Changes in activities of enzymes in erythrocytes from ddY mice supplemented with dietary selenium.

Plasma and erythrocyte enzyme activities were measured in ddY mice supplemented with dietary selenium (Se) from baker's yeast (Saccharomyces serevisiae) or selenious acid at 0.3 ppm Se content. Glutathione peroxidase (GSHpx) activities increased significantly in erythrocytes from mice supplemented with dietary Se. It was concluded that addition of dietary Se as food additive is very effective for activation of GSHpx in mice.     

Naringin alters the cholesterol biosynthesis and antioxidant enzyme activities in LDL receptor-knockout mice under cholesterol fed condition

The purpose of the current study was to evaluate the lipid lowering and antioxidant capacity of naringin in LDL receptor knockout (LDLR-KO) mice fed a cholesterol (0.1 g/100 g) diet. As such, naringin or lovastatin (0.02 g/100 g) was supplemented in a cholesterol diet for 6 weeks. The naringin and lovastatin supplementation significantly lowered the plasma total cholesterol level compared to the control group. The plasma and hepatic triglyceride level was only lowered by the lovastatin supplement, while the hepatic cholesterol content was lowered by both the naringin and lovastatin supplements compared to the control group. The hepatic HMG-CoA reductase activity was significantly lower in the naringin and lovastatin supplemented groups than in the control group, whereas the ACAT activity was unaffected. The excretion of total sterol was significantly higher in the naringin and lovastatin groups compared to the control group due to significant changes in the acidic and neutral sterol, respectively. When comparing the hepatic antioxidant enzyme activities, the superoxide dismutase, catalase, and glutathione reductase activities were all significantly higher in the naringin-supplemented group than in the control group, while only the lovastatin supplement increased the glutathione reductase activity. Accordingly, the current results confirmed that naringin lowers the plasma cholesterol level via the inhibition of hepatic HMG-CoA reductase activity and increases the excretion of fecal sterol. Naringin was also found to improve the activities of hepatic antioxidant enzymes against oxidative stress in a hypercholesterolemic animal model, i.e. cholesterol-fed LDLR-KO mice.     

Supplementation of a novel microbial biopolymer, PGB1, from new Enterobacter sp. BL-2 delays the deterioration of type 2 diabetic mice

Antidiabetic effects of a novel microbial biopolymer (PGB)1 excreted from new Enterobacter sp. BL-2 were tested in the db/db mice. The animals were divided into normal control, rosiglitazone (0.005%, wt/wt), low PGB1 (0.1%, wt/wt), and high PGB1 (0.25%, wt/wt) groups. After 5 weeks, the blood glucose levels of high PGB1 and rosiglitazone supplemented groups were significantly lower than those of the control group. In hepatic glucose metabolic enzyme activities, the glucokinase activities of PGB1 supplemented groups were significantly higher than the control group, whereas the PEPCK activities were significantly lower. The plasma insulin and hepatic glycogen levels of the low and high PGB1 supplemented groups were significantly higher compared with the control group. Specifically, the insulin and glycogen increases were dose-responsive to PGB1 supplement. PGB1 supplement did not affect the IPGTT and IPITT compared with the control group; however, rosiglitazone significantly improved IPITT. High PGB1 and rosiglitazone supplementation preserved the appearance of islets and insulin-positive cells in immunohistochemical photographs of the pancreas compared with the control group. These results demonstrated that high PGB1 (0.25% in the diet) supplementation seemingly contributes to preventing the onset and progression of type 2 diabetes by stimulating insulin secretion and enhancing the hepatic glucose metabolic enzyme activities.     

