Growing interest lies in the assessment of the metabolic status of patients with a univentricular circulation after Fontan operation, especially in changes of amino acid metabolism. Using targeted metabolomic examinations, we investigated amino acid metabolism in a homogeneous adult Fontanpatient group with a dominant left ventricle, seeking biomarker patterns that might permit better understanding of fontan pathophysiology and early detection of subtle ventricular or circulatory dysfunction. We compared serum amino acid levels (42 analytes; AbsoluteIDQ p180 kit, Biocrates Life Sciences, Innsbruck, Austria) in 20 adult Fontan patients with a dominant left ventricle and those in age-and sex-matched biventricular controls. Serum concentrations of asymmetric dimethylarginine, methionine sulfoxide, glutamic acid, and trans-4-hydroxyproline and the methionine sulfoxide/ methionine ratio (Met-SO/Met) were significantly higher and serum concentrations of asparagine, histidine, taurine, and threonine were significantly lower in patients than in controls. Met-SO/ Met values exhibited a significant negative correlation with oxygen uptake during exercise. The alterations in amino acid metabolome that we found in fontan patients suggest links between fontan pathophysiology, altered cell energy metabolism, oxidative stress, and endothelial dysfunction like those found in biventricular patients with congestive heart failure. Studies of extended amino acid metabolism may allow better understanding of fontan pathophysiology that will permit early detection of subtle ventricular or circulatory dysfunction in Fontan patients. Ventricular dysfunction and circulatory failure with progressing end-organ impairment like renal or liver dysfunction are an important cause of morbidity and mortality in adults with complex congenital heart disease (CHD), especially in patients with single-ventricle types of CHD and Fontan circulation 1,2. Besides limited cardiac output, alterations that mark Fontan hemodynamics are passive flow to the lungs, chronically elevated venous pressures, and congestion. Unfortunately, the clinical use of traditional markers such as N-terminal prohormone of brain natriuretic peptide (NT-proBNP) levels for non-invasive diagnostics and monitoring in such patients is limited 3,4. Thus, for early detection of cardiac and circulatory derangement and for evaluation and tailoring of treatment options, regular functional assessment of these patients is crucial, with complete clinical examination, electrocardiogram, imaging studies, determination of values for traditional laboratory markers, or exercise capacity testing.

Background: Patients with a Fontan circulation have altered cholesterol and lipoprotein values. We analysed small organic molecules in extended phopsholipid and acylcarnitine metabolic pathways (‘metabolomes’) in adult Fontan patients with a dominant left ventricle, seeking differences between profiles in baseline and Fontan circulations. Methods: In an observational matched cross-sectional study, we compared phosphatidylcholine (PC), sphingomyelin (SM), and acylcarnitine metabolomes (105 analytes; AbsoluteIDQ® p180 kit (Biocrates Life Sciences AG, Innsbruck, Austria) in 20 adult Fontan patients having a dominant left ventricle with those in 20 age- and sex-matched healthy controls. Results: Serum levels of total PC ( q-value 0.01), total SM ( q-value 0.0002) were significantly lower, and total acylcarnitines ( q-value 0.02) were significantly higher in patients than in controls. After normalisation of data, serum levels of 12 PC and 1 SM Fontan patients were significantly lower ( q-values <0.05), and concentrations of 3 acylcarnitines were significantly higher than those in controls ( q-values <0.05). Conclusion: Metabolomic profiling can use small specimens to identify biomarker patterns that track derangement in multiple metabolic pathways. The striking alterations in the phospholipid and acylcarnitine metabolome that we found in Fontan patients may reflect altered cell signalling and metabolism as found in heart failure in biventricular patients, chronic low-level inflammation, and alteration of functional or structural properties of lymphatic or blood vessels. Trial registration number: ClinicalTrials.gov Identifier NCT03886935

Canine inflammatory bowel disease (IBD) is a chronic, immunologically mediated intestinal disorder, resulting from the complex interaction of genetic, environmental and immune factors. Hydrolyzed diets are used in dogs with food-responsive diarrhea (FRD) to reduce adverse responses to immunostimulatory proteins. Prebiotics (PRBs) and glycosaminoglycans (GAGs) have previously been demonstrated to show anti-inflammatory activity in the intestinal mucosa. Notably, hydrolyzed diets combined with the administration of PRBs and GAGs offer a promising approach for the treatment of canine IBD. Our aim was to investigate the effects of hydrolyzed diet and GAG+PRB co-treatment on the serum metabolomic profile of IBD dogs. Dogs with IBD randomly received either hydrolyzed diet supplemented with GAGs and PRBs (treatment 1) or hydrolyzed diet alone (treatment 2) for 10 weeks. A targeted metabolomics approach using mass spectrometry was performed to quantify changes in the serum metabolome before and after treatment and between treatment 1 and 2. Principal component analysis (PCA), partial least squares-discriminant analysis (PLS-DA), hierarchical cluster analysis (HCA) and univariate statistics were used to identify differences between the treatment groups. PCA, PLS-DA, and HCA showed a clear clustering of IBD dogs before and after hydrolyzed diet, indicating that the treatment impacted the serum metabolome. Univariate analysis revealed that most of the altered metabolites were involved in lipid metabolism. The most impacted lipid classes were components of cell membranes, including glycerophospholipids, sphingolipids, and di-and triglycerides. In addition, changes in serum metabolites after GAG+PRB co-treatment suggested a possible additional beneficial effect on the lipid metabolism in IBD dogs. In conclusion, the present Ambrosini et al. Lipid Metabolism in Canine IBD study showed a significant increase in metabolites that protect gut cell membrane integrity in response to hydrolyzed diet alone or in combination with GAG+PRB co-treatment. Administration of such treatment over 70 days improved selected serum biomarkers of canine IBD, possibly indicating improved intestinal membrane integrity.

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Introduction Metabolomics studies are not routine when quantifying amino acids (AA) in congenital heart disease (CHD). Objectives Comparative analysis of 24 AA in serum by traditional high-performance liquid chromatography (HPLC) based on ion exchange and ninhydrin derivatisation followed by photometry (PM) with ultra-high-performance liquid chromatography and phenylisothiocyanate derivatisation followed by tandem mass spectrometry (TMS); interpretation of findings in CHD patients and controls. Methods PM: Sample analysis as above (total run time, ~ 119 min). TMS: Sample analysis by AbsoluteIDQ® p180 kit assay (BIOCRATES Life Sciences AG, Innsbruck, Austria), which employs PITC derivatisation; separation of analytes on a Waters Acquity UHPLC BEH18 C18 reversed-phase column, using water and acetonitrile with 0.1% formic acid as the mobile phases; and quantification on a Triple-Stage Quadrupole tandem mass spectrometer (Thermo Fisher Scientific, Waltham, MA) with electrospray ionisation in the presence of internal standards (total run time, ~ 8 min). Calculation of coefficients of variation (CV) (for precision), intra- and interday accuracies, limits of detection (LOD), limits of quantification (LOQ), and mean concentrations. Results Both methods yielded acceptable results with regard to precision (CV < 10% PM, < 20% TMS), accuracies (< 10% PM, < 34% TMS), LOD, and LOQ. For both Fontan patients and controls AA concentrations differed significantly between methods, but patterns yielded overall were parallel. Conclusion Serum AA concentrations differ with analytical methods but both methods are suitable for AA pattern recognition. TMS is a time-saving alternative to traditional PM under physiological conditions as well as in patients with CHD. Trial registration number ClinicalTrials.gov Identifier NCT03886935, date of registration March 27th, 2019 (retrospectively registered).