Assembly of biliary lipids in native hepatic bile after orthotopic liver transplantation: A biochemical and ultra-structural study in humans

Background: In gallbladder bile, lipids aggregate as micelles and vesicles, yet the presence of lamellae remains controversial. Little is known on lipid assembly in dilute hepatic bile. Liver transplantation represents a condition in which bile is diluted immediately after transplant and tends to normalize thereafter. Aim: To study biliary lipidic carriers after liver transplantation in relation to the increasing bile lipid concentration. Methods: Three bile samples were harvested from six patients (3M/3F) with normal post-transplant outcome: sample 1 at days 2-3, sample 2 at 1 week, and sample 3 at 2 weeks after transplant. Samples were analyzed by biochemical, morphological and quasi-elastic light scattering methodology. Results: Lipid concentration increased from 0.6 g/dl at day 2-3 to 3.6 g/dl at week 2. Electron microscopy showed the presence of unilamellar vesicles in all samples. Large amorphous particles interpreted as proteic aggregates were also present at day 2-3, while lamellae coexisted with vesicles later. Quasi-elastic light scattering data were consistent with electron microscopic findings. Liquid crystals were observed at polarizing microscopy with increasing bile lipid concentration. Conclusions: Normalization of biliary lipid secretion after liver transplantation is associated with: (i) increased proportion of vesicles and reduction of their size; (ii) presence of lamellae.