Diet-induced structural and functional modifications in the pig liver endoplasmic reticulum membrane: effect of polyunsaturated fatty acid deficiency

Phospholipid hydroperoxide glutathione peroxidase activity and vitamin E level in the liver microsomal membrane: effects of age and dietary alpha-linolenic acid deficiency

Age and diet-induced variations of phospholipid hydroperoxide glutathione peroxidase (PHGPx) activity and alpha-tocopherol concentration in the liver microsomal membrane were studied in male Wistar rats fed a semipurified diet either balanced in n-6 and n-3 polyunsaturated fatty acids (PUFA) (Control) or deprived of alpha-linolenic acid, i.e. n-3 PUFA (Deficient) over two generations. The animals were studied at the age of 6 months (adult) or 24 months (old). Both PHGPx activity and vitamin E level were significantly higher in 24-month old rats as compared to 6-month old rats. By contrast, the thiobarbituric acid reactive substances (TBARS) following stimulated in vitro peroxidation of membrane lipids were markedly lower (P < 0.01) with aging. The fatty acid composition of microsomal membrane phospholipids (PL) was also considerably modified by age. In particular, the levels of arachidonic acid and total n-6 PUFA were lower (P < 0.001) whereas n-3 PUFA levels were higher (P < 0.001) in most PL main classes. The alpha-linolenic acid deficiency markedly influenced these age-related changes. The higher PHGPx activity in the old rats as compared to the adult rats was only significant in those fed the control diet. In the 6-month old rats (but not in the 24-month old rats), the deficient diet led to a higher membrane vitamin E level and to lower TBARS production than the control diet. The results suggest that the nature of dietary PUFA may influence the age-related variations in this pair of membrane antioxidants and also in the fatty acid composition of microsomes.

Phospholipid fatty acid and lipid peroxidation in liver microsomes from guinea pigs fed oil related to the toxic oil syndrome

The potential effects of oil specimens both related and unrelated to cases of Toxic Oil Syndrome (TOS) on the phospholipid fatty acid composition, some antioxidant enzyme activities, and lipid peroxidation in guinea pig liver microsomes were investigated. For 4 weeks, animals were fed diets supplemented with either oil related to cases of TOS or control oil, previously heated or not. In all cases, the fat diet produced the incorporation of approximately 7% of linoleic acid exclusively in the phosphatidylethanolamine (PE) of liver microsomes. A pronounced increase in lipid peroxidation products, measured as malondialdehyde (MDA) and 4-hydroxyalkenals, was detected in animals fed nonheated control oil. Heated oil diets produced significant increases in superoxide dismutase and glutathione peroxidase activities with concomitant decreases in the lipid peroxidation status. Heated oils also increased the oleic/stearic acid ratio in the phosphatidylserine plus phosphatidylinositol (PS + PI) fraction. This ratio was also increased in the same fraction from animals fed non heated case oil. The study shows that case oil produces a decrease in the lipid peroxidation products with minimal alterations in phospholipid fatty acid composition of liver microsomes, which is dependent rather on the composition of dietary fat than on toxic effects.

Influence of administration of long-chain polyunsaturated fatty acids on process of histological recovery in liver cirrhosis produced by oral intake of thioacetamide

Patients with liver cirrhosis frequently show some degree of protein-energy malnutrition and obviously require nutritional support. In this study, the treatment of rats consisted of the ad libitum oral intake of a 300 mg/liter thioacetamide solution, used as drinking water for four months. Thioacetamide treatment produced a severe alteration in the plasma fatty acid profile with significant decreases of these, which mimicked changes described in human cirrhosis. This hepatotoxic agent causes nodular cirrhosis, with loss of the normal architecture of the liver and disruption of the vascular pattern. The goal of the study was to evaluate the influence of n-3 and n-6 series long-chain polyunsaturated fatty acid dietary supplementation in experimental animals and to assess the effects of those dietary components on structural recovery in the liver. Significant increases of saturated and monounsaturated fatty acids as well as n-6 polyunsaturated fatty acids were seen only in the animals given the n-6 polyunsaturated fatty acid supplemented diet. However, only rats given the standard diet exhibited some degree of histological regeneration.

