Alloxan Diabetic Rats Research Articles

Restoration of the disordered glucose-fatty acid cycle in alloxan-diabetic rats by trihydroxyoctadecadienoic acids from Bryonia alba, a native Armenian medicinal plant.

We studied how administration of trihydroxyoctadecadienoic acids obtained from the roots of the native Armenian plant Bryonia alba L. (0.05 mg/kg/day for 15 days. i.m.) restores the disordered lipid metabolism of alloxan-diabetic rats. Diabetes was accompanied by an increase in total non-esterified fatty acid content of blood together with decreases in muscle and adipose tissue of total non-esterified fatty acids and triglycerides, together with marked alterations of phospholipid fatty acid distribution within the membranes from muscle, including increased short chain fatty acid and decreased arachidonate content. All these metabolic changes induced in diabetes were significantly restored by trihydroxyoctadecadienoic acid treatment towards their normal values (P < 0.005) with the exception of diminished triglyceride content of muscle which was not restored. In experiments on rat neutrophil leukocytes in vitro, it was found that the standardised preparation of Bryonia C-18 fatty acids (a mixture of four diastereoisomeric forms of the positional isomers I 12,13,16-trihydroxy-9Z,14E-octadecadienoic acid, II 12,15,16-trihydroxy-9Z,13E-octadecadienoic acid, III 9,10, 13-trihydroxy-11E,15Z-octadecadienoic acid and IV 9,12,13-trihydroxy-10E,14Z-octadecadienoic acid) had no effect on granular enzyme secretion or 5-lipoxygenase activity at 5-50 micrograms/ml, but dose-dependently reduced thromboxane B2 generation, with a corresponding increase in prostaglandin E2 release. We conclude that trihydroxyoctadecadienoic acids from B. alba can correct major metabolic abnormalities typical of severe diabetes mellitus, and that they can influence the profile of the formation of stable prostaglandins by actions downstream of prostaglandin endoperoxides.

Hypoglycaemic activity of Syzigium cumini seeds: effect on lipid peroxidation in alloxan diabetic rats

Syzigium cumini, commonly known as ‘jamun’, is widely used in Indian folk medicine for the treatment of diabetes mellitus. Oral administration of 2.5 and 5.0 g/kg body weight of the aqueous extract of the seed for 6 weeks resulted in a significant reduction in blood glucose and an increase in total haemoglobin, but in the case of 7.5 g/kg body weight the effect was not significant. It also prevents decrease in body weight. The aqueous extract also resulted in decreased free radical formation in tissues studied. Thus the study shows that Jamun seed extract (JSEt) has hypoglycaemic action. The decrease in thiobarbituric acid reactive substances (TBARS) and increase in reduced glutathione (GSH), superoxide dismutase (SOD) and catalase (CAT) clearly show the antioxidant property of the JSEt. The effect of JSEt was most prominently seen in the case of animals given 5.0 g/kg body weight. JSEt was more effective than glibenclamide.

Pancreas Transplantation Versus Islet Transplantation Versus Insulin Therapy in the Prevention of Nephropathy in Alloxan-Induced Diabetic Rats

CLINICAL and experimental studies have shown that careful glucose control may prevent, stabilize, or reverse renal and other chronic diabetic complications. However, the results of these studies are controversial because progression of diabetic lesions has been observed in a large number of patients after strict control of blood glucose using insulin therapy or insulin pumps. On the other hand, there are no definitive conclusions on the real effects of pancreas and islet transplantation on the prevention of kidney or other chronic lesions of diabetes. The study protocols are numerous, and the results are varied and conflicting. In this study we addressed the kidney lesions of alloxandiabetic rats and the long-term effect of insulin treatment and pancreas and islet transplantation as a means of prevention of these lesions. We hope to contribute to a better understanding of diabetes and the above mentioned issues.

