Effect of LCAT on HDL-mediated cholesterol efflux from loaded EA.hy 926 cells

• 1.1. Human endothelial cells (EA.hy 926 line) were loaded with cholesterol, using cationized LDL, and the effect of lecithin:cholesterol acyltransferase (LCAT) on cellular cholesterol efflux mediated by high density lipoproteins (HDL) was measured subsequently.
• 2.2. In plasma, lecithin:cholesterol acyltransferase (LCAT) converts unesterified HDL cholesterol into cholesteryl esters, thereby maintaining the low UC/PL ratio of HDL. It was tested if further decrease in UC/PL ratio of HDL by LCAT influences cellular cholesterol efflux in vitro.
• 3.3. Efflux was measured as the decrease of cellular cholesterol after 24 hr of incubation with various concentrations of HDL in the presence and absence of LCAT. LCAT from human plasma (about 3000-fold purified) was added to the cell culture, resulting in activity levels in the culture media of 60–70% of human serum.
• 4.4. Although LCAT had a profound effect on HDL structure (UC/TC and UC/PL ratio's decreased), the enzyme did not enhance efflux of cellular cholesterol, using a wide range of HDL concentrations (0.05–2.00 mg HDL protein/ml).
• 5.5. The data indicate that the extremely low unesterified cholesterol content of HDL, induced by LCAT, does not enhance efflux of cholesterol from loaded EA.hy 926 cells. It is concluded that the HDL composition (as isolated from plasma by ultracentrifugation) is optimal for uptake of cellular cholesterol.

     

The phospholipase activities present in preheparin mouse plasma are inhibited by antiserum to hepatic lipase

• 1.1. Preheparin plasma from mice, but not rats or man, contains high levels of phospholipase A and lysophospholipase activities which are distinct from lecithin:cholesterol acyltransferase (LCAT).
• 2.2. Neither the phospholipase A nor the lysophospholipase activities in preheparin plasma are inhibited by incubation in the presence of protamine sulphate or high salt concentrations.
• 3.3. When mouse plasma is incubated in the presence of an antiserum specific for rat hepatic triacylglycerol lipase (HTGL), the phospholipase activities are abolished.
• 4.4. These observations suggest that the phospholipase activities are attributable to the action of HTGL, which, in the mouse appears to be a freely circulating enzyme, whereas for other species this enzyme only appears in the blood following administration of heparin.

     

Interaction of N-methyl-anthraniloyl-labelled porcine apolipoprotein A-I with porcine lecithin: Cholesterol acyltransferase: An energy transfer study

• 1.1. To investigate whether a direct protein-protein interaction between apoA-I and lecithin: cholesterol acyltransferase (LCAT) is necessary for the activation of the enzyme, apoA-I was labelled with N-methylisatoic anhydride at lysine residues. The intermolecular resonance energy transfer from tryptophan residues of LCAT (donor) to N-methyl-anthraniloyl (NMA)-labelled apoA-I (NMA-apoA-I) (acceptor) was used as a sensitive fluorescence method for studying molecular interactions.
• 2.2. In the absence of lipids no fluorescence energy transfer was measurable.
• 3.3. Fluorescence energy transfer occurred from LCAT to NMA-apoA-I in the presence of liposomes with phospholipid/cholesterol ratios ranging from 5:1 to 18:1 and regardless whether only 1 or up to 5 NMA-apoA-I molecules resided at the liposome surface.
• 4.4. This indicates a preferred binding of the enzyme directly to or in spatial proximity to the activator protein NMA-apoA-I even if enough space at the liposome surface is available to allow LCAT binding at a distance, where no energy transfer is measurable.

