Choline Supplementation in Cystic Fibrosis-The Metabolic and Clinical Impact

Abstract

Background: Choline is essential for the synthesis of liver phosphatidylcholine (PC), parenchymal maintenance, bile formation, and lipoprotein assembly to secrete triglycerides. In choline deficiency, the liver accretes choline/PC at the expense of lung tissue, thereby impairing pulmonary PC homoeostasis. In cystic fibrosis (CF), exocrine pancreas insufficiency results in impaired cleavage of bile PC and subsequent fecal choline loss. In these patients, the plasma choline concentration is low and correlates with lung function. We therefore investigated the effect of choline supplementation on plasma choline/PC concentration and metabolism, lung function, and liver fat.

Methods: 10 adult male CF patients were recruited (11/2014⁻1/2016), and orally supplemented with 3 × 1 g choline chloride for 84 (84⁻91) days. Pre-/post-supplementation, patients were spiked with 3.6 mg/kg [methyl-D₉]choline chloride to assess choline/PC metabolism. Mass spectrometry, spirometry, and hepatic nuclear resonance spectrometry served for analysis.

Results: Supplementation increased plasma choline from 4.8 (4.1⁻6.2) µmol/L to 10.5 (8.5⁻15.5) µmol/L at d84 (p < 0.01). Whereas plasma PC concentration remained unchanged, D₉-labeled PC was decreased (12.2 [10.5⁻18.3] µmol/L vs. 17.7 [15.5⁻22.4] µmol/L, p < 0.01), indicating D₉-tracer dilution due to higher choline pools. Supplementation increased Forced Expiratory Volume in 1 second percent of predicted (ppFEV1) from 70.0 (50.9⁻74.8)% to 78.3 (60.1⁻83.9)% (p < 0.05), and decreased liver fat from 1.58 (0.37⁻8.82)% to 0.84 (0.56⁻1.17)% (p < 0.01). Plasma choline returned to baseline concentration within 60 h.

Conclusions: Choline supplementation normalized plasma choline concentration and increased choline-containing PC precursor pools in adult CF patients. Improved lung function and decreased liver fat suggest that in CF correcting choline deficiency is clinically important. Choline supplementation of CF patients should be further investigated in randomized, placebo-controlled trials.

Keywords: choline deficiency; choline supplementation; cystic fibrosis; liver; lung function; magnetic resonance spectroscopy; stable isotope labeling; steatosis.

Figure A1

Patient flow of choline supplementation pilot study in adult male CF patients. The protocol was approved by The Institutional Review Board, and registered at ClinicalTrials.gov (Identifier: NCT 03312140).

Figure 1

Effect of oral choline supplementation on the plasma concentration of choline (A) and its water-soluble metabolites betaine, dimethylglycine (DMG) and trimethylamine oxide (TMAO) (B–D). Bars represent values prior to (visit [V] 2), after 49 (45–51) days (V5) and after 84 (84–91) days (V6) supplementation with 3 × 1 g choline chloride. Data are medians and interquartile ranges of CF patients prior to (V2), and after 49 (45–51) days (V5) and 84 (84–91) days (V6) choline supplementation. * p < 0.05; ** p < 0.01 vs. V2.

Figure 2

Plasma concentrations of choline (A) and its metabolites betaine (B) and trimethylamine oxide (TMAO) (C). Data are values of 10 adult male CF patients over 48 h prior to choline supplementation (visit 2–4 [V2–4], white symbols) and from 12 h after the end of choline supplementation (84 (84–91) days) onwards (V6–8, filled symbols). Abbreviations: ρ, Spearman rank correlation coefficient; p, significance level.

Figure 3

Kinetics of D₉-Choline and D₉-Betaine prior to (visit 2–4 [V2–4], white symbols) and from 12 h after the end of 84 (84–91) days choline supplementation (V6–8, filled symbols). CF patients (N = 10) were orally supplemented with 3 × 1 g choline chloride for 84 (84–91) d. Prior to (V2, open symbols) and 12 h after the end of supplementation (V6, filled symbols) patients were spiked orally with 3.6 mg/kg body weight [D₉-methyl]choline chloride (D₉-choline) and the kinetics of plasma D₉-choline (A) and D₉-betaine (C) concentration and of D₉-enrichment of choline (B) and betaine (D) analyzed for 48 h (V2–4 and V6–8, respectively). Data are medians and interquartile ranges from −5 min to 48 h after D₉-choline ingestion. Abbreviations: p, significance level.

Figure 4

Effects of choline supplementation on lung function. Data indicate values prior to (V2) and after 84 (84–91) days (V6) supplementation with 3 × 1 g/day choline chloride. Data indicate age-corrected Relative Forced Expiratory Volume in 1 second (Tiffeneau Index; ppFEV1) (A), Forced Vital Capacity (FVC) (B) and Forced Expiratory Flow at 25–75% of the pulmonary volume (FEF25-75) (C). Small symbols and thin lines indicate individual values of patients, whereas large symbols and thick bars indicate medians and interquartile ranges. p significance level.

Figure 5

Effects of choline supplementation on liver and muscle tissue. Liver (A) and muscle fat (B), and muscle creatine (C) and choline (D) were investigated with magnetic resonance spectroscopy as shown in Materials and Methods. Small symbols and thin lines indicate individual values of patients, whereas large symbols and thick bars indicate medians and interquartile ranges. p, significance level.

Figure 6

Molecular composition and kinetics of plasma phosphatidylcholine (PC) in response to choline supplementation. (A) PC molecular species grouped according to their content of different fatty acid residues in sn-position 2 (Sat. PC, C18:1-PC, C18:2-PC, C20:4-PC or C22:6-PC). White panels indicate the median PC composition prior to choline supplementation (visit [V] 2‒4, whereas grey panels are values after 84 d choline supplementation (V6-8). Striped panels indicate the molecular composition of PC synthesized de novo (D₉-PC), whereas dotted panels indicate synthesis via methylation of phosphatidylethanolamine (D₃-PC) [13,27]. (B) D₉- and D₃-enrichment of PC prior to and after choline supplementation. (C) The relative synthesis rates and kinetics of plasma PC sub-groups are identical prior to (visit [V] 2–4) and after (V6–8) 84 d choline supplementation. Data are medians and interquartile ranges of N = 10. Abbreviations: ** p < 0.01; *** p < 0.001.