Physiology and Endocrinology 1

摘要

Enhanced post-ruminal supply of choline (CHL) may increase fluxthrough the methionine (Met) cycle to improve immunometabolicstatus during a negative nutrient balance (NNB). The objective was toinvestigate effects of post-ruminal CHL supply during a feed restrictioninducednegative NNB on: 1) hepatic activity of cystathionine β-synthase(CBS) and methionine synthase (MTR) and expression of enzymes andmetabolite concentrations in the transsulfuration pathway and Met cycleand 2) plasma biomarkers of liver function, inflammation and oxidativestress. Ten primiparous rumen-cannulated Holstein cows (158 ± 24 DIM)were used in a replicated 5 × 5 Latin square design with 4-d treatmentperiods and 10 d of recovery (14 d/period). Treatments were unrestrictedintake with abomasal infusion of water (A0), restricted intake (R; 60%of NE_L requirements) with abomasal infusion of water (R0) or R plusabomasal infusion of 6.25, 12.5, or 25g/d CHL ion. Liver tissue wascollected on d 5 when infusions ended for metabolomics and radioactiveenzyme assays, and blood on d 1, 3 and 5 for measurement of plasmabiomarkers via commercial kits. Statistical contrasts were A0 vs. R0, Rvs. the average of CHL doses and tests of linear and quadratic effects.While R decreased MTR activity (P = 0.02), it tended to increase linearlywith CHL (P = 0.07). Activity of CBS tended to be lower with R (P =0.07) and decreased linearly with CHL (P = 0.03). Hepatic glutathionecontent was not different with R or CHL (P > 0.10) but taurine tendedto be greater with CHL (P = 0.09). Betaine and carnitine were greaterwith R (P < 0.05) and further increased with CHL (P < 0.05). Plasmaaspartate aminotransferase and bilirubin increased with R (P < 0.05) butdecreased with CHL (P < 0.05). Data suggest that enhanced supply ofCHL during NNB decreases entry of homocysteine to the transsulfurationpathway, potentially favoring remethylation to Met by acquiring amethyl group from betaine. As such, Met may provide methyl groups forsynthesis of carnitine. Changes in blood biomarkers suggest a beneficialeffect of CHL on liver function during NNB.