Lipids are important for structural and physiological functions of neuronal cell membranes. They exhibit a range of biological effects many are bioactive lipid mediators derived from polyunsaturated fatty acids such as sphingolipids, fatty acid ethanolamides (FA-EA) and endocannabinoids (EC). These lipid mediators and oxysterols elicit potent bioactive functions in many physiological and pathological processes of the brain and neuronal tissues. They have been investigated for biomarker discovery of ageing, neuroinflammation and neurodegenerative disorders. The n-3 fatty acids EPA and DPA are thought to exhibit a range of neuroprotective effects many of which are mediated through production of such lipid mediators. The aims of this study were to evaluate the effects of n-3 EPA and n-3 DPA supplementation on RBC membranes and in this way assess dietary compliance and to investigate brain sphingomyelin species of adult and aged rats supplemented with n-3 EPA and n-3 DPA to evaluate the effects and benefits on age-related changes in the brain. Furthermore, to study the effects of lithium on the brain FA-EAs and ECs to further understand the neuroprotective effects of lithium neuroprotective action on neuroinflammation as induced by LPS. Finally to examine if circulating oxysterols are linked to the prevalence of ALS and whether RBC fatty acids are markers of this action in relation to age and disease stages. These analytes were extracted from tissue samples and analysed with GC, LC/ESI-MS/MS and GC-MS. It was found that aged rats exhibited a significant increase in brain AA and decrease in Σn-3 and Σn-6 PUFAs when compared to adult animals. The observed increase of brain AA was reversed following n-3 EPA and n-3 DPA supplementation. Sphingomyelin was significantly increased when aged animals were supplemented with n-3 DPA. LPS treatment following lithium supplementation increased LA-EA and ALA-EA, while it decreased DHA-EA. Both oxysterols 24-OH and 27-OH increased in ALS patients and SOD1-mice. Eicosadienoic acid was different in ASL-patients compared to aged SOD1-mice. These studies demonstrated that dietary intake of n-3 EPA and n-3DPA significantly altered RBC fatty acids and sphingolipids in rat brain. They suggest that n-3 DPA can be a potential storage form for EPA, as shown by retro-conversion of n-3 DPA into EPA in erythrocyte membranes, ensuring supply of n-3 EPA. Also, n-3 EPA and n-3 DPA supplementation can contribute to an increase in brain sphingomyelin species with implications for age effects and regulation of brain development. Effects of lithium highlight novel anti-neuroinflammatory treatment pathways. Both 24-hydroxycholesterol and eicosadienoic acid may be used as biomarkers in ALS thereby possibly helping to manage the progressive stages of disease.

Lipids are important for structural and physiological functions of neuronal cell membranes. They exhibit a range of biological effects many are bioactive lipid mediators derived from polyunsaturated fatty acids such as sphingolipids, fatty acid ethanolamides (FA-EA) and endocannabinoids (EC). These lipid mediators and oxysterols elicit potent bioactive functions in many physiological and pathological processes of the brain and neuronal tissues. They have been investigated for biomarker discovery of ageing, neuroinflammation and neurodegenerative disorders. The n-3 fatty acids EPA and DPA are thought to exhibit a range of neuroprotective effects many of which are mediated through production of such lipid mediators. The aims of this study were to evaluate the effects of n-3 EPA and n-3 DPA supplementation on RBC membranes and in this way assess dietary compliance and to investigate brain sphingomyelin species of adult and aged rats supplemented with n-3 EPA and n-3 DPA to evaluate the effects and benefits on age-related changes in the brain. Furthermore, to study the effects of lithium on the brain FA-EAs and ECs to further understand the neuroprotective effects of lithium neuroprotective action on neuroinflammation as induced by LPS. Finally to examine if circulating oxysterols are linked to the prevalence of ALS and whether RBC fatty acids are markers of this action in relation to age and disease stages. These analytes were extracted from tissue