen resistències al tractament. Els microRNAs són xicotets RNAs no codificants capaços de regular l'expressió gènica epigenèticament, i poden ser secretats de la cèl·lula en vesícules anomenades exosomes. L'objectiu d'aquest treball és abordar aquestes dues problemàtiques en càncer de mama. Són necessaris estudis dels mecanismes d'acció o resistència d'aquests fàrmacs a través de la regulació epigenètica per microRNAs. Volem determinar la relació del miR-26a i les seues dianes amb l'efecte de la metformina en càncer de mama triple negatiu i estudiar les diferències d'expressió dels microRNAs que generen resistències al trastuzumab en càncer de mama HER2+, així com estudiar la seua manera de transmissió entre cèl·lules. Es van realitzar assajos cel·lulars tractant amb metformina les línies MDA-MB-231, MDA-MB-468 i MCF-7 així com sobreexpressant o inhibint miR-26a i es van mesurar les seues dianes teòriques per qPCR. Per a les línies HER2+ es va realitzar un Affymetrix Genechip miRNA 4.0 microarray comparant línies SKBR-3wt i BT-474wt amb les seues respectives línies amb resistència generada a trastuzumab i HCC-1954 com resistent innata. Es van estudiar els microRNAs més rellevants de l'array en les línies cel·lulars i en pacients i es va comprovar la seua presència a exosomes, així com l'efecte dels exosomes en la transmissió de la resistència. La sobreexpressió de miR-26a resultà en una reducció de la viabilitat cel·lular que es recuperà parcialment en inhibir-la. E2F3, MCL-1, EZH2, MTDH i PTEN foren regulats negativament per miR-26a i la proteïna PTEN també es va reduir en sobreexpressar miR-26a. El tractament amb metformina va reduir la viabilitat de les cèl·lules de càncer de mama, va augmentar l'expressió de miR-26a i va conduir a una reducció en l'expressió de BCL-2, EZH2 i PTEN. La inhibició de miR-26a prevé part de l'efecte en la viabilitat de la metformina i la reducció de l'expressió de PTEN i EZH2. En les línies HER2+, miR-23b-3p i miR-146a-5p foren els principals candidats extrets de l'array. miR-23b-3p va inhibir PTEN significativament en la línia BT-474. miR-146a-5p va augmentar la resistència de les cèl·lules SKBR-3 al trastuzumab i la seua inhibició va reduir la resistència de les SKBR-3r. L'augment de miR-146a-5p en SKBR-3wt va tindre un efecte en cicle cel·lular augmentant la fase S i la G2/M, inhibint l'expressió de CDKN1A i augmentant la de CCNB1. Els exosomes de les SKBR-3 contenien miR-146a-5p, amb majors nivells en els de les resistents (exoR). Els exoR van augmentar la resistència a trastuzumab, la transició epiteli-mesenquimal i la migració en co-cultivar-los amb SKBR-3wt, i l'angiogènesi de les HUVEC. Els nostres resultats suggereixen que l'efecte de la metformina està intervingut per una major expressió de miR-26a i reducció de les seues dianes, PTEN i EHZ2. Per tant, l'ús de metformina al tractament de el càncer de mama constitueix una prometedora potencial teràpia. En HER2+, miR-23b sembla provocar resistència a trastuzumab mitjançant PTEN i miR-146a a través del cicle cel·lular. A més, miR-146a es transmet en exosomes, que són capaços de reduir la sensibilitat al trastuzumab de les cèl·lules sensibles i augmentar la TEM, migració i angiogènesi. / Cabello Navarro, P. (2020). Epigenetic regulation of resistance to treatments in triple negative and HER2+ breast cancer: miRNAs involved [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/153807

Die Arbeit beschäftigt sich mit dem Problem der Fettlebererkrankung. In der Einleitung wird auf die aktuelle Relevanz der Gesundheitsstörung und Therapiemöglichkeiten eingegangen, insbesondere durch das, in der Therapie des Diabetes mellitus Typ 2 gebräuchliche Biguanid Metformin. Der Bezug zu molekularbiologischen Signalwegen wird hergestellt und verschiedene in vitro Modellsysteme werden vorgestellt. Anschließend wird auf die Herkunft und genetische Besonderheiten der verwendeten primären Maushepatozyten und Hepatomzellen eingegangen, bevor die angewandten Methoden vorgestellt werden. Zum Einsatz kam in dieser Arbeit vor allem die Lipidmessung mittels Fettrot, um das Ausmaß an Steatosis quantifizierbar