Radiotherapy is the primary treatment for patients with head and neck cancer, which account for roughly 60,000 annual diagnoses in the U.S. and approximately 500,000 worldwide. About 90% of these individuals receive radiation therapy, and salivary hypofunction and xerostomia occur in 60-85% of these patients due to irreversible damage to the salivary glands. Current preventative and palliative care fail to improve quality of life, accentuating the need for regenerative therapies. Stem/progenitor-cell based therapies have been proposed to regenerate the irradiated glands; however, the identity of stem and progenitor cells in the adult salivary glands has remained somewhat elusive. Moreover, it is unclear how salivary progenitors respond to radiation and whether they can be stimulated to effectively reinstate salivary function. The second chapter of the present study describes the development of a label-retaining assay in salivary glands using EdU. The label-retaining cells (LRCs) identified in murine salivary glands have proliferative potential in vitro and expressed markers of putative salivary progenitors, such as Keratin 5, Keratin 14, and c-Kit. Interestingly, LRCs were still present 30 days following radiation, when chronic loss of saliva is evident. The significance of these findings lies in the potential of this model to study the mechanisms that prevent salivary progenitors from maintaining salivary gland homeostasis upon exposure to radiation, which will in turn facilitate the development of regenerative therapies for salivary gland dysfunction. In the following chapter, we show that a unique population of murine salivary gland LRCs undergo compensatory proliferation in response to radiation. The initiation of compensatory proliferation is tightly associated with inactivation of the kinase aPKCζ and increased nuclear localization of YAP. This part of the study provides novel insights into the regulation of function of salivary gland progenitors, which can be utilized for the development of therapeutic agents to treat salivary hypofunction. Finally, the last chapter describes how the mechanisms found to initiate compensatory proliferation in acinar LRCs as a response to radiation are involved in the regeneration of salivary glands with IGF-1. Administration of IGF-1 post-radiation restores salivary function in mice, but the mechanisms of regeneration are still unknown. Here, we show that IGF-1 requires aPKCζ to restore saliva production. Further, IGF-1 inhibits nuclear translocation of Yap in an aPKCζ-dependent fashion. We propose that a tightly regulated balance in the levels of aPKCζ and Yap in acinar LRCs has to be maintained in order to restore function following radiation. In conclusion, the findings from this study provide new knowledge in regards to the regulation of function of salivary progenitors during a state of injury (by radiation) and during regeneration (with IGF), and offer potential targets of study for the development of new therapeutics for salivary gland dysfunction. Future studies will determine whether aPKCζ and Yap can be effectively targeted in salivary progenitors to restore salivary function in head and neck cancer patients who receive radiation therapy.

Advanced melanoma poses a major therapeutic challenge, and despite the development of recent promising therapeutic agents, resistance to treatment remains a problem. Until recently, despite low response rates, alkylating agents dacarbazine and temozolomide (TMZ) were the standard of care for the treatment of advanced melanoma. The cytotoxic effects of these agents relies upon the formation of alkylated base lesions such as O⁶-methylguanine (O⁶MeG), which is repaired by a protein implicated in TMZ resistance called O⁶-methylguanine-DNA methyltransferase (MGMT). Failure to resolve such alkylated bases results in DNA replication-associated double-strand breaks (DSBs). The type 1 insulin-like growth factor receptor (IGF-1R) mediates a number of characteristics common