The metabolic modification of low-density lipoproteins in normal and hypercholesterolaemic guinea pigs.
ABSTRACT: 1. Low-density lipoproteins were isolated by ultracentrifugation from the serum of guinea pigs that were fed either on a normal diet, or on a diet supplemented with corn oil and cholesterol. 2. After labelling with tracer amounts of radioactive iodine, these lipoproteins were injected into the bloodstream of guinea pigs that were fed either on the normal or on the supplemented diet. 3. In all cases, the density of the labelled lipoproteins was increased by exposure for 24-48 h to the metabolic processes of the guinea pig. 4. The final density reached by lipoproteins isolated from fat-fed guinea pigs was less than that reached by lipoproteins from normal animals. 5. Fat-fed guinea pigs were unable to increase the density of either normal lipoproteins, or those from fat-fed guinea pits, to the same extent as animals fed on the normal diet. 6. It is concluded that the lipid-rich diet brings about a modification of lipoprotein metabolism in the guinea, pig, which plays an important part in determining the nature of the nature of the low-density lipoprotein that is present in the plasma.
Project description:1. Hypercholesterolaemia was induced in male guinea pigs after 6 days on a chow diet supplemented with 1.6% (w/w) cholesterol and 15% (w/w) corn oil. Both the VLD (very-low-density) and LD (low-density) lipoproteins were increased in cholesterol-fed animals, although the low concentrations of HD (high-density) lipoproteins remained essentially unchanged. LD lipoproteins of d 1.019-1.100 were the major class, accounting for 74% of the total substances of d less than 1.100. 2. Both VLD and LD lipoproteins exhibited alterations in their chemical composition, physical properties and apolipoprotein content. The VLD lipoproteins in cholesterolaemic animals were rich in cholesterol (25.9%), deficient in protein (4.9%) and exhibited electrophoretic mobility greater than that of beta-globulin; their average particle size (64.5 nm) was larger than that in controls (46.3 nm). The LD lipoproteins in animals fed on the experimental diet were also richer in cholesterol (53.1%) and of larger diameter (24.3 nm) than in the control group (41.1% and 21.4 nm respectively). 3. The apolipoprotein-B content of both VLD and LD lipoproteins was elevated in cholesterolaemic animals, particularly in the VLD class, where it represented 74.8% of the total protein moiety. 4. Apo-VLD lipoprotein exhibited an increase from 6 to 19% in its complement of tetramethylurea-soluble apolipoproteins with low electrophoretic mobility (relative mobility less than 0.29); this was primarily accounted for by apolipoproteins characterized by high arginine (7.2 and 6.4% respectively) and glutamic acid (20.1 and 20.0% respectively) contents. 5. By contrast, there was little change in the soluble apolipoproteins of LD lipoproteins in hypercholesterolaemic animals.6. These studies show the response of the guinea pig to dietary fat and cholesterol to be distinct from that elicited by similar stimuli in the rabbit, rat, pig and dog.
Project description:1. A cell fraction rich in Golgi apparatus was isolated from the livers of guinea pigs fed on a lipid-rich diet (1.6% cholesterol, 15% corn oil). 2. The Golgi cisternae and secretory vesicles contained electron-dense particles which were tentatively identified as VLD (very-low-density) and LD (low-density) lipoproteins. Particles of moderate electron density, 150-500nm in diameter, were seen associated with membranous elements of the Golgi-apparatus cell fraction. Disruption of this cell fraction permitted the release of these three species of particles, which were separated into particulate lipid, and VLD and LD lipoproteins. 3. The large particles of moderate electron density, isolated as particulate lipid, were distinct from both species of Golgi particles in their chemical composition and in possessing an immunochemically unreactive apolipoprotein(s). Morphological observations suggest that the particulate lipid arose from cytoplasmic lipid droplets which were present as contaminants of the Golgi-rich fraction. 4. The chemical and immunochemical results are consistent with the suggestion that the Golgi LD particles are precursors of the VLD particles, into which they may be transformed by the addition of both triglyceride and cholesteryl ester. The present results provide further support for the proposal that the Golgi VLD particles are precursors of the serum VLD lipoproteins in the guinea pig. 5. Hepatic Golgi VLD particles isolated from guinea pigs fed on the lipid-rich diet contained significantly higher molar amounts (relative to protein) of both cholesteryl ester and triglyceride than similar particles from animals fed on a normal diet. These results suggest that the type of Golgi VLD particle produced from the LD particle is a direct consequence of the amount and composition of the dietary lipid. 6. Hepatic Golgi LD particles isolated from guinea pigs fed on different diets were similar in chemical composition and contained approx. 50% by weight of phospholipid. We conclude that the Golgi LD particle is normally present in the Golgi-apparatus cell fraction from guinea-pig liver, and may represent the end product of lipoprotein biosynthesis in the smooth endoplasmic reticulum. 7. The serum LD lipoproteins and Golgi LD particles were quite distinct in chemical composition. However, these two lipoprotein species were immunochemically identical and exhibited a similar range of flotation rate. It appears unlikely that the Golgi LD particles are secreted as the precursors of the serum LD lipoproteins.
