褪黑素抑制四氧嘧啶糖尿病大鼠垂体-肾上腺轴功能

观察褪黑素对以四氧嘧啶诱发大鼠糖尿病时垂体-肾上腺轴的影响。结果提示褪黑素对糖尿病模型大鼠的垂体-肾上腺轴有抑制作用，对急性代谢紊乱有保护作用。     

Acetylcholinesterase activity in the brain of alloxan diabetic albino rats: Presence of an inhibitor of this enzyme activity in the cerebral extract

Background and Aim:

Ischemic manifestations and cerebral dysfunction have been demonstrated in diabetes. However, the pathogenesis of diabetes-induced cerebral dysfunction still remains to be elucidated. Hence, the present study was initiated.

Materials and Methods:

Type-2 diabetes was induced in albino rats (280–300g) with alloxan monohydrate (40 mg/Kg i.v.,) and the cerebrum, cerebellum and medulla oblongata of the brain were used 48 h after alloxan injection for modulations in acetylcholinesterase (AChE, EC 3.1.1.7) activity.

Results:

AChE activity in the discrete regions of the brain of rats decreased significantly (P<0.01, 0.05 and 0.05 respectively) in diabetes. In vitro studies using cerebral extract from alloxan diabetic rats demonstrated significant (P<0.05) inhibition of AChE activity in the brain of normal animals. Feeding with Cichorium intybus (chicory) leaf extract (500 mg/Kg) for 10 days resulted in an increase in AChE activity.

Conclusion:

The impairment in the glycemic control is the basic mechanism causing inhibition of neuronal activity. Cerebral extract from alloxan diabetic rats significantly inhibited the brain AChE activity of normal animals, indicating the presence of an inhibiting factor in the cerebrum of diabetic rats. Cichorium intybus when fed for 10 days offered neuroprotection by stimulating AChE activity.     

Phytopharmacological evaluation of Byesukar for hypoglycaemic activity and its effect on lipid profile and hepatic enzymes of glucose metabolism in diabetic rats: Original Article

Many anti-diabetic herbal preparations have been recommended in alternative systems of medicine for the treatment of diabetes. No systematic study has been done on the anti-diabetic efficacy of Byesukar, a polyherbal formulation to treat diabetes. The anti-diabetic efficacy of byesukar ethanol extract was evaluated in an animal model of diabetes induced by alloxan. Male Wistar rats were divided in to four groups. Group 1 was normal control group; group 2 and 3 received alloxan. After inducing experimental diabetes group 2 served as diabetic control; group 3 received byesukar (500 mg/kg body weight) orally for 30 consecutive days. Group 4 were normal rats which received byesukar extract alone. The effect of byesukar on glucose level in diabetic rats was studied and the level of glucose metabolizing enzymes (Hexokinase, glucose-6-phosphatase and fructose 1, 6-bisphosphatase) in the liver and kidney were estimated. The effect of byesukar on the serum and tissue lipid profile (Cholesterol, triglycerides, phospholipids and free fatty acids) were also estimated in diabetic rats. Our results indicate that treatment with byesukar resulted in significant reduction of blood glucose, tissue glucose-6-phosphatase and fructose 1, 6-bisphosphatase activity. The decreased tissue hexokinase activity in diabetes state was found to be significantly increased by byesukar treatment. Also the byesukar treated diabetic rats showed a significant decrease in the tissue lipid profile compared to the diabetic rats. In conclusion the decreased blood glucose accompanied with decreased lipid profile and changes in the activities of the glucose metabolizing enzymes shows the antidiabetic effect of byesukar.     

Effect of insulin on glycogen and protein synthesis in monolayer cultures of hepatocytes from normal and alloxan diabetic rats

Summary The effects of insulin on net glycogen synthesis and amino acid incorporation into protein were studied in cultured hepatocytes from adult normal and alloxan diabetic rats. Insulin stimulated glycogen synthesis in monolayer cells throughout a four day culture period and enhanced leucine incorporation into protein more effectively in normal cells with high glycogen levels than in cultured diabetic cells. These differences correlate well with the observed cellular ultrastructures which were maintained much better in the presence of insulin. Restoration of the morphological changes of alloxan diabetic hepatocytes to normal liver cell structures can be observed at any time during the culture period by giving insulin continuously.     

