Effects of n-3 and n-6 polyunsaturated fatty acid-enriched diets on lipid metabolism in periportal and pericentral compartments of female rat liver lobules and the consequences for cell proliferation after partial hepatectomy

Effects of bioflavonoid ternatin on liver regeneration and oxidative stress in rats

PURPOSE

To evaluate the effect of bioflavonoid ternatin (TRT) on rat liver regeneration and oxidative stress after 70% partial hepatectomy (PH).

METHODS

Thirty six young male Wistar rats were randomly assigned to two groups of 18 animals each - control (G1) and experimental (G2) - and were submitted to PH under inhalatory diethylether anesthesia. G1 rats received daily intraperitoneal (ip) injections of saline (NaCl 0.9% solution) 0.1 mL/kg for 14 days; G2 animals received daily ip injections of TRT 0.1% 1.0mg/kg for 14 days. At 36h (T1), 168h (T2) and 336h (T3) post-PH timepoints, a subgroup of six rats in each group was chosen in a randomized way to complementary hepatectomy (CH) and blood samples haversting. Collected material was saved for laboratory analysis (total bilirubin (TB), D-Glucose, glutathione (GSH) and thiobarbituric acid reactive substances (TBARS) and assessment of liver regeneration.

RESULTS

TRT induced a significant decrease in liver and plasma GSH concentrations; liver regeneration process was not affected. TRT promoted a significant decrease in blood glucose levels 168h after partial hepatectomy compared with controls. TB levels remained unchanged.

CONCLUSION

Intraperitoneal bioflavonoid ternatin injection in partially hepatectomized rats induces a decrease in oxidative stress and a significant hypoglycemic state, but does not promote any change in the evolution of liver regeneration.

Efeitos dos ácidos graxos sobre a regeneração hepática em ratos

OBJETIVO: Estudar os efeitos dos ácidos graxos poli-insaturados (PUFA) ômega-3 e ômega-6 no estresse oxidativo e na regeneração hepática em ratos submetidos à hepatectomia parcial à 70% (HP, hepatectomia a 70%, hepatectomia parcial à Higgins-Anderson). MÉTODOS: 72 ratos Wistar machos jovens foram aleatoriamente distribuídos em quatro grupos de mesmo tamanho: controle, parcialmente hepatectomizados, e parcialmente hepatectomizados com aporte diário intraperitoneal, por duas semanas, de ou ômega-3 ou ômega-6. Nos tempos 36h (T1), 168h (T2) e 336h (T3) pós-HP, substâncias reativas ao ácido tiobarbitúrico (TBARS) e glutationa reduzida (GSH) foram medidos no plasma e no tecido hepático, enquanto glicose e bilirrubina total foram aquilatados no sangue. A massa do fígado residual, nos mesmos tempos, foi o parâmetro utilizado para estimar a evolução da regeneração hepática. RESULTADOS: PUFA ômega-3 inibiu a regeneração hepática e induziu redução na concentração de GSH hepático sete dias pós-HP. PUFA ômega-6, ao contrário, não mostrou efeito inibitório sobre a regeneração. Houve aumento da peroxidação lipídica tanto no sangue como no fígado com a administração de ômega-6. CONCLUSÃO: PUFA ômega-3 retardou a regeneração hepática pós-HP provavelmente por inibição do estresse oxidativo. PUFA ômega-6 aumentou as concentrações de TBARS no sangue e no fígado mas não alterou a evolução do processo regenerativo hepático.

Effects of dietary fats (fish, olive and high-oleic-acid sunflower oils) on lipid composition and antioxidant enzymes in rat liver

The effects of two oleic-acid-rich diets (containing olive oil, OO, and high-oleic-acid sunflower oil, HOSO) on plasma and liver lipid composition detoxification enzyme activities, were compared with those of a fish-oil (FO) diet and a control diet. Compared with the control diet, plasma and hepatic total triacylglycerol concentrations were increased in the animals fed on the HOSO and OO diets and decreased in those fed on the FO diet. The animals fed on FO showed the highest level of cholesterol in the liver and had lower plasma cholesterol concentrations when compared with those fed on the two oleic-acid-rich diets. In comparison with the animals fed on the diets enriched in oleic acid, the FO group showed higher hepatic levels of polyunsaturated fatty acids of then-3 series and lower levels of fatty acids of then-6 series. Livers of FO-fed rats, compared with those of OO- and HOSO-fed rats showed: (1) significantly higher activities of catalase (EC1.11.1.6) glutathione peroxidase (EC1.11.1.9) and Cu/Zn superoxide dismutase (EC1.15.1.1); (2) no differences in the NADPH-cytochromecreductase (EC1.6.99.3) activity. The HOSO diet had a similar effect on liver antioxidant enzyme activities as the OO diet. In conclusion, it appears that changes in the liver fatty acid composition due mainly ton-3 lipids may enhance the efficiency of the antioxidant defence system. The two monounsaturated fatty acids oils studied (OO and HOSO), with the same high content of oleic acid but different contents of natural antioxidants, had similar effects on the antioxidant enzyme activities measured.