Project description:OBJECTIVES:To develop an adult guinea pig model of lipotoxicity and explore the underlying mechanisms associated with changes in the expression of the delayed rectifier potassium current (IK). BACKGROUND:Lipotoxicity may represent a common link among metabolic disorders and a higher vulnerability to arrhythmias. METHODS:Whole-cell patch clamp, and palmitic acid (PA, a potent inducer of lipotoxicity), were used to assess mechanisms of short-term (?50 days) high-fat diet (HFD) feeding on atrial electrophysiology in guinea pig hearts and myocytes. RESULTS:HFD fed guinea pigs were significantly heavier, displayed hypertriglyceridemia and hypercholesterolemia; but no signs of hyperglycemia or inflammation compared to low-fat diet fed controls. Increasing cardiac PA levels, resulted in shortened atrial action potential duration, and increased IK density. Inhibition of phosphoinositide 3-kinase (PI3K) prevented increases in IK due to PA. Acute (?1hr) exposure of atrial myocytes to exogenous PA (1?mM) increased the density of the rapid delayed rectifier potassium current IKr, while it was decreased with the unsaturated oleic acid (OA, 1?mM). Serine-threonine protein phosphatase-2 (PP2A) inhibition with cantharidin reversed the effect of OA on IKr. CONCLUSION:Our data provide evidence of a novel lipotoxic guinea pig model with signs of vulnerability to arrhythmias. Inhibition of PA/PI3K/IK and/or activation of the OA/PP2A/IKr pathways may be therapeutically beneficial for lipotoxic arrhythmias.
Project description:The Göttingen minipig is an excellent model for studying effects of dietary high-fat intake on obesity. In this study, we analyzed the expression level of microRNA-122 (miRNA-122) and its target mRNA, CAT1, in intact young male minipigs fed either high-cholesterol or standard diet for 11 wk. MiRNA-122 and CAT1 are known to be important regulators of lipid metabolism. The weight of the young minipigs was monitored once a week during the feeding period; measurements of total cholesterol, triglycerides, high-density lipoproteins, and low-density lipoproteins were recorded at 4 time points (8, 14, 16, and 19 wk of age) in fasting animals during the feeding scheme. Body weight, total cholesterol, and high-density lipoproteins were higher in pigs fed the high-cholesterol compared with the standard diet. In contrast, the level of triglycerides was lower in pigs on the high-cholesterol diet than those receiving the standard diet. Pigs fed high-cholesterol also had lower miRNA-122 levels than did those fed the standard diet. These results suggest that in our minipigs, the increase in weight and cholesterol levels resulting from subchronic (11 wk) feeding of a high-cholesterol diet is correlated with a decrease in the expression of miRNA-122, confirming the implication of this microRNA in obesity. Gene expression levels of CAT1 did not differ between groups.
