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

Abstract

AimsThe 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).MethodsC57BL/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.ResultsCCF 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.ConclusionsThe 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.

Carbohydrate Sensing Through the Transcription Factor ChREBP

“…They reported that ChREBP binding is enriched in pathways involved in insulin signaling, adherent junctions and cancer, suggesting a novel involvement of ChREBP in tumorigenesis and cancer progression. Further, a recent study reported the importance of ChREBP in hepatocellular carcinoma (HCC) (Ribback et al, 2017). The authors found that genetic deletion of ChREBP (in ChREBP KO mice) impaired hepatocarcinogenesis driven by protein kinase B/Akt overexpression in mice.…”

Oncogene-dependent addiction to carbohydrate-responsive element binding protein in hepatocellular carcinoma

“…In light of these previous findings, considerable efforts should be devoted to identify key metabolic candidates whose inactivation might severely impair hepatocarcinogenesis while sparing normal cells. Previously, it has been demonstrated that alterations of glucose and lipid metabolism in HCC of humans and rodents are paralleled by the strong upregulation of carbohydrate-responsive element binding protein (ChREBP) transcription factor [13,19,20]. Together with the sterol regulatory element binding protein-1c (SREBP-1c) gene, ChREBP is a major positive regulator of glucose and lipid metabolism in the liver [21][22][23][24][25].…”

Transcriptomic and Proteomic analysis of clear cell foci (CCF) in the human non-cirrhotic liver identifies several differentially expressed genes and proteins with functions in cancer cell biology and glycogen metabolism

“…Specifically, we found an increased glycogen storage, reduced glucose-6-phosphatase activity and upregulated enzymes of glycolysis and de novo lipogenesis, beta-oxidation as well as overexpression of the insulin receptor and activated AKT/mTOR and Ras/MAPK pathways in CCF from both human livers and the rat model [20]. Similiarly, in the mouse, hepatocarcinogenesis is associated with activation of the insulin/AKT/mTOR signaling pathway, the transcriptional regulator ChREBP [16,21], as well as the lipogenic pathway [18,22,23]. Although these data hint to several pathways and regulators, a comprehensive inventory of gene and protein expression in human CCF is missing.…”