Diethylnitrosamine enhances hepatic tumorigenic pathways in mice fed with high fat diet (Hfd).

Obesity has been implicated in the genesis of metabolic syndromes including insulin resistance and Type 2 Diabetes Mellitus (T2DM). Given the association between T2DM and the risk of hepatocellular carcinoma (HCC), our specific goal was to determine whether the liver of HFD-induced T2DM mice is more sensitive to the carcinogen diethylnitrosamine (DEN), due to a modification of the molecular pathways implicated in the early stages of HCC pathogenesis. C57BL/6 male mice (five-week-old) were divided into 4 groups: C, C + DEN, HFD and HFD + DEN. Mice were euthanized twenty-five weeks after DEN-injection. Livers of HDF-fed mice showed a higher proliferative index than Control groups. In line with this, HFD groups showed an increase of nuclear ß-catenin, and interestingly, DEN treatment led to a slight increase in the expression of this protein in HFD group. Based on these results, and to confirm this effect, we analyzed ß-catenin target genes, finding that DEN treatment in HFD group led to a significant increase of Vegf, c-myc, c-jun and cyclin D1 expression levels. According to our results, the expression of TCF4 showed to be significantly increased in HFD + DEN vs. HFD. In this regard, the ß-catenin/TCF4 complex enhanced its association with pSmads 2/3, as we observed an increase of nuclear Smads expression in HFD + DEN, suggesting a possible role of TGF-ß1/Smads signaling pathway in this phenomenon. Our results show that the liver of HFD fed model that resembles early T2DM pathology in mice, is more sensitive to DEN, by inducing both Wnt/ß-catenin and TGF ß1/Smads tumorigenic pathways.

Diethylnitrosamine Increases Proliferation in Early Stages of Hepatic Carcinogenesis in Insulin-Treated Type 1 Diabetic Mice.

Diethylnitrosamine (DEN) induces hepatocarcinogenesis, increasing mitotic hepatocytes and leading to chronic inflammation. In addition, type 1 diabetes mellitus (T1DM) is also characterized by a proinflammatory state and by requiring insulin exogenous treatment. Given the association of diabetes, insulin treatment, and cell proliferation, our specific goal was to determine whether the liver in the diabetic state presents a greater response to DEN-induced cell cycle alteration, which is essential for the malignant transformation. Male C57BL/6 mice (four-week-old) were divided into 4 groups: C, C + DEN, T1DM, and T1DM + DEN. Mice were euthanized ten weeks after DEN injection. DEN per se produced an increase in liver lipid peroxidation levels. Besides, in T1DM + DEN, we found a greater increase in the proliferation index, in comparison with C + DEN. These results are in agreement with the increased expression observed in cell cycle progression markers: cyclin D1 and E1. In addition, a proapoptotic factor, such as activated caspase-3, evidenced a decrease in T1DM + DEN, while the Vascular Endothelial Growth Factor (VEGF) and the protooncogene p53 showed a higher increase with respect to C + DEN. Overall, the results allow us to highlight a major DEN response in T1DM, which may explain in part the greater predisposition to the development of hepatocarcinoma (HCC) during the diabetic state.

Lipopolysaccharide (LPS) induction of nitric oxide synthase-2 and cyclooxygenase-2 is impaired in fructose overloaded rats.

AIMS: Fructose (F) overload in rats induces metabolic dysfunctions that resemble the human metabolic syndrome. In this paper, we aimed to investigate the response of F overload rats to lipopolysaccharide (LPS) challenge in terms of nitric oxide (NO) production and prostanoids (PR) release. MAIN METHODS: NO blood steady-state concentration was monitored through the detection of nitrosyl-hemoglobin complexes (NO-Hb) by electronic spin resonance. Production of 6-keto PGF(1)α, PGE(2), PGF(2)α and TXB(2) was measured in aorta and mesenteric beds by HPLC. Western blot analysis was used to examine the changes in the expression levels of NOS-2 and COX-2 in aorta. KEY FINDINGS: Our results showed that increases in NO circulating steady-state concentration and PR production by aorta and mesenteric beds 6h after LPS administration were significantly attenuated in F overload rats with respect to control animals. Oxidative stress parameters were equally affected in the presence or absence of the F treatment. Aorta protein levels of NOS-2 and COX-2, two enzymes inducible by LPS, were significantly lower in F overload rats with respect to control rats at the end of the treatment (-39% and -61% for NOS-2 and COX-2 respectively). SIGNIFICANCE: These results suggest that the metabolic alterations established by 15 weeks of F overload should affect the response to LPS challenge due to an attenuation in the induction of NOS-2 and COX-2. This effect would be one of the components contributing to abnormalities in the course of the inflammatory response in other conditions associated to insulin resistance, such as diabetes.