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Title: Genetic variation in carbohydrate digestion enzymes in human populations and its physiological consequences
Author: Brown, K. D.
ISNI:       0000 0004 8498 6638
Awarding Body: UCL (University College London)
Current Institution: University College London (University of London)
Date of Award: 2017
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The variety and complexity of dietary carbohydrates is reflected in the complementary and overlapping substrate specificity of the enzymes needed to optimise their digestion. The extent to which genetic variation in genes associated with carbohydrate digestive enzymes affects digestion rates and postprandial glycaemia in response to starch con¬sumption, remains largely unknown. Three investigations are presented, each concerning different aspects of genetic variation in carbohydrate digestion enzymes. The first study uses publically available data to identify patterns of potentially func¬tional variations (pfVars) in the genes encoding carbohydrate digestion at the intestinal brush-border. After creation of a database cataloguing pfVars in glucosidases, this work presents a method which can be used to identify pfVars that may be associated to dietary specialisation or adaptation. The results highlight sucrase-isomaltase and trehalase as potential targets of positive selection. The second study details a population genetic investigation into copy number variation (CNV) of salivary (AMY1) and pancreatic (AMY2) amylase genes. It has been proposed that increased amylase copy number may have been evolutionarily advantageous with the advent of fire, and with the agricultural transition. The copy number of AMY1 and AMY2 genes were investigated in 15 global populations, with varying subsistence strategies. Geographic origin was found to significantly affect every measure of amylase gene CNV, and was shown to better explain the distribution of amylase gene copy number compared to subsistence strategy. Finally, the third study investigates the relationship between AMY1 CNV and postpran¬dial glycaemic response after starch consumption. The results from this investigation demonstrate that individuals with high AMY1 copy number have an increased glycaemic response and a delayed insulin response after starch consumption. If these data are rep¬resentative of the larger population, it is possible that individuals with high AMY1 copy number are at greater risk of developing type-2 diabetes.
Supervisor: Thomas, M. G. Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available