to cancers, including proliferation and survival, and evidence suggests it may also contribute to resistance to many anticancer agents. The aims of this study were to test whether melanoma cells could be sensitized to TMZ by small molecule IGF1R inhibitors, and to explore the mechanism of any chemosensitization. This study found an association between basal IGF1R phosphorylation and in vitro TMZ resistance in seven MGMT-proficient melanoma cell lines, suggesting that IGF1R activation may be linked with TMZ resistance. Furthermore, IGF1R inhibition caused dose-dependent sensitization of melanoma cells to TMZ, regardless of BRAF mutation status. This reduction in cell survival was not accompanied by an increase in apoptosis, but rather Chk2 activation and an accumulation of cells in the G2/M phase of the cell cycle, suggesting a possible effect of IGF1R inhibition on DNA repair. IGF1R depletion was found to increase MGMT protein levels and activity, but this effect was not seen in IGF1R inhibited cells. In addition, IGF1R inhibition was not epistatic with MGMT inhibition, and IGF1R inhibition reduced survival of TMZ treated MGMT-null cells. This suggested that TMZ sensitization by IGF1R inhibition was independent of MGMT. IGF1R inhibition did however cause an increase in the accumulation of TMZ-induced RPA foci, and delay in resolution of RAD51 foci. Together with the finding that IGF1R inhibition reduced survival in PARP inhibited melanoma cells, these results suggested that IGF1R inhibition influenced DSB repair by homologous recombination. Finally, the combination of IGF1R inhibition with TMZ was tested in a mouse model and was found to be tolerable. TMZ or IGF-1R inhibitor alone caused minor reduction in melanoma xenograft growth rates (rate reduction by 13% and 25% respectively), while combination treatment caused supra-additive growth delay (72%) that was significantly different from other treatment groups (p<0.05). The findings of this study suggest IGF1R inhibition as a possible option in overcoming alkylating drug resistance in melanoma.

Resumo:O presente trabalho teve como objetivo avaliar diferenças na idade e peso à puberdade entre novilhas Nelore (260±34 kg; 12±1 meses de idade) tratadas com salina (n=15) ou somatotrofina bovina recombinante (rbST; n=16) a cada 14 dias desde os 12 até os 22 meses de idade, ou até atingir a puberdade. Adicionalmente, verificamos o efeito do rbST sobre o crescimento, o revestimento de gordura subcutânea, as concentrações plasmáticas de GH, IGF-I, leptina, glicose e insulina, e a taxa de prenhez na primeira estação de monta. Todas as novilhas foram mantidas à pasto no mesmo piquete e foram expostas durante todo o experimento a um rufião com buçal marcador. O peso corporal e a espessura da gordura subcutânea foram mensurados a cada dois meses durante o período experimental. Avaliação por ultrassom dos ovários para monitorar a presença de CL e amostras de sangue foram coletadas a cada 14 dias para quantificações hormonais. Não houve efeito do tratamento (p≥0,05) na idade e peso à puberdade, ou taxa de prenhez na primeira estação de monta. A espessura da gordura subcutânea entre a 12ª e 13ª costela não foi alterada pelo tratamento (p≥0,05), no entanto a espessura da gordura subcutânea na garupa foi menor nas novilhas do grupo rbST aos 18 (p=0,04) e 22 (p<0,01) meses de idade. Não houve efeito de tratamento (p≥0,05) sobre o ganho de peso e as concentrações plasmáticas de glicose, GH e IGF-I. O diâmetro do maior folículo foi menor nos animais do grupo salina aos 12 meses de idade (p= 0,01) e se correlacionou com a concentração de IGF-I no grupo rbST (r= 0,13; p=0,05). No grupo salina a concentração de leptina foi maior aos 12,7 (p=0,02), 13,4 (p= 0,01), 14,3 (p=0,04) e 16,2 (p=0,03) meses de idade e a concentração de insulina foi maior aos 20,1 meses de idade (p=0,06). Em resumo, o tratamento prolongado com 250 mg de rbST não alterou a idade ou peso...