Pancreatic alpha- and beta-cells play vital roles in maintaining glucose homeostasis. While much work has investigated beta-cell biology, alpha-cell research has been scarce. This is due to limitations in conventional methods of alpha-cell preparation, which expose alpha-cells on the islet mantle to enzymatic and mechanical injury inherent in the preparation. I have employed the pancreas tissue slice preparation, which surmounts these limitations. Pancreas slices can be prepared efficiently, and islet cells examined in situ without requiring culture conditions. Alpha-cells are preserved in their native cellular environment not only in health, but more remarkably, also in disease (type 1 diabetes; T1D) states, which was not previously feasible. In the first part of my study, I deployed this preparation to assess normal mouse alpha-cell physiology. Alpha-cells exhibited well-described features of INa, IKATP, small cell size, low resting membrane conductance, and inducible low and high voltage-activated ICa, the latter correlating with exocytosis determined by capacitance measurements. In contrast to previous reports, our large sampling of alpha-cells revealed a wide-range data distribution of several ion channel parameters. My findings explain the apparent inconsistency of previous reports wherein alpha-cell ion channel properties appeared skewed within narrow portions of this wide distribution, likely caused by different preparations. In the second part of my thesis, I assessed alpha-cell perturbation in streptozotocin-induced T1D in the GluCre-ROSA26EYFP (GYY) mouse. In this T1D model, alpha-cells exhibited more glucagon content per cell, which can be exocytosed in greater quantity upon serial depolarization. Membrane electrical properties revealed larger Na+ current and reduced KV-transient current, which contributed to the apparent increased amplitude and firing frequency of action potentials in membrane electrical recording. These electrical events likely prime alpha-cells to release more glucagon, culminating in larger in vivo glucagon secretory responses to low glucose stimulation in this T1D model. We are now well-positioned to employ this in situ model of pancreas slice preparation to address many other apparently unanswerable questions in alpha-cells in normal and pathophysiologic states, such as diabetes.

Over 220 million people worldwide are diagnosed with diabetes and rising prevalence is reported in nearly all surveyed populations. Accordingly, the percentage of pregnancies affected by pre-existing type 1 or 2 diabetes or by diabetes that develops during pregnancy, called gestational diabetes mellitus (GDM), is also on the rise. Today, approximately 8% of all pregnancies are complicated by diabetes. Diabetes alters drug disposition mechanisms in non-pregnant subjects but the impact of diabetes on drug disposition in pregnancy has not been properly evaluated. Atypical drug disposition in pregnancy has implications for maternal and fetal health. Because liver tissue from pregnant women is not readily available, this thesis investigated drug disposition mechanisms primarily in a rat model of experimental GDM. This model consisted of administering streptozotocin, a diabetogenic toxin, to pregnant rats on gestational day 6. One key finding was that elevated circulating lipids in GDM rats competed with drugs (e.g., glyburide and saquinavir) for plasma protein binding so as to increase free drug concentrations. Another key finding was that important hepatic drug efflux transporters (e.g., Mdr1a/b) and metabolic enzymes (e.g., Cyp3a2 and Ugt1a1) were upregulated in GDM as a consequence of, most likely, enhanced nuclear receptor activity (e.g., pregnane X receptor upregulation). Upregulation of hepatic drug efflux transporters and metabolic enzymes, coupled with larger unbound drug fractions, would be expected to increase the hepatic clearance of many drugs. Consistent with this, in GDM, maternal and fetal exposure to the Mdr1 and Cyp3a2 substrate lopinavir was substantially lower than controls post-administration and data supporting enhanced lopinavir metabolite formation were obtained. Placental drug efflux transporters were also examined in this lopinavir study. Elevated placental Mdr1b and Bcrp expression was observed in GDM, which was associated with decreased fetal exposure to lopinavir (even after correcting for maternal unbound concentrations). Taken together, this thesis demonstrates that experimental GDM can significantly impact drug disposition by altering key drug disposition mechanisms. If confirmed in humans, this drug-disease interaction would need to be considered when atypical therapeutic outcomes occur in diabetic pregnancies. Data from experiments with human placentas, obtained from pregnancies complicated by insulin-managed diabetes, is included/discussed.

