The influence of dietary lipid composition on liver mitochondria from mice following 1 month of calorie restriction

To investigate the role mitochondrial membrane lipids play in the actions of CR (calorie restriction), C57BL/6 mice were assigned to four groups (control and three 40% CR groups) and the CR groups were fed diets containing soya bean oil (also in the control diet), fish oil or lard. The fatty acid composition of the major mitochondrial phospholipid classes, proton leak and H₂O₂ production were measured in liver mitochondria following 1 month of CR. The results indicate that mitochondrial phospholipid fatty acids reflect the PUFA (polyunsaturated fatty acid) profile of the dietary lipid sources. CR significantly decreased the capacity of ROS (reactive oxygen species) production by Complex III but did not markedly alter proton leak and ETC (electron transport chain) enzyme activities. Within the CR regimens, the CR-fish group had decreased ROS production by both Complexes I and III, and increased proton leak when compared with the other CR groups. The CR-lard group showed the lowest proton leak compared with the other CR groups. The ETC enzyme activity measurements in the CR regimens showed that Complex I activity was decreased in both the CR-fish and CR-lard groups. Moreover, the CR-fish group also had lower Complex II activity compared with the other CR groups. These results indicate that dietary lipid composition does influence liver mitochondrial phospholipid composition, ROS production, proton leak and ETC enzyme activities in CR animals.     

The influence of lipid composition on glycophorin-induced bilayer permeability

Glycophorin was incorporated into large unilamellar vesicles and the bilayer permeability was measured as a function of the lipid composition. In agreement with previous data (Van der Steen, A.T.M., De Kruijff, B. and De Gier, J. (1982) Biochim. Biophys. Acta 691, 13-23) it was found that glycophorin greatly increased the bilayer permeability of DOPC vesicles. This effect was observed for a large variety of phosphatidylcholines, differing in their fatty acid composition and homogeneity. In sharp contrast, it was observed that variations in the polar headgroups by incorporation of DOPE, DOPS and, to a lesser extent, cholesterol, into the DOPC/glycophorin vesicles restored the barrier function. These results are compared to the size of the particles, revealed by freeze-fracture electron microscopy on the glycophorin-containing bilayer and are discussed in the light of various types of lipid-protein interactions and protein aggregation state.     

The role of lipid peroxidation in liver damage

The consequences of the peroxidative breakdown of membrane lipids have been considered in relation to both the subcellular and tissue aspects of liver injury. Mitochondrial functions can be impaired by lipid peroxidation probably through the oxidation of pyridine nucleotides and the consequent alteration in the uptake of calcium. Several enzymatic functions of the endoplasmic reticulum are also affected as a consequence of peroxidative events and among these are the activities of glucose 6-phosphatase, cytochrome P-450 and the calcium sequestration capacity. Moreover, a release of hydrolytic enzymes from lysosomes and a decrease in the fluidity of plasma membranes can contribute to the liver damage consequent to the stimulation of lipid peroxidation. Extensive studies carried out in vivo and integrated with the use of isolated hepatocytes have shown that lipid peroxidation impairs lipoprotein secretion mainly at the level of the dismission from the Golgi apparatus, rather than during their assembly. However, such an alteration appears to give a late and not essential contribution to the fat accumulation. A more critical role is played by peroxidative reactions in the pathogenesis of acute liver necrosis induced by several pro-oxidant compounds as indicated by the protective effects against hepatocyte damage exerted by antioxidants. In addition, even in the cases where lipid peroxidation has been shown not to be essential in causing cell death there is evidence that it can still act synergistically with other damaging mechanisms in the amplification of liver injury.     

The influence of lipid composition on the barrier properties of band 3-containing lipid vesicles

