Postweaning exposure to aflatoxin results in impaired child growth: A longitudinal study in Benin, west Africa

Aflatoxins are dietary contaminants that are hepatocarcinogenic and immunotoxic and cause growth retardation in animals, but there is little evidence concerning the latter two parameters in exposed human populations. Aflatoxin exposure of West African children is known to be high, so we conducted a longitudinal study over an 8-month period in Benin to assess the effects of exposure on growth. Two hundred children 16-37 months of age were recruited from four villages, two with high and two with low aflatoxin exposure (50 children per village). Serum aflatoxin-albumin (AF-alb) adducts, anthropometric parameters, information on food consumption, and various demographic data were measured at recruitment (February) and at two subsequent time points (June and October). Plasma levels of vitamin A and zinc were also measured. AF-alb adducts increased markedly between February and October in three of the four villages, with the largest increases in the villages with higher exposures. Children who were fully weaned at recruitment had higher AF-alb than did those still partially breast-fed (p < 0.0001); the major weaning food was a maize-based porridge. There was no association between AF-alb and micronutrient levels, suggesting that aflatoxin exposure was not accompanied by a general nutritional deficiency. There was, however, a strong negative correlation (p < 0.0001) between AF-alb and height increase over the 8-month follow-up after adjustment for age, sex, height at recruitment, socioeconomic status, village, and weaning status; the highest quartile of AF-alb was associated with a mean 1.7 cm reduction in growth over 8 months compared with the lowest quartile. This study emphasizes the association between aflatoxin and stunting, although the underlying mechanisms remain unclear. Aflatoxin exposure during the weaning period may be critical in terms of adverse health effects in West African children, and intervention measures to reduce exposure merit investigation.

Determinants of aflatoxin exposure in young children from Benin and Togo, West Africa: the critical role of weaning

Background Dietary exposure to high levels of the fungal toxin, aflatoxin, occurs in West Africa, where long-term crop storage facilitates fungal growth.

Methods We conducted a cross-sectional study in Benin and Togo to investigate aflatoxin exposure in children around the time of weaning and correlated these data with food consumption, socioeconomic status, agro-ecological zone of residence, and anthropometric measures. Blood samples from 479 children (age 9 months to 5 years) from 16 villages in four agro-ecological zones were assayed for aflatoxin-albumin adducts (AF-alb) as a measure of recent past (2-3 months) exposure.

Results Aflatoxin-albumin adducts were detected in 475/479 (99%) children (geometric mean 32.8 pg/mg, 95% CI: 25.3-42.5). Adduct levels varied markedly across agro-ecological zones with mean levels being approximately four times higher in the central than in the northern region. The AF-alb level increased with age up to 3 years, and within the 1-3 year age group was significantly (P=0.0001) related to weaning status; weaned children had approximately twofold higher mean AF-alb adduct levels (38 pg AF-lysine equivalents per mg of albumin [pg/mg]) than those receiving a mixture of breast milk and solid foods after adjustment for age, sex, agro-ecological zone, and socioeconomic status. A higher frequency of maize consumption, but not groundnut consumption, by the child in the preceding week was correlated with higher AF-alb adduct level. We previously reported that the prevalence of stunted growth (height for age Z-score HAZ) and being underweight (weight for age Z-score WAZ) were 33% and 29% respectively by World Health Organziation criteria. Children in these two categories had 30-40% higher mean AF-alb levels than the remainder of the children and strong dose- response relationships were observed between AF-alb levels and the extent of stunting and being underweight.

Conclusions Exposure to this common toxic contaminant of West African food increases markedly following weaning and exposure early in life is associated with reduced growth. These observations reinforce the need for aflatoxin exposure intervention strategies within high-risk countries, possibly targeted specifically at foods used in the post-weaning period.

