This study was designed to evaluate the effect of glucose on plasma pyridoxal 5'- phosphate (PLP) concentration. The objective was to determine whether there was a negative relationship between glucose ingestion and plasma PLP concentration and to evaluate the possible mechanism of decreased PLP after acute glucose ingestion. Seven healthy subjects (three males and four females) completed the oral glucose tolerance test (OGTT) on three separate occasions over a period of three weeks. Each week, subjects ingested the assigned solutions (a water solution with artificial sweetener equivalent to 25g glucose, a 25g glucose or a 75g glucose load) in a randomized order. Plasma PLP, pyridoxal (PL), 4-pyridoxic acid (4-PA), pyridoxine (PN), glucose, insulin, alkaline phosphatase (AP) activity and red blood cell PLP concentrations were measured at 0 (fasting) (TO), 1 (T1), 2 (T2) and 3 (T3) hours. The mean vitamin B-6 intake based on two 3-day dietary records was 1.57 ± 0.34 mg/day. All subjects had normal glucose tolerance. There were gender differences among the three solutions. Both the water solution and the 75g glucose load showed a significant decrease in the mean plasma PLP concentration was observed at T3 for males and at T2 for females (p<0.05). An overall mean decrease of 20% (9nmol/L) and 15% (7 nmol/L) was observed for males and females, respectively, after the 75g glucose load. The 25g glucose load resulted in a lower decrease in the mean plasma PLP concentration at each time point compared with the 75g glucose load, but no significant difference was found in the level of decrease between the two glucose loads. Both genders had a non-significant increase in the mean plasma PL and PN concentrations for the three solutions. Mean plasma 4-PA concentration was decreased at T1 with the three solutions. There was no significant change in the plasma AP activity at any time points after the three solutions. In addition, no significant increase in mean red blood cell PLP concentration was observed at all time points after the three solutions. This study found a negative relationship between glucose ingestion and plasma PLP concentration. However, it did not provide clear evidence for the hypothesized mechanism of the decreased plasma PLP concentration after acute glucose load. Further studies are required to determine the mechanism by which glucose decreases plasma PLP concentration. / Graduation date: 2000

The peripheral and central mechanisms mediating the modulatory effects of glucose and acute stress in rats were investigated using two versions of an appetitive win-stay task. Post-training injections of glucose, but not fructose, enhanced retention on the closed maze task. Acquisition of this task was found to be impaired by lesions of the fimbria-fornix (FF). Further experiments showed that while the celiac ganglion and the FF normally participate in suppressing the memory-enhancing effect of an acute stressor, neither structure is involved in mediating the effect of glucose on memory. Post-training injections of glucose, but not fructose, enhanced retention on the open maze task. Although acquisition of this task was not affected by FF lesions, both the celiac ganglion and the FF participate in mediating the memory-enhancing effect of glucose. Together, the results suggest that the peripheral and central mechanisms studied here are both substance- and task-specific. The modulatory effects of different types of stress, and the issue of whether task acquisition and memory modulation are anatomically distinct are discussed.

No description available.