Hypolipidaemic action of Tinospora cordifolia roots in alloxan diabetic rats

We undertook the present study to evaluate the hypolipidaemic effect of an aqueous extract of Tinospora cordifolia roots, an indigenous plant used in Ayurvedic medicine in India. Administration of the extract of T. cordifolia roots (2.5 and 5.0 g/kg body weight) for 6 weeks resulted in a significant reduction in serum and tissue cholesterol, phospholipids and free fatty acids in alloxan diabetic rats. The root extract at a dose of 5.0 g/kg body weight showed highest hypolipidaemic effect. The effect of T. cordifolia roots at 2.5 and 5.0 g/kg body weight was better than glibenclamide. Insulin restored all the parameters to near normal values.

Effect of Syzigium cumini in Plasma Antioxidants on Alloxan-Induced Diabetes in Rats.

We undertook the present study to evaluate the antioxidant activity of an aqueous extract of the seeds of Syzigium cumini, an indigenous plant present in different parts of India, South-East Asia and Eastern Africa, toward experimental diabetes. Administration of the extract for 6 weeks resulted in significant reductions in plasma lipid peroxide, ceruloplasmin and α-tocopherol and a significant elevation in plasma reduced glutathione and vitamin C in alloxan diabetic rats. Insulin restored all the parameters to their normal values. The seed extract was also more effective than glibenclamide in restoring the values of these parameters.

Hypoglycaemic and antihyperglycaemic effects of Trigonella foenum-graecum leaf in normal and alloxan induced diabetic rats

The aqueous and alcoholic extracts of Trigonella foenum-graecum leaf were tested for hypoglycaemic activity in normal and alloxan-diabetic rats. Graded amounts (0.06, 0.2, 0.5, 1 g/kg, i.p. and 1, 2, 8 g/kg, p.o.) of the aqueous extract of Trigonella foenum-graecum leaf when given to both normal and alloxan-diabetic rats, a significant reduction of blood glucose concentration was noticed. On the other hand ethanolic extract of Trigonella foenum-graecum leaf produced no reduction in blood glucose concentration in normal rats but intra-peritoneal administration of 0.8 g/kg of the ethanolic leaf extract to diabetic rats produced a significant reduction of blood glucose concentration ( p<0.02) at 2 and 24 h only. Intraperitoneal and oral acute toxicity (LD50) and target organ effects were studied for the aqueous extract of Trigonella leaf in mice. LD50 of i.p. and oral administration were 1.9 and 10 g/kg respectively. The main organ affected after i.p. administration of the aqueous extract was the liver while oral administration of the aqueous extract of Trigonella did not produce any sign of organ damage. These results suggest that the aqueous extract of Trigonella foenum-graecum leaves given both orally and intraperitoneally possesses a hypoglycaemic effect in normoglycaemic and alloxan induced hyperglycaemic rats.

Alloxan diabetes abolishes the increased negativity of interstitial fluid pressure in rat trachea induced by vagal nerve stimulation.

Increased negativity of interstitial fluid pressure (Pif) occurs concomitantly with oedema formation in acute airway inflammation. This observation is principally important because the loose connective tissues become 'active' and provide the driving force for the rapid oedema formation via Pif. The present study reports Pif in acute airway inflammation in alloxan diabetic rats. The basis for the study was, firstly, that inflammation is important in the pathogenesis of asthma. Secondly, that clinically there is almost a mutual exclusion between diabetes and asthma and, lastly, that the inflammatory response is attenuated in alloxan diabetic rats. Pif was measured on the ventral side of the trachea with sharpened glass capillaries (3-6 microns) connected to a servocontrolled counterpressure system. Measurements and nerve stimulation were performed after circulatory arrest, since oedema formation associated with inflammation will increase Pif, causing an underestimation of a potentially increased negativity of Pif. Control or diabetic rats (alloxan 45 mg kg-1 i.v. 5 days earlier) received either the mast cell degranulating substance compound 48/80 (100 micrograms), dextran 70 (60 mg) i.v. or vagal nerve stimulation. After dextran, Pif was -4.7 +/- 0.9 (SD) mmHg (n = 6) and -1.3 +/- 0.3 mmHg (n = 6) (P < 0.01) in normal and diabetic rats, respectively. Corresponding values after vagal nerve stimulation were -5.3 +/- 1.8 mmHg (n = 5) and -0.7 +/- 0.2 mmHg (P < 0.01). Insulin treatment restored the Pif response to dextran and vagal stimulation. Pif after Compound 48/80 did not differ between control and diabetic rats. Interstitial volume, total tissue water and transcapillary albumin extravasation increased significantly in controls after vagal nerve stimulation, but was attenuated in diabetic rats.