Dietary exposure to aflatoxin and fumonisin among Tanzanian children as determined using biomarkers of exposure

SCOPE: The study aims to evaluate the status of dietary exposure to aflatoxin and fumonisin in young Tanzanian children, using previously validated biomarkers of exposure. METHODS AND RESULTS: A total of 148 children aged 12-22 months, were recruited from three geographically distant villages in Tanzania; Nyabula, Kigwa, and Kikelelwa. Plasma aflatoxin-albumin adducts (AF-alb) and urinary fumonisin B1 (UFB1) were measured by ELISA and LC-MS, respectively. AF-alb was detectable in 84% of children, was highest in fully weaned children (p <0.01) with higher levels being associated with higher maize intake (p <0.05). AF-alb geometric mean (95% CI) was 43.2 (28.7-65.0), 19.9 (13.5-29.2), and 3.6 (2.8-4.7) pg/mg albumin in children from Kigwa, Nyabula, and Kikelelwa, respectively. UFB1 was detectable in 96% of children and the level was highest in children who had been fully weaned (p <0.01). The geometric UFB1 mean (95% CI) was 327.2 (217.1-493.0), 211.7 (161.1-278.1), and 82.8 (58.3-117.7) pg/mL in Kigwa, Nyabula, and Kikelelwa, respectively. About 82% of all the children were exposed to both mycotoxins. CONCLUSION: Young children in Tanzania are chronically exposed to both aflatoxin and fumonisin through contaminated diet, although the level of exposure varies markedly between the three villages studied.

Seasonal and gestation stage associated differences in aflatoxin exposure in pregnant Gambian women

Objective: Aflatoxin is known to cross the placental barrier and exposures in utero could influence genomic programming, foetal growth and development, resulting in long-term health effects. We aimed to determine aflatoxin exposure in Gambian women at two stages of pregnancy and during the rainy and dry seasons.

Methods: We examined aflatoxin exposure in pregnant Gambian women at early (<16 weeks) and later (16 weeks onward) stages of pregnancy and at different times of the year, during the rainy (June to October 2009) or dry (November to May 2010) season, using aflatoxin–albumin adducts (AF-alb).

Results: Mean AF-alb was higher during the dry season than in the rainy season, in both early and later pregnancy although the difference was strongest in later pregnancy. There was a modest increase in AF-alb in later than early pregnancy (geometric mean 41.8 vs. 34.5 pg/mg, P < 0.05), but this was restricted to the dry season when exposures were generally higher.

Conclusions: The study confirmed that Gambian pregnant women were exposed to aflatoxin throughout the pregnancy, with higher levels in the dry season. There was some evidence in the dry season that women in later pregnancy had higher AF-alb levels than those in earlier pregnancy. Further research on the effects of exposure to this potent mutagen and carcinogen throughout pregnancy, including the epigenetic modification of foetal gene expression and impact on pre- and post-natal growth and development, are merited.

A pilot study to evaluate aflatoxin exposure in a rural Ugandan population

Objectives: The fungal metabolite aflatoxin is a common contaminant of foodstuffs, especially when stored in damp conditions. In humans, high levels can result in acute hepatic necrosis and death, while chronic exposure is carcinogenic. We conducted a pilot study nested within an existing population cohort (the General Population Cohort), to assess exposure to aflatoxin, among people living in rural south-western Uganda. Methods: Sera from 100 adults and 96 children under 3 years of age (85 male, 111 female) were tested for aflatoxin-albumin adduct (AF-alb), using an ELISA assay. Socio-demographic and dietary data were obtained for all participants; HIV serostatus was available for 90 adults and liver function tests (LFTs) for 99. Results: Every adult and all but four children had detectable AF-alb adduct, including five babies reported to be exclusively breastfed. Levels ranged from 0 to 237.7 pg/mg albumin and did not differ significantly between men and women, by age or by HIV serostatus; 25% had levels above 15.1 pg/mg albumin. There was evidence of heterogeneity between villages (P = 0.003); those closest to trading centres had higher levels. Adults who consumed more Matooke (bananas) had lower levels of AF-alb adduct (P = 0.02) than adults who did not, possibly because their diet contained fewer aflatoxin-contaminated foods such as posho (made from maize). Children who consumed soya, which is not grown locally, had levels of AF-alb adduct that were almost twice as high as those who did not eat soya (P = 0.04). Conclusions: Exposure to aflatoxin is ubiquitous among the rural Ugandans studied, with a significant number of people having relatively high levels. Sources of exposure need to be better understood to instigate practical and sustainable interventions. © 2014 John Wiley & Sons Ltd.

