The effect of acute phase proteins on hepatic insulin signalling
| dc.contributor.advisor | Verhoog, Nicolette J. D. | en_ZA |
| dc.contributor.advisor | Louw, Ann | en_ZA |
| dc.contributor.author | Speelman, Tammy | en_ZA |
| dc.contributor.other | Stellenbosch University. Faculty of Science. Dept. of Biochemistry. | en_ZA |
| dc.date.accessioned | 2020-02-25T14:18:47Z | |
| dc.date.accessioned | 2020-04-28T15:13:47Z | |
| dc.date.available | 2020-02-25T14:18:47Z | |
| dc.date.available | 2020-04-28T15:13:47Z | |
| dc.date.issued | 2020-03 | |
| dc.description | Thesis (MSc)--Stellenbosch University, 2020. | en_ZA |
| dc.description.abstract | ENGLISH ABSTRACT: Insulin resistance is the main risk factor for the development of type-2 diabetes (T2D). It is described as perturbed insulin signalling in the peripheral target tissues (which include the liver, skeletal muscle and adipose tissue), resulting in deficient insulin action. In the liver, this leads to the inability of insulin to regulate glucose metabolism by decreasing hepatic glucose production (HGP), and thus decrease blood glucose concentrations, aiding in the progression to T2D. Numerous factors contribute to the development of insulin resistance, such as stress and obesity, however inflammation is known to play a key role. An increased inflammatory state is associated with enhanced production of acute phase proteins (APPs). Increased serum levels of APPs, such as plasminogen activator inhibitor-1 (PAI-1), serum amyloid A (SAA), and C-reactive protein (CRP) have additionally been associated with T2D and are commonly used as biological markers for this disease state. However, whether these APPs are more than just biological markers for T2D and could contribute to the development of insulin resistance has not yet been established. Although some studies support the possibility that PAI-1, SAA, and CRP impair insulin signalling, their role in the development of hepatic insulin resistance requires investigation. The aim of this study was thus to investigate the effect of PAI-1, SAA, and CRP on hepatic insulin signalling by investigating key proteins in the insulin signalling pathway which, comprise the insulin receptor (IR), insulin receptor substrate-2 (IRS-2), and the central protein, Akt, in a murine hepatoma and human liver carcinoma cell line, BWTG3 and HepG2, respectively. Additionally, HGP was investigated as well as the transcriptional regulation of G6Pase and PEPCK, two key enzymes involved in gluconeogenesis, which is an important process contributing to HGP. The overall results in this study showed that all three APPs impair hepatic insulin signalling in both liver cell models although to different degrees depending on the dose and length of exposure. Specifically, CRP was most effective in modulating the activation of key proteins (the IR and Akt) in the insulin signalling pathway, which subsequently correlated to its ability to increase G6Pase and PEPCK mRNA levels as well as HGP. The length of exposure played an integral role in this study as pro-longed exposure to PAI-1 and CRP enhanced their inhibitory effect on insulin signalling. This was not shown for SAA, which rather displayed dose-dependent effects. As far as could be determined, the results in this study is the first to support the role of PAI-1, SAA, and CRP in the development of hepatic insulin resistance as well as to directly compare the effects of these three APPs in the same experimental model. Although the molecular mechanism of these observed effects require further investigations, the findings in this study cement a foundation in the research linking APPs to hepatic insulin resistance. | en_ZA |