不同糖源及糖水平对大菱鲆糖代谢酶活性的影响

采用34双因素实验设计, 以初始质量为(8.060.08) g的大菱鲆幼鱼(Scophthalmus maximus L.)为对象, 研究在饲料中添加3种糖源(葡萄糖、蔗糖和糊精)及4个水平(0、5%、15%、28%)对大菱鲆肝脏糖酵解关键酶己糖激酶(HK)、葡萄糖激酶(GK)、磷酸果糖激酶(PFK)、丙酮酸激酶(PK)和糖异生关键酶磷酸烯醇式丙酮酸羧激酶(PEPCK)、1, 6-二磷酸果糖酶(FBPase)活性的影响。结果表明: 饲料糖添加量从0升高到15%时, 大菱鲆的糖酵解酶GK和PK活性随饲料葡萄糖或糊精含量的增加而增加; 当饲料中葡萄糖或糊精含量为28%时, GK和PK活性有下降的趋势。3种糖源的4个添加水平对HK和PFK活性均无显著影响(P 0.05)。添加不同水平的葡萄糖对大菱鲆糖异生途径的PEPCK活性无显著影响(P 0.05), 但在饲料中葡萄糖添加量为5%时显著促进了FBPase活性(P 0.05), 当葡萄糖添加量升高为15%或28%时, FBPase活性与对照组无显著差异(P 0.05)。糊精作为饲料糖源时抑制了大菱鲆肝脏FBPase和PEPCK的活性, 而添加不同水平的蔗糖对FBPase和PEPCK活性的影响均不显著(P 0.05)。总的来说, 从大菱鲆幼鱼肝脏糖代谢角度而言, 在饲料中添加15%的葡萄糖或糊精时, 可以有效促进大菱鲆肝脏糖酵解能力; 较添加葡萄糖, 糊精在促进大菱鲆肝脏糖酵解的同时对糖异生存在一定程度的抑制。蔗糖作为饲料糖源时, 仅在添加量为28%时显著促进糖酵解酶GK活性, 糖酵解其他酶活性以及糖异生酶活性均不受蔗糖水平的显著影响。       

The effects of dietary sulfur on selenium utilization by the rat

The antagonistic effects of S on Se utilization were studied by measurement of tissue Se concentrations and glutathione peroxidase (GSHpx, E.C.1.11.1.9) activities in rats offered Torula yeast-based diets supplemented with sodium sulfate to provide 1.5, 3, or 5 g S/kg diet. Increasing sulfur concentrations in the diet caused small but significant decreases in GSHpx activity of liver, spleen, heart, lung small intestine, and skeletal muscle. Also significantly decreased were Se concentrations in liver and hair. Dietary sulfur content had no significant effect on body weight gain of the rats. With an adequate supply of Se in the diet, there are probably no major deleterious effects of dietary S on Se metabolism in the rat.     

The ddY mouse: a model of postprandial hypertriglyceridemia in response to dietary fat

Postprandial hyperlipidemia (lipemia) is a risk factor for atherosclerosis. However, mouse models of postprandial hyperlipidemia have not been reported. Here, we report that ddY mice display marked postprandial hypertriglyceridemia in response to dietary fat. In ddY mice, the fasting serum total triacylglyceride (TG) concentration was 134 mg/dl, which increased to 571 mg/dl after an intragastric safflower oil load (0.4 ml/mouse). In C57BL/6J mice, these concentrations were 57 and 106 mg/dl, respectively. By lipoprotein analysis, ddY mice showed increases in chylomicron- and VLDL-sized TG fractions (remnants and VLDL) after fat load. In C57BL/6J mice, post-heparin plasma LPL activity after fat load was increased 4.8-fold relative to fasting. However, in ddY mice, the increase of LPL activity after fat load was very small (1.2-fold) and not significant. High fat feeding for 10 weeks led to obesity in ddY mice. A difference in LPL amino acid composition between C57BL/6J and ddY mice was detected but was deemed unlikely to cause hypertriglyceridemia because hypertriglyceridemia was not evident in other strains harboring the ddY-type LPL sequence. These findings indicate that postprandial hypertriglyceridemia in ddY mice is induced by decreased LPL activity after fat load and is associated with obesity induced by a high-fat diet.     