     

Plasma lipoprotein profiles and arylesterase activities in two inbred strains of rabbits with high or low response of plasma cholesterol to dietary cholesterol

• 1.1. Cholesterol feeding for 4 weeks of female and male rabbits of two inbred strains increased plasma cholesterol concentrations by about 11 and 48 mmole/I in the hypo- and hyperresponsive strain, respectively.
• 2.2. On the low-cholesterol pre-experimental diet, the hyporesponsive animals had significantly higher plasma HDL (high density protein) cholesterol levels than hyperresponders.
• 3.3. In both strains, cholesterol feeding caused elevations of cholesterol in all lipoprotein classes, the difference between the hypo- and hyperresponsive strains in essence only being observed in the VLDL (very low density lipoprotein) fraction.
• 4.4. Basal plasma total arylesterase activity was significantly higher in the hypo- than in the hyperresponsive rabbits.
• 5.5. Dietary cholesterol caused an increase in plasma esterase activity in both strains.
• 6.6. We suggest that in rabbits a low plasma arylesterase activity and a low concentration of HDL cholesterol are associated with an increased sensitivity to dietary cholesterol.

     

Altering erythrocyte membrane composition with phospholipid exchange protein

• 1.1. In establishing a protocol for the use of a phospholipid (PL) 2 exchange protein (PLEP) preparation to incorporate fluorescent lipids into membrane fragments, the potential for the PLEP preparation to alter membrane composition was investigated.
• 2.2. Cholesterol was removed from erythrocyte ghosts and PL content was increased after incubation of the membranes with phosphatidylcholine (PC) vesicles and a nonspecific bovine liver PLEP preparation.
• 3.3. The elevated PL/cholesterol ratio of the ghosts decreased fluorescence polarization of diphenylhexatriene (DPH), indicating an increased average membrane fluidity.
• 4.4. The increased PL/cholesterol ratio and reduced DPH fluorescence polarization were prevented by including cholesterol in the PC vesicles during the initial incubation of ghosts with PLEP preparation and lipid.
• 5.5. In addition, the PC content of ghost membranes was elevated after incubation with PLEP preparation and either PC or mixed PC-cholesterol vesicles.

     

The effects of cholesterol feeding on the membranes of liver cells and on the cholesterol metabolism in the rat

• 1.1. Feeding of rats with a 2% cholesterol diet for 6 weeks increased the serum cholesterol concentration. The activity of lecithin cholesterol acyltransferase was also increased during the feeding time.
• 2.2. The activities of aspartate aminotransferase and alanine aminotransferase remained on a constant level during the experiment on rats having cholesterol in their diet. Omitting cholesterol from the diet enhanced the activities of both enzymes and the increase in alanine aminotransferase activity was more pronounced.
• 3.3. The activity of alkaline phosphatase was on higher level during the whole experiment in the rats having cholesterol in the diet than in those fed a cholesterol-free diet.
• 4.4. Present data suggest that excluding cholesterol from the diet labilizes the membranes of hepatocytes and facilitates the release of aspartate and alanine aminotransferases in the blood.

     

Cholesterol metabolism in new world primates: Comparative studies in two tamarin species (Saguinus oedipus and Saguinus fuscicollis) and the squirrel monkey (Saimiri sciureus)

• 1.1. Cholesterol metabolism has been characterized in three species of New World primates, the cotton-top tamarin, the saddle-back tamarin, and the squirrel monkey.
• 2.2. When fed a diet containing cholesterol, the three species exhibited differing responses of plasma cholesterol levels.
• 3.3. Dietary cholesterol absorption was determined and plasma cholesterol die-away kinetics were analyzed in terms of a two-pool model.
• 4.4. The results of the analyses of cholesterol turnover are consistent with the observed species-specific differences in plasma cholesterol values and cholesterol absorption.
• 5.5. Cholesterol metabolism differs between the two tamarin species, as well as between the tamarins and the squirrel monkey.
• 6.6. Implications of species-specific differences between tamarin species are discussed in terms of the use of tamarin species as animal models for comparative studies of cholesterol metabolism and the etiology of cancer and cardiovascular disease.

