Etwa 3-5% der Neugeborenen werden kleinwüchsig geboren. Bei einem Teil dieser Kinder bleibt auch nach der Geburt ein Aufholwachstum aus. Eine prä- und postnatale Wachstumsverzögerung kann neben unmittelbaren Folgen wie zum Beispiel psychosozialen Problemen auch mit Langzeitrisiken im Erwachsenenalter, vor allem Diabetes mellitus und kardiovaskulären Erkrankungen einhergehen. In den letzten 10 Jahren konnten verschiedene Mutationen im Gen des IGF1 Rezeptors (IGF1R) bei Patienten mit Kleinwuchs, Mikrozephalie und erhöhten IGF1-Spiegeln identifiziert werden. Aufgrund eines gestörten IGF1 Signales kommt es hauptsächlich zu einem fehlenden Längenwachstum. Aber auch Funktionen des Glukosestoffwechsels sind bei manchen Patienten gestört. In dieser Arbeit wurde eine solche IGF1R Mutation in der Tyrosinkinasedomäne bei zwei Brüdern und deren Vater nachgewiesen. Auffällig waren neben einem Kleinwuchs und Mikrozephalie auch ein zunehmend gestörter Glukosemetabolismus unter Wachstumshormontherapie. Der IGF1R Gendefekt liegt in einer über Speziesgrenzen hinweg hochkonservierten Region und ließ sich mittels dHPLC und Genotypisierungsuntersuchungen bei über 1200 Kontrollen nicht nachweisen. Zusätzlich machen Vererbungsmodus und klinische Manifestationsform die IGF1R Mutation als Ursache der beobachteten prä- und postnatalen Wachstumsverzögerung sehr wahrscheinlich. Eine aufgezeichnete zunehmende Glukoseintoleranz der IGF1R Mutationsträger unter Wachstumshormontherapie spricht für eine komplexe Mitbeteiligung des IGF1R im Glukosestoffwechsel. Bei der Resequenzierung des AKT1 Gens, einem Haupteffektormolekül des IGF1R, wurden bei 70 kleinwüchsigen Kindern fünf neue Genpolymorphismen identifiziert. Eine die Proteinsequenz verändernde Mutation konnte jedoch ausgeschlossen werden. Insgesamt bestätigen diese Ergebnisse die wichtige Funktion des IGF1R im menschlichen Wachstumsprozess und geben Hinweise auf eine mögliche Mitbeteiligung des IGF1R Signalweges bei Störungen des Glukosestoffwechsels.:Inhaltsverzeichnis Bibliographische Beschreibung I. Abkürzungen 1. Einführung 1.1 Epidemiologie und Ätiologie prä- und postnatalen Kleinwuchses 1.2 Das IGF-System im Wachstumsprozess 1.3 Der IGF Typ 1 Rezeptor 1.4 Die Protein Kinase PKBα/AKT1 1.5 Die Rolle des IGF-Systems im Glukosestoffwechsel 2. Das Promotionsprojekt 2.1 Hintergrund und Fragestellung 2.2 Gen-Sequenzierung des AKT1 bei 70 SGA-Kindern 2.2.1 Methoden 2.2.2 Ergebnisse der AKT1 Resequenzierung 2.3 Geno- und phänotypische Charakterisierung der heterozygoten C1248Y IGF Typ 1 Rezeptor Mutation 2.3.1 Patienten und Methoden 2.3.2 Ergebnisse 2.4 Anmerkungen 3. Publikation 4. Zusammenfassung und Interpretation 5. Literaturverzeichnis II. Erklärung über die eigenständige Abfassung der Arbeit III. Lebenslauf IV. Danksagung