| dc.description.abstract | AFRIKAANSE OPSOMMING: Insulienweerstandigheid is die hoof-risikofaktor vir die ontwikkeling van tipe-2 diabetes (T2D). Dit word beskryf as versteurde insulien-seintransduksie in die perifere teikenweefsel (waaronder die lewer, skeletale spiere en adipose weefsel), wat tot ’n tekort aan insulien-aksie lei. In die lewer lei dit tot die onvermoë van insulien om glukose-metabolisme te reguleer deur die hepatiese glukose-produksie (HGP) te verminder, en gevolglik bloedglukosekonsentrasie verminder, wat die progressie van T2D aanhelp. Talle faktore dra by tot die ontwikkeling van insulienweerstandigheid, soos stres en vetsug, maar dit is bekend dat inflammasie ’n sleutelrol speel. ’n Verhoogde inflammatoriese staat word verbind met versterkte produksie van akute fase-proteïene (APP’s). Verhoogde serumvlakke van APP’s, soos plasminogeenaktivator-remmer-1 (PAI-1), serum amiloïed A (SAA), en C-reaktiewe proteïene (CRP) is bykomend ook geassosieer met T2D en meer algemeen gebruik as biologiese merkers vir hierdie siektetoestand. Maar of hierdie APP’s meer is as slegs biologiese merkers vir T2D en kan bydra tot die ontwikkeling van insulienweerstandigheid is nog nie bevind nie. Al het sommige studies die moontlikheid ondersteun dat PAI-1, SAA en CRP insulien-seintransduksie benadeel, vereis hul rol in die ontwikkeling van hepatiese insulienweerstandigheid verdere ondersoek. Die doel van hierdie studie was dus om die effek van PAI-1, SAA en CRP op hepatiese insulien-seintransduksie te ondersoek deur ondersoek in te stel na die sleutelproteïene in die insulien-seintransduksie-weg, wat bestaan uit die insulienreseptor (IR), insulienreseptor subtraat-2 (IRS-2), en die sentrale proteïen, Akt, in ’n muriene hepatoom en menslik lewer karsinoom-sellyn, onderskeidelik BWTG3 en HepG2. Daarby is HGP ondersoek, asook die transkripsionele regulering van G6Pase en PEPCK, twee sleutel-ensieme betrokke in glukoneogenese, wat ’n belangrike proses is wat bydra tot HGP. Die algehele resultate in hierdie studie wys dat al drie APP’s benadeel hepatiese insulien-seintransduksie in albei lewerselmodelle, maar tot ’n ander graad afhangend van die dosis en lengte van blootstelling. Spesifiek CRP was die mees effektiewe in die modulering van die aktivering van sleutelproteïene (die IR en Akt) in die insulien- seintransduksie-weg, wat gevolglik gekorreleer het met sy vermoë om G6Pase en PEPCK mRNA- vlakke te verhoog, asook HGP. Die lengte van blootstelling speel ’n integrale rol in hierdie studie omdat langdurige blootstelling aan PAI-1 en CRP hul inhiberende effek van insulien-seintransduksie te vergroot. Dit is nie vir SAA getoon nie, wat aan die ander kant dosis-afhanklike effekte getoon het. So ver vasgestel kon word, is die resultate in hierdie studie die eerste om die rol van PAI-1, SAA en CRP te ondersteun in die ontwikkeling van hepatiese insulienweerstandigheid, asook om direk die effekte van hierdie drie APP’s te vergelyk in dieselfde eksperimentele model. Al verg die molekulêre meganismes van hierdie waargeneemde effekte verdere ondersoek, bied die bevindings in hierdie studie ’n basis in die navorsing oor wat APP’s aan hepatiese insulienweerstandigheid verbind. | af_ZA |
| dc.description.version | Masters | en_ZA |
| dc.embargo.terms | 2021-02-28 | |
| dc.format.extent | viii, 133 pages : illustrations | en_ZA |
| dc.identifier.uri | http://hdl.handle.net/10019.1/108435 | |
| dc.language.iso | en_ZA | en_ZA |
| dc.publisher | Stellenbosch : Stellenbosch University | en_ZA |
| dc.rights.holder | Stellenbosch University | en_ZA |
| dc.subject | Insulin signalling | en_ZA |
| dc.subject | Acute phase proteins | en_ZA |
| dc.subject | Insulin resistance | en_ZA |
| dc.subject | Diabetes -- Complications | en_ZA |
| dc.subject | Insulin-like growth factor-binding proteins | en_ZA |
| dc.subject | Protein kinases | en_ZA |
| dc.subject | Diabetes | en_ZA |
| dc.subject | UCTD | en_ZA |
| dc.title | The effect of acute phase proteins on hepatic insulin signalling | en_ZA |
| dc.type | Thesis | en_ZA |