Thesis (MMedSc)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: The aetiology of multiple sclerosis (MS) remains largely unknown due to the
multifactorial nature of disease susceptibility determined by both environmental and
genetic factors. Progress has been made in identifying the genetic component of MS
,
as well as the possible interactions with the environment. In this study single
nucleotide polymorphisms (SNPs) in the
FTO
(rs9939609, Intron 1 T>A),
MTR
(rs1805087, 2756 A>G),
MTRR
(rs1801394, 66 A>G),
MTHFR
(rs1801133, 677 C>T
and
rs1801131, 1298 A>C) and
COMT
(rs4680, 472 G>A) genes involved in the
methylation metabolic pathway were studied in the context of MS.
The overall objective of this study was to elucidate the mechanism underlying raised
homocysteine levels in MS patients. The specific aims were 1) to analytically validate
high throughput real-time polymerase chain reaction (RT-PCR) genotyping assays
for the 6 selected SNPs against direct sequencing as the gold standard for 2)
possible integration into a pathology-supported genetic testing strategy aimed at
improved clinical management of MS. The study population included a total of 114
unrelated Caucasian MS patients (98 females and 16 males) and 195 unrelated
Caucasian control individuals without a diagnosis of neurological disease (128
females and 67 males).
A novel finding of this study was that the risk-associated FTO rs9939609 A-allele was
associated with raised homocysteine levels (p=0.003) in patients diagnosed with MS,
but not in controls. Furthermore, homocysteine levels correlated significantly with
bo
dy mass index (BMI) (p=0.046) and total cholesterol levels (p=0.048). Both
homocysteine (p=0.011) and BMI (p=0.017) were significantly reduced with
increasing intake of folate in the diet, while high saturated/trans fat intake correlated
significantly with increased BMI (p<0.001). High physical activity correlated with
reduced BMI (p<0.006) in the study population, adjusted for age, gender and disease
status. Daily intake of at least five fruit and vegetable portions and the
COMT
rs4680
(472 G>A) AA genotype had a favourable lowering effect on MS disability as
assessed by the expanded disability status scale (EDSS) (p=0.035), while smoking
increased MS disability significantly (p<0.001). All SNPs studied were found to be in
Hardy-Weinberg equilibrium (HWE), with no significant differences detected between
patients and control individuals in genotype distribution or allele frequencies. This study has shown for the first time that the underlying disease process of MS
moderates the effect of the FTO rs9939609 polymorphism on homocysteine levels
,
which is consistent with the role of FTO in demethylation and epigenetic changes.
Identification of FTO rs9939609 reinforces the importance of adequate folate intake
in the diet that can be assessed accurately with use of the Medical History and
Lifestyle Questionnaire applied in this study.
Finally, the finding that raised homocysteine levels and BMI are significantly
influenced by lifestyle factors such as diet and physical activity in our study cohort
,
offers a solution to counteract the detrimental effects of genetic risk factors
contributing to the development of these established vascular risk factors for MS.
Combining this information with
FTO
rs9939609 and
COMT
rs4680 genotyping may
in future translate into a comprehensive pathology supported genetic testing strategy
aimed at improved risk management and quality of life in MS patients. / AFRIKAANSE OPSOMMING: Die etiologie van meervoudige sklerose (MS)
is
grootliks onbekend as gevolg van die
multifaktoriale aard van siekte vatbaarheid wat bepaal word deur beide genetiese en
omgewingsfaktore. Vordering is reeds gemaak in die identifisering van die genetiese
component van MS, asook moontlike interaksie met die omgewing. In hierdie studie
is enkel nukleotied polimorfismes (SNPs) in die
FTO
(rs9939609, Intron 1 T > A),
MTR
(rs1805087, 2756 A> G),
MTRR
(rs1801394, 66 A> G),
MTHFR
(rs1801133,
677 C > T en rs1801131, 1298 A> C) en
COMT
(rs4680, 472 G > A) gene, wat
betrokke is in die metilering metaboliese padweg, in die konteks van
MS
bestudeer.