zu machen. Im Ergebnisteil folgen zuerst Versuche zur Zytotoxizität der einzelnen Chemikalien und deren Einfluss auf intrazelluläre Energieniveaus, bevor der Einfluss auf die hepatozellulären Fetteinlagerungen im Detail untersucht wird. Unterstützt werden die Ergebnisse durch mikroskopische Bilder der Hepatozyten, welche die beschriebenen Effekte verdeutlichen. Insgesamt konnten folgende Thesen aufgestellt werden: • Zwischen primären Hepatozyten von Wildtyp- und Knockout-Mäusen, bestehen nach 24 stündiger Kultivierung Unterschiede bezüglich des intrazellulären Lipidgehaltes, welche sich nach 72 stündiger Kultivierungszeit nivellieren. • Metformin- und Fructoseinkubation senken den intrazellulären ATP-Gehalt, gleichzeitige Anwesenheit von Metformin und Glucose vermindern den Effekt. • Durch 72-stündige Inkubation der primären Hepatozyten und Behandlung mit Metformin konnte der intrazelluläre Lipidgehalt um circa 40% gesenkt werden. • Durch 72-stündige Inkubation der primären Hepatozyten mit Glucose konnte der intrazelluläre Lipidgehalt um circa 100% gesteigert werden. • Bei humanen Hepatomzellen (HuH7) konnte kein Metformin- und kein Glucoseeffekt beobachtet werden. • Der LXR-Agonist TO901317 wirkt auf den intrazellulären Lipidgehalt Metformin entgegen.

Introduction The adult brain exhibits low regenerative ability. Stem cell-based transplantation approaches have been largely unsuccessful, due to the difficulty to recapitulate the complex cytoarchitecture of the central nervous system (CNS). eNSCs are a new therapeutic option as pharmacological activation and increase of their number in vivo is accompanied by powerful neuroprotection in various disease models. Hes3 is expressed in both proliferating and quiescent NSCs, which makes it a useful biomarker for NSC identification. Direct injections of insulin in the adult brain increase the number of eNSCs and promote rescue of injured neurons via a novel molecular mechanism, the STAT3-Ser/Hes3 Signaling Axis. This molecular pathway with the STAT3-Ser phosphorylation at its core regulates Hes3 and together they form a merging point for several signals including insulin receptor activation. Main aim and Hypothesis Beyond the brain, STAT3-Ser/Hes3 signaling regulates various plastic cell populations in other organs of the endocrine/neuroendocrine system. In the pancreas, Hes3 is expressed in islets cells and regulates their growth, regeneration, and insulin release. Hes3 is also expressed in mouse hypothalamic tanycytes, which are diet responsive cells and play a very crucial role for the communication between the brain and the endocrine system. Also, Hes3 is expressed in the adrenal gland (both in the cortex and medulla); cultured adrenal progenitors express Hes3 and various treatments that induce Hes3 expression promote their growth. Therefore, STAT3-Ser/Hes3 Signaling may be involved in tissue problems that result from metabolic dysfunction. Metabolic syndrome often results in diabetes (Type I, Type II) and insulin resistance, suggesting that eNSCs may be affected by the condition. There is evidence that obesity induces inflammatory reactions in the hypothalamus, leading to NSC loss. However, it is not clear if damage to NSCs is also directly linked to insulin signaling disruption. Results Our results show that various parameters affect Hes3 levels in the brain. Aging decreased Hes3 mRNA expression. Type I diabetes increased Hes3 expression. Type II diabetes decreased Hes3 expression. Thus, we conclude that eNSCs are modulated by diabetes in an age-dependent manner. We also investigated whether common medication for metabolic related dysfunction also affects Hes3 expression in the adult brain. Indeed, our results show that metformin decreases Hes3 expression in the mouse hypothalamus. To address whether metformin has a direct effect on NSCs we treated primary mouse fNSCs with metformin. Metformin decreases cell number, proliferation and affects cell morphology, giving a more differentiated appearance (large, flat cell body with wider projections). Hes3 expression increases significantly at 72 hours of treatment. The