Partial recovery of erythrocyte glycogen in diabetic rats treated with phenobarbital.

Erythrocytes may play a role in glucose homeostasis during the postprandial period. Erythrocytes from diabetic patients are defective in glucose transport and metabolism, functions that may affect glycogen storage. Phenobarbital, a hepatic enzyme inducer, has been used in the treatment of patients with non-insulin-dependent diabetes mellitus (NIDDM), increasing the insulin-mediated glucose disposal. We studied the effects of phenobarbital treatment in vivo on glycemia and erythrocyte glycogen content in control and alloxan-diabetic rats during the postprandial period. In control rats (blood glucose, 73 to 111 mg/dl in femoral and suprahepatic veins) the erythrocyte glycogen content was 45.4 +/- 1.1 and 39.1 +/- 0.8 micrograms/g Hb (mean +/- SEM, N = 4-6) in the femoral artery and vein, respectively, and 37.9 +/- 1.1 in the portal vein and 47.5 +/- 0.9 in the suprahepatic vein. Diabetic rats (blood glucose, 300-350 mg/dl) presented low (P < 0.05) erythrocyte glycogen content, i.e., 9.6 +/- 0.1 and 7.1 +/- 0.7 micrograms/g Hb in the femoral artery and vein, respectively, and 10.0 +/- 0.7 and 10.7 +/- 0.5 in the portal and suprahepatic veins, respectively. After 10 days of treatment, phenobarbital (0.5 mg/ml in the drinking water) did not change blood glucose or erythrocyte glycogen content in control rats. In diabetic rats, however, it lowered (P < 0.05) blood glucose in the femoral artery (from 305 +/- 18 to 204 +/- 45 mg/dl) and femoral vein (from 300 +/- 11 to 174 +/- 48 mg/dl) and suprahepatic vein (from 350 +/- 10 to 174 +/- 42 mg/ dl), but the reduction was not sufficient for complete recovery. Phenobarbital also stimulated the glycogen synthesis, leading to a partial recovery of glycogen stores in erythrocytes. In treated rats, erythrocyte glycogen content increased to 20.7 +/- 3.8 micrograms/g Hb in the femoral artery and 30.9 +/- 0.9 micrograms/g Hb in the suprahepatic vein (P < 0.05). These data indicate that phenobarbital activated some of the insulin-stimulated glucose metabolism steps which were depressed in diabetic erythrocytes, supporting the view that erythrocytes participate in glucose homeostasis.

Oral Hypoglycemic Effect of Caesalpinia bonducella

The blood sugar lowering efficacy of the aqueous extract of Caesalpinia bonducella F. (seed shell) was evaluated in fasted, fed, glucose loaded, streptozotocin diabetic, and alloxan diabetic rat models. The extract was administered orally at a dose of 250 mg/kg of rat body weight. It produced very significant blood sugar lowering (at least P < 0.005) in glucose loaded, streptozotocin diabetic, and alloxan diabetic models. However, effects were not so pronounced in fasted and fed models. As a whole, Caesalpinia bonducella can be regarded as a good oral hypoglycemic agent in rat.

L-Carnitine treatment improves brain stem auditory evoked potentials in diabetic rats

The effect of L-carnitine (LC) on brain stem auditory evoked potentials (BAEP), was examined in alloxan-diabetic rats. LC (200 mg kg-1, i.p., once daily) was given to diabetic rats starting from the third week after the induction of diabetes, lasting for 4 weeks. Age-matched non-diabetic rats served as controls. The latency of wave I and interpeak latency I-IV were measured once weekly. Diabetes-induced deficits in BAEP latencies (p < 0.05, diabetics vs non-diabetic controls) were improved after LC treatment (p < 0.05, LC-treated diabetic rats vs non-diabetic controls). Weight and glucose levels were not influenced by LC treatment. Our results suggest that LC had beneficial effects on diabetic central neuropathy but these effects are not associated with the regulation of glycaemia in alloxan-diabetic rats.