     

Fetal lung metabolism: Response to maternal fasting

• 1.1. Fetal lung metabolic response to maternal fasting late in gestation was investigated.
• 2.2. Maternal fasting 4 days before term was associated with low fetal plasma glucose and insulin levels but increased levels of fetal plasma glucagon, glycerol, lactate and fatty acids.
• 3.3. Fetuses from fasted mothers showed a significant decrease in body weight (30%), lung weight (30%) and lung glycogen (46%), but no change in lung protein, phospholipid or total lung DNA, suggesting that lung size is affected more than maturation.
• 4.4. Fetal lung slices incubated in vitro showed that lactate oxidation to CO₂ equalled that of glucose in control fetal lungs and was unaffected by maternal fasting, while glucose oxidation was depressed (23%).
• 5.5. Maternal fasting significantly decreased in vitro incorporation of [U-¹⁴C]-glucose, [U-¹⁴C]lactate and [1-¹⁴C]palmitate into lung phospholipids.
• 6.6. Fetal lungs from fasted mothers showed increased conversion of lactate to glucose, indicating gluconeogenic potential by fetal lung.
• 7.7. These studies show that plasma lactate serves as an important energy fuel and substrate for lipid synthesis for the fetal lung, and maternal fasting markedly alters fetal lung metabolism.

     

The effect of sodium monofluoroacetate on plasma testosterone concentration in Tiliqua rugosa (gray)

• 1.1. Administration of multiple or single doses of sodium fluoroacetate (1080) to male Tiliqua rugosa caused a decrease in plasma testosterone concentration.
• 2.2. A single dose of 100 or 250 mg 1080 kg⁻¹ body weight decreased plasma testosterone by 52%. However, 25 mg kg⁻¹ had little apparent effect on testosterone levels. When lizards were given the multiple dose equivalent of these doses over 12 days at 3 day intervals, the effect was much less dramatic with plasma testosterone concentration steadily declining over 15 days for the two higher doses.
• 3.3. There was a suggestion of degeneration of seminiferous tubules in some individuals.

     

Changes in plasma glucose and lipid concentrations during treadmill exercise in domestic fowl

• 1.1. Plasma glucose, non-esterified fatty acid, triglyceride, cholesterol and lactate concentrations were measured during 90 min treadmill exercise at a work intensity of 55–60% maximum.
• 2.2. After 90 min exercise plasma glucose fell by 35% whilst the non-esterified fatty acid concentration rose to as much as 3–4 times resting.
• 3.3. Exercise had no significant effect on plasma cholesterol, triglyceride or lactate concentrations.
• 4.4. The findings indicate a progressive increase in fat utilization during prolonged exercise. Possible hormonal mechanisms underlying exercise-induced changes in lipid and carbohydrate metabolism are discussed.

     

Serum chemistry profiles for Lechwe waterbucks (Kobus leche): Variations with age and sex

• 1.1. Over an 8-year period, 19 biochemical parameters have been determined at various ages in the blood serum of 92 clinically healthy Lechwe waterbucks (Kobus leche), 33 males and 59 females.
• 2.2. Significant differences have been noted with age. In neonates, the lowest values of total proteins, glucose, creatinine, urea, AST, ALT and iron have been noted; the highest ones have been seen for cholesterol, alkaline phosphatase, calcium and phosphorus.
• 3.3. With regard to sex, raised values of glucose, urea, alkaline phosphatase and ALT, and lowered values of cholesterol, have been noted in juvenile females compared with males of the same age.
• 4.4. In adult females, higher levels of urea and cholesterol and lower levels of glucose, triglycerides and natrium have been recorded compared with males.
• 5.5. With sex and age, no significant changes have been found in the levels of GGT, magnesium, chlorides and copper.
• 6.6. Out findings are discussed with those abstracted from the literature for related species.

