Thesis (MSc)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: Context: There are serious deficiencies in the current tests and criteria available for the diagnosis of diabetes. A novel screening method for the earlier and more efficient detection of type 2 diabetes would be a significant clinical advance. Objective: The hexosamine biosynthetic pathway (HBP) usually acts as a fuel sensor and its activation leads to O-GlcNAcylation of target proteins in a glucose-responsive manner. O-GlcNAc transferase (OGT) and O-GlcNAcase (OGA) are responsible for O-GlcNAc addition and removal, respectively. As higher HBP flux is linked to insulin resistance/type 2 diabetes, we hypothesized that increased O-GlcNAcylation of leukocyte proteins can detect the onset of pre- and overt diabetes. Materials and methods: 74 participants from Bellville and Stellenbosch (Western Cape, South Africa) were recruited and characterized as normal, pre-diabetic or diabetic. Leukocytes (granulocytes and lymphocytes) isolated from study subjects were evaluated for O-GlcNAcylation, OGA and OGT expression by flow cytometry, immunofluorescence microscopy and Western blotting. Results: Leukocyte O-GlcNAcylation increased in both pre-diabetic and diabetic individuals, with leukocyte sub-population data showing the greatest sensitivity. OGA expression and O-GlcNAc/OGA ratios elevated in parallel with increasing glucose concentrations. OGT expression did not significantly change for any of the study subjects investigated. Conclusions: The initial and significant increases in leukocyte O-GlcNAcylation demonstrate great potential for the earlier detection of pre-diabetic and diabetic individuals. OGA expression and O-GlcNAc/OGA ratios may also have diagnostic value. Together our data show strong promise for eventual diagnostic utility and the more efficient detection of type 2 diabetes. / AFRIKAANSE OPSOMMING: Die konteks: Daar is ernstige tekortkominge in die huidige toetsing en kriteria vir die diagnose van diabetes. ʼn Nuwe metode vir die vroeë en meer effektiewe opsporing van tipe 2 diabetes sal beduidende kliniese voordeel inhou. Doelstelling: Onder normale omstandighede tree die heksosamienbiosintetiese pad (HBP) as energie sensor op, en die aktivering daarvan gee aanleiding tot O-GlcNAsetilering van proteïene in ʼn glukose-afhanglike wyse. O-GlcNAs transferase (OGT) en O-GlcNAse (OGA) is onderskeidelik verantwoordelik vir O-GlcNAs toevoeging en verwydering. Aangesien hoër HBP fluks verband hou met insulienweerstandigheid /tipe 2 diabetes, stel ons ʼn hipotese voor dat opsporing van verhoogde O-GlcNAsilasie van leukosietproteïene, die aanvang van pre-diabetes en diabetes kan voorspel. Materiale en metodes: 74 vrywillige deelnemers van Bellville en Stellenbosch (Wes Kaap Provinsie, Suid Afrika) is gewerf en gekarakteriseer as normaal, pre-diabeties of diabeties. Leukosiete (granulosiete en limfosiete), uit bloed van deelnemers geïsoleer, is vir O-GlcNAsilasie, OGA en OGT uitdrukking deur vloeisitometrie, immunofluoressensie-mikroskopie en Western blotting, ondersoek. Resultate: Leukosiet O-GlcNAsetilering is verhoog in beide pre-diabetiese en diabetiese individue, met leukosiet sub-populasie wat die mees sensitiewe data gelewer het. OGA uitdrukking en O-GlcNAs/OGA verhoudings in parallel verhoog tot ʼn toename in glukose konsentrasies. OGT uitdrukking het nie betekenisvol verander in enige van die individue wat ondersoek is nie. Gevolgtrekkings: Die vroeë en betekenisvolle toename in leukosiet O-GlcNAsetilering toon groot potensiaal vir die vroeë opsporing van pre-diabetiese en diabetiese individue. OGA uitdrukking en O-GlcNAs/OGA verhoudings het ook moontlik diagnostiese waarde. Ons data toon belowende resultate vir die gevolglike diagnostiese waarde en ʼn meer effektiewe opsporing van tipe 2 diabetes.