Inhibitory effect of fenugreek galactomannan on digestive enzymes related to diabetes,hyperlipidemia, and liver-kidney dysfunctions

The present study was undertaken to investigate the effect of fenugreek galactomannan on intestinal glucose uptake in surviving diabetic rats. It explored their potential action with respect to lowering maltase, lactase, and sucrase activities in the small intestine of galactomannan-treated diabetic group compared to the diabetic control group. The findings indicate that the increase of blood glucose levels was significantly suppressed in the galactomannan-treated group than those in the diabetic rats. Moreover, the galactomannan isolated from fenugreek exhibited a prominent selective inhibitory effect against intestinal lipase activity. It was found to significantly delay the absorption of LDL-cholesterol and triglycerides and the increase in HDL-cholesterol. In addition, fenugreek galactomannan efficiently protect the hepatic function observed by the considerable decrease of aspartate and alanine transaminases (AST and ALT) and lactate deshydrogenase (LDH) contents in the serum of diabetic rats. The beneficial effects of fenugreek galactomannan were also evidenc-ed by their capacity to inhibit diabetes-induced kidney injury through lowering the urea and creatinine content in plasma. Overall, the conclusion of the present study indicate that fenugreek galactomannan displays a number of promising properties and attributes for future applications as therapeutic agents in biotechnological and bioprocess-based technologies, particularly those interested in the development of anti-diabetic and hypolipidemic drugs.     

The Effect of Lipid Peroxide on the Lipid and Carbohydrate Metabolism in Rat Liver

Feeding tests were carried out on rats to clarify the mechanisms of fatty liver formation induced by autoxidized methyl linoleate. Lipid peroxides prepared by autoxidation of highly purified methyl linoleate were given orally to rats. Triglyceride and glycogen contents in liver were determined and enzyme activities including triglyceride synthetase and α-glycerophosphate dehydrogenase were also examined. The following results were obtained. 1. Triglyceride accumulation in rat liver fed autoxidized methyl linoleate was observed. 2. Increase in triglyceride content in rat liver was soon followed by the decrease of hepatic glycogen. 3. When rats were starved prior to introduction of autoxidized methyl linoleate, hepatic triglyceride accumulation did not occur. 4. The activities of α-glycerophosphate dehydrogenase and triglyceride synthetase in liver, and those of glutamic oxalacetic transaminase and leucine aminopeptidase in plasma were practically similar among the rats of test groups fed fresh or autoxidized methyl linoleate and the control fed diet without methyl linoleate. 5. The addition of l-carnitine which is a stimulator of fatty acid oxidation retarded the accumulation of the hepatic triglyceride mentioned above.     

Age-related augmentation of phosphorylase b kinase in hepatic tissue from the glycogen-storage-disease (gsd/gsd) rat.

The effects of food deprivation on body weight, liver weight, hepatic glycogen content, glycogenolytic enzymes and blood metabolites were compared in young and old phosphorylase b kinase-deficient (gsd/gsd) rats. Although the concentration of glycogen in liver from 9-week-old female gsd/gsd rats (730 mumol of glucose equivalents/g wet wt.) was increased by 7-8% during starvation, total hepatic glycogen was decreased by 12% after 24 h without food. In 12-month-old male gsd/gsd rats the concentration of liver glycogen (585 mumol of glucose equiv./g wet wt.) was decreased by 16% and total hepatic glycogen by nearly 40% after food deprivation for 24 h. Phosphorylase b kinase and phosphorylase a were present at approx. 10% of the control activities in 9-week-old gsd/gsd rats, but both enzyme activities were increased more than 3-fold in 12-month-old affected rodents. It is concluded that the age-related ability to mobilize hepatic glycogen appears to result from the augmentation of phosphorylase b kinase during maturation of the gsd/gsd rat.     

