Lipogenic enzymes of rat liver and adipose tissue. Dietary variations and effect of polychlorinated biphenyls

Nutritional hepatic steatosis and mortality after burn injury in rats

AIMS

To investigate the effects of diet composition and starvation on hepatic steatosis and mortality after severe burn injury in rats.

METHODS

Experiment 1: rats received either normal chow (55 cent of energy carbohydrates, 14 cent fat, 31 cent protein), a high-fat (40 cent carbohydrates, 40 cent fat, 20 cent protein), or a high-carbohydrate diet (81 cent carbohydrates, 4 cent fat, 15 cent protein) ad libitum for 6 days. Another three groups received these diets ad libitum for 6 days after 48|h starvation. Experiment 2: mortality after 60 cent total body surface area scald burn was determined in a control group of rats and a group with nutritionally induced hepatic steatosis. Hepatic steatosis was induced by feeding the rats a high-fat diet (40 cent carbohydrates, 4 cent fat, 15 cent protein) ad libitum for 6 days.

RESULTS

Without starvation, liver triglyceride content (mg/g liver) increased in response to the high-fat diet (25.6'6.9) compared to normal chow (9.4'3.8; P < 0. 05); the high-carbohydrate diet had no influence on liver triglyceride content (12.4'3.7). Refeeding after starvation resulted in elevated (P < 0.05) liver triglyceride content in the high-fat (18.8'8.3) and the high-carbohydrate group (28.7'14.4 vs control 6. 7'3.7). Liver triglyceride content correlated (R2=0.72; P < 0.05) to non-protein energy intake but not to total energy intake. Burn caused 33 cent mortality in the hepatic steatosis group and no deaths in the control group (P < 0.05).

CONCLUSIONS

Diet composition and preceding starvation independently manipulate hepatic fat content in rats. Hepatic steatosis increases mortality after burn injury. Thus, nutritional interventions to reduce hepatic fat accumulation may be beneficial.

Involvement of lipogenesis in the lower VLDL secretion induced by oligofructose in rats

Dietary supplementation with oligofructose (OFS; 100 g/kg), a non-digestible oligomer of beta-D-fructose, decreases serum triacylglycerols in serum and VLDL of rats. In order to investigate the role of hepatic metabolism in the hypolipidaemic effect of OFS, male Wistar rats were fed on a standard diet with or without 100 g Raftilose P95/kg as OFS source for 30 d. OFS feeding (1) significantly decreased triacylglycerol and phospholipid concentrations in both blood and liver, (2) increased the glycerol-3-phosphate liver content but decreased the hepatic activity of glycerol-3-phosphate acyltransferase (EC 2.3.1.15), suggesting a decrease in acylglycerol synthesis, (3) did not affect the blood non-esterified fatty acid concentrations, but (4) reduced by 54% the capacity of isolated hepatocytes to synthesize and secrete triacylglycerols from labelled acetate; the activity of fatty acid synthase, a key lipogenic enzyme was also significantly decreased. These findings suggest that OFS decreases serum triacylglycerols by reducing de novo fatty acid synthesis in the liver; the lower insulin level in the serum of OFS-fed rats could explain, at least partly, the metabolic effect induced by such non-digestible carbohydrates.

Reversed-phase chromatographic study of the binding of polychlorinated biphenyls to cyclodextrins and sodium dodecylsulphate

The binding of polychlorinated biphenyls (PCBs) to hydroxypropyl-beta-cyclodextrin (HP-beta-CD), tau-cyclodextrin (tau-CD) and sodium dodecylsulphate (SDS) was studied by reversed-phase thin-layer chromatography and the relative strength of interaction was calculated. HP-beta-CD and SDS did not bind to PCBs making it unlikely that these compounds modify the adsorption capacity or decomposition rate of PCBs. Each PCB formed inclusion complexes with tau-cyclodextrin. The inclusion-forming capacity of PCBs increased with an increase in the number of chloro substitutions in the molecule, indicating that tau-CD can be successfully used for the modification of the physicochemical and biochemical characteristics of PCBs. The linear correlation between the hydrophobicity and specific hydrophobic area of PCBs indicated that they can be considered as a homologous series of compounds.