Hypoglycemic effect of aqueous extract of seabuckthorn (Hippophae rhamnoides L.) seed residues in streptozotocin‐induced diabetic rats

An extract of seabuckthorn (Hippophae rhamnoides L.) seed residues has been shown to possess hypoglycemic and hypolipidemic properties in normal mice. The present study investigated the effects of an aqueous extract of seabuckthorn seed residues (ASSR) on serum glucose, lipid profiles and antioxidant parameters in streptozotocin‐induced diabetic rats. Male Sprague‐Dawley rats were divided into four groups: a normal control group; diabetic control group; diabetic groups supplemented with 5 mg/kg body weight glibenclamide (reference drug) and 400 mg/kg body weight ASSR. Diabetes in rats was induced by intraperitoneal injection of streptozotocin (45 mg/kg body weight). Vehicle (distilled water), glibenclamide and ASSR were administered orally to normal and diabetic rats once a day lasting for 4 weeks. The data showed that administration of ASSR significantly lowered the serum glucose, triglyceride and nitric oxide levels in diabetic rats. Moreover, ASSR treatment also increased serum superoxide dismutase activity and glutathione level markedly. These results show that ASSR has hypoglycemic, hypotriglyceridemic and antioxidant effects in streptozotocin‐induced diabetic rats, suggesting that ASSR supplementation can be useful in preventing diabetic complications associated with hyperlipidemia and oxidative stress. Copyright © 2009 John Wiley & Sons, Ltd.     

Effect of guava (Psidium guajava Linn.) leaf soluble solids on glucose metabolism in type 2 diabetic rats

This study investigated the effect of aqueous and ethanol soluble solid extracts of guava (Psidium guajava Linn.) leaves on hypoglycemia and glucose metabolism in type 2 diabetic rats. Low-dose streptozotocin (STZ) and nicotinamide were injected into Sprague-Dawley (SD) rats to induce type 2 diabetes. Acute and long-term feeding tests were carried out, and an oral glucose tolerance test (OGTT) to follow the changes in plasma glucose and insulin levels was performed to evaluate the antihyperglycemic effect of guava leaf extracts in diabetic rats.The results of acute and long-term feeding tests showed a significant reduction in the blood sugar level in diabetic rats fed with either the aqueous or ethanol extract of guava leaves (p < 0.05). Long-term administration of guava leaf extracts increased the plasma insulin level and glucose utilization in diabetic rats. The results also indicated that the activities of hepatic hexokinase, phosphofructokinase and glucose-6-phosphate dehydrogenase in diabetic rats fed with aqueous extracts were higher than in the normal diabetic group (p < 0.05). On the other hand, diabetic rats treated with the ethanol extract raised the activities of hepatic hexokinase and glucose-6-phosphate dehydrogenase (p < 0.05) only. The experiments provided evidence to support the antihyperglycemic effect of guava leaf extract and the health function of guava leaves against type 2 diabetes.     

Hypoglycaemic Effects of Shokatsu-Cha (Xiao-Ke-Ca ) in Streptozotocin-induced Diabetes Mellitus

Shokatsu-cha is a novel formula for diabetic mellitus based on the traditional Chinese medicine and composed of Dioscoreae rhizoma, Adenophorae radix, Rehmanniae radix, Anemarrhenae rhizoma, Platycodi radix, Salviae miltiorrhizae radix, Epimedii folium and Lycii fructus . The hypoglycaemic effect of Shokatsu-cha was evaluated in streptozotocin (STZ)-induced diabetic mice and rats. When orally administered once a day for 10 days to the mice intraperitoneally injected with STZ, the Shokatsu-cha extract suppressed the increase of the blood glucose level during administration. In the in situ intestine circulation method, the Shokatsu-cha extract and its ethanol-eluted fraction inhibited the glucose absorption in STZ-induced diabetic rats. The ethanol-eluted fraction also inhibited the increase of blood glucose level in an oral glucose tolerance test using diabetic mice. This study indicates that a part of the hypoglycaemic effect of Shokatsu-cha is based on its inhibitory action on intestinal glucose absorption in diabetes.     