Hyperglycaemia, stress oxidant, liver dysfunction and histological changes in diabetic male rat pancreas and liver: protective effect of 17 beta-estradiol

Oxidative stress is thought to play a crucial role in the pathogenesis of chronic diabetic complications. We investigated the protective effects of 17 beta-estradiol (E2) on alloxan-induced stress oxidant, hepatic dysfunction and histological changes in male rats liver and pancreas. Our results showed that 17 beta-estradiol could attenuate the increase of blood glucose in plasma and normalise the hepatic glycogen level. In addition, E2 enhanced superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPX) (by 207, 52 and 72%, respectively, as compared to diabetic rats), reduced lipid peroxidation in the hepatic tissue (by 54%) and improved the liver dysfunction parameters by the significant decrease of gamma-glytamyl transferase (GGT), phosphatases alkalines (PAL), lactate deshydrogenase (LDH) and aspartate and lactate transaminases (AST and ALT) activities which increased in diabetic rats. Moreover, 17 beta-estradiol treatment in diabetic rats protects against alloxan-induced pancreatic beta-cells and hepatic cells damages.     

Mechanisms of antihyperglycemic effect of p-methoxycinnamic acid in normal and streptozotocin-induced diabetic rats

We investigated the antihyperglycemic effect of p-methoxycinnamic acid (p-MCA), a cinnamic acid derivative, on plasma glucose and insulin concentrations, activities of hepatic glucose-regulating enzymes and hepatic glycogen content in normal and streptozotocin (STZ)-induced diabetic rats. p-MCA (10-100 mg/kg, PO) dose-dependently decreased plasma glucose concentration in both normal and diabetic rats in the oral glucose tolerance test. To investigate the chronic effects of p-MCA on glucose metabolism, p-MCA (40 mg/kg, PO) was administered to normal and diabetic rats once a day for 4 weeks. p-MCA reduced plasma glucose concentration in diabetic rats, which was observed during the 4-week study. However, p-MCA treatment did not change plasma glucose concentrations in normal rats during the 4-week study. p-MCA also reduced the excessive activities of hepatic glucose-6-phosphatase, hepatic hexokinase, glucokinase and phosphofructokinase in diabetic rats and increased hepatic glycogen in these rats. In p-MCA-treated normal rats, there were no changes in the activities of hepatic glucose-regulating enzymes, hepatic glycogen and glucose-6-phosphate. Our findings suggested that p-MCA exert its antihyperglycemic effect by increasing insulin secretion and glycolysis, and by decreasing gluconeogenesis.     

Influence of oral administration of 3,5,3'-triiodo-thyronine on growth, digestion, food conversion and metabolism in the underyearling red sea bream, Chrysophrys major (Temminck & Schlegel)

The effect of inclusion of 3,5,3'-triiodo-∼-thyronine (T₃) in the diet was examined in underyearling red sea bream Chrysophrys major (Temminck & Schlegel). The treatment brought about increases in growth rate, appetite, food conversion efficiency and activities of intestinal enzymes including leucine nitroanilidase, alkaline phosphatase, α-glutamyltransferas, α-amylase and disaccharidase. There were no changes in the muscle content of water, protein, lipid and glycogen. Liver glycogen content was elevated, as well as activities of the hepatic enzymes glycogen phosphory-lase, glycogen synthetase, glutamate-pyruvate transaminase, fructose- 1, 6-diphosphatase and glucose-6-phosphatase. The serum concentrations of total protein, albumin, globulin, α-amino acids. glucose, ammonia and calcium were increased by the treatment whereas the serum concentrations of free fatty acids, cholesterol and triglyceride remained unaltered. The results suggest that in the red sea bream T, stimulated protein and carbohydrate but not lipid metabolism and that the hormone promoted growth by improving appetite, digestion and absorption.     

Fenugreek seeds modulate 1,2-dimethylhydrazine-induced hepatic oxidative stress during colon carcinogenesis

1,2-dimethylhydrazine (DMH) is a colon carcinogen which undergoes oxidative metabolism in the liver. We have investigated the modulatory effect of fenugreek seeds (a spice) on colon tumor incidence as well as hepatic lipid peroxidation (LPO) and antioxidant status during DMH-induced colon carcinogenesis in male Wistar rats. In DMH treated rats, 100% colon tumor incidence was accompanied by enhanced LPO and a decrease in reduced glutathione (GSH) content as well as a fall in glutathione peroxidase (GPx), glutathione S-transferase (GST), superoxide dismutase (SOD) and catalase (CAT) activities. Inclusion of fenugreek seed powder in the diet of DMH treated rats reduced the colon tumor incidence to 16.6%, decreased the LPO and increased the activities of GPx, GST, SOD and CAT in the liver. We report that fenugreek modulates DMH-induced hepatic oxidative stressduring colon cancer     