Antidiabetic activity of gossypin, a pentahydroxyflavone glucoside, in streptozotocin-induced experimental diabetes in rats

Background: Most of the currently available oral hypoglycemic drugs for the treatment of diabetes mellitus elicit detrimental side effects. Hence, the search for plant‐derived products for the treatment of diabetes continues. Gossypin, a pentahydroxy flavone glucoside found in the flowers of Hibiscus vitifolius, has many biological properties, including as an antioxidant, anti‐inflammatory and anticancer agent. The aim of the present study was to evaluate the effect of gossypin in streptozotocin (STZ)‐induced experimental diabetes in rats. Methods: Diabetic rats were administered 20 mg/kg per day gossypin orally for 30 days. On the 28th day, rats were subjected to an oral glucose tolerance test. In addition, blood glucose, plasma insulin, hemoglobin, and HbA1c levels were determined, as was the glycogen content of the liver and muscles. Plasma protein and blood urea were also estimated. Results: Oral administration of gossypin to diabetic rats resulted in improved glucose tolerance. Increased blood glucose and HbA1c levels and the reduced plasma insulin and hemoglobin levels in diabetic rats were significantly reversed to near normal after oral administration of gossypin. Furthermore, the glycogen content of the liver and muscles was significantly improved after gossypin treatment of diabetic rats, and plasma protein and blood urea levels were almost normalized. The data obtained in gossypin‐treated rats were comparable with those obtained following gliclazide treatment of rats, a standard reference drug for diabetes. Conclusions: The results of the present study indicate that gossypin has potent antidiabetic activity in STZ‐induced experimental diabetes in rats.     

Detection of tissue origin of a 43 kDa diabetogenic protein from alloxan-induced diabetic rats

BACKGROUND:

Earlier, we had found high levels of circulating immune complexes (CICs) in the serum of type 2 diabetes mellitus patients along with a novel 43 kDa protein.

METHODS:

Different tissues of alloxan-induced, diabetic, male albino rats (200–250 g in body weight) were collected for the present study. Tissue proteins were isolated and separated by 10% SDS-polyacrylamide gel electrophoresis (SDS-PAGE). A primary cell culture of polymorphonuclear neutrophils (PMNs) was used to evaluate the effects of the diabetogenic protein. Cell proliferative index, oxidant/antioxidant status, and ion-transporting ability were chosen as study parameters.

RESULTS:

SDS-PAGE of different tissues shows that the diabetic liver alone was the only tissue that contained the 43 kDa protein band compared to the normal liver. In vitro effects of the new liver protein on PMNs include significantly decreased cell proliferative activity, increased free radical levels, and decreased levels of antioxidant enzymes as well as ionic transporters. The new liver protein also exhibited protease activity when compared with standard trypsin.

CONCLUSIONS:

This study concluded that a novel 43 kDa protein obtained from the livers of alloxan-induced diabetic rats shows protease activity as well as antiproliferative activity. Also, this protein may act as a diabetogenic factor as it elicited a significantly gross elevation in the oxidant status level as well as in the levels of lysosomal enzymes and a decrease in the levels of antioxidative enzymes and ionic transporters of PMNs.     

Cardiac myofibrillar ATPase activity in diabetic rats

Diabetes was induced by an intravenous injection of 65 mg/kg streptozotocin and hearts were removed 8 weeks later for the isolation of myofibrils. The basal ATPase activity of myofibrils from diabetic hearts was significantly lower than the controls. Although Ca²⁺-stimulated ATPase activity was also depressed in diabetic myocardium, the dependency of diabetic myofibrils on free calcium concentration was not different from that of control. The basal and Ca²⁺-stimulated ATPase activities in diabetic rats demonstrated a greater sensitivity to KCl than control preparations. The myofibrillar basal ATPase, unlike Ca²⁺-stimulated ATPase, in diabetic animals exhibited a greater sensitivity to ethylene glycol. These results support the view regarding the presence of some subtle structural and conformational changes in diabetic myofibrils.     