     

Seasonal effects of prolactin on aspects of carbohydrate and lipid metabolism in the goldfish,Carassius auratus

• 1.1. Diurnal and seasonal variations of certain aspects of carbohydrate and lipid metabolism to ovine prolactin (PRL) treatment in the goldfish, Carassius auratus, were examined.
• 2.2. PRL treatment late in the light phase of a long photoperiod during spring depletes liver glycogen stores. During fall liver glycogen levels are not affected by PRL treatment in fishes acclimated to long or short photoperiods. PRL is hypoglycaemic in fall and spring.
• 3.3. PRL administered late in the light phase of a long photoperiod during spring increases plasma and liver total lipids and plasma cholesterol, while decreasing plasma triglycerides. In fall PRL may increase or decrease plasma organic-bound P levels dependent upon injection time.

     

Breeding and moulting fasts in macaroni penguins: Do birds exhaust their fat reserves?

• 1.1. Plasma concentrations of urea, uric acid and total lipid were compared in pre- and late-fast breeding and moulting macaroni penguins (Eudyptes chrysolophus) to test the hypothesis that birds exhaust their lipid reserves and initiate marked protein utilisation towards the end of natural fasts.
• 2.2. Male and female macaroni penguins fasted for a minimum of 29–32 days and 20 days during the breeding and moult fasts, and the difference in body weight over the sample period (reflecting body weight loss) was 31–34% and 41–47%, respectively.
• 3.3. There was no significant increase in plasma urea or uric acid at the end of either fast, nor any decrease in plasma lipid concentrations compared to pre-fast birds.
• 4.4. These results suggest that macaroni penguins continue to rely mainly on lipid reserves during the later stages of natural fasts. This is consistent with post-fast body composition data for other small penguin species.

     

Relationships among serum lipids,milk production and physiological status in dairy cows

• 1.1. Serum concentrations of cholesterol, triglyceride and alpha lipoprotein cholesterol were determined in nine Holstein cows during different stages of their gestation and lactation cycles.
• 2.2. Serum cholesterol concentrations and daily milk yields were significantly correlated during early and late lactation. The correlations were not significant over the entire lactation.
• 3.3. Maximum values for serum cholesterol were observed at mid lactation and minimum at or near parturition. Serum triglyceride concentrations ranged from 4 to 33 mg/dl. Although prepartum levels for triglyceride tended to be higher than postpartum concentrations, no correlation with milk yield was noted.
• 4.4. These data are compared with lipid changes which take place in other mammals during lactation.

     

Plasma lipid transport in the horse (Equus caballus)

• 1.1. Equine plasma contains lipoproteins corresponding to very low density (VLDL), low density (LDL) and high density lipoproteins (HDL).
• 2.2. HDL accounts for approximately 60% of plasma lipoprotein mass and consists of a single population of particles.
• 3.3. LDL is heterogeneous comprising three discrete subfractions.
• 4.4. Two proteins are found in the region of apolipoprotein (apo) B-100 in VLDL and LDL and a third similar to apo B-48 is in VLDL.
• 5.5. Lecithin:cholesterol acyl transferase is active in plasma and hepatic lipase and lipoprotein lipase are evident in post-heparin plasma.
• 6.6. There is no significant cholesteryl ester transfer protein activity.

     

Effects of photoperiod on plasma corticoid levels in the goldfish,Carassius auratus—role of the pineal

• 1.1. The effects of photoperiod and pinealectomy on plasma corticoid levels in the goldfish (Carassius auratus) were examined.
• 2.2. Plasma corticoid levels differed in goldfish maintained under different photoperiod regimes, but this response varied seasonally.
• 3.3. Pinealectomy altered the effects of photoperiod on plasma corticoid levels but this effect varied with season.
• 4.4. Plasma corticoid levels were correlated with ovarian activity. The effects of photoperiod on plasma corticoid levels appear to be related to the influence of light on reproduction.
• 5.5. The alteration of plasma corticoid levels in pinealectomized fish may be due to the role this organ plays in mediating photoperiod effects on gonadal activity.

