1. Fibrates induce hepatic peroxisome and mitochondrial proliferation without overt evidence of cellular proliferation and oxidative stress in cynomolgus monkeys.
- Author
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Hoivik DJ, Qualls CW Jr, Mirabile RC, Cariello NF, Kimbrough CL, Colton HM, Anderson SP, Santostefano MJ, Morgan RJ, Dahl RR, Brown AR, Zhao Z, Mudd PN Jr, Oliver WB Jr, Brown HR, and Miller RT
- Subjects
- Acyl-CoA Oxidase metabolism, Animals, Apoptosis, Area Under Curve, Catalase genetics, Catalase metabolism, Cell Division drug effects, Cyclin D1 metabolism, Cyclin-Dependent Kinase Inhibitor p21, Cyclins metabolism, Endoplasmic Reticulum, Smooth drug effects, Endoplasmic Reticulum, Smooth metabolism, Fibric Acids, Gene Expression Profiling, Glutathione Peroxidase genetics, Glutathione Peroxidase metabolism, Liver cytology, Macaca fascicularis, Male, Mitochondria drug effects, Mitotic Index, Organ Size drug effects, Peroxisomes drug effects, Proliferating Cell Nuclear Antigen metabolism, RNA, Messenger metabolism, Receptors, Cytoplasmic and Nuclear metabolism, Thioredoxin-Disulfide Reductase metabolism, Transcription Factors metabolism, Clofibric Acid analogs & derivatives, Clofibric Acid toxicity, Fenofibrate toxicity, Liver metabolism, Mitochondria metabolism, Oxidative Stress drug effects, Peroxisomes metabolism
- Abstract
There is little primate risk factor data in the literature evaluating the relationship between proposed mechanisms of PPAR agonist-induced hepatocarcinogenesis at clinically relevant therapeutic exposures. These studies were conducted to characterize the hepatic effects of fenofibrate and ciprofibrate in the cynomolgus monkey. Male cynomolgus monkeys were given fenofibrate (250, 1250 or 2500 mg/kg/day) or ciprofibrate (3, 30, 150 or 400 mg/kg/day) for up to 15 days. The highest doses used were approximately 4 times (fenofibrate) and 9.4 times (ciprofibrate) the human therapeutic exposure for these agents based on AUC (area under the curve). For both compounds, there was a treatment-related increase in liver weight and periportal hepatocellular hypertrophy, which was related to increases in peroxisomes (up to 2.8 times controls) and mitochondria (up to 2.5 times controls). An increase in smooth endoplasmic reticulum probably contributed to the hypertrophy. There was no indication of cell proliferation as determined by the number of mitotic figures and this was confirmed by evaluating cell proliferation by immunohistochemical staining for the Ki-67 antigen. Consistent with the findings by light microscopy, there was no treatment-related effect on the level of mRNA for proteins known to be involved in the control of hepatocyte cell division or apoptosis (e.g. P21, Cyclin D1, PCNA, CDKN1A). Furthermore, there was minimal indication of oxidative stress. Thus, there was no evidence of lipofuscin accumulation, and there was no remarkable increase in the mRNA levels for most proteins known to respond to oxidative stress (e.g. catalase, glutathione peroxidase). A mild induction in the mRNA levels of cellular beta-oxidation and detoxification enzymes (e.g. acyl CoA oxidase, thioredoxin reductase) was observed. Collectively, the data from these studies suggest that the primate responds to PPARalpha agonists in a manner that is different from the rodent suggesting that the primate may be refractory to PPAR-induced hepatocarcinogenesis.
- Published
- 2004
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