The Australian HIV Observational Database (AHOD) is a collaboration of hospitals, sexual health clinics and specialist general practices throughout Australia, established in April 1999. Core data variables collected include demographic data, immunological and virological markers, AIDS diagnosis, antiretroviral and prophylactic treatment and cause of death. The first electronic data transfer occurred in September 1999 followed by six monthly data transfers thereafter. All analyses included in this thesis are based on patients recruited to AHOD by March 2004. By March 2004, 2329 patients had been recruited to AHOD from 27 sites throughout Australia. Of these, 352 (15%) patients were recruited from non-metropolitan clinics. The majority of patients were male (94%), and infected with HIV through male homosexual contact (73%). Almost 90% of AHOD patients are antiretroviral treatment experience, and the majority of patients are receiving triple therapy as mandated by standard of care guidelines in Australia. Antiretroviral treatment use has changed in Australia reflecting changes in the availability of new treatment strategies and agents. The crude mortality rate was 1.58 per 100 person years, and of the 105 deaths, more than half died from HIV-unrelated deaths. The prevalence of HBV and HCV in AHOD was 4.8% and 10.9%, respectively. HIV disease progression in the era of highly active antiretroviral treatment (HAART) among AHOD patients is consistent with what has been reported in developed countries. Common factors associated with HIV disease progression were low CD4 cell count, high viral load and prior treatment with mono or double therapy at the time of commencing HAART. This was demonstrated in AHOD in terms of long-term CD4 cell response, the rate of changing combination antiretroviral therapy and factors predicting death. HBV and HCV coinfection is also relatively common in AHOD, similar to other developed country cohorts. Coinfection does not appear to be serious impediments to the treatment of HIV infected patients. However, HIV disease outcome following HAART does appear to be adversely affected by HIV/HCV coinfection but not in terms of HIV/HBV coinfection. Patients attending non-metropolitan sites were found to be similar to those attending metropolitan sites in terms of both immunological response and survival.

[Formulae and special characters can only be approximated here. Please see the pdf version of the abstract for an accurate reproduction.] Atherosclerosis is a common degenerative disease in which the clinical manifestations are often through stroke or myocardial infarction. Some of the established risk factors for atherosclerosis include elevated plasma low-density lipoprotein (LDL)-cholesterol levels, obesity, diabetes mellitus (DM) and cigarette smoking. Of the risk factors, an elevation in plasma LDL is one of the most established and the most researched. This is partly a consequence of the deposition of cholesterol within arterial intima being a crucial step in the progression of atherosclerosis, combined with the finding that LDL particles are a major transporter of cholesterol in circulation. Recently there is increasing evidence showing a role of the other major transporter of cholesterol in circulation, chylomicron remnants, in the progression of atherosclerosis. The notion of atherosclerosis as a postprandial phenomenon has been further substantiated by the emergence of evidence showing a direct role of chylomicron remnants in arterial cholesterol deposition. Based on evidence that chylomicron remnants are proatherogenic, the suggestion arises that accumulation of postprandial lipoproteins in plasma may add another dimension of risk to the development of coronary artery disease (CAD). This thesis tests the general hypothesis that individuals with or at high risk of CAD have postprandial dyslipidaemia and that this metabolic abnormality is correctable with a class of lipid-lowering drugs called statins. To test the hypothesis, clinical studies were conducted in normolipidaemic CAD patients, heterozygous familial hypercholesterolaemia (FH) and postmenopausal women with type 2 DM. Determination of postprandial dyslipidaemia by comparison with control populations were conducted initially in each patient group (Studies 1, 3 and 5), followed by intervention studies investigating possible modulation of the dyslipidaemia with a statin (Studies 2, 4 and 6). Six observation statements based on case-control comparisons of postprandial lipaemia in patients with or at risk of CAD and the effects of statins on postprandial dyslipidaemia in the patient groups were derived from the general hypothesis. The observation statements were examined in the individual studies described below. Postprandial lipoprotein metabolism was assessed using a number of methods. For comparison of postprandial