Effects of vanadate and insulin on the activities of selected enzymes of amino acid metabolism in alloxan diabetic rat kidney.

The effects of insulin and the insulin mimetic agent "vanadate" were studied on the activities of alanine aminotransferase, aspartate aminotransferase, glutamate dehydrogenase and arginase in the cytosolic and the mitochondrial fractions of the kidney in control and alloxan induced diabetic rats. An enhancement in the activities of these enzymes were noted in both the fractions of diabetic kidney. Vanadate treatment (0.6 mg/ml in drinking water) of alloxan induced diabetic rats restored the activities of these enzymes almost completely in the cytosolic and partially in the mitochondrial fractions. Vanadate treatment also normalized hyperglycaemia without altering the depressed levels of insulin secretion in diabetic rats. The effect of insulin treatment was found to be the same as that of vanadate in diabetic rats.

Comparison of the effects of aminoguanidine and L-carnitine treatments on somatosensorial evoked potentials in alloxan-diabetic rats.

The effects of aminoguanidine (AG) and L-carnitine (LC) on somatosensorial evoked potential (SEP) latency and neural levels of thiobarbituric acid reactive substances (TBARS), products of lipid peroxidation, were compared in alloxan-diabetic rats. AG and LC were given to diabetic rats starting from the 3rd week after the induction of diabetes and lasting for 4 weeks. SEP latency was measured by stimulating via caudal nerve and recording via cortex, once weekly during the treatments. Diabetes caused deficits in SEP (P < 0.05 vs non-diabetic control rats, respectively). AG and LC restored SEP latencies slightly but not significantly, with the exception of the prominent effect of AG at the first week and both treatments at the 4th week of the treatments (P < 0.05 vs untreated diabetic rats, respectively). Diabetes caused elevation in neural TBARS levels (P < 0.05 vs non-diabetic group), which was prevented by both AG and LC (P < 0.05 vs untreated diabetic rats, respectively). Weight and the glucose levels were not influenced by the treatments. Our results suggest that AG improves SEP latencies better than LC. Our results also suggest that the beneficial effects of both AG and LC on diabetic neuropathy are not associated with the regulation of glycemia, but these effects may be related in part with prevention of lipid peroxidation.

Duration-dependent changes in calcium responsiveness in the alloxan-diabetic rat intestine

Disturbances of the gastrointestinal tract that are common in diabetes mellitus seem to be related to intestinal motility. In experimental models of diabetes, decreased calcium sensitivity has been demonstrated in various smooth muscles including those in the gastrointestinal tract. The main purpose of the present study was to examine further the calcium sensitivity in diabetic rat intestine and to understand if changes in the calcium sensitivity occur at an earlier stage of the disease. For this purpose, the effects of potassium and calcium were evaluated on nondepolarized and depolarized duodenum from rats with alloxan diabetes for 1 and 8 weeks and their age-matched controls. To evaluate the calcium sensitivity in rat duodenum, apparent affinity constants (pD 2 values) and intrinsic activities (α E values) were calculated for every experimental conditions examined in this study. Both values (pD 2 and α E) for the effects of potassium and calcium on the nondepolarized and depolarized duodenum, respectively, were not changed in 1-week diabetic rats. In contrast, intrinsic activities for the effects of potassium and calcium were found to be significantly decreased ( p < 0.001) in the nondepolarized and depolarized duodenum from rats with alloxan diabetes for 8 weeks, whereas apparent affinity constants were not altered in this case. Taking into consideration all these experimental findings, the decreased calcium sensitivity in gastrointestinal tract seems to be closely related to decreased calmodulin levels and may occur at a later stage of diabetes as a linkage to long-term gastrointestinal complications.