Band 3 protein has been incorporated into lipid vesicles consisting of 94:6 (molar ratio) egg phosphatidylcholine-bovine heart phosphatidylserine or total erythrocyte lipids by means of a Triton X-100 Bio-Beads method, with an additional sonication step prior to the removal of the detergent. This methods results, for both types of band 3 lipid vesicles, in rather homogeneous vesicles with comparable protein content and vesicle trap. Freeze-fracture electron microscopy revealed that band 3-egg phosphatidylcholine-bovine heart phosphatidylserine vesicles have considerably more intramembrane particles as compared to the band 3-erythrocyte lipid vesicles. The dimensions of the nonspecific permeation pathways present in the band 3-lipid vesicles were measured using an influx assay procedure for nonelectrolytes of different size, in which the vesicles were sampled and subsequently freed from nonenclosed labeled permeant by means of gel-filtration. The band 3-egg phosphatidylcholine-bovine heart phosphatidylserine vesicles have nonspecific permeation pathways (pores), with diameters of up to 60 A. In contrast, the band 3-total erythrocyte lipid vesicles are more homogeneous and show much smaller nonspecific permeation pathways, having a diameter of about 12 A. These results suggest that the nonspecific permeability of the band 3-lipid vesicles is strongly lipid-dependent. Increase in specific anion permeability expected as a consequence of the presence of band 3 in the erythrocyte lipid vesicles was found to be very limited. However, stereospecific, phloretin-inhibitable D-glucose permeability could clearly be demonstrated in these vesicles. The difference of the nonspecific permeability of the band 3-egg phosphatidylcholine-bovine heart phosphatidylserine vesicles and band 3-erythrocyte lipid vesicles, is discussed in the light of the presence of defects at the lipid/protein interface and protein aggregation, which may induce formation of pores.     

The influence of the lipid composition on the degree of lipid-peroxidation of liposomes

Liposomes containing dilinoleoyl lecithin (di-18(2)PC) and diarachidonyl lecithin (di-20(4)PC) were peroxidized with Fe++/ascorbate. Lipidperoxidation was measured as generated malondialdehyde, the disappearance of polyunsaturated fatty acids, conjugated diene formation and chemiluminescense. It was found that di-20(4)PC was oxidized rapidly, while in the same time period hardly any oxidation of di-18(2)PC took place. Incorporation of different lipid classes into the di-20(4)PC liposomes influenced the peroxidation for each lipid in a characteristic way. Phosphatidylethanolamine stimulated the formation of fluorescent chromolipids. The possible meaning of these reactions in human pathology is discussed.     

Changes in lipid composition of cortical synaptosomes from different age groups of mice

Lipid composition of cortical synaptosomes differed with age in C57BL/6NNIA mice. Significant age differences were observed for cholesterol and the ratio of cholesterol to total phospholipid phosphorus content. The phospholipid to protein ratio of individual phospholipids also increased with age with diacyl-$\text{sn}$-glycero-3-phosphocholine (PC) increasing the most. Acyl group composition of individual phospholipids, however, showed little age difference. The double bond index for PC decreased significantly with age. Changes in membrane composition may help explain differences in the effects of ethanol on the physical and biochemical properties of membranes from different age groups that have been reported previously.     

电针对快速衰老小鼠肝脏自噬及脂质代谢的影响

目的:研究电针对快衰老小鼠(SAMP8)肝脏中自噬相关因子LC3-Ⅱ、Beclin1、Atg7、P62表达的影响,探讨电针改善衰老小鼠肝脏脂质代谢的机制.方法:30周龄雄性SAMP8小鼠随机分为模型组、药物组、电针组,每组7只,以同周龄抗快速老化SAMR1小鼠7只作为对照组.对照组和模型组动物常规饲养4周,不进行任何干...     

Streptozotocin-induced liver damage in mice

Diabetes incidence and liver damage was studied and identified in C3H-s mice 21 days after Streptozotocin (SZ) administration (250 mg/kg/i.v.) at 04 hs (4 a.m.) and 16 hs (4 p.m.). Metabolic disturbances were assessed by daily control of glycosuria and serum glucose determined at the end of the experiment. Liver damage was controlled by light and electron microscopy. Both effects showed a circadian variation, with significant greatest values in the 16-h-injected group. Liver damage appeared whether the animals became diabetic or not, consisting in degranulation of the rough-surfaced endoplasmic reticulum, mitochondrial swelling with loss of cristae and edema of the ground substance, with flocculent amorphous precipitate. In some hepatocytes, a dilated cisternae of the endoplasmic reticulum was seen. It was concluded that: a) beta-cell and hepatocytes have a synchronic circadian sensitivity to SZ; b) liver damage was present whether the animals became diabetic or not, suggesting the presence of a different threshold for SZ effect in hepatocytes. These results might be taken into account when planning SZ use, either for experimental or clinical purposes.     

