Different choline supplement metabolism in adults using deuterium labelling.

BACKGROUND: Choline deficiency leads to pathologies particularly of the liver, brain and lung. Adequate supply is important for preterm infants and patients with cystic fibrosis. We analysed the assimilation of four different enterally administered deuterium-labelled (D9-) choline supplements in adults. METHODS: Prospective randomised cross-over study (11/2020-1/2022) in six healthy men, receiving four single doses of 2.7 mg/kg D9-choline equivalent each in the form of D9-choline chloride, D9-phosphorylcholine, D9-alpha-glycerophosphocholine (D9-GPC) or D9-1-palmitoyl-2-oleoyl-glycero-3-phosphoryl-choline (D9-POPC), in randomised order 6 weeks apart. Plasma was obtained at baseline (t = - 0.1 h) and at 0.5 h to 7d after intake. Concentrations of D9-choline and its D9-labelled metabolites were analysed by tandem mass spectrometry. Results are shown as median and interquartile range. RESULTS: Maximum D9-choline and D9-betaine concentrations were reached latest after D9-POPC administration versus other components. D9-POPC and D9-phosphorylcholine resulted in lower D9-trimethylamine (D9-TMAO) formation. The AUCs (0-7d) of plasma D9-PC concentration showed highest values after administration of D9-POPC. D9-POPC appeared in plasma after fatty acid remodelling, predominantly as D9-1-palmitoyl-2-linoleyl-PC (D9-PLPC), confirming cleavage to 1-palmitoyl-lyso-D9-PC and re-acylation with linoleic acid as the most prominent alimentary unsaturated fatty acid. CONCLUSION: There was a delayed increase in plasma D9-choline and D9-betaine after D9-POPC administration, with no differences in AUC over time. D9-POPC resulted in a higher AUC of D9-PC and virtually absent D9-TMAO levels. D9-POPC is remodelled according to enterocytic fatty acid availability. D9-POPC seems best suited as choline supplement to increase plasma PC concentrations, with PC as a carrier of choline and targeted fatty acid supply as required by organs. This study was registered at Deutsches Register Klinischer Studien (DRKS) (German Register for Clinical Studies), DRKS00020498, 22.01.2020. STUDY REGISTRATION: This study was registered at Deutsches Register Klinischer Studien (DRKS) (German Register for Clinical Studies), DRKS00020498.

Combined choline and DHA supplementation: a randomized controlled trial.

OBJECTIVE: Choline and docosahexaenoic acid (DHA) are essential nutrients for preterm infant development. They are metabolically linked via phosphatidylcholine (PC), a constitutive plasma membrane lipid and the major transport form of DHA in plasma. Plasma choline and DHA-PC concentrations rapidly decline after preterm birth. To improve preterm infant nutrition, we evaluated combined compared to exclusive choline and DHA supplementation, and standard feeding. DESIGN: Randomized partially blinded single-center trial. SETTING: Neonatal tertiary referral center in Tübingen, Germany. PATIENTS: 24 inborn preterm infants < 32 week postmenstrual age. INTERVENTIONS: Standard nutrition (control) or, additionally, enteral choline (30 mg/kg/day), DHA (60 mg/kg/day), or both for 10 days. Single enteral administration of 3.6 mg/kg [methyl-D9-] choline chloride as a tracer at 7.5 days. MAIN OUTCOME MEASURES: Primary outcome variable was plasma choline following 7 days of supplementation. Deuterated and unlabeled choline metabolites, DHA-PC, and other PC species were secondary outcome variables. RESULTS: Choline supplementation increased plasma choline to near-fetal concentrations [35.4 (32.8-41.7) µmol/L vs. 17.8 (16.1-22.4) µmol/L, p < 0.01] and decreased D9-choline enrichment of PC. Single DHA treatment decreased DHA in PC relative to total lipid [66 (60-68)% vs. 78 (74-80)%; p < 0.01], which was prevented by choline. DHA alone increased DHA-PC only by 35 (26-45)%, but combined treatment by 63 (49-74)% (p < 0.001). D9-choline enrichment showed preferential synthesis of PC containing linoleic acid. PC synthesis via phosphatidylethanolamine methylation resulted in preferential synthesis of DHA-containing D3-PC, which was increased by choline supplementation. CONCLUSIONS: 30 mg/kg/day additional choline supplementation increases plasma choline to near-fetal concentrations, dilutes the D9-choline tracer via increased precursor concentrations and improves DHA homeostasis in preterm infants. TRIAL REGISTRATION: clinicaltrials.gov. Identifier: NCT02509728.

Abnormal liver phosphatidylcholine synthesis revealed in patients with acute respiratory distress syndrome.

Acute respiratory distress syndrome (ARDS) is associated with a severe pro-inflammatory response; although decreased plasma cholesterol concentration has been linked to systemic inflammation, any association of phospholipid metabolic pathways with ARDS has not been characterized. Plasma phosphatidylcholine (PC), the major phospholipid of circulating lipoproteins, is synthesized in human liver by two biologically diverse pathways: the cytidine diphosphocholine (CDP):choline and phosphatidylethanolamine N-methyltransferase (PEMT) pathways. Here, we used ESI-MS/MS both to characterize plasma PC compositions and to quantify metabolic fluxes of both pathways using stable isotopes in patients with severe ARDS and in healthy controls. Direct incorporation of methyl-D9-choline estimated CDP:choline pathway flux, while PEMT flux was determined from incorporations of one and two methyl-D3 groups derived from methyl-D9-choline. The results of MS/MS analysis showed significant alterations in plasma PC composition in patients with ARDS versus healthy controls. In particular, the increased overall methyl-D9-PC enrichment and, most importantly, the much lower methyl-D3-PC and methyl-D6-PC enrichments suggest increased flux through the CDP:choline pathway and reduced flux through the PEMT pathway in ARDS. To our knowledge, this study is the first to demonstrate significant plasma PC molecular compositional changes combined with associated alterations in the dynamics of PC synthetic pathways in patients with ARDS.

In Vivo Cellular Phosphatidylcholine Kinetics of CD15+ Leucocytes and CD3+ T-Lymphocytes in Adults with Acute Respiratory Distress Syndrome.

Mammalian cell membranes composed of a mixture of glycerophospholipids, the relative composition of individual phospholipids and the dynamic flux vary between cells. In addition to their structural role, membrane phospholipids are involved in cellular signalling and immunomodulatory functions. In this study, we investigate the molecular membrane composition and dynamic flux of phosphatidylcholines in CD15+ leucocytes and CD3+ lymphocytes extracted from patients with acute respiratory distress syndrome (ARDS). We identified compositional variations between these cell types, where CD15+ cells had relatively higher quantities of alkyl-acyl PC species and CD3+ cells contained more arachidonoyl-PC species. There was a significant loss of arachidonoyl-PC in CD3+ cells in ARDS patients. Moreover, there were significant changes in PC composition and the methyl-D9 enrichment of individual molecular species in CD15+ cells from ARDS patients. This is the first study to perform an in vivo assessment of membrane composition and dynamic changes in immunological cells from ARDS patients.