Recovery of oral glucose tolerance by wistar rats after treatment with Coreopsis tinctoria infusion

Infusions of Coreopsis tinctoria flowering tops have traditionally been used in Portugal to control hyperglycaemia but no pharmacological or toxicological studies have been reported until now. The chalcones marein and okanin were isolated from the aqueous extract, together with the 2S‐3′,4′,7,8‐tetrahydroxyflavanone. The content of marein in extracts was determined by HPLC‐UV and the radical scavenging capacity evaluated by the DPPH method (EC₅₀ = 21 µg/mL). Glucose intolerance was induced by a single intraperitoneal injection of streptozotocin in saline (40 mg/Kg). After three weeks of oral treatment with C. tinctoria extract (500 mg/Kg/day) the animals were no longer glucose‐intolerant (p > 0.05). Additionally, this oral treatment caused no hepatotoxicity in the rats, as determined by blood alanine and aspartate transaminases. A single administration of extract had no effect on oral glucose tolerance in normal Wistar rats. The extract also had no effect on insulin secretion by MIN6 cells. In conclusion, C. tinctoria infusion is able to abolish the streptozotocin‐induced glucose‐intolerance in rats after three weeks of oral treatment by a mechanism other than induction of insulin secretion. The recovery of β‐pancreatic function mediated by an antioxidant mechanism is a possibility that deserves further investigation. Copyright © 2009 John Wiley & Sons, Ltd.     

Mechanistic Evidence of Viscum schimperi (Viscaceae) Antihyperglycemic Activity: From a Bioactivity‐guided Approach to Comprehensive Metabolite Profiling

Diabetes mellitus is possibly the world's largest growing metabolic disorder. Effective treatment of diabetes is increasingly dependent on active constituents of medicinal plants capable of controlling hyperglycemia as well as its secondary complications. Viscum schimperi Engl. is a plant growing in Saudi Arabia and known for its antidiabetic activity. The potential antidiabetic activity of its methanol extract as well as its chloroform, n‐butanol, and the remaining water fractions was evaluated in streptozotocin‐induced diabetic rats at two dose levels. The antidiabetic activity was assessed through the determination of fasting blood glucose level, insulin levels, area under the curve (AUC) in oral glucose tolerance test, glucose absorption in isolated rat gut assay, and glucose uptake by psoas muscle. Moreover, large‐scale untargeted metabolite profiling of methanol extract was performed via UPLC‐PDA and qTOF‐MS (ultra‐performance liquid chromatography photodiode array detection and quadrupole time‐of‐flight mass spectrometry) respectively, to explore its chemical composition and standardization of its extract. Multivariate statistical analysis including principal component analysis and orthogonal projection to latent structures discriminant analysis was used to determine bioactives in its fractions. In conclusion, oleanane triterpenes and O‐caffeoyl quinic acid conjugates were the major compounds that might account for antihyperglycemic effect of the plant. Copyright © 2015 John Wiley & Sons, Ltd.     

Effect of Sclerocarya birrea (Anacardiaceae) stem bark methylene chloride/methanol extract on streptozotocin-diabetic rats

Sclerocarya birrea (Anacardiaceae) is used as a traditional treatment of diabetes in Cameroon. In this study, we investigated the possible antidiabetic effect of the stem bark extract in diabetic rats. Diabetes was induced by intravenous injection of streptozotocin (STZ, 55 mg/kg) to male Wistar rats. Experimental animals (six per group), were treated by oral administration of plant extract (150 and 300 mg/kg body weight) and metformin (500 mg/kg; reference drug) for comparison, during 21 days. The stem bark methanol/methylene chloride extract of Sclerocarya birrea exhibited at termination, a significant reduction in blood glucose and increased plasma insulin levels in diabetic rats. The extract also prevented body weight loss in diabetic rats. The effective dose of the plant extract (300 mg/kg) tended to reduce plasma cholesterol, triglyceride and urea levels toward the normal levels. Four days after diabetes induction, an oral glucose tolerance test (OGTT) was also performed in experimental diabetic rats. The results showed a significant improvement in glucose tolerance in rats treated with Sclerocarya birrea extract. Metformin, a known antidiabetic drug (500 mg/kg), significantly decreased the integrated area under the glucose curve. These data indicate that Sclerocarya birrea treatment may improve glucose homeostasis in STZ-induced diabetes which could be associated with stimulation of insulin secretion.     

