Development of a Microminipig Model of Atherosclerosis for the Evaluation of a HMGCR Inhibitor.

BACKGROUND/AIM: Atherosclerosis is known as a major risk factor for cardiovascular disease, and development of an animal model of atherosclerosis is required to investigate its clinical pathogenesis. We studied the optimal amount of cholesterol in the diet and the optimal experimental period for development of a Microminipig model of atherosclerosis for the evaluation of a hydroxymethylglutaryl-CoA reductase (HMGCR) inhibitor (atorvastatin). MATERIALS AND METHODS: Eighteen male animals (3-4 months old) were divided into 3 groups. Group 1 consisted of control animals receiving a normal chow diet, Group 2 animals received a high fat (12% w/w) and low cholesterol (0.1% w/w) diet (HFLCD), and Group 3 animals received HFLCD+statin for 12 weeks. Animals received statin at 3 mg/kg body weight per day. HFLCD did not down-regulate the hepatic expression of HMGCR mRNA. RESULTS: HFLCD increased body, omentum, and mesenteric adipose tissue weight, and induced hypercholesterolemia and atherosclerotic lesions in the abdominal aorta. HFLCD+statin inhibited hypercholesterolemia and atherosclerotic lesions, but not obesity. CONCLUSION: A microminipig atherosclerosis model induced by HFLCD can be used in the evaluation of HMGCR inhibitors for the treatment of hypercholesterolemia and atherosclerosis.

Association Between HMGB1 and Thrombogenesis in a Hyperlipaemia-induced Microminipig Model of Atherosclerosis.

BACKGROUND/AIM: An appropriate animal model is essential to investigate the relationship between inflammation, atherosclerosis, and thrombogenesis, and the development of preventive measures and therapies for atherosclerosis. MATERIALS AND METHODS: Atherosclerosis was induced in Microminipigs (MMPs) using a high-fat diet. We assessed high mobility group box 1 (HMGB1) expression levels and measured thrombus formation using a Total Thrombus Formation Analysis System (T-TAS). MMPs were divided into a normal diet (control) group and four high-fat diet groups, with differing amounts of cholesterol. After 8 weeks, blood was collected for analysis. RESULTS: HMGB1 levels increased with increasing dietary cholesterol, and a negative correlation was found between HMGB1 levels and thrombus formation time. CONCLUSION: T-TAS is useful in the assessment of thrombogenesis in MMPs and HMGB1 is associated with thrombus formation.

Cholic Acid Enhances Visceral Adiposity, Atherosclerosis and Nonalcoholic Fatty Liver Disease in Microminipigs.

AIM: We have recently established a novel swine model for studies of atherosclerosis using MicrominipigsTM (µMPs) fed a high-fat/high-cholesterol diet (HcD). Using this swine model, we re-evaluated the effects of dietary cholic acid (CA) on serum lipid profile, atherosclerosis and hepatic injuries. METHODS: The µMPs were fed HcD supplemented with 0.7% CA (HcD＋CA) for eight weeks, and the effect of CA on serum lipoprotein levels, expression of oxidative stress markers, adiposity and lesion formation in the aorta, liver, and other organs was investigated. RESULTS: The HcD＋CA-fed group exhibited more visceral adiposity, progression of atherosclerosis and higher serum levels of oxidative stress markers than the HcD-fed group, even though they showed similar serum lipid levels. The liver demonstrated increased lipid accumulation, higher expression of oxidative stress markers, accelerated activation of foamy Kupffer cells and stellate cells, and increased hepatocyte apoptosis, indicating non-alcoholic fatty liver disease (NAFLD). Intriguingly, foamy macrophage mobilization was observed in various organs, including the reticuloendothelial system, pulmonary capillary vessels and skin very often in HcD＋CA-fed µMPs. CONCLUSION: To our knowledge, this is the first large animal model, in which visceral obesity, NAFLD and atherosclerosis are concomitantly induced by dietary manipulation. These data suggest the detrimental effects of CA, potentially through local and systemic activation of oxidative stress-induced signaling to macrophage mobilization, on the acceleration of visceral adiposity, atherosclerosis and NAFLD.

Rapid development of atherosclerosis in the world's smallest Microminipig fed a high-fat/high-cholesterol diet.