Project description:1. Very-low-density (VLD), low-density (LD) and high-density (HD) lipoproteins were isolated by sequential ultracentrifugation from the serum of male guinea pigs fed on a diet containing 3--4% fat. The apoproteins of these lipoproteins (apo-VLD, apo-LD and apo-HD lipoproteins) were studied after delipidation with organic solvents or extraction with tetramethylurea. 2. The major apolipoprotein of LD lipoprotein isolated by gel filtration was found to closely resemble apolipoprotein B of human serum in its chemical and physical properties. Electrophoresis in sodium dodecyl sulphate-polyacrylamide gel showed that this apoprotein consisted of a number of polypeptides. 3. Tetramethylurea precipitated an apoprotein from guinea-pig serum lipoproteins that is probably the apolipoprotein B-like component. This apoprotein accounted for about 80% of the apo-LD lipoprotein, about 55% of the apo-VLD lipoprotein and about 50% of the apo-HD lipoprotein. 4. The distribution of apolipoproteins soluble in tetramethylurea was determined by densitometric scanning of stained polyacrylamide disc gels. 5. A glycine-rich component of high electrophoretic mobility (band I) and a triplet of soluble apolipoproteins (bands II-IV) were present in both VLD and LD lipoprotein classes. These components constituted a higher proportion of the tetramethylurea-soluble apoproteins of VLD lipoprotein (60--80%) than of LD lipoprotein (40--55%). 6. Small amounts (10--15%) of a component of intermediate mobility, which contained traces of half-cystine, were also present in both VLD and LD lipoproteins. 7. A group of soluble components of basic character (bands VI-X), present as minor components of VLD lipoprotein (10--20%), constituted a major proportion (30--45%) of the soluble apoproteins of LD lipoprotein. Two of these apoproteins were rich in lysine, and two of lower electrophoretic mobility were rich in arginine. 8. The pattern of tetramethylurea-soluble apoproteins in HD lipoprotein was distinguished by the presence of two polypeptides of low electrophoretic mobility as its predominant components. One of these components, band VI, resembled the A-I apolipoprotein of man in both its amino acid profile and in its electrophoretic mobility. The second major component, band VI-B, was rich in lysine and resembled the C-I apolipoprotein of man in amino acid composition. 9. The soluble components of bands I and IX were analogous in physicochemical properties to the R-X1 and R-X2 (high-arginine polypeptide) peptides of human serum lipoproteins respectively.
Project description:The feeding system is one of the main factors influencing the Iberian pig meat quality. This experiment was undertaken to evaluate the influence of feeding diets containing different levels of protein on performance, carcass, and meat quality of Iberian pigs. To that aim, 24 castrated male Retinto Iberian pigs with an average weight of 116 kg were fed under free-range conditions with acorns and grass (FR), and on concentrated diets in confinement with standard (SP) and low protein content (LP). The crude protein content in acorns was lower than that in the grass and SP diet, but similar to that in the LP diet. FR pigs needed more time to achieve slaughter weight than LP and SP pigs. Iberian pigs fed on low-protein diet (FR and LP) had a higher intramuscular fat content in the musculus serratus ventralis than SP pigs. The influence of diet on the fatty-acid composition was reflected more markedly in subcutaneous fat than in muscles. FR pigs showed a higher level of C18:1 n-9 and total polyunsaturated fatty acids and lower total saturated fatty acids in subcutaneous fat than LP and SP. It is concluded that diets with low protein levels do not affect Iberian pig productive traits but change the meat composition, rendering them an interesting strategy to improve the quality of Iberian pig meat and dry-cured products.
Project description:The very-low-density-lipoprotein secretion rate of isolated hepatocytes obtained from rats fed a high-fat diet was half that of cells from control animals. In fat-fed rats, the initial cellular uptake of [l-14C]oleate in vitro was decreased by 25%, its esterification to triacylglycerols and phospholipids by 50% and its incorporation into very-low-density-lipoprotein triacylglycerols by 70%. Exogenous oleate was not the main precursor of very-low-density lipoproteins in these animals. Lipogenesis, a minor source of very-low-density lipoproteins with the control diet in our experimental conditions, was inhibited by 84% after fat-feeding. A short-term inhibition of lipogenesis in vitro did not result in a decrease in very-low-density-lipoprotein secretion rate. The results suggest that fat-feeding decreased availability of exogenous as well as endogenous fatty acids for synthesis of very-low-density lipoproteins.
