Evidence for fumonisin inhibition of ceramide synthase in humans consuming maize-based foods and living in high exposure communities in Guatemala.

SCOPE: Fumonisin (FB) occurs in maize and is an inhibitor of ceramide synthase (CerS). We determined the urinary FB1 (UFB1 ) and sphingoid base 1-phosphate levels in blood from women consuming maize in high and low FB exposure communities in Guatemala. METHODS AND RESULTS: FB1 intake was estimated using the UFB1 . Sphinganine 1-phosphate (Sa 1-P), sphingosine 1-phosphate (So 1-P), and the Sa 1-P/So 1-P ratio were determined in blood spots collected on absorbent paper at the same time as urine collection. In the first study, blood spots and urine were collected every 3 months (March 2011 to February 2012) from women living in low (Chimaltenango and Escuintla) and high (Jutiapa) FB exposure communities (1240 total recruits). The UFB1 , Sa 1-P/So 1-P ratio, and Sa 1-P/mL in blood spots were significantly higher in the high FB1 intake community compared to the low FB1 intake communities. The results were confirmed in a follow-up study (February 2013) involving 299 women living in low (Sacatepéquez) and high (Santa Rosa and Chiquimula) FB exposure communities. CONCLUSIONS: High levels of FB1 intake are correlated with changes in Sa 1-P and the Sa 1-P/So 1-P ratio in human blood in a manner consistent with FB1 inhibition of CerS.

Urinary fumonisin B1 and estimated fumonisin intake in women from high- and low-exposure communities in Guatemala.

SCOPE: Fumonisin (FB) intake can be high when maize is a dietary staple. We determined (i) urinary FB (UFB) in women consuming maize in high- and low-exposure communities in Guatemala, (ii) the FB levels in maize, (iii) the relationship between UFB and FB intake, and (iv) the relative excretion of UFB1 , UFB2 , and UFB3 . METHODS AND RESULTS: Urine and maize were analyzed for FB for 1 year in three departments. Maize consumption was estimated by an interview questionnaire. Fumonisin B1 , B2 , and B3 (FB1 , FB2 and FB3 ), were detected in 100% of maize samples. FB1 in maize and urine was significantly higher in Jutiapa compared to Chimaltenango or Escuintla. The FB intake paralleled UFB1 in a dose-dependent manner but UFB1 was present in much higher levels than UFB2 or UFB3 compared to maize. CONCLUSION: In Jutiapa, agroecological conditions favored FB production. UFB1 mirrored the estimated FB intake. UFB1 > 0.1 ng/mL resulted in a dose-dependent increase in the risk of exceeding FB intake of 2 µg/kg b.w./day compared to women with no detectable UFB1 . More than 50% exceeded 2 µg/kg b.w./day when UFB1 was >0.5 ng/mL. UFB2 and UFB3 were rarely detected confirming that FB1 is either absorbed better or preferentially excreted in urine.

The kinetics of urinary fumonisin B1 excretion in humans consuming maize-based diets.

SCOPE: Fumonisins (FB) are mycotoxins found in maize. The purpose of this study was to (i) determine the relationship between FB(1) , FB(2) , and FB(3) intake and urinary excretion in humans, (ii) validate a method to isolate urinary FB on C(18) -SPE cartridges for international shipment, and (iii) test the method using samples from Guatemala. METHODS AND RESULTS: Volunteers (n = 10) consumed 206 grams/day of tortillas and biscuits prepared from masa flour and a product containing maize flour. Volunteers estimated their daily urine output and samples were analyzed for FB(1) , FB(2) , and FB(3) and hydrolyzed FB(1) . Only FB(1) was detected in urine suggesting lower absorption of FB(2) and FB(3) . Excretion was highly variable peaking soon after consumption began and decreasing rapidly after consumption stopped. Within 5 days after consumption ended, FB(1) was not detected in urine. In a study with eight volunteers, the average total urinary FB(1) was 0.5% of the intake. FB(1) was detected in 61% (107/177) of the samples collected in Guatemala. CONCLUSION: The results support the use of urinary FB(1) to assess ongoing exposure in population-based studies. However, relating the FB(1) concentration in urine to dietary intake of FB by individual subjects will be complicated due to interindividual variability and the rapidity of clearance.

Fumonisins disrupt sphingolipid metabolism, folate transport, and neural tube development in embryo culture and in vivo: a potential risk factor for human neural tube defects among populations consuming fumonisin-contaminated maize.

Fumonisins are a family of toxic and carcinogenic mycotoxins produced by Fusarium verticillioides (formerly Fusarium moniliforme), a common fungal contaminant of maize. Fumonisins inhibit ceramide synthase, causing accumulation of bioactive intermediates of sphingolipid metabolism (sphinganine and other sphingoid bases and derivatives) as well as depletion of complex sphingolipids, which interferes with the function of some membrane proteins, including the folate-binding protein (human folate receptor alpha). Fumonisin causes neural tube and craniofacial defects in mouse embryos in culture. Many of these effects are prevented by supplemental folic acid. Recent studies in LMBc mice found that fumonisin exposure in utero increases the frequency of developmental defects and administration of folate or a complex sphingolipid is preventive. High incidences of neural tube defects (NTD) occur in some regions of the world where substantial consumption of fumonisins has been documented or plausibly suggested (Guatemala, South Africa, and China); furthermore, a recent study of NTD in border counties of Texas found a significant association between NTD and consumption of tortillas during the first trimester. Hence, we propose that fumonisins are potential risk factors for NTD, craniofacial anomalies, and other birth defects arising from neural crest cells because of their apparent interference with folate utilization.