Hypoglycaemic effect of Berberis vulgaris L. in normal and streptozotocin-induced diabetic rats

OBJECTIVE

To achieve a primary pharmacological screening contained in the aqueous extract of Berberis vulgaris (B. vulgaris) and to examine the hypoglycaemic effect and biochemical parameters of aqueous and saponins extract on groups of rats rendered diabetic by injection of streptozotocin.

METHODS

The phytochemical tests to detect the presence of different compounds were based on the visual observation of color change or formation of precipitate after the addition of specific reagents. Diabetes was induced in rats by intraperitoneal (i.p.) injection of streptozotocin (STZ) at a dose of 65 mg/kg bw. The fasting blood glucose levels were estimated by glucose oxidase-peroxidase reactive strips (Dextrostix, Bayer Diagnostics). Blood samples were taken by cutting the tip of the tail. Serum cholesterol and serum triglycerides were estimated by enzymatic DHBS colorimetric method.

RESULTS

Administration of 62.5 and 25.0 mg/kg of saponins and aqueous extract respectively in normal rats group shows a significant hypoglycemic activity (32.33% and 40.17% respectively) during the first week. However, diabetic group treated with saponin extract produced a maximum fall of 73.1% and 76.03% at day 1 and day 21 compared to the diabetics control. Also, blood glucose levels of the diabetic rats treated with aqueous extract showed decrease of 78.79% on the first day and the effect remains roughly constant during 3 week. Both extracts also declined significantly biochemical parameters (20.77%-49.00%). The control in the loss of body weight was observed in treated diabetic rats as compared to diabetic controls.

CONCLUSIONS

These results demonstrated significant antidiabetic effects and showed that serum cholesterol and serum triglycerides levels were decreased, significantly, consequently this plant might be of value in diabetes treatment.

Functional and physiological properties of total, soluble, and insoluble dietary fibres derived from defatted rice bran

Enzymatic- gravimetric method was used to obtain three fractions of dietary from defatted rice bran. The functional and physiological properties such as viscosity, cation exchange capacity (CEC), and glucose dialysis retardation index (GDRI), cholesterol and bile salt adsorption capacity of the resultant fractions were evaluated. Insoluble dietary fibre (IDF) and soluble dietary fibre (SDF) when compared showed that SDF exhibited significantly (p < 0.05) higher viscosity (2.35 mPa.s), greater GDRI value (17.65 %) at 60 min and significantly lowered concentration of cholesterol at pH 7 (29.90 %, p < 0.05). However IDF showed the highest CEC and its adsorption capacity of bile salt was higher than SDF (18.20 % vs. 13.76 %; p < 0.05), while CEC and cholesterol absorption capacity of TDF were similar to SDF. These properties indicate that rice bran soluble, insoluble and total fibres are functional ingredients which can be added to various food products and dietetic, low-calorie high-fiber foods to enhance their nutraceutical properties and health benefits.

Hypoglycaemic activity of ethanolic extract of Garcinia mangostana Linn. in normoglycaemic and streptozotocin-induced diabetic rats

Background

Various parts of Garcinia mangostana Linn., including its pericarp, have been traditionally used to treat a variety of ailments. In an attempt to establish its medicinal value, the present study was carried out to determine the hypoglycaemic potential of G. mangostana pericarp ethanolic extract (GME) using the streptozotocin-induced (STZ) diabetic rats.

Methods

GME at 2,000 mg/kg was subjected to a single-dose acute toxicity test. Following this, the effect of GME (50, 100, and 200 mg/kg) on blood glucose level of normoglycaemic and STZ-induced diabetic rats was determined using single-dose (acute) and multiple-dose (subacute) approaches. Subsequent to the multiple-dose study, serum biochemical analysis and liver histopathological examination were also performed. Throughout the experiments, the effect of GME was compared against the standard hypoglycaemic drug, glibenclamide.

