Sphinganine/Sphingosine ratio in plasma and urine as a possible biomarker for fumonisin exposure in humans in rural areas of Africa

Abstract

This study was conducted in the Transkei region of the Eastern Cape and KwaZulu-Natal province, South Africa and in the Bomet district, western Kenya. The sphinganine (Sa)/sphingosine (So) ratios in the plasma and urine of male and female volunteers consuming a staple diet of home-grown maize in Transkei, were 0.34±0.36 (mean±standard deviation) (n=154) and 0.41±0.72 (n=153), respectively and in plasma samples from KwaZulu-Natal it was 0.44±0.23 (n=26). In Kenya, the ratios in plasma and urine were 0.28±0.07 (n=29) and 0.34±0.20 (n=27), respectively. Mean total fumonisin level in home-grown maize, randomly collected in Transkei from the same region where the human volunteers lived, was 580 ng/g (n=40), as compared to the KwaZulu-Natal province, where no fumonisin (n=17) were detected (<10 ng/g) in the home-grown maize. In Kenya, only one of seven samples was contaminated with 60 ng/g fumonisins. No significant differences were found in the Sa/So ratios between males and females within the regions nor between the different regions ( P>0.05). It is possible that the ratio is not sensitive enough to act as a biomarker for fumonisin exposure in humans at these levels of contamination in maize. This is the first report on Sa/So ratios determined in rural populations in Africa consuming home-grown maize as their staple diet.