Plasmodium berghei: Glycolytic enzymes of the infected mouse erythrocyte

This paper documents the maximal activities of the glycolytic enzymes in the red blood cells of normal mice and mice infected with Plasmodium berghei. There appears to be sufficient parasite-related activity of each glycolytic enzyme to support the increased glycolytic rate, i.e., increased glucose consumption, of the parasite-infected red blood cell. The relative proportions of glycolytic enzyme activities in parasite-infected red cells are different from the proportions in either normal or reticulocyte-rich blood, indicating that the increased enzyme activities associated with infected cells are not due to contaminating host red cells or reticulocytes. A comparison of maximal enzyme activities to the rate of whole cell glucose consumption indicates that different glycolytic control mechanisms are operating in the infected RBC from those in the uninfected cells.     

Influence of thyroid hormone on glycogen metabolism in rat liver.

The livers removed from thyroidectomized and L-T4 supplemented rats were rapidly frozen by Freon-12 chilled with liquid nitrogen, and concentrations of metabolites which affect glycogen synthetase and phosphorylase were determined. Serum and liver glycose levels were not changed in any thyroid functioning. But liver G6P and ATP were increased by thyroidectomy and decreased by L-T4 supplement, while cAMP was increased by the hormone supplement. The "enzyme activity" ratio of glycogen synthetase a to phosphorylase a was increased by thyroidectomy and decreased by L-T4 supplement. The most intimate correlation was observed between the "enzyme activity" ratio and the ratio of the "energy charge" ratio of cAMP among other indices calculated from changes in the metabolite concentrations in the various thyroid functioning. The change in the substrate levels brought about by thyroidectomy and L-T4 supplement appeared to modulate both the enzyme activities which in turn regulate the glycogen metabolism.     

Influence of selenium on heat shock protein 70 expression in heat stressed turkey embryos (Meleagris gallopavo)

Heat shock protein 70 (hsp70) family of proteins, which functions as molecular chaperones, has been associated with tolerance to stressors in avian species. Selenium (Se) is an essential trace mineral incorporated into the seleno-enzymes such as glutathione peroxidase (GSHpx). GSHpx reduces oxidized glutathione (GSSG) to reduced glutathione (GSH) in the GSH/GSSG antioxidant system and protects cells from oxidative damage. This study was conducted to examine if the relationship between dietary supplementation of selenium to turkey (Meleagris gallopavo) hens and the embryonic expression of hsp70 and GSHpx activity in heat stressed embryos. Livers of embryos developing in eggs from turkey hens fed diets with or without supplemental Se were analyzed for hsp70 concentration and GSHpx activity before and after recovery from a heating episode. Before heat stress, hsp70 concentrations were equivalent in each treatment, but GSHpx activity was maximized in the SE treatment group. After recovery from the heating episode, hsp70 concentrations were significantly higher (P<0.05) in the non-Se-supplemented groups, but in the Se-supplemented groups the hsp70 concentrations were not different from pre-stress concentrations. In the pre-stress Se-supplemented group, liver GSHpx activity was significantly higher than GSHpx activity in the non-Se-supplemented embryo livers, and in the livers from embryos recovering from heat stress, GSHpx activity in the non-Se-supplemented group was lower than the pre-stress activity and significantly lower than the GSHpx activity in liver from Se-supplemented embryos recovering from heat distress. Se supplementation to the dams resulted in a significant increase in their embryos and that condition would facilitate a decreased incidence of oxidative damage to cells. A more reduced redox status in embryos from Se-supplemented dams decreased the need for cellular protection attributed to stress induced hsp70 and presumably allows heat distressed embryos to resume normal growth and development than embryos from dams with inadequate selenium nutrition.     

Plasmodium knowlesi: glycolytic intermediate levels of enzyme activities of infected rhesus monkey erythrocytes

In vitro glycolytic enzyme activities and in vivo glycolytic intermediate concentrations were assayed in Plasmodium knowlesi-infected rhesus monkey erythrocytes and control erythrocytes. The enzyme activities of infected erythrocytes were greater than controls indicating that P. knowlesi had its own glycolytic system and that parasite glycolysis was the source of the increased rate of glucose consumption by infected erythrocytes. The P. knowlesi glycolytic enzymes phosphofructokinase and hexokinase were less sensitive to acid inhibition than uninfected red cells.P. knowlesi-infected monkey erythrocytes and Plasmodium berghei-infected mouse erythrocytes had similar in vivo glycolytic profiles and in vitro enzyme activity increases.     

