ALBERT

Notes: Summary Background: Metallothionein (MT)# synthesis can be stimulated in many organs not only by various metals such as cadmium, zinc, and copper, but also by many nonmetalic compounds or experimental conditions such as oxidative stress. The latter lead to the hypothesis that MT is induced in response to free radicals formed in tissues and lipid peroxidation. Aims of the study: Whether the relationship between lipid peroxidation amd MT synthesis is a common phenomenon also valid for lipid peroxidation induced by dietary factors such as chronic vitamin E inadequacy and autoxidation products of polyenoic fatty acids derived from thermally oxidized oil was investigated in the presence study. Methods: The relationship between the induction of metallothionein isoforms I and II (MT-I and MT-II) in response to diet-induced lipid peroxidation using a rat model system in which lipid peroxidation was examined in vivo by chronic vitamin E inadequacy or by administration of lipid peroxidation products from a thermally treated polyenoicrich oil with either basal (dietary zinc concentration: 48 mg/kd; experiment 1) or Zn-stimulated MT levels (dietary zinc concentration: 305 mg/kd; experiment 2) was studied. In both experiments, growing male rats were fed diet containing either a fresh or a thermally treated soybean oil with deficient of sufficient amounts of vitamin E (14 and 11 vs. 648 and 560 mg α-tocopherol equivalents per kg diet) over 40 days according to a bifactorial experimental design. Plasma and liver concentrations of tocopherols and hepatic levels of thiobarbituric acid-reacitve substances (TBARS) were measured by high performance liquid chromatography. MT isoform concentrations in rat liver were isolated and quantified by ion-exchange high performance liquid chromatography and atomic absorption spectrometry. Results: Irrespective of the zinc supply, rats receiving inadequate amounts of vitamin E with the diet had markedly lower plasma and liver concentrations of α-tocopherol and total tocopherols than vitamin E-sufficient rats. ANOVA also revealed an interaction between the diet factors vitamin E and oil on tocopherols in plasma and liver of rats from both experiments. In experiment 1, where rats received normal amounts of dietary zinc, ingestion of the thermally treated oil impaired the tocopherol status compared to the treatment with the fresh oil, although this effect was only obvious in the vitamin E-deficient groups. In experiment 2, where rats received excessive amounts of zinc, the thermally treated oil did not contribute to a reduction of the tocopherol status in plasma and liver. In both experiments a significant increase in TBARS level, indicative of lipid peroxidation, was observed in the liver at chronic vitamin E inadequacy, but no effect of the oil was observed. Here, we show that the dietary treatment had some effects on the synthesis of liver metallothionein isoforms. In groups, receiving normal amounts of zinc, there was a significant interaction between the dietary treatments on the levels of MT-I and MT-II in liver. Chronic vitamin E inadequacy which was accompanied by diminisched tocopherol levels in liver induced the synthesis of MT-I and MT-II. When vitamin E inadequacy was combined with the ingestion of a thermally treated polyenoic acid-rich oil hepatic levels of MT-I and MT-II remained low. In experiment 2, where rats were fed the high zinc diet, vitamin E inadequacy caused an increase of hepatic MT-I level just as in experiment 1, although this MT stimulating effect was irrespective of the oil. For MT-II there was a 43% increase in the vitamin E-deficient group fed the fresh oil compared to all the other groups, although this effect was not statistically significant. The liver MT isoform response to stress was similar in rats with basal MT levels and Zn-induced liver MT levels. The failing effect of the thermally treated oil on MT levels which were stimulated by vitamin E deficiency in experiment 2 was possibly due to the low oxidation grade of the thermally treated oil. Conclusion: The present results are strongly indicative of an apparent induction of MT isoform synthesis in response to an impaired antioxidant defence system in the lipid regions of liver cells induced by vitamin E inadequacy. In contrast, thermally treated polyenoic-rich oils with a certain oxidation grade seem to restrain the induction of MT isoform synthesis under the present experimental conditions.