Influence of aldose reductase inhibition on the microvascular reactivity in experimental diabetes

1. 1. To verify if tolrestat, an aldose reductase inhibitor, corrects the impaired responses of microvessels to histamine and bradykinin in alloxan-diabetic rats, the mesenteric microcirculation was studied in vivo in anaesthetised animals. 2. 2. The impaired responses were corrected by tolrestat 5 mg/kg/day for 7 days p.o. Similar responses to acetylcholine and sodium nitroprusside were obtained in preparations of diabetic and control rats and were not altered by tolrestat treatment. 3. 3. As in diabetes, galactosemia induced impaired responses to histamine and bradykinin; these altered responses were corrected by tolrestat treatment. 4. 4. These data allow us to suggest that the polyol pathway activity might be involved in the altered responses of microvessels observed in diabetic rats. It is possible that polyol activation may play an important role in the development of vascular dysfunction in diabetes mellitus.

Antiperoxide effect of S-allyl cysteine sulfoxide, an insulin secretagogue, in diabetic rats.

Treatment of alloxan diabetic rats with the antioxidant S-allyl cysteine sulfoxide (SACS) isolated from garlic (Allium sativum Linn), ameliorated the diabetic condition almost to the same extent as did glibenclamide and insulin. In addition, SACS controlled lipid peroxidation better than the other two drugs. Furthermore, SACS significantly stimulated in vitro insulin secretion from B cells isolated from normal rats. Hence it can be surmised that the beneficial effects of SACS could be due to both its antioxidant and its secretagogue actions. The former effect is more predominant and the latter is only secondary. These effects highlight the therapeutic value of garlic, which is a component of many diets.

Altered bile acid metabolism related to atherosclerosis in alloxan diabetic rats.

Normal and alloxan diabetic rats were kept on a 0.25% cholesterol diet for 12 months and the changes in serum cholesterol levels, and fecal excretion of sterols and bile acids were examined to elucidate the influence of changes in bile acid metabolism on manifestations of hypercholesterolemia and development of atheromatous lesions. Diabetic rats fed the cholesterol diet showed increases in bile acid synthesis and in the cholic acid group/chenodeoxycholic acid group (CA/CDCA) ratio, and developed significant hypercholesterolemia and atheromatous lesions. In contrast, normal rats showed increased bile acids synthesis but a decreased CA/CDCA ratio after feeding with the cholesterol diet, and developed neither hypercholesterolemia nor atheromatous lesions. Fecal sterol excretion and the cholesterol/sitosterol ratio decreased in diabetic rats. Positive correlations were found between the cumulative serum cholesterol level and the atheromatous lesion area, and between the fecal CA/CDCA ratio and the serum cholesterol level, in the latter of which the correlation was higher in rats on the cholesterol diet than in those on the standard diet. These findings suggest that alteration of bile acid metabolism with increases in cholic acid synthesis and CA/CDCA ratio in diabetic rats enhances cholesterol absorption to produce significant hypercholesterolemia, which in turn leads to development of atheromatous lesions.

Improved hepatocyte culture system for studying the regulation of glycogen synthase and the effects of diabetes

When 3-4-week-old rats (young rats) are used as a source of hepatocytes, primary culture cells express the adult, differentiated, liver-specific isoform of glycogen synthase. Synthase enzyme protein levels are relatively stable over a 3 day culture period in young but not in adult (> 150 g rat) hepatocyte cultures. Corresponding synthase enzyme activity and mRNA levels decrease over time in culture in adult but not in young hepatocyte cultures. Young rat hepatocytes also have the ability to proliferate in chemically defined medium in the absence of added mitogens. A diabetes-induced increase in total synthase activity has been demonstrated by our lab and others, using cultured hepatocytes, liver homogenates, and perfused livers. In the present study, utilizing synthase-specific antibody and primary cultures of cells from young normal and alloxan diabetic rats, we found that greater total synthase activity in the diabetic cells was associated with higher levels of enzyme protein. Immuneprecipitation of 35S methionine-labeled freshly plated cells demonstrates an increase in the rate of protein synthesis in diabetic as compared with normal cells. Synthase mRNA levels are correspondingly increased in the diabetic relative to normal cells. Chronic exposure of young, normal hepatocytes to increasing levels of glucose induces a dose-dependent increase in total synthase activity, total synthase protein, and synthase message levels. By comparison, cells from diabetic animals do not respond by any of these measures to increased glucose concentrations. We conclude that this defined primary culture system represents a useful model for investigating the regulation of hepatic glycogen synthase and the defects which occur as a result of diabetes.