Murraya paniculata (L.) (Orange Jasmine): Potential Nutraceuticals with Ameliorative Effect in Alloxan‐Induced Diabetic Rats

Orange jasmine, Murraya paniculata (Rutaceae), is a plant from India widely used in folk medicine as antinociceptive, antiinflammatory, and antioxidant. Although oral hypoglycemic agents and insulin are the mainstays of treatment of diabetes mellitus (DM), there is a significant demand for new natural products to reduce the development of diabetic complications. Alloxan‐induced diabetic rats were treated for 60 days with a hydroalcoholic extract of M. paniculata (MPE), at doses of 100, 200, and 400 mg/kg. MPE decreased glycemia and also cholesterol and triglyceride levels, starting 1 week after treatments, as compared with the same group before treatments. Glucose values were reduced toward normality after 1 week of treatment. MPE hypoglycemic effects were potentiated by glibenclamide and metformin. MPE also decreased fructosamine and glycated hemoglobin values. MPE reduced diabetes‐induced morphological alterations of the kidney, pancreas, and liver. MPE acts similarly to glibenclamide and metformin, and its glucose‐lowering action is partly a consequence of ATP‐sensitive K⁺ channel inhibition. MPE may be a potential therapeutic alternative for the treatment of diabetes and its complications. Copyright © 2017 John Wiley & Sons, Ltd.     

Improvement of Insulin Resistance by Chlorella in Fructose‐rich Chow‐fed Rats

Chlorella is a type of unicellular fresh water algae. In an attempt to develop new agents for handling insulin resistance, Chlorella was employed to screen the effect on insulin resistance in rats induced by fructose‐rich chow. A single oral administration of Chlorella for 90 min decreased the plasma glucose in a dose‐dependent manner in rats receiving 4‐week fructose‐rich chow. In addition, chronic treatment with Chlorella for 15 days also lowered plasma glucose in the same manner. Then, the insulin action on glucose disposal rate was measured using the glucose‐insulin index, values of the areas under the curves of glucose and insulin during the intraperitoneal glucose tolerance test (IPGTT). Oral administration (three times daily for 5 days) of Chlorella to rats receiving 4 weeks of fructose‐rich chow abolished the elevated value of the glucose‐insulin index, indicating that Chlorella has an ability to improve insulin resistance. An increase of insulin sensitivity by Chlorella was further evaluated using the plasma glucose lowering action of exogenous insulin in streptozotocin‐induced diabetic rats (STZ‐diabetic rats). Oral administration of Chlorella three times daily to STZ‐diabetic rats increased the response to exogenous insulin 15 days later. The obtained results suggest that oral administration of Chlorella has the ability to improve insulin sensitivity, which may be used as an adjuvant therapy for patients with insulin resistance. Copyright © 2011 John Wiley & Sons, Ltd.     

Upregulation of PPARγ by Aegle marmelos ameliorates insulin resistance and β-cell dysfunction in high fat diet fed-streptozotocin induced type 2 diabetic rats

The global epidemic of type 2 diabetes demands the rapid evaluation of new and accessible interventions. This study investigated whether Aegle marmelos fruit aqueous extract (AMF; 250, 500 and 1000 mg/kg) improves insulin resistance, dyslipidemia and β‐cell dysfunction in high fat diet fed‐streptozotocin (HFD‐STZ)‐induced diabetic rats by modulating peroxisome proliferator‐activated receptor‐γ (PPARγ) expression. The serum levels of glucose, insulin, homeostasis model assessment of insulin resistance (HOMA‐IR), homeostasis model assessment of β‐cell function (HOMA‐B), lipid profile, TNF‐α and IL‐6 were evaluated. Further, the TBARS level and SOD activity in pancreatic tissue and PPARγ protein expression in liver were assessed. In addition, histopathological and ultrastructural studies were performed to validate the effect of AMF on β‐cells. The HFD‐STZ treated rats showed a significant increase in the serum levels of glucose, insulin, HOMA‐IR, TNF‐α, IL‐6, dyslipidemia with a concomitant decrease in HOMA‐B and PPARγ expression. Treatment with AMF for 21 days in diabetic rats positively modulated the altered parameters in a dose‐dependent manner. Furthermore, AMF prevented inflammatory changes and β‐cell damage along with a reduction in mitochondrial and endoplasmic reticulum swelling. These findings suggest that the protective effect of AMF in type 2 diabetic rats is due to the preservation of β‐cell function and insulin‐sensitivity through increased PPARγ expression. Copyright © 2011 John Wiley & Sons, Ltd.     