Notes: Summary Background: Conjugated linoleic acids (CLA)# refer to a group of linoleic acid (18:2)-derived isomers with conjugated double bonds mostly at carbon atoms 9 and 11 or 10 and 12, and with all possible cis and trans combinations. CLA is a newly recognized nutrient that functions to regulate energy retention and metabolism and that causes a serum lipoprotein profile considered to be less atherogenic. However, rodent models that have been frequently used for these studies are only of limited use because of distinct differences in physiology, compared with man. Additionally, possible differences in food intake between the experimental groups remained often unconsidered in those studies. Thus, it can not be excluded that the beneficial effects of CLA reported in a series of studies may be due, at least partially, to differences in nutrient and energy ingested. Aim of the study: This prompted us to undertake an investigation on the action of CLA by using a pig model and a feeding regimen with controlled amounts of food and antioxidants. The parameters used to assess CLA-specific action were selected hormones and metabolites involved in energy metabolism, individual lipoproteins and the appearance of CLA in fasting serum and erythrocyte membranes. Blood as an easily available biological sample was used for investigation. Methods: For that purpose 16 adult female pigs were divided into two groups of 8 each, and were isoenergetically fed diets containing 0 (control diet) or 1% level of CLA (by weight) for 6 weeks. Plasma concentrations of total and free thyroxine (T4), total and free triiodothyronine (T3), and insulin were measured by radioimmunoassays. Plasma non-esterified fatty acids (NEFA), β-hydroxybutyrate, circulating blood ATP and other clinical chemical variables were determined using enzymatic assays. The concentration of α-tocopherol was determined by high perfomrance liquid chromatography. The lipoproteins VLDL (density 〈1.019 kg/L), LDL (density 1.019 – 1.063 kg/L), and HDL (density 〉1.063 kg/L) were isolated by step-wise ultracentrifugation. Fatty acids of the dietary oils, serum and blood cell membranes were separated and quantified by gas chromatography. Results: At week 6, body weights of the pigs fed the CLA-supplemented diet were not different from that of the controls. CLA-treated pigs exhibited a 37% higher concentration of fasting serum insulin than their controls receiving no CLA (P = 0.11). Circulating free and total T4 and T3 as well as serum levels of β-hydroxybutyrate, α-tocopherol, protein, glucose, urea, creatinine and circulating blood ATP remained unaffected by CLA supplementation. Serum concentrations of non-esterified fatty acids were reduced by 38% in CLA-treated pigs relative to the controls, although this difference was not significant. CLA-treated pigs tended to have lower leukocyte counts in blood than their controls (P 〈0.1). Erythrocyte and platelet counts, the hematocrit and hemoglobin concentration were similar between the groups. Serum of CLA-treated pigs showed a trend toward increased levels of triacylglycerols, cholesterol and phosphatidylcholine in the very low density and low density lipoproteins (LDL), without distinct changes in the high density lipoprotein fraction (HDL). The LDL cholesterol to HDL cholesterol ratio was significantly increased by CLA. When pigs were fed CLA at a dietary level of 1%, limited proportions of CLA appeared in fasting serum (1.6%) and erythrocyte membranes (1.1%). Conclusions: Under the present experimental conditions there appeared to be parallels between the effects of CLA and the reported effects of trans fatty acids in the mode of action on lipoproteins and insulin. The failure to demonstrate significant beneficial effects of CLA on the lipoprotein profile which have been observed in other studies requires further research.

Notes: Summary Severe iron deficiency results in complex systemic disorders e.g., including metabolism of energy and minerals. To investigate whether also moderate iron depletion may alter the activities of citric cycle enzymes and the cytochrome oxidase, the trace element status, and serum enzymes indicative of cell damage, this experiment was carried out with rats supplied with sub-optimal iron (9, 13 and 18 mg iron per kg diet) over a total of 5 weeks. The study included 3 pair-fed groups and an ad libitum group, fed with 50 mg iron/kg diet. All iron-restricted rats were classified as iron-deficient on the basis of reduced iron concentrations in body and iron-depending blood parameters. Body weight gain and catalase activity in kidney were lowered in rats receiving the lowest dietary iron level, exclusively. Rats fed 9 and 13 mg iron per kg diet had nearly 6- and 3-fold, respectively higher platelet counts in blood than their corresponding pair-fed controls. The activities of transaminases ASAT and ALAT, alkaline phosphatase, glutamate dehydrogenase and lactate dehydrogenase in serum which are indicative of cell damage were also markedly influenced by moderate dietary iron restriction, in which the enzyme levels in serum increased with intensifying iron depletion. Although, moderate iron restriction to young male rats was associated with marked alterations in iron status and serum enzymes, the activities of tricarboxylic acid cycle enzymes including malic dehydrogenase, fumarase, and isocitric dehydrogenase as well as cytochrome oxidase in liver remained largely unaffected. Only hepatic aconitase showed a somewhat reduction with iron depletion. Moreover, iron restriction was also accompanied with an accumulation of copper in liver which was significant for rats fed 9 and 13 mg iron per kg diet, whereas zinc status remained completely unaffected by moderate iron deficiency.