Identification of novel serum markers for the progression of coronary atherosclerosis in WHHLMI rabbits, an animal model of familial hypercholesterolemia.

BACKGROUND AND AIMS: The development of serum markers specific for coronary lesions is important to prevent coronary events. However, analyses of serum markers in humans are affected by environmental factors and non-target diseases. Using an appropriate model animal can reduce these effects. To identify specific markers for coronary atherosclerosis, we comprehensively analyzed the serum of WHHLMI rabbits, which spontaneously develop coronary atherosclerosis. METHODS: Female WHHLMI rabbits were fed standard chow. Serum and plasma were collected under fasting at intervals of 4 months from 4 months old, and a total of 313 lipid molecules, 59 metabolites, lipoprotein lipid levels, and various plasma biochemical parameters were analyzed. The severity of coronary lesions was evaluated with cross-sectional narrowing (CSN) corrected with a frequency of 75%-89% CSN and CSN> 90%. RESULTS: There was a large variation in the severity of coronary lesions in WHHLMI rabbits despite almost no differences in plasma biochemical parameters and aortic lesion area between rabbits with severe and mild coronary lesions. The metabolites and lipid molecules selected as serum markers for coronary atherosclerosis were lysophosphatidylcholine (LPC) 22:4 and diacylglycerol 18:0-18:0 at 4 months old, LPC 20:4 (sn-2), ceramide d18:1-18:2, citric acid plus isocitric acid, and pyroglutamic acid at 8 months old, and phosphatidylethanolamine plasminogen 16:1p-22:2 at 16 months old. CONCLUSIONS: These serum markers were coronary lesion-specific markers independent of cholesterol levels and aortic lesions and may be useful to detect patients who develop cardiovascular disease.

Distribution of atherosclerotic lesions in various arteries of WHHLMI rabbits, an animal model of familial hypercholesterolemia.

In WHHLMI rabbits, arterial lesions develop spontaneously in various arteries even with standard chow. Here, we examined the development of arterial lesions in various arteries to demonstrate standard characteristics of arterial lesions in WHHLMI rabbits. For WHHLMI rabbits at 6, 12, 20, and 30 months of age, lesion areas and areas of arterial lumen surfaces were measured using image analysis software. Histopathological sections of arterial lesions were stained with elastic van Gieson staining. Arterial lesions developed around bifurcations and expanded with aging. In the aorta, atheromatous lesions were severe in the thoracic aorta but were mild in the distal part of the abdominal aorta. Carotid artery lesions progressed in the proximal region and at bifurcations, and the histopathological features were similar to those of coronary lesions. Pulmonary artery lesions contained many foam cells. Fibrous lesions were observed in the proximal and distal areas of the renal arteries, at the bifurcation of the iliac-femoral artery and mesenteric artery, and around the anastomosis of vertebral arteries. Lesions in the celiac artery contained foam cells and/or lipid droplets within fibrous lesions. In a pair of right and left arteries, the arterial lesions tended to progress more in the right artery. Gender did not affect analysis of arterial lesions. In conclusion, the arterial lesions expanded from bifurcations, and the morphological features of the arterial lesions varied depending on the type of artery. These results serve as reference data for arterial lesions in studies using WHHLMI rabbits.

Species differences in lipoprotein lipase and hepatic lipase activities: comparative studies of animal models of lifestyle-related diseases.

Lipoprotein lipase (LPL) and hepatic triglyceride lipase (HTGL) have an important role in lifestyle-related diseases. To evaluate species differences, we compared LPL and HTGL activities in different animal models of lifestyle-related diseases using the same assay kit. Normal animals (JW rabbits, ICR mice, and SD rats), a hypercholesterolemic animal model (WHHLMI rabbits), and obese animal models (KK-Ay mice and Zucker fatty rats) fed standard chow were used in this study. Plasma was prepared before and after an intravenous injection of heparin sodium under fasting and feeding. LPL and HTGL activities were measured with the LPL/HTGL activity assay kit (Immuno-Biological Laboratories) using an auto-analyzer. Only in mice, high HTGL activity was observed in pre-heparin plasma. In normal animals, LPL and HTGL activities were high in ICR mice and SD rats but low in JW rabbits. Compared to normal animals, LPL activity was high in Zucker fatty rats and WHHLMI rabbits at both fasting and feeding, while LPL activity after feeding was low in KK-Ay mice. HTGL activity was higher in fasted and fed WHHLMI rabbits and fasted Zucker fatty rats, but was lower in fed KK-Ay mice. Gender difference was observed in HTGL activity in SD rats and LPL activity in WHHLMI rabbits but not in ICR mice. In conclusion, this simple assay method was effective for measuring LPL and HTGL activities of experimental animals, and the activities are highly regulated depending on animal species, animal models, feeding/fasting conditions and genders.

Lipid-rich carcinoma in the mammary gland of a Djungarian hamster (Phodopus sungorus).

A lipid-rich carcinoma of the mammary gland was diagnosed in a female Djungarian hamster (Phodopus sungorus), which was kept as an indoor pet. The animal underwent surgery for a primary tumor arising in the mammary gland at the age of 16 months, and also for a recurrent tumor 6 months later. Histologically, the primary neoplasm was composed of 2 different cell populations: nonvacuolated glandular neoplastic cells with moderate atypia, and vacuolated neoplastic cells with marked atypia. Transition from the nonvacuolated glandular cells to the vacuolated cells was frequently seen. The recurrent neoplasm was composed predominantly of vacuolated neoplastic cells that often invaded the surrounding soft tissue. The cytoplasmic vacuoles contained neutral lipids, as confirmed by oil red O and Nile blue staining. The vacuolated neoplastic cells were immunopositive for cytokeratin and negative for vimentin, alpha-smooth muscle actin, p63, estrogen receptor alpha, and androgen receptor. Presumably, this high-grade, lipid-rich mammary carcinoma had developed from a low-grade mammary adenocarcinoma.