(Resumo completo, clicar acesso eletrônico abaixo) / Abstract:The present experiment evaluated differences in age and weight at puberty between Nellore heifers (260±34 kg; 12±1 months old) treated with saline (n=15) or recombinant bovine somatotropin (rbST; n=16) every 14 days from 12 until 22 months of age or until puberty attainment. Additionally, we assessed the effect of rbST in subcutaneous fat thickness, plasma GH, IGF-I, leptin, glucose, insulin, and pregnancy in the first breeding season. All heifers were maintained on the same pasture and exposed to a teaser bull with a neck-marker device. Heifers body weight and subcutaneous backfat thickness were obtained every two months, ovaries were evaluated by ultrasound and blood samples collected every 14 days to monitor the presence of CL and plasma hormones concentration. There was no effect of treatment (p≥0.05) on age and weight at puberty or pregnancy in the first breeding season. The backfat thickness between the 12th and 13th rib was not affected by treatment (p≥0.05), however the rump backfat thickness was lower in rbST heifers at 18 and 22 months (respectively, p=0.04; p<0.01). Treatments had no effect (p≥0.05) on weight gain, plasma glucose, GH and IGF-I. The diameter of the largest follicle was smaller in animals of the saline group at 12 months of age (p=0.01) and was correlated with plasma IGF-I in the rbST group (r=0.13; p=0.05). In the saline group, leptin concentration was higher at 12.7 (p=0.02), 13.4 (p=0.01), 14.3 (p=0.04) and 16.2 (p=0.03) months, and insulin concentration was increased at 20.1 months of age (p=0.06). In summary, prolonged treatment with rbST did not change the weight or age at puberty, plasma glucose, GH and IGF-I, however it decreased subcutaneous fat and insulin, increased leptin concentration. It was demonstrated that treatment with rbST did not affect pregnancy in the first breeding season. / Orientador:Guilherme de Paula Nogueira / Banca:Maria Carolina Villani Miguel / Banca:José Fernando Garcia / Mestre

Die Osteoporose des Mannes ist eine unterdiagnostizierte Erkrankung. Die Zahl der betroffenen Männer in Deutschland wird auf 0,8 bis 1 Million geschätzt, aber die reale Inzidenz ist wahrscheinlich höher. Die Osteoporose des Mannes ist Schätzungen zufolge in bis zu 60% mit Begleiterkrankungen assoziiert. Hypophysäre Störungen wie Hypogonadismus und Wachstumshormonmangel sind starke Risikofaktoren für die Entwicklung einer Osteoporose. Es gibt in der Literatur nur wenige Daten über Hypophysenerkrankungen und Osteoporose, abgesehen davon, dass bei bestehendem Wachstumshormonmangel die Assoziation der Osteopenie / Osteoporose gesichert ist. Für die nicht diagnostizierten Fälle von GH-Defizienz kann jedoch die Manifestation einer Osteoporose ein erstes und führendes Symptom sein. Es gibt Evidenzen dafür, dass IGF-1 im Serum in gesunden Populationen positiv mit der Knochendichte korreliert. Das Ziel dieser Studie ist, eine große Anzahl an Patienten mit Osteoporose auf die Inzidenz niedriger IGF-1-Spiegel hin zu untersuchen. / The osteoporosis of the man is an unterdiagnosed disease. The number of the affected men in Germany is estimated at 0.8 to 1 millions, but the real Inzidenz is probably higher. The osteoporosis of the man is associated according to estimates in up to 60% with accompanying illnesses. Hypophysis disturbances like Hypogonadism and growth hormone lack are strong risk factors for the development of an osteoporosis. There are in the literature only few data about hypophysis illnesses and osteoporosis, apart from the fact that with existing growth hormone lack the association of the Osteopenie / osteoporosis is protected. Nevertheless, for the not diagnosed cases of GH-Defizienz the manifestation of an osteoporosis can be the first and leading symptom. There is evidence for the fact that IGF-1 correlates in the Serum in healthy populations positively with the osseous density. The purpose of this study is, a great number to patient with osteoporosis examine for the Inzidenz of low IGF-1-levels.