Comparison of streptozotocin and alloxan-induced diabetes in the rat,including volumetric quantitation of the pancreatic islets

Summary Diabetes was induced in rats with equal molar dosages of either streptozotocin or alloxan. The clinical course of the diabetes (mortality, hyperglycemia, weight loss, polydipsia, hyperphagia, polyuria, glycosuria and diabetic indices) was recorded for six weeks before the animals were sacrificed for volumetric quantitation of the pancreatic islets. No significant differences in the pancreas (islet volumes of pancreas; beta, alpha and non-granular cell volumes and vessel volumes of both islet and total pancreas) were seen between the two groups, although differences in the clinical parameters were observed. The diabetic index at three and four weeks post injection was the clinical parameter which best reflected the terminal pancreatic beta cell volume. Analysis of the scanning data adds further empirical support for the accuracy of the linear scan method of quantitation.Supported by USPHS Training Grant No. GM 114.     

Antidiabetic and antihyperlipidemic effects of the stem of Musa sapientum Linn. in streptozotocin‐induced diabetic rats

Background: Musa sapientum Linn. is a herbaceous plant of the Musaceae family. It has been used in India for the treatment of gastric ulcer, hypertension, diarrhea, dysentery, and diabetes. The antidiabetic effect of the fruit, root, and flower has been demonstrated. The aim of the present study was to assess the antidiabetic and antihyperlipidemic effects of the stem of M. sapientum Linn. Methods: Diabetes was induced in rats by streptozotocin injection (45 mg/kg, i.p.). Diabetic rats were treated for 2 weeks with different doses of lyophilized stem juice of M. sapientum Linn. (25, 50, and 100 mg/kg) to select the most effective dose. The effects of 4 weeks treatment with this dose (50 mg/kg) on fasting and postprandial plasma glucose (FPG, PPG) levels, body weight, lipid profile, HbA1c, insulin, liver enzymes (i.e. glucokinase, glucose‐6‐phosphatase and 3‐hydroxy‐3‐methylglutaryl coenzyme A [HMG‐CoA] reductase) and muscle and liver glycogen were evaluated. Results: The most effective dose of lyophilized stem juice of M. sapientum Linn. was 50 mg/kg. Four weeks treatment with this dose resulted in significant decreases in FPG and PPG (P < 0.05). Serum insulin increased (P < 0.05) whereas HbA1c decreased (P < 0.05). Diabetes‐induced changes to the lipid profile, muscle and liver glycogen, and enzyme activity (i.e. glucokinase, glucose‐6‐phosphatase, and HMG‐CoA reductase) were restored near to normal levels (P < 0.05). Conclusion: Diabetic rats responded favorably to treatment with lyophilized stem juice of M. sapientum Linn., which exhibits antidiabetic and antihyperlipidemic effects.     

Electrophysiological analysis of the sensitivity to calcium in ventricular muscle from alloxan diabetic rats

Summary The effects of acute and chronic alloxan diabetes on the transmembrane electrical activity of rat heart papillary muscle were investigated. The action potential duration (APD) appeared markedly prolonged in all diabetic papillary muscles, as compared to normal. This prolongation of ADP, with no difference in the resting potential (RP), resulted from both a lengthening of the complex time course plateau and a slower rate of repolarisation. APD₀ (at 0mV) and APD₁₀ (+10mV from RP) increased, respectively, an average of 50% and 24% in the acute, and 72% and 98% in the chronic diabetics as compared to control, whereas Vmax and overshoot (OS) were unchanged. Varying [Ca l₀ between 0.5 and 3.5 mM did not induce any change in the RP of either control or diabetic papillary muscles. Conversely, there were differences, within and between groups, in the amplitude of the OS and in Vmax, depending on the [Ca]_o concentration. In particular, OS and Vmax of acute diabetics were markedly reduced at 1.5 mM. This reduction was maintained at concentrations of [Ca]_o lower than 1.5, attesting to the greater sensitivity of both acutely and chronically diabetic muscles to a decrease in external calcium. Cd, a Ca-channel blocker, reduced in diabetics the duration of both the complex plateau and the repolarisation phase, suggesting that a Ca inward current was maintained throughout these two phases. Direct evidence for elucidating the mechanism(s) of the observed APD change in diabetics will be obtained only by transmembrane current analysis.     

