Metabolomics reveals rapid alterations and adaptations in canine plasma in response to changes in dietary methionine:cystine and choline

Metabolomics reveals rapid alterations and adaptations in canine plasma in response to changes in dietary methionine:cystine and choline

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  Proprietary information: Notto be reproduced or distributed without the express consent of Mars, Inc.© Mars 2017 D Allaway, G Thomas, R Staunton & P Watson, WALTHAM Centre for Pet Nutrition, Melton Mowbray, Leics. UK LE14 4RT Study Objectives • To identify changes in plasma metabolite pools following a reduction in dietary Met, whilst maintaining total sulphur amino acids with cysteine (Cys) • To determine whether additional choline would support Met functions at the lower dietary Met:Cys (Cys in diet as cystine) . Summary • The study highlights wide-ranging short-term metabolic effects of, and adaptations to, a change in dietary Met:Cys and choline • The Met pool reduced with a lower dietary Met:Cys but was supported by choline and adaptations after 2 weeks of diet feeding • Longer term consequences of the metabolic changes require elucidation before recommending a restricted Met diet for dogs Metabolomics Reveals Rapid Alterations and Adaptation in Canine Plasma in Response to Changes in Dietary Methionine:Cystine and Choline Material & Methods Study design: A 3-way crossover design with 18 dogs (Labrador retriever) randomised into 6 rotation groups. Each dog was fed each of the three diets for a period of 2 weeks, with a 6-7 day washout between diets. Each dog was fed 1 meal daily (100% MER) Blood samples taken 20 mins pre- and 1hr and 2 hr post diet on each sampling day All housing and study procedures complied with the Animals (Scientific Procedures) Act 1986 Figure 1 Study design schematic Diets: Semi-purified experimental diets formulated to be isonitrogenous / isocaloric and differing only in S amino acid ratio and choline content. Control diet A was fed in a 3 week baseline phase and in the washout phases. Metabolic profiling: Metabolic profiling used UHPLC/MS/MS and GC/MS (Metabolon Inc.). Statistical analysis: Univariate linear mixed effect models were fitted for 472 metabolites from 321 samples. Fixed effects were interactions of diet, time relative to meal, and days on diet, with covariates of age and gender, and random effects were diet nested in dog. Pairwise comparisons between fixed effects levels were significant at adjusted p-value <0.05 (Benjamini & Hochberg, 1995). Figure 3 An illustration of the data- driven observations made within the context of methionine cycle metabolism Results & Interpretation Diet Met Cys Choline A: Control 100% 100% 100% B: Low Met:Cys 40% 163% 100% C: Low Met:Cys & 2x Choline 40% 163% 200% Figure 2 Fasted plasma metabolite fold-change relative to control diet (Diet A), on day 2 and day 14 after a diet change (left and right symbols respectively). Metabolites are grouped by metabolic pathway ontology. Metabolites have at least one significant fold-change from control (red). 1. Betaine increased rapidly with low Met:Cys, and rose further with 2 weeks feeding or with additional choline 2. After 2 weeks, elevated GAA and creatine indicate that the dominant methyl-demanding pathway may be augmented by increased flux through the methionine cycle 3. Whilst dietary choline may support Met in the acute phase, adaptation within two weeks re- establishes fasted Met when fed a low Met:Cys diet 4. FIGLU increased with low Met:Cys, and further with additional choline, potentially as a consequence of alterations in 1C partitioning 5. Increased deoxycarnitine (γ-butyrobetaine) and carnitine pools at all time points, enhanced by choline on day 2 suggest a change in carnitine synthesis and/or transport 6. The acute increase in short-chain acylcarnitines suggests a disturbance in BCAA metabolism in response to choline 7. Additional choline resulted in increased TMAO production 8. Specific lipids decreased after 2 weeks adaptation to low Met:Cys, indicating reduced PEMT activity, with additional choline having variable effects Introduction • Dietary methionine (Met) restriction may provide health and longevity benefits • In susceptible dogs, dietary Met too low for sufficient taurine production has been implicated in the development of dilated cardiomyopathy • It was hypothesised that some health benefits of restricted Met diets in dogs may be possible if taurine production was maintained through provision of cysteine (Cys) or choline, which can support the Met cycle Metabolic Pathway Ontology 1 2 3 4 5 6 7 8