Thesis (PhD (MedSc))--University of Stellenbosch, 2011. / ENGLISH ABSTRACT: Fumonisins are carcinogenic mycotoxins which occur world-wide in maize and
maize-based products intended for human consumption. Consumption of fumonisin contaminated
maize as a staple diet has been associated with oesophageal and liver
cancer incidence as well as neural tube defects. This study has confirmed the State
of Santa Catarina, Brazil as another region where the consumption of maize
contaminated with fumonisins and high oesophageal cancer incidence co-occur.
Since fumonisins exert their main biochemical effect by disruption of the sphingolipid
biosynthetic pathway and are implicated in cancer, the role of fumonisin B1 (FB1) in
FB1–induced rat hepatocyte nodules was investigated. The current study showed
that FB1 exposure activated sphingosine accumulation in the nodules which could
induce the bio-active sphingosine 1-phosphate to provide a selective growth stimulus
on subsequent FB1 exposure. Since the FB1-induced hepatocyte nodules were not
resistant to the disruption of sphingolipid biosynthesis, it was not the mechanism
whereby the altered hepatocytes escaped the mitoinhibition of FB1 and selectively
proliferated into hepatocyte nodules. A study in maize subsistence farming
communities investigated the sphingosine and sphinganine levels in blood and urine
of participants. Fumonisin exposure was assessed in these communities based on
fumonisin levels in maize that was concurrently collected from the areas where the
participants resided. Subsequently fumonisin exposure was assessed in individuals
based on the fumonisin levels in maize collected from each household and by
acquiring weighed food records for each member of the household. It was confirmed
in both these studies that communities are chronically exposed to fumonisin levels
well above the provisional maximum tolerable daily intake determined by the Joint FAO/WHO Expert Committee on Food Additives. Since the sphinganine and
sphingosine levels in blood and urine of the participants exposed to various levels of
fumonisin were not significantly different, the sphingoid bases and their ratios could
not be established as a biomarker of fumonisin exposure. Therefore, an alternative
biomarker of exposure was investigated during studies into a practical cost effective
method to reduce fumonisin. The customary maize food preparation practices were
assessed in a maize subsistence farming community and subsequently optimised to
reduce the fumonisin levels in the maize under laboratory-controlled conditions.
Implementation of this optimised and culturally acceptable intervention method of
sorting and washing maize in a rural community reduced fumonisin contamination in
home-grown maize by 84%. The intervention study attained a 62% reduction in
fumonisin exposure based on fumonisin levels in maize-based food and
consumption as assessed by 24-h dietary recall questionnaires. The alternative
biomarker of fumonisin exposure, urinary FB1, was investigated during the
intervention study. The FB1 urinary biomarker measured fumonisin intake at the
individual level and confirmed the reduction achieved as assessed by food analysis
and food intake data. The biomarker was thus well correlated with fumonisin
exposure and confirmed the efficacy of the simple and culturally acceptable
intervention method. Utilisation of the urinary FB1 biomarker and the customised
hand-sorting and washing of maize to reduce fumonisin exposures has the potential
to improve food safety and health in subsistence maize farming communities. / AFRIKAANSE OPSOMMING: Fumonisien is kankerverwekkende mikotoksiene wat wêreldwyd voorkom op mielies
en mielie-verwante produkte bestem vir menslike verbruik. Daar is ‘n verband tussen
die voorkoms van slukderm en lewer kanker, sowel as neuraalbuisdefekte, in
gemeenskappe waar fumonisien-gekontamineerde mielies die stapel voedsel is. Die
Brasiliaanse Staat, Santa Catarina is uitgewys as nog 'n area waar hoë voorkoms
van slukdermkanker en hoë fumonisin vlakke in mielies gesamentlik voorkom.