Die Reifung der Zona reticularis der Nebennieren-Rinden (NNR) und ihrer Androgen-Sekretion vor der Pubertät unterscheidet sich bei Menschen und höheren Primaten von der NNR-Reifung anderer Species, z.B. der Nager. Die Sekretion der NNR-Androgene leitet die Pubertätsentwicklung ein. Die NNR-Androgene erlangen medizinische Bedeutung dadurch, dass sie bei Frauen zu Hirsutismus und Fertilitätsstörungen führen können. Neben diesen Symptomen stellen sie einen Risikofaktor für die Entwicklung eines Polycystischen-Ovar-Syndroms (PCOS) dar, das ungefähr 7 % der prämenopausalen Frauen betrifft. Lange Zeit war nicht bekannt, wie die Differenzierung der Zona reticularis beim Menschen reguliert wird. Sicher ist ACTH bei weitem das bedeutsamste übergeordnete Hormon für die globale adrenocorticale Differenzierung und Funktion. Weitere Faktoren sind speziell für die Androgensekretion verantwortlich, aber nicht genau definiert. Nun wurde zunächst in zellbiologischen Experimenten belegt, dass die ACTH-Wirkung durch ein Spezies-spezifisches Muster von Wachstumsfaktoren autokrin moduliert wird und so die postnatale Entwicklung der Nebenniere steuern kann. Die vorliegenden Untersuchungen an menschlichen NNR-Zellen von Kindern und Erwachsenen in Primärkultur zeigen erstmals, dass IGF-I und IGF-II differenzierte Funktionen dieser Zellen aufrecht erhalten. IGF-I und, mehr noch, IGF-II steigern die Steroid-Biosynthese und ACTH-Ansprechbarkeit, und sie fördern die Bildung von Androstendion, einem delta5-Androgen der Zona reticularis. Darüberhinaus bewirkt Insulin in physiologischen sowie in micromolaren Konzentrationen den IGFs ähnliche Änderungen der Steroidsynthese. In Querschnittsuntersuchungen an gesunden Kindern vor der Pubertät sowie Kindern mit einfacher Adipositas konnte gezeigt werden, dass die Körperzusammensetzung mit den NNR-Androgenen zusammenhängt. Über die Mediatoren IGF-I, Insulin und Leptin wird offensichtlich der NNR der Zustand von Gewicht und Wachstum des Kindes signalisiert, auch bei pathologischer Körperzusammensetzung, wie dem Prader-Willi-Syndrom. Während die Adipositas die Androgen-Bildung steigern kann, ist sie jedoch selbst nicht der kausale Faktor einer vorzeitigen Nebennierenrindenreifung. Der Prämaturen Pubarche können in 5 - 10 % der untersuchten weiblichen Population ein nicht-klassisches AGS oder NNR-Tumoren zugrunde liegen. Bei den verbleibenden Kindern besteht eine eigentlich harmlose Reifungsbeschleunigung mit normaler Wachstumsprognose. Betrachtet man diese Kinder mit idiopatischer Prämaturer Adrenarche jedoch genauer, so finden sich zwei Untergruppen mit langfristigen Risiken: erstens zeigen Kinder mit einer sogenannte manifesten Heterozygotie für einen 21-Hydroxylase-Defekt Auffälligkeiten des Wachstums, die eine Endgrössenreduktion bewirken könnten, und zweitens wird bei Jugendlichen mit einer Überstimulierbarkeit der NNR diese "Exaggerated Adrenarche" für ein nachfolgendes PCOS verantwortlich gemacht. Schliesslich scheint es vor dem Hintergrund der sich epidemieartig ausbreitenden Zunahme des Übergewichts im Kindesalter angezeigt, den Bezug dieser NNR-Störungen zur Adipositas und der Hyperinsulinämie weiter zu klären. / The prepubertal maturation of the zona reticularis of the adrenal cortex and its androgen secretion in man and higher primates differs from other species, e.g. rodents. The secretion of adrenal androgens induces the pubertal development. The importance of adrenal androgens is derived from them being the cause for hirsutism and fertility disorders in women. In addition they represent a risk factor for the development of the polycystic ovary syndrome (PCOS), that affects about 7% of all pre-menopausal women. The regulation of the differentiation of the zona reticularis was unknown for a long time. However, ACTH is by far the most important hormone to regulate the global adrenocortical differentiation and function. In addition, other yet undefined factors are specifically responsible for the secretion of adrenal androgens. The cell-biological experiments presented here