The influence of acute diabetes (8 days), induced by streptozotocin (45 mg.kg'1 body weight) on myocardial and renal antioxidative conditions was investigated. The animals were given subtherapeutical doses of insulin (Interdep 6 (J. kg'1 body weight, s.c.). Considerably increased levels of malondialdehyde (MDA), as well as of superoxide dismutase (SOD) and catalase (CAT) activity were found in the myocardium of diabetic animals. The oxidized glutathione (GSSG) level and glutathione peroxidase (GSH-PX) activity remained unchanged. The reduced glutathione (GSH) level as well as the activity of glutathione S-transferase (GST) were significantly lower. The activity of GSH-PX in the kidneys of diabetic rats increased by 60 % and that of GST by 105 %, respectively. CAT and SOD activity values were unchanged.
The effect of adding 5 % powdered oyster mushroom (Pleurotus ostreatus) during 12 weeks on kinetic parameters of cholesterol metabolism was studied in male rats (Wistar, initial body weight 85 g) fed a semisynthetic diet containing 0.3 % of cholesterol. The plasma cholesterol decay curve (examined for the final 29 days of the experiment after a single dose of cholesterol-4- 14C) was evaluated by mathematical analysis using a two-pool model of plasma cholesterol metabolism. The oyster mushroom in the diet reduced the half-times of both exponentials resulting in lower calculated values (by 28 %) of total entry of cholesterol into the body cholesterol pool (absorption + endogenous synthesis) and lower sizes of both pools (with slower and faster cholesterol exchange). The rate of cholesterol exchange between the pools was enhanced and the rate of total clearance of cholesterol from the system (metabolic turnover rate of cholesterol, i.e. the rate of degradation and excretion of cholesterol from the organism) was enhanced by 50 %. The oyster mushroom diet effectively prevented the progress of hypercholesterolaemia (decrease by 38 %) and cholesterol accumulation in liver
(decrease by 25 %) that were induced by the cholesterol diet.
A highly significant negative correlation (r= -0.981, p< 0.001) between the amount of oyster mushroom (Pleurotus ostreatus) in the diet and cholesterol levels in the serum has been found in male Wistar rats fed shortly after weaning by a a diet with 0.3 % cholesterol. The addition of 1.0, 2.5 and 5.0 % of oyster mushroom to the diet reduced the levels of serum cholesterol by 11, 31 and 46 %, respectively. The diet containing 5 % of oyster mushroom suppressed cholesterol accumulation in the liver and increased the fraction of cholesterol carried by high-density lipoproteins.
We have investigated the effect of a diet containing of 4 % oyster fungus (Pleurotus ostreatus) and 0.1 % cholesterol on glycaemia and hyperlipoproteinaemia in rats with insulin-dependent diabetes (streptozotocin 45 mg/kg). After two months, the rats with diabetes kept on the oyster fungus diet, had a significantly lower basal and postprandial glycaemia, the insulinaemia remained unchanged. The cholesterol concentration was decreased by more than 40 %, the lipoprotein profile was upgraded by the decrease of the cholesterol in both the low density and very low density lipoproteins. The oyster fungus decreased the cholesterol accumulation in the liver and had no significant effects on the levels of serum and liver triacylglycerols.
Male weaning rats were put on a diet with a physiological nutrient combination adjusted for age, milk casein (E7N = 0.79) and wheat gluten (E/M = 0.30) being the sources of protein. The net protein ratio (NPR) was evaluated weekly until 140 days of age. On days 70 and 140, L-((J-14C)-tyrosine was administered intraperitoneally and 12 h later specific tyrosine activity was determined in the protein fraction of liver and muscle by measuring the incorporation of the labeled amino acid in order to assess protein synthesis over the corresponding time period. Regression lines describing the relationship between animals' weight, age and protein source suggested that the daily weight increase was 6.99 g between days 30-77, 2.97 g between days 77-105 and 0.64 g between days 105-140. Muscle tyrosine levels in rapidly growing animals aged 70 days were 91.0 /¿g/g/12 h for casein and 65.6/ig/g/12 h for gluten. Liver tyrosine levels were 336.4 and 189.6 /rg/g/12 h, respectively. The differences observed at this age were highly significant. In adult animals (140 days old) there were non-significant differences between tyrosine levels in the casein- and gluten-fed groups. The isotope study clearly showed that protein synthesis was reduced in growing and developing animals on vegetable nutrition, which is deficient in essential amino acids, (especially the limiting amino acid lysine, crucial for the utilization of all other amino acids in peptide chain synthesis). The low rate of amino acid utilization found in animals younger than 105 days is consistent with the findings obtained by the isotope method.
The effect of 3 months feeding with diets of different protein and sucrose content (9 % casein -f 70 % sucrose vs. 18 % casein + 61 % sucrose) on the development of diabetic nephropathy and changes in serum lipid spectrum was investigated in rats with insulin-dependent diabetes (streptozotocin 45 mg.kg-1). Metabolism of diabetic animals (before the nutritional regimen) was characterized by hyperglycaemia, moderate hyperlipidaemia, lipid accumulation in the liver and elevated creatinine concentration in the blood. Kidney weight and protein content were not significantly changed. Histological picture of kidneys showed initial changes of glomerular structure. After three months hyperlipoproteinaemia was more accentuated in animals given either of the two diets, the kidneys were hypertrophic with a higher protein content and displayed morphological changes of diabetic nephropathy. Animals given the low-protein diet developed smaller morphological changes both in glomeruli and tubuli. The study indicates that dietary protein and not hyperlipoproteinaemia is the major factor, which may significantly influence the progress of diabetic nephropathy.