Stress and interpopulation variation in glycolytic enzyme activity and expression in a teleost fish Fundulus heteroclitus

Northern populations of Fundulus heteroclitus have twofold greater activity of lactate dehydrogenase-B (LDH-B) than southern populations, but exposure to stress increases LDH-B in southern populations, abolishing this difference. To test whether differences in the activity of other hepatic glycolytic enzymes between populations are sensitive to stress, we injected fish with a pharmacological dose of cortisol in coconut oil (400 microg g(-1)) or exposed them to handling stress and measured the activities of all the glycolytic enzymes. At rest, liver phosphofructokinase (PFK) and aldolase (ALD) activities were greater in southern fish, whereas LDH-B activity was greater in northern fish. No other glycolytic enzymes differed in activity between populations in control fish. Cortisol injection and handling stress decreased PFK and ALD and increased LDH activities in the southern but not the northern population, such that the populations no longer differed in the activity of any enzyme following treatment. Unlike Ldh-B mRNA, Pfk and Ald mRNA levels did not parallel enzyme activity, suggesting complex kinetics or regulation at multiple levels. Plasma cortisol did not differ between populations at rest but was significantly different between populations in treated fish. These data suggest that differences in liver enzyme activity may be related to differences in stress hormone physiology between populations.     

Lipogenic enzyme activity and fructose 2,6-bisphosphate concentration in livers of two lines of domestic fowl (Gallus domesticus) selected for different body fat content

Livers were obtained from two lines of domestic broiler which had been selected for low (lean) and high (fat) plasma very-low-density lipoprotein concentration over three generations. The fat line possessed significantly higher hepatic specific activities of malate dehydrogenase (NADP), ATP citrate lyase and fatty acid synthase, and lower glucose bisphosphatase than the lean line. The glycolytic enzymes, pyruvate kinase and phosphofructokinase, were similar and so was the concentration of fructose 2,6-bisphosphate. This recently discovered metabolic regulator was present at somewhat higher concentrations than previously reported in rats or mice. It exhibited a positive correlation with phosphofructokinase activity (only data for the fat line are shown), and stimulated enzyme activity when added to crude preparations.     

Involvement of D-amino acid oxidase in elimination of free D-amino acids in mice.

The physiological role of D-amino acid oxidase was investigated by using mutant ddY/DAO- mice lacking the enzyme. Free D-amino acid concentrations in the mutant mice were significantly higher than those of control ddY/DAO+ mice in kidney, liver, lung, heart, brain, erythrocytes, serum and urine. The results suggest that the enzyme is involved in the catabolism of free D-amino acids in the body, and that free D-amino acids are also excreted into urine.     

Effects of dietary carbohydrate and myo-inositol on metabolic changes in rats fed 1,1,1-trichloro-2,2-bis (p-chlorophenyl) ethane (DDT)

This study was conducted to examine the effects of dietary carbohydrate [starch or sucrose (500 g/kg diet)] and myo-inositol (2 g/kg diet) on metabolic changes in rats fed 1,1,1-trichloro-2,2-bis (p-chlorophenyl) ethane (DDT) (0.7 g/kg diet). Dietary DDT enhanced serum and hepatic lipids and hepatic thiobarbituric acid reactive substances (TBA-RS), elevated hepatic activities of lipogenic enzymes such as malic enzyme (ME), glucose-6-phosphate dehydrogenase (G6PD) and fatty acid synthetase (FAS), increased hepatic cytochrome P-450 content and the activities of drug-metabolizing enzymes such as aminopyrine N-demethylase, glutathione S-transferase and 4-nitrophenol-UDP glucuronosyltransferase (4NP-UDPGT) and raised hepatic ascorbic acid and serum copper. Dietary sucrose promoted the increases in hepatic concentrations of total lipids, triglyceride and cholesterol, hepatic activity of ME, hepatic TBA-RS, cytochrome P-450 content and serum copper due to DDT feeding when compared to DDT administered in a starch based diet. Dietary myo-inositol significantly depressed the rises in hepatic concentrations of total lipids, triglyceride and cholesterol and the activities of ME and G6PD due to DDT feeding regardless of dietary carbohydrate quality. Dietary starch supplemented with myo-inositol potentiated the enhancements in hepatic activities of Phase II drug-metabolizing enzymes such as glutathione S-transferase and 4NP-UDPGT due to DDT feeding. These results suggest that dietary starch and myo-inositol can protect DDT fed rats against an accumulation of hepatic lipids, which might be mainly ascribed to the depression of hepatic lipogenesis. In addition, the present study implies that the supplementation of myo-inositol to high starch diet might improve the function of drug-metabolizing enzymes exposed to DDT.     