Yeung Ho Lam. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2006. / Includes bibliographical references (leaves 93-107). / Abstracts in English and Chinese. / Thesis Committee --- p.i / Abstract --- p.ii / 摘要 --- p.iv / Acknowledgments --- p.v / Table of Contents --- p.vi / List of Abbreviations --- p.x / List of Figures --- p.xiii / List of Tables --- p.xv / Chapter CHAPTER 1 --- INTRODUCTION --- p.1 / Chapter 1.1 --- Glucose Transport through the Blood Brain Barrier --- p.1 / Chapter 1.2 --- Roles of Astrocytes in the Brain --- p.4 / Chapter 1.3 --- Glucose Metabolism in Astrocytes --- p.8 / Chapter 1.4 --- Diseases Associated with Reduced Glucose Transport --- p.10 / Chapter 1.5 --- Extracellular Accumulation of Glutamate as a Cause for Epilepsy --- p.13 / Chapter 1.6 --- Regulations of Astrocyte-mediated Glutamate Uptake --- p.17 / Chapter 1.7 --- Aim and Hypothesis of the Project --- p.22 / Chapter CHAPTER 2 --- MATERIALS AND METHODS --- p.24 / Chapter 2.1 --- Materials --- p.24 / Chapter 2.1.1 --- Primary Rat Astrocytes --- p.24 / Chapter 2.1.2 --- Cell Culture Materials --- p.24 / Chapter 2.1.3 --- Chemicals --- p.26 / Chapter 2.1.4 --- Reagents for the Determination of Gene Expressions --- p.26 / Chapter 2.1.5 --- Reagents for the Determination of Protein Expressions --- p.29 / Chapter 2.1.6 --- Reagents for Functional Assays --- p.33 / Chapter 2.1.6.1 --- Reagents for Enzyme-Linked Immunosorbent Assay (ELISA) of IL-6 --- p.33 / Chapter 2.1.6.2 --- Reagents for Glutamate Uptake Assay --- p.33 / Chapter 2.1.6.3 --- Reagents for Extracellular Glutamate Determination Assay --- p.33 / Chapter 2.1.6.4 --- Reagents for Glucose Uptake Assay --- p.34 / Chapter 2.1.6.5 --- Reagents for MTT Assay --- p.34 / Chapter 2.1.6.6 --- Reagents for GFAP Immunostaining --- p.35 / Chapter 2.2 --- Methods --- p.36 / Chapter 2.2.1 --- Preparation of Primary Astrocytes --- p.36 / Chapter 2.2.2 --- Determination of Gene Expressions by Reverse Transcription-Polymersase Chain Reaction (RT-PCR) --- p.37 / Chapter 2.2.3 --- Determination of Protein Expressions by Western Blotting --- p.40 / Chapter 2.2.4 --- ELISA --- p.43 / Chapter 2.2.5 --- Glutamate Uptake Assay --- p.44 / Chapter 2.2.6 --- Extracellular Glutamate Determination Assay --- p.44 / Chapter 2.2.7 --- Glucose Uptake --- p.45 / Chapter 2.2.8 --- MTT Assay --- p.46 / Chapter 2.2.9 --- GFAP Immunostaining --- p.46 / Chapter 2.2.10 --- Band Intensity Quantification --- p.47 / Chapter 2.2.11 --- Statistical Analysis --- p.47 / Chapter CHAPTER 3 --- RESULTS --- p.49 / Chapter 3.1 --- Preparation of Primary Astrocyte Culture --- p.49 / Chapter 3.2 --- Effects of Glucose Deficiency on Astrocyte-mediated Glutamate Uptake --- p.51 / Chapter 3.2.1 --- Effects of Glucose Deficiency on the Expressions of Glutamate Transporters --- p.51 / Chapter 3.2.2 --- Effects of Glucose Deficiency on Glutamate Uptake in Primary Astrocytes --- p.56 / Chapter 3.3 --- Astrocytic Glucose Transport under Glucose Deficiency --- p.61 / Chapter 3.3.1 --- Effects of Glucose Deficiency on the Expressions and Secretion of Inflammatory Cytokines --- p.64 / Chapter 3.3.2 --- Effects of Exogenous Interleukin-6 on Energy Availability in Primary Astrocytes upon Glucose Deficiency --- p.70 / Chapter 3.4 --- Signaling Mechanism Mediating the Astrocytic Responses under Glucose Deficiency --- p.74 / Chapter 3.4.1 --- Effects of Glucose Deficiency on the Expressions of Total and Phosphorylated ERK1/2 in Primary Astrocytes --- p.74 / Chapter CHAPTER 4 --- DISCUSSIONS AND CONCLUSIONS --- p.81 / Chapter 4.1 --- Role of Astrocytes in Preventing Glutamate Excitotoxicity under Glucose Deficiency --- p.81 / Chapter 4.1.1 --- Neonatal Astrocytes as the Cell Model for Chronic Glucose Deficiency --- p.81 / Chapter 4.1.2 --- Effects of Glucose Deficiency on the Expressions of Glutamate Transporters and Glutamate Uptake --- p.83 / Chapter 4.1.3 --- Cytokines: Mediators for Energy Production in Astrocytes --- p.85 / Chapter 4.1.4 --- Summary of the Roles of Astrocyets under Prolonged Glucose Deficiency --- p.88 / Chapter 4.2 --- Establishment of an in vitro GlutlDS model --- p.89 / Chapter 4.3 --- Future Directions of the Project --- p.90 / Chapter 4.4 --- Conclusion --- p.92 / REFERENCES --- p.93 / APPENDIX --- p.108