Oral hypoglycemic effect of Salacia reticulata in the streptozotocin induced diabetic rat

The oral hypoglycemic activity of Salacia reticulata extract was evaluated in streptozotocin induced diabetic rats. The diabetic rats were orally administered an aqueous extract of Salacia reticulata and the plasma glucose concentration was determined at regular intervals following administration. The drug was effective as a hypoglycemic agent at all the doses tested (0.5 g/kg, 1.0 g/kg and 5.0 g/kg). The maximum percentage decrease in plasma glucose was observed between 1–5h following administration of the drug.     

Effect of coriander seed (Coriandrum sativum L.) ethanol extract on insulin release from pancreatic beta cells in streptozotocin‐induced diabetic rats

Coriander (Coriandrum sativum L.) is grown as a spice crop all over the world. The seeds have been used to treat indigestion, diabetes, rheumatism and pain in the joints. In the present study, an ethanol extract of the seeds was investigated for effects on insulin release from the pancreatic beta cells in streptozotocin‐induced diabetic rats. Blood samples were drawn from the retro‐orbital sinus before and 1.5, 3 and 5 h after administration of the seed extract. Serum glucose levels were determined by the glucose oxidase method. To determine the insulin releasing activity, after extract treatment the animals were anaesthetized by diethyl ether, the pancreas was excised, fixed in 10% formaldehyde and embedded in paraffin for sectioning. Pancreatic sections of 5 µm were processed for examination of insulin‐releasing activity using an immunocytochemistry kit. The results showed that administration of the ethanol extract (200 and 250 mg/kg, i.p.) exhibited a significant reduction in serum glucose. Administration of streptozotocin decreased the number of beta cells with insulin secretory activity in comparison with intact rats, but treatment with the coriander seed extract (200 mg/kg) increased significantly the activity of the beta cells in comparison with the diabetic control rats. The extract decreased serum glucose in streptozotocin‐induced diabetic rats and increased insulin release from the beta cells of the pancreas. Copyright © 2008 John Wiley & Sons, Ltd.     

Antidiabetic effect of alcoholic extract of Caralluma sinaica L. on streptozotocin-induced diabetic rabbits

People of Asir region of Saudi Arabia chew Caralluma sinaica (CS) to lower glucose level. To establish its utility in diabetes mellitus we have under taken this study. The effect of CS on streptozotocin (STZ)-induced diabetic model as well as effect on oral glucose tolerance test were studied. The extract was shown to have positive test for possessing following chemical constituents like phenolic alkaloids, glycosides, flavonoids, coumarins, steroids and tannins. Administration of CS in different doses (50, 100, 150 and 200mg/kg, p.o.) to normal animals caused significant (P<0.01) decrease in glucose level. Prior administration of either CS (100mg/kg, p.o.) or glibenclamide (GB) (5mg/kg, p.o.) blocked the rise of glucose caused by the streptozotocin. Antidiabetic activity of CS was compared with clinically available drug GB. Administration of CS (100mg/kg, p.o.) to diabetic rabbits for 30 days has been shown to decrease plasma glucose level to almost normal level (P<0.001). Liver and kidney weight expressed as percentage of body weight significantly (P<0.05; P<0.01) increased in diabetic rabbits versus normal control (CNT). CS significantly (P<0.05) reversed the increasing weight of liver caused by STZ but not GB. STZ induced lowering of glycogen content of liver and muscle was reversed by both CS and GB. STZ induced a significant (P<0.001) increase in renal glycogen content this was almost normalized by CS (P<0.001) whereas GB significantly decreased (P<0.002) glycogen content. In oral glucose tolerance test administration of glucose increased plasma glucose level significantly in the diabetic control over the 2-h period. Compared to diabetic control plasma glucose levels in rabbits given CS or GB were significantly lower at all the time points that blood was sampled after oral glucose load. Comparing with the GB treatment blood glucose lowering effect was more pronounced for diabetic rabbits given CS. All these effects could explain the basis for use of this plant extract to manage diabetes mellitus.     