Effect of probucol on the lipid composition of blood plasma, erythrocyte ghosts and liver membranes in mice

1. Probucol treatment of mice (0.6 g/kg) induced a decrease of cholesterol (CH) and total phospholipids (PLs) in blood plasma, erythrocyte ghosts, liver plasma and microsomal membranes. 2. The incorporation of [14C]acetate in the microsomal lipids of probucol-treated mice was lowered by 23% compared to controls. 3. Probucol administration induced a reduced specific activity of PLs, CH and CH esters, whereas in triacylglycerols it was augmented. 4. Phospholipase A2 and neutral sphingomyelinase activities were not enhanced, indicating that the catabolism of the membrane PL was not elevated.     

Effect of the lipid composition of liposomes on their clearance from the circulation and accumulation in the liver of mice

The effect of phospholipid and ganglioside liposome composition on the liposome clearance from the circulation and accumulation in the mouse liver has been studied. It has been shown that liposomes constituting of liver lipids are quicker removed from the circulation and accumulated in the liver. Liver gangliosides increased liposome uptake by the mouse liver and their clearance from the circulation.     

The influence of hypothyroidism on the transport of phosphate and on the lipid composition in rat-liver mitochondria.

The influence of hypothyroidism on the transport of phosphate and on the lipid composition in rat-liver mitochondria was examined. It was found that the rate of phosphate transport is reduced (around 40%) in mitochondria from hypothyroid rats compared to that obtained in mitochondria from normal rats. Treatment of hypothyroid rats with thyroid hormone reverses this effect completely. Kinetic analysis of the phosphate transport indicates that only the Vmax of this process is affected, while there is no change in the Km values. The lower rate of phosphate transport in mitochondria from hypothyroid rats is also demonstrated by swelling experiments. There is no significant difference either in the respiratory control ratios or in the ADP/O ratios between these two types of mitochondria. The hepatic mitochondrial lipid composition is altered significantly in hypothyroid rats. The total cholesterol increases, the phospholipids decrease and the cholesterol/phospholipid molar ratio increases (around 40%). Among the phospholipids, cardiolipin shows the greatest alteration (30% decrease in the hypothyroid rats). The phosphatidylethanolamine/phosphatidylcholine ratio also decreases. Alterations were also found in the pattern of fatty acids. These changes in lipid composition may be responsible, at least in part, for the depression of the phosphate carrier activity in mitochondria from hypothyroid rats.     

双歧杆菌对高胆固醇饮食小鼠血脂影响的研究

目的了解双歧杆菌对高胆固醇饮食水平异常的动物个体血脂及脂蛋白代谢的影响.方法将高胆固醇饮食小鼠分为2组,一组饮用双歧杆菌菌液,另一组常规饮水.经28 d喂养后,将全部动物处死,并立即取血,取上清液测定血脂及脂蛋白各项指标:血清总胆固醇(TC)、甘油三酯(TG)和高密度脂蛋白(HDL-C).结果高脂饮食 双歧杆菌组TG、TC水平显著低于高脂饮食组(P<0.01),HDL-C/TC显著高于高脂膳食组(P<0.01).结果表明灌胃双歧杆菌,小鼠血清中TC、TG浓度较高脂饮食显著降低(P＜0.01),同时HDL-C浓度有所增加.结论饮用双歧杆菌能显著改善高胆固醇饮食小鼠血脂及脂蛋白代谢状况.     

Effects of lipid physicochemical characteristics on interrelations between lipid composition and the mouse liver index

Interrelations between the liver index (the relative mass) and various parameters of the liver lipid composition in 9 groups of intact female SHK mice sacrificed at different Seasons and years groups were studied depending on physicochemical characteristics of their lipids. There were revealed correlations between the liver index and the following parameters of the lipid composition: relative content of cardiolipin, lysoforms of the phospholipid/phosphatidylcholine ratio in liver phospholipids, and the [serine]/[phospholipids] molar ratio. The direction of these correlations has been established to depend on the lipid physicochemical characteristics. In all cases, there is observed a direct correlation if lipids have prooxidant properties and antiperoxide activity and an inverse correlation if lipids are characterized by antioxidant and antiperoxide activities.     

