[Synopsis] Fumonisins are fungal toxins commonly found on corn worldwide.They are produced by species of Fusarium, most notably Fusarium moniliforme. Typically, the fumonisin B_1 (FB_1) level in processed corn products averages 5 ppm sometimes occur in corn-products and home-grown corn. High levels of fumonisins in feed are correlated with outbreaks of equine leucoencephalomalacia and porcine pulmonary oedema syndrome. The liver is a target in most species and kidney is a target in some species. FB_1 is considered non-genotoxic but produced liver tumors in male BDIX rats and female B6C3F1 mice, and renal tumors in male F344N rats. Reproductive effects are secondary to maternal toxicity. FB_1 induces apoptosis and alters cell growth, can modify immune response, inhibit the biosynthesis of receptors for pathogens and toxins, can sensitize macrophages to endotoxins, and alters cytokine expression in vivo. FB_1 is an inhibitor of ceramide synthase, a key enzyme in sphingolipid biosynthesis. Inhibition results in an elevation in sphingoid bases and alters the amounts of the 1- phosphates and N-acetyl-derivatives of sphinganine. Disruption of sphingolipid metabolism is correlated with the animal toxicity and rodent carcinogenicity of FB_1. FB_1 also inhibits processes mediated by ceramide generated de novo. All of these changes must be considered when evaluating the effects of fumonisins