Amelioration of altered antioxidant enzymes activity and glomerulosclerosis by coenzyme Q10 in alloxan-induced diabetic rats

Coenzyme Q10 is a natural antioxidant and scavenging free radicals. In the present study, we examined antioxidative activities of coenzyme Q10 and possible protective effect of coenzyme Q10 on in vivo and in vitro lipid peroxidation, antioxidant enzymes activity and glomerulosclerosis in alloxan-induced type 1 diabetic rats. Thirty Sprague–Dawley male rats were divided into three groups randomly: group 1 as control, group 2 as diabetic untreatment, and group 3 as treatments with coenzyme Q10 by 15 mg/kg i.p. daily, respectively. Diabetes was induced in the second and third groups by alloxan injection subcutaneously. After 8 weeks, animals were anaesthetized, liver and kidney were then removed immediately and used fresh or kept frozen until their lipid peroxidation analysis. Blood samples were also collected before killing to measure the lipid peroxidation and antioxidant enzymes activity. Kidney paraffin sections were prepared and stained by periodic acid-Schiff method. Glomerular volume and leukocyte infiltration were estimated by stereological rules and glomerular sclerosis was studied semi-quantitatively. Coenzyme Q10 significantly inhibited leukocyte infiltration, glomerulosclerosis and the levels of malondialdehyde (MDA) serum and kidney content in treated group compared with the diabetic untreated group. Coenzyme Q10 significantly inhibited LDL oxidation in vitro. Coenzyme Q10 significantly increased the serum levels of glutathione (GSH) and serum activity of catalase (CAT) and superoxide dismutase (SOD) in treated group compared with the diabetic untreated group. Coenzyme Q10 alleviates leukocyte infiltration and glomerulosclerosis and exerts beneficial effects on the lipid peroxidation and antioxidant enzymes activity in alloxan-induced type 1 diabetic rats.     

Impairment of pituitary and gonadal functions in alloxan-induced diabetic male rats

The inhibitory effect of treatment with a potent LHRH agonist on testicular gonadotropin-receptor levels was compared in intact and diabetic rats. Basal and LHRH-induced pituitary gonadotropin secretion as well as the testicular steroidogenic response to oLH were assessed. A single injection of alloxan (65 mg/kg) led, after 6 weeks, to a 40% decrease of testicular LH- and prolactin-receptor levels. Treatment for 2 weeks with [D-Ala6,des-Gly-NH 1/2 0] LHRH ethylamide (100 ng every second day) led to a 70% reduction of LH-receptor levels accompanied by decreased testicular weight, a similar inhibition being found in intact and diabetic animals. Seminal vesicle and ventral prostate weight were markedly reduced in diabetic animals, a further decrease being obtained after treatment with the LHRH agonist. The loss of accessory sex-organ weight in alloxan-diabetic rats was accompanied by a reduction in the basal testicular content of pregnenolone, progesterone, 17-OH-progesterone, androstenedione, testosterone and dihydrotestosterone whereas the steroid response to oLH was within normal limits. We next examined the possible changes of LH and FSH secretion which could be responsible for the reduced testicular function in diabetic animals. Basal plasma-LH levels were 30% reduced in rats 6 weeks after treatment with alloxan while basal plasma-FSH levels remained unchanged. When the pituitary gonadotropin response to LHRH was measured in chronically cannulated freely-moving intact and diabetic rats, an approx. 50% inhibition of the LH and FSH responses to LHRH was observed in diabetic animals.     