Cytotoxic assessment of the regulated, co-existing mycotoxins aflatoxin B1, fumonisin B1 and ochratoxin, in single, binary and tertiary mixtures

Aflatoxin B1 (AFB1), ochratoxin A (OTA) and fumonisin B1 (FB1) are contaminants which have been shown to regularly co-occur in a range of foods. However, only a small number of studies have evaluated the interactive effect of binary and tertiary mycotoxins. The present study evaluated the effects of low levels of each mycotoxin in combination at their EU regulatory limits. Toxic effect with respect to cell viability was measured by MTT and neutral red assays, assessing mitochondria and lysosome integrities respectively. Individual toxicity showed that OTA (10 μg/ml) was the most cytotoxic mycotoxin in all three cell lines studied (caco-2, MDBK and raw 264.7). Binary combinations were cytotoxic to the MDBK cell line in the order [OTA/FB1] > [AFB1/FB1] > [AFB1/OTA], whilst all effects observed were classified as being additive. Tertiary combinations of AFB1, FB1 and OTA at the EU regulatory limits were tested and not found to exhibit measurable cytotoxicity in MDBK, caco-2 or raw 264.7 cells. However by increasing these concentrations above the legal limits to OTA (3 μg/ml), FB1 (8 μg/ml) and AFB1 (1.28 μg/ml), cytotoxicity was observed with up to 26% reduction in cell viability and synergistic effects were evident with regard to mitochondrial integrity. © 2014 Elsevier Ltd. All rights reserved.

Quantitative correlation of aflatoxin biomarker with dietary intake of aflatoxin in Tanzanian children

The association between aflatoxin intake from maize-based weaning food and aflatoxin albumin adducts (AF-alb) was investigated in 148 Tanzanian children aged between 12 and 22 months, at 2 visits 6 months apart. At the first visit (storage season) there was a significant correlation at the individual level between AF-alb (geometric mean 43.2 pg/mg albumin) and aflatoxin intake (geometric mean 81.7 ng/kg b.w./d) through maize-based weaning food (r = 0.51, p < 0.01). Overall, this correlation was r = 0.43 (p < 0.01). The AF-alb level in weaning-age children in Tanzania closely reflects aflatoxin intake from maize in weaning food. Exposure levels suggest children may be at risk from aflatoxin associated health effects.

A Prospective Study of Growth and Biomarkers of Exposure to Aflatoxin and Fumonisin during Early Childhood in Tanzania

BACKGROUND: Aflatoxin and fumonisin are toxic food contaminants. Knowledge about effects of their exposure and co-exposure on child growth is inadequate.

OBJECTIVE: To investigate the association between child growth and aflatoxin and fumonisin exposure in Tanzania.

METHODS: A total of 166 children were recruited at 6 to 14 months of age and studied at recruitment, and at the sixth and twelfth month following recruitment. Blood and urine samples were collected and analysed for plasma aflatoxin albumin adducts (AF-alb) using ELISA, and urinary fumonisin B1 (UFB1) using LC-MS, respectively. Anthropometric measurements were taken and growth index Z-scores were computed.

RESULTS: AF-alb geometric mean concentrations (95% confidence intervals) were 4.7 (3.9, 5.6), 12.9 (9.9, 16.7) and 23.5 (19.9, 27.7) pg/mg albumin at recruitment, six months, and 12 months from recruitment, respectively. At these respective sampling times, geometric mean UFB1 concentrations (95% CI) were 313.9 (257.4, 382.9), 167.3 (135.4, 206.7) and 569.5 (464.5, 698.2) pg/mL urine, and the prevalence of stunted children were 44%, 55% and 56%, respectively. UFB1 concentrations at recruitment were negatively associated with length for age Z-scores (LAZ) at six months (p = 0.016) and at 12 months from recruitment (p = 0.014). The mean UFB1 of the three sampling times (at recruitment, at six and 12 months from recruitment) in each child was negatively associated with LAZ (p < 0.001) and length velocity (p = 0.004) at 12 months from recruitment. The negative association between AF-alb and child growth did not reach statistical significance.

