Effect of iridoid glucoside on streptozotocin induced diabetic rats and its role in regulating carbohydrate metabolic enzymes

Ameliorative property of Sesbania grandiflora on carbohydrate metabolic enzymes in the liver and kidney of streptozotocin-induced diabetic rats

In diabetic condition, endogenous glucose synthesis will be elevated due to defect in the action of vital enzymes involved in carbohydrate metabolism, which is the main cause for hyperglycemia. The current study was designed to explore the anti-hyperglycemic efficacy of Sesbania grandiflora flower (SGF) extract by evaluating the concentration of C-peptide, insulin, glucose, glycosylated hemoglobin (HbA1C), hemoglobin (Hb), glycogen and carbohydrate metabolic enzymes activities in diabetic rats. The study found to lower the level of glucose, HbA1C and simultaneously ameliorated concentrations of C-peptide, insulin, hemoglobin (Hb), glycogen and carbohydrate metabolic enzymes activities in SGF treated (250 mg/kg body weight for 45 days) diabetic rats. Moreover, SGF administered diabetic rats showed diminished consumption of food and water at the same time improved body weight. The results obtained from the present study were compared with glibenclamide treated (600 µg/kg body weight) diabetic rats. SGF were supplemented to normal rats to rule out toxic effect of SGF, to explore any significant alteration in the above parameters. Hence, the results depict that SGF modulated the carbohydrate metabolic enzymes activities through ameliorating the secretion of insulin and diminishing the level of glucose concentration in STZ-induced diabetic rats by its bioactive compounds.

Antioxidant potential of biflavonoid attenuates hyperglycemia by modulating the carbohydrate metabolic enzymes in high fat diet/streptozotocin induced diabetic rats

Objectives: The present study was to isolate the biflavonoid (a bimolecular kaemferol structured molecule) and test its efficacy on oxidative stress and carbohydrate metabolic key enzymes in control and high fat diet and streptozotocin -induced diabetic rats.

Methods: Type 2 diabetes was induced in male albino wistar rats by feeding them with high fat diet comprising of 84.3% standard laboratory chow, 5% lard, 10% yolk powder, cholesterol 0.2%, and 0.5% bile salt for 2 weeks. After 2 weeks, the animals were kept in an overnight fast and injected with low dose of streptozotocin (35 mg/kg, dissolved in 0.1 M sodium citrate buffer, pH 4.5).

Results: At the end of the experimental period, diabetic control rats showed significant increase in plasma glucose, homeostatic model assessment of insulin resistance (HOMA-IR), glycosylated hemoglobin (HbA1c) with concomitant decrease in plasma insulin, total hemoglobin and body weight. The activities of key enzymes of carbohydrate metabolism, lipid peroxidation markers, antioxidant enzymes, glycogen content and glycogen synthase and glycogen phosphorylase were also altered in diabetic rats.

Discussion: Oral administration of biflavonoid to diabetic rats significantly ameliorated all the biochemical alterations to near normal levels. The effect produced by the biflavonoid on various parameters was comparable to that of metformin.

Effect of Curculigo pilosa supplemented diet on blood sugar, lipid metabolism, hepatic oxidative stress and carbohydrate metabolism enzymes in streptozotocin-induced diabetic rats

BACKGROUND

Diabetes mellitus (DM) has continued to raise concern globally and Curculigo pilosa (CP) is used for its treatment and management in folkloric medicine. In this study, the in vitro antioxidant abilities of CP and the effects of CP-supplemented diets on blood sugar, lipid metabolism, oxidative stress and key carbohydrate metabolizing enzymes in streptozotocin (STZ)-induced diabetic rats were investigated.

METHODS

Polyphenol contents (total phenolic and total flavonoid) and antioxidant ability of different extracts of CP were determined in vitro. Diabetes mellitus were stimulated in healthy rats by single intraperitoneal administration of 50 mg/kg streptozotocin and it was confirmed by elevated blood glucose level after 3 days. Thirty six rats were distributed into six groups of six rats each and diabetic rats were fed with 5 and 10% CP-supplemented diet for 21 days. Thereafter, the effects of the dietary regimen were evaluated on blood glucose, body weight, hepatic carbohydrate metabolizing enzymes, lipid profile, oxidative stress markers, serum markers of hepatic and renal damages and histopathology studies.

