Current Metabolomics (v.3, #2)

Meet Our Editorial Board Members by Martin von Bergen (77-77).

Meet Our Editorial Board Members by Yulan Wang (78-78).

This review describes how metabolomic analysis has been used in support of nutritional research in companion animals, focusing on healthy dogs and cats, and highlights issues that may help those considering metabolomics to support traditional nutritional studies in other mammalian species. Factors that influence the plasma and urinary metabolome in companion animals are known, and include the individual, breed, gender, neuter status, life stage and environment, including diet. Many of these effectors can be controlled or accounted for and it is possible to consider metabolomics as an approach to investigate nutritional status using appropriate study designs. Whilst some research objectives may benefit from taking a discovery approach, the investment in time and resource to generate hypotheses using metabolomics needs to be justified through a good study design with clear objectives and a long-term commitment to the research area to invest in the necessary follow-up studies. As such, whilst metabolomics has immense potential value, the strategic application of it to best serve nutritional sciences requires further development. Different metabolomics study designs and the collection of relevant metadata are discussed to assist those considering nutritional metabolomics.

Consumption of Cooked Navy Bean Powders Modulate the Canine Fecal and Urine Metabolome by Genevieve M. Forster, Adam L. Heuberger, Corey D. Broeckling, John E. Bauer, Elizabeth P. Ryan (90-101).
Common beans (Phaseolus vulgaris, L.), are a safe and digestible source of macro- and micro- nutrients for dogs and supply phytochemicals that are associated with improving human and animal health. In this study, we utilized a targeted and non-targeted metabolomic approach to evaluate dietary cooked navy bean powder (25% weight/weight) as part of the canine food metabolome. GC- and LC-MS were used to evaluate the effects of a navy bean diet on serum biochemistry and chemical composition of feces and urine in clinically healthy adult dogs (n=10), compared to a control diet (n=11). The navy bean diet was higher in 2-piperdinecarboxylic acid, s-methyl cysteine, β-sitosterol, γ-tocopherol, sucrose, and fructose. Companion dogs consuming the 25% navy bean diet for one month had lower serum cholesterol and showed changes in fecal and urine metabolites that were consistent with modulation of lipid and carbohydrate metabolism. Metabolite biomarkers of bean intake were identified in canine diets and urine. These data support the continued investigation of the potential for bean-based diets to improve companion dog health and the utility of nutritional metabolomics in companion animal studies.

Plasma Metabolite Profiling and Search for Biomarkers of Metabolic Dysfunction in Dogs Undergoing Rapid Weight Gain by Maria R. C. de Godoy, Kirk L. Pappan, Ryan W. Grant, Kelly S. Swanson (102-121).
The objective of this experiment was to use untargeted plasma metabolite profiling to identify metabolite changes and potential biomarkers of metabolic dysfunction that accompanies rapid weight gain in dogs. Five intact female beagles were fed ad libitum for a period of 24 wk. Blood samples were collected after an overnight fast via jugular venipuncture at 0, 4, 8, 12, and 24 wk of feeding. Plasma was stored at -80A°C until GC-MS and LC-MS-MS analyses. A total of 284 named biochemicals were identified, with as many as 175 metabolites being altered (p<0.05) at each time point. Principal component analysis (PCA) clearly indicated two distinct clusters over time during obesity development. The first, comprised of wk 0, 4, 8, and 12 (acute phase), and the second, comprised of wk 24 (chronic phase). Random forest (RF) analysis highlighted several metabolites having a high degree of predictive accuracy between acute and chronic phases. Of carbohydrate metabolism-related pathways, plasma mannose, citrate, and α-ketoglutarate seem to be promising biomarkers of chronic obesity. Metabolites associated with amino acid and lipid metabolism were drastically affected by weight gain and, in general, displayed a bi-phasic pattern with several plasma metabolites being increased during the acute phase and decreased at the chronic phase of weight accretion. At wk 24, lysophospholipids were increased, suggesting acylchain remodeling and potential phospholipid synthesis. Given the distinct metabolite profiles at wk 12 and 24, this study identified several potential biomarkers of metabolic dysfunction that develops with weight gain in dogs.

Metabolomics Analysis of Galium odoratum (L.) Scop.: Impact of the Plant Population Origin and Growth Conditions by B. Martin, Michel Frederich, P. de Tullio, M. Tits, J. -N. Wauters, Y. H. Choi, M. Bodson (122-129).
Introduction: Galium odoratum is a plant used in traditional medicine and to prepare beverages.
Objective: To study the impact of plant origin and growth conditions on the metabolite content of the plant.
Material and methods: Aerial biomass of Galium odoratum was collected from five natural populations (in situ conditions) and from controlled environment (ex situ conditions). NMR-based fingerprinting method was successfully applied to the discriminating chemical profiling of the in situ and ex situ samples.
Results: Quantitative analysis of selected phytochemicals including phenylpropranoids and iridoids showed clear differences between the plants from nature and those of controlled growth conditions as well as internal variation within the group. The metabolomic approach emphasized the decrease of the secondary metabolites pool paralleled by an increase of the carbohydrates in ex situ conditions. The quantitative HPLC-UV points out slight variations of each of the analyzed secondary metabolites between populations in natural environment, variations maintained for three populations in the controlled conditions.
Conclusion: Metabolomics approaches using 1H-NMR and HPLC are worth to consider for studying the impact of climate factors on the regulation of the phytochemical profile in relation to the origin of the plant material.

MALDI Mass Spectrometric Imaging of the Nematode Caenorhabditis elegans by Robert F. Menger, Chaevien S. Clendinen, Louis A. Searcy, Arthur S. Edison, Richard A. Yost (130-137).
Matrix-assisted laser desorption/ionization mass spectrometric imaging (MALDI-MSI) is a technique that records mass spectra as a function of position across a biological tissue sample, yielding images of chemical distribution. Until now, MALDI-MSI has typically been performed on thinly sliced tissue sections that are coated with a UV-absorbing matrix. We have developed protocols to apply MALDI-MSI to chemically interrogate intact Caenorhabditis elegans, a nematode approximately 1-mm in length. C. elegans is a model organism with numerous available genetic mutants, three of which were used in this study to validate the MALDI-MSI results using principal component analysis (PCA). In comparison to traditional chemical biology analyses of nematodes that require large-scale cultures, MALDIMSI has the selectivity and sensitivity to record chemically relevant data from analysis of a single worm. This study demonstrates the feasibility of MALDI-MSI as an important new tool to study the chemistry of individual nematodes as well as the potential to conduct chemical biology and metabolomics studies of parasitic species that are impossible to culture outside of the host.