Results

GME was safe for oral consumption up to the dose of 2,000 mg/kg. In both single- and multiple-dose studies, GME significantly (p < 0.05) reduced the blood glucose level in normoglycaemic rats and STZ-induced diabetic rats when compared against the normal control group or diabetic control group, respectively. Moreover, GME also significantly (p < 0.05) increased the rats’ body weight in comparison to the diabetic control group in the multiple-dose study. GME also significantly (p < 0.05) reduced the levels of certain biochemical parameters [i.e., triglycerides (TG), total cholesterol (TC), low density lipoprotein (LDL), very low density lipoprotein (VLDL), serum glutamic oxaloacetic transaminase (SGOT), serum glutamic pyruvic transaminase (SGPT), urea, and creatinine] while increased the others [i.e., high density lipoprotein (HDL) and total protein (TP)] when compared to the diabetic control group. Histopathological assessment of the collected liver revealed a mild increase in the population of β-cells in the diabetic rats.

Conclusion

GME exerts the hypoglycaemic activity possibly by increasing the population of insulin-producing β-cells. This activity could be attributed to the presence of antioxidant-bearing tannins like epicathecin, and xanthones like α-mangostin. Thus, the findings demonstrated that GME could be a potential candidate in the management of diabetes owing to its hypoglycaemic effect.

Cell-penetrating peptide enhanced insulin buccal absorption

Non-injectable delivery of peptides and proteins is not feasible due to the limitations of large molecular mass, high hydrophilic properties, and gastrointestinal degradation. Therefore, proposing a new method to solve this problem is a burning issue. The objective of this study was to propose a novel protein delivery strategy to overcome the poor efficacy and irritation of buccal insulin delivery. In this study, we applied a conjugate of cell-penetrating peptides (LMWP) and insulin (INS-PEG-LMWP) for buccal delivery. INS-PEG-LMWP was prepared using insulin solution and mixture as references. The transport behaviour, in vivo bioactivity, hypoglycaemic effect, and safety of INS-PEG-LMWP were systematically characterised. An in vitro study demonstrated that the uptake and transportation of INS-PEG-LMWP across buccal mucosal multilayers significantly increased. By comparing the effects of different endocytic inhibitors on INS-PEG-LMWP uptake, the conjugate might be delivered via an energy independent, electrostatically adsorbed pathway. INS-PEG-LMWP's relative pharmacological bioavailability was high and its relative bioavailability was up to 26.86%, demonstrating no visible mucosal irritation. Cell-penetrating peptides are likely to become a reliable and safe tool for overcoming insulin's low permeability through the epithelial multilayers, the major barrier to buccal delivery.

Comparison of PEGylated FGF-21 with insulin glargine for long-lasting hypoglycaemic effect in db/db mice

AIM

This study investigated the long-acting antidiabetic efficacy of PEGylated fibroblast growth factor (FGF)-21 in type 2 diabetic db/db mice.

METHODS

PEGylated FGF-21 was prepared by modifying the N-terminus of human FGF-21 (hFGF-21) using mPEG-ALD. To compare the long-lasting hypoglycaemic effects of PEGylated FGF-21 and insulin glargine in diabetic db/db mice, their pharmacological efficacy was evaluated by changes in blood glucose levels, body weight, insulin levels, glycosylated haemoglobin levels, lipid profile and liver function parameters, and by oral glucose tolerance tests (OGTTs).

RESULTS

Both PEGylated FGF-21 and insulin glargine decreased plasma glucose in db/db mice. However, compared with insulin glargine treatment, PEGylated FGF-21 therapy had more significant effects in lowering blood glucose and glycosylated haemoglobin levels, improving lipid profile and liver function parameters, alleviating insulin resistance and reducing the glucose area under the curve in OGTTs.

CONCLUSION

Our results suggest that PEGylated FGF-21 is an ideal candidate as a long-acting antidiabetes drug, and holds significant promise as an effective therapeutic agent in the treatment of type 2 diabetes patients.

Bitter melon fruit extract enhances intracellular ATP production and insulin secretion from rat pancreatic β-cells