RESULTS

Different extracts of CP contained polyphenol contents and exhibited antioxidant properties in different models used. Diabetic rats showed elevated level of blood glucose and body weight loss. Treatment of diabetic rats with CP-supplemented diet significantly (p < 0.05) lowered the blood glucose and improved body weight loss. Also, the treatment with the CP-supplemented diet significantly (p < 0.05) enhanced the activities of hepatic glycolytic (hexokinase and glucose-6-dehydrogenase) and lowered the gluconeogenic (fructose 1, 6 biphosphatase and glucose-6-phosphatase) enzymes in diabetic rats. The lipid profile, oxidative stress markers and serum markers of hepatic and renal damages were significantly (p < 0.05) restored to near normalcy in the diabetic rats. Histopathological slides also showed improvements in pancreas and hepatic tissues of diabetic rats treated with CP-supplemented diet.

CONCLUSION

Data obtained in this study suggested that CP-supplemented diet could be used as dietary regimen in the management of DM.

Catalpol ameliorates Sjögren's Syndrome by modulating interplay of T and B cells

Catalpol is an active ingredient of Rehmanniae Radix, a medical herb used frequently in treating primary Sjogren's Syndrome (pSS). However, no study has assessed the therapeutic effects of catalpol in treating Sjogren's Syndrome. This study aimed to investigate the therapeutic effects of catalpol for pSS by evaluating the water consumption, stimulated salivary flow rates, sialadenitis, T cell subsets and related cytokine levels. Catalpol treated mice had improved stimulated salivary flow rates and water consumption compared to mice from the control group. Catalpol also reduced the lymphocytic infiltration and prevented the formation of ectopic germinal centers. These effects, especially in the catalpol high dose group, were associated with elevated CD4⁺ CXC-R5⁺ PD-1⁺ Foxp3⁺ T follicular regulatory (Tfr) cells (1.572 % vs 1.118 %, P = 0.0005) and a higher ratio of Tfr cells to T follicular helper (Tfh) cells (2.137 vs 1.541, P = 0.0007). Downregulated levels of IFN-γ and BAFF in serum and submandibular glands were also noted in catalpol treated groups. Our work indicated that catalpol might be a potential drug for treating pSS by regulating the interplay between T and B cells.

Hesperidin, a citrus flavonoid ameliorates hyperglycemia by regulating key enzymes of carbohydrate metabolism in streptozotocin-induced diabetic rats

The present study investigated the protective effect of hesperidin on carbohydrate metabolizing enzymes in streptozotocin-induced diabetic rats. Hesperidin was administered to streptozotocin-induced (40 mg/kg b.w.) diabetic rats at different dosages of (25, 50, 100 mg/kg b.w.) respectively for 30 days to evaluate its effect on fasting plasma glucose, insulin, glycosylated hemoglobin, hemoglobin, and carbohydrate metabolic enzymes. The plasma glucose levels were significantly reduced in a dose-dependent manner in hesperdin-treated group of rats when compared to the diabetic control rats. In addition, concomitant increase in hemoglobin and insulin levels and a decrease in glycosylated hemoglobin were observed in treated group of rats. The activities of the hepatic key enzymes of carbohydrate metabolism such as hexokinase and glucose-6-phosphate dehydrogenase were significantly increased, whereas glucose-6-phosphatase and fructose-1,6-bisphosphatase were significantly decreased. Furthermore, hesperidin administration prevented the loss in body weight and improved the glycogen content in the hepatic tissue of diabetic animals by reinstating the activities of glycogen synthase and glycogen phosphorylase. These results showed that hesperidin has potential antihyperglycemic activity in streptozotocin-induced diabetic rats. This was further supported by the histological studies of pancreas and liver.

Ethnomedicinal Investigation of Medicinal Plants of Chakrata Region (Uttarakhand) Used in the Traditional Medicine for Diabetes by Jaunsari Tribe