The influence of different membrane components on the electrical stability of bilayer lipid membranes

A good understanding of cell membrane properties is crucial for better controlled and reproducible experiments, particularly for cell electroporation where the mechanism of pore formation is not fully elucidated. In this article we study the influence on that process of several constituents found in natural membranes using bilayer lipid membranes. This is achieved by measuring the electroporation threshold (V_th) defined as the potential at which pores appear in the membrane. We start from highly stable 1,2-diphytanoyl-sn-glycero-3-phosphocholine (DPhPC) membranes (V_th ∼ 200 mV), and subsequently add therein other phospholipids, cholesterol and a channel protein. While the phospholipid composition has a slight effect (100 mV ≤ V_th ≤ 290 mV), cholesterol gives a concentration-dependent effect: a slight stabilization until 5% weight (V_th ∼ 250 mV) followed by a noticeable destabilization (V_th ∼ 100 mV at 20%). Interestingly, the presence of a model protein, α-hemolysin, dramatically disfavours membrane poration and V_th shows a 4-fold increase (∼ 800 mV) from a protein density in the membrane of 24 × 10^− 3 proteins/μm². In general, we find that pore formation is affected by the molecular organization (packing and ordering) in the membrane and by its thickness. We correlate the resulting changes in molecular interactions to theories on pore formation.     

Effect of thyroid status on lipid composition and peroxidation in the mouse liver

In order to analyze the possible relationship between metabolic rate and oxidative stress, OF1 female mice were rendered hyper- or hypothyroid for 4–5 weeks by administration of 0.0012%l-thyroxine (T₄) or 0.05% 6-n-propyl-2-thiouracil (PTU), respectively, in their drinking water. Treatment with T₄ resulted in increased basal metabolic rate measured by oxygen consumption and liver cytochrome oxidase activity without altering the glutathione redox system. Endogenous lipid peroxidation, sensitivity to lipid peroxidation and fatty acid unsaturation were decreased in the hyperthyroid group. Hypothyroidism also decreased phosphatidylcholine and cardiolipin fatty acid unsaturation but not in total lipids, and thus lipid peroxidation was not altered. Cardiolipin, a mainly mitochondrial lipid, was the most profoundly altered fraction by both hyper- and hypothyroidism. It is suggested that the lipid changes observed in hyperthyroid animals can protect them against an increased oxidative attack to tissue lipids due to their increased mitochondrial activities.     

The influence of membrane lipid composition and procaine on hyperthermic death of cells.

The mechanism of hyperthermic killing, a component of some cancer therapy, is not known. Cell-survival curves during hyperthermic exposure can be used to elucidate the effects of membrane modifying procedures on cell death. Experiments were designed to test whether procedures that were reported to increase membrane fluidity also resulted in increased killing on hyperthermic exposure. An E. coli K12 mutant, K1060, is used to predictably alter the degree and amount of unsaturated fatty acids incorporated into membranes. Changing from an 18:1 to an 18:3 unsaturated fatty acid increases killing. Decreasing the amount of unsaturated fatty acid cells incorporated by increasing growth temperature decreases killing. Procaine, a drug known to decrease membrane viscosity, increases heat killing. These data are most simply explained by the hypothesis that membrane disorganization occurs as a result of temperature increasing to a point where a lipid transition causes a membrane structural change, which results in cell-death.     

Effect of lipid composition on rat liver nuclear membrane fluidity

Nuclear membrane fluidity is measured in rat liver by use of the fluorescence anisotropy of two probes: diphenylhexatriene and its cationic derivative trimethylammonium-diphenylhexatriene. It has been shown that, in 2-month-old rat liver cells, the bilayer surface is less fluid than the hydrophobic core. The fluidity was higher in 6-day-old rat liver nuclei, in which both the amount of cholesterol and the cholesterol/phospholipid ratio decreased. The influence of the single phospholipids, and in particular of phosphatidylcholine, has been studied by increasing the phosphatidylcholine with a choline base exchange reaction in isolated nuclear membranes. After this reaction, the fluorescence anisotropy of the bilayer surface increased, whereas at the hydrophobic core it decreased. Analysis of fatty acid composition shows an increase of phosphatidylcholine unsaturated fatty acids. The results show that the fluidity of nuclear membranes changes in relation to the lipid content and to the fatty acid composition. The role of nuclear membrane fluidity in cell function is discussed. © 1997 John Wiley & Sons, Ltd.