     

The effect of feed restriction on certain haematological indices,enzymes and metabolites in Nubian goats

• 1.1. Some effects of restricting feed intake for 96 or 168 hr were determined in male Nubian goats.
• 2.2. Goats restricted for 96 hr lost 11.6% of their body weight, and goats restricted for 168 hr lost 19.8%.
• 3.3. Feed restriction for up to 168 hr did not produce significant effects on the heart rate, respiratory rate or rectal temperature.
• 4.4. Haemoglobin concentration, packed cell volume and erythrocyte number were all decreased by feed restriction. There was also a tendency towards eosinopenia and lymphopenia.
• 5.5. Feed restriction for 96 or 168 hr raised the plasma activity of aspartate transaminase, and did not affect significantly cholinesterase activity. Plasma amine oxidase activity was significantly reduced in goats restricted for 168 hr.
• 6.6. Feed restriction produced significant increases in the blood or plasma concentrations of lactate. pyruvate, non-esterified fatty acids, cholesterol, ketone bodies and bilirubin.
• 7.7. Significant decreases were found in the concentrations of total protein and calcium.
• 8.8. No significant changes were observed in the plasma concentrations of glucose, sodium or potassium.

     

Superoxide dismutase,reduced glutathione and TBA-reactive products in erythrocytes of patients with multiple sclerosis

• 1.1. Superoxide dismutase, reduced glutathione and lipid peroxides levels were determined in the erythrocytes of multiple sclerosis patients.
• 2.2. Superoxide dismutase activity and the malonyldialdehyde production rate were found to be significantly enhanced.
• 3.3. The isoelectric focusing pattern of Superoxide dismutase from multiple sclerosis and normal subjects erythrocytes was substantially overlapping.
• 4.4. Our results indicate the occurrence of a higher susceptibility of multiple sclerosis erythrocytes to lipid peroxidation.

     

Flight effects on certain blood parameters in homing pigeons Columba livia

• 1.1. Various blood parameters were monitored in resting and flown homing pigeons. A homing flight of 48 km lasting 60–80 min did not significantly alter plasma levels of total protein, electrolytes and plasma osmolality, which indicated maintenance of the homeostatic stability of the internal milieu during moderate exercise.
• 2.2. Plasma concentrations of marker enzymes such as alanine aminotransferase (ALAT), aspartate aminotransferase (ASAT), laetate dehydrogenase (LDH) and creatine phosphokinase (CPK) that tend to denote muscle damage and metabolic flux in prolonged exercise, were also not altered, thereby indicating the steady state of tissue structure and function during a flight of this magnitude.
• 3.3. Significant increases in plasma levels of uric acid and creatinine and decreases in plasma albumin were observed in the flown pigeons.
• 4.4. The flight-induced increase in blood uric acid could be attributed to increased purine catabolism and the increase in creatinine to increased nucleotide turnover.
• 5.5. It is suggested that the higher uric acid levels should not only enhance water conservation, but may also reduce flight-induced hyperthermia besides acting as an antioxidant defence against oxidative tissue injury.
• 6.6. The rise in creatinine is indicative of the breakdown of phosphocreatine for energy during the initial period of flight prior to the utilization of carbohydrate and lipid as fuels.
• 7.7. The decrease in plasma albumin should account for the albumin as lipid carrier lost in transport to the muscles during flight.

     

Transport of cholesterol in the hemolymph of the mollusc Diplodon delodontus

• 1.1. The dietary and inter-organ cholesterol transport in the hemolymph of the bivalve mollusc Diplodon delodontus, was studied. Plasma and hemocytes were obtained after feeding labeled cholesterol to animals or injecting it into the posterior adductor muscle.
• 2.2. In both cases, cholesterol was incorporated either into plasma or hematic cells.
• 3.3. Two plasmatic fractions differing in their hydrated densities were recognized as cholesterol carriers and were isolated. They have characteristics of high density (HDL) and very high density (VHDL) lipoproteins, respectively.
• 4.4. The major lipids in the different classes of lipoproteins were free sterols in HDL and phospholipids in VHDL.
• 5.5. Neither low nor very low density lipoprotein transporting cholesterol was detected.