Effect of Hibiscus rosa sinensis Linn. ethanol flower extract on blood glucose and lipid profile in streptozotocin induced diabetes in rats

Blood glucose and total lipid levels were determined in streptozotocin induced diabetic rats after oral administration of an ethanol flower extract of Hibiscus rosa sinensis. A comparable hypoglycemic effect was evidenced from the data obtained after 7 and 21 days of oral administration of the extract and glibenclamide. Maximal diminution in blood glucose (41-46%) and insulin level (14%) was noticed after 21 days. The extract lowered the total cholesterol and serum triglycerides by 22 and 30%, respectively. The increase in HDL-cholesterol was much higher (12%) under the influence of the extract as compared to that of glibenclamide (1%). The hypoglycemic activity of this extract is comparable to that of glibenclamide but is not mediated through insulin release. Other possible mechanisms are discussed.     

Antidiabetic effect of Symplocos cochinchinensis (Lour.) S. Moore. in type 2 diabetic rats

Aim

Symplocos cochinchinensis (Lour.) S. Moore. is used in Indian system of traditional medicine to treat diabetes mellitus. The present study aims to investigate the antidiabetic efficacy of the hexane extract of Symplocos cochinchinensis leaves in high fat diet-low streptozotocin (STZ) induced type 2 diabetic rats.

Materials and methods

The doses for the study were fixed based on Irwin test. The hypoglycemic effect of the hexane extract of Symplocos cochinchinensis leaves were studied in normal rats. Oral glucose and insulin tolerance tests were carried out. The antihyperglycemic effect of the hexane extract at 250 and 500 mg/kg was studied in high fat diet-low STZ induced type 2 diabetic rats for 28 days.

Results

The extracts showed no adverse effects up to 5 g/kg concentration. In hypoglycemic study, after treatment with hexane extract at 250 and 500 mg/kg the blood glucose was mildly reduced. In oral glucose tolerance test, the treatment with the hexane extract at 250 and 500 mg/kg showed a highly significant reduction of 12.07% and 23.58% in plasma glucose levels, respectively 30 min after glucose load. The insulin tolerance test also showed improved insulin sensitivity after 60 min of insulin treatment. In high fat diet-low STZ induced type 2 diabetic rats, after 28 days treatment with the hexane extract at 250 and 500 mg/kg reduced the plasma glucose level by 17.04% and 42.10%, respectively. A significant reduction in plasma insulin, plasma and hepatic total cholesterol (TC), triglycerides (TG) and free fatty acids (FFA) and a significant increase in liver glycogen were observed in treated diabetic rats.

Conclusion

This study demonstrated the potential antidiabetic property of hexane extract of Symplocos cochinchinensis leaves on type 2 diabetes mellitus, thus justifying its traditional usage.     

Antihyperglycemic effect of the traditional Chinese scutellaria–coptis herb couple and its main components in streptozotocin-induced diabetic rats

Ethnopharmacological relevance

Scutellaria–coptis herb couple (SC) is the main herb couple in many traditional Chinese compound formulas used for the treatment of diabetes mellitus, which has been used to treat diabetes mellitus for thousands of years in China. In this study we provide experimental evidence for the clinical use of SC in the treatment of diabetes mellitus.

Aim of the study

To confirm the anti-diabetic effect of SC extract and its main components, and to explore its mechanism from the effect on intestinal disaccharidases by in vivo and in vitro experiment.

Materials and methods

SC extract was prepared and the main components (namely berberine and baicalin) contained in the extract were assayed with high performance liquid chromatography (HPLC). And diabetic model rats were induced by intraperitoneal injection of streptozotocin (STZ). After grouped randomly, diabetic rats were administered SC extract, berberine, baicalin, berberine+baicalin, acarbose and vehicle for 33 d, respectively. Body weight, food intake, urine volume, urine sugars, fasting plasma glucose and fasting plasma insulin were monitored to evaluate the antidiabetic effects on diabetic rats. Intestinal mucosa homogenate was prepared and the activities of intestinal disaccharidases were assayed. Moreover, oral sucrose tolerance test (OSTT) was performed and the inhibitory effects of SC extract and its main components (berberine and baicalin) on the maltase and sucrase in vitro was evaluated.

