Sphinganine and sphingosine levels and ratio in urine and blood samples from a Catalonian population, Spain.

Fumonisins occur mainly in maize and they produce alterations on sphingolipid metabolism, unbalancing the sphinganine (Sa)/sphingosine (So) ratio. This alteration has been proposed as a biomarker of fumonisin exposure. The objective of this study was to establish the urinary and plasmatic levels of Sa, So as well as the ratio Sa/So from a sample of the Catalonian (Spain) population exposed to fumonisins at low levels. Firstly, plasma and urinary Sa and So levels and the ratio Sa/So were compared between two population groups, and later urinary Sa and So levels from corn food consumers and a control group were monitored for 2 weeks under controlled intake of corn foods. Sa and So levels were determined in urine and blood samples using validated methods using HPLC with fluorescence detection. Significant differences were not found in urine samples when Sa/So ratios were compared from corn food consumers and non-consumers, while significant differences were found in urine and plasma samples, but evidence of the mechanism of action of fumonisins was not apparent. Through a time-course study we have narrowed down the day in which the maximum alteration of Sa/So ratio should be expected in humans. This paper reports some useful information to improve the design of studies to validate the ratio Sa/So as a possible biomarker of fumonisin exposure.