Antihyperglycemic effect of aqueous and ethanolic extracts of Gongronema latifolium leaves on glucose and glycogen metabolism in livers of normal and streptozotocin-induced diabetic rats

The present study was designed to investigate the antihyperglycemic effects of aqueous and ethanolic extracts from Gongronema latifolium leaves on glucose and glycogen metabolism in livers of non-diabetic and streptozotocin-induced diabetic rats. To investigate the effects of aqueous or ethanolic leaf extracts of G. latifolium, non-diabetic and STZ diabetic rats were treated twice daily (100 mg/Kg) for two weeks. Diabetic rats showed a significant decrease in the activities of hepatic hexokinase (HK), phosphofructokinase (PFK) and glucose-6-phosphate dehydrogenase (G6PDH) and an increase in glucokinase (GK) activity. The levels of hepatic glycogen and glucose were also increased in diabetic rats. However, there were no significant differences in the activities of glucose-6-phosphatase (G6Pase) in treated and untreated diabetic rats. The ethanolic extract significantly increased the activities of HK (p<0.01), PFK (p<0.001) and G6PDH (p<0.01) in diabetic rats, decreased the activity of GK (p<0.05) and the levels of hepatic glycogen (p<0.01) and both hepatic (p<0.001) and blood glucose (40%). The aqueous extract of G. latifolium was only able to significantly increase the activities of HK and decrease the activities of GK but did not produce any significant change in the hepatic glycogen and both hepatic and blood glucose content of diabetic rats. Our data show that the ethanolic extract from G. latifolium leaves has antihyperglycemic potency, which is thought to be mediated through the activation of HK, PFK, G6PDH and inhibition of GK in the liver. The ethanolic extract is under further investigation to determine the chemical structure of the active compound(s) and its/their mechanism of action.     

Hepatic morphological alterations,glycogen content and cytochrome P450 activities in rats treated chronically with N<Superscript>ω</Superscript>-nitro-L-arginine methyl ester (L-NAME)

Chronic treatment of rats with N(omega)-nitro-L-arginine methyl ester (L-NAME), an inhibitor of nitric oxide (NO) biosynthesis, results in hypertension mediated partly by enhanced angiotensin-I-converting enzyme (ACE) activity. We examined the influence of L-NAME on rat liver morphology, on hepatic glycogen, cholesterol, and triglyceride content, and on the activities of the cytochrome P450 isoforms CYP1A1/2, CYP2B1/2, CYP2C11, and CYP2E1. Male Wistar rats were treated with L-NAME (20 mg/rat per day via drinking water) for 2, 4, and 8 weeks, and their livers were then removed for analysis. Enzymatic induction was produced by treating rats with phenobarbital (to induce CYP2B1/2), beta-naphthoflavone (to induce CYP1A1/2), or pyrazole (to induce CYP2E1). L-NAME significantly elevated blood pressure; this was reversed by concomitant treatment with enalapril (ACE inhibitor) or losartan (angiotensin II AT(1) receptor antagonist). L-NAME caused vascular hypertrophy in hepatic arteries, with perivascular and interstitial fibrosis involving collagen deposition. Hepatic glycogen content also significantly increased. L-NAME did not affect fasting glucose levels but significantly reduced insulin levels and increased the insulin sensitivity of rats, based on an intraperitoneal glucose tolerance test. Immunoblotting experiments indicated enhanced phosphorylation of protein kinase B and of glycogen synthase kinase 3. All these changes were reversed by concomitant treatment with enalapril or losartan. L-NAME had no effect on hepatic cholesterol or triglyceride content or on the basal or drug-induced activities and protein expression of the cytochrome P450 isoforms. Thus, the chronic inhibition of NO biosynthesis produced hepatic morphological alterations and changes in glycogen metabolism mediated by the renin-angiotensin system. The increase in hepatic glycogen content probably resulted from enhanced glycogen synthase activity following the inhibition of glycogen synthase kinase 3 by phosphorylation.     

Glucose activation of liver glycogen synthase. Insulin-mediated restoration of glucose effect in diabetic rats is blocked by protein synthesis inhibitor.