The Himalayan region is the treasure house of natural wealth, particularly of medicinal and aromatic plants. These plants are used by the Indian traditional healers for the past many centuries to treat various ailments such as skin disorders, asthma, diabetes, snake bite, fever, pain, eye diseases, diarrhoea, indigestion, jaundice, burn, wound, liver disorder, CNS disorders and urinary tract infection. The indigenous traditional knowledge of medicinal plants and therapies of various local communities has been lost due to changes in traditional culture and the introduction of modern technologies. Therefore, it is essential to explore the traditional knowledge of the indigenous medicinal plants mainly in such areas where there is a severe threat to natural vegetation owing to human inhabitation. The present study aimed to explore the medicinal plants of Chakrata region (Jaunsar-Bawar Hills), Uttarakhand, India used in the folk medicine for the management of diabetes by Jaunsari Tribe. In a comprehensive field survey, the information about the medicinal plants have been mainly collected from the traditional healers and other elderly people belong to the tribal community. All the information about the medicinal plants of the study area was documented in a field book. Various tools have been used to collect the samples for identification purpose and the authentication of the plants was done with the help of taxonomists. The literature on these plants was also searched from online (PubMed and Scopus) as well as from some textbooks and Ayurvedic classical texts. The present survey-based work described a total of 54 plants belonging to 47 genera and 30 families used in the traditional medicine for the management of diabetes in Chakrata region. The information gathered from the local community revealed that the plants are effective in diabetes and one can use most of them without consulting a practitioner or traditional healer. The literature revealed that most of the surveyed plants are already used in the preparation of various antidiabetic formulations such as Chandraprabha vati, Nishamalaki chunra, Amritamehari churna and Nisakathakadi kashayam along with various patent drugs which are frequently prescribed by the Ayurvedic practitioners in India. The present study explored the traditional as well as scientific knowledge on the antidiabetic plants used by the tribal community. The documented information on these plants can be further used by the scientific community to develop new drugs/formulations with the help of modern techniques.

Antihyperglycemic Potential of Back Tea Extract Attenuates Tricarboxylic Acid Cycle Enzymes by Modulating Carbohydrate Metabolic Enzymes in Streptozotocin-Induced Diabetic Rats

The present study was aimed to investigate the effect of black tea extract on blood glucose, plasma insulin, Hemoglobin, carbohydrate metabolic enzymes and tricarboxylic enzymes in streptozotocin (STZ) induced diabetic rats. Diabetes was induced in male albino Wistar rats by intraperitoneal administration of STZ (40 mg/kg b wt). Black tea extract was administered to diabetic rats at a dose of 25, 50 and 100 mg/kg body weight for 30 days. The effects of black tea extract on glucose, insulin and HbA1c levels were analyzed to confirm the effective dose. Administration of black tea extract to diabetic rats was significantly decreased the level of glucose, glycated hemoglobin and increased the levels of insulin in a dose dependent manner. The black tea extracts at a dose of 100 mg/kg b wt showed a highly significant effect compared to other two doses (25 and 50 mg/kg b wt). The effect produced by black tea extract (100 mg/kg b wt) was comparable to that of glibenclamide (5 mg/kg b wt) a reference anti diabetic drug. Therefore, 100 mg/kg b wt was fixed as an effective dose and used for further analyses. Black tea extract was administered to diabetic rats at a dose of 100 mg/kg b wt for 30 days reinstated the altered levels of the plasma glucose, insulin, hemoglobin, glycosylated hemoglobin, carbohydrate metabolizing enzymes and tricarboxylic cycle enzymes in diabetic rats. Black tea extract administered to diabetic rats at a dose of 100 mg/kg b wt for 30 days reinstated the altered levels of the plasma glucose, insulin, hemoglobin, glycosylated hemoglobin, carbohydrate metabolizing enzymes and tricarboxylic cycle enzymes in diabetic rats. The effect produced by black tea extract of all the biochemical parameters were comparable with glibenclamide-used as a reference drug.

Identification of Bioactive Compounds and Analysis of Inhibitory Potential of the Digestive Enzymes from Syzygium sp. Extracts

Diabetes and obesity represent major public health problems worldwide. High cost of medicines and drug treatments propose the research for less expensive alternatives, such as enzymatic inhibitors present in medicinal plants from natural sources. An example of such medicinal plant is the jambolan Syzygium sp., which is referred to be hypoglycemic and efficient in weight loss. With this in mind, we identified the bioactive compounds from Syzygium sp. commercial teas and evaluated the inhibitory potential and the antioxidant activity of digestive enzymes from a simulated gastric fluid. Syzygium sp. samples showed low percentages of enzymatic inhibition at 1 : 200 dilution. Antioxidant activity was significant, although it was not expressive of the contents of total phenolic compounds, tannins, flavonoids, flavones, and alkaloids. Maldi-Tof spectroscopy suggested the presence of luteolin in Syzygium sp. samples. Molecular docking predicted that luteolin binds at the α-amylase catalytic site in a similar manner as acarbose, the carbohydrate inhibitor from the enzyme crystallographic structure. The phytochemical content and biological activity were distinct among samples from commercial teas. Thus, additional studies should be conducted to elucidate efficacy and safety of Syzygium sp. extracts, especially in vivo experiments. Syzygium sp. might be in the near future recommended as a medicinal plant in low cost diabetes and obesity treatments.