Results

After the treatment of SC extract and its main components, the body weight and the fasting plasma insulin level were found to be increased while food intake, urine volume, urine sugars and fasting plasma were decreased. OSTT showed that SC extract and its main components could lower the postprandial plasma glucose level of diabetic rats. Furthermore, SC extract and its main components could inhibit the activities of intestinal disaccharidases in diabetic rats, whereas only SC extract and berberine could inhibit the activity of maltase in vitro.

Conclusions

According to our present findings, scutellaria–coptis herb couple (SC) possessed potent anti-hyperglycemic effect on STZ-induced diabetic rats. And SC extract and its main components exerted anti-hyperglycemic effect partly via inhibiting the increased activities of intestinal disaccharidases and elevating the level of plasma insulin in diabetic rats induced by STZ.     

Pharmacological characterization of different fractions of Calotropis procera (Asclepiadaceae) in streptozotocin induced experimental model of diabetic neuropathy

Ethnopharmacological relevance

Calotropis procera (Ait.) R.Br. is one of an ancient traditional shrub, which has been used for the treatment of diabetes, pain and inflammation for thousands of years in India. The root extract of Calotropis procera has been widely used by the tribal?s of district Udaipur, Rajasthan (India) for treatment of diabetes mellitus and its associated complications like diabetic neuropathy. The present study was performed to explore the protective effect of root, stem and leaf extracts of Calotropis procera in diabetes and diabetic neuropathy against tactile allodynia, mechanical hyperalgesia and thermal hyperalgesia in streptozotocin induced diabetic rats.

Materials and methods

Diabetes and peripheral neuropathy were induced in Wistar rats by injection of streptozotocin (45 mg/kg/intraperitoneally). The roots, stem and leaves of Calotropis procera were sequentially extracted with petroleum ether, chloroform, ethyl acetate and methanol. All the extracts were assessed by oral administration at 100 and 250 mg/kg in streptozotocin diabetic rats. The following compounds were used as positive controls: insulin NPH (1 IU/kg/day), metformin (500 mg/kg/day), glibenclamide (2.5 mg/kg/day) and a combination of acarbose (20 mg/kg/day) with methylcobalamine (500 µg/kg/day). In contrast, the streptozotocin induced untreated diabetic rats termed as negative control. Thermal hyperalgesia, mechanical hyperalgesia and tactile allodynia were evaluated in all groups of streptozotocin diabetic rats to assess the extent of neuropathy by Eddy?s hot plate, tail immersion, Randall–Selitto and Von Frey hair tests. The basal nociceptive thresholds were assessed in week 4 of post streptozotocin injection. All groups received their treatment on a regular basis from 28 to 42 days following a confirmation of diabetic neuropathy. The nociceptive thresholds were assessed in all groups in week 5 and 6. The histopathology of pancreas and biochemical estimations of plasma insulin and glycosylated haemoglobin (HbA₁C%) levels were also performed in week 6 of post streptozotocin injection.

Results

The negative control rats developed diabetes and diabetic neuropathy after 6 week of streptozotocin administration distinguished by significant (p<0.01) hyperalgesia and tactile allodynia with enhanced HbA₁C% level compared to normoglycemic rats. Chronic administration of root methanol, stem methanol and leaf ethyl-acetate extracts of Calotropis procera for 2 weeks at 100 and 250 mg/kg doses significantly (p<0.01) attenuated the diabetes induced mechanical hyperalgesia, thermal hyperalgesia, tactile allodynia and HbA₁C% level in streptozotocin diabetic rats as compared to negative control rats. Further, the root methanol extract of Calotropis procera in 100 mg/kg dose showed the regeneration capability of β cells in the histology of pancreas with significant (p<0.01) improvement in plasma insulin level in streptozotocin diabetic rats compared to negative control rats.