AIM: Experimental studies of human atherogenesis require an appropriate animal model that mimics human physiology and pathology. Because swine physiology is similar to human physiology, we developed a hyperlipidemia-induced atherosclerosis model using the recently developed world's smallest Microminipig(TM). METHODS: These animals weigh only 5kg at 3months of age, much smaller than any other miniature pig. We found that the administration of a high-fat/high-cholesterol diet containing at least 0.2% cholesterol without cholic acid for as little as eight weeks induces hypercholesterolemia and subsequent atherosclerosis in these animals. RESULTS: The serum levels of low-density lipoprotein cholesterol(LDL-C) and the percent distribution of cholesterol in the LDL fractions were markedly increased. The hepatic expression of LDL receptor and hydroxymethylglutaryl-CoA reductase was coordinately decreased. The cholesteryl ester transfer protein activity, which plays a role in reverse cholesterol transport, was detected in the serum of the Microminipigs. Niemann-Pick C1-like 1 protein was expressed in both the liver and small intestine; however, hepatic apoB mRNA editing enzyme was not expressed. As in humans, and in contrast to that observed in mice, most of the hepatic lipase activity was localized in the liver. These results suggest that the hyperlipidemia-induced gene expression profile linked to cholesterol homeostasis and atherogenesis is similar in Microminipigs and humans. CONCLUSION: We conclude that the characteristics of the Microminipig, including its easy handling size, make it an appropriate model for studies of atherosclerosis and related conditions.

Sex differences of serum lipid profile in novel microminipigs.

Swine have been used extensively in biomedical research, with a significant increase in recent decades. Minipigs are increasingly becoming an especially attractive animal model in life science research because of their physiological and anatomical similarities to humans. The Microminipig (MMPig) has emerged as a novel and small minipig for non-clinical pharmacological/toxicological use. The MMPig is docile, weighs less than 10 kg in early maturity, and has an easily manageable size. In this study, we report on sex and age patterns in serum biochemistry parameters, including lipid analysis items and lipid profiles in healthy MMPigs. In total, 58 males and 67 females aged 0-34 months underwent serum biochemistry parameter measurements. Most parameters showed no effect of age or sex (although some did). Lipid analyses showed that the serum levels of total cholesterol, but not those of triglycerides (TG), were consistently higher in females at 0-34 months of age. Lipid profiles in 5-month-old MMPigs were investigated in greater detail. Serum low-density lipoprotein-cholesterol (LDL-C) values were higher in females. The percentage of LDL-C against total cholesterol was also higher, although high-density lipoprotein-cholesterol was lower, in females. There were no sex differences in the TG fraction. Although the sex difference in the serum lipid profile remains unexplained, the reference values obtained in this study could help facilitate the use of MMPigs in life science research.

Coagulation activity and white thrombus formation in the microminipig.

Swine are becoming increasingly attractive as animal models for clinical research and the recently developed Microminipig (MMPig) has emerged as a possible experimental animal model. In this study, we demonstrated age-dependent changes in hematological parameters and coagulation activity in healthy MMPigs (58 male and 67 females, aged 0-34 months), and investigated white thrombus formation (WTF) using an in vitro microchip flow-chamber system (four males and four females, aged 22-23 months). There was no clear sex or age-dependent differences in any hematological parameters. While activated partial thromboplastin time (APTT) was shorter than prothrombin time (PT), with APTT:PT of 0.88:1, microchip flow-chamber system analysis showed that WTF time was shorter than that in humans, suggesting a possible thrombotic tendency in the MMPig. These results could be useful to life science researchers in the use of the MMPig as an experimental model animal for thrombus formation.

Reference values of hematological and biochemical parameters for the world smallest microminipigs.

In this study, we demonstrated growth curves and reference values for hematological and serum biochemical parameters of Microminipigs, the world smallest experimental minipigs. In both male and female animals, the body weights (BWs) at 3 and 6 months of age were <5 kg and <10 kg, respectively, and growth curve revealed almost plateau (approximately 20 kg BW) after 18 months of age. Major hematological and serum biochemical parameters showed no gender differences and the values were very similar to those in Göttingen and Yukatan minipigs. The values obtained in this study can serve as fundamental reference, and thereby facilitate the use of Microminipig in life science research.