Reduction of gastrointestinal serotonin in alloxan-diabetic rats: reversal by 5-hydroxytryptophan treatment

A rat model of alloxan-induced diabetes was used to investigate the effect of diabetic state on serotonin (5-HT) levels in peripheral body compartments, gastrointestinal (GI) and platelet, and the metabolic response of these compartments to serotonin precursor (5-hydroxytryptophan, 5-HTP) loading in diabetes. In all segments of diabetic gut a massive reduction in 5-HT concentration (to 45–64% at 6th week after induction of diabetes, with further progression to 30–52% at 14th week) was shown. After parenteral loading with 5-HTP for 6 days (30 mg/kg per day) 5-HT concentration in all parts of the GI tract returned to the control values (82–108%), indicating reduced serotonin precursor availability in diabetes. Platelet serotonin levels (PSL) in diabetic rats demonstrated a slight gradual reduction that became significant at 14th week of diabetic state. On the mentioned 5-HTP challenge only blunted response of PSL in diabetics, as contrasted to control animals (54% vs. 113%) was shown, indicating possible suppression of the membrane 5-HT transporter. The observed alterations in peripheral 5-HT homeostasis in diabetic rats as well as the possibility of their reversal by 5-HTP treatment could be of clinical interest.

Differential expression of islet amyloid polypeptide (amylin) and insulin in experimental diabetes in rodents

An increased ratio of islet amyloid polypeptide (IAPP) to insulin for mRNA and peptide content in pancreatic extracts and for secretion has been observed in experimental diabetes, suggesting a differentially regulated IAPP and insulin expression. Therefore, we investigated the islet expression of IAPP and insulin in streptozotocin and alloxan diabetic rats and mice, using in situ hybridization and immunocytochemistry. A low dose of streptozotocin equivalently reduced IAPP and insulin mRNA levels to approximately 45% of controls. In contrast, a high dose of streptozotocin or alloxan reduced IAPP mRNA levels significantly less than those of insulin mRNA (streptozotocin: 24 vs. 15%, P = 0.011; alloxan: 15 vs. 6%, P < 0.0001). In situ hybridization and immunocytochemistry revealed expression of IAPP in experimental diabetes to occur predominantly in insulin cells. Thus, IAPP and insulin gene expression are differentially regulated in experimental diabetes in rodents and IAPP is predominantly expressed in insulin cells.

Diabetic neuropathy in the rat: 1. Alcar augments the reduced levels and axoplasmic transport of substance P

This study examined the sciatic nerve axonal transport of substance P-like immunoreactivity (SPLI) and its basal content in stomach, sciatic nerve and lumbar spinal cord of 8- and 12-week alloxan-diabetic rats, respectively. One group of diabetic rats received acetyl-l-carnitine (ALCAR) throughout the experimental period. Alloxan treatment caused hyperglycemia and reduced boy growth. Axonal transport of SPLI was studied by measurement of 24-hour accumulation at a ligature on the sciatic nerve. There was a marked reduction (from 50% to 100% according to the nerve segment examined) of anterograde and retrograde accumulation of SPLI in the constricted nerve of 8-week diabetic rats. In the sciatic nerve of ALCAR-treated diabetic rats, the accumulation of SPLI was comparable to control values. In the sciatic nerve, lumbar spinal cord and stomach of 12-week diabetic rats, there is a significant reduction of SPLI content. ALCAR treatment prevented SPLI loss in these tissues. Sciatic nerves showed the typical sorbitol increase and myo-inositol loss that were significantly counteracted by ALCAR. This study suggests that ALCAR treatment prevents diabetes-induced sensory neuropathy by improving altered metabolic pathways such as polyol activity and myo-inositol synthesis, and by preventing the reduction of synthesis and axonal transport of substance P.