Thesis (Ph. D.)--University of Hong Kong, 2010. / Includes bibliographical references (leaves 168-194). Also available in print.

The purpose of this study was to design and develop anti-hyperglycemic functional foods containing phenolic carbohydrate absorption modulator. Physical, chemical, structural and digestive aspects of the reactions of carbohydrates in the presence of phenolic extracts of traditional Chinese medicines were investigated. Water extracts of 14 traditional Chinese medicinal (TCM) plants with reputation of usefulness in treating diabetes were examined for total phenolic contents, antioxidant activities and α-amylase inhibitory activities through in vitro assays. A positive and significant linear relationship between total phenolic content and antioxidant capacity was found (R2=0.99), indicating that the phenolic compounds are the major antioxidant components in the tested materials. Extract of Chinese galls from Rhus chinensis exhibited highest total phenolic content, antioxidant capacity and α-amylase inhibitory activities. The results of this study demonstrate that the extract of Rhus chinensis would be the most effective carbohydrate modulator among the samples tested. Swelling, pasting and thermal properties of wheat and potato starch were studied in the presence of aqueous extract of Galla chinensis (GAC), also known as Chinese galls. The swelling factor was reduced in both starches after GAC extract addition. The extract increased peak viscosity and cold paste viscosity of wheat starch, but decreased those of potato starch. Increased breakdown has shown for wheat starch, but that for potato starch decreased. GAC extract also delayed gelatinization of both starches with higher onset temperature (To). The results of this study demonstrated that GAC extract supplementation can alter the physicochemical properties of wheat and potato starch. To examine the potential application of Galla chinensis (GAC) extract supplementation in Asian white salted noodles, the effects of various GAC extract addition levels on microstructure and in vitro starch digestibility of noodles were investigated. Scanning electron microscopy (SEM) indicated that the gluten protein network was improved (more compact and smooth) by GAC extract in both raw and cooked noodles. The estimated glycemic index (GI) was significantly decreased from 100 to 90.6 after 0.5% GAC extract was added. This indicated that GAC extract supplementation could reduce starch digestibility and blood glucose response. This feature might make GAC extract-enriched noodles sufficiently attractive to health-conscious consumers. / published_or_final_version / Biological Sciences / Master / Master of Philosophy