The loss of glucose regulation of glycogen synthase in perfused livers from diabetic rats was associated with a substantial reduction in synthase phosphatase activity. Treatment of diabetic rats with insulin alone resulted in total restoration of the glucose effect and synthase phosphatase activity, while simultaneous treatment with cycloheximide severely reduced the hormonal effect. Although treatment of normal rats with cycloheximide had no effect on glucose activation of synthase, it did result in severe depletion of liver glycogen, increased liver glycogen phosphorylase activity, and elevation of liver adenosine 3',5'-monophosphate (cyclic AMP), but without elevation of liver protein kinase activity. Simultaneous treatment of alloxan-diabetic rats with insulin and cycloheximide resulted in reduction of total liver glycogen, increased phosphorylase activity, a reduction in the ability of insulin to lower hepatic cyclic AMP, and a further reduction of protein kinase activity. In summary, the effect of insulin treatment of diabetic rats to restore glucose regulation of hepatic glycogen synthase probably involves synthesis of new protein, and the data remain consistent with the hypothesis that the defect may be due to a diabetes-related deficiency in a specific synthase phosphatase and/or alteration of the synthase molecule itself.     

Glucose activation of liver glycogen synthase. Insulin-mediated restoration of glucose effect in diabetic rate is blocked by protein synthesis inhibitor

The loss of glucose regulation of glycogen synthase in perfused livers from diabetic rats was associated with a substantial reduction in synthase phosphatase activity. Treatment of diabetic rats with insulin alone resulted in total restoration of the glucose effect and synthase phosphatase activity, while simultaneous treatment with cycloheximide severely reduced the hormonal effect. Although treatment of normal rats with cycloheximide had no effect on glucose activation of synthase, it did result in severe depletion of liver glycogen increased liver glycogen phosphorylase activity, and elevation of liver adenosine 3′,5′-monosphosphate (cyclic AMP), but without elevation of liver protein kinase activity. Simultaneous treatment of alloxan-diabetic rats with insulin and cycloheximide resulted in reduction of total liver glycogen, increased phosphorylase activity, a reduction in the ability of insulin to lower hepatic cyclic AMP, and a further reduction of protein kinase activity.In summary, the effect of insulin treatment of diabetic rats to restore glucose regulation of hepatic glycogen synthase probably involves synthesis of new protein, and the data remain consistent with the hypothesis that the defect may be due to a diabetes-related deficiency in a specific synthase phosphatase and/or alteration of the synthase molecule itself.     

Augmentation of hepatic and renal oxidative stress and disrupted glucose homeostasis by monocrotophos in streptozotocin-induced diabetic rats

Several recent studies have demonstrated that organophosphorus insecticides (OPI) possess the potential to disrupt glucose homeostasis leading to hyperglycemia in experimental animals. The propensity of OPI to induce hyperglycemia along with oxidative stress may have far-reaching consequences on diabetic outcomes and associated complications. The primary objective of this study was to assess the potential of monocrotophos (MCP), an extensively used OPI, on hepatic and renal oxidative stress markers and dysregulation of hepatic glucose homeostasis in experimentally induced diabetic rats. Rats rendered diabetic by a single dose of streptozotocin (60 mg/kg b.w) were orally administered MCP (0.9 mg/kg b.w/d for 5 d). Monocrotophos per se caused only a marginal increase in blood glucose levels but significantly elevated the blood glucose levels and also disrupted glucose homeostasis by depleting liver glycogen content and increasing the gluconeogenetic enzyme activities in diabetic rats. Experimentally induced diabetes was also associated with alterations in antioxidant enzymes in liver and kidney. MCP markedly enhanced lipid peroxidation in kidney and altered the enzymatic antioxidant defense mechanisms in both liver and kidney of diabetic rats. Collectively our data provides evidence that MCP has the propensity to augment the oxidative stress and further disrupt glucose homeostasis in diabetic rats.     

