Determination of sphinganine, sphingosine and Sa/So ratio in urine of humans exposed to dietary fumonisin B1

Fumonisin B₁ (FB₁) is an inhibitor of sphinganine N-acyltransferase and the increase in the sphinganine/sphingosine (Sa/So) ratio in urine or serum has been proposed as a biomarker to evaluate exposure to fumonisins. The objectives of this study were to (1) develop a liquid chromatographic method sufficiently sensitive to determine the low concentration of free Sa in male human urine, and (2) analyse So and Sa in human urine and monitor the Sa/So ratio in urine of humans exposed to FB₁ in corn diets over 1 month. The liquid chromatographic method involved isolation from human urine of exfoliated cells followed by an extraction of free sphingoid bases and their separation and quantification by high performance liquid chromatography. The detection limits for So and Sa were 0.15ng/ml in female urine (2ml used) and 0.005ng/ml in male urine (60ml used). Twenty-eight healthy adult volunteers consumed for 1 month a normal diet containing their homegrown corn potentially contaminated with FB₁. Immediately preceding the start of the test, morning urine samples for the determination of So and Sa were collected from each person, and the corn samples used in cooking were obtained from each family for the determination of FB₁. At the end of the test period, morning-urine samples were collected from each person and analysed again. The daily FB₁ intakes were estimated and used to assess the relationship between them and the urinary Sa/So ratios in humans exposed to dietary FB₁ over 1 month. All the home grown corn samples contained FB₁ ranging from 0.08 to 41.1mg/kg, and the estimated daily FB₁     

Sphingoid bases in infant formulas

Sphingolipids are a group of lipids present in all eukaryotic cells. They consist of a long-chain sphingoid base that is amide-bound to a fatty acid and a polar group on C-1 sphingosine. Sphingosine is the most widespread base in mammals. The goal of this study is to determine the concentrations of free and total sphingosine and sphinganine in infant formulas and human milk. Following the extraction of sphingolipids, base and acidic hydrolysis was preformed. Sphinganine and sphingosine were determined by means of high-performance liquid chromatography. The results of this research illustrate the differences between the concentrations of sphingoid bases in infant formulas and human milk. On the basis of the obtained results, it can be concluded that despite all efforts made to produce infant formulas as similar to human milk as possible, in terms of their structure and the amount of their constituents, there are differences that could be biologically significant and thus need to be further researched.     

The induction and persistence of altered sphingolipid biosynthesis in rats treated with fumonisin B1

The fumonisins produced by Fusarium spp. are carcinogenic in rodents and possibly carcinogenic to humans. One action of fumonisins is to inhibit the enzyme ceramide synthase and as a consequence disrupt de novo sphingolipid biosynthesis. Measurement of the ratio of sphinganine (Sa) to sphingosine (So) in urine, serum and tissues has thus been made in various animal species as a marker of exposure to this mycotoxin. In this study in male BDIV rats, the effect of increasing daily gavage doses (0.01?5mg/kg b.w.) of fumonisin B₁ (FB₁) on the Sa/So ratio in various tissues and urine was examined as was the persistence of the effects after cessation of treatment. The lowest dose of FB₁ which induced an alteration of Sa/So in any tissue was 1mg/ kg b.w. The tissue most affected was the kidney, with the liver affected to a much lesser extent and the lung and oesophagus not at all. Only a modest indication of an alteration in Sa/So ratio was obtained in the urine. The large interindividual variations in urinary Sa and So in this strain of rat, even in the absence of FB₁ treatment, made interpretation of these data difficult. After cessation of treatment, the Sa/So ratio returned to normal in kidney after a period of 1?3 weeks. These data suggest that altered Sa/So ratios reflect recent exposure to FB₁ in the rat.