Project description:The Ossabaw pig is emerging as an attractive model of human cardiometabolic disease because of its size and susceptibility to atherosclerosis, among other characteristics. The relationship between adipose tissue inflammation and metabolic dysfunction in this model was investigated here.Young female Ossabaw pigs were fed a Western-style high-fat diet (HFD) (n?=?4) or control low-fat diet (LFD) (n?=?4) for a period of 9 months and compared for cardiometabolic outcomes and adipose tissue inflammation.The HFD-fed "OBESE" pigs were 2.5 times heavier (P?<?0.001) than LFD-fed "LEAN" pigs and developed severe obesity. HFD feeding caused pronounced dyslipidemia, hypertension, and insulin resistance (systemic and adipose), as well as induction of inflammatory genes, impairments in vasomotor reactivity to insulin, and atherosclerosis in the coronary arteries. Remarkably, visceral, subcutaneous, and perivascular adipose tissue inflammation (via FACS analysis and RT-PCR) was not increased in OBESE pigs, nor were circulating inflammatory cytokines.These findings reveal a disconnect between adipose tissue inflammation and cardiometabolic dysfunction induced by Western diet feeding in the Ossabaw pig model.
Project description:In order to study the heart disorder that the long term, high energy diet caused, Bama miniature pigs were fed a high-fat, high-sucrose diet for 23 months. These pigs developed symptoms of metabolic syndrome and showed cardiac steatosis and hypertrophy with a greatly increased heart weight (1.82-fold, P<0.05) and heart volume (1.60-fold, P<0.05) compared with the control pigs. To understand the molecular mechanisms of cardiac steatosis and hypertrophy, nine pig heart cRNA samples were hybridized to porcine GeneChips. The control group consisted of 6 Bama pigs fed a control diet, and the HFHSD group comprised 6 pigs that were induced with a HFHS diet, which included 37% sucrose, 53% control diet and 10% pork lard. The pigs were fed twice every day and provided water ad libitum for 23 months. The pigs were fasted for 12 hours and euthanized with ketamine and xylazine. Pig hearts from the HFHSD group pigs (120, 126, 138, 140, 144, and 146) and three control group pigs (157, 159, and 161) were sampled and preserved in liquid nitrogen and then for RNA extraction and hybridization on Affymetrix microarrays.
Project description:Fat is one of the most important nutrients which provides concentrated energy and essential fatty acids. High fat diet markedly changes the gut microbial composition in mammals, whereas little is known about the impact of fat type on gut microbiome. This study was to evaluate the effects of fat sources on intestinal microbiota of nursery pigs. Eighteen pigs (28 days of age, 8.13 ± 0.10 kg BW) were housed individually (n = 6 per treatment) and allotted to three treatments based on a randomized complete block design. Pigs were fed basal diets with three different fat sources: 6.0% soybean oil (SBO), 6.0% palm oil (PO), and 7.5% encapsulated palm oil (EPO, contains 80% palm oil) respectively. Pigs were euthanized after 28 days of ad libitum feeding, and the digesta in the distal duodenum, jejunum, ileum, cecum and colon of each pig were obtained for microbial composition analysis. Correlation analyses were also performed between microbial composition with nutrients digestibility or growth performance. The results showed that pigs fed PO had marked changes in the bacteria community composition with increasing the richness and diversity in duodenum and jejunum (P < 0.05). Increased abundances of Proteobacteria in duodenum, jejunum and cecum, and decreased abundance of Firmicutes in jejunum were observed in pigs fed PO compared to SBO and EPO. Pigs fed EPO decreased abundances of Proteobacteria in duodenum and jejunum, and increased abundance of Firmicutes compared to pigs fed PO, and was similar to pigs fed SBO. The microbial changes (genus) had significant negative correlation with the fat digestibility. These results indicate that palm oil supplementation in nursery pig diet alters the gut microbial composition, with the most significant changes observed in small intestine. Encapsulation of palm oil, which helps increase the digestibility of palm oil, have beneficial effect on the microbial disturbance caused by palm oil supplementation. Our findings provide a better understanding of how different fat types influence microbial composition in different parts of the intestinal tract and the correlation between bacteria composition and nutrients digestibility, which may provide a new perspective for the rational application of fat in diet.