Hepatocellular glycogenotic foci after combined intraportal pancreatic islet transplantation and knockout of the carbohydrate responsive element binding protein in diabetic mice

Abstract

Aims: The intraportal pancreatic islet transplantation (IPIT) model of diabetic rats is an insulin mediated model of hepatocarcinogenesis characterized by the induction of clear cell foci (CCF) of altered hepatocytes, which are pre-neoplastic lesions excessively storing glycogen (glycogenosis) and exhibiting activation of the AKT/mTOR protooncogenic pathway. In this study, we transferred the IPIT model to the mouse and combined it with the knockout of the transcription factor carbohydrate responsive element binding protein (chREBP).

Methods: C57BL/6J Wild-type (WT) and chREBP-knockout (chREBP-KO) mice (n = 297) were matched to 16 groups (WT/ chREBP-KO, experimental/control, streptozotocine-induced diabetic/not diabetic, one/four weeks). Experimental groups received the intraportal transplantation of 70 pancreatic islets. Liver and pancreatic tissue was examined using histology, morphometry, enzyme- and immunohistochemistry and electron microscopy.

Results: CCF emerged in the liver acini downstream of the transplanted islets. In comparison to WT lesions, CCF of chREBP-KO mice displayed more glycogen accumulation, reduced activity of the gluconeogenic enzyme glucose-6-phosphatase, decreased glycolysis, lipogenesis and reduced levels of the AKT/mTOR cascade members. Proliferative activity of CCF was ~two folds higher in WT mice than in chREBP-KO mice.

Conclusions: The IPIT model is applicable to mice, as murine CCF resemble preneoplastic liver lesions from this hepatocarcinogenesis model in the rat in terms of morphological, metabolic and molecular alterations and proliferative activity, which is diminished after chREBP knockout. chREBP appears to be an essential component of AKT/mTOR mediated cell proliferation and the metabolic switch from a glycogenotic to lipogenic phenotype in precursor lesions of hepatocarcinogenesis.