demonstrate that the effects of ACTH can be modulated in an autocrine manner by a species-specific pattern of growth factors so as to allow for the control of the postnatal development of the adrenal gland. The present investigations in human adrenocortical cells of children and adults in primary culture show for the first time that IGF-I and IGF-II maintain the differentiated function of these cells. IGF-I and to an even greater extent IGF-II enhance the biosynthesis of steroids and ACTH-responsiveness, and they promote the production of androstenedione, a delta5-androgen of the zona reticularis. Moreover, insulin, in physiological as well as in micromolar concentrations, induces changes in steroid production similar to the IGFs. In cross-sectional studies of healthy pre-pubertal children and children with simple obesity, it was shown that body composition is associated with adrenal androgens. Mediated by IGF-I, insulin and leptin, body composition apparently signals the child's state of weight and growth to the adrenals, even in patients with abnormal body composition, e.g. the Prader-Willi syndrome. While obesity may enhance androgen production, it is not the direct causal factor to induce premature adrenal maturation. In 5-10% of the female population investigated, premature pubarche is caused by non-classical adrenal hyperplasia or an adrenocortical tumour. In the remaining children, there is merely a harmless acceleration of maturation with normal growth prediction. A closer look at the children with idiopathic premature adrenarche, however, reveals two subgroups with long-term risks: First, children with a so called manifest heterozygosity of a 21-hydroxylase-defect show growth abnormalities, possibly reducing final height. Second, in adolescents with enhanced stimulation of the adrenal cortex, this 'exaggerated adrenarche' is held responsible for the subsequent development of PCOS. Finally, with regard to the rapidly spreading epidemic of overweight in children, it seems essential to study into greater depth the relationship between these adrenal dysfunctions and obesity or hyperinsulinism.

The ability of insulin-like growth factor-I (IGF-I) to impact the hippocampus and associated behaviors may vary depending upon estrogenic status. Previous work from our lab demonstrated that chronic antagonism of brain IGF-I receptors (IGF-IR) resulted in increased levels of hippocampal synaptic proteins in control-treated ovariectomized (OVX) rats. In contrast, antagonism of brain IGF-IR decreased levels of synaptic proteins in estradiol-treated OVX rats. The goal of the current experiment was to test the hypothesis that effects of chronic agonism of IGF-IR, via peripheral treatment with IGF-I, on hippocampal-dependent memory would also vary with estrogenic status. Furthermore, we assessed the influence of estrogenic status on the ability of IGF-I to impact levels of hippocampal synaptic proteins. OVX rats received chronic peripheral treatment with estradiol or cholesterol control via silastic implants, as well as IGF-I or vehicle via osmotic minipumps. One week after surgeries, place learning and memory on the Morris water maze was assessed via eight place-training trials on the first day and four place-training trials on the second day of testing. Place learning and memory was measured using mean swim path length. Following place training, a probe trial was conducted to assess memory for the location of the hidden platform. Memory on the probe trial was measured via percent time in the target quadrant. Animals were euthanized 24 hours following behavioral testing, and hippocampi were processed for western blotting to determine levels of hippocampal synaptic proteins PSD-95, spinophilin, and synaptophysin. Results revealed no effects of treatment on behavioral measures or on levels of hippocampal synaptic proteins. These data indicate that chronic peripheral administration of IGF-I does not affect hippocampal-dependent memory in a Morris water maze task and does not impact hippocampal synaptic protein levels in the presence or absence of peripheral estradiol. / acase@tulane.edu