Effect of β-alanine administration on carbon tetrachloride-induced acute hepatotoxicity

Summary. Mice were supplemented with β-alanine (3%) in drinking water for one week. β-Alanine intake reduced hepatic taurine levels, but elevated cysteine levels significantly. Hepatotoxicity of CCl₄ in mice fed with β-alanine was decreased as determined by changes in serum enzyme activities. Hepatic glutathione and taurine concentrations after CCl₄ challenge were increased markedly by β-alanine intake. The enhanced availability of cysteine for synthesis of glutathione and/or taurine appears to account for the hepatoprotective effects of β-alanine against CCl₄-induced liver injury.     

Enzymes of glycerol and glyceraldehyde metabolism in mouse liver: effects of caloric restriction and age on activities

The influence of caloric restriction on hepatic glyceraldehyde- and glycerol-metabolizing enzyme activities of young and old mice were studied. Glycerol kinase and cytoplasmic glycerol-3-phosphate dehydrogenase activities were increased in both young and old CR (calorie-restricted) mice when compared with controls, whereas triokinase increased only in old CR mice. Aldehyde dehydrogenase and aldehyde reductase activities in both young and old CR mice were unchanged by caloric restriction. Mitochondrial glycerol-3-phosphate dehydrogenase showed a trend towards an increased activity in old CR mice, whereas a trend towards a decreased activity in alcohol dehydrogenase was observed in both young and old CR mice. Serum glycerol levels decreased in young and old CR mice. Therefore increases in glycerol kinase and glycerol-3-phosphate dehydrogenase were associated with a decrease in fasting blood glycerol levels in CR animals. A prominent role for triokinase in glyceraldehyde metabolism with CR was also observed. The results indicate that long-term caloric restriction induces sustained increases in the capacity for gluconeogenesis from glycerol.     

The effects of a low vitamin E diet on dichloroacetate- and trichloroacetate-induced oxidative stress in the livers of mice

Groups of mice were fed either a standard (Std) diet or a diet not supplemented with vitamin E (Low-E) and were divided into three subgroups that were treated subchronically by gavage, with water (control), dichloroacetate (DCA), or trichloroacetate (TCA). The livers of the animals were assayed for various biomarkers of oxidative stress (OS), antioxidant enzyme activities, and total glutathione (GSH). In general, livers from the low-E diet group expressed lower levels of biomarkers of OS associated with greater increases in various antioxidant enzymes activities and GSH when compared with the corresponding treatments in the Std diet group. These results suggest that vitamin E supplementation to the diet, while essential to maintain certain body functions, can compromise the effectiveness of the hepatic antioxidant enzymes and GSH resulting in an increase in DCA- and TCA-induced OS and a possible increase in the compounds-induced hepatotoxic/hepatocarcinogenic effects in mice.     

Metabolic control of hepatic gluconeogenesis during exercise.

