Thesis--Ph. D., University of Hong Kong. / Typewritten.

published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy

published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy

published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy

Dietary fatty acids are precursors of the lipid mediator group of compounds termed fatty acid ethanolamides (FAE). Prolonged intake of specific types of dietary fats has been shown to increase FAE levels. However, the short term effects of qualitative dietary fat intake on FAE levels remain understudied. Hence, the objective of this study was to identify the effect of diets containing varying concentrations of n-9 from canola oil (CO) and n-3 fatty acids from DHA rich oil (DRO) on plasma and organ FAE levels after different time points in male Sprague Dawley rats. Sixty-four rats were randomly assigned into four groups and were fed diets containing 40% as energy of either safflower, 95% CO: 5% DRO, 50% CO: 50% DRO and 5% CO: 95% DRO. These diets were consumed within a 2hr window in all groups. Circulating fatty acid and FAE levels were measured at 3, 6, 12 and 24hr within each group. At 3hr, significant differences (p<0.05) in plasma oleoylethanolamide (OEA) levels were seen in the 95% CO group: 5% DRO group and 5% CO group: 95% DRO group as well as between 50% canola oil group: 50% DRO and 5% CO group: 95% DRO. In all dietary groups, palmitoylethanolamide (PEA) levels were not significantly different at 3, 6 and 24hr compared to 0hr, but did at 12hr where the 50% CO:50% DRO group showed significantly lower levels than seen in the 95% CO group, but PEA levels were not different from the 5% canola oil group. Although plasma FAE levels were generally multiple times lower than observed in small intestine, liver or brain, arachidonoylethanolamide (AEA) levels were significantly lower in the 95% DRO group than in the remaining two groups. Plasma docosahexanoylethanolamide (DHEA) showed no difference across all time points except at 24hr where levels were higher (p<0.05) in the 95% DRO group than in the remaining two groups. In liver at 3hr, OEA levels were higher (p<0.05) in the 95% CO group than the groups with lesser concentrations of oleic acid, while liver OEA levels showed no difference at any other time points across dietary groups. LEA levels were higher in 95% CO: 5% DRO group compared to the 5% CO group: 95% DRO group after 3hr of feeding. Liver DHEA levels were observed to be highest in the 5% CO group: 95% DRO group at 3 and 12, but not at 6 or 24hr. The dietary fatty acid composition affects plasma and organ fatty acid profiles in a time dependent manner and also produces time shifts in plasma and organ FAE levels. These dietary induced changes according to time points in the levels of FAEs may translate into discernible changes in energy expenditure and lipid levels which may in turn influence the risk of obesity. / February 2017

Thesis (Ph. D.)--University of Texas at Austin, 2001. / Vita. Includes bibliographical references. Available also from UMI/Dissertation Abstracts International.

published_or_final_version / Medicine / Master / Master of Philosophy

Flax (Linum usitatissimum L.) is one of the richest plant sources of omega-3 fatty acids praised for their health benefits. In this study, the extent of the genetic variability for genes encoding stearoyl-ACP desaturase (SAD), fatty acid desaturase 2 (FAD2) and 3 (FAD3) was determined by sequencing the six paralogous genes from 120 flax accessions representing a broad range of germplasm including some EMS mutant lines. A total of 6 alleles for sad1 and sad2, 21 for fad2a, 5 for fad2b, 15 for fad3a and 18 for fad3b were identified. Deduced amino acid sequences of the alleles predicted 4, 2, 3, 4, 6, and 7 isoforms, respectively. Allele frequencies varied greatly across genes. Fad3a, with 110 SNPs and 19 indels, and fad3b, with 50 SNPs and 5 indels, showed the highest levels of genetic variation. While most of the SNPs and all the indels were silent mutations, both genes carried non-sense SNP mutations resulting in premature stop codons, a feature not observed in sad and fad2 genes. Some alleles and isoforms discovered in induced mutant lines were absent in the natural germplasm. Correlation of these genotypic data with fatty acid composition data of 120 flax accessions phenotyped in six field experiments revealed statistically significant correlations of some of the SAD and FAD isoforms on fatty acid composition, oil content and iodine value. The novel allelic variants and isoforms identified for the six desaturases will be a resource for the development of oilseed flax with unique and useful fatty acid profiles. / October 2015

