High Fat Diet Exacerbates 4NQO‐Induced Liver Pathology in Mice

Abstract

IntroductionA variety of factors, including use of tobacco, diet, gender, and genetics impact cancer risk. It is well established that administration of 4‐nitroquinonline 1‐oxide (4NQO) in drinking water mimics the effects of tobacco and leads to development of oral carcinoma in mice. The purpose of this study was to determine whether administration of 4NQO induced liver pathology and to examine the effects of gender, and high and low saturated fat diets (HF and LF, respectively) on the liver histopathology. We hypothesized that 4NQO's carcinogenic effects would cause pathological changes in liver and a HF diet would exacerbate this process.Materials and methodsMale and female C57Bl/6 mice (36 each gender), 5 weeks old, were divided into a low fat (10 kcal% fat; LF) or HF (60 kcal% fat) diet. Within each dietary group, mice were randomly assigned to one of 3 water treatment groups for 17 weeks: water alone (control); propylene glycol in water (1.25%; PG‐H2O); or 4NQO in PG‐H2O (50 mg/ml; 4NQO). After 17 weeks, all mice were given water alone for 6 more weeks. Livers harvested from the euthanized animals were weighed, then fixed in formalin and processed for histological examination. In addition, neutrophils and macrophages were detected by immunocytochemistry (Ly6 and CD68 positive cells, respectively) and counted in a standard area in liver sections. T‐tests were used to confirm no difference between water and PG controls, which were then combined for further statistical analysis using GraphPad Prism 7.0.ResultsAdministration of 4NQO resulted in histopathological changes in liver in all treatment groups. Morphological changes in hepatocytes, the presence of lobular and portal lymphoid cell infiltrates, and periportal fibrosis were observed in hematoxylin and eosin‐stained tissues. In addition, HF diet resulted in severe steatosis and liver enlargement (3× higher liver index in HF males versus all other treatment groups) of male but not female controls. Treatment with 4NQO significantly increased the number of neutrophils in liver, when compared to non‐4NQO‐treated control livers in HF males (208 versus 24.7), HF females (100 versus 29.2), and LF females (80 versus 26.7; for all groups, p<0.05). Also, treatment with 4NQO increased the number of macrophages in HF males, when compared to non‐4NQO‐treated males (121 versus 55, p<0.05). In addition, HF diet exacerbated the effect of 4NQO in males, with 121 neutrophils in HF 4NQO‐treated males versus 94.1 neutrophils in LF 4NQO‐treated males (p = 0.05).ConclusionOral administration of 4NQO, which mimics the effects of tobacco, induces histopathological changes in the liver, and those changes are exacerbated by a HF diet, especially in males.Support or Funding InformationWe recognize the Midwestern University Deans of the College of Dental Medicine and the Basic Science Division for their support of this research. Student research was supported by the Office of Research and Sponsored Programs and the Biomedical Sciences Division.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.