Vascular dysfunction is linked with increased free radical generation and is a major contributor to the high mortality rates observed in diabetes. Several probable sources of free radical generation have been suggested in diabetes, including cytochrome P450 (CYP) monooxygenase-dependent pathways. CYP-mediated superoxide production reduces nitric oxide (NO) bioavailability. In this study, we focus on the contribution of CYP monooxygenase enzyme-generated reactive oxygen species in vascular dysfunction in an experimental model of type II diabetes mellitus. The purpose of this study is to test the hypothesis that sulfaphenazole treatment can restore diabetic endothelial function in db/db mice. Diabetic male mice (db/db strain) and their age-matched controls received daily intraperitoneal injections of either the CYP 2C inhibitor sulfaphenazole (5 mg/kg) or saline (vehicle control) for 8 weeks. Fasting plasma glucose levels were measured before starting, during, and after finishing the treatment. As well, plasma levels of 8-isoprostane (as a marker of oxidative stress) and nitrite levels of aortic tissue (as a marker of NO bioavailability) were determined. Although sulfaphenazole did not change endothelium-dependent vasodilation in WT mice, it restored endothelial-mediated relaxation in treated db/db mice. We concluded that CYP 2C inhibition by sulfaphenazole reduces oxidative stress (measured as plasma levels of 8-isoprostane), increases NO bioavailability (measured as NOj) and restores endothelial function in db/db mice without affecting plasma glucose levels. Based on our findings, we speculate that inhibition of free radical generating CYP monooxygenase enzymes restores endothelium-dependent vasodilation induced by acetylcholine. In addition, it reduces oxidative stress and increases NO bioavailability.

Syftet med litteraturstudien var att ta reda vad olika studier kommit fram till angående patientutbildning om diabeteskost, motion, hur patientutbildningen bedrivs och uppföljning av vad patienterna fått med sig för kunskaper genom utbildningen. Datainsamlingen har skett i databaserna Elin, Blackwell-Synergy, PubMed och Elsevier. Vid sökningen gjordes begränsning till svensk, norsk och engelskspråkiga tidskrifter och alla artiklar var vetenskapliga. Sökorden som användes i olika kombinationer var: patient education, diabetes, education, exercise och diet. I de artiklar som hämtades via databassökningen valdes ytterligare artiklar från referenslistor. Urvalet gjordes med tanke på litteraturstudiens syfte och frågeställningar. De valda artiklarna granskades med avseende på vetenskaplig kvalité och poängsattes med hjälp av granskingsmallar. Studien baseras på 23 vetenskapliga artiklar, 16från databassökning och 7 artiklar från referenslistor, daterade från år 2000 och fram till år 2005. Resultatet visade att patientutbildningen i samband med diabetes är nödvändigt, och det är viktigt att den anpassas utifrån patientens egna behov och resurser. Patienterna har olika motivation och förståelse för att ändra sitt förhållningssätt till kost och motion. Det är viktigt att patientundervisningen innehåller både grupp- och individuell undervisning i kombination med teoretisk- och praktisk undervisning under en längre tidsperiod.

The need for overnight and continuous monitoring of glucose levels in diabetic patients is profound, especially among juveniles. Implantation of a chemical assay which responds optically to changes in glucose concentration shows promise as a technology capable of continuously monitoring blood sugar with little invasion into the body. Previous fluorescent chemical assays, based on the affinity binding reaction between Concanavalin A protein and dextran, performed well but suffered from limited dermal penetration. In this work, a novel replacement for the dextran molecule (glycosylated dendrimer) was fabricated and tested to determine if it would improve the overall response of the sensing chemistry to glucose. Experiments were carried out and it was found that the assay’s functionality was based on the controlled aggregation of the Con A protein and the modified dendrimer molecule. This new assay proved to be specific to glucose, reversible, and independent of fluorophore dye attached to the protein. This research was furthered by encapsulation of the new assay into a PEG hydrogel which showed response to glucose but, due to leeching, did not perform well under repeated exposures. A new method for encapsulation was proposed based on poration of the hydrogel to create micropores capable of holding the assay chemistry and allowing it to react to incoming glucose, while the surrounding polymer restricted leeching. Preliminary results with previous assays proved the potential of a mannitol based poration procedure, but unforeseen complications in lyophilization of the new sensor assay restricted its completion. Due to instability of Con A in solution, it was hypothesized that the immobilization of it onto the surface of an active substrate would increase its stability overtime as seen in previous works. The immobilization procedure was performed on Con A for both polystyrene spheres and gold (nanoshells and colloid). Both results showed an adequate amount of protein on the surface of the particles, but little binding activity was demonstrated. Overall, the improvements to the sensor chemistry response were notable and the potential for stabilization and enhancement of the response through the use of an active substrate is promising.

