Spontaneous development of fatty liver in ferrets in a toxicology study

Dietary lycopene attenuates cigarette smoke-promoted nonalcoholic steatohepatitis by preventing suppression of antioxidant enzymes in ferrets

Cigarette smoke (CS) is an independent risk factor in development of nonalcoholic steatohepatitis (NASH) and fibrosis. Lycopene, a carotenoid naturally occurring in tomatoes, has been shown to be a protective agent against tobacco carcinogen 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK)-induced NASH. In the present study using a ferret model we investigated whether CS promotes NASH and whether dietary lycopene can inhibit CS-promoted NASH development, and if so, what potential mechanisms were involved. Ferrets were divided into 4 groups (n=12-16/group): control, NNK/CS exposed, NNK/CS plus low-dose lycopene (2.2 mg/kg BW/day), and NNK/CS plus high-dose lycopene (6.6 mg/kg BW/day) groups, for 26 weeks. Results showed that hepatic steatosis, infiltrates of inflammatory cells, and the number and size of inflammatory foci in liver, together with key genes involved in hepatic fibrogenesis were higher in the NNK/CS group compared to the control group; a lycopene diet reversed these changes to the levels of the control group. Interestingly, a major lycopene cleavage enzyme, beta-carotene 9',10'-oxygenase (BCO2), which recently has been recognized to play metabolic roles beyond cleavage function, was down-regulated by NNK/CS exposure, but this decrease was prevented by lycopene feeding. NNK/CS exposure also downregulated liver expression of antioxidant enzymes and upregulated oxidative stress marker, which were all prevented by lycopene. In conclusion, our results suggest that CS can promote development of NASH and liver fibrosis in ferrets, which is associated with downregulation of BCO2 and impairment of antioxidant system in liver; dietary lycopene may inhibit CS-promoted NASH by preventing suppression of BCO2 and decline in antioxidant network.

Pigs and Ferrets as Models in Toxicology and Biological Safety Assessment

Both the pig and the ferret are used as animal models in toxicology and drug development, with the pig having been subject to a significant increase in usage (particularly in Europe) over the last 5 years. These two species are quite different from primates and dogs, the “standard” nonrodent models. This article seeks to both survey the rationales for and extent of use of the pig and ferret, and to highlight consideration and key factors in their use in studies.

Response to Fasting in an Unnaturally Obese Carnivore, the Captive European Polecat Mustela putorius

The European polecat ( Mustela putorius) is a naturally lean carnivore prone to excessive weight gain in captivity. This study assessed its suitability to investigate the natural history of the obese phenotype displayed in overweight humans, domestic animals, and seasonally obese wild mammals. Ten farm-bred polecats were subjected to a 5-day fast with 10 controls. Obesity (40% body fat) was associated with an unfavorable plasma lipid profile and high glucose and insulin concentrations. The polecats were in phase II of fasting with normoglycemia, low liver carbohydrate stores, and decreased plasma concentrations of urea and most amino acids. Although the plasma nonesterified fatty acid (NEFA) levels were elevated, the adipose tissue lipase activities suggested a blunted lipolytic response. Lipid mobilization was more efficient from intraabdominal fat. The animals developed hepatic lipidosis with elevated NEFA influx into the liver and losses of n-3 polyunsaturated fatty acids and arginine as hypothetical etiological factors. The plasma leptin, insulin, and triiodothyronine levels decreased but were not accompanied by reduced sex steroid or increased stress hormone concentrations. The blunted lipolytic response often encountered in obesity suggests that the organism is trying to defend the obese phenotype. Liver lipidosis and decreased insulin and triiodothyronine levels seem to be among the most consistent responses to fasting manifested in diverse mammalian orders and different levels of body fatness. The polecat could be recommended as an easily accessible carnivorean model to study the natural history of the obese phenotype and its comorbidities.

Fatty Acid Composition and Development of Hepatic Lipidosis During Food Deprivation—Mustelids as a Potential Animal Model for Liver Steatosis

Non-alcoholic fatty liver disease (NAFLD) is the hepatic manifestation of the metabolic syndrome characterized by asymptomatic hepatic steatosis. It is present in most cases of human obesity but also caused e.g., by rapid weight loss. The patients have decreased n-3 polyunsaturated fatty acid (PUFA) proportions with decreased percentages of 18:3(n-3), 20:5(n-3) and 22:6(n-3) and an increased n-6/n-3 PUFA ratio in liver and/or white adipose tissue (WAT). The present study examined a new experimental model to study liver steatosis with possible future applications to NAFLD. Ten European polecats ( Mustela putorius), the wild form of the domestic ferret, were food-deprived for 5 days with 10 fed animals as controls. The food-deprived animals showed micro- and macrovesicular hepatic steatosis, decreased proportions of 20:5(n-3), 22:6(n-3) and total n-3 PUFA and increased n-6/n-3 PUFA ratios in liver and WAT. At the same time, the product/precursor ratios decreased in liver. The observed effects can be due to selective fatty acid mobilization preferring n-3 PUFA over n-6 PUFA, decreased Δ5 and Δ6 desaturase activities, oxidative stress, decreased arginine availability and activation of the endocannabinoid system. Hepatic lipidosis induced by food deprivation was manifested in the fatty acid composition of the polecat with similarities to human NAFLD despite the different principal etiologies.

Morphology of ferret subcutaneous adipose tissue after 6-month daily supplementation with oral beta-carotene

Adipose tissue is an important retinoid depot and retinoids are known to influence white and brown adipocyte metabolism. Identifying nutrients that can affect the biological activity of the adipose organ would be of great medical interest in the light of the current obesity epidemic and related disorders in developed countries. The vast majority of mammal studies of chronic administration of oral beta-carotene have used murine models, while few have employed mammals exhibiting uptake and processing of intestinal beta-carotene similar to those of humans. While rodents transform practically all ingested beta-carotene into retinol, in ferrets, as in humans, part of the beta-carotene is absorbed and released into the circulation intact. We studied the effects of 6-month daily administration of two doses of oral beta-carotene (0.8 or 3.2 mg/kg/day) on ferret body weight, size of body fat depots, and, using morphological and morphometric methods, on subcutaneous (inguinal) white adipose tissue (WAT). Because of the oral mode of administration, liver, stomach, and small and large intestine were also studied. Control animals received the vehicle. Data show that at the end of treatment the higher dose induced significantly higher body weight compared with controls and significantly higher inguinal fat depot compared with animals treated with the lower dose. In addition, chronic treatment with beta-carotene induced a dose-dependent hypertrophy of white adipocytes and increased neoangiogenesis in subcutaneous WAT in all treated ferrets. Vasculogenesis was independent of adipocyte hypertrophy. We also found focally evident liver steatosis in the ferrets treated with the higher dose of beta-carotene. The other gastrointestinal tract organs studied were not significantly different from those of control animals.