Replacement of saturated fatty acids (SFA) with monounsaturated fatty acids (MUFA) or polyunsaturated fatty acids (PUFA) impacts risk of atherosclerosis and cardiovascular disease (CVD). However, although dietary fatty acids (DFA) have been established as an important factor related to CVD, their exact mechanisms of action have not been clearly established. One of the possible mechanisms is that DFA convert to fatty acid ethanolamides (FAEs), such as oleoylethanolamide (OEA), palmitoylethanolamide (PEA) and arachidonoylethanolamide (AEA), which are thought to associate with lipid signalling, fat oxidation and appetite control. Hence, the objectives of this thesis were to identify the impact of diets containing corn oil, canola oil, DHA + canola oil and fish oil on plasma and organ levels of FAEs as well as energy metabolism and lipid profiles in Syrian Golden hamsters. Forty-eight hamsters were provided diets containing 6% treatment oil for 30 d before sacrifice. Across all diets, in proximal small intestine and liver, animals fed canola oil showed higher (p<0.05) levels of OEA than corn oil and fish oil fed groups, but no difference compared to those fed DHA +canola oil. In plasma, fish oil fed animals showed higher (p<0.05) OEA and PEA levels and lower (p<0.05) AEA levels compared to all other groups. Feed intakes (g/d), oxygen consumption (ml/g) and body composition of total fat (%) and mass (g) did not differ across groups. However, energy expenditure associated with fat oxidation (%) was higher (p<0.01) in canola oil and DHA + canola oil fed hamsters compared to those consuming corn oil and fish oil. Also, body composition of fish oil fed animals showed a lower (p<0.01) total lean mass (g) compared to other three groups and a lower (p<0.01) total mass (g) compared to DHA + canola oil diets, but no difference compared to animals fed the canola oil diet. None of the treatments had any effect on triglyceride (TG) or C-reactive protein (CRP) levels. The fish oil group showed a higher (p<0.01) plasma total cholesterol (TC) levels than all other three groups. No differences existed between DHA + canola oil and fish oil groups in HDL or Non-HDL levels, but these levels were different (p<0.01) compared to corn oil group and canola oil groups. To conclude, different DFA affect whole body energetics and plasma lipid profiles. Also DFA produced marked shifts in plasma and organ levels of OEA, PEA and AEA. These dietary induced shifts in FAEs may translate into discernable changes in energy expenditure and lipid levels which in turn influence CVD risk.

Replacement of saturated fatty acids (SFA) with monounsaturated fatty acids (MUFA) or polyunsaturated fatty acids (PUFA) impacts risk of atherosclerosis and cardiovascular disease (CVD). However, although dietary fatty acids (DFA) have been established as an important factor related to CVD, their exact mechanisms of action have not been clearly established. One of the possible mechanisms is that DFA convert to fatty acid ethanolamides (FAEs), such as oleoylethanolamide (OEA), palmitoylethanolamide (PEA) and arachidonoylethanolamide (AEA), which are thought to associate with lipid signalling, fat oxidation and appetite control. Hence, the objectives of this thesis were to identify the impact of diets containing corn oil, canola oil, DHA + canola oil and fish oil on plasma and organ levels of FAEs as well as energy metabolism and lipid profiles in Syrian Golden hamsters. Forty-eight hamsters were provided diets containing 6% treatment oil for 30 d before sacrifice. Across all diets, in proximal small intestine and liver, animals fed canola oil showed higher (p<0.05) levels of OEA than corn oil and fish oil fed groups, but no difference compared to those fed DHA +canola oil. In plasma, fish oil fed animals showed higher (p<0.05) OEA and PEA levels and lower (p<0.05) AEA levels compared to all other groups. Feed intakes (g/d), oxygen consumption (ml/g) and body composition of total fat (%) and mass (g) did not differ across groups. However, energy expenditure associated with fat oxidation (%) was higher (p<0.01) in canola oil and DHA + canola oil fed hamsters compared to those consuming corn oil and fish oil. Also, body composition of fish oil fed animals showed a lower (p<0.01) total lean mass (g) compared to other three groups and a lower (p<0.01) total mass (g) compared to DHA + canola oil diets, but no difference compared to animals fed the canola oil diet. None of the treatments had any effect on triglyceride (TG) or C-reactive protein (CRP) levels. The fish oil group showed a higher (p<0.01) plasma total cholesterol (TC) levels than all other three groups. No differences existed between DHA + canola oil and fish oil groups in HDL or Non-HDL levels, but these levels were different (p<0.01) compared to corn oil group and canola oil groups. To conclude, different DFA affect whole body energetics and plasma lipid profiles. Also DFA produced marked shifts in plasma and organ levels of OEA, PEA and AEA. These dietary induced shifts in FAEs may translate into discernable changes in energy expenditure and lipid levels which in turn influence CVD risk.