Dietary fat and cholesterol induced modification of minipig lipoprotein fluidity and composition

High levels of endogenous DNA adducts (I-compounds) in pig liver. Modulation by high cholesterol/high fat diet

I (indigenous)-compounds are bulky endogenous DNA adducts which are detected by 32P-postlabeling in unexposed animals. I-compound levels in rodents depend on age, species, strain, gender, tissue, diet, and chemical exposure. There are two classes of I-compounds, type I and type II. While many type I I-compounds may not reflect DNA damage, type II I-compounds have been identified as oxidative DNA lesions some of which can be produced in vitro under Fenton reaction conditions. In rats, caloric restriction (CR) increases the levels of many type I I-compounds compared with ad libitum fed animals, while high fat diet has the opposite effect. Here, we have tested whether hepatic DNA of a non-rodent mammal, the pig, contains I-compounds and whether feeding a high cholesterol/high fat (HC/HF) diet modulates their levels, assuming this would affect the formation of lipid-related precursors and cause oxidative stress. Male Yorkshire pigs aged 2 months old, were fed either control or HC/HF diet (control diet supplemented with 2% cholesterol and 19% lard) for 2 months. Pig liver DNA contained at least 19 type I and five type II I-compounds. Among the former, only five matched corresponding spots in rat liver DNA, while all the latter DNA lesions were detected in both species. The levels of both types of DNA modifications were six to eight-fold higher in pig DNA. HC/HF diet reduced levels of many type I I-compounds up to several fold but had little effect on the oxidative lesions. Several type I I-compounds showed negative linear correlations with serum cholesterol levels, while this association was positive for total type II I-compounds. The substantially elevated steady-state levels of bulky endogenous DNA adducts in the species with the longer life expectancy were surprising. Thus, for the first time, an intimate link between nutritional status and endogenous DNA modifications has been established in a non-rodent system. We propose that in order to explain our observations, differences in diet composition, antioxidant defenses, and DNA repair, as well as cytochrome P450 modulation of precursor levels and hormonal effects need to be considered.

Dietary menhaden and corn oils and the red blood cell membrane lipid composition and fluidity in hyper- and normocholesterolemic miniature swine

Fatty acids in the diet are readily incorporated into lipids in various tissues. However, it is not clear whether all tissues have the same level of incorporation. Second, (n-6) unsaturated fatty acids increase the fluidity of membranes, but this has not been shown for (n-3) fatty acids. In this study, we measured the incorporation of (n-6) and (n-3) fatty acids into erythrocyte membrane lipids and studied their effects on the fluidity of erythrocyte membranes. One group of female miniature swine was made hypercholesterolemic by feeding the swine cholesterol and lard for 2 mo; the other group served as controls and was fed a stock diet. Both groups were then fed either corn oil or menhaden oil or a mixture of the two for 23 additional weeks. Blood was collected at 0, 2, 4, 12 and 23 wk after initialization of the experimental diets, and fatty acid composition of phospholipids was assessed. Membrane phospholipids of pigs fed menhaden oil had elevated (n-3) fatty acids (20:5 and 22:6), and lower 18:2 than those fed corn oil. There was no difference in 20:4 content. The fatty acid changes occurred as early as 2 wk after consumption of the corn oil or menhaden oil in pigs previously fed a stock diet, but it took longer in pigs previously fed lard + cholesterol, indicating residual effects of pretreatment. Menhaden oil increased anisotropy (indicating decreased fluidity) more than corn oil for the nonpolar probe diphenylhexatriene (DPH) at earlier time points, but not at 23 wk. Erythrocyte membrane fluidity was significantly related to membrane polyunsaturate content, with (n-6) fatty acids having a greater influence than (n-3) fatty acids. A comparison of the present red blood cell fatty acid compositions with brain synaptosome fatty acid compositions for the same animals showed poor correlations for some of the fatty acids. There was no significant direct relationship between docosahexaenoate (DHA) concentrations in erythrocyte membranes with DHA concentrations in brain synaptosomes from cerebellum, forebrain and caudate nucleus.