Prolonged exercise increased the concentrations of the hexose phosphates and phosphoenolpyruvate and depressed those of fructose 1,6-bisphosphate, triose phosphates and pyruvate in the liver of the rat. Since exercise increases gluconeogenic flux, these changes in metabolite concentrations suggest that metabolic control is exerted, at least, at the fructose 6-phosphate/fructose 1,6-bisphosphate and phosphoenolpyruvate/pyruvate substrate cycles. Exercise increased the maximal activities of glucose 6-phosphatase, fructose 1,6-bisphosphatase, pyruvate kinase and pyruvate carboxylase in the liver, but there were no changes in those of glucokinase, 6-phosphofructokinase and phosphoenolpyruvate carboxykinase. Exercise changed the concentrations of several allosteric effectors of the glycolytic or gluconeogenic enzymes in liver; the concentrations of acetyl-CoA, ADP and AMP were increased, whereas those of ATP, fructose 1,6-bisphosphate and fructose 2,6-bisphosphate were decreased. The effect of exercise on the phosphorylation-dephosphorylation state of pyruvate kinase was investigated by measuring the activities under conditions of saturating and subsaturating concentrations of substrate. The submaximal activity of pyruvate kinase (0.5 mM-phosphoenolpyruvate), expressed as percentage of Vmax., decreased in the exercised animals to less than half that found in the controls. These changes suggest that hepatic pyruvate kinase is less active during exercise, possibly owing to phosphorylation of the enzyme, and this may play a role in increasing the rate of gluconeogenesis.     

Fucoxanthin-rich seaweed extract suppresses body weight gain and improves lipid metabolism in high-fat-fed C57BL/6J mice

An ethanol extract of fucoxanthin-rich seaweed was examined for its effectiveness as a nutraceutical for body fat-lowering agent and for an antiobese effect based on mode of actions in C57BL/6J mice. Animals were randomized to receive a semi-purified high-fat diet (20% dietary fat, 10% corn oil and 10% lard) supplemented with 0.2% conjugated linoleic acid (CLA) as the positive control, 1.43% or 5.72% fucoxanthin-rich seaweed ethanol extract (Fx-SEE), equivalent to 0.05% or 0.2% dietary fucoxanthin for six weeks. Results showed that supplementation with both doses of Fx-SEE significantly reduced body and abdominal white adipose tissue (WAT) weights, plasma and hepatic triglyceride (TG), and/or cholesterol concentrations compared to the high-fat control group. Activities of adipocytic fatty acid (FA) synthesis, hepatic FA and TG synthesis, and cholesterol–regulating enzyme were also lowered by Fx-SEE supplement. Concentrations of plasma high-density lipoprotein-cholesterol, fecal TG and cholesterol, as well as FA oxidation enzyme activity and UCP1 mRNA expression in epididymal WAT were significantly higher in the Fx-SEE groups than in the high-fat control group. CLA treatment reduced the body weight gain and plasma TG concentration. Overall, these results indicate that Fx-SEE affects the plasma and hepatic lipid profile, fecal lipids and body fat mass, and alters hepatic cholesterol metabolism, FA synthesis and lipid absorption.     

Gluconeogenesis in the cow. The effects of a glucocorticoid on hepatic intermediary metabolism

1. The hepatic concentrations of the ketone bodies and of metabolites and activities of enzymes involved in gluconeogenesis were measured in healthy lactating and non-lactating cows 48h after administration of Voren, an ester of dexamethasone, and compared with those found in control animals given saline. Parallel measurements were also made of the blood concentrations of several of the metabolites. 2. Blood glucose concentrations were raised in the Voren-treated animals, whereas blood ketone body and free fatty acid concentrations were unaltered. Similarly there was no change in the hepatic concentrations of the ketone bodies. 3. Significant increases were found in the hepatic concentrations of citrate, 2-oxo-glutarate and malate in both groups of animals given Voren. 4. The hepatic concentrations of those glycolytic intermediates that were measured either decreased or did not change after Voren treatment. 5. The enzymes aspartate transaminase and fructose 1,6-diphosphatase were unchanged in activity after Voren administration, whereas phosphopyruvate carboxylase (EC 4.1.1.32) activity was depressed in the lactating group. However, glucose 6-phosphatase, tryptophan oxygenase and tyrosine aminotransferase increased in activity. 6. In several cases those hepatic metabolites that increased in concentration after Voren administration were present in lower concentration in normal lactating cows than in normal non-lactating cows. The same applied mutatis mutandis to those metabolites that were decreased by Voren. 7. These findings are discussed in relation to the use of glucocorticoids in the treatment of bovine ketosis.