Die oorhoofse doel van hierdie studie was om die onderliggende meganisme
betrokke by verhoogde homosisteïen vlakke in MS pasiënte uit te lig. Die spesifieke
doelwitte was 1) om die analitiese geldigheid van die hoë deurvoer riëeltyd
polymerase kettingreaksie (RT-PCR) genotipering metode soos toegepas vir die 6
geselekteerde SNPs te bevestig teen direkte DNA volgorde bepaling as die goue
standaard, vir 2) moontlike integrasie in 'n patologie-gesteunde genetiese toetsing
(PSGT) stategie wat gemik is op verbeterde kliniese hantering van MS. Die
studiepopulasie bestaan uit 'n totaal van 114 nie-verwante Kaukasiese
MS
pasiënte
(98 vroue en 16 mans) en 195 nie-verwante Kaukasiese kontroles sonder
‘n
diagnose van neurologiese siektes (128 vroue en 67 mans).
'n Nuwe bevinding van hierdie studie was dat die risiko-verwante
FTO
rs9939609 A-
alleel geassosieer was met verhoogde homosisteïen vlakke (p = 0,003) in pasiënte
gediagnoseer met MS, maar nie in kontroles nie. Homosisteïen vlakke was verder
beduidend geassosieer met liggaamsmassa-indeks (BMI) (p=0,046) en totale
cholesterol vlakke (p=0.048). Beide homosisteïen (p=0,011) en BMI (p=0,017) het
aansienlik verminder met 'n hoër inname van folaat in die dieet, terwyl 'n hoë
versadigde/trans vet en koolhidrate inname beduidend gekorreleer het met 'n
verhoogde BMI (p <0.001). Hoë fisiese aktiwiteit was gekorreleer met 'n verminderde
BMI (p< 0.006) in die gekombineerde groep, aangepas vir die ouderdom, geslag en
MS diagnose. Daaglikse inname van ten minste vyf vrugte en groente porsies en die
COMT
rs4680 (472 G>A) AA genotipe het 'n gunstige uitwerking op vermindering
van gestremdheid gehad, soos bepaal deur die uitgebreide gestremdheid status
skaal (EDSS) (p=0,035), terwyl rook MS gestremdheid beduidend verhoog het (p
<0.001). Alle SNPs bestudeer was in Hardy-Weinberg ewewig (HWE), met geen beduidende verskille waargeneem in genotipe verspreiding of alleelfrekwensies
tussen pasiënte en kontroles nie.
Hierdie studie het vir die eeste keer
aangetoon dat ‘n diagnose van MS die effek van
die FTO rs9939609 polimorfisme op homosisteïen vlakke modereer, wat ooreenstem
met die rol van FTO in demetilering en epigenetiese veranderinge. Identifikasie van
FTO rs9939609 versterk die belangrikheid van genoegsame folaat inname in die
dieet wat akkuraat gemeet kon word deur gebruik te maak van die Mediese
Geskiedenis en Leefstyl Vraelys soos toegepas in hierdie studie.
Ten slotte, die bevinding dat verhoogde homosisteïen vlakke en BMI statisties
betekenisvol beïnvloed word deur leefstylfaktore soos dieet en fisiese aktiwiteit in ons
studie populasie, verskaf 'n oplossing om die genetiese bydrae tot hierdie gevestigde
vaskulêre risikofaktore vir MS teen te werk. Kombinasie van hierdie inligting met
FTO
rs9939609 en COMT rs4680 genotipering kan moontlik in die toekoms benut word as
deel van 'n omvattende patologie-
gesteunende genetiese toetsing strategie wat
daarop gemik is om die risikobestuur en kwaliteit van lewe te verbeter in MS
pasiënte.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/95457 |
| Date | 12 1900 |
| Creators | Davis, William Henry |
| Contributors | Janse van Rensburg, Susan, Kotze, Maritha J., Stellenbosch University. Faculty of Medicine and Health Sciences. Dept. of Pathology. Chemical Pathology. |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | English |
| Type | Thesis |
| Format | xiv, 125 pages : illustrations (some colour) |
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