Essential fatty acid deficiency in the pig: effects on eicosanoid basal levels and in vitro synthesis by the small intestine

The influence of nutritional essential fatty acid (EFA) deficiency on arachidonate metabolism by porcine small intestine has been studied. Great care was exercised in the manipulation of the jejunal wall to avoid artefactual metabolism of arachidonate. Thus, jejunal wall was frozen in liquid nitrogen after organ removal and washing, and subsequently lyophilized. This lyophilized tissue was used as starting material for all experiments, including organic solvent extractions (for basal level determinations) and reconstitution in aqueous buffer (for neosynthesis experiments). Feeding pigs with a low linoleate diet for 12 weeks resulted in a 36% diminution in the % of arachidonate in jejunal phospholipids. Basal levels of 6-keto prostaglandin F1 alpha (6-keto PGF1 alpha), thromboxane B2 (TXB2), PGF2 alpha, PGE2, PGD2 and leukotriene B4 (LTB4) were not altered in the EFA-deficient state. However, we observed a significant lowering of the synthesis of each of these eicosanoids (except LTB4) by the EFA-deficient jejunum during brief (15s) in vitro neosynthesis experiments. The origin of arachidonate as a substrate of PG endoperoxide synthase, also named PGH synthase or cyclooxygenase (Cox) in these neosynthesis experiments is probably a non-esterified fatty acid pool since, (1) neosynthesis was not inhibited by the phospholipase A2 (PLA2) inhibitor parabromophenacylbromide, and (2) substantial amounts of arachidonic acid were found in the jejunum, frozen or lyophilized. Cox activity of the lyophilized jejunum and Cox content of liver and intestine microsomes were not modified in the EFA-deficient state.(ABSTRACT TRUNCATED AT 250 WORDS)

Ca-efflux, from direct membrane injury by CCl4, is elicited by amphiphilic vehicles in vitro

Direct membrane injury by CCl4, in situations excluding metabolic activation, was evaluated in saponin-permeabilized hepatocytes and in microsomes by measuring immediate Ca2+ efflux. A good correlation appears between the Ca2+ efflux and the level of CCl4 in the membrane and also the variations in fluidity. Mixtures of CCl4 with water-soluble vehicles were used to improve the dispersion of CCl4 in the medium. The mixtures varied in their ability to elicit the membrane effects of CCl4. The performance of ethanol and, to a lesser degree, other alcohols, suggests the existence of a water stable structural organization between CCl4 and these amphiphilic vehicles, facilitating the transfer of CCl4 to the membrane.

Simultaneous changes in lipid composition, fluidity and enzyme activity in piglet intestinal brush border membrane as affected by dietary polyunsaturated fatty acid deficiency

The effects of dietary polyunsaturated fatty acid (PUFA) deficiency on intestinal brush border membrane (BBM) fluidity, lipid composition and 5'-nucleotidase activity were examined in piglets. Cholesterol/phospholipid and sphingomyelin (SM)/phosphatidylcholine (PC) ratios were unaffected. However, fluidity was decreased in the external regions and also tended to decrease in the core of the PUFA-deficient pig membrane lipid bilayer. Therefore, the change in the membrane physical properties seemed to be due to the large diet-induced alteration in the phospholipid (PL) fatty acid composition and to the concomitant decrease in PC and increase in phosphatidylserine levels. In the membrane total PL, the arachidonic acid level was slightly lowered, while linoleic, eicosapentaenoic and docosahexaenoic acid levels markedly decreased. PC was mainly concerned by the altered distribution of unsaturated fatty acids, but not SM. However, a significant decrease in (n-6)/(n-3) ratio occurred in the latter. These structural changes were associated with a higher 5'-nucleotidase activity in the intestinal BBM of PUFA-deficient as compared to control piglets.

Lipid intake during pregnancy in developing countries: possible effect of essential fatty acid deficiency on fetal growth

There is a strong epidemiological association between poor nutritional status and low-birthweight (LBW) newborns. According to the World Health Organization (WHO), 95% of total LBW in the world are born in developing countries. Nevertheless, the nutritional etiology of intra uterine growth retardation (IUGR) is still controversial and not yet established largely because of contradictory nutritional studies in pregnancy. In 1981 Menon et al described an animal model of IUGR due to mild deficiency in essential fatty acids (EFA, linoleic and alpha linolenic acids), with a strong correlation between EFA intake during pregnancy and fetal growth. According to the WHO reports in the last decade, there was a dramatic deficiency of lipid intakes (less than 10% of total caloric amounts) in the majority of developing countries while the EFA requirements alone of normal nourished women are evaluated at 6% of total caloric amounts during pregnancy. A mild deficiency in dietary EFA may be a limiting factor in fetal growth processes in humans as it has been shown in animals. Such a mechanism could be easily verified. Research proposals are made in an attempt to test this hypothesis in developing countries with possible applications in further nutritional interventions in pregnancy.