Targeted Analysis of Sphingolipids in Turkeys Fed Fusariotoxins: First Evidence of Key Changes That Could Help Explain Their Relative Resistance to Fumonisin Toxicity

Abstract

The effects of fumonisins on sphingolipids in turkeys are unknown, except for the increased sphinganine to sphingosine ratio (Sa:So) used as a biomarker. Fumonisins fed at 20.2 mg/kg for 14 days were responsible for a 4.4 fold increase in the Sa:So ratio and a decrease of 33% and 36% in C14-C16 ceramides and C14-C16 sphingomyelins, respectively, whereas C18-C26 ceramides and C18-C26 sphingomyelins remained unaffected or were increased. Glucosyl- and lactosyl-ceramides paralleled the concentrations of ceramides. Fumonisins also increased dihydroceramides but had no effect on deoxysphinganine. A partial least squfares discriminant analysis revealed that all changes in sphingolipids were important in explaining the effect of fumonisins. Because deoxynivalenol and zearalenone are often found in feed, their effects on sphingolipids alone and in combination with fumonisins were investigated. Feeding 5.12 mg deoxynivalenol/kg reduced dihydroceramides in the liver. Zearalenone fed at 0.47 mg/kg had no effect on sphingolipids. When fusariotoxins were fed simultaneously, the effects on sphingolipids were similar to those observed in turkeys fed fumonisins alone. The concentration of fumonisin B1 in the liver of turkeys fed fumonisins was 0.06 µmol/kg. Changes in sphingolipid concentrations differed but were consistent with the IC50 of fumonisin B1 measured in mammals; these changes could explain the relative resistance of turkeys to fumonisins.

Keywords: ceramide; deoxysphinganine; dihydroceramide; fumonisin; glucosylceramide; lactosylceramide; sphingomyelin; turkey.

Figure 1

Different sphingolipid synthesis pathways. Fumonisin B (FB) inhibits ceramide synthases (red arrow) leading to marked changes in the sphingolipid profile. Different ceramide synthases have been identified in mammals, their specificity varied depending on the length of the carbon chain of the fatty acid. CerS2, CerS4, and CerS5 are the most abundant in the liver [4,12].

Figure 2

Concentrations of sphingolipids reported as the total of the different sphingolipids measured within a class in the liver of turkeys fed the mycotoxin-free control diet (CON) and different diets containing fumonisins (FB) at 20.2 mg/kg expressed as the sum of FB1 + FB2, deoxynivalenol (DON) at 5.12 mg/kg, zearalenone (ZEN) at 0.47 mg/kg, and fumonisins, deoxynivalenol, and zearalenone (FDZ). * Significant difference among groups (ANOVA, p< 0.05). Different letters in the same row indicate statistically different means (Duncan, p < 0.05).

Figure 3

Sa:So ratio (A) and the total (B) and relative (C) abundance of the different classes of sphingolipids measured in the liver of turkeys fed a mycotoxin-free control diet (CON) or a diet containing fumonisins (FB) at a concentration of 20.2 mg FB1 + FB2/kg.

Figure 4

Partial least squares discriminant analysis (PLS-DA) of sphingolipids measured in the livers of turkeys fed a mycotoxin-free control diet (CON, T1) or a diet containing fumonisins (FB, T3) at a concentration of 20.2 mg FB1 + FB2/kg. Scores of the variables that are important in the projection (VIP) for the first (A) and the second (B) components. (C) Discrimination on the factor axes extracted from the original explanatory variables. (D) Quality of the model and confusion matrix for the training sample (variable groups).

Figure 5

Partial least squares discriminant analysis (PLS-DA) of sphingolipids measured in the livers of turkeys fed a mycotoxin-free control diet (CON, T1) or a diet containing deoxynivalenol (DON, T2) at a concentration of 5.12 mg/kg. Scores of the variables that are important in the projection (VIP) for the first (A) and the second (B) components. (C) Discrimination on the factor axes extracted from the original explanatory variables. (D) Quality of the model and confusion matrix for the training sample (variable groups).

Figure 6

Partial least squares discriminant analysis (PLS-DA) of sphingolipids measured in the livers of turkeys fed 5 experimental diets according to the presence (yes) or absence (no) of fumonisins in their diet. The 5 experimental diets corresponded to a mycotoxin-free control diet (CON, T1), a diet containing fumonisins (FB, T3) at a concentration of 20.2 mg FB1 + FB2/kg, a diet containing deoxynivalenol (DON, T2) at a concentration of 5.12 mg/kg, a diet containing zearalenone (ZEN, T4) at a concentration of 0.47 mg/kg, and a diet containing fumonisins, deoxynivalenol, and zearalenone in combination (FDZ, T5) at respective concentrations of 25.7, 5.15, and 0.57 mg/kg of feed. Scores of the variables that are important in the projection (VIP) for the first (A) and the second (B) components. (C) Discrimination on the factor axes extracted from the original explanatory variables. (D) Quality of the model and confusion matrix for the training sample (variable groups). * 18:1/24:0 has a VIP score of 0.99 for the second component in the PLS-DA of sphingolipids obtained from chickens fed the DON and the CON diets. SM18:0/16:0 and SM18:1/20:0 have VIP scores of 1.037 and 1.068, respectively, for the first component in the PLS-DA of sphingolipids obtained from chickens fed the FB and the CON diets.