Rupture of atherosclerotic plaque can cause acute life-threatening events such as myocardial infarction and ischemic stroke; therefore, there is much interest in developing therapies aimed at increasing plaque stability. More stable lesions are characterized as having high collagen content and containing a large number of vascular smooth muscle cells (SMCs) of contractile/differentiated phenotype. In our previous studies using an apolipoprotein E-deficient (Apoe-/-) mouse model of atherosclerosis, we found that insulin-like growth factor-1 (IGF-1)-infusion not only reduced total plaque burden, but also increased collagen expression and the number of alpha-smooth muscle actin (αSMA)-positive cells in plaque. In this study, we identify cellular mechanisms responsible for these observations. We found that in human aortic smooth muscle cells (HASMCs) grown in culture, IGF-1 post-transcriptionally upregulated expression of the procollagen type I alpha-1 subunit (pro-α1(I)) as well as contractile proteins, αSMA and smooth muscle 22-alpha (SM22α), via a PI3K-dependent but Erk1/2- and mTOR-independent signaling mechanism. Furthermore, experiments using an inhibitor of collagen synthesis or a blocking antibody against the alpha2beta1-integrin (α2β1) suggested that interaction with collagen type I promotes HASMC contractile phenotype. To elucidate mechanisms underlying IGF-1 upregulation of collagen synthesis we investigated the effect of IGF-1 on the mRNA-binding protein, la ribonucleoprotein domain family member 6 (LARP6), which had been shown to bind a conserved stem-loop secondary motif in the 5’UTR of COL1a1 and COL1a2 mRNA. IGF-1 rapidly increased LARP6 expression in HASMCs leading to increased COL1a1 and COL1a2 mRNA bound LARP6 and increased synthesis of collagen type I. Mutation of the 5’stem-loop of Col1a1 mRNA (that inhibited binding by LARP6) or overexpression of a 5’stem-loop RNA molecular decoy (that sequesters LARP6) both prevented the ability of IGF-1 to increase pro-α1(I) synthesis as well as mature α1(I) expression in cultured medium. Furthermore, IGF-1-infusion in Apoe-/- mice increased LARP6 and pro-α1(I) expression in aortic lysates, and SMC-specific IGF-1-overexpression in transgenic mice robustly increased collagen fibrillogenesis in atherosclerotic plaque. In conclusion, this work identifies LARP6 as a critical mediator by which IGF-1 augments synthesis of collagen type I in vascular smooth muscle, and uncovers key mechanisms whereby IGF-1 promotes atherosclerotic plaque stability. / acase@tulane.edu

Cancer develops in many organs and tissues in the body through genetic and environmental modifications to acquire the hallmarks of cancer. The hallmarks of cancer allow the cells to become malignant and progress to a tumorigenic state. It has previously been shown in various carcinomas that HIF-2a, a key component in hypoxia adaptation, has a role in autonomous growth, the first hallmark of cancer. Ovarian cancer is the most lethal of the gynecological malignancies and accounts for 3% of new cases in women annually but is the fifth most common cause of death due to cancer. Here, it is shown in two ovarian carcinoma cell lines that HIF-2a is involved in in vitro and in vivo growth. It is also shown that the effect of HIF-2a is due to its role in autonomous growth and not vascularization with the use of in vitro spheroids. From recent findings in the laboratory the oxygen-stimulated translation initiation complex was discovered and HIF-2a is one of its components. In the absence of HIF-2a there is a downregulation in translation in hypoxia in ovarian carcinoma. This is also seen in a HIF-2a translational target, IGF1R and its downstream signaling pathway, which may be involved in autonomous growth as well as other hallmarks of cancer. Taken together, the data in this thesis presents the importance of HIF-2a in autonomous growth and cancer progression in ovarian carcinoma, as well as verifying its role in translation.

