Research Projects

Assessment of cardiovascular risk: application of the Friedewald equation for the estimation of LDL-cholesterol

We have been assessing the utility of the Friedewald equation in the estimation of LDL-cholesterol and have found that is relatively inaccurate at extremes of lipid values. This was done using results from more than 14 000 patients.

The research has been published in Clinica Chimica Acta.

Molecular basis of insulin resistance caused by antiretroviral drugs 

Antitretroviral drugs cause insulin resistance in vivo and in vitro. We have investigated the molecular basis by which these drugs perturb insulin receptor signalling using a cell culture system. We have demonstrated a role for the NFkB pathway.

The research is described in the Journal of Cellular Biochemistry

Molecular modelling of ligand-receptor interactions: application to the Estrogen receptor, insulin receptor and HIV protease systems. Molecular modelling of the insulin receptor and its ligand (postdoctoral fellow-Dr Ataul Islam) 
Using the solved three-dimensional structure of the insulin receptor complexed with its ligand, we have been modelling the interactions of different insulin analogues with the insulin receptor.

We have also explored the structural requirements of HIV-protease inhibitors using molecular modelling.This research is described in the Journal of Molecular Graphics and Modelling.

Mutations in the androgen receptor gene and the fibrillin-3 gene in South African women with polycystic ovary syndrome 
Researchers: Dr C van Niekerk, Dr NM Oosthuizen, Miss M Nöthling 
Funding: NHLS Research Trust, University of Pretoria 
Polycystic ovary syndrome (PCOS) is the most prevalent endocrinological disorder in women worldwide, characterised by menstrual dysfunction, infertility, obesity and metabolic syndrome. This study investigates microsatellites and methylation differences in the androgen receptor and fibrillin-3 genes between cases and controls. 

Identification of CYP21A2 mutations within South African patients suffering from congenital adrenal hyperplasia caused by 21-hydroxylase deficiency. 
Researchers: Dr C van Niekerk, Dr NM Oosthuizen, Mr J Lombard 
Funding:  NHLS Research Trust 
Congenital adrenal hyperplasia (CAH) is an autosomal recessive disorder caused in 90% of cases by mutations in the CYP21A2 gene. The main aim of the study is to identify and compare mutations in South African CAH patients to those documented in European populations by utilising HRM-Real-Time PCR and sequencing. 

Analysis of the FOXL2, RSPO1 and WNT4 genes in South African patients with ovotesticular disorders of sexual development (DSD) 
Researchers: Dr C van Niekerk, Dr NM Oosthuizen, Miss P Yu 
Funding: NHLS Research Trust, University of Pretoria, RESCOM grant 2010 
The genes FOXL2, RSPO1 and WNT4 play an important role in ovarian differentiation of the bipotential gonad, and may be the female equivalent of sex-determining region of the Y chromosome (SRY). The objective of the study is to characterise these molecular markers in South African patients with ovotesticular disorders of sexual development (DSD). It is anticipated that the findings of this study will increase our understanding of testicular differentiation of the bipotential gonad in the absence of the SRY.    

Genetic analysis of inherited forms of hypophosphataemic rickets in South African patients 
Researchers: Dr C van Niekerk, Dr NM Oosthuizen, Ms E Pretorius 
Collaborators: Prof J Pettifor, Dr K Thandrayen, Department of Paediatrics, University of the Witwatersrand 
Funding:  NHLS Research Trust 
The aim of this study is to identify and characterise mutations prevalent in South African patients with hypophosphataemic rickets. Mutations in the PHEX, FGF-23, DMP-1 and SLC34A3 are responsible for X-linked, autosomal dominant, autosomal recessive and hypercalciuric forms of inherited hypophosphataemic rickets respectively. Causative genes will be analysed by means of conventional PCR, HRM real-time PCR and DNA sequencing. 

Quantifying and analysing three genes from fetal DNA extracted from maternal plasma to establish fetal sex and RhD blood grouping for routine testing
Researchers: Dr C van Niekerk, Ms N Matthee 
Collaborators: Dr H Lombaard, Maternal and Fetal Medicine Unit, Steve Biko Academic Hospital 
Funding:  NHLS Research Trust (applied for) 
The aim of this study is to quantify and analyse fetal DNA, extracted from maternal plasma, to establish routine tests for fetal sex determination and RhD blood grouping in the Department of Chemical Pathology.  This will be done by employing restriction enzyme digestion, real-time PCR and multiplex PCR. 

The utility of absolute vs relative changes in highly-sensitive cardiac troponin I (cTnI) concentrations in the early diagnosis of acute myocardial infarction (AMI) 
Researchers: Dr ESP Dlamini, Dr NM Oosthuizen 
Funding:  NHLS Research Trust (applied for) 
According to current South African guidelines, patients presenting with a cTnI concentration between the 99th percentile and the WHO AMI cut-off require a 50% increase in cTnI 3 hours later in order to diagnose AMI. However, recent studies using the ADVIA Centaur c-TnI-ultra assay suggest that absolute changes have a higher diagnostic accuracy for AMI than relative changes. Furthermore, other studies have proposed that abbreviating the time between successive samples from 3 hours to 2 hours may allow earlier diagnosis. Using the Beckman Coulter Accu-TnI assay, this study has two aims: firstly to investigate the utility of absolute vs relative changes in cTnI concentrations and secondly to identify the best time interval for serial measurements for diagnosis of AMI. 

Clinical validation of faecal pyruvate kinase M2 (M2PK) for detection of patients with non-bleeding precancerous colorectal lesions 
Researchers: Dr LS Masika, Dr NM Oosthuizen 
Collaborators: Prof JHR Becker, Department of General Surgery, University of Pretoria 
Funding:  NHLS Research Trust (applied for) 
Although colonoscopy is the gold standard for early detection of colorectal carcinoma and adenomatous polyps, high cost and invasiveness detract from its clinical utility. Currently the best available screening test for colorectal cancer is the immunological faecal occult blood test (iFOBT), but its usefulness is limited to patients with bleeding lesions. M2PK has been proposed as a new marker with higher sensitivity for detection of non-bleeding lesions at risk for malignant transformation. The aim of this study is to compare urine Hb test strips to the ACTIM iFOBT for detection of bleeding colorectal lesions and to determine the utility of a faecal M2PK ELISA in selecting patients with negative FOBT for urgency in colonoscopy waiting lists. 


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