samples and analysed with GC, LC/ESI-MS/MS and GC-MS. It was found that aged rats exhibited a significant increase in brain AA and decrease in ¿n-3 and ¿n-6 PUFAs when compared to adult animals. The observed increase of brain AA was reversed following n-3 EPA and n-3 DPA supplementation. Sphingomyelin was significantly increased when aged animals were supplemented with n-3 DPA. LPS treatment following lithium supplementation increased LA-EA and ALA-EA, while it decreased DHA-EA. Both oxysterols 24-OH and 27-OH increased in ALS patients and SOD1-mice. Eicosadienoic acid was different in ASL-patients compared to aged SOD1-mice. These studies demonstrated that dietary intake of n-3 EPA and n-3DPA significantly altered RBC fatty acids and sphingolipids in rat brain. They suggest that n-3 DPA can be a potential storage form for EPA, as shown by retro-conversion of n-3 DPA into EPA in erythrocyte membranes, ensuring supply of n-3 EPA. Also, n-3 EPA and n-3 DPA supplementation can contribute to an increase in brain sphingomyelin species with implications for age effects and regulation of brain development. Effects of lithium highlight novel anti-neuroinflammatory treatment pathways. Both 24-hydroxycholesterol and eicosadienoic acid may be used as biomarkers in ALS thereby possibly helping to manage the progressive stages of disease. / Libyan Government

<p> G93A SODI mice (G93A mice) are a transgenic model over-expressing a mutant human Cu/Zn-SOD gene, and are a model for amyotrophic lateral sclerosis (ALS), a predominantly motor neurodegenerative disease. Hippocampal neurogenesis in the subgranular zone (SGZ) of dentate gyms (DG) occurs throughout the life. It is regulated by many pathological and physiological processes. There is controversy with respect to the basal level of hippocampal neurogenesis and its response to exercise in neurodegenerative diseases and their mouse models. Little information regarding hippocampal neurogenesis is available in G93A mice. The present study was designed to study the impact of treadmill exercise and sex differences on hippocampal neurogenesis in this model. In addition, potential molecular mechanisms regulating hippocampal neurogenesis including growth factors (BDNF and IGFl) and oxidative stress (SOD2, catalase, 8-0Hdg, and 3-NT) were also addressed in the study. Bromodeoxyuridine (BrdU) was used to label newly generated cells. G93A and wild type (WT) mice were subjected to treadmill exercise (EX) or a sedentary (SEO) lifestyle. Immunohistochemistry was used to detect BrdU labeled newly proliferating cells, surviving cells, and their phenotype, as well as for determination of oxidative stress. BDNF and IGFl mRNA expression was assessed by in situ hybridization. Results showed that (1) G93A mice had an elevated basal level of hippocampal neurogenesis for both cell survival and neuronal differentiation, a growth factor (BDNF mRNA), and an oxidative stress marker (NT), as compared to wild type sedentary mice. (2) Treadmill running did not show any further effect on hippocampal neurogenesis, growth factors, oxidative stress, and antioxidant enzymes in G93A mice, while treadmill running promoted hippocampal neurogenes1s and expression of the growth factor (BDNF mRNA), and lowered oxidative stress (8-0Hdg) in WT mice. (3) There also were sex differences in hippocampal neurogenesis in G93A mice, whereby male G93A mice had a significant higher level of cell proliferation but a lower level of survival than female G93A mice. (4) The DG BDNF mRNA was associated with cell survival and neuronal differentiation in sedentary G93A mice, suggesting that BDNF is associated with a higher basal level of hippocampal neurogenesis in G93A mice. We conclude that G93A mice are more permissive in the context of hippocampal neurogenesis, which is associated with elevated DG BDNF mRNA expression. Running did not have impact on hippocampal neurogenesis and BDNF mRNA expression in G93A mice, probably due to a 'ceiling effect' of the already heightened basal levels of hippocampal neurogenesis and BDNF mRNA in this model. In addition, sex differences also affect hippocampal neurogenes1s, but the further study is needed to clarify the underlying molecular mechanisms. </p> / Thesis / Doctor of Philosophy (PhD)