PHIP1 is a novel downstream transcriptional co-regulator of insulin-like growth factor-I receptor (IGF-IR), a tyrosine kinase receptor that is often elevated and autophosphorylated in breast cancer. In this study, I show that PHIP1 is upregulated in MCF10A cells stably overexpressing IGF-IR signaling components and that knock-down of PHIP1 significantly inhibits breast cancer cell proliferation by inducing transcriptional upregulation of p21 and downregulation of cyclin D2. I also show that stable overexpression of PHIP1 in MCF10A cells can lead to its proteasomal degradation. Together, our data indicate that PHIP1 is implicated in breast cancer cell growth and suggest a number of avenues that await exciting discovery.

La diabetis mellitus tipus 1 i la tipus 2 són malalties metabòliques que afecten col·lectivament a un 10% de la població mundial. En ambdós casos l'alteració metabòlica més important és la hiperglucèmia, resultant de la deficiència absoluta (tipus 1) o bé relativa (tipus 2) d'insulina. Concretament, la diabetis tipus 2 es caracteritza per una resistència a la insulina, per part dels teixits perifèrics, acompanyada d'un defecte en la secreció de la hormona, per part de les cèl·lules ? pancreàtiques. La diabetis oberta, però, només es dóna quan les cèl·lules ? no són capaces de continuar compensant la resistència a la insulina. Així doncs, les alteracions en la funcionalitat de les cèl·lules ? serien un component clau en el desenvolupament de la diabetis tipus 2, i no una simple conseqüència de la patologia. Per tant, l'estudi de les cèl·lules ? en els estadis inicials del procés diabètic, resulta ser d'enorme interès per tal d'investigar els mecanismes i les causes que condueixen a la diabetis oberta, Ratolins transgènics que sobreexpressen el factor de creixement IGF-II específicament a les cèl·lules ? pancreàtiques (RIP/IGF-II) presenten un estat pre-diabètic. En aquest treball es van utilitzar aquests animals com a model per estudiar les cèl·lules ? en les fases inicials del procés diabètic i la possible implicació d'IGF-II en el desenvolupament d'aquesta patologia. Es va observar que les cèl·lules ? d'aquests ratolins transgènics presentaven una disminució en la secreció d'insulina en resposta a glucosa. Aquesta disminució podria venir donada per les alteracions funcionals i estructurals presents en aquests illots. S'observava una disminució en l'expressió de Glut2 i insulina, probablement deguda a una reducció dels factors de transcripció que regulen la seva expressió, com Pdx1 i HNF3?. Els illots dels ratolins transgènics presentaven també hiperexpressió de molècules involucrades en la resposta immunitària, com els MHC de classe I i II, tot i no presentar infiltració limfocitària. Així doncs, l'expressió d'IGF-II en les cèl·lules ? dels ratolins transgènics provocava alteracions funcionals en els illots similars a les descrites en models animals o en pacients diabètics.L'evolució del procés diabètic és un procés llarg i varia molt entre individus. En l'evolució d'aquest procés hi intervindrien tant les alteracions presents en les cèl·lules ? de cada individu, com la influència de factors externs. En aquest treball es va estudiar si les alteracions descrites en les cèl·lules ? dels ratolins RIP/IGF-II, podrien predisposar-los a desenvolupar diabetis oberta enfront a factor accelerador. Vam determinar la susceptibilitat dels ratolins RIP/IGF-II enfront dos estímuls diferents: a) el tractament amb molt baixes dosis d'estreptozotocina (STZ), i b) un procés autoimmune, que seria un procés més crònic i comú en la patologia diabètica. Després del tractament amb STZ, es va observar que aquest ratolins transgènics resultaven ser més sensibles a dosis molt baixes, considerades no diabetogèniques pels ratolins control. En segon lloc, per tal d'induir la infiltració limfocitària als ratolins RIP/IGF-II, aquests es creuaren amb ratolins transgènics RIP/hIFN?. L'expressió d'IFN? en cèl·lules ? resulta en una important infiltració dels illots dels ratolins transgènics. D'aquest creuament s'obtingueren ratolins doble transgènics IFN?