lipaemia in Studies 1 and 2, a classic oral fat challenge was utilised. As markers of chylomicrons and chylomicron remnants, retinyl palmitate and triglyceride were measured postprandially as well as apolipoprotein (apo) B48 concentrations, a specific marker of intestinal lipoproteins. ApoB48 was also measured in the fasting state and found to predict the postprandial responses of retinyl palmitate, triglyceride and apoB48. This suggested that fasting measurement of apoB48 could be used as a simple indicator of postprandial dyslipidaemia. Consequently for Studies 3 - 6, fasting apoB48 measurements were used as primary markers of postprandial dyslipidaemia. Other markers for chylomicrons and their remnants utilised were fasting plasma concentrations of remnant-like particle-cholesterol (RLP-C) and apoC-III. As well as these static markers, chylomicron remnant catabolism was measured using a stable isotope breath test. The breath test involves the intravenous injection of a chylomicron remnant-like emulsion labelled with ¹³C-oleate and measurement of enriched ¹³CO2 in expired breath by isotope ratio mass spectrometry. The fractional catabolic rate (FCR) of the injected emulsion was subsequently calculated using multi-compartmental modeling (SAAM II). The studies are presented in this thesis as published and unpublished works. In Study 1, postprandial lipoprotein metabolism was compared between 18 normolipidaemic CAD patients (cholesterol 4.54 ± 0.12 mmol/L, triglyceride 1.09 ± 0.16) with 13 asymptomatic healthy controls using an oral fat challenge. Normolipidaemic CAD patients had higher postprandial area-under-curve (AUC) for triglyceride (+34%, p=0.019), retinyl palmitate (+74%, p=0.032) and apoB48 (+36%, p<0.001). Fasting apoB48 was also higher (+41%, p=0.001) and found to correlate significantly with AUC of triglyceride (p=0.017), retinyl palmitate (p=0.001) and apoB48 (p<0.001). The data suggest that normolipidaemic CAD patients have increased concentrations of intestinal lipoproteins in the fasting and postprandial state. In addition to these findings, significant correlations of fasting apoB48 with postprandial markers (p<0.02) suggests the fasting marker to be a simpler surrogate marker for the degree of total postprandial lipaemia. Study 2 investigated the effect of atorvastatin treatment on postprandial dyslipidaemia found in the 18 near-normolipidaemic CAD patients from Study 1. The trial was conducted in a randomised, placebo-controlled design, using oral fat challenges before and after 12-weeks atorvastatin/placebo treatment. Compared with the placebo group, atorvastatin decreased the total postprandial AUC for iii triglyceride (-22%, p=0.05) and apoB48 (-34%, p=0.013). Fasting markers of apoB48 (-35%, p=0.019) and RLP-C (-36%, p=0.032) also decreased significantly. Atorvastatin was also found to increase LDL-receptor activity by +218% (p<0.001) as reflected in binding studies. The data suggest atorvastatin reduces the fasting levels of intestinal lipoproteins as well as total postprandial lipaemia, but without acute dynamic changes in postprandial lipaemia. The reduction in fasting and total postprandial lipoprotein levels could be partly attributed to an increase in LDL-receptor mediated removal from circulation. In Study 3, postprandial lipaemia was compared in 15 heterozygous FH patients with 15 healthy controls. FH patients had higher fasting concentrations of apoB48 (+56%, p<0.001) and RLP-C (+48%, p=0.003). The elevation in these fasting markers of chylomicrons and their remnants suggests FH patients have postprandial dyslipidaemia due to an accumulation of these particles in plasma. Study 4 examined the effects of long- (> 6 months) and short-term (4 weeks) simvastatin treatment on modulating postprandial dyslipidaemia found in the 15 FH patients from Study 3. Short- and long-term simvastatin treatment decreased the fasting concentrations of apoB48 (-29% and 15% respectively, p<0.05) and RLP-C (both -38%, p<0.001), but did not significantly alter the FCR of the injected chylomicron remnant-like emulsion. The data suggest that in heterozygous FH both long- and short-term simvastatin treatments decrease the fasting markers of postprandial lipoproteins by mechanisms that may not be mediated via processes differentiated by the 13CO2 breath test. This implies that the effect on postprandial lipaemia may be from a decrease in production and/or a possible increase in catabolism of triglyceride-rich lipoproteins (TRLs). In Study 5, postprandial lipaemia was compared in 24 postmenopausal women age and body mass index matched with 14 postmenopausal women with type 2 DM. Postmenopausal diabetic women were found to have higher fasting concentrations of apoB48 (+21%, p=0.021) and apoC-III (+16%, p=0.042) as well as lower FCR of the chylomicron remnant-like emulsion (-50%, p<0.001). The data suggest