Bio F1B hamster: a unique animal model with reduced lipoprotein lipase activity to investigate nutrient mediated regulation of lipoprotein metabolism

<p>Abstract</p> <p>Background</p> <p>Bio F₁B hamster is an inbred hybrid strain that is highly susceptible to diet-induced atherosclerosis. We previously reported that feeding a high fat fish oil diet to Bio F₁B hamster caused severe hyperlipidaemia. In this study we compared the effects of various diets in the Bio F₁B hamster and the Golden Syrian hamster, which is an outbred hamster strain to investigate whether genetic background plays an important role in dietary fat mediated regulation of lipoprotein metabolism. We further investigated the mechanisms behind diet-induced hyperlipidaemia in F₁B hamster.</p> <p>Methods</p> <p>The Bio F₁B and Golden Syrian hamsters, 8 weeks old, were fed high fat diets rich in either monounsaturated fatty acids, an n-6: n-3 ratio of 5 or a fish oil diet for 4 weeks. Animals were fasted overnight and blood and tissue samples were collected. Plasma was fractionated into various lipoprotein fractions and assayed for triacylglycerol and cholesterol concentrations. Plasma lipoprotein lipase activity was measured using radioisotope method. Microsomal triglyceride transfer protein activity was measured in the liver and intestine. Plasma apolipoproteinB48, -B100 and apolipoprotein E was measured using Western blots. Two-way ANOVA was used to determine the effect of diet type and animal strain.</p> <p>Results</p> <p>The fish oil fed F₁B hamsters showed milky plasma after a 14-hour fast. Fish oil feeding caused accumulation of apolipoproteinB48 containing lipoprotein particles suggesting hindrance of triglyceride-rich lipoprotein clearance. There was no significant effect of diet or strain on hepatic or intestinal microsomal triglyceride transfer protein activity indicating that hyperlipidaemia is not due to an increase in the assembly or secretion of lipoprotein particles. F₁B hamsters showed significantly reduced levels of lipoprotein lipase activity, which was inhibited by fish oil feeding.</p> <p>Conclusion</p> <p>Evidence is presented for the first time that alterations in lipoprotein lipase activity and mRNA levels contribute to varied response of these hamsters to dietary fat, highlighting the importance of genetic background in the regulation of lipid and lipoprotein metabolism by dietary fats. Bio F₁B hamster may prove to be an important animal model to investigate nutrient mediated regulation of metabolic parameters under lipoprotein lipase deficiency.</p

The levels of plasma low density lipoprotein are independent of cholesterol ester transfer protein in fish-oil fed F1B hamsters

BACKGROUND: Cholesterol ester transfer protein (CETP) plays a major role in regulating the levels of LDL- and HDL-cholesterol. We previously observed a fish-oil-induced elevation of low-density lipoprotein (LDL)-and very-low-density lipoprotein (VLDL)-cholesterol concentrations and a decrease in high-density lipoprotein (HDL)-cholesterol concentration in F1B hamsters. The molecular mechanism/s by which fish oil induces hyperlipidaemic effect was investigated in this study. We examined whether the effects of dietary fish oil on plasma lipoprotein concentrations are due to fish-oil-induced alterations in plasma CETP activity. MIX diet, a diet supplemented with a mixture of lard and safflower oil, was used as the control diet. RESULTS: We found that fish oil feeding in hamsters reduced CETP mass as well as CETP activity. Increasing the dietary fat level of fish-oil from 5% to 20% (w/w) led to a further decrease in CETP mass. Supplementation with dietary cholesterol increased both CETP mass and CETP activity in fish-oil and MIX-diet fed hamsters. However, there was no correlation between CETP mass as well as CETP activity and LDL-cholesterol concentrations. CONCLUSION: These findings suggest that cholesterol ester transfer between HDL and LDL is not likely to play a major role in determining fish-oil-induced changes in LDL- and HDL-cholesterol concentrations in F1B hamsters. A possible role of reduced clearance of LDL-particles as well as dietary fat level and dietary cholesterol dependent changes in LDL-lipid composition have been discussed

Arachidonic acid has a dominant effect to regulate lipogenic genes in 3T3-L1 adipocytes compared to omega-3 fatty acids

