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Effects of Natural Products on Sugar Metabolism and Digestive Enzymes

Aydin, Ebru (2015) Effects of Natural Products on Sugar Metabolism and Digestive Enzymes. PhD thesis, University of Leeds.

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The risk of diabetes is increasing and it is anticipated that people with diabetes will double by 2030 with about 90% of patients having type-2 diabetes. The use of herbal remedies in the treatment of diabetes has increased because of the side effects (flatulence, diarrhoea, tiredness and upset stomach) of some common drugs. To prevent or delay type-2 diabetes, the blood glucose level needs to be controlled. The objective of this research was to make a preliminary assessment of the capacity of PFS (Plant Food Supplement) extracts to reduce glucose, fructose and sucrose transport (acarbose-like activity) across the Caco-2 cell monolayers and inhibit digestive enzymes by PFS extracts. Sucrase activity is responsible for the hydrolysis of sucrose to fructose and glucose in the brush border membrane of the small intestine. Accordingly, inhibiting glucose uptake in the intestine may be beneficial for diabetic patients in controlling their blood glucose level. The initial steps of the in vitro tests development involved determining the activities of sucrase, maltase, isomaltase and human salivary α-amylase in an acetone-extract of rat intestinal tissues, improving on a previously published method by analysing glucose concentration via the hexokinase assay, and analysing the effect of PFS on sugar transporters using a previously published method using the Caco-2 cell monolayer. The literature evidence for the inhibition of cellular glucose uptake and transport by polyphenols across Caco-2 cells is limited. Also, to the best of our knowledge, this research is the first report regarding the analysis of cellular uptake and transport of 14C-sucrose and 14C-fructose using the Caco-2 cell monolayer with polyphenol-containing extracts. Additionally, 14C radioactivity was used due to its easy detection and allowed high sensitivity. Glucose, fructose and sucrose transport across the Caco-2 cell monolayer was significantly attenuated in the presence of PFS. Green tea, German chamomile and Vitis Viniferae extracts inhibited the transport of glucose, fructose and sucrose when tested independently. However, the Vitis Viniferae extracts were not able to achieve 50% inhibition for the sucrose and fructose transport. While the cellular uptake of glucose and fructose was inhibited by the PFS extracts, they were effective on the cellular uptake of sucrose. By contrast, Pelargonium and Echinacea were ineffective for both the transport and cellular uptake of sugars. Purified German chamomile and green tea extracts were found to be moderate inhibitors of α-amylase digestion of amylopectin and α-glucosidase enzymes. Due to the acarbose-like activity of the PFS extracts, they may have a potential role to reduce the risk of diabetes by inhibiting the hydrolysis of starches and reducing post-prandial blood glucose spikes. PFS may be seen as beneficial for use by diabetics as part of a nutritional intervention and in combination with exercise and drug treatment.

Item Type: Thesis (PhD)
Keywords: PFS, type-2 diabetes, sugar metabolism, digestive enzymes, GLUT2, GLUT5, SGLT1
Academic Units: The University of Leeds > Faculty of Maths and Physical Sciences (Leeds)
The University of Leeds > Faculty of Maths and Physical Sciences (Leeds) > Food Science (Leeds)
Identification Number/EthosID: uk.bl.ethos.668762
Depositing User: MRS EBRU AYDIN
Date Deposited: 29 Oct 2015 09:59
Last Modified: 25 Nov 2015 13:49
URI: http://etheses.whiterose.ac.uk/id/eprint/10536

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