that postmenopausal diabetic women have postprandial dyslipidaemia, and that this is due to delayed catabolism of chylomicron remnants. Study 6 was an hypothesis-generating exercise examining the effects of 4-weeks pravastatin treatment on postprandial dyslipidaemia found in 7 postmenopausal women with type 2 DM from Study 5. Although plasma LDL-cholesterol was reduced (-19%, p=0.028), there were no significant effects found on fasting apoB48 concentrations (-12%, p=0.116) or the FCR of the chylomicron remnant-like emulsion (+38%, p=0.345). A larger sample size of patients and/or treatment with a more potent statin at a dosage known to affect chylomicron remnant metabolism would be required to demonstrate a significant reduction in postprandial dyslipidaemia in postmenopausal women with type 2 DM. The results of the above mentioned studies combined support the general hypothesis that postprandial dyslipidaemia is a feature of patients with or at risk of CAD. This defect may be demonstrated using fasting apoB48 as an indicator of the degree of postprandial lipaemia. Postprandial dyslipidaemia may reflect a reduction in catabolism, as suggested with the breath test in type 2 DM, and/or an over overproduction of chylomicrons. Both these mechanisms would also increase competition for lipolysis and clearance pathways between hepatically and intestinally-derived lipoproteins. The exact mechanisms by which postprandial dyslipidaemia occurs are yet to be determined. Statins appear to improve defective postprandial lipaemia in patients with or at risk of CAD, which is in agreement with the general hypothesis. The effectiveness of a statin is dependant on their potency in inhibiting cholesterol biosynthesis and increasing receptor mediated clearance of LDL and chylomicron remnants. The studies conducted in this thesis show that postprandial dyslipidaemia can be reduced by statins but not to the extent demonstrated in controls. However, the demonstrated reduction in fasting and total postprandial lipaemia translates to a lowering in overall arterial exposure to circulating proatherogenic particles. The elevation in fasting and postprandial levels of proatherogenic chylomicron remnants found in the patient groups described in this thesis indicates another dimension to their risk of coronary disease. The reductions in the overall levels of proatherogenic particles in patients with or at high CAD risk, infers a possible reduction in the risk of coronary disease in these patients.

Doctorat en Sciences médicales / info:eu-repo/semantics/nonPublished

Tuberous sclerosis complex (TSC) is a multisystem tumor-forming disorder caused by biallelic inactivation of TSC1 or TSC2. The primary cause of mortality arises from mesenchymal manifestations in the lung and kidney: pulmonary lymphangioleiomyomatosis (LAM) and renal angiomyolipomas (RAMLs). Despite a well-described monogenic etiology, there remains an incomplete understanding of disease pathogenesis. Consequentially, tractable models which fully recapitulate disease characteristics are lacking. Here, I develop and study novel tissue-engineered models of TSC lung and kidney disease. In my first chapter, I demonstrate that lung-mimetic hydrogel culture of pluripotent stem cell-derived diseased cells more faithfully recapitulates human LAM biology compared to conventional culture on two-dimensional plastic. Leveraging this culture system, I conducted a three-dimensional drug screen using a custom 800-compound library, tracking cytotoxicity and invasion modulation phenotypes at the single cell level. I identified histone deacetylase (HDAC) inhibitors as a group of anti-invasive agents that are also selectively cytotoxic towards TSC2-/- cells. HDAC inhibitor therapeutic effects remained consistent in vivo upon xenotransplantation of LAM cellular models into zebrafish. In my second chapter, I develop a genetically-engineered human renal organoid model which recapitulates pleiotropic features of RAMLs in vitro and upon orthotopic xenotransplantation. I find that loss of TSC1/2 affects multiple developmental processes in the renal epithelial, stromal, and glial compartments. First, loss of TSC1/2 leads to an expanded stroma by favouring stromal cell fate acquisition and alters terminal stromal cell identity. Second, epithelial cells in the TSC1/2-/- organoids exhibit a rapamycin-insensitive epithelial-to-mesenchymal transition. Third, a melanocytic population forms exclusively in TSC1/2-/- organoids, branching from MITF+ Schwann cell precursors of a bona fide neural crest-to-Schwann cell differentiation trajectory. Through these two thesis chapters, I realize the power of tissue-engineered models for the study of TSC. This work offers novel insights into the pathogenesis of RAMLs and identifies a new class of therapeutics suitable for trialing in patients with pulmonary LAM.