Background: The effects of long-chain n-3 and n-6 polyunsaturated fatty acids (PUFA) on the regulation of adipocytes metabolism are well known. These fatty acids are generally consumed together in our diets; however, the metabolic regulation of adipocytes in the presence of these fatty acids when given together is not known. Objective: To investigate the effects of n-3 PUFA and arachidonic acid (AA), an n-6 PUFA, on the regulation of adipogenic and lipogenic genes in mature 3T3-L1 adipocytes. Methods: 3T3-L1 adipocytes were incubated in the presence or absence of 100 µM of eicosapentaenoic acid, EPA; docosahexaenoic acid, DHA; docosapentaenoic acid, DPA and AA, either alone or AA+n-3 PUFA; control cells received bovine serum albumin alone. The mRNA expression of adipogenic and lipogenic genes was measured. The fatty acid composition of adipocytes was analyzed using gas chromatography. Results: Individual n-3 PUFA or AA had no effect on the mRNA expression of peroxisome-proliferator-activated receptor-γ; however, AA+EPA and AA+DPA significantly increased (P<0.05) the expression compared to control cells (38 and 42%, respectively). AA and AA+EPA increased the mRNA expression of acetyl-CoA carboxylase 1 (P<0.05). AA treatment decreased the mRNA expression of stearoyl-CoA desaturase (SCD1) (P<0.01), while n-3 PUFA, except EPA, had no effect compared to control cells. AA+DHA and AA+DPA inhibited SCD1 gene expression (P<0.05) suggesting a dominant effect of AA. Fatty acids analysis of adipocytes revealed a higher accretion of AA compared to n-3 PUFA. Conclusions: Our findings reveal that AA has a dominant effect on the regulation of lipogenic genes in adipocytes

A balance of omega-3 and omega-6 polyunsaturated fatty acids is important in pregnancy

Emerging evidence suggests that omega (n)-3 PUFA and their metabolites improve maternal and neonatal health outcomes by modifying gestation length, and reducing the recurrence of pre-term delivery. N-3 PUFA has been associated with prolonged gestation and increased birth dimensions such as birth weight and head circumference. However, mothers giving birth to larger babies are at an increased risk of having dysfunctional labour, genital tract laceration, and delivery via caesarean section. Likewise, high infant weight at birth has been linked to several metabolic and cardiovascular disorders in the offspring. Prolonged gestation also leads to reduced placental function which has been implicated in fetal distress, and perinatal death. Till date, the mechanism through which high n-3 PUFA intake during pregnancy increases gestation length and birth weight is vaguely understood. Early and later stages of pregnancy is characterised by increased production of pro-inflammatory cytokines which are required for pregnancy establishment and labour regulation respectively. Conversely, mid-stage of pregnancy requires anti-inflammatory cytokines necessary for uterine quiescence, pregnancy maintenance and optimal fetal growth. Apparently, changes in the profiles of local cytokines in the uterus during different stages of pregnancy have a profound effect on pregnancy progression. This review focuses on the intake of n-3 and n-6 PUFA during pregnancy and the impact it has on gestation length and infant weight at birth, with a particular emphasis on the expression of inflammatory cytokines required for timely pregnancy establishment (embryo reception and implantation) and labour induction. It is concluded that an appropriate dose of n-3 and n-6 PUFA needs to be established during different stages of pregnancy

Bio FB hamster: a unique animal model with reduced lipoprotein lipase activity to investigate nutrient mediated regulation of lipoprotein metabolism-4

<p><b>Copyright information:</b></p><p>Taken from "Bio FB hamster: a unique animal model with reduced lipoprotein lipase activity to investigate nutrient mediated regulation of lipoprotein metabolism"</p><p>http://www.nutritionandmetabolism.com/content/4/1/27</p><p>Nutrition & Metabolism 2007;4():27-27.</p><p>Published online 10 Dec 2007</p><p>PMCID:PMC2235869.</p><p></p>e specified diets for four weeks. Upon sacrifice, the liver and intestine were removed and snap frozen in liquid nitrogen and stored at -70°. Tissues were then analyzed for MTTP activity as described in the materials and methods section. Means for a variable with a different letter are significantly different (p < 0.05) by two-way ANOVA and the Newman-Keuls post-hoc test