MRC PhD students

Liana van der Westhuizen is a PhD student investigating the effect of fumonisin contaminated maize staple diets on sphingoid base levels in humans.

Fumonisins, produced predominantly by Fusarium verticillioides occur widely around the world in maize and cause various syndromes in different animal species. High levels of fumonisins have been found in naturally contaminated maize from various areas in the world such as in China, Italy and South Africa, where high incidences of oesophageal cancer occur. Previous studies have shown that subsistent rural communities that consume maize as a staple diet can be exposed to fumonisin levels that exceed the suggested maximum tolerable daily intake.

The rapid elimination of fumonisins and the lack of a major metabolite in vivo required a biomarker for fumonisins exposure. Fumonisins inhibit a key enzyme in the sphingoid lipid pathway causing an elevation of sphinganine levels and an increase in the sphinganine/sphingosine ratio in various animal models. The inhibition of ceramide synthase has much wider implications in the mechanism of cancer than the disruption of the sphingoid base ratio and was further investigated in a rat liver cancer model.

Further studies in the former Transkei region investigated the sphinganine/ sphingosine ratio in blood and urine of these communities and the individual fumonisin exposure. As the sphinganine/ sphingosine ratio was too variable an alternative reliable biomarker for fumonisin exposure in humans needs to be validated. Another objective is to evaluate easily achievable measures to reduce fumonisin contamination in the maize-based food consumed by these communities.

The promoter is Dr. Gordon S. Shephard (PROMEC Unit, MRC) while Prof. Paul D. van Helden (Medical Biochemistry, Faculty of Science, University of Stellenbosch) is the co-promoter.