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Made available in DSpace on 2014-06-11T19:35:12Z (GMT). No. of bitstreams: 0 Previous issue date: 2011-07-01Bitstream added on 2014-06-13T18:46:39Z : No. of bitstreams: 1 vinagre_rco_dr_botfm.pdf: 1054866 bytes, checksum: ee066b9cb1949e3009b9f6c77af3b92c (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / A isquemia/reperfusão (I/R) provoca lesão nas células renais, que pode ser potencializada pela ocorrência de hiperglicemia, em ratos anestesiados com isoflurano. Sabe-se que a melatonina apresenta efeito protetor em órgãos, atuando nos produtos do estresse oxidativo. Os objetivos foram avaliar se a melatonina oferece proteção renal na I/R associada à hiperglicemia transitória e se potencializa a ação protetora do isoflurano. Foram estudados 36 ratos Wistar machos distribuídos, aleatoriamente, em seis Grupos: MH – Melatonina e Hiperglicemia; M - Melatonina; H - Hiperglicemia; I - Isoflurano SH – Sham e Hiperglicemia e S - Sham. Todos os ratos foram anestesiados com isoflurano em concentrações entre 1 a 3%. A pressão arterial média (PAM), a temperatura e saturação de oxigênio foram aferidas ao longo do experimento. Hiperglicemia foi induzida com 2,5 g.kg-1 de solução de glicose a 50% e a melatonina utilizada na dose de 20 mg.kg-1, ambas por via intraperitoneal. Todos os animais foram submetidos à nefrectomia direita. Nos grupos SH e S não houve isquemia. Os valores da glicemia (mg.dL-1) e da creatinina (mg.dL-1) foram obtidos através de coleta de sangue na artéria carótida em três momentos: após finalizada a dissecção da artéria carótida esquerda (M1), imediatamente antes da retirada do “clamp” da artéria renal esquerda (M2) e 24 horas após, imediatamente após a nefrectomia esquerda (M3), quando os animais retornaram ao laboratório foram anestesiados com a mesma técnica para coleta da última amostra sanguínea. O rim retirado foi preparado e enviado para análise histológica, realizada através da escala para avaliação da necrose tubular (0 a 5 = lesão máxima). Houve tratamento estatístico para os valores: peso, temperatura, saturação de oxigênio, PAM, glicose, creatinina e escore de lesão histológica. Não houve diferença entre o peso... / Ischemia/reperfusion (I/R) cause renal cell injury that may be worsened by hyperglycemia in rats anesthetized with isoflurane. N-acetyl-5- methoxytryptamine (melatonin) is known to have a protective effect on multiple organs by acting on the products of oxidative stress. The objectives of this study were to determine whether melatonin provides renal protection during I/R associated with transient hyperglycemia, and whether it enhances isoflurane protective action. Thirty-six Wistar male rats were randomly allocated into six groups: MH – hyperglycemia and melatonin; M - melatonin; H - hyperglycemia; I – isoflurane, SH – sham and hyperglycemia, and S - sham. All rats were anesthetized with isoflurane at concentrations of 1 to 3%. Mean arterial pressure (MAP), temperature and oxygen saturation were measured throughout the experiment. Hyperglycemia was induced by intraperitoneal 2.5 g.kg-1 of glucose solution at 50%, and 20 mg.kg-1 of melatonin. All animals underwent right side nephrectomy. There was no ischemia in groups SH and S. Glycemia (mg.dL-1) and creatinine (mg.dL-1) values were obtained through the collection of blood from the carotid artery at three time points: following anesthesia and dissection of the left carotid artery (M1), immediately before left renal artery declamping (M2), and 24 hours after the end of the experiment, immediately following left nephrectomy (M3), when the animals returned to the laboratory and were anesthetized by the same technique for the last blood collection. The kidney was removed for histologic analysis, which was performed using the tubular necrosis score system (0 to 5 = maximum lesion). Weight, temperature, oxygen saturation, MAP, glucose, creatinine and histologic lesion score values were statistically treated. No difference in weight, temperature and oxygen saturation were observed. MAP parameters showed statistically significant... (Complete abstract click electronic access below)

This work investigates ways to prevent and manage hyperglycemia using preventive nutrition. Uncontrolled and chronic hyperglycemia is a global health issue leading to many health problems including diabetes. This thesis details the manipulation of highly retrograded starch particles in order to produce particles that are digested slowly to release glucose at a prolonged and moderate rate to prevent this. The first section of this study utilized acid hydrolysis to alter starch structure and change digestibility. The hydrolysis treatment showed that hydrolysis of native starch prior to particle formation changed the structure in a way that increased digestibility. The second section of this work introduced polyphenols into the particles which only a marginal effect on digestion. Overall the actual process of retrograding and making the particles themselves appeared to create particles that were more resistant to digestion. These could be used in a product to deliver a moderate glycemic response.