New iridoids from Lyonia ovalifolia and their anti-hyperglycemic effects in mice pancreatic islets

Phytochemical investigation on the aerial parts of Lyonia ovalifolia (Wall.) Drude led to the isolation of three new iridoids, lyonofolin A (1), lyonofolin B (2), and lyonofolin C (3), and a known iridoid, gelsemiol (4). Structures of compounds 1-4 were determined by extensive spectroscopic analyses, including EI-MS, HREI-MS, UV, IR, and 1D- and 2D-NMR (HMBC, HSQC, COSY, NOESY) spectroscopic methods. The effect of insulin secretion of compounds 1, 2, and 4 were evaluated in mice pancreatic islets cellular model. This insulin secretory assay demonstrated that compound 2 potentiates glucose-induced insulin secretion, and thus can serve as a new insulin secretagogue for the treatment of diabetes. The newly isolated compounds were further evaluated against normal 3 T3 cell lines for cytotoxicity, where they did not show any cytotoxicity.

A Review on the Terpenes from Genus Vitex

The genus Vitex, which belongs to the Verbenaceae family, includes approximately 250 species. Some species of the genus Vitex have traditionally been used for the treatment of headaches, ophthalmodynia, coughs, asthma, premenopausal syndrome, etc. Chemical investigations indicate that the characteristic constituents of the genus Vitex are terpenes, and 210 of these compounds, including monoterpenoids, sesquiterpenoids, diterpenoids and triterpenoids, have been obtained from 12 species. Pharmacological studies had shown that these terpenes possess anti-inflammatory, antitumor, antibacterial, antioxidant activities, and so on. In this paper, the identity of these terpenes and their pharmacological effects are reviewed, which can provide references for further research regarding the chemistry and utilization of the Vitex species.

Antidiabetic effects of Swertia macrosperma extracts in diabetic rats

ETHNOPHARMACOLOGICAL RELEVANCE

Swertia macrosperma is a traditional folk medicine used for its anti-hepatitis, antipyretic and antidotal effects as "Dida" or "Zangyinchen" in Tibet, Yunnan and Guizhou province for a long time, and it has been reported for its anti-diabetic effects in a Chinese patent. Swertia macrosperma was reported rich in xanthones, iridoids, seco-iridoids and their glycosides, several of which had been documented as potential antidiabetic agents. The objective of this study was to investigate the antidiabetic effect of Swertia macrosperma in diabetic rats.

MATERIALS AND METHODS

This study was designed firstly to evaluate the effect of Swertia macrosperma on glucose consumption in HepG2 cells. Based on the result in HepG2 cells, the antidiabetic effect of ethanol extract (EE) and n-butanol extract (BE) were investigated in diabetic rats induced by high fat fed and streptozotocin. The effects of EE and BE on fasting blood glucose, oral glucose tolerance test, serum insulin, glycosylated hemoglobin, serum lipid level, serum antioxidant parameters, glucokinase, glucose-6-phosphatase activities and glycogen content in liver tissue were measured, histology examination of pancreatic tissue was also carried out.

RESULTS

After 4 weeks treatment with EE and BE, apparently decreased fasting blood glucose concentrations were observed in these treated groups, compared with the diabetic control groups. Additionally, improvement in serum antioxidant parameters and lipid profile were evidenced clearly. Moreover, EE and BE had effects of protecting the pancreatic β-cells and stimulating insulin secretion from the remaining pancreatic β-cells, evidenced by pancreatic histology examination. Increased glucokinase activity and decreased glucose-6-phosphatase activity were observed in liver.

CONCLUSION

The results of in vivo and in vitro experiment suggested that EE and BE of Swertia macrosperma had excellent effects on controlling the hyperglycemia and hyperlipidemia in diabetic rats.

Cooperative anti-diabetic effects of deoxynojirimycin-polysaccharide by inhibiting glucose absorption and modulating glucose metabolism in streptozotocin-induced diabetic mice

