Graduation date: 1984

It has been well established that both carbohydrate-loading before and carbohydrate ingestion during exercise can enhance endurance performance by supplying carbohydrate for oxidation. However, the precise mechanism(s) underlying the proposed ergogenic effects of these procedures remain to be established. The studies in this thesis were therefore designed to examine the effects of carbohydrate-loading and carbohydrate ingestion on fuel substrate kinetics.

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Hormonal and metabolic responses to submaximal exercise were studied in 11 sedentary, overweight women who participated in an 8 week aerobic exercise program (80% VO2 max) while consuming a hypocaloric diet. A maximal and submaximal treadmill exercise test were performed before and after the program. During the submaximal exercise test, a graded portion (mean time 6.4 min) preceded the submaximal phase during which subjects worked at 80% VO2 max until exhaustion (mean time l2 min). Blood was sampled before and after the work via venipuncture. Whole blood was immediately analyzed for lactate accumulation. The remaining blood was centrifuged, separated, and frozen for subsequent serum glucose, cortisol, and insulin measurement. There was a significant increase in oxygen uptake (ml/kg/min), and a decrease in body weight, ( 6.7%), and body fat (14%). Resting heart rate was significantly lower post-training (5.4%), as were exercise RQ (VCO2/VO2) ratios. Pretraining serum glucose and blood lactate significantly increased while nonsignificant decreases were noted in insulin and cortisol as a result of the submaximal exercise bout. The significant increases in glucose and lactate during exercise were blunted after the training program. However, only the post-training response of lactate was significantly different from the pretraining response. The insulin and cortisol response was not significantly different from that during the pretraining exercise test. A correlation was observed between RPE and lactate at the end of exercise both pretraining and post-training. In summary, the combined exercise and weight loss program resulted in exercise being less stressful, both metabolically and subjectively. This improvement enables greater exercise intensity to be performed prior to the significant accumulation of lactate and perception of fatigue which may inspire the sedentary, overweight female to establish and/or continue a regular exercise program. / Master of Science

In conclusion, the studies reported in this thesis suggested that the CHO amount, whether provided by a pre-exercise CHO meal or short-time, i.e., 3-day, CHO loading, plays a pivotal role in regulating the immune responses before, during, and after endurance exercise. Although GI and GL independently affect the exercise performance and immune responses, the amount of CHO consumed remains a determining factor. The potential benefits on immune system and endurance performance after the low GI and low GL diet (L-L) should be noted and warrant further investigation. Although the HGI and LGI meals demonstrated similar effects on endurance performance when large amount of CHO-electrolyte solution consumed during the exercise, pre-exercise LGI meal can hasten the IL-6 responses during the recovery. (Abstract shortened by UMI.) / The aim of this thesis was to investigate the influence of pre-exercise carbohydrate (CHO) meal(s) with different glycemic index (GI) and glycemic load (GL) on endurance running performance, physiological, and immune responses. / The first study (Chapter 4) examined the influence of a pre-exercise meal with different GI and GL on subsequent endurance running performance, physiological, and immune responses. Eight endurance-trained male runners completed three trials in a randomized order, separated by at least seven days. These responses were characterized by a lower CHO oxidation with a concomitant higher glycerol and FFA in the H-L trial. Consumption of a pre-exercise high CHO meal, i.e., H-H and L-L, resulted in less perturbation of circulating numbers of leukocytes, neutrophils, and T lymphocyte subsets, decreased elevation of plasma IL-6 concentrations immediately after exercise and during the 2 h recovery period when compared to the H-L trial. These responses were accompanied by an attenuated increase in plasma IL-10 concentrations and plasma cortisol concentrations at the end of 2 h recovery. It was concluded that the amount of CHO consumed 2 h before endurance exercise appears to be the main influencing factor on immune responses irrespective of its GI and GL value. / The second study (Chapter 5) examined the influence of a 3-day CHO loading with different GI and GL meals on the supercompensation status, running performance, physiological and immune responses. Nine endurance-trained male runners were recruited in this study. The procedures basically involved a 3-day CHO loading with different GI and GL meal [CHO intake (% of energy intake), GI, and GL per day are 73%, 80, and 553 for the high-GI and high-GL (H-H); 73%, 42, and 249 for the low-GI and low-GL (L-L); 31%, 78.5, and 227 for the high-GI and low-GL (H-L) respectively] after a glycogen-lowering exercise. Two hours after the breakfast on day 4, participants performed the running protocol as described in the first study. There was no difference in time to complete the 10-km TT between the two trials with high-CHO loading, i.e., H-H and L-L (51.3 +/- 5.3 min vs 48.6 +/- 1.3 min, NS). These results suggested that 3-day CHO loading with low GI and low GL (L-L) is more effective in improving endurance performance when compared to a high GI but low GL diet (H-L). It appears that the amount of CHO consumed during the 3-day CHO loading remains the key influencing factor on immune responses despite of the differences in the GI and GL value. / The third study (Chapter 6) investigated the influence of pre-exercise meal with different GI on subsequent endurance running performance and immune responses when CHO-electrolyte solution was consumed during exercise. Pre-exercise LGI meal attenuated the increases of cortisol when compared with CON and hastened the recovery of the IL-6 value to baseline when compared to that in HGI and CON trials during the first hour of the recovery. The results suggested that beside of CHO quantity (CHO content), the role of CHO quality (GI) in the diet consumed 2 h before exercise should be considered when investigating the influence of CHO supplementation on the exercise-induced transitory immunosuppressive effects. / Chen Yajun. / "August 2006." / Adviser: Stephen Wong Heung-Sang. / Source: Dissertation Abstracts International, Volume: 68-03, Section: B, page: 1597. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2006. / Includes bibliographical references (p. 199-225). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts in English and Chinese. / School code: 1307.

