Fecal microbiota transplantation (FMT) has emerged as a highly effective therapy for recurrent Clostridioides difficile infection (rCDI) and also a potential therapy for other diseases associated with dysbiotic gut microbiota. Monitoring metabolic changes in biofluids and excreta is a noninvasive approach to identify the biomarkers of microbial recolonization and to understand the metabolic influences of FMT on the host. In this study, the pre-FMT and post FMT urine samples from 11 rCDI patients were compared through metabolomic analyses for FMT-induced metabolic changes. The results showed that p-cresol sulfate in urine, a microbial metabolite of tyrosine, was rapidly elevated by FMT and much more responsive than other microbial metabolites of aromatic amino acids (AAAs). Because patients were treated with vancomycin prior to FMT, the influence of vancomycin on the microbial metabolism of AAAs was examined in a mouse feeding trial, in which the decreases in p-cresol sulfate, phenylacetylglycine, and indoxyl sulfate in urine were accompanied with significant increases in their AAA precursors in feces. The inhibitory effects of antibiotics and the recovering effects of FMT on the microbial metabolism of AAAs were further validated in a mouse model of FMT. Overall, urinary p-cresol sulfate may function as a sensitive and convenient therapeutic indicator on the effectiveness of antibiotics and FMT for the desired manipulation of gut microbiota in human patients.

Genetic selection of dairy cattle has dramatically increased milk yield of dairy cows, but its influences on the chemical composition of milk, especially during early lactation, are not well characterized. A continuous selective breeding practice in Minnesota generated unselected Holsteins (UH) that represent US Holsteins in the early 1960s and contemporary Holsteins (CH) that produced much more milk and experienced greater negative energy balance than the UH cows. In this study, milk samples were collected weekly in the first 9 weeks of lactation from CH and UH cows (n = 12/genotype), and their metabolite profiles were defined by macronutrient analysis, liquid chromatography-mass spectrometry (LC-MS) analysis, multivariate analysis, structural elucidation, and quantitative analysis. The CH milk contained more triacylglycerols (TAGs) than the UH milk. Lipidomic profiling showed that the CH milk had more TAGs with at least two preformed fatty acid moieties while the UH milk had more TAGs with at least two de novo synthesized fatty acid moieties. Subsequent quantitative fatty acid analysis determined that the increase in preformed fatty acids in CH milk was responsible for different TAG profiles between the two genotypes. Moreover, the analysis of short-chain carboxylic acids in milk showed that episodes of transient and persistent ketosis were more frequent in CH than in UH cows. Interestingly, CH milk contained less free carnitine and short-chain acylcarnitines in the UH milk indicating the greater utilization of mobilized lipids increased the utilization of carnitine. These observations warrant further mechanistic investigations on the metabolic consequences of genetic selection on dairy cows.

Background: Genetic selection and improved nutrition and management practices have transformed the Holstein cow. Objectives: This study examined the impacts of 50 years of selection on milk composition during early lactation by comparing milk from contemporary Holsteins (CH) and a unique population of unselected Holsteins (UH) that produce less than half as much milk as their CH herdmates. Methods: Multiparous UH and CH cows (n = 12/genotype) were housed in the same facility, fed the same diets and subjected to the same management procedures. Milk samples were collected weekly through to week 9 of lactation. The proximate composition of milk was determined by infrared spectroscopy and its lipidome by liquid chromatography–mass spectrometry and structural analysis. Data were analyzed as repeated measures using mixed-model procedures with the week of lactation as the repeated effect. Results: An energy balance nadir occurred at week 1 for UH and CH cows but was more severe (−4.5 vs. −14.8 Mcal net energy per day, respectively) for the CH cows. Lipidomic comparison of the 50 most abundant triacylglycerols (TAGs) revealed that CH milk had more TAGs with at least two preformed fatty acids and fewer TAGs with at least two de novo synthesized fatty acids than UH milk. Fatty acid analysis revealed that the increase in preformed fatty acids in CH cows was responsible for the different TAG profiles in UH and CH milk. Furthermore, CH milk contained less free carnitine, short-chain acylcarnitines and lactic acid but more butyric and 3-hydroxybutyric acid than UH milk in early lactation. Conclusions: These results demonstrate that differences in energy balance were primarily responsible for the differences in milk composition between the UH and CH genotypes in early lactation.