Bitter melon (Momordica charantia L.) has been shown to have various health-promoting activities, including antidiabetic and hypoglycaemic effects. Improvement in insulin sensitivity and increase in glucose utilisation in peripheral tissues have been reported, but the effect on insulin secretion from pancreatic β-cells remains unclear. In this study, we investigated the effect of bitter melon fruit on insulin secretion from β-cells and the underlying mechanism. The green fruit of bitter melon was freeze-dried and extracted with methanol. The bitter melon fruit extract (BMFE) was fractionated using ethyl acetate (fraction A), n-butanol (fraction B) and water (fraction C). Insulin secretory capacity from INS-1 rat insulinoma cell line and rat pancreatic islets, as well as glucose tolerance in rats by oral glucose tolerance test (OGTT), was measured using BMFE and fractions. ATP production in β-cells was also examined. BMFE augmented insulin secretion from INS-1 cells in a dose-dependent manner. The significant augmentation of insulin secretion was independent of the glucose dose. Fraction A (i.e. hydrophobic fraction), but not fractions B and C, augmented insulin secretion significantly at the same level as that by BMFE. This finding was also observed in pancreatic islets. In OGTT, BMFE and fraction A decreased blood glucose levels and increased serum insulin levels after glucose loading. The decrease in blood glucose levels was also observed in streptozotocin-induced diabetic rats. In addition, BMFE and fraction A increased the ATP content in β-cells. We concluded that hydrophobic components of BMFE increase ATP production and augment insulin secretion from β-cells, consequently decreasing blood glucose levels.

Contribution of fasting and postprandial glucose-lowering mechanisms to the acute hypoglycemic effect of traditionally used Eryngium cymosum F.Delaroche

ETHNOPHARMACOLOGICAL RELEVANCE

Eryngium cymosum F. Delaroche was detected as a traditional remedy against type 2 diabetes consumed by patients of Tlanchinol in the state of Hidalgo, Mexico.

AIM OF THE STUDY

Assessing the hypoglycemic effect and safety of the traditional extract of E. cymosum and relating it to key glucose-lowering mechanisms both in fasting and postprandial state.

MATERIALS AND METHODS

The aqueous extract of E. cymosum was subjected to HPLC analysis to identify its main components. Hyperglycaemic STZ-NA Wistar rats were administered with the extract to evaluate its effect on blood glucose levels and a possible dose-dependence. Afterward, it was evaluated in both pyruvate and maltose tolerance tests in STZ-NA rats to characterize its effect on gluconeogenesis and carbohydrate breakdown, two of the main mechanisms responsible for fasting and postprandial hyperglycaemia in type 2 diabetes patients. In addition, the inhibitory capacity of the extract was evaluated on key enzymes involved in gluconeogenesis and a-glucosidases. Moreover, insulin concentrations were measured in normoglycemic rats in both conditions to establish a link between the hypoglycaemic effect of the extract with insulin release and functioning.

RESULTS

Caffeic acid (1), chlorogenic acid (2), and rosmarinic acid (3) were identified as the main constituents of the aqueous extract of E. cymosum, which exerted a hypoglycaemic effect in hyperglycaemic STZ-NA rats. It has a significant antihyperglycemic effect in the pyruvate tolerance test, and it was able to reduce the postprandial hyperglycaemia in maltose tolerance tests significantly. Moreover, it effectively reduced the activity of both gluconeogenic enzymes reaching almost 100% of inhibition, while it presented a modest 32% inhibition of aglucosidases. On the other hand, the extract decreased insulin levels after its oral administration in healthy rats in both nutritional states, without affecting normoglycemia in normal curves and reducing the postprandial peak in glucose load curves.

CONCLUSIONS

The traditional consumed form of aerial parts of E. cymosum is safe and regulated glucose levels both in fasting and in postprandial state.

Myrianthus libericus: Possible mechanisms of hypoglycaemic action and in silico prediction of pharmacokinetics and toxicity profile of its bioactive metabolite, friedelan-3-one

The hypoglycaemic and anti-hyperlipidaemic effects of the 70% ethanol stem bark extract of Myrianthus libericus (MLB), used traditionally in the management of diabetes in Ghana, was evaluated in this study using streptozotocin (45 mg/kg)-induced diabetic rats. In vitro hypoglycaemic activities of the extract and one of its principal compounds, friedelan-3-one were then investigated using α-amylase inhibitory and glucose uptake assay in C2C12 myotubes. In silico analysis of the pharmacokinetic and toxicity properties of the compound was also performed. MLB significantly (p < 0.001) reduced the elevated blood glucose levels and corrected considerably (p < 0.01) the altered serum lipid profiles of the diabetic rats which was comparable to glibenclamide (5 mg/kg). Together with friedelan-3-one, the extract markedly inhibited the activity of α-amylase and promoted glucose uptake in C2C12 cells. Whereas MLB significantly (p < 0.001) up-regulated PI3K and PPARγ transcripts with a corresponding increase in GLUT-4 transcripts within the muscle cells, friedelan-3-one only up-regulated PI3K and GLUT-4 transcripts to promote glucose transport. Friedelan-3-one was shown to be non-carcinogenic, non-hepatotoxic, has decent oral bioavailability and a good compound for optimisation into a drug candidate. The study has demonstrated that MLB possess hypoglycaemic and anti-hyperlipidaemic activities and could be used as a therapeutic agent in the management of diabetes mellitus.

