Ischemia-reperfusion injury in a diet-induced rat fatty liver

The increased incidence of primary non–function observed when donor livers with moderate–massive fatty infiltration are transplanted is caused by a reduced tolerance to the ischemia–reperfusion (I–R) injury occurring during the transplant procedure.1 The animal nutritional status influences I–R injury in normal livers, but no data are available in the specific setting of fatty livers. Thus, this study aimed to determine whether fasting affects the extent of warm I–R injury in rat fatty liver. Materials and methods Fed and 18 hour fasted male Wistar rats with normal or with fatty liver induced by 10 days of choline–deficient diet (Dyets Inc, Bethlehem, Pa, USA) were subjected to 1 hour lobar ischemia followed by reperfusion and partial hepatectomy of the non–involved liver according to a modification of the technique described by Kawano et al.2 The animals were divided in groups of 5–6 units, sacrificed before and after ischemia, and at 30 minutes, 2 hours, 8 hours, and 24 hours after reperfusion to collect liver and blood samples. Hepatic injury was assessed by measuring the serum alanine aminotransferase (ALT), aspartate aminotransferase (AST), and lactate dehydrogenase (LDH), and by evaluating liver histology. Statistically significant differences between groups were determined with the Student’s t–test. Results Following reperfusion, serum enzymes increased several folds above the pre–ischemic levels in all groups. Fasting exacerbates such an increase both in rats with normal and with fatty liver; however, the difference was significantly greater in presence of fatty infiltration. At 8 hours of reperfusion: ALT level (mean ± SD) was 7026 ± 1781 U/L, AST 16700 ± 1369, and LDH 290620 ± 113452 in fatty fasted rats compared to 4644 ± 1575 U/L (P < .05), 5460 ± 2966 U/L (P < .01), 24040 ± 19615 U/L (P < .01), respectively, in fatty fed rats. Histological liver injury during reperfusion was much more evident in steatotic livers. However, while the lobular architecture was well maintained in fatty livers from fed rats, a massive hemorrhagic necrosis with disruption of sinusoidal architecture and wide areas of red cell extravasation was documented in fatty livers from fasted animals. Conclusions Characterization of the cellular, vascular, and metabolic events that occur in a failing fatty liver graft is needed to increase the use of these “marginal” donor organs. Hepatic microcirculatory injury is generally considered the initial event for the development of cell death during post–ischemic reperfusion.3 However, other additional factors can be important. For instance, it is well known that the preexisting nutritional status greatly influences the degree of I–R injury in normal livers. This study indicates that rat fatty livers subjected to warm I–R injury are adversely affected by fasting much more than normal livers are. Based on this observation, a nutritional repletion procedure could be beneficial to prevent this injury and, ultimately, to improve the acceptance of donor fatty livers for liver transplantation.