Modulation of antioxidant defence system by dietary fat in rats intoxicated with o-toluidine

o-Toluidine was administered to rats in the diet for four weeks at levels approximately 40, 80 and 160 mg/kg b.w. per day. Two types of diet have been used, standard (4% fat) and high fat (14% fat). Activity of antioxidant enzymes, level of glutathione and thiobarbituric acid reactive substances were measured in liver. Glutathione peroxidase was significantly increased in all treated groups while glutathione S-transferase and glutathione reductase were elevated in rats fed high-fat diet. o-Toluidine slightly enhanced catalase activity regardless of the kind of diet. Superoxide dismutase was the only enzyme whose activity was lowered in almost all treated groups. Enzymatic and nonenzymatic microsomal lipid peroxidation was enhanced 2- to 3-fold in both diet groups. Reduced glutathione level in liver was 2.3- to 4.0-fold increased in all treated groups. Our findings indicate that free radical processes can be involved in the toxic effects of o-toluidine and dietary fat can modify the response of some antioxidant enzymes to this compound.

Central role of PPARalpha in the mechanism of action of hepatocarcinogenic peroxisome proliferators

Peroxisome proliferators (PP) are a large class of structurally dissimilar chemicals. These chemicals have diverse effects in rodents and humans, including regulation of lipid metabolism, growth promotion, and induction of hepatocarcinogenesis. Most, if not all, effects of PP are mediated by three members of the nuclear receptor superfamily called PP-activated receptors (PPAR). In this review, we discuss the evidence that PPARalpha, the predominant PPAR in the, liver is involved in the growth promoting and hepatocarcinogenic effects of PP.

Eicosapentaenoic acid inhibits the growth of liver preneoplastic lesions and alters membrane phospholipid composition and peroxisomal beta-oxidation

The purpose of this study was to determine whether individual administration of highly purified eicosapentaenoic acid (EPA), one of the main components of the n-3 polyunsaturated fatty acid family, would alter the growth of focal lesions during hepatocarcinogenesis. The protocol used to induce chemical carcinogenesis in liver was the Solt-Farber model (diethylnitrosamine as initiator and 2-acetylaminofluorene and carbon tetrachloride associated with partial hepatectomy as promoters). Proliferative lesions were quantified with the histochemical marker gamma-glutamyltranspeptidase at partial hepatectomy and at sacrifice. The number and size of the gamma-glutamyltranspeptidase-positive foci observed were significantly lower in rats supplemented with EPA. Fatty acid treatment increased EPA and docosapentaenoic acid content in membrane total phospholipids, in phosphatidylethanolamine, and in phosphatidylcholine. The content of arachidonic acid decreased significantly only in total phospholipids and in phosphatidylethanolamine. Fatty acid content of phosphatidylinositol was not modified. Moreover, we observed an increase in the activity of palmitoyl-CoA oxidase, the limiting enzyme of peroxisomal beta-oxidation, the preferential metabolic pathway of n-3 polyunsaturated fatty acid. Conversely, unmodified levels of alpha-tocopherol and unchanged production of lipid peroxidation products (malondialdehyde) were observed. These results suggest that the EPA inhibitory effect on preneoplastic foci development may be related to alteration of fatty acid composition in phospholipid classes and to enhancement of peroxisomal beta-oxidation and H2O2 production.

Oxygen insensitivity of the histochemical assay of glucose-6-phosphate dehydrogenase activity for the discrimination between nonmalignant and malignant cells

We review here the oxygen insensitivity of the histochemical assay of glucose-6-phosphate dehydrogenase (G6PDH) activity to detect cancer cells. This inexpensive and rapid assay can be performed within half an hour. Discrimination between cancerous and noncancerous cells is based on a combination of elevated G6PDH activity, decreased superoxide dismutase (SOD) activity, and decreased lipid peroxidation in cancer cells. The test discriminates between adenomas and carcinomas of the colon with a certainty of >80% and has a high prognostic value for survival of colon cancer patients. Pancreatitis and pancreatic cancer are discriminated with a certainty of 100%. Therefore, the test can be applied by pathologists to provide additional information in difficult cases of diagnosis of cancer and for prognosis.

Bromodeoxyuridine: a diagnostic tool in biology and medicine, Part III. Proliferation in normal, injured and diseased tissue, growth factors, differentiation, DNA replication sites and in situ hybridization

This paper is a continuation of parts I (history, methods and cell kinetics) and II (clinical applications and carcinogenesis) published previously (Dolbeare, 1995 Histochem. J. 27, 339, 923). Incorporation of bromodeoxyuridine (BrdUrd) into DNA is used to measure proliferation in normal, diseased and injured tissue and to follow the effect of growth factors. Immunochemical detection of BrdUrd can be used to determine proliferative characteristics of differentiating tissues and to obtain birth dates for actual differentiation events. Studies are also described in which BrdUrd is used to follow the order of DNA replication in specific chromosomes, DNA replication sites in the nucleus and to monitor DNA repair. BrdUrd incorporation has been used as a tool for in situ hybridization experiments.