Objetivo: Establecer la prevalencia y factores de riesgo para disfunción eréctil (DE) en diabéticos del Hospital Alberto Sabogal 2003. Metodología: Se diseño un estudio descriptivo-explicativo, y transversal. Se incluyeron 100 diabéticos tipo 2 con actividad sexual en últimos 6 meses, excluyéndose otras causas de DE. Todos los pacientes fueron sometidos a una encuesta sobre diabetes mellitus, comorbilidad, medicación y el Índice Internacional de Disfunción Eréctil score abreviado (IIDE-5); se revisaron las historias clínicas. Se utilizo el programa Epi-info 2000. Resultados: La edad promedio era 62.63±9.65 años. El tiempo de diabetes fue 9.63±10.43 años, los niveles de hemoglobina glicosilada 6.19±2.61%, el 69% se trataba con hipoglicemiantes orales, 13% con insulina, 14% solo dieta y 4% terapia combinada. El promedio de relaciones sexuales fue 3.84±3.74 al mes. La prevalencia de DE fue del 70%. La prevalencia se incremento con la edad, en el grupo de 31-50 años fue 46.7%, llegando al 85.7% en aquellos de 71-80 años de edad (p =0.0239). La severidad DE. aumento con la edad (p =0.022). DE fue asociado a: tiempo de diabetes mayor de 20 años (p =0.000026), indicadores indirectos severidad de la diabetes como uso hipoglicemiantes (p =0.011) , insulina (p =0.0043). No se encontrarón relación .con otras variables. Conclusión: Existe una alta prevalencia DE en la población diabética. La edad y el tiempo de diabetes fueron los principales factores asociados. / Objective: To determine the prevalence and risk factors of erectile dysfunction (ED) in diabetics type 2 from Alberto Sabogal Hospital 2003. Methods: I designed a cross over and descriptive and explicative study. A total of 100 diabetics type 2 with sexual activity in last 6 months were evaluated; others causes of ED were excluded. All patients were interviewed and asked to about diabetes mellitus, morbility, drugs, and abbreviate form of International Index of Erectile Dysfunction (IIED), To revised clinical archives. It analysed Epi-info 2000 program. Results: The average age was 62.63±9.65 years. The diabetes time was 9.63±10.43 years, the level of glycosylated haemoglobin was 6.19±2.61%, the diabetes treatments were hypoglycaemic drugs 69%, insulin 13%, only diet 14% and mixed treatment 4%. The average rate of sexual activity was 3.84±3.74 coitus monthly. The prevalence of ED was 70%. The ED prevalence increase with age, It was 46.7% in the 31-50 years group, rather It was 85.7% in 71-80 years group (p =0.0239). On other hand the ED severity was directly associated with age (p =0.022). ED was associate with diabetes time major of 20 years (p =0.000026), hipoglicemiantes treatment (p =0.011) , insulin treatment (p =0.0043). I did not find association with other variables. Conclusions: Diabetic population have a high prevalence of DE. The age, and diabetes time were strong associated to ED.

Thesis (M.Med.Sc.)--University of Hong Kong, 2009. / Includes bibliographical references (p. 72-83).

Thesis (M.Res.(Med.))--University of Hong Kong, 2009. / Includes bibliographical references (p. 73-99).

Thesis (M.P.H.)--University of Hong Kong, 2009. / Includes bibliographical references (p. 39-44).

Thesis (Ph. D.)--University of Texas at Austin, 2002. / Vita. Includes bibliographical references. Available also from UMI Company.