Thesis (PhD (Genetics. Plant Biotechnology))--University of Stellenbosch, 2005. / The current understanding of the regulation of sucrose accumulation is still incomplete even though many scientists have investigated this subject. Components of trehalose metabolism have been implicated in the regulation of carbon flux in bacteria, yeast and more recently in plants. With a view to placing trehalose metabolism in the context of cytosolic sugarcane sucrose metabolism and carbon partitioning we have investigated the metabolites, transcripts and enzymes involved in this branch of carbohydrate metabolism in sugarcane internodal tissues. Sugarcane internodal trehalose levels varied between 0.31 ± 0.09 and 3.91 ± 0.99 nmol.g-1 fresh weight (FW). From statistical analysis of the metabolite profile it would appear that trehalose does not directly affect sucrose accumulation, although this does not preclude involvement of trehalose- 6-phosphate in the regulation of carbon partitioning. The metabolite data generated in this study demanded further investigation into the enzymes (and their transcripts) responsible for trehalose metabolism. Trehalose is synthesised in a two step process by the enzymes trehalose-6-phosphate synthase (EC 2.4.1.15, TPS) and trehalose-6-phosphate phosphatase (EC 3.1.3.12, TPP), and degraded by trehalase (EC 3.2.1.28). Two novel sugarcane partial cDNAs that coded for trehalase (tre) and actin (required for normalisation in profiling experiments) were isolated and used along with partial transcripts for TPS and TPP to determine transcript levels in different tissue- and genotypes. A putative full-length SugTPS cDNA was isolated and characterised. Enzyme activities for TPS, TPP and trehalase were measured at levels of 2.7 nmol.min-1.mg-1protein, 8.5 nmol.min-1.mg-1protein and 6.2 nmol.min-1.mg-1protein respectively, from young internodal protein extracts of sugarcane, variety N19. TPP enzyme activity and transcript levels were higher in S. spontaneum than Saccharum interspecific hybrids. Kinetic analysis of TPP and trehalase activities were performed with the purpose of providing parameters for an in silico kinetic model of trehalose and sucrose metabolism. Three isoforms of TPP were identified and desingated TPPAI, TPPAII and TPPB. Both TPPA isoforms had pH optima of 6.0, and TPPB of pH 6.5. Apparent Km values were determined as 0.447 ± 0.007 mM for TPPAI, 13.82 ± 1.98 mM for TPPAII and 1.387 ± 0.18 mM for TPPB. Partial purification and characterisation of trehalase demonstrated dual pH optima of 3.5 and 6.0, with Km values between 0.345 and 0.375 mM. These data were used as the basis for a kinetic model of trehalose metabolism. A previously described kinetic model of cytosolic sucrose metabolism has been expanded to include the trehalose pathway (TPS, TPP and trehalase). The aim was to supplement the available information on cytosolic metabolism in sugarcane storage parenchyma, identify points of control between sucrose and trehalose metabolism, and provide a platform from which further experimental and in silico modelling can be launched. The model predicted trehalose in the same order of magnitude as those determined in the metabolite profiling experiments. The majority of control of flux over the trehalose pathway resided in the TPS step, with flux control coefficients > 70% of the total pathway. Incorporation of the trehalose branch into the original sucrose model showed that reactions from the original model significantly affected the steady-state attributes of the trehalose pathway. Due to the relatively low flux through the trehalose branch of the expanded model, complete recycling of trehalose, and the lack of allosteric regulation by trehalose-6-phosphate or trehalose on any of the reactions from the original sucrose model, incorporation of the trehalose branch had no significant effect on either steady-state cytosolic sucrose concentration or flux of sucrose into the vacuole. The expanded model affords a basis from which to further investigate trehalose metabolism in the context of plant sucrose accumulation.

