Postprandial hypertriglyceridemia (PPHT), an independent risk factor for atherosclerosis (Smyth and Heron 2006; Nordestgaard, Benn et al. 2007), is strongly associated with metabolic syndrome and cardiovascular diseases (CVD) (Kolovou, Anagnostopoulou et al. 2005). It has been proposed that elevated triglycerides after a high-fat meal may be a postprandial phenomenon (Zilversmit 1979). PPHT are commonly concurrent with sedentary behaviors, such as extended sitting, which amplify PPHT (Levine, Vander Weg et al. 2006). The purpose of this study was to examine the effects of prolonged sitting with or without a balanced caloric diet and walking with a balanced diet on postprandial triglycerides (PPTG). Seven healthy, young men (age, 25.6 ± 3.7 y; height, 174 ± 5 cm; weight, 71.4 ± 6.2kg; VO2max, 49.3 ± 7.7 ml/kg/min) were recruited from a college and from within the Austin community. After 2 days of food and activity control (D1and D2), subjects performed one of three trials in a randomized, cross-over design for 2 days (D3 and D4); (1) active walking with a balanced diet (WB), (2) prolonged sitting with a hyper-caloric diet (SH), and (3) prolonged sitting with a balanced diet (SB). High fat tolerance tests (HFTT) were conducted on the following day, (D5), after 13 hour over-night fasting. Blood samples were obtained in the fasting state and every hour for 6 hours after subjects had eaten a high fat test meal consisting of 1.2 g fat, 1.1 g CHO, 0.2 g protein/kg body mass. All food was provided during the 5-day duration of the study. Body postures, heart rate, and daily steps were monitored. In both sit trials (SH and SB), subjects sat ~320 minutes longer and took 10 times fewer steps than WB. In WB, the total area under the curves for plasma triglycerides (AUC[subscript T] TG) was lower, compared to SH by 21.3% (p<0.001) and to SB by 19.7% (N.S.; p = 0.055), respectively. In WB, the incremental AUC TG (AUC[subscript I] TG), an index of postprandial response, was lower than both SH by 17.4% (p <0.005) and SB by 20.1% (p <0.05), respectively. Postprandial plasma insulin concentration was lower in WB, compared to SH by 19.4% (p <0.005) in AUC[scubscript T] and 18.8 % (p < 0.05) in AUC[subscript I]. No differences were shown in the metabolic responses between SB and SH despite the diet modifications. These findings indicate that two days of prolonged sitting significantly amplifies PPTG and suppresses insulin action. / text

published_or_final_version / Molecular Biology / Master / Master of Philosophy

No description available.

Localised accumulation of body fat significantly influences the development of obesity related co-morbidities and cardiovascular disease (CVD) risk. Medium chain triglycerides (MCT) have been suggested to modulate body fat distribution. Phytosterols (PS) have demonstrated unequivocal cholesterol-lowering effects. A healthy dietary solution combining MCT and PS could thus become first-line obesity and CVD prevention. The aim of this study was therefore to investigate the effects of a functional oil (FctO) rich in MCT and PS on blood lipid levels and body adiposity, compared to olive oil. Twenty-three hypercholesterolemic, overweight men, were randomly assigned, in a single-blind crossover study, to consume a FctO, or olive oil, incorporated into a 40% fat diet for 6 wks. Blood lipid levels were measured and body composition was assessed. Total and LDL cholesterol were significantly reduced in subjects consuming the FctO versus the control oil. No significant differences for weight or adiposity loss of subjects were observed between the two oils. Results support the cardio-protective role of this FctO.