We had previously shown that deoxynojirimycin-polysaccharide mixture (DPM) not only decreased blood glucose but also reversed the damage to pancreatic β-cells in diabetic mice, and that the anti-hyperglycemic efficacy of this combination was better than that of 1-deoxynojirimycin (DNJ) or polysachharide alone. However, the mechanisms behind these effects were not fully understood. The present study aimed to evaluate the therapeutic effects of DPM on streptozotocin (STZ)-induced diabetic symptoms and their potential mechanisms. Diabetic mice were treated with DPM (150 mg/kg body weight) for 90 days and continued to be fed without DPM for an additional 30 days. Strikingly, decrease of blood glucose levels was observed in all DPM treated diabetic mice, which persisted 30 days after cessation of DPM administration. Significant decrease of glycosylated hemoglobin and hepatic pyruvate concentrations, along with marked increase of serum insulin and hepatic glycogen levels were detected in DPM treated diabetic mice. Results of a labeled (13)C6-glucose uptake assay indicated that DPM can restrain glucose absorption. Additionally, DPM down-regulated the mRNA and protein expression of jejunal Na(+)/glucose cotransporter, Na(+)/K(+)-ATPase and glucose transporter 2, and enhanced the activities as well as mRNA and protein levels of hepatic glycolysis enzymes (glucokinase, phosphofructokinase, private kinase and pyruvate decarboxylas E1). Activity and expression of hepatic gluconeogenesis enzymes (phosphoenolpyruvate carboxykinase and glucose-6-phosphatase) were also found to be attenuated in diabetic mice treated with DPM. Purified enzyme activity assays verified that the increased activities of glucose glycolysis enzymes resulted not from their direct activation, but from the relative increase in protein expression. Importantly, our histopathological observations support the results of our biochemical analyses and validate the protective effects of DPM on STZ-induced damage to the pancreas. Thus, DPM has significant potential as a therapeutic agent against diabetes.

Effect of iridoid glucoside on plasma lipid profile, tissue fatty acid changes, inflammatory cytokines, and GLUT4 expression in skeletal muscle of streptozotocin-induced diabetic rats

The present study was designed to examine the antihyperlipidaemic potential of iridoid glucoside isolated from Vitex negundo leaves in STZ-induced diabetic rats. The levels of cholesterol (TC), triglycerides, lipoproteins, free fatty acids, phospholipids, fatty acid composition, proinflammatory cytokines, muscle glycogen content, and glucose transporter 4 (GLUT4) expression were estimated in control and diabetic rats. Oral administration of iridoid glucoside at a dose of 50 mg/kg body weight per day to STZ-induced diabetic rats for a period of 30 days resulted in a significant reduction in plasma and tissue (liver and kidney) cholesterol, triglycerides, free fatty acids, and phospholipids. In addition, the decreased plasma levels of high-density lipoprotein-cholesterol and increased plasma levels of low density lipoprotein- and very low density lipoprotein-cholesterol in diabetic rats were restored to near normal levels following treatment with iridoid glucoside. The fatty acid composition of the liver and kidney was analyzed by gas chromatography. The altered fatty acid composition in the liver and kidney of diabetic rats was also restored upon treatment with iridoid glucoside. Moreover, the elevated plasma levels of proinflammatory cytokines and decreased levels of muscle glycogen and GLUT4 expression in the skeletal muscle of diabetic rats were reinstated to their normal levels via enhanced secretion of insulin from the remnant β cells of pancreas by the administration of iridoid glucoside. The effect produced by iridoid glucoside on various parameters was comparable with that of glibenclamide, a well-known antihyperglycemic drug.

Efficacy of asiatic acid, a pentacyclic triterpene on attenuating the key enzymes activities of carbohydrate metabolism in streptozotocin-induced diabetic rats

Asiatic acid (AA), a triterpenoid derivative of Centella asiatica, has shown significant biological effects of antioxidant and anti-inflammatory activities. Aim of this investigation was to evaluate the antihyperglycemic effect of AA on the activities of hepatic enzymes of carbohydrate metabolism in streptozotocin (STZ)-induced diabetic rats. To induce diabetes mellitus, rats were injected with streptozotocin intraperitoneally at a single dose of 40 mg/kg b.w. Diabetic rats showed significant (p<0.05) increased in plasma glucose, glycosylated hemoglobin and significant (p<0.05) decreased in circulating insulin and hemoglobin. The altered activities of key enzymes such as glucose-6-phosphatase and fructose-1,6-bisphosphatase of carbohydrate metabolism significantly (p<0.05) increased whereas hexokinase, pyruvate kinase, glucose-6-phosphate dehydrogenase and glycogen content significantly (p<0.05) decreased in the liver of diabetic rats and also increased activities of aspartate transaminase (AST), alanine transaminase (ALT) and alkaline phosphatase (ALP). Oral administration of AA (5, 10 and 20 mg/kg b.w.) and glibenclamide (600 μg/kg b.w.) to diabetic rats for 45 days prevented the above alteration and reverted to near normalcy. Protection of body weight loss of diabetic rats by AA was also observed. No significant effect was observed in normal rats treated with AA (20 mg/kg b.w.). In this search, AA found to be potential bioactive compound to regulate the carbohydrate metabolism by modulating the key regulatory enzymes in diabetic rats. These findings merit further research in this field.