Abstract
A significant body of evidence demonstrates that isoflavone metabolites are good markers of soy intake, while research is lacking on specific markers of other leguminous sources such as peas. In this context, the objective of our current study was to identify biomarkers of pea intake using an untargeted metabolomics approach. A randomized cross-over acute intervention study was conducted on eleven participants who consumed peas and couscous (control food) in random order. The urine samples were collected in fasting state and postprandially at regular intervals and were further analysed by ultra-performance liquid chromatography coupled to quadrupole time of flight mass spectrometry (UPLC-QTOF-MS). Multivariate statistical analysis resulted in robust Partial least squares Discriminant Analysis (PLS-DA) models obtained for comparison of fasting against the postprandial time points (0 h vs. 4 h, (R2X = 0.41, Q2 = 0.4); 0 h vs. 6 h, ((R2X = 0.517, Q2 = 0.495)). Variables with variable importance of projection (VIP) scores ≥1.5 obtained from the PLS-DA plot were considered discriminant between the two time points. Repeated measures analysis of variance (ANOVA) was performed to identify features with a significant time effect. Assessment of the time course profile revealed that ten features displayed a differential time course following peas consumption compared to the control food. The interesting features were tentatively identified using accurate mass data and confirmed by tandem mass spectrometry (MS using commercial spectral databases and authentic standards. 2-Isopropylmalic acid, asparaginyl valine and N-carbamoyl-2-amino-2-(4-hydroxyphenyl) acetic acid were identified as markers reflecting pea intake. The three markers also increased in a dose-dependent manner in a randomized intervention study and were further confirmed in an independent intervention study. Overall, key validation criteria were met for the successfully identified pea biomarkers. Future work will examine their use in nutritional epidemiology studies.
Highlights
Diet is one of the major lifestyle related risks associated with a wide range of chronic diseases [1,2,3].the exact relationship between diet components and health still needs to be determined and it is a prerequisite to achieve accurate measurement of food intake
An important aspect of the validation of biomarkers is the biological plausibility of such markers; we argue here that all three metabolites associated with pea intake have plausible biological interpretations [48]. 2-Isopropylmalic acid (2-IPMA) has been reported to be present in common peas
The present study demonstrates a successful application of an untargeted metabolomics approach to discover biomarkers of pea intake. 2-IPMA, Asp-Val and N-Carbamoyl-2-amino-2-(4-hydroxyphenyl) acetic acid (NC) were discovered as potential biomarkers of pea intake
Summary
Diet is one of the major lifestyle related risks associated with a wide range of chronic diseases [1,2,3].the exact relationship between diet components and health still needs to be determined and it is a prerequisite to achieve accurate measurement of food intake. Traditional dietary assessment methods include self-reporting platforms such as food frequency questionnaires (FFQ), 24 h dietary recalls and food diaries. These self-reported tools have a number of well documented limitations such as energy underreporting, recall errors and misjudgement in the estimation of portion sizes and attenuate the diet and disease relationship [4,5,6]. Nutrients 2018, 10, 1911 food intake biomarkers have emerged as a more objective measurement and could be an adjunct to the existing assessment methods [7,8,9]. The emergence of metabolomics technology has resulted in the discovery of putative biomarkers of exposure to a range of foods and food groups such as cruciferous vegetables [11,12], citrus fruits [13,14,15], red meat [16], sugar-sweetened beverages [17], coffee [18], and black tea [19]
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