CONCLUSIONS: Exposure to fumonisin alone, or co-exposure with aflatoxins may contribute to child growth impairment.

Aflatoxin exposure is inversely associated with IGF1 and IGFBP3 levels in vitro and in Kenyan schoolchildren

SCOPE: This study explores the relationship between aflatoxin and the insulin-like growth factor (IGF) axis and its potential effect on child growth.

METHODS AND RESULTS: One hundred and ninety-nine Kenyan schoolchildren were studied for aflatoxin-albumin adduct (AF-alb), IGF1 and IGF-binding protein-3 (IGFBP3) levels using ELISA. AF-alb was inversely associated with IGF1 and IGFBP3 (p < 0.05). Both IGF1 and IGFBP3 were significantly associated with child height and weight (p < 0.01). Children in the highest tertile of AF-alb exposure (>198.5 pg/mg) were shorter than children in the lowest tertile (<74.5 pg/mg), after adjusting for confounders (p = 0.043). Path analysis suggested that IGF1 levels explained ∼16% of the impact of aflatoxin exposure on child height (p = 0.052). To further investigate this putative mechanistic pathway, HHL-16 liver cells (where HHL-16 is human hepatocyte line 16 cells) were treated with aflatoxin B1 (0.5, 5 and 20 μg/mL for 24-48 h). IGF1 and IGFBP3 gene expression measured by quantitative PCR and protein in culture media showed a significant down-regulation of IGF genes and reduced IGF protein levels.

CONCLUSION: Aflatoxin treatment resulted in a significant decrease in IGF gene and protein expression in vitro. IGF protein levels were also lower in children with the highest levels of AFB-alb adducts. The data suggest that aflatoxin-induced changes in IGF protein levels could contribute to growth impairment where aflatoxin exposure is high.

Exposure to aflatoxin B1 in utero is associated with DNA methylation in white blood cells of infants in The Gambia

BACKGROUND: Exposure to environmental toxins during embryonic development may lead to epigenetic changes that influence disease risk in later life. Aflatoxin is a contaminant of staple foods in sub-Saharan Africa, is a known human liver carcinogen and has been associated with stunting in infants.

METHODS: We have measured aflatoxin exposure in 115 pregnant women in The Gambia and examined the DNA methylation status of white blood cells from their infants at 2-8 months old (mean 3.6 ± 0.9). Aflatoxin exposure in women was assessed using an ELISA method to measure aflatoxin albumin (AF-alb) adducts in plasma taken at 1-16 weeks of pregnancy. Genome-wide DNA methylation of infant white blood cells was measured using the Illumina Infinium HumanMethylation450beadchip.

RESULTS: AF-alb levels ranged from 3.9 to 458.4 pg/mg albumin. We found that aflatoxin exposure in the mothers was associated to DNA methylation in their infants for 71 CpG sites (false discovery rate < 0.05), with an average effect size of 1.7% change in methylation. Aflatoxin-associated differential methylation was observed in growth factor genes such as FGF12 and IGF1, and immune-related genes such as CCL28, TLR2 and TGFBI. Moreover, one aflatoxin-associated methylation region (corresponding to the miR-4520b locus) was identified.

CONCLUSIONS: This study shows that maternal exposure to aflatoxin during the early stages of pregnancy is associated with differential DNA methylation patterns of infants, including in genes related to growth and immune function. This reinforces the need for interventions to reduce aflatoxin exposure, especially during critical periods of fetal and infant development.