Protective effect of ascorbic acid against lipid peroxidation and oxidative damage in cardiac microsomes

Effects of feeding sucrose rich diet supplemented with and without the insulinmimetic agent vanadate for a period of six weeks were studied in rats. Sucrose diet caused hypertriglyceridemia (140% increase), hyperinsulinemia (120% increase) and significant elevations in the levels of glucose (p<0.001) and cholesterol (p<0.05) in plasma as compared to control starch fed rats. Activities of hepatic lipogenic enzymes, ATP-citrate lyase, glucose 6-phosphate dehydrogenase and malic enzyme increased by 100–150% as a result of sucrose feeding. However, glycogen content and the activities of glycogen synthase and phosphorylase in liver remained unaltered in these animals. The plasma levels of triacylglycerols and insulin in the rats fed on vanadate supplemented sucrose diet were 65% and 85% less, respectively as compared to rats on sucrose diet without vanadate. The concentrations of glucose and cholesterol in plasma and the activities of lipogenic enzymes in liver did not show any elevation in sucrose fed rats when supplemented with vanadate. These data indicate that the sucrose diet-induced metabolic aberrations can be prevented by the insulin-mimetic agent, vanadate.     

Antihepatotoxic effect of beta-carotene on paracetamol induced hepatic damage in rats

Enzyme levels of serum glutamate oxaloacetate transaminase (SGOT), serum glutamate pyruvate transaminase (SGPT) and alkaline phosphatase (ALP) increased following paracetamol induction were significantly lowered due to pretreatment with the beta-carotene (BC). This supplementation reversed the trend inducing a significant decrease in bilirubin and urea levels. Paracetamol administration significantly reduced hepatic glycogen, glutathione (GSH), glutathione-S-transferase (GST), glutathione peroxidase (GPX) and glutathione reductase (GSH-R). Pretreatment of rats with BC significantly increased the enzyme activities. The results suggest hepatoprotective activity of BC.     

Protective effect of naringenin on hepatic and renal dysfunction and oxidative stress in arsenic intoxicated rats

Arsenic has a long history as a potent human poison, chronic exposure over a period of time may result in the manifestation of toxicity in practically all systems of the body. In the present investigation the efficacy of naringenin (NRG), a naturally occurring citrus flavanone against arsenic-induced hepatotoxic and nephrotoxic manifestations have been studied in rats. Arsenic trioxide was administered orally at the dose of 2 mg/kg/day with or without combination of NRG (20 or 50 mg/kg/day) for 28 days. At the end of the experimental period the hepatic and renal dysfunction was evaluated by histological examination, serum biomarkers and markers of oxidative stress; lipid peroxidation (LPO), reduced glutathione (GSH) and antioxidant enzymes. Arsenic intoxication increased serum bilirubin, urea, uric acid and creatinine levels, additionally enhanced the activities of hepatic marker enzymes aspartate transaminase, alanine transaminase and alkaline phosphatase. Also, the hepatic and renal tissues showed a marked elevation in LPO levels with a decrease in GSH content and the activities of antioxidant enzymes such as superoxide dismutase, catalase, glutathione peroxidase and glutathione-S-transferase on arsenic treatment. Simultaneous treatment with NRG restored the activities of serum biomarkers and antioxidant enzymes in the tissues in a dose-dependent manner. Furthermore, the histopathological studies confirmed the protective effect of NRG co-treatment by reducing the pathological changes due to arsenic intoxication in both liver and kidney. Thus, our present study demonstrates that NRG has a potential to protect arsenic-induced oxidative hepatic and renal dysfunction.     

Non-hormonal and hormonal control of glycogen metabolism in isolated sheep liver cells

1. Control of glycogen metabolism by various substrates and hormones was studied in ruminant liver using isolated hepatocytes from fed sheep. 2. In these cells glucose appeared uneffective to stimulate glycogen synthesis whereas fructose and propionate activated glycogen synthase owing to (i) a decrease in phosphorylase a activity and (ii) changes in the intracellular concentrations of glucose 6-phosphate and adenine nucleotides. 3. The activation of hepatic glycogenolysis by glucagon and alpha 1-adrenergic agents was associated with increased phosphorylase a and decreased glycogen synthase activities. 4. The simultaneous changes in these two enzyme activities suggest that in sheep liver, activation of phosphorylase a is not a prerequisite step for synthase inactivation. 5. In sheep hepatocytes, in the presence of propionate and after a lag period, insulin activated glycogen synthase without affecting phosphorylase a. 6. This latter result suggests that the direct activation of glycogen synthase by insulin is mediated by a glycogen synthase-specific kinase or phosphatase. Insulin also antagonized glucagon effect on glycogen synthesis by counteracting the rise of cAMP.     