metformin result opens the question if the increase in the Hes3 expression is a direct effect of the signal transduction pathways activated by metformin or due to a stress reaction. To address this we treated NSCs with exendin-4, another diabetes drug that we previously showed to both elevate Hes3 expression and cell number using a mouse insulinoma cell line (MIN6). Exendin-4 increases fNSC cell number but it did not affect the morphology. Similar to metformin proliferation was not affected. Hes3 expression increased significantly at 72 hours of treatment as well. This result indicates the distinctive action of the drugs on the STAT3-Ser/Hes3 signaling pathway. Specifically it dissociates Hes3 levels from other cellular parameters. Importantly it shows that two common diabetes medications have very different effects on NSCs. Because Hes3 is strongly regulated by metabolic parameters and medication we addressed potential roles of Hes3 using an established Hes3 null mouse line. Hes3 null mice exhibit no obvious phenotypes under normal conditions. However, we previously showed that when stressed by chemical induced damage, they exhibit low regenerative potential in the pancreas and brain. To identify additional phenotypes, we performed a phenotypic analysis of the Hes3 null mouse line under normal diet and HFD conditions (which induced type II diabetes). We found mild phenotypes that relate to the nervous system, the immune system and metabolism. At the molecular level, Hes3 deletion affects the expression of other genes within the Hes superfamily in the adult mouse brain. However, we did not observe these molecular differences in the HFD condition, suggesting an interplay between metabolic parameters (possibly, circulating insulin) and the regulation of Hes/Hey genes in the brain. Our data suggest a broad range of roles for Hes3, particularly under abnormal conditions. Conclusions Our work establishes that multiple parameters of metabolic state as well as diabetes medication affect Hes3 expression in the brain. Metabolic syndrome is a risk factor for many neurological disorders such as Alzheimer’s disease, Parkinson’s disease and Multiple Sclerosis. It is important to understand at the molecular and cellular level how metabolic dysfunction affects the brain. Here, we introduced a new cellular biomarker and signaling component that is greatly regulated in metabolic dysfunction.:1 Introduction 18 1.1 The ''plastic brain'': Neural Stem Cells, progenitors and precursors 19 1.2 Functional adult neurogenesis 19 1.3 NSCs in conventional and nonconventional regions of the adult brain 20 1.4 Neurodegenerative diseases, cell replacement and endogenous NSCs 21 1.5 The STAT3-Ser/Hes3 signaling axis in NSCs 24 1.6 Beyond the brain: The STAT3-Ser/Hes3 signaling axis operates in plastic cells 27 1.6.1 STAT3-Ser/Hes3 Signaling Axis in the pancreatic islet 27 1.6.2 STAT3-Ser/Hes3 Signaling Axis in the adrenal cortex and medulla 28 1.6.3 STAT3-Ser/Hes3 Signaling Axis in tanycytes of the hypothalamus? 28 1.6.4 STAT3-Ser/Hes3 Signaling: A new molecular component of the neuroendocrine system? 29 1.7 Metabolic syndrome and neurological disease 31 1.7.1 Metabolic dysfunction and Alzheimer's disease 31 1.7.2 Metabolic dysfunction and Parkinson's disease 31 1.7.3 Metabolic dysfunction and Multiple Sclerosis 32 1.7.4 Metabolism and neurodegenerative disease: Are they connected? 32 1.8 Main Aim – Hypothesis 33 2 Materials and Methods 34 2.1 Animal experiments 34 2.1.1 Animal use authorization 34 2.1.2 Genotyping 34 2.1.3 In vivo models 36 2.1.4 In vivo metabolic Analyses 36 2.1.5 Nociception 37 2.1.6 Histology 38 2.1.7 PCR and Real-Time quantitative PCR (qPCR) 39 2.1.8 Western Blot 41 2.2 Mouse phenotyping 42 2.3 Neural stem cell cultures 43 2.3.1 Preparation – Coatings 43 2.3.2 Cell Isolation and Cell Culture 43 2.3.3 Pharmacological Manipulation (Metformin – Exendin-4) 43 2.4 Heat maps 44 2.5 Statistical analyses 44 3 Results 45 3.1 Hes3 is expressed in the mouse brain 46 3.2 Aging and diabetes models alter Hes3 in the brain 48 3.2.1 Hes3 expression decreases with age 48 3.2.2 Pancreatic