Alzheimer's disease (AD) is the most common form of dementia. As the prevalence of AD increases with age, population aging will inevitably lead to an exponential increase in the proportion of older persons suffering from this disease. According to 2005 WHO estimate, 26.6 million people (approximately 0.55% of the general population) suffered from this disease. AD not only affects intellectual and functional abilities, it is also associated with significant neuropsychiatric disturbances. The pathogenesis of AD is characterized by widespread cerebral atrophy, abnormal deposition of amyloid plaques and tau protein in the central nervous system. While the classical histopathological features of AD are well recognized, exact physiological mechanisms that initiate the cascade of neural degeneration are still under active investigation. / As mentioned, the telomere length studies focused on ethically Chinese subjects recruited from two independent samples. The first clinical sample consisted of 411 older people and the other sample from healthy aging study, 976 community dwelling men were recruited. All subjects were assessed with the Cantonese version of the Mini-mental State Examination (CMMSE) for global cognitive function. Genomic DNA of the subjects was extracted from the peripheral whole blood sample. Lengths of the telomere were measured with Quantitative Real-Time PCR and the Ct ratio of the telomere and a control gene (36B4) of each sample was compared with the standard curve constructed with 4 selected sample's telomere lengths measured previously by Southern blotting. / For the first association study of the cell cycle checkpoint genes and AD, sample was recruited from a prospective study of cognitive function and risk factors for development of AD. 701 elderly were clinically evaluated for diagnosis of AD by psychiatrists. For this sample, genotyping of tagging SNPs of the 10 cell-cycle checkpoint genes were carried out by Restriction Fragment Length Polymorphism (RFLP) analysis. All tagging SNPs were selected from HapMap database and 5000bp upstream and downstream regions of each gene was also included. / For the results, the association study with cell cycle checkpoint genes, there was no SNPs found to be associated with diagnosis of clinical AD. We also found out that telomere length was associated with age in both two healthy aging men and clinical samples. There was no association between education and telomere lengths. For subjects in the healthy aging study, participants with CMMSE scores fell into the lowest 25% were found to have shorter telomere lengths. Similar result was found in the clinical AD sample. / In the study, telomere lengths were negatively associated with age. As the telomere will be shortened for each cell cycle, this finding correlated with physiological function at a cellular level. Statistical analysis also showed that shorter telomere lengths were found in subjects with poorer cognitive function. However, as age is a major determinant for cognitive impairments, further studies are recommended to evaluate the interaction effects of age in this association. Telomere shortening will cause cell senescence, and may be associated with faster neuronal degeneration, thus affecting cognitive function. Further studies should be conducted to examine its usefulness as an adjuvant biomarker for risk stratification of AD intervention trials. / Recent researches begin to unfold the physiological significance of telomere. A telomere is a repetitive region at the end of a chromosome. Basic functions of telomeres are involved with protection of the chromosome during replication and preventing chromosomal rearrangement or fusion. Abnormal telomere lengthening may be related to cancerous conditions. At a cellular level, telomere may also be related to aging and limitation in cell lifespan. In my study, I aimed to evaluate the association between the lengths of telomere and global cognitive function in community dwelling Chinese older persons in Hong Kong. As the length of telomere is also determined by the turnover rates of cells, apart from association study of telomere lengths and cognitive function, I also tried to study the association of genes related to cell cycles and AD. Polymorphisms of ten cell-cycle checkpoint genes, i.e. RB1, CDKN1A, CDK5R1, CDK2AP1, CDKN2A, CDKN2C, MDM2, P53, GSK3B, TPND1 and CDKN1B genes, were chosen in my project. / The thesis comprised of three studies. The first study was an association study of cell cycle checkpoint gene single nucleotide polymorphisms (SNPs) with clinical diagnosis of AD. The second study was an association study of telomere lengths and clinical diagnosis of AD in a clinical sample of patients suffering from the disease. The third study was an association study of the telomere lengths and global cognitive status in a group of active community dwelling older men who participated in a healthy aging study. / Lau, San Shing. / Adviser: Linda C.W. Lam. / Source: Dissertation Abstracts International, Volume: 73-01, Section: B, page: . / Thesis (Ph.D.)--Chinese University of Hong Kong, 2010. / Includes bibliographical references (leaves 101-124). / 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, [201-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese.