Thesis (DTech (Biomedical Technology))--Cape Peninsula University of Technology, 2009 / Multiple sclerosis (MS) is a chronic inflammatory disease of the central nervous system
(CNS), which leads to neuronal demyelination, and eventually to oligodendrocyte and axon
loss, with subsequent lesion formation. The wide distribution of lesions in the CNS results in
a variety of clinical features, such as cognitive impairment, vertigo, spasticity, ataxia tremors,
progressive quadriparesis, pain and depression. Currently no cure exists for CNS disorders,
resulting in a decline in quality of life, and an economic burden on society. Metabolic
disturbances, especially lipid metabolic abnormalities, have been implicated in the
development of MS. Although the disease cannot be cured, disease-modifiers, such as
interferon beta, glatiramer acetate and mitoxantrone, as well as fatty acid supplementatlon
have been used to delay the progression of the disease. Membrane fatty acids are
precursors for mediators of inflammation, the eicosanoids, which are produced soon after
stimulation and which regulate a number of inflammatory effects, such as the induction of
fever, vasodilation and production of macrophage- and Iymphocyte-derived cytokines.
Eicosanoids, in contrast to their fatty acid precursors, have a short half-life and are therefore
difficult to measure.
The objective in the present study was to determine the role of fatty acids from South African
MS patients, by measuring the fatty acid composition of phosphatidylcholine (PC),
phosphatidylethanolamine (PE), phosphatidylserine (PS), phosphatidylinositol (PI) and
sphingomyelin (SM) phospholipids in the plasma, red blood cell (RBC) and peripheral blood
mononuclear cell (PBMC) membranes and correlate abnormalities with the neurological
outcome as measured by the Kurtzke Expanded Disability Status Scale (EDSS) and
inflammation assessed by C-reactive protein (CRP). A second objective was to establish
whether possible changes in membrane lipids (phospholipids, fatty acids and cholesterol)
would have an effect on membrane fluidity, and whether this would correlate with the EDSS
and CRP.
The plasma, RBC and PBMC membrane lipid composition from 31 white female patients with
MS and 30 age- and gender-matched control subjects were assessed. Fatty acids were
quanflfied by gas chromatography (GC), phospholipids by colorimetric and cholesterol by
enzymatic assays. Membrane fluidity, as measured by the membrane lipid composition, was
calculated, using previously established formulae, and includes the following: the saturated
nature of the membrane was measured by the phospholipid PC+PS/PE+PS ratio, fluidity and
permeability were measured by the cholesterol concentratlon and the cholesterol to total
phospholipid ratio and membrane deformability was measured by the phospholipid PE to PS
ratio. Membrane fluidity was also measured by the ordered-erystalline-phase to liquidcrystalline-
phase lipid composition, which correlates with the phospholipid PE to PC ratio.
The membrane saturated (SATS) to polyunsaturated fatty acid (PUFA) ratio was further used
as an indication- of the fluidity status of the membranes. CRP was measured in all
participants using a Beckman nephelometer.
In MS, the n-6 fatty acids, particularly C18:2n-6, C20:4n-6 and C22:4n-6, were significantly
decreased in plasma, RBC and/or PBMC membranes. In addition, the relationship between
C20:3n-6 and C20:4n-6 showed a metabolic disturbance in both RBC and PBMC
membranes from patients with MS, as compared to the control group. C20:4n-6 showed
significant inverse correlations with the EDSS and CRP in MS patients, indicating that loss of
these fatty acids from membranes correlated with higher disability as well as with increased
inflammation. There were significant increases in free fatty acids C18:2n-6 and C20:4n-6 in
plasma from MS patients. Saturated fatty acids, SM C14:0 and PI C22:0 were significantly
increased in PBMC membranes from MS patients, and SM C14:0, C16:0 and C20:0 showed
inverse correlations with the Functional System Scores. In contrast, the longer-ehain SATS,
C22:0 and C24:0 showed positive correlations with the Functional System Scores. Red blood
cell membrane fluidity as measured by the SATS to PUFA ratio was significantly higher in
patients than in controls. In patients with CRP ~ 5.00 Ilglml the ratio showed significant
inverse correlation with disease outcome. The saturated nature correlated positively, whilst
the .ordered-erystalline-phase to liquid-crystalline-phase lipid ratio correlated inversely with
the Functional System Scores.
In this study it was consistently shown that C20:4n-6, or its precursor and elongation
products, C18:2n-6 and C22:4n-6 respectively, was lower in plasma, RBC and/or PBMC
membranes from MS patients. Red blood cells lack the desaturase enzymes and depend on
fatty acids sourced from the plasma. Therefore, lower C20:4n-6 in the RBC membranes from
MS patients may be due to depleted plasma stores, or an indication of an increased demand
of this fatty acid elsewhere. Furthermore, this study has demonstrated that lower RBC
C20:4n-6, with an increase in plasma FFA C20:4n6, resulted in worse disease outcome,
perhaps due to the pro-inflammatory effect of eicosanoid production. This. study also
characterized the specific SATS, that is, longer-ehain SATS that may increase the risk of
developing MS, as higher shorter-ehain SATS, C14:0 and C16:0 reflected better disease
outcome, demonstrated by the inverse correlation with the EDSS and FSS. Lastly, this study
has shown that in the presence of uncontrolled inflammation such as in MS, the altered lipid
composition indirectly compromised cell membrane, structure and fluidity, and thereby
contributed to the disease progression in MS patients.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:cput/oai:localhost:20.500.11838/1514 |
| Date | January 2009 |
| Creators | Hon, Gloudina Maria |
| Publisher | Cape Peninsula University of Technology |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Rights | http://creativecommons.org/licenses/by-nc-sa/3.0/za/ |
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