Conclusion

Root methanol extract of Calotropis procera (100 mg/kg) has shown ameliorative effect in diabetic neuropathy which may be attributed by its multiple actions including potent hypoglycemic and antioxidant.     

Hypoglycaemic effects of Mammea africana (Guttiferae) in diabetic rats

Aim of the study

The stem bark of Mammea africana Sabine (Guttiferae) is used in African rain forest to treat various diseases, including diabetes mellitus. We investigated whether Mammea africana extract induced hypoglycaemic activity in rats.

Materials and methods

We tested the effects of acute (5 h) and sub-acute (21 days) oral administrations of the CH₂Cl₂–MeOH stem bark extract of Mammea africana (19–300 mg/kg body weight) on blood glucose levels of normal and streptozotocin (STZ)-induced type 1 diabetic rats. The effects were compared with those of glibenclamide.

Results

Acute administration reduced blood glucose in the diabetic rats only (33.87%, P < 0.01). Sub-acute treatment for 21 days also reduced blood glucose level in diabetic rats (73.29%, P < 0.01). A reduction or stabilization in total serum protein, triglyceride, cholesterol and alanine amino transferase levels was also observed. No effect was observed on body weight loss but food and water intakes were significantly reduced (P < 0.01) in diabetic rats. The maximal anti-diabetic effect was obtained with the dose of 75 mg/kg and was more important than that of glibenclamide.

Conclusion

It can be concluded that extracts of Mammea africana exhibited a significant anti-hyperglycaemic activity and improved the metabolic alterations in STZ-diabetic rats. These results provide a rationale for the use of Mammea africana to treat diabetes mellitus and hypercholesterolemia.     

Effects of Crataegus microphylla on Vascular Dysfunction in Streptozotocin‐induced Diabetic Rats

Vascular dysfunction plays a key role in the pathogenesis of diabetic vascular disease. In this study, we aimed to investigate whether chronic in vivo treatment of Crataegus microphylla (CM) extract in diabetic rats induced with streptozotocin (STZ, intraperitoneal, 65 mg/kg) preserves vascular function and to evaluate whether the reduction of inducible nitric oxide synthase (iNOS), proinflammatory cytokines, and lipid peroxidation mediates its mechanisms of action. Starting at 4 weeks of diabetes, CM extract (100 mg/kg) was administrated to diabetic rats for 4 weeks. In aortic rings, relaxation to acetylcholine and vasoreactivity to noradrenaline were impaired, whereas aortic iNOS expression and plasma tumor necrosis factor‐α (TNF‐α) and interleukin‐6 (IL‐6), total nitrite–nitrate, and malondialdehite levels were increased in diabetic rats compared with controls. Chronic CM treatment significantly corrected all the above abnormalities in diabetic rats. In comparison, pretreatment of the aorta of diabetic rats with N‐[3(aminomethyl) benzyl]‐acetamidine, dihydrochloride (10^–5 M), a selective inhibitor of iNOS, produced a similar recovery in vascular reactivity. These results suggest that chronic in vivo treatment of CM preserves endothelium‐dependent relaxation and vascular contraction in STZ‐induced diabetes, possibly by reducing iNOS expression in the aorta and by decreasing plasma levels of TNF‐α and IL‐6 and by preventing lipid peroxidation. Copyright © 2012 John Wiley & Sons, Ltd.     

The basis for the antihyperglycemic activity of Indigofera arrecta in the rat

The basis for the antihyperglycaemic property of Indigofera arrecta, a plant used for the treatment of diabetes, was evaluated using normoglycemic and streptozotocin-induced diabetic rats. The rats were given different doses of the freeze-dried extract of the plant material orally and intraperitoneally. The extract decreased the plasma glucose levels of fasting normoglycemic rats, but did not prevent the rise in plasma glucose after an oral glucose load in these rats. The extract increased plasma insulin levels. In the diabetic rats, the rise in blood glucose after an oral glucose load was not affected when the extract was administered 17 days after induction of diabetes. When administered 7 days after induction of diabetes, the rise in blood glucose was decreased, and was stabilized after 30 min. The results indicate that I. arrecta is insulinotropic, requiring functional beta cells to express its effect.