Effect of Lupinus rotundiflorus gamma conglutin treatment on JNK1 gene expression and protein activation in a rat model of type 2 diabetes

CONTEXT

Gamma conglutin (Cγ) from lupine species represents a potential complementary treatment for type 2 diabetes mellitus (T2DM) because of its hypoglycaemic effect. However, its underlying mechanism of action is not fully known.

OBJECTIVE

To evaluate whether Cγ from Lupinus rotundiflorus M. E. Jones (Fabaceae) modulates c-Jun N-terminal kinase 1 (JNK1) expression and activation in a T2DM rat model.

MATERIALS AND METHODS

Gamma conglutin isolated from L. rotundiflorus seeds was characterized by SDS-PAGE. Fifteen Wistar rats with streptozotocin-induced T2DM (HG) were randomized into three groups (n = 5): vehicle administration (HG-Ctrl), oral treatment with Cγ (120 mg/kg/day) (HG-Lr) for one week, and treatment with metformin (300 mg/kg/day) (HG-Met); a healthy group (Ctrl, n = 5) was included as control. The levels of glucose and biomarkers of renal and hepatic function were measured pre- and post-treatment. Hepatic Jnk1 expression and phosphorylation of JNK1 were evaluated by qRT-PCR and western blot, respectively.

RESULTS

Oral treatment with either Cγ or metformin reduced serum glucose level to 86.30 and 74.80 mg/dL, respectively (p ˂ 0.05), from the basal levels. Jnk1 expression was 0.65- and 0.54-fold lower (p ˂ 0.05) in the HG-Lr and HG-Met groups, respectively, than in HG-Ctrl. Treatment with Cγ decreased JNK1 phosphorylation. However, Cγ did not change the levels of kidney and liver biomarkers.

DISCUSSION AND CONCLUSIONS

Treatment with Cγ from L. rotundiflorus inhibited Jnk1 expression, in vivo, suggesting JNK1 as a potential therapeutic target in diabetes and revealing one mechanism underlying the hypoglycaemic effect of lupine Cγ. Nevertheless, further studies are required.

The Anti-hyperglycemic and Anti-hyperlipidemic Effects of Trigonella foenum-graecum L. Seeds on Fructose-induced Diabetic Wistar Rats

Trigonella foenum-graecum L. (fenugreek) seeds are widely used in the preparation of various meals and in traditional health care to treat various disorders and diseases, especially Diabetes mellitus. This study was conducted to investigate the antihyperglycemic and antihyperlipidemic effects of the fenugreek seed extract on fructose-induced diabetic wistar rats. Indeed, 5 groups of rats were formed; the first and second groups were composed of normal rats treated with distilled water and fenugreek seed extract, respectively. The third, fourth, and fifth groups composed of diabetic rats were administered distilled water, 500 mg/kg of fenugreek seed extract, and 25 µg/kg. bw of a standard antidiabetic drug consecutively for 28 days. The repeated ingestion of fenugreek seed generated a significant rise (p < 0.05) of food and water consumption in diabetic rats as compared to the rats treated with distilled water. Furthermore, fenugreek seed extract caused a remarkable elevation of the body weights of diabetic rats in comparison with other groups. Additionally, chronic treatment of rats with fenugreek seed extract improved fasting blood sugar, total cholesterol and triglycerides levels in diabetic rats. Fenugreek seed extract has significant anti-diabetic activity by reducing the fasting blood sugar and ameliorating the lipid parameters of diabetic rats. However, more studies are required to isolate the phytochemical constituents that possess these activities and elucidate their mechanisms of action.