/IGF-II, un 75% dels quals desenvoluparen diabetis espontània durant els dos primers mesos de vida. Demostrant així que les alteracions pre-diabètiques descrites en les cèl·lules ? dels ratolins IGF-II, incrementaven la susceptibilitat a desenvolupar diabetis oberta en presència d'un factor accelerador.Els resultats d'aquest treball indiquen que alteracions en la funcionalitat de les cèl·lules ? pancreàtiques serien necessàries per incrementar la susceptibilitat a certs factors ambientals que desencadenen la diabetis mellitus. A més, el nostre estudi suggereix que l'increment d'IGF-II en cèl·lules ? podria ser un factor clau en l'inici del procés diabètic. / Type 1 and type 2 diabetes are metabolic diseases with very different etiology that affect collectively 10% of the world-wide population. In both cases the most important metabolic alteration is hyperglycemia, resulting from the absolute (type 1) or relative (type 2) insulin deficiency. In particular, type 2 diabetes mellitus is characterized by decreased response of the liver and peripheral tissues to insulin (insulin resistance) and by inadequate compensatory insulin secretory response. However, overt diabetes only develops when ?-cells fail to compensate for increased insulin demand. Alterations in the functionality of ?-cells would be a primary defect, and not only a simple consequence, in the diabetic pathology. Therefore, studying ?-cells during the initial stages of the diabetic process would be interesting for finding the mechanisms and causes that lead to overt diabetes. Transgenic mice overexpressing IGF-II specifically in ?-cells (RIP-I/IGF-II) develop pre-diabetes. We decided to use these animals as a model in which to study ?-cells in the initial stages of the diabetic process. After the analysis of RIP/IGF-II ?-cells, we observed that transgenic mice showed a decreased insulin secretion in response to glucose. This decrease was likely due to functional and structural alterations found in these islets. Reduction in Glut2 and insulin was observed, probably due to a reduction in the transcription factors that regulate their expression, such as Pdx1 and HNF3?. At structural level these islets showed an increase in the expression of important extracellular matrix components, but showed a decrease in molecules implicated in the intracellular adhesion. Transgenic islets also showed hyperexpression of molecules involved in the immune response, such as MHC class I and II, although no lymphocyte infiltration was observed in their islets. These results suggest that expression of IGF-II in ?-cells of these transgenic mice leads to similar changes to the ones described in other type 2 animal models and diabetic patients. The progression to type 2 diabetes is a long process and varies greatly among individuals. In each individual, alterations present in ?-cells and the influence of external factors would both contribute to the process. In this study, we determined if the alterations described in RIP/IGF-II ?- cells could predispose those animals to develop overt diabetes in the presence of a stimulus that acted as an accelerator factor. We tested the susceptibility of RIP/IGF-II mice to two different stimuli: a) treatment with streptozotocin (STZ), which would stimulate a toxic response specific for ?-cells; and b) an autoimmune process, which would simulate a more chronic effect, more similar to the diabetic pathology.STZ treatment demonstrates that transgenic mice were more sensitive to very low doses of STZ, considered non-diabetogenic for control mice. On the other hand, in order to induce the lymphocyte infiltration to RIP/IGF-II mice, we crossed them with RIP/hIFN transgenic mice. These later mice show a significant infiltration in their islets, induced by the expression of hIFN in their pancreatic ? cells. From this crossbreeding we obtained IFN?/IGF-II double transgenic mice, 75% of which developed spontaneous diabetes during the first two months of age. These results showed that pre-diabetic alterations described in the RIP/IGF-II ?-cells increased their susceptibility to develop overt diabetes in the presence of an accelerator factor.All these results indicate that correct functionality of pancreatic ?-cells is crucial for being able to resist the effect of environmental factors that would lead to the diabetic process. Moreover, our study suggests that the increase of IGF-II in ?-cells could be a key factor in the beginning of the diabetic process.