Decreased osteoblast activity in spontaneously diabetic rats

Diabetes in both humans and rats is accompanied by low bone formation, which is presumably caused by serum-borne factors. To explore its pathogenesis, we carried out experiments in diabetic and nondiabetic BB rats, using plasma osteocalcin concentrations (OC) as a marker for osteoblast activity. In nondiabetic rats, the iv infusion of glucose (30%, 4 d) did not change OC; sc insulin infusion (4 U/d, 14 d) reduced OC by 27% (p<0.01). In diabetic rats, OC were decreased from the first day of glycosuria (71±5% of paired controls), declining exponentially to 24±3% after 5 wk. Insulin infusion (1,2, and 3 U/d, 14 d) produced gradual restoration of OC. OC were better correlated with insulin-like growth factor-I (IGF-I) than with insulin levels in these experiments. OC were dramatically increased 4 d after adrenalectomy (ADX) in all diabetic rats (73±8 vs 22±4 μg/L before ADX;p<0.001), but not if corticosterone was administered. Ligand blotting of IGF binding proteins showed a marked decrease in two bands (44–49 and 32–35 kDa) 10–14 d after diabetes onset; the density of these bands was increased, but not normalized after ADX. Thus, decreased osteoblast activity is present from the onset of diabetes, is dependent on endogenous corticosterone, and cannot be reproduced by hyperglycemia in nondiabetic rats.     

Antidiabetic effect of diasulin, a herbal drug, on blood glucose, plasma insulin and hepatic enzymes of glucose metabolism in hyperglycaemic rats

AIM: The present study was designed to investigate the effect of diasulin, a polyherbal drug, on blood glucose, plasma insulin and the activities of hepatic glucose metabolic enzymes in alloxan-induced diabetic rats. METHODS: Male Wistar rats, body weight of 180-200 g (12 normal and 30 diabetic rats), were used in this study. The rats were divided into seven groups after the induction of alloxan diabetes. In the experiment, six rats were used in each group. Group 1: normal rats given 2 ml of saline; group 2: normal rats given aqueous solution of diasulin (0.20 g/kg of body weight); group 3: diabetic control rats given 2 ml of saline; group 4: diabetic rats given aqueous solution of diasulin (0.05 g/kg of body weight); group 5: diabetic rats given aqueous solution of diasulin (0.10 g/kg of body weight); group 6: diabetic rats given aqueous solution of diasulin (0.20 g/kg of body weight) and group 7: diabetic rats given aqueous solution of glibenclamide (600 micro g/kg of body weight). The treatment was given for 30 days. After the treatment, fasting blood glucose, plasma insulin, urine sugar and the activities of hepatic glucose metabolic enzymes were determined in normal and experimental animals. RESULTS: Treatment with diasulin resulted in a significant reduction in blood glucose, glycosylated haemoglobin and an increase in plasma insulin and total haemoglobin and a significant improvement in glucose tolerance. Diasulin also resulted in a significant reduction in the activities of glucose-6-phosphatase and fructose-1,6-bisphosphatase in the liver, whereas the level of plasma insulin and hepatic hexokinase activity was significantly increased in alloxan diabetic rats. CONCLUSIONS: The present investigation suggests that diasulin, a polyherbal drug, controls the blood glucose level by increasing glycolysis and decreasing gluconeogenesis with a lower demand of pancreatic insulin than in untreated rats. This is possible, because it regulates the activities of hepatic glucose metabolic enzymes.     

Hypoglycaemic effect of Artemisia sphaerocephala Krasch seed polysaccharide in alloxan-induced diabetic rats

The purpose of this study was to examine the hypoglycaemic activity of a new polysaccharide extracted from seed polysaccharide (ASP) was administered orally for 4 weeks and the blood glucose changes were determined in fasted rats. Plasma insulin, cholesterol and triglycerides levels were also determined. The ASP at a dose of 200 mg/kg body weight (bw) produced a significant decrease in blood glucose levels in diabetic rats (P <0.01). In the other hand, the effect of the ASP on the plasma cholesterol were also significant in diabetic rats (P <0.05). Furthermore, there was a significant effect of ASP on plasma triglycerides in both normal and diabetic groups. In order to characterise the active principle(s), which could be responsible for the therapeutic effect, a preliminary phytochemical analysis of the ASP was performed. The monosaccharides of ASP were composed of L-Ara, D-Xyl, D-Lyx, D-Man, D-Glc, D-Gal. Their molar proportions were 1, 4.98, 1.69, 27.86, 3.76 and 13.92, respectively.     

Lysophosphatidylcholine molecular species in low density lipoprotein and high density lipoprotein in alloxan-induced diabetic rats: effect of probucol.