Experimental hyperprolinemia induces mild oxidative stress, metabolic changes, and tissue adaptation in rat liver

The present study investigated the effects of chronic hyperprolinemia on oxidative and metabolic status in liver and serum of rats. Wistar rats received daily subcutaneous injections of proline from their 6th to 28th day of life. Twelve hours after the last injection the rats were sacrificed and liver and serum were collected. Results showed that hyperprolinemia induced a significant reduction in total antioxidant potential and thiobarbituric acid-reactive substances. The activities of the antioxidant enzymes catalase and superoxide dismutase were significantly increased after chronic proline administration, while glutathione (GSH) peroxidase activity, dichlorofluorescin oxidation, GSH, sulfhydryl, and carbonyl content remained unaltered. Histological analyses of the liver revealed that proline treatment induced changes of the hepatic microarchitecture and increased the number of inflammatory cells and the glycogen content. Biochemical determination also demonstrated an increase in glycogen concentration, as well as a higher synthesis of glycogen in liver of hyperprolinemic rats. Regarding to hepatic metabolism, it was observed an increase on glucose oxidation and a decrease on lipid synthesis from glucose. However, hepatic lipid content and serum glucose levels were not changed. Proline administration did not alter the aminotransferases activities and serum markers of hepatic injury. Our findings suggest that hyperprolinemia alters the liver homeostasis possibly by induction of a mild degree of oxidative stress and metabolic changes. The hepatic alterations caused by proline probably do not implicate in substantial hepatic tissue damage, but rather demonstrate a process of adaptation of this tissue to oxidative stress. However, the biological significance of these findings requires additional investigation.     

Decreased response to cAMP in the glucose and glycogen catabolism in perfused livers of Walker-256 tumor-bearing rats

The hepatic response to cyclic adenosine monophosphate (cAMP) and N6-monobutyryl-cAMP (N6-MB-cAMP) in the glucose and glycogen catabolism and hepatic glycogen levels were evaluated in Walker-256 tumor-bearing rats, on days 5 (WK5), 8 (WK8), and 11 (WK11) after the implantation of tumor. Rats without tumor fed ad libitum (fed control rats) or that received the same daily amount of food ingested by anorexics tumor-bearing rats (pair-fed control rats) or 24 h fasted (fasted control rats) were used as controls. Glucose and glycogen catabolism were measured in perfused liver. Hepatic glycogen levels were lower (p < 0.05) in WK5, WK8, and WK11 rats in comparison with fed control rats, but not in relation to the pair-fed control rats. However, the stimulatory effect of cAMP (3 and 9 μM) in the glycogen catabolism was lower (p < 0.05), respectively, in WK5 and WK8 rats compared to the pair-fed and fed control rats. Accordingly, the suppressive effect of cAMP (6 μM) in the glucose catabolism, under condition of depletion of hepatic glycogen (24 h fast), was lower (p < 0.05) in WK5 and WK11 rats than in fasted control rats. Similarly, the suppressive effect of N6-MB-cAMP (1 μM), a synthetic analogue of cAMP that it is not degraded by phosphodiesterase 3B (PDE3B), in the glucose catabolism was lower (p < 0.05) in WK5 rats compared to fasted control rats. In conclusion, livers of Walker-256 tumor-bearing rats showed lower response to cAMP in the glucose and glycogen catabolism in various stages of tumor development (days 5, 8 and 11), which was probably not due to the lower hepatic glycogen levels nor due to the increased activity of PDE3B.     

Use of deuterium labelled glucose in evaluating the pathway of hepatic glycogen synthesis

Deuterium labelled glucose has been used to study the pathway of hepatic glycogen synthesis during the fasted-refed transition in rats. Deuterium enrichment of liver glycogen was determined using nuclear magnetic resonance as well as mass spectroscopy. Sixty minutes after oral administration of deuterated glucose to fasted rats, the portal vein blood was fully enriched with deuterated glucose. Despite this, less than half of the glucose molecules incorporated into liver glycogen contained deuterium. The loss of deuterium label from glucose is consistent with hepatic glycogen synthesis by an indirect pathway requiring prior metabolism of glucose. The use of deuterium labelled glucose may prove to be a useful probe to study hepatic glycogen metabolism. Its use may also find application in the study of liver glycogen metabolism in humans by a noninvasive means.