The overall objective of this thesis was to test the hypothesis that through developmental programming maternal overnutrition-induced metabolic derangements in the offspring could be offset by supplementing the maternal diet with green tea epigallocatechin gallate (GTEG). The obesogenic diet was a high-fat (HF, 30%) diet. Female Sprague-Dawley rats were fed the HF, low-fat (LF, 7%) or HF diet containing 0.75% or 1.0% GTEG (GT1, GT2) from before conception and throughout gestation and lactation. Both doses of GTEG significantly improved metabolic control of the HF-fed lactating dams. The weaned male pups received the HF, GT1 or GT2 diet forming 6 dam/pup groups: LF/HF, HF/HF, HF/GT1, HF/GT2, GT1/HF and GT2/HF. At wk 13 they had similar weight but insulin resistance index (IRI), serum non-esterified fatty acid (NEFA) and liver triglyceride of rats born to GTEG dams was 57, 23 and 26% lower and accompanied by improved gene/protein expressions related to lipid and glucose metabolism compared to HF/HF rats (P < 0.05). Although the HF/GT1 and HF/GT2 rats had lower serum NEFA, their serum insulin and IRI remained comparable with the HF/HF rats. To determine if there is a critical time period for the actions of GTEG, in the second experiment female rats were fed the LF, HF, or GT1 diet prior to conception and throughout gestation. During lactation, half of the dams had their diet switched from HF to GT1 and vice versa. Pups were weaned to the HF or LF diet, forming the LF/LF/LF, LF/LF/HF, HF/HF/LF, HF/HF/HF, HF/GT1/LF, HF/GT1/HF, GT1/GT1/LF, GT1/GT1/HF, GT1/HF/LF and GT1/HF/HF groups. Metabolic controls of dams given GT1 during gestation or lactation were improved compared with the HF/HF dams (P < 0.05). Three-way ANOVA revealed that 22 wk old offspring born to dams fed the HF diet during gestation had higher serum and muscle triglyceride (TG) concentration and lower ferric reducing ability of plasma (FRAP) (P < 0.05), all of which were reversed by supplementing GT1 to the gestational diet. Oral glucose tolerance at wk 15 was improved in those offspring born to dams given GT1 supplementation during lactation (P < 0.05). The increased serum NEFA concentration and IRI in offspring of dams fed the HF diet during gestation or lactation were reversible upon GT1 supplementation during either time period (P < 0.05). These rats (HF/GT1/HF, GT1/GT1/HF and GT1/HF/HF) had similar level of hepatic insulin receptor gene expression as well as protein abundance for muscle glucose transporter 4 and hepatic sterol regulatory element binding protein-1c but lower protein mass for hepatic glucose-6-phosphatase (P < 0.05) compared with the LF/LF/HF rats. Hence, maternal overnutrition-induced metabolic derangements in male offspring are reversible through supplementing GTEG to the maternal diet during gestation or lactation and this approach is more effective than giving GTEG to offspring born to overnourished mothers. Offspring metabolism could be programmed via manipulations of the maternal diet. / published_or_final_version / Biological Sciences / Doctoral / Doctor of Philosophy

published_or_final_version / Medical Sciences / Master / Master of Medical Sciences

published_or_final_version / Medical Sciences / Master / Master of Medical Sciences

published_or_final_version / Pharmacology / Doctoral / Doctor of Philosophy

The overall objective of this thesis was to test the hypothesis that maternal overnutrition has adverse effects on the expression of central metabolic regulators in offspring but could be offset by supplementing green tea extract (GTE) to the dams during gestation and/or lactation. This thesis focuses on two aspects of central metabolic regulation: the leptin signaling that links to appetite regulation and the sirtuin 1(SIRT1)/oxidative stress pathway that links to insulin sensitivity (IS). This study was initiated based on previous findings of this laboratory that via developmental programming energy intake of offspring born to dams given GTE during lactation was suppressed and that IS was improved in offspring of dams supplemented with GTE during gestation and/or lactation. The diets used included low fat (LF), high-fat (HF), and HF diet added with 0.75% or 1%GTE (GT1, GT2). In experiment 1, female rats were given the respective diet 8 weeks prior to mating till the end of lactation. Male offspring were weaned to the HF, GT1 or GT2 diet for 10 weeks forming the LF/HF, HF/HF, GT1/HF, GT2/HF, HF/GT1 and HF/GT2 groups. Maternal and postweaning GTE supplementation increased hypothalamic leptin receptor (OB-Rb) and signal transducer activator of transcription 3 (STAT3) mRNA suggestive of enhanced leptin signaling but pro-opiomelanocortin (POMC) mRNA expression, an appetite inhibitor was only elevated in the HF/GT1 group which was associated with reduction in food intake in this group. Central oxidative status was improved in GT1/HF and GT2/HF offspring through enhanced hypothalamic SIRT1 and peroxisome proliferator-activated receptor gamma coactivator 1 alpha (PGC-1α) expression compared with the HF/HF group. These improvements coincided with better IS in the HF offspring born of GTE supplemented dams. Experiment 2 was designed to determine the relative importance of gestation and lactation as the critical period for GTE supplementation. Female rats were assigned to LF, HF or GT1 diet 9 weeks prior to mating till the end of pregnancy. During lactation half of the HF and GT1 dams had the diet switched to GT1 and HF, respectively. Male offspring were fed the LF or HF diet until 22 weeks of age forming 10 offspring groups: LF/LF/LF, LF/LF/HF, HF/HF/LF, HF/HF/HF, HF/GT1/LF, HF/GT1/HF, GT1/HF/LF, GT1/HF/HF, GT1/GT1/LF, and GT1/GT1/HF. Consistent with a reduction in energy intake in offspring born to dams receiving GTE supplementation during lactation, there was an increase in melanocortin 4 receptor (MC4R) expression in the hypothalamus (P<0.05). Regardless of postweaning diet, offspring of dams given GTE during gestation and/or lactation had elevated hypothalamic PGC-1α and reduced protein phosphorylation of c-Jun N-terminal kinase-1 when compared with offspring of unsupplemented dams(P<0.05) which was associated with improved IS. Hence, leptin signaling and appetite regulators in the offspring were selectively affected by GTE supplementation during lactation whereas offspring exhibited improved ability to handle oxidative stress if dams received GTE supplementation during gestation and/or lactation. Collectively, these results support the notion that central mechanisms with roles in appetite control and oxidative status are susceptible to the programming phenomenon triggered by maternal nutritional status. / published_or_final_version / Biological Sciences / Master / Master of Philosophy

Risks of metabolic syndrome including cardiovascular disease and diabetes are significantly affected by maternal nutrition. This concept of developmental programming had been investigated in our laboratory and in an earlier study, it was established that maternal high-fat diet predisposed rat offspring to insulin resistance and higher triglyceride in serum, liver, skeletal muscle and adipose tissue. These abnormalities, however, were ameliorated by supplementing green tea extract to dam’s diet throughout gestation and lactation. The overall objective of this thesis was to examine lipid metabolism, oxidative stress and inflammatory responses in heart of offspring born to dams receiving high-fat diet with or without green tea supplementation during pregnancy and lactation. Female Sprague-Dawley rats were fed an obesogenic diet which was a high-fat diet (HF,30%), low-fat diet (LF,7%) or HF diet containing 0.75% green tea extract prior to conception and throughout gestation. During lactation, half of the dams had their diet switched from HF to GT and vice versa. Pups were weaned to the HF or LF diet, forming 10 offspring groups (gestation/lactation/postweaning): LF/LF/LF, LF/LF/HF, HF/HF/LF, HF/HF/HF, HF/GT/LF, HF/GT/HF, GT/GT/LF, GT/GT/HF, GT/HF/LF and GT/HF/HF. Except a larger fibrotic area, maternal HF diet did not affect lipid accumulation, oxidative status and inflammatory response in the heart of offspring. Analysis of variance revealed different, and even opposite, effects of GT supplementation during gestation and lactation. In offspring born to dams receiving GT supplementation during gestation, they had suppressed fatty acid oxidation (FAO) and higher triglyceride (TG) level in the heart. In contrast, when GT was supplemented to dams during lactation, offspring had elevated heart TG, cholesterol and free fatty acid levels but up-regulated FAO. Since FAO is associated with reactive oxygen species (ROS) production, modulation of FAO is believed to affect cellular stress responses in heart. Consistent with FAO, cardiac stress, apoptotic and inflammatory biomarkers including B-type natriuretic peptide (BNP), bcl 2 associated-x (bax) and interleukin-1β (IL1b) were down-regulated in offspring born to dams given GT during gestation, whereas GT supplementation during lactation increased the expression of pro-apoptotic markers: bax and caspase-3 (Cas3) concurrent with activation of antioxidant defense system: catalase, glutathione peroxidase (GPx) and glutathione S-transferase (GST) as adaptive mechanism against increased ROS. Uncoupling protein 2 (UCP 2) and subsequent higher bcl 2 /bax ratio has been reported to stimulate apoptosis. In agreement with this, mRNA expression of BNP, bax and Cas3 were found to correlate with that of UCP 2. This suggests UCP 2may play an important role in apoptosis under the impact of maternal GT supplementation. The present data suggest that the effect of maternal high-fat diet is organ specific causing apparently lesser damage to the heart. When GT is given in conjunction with a high-fat diet to dams during gestation, there is no clear cut advantage to the offspring. However, potential adverse effects could not be ruled out when GT is supplemented to dams during lactation possibly due to higher catechin exposure via milk. Future study should focus on establishing the benefits and safety use of GT during gestation. / published_or_final_version / Biological Sciences / Master / Master of Philosophy

published_or_final_version / Medical Sciences / Master / Master of Medical Sciences

published_or_final_version / Medical Sciences / Master / Master of Medical Sciences

published_or_final_version / Physics / Doctoral / Doctor of Philosophy

Hypoxia and reperfusion can result in many pathological complications in the fetus including retinopathy, ischemic encephalopathy and even stillbirth. The adverse effects are due to excess production of free radicals that attack vital bio-molecules such as DNA and enzymes. Antioxidant treatment may be a way to alleviate oxidative stress. Green tea is a source of antioxidants. It contains polyphenols mainly catechins, that possess high reducing power and low toxicity. Major catechin compounds in green tea are (+)-catechin (C), (-)-epicatechin (EC, (-)-gallocatechin (GC), (-)-epigallocatechin (EGC), (-)-catechin gallate (CG), (-)-epicatechin gallate (ECG), (-)-gallocatechin gallate (GCG) and (-)-epigallocatechin gallate (EGCG). Accordingly, catechins may be ideal agents for antioxidant treatment of the fetus exposed to hypoxia during pregnancy. / In the animal experiments, rat mothers, at the 15.5th gestation day, were intragastrically administrated a single dose of green tea extract. The pharmacokinetic profiles of catechins in maternal plasma, whole embryos and embryonic organs were investigated. The catechins GC, ECG, C, EC, were found to exhibit non-linear capacity limited pharmacokinetic behaviour implying their metabolism or absorption was saturated. Catechin gallates, EGCG and ECG, appeared to exhibit enterohepatic re-circulation behaviour. Peak time was about 1 hour for both groups of catechins; the half life of the catechin group was about 1 hour while that of EGCG and ECG was about 3.7 hours. EC, EGC and EGCG were the dominant compounds present in plasma. All catechins exhibited a consecutive one-compartment model in the embryo, where EGCG, ECG, EGC and EC were dominant compounds and ECG had the highest penetrability. (Abstract shortened by UMI.) / In this study, pregnant rat dams were fed green tea extract in an attempt to raise catechin levels in the rat embryo in order to scavenge free radicals. To test this hypothetical application, we first established analytical methods to evaluate oxidative stress and catechins levels of the fetus in vivo. The methodologies included assaying F2-isoprostanes in cord blood and determining catechin levels in biological fluids and tissues. We further utilized these new sensitive analytical methods to investigate the pharmacokinetics of the catechins in maternal rat plasma, whole embryos and embryonic organs. Since no data has been previously reported on the toxic effects of catechins on embryos, we also tested the toxic effects of various concentrations of catechins on the developing embryonic features in embryo culture. / Chu Kai On. / "April 2005." / Advisers: Michael Scott Rogers; Chi Pui Pang. / Source: Dissertation Abstracts International, Volume: 67-01, Section: B, page: 0244. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2005. / Includes bibliographical references (p. 208-241). / 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. / Abstract in English and Chinese. / School code: 1307.