Aangesien fumonisien verbind word met van kanker en die hoof biochemiese effek
die ontwrigting van die sfingolipiedbiosintese weg is, is die rol van fumonisien B1
(FB1) in FB1-geinduseerde rot hepatosietnodules ondersoek. Die studie het getoon
dat FB1 blootstelling aktiveer sfingosien ophoping in die hepatosietnodules wat
moontlik die bio-aktiewe sfingosien 1-fosfaat aktiveer om op daaropvolgende FB1
blootstellings geselekteerde groei stimulasie te ondergaan. Die FB1-geïnduseerde
hepatosietnodules was nie bestand teen die inhibisie van die sfingolipied biosintese
nie en dus nie die meganisme waardeur die veranderde hepatosiete mito- inhibisie
van FB1 vryspring, en selektief ontwikkel in hepatosietnodules nie. ‘n Studie in
bestaansboerdery gemeenskappe het die sfingosien en sfinganien vlakke in bloed
en uriene vergelyk met individuele fumonisien blootstelling. Laasgenoemde is
gebaseer op fumonisien vlakke in gekolleekterde mielies vanuit die deelnemers se
huise en aannames vanuit die literatuur. Die opvolg studie in die areas het
individuele fumonisien blootstelling bepaal gebaseer op fumonisien vlakke in die
mielies van elke huishouding en die inname van mielies deur die voedsel van elke
individu te weeg. Albei hierdie studies het bevestig dat die gemeenskappe
blootgestel is aan kroniese fumonisien vlakke wat die maksimum toelaatbare daaglikse inname wat deur die gesamentlike FAO/WHO deskundige komitee op
voedsel toevoegsels vasgestel is, oorskei. Aangesien die sfingosien en sfinganien
vlakke nie beduidend verskil in bloed of uriene van mense wat aan verskillende
fumonisien-kontaminasie vlakke blootgestel is nie, kan die lipiedbasisse en hul
verhouding nie as ‘n biologiese merker vir fumonisien blootstelling bevestig word nie.
Dus is ‘n alternatiewe biologiese merker vir fumonisien blootstelling ondersoek
gedurende ‘n studie oor praktiese bekostigbare maniere om fumonisin blootstelling
te verlaag. Die tradisionele voedsel voorbereidingspraktyke in ‘n bestaansboerdery
gemeenskap is bestudeer en onder laboratorium-gekontroleerde toestande
aangepas om fumonisien vlakke in die mielies optimaal te verlaag. Die kultureel
aanvaarbare intervensie metode, sortering en was van die mielies, is in ‘n
bestaansboerdery gemeenskap toegepas waar ‘n 84% verlaging in fumonisien
vlakke van die mielies verkry is. Die intervensie metode het ‘n 62% verlaging in
fumonisien blootstelling te weeggebring deur fumonisien vlakke in die mieliegebasserde
disse te meet en inname daarvan deur die deelnemers met 24-h
diëetkundige vraelyste vas t e stel. Gedurende die intervensie studie is urienêre FB1,
die alternatiwe biologiese merker van fumonisien blootstelling, ondersoek.
Individuele fumonisien blootstelling data, bepaal met die urienêre FB1 biomerker, het
goed ooreengestem met die voedsel analise en voedsel inname data en het dus die
doeltreffendheid van die praktiese kultuur aanvaarbare intervensie metode bevestig.
Benutting van die FB1 urienêre biologies merker en die optimale sortering en was
van die mielies om die fumonisien blootstelling te verlaag het die potensiaal om
voedselveiligheid en gesondheid in hierdie bestaansboerdery gemeenskappe
aansienlik te verbeter.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/6461 |
| Date | 03 1900 |
| Creators | Van der Westhuizen, Liana |
| Contributors | Shephard, Gordon S., Van Helden, Paul D., University of Stellenbosch. Faculty of Health Sciences. Dept. of Biomedical Sciences. |
| Publisher | Stellenbosch : University of Stellenbosch |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | Unknown |
| Type | Thesis |
| Format | 222 p. : ill. |
| Rights | University of Stellenbosch |
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