Radiative rates for E1, E2, M1, and M2 transitions in the Br-like ions Sr IV, Y V, Zr VI, Nb VII, and Mo VIII

Energies and lifetimes are reported for the lowest 375 levels of five Br-like ions, namely SrIV, YV, ZrVI, NbVII, and MoVIII, mostly belonging to the 4s²4p⁵, 4s²4p⁴4ℓ, 4s4p⁶, 4s²4p⁴5ℓ, 4s²4p³4d², 4s4p⁵4ℓ, and 4s4p⁵5ℓ configurations. Extensive configuration interaction has been included and the general-purpose relativistic atomic structure package (grasp) has been adopted for the calculations. Additionally, radiative rates are listed among these levels for all E1, E2, M1, and M2 transitions. From a comparison with the measurements, the majority of our energy levels are assessed to be accurate to better than 2%, although discrepancies between theory and experiment for a few are up to 6%. An accuracy assessment of the calculated radiative rates (and lifetimes) is more difficult, because no prior results exist for these ions.

Radiative rates for E1, E2, M1, and M2 transitions among the 3s23p5, 3s3p6, and 3s23p43d configurations of Cl-like W LVIII

We report calculations of energy levels, radiative decay rates, and lifetimes for transitions among the 3s²3p⁵, 3s3p⁶, and 3s²3p⁴3d configurations of Cl-like W LVIII. The general-purpose relativistic atomic structure package (GRASP) has been adopted for our calculations. Comparisons are made with the most recent results of Mohan et al. (Can. J. Phys. 92, 177 (2014). doi:10.1139/cjp-2013-0348) and discrepancies in lifetimes are noted, up to four orders of magnitude in some instances. Our energy levels are estimated to be accurate to better than 0.5%, whereas results for radiative rates and lifetimes should be accurate to better than 20%.

Interventions Targeting Child Undernutrition in Developing Countries May Be Undermined by Dietary Exposure to Aflatoxin

Child undernutrition, a form of malnutrition, is a major public health burden in developing countries. Supplementation interventions targeting the major micronutrient deficiencies have only reduced the burden of child undernutrition to a certain extent, indicating that there are other underlying determinants that need addressed. Aflatoxin exposure, which is also highly prevalent in developing countries, may be considered to be an aggravating factor for child undernutrition. Increasing evidence suggests that aflatoxin exposure can occur in any stage of life including in utero through a trans-placental pathway and in early childhood (through contaminated weaning food and family food). Early life exposure to aflatoxin is associated with adverse effects on low birth weight, stunting, immune suppression and liver function damage. The mechanisms underlying impaired growth and aflatoxin exposure are still unclear but intestinal function damage, reduced immune function and alteration in the insulin-like growth factor axis caused by liver damage, are suggested hypotheses. Given the fact that both aflatoxin and child undernutrition are common in sub-Saharan Africa, effective interventions aimed at reducing undernutrition cannot be satisfactorily achieved until the interactive relationship between aflatoxin and child undernutrition is clearly understood, and an aflatoxin mitigation strategy has taken effect in those vulnerable mothers and children.

Seasonal and geographical differences in aflatoxin exposures in Senegal

The aim of the study was to determine the geographical and seasonal variations in aflatoxin dietary exposure levels in adults from Senegal. A total of 168 adults (50% male) were recruited from three districts: Nioro du Rip (n=90), located in the Sudan Savannah agro-ecological zone where rainfall is sufficient for groundnut growth; Saint-Louis (n=40) and Mboro (n=38), located in the Sahel zone where groundnuts are produced under irrigated conditions. Diet information and samples were collected at groundnut harvest and post-harvest seasons. Plasma aflatoxin-albumin adducts (AF-alb) and total aflatoxin in household groundnut samples were measured by ELISA and a quantitative thin layer chromatography method, respectively. The blood AF-alb geometric mean was 45.7 pg/mg albumin (range 5.5-588.2 pg/mg). Nioro du Rip had a higher AF-alb level at harvest than Saint-Louis and Mboro (80.0 vs 15.6 and 33.3 pg/mg, P<0.001). Similar trends were observed at post-harvest (P<0.05). Seasonal trends were not consistent across the districts as Nioro du Rip had a higher AF-alb level at harvest than post-harvest (80.0 vs 58.6 pg/mg, P=0.026), whereas Saint-Louis had a higher level at post-harvest than harvest (25.6 vs 15.6 pg/mg, P=0.032). It is clear that aflatoxin exposure is prevalent in adults from Senegal and that season and geographical location are strong determinants of aflatoxin exposure.