{'fraction_non_alphanumeric': 0.03624939584340261, 'fraction_numerical': 0.03866602223296278, 'mean_word_length': 5.124260355029586, 'pattern_counts': {'":': 0, '<': 2, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
402 Cholesterol Synthesis in vivo in Premature Infants from Deuterated Water (D2O)

Background: Cholesterol is one of the main components of cell membranes and is required as precursor for many metabolically active compounds. To date cholesterol metabolism is uncompletely defined in premature infants. Using a 12 h i.v. constant infusion of 13C acetate, Renfurm (Pediatr Res 2004) studied de novo cholesterol synthesis in premature infants. This method required indwelling lines.Objective: To assess if cholesterol synthesis can be measured with a less invasive method based on D2O as precursor (Matthan Lipids 2000).Material and Methods: Cholesterol synthesis was studied in 15 newborns (BW<1500 gr, age<48 h) on parenteral nutrition without lipids. Subjects received orally a bolus of D2O (0.1 gr/kg), followed by 0.000625 gr/kg every 12 for 48 h. Urine and plasma samples (200 ul) were collected before study start and every 12 h thereafter till 48 h. Unesterified cholesterol was obtained from plasma lipid extraction and thin layer chromatography separation, and cholesterol deuterium enrichments measured by Gas-Chromatography-Isotope Ratio- Mass Spectrometry (GC-IRMS). Deuterium enrichment of urine samples were measured by GC-IRMS and regarded as the precursor enrichment pool. Cholesterol Fractional Synthesis Rate (FSR) and secretion time (ST) were measured as previously described (Matthan Lipids 2000). Data are given as mean±SD.Results: Study weight was 1084±546 gr, gestational age 28±2 wks, mean age 23±19 h. Energy Intake was 30±8 kcal/kg/day. Cholesterol FSR was 16±12% and ST 11±11 h.Conclusion: This method has the advantage that tracer can be given orally, steady state of precursor is easily achieved and very small amount of blood is needed. We measured cholesterol synthesis from D2O in vivo in premature infants and the calculated rate was approximately that found in adults (Jones J Lipid Res 1994). Given the high variability between patients larger study will better define factors related to endogenous cholesterol synthesis early in life.