Fung Man-yi, Wendy. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2000. / Includes bibliographical references (leaves 84-106). / Text in English; abstracts and appendices in English and Chinese. / Fung Man-yi, Wendy. / Acknowledgments --- p.i / Presentation --- p.iii / Abstract --- p.iv / Table of Contents --- p.viii / List of Tables --- p.x / List of Figures --- p.xi / Chapter CHAPTER ONE --- Introduction --- p.1 / Research Background --- p.1 / Purpose of the Study --- p.5 / Justification of the Study --- p.6 / Hypotheses --- p.6 / Definition of Terms --- p.7 / Assumptions --- p.8 / Delimitations --- p.8 / Limitations --- p.9 / Significance of the Study --- p.9 / Chapter CHAPTER TWO --- Review of Literature --- p.10 / "Engergy Metabolism During Prolonged, Submaximal Exercise" --- p.10 / "Causes of Fatigue During Prolonged, Submaximal Exercise" --- p.16 / Factors Influencing Muscle Glycogen Resynthesis During Recovery --- p.21 / Factors Influencing Rehydration During Recovery --- p.27 / Effect of Muscle Glycogen Replenishment During Recovery on Subsequent Endurance Capacity --- p.30 / Effect of Rehydration During Recovery on Subsequent Endurance Capacity --- p.32 / Effect of Glycemic Index Meals Before Exercise on Exercise Performance --- p.33 / Chapter CHAPTER THREE --- Methodology --- p.37 / Participants --- p.37 / Equipment and Instrumentation --- p.37 / Standardized Experimental Procedures --- p.38 / Collection and Analysis of Blood Samples --- p.42 / Preliminary Measurements --- p.45 / Dietary Analyses and Training Control --- p.50 / Preliminary Testing --- p.51 / Statistical Analysis --- p.54 / Chapter CHAPTER FOUR --- Results --- p.56 / Run Time to Exhaustion --- p.56 / Dietary Analysis --- p.57 / Postprandial Responses of the Test Meals During Screening Session --- p.58 / Postprandial Responses During Recovery --- p.60 / Responses During Exercise and Recovery --- p.62 / Body Mass Changes and Fluid Balance --- p.74 / Changes in Plasma Volume and Urine Volume --- p.75 / Summary of the Results --- p.76 / Chapter CHAPTER FIVE --- Discussion --- p.77 / Recommendations and Applications --- p.83 / References --- p.84 / Appendixes --- p.107

Siu Ming Fai Parco. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2001. / Includes bibliographical references (leaves 101-117). / Text in English; abstracts in English and Chinese. / Siu Ming Fai Parco. / Acknowledgments --- p.i / Abstract --- p.iii / Table of Contents --- p.vii / List of Tables --- p.ix / List of Figures --- p.x / Chapter CHAPTER ONE --- Introduction --- p.1 / Research Background --- p.1 / Purpose of the Study --- p.6 / Hypotheses --- p.6 / Definition of Terms --- p.7 / Assumptions --- p.8 / Delimitations --- p.9 / Limitations --- p.9 / Chapter CHAPTER TWO --- Review of Literature --- p.10 / Importance of Muscle Glycogen Resynthesis During Recovery from Exercise --- p.10 / Factors Affecting Muscle Glycogen Resynthesis --- p.10 / Muscle Glycogen Resynthesis and Subsequent Endurance Capacity --- p.17 / Importance of Rehydration on Recovery from exercise --- p.22 / Factors Affecting Rehydration --- p.22 / Rehydration and Subsequent Endurance Capacity --- p.25 / Glycemic Index Foods and Exercise --- p.26 / Definition of Glycemic Index (GI) --- p.26 / Ingestion of GI Foods Before Exercise --- p.28 / Ingestion of GI Foods During Recovery --- p.33 / Frequency of CHO Ingestion and Exercise --- p.36 / Chapter CHAPTER THREE --- Methodology --- p.39 / Participants --- p.39 / Equipment and Instrumentation --- p.39 / Preliminary Measurements --- p.40 / Dietary Analysis and Training Control --- p.45 / Preliminary Testing --- p.46 / Standardized Experimental Procedure --- p.51 / Collection and Analysis of Blood Sample --- p.57 / Statistical Analysis --- p.61 / Chapter CHAPTER FOUR --- Results --- p.62 / Run Time to Exhaustion --- p.63 / Dietary Analysis --- p.63 / Postprandial Responses of the Prescribed Foods During Screening Test --- p.64 / Postprandial Responses During Recovery of Main Trial --- p.67 / Metabolic and Physiological Responses During Exercise and Recovery --- p.70 / "Body Mass Change, Fluid Balance and Urine Volume" --- p.89 / Changes in Plasma Volume --- p.90 / Summary of the Results --- p.91 / Chapter CHAPTER FIVE --- Discussion --- p.92 / Recommendations and Applications --- p.99 / References --- p.101 / Appendices --- p.118