islet damage by streptozotocin increases Hes3 expression in the brain 48 3.2.3 High Fat Diet reduces Hes3 expression in the brain 49 3.3 Common diabetes medication affect neural stem cells (NSCs) in the brain 53 3.3.1 Metformin decreases Hes3 expression in the brain 53 3.3.2 Metformin opposes growth but increases Hes3 expression in cultured NSCs 54 3.3.3 Exendin-4 promotes growth and increases Hes3 expression in cultured NSCs 54 3.3.4 Metformin and Exendin-4 affect the STAT3-Ser/Hes3 signaling axis 59 3.4 Hes3 null mice exhibit a quasi-normal phenotype 60 3.4.1 Phenotypic Analysis - Normal Diet (ND) 60 3.4.2 Metabolism Relevant Phenotypes – HFD challenge 63 3.4.3 Phenotypic Analysis – Molecular 67 4 DISCUSSION 70 4.1 Diabetes affects the brain 71 4.2 STAT3-Ser/Hes3: a putative mediator 71 4.3 Hes3 is a special member of the Hes/Hey gene family 72 4.4 Patterns of Hes3 expression may be specific to cell type and microenvironment 72 4.5 Metabolic dysfunction and diabetes medication affect brain Hes3 73 4.5.1 Age regulates Hes3 73 4.5.2 Diabetes models regulate Hes3 expression in the brain 74 4.5.3 Metformin regulates Hes3 expression in the brain 74 4.6 Hes3 phenotyping provides clues to Hes3 functions 76 4.7 Hes3 and metabolic dysfunction: Are they connected? 77 5 Conclusions and Future Remarks 79 References 81

Das Equine Metabolische Syndrom (EMS) beschreibt einen Cluster von metabolischen Störungen, die durch Adipositas, Insulinresistenz und Hufrehe im Zusammenhang stehen. Ziel dieser Arbeit war es, den Einfluss einer achtwöchigen oralen Supplementierung von Chrom, Metformin beziehungsweise von einer Kombination aus Chrom und Metformin auf die Insulinsensitivität und die Glukosetoleranz bei adipösen Pferden und Ponys zu untersuchen. Für diese Studie standen 24 Pferde und Ponys (14,4 ± 3,87 Jahre, 14 Stuten und 10 Wallache) mit Adipositas, Insulinresistenz und Hufrehe zur Verfügung. Während der achtwöchigen Versuchsphase bekamen die Tiere eine Heuration (1,5 kg Heu/100 kg Körpermasse (KM)) und zweimal täglich das ihnen zugewiesene Supplement (Chrom: 25 µg/kg KM, Metformin: 15 mg/kg KM, Chrom+Metformin: 25 µg/kg KM Chrom + 15 mg/kg KM Metformin in jeweils 25 g Grünmehl/100 kg KM) verabreicht. Eine vierte Gruppe erhielt als Placebo 25 g Grünmehl/100 kg KM ohne Supplement. Vor Versuchsbeginn und nach Versuchsende durchliefen die Pferde und Ponys, an zwei aufeinanderfolgenden Tagen, nach jeweils einer zwölfstündigen Fastenperiode einen kombinierten Glukose-Insulin-Toleranztest (KGIT) zur Bestimmung der Insulinsensitivität und einen oralen Glukose-Toleranz-Test (OGTT) zur Bestimmung der Glukoseabsorption und -toleranz. Im Verlauf des Versuchszeitraums konnte bei den Pferden ein durchschnittlicher Gewichtsverlust von 2,77 ± 2,99 % verzeichnet werden (Behandlung p > 0,05). Beim OGTT zeigte sich keine signifikante Veränderung der Glukose- und Insulinreaktionen zwischen Versuchsbeginn und Versuchsende. Die Seruminsulinmaximalwerte der mit Metformin und der mit Chrom+Metformin supplementierten Gruppen waren nach der Versuchszeit numerisch gesunken (Metformin Versuchsbeginn: 452 ± 642 µU/ml, Versuchsende: 202 ± 121 µU/ml; Chrom+Metformin Versuchsbeginn: 388 ± 347 µU/ml, Versuchsende: 342 ± 164 µU/ml, Behandlung p > 0,05). Im KGIT zeigten sich bei den Glukosewerten keine signifikanten Unterschiede zwischen den einzelnen Behandlungsgruppen und zwischen den Werten vor Versuchsbeginn und nach Versuchsende. Die Seruminsulinkonzentrationen lagen im KGIT vor Versuchsbeginn bei allen Probanden zum Zeitpunkt Minute 45 über 100 µU/ml. Somit gelten alle Versuchsteilnehmer per definitionem als insulinresistent. Nach den acht Wochen Supplementierung befanden sich beim KGIT zum Zeitpunkt Minute 45, mit Ausnahme eines Probanden aus der Chrom+Metformin-Gruppe, alle Seruminsulinwerte weiterhin >100 µU/ml. Somit sind die übrigen 23 Pferde und Ponys weiterhin als insulinresistent einzustufen. Weder Chrom, noch Metformin oder die Kombination von Chrom+Metformin konnte in den hier im Versuch angewandten Dosierungen die Insulinsensitivität und Glukosetoleranz der erkrankten Pferde und Ponys verbessern.