To elucidate the contribution of diabetic state toward the accumulation of lysophosphatidylcholine (LPC) in low density lipoprotein (LDL), the LPC molecular species in LDL and high density lipoprotein (HDL) obtained from alloxan-induced diabetic rats were determined by high performance liquid chromatography. The palmitoyl LPC (PLPC) per protein was increased in the LDL of diabetic rats (p < 0.05), whereas the stearoyl LPC (SLPC) decreased in both the LDL and HDL of diabetic rats (p < 0.001) in comparison to nondiabetic rats. After the dietary administration of probucol for 4 weeks, the concentrations of SLPC and PLPC in the LDL of diabetic rats and of SLPC in the LDL of nondiabetic rats all significantly decreased by probucol (all; p < 0.01), with a concomitant decrease of the plasma concentrations of total and HDL cholesterol, and phospholipid, compared with those without probucol. The level of TBARS per protein in LDL increased in diabetic rats, and decreased by probucol (p < 0.01). In conclusion, the oxidative stress is thought to be an important factor to accumulate LPC in LDL, although the paradoxical decrease of SLPC in diabetic LDL suggests a non-oxidative metabolism with a preference for the LPC molecular species. The reducing effect of probucol on LPC may not be solely attributed to its antioxidative effect.     

Kidney function in experimental diabetic ketosis

Summary Rats both with streptozotocin and alloxan diabetes were used. Ketosis developed in the first days following the application of the diabetogenic agents, and also in rats with long term diabetes in the first days after the insulin previously administered daily, had been withdrawn. The rats with more elevated blood ketone levels also demonstrated strikingly high serum urea levels, oliguria and a diminished food intake. In the groups of rats which in spite of insulin deficiency revealed no or only mild ketonaemia, food intake was increased, and marked polyuria as well as near to normal serum urea levels were observed. Our results showed that the symptoms of uraemia occurred independently of the nature of the diabetic agent, and also of the time at which these agents were administered. Thus it can be concluded that in that case acute renal insufficiency was not due to the nephrotoxicity of the agents employed but rather to the severity of diabetic ketosis.Presented in part at the Jahresversammlung der Österreichischen Diabetes-Gesellschaft, Innsbruck 1970.     

Antidiabetic activity of aqueous leaf extract of Atriplex halimus L. (Chenopodiaceae) in streptozotocin-induced diabetic rats

Objective

To investigate the antidiabetic effect of A. halimus leaf in streptozotocin-induced diabetic rats.

Methods

The aqueous extract of the plant leaf was tested for its efficacy in streptozotocin-induced diabetic rats. The extract was evaluated for its acute and short term general toxicity in male mice and for its antihyperglycemic activity using glucose tolerance test in rats. The aqueous extract was subjected to phytochemical screening and determination of total phenolic contents.

Results

The statistical data indicated the significant increase in the body weight and decrease in the blood glucose and hepatic levels. The total protein level was significantly increased when treated with the extract.

Conclusions

These results suggest that the aqueous leaf extract of A. halimus has beneficial effects in reducing the elevated blood glucose level and hepatic levels in streptozotocin-induced diabetic rats.     

Antidiabetic effects of chitooligosaccharides on pancreatic islet cells in streptozotocin-induced diabetic rats

AIM： To investigate the effect of chitooligosaccharides on proliferation of pancreatic islet cells, release of insulin and 2 h plasma glucose in streptozotocin-induced diabetic rats. METHODS： In vitro, the effect of chitooligosaccharides on proliferation of pancreatic islet cells and release of insulin was detected with optical microscopy, colorimetric assay, and radioimmunoassay respectively. In vivo, the general clinical symptoms, 2 h plasma glucose, urine glucose, oral glucose tolerance were examined after sixty days of feeding study to determine the effect of chitooligosaccharides in streptozotocin-induced diabetic rats. RESULTS： Chitooligosaccharides could effectively accelerate the proliferation of pancreatic islet cells. Chitooligosaccharides （100 mg/L） had direct and prominent effect on pancreastic β cells and insulin release from islet cells. All concentrations of chitooligosaccharides could improve the general clinical symptoms of diabetic rats, decrease the 2 h plasma glucose and urine glucose, and normalize the disorders of glucose tolerance. CONCLUSION： Chitooligosaccharides possess various biological activities and can be used in the treatment of diabetes mellitus.