Housing conditions effect plasma lipid concentrations and early atherogenesis independent of treatment in hamsters

Abstract

The purpose of these studies was to evaluate the affect of housing conditions on various lipid parameters and early atherogenesis. In experiment 1, 35 Golden Syrian hamsters, nine weeks of age, were initially housed five to a cage and fed a hypercholesterolemic diet (HCD) for 26 weeks. Plasma total lipoprotein cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C) and triglycerides (TG) were measured enzymatically at 4, 6, 9, 12, 14, 16, 19, 23, and 26 weeks of the study. At week 9, the animals were placed in individual cages for 7 weeks and then regrouped a second time at week 16 of the study. Three blood samples were taken during each of the 3 treatment periods. In experiment 2, part 1, two groups of hamsters (n=6) were either housed individually or grouped and fed the same HCD for 14 weeks. In part 2, two groups of hamsters (n=5) were either housed individually or grouped and fed a chow diet for 14 weeks. Plasma lipids were measured enzymatically at weeks 4, 7, 10, 12, and 14 in experiment 2. Also, the hamsters in part 1 of experiment 2 were euthanized at week 14 and examined for aortic fatty streak formation. In experiment 1, animals fed HCD that were grouped for the first 9 weeks had significantly higher plasma TC (59%, p < 0.008), LDL-C (71%, p < 0.007), and TG (77%, p < 0.007) than when the hamsters were housed individually. Also in experiment 1, the hamsters fed the HCD that were grouped for the last 9 weeks had significantly higher plasma TC (55%, p < 0.01), LDL-C (69%, p < 0.007), and TG (83%, p < 0.005) than when the hamsters were individually housed. In experiment 2, part 1, the hamsters fed HCD and group caged had significantly higher plasma TC (37%, p < 0.008), LDL-C (46%, p < 0.007), TG (53%, p < 0.003), body weights (11%, p < 0.009), and aortic fatty streak area (43%, p < 0.05) and significantly lower HDL-C (−33%, p < 0.0001) compared to the hamsters housed individually. In part 2, the hamsters fed the chow diet and group caged had significantly higher plasma TG (24%, p < 0.003) and body weights (22%, p < 0.004) compared to the hamsters housed individually. The results of the following study suggest that housing conditions by unknown mechanisms can significantly affect plasma lipids and early atherosclerosis development in hamsters fed a hypercholesterolemic diet.