Cardiovascular disease (CVD) risk can be lowered by introduction of plant sterols (PS) in the diet, since PS have been shown to reduce low-density lipoprotein cholesterol (LDL-C). Given that the efficacy of PS as cholesterol-lowering agents depends on their appropriate solubilization, the cholesterol-lowering efficacy of PS in non-traditional matrices needs to be determined. The primary aim of this thesis was to examine the consumption of PS (a) in an oil rich in medium chain triglycerides (MCT) or (b) low-fat yogurt with or without a meal, on changes in lipid parameters. Additional objectives were: (1) to assess the effects of MCT with PS on body composition and energetics, (2) to compare the effects of PS in low-fat matrix consumed with or without a meal on cholesterol synthesis, (3) to evaluate the risks of PS in low-fat matrix on blood levels of carotenoids and fat-soluble vitamin, and (4) to investigate the relationship between the response to PS, cholesterol kinetics and genotyping. For this purpose two randomized, controlled, crossover-feeding trials were conducted. First, 23 overweight, hyperlipidemic men consumed PS in MCT or olive oil control for six weeks each. In the second trial, 26 hyperlipidemic subjects consumed a placebo yogurt, a PS-enriched yogurt consumed with a meal, or afternoon PS-enriched yogurt as a snack for four weeks each. PS, mixed within a MCT matrix, lower plasma total cholesterol (TC) and LDL-C without changing the high-density-lipoprotein cholesterol concentrations. However, no changes in body composition or energetics were observed. Secondly, a PS-enriched low-fat yogurt as snack lowered TC, along with a lowering trend in LDL-C, to greater extent compared to when consumed with a meal without any risk of deficiency in fat-soluble antioxidants. An increase in cholesterol biosynthesis was also observed in both PS phases compared to control phase. In addition, three non-responsive subjects to PS intervention who had higher cholesterol absorption rates were observed; however, no recognizable pattern of genetic polymorphisms was detected. Overall, these novel matrices for PS incorporation consumed with or between meals may be an effective way of decreasing the risk of CVD; however, some individuals respond better to PS intervention.

<p>The production of biodiesel (methyl esters) from vegetable oils represents analternative means of producing liquid fuels from biomass, and one which is growing rapidly in commercial importance and relevance due to increase in petroleum prices and the environmental advantages the process offers. Commercially, biodiesel is produced from vegetable oils, as well as from waste cooking oils and animal fats. These oils are typically composed of C14-C20 fatty acid triglycerides. In order to produce a fuel that is suitable for use in diesel engines, these triglycerides are usually converted into the respective mono alkyl esters by base-catalyzed transesterification with short chain alcohol, usually methanol. In the first part of this study, the transesterification reactions of three different vegetable oils / sunflower (SFO), soybean (SBO) and waste cooking oil (WCO) with methanol was studied using potassium hydroxide as catalyst in a conventional batch process. The production of biodiesel from waste cooking oil was also studied via continuous operation systems (employing the use of low frequency ultrasonic technology and the jet loop reactor). The characterisation of the feedstock used and the methyl ester products were determined by different analytical techniques such as gas chromatography (GC), high performance liquid chromatography (HPLC) and thin layer chromatography (TLC). The effects of different reaction parameters (catalyst amount, methanol to oil ratio, reaction temperature, reaction time) on methyl ester/FAME yield were studied and the optimum reaction conditions of the different process systems were determined. The optimum reaction conditions for production of methyl esters via the batch process with the fresh oil samples (SFO and SBO) were established as follows: a reaction time of 60 min at 60 &ordm / C with a methanol: oil ratio of 6:1 and 1.0 KOH % wt/wt of oil / while the optimum reaction conditions for the used oil (WCO) was observed at a reaction time of 90 min at 60 &ordm / C, methanol: oil ratio of 6:1 and 1.5% KOH wt/wt of oil. The optimum reaction conditions for the transesterification of the WCO via ultrasound technology applied in a continuous system in this study were: a reaction time of 30 min, 30 &ordm / C, 6:1 methanol/oil ratio and a 0.75 wt% (KOH) catalyst concentration. The ultrasound assisted transesterification reactions performed at optimum conditions on the different oil samples led to higher yields of methyl esters (96.8, 98.32 and 97.65 % for WCO, SFO and SBO respectively) compared to methyl esters yields (90, 95 and 96 % for WCO, SFO and SBO respectively) obtained when using conventional batch procedures. A considerable increase in yields of the methyl esters in the ultrasound assisted reaction process were obtained at room temperature, in a remarkably short time span (completed in 30 min) and with a lower amount of catalyst (0.75 wt % KOH) while the results from the continuous jet loop process system showed even better results, at an optimum reaction condition of 25 min of reaction, a methanol: oil ratio of 4:1 and a catalyst amount of 0.5 wt%. This new jet loop process allowed an added advantage of intense agitation for an efficient separation and adequate purification of the methyl esters phase at a reduced time of 30 min. The use of homogeneous catalysts in conventional processes poses many disadvantages / heterogeneous catalysts on the other hand are attractive on the basis that their use could enable the biodiesel production to be more readily performed as a continuous process resulting in low production costs. Consequently, a solid base catalyst (KNO3/FA) prepared from fly ash (obtained from Arnot coal power station, South Africa) and a new zeolite, FA/Na-X synthesized from the same fly ash were used as solid base catalysts in the transesterification reactions in the conversion of a variety of oil feedstock with methanol to methyl esters. Since fly ash is a waste product generated from the combustion of coal for power generation, its utilization in this manner would allow for its beneficiation (as a catalytic support material and raw material for zeolite synthesis) in an environmentally friendly way aimed at making the transesterification process reasonably viable. Arnot fly ash (AFA) was loaded with potassium (using potassium nitrate as precursor) via a wet impregnation method while the synthesized zeolite FA/Na-X was ion exchanged with potassium (using potassium acetate as precursor) to obtain the KNO3/FA and FA/K-X catalysts respectively. Several analytical techniques were applied for characterization purposes. The results of the XRD and XRF showed that the AFA predominantly contained some mineral phases such as quartz, mullite, calcite and lime. The high concentration of CaO in AFA was apparent to be beneficial for the use of fresh fly ash as a support material in the heterogeneous catalysed transesterification reactions. XRD characterisation of KNO3/FA results indicated that the structure of KNO3/FA gradually changed with the increase in KNO3 loading. The catalyst function was retained until the loading of KNO3 was over 10 %. IR spectra showed that the KNO3 was decomposed to K2O on the fly ash support during preparation at a calcination temperature of 500 &ordm / C. The CO2-TPD of the KNO3/FA catalysts showed that two basic catalytic sites were generated which were responsible for high catalytic abilities observed in the transesterification reactions of sunflower oil to methyl esters. On the other hand, XRD results for the as- received zeolite synthesized from AFA showed typical diffraction peaks of zeolite NaX. SEM images of the FA /NaX showed nano platelets unique morphology different from well known pyramidal octahedral shaped crystal formation of faujasite zeolites and the morphology of the FA /KX zeolite did not show any significant difference after ion exchange. The fly ash derived zeolite NaX (FA /NaX) exhibited a high surface area of 320 m2/g. The application of the KNO3/FA catalysts in the conversion reactions to produce methyl esters (biodiesel) via transesterification reactions revealed methyl ester yield of 87.5 % with 10 wt% KNO3 at optimum reaction conditions of methanol: oil ratio of 15:1, 5 h reaction time, catalyst amount of 15 g and reaction temperature 160 &deg / C, while with the use of the zeolite FA/K-X catalyst, a FAME yield of 83.53 % was obtained for 8 h using the ion exchanged Arnot fly ash zeolite NaX catalyst (FA/KX) at reaction conditions of methanol: oil ratio of 6:1, catalyst amount of 3 % wt/wt of oil and reaction temperature of 65 &ordm / C. Several studies have been carried out on the production of biodiesel using different heterogeneous catalysts but this study has been able to uniquely demonstrate the utilization of South African Class F AFA both as a catalyst support and as a raw material for zeolite synthesis / these catalyst materials subsequently applied sucessfully as solid base catalysts in the production of biodiesel.</p>

