George Chan

Intravenous ursodeoxycholic acid reduces cholestasis in parenterally fed newborn piglets

BACKGROUND & AIMS Cholestasis complicates total parenteral nutrition (TPN) in preterm infants. Ursodeoxycholic acid (UDCA) is used for several cholestatic problems. The hypothesis of this study was that intravenous UDCA prevents TPN-induced cholestasis by (1) maintaining normal basal and stimulated bile flow, (2) altering bile composition, and (3) changing hepatocyte membrane composition and Na+,K(+)-adenosine triphosphatase (ATPase) activity. METHODS Three groups of piglets were studied: group 1 received sows milk, groups 2 and 3 received TPN, and group 3 also received 100 mumol.kg-1.day-1 UDCA intravenously. After 3 weeks, basal and stimulated bile flow were measured. Cholesterol, bile acids, phospholipids, and phospholipid fatty acids were analyzed in bile, and fluidity, phospholipid fatty acid composition, and Na+,K(+)-ATPase were analyzed in hepatocyte membranes. RESULTS Bile acid secretion and basal and stimulated bile flow were similar in control and UDCA-treated animals but reduced to < 50% in the TPN group. Bile acid-dependent and -independent bile flow were lower in the TPN group. UDCA did not normalize abnormalities in TPN-induced bile composition. Sinusoidal but not canalicular membrane fluidity was different in TPN than in control and UDCA-treated animals. UDCA also increased Na+,K(+)-ATPase activity. Bile and membrane phospholipid fatty acids reflected dietary fatty acids. CONCLUSIONS Intravenous UDCA improves bile flow and reduces bilirubin levels in the serum and liver in piglets with TPN-induced cholestasis.

Total parenteral nutrition impairs bile flow and alters bile composition in newborn piglet

Cholestatic liver disease complicates total parenteral nutrition (TPN) in premature neonates. We investigated TPN-induced liver disease in the newborn piglet, hypothesizing that: (1) TPN impairs bile flow by reducing the bile acid-dependent (BADF) and the bile acid-independent component of bile flow (BAIF); and (2) TPN changes bile composition. For three weeks, eight piglets received TPN and nine piglets were fed milk. Basal bile flow was measured and bile composition analyzed for bile acids, cholesterol (C), phospholipids (PL), and PL fatty acids. Bile flow was also measured after stimulation with 20, 50, and 100 µmol/kg taurocholic acid (TCA). Liver histology and bilirubin content were examined. Basal bile flow was reduced from 11.6±1.2 µl/g liver/10 min in orally fed animals to 1.6±0.4 µl/g liver/10 min in the TPN group. The stimulated bile flow in the TPN group did not respond to TCA and was lower than in the orally fed animals at each TCA dose. Both BADF and BAIF were significantly lower in the TPN group. Bile acid secretion was less than 50% of control values and total C and PL secretions were less than 5% of control. Liver and serum bilirubin were elevated in the TPN group. The newborn piglet is a valid model to study TPN-induced cholestasis, characterized by decreased bile acid secretion, impaired BADF and BAIF, and reduced bile flow stimulation after intravenous TCA.

Lipid metabolism in the neonate: III. The ketogenic effect of Intralipid infusion in the neonate

The ketogenic potential of Intralipid was studied in two groups of infants: 12 were SGA and 15 AGA; all were clinically stable and less than 48 hours of age. During four-hour Intralipid tolerance tests, the SGA infants achieved significantly higher plasma TG and FFA levels. Both groups of infants significantly increased the concentration of ketone bodies; however, there was no difference in the levels achieved. In view of the slower clearance rate of TG and the higher levels of FFA in SGA infants, it is speculated that in addition to a possible defective lipoprotein lipase system and a decrease in number and size of the adipose cells, beta-oxidation of FFA to ketones may be occurring at a slower rate. The generation of high levels of ketones during Intralipid infusion period in both groups of infants indicates that SGA infants can handle ketone bodies as readily as AGA infants.

Bilirubin diffusion through lipid membranes

The possibility that bilirubin can diffuse through lipid bilayers is investigated with liposomes prepared from dipalmitoylphosphatidylcholine (DPPC), egg phosphatidylcholine (egg PC) with 22 mole percent cholesterol, and a lipid extract preparation from N115 neuroblastoma cells. Liposomes were prepared with internalized bilirubin and bovine or human serum albumin, and bilirubin efflux into an exogenous solution of human serum albumin was measured. Efflux from DPPC liposomes was significantly higher above the phase transition temperature than below it. This change was dependent on the lipid undergoing a phase transition and could not be accounted for by 6 K change in temperature. Maximum bilirubin efflux from egg PC-cholesterol liposomes was found to depend on the relative internal and external albumin pools, suggesting an equilibrium distribution of bilirubin between them. These observations demonstrate that bilirubin can diffuse freely through these lipid membranes.

Variance in albumin loading in exchange transfusions

To assess the rationale of albumin priming prior to exchange transfusions, 42 hyperbilirubinemic infants who required exchange transfusions were randomly assigned to one of two groups. Group I consisted of 15 infants who were given intravenously 1 gm/kg of salt-poor human serum albumin one hour before the exchanges. Group II, which consisted of 27 infants, received simple exchanges. No statistical differences were found in variations in reserve albumin-binding capacity, bilirubin, albumin, or red cell bilirubin at pre and one-hour post albumin infusion in the primed infants. The amount of bilirubin removed per kilogram is directly correlated to plasma bilirubin concentration (r=0.87). No significant difference in efficiency on bilirubin removal was seen between the two groups. Beneficial effects of albumin therapy was apparent only in those infants with low RABC as determined by the sephadex gel filtration technique.

Gentamicin and albumin-bilirubin binding. An in vivo study.

Ten newborn infants were given gentamicin intramuscularly. Over a postinjection interval of 12 hours, no significant change occurred in the total binding capacity of serum albumin for bilirubin or in concentrations of serum bilirubin levels. There was no correlation between concentrations of serum gentamicin and the total binding capacity or serum bilirubin. This study provides in vivo data that supports recent in vitro experiments showing that gentamicin does not alter bilirubin-albumin binding.

Bilirubin quantitation with lipemic plasma

1. In the presence of lipemia, the estimation of BR by diazo method is variable and hence unreliable. 2. The estimation of BR in lipemic plasma by the use of the A-O bilirubinometer yielded BR levels which were consistently lower than theoretical values. 3. By regression analysis of the percent error in BR estimation, (using the A-O bilirubinometer) and TG Concentrations, a straight line is obtained. Based upon this line, a correction factor for plasma BR concentration in the range of 5–25 mg/dl can be obtained if the degree of lipemia is known.