Metabolomic analysis of a human oral glucose tolerance test reveals fatty acids as reliable indicators of regulated metabolism

Abstract

Gas chromatography/mass spectrometry-based metabolomics was applied to investigate dynamic changes in the plasma metabolome upon an oral glucose tolerance test (OGTT). The OGTT is a frequently used diagnostic test of glucose homeostasis and diabetes. Diabetes is diagnosed either when glucose levels C7.0 mM in the fasting state or C11.0 mM at 2 h after oral glucose intake. The accuracy of the OGTT would, however, most likely improve if additional variables could be identified. In the present study, plasma samples were drawn every 15 min for 2 h after an oral glucose load of 75 g preceded by an overnight fast in healthy individuals. Blood plasma levels of more than 200 putative metabolites were measured. Multivariate modelling was used to distinguish metabolic regulation due to the glucose challenge from that of other variability. Two data scaling methods were applied, yielding similar results when evaluated by appropriate diagnostic tools. Fatty acid levels were found to be strongly decreased during the OGTT. Also, the levels of amino acids were shown to decrease. However, technical and uninduced biological variations were found to affect the amino acid levels to a greater extent than the fatty acid levels, making the fatty acids more reliable as indicators of metabolic regulation. Levels of several metabolites correlated with the quadratic glucose profile and two were found having an inverse correlation. Raw data plots of all identified significantly altered metabolites confirmed the excellent performance of the multivariate models. Using this approach, a better understanding of the metabolic response to an OGTT can be achieved, paving the way for inclusion of other variables describing appropriate metabolic control.

Effects of Ingestion Routes on Hormonal and Metabolic Profiles in Gastric-Bypassed Humans

“…Metabolites were profiled by gas chromatography/mass spectrometry as detailed in the Supplemental Material and previously described in detail (9).…”

Metabolomics in diabetes research

“…In fact, increases in lysophosphatidylcholine (Zhao et al 2009) and decreases in amino acids (Table 1; Shaham et al 2008, Spegel et al 2010, acylcarnitines (Zhao et al 2009) and fatty acids (Table 2; Zhao et al 2009, Spegel et al 2010 were reported. The study by Zhao et al (2009) provided a more systematic overview of fatty acid plasma changes during an OGTT; although the levels of fatty acids declined during an OGTT, the levels of saturated (SFA) and monounsaturated fatty acids (MUFA) were more significantly decreased than those of polyunsaturated fatty acids (PUFA).…”

“…Several studies have investigated changes in the metabolic profile in relation to glucose ingestion (Shaham et al 2008, Zhao et al 2009, Spegel et al 2010, Matysik et al 2011). An investigation (Shaham et al 2008) among participants in the Metabolic Abnormalities in College Students (MACS) study, who demonstrated normal glucose tolerance, revealed significant kinetic alterations in 21 out of 191 plasma metabolites, measured by LC-MS, in response to an OGTT.…”

Time-resolved metabolomics analysis of β-cells implicates the pentose phosphate pathway in the control of insulin release

“…The QC samples were used to select the appropriate normalization for each of the detected peaks. Thus the scores from either a PCA (principal component analysis) model calculated in SIMCA P + 12.0 (Umetrics AB) on the non-centred and UV (unit variance) scaled peak areas for the internal standards [23] or a single internal standard peak area was applied in accordance with a previously published method [24]. Internal standards and artefact peaks identified from extracted blank samples were removed before modelling.…”