Medium chain triglycerides (MCT) have long been advocated as potential weight-lowering agents or potential tools in the treatment and prevention of human obesity. These statements have been made after findings from human and animal trials that consumption of MCT increases energy expenditure and fat oxidation compared to long chain triglycerides (LCT). In addition, animal studies have resulted in lower body weight gain and smaller fat depots when animals were fed MCT compared to those fed LCT. However, long-term controlled trials studying the effects of consumption of MCT in humans have not been conducted and the longest trial to date, 14 d of duration, has shown that the effect of MCT on energy expenditure may be transient. Therefore, we aimed to determine whether, in controlled feeding conditions, consumption of MCT for 4 wk would lead to differences in energy expenditure and substrate oxidation versus consumption of an isocaloric diet rich in LCT. Furthermore, our aim was to establish whether consumption of MCT for 4 wk would lead to greater changes in body composition than would LCT consumption. We conducted two randomized, controlled, crossover feeding trials involving overweight women and men to test our objectives. A secondary objective was to examine the potential satiating effect of MCT, and this was tested in men. Finally, a third objective was to determine whether, when combined with phytosterols and flaxseed oil, MCT consumption would result in different blood lipid profile compared to LCT. Nineteen healthy overweight women and 24 healthy overweight men participated in two separate randomized controlled trials to test these objectives. Energy expenditure and body composition were assessed at the beginning and end of each experimental phases, which differed only in the type of fat included in the controlled diets. Blood samples were also taken at baseline and endpoint of each phase to determine plasma lipid concentrations. Result

Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniversitet, 2004. / Härtill 4 uppsatser.

Thesis (M. Phil.)--University of Hong Kong, 2009. / Includes bibliographical references (leaves 81-92) Also available in print.

Thesis (M.S.)--University of Alabama at Birmingham, 2007. / Title from first page of PDF file (viewed June 30, 2007). Includes bibliographical references (p. 59-65).