Postprandial lipid metabolism in healthy men and in patients with type II diabetes mellitus
Postprandial lipid metabolism in healthy men and in patients with type II diabetes mellitus
Increasing age, obesity and type II diabetes are associated with disturbed postprandial lipid metabolism and increased risk for developing atherosclerosis. However, the exact mechanisms remain unclear partly due to problems in differentiating between exogenous and endogenous lipids in circulation.
The main purpose of this thesis was to use novel stable isotope tracer methodology for tracing the metabolism of exogenous lipids in healthy subjects and in those with type II diabetes. After an overnight fast, subjects ingested [1,1,1-13C]tripalmitin with an emulsion and test meal (3.2 MJ; 90g carbohydrate, 36g lipid; 27g protein), followed by a second identical unlabelled meal 6 hours later. Blood and breath samples were collected and whole body CO2 excretion was measured, by indirect calorimetry, before and at hourly intervals for 10 h following label administration. A chylomicron-rich fraction (CRF, Sf>400) was separated by discontinuous-gradient ultracentrifugation. The fatty acid profile of CRF triglycerides (CRF-TAG) and plasma non-esterified fatty acids (NEFA) and the 13C-enrichment of palmitic acid (PA) methyl esters were determined by gas chromatography-combustion-isotope ration mass spectrometry (GC-C-IRMS). 13C-enrichment of breath and stool was analysed by continuous flow isotope ratio mass spectrometry. Plasma TAG, NEFA and glucose concentrations were determined enzymically. Plasma insulin was determined by radio-immuno assay.
In the first study the validation of tracer methodology protocol was examined and repeatability of postprandial lipid metabolism was determined in healthy young men. The results of the validation study demonstrated precision in the lipid extraction procedures and in the measurement of enrichments and concentrations of 13C palmitic acid by GC-C-IRMS system. The results of the repeatability study suggested that except for plasma glucose, the postprandial responses of plasma TAG, NEFA, 13C palmitic acid in CRF-TAG and breath 13CO2 were sufficiently repeatable to make it possible to explore potential differences between groups. Furthermore, 13C excretion in stools was minimal in healthy subjects thereby eliminating the need to take faecal collections in subsequent studies.
University of Southampton
Humayun, Mohammed Arshad
9025e6af-f22f-4c3b-b3b3-26958043cdba
2000
Humayun, Mohammed Arshad
9025e6af-f22f-4c3b-b3b3-26958043cdba
Humayun, Mohammed Arshad
(2000)
Postprandial lipid metabolism in healthy men and in patients with type II diabetes mellitus.
University of Southampton, Doctoral Thesis.
Record type:
Thesis
(Doctoral)
Abstract
Increasing age, obesity and type II diabetes are associated with disturbed postprandial lipid metabolism and increased risk for developing atherosclerosis. However, the exact mechanisms remain unclear partly due to problems in differentiating between exogenous and endogenous lipids in circulation.
The main purpose of this thesis was to use novel stable isotope tracer methodology for tracing the metabolism of exogenous lipids in healthy subjects and in those with type II diabetes. After an overnight fast, subjects ingested [1,1,1-13C]tripalmitin with an emulsion and test meal (3.2 MJ; 90g carbohydrate, 36g lipid; 27g protein), followed by a second identical unlabelled meal 6 hours later. Blood and breath samples were collected and whole body CO2 excretion was measured, by indirect calorimetry, before and at hourly intervals for 10 h following label administration. A chylomicron-rich fraction (CRF, Sf>400) was separated by discontinuous-gradient ultracentrifugation. The fatty acid profile of CRF triglycerides (CRF-TAG) and plasma non-esterified fatty acids (NEFA) and the 13C-enrichment of palmitic acid (PA) methyl esters were determined by gas chromatography-combustion-isotope ration mass spectrometry (GC-C-IRMS). 13C-enrichment of breath and stool was analysed by continuous flow isotope ratio mass spectrometry. Plasma TAG, NEFA and glucose concentrations were determined enzymically. Plasma insulin was determined by radio-immuno assay.
In the first study the validation of tracer methodology protocol was examined and repeatability of postprandial lipid metabolism was determined in healthy young men. The results of the validation study demonstrated precision in the lipid extraction procedures and in the measurement of enrichments and concentrations of 13C palmitic acid by GC-C-IRMS system. The results of the repeatability study suggested that except for plasma glucose, the postprandial responses of plasma TAG, NEFA, 13C palmitic acid in CRF-TAG and breath 13CO2 were sufficiently repeatable to make it possible to explore potential differences between groups. Furthermore, 13C excretion in stools was minimal in healthy subjects thereby eliminating the need to take faecal collections in subsequent studies.
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Published date: 2000
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Local EPrints ID: 467008
URI: http://eprints.soton.ac.uk/id/eprint/467008
PURE UUID: 8e60b91d-08ff-4f6c-a4e4-a88e5ae00fb9
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Date deposited: 05 Jul 2022 08:07
Last modified: 16 Mar 2024 20:55
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Author:
Mohammed Arshad Humayun
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