Towards the creation of the next generation of biomedical implants that effectively integrate in tissues, understanding cell behaviour at the material-host interface to control and optimize the biological outcome is a crucial endeavour. It is now well known that the nanoscale surface properties of biomaterials play a significant role in directing the activity of adherent cells at the implant-host tissue interface. A variety of cellular functions, ranging from adhesion and proliferation to differentiation along specific lineages, are guided by the nanoscale topographical and physicochemical features of the substrate. This evidence reaffirms the role of surface features on eliciting an enhanced response of cells towards improved biological outcomes (e.g., bone integration) of implanted biomaterials. In this context, Titanium (Ti) and its alloys are popular biomaterials widely used in orthopedic, dental, and cardiovascular applications. In particular, in the field of osseointegrated devices, chemical treatments of titanium, specifically oxidative nanopatterning (i.e., a simple yet effective treatment with a H₂SO₄/H₂O₂ solution), have shown to be a promising strategy for guiding and controlling the fate of relevant cells (e.g., osteoblasts, stem cells), thereby achieving the ability to direct the biological response towards the desired outcome. In this context, the sponge-like nanoporous surface resulting from oxidative nanopatterning of titanium allows direct surface cueing to bone cells. It also has the capacity to selectively regulate cell behaviour, modulate the expression of crucial determinants of cell activity, and offers the potential to harness the power of stem cells. However, the mechanisms that control how cells sense and respond to these nanometric cues are still elusive. A novel strategy to elucidate them takes inspiration from in-vivo protocols, where "knock-out" animal models are used to determine the role of a specific gene. Based on this, I propose an original approach aimed at investigating cell response under conditions known to affect specific cellular processes, thereby determining whether these activities can be rescued by direct cueing by the substrate, ultimately elucidating their implication in responding to a given nanostructured substrate. In particular, hyperglycemic culturing conditions often used to mimic diabetes in-vitro are known to exert detrimental effects on the proliferation and differentiation of osteoblasts, and thereby could be an excellent opportunity to test whether the nanometric surface features resulting from oxidative nanopatterning of titanium also possess the ability to compensate to the cell-level changes caused by higher levels of glucose. This would ultimately demonstrate a direct effect of the substrate on these events and help us understand the mechanisms involved in cell-biomaterial interactions. To address this challenge, I propose to investigate the response of human MG-63 osteoblastic cells to nanoporous titanium under hyperglycemic conditions. The goal is, therefore, to understand whether direct nanotopographical cueing at the nanoscale can rescue MG-63 cells from the effects of hyperglycemia, thereby casting new light on the mechanisms underlying the interactions between this widely used cell line and nanoporous titanium. In parallel, results from my work aim at providing new fundamental evidence to interpret results from that body of literature that uses high glucose content as a way to mimic the osseointegration of biomaterials in diabetic conditions.

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Obesity is a major predictor for type 2 diabetes. The etiology and comorbidities of these two diseases are associated. Diabetics are twice as likely to contract any type of infection and at greater risk of worse clinical outcomes to infection. However, the individual effects of diet, glycemia and obesity on risk and severity of enteric infection has not been elucidated. Here we show that high blood glucose (i.e. hyperglycemia), independent of obesity, is sufficient to promote mortality during infection with Citrobacter rodentium, a diarrhea-causing pathogen in mice. Mortality was caused by dehydration as a result of excessive Wnt/β-catenin signalling. Our findings highlight the importance of glucose lowering and fluid therapy as opposed to immunological dysfunction, gut barrier defects or bacteraemia as modifiers of outcomes from enteric infection during diabetes. Future work should develop a more comprehensive understanding of the molecular changes that connect hyperglycemia, Wnt/β-catenin pathway and fluid balance during infection. We used the most common model to cause diet-induced obesity in mice to study another enteric pathogen. We showed that long- and short-term high-fat diet (HFD) feeding promoted the colonization and expansion of adherent-invasive Escherichia coli. Higher pathogen burdens in the intestinal tissues and feces were detected in diet-induced obese mice, which coincided with increased distal gut pathology. Initiating the diet one day prior or after infection was sufficient to promote the expansion of adherent-invasive E. coli in the absence of robust weight gain implicating components of diet as a major determinant of pathogen burden. We isolated the dietary factor and found that low fibre content of the high-fat diet was partially responsible for the increased intestinal pathogen burden. Future work should determine how lower fibre alters host and bacterial metabolism in order to promote overgrowth of adherent-invasive E. coli in the gut. / Thesis / Doctor of Philosophy (PhD) / Obesity and diabetes are major public health issues that are connected in many ways, including how diet changes glucose metabolism. Diabetics have a higher risk of contracting infections and also have worse outcomes from infections. It was unknown what factors of obesity or diabetes influence how the immune system combats bacterial infections. The gut is an important site as it is where diet, the immune system, and metabolism all directly interact. We discovered that high blood sugar was associated with death related to dehydration in diabetic, but not necessarily obese mice infected with a diarrhea causing bacteria. Diet-induced obesity in mice infected with bacteria associated with Crohn's disease, showed an overgrowth of bacteria and worse intestinal damage. We isolated the key dietary factor responsible, which was low fibre rather than high fat or sugar. Even one day of lower dietary fibre promoted overgrowth of infectious bacteria in the gut.

published_or_final_version / Obstetrics and Gynaecology / Master / Master of Philosophy

published_or_final_version / Obstetrics and Gynaecology / Doctoral / Doctor of Philosophy