Typ 2 Diabetes gehört zu den häufigsten Stoffwechselkrankheiten in Deutschland. Zur Basistherapie des Typ 2 Diabetes gehören eine gesunde Ernährungsweise und die Erhöhung der körperlichen Aktivität. Körperliches Training führt insbesondere bei Patienten mit Typ 2 Diabetes neben der Verbesserung der körperlichen Leistungsfähigkeit zu einer Reihe metabolischer Veränderungen, wie zur Reduktion der Fettmasse, zur Verbesserung von chronischer Hyperglykämie, des Lipidstoffwechsels und des atherogenen, pro-inflammatorischen Adipokin-Serumprofils. Chemerin ist ein erst kürzlich identifiziertes 16 kDa großes Adipokin, dessen Serumkonzentrationen bei Adipositas und Typ 2 Diabetes erhöht sind. Ziel dieser Arbeit war es deshalb, die Auswirkungen eines 12monatigen, kontrollierten, praxisnahen, kombinierten Kraft-Ausdauer-Trainingsprogramms auf die Chemerin-Serumkonzentration, das Körpergewicht, sowie Parameter des Glukosestoffwechsels (Nüchtern-Plasmaglukose, HbA1c, Nüchterninsulin, HOMA) bei Patienten mit Typ 2 Diabetes zu untersuchen. Zusätzlich wurde die Chemerin mRNA-Expression im humanen omentalen und subkutanen Fettgewebsproben von 79 Patienten charakterisiert und bei 15 Patienten der Einfluß eines Gewichtsverlustes von 45,3 ± 7,4kg ein Jahr nach bariatrischer Chirurgie auf zirkulierende Chemerin-Werte untersucht. Für die prospektive offene Interventionsstudie wurden initial 710 Patienten mit Typ 2 Diabetes untersucht, von denen 156 die Ein- und Ausschlusskriterien für die Studie erfüllten. Es wurden die Daten von 120 Patienten (77 Frauen, 43 Männer) analysiert, von denen nach Abschluss des 12monatigen Trainingsprogramms vollständige Datensätze vorlagen. Die Patienten trainierten zweimal pro Woche für jeweils 60 ± 15 Minuten bei 50-70% ihrer individuellen maximalen Leistungsfähigkeit, die zu Beginn der Studie mittels Spiroergometrie ermittelt wurde. Die Messung der Zielparameter erfolgte vor Beginn der Intervention, sowie nach 3, 6 und 12 Monaten körperlichen Trainings. Das 12monatige Trainingsprogramm führte zu einer signifikanten Reduktion der Chemerin-Serumkonzentration und zu signifikanten Verbesserungen der Nüchterninsulin-Serumkonzentrationen und des HOMA-Index´, während sich die Nüchtern-Plasmaglukose und der HbA1c-Wert kaum veränderten. Die signifikanten Veränderungen waren unabhängig von der Entwicklung des Körpergewichts, das sich im Verlauf der Studie nicht signifikant veränderte. Die Chemerinserumkonzentration war geschlechtsabhängig und bei Patienten mit T2D höher als bei gesunden Kontrollpatienten. Sie korrelierte mit dem BMI, dem Körperfettgehalt, dem HbA1c, Serum Triglyzerid- sowie hsCrP-Spiegeln und wird durch starken Gewichtsverlust nach einer bariatrischen Operation signifikant gesenkt. Außerdem konnte ein signifikanter Zusammenhang der omentalen Chemerin mRNA-Expression mit dem BMI, der Hyperinsulinämie, der Adipozytengröße, der Serum-Chemerin- und CrP-Konzentration nachgewiesen werden. Zusammengefasst zeigt die Untersuchung, dass die bei Patienten mit Typ 2 Diabetes deutlich erhöhte Chemerin-Serumkonzentration parallel zur Verbesserungen der Leistungsfähigkeit und Insulinsensitivität (Sportprogramm) auch durch eine signifikante BMI-Reduktion (Adipositas-Chirurgie) gesenkt werden kann.

In the late 90’s, emerging evidence revealed that the brain is insulin-sensitive, highlighted by broad expression of brain-specific insulin receptors and reports of circulating brain insulin. Contemporary literature robustly supports the role of insulin signaling in normal brain function and suggests that insulin-related processes diminish with aging, evidenced by decreased signaling markers, reduced insulin receptor density, and lower levels of insulin transport across the blood-brain barrier. In the context of pathological cognitive decline, clinical trials using intranasal insulin delivery have reported positive outcomes on memory and learning in patients with mild cognitive decline or early-stage Alzheimer’s disease. However, while the importance of insulin and its related actions in the brain are robustly supported, the distinct mechanisms and pathways that mediate these effects remain unclear. To address this, I conducted a series of experiments exploring the impact of insulin on memory and learning in two models: primary hippocampal cell cultures and the Fisher 344 animal model of aging. These studies attempted to identify relationships between insulin receptor signaling, neuronal gene expression, glucose metabolism, and calcium homeostasis in the hippocampus using either expression of a constitutively active human insulin receptor or administration of intranasal insulin. The following dissertation summarizes this work and provides valuable insights into the potential pathways mediating these relationships. Of note, intranasal studies reported that insulin is able to significantly alter gene expression patterns in the hippocampus of both young and aged rats following chronic, repeated exposure to the ligand. In cell culture, constitutive insulin signaling correlated with significantly elevated neuronal glucose uptake and utilization, as well as with significant alterations in the overall expression and localization of the neuron-specific glucose transporter 3. Interestingly, continued activity of the insulin receptor did not appear to alter voltage-gated calcium channels in hippocampal neurons despite prior evidence of the ligand’s role in other calcium-related processes. The results reported in this manuscript suggest that in the brain, insulin may be involved in a myriad of complex and dynamic events dependent on numerous variables, such as age, length of the exposure, and/or the insulin formulation used. Nevertheless, this work highlights the validity of using insulin to ameliorate age-related cognitive decline and supports the need for further studies exploring alternative approaches to enhance insulin receptor signaling in the brain.

Indiana University-Purdue University Indianapolis (IUPUI) / Diabetes mellitus is a group of metabolic diseases characterized by disordered insulin secretion from the pancreatic β cell and chronic hyperglycemia. In order to maintain adequate levels of insulin secretion, the β cell relies on a highly developed and active endoplasmic reticulum (ER). Calcium localized in this compartment serves as a cofactor for key proteins and enzymes involved in insulin production and maturation and is critical for ER health and function. The ER Ca2+ pool is maintained largely through activity of the sarco-endoplasmic reticulum Ca2+ ATPase 2 (SERCA2) pump, which pumps two Ca2+ ions into the ER during each catalytic cycle. The goal of our research is to understand the molecular mechanisms through which SERCA2 maintains β cell function and whole body glucose metabolism. Our previous work has revealed marked dysregulation of β cell SERCA2 expression and activity under diabetic conditions. Using a mixture of pro-inflammatory cytokines to model the diabetic milieu, we found that SERCA2 activity and protein stability were decreased through nitric oxide and AMP-activated protein kinase (AMPK)mediated signaling pathways. Moreover, SERCA2 expression, intracellular Ca2+ storage, and β cell death under diabetic conditions were rescued by pharmacologic or genetic inhibition of AMPK. These findings provided novel insight into pathways leading to altered β cell Ca2+ homeostasis and reduced β cell survival in diabetes. To next define the role of SERCA2 in the regulation of whole body glucose homeostasis, SERCA2 heterozygous mice (S2HET) were challenged with high fat diet (HFD). Compare to wild-type controls, S2HET mice had lower serum insulin and significantly reduced glucose tolerance with similar adiposity and systemic and tissue specific insulin sensitivity, suggesting an impairment in insulin secretion rather than insulin action. Consistent with this, S2HET mice exhibited reduced β cell mass, decreased β cell proliferation, increased ER stress, and impaired insulin production and processing. Furthermore, S2HET islets displayed impaired cytosolic Ca2+ oscillations and reduced glucose-stimulated insulin secretion, while a small molecule SERCA2 activator was able to rescue these defects. In aggregate, these data suggest a critical role for SERCA2 and the maintenance of ER Ca2+ stores in the β cell compensatory response to diet induced obesity.

Background: Polycystic ovary syndrome (PCOS) affects 5–20% of women of reproductive age worldwide and is associated with disorders of glucose metabolism. Hormone and metabolic signaling may be influenced by phytoestrogens, such as isoflavones. Their endocrine effects may modify symptom penetrance in PCOS. Equol is one of the most active isoflavone metabolites, produced by intestinal bacteria, and acts as a selective estrogen receptor modulator. Method: In this interventional study of clinical and biochemical characterization, urine isoflavone levels were measured in PCOS and control women before and three days after a defined isoflavone intervention via soy milk. In this interventional study, bacterial equol production was evaluated using the log(equol: daidzein ratio) and microbiome, metabolic, and predicted metagenome analyses were performed. Results: After isoflavone intervention, predicted stool metagenomic pathways, microbial alpha diversity, and glucose homeostasis in PCOS improved resembling the profile of the control group at baseline. In the whole cohort, larger equol production was associated with lower androgen as well as fertility markers. Conclusion: The dynamics in our metabolic, microbiome, and predicted metagenomic profiles underline the importance of external phytohormones on PCOS characteristics and a potential therapeutic approach or prebiotic in the future.

No description available.

No / Vitamin D deficiency is thought to impair insulin action and glucose metabolism; however, previous studies have not examined ethnic differences or the influence of calcium and parathyroid hormone. We investigated this in a cohort of predominantly white European and south Asian women during pregnancy. Methods: In this cross-sectional study from an urban population in northern England (53.8°N), 1467 women were recruited when undergoing glucose tolerance testing (75 g oral glucose tolerance test) at 26 weeks' gestation. Results: Gestational diabetes mellitus (GDM) was diagnosed in 137 women (9.3%). Median 25-hydroxyvitamin D concentration for the study population was 9.3 ng/mL (interquartile range 5.2, 16.9) and was higher in European [15.2 ng/mL (10.7, 23.5)] than in south Asian women [5.9 ng/mL (3.9, 9.4), P < .001]. After appropriate adjustment for confounders, 25-hydroxyvitamin D showed a weak inverse association with fasting plasma glucose (FPG; mean difference 1.0% per 1 SD; the ratio of geometric means (RGM) 0.99, 95% confidence interval (CI) 0.98, 1.00), and PTH was weakly associated with FPG (RGM 1.01, 95% CI 1.00, 1.02), but neither was associated with fasting insulin, postchallenge glucose, or GDM. Serum calcium (albumin adjusted) was strongly associated with fasting insulin (RGM 1.06; 95% CI 1.03, 1.08), postchallenge glucose (RGM 1.03, 95% CI 1.01, 1.04), and GDM (odds ratio 1.33, 95% CI 1.06, 1.66) but not with FPG. Associations were similar in European and south Asian women. Conclusions: These findings do not indicate any important association between vitamin D status and glucose tolerance in pregnancy. Relationships between circulating calcium and glucose metabolism warrant further investigation.

<p dir="ltr">The periparturient period involves coordinated physiological adaptations as the dairy cow transitions from a non-lactating to lactating state. The ability of dairy cattle to adapt to the onset of lactation is impacted both by physiological and nutritional factors, and a poor transition can result in reduced productivity and welfare for the animal. Additionally, disease and disorder development are heightened in the transition period, with increased risk for involuntary culling occurring in early lactation. This study aimed to evaluate if the amount of late gestational muscle reserves and prepartum supplementation of branched-chain volatile fatty acids (BCVFA) impacts health and production parameters in multiparous, periparturient dairy cattle. Forty-eight multiparous Holstein dairy cattle were assigned to either a high or low muscle group (HM or LM, respectively) based on their <i>longissimus dorsi</i><i> </i>muscle depth 42 days before expected (BEC). After assignment to group, cattle were then randomly assigned to a control (CON; 80 g/d soyhull pellets as-fed basis) or BCVFA (40 g/d isobutyrate product, 20 g/d isovalerate product, 20 g/d 2-methybutyrate product, fed as calcium salt products on an as-fed basis) treatment, which was top-dressed in the prepartum period only. After parturition, treatment was no longer provided and cattle were fed a common lactating diet. Blood samples, ultrasound images, and feed intake were collected and recorded from 42 BEC through 28 days in milk (DIM), milk yield and composition data was collected from parturition until 28 DIM.</p><p dir="ltr">HM cattle began mobilizing muscle reserves prior to parturition, while LM cattle began to accrete muscle reserves prior to parturition. This difference in prepartum muscle utilization did not impact other body measurements (i.e. body weight or body condition score) between the groups of cows but did result in increased blood glucose concentrations prepartum for HM cows compared with LM. This increase in glucose concentrations is likely due to the increased supply of gluconeogenic precursors as a result of the degradation of muscle tissue. The difference in glucose concentration was not observed postpartum, neither was there a difference in tissue mobilization between the groups postpartum. HM cattle had greater DMI both pre- and postpartum, and produced greater yields of milk, milk fat, milk protein, and milk lactose postpartum compared to the LM group. Despite the increased milk yield, there was no difference in feed efficiency between the groups, as the HM cows consumed more feed. Prepartum supplementation of BCVFA did not impact body measurement changes throughout the entire transition period, but did increase pre- and postpartum DMI, likely due to increased fiber digestibility. The BCVFA treatment increased blood glucose concentrations both pre- and postpartum and reduced milk urea nitrogen concentrations postpartum, likely due to improved nitrogen efficiency. Results show that prepartum supplementation of BCVFA has an improved ruminal carryover effect into early lactation.</p><p dir="ltr">At 14 days BEC and 7 DIM, an intravenous glucose tolerance test (IVGTT) was performed on a sub-set of cows, to evaluate if insulin response could be a mechanism impacting the efficiency and production differences observed between muscle groups and BCVFA supplementation. BCVFA supplementation increased glucose area under the curve in the prepartum period only. No other differences were observed between muscle group or treatment in either the pre- or postpartum period. Because there were no major differences between the cows in response to an IVGTT, we cannot conclude that glucose metabolism is a mechanism to explain differences in production responses observed. IVGTT cannot measure peripheral tissue insulin sensitivity, which is a limitation of this assessment, so our conclusions cannot assess if muscle reserves or BCVFA treatment impact peripheral tissue insulin sensitivity response. These results highlight that the amount of muscle plays a key role in the production responses observed in early lactation and that providing a BCVFA supplement could increase DMI during a period of negative nutrient balance and improve rumen efficiency.</p>

Thesis (MSc)--Stellenbosch University, 2008. / ENGLISH ABSTRACT: Gene expression of the cardiac isoform of acetyl-CoA carboxylase (ACCb) is induced in a glucose-dependent manner. ACCb produces malonyl-CoA, a potent inhibitor of mitochondrial fatty acid uptake. Previous studies show that increased flux through the hexosamine biosynthetic pathway (HBP) under hyperglycaemic conditions may contribute to the development of insulin resistance. In light of this, we hypothesised that increased HBP flux induces cardiac ACCb gene expression thereby contributing to the onset of insulin resistance. We tested our hypothesis by transiently transfecting cardiac-derived rat H9c2 myoblasts with a 1,317 bp human ACCb promoter-luciferase construct (pPIIb-1317) and an expression construct encoding the rate-limiting step of the HBP i.e. glutamine: fructose 6-phosphate amidotransferase (GFAT). Overexpression of GFAT increased ACCb gene promoter activity by 75 ± 23% versus controls (n=6, p<0.001). When cotransfection experiments were repeated in the presence of varying concentrations of L-glutamine (0 mM, 4 mM, 8 mM), a substrate for the HBP, ACCb promoter activity was dose-dependently increased. To further corroborate these findings, we employed two inhibitors of GFAT, i.e. 40 μM azaserine and 40 μM 6-diazo-5-oxo-Lnorleucine were administered to transfected cells for a period of 24 hours. Here both azaserine and 6-diazo-5-oxonorleucine attenuated ACCb gene promoter activity. In agreement, co-transfections with two dominant negative GFAT constructs also diminished ACCb gene promoter activity. We next inhibited two enzymes of the HBP acting downstream of GFAT, i.e. O-GlcNAc transferase and O-GlcNAcase using alloxan (0.1 mM, 1 mM and 2 mM) and streptozotocin (5 mM and 10 mM), respectively, for a period of 24 hours. Addition of alloxan attenuated ACCb gene promoter activity by 35.6 ± 1.9% (n=16, p<0.001) and streptozotocin increased activity by 32 ± 12% (n=12, p<0.001). We also investigated USF1 and USF2 as transcriptional regulatory candidates for HBP-induced ACCβ promoter regulation. Our data implicates USF2 as an important transcriptional regulator of HBP-induced ACCβ promoter regulation. In summary, this study demonstrates that increased flux through the hexosamine biosynthetic pathway induces ACCb gene promoter activity. We further propose that such an induction would reduce cardiac fatty acid oxidation, thereby leading to intracellular lipid accumulation due to a mismatch between sarcolemmal FA uptake and mitochondrial FA oxidation in the insulin resistant setting (i.e. hyperlipidaemia). / AFRIKAANSE OPSOMMING: Geen uitdrukking van die kardiale isoform asetiel-KoA karboksilase (ACCb) word in ‘n glukose afhanklike wyse geïnduseer. ACCb produseer maloniel-KoA, ‘n kragtige inhibeerder van mitochondriale vetsuuropname. Vorige studies toon aan dat verhoogde fluks deur die heksosamien biosintestiese weg (HBW) onder hiperglukemiese toestande bydra tot die ontwikkeling van insulienweerstand. In die lig hiervan, word daar gehipotetiseer dat verhoogde HBP fluks kardiale ACCb geenuitdrukking induseer en so bydra tot die ontstaan van insulienweerstand. Ons hipotese is getoets deur die kardiale afkomstige rot H9c2 mioblaste met ‘n 1.317 bp mens ACCb-lusiferase promotor konstruk (pPII-1317) te transfekteer en ‘n uitdrukking te konstrueer wat die tempo bepalende stap van HBP i.e. glutamien: fruktose-6-fosfaat amidotransferase (GFAT) kodeer. Ooruitdrukking van GFAT verhoog ACCb geenpromotor aktiviteit deur 75 ± 23% teenoor kontrole (n=6, p<0.001). Die herhaling van ko-transfeksie eksperimente is herhaal in die teenwoordigheid van variëerbare L-glutamienkonsentrasies (0 mM, 4 mM, 8 mM), ’n substraat vir die HBP, ACCb promotor aktiwiteit is dosisafhanglik verhoog. Om die bevindinge verder te staaf, is twee inhibeerders van GFAT, i.e. 40 μM azaserien en 40 μM 6-diazo-5-oxo-L-norleusien aan transfeksie selle toegedien vir ’n tydperk van 24 uur. Beide azaserien en 6-diazo-5-oxo-L-norleusien verlaag ACCb geenpromotor aktiwiteit. In ooreenstemming met die bogenoemde het ko-transfeksies met twee dominante negatiewe GFAT konstrukte ook ACCb geenpromoter aktiwiteit verminder. Die volgende stap is om twee ensieme van die HBP wat stroomaf van GFAT aktief is, vir ‘n periode van 24 uur te inhibeer i.e. O-GlcNAc transferase en O-GlcNAcase deur alloxan (0.1 mM, 1 mM en 2 mM) and streptozotosien (5 mM en 10 mM) onderskeidelik vir ‘n 24 uur periode te gebruik. Toevoeging van alloxan het die ACCb geenpromotor aktiwiteit by 35.6 ± 1.9% (n=16, p<0.001) verlaag en streptozotosien aktiwiteit verhoog by 32 ± 12% (n=12, p<0.001). Ons het ook die USF1 en USF2 as transkripsie regulerings kandidate vir HBP-geïnduseerde ACCβ promotor regulering ondersoek. Ons data impliseer dat USF2 as ‘n belangrike transkripsie reguleerder van HBP-geïndiseerde ACCβ promotor regulering is. Samevattend het hierdie studie demonstreer dat verhoogde fluks deur die hexosamien biosintetiese weg ACCb geenpromotor aktiwiteit induseer. Ons stel verder voor dat hierdie induksie die kardiale vetsuuroksidasie verlaag wat daartoe lei dat intrasellulêre lipied akkumulasie as gevolg van onparing tussen sarkolemma vetsuuropname en mitochondriale vetsuuroksidasie in ’n insulien weerstandige situasie (i.e. hiperlipidaemia).

No description available.