The burgeoning adoption of modern technologies provides a great opportunity for gathering multiple modalities of comprehensive personalized data on individuals. The thesis aims to address statistical challenges in analyzing these data, including patient-specific biomarkers, digital phenotypes and clinical data available from the electronic health records (EHRs) linked with other data sources to achieve precision medicine. The first part of the thesis introduces a dimension reduction method of microbiome data to facilitate subsequent analysis such as regression and clustering. We adopt the proposed zero-inflated Poisson factor analysis (ZIPFA) model on the Oral Infections, Glucose Intolerance and Insulin Resistance Study (ORIGINS) and provide valuable insights into the relation between subgingival microbiome and periodontal disease. The second part focuses on modeling the intensive longitudinal digital phenotypes collected by mobile devices. We develop a method based on a generalized state-space model to estimate the latent process of patient's health status. The application to the Mobile Parkinson's Observatory for Worldwide Evidence-based Research (mPower) data reveals the low-rank structure of digital phenotypes and infers the short-term and long-term Levodopa treatment effect. The third part proposes a self-matched learning method to learn individualized treatment rule (ITR) from longitudinal EHR data. The medical history data in EHRs provide the opportunity to alleviate unmeasured time-invariant confounding by matching different periods of treatments within the same patient (self-controlled matching). We estimate the ITR for type 2 diabetes patients for reducing the risk of diabetes-related complications using the EHRs data from New York Presbyterian (NYP) hospital. Furthermore, we include an additional example of self-controlled case series (SCCS) study on the side effect of stimulants. Significant associations between the use of stimulants and mortality are found from both FDA Adverse Event Reporting System and the SCCS study, but the latter uses a much smaller sample size which suggests high efficiency of the SCCS design.

Exercise has a wide range of benefits for patients with type 1 diabetes, including improvements in body composition, cardiovascular risk profile and glycaemic control. Unfortunately, exercise also increases the risk of hypoglycaemia in children with type 1 diabetes, both at the time of exercise and for many hours afterwards. The availability of clear, evidence-based guidelines regarding appropriate adjustments in carbohydrate intake or insulin doses may help to prevent this exercise associated hypoglycaemia. However, current guidelines regarding exercise in children with type 1 diabetes rely heavily on adult literature or the consensus of experts. Therefore, further studies are needed in young people with diabetes to document the metabolic responses during and following exercise. In particular, the mechanisms underlying hypoglycaemia occurring many hours after exercise require further exploration. In addition, as children often exercise in the afternoon, studies performed at this time of the day are more likely to be transferrable to a real life situation. For this reason, we studied adolescents with type 1 diabetes to investigate physiological responses to exercise, focusing on afternoon activity and employing a novel variation of the euglycaemic insulin clamp technique. The core experiments involved studying diabetic adolescents on two occasions in a counterbalanced, paired design during and after afternoon exercise. Insulin was infused at a constant rate based on the subjects' usual daily insulin dose and glucose was infused to maintain euglycaemia. At 1600 hrs subjects either exercised at a moderate intensity (95% of their lactate threshold) for 45 minutes on a cycle ergometer (exercise study), or sat on the ergometer without exercising (rest study). Using this experimental design, it was found that glucose infusion rates (GIR) to maintain euglycaemia were elevated during and shortly following exercise and again from 7-11 hours after exercise compared with the rest study. Counterregulatory hormone levels were similar between the exercise and rest studies except for peaks in noradrenaline, cortisol and growth hormone levels at the end of exercise. Glucagon and adrenaline levels did not increase with exercise. The observed biphasic increase in glucose requirements paralleled the observed clinical risk of hypoglycaemia immediately during exercise and the delayed risk of hypoglycaemia which often occurs overnight.

TRPV channels play a role in both mammalian insulin signaling, with TRPV1 expression in pancreatic beta-cells, and in C. elegans insulin-like signaling through expression of OSM-9, OCR-1, and OCR-2 in stress response pathways. In response to a glucose-supplemented diet, C. elegans are know to have sensitivity to anoxic stress, exhibit chemotaxis attraction, and display reduced egg-laying rate. Transcriptome analysis reveals that glucose stimulates nervous system activity with increased transcript levels of genes regulating neurotransmitters. Ciliated sensory neurons are needed for a reduced egg-laying phenotype on a glucose-supplemented diet. Egg-laying rate is not affected when worms graze on glucose-supplemented Delta-PTS OP50 E. coli, which is defective in glucose uptake. This suggests a possible sensory neuron obstruction by exopolysaccharides produced by standard OP50 E. coli on glucose, eliciting a starvation response from the worm and causing reduced egg-laying rate. Glucose chemotaxis is affected in specific TRPV subunit allele mutants: ocr-2(vs29) and osm-9(yz6), serotonin receptor mutants: ser-1(ok345) and mod-1(ok103), and G-alpha protein mutant: gpa-10(pk362). TRPV deletion mutants had no effect on glucose chemotaxis, alluding to the modality role pf TRPV alleles in specific sensory neurons. The role of serotonin in a reduced egg-laying rate with glucose remains unclear.