published_or_final_version / Medicine / Master / Doctor of Medicine

Thesis (MSc (Genetics. Plant Biotechnology))--University of Stellenbosch, 2007. / Despite numerous attempts involving a variety of target genes, the identity of the key regulatory genes of sucrose metabolism in sugarcane is still illusive. To date, genomic research into sucrose accumulation in sugarcane has focused on genes that are expressed in association with stalk development/maturation, with the aim of identifying key regulatory steps in sucrose metabolism. The identification of possible controlling points, however, is complicated by the polyploid nature of sugarcane. Although these studies have yielded extensive annotated gene lists and correlative data, the identity of key regulatory genes remains elusive. A close relative of sugarcane, Sorghum bicolor, is diploid, has a small genome size and accumulates sucrose in the stalk parenchyma. The main aim of the work presented in this thesis was to use S. bicolor as a model to identify genes that are differentially expressed during sucrose accumulation in the stalk of low and high sucrose genotypes. In the first part of the study, a macroarray protocol for identification of differentially expressed genes during sorghum development was established. Firstly, the macroarray sensitivity of probe-target hybridisation was optimised with increasing amounts of target DNA i.e. 0.005-0.075 pmol. The hybridisation signal intensity increased as expected with increasing amounts of probe until the hybridisation signals reached maximum levels at 0.05 pmol. As a result, to ensure quantitative cDNA detection, probes were arrayed at 0.05 pmol when 1 μg target cDNA was used. Secondly, intra-array and inter-array membrane reproducibility was found to be high. In addition, the protocol was able to detect species of mRNA at the lowest detection limit tested (0.06%) and permits the detection of an eight-fold variation in transcript levels. The conclusion was therefore that the protocol was reproducible, robust and can reliably detect changes in mRNA levels. In the second part of the study, sugar accumulation levels in the immature and maturing internodal tissues of sorghum GH1 and SH2 genotypes were compared during the boot and softdough stages. Sugars (i.e. fructose, glucose and sucrose) accumulated differently in the immature and maturing internodes in both sorghum genotypes during the boot and softdough stages, with sucrose being the dominant sugar in both stages. Based on these differences in sugar accumulation patterns, immature and maturing internodal tissues of sorghum genotypes were compared for differentially expressed genes. A number of genes were found to be significantly differentially expressed during both stages. In order to validate the reliability of the macroarray analysis, fourteen genes were arbitrarily selected for semi-quantitative RT-PCR. Seven genes (50%) revealed a similar pattern of transcript expression, confirming the macroarray results. The other seven genes, however, showed a different expression trend compared with the macroarrays. In this study, ESTs from rice and sugarcane were used for probing sorghum. The probability of cross-hybridisation between the probes and various isoforms of the homologous sorghum sequences is thus high, potentially leading to the identification of false positives. In addition, variation in expression patterns could have been introduced by technical and biological variation. Lastly, to verify that changes in the levels of a transcript are also reflected in changes in enzyme activity, seven candidates were tested for enzyme activity. Only three i.e. soluble acid invertase (SAI), sucrose synthase (SuSy) and alcohol dehydrogenase (ADH), out of these seven genes showed enzyme activity levels reflective of the relative transcript expression. We concluded that changes in transcript levels may or may not immediately lead to similar changes in enzyme activity. In addition, enzyme activity may be controlled at transcriptional and at posttranscriptional levels. In conclusion, sugar accumulation in low (GH1) and high (SH2) sucrose sorghum genotypes is influenced by differences in gene expression. In addition, the power of macroarrays and confirmation with semi-quantitative RT-PCR for identification of differentially expressed genes in sorghum genotypes was demonstrated. Moreover, the transcript and enzyme activity patterns of SAI, SuSy and ADH genes showed expression patterns similar to those of sugarcane during sucrose accumulation. Therefore, using sorghum as a model promises to enhance and refine our understanding of sucrose accumulation in sugarcane.