THE EFFECTS OF Syzygium aromaticum-DERIVED TRITERPENES ON GASTROINTESTINAL GHRELIN EXPRESSION IN STREPTOZOTOCIN-INDUCED DIABETIC RATS

Syzygium cumini ameliorates high fat diet induced glucose intolerance, insulin resistance, weight gain, hepatic injury and nephrotoxicity through modulation of PTP1B and PPARγ signaling

Metabolic disorders are majorly associated with insulin resistance and an impaired glucose tolerance. Since, many of the currently available drugs exhibit adverse effects and are resistant to therapies, natural products are a promising alternate in the alleviation of complex metabolic disorders. In the current study, Syzygium cumini methanolic extract (SCE) was investigated for its anti-diabetic and anti-adipogenic potential using C57BL/6 mice fed on high fat diet (HFD). The HFD fed obese mice were treated with 200 mg/kg SCE and compared with positive controls Metformin, Pioglitazone and Sodium Orthovanadate. The biometabolites in SCE were characterized using Fourier transform infrared and gas chromatography and mass spectroscopy. A reduction in blood glucose levels with improved insulin sensitivity and glucose tolerance was observed in SCE-treated HFD obese mice. Histopathological and biochemical investigations showed a reduction in hepatic injury and nephrotoxicity in SCE-administered HFD mice. Results showed inhibition of PTP1B and an upregulation of IRS1 and PKB-mediated signaling in skeletal muscle. A significant decrease in lipid markers such as TC, TG, LDL-c and VLDL-c levels were observed with increased HDL-c in SCE-treated HFD mice. A significant decrease in weight and adiposity was observed in SCE-administered HFD mice in comparison to controls. This decrease could be due to the partial agonism of PPARγ and an increased expression of adiponectin, an insulin sensitizer. Hence, the dual-modulatory effect of SCE, partly due to the presence of 26% Pyrogallol, could be useful in the management of diabetes and its associated maladies.

Evaluation of the effects of bredemolic acid on selected markers of glucose homeostasis in diet-induced prediabetic rats

CONTEXT

Pentacyclic triterpenes (such as maslinic acid) are natural anti-diabetic agents that ameliorate glucose metabolism in diet-induced prediabetes. However, the effects of bredemolic acid (BA), maslinic acid isomer, is yet unknown in prediabetic (PD) conditions.

OBJECTIVES

To investigate the effects of BA on some glucose homeostasis parameters in high-fat high-carbohydrate (HFHC) diet-induced PD rats.

METHODS

Thirty-six (36) male rats (150-180 g) were divided into two groups, the normal diet (ND) non-prediabetic, NPD (n = 6) and the HFHC diet PD groups (n = 30). The PD animals were further sub-divided into five groups (n = 6) where they were treated with BA for 12 weeks while monitoring changes in blood glucose, caloric intake, and body weight.

RESULTS

Diet-induced prediabetes resulted in increased body weight, caloric intake, glycated haemoglobin, and glucose tolerance. BA treatment ameliorated glucose tolerance, lowered plasma insulin and increased expression of glucose transporter 4 (GLUT 4) in rats.

CONCLUSIONS

BA administration restored glucose homeostasis in diet-induced prediabetes regardless of diet intervention.

Anti-Diabetic Potential of Plant-Based Pentacyclic Triterpene Derivatives: Progress Made to Improve Efficacy and Bioavailability

Diabetes mellitus (DM) results from the inability of the pancreas to produce sufficient insulin or weakened cellular response to the insulin produced, which leads to hyperglycemia. Current treatments of DM focus on the use of oral hypoglycemic drugs such as acarbose, alpha-glucose inhibitors, sulphonylureas, thiazolidinediones, and biguanides to control blood glucose levels. However, these medications are known to have various side effects in addition to their bioavailability, efficacy, and safety concerns. These drawbacks have increased interest in the anti-diabetic potential of plant-derived bioactive compounds such as oleanolic and maslinic acids. Although their efficacy in ameliorating blood glucose levels has been reported in several studies, their bioavailability and efficacy remain of concern. The current review examines the anti-diabetic effects of oleanolic, maslinic, asiatic, ursolic, and corosolic acids and their derivatives, as well as the progress made thus far to enhance their bioavailability and efficacy. The literature for the current review was gathered from leading academic databases-including Google Scholar and PubMed-the key words listed below were used. The literature was searched as widely and comprehensively as possible without a defined range of dates.

Prophylactic and therapeutic roles of oleanolic acid and its derivatives in several diseases

Oleanolic acid (OA) and its derivatives are widely found in diverse plants and are naturally effective pentacyclic triterpenoid compounds with broad prophylactic and therapeutic roles in various diseases such as ulcerative colitis, multiple sclerosis, metabolic disorders, diabetes, hepatitis and different cancers. This review assembles and presents the latest in vivo reports on the impacts of OA and OA derivatives from various plant sources and the biological mechanisms of OA activities. Thus, this review presents sufficient data proposing that OA and its derivatives are potential alternative and complementary therapies for the treatment and management of several diseases.

Bredemolic Acid Ameliorates Selected Liver Function Biomarkers in a Diet-Induced Prediabetic Rat Model

BACKGROUND

Prediabetes is an intermediary hyperglycaemic state that precedes type 2 diabetes mellitus (T2DM) in which abnormal metabolism of glucose and lipids occurs in organs such as the liver. Evidence has shown that, about 70% of T2DM patients develop hepatic dysfunction which is found to begin during the prediabetic stage. Bredemolic acid, a pentacyclic triterpene, has been found to improve insulin sensitivity in diet-induced prediabetic rats. The effects of this compound on liver function, however, are unknown. This study was therefore designed to investigate the effects of BA on liver function in high fat-high carbohydrate (HFHC) diet-induced prediabetic rats.

METHODS

Thirty-six (36) male rats that weigh 150 g-180 g were divided into two groups, the non-prediabetic (n = 6) and the prediabetic groups (n = 6) and the prediabetic groups (n = 6) and the prediabetic groups (.

RESULTS

The induction of prediabetes resulted in increased release of liver enzymes (AST and ALT), increased liver glycogen and triglyceride, lipid peroxidation, and decreased sterol regulatory element-binding protein (SREBP1c) and antioxidant enzymes. However, the administration of BA decreased liver enzyme concentrations, decreased hepatic oxidative stress, and improved antioxidant enzymes such as SOD and GPx.

CONCLUSION

BA administration improved liver function in diet-induced prediabetic rats in the presence or absence of dietary intervention.

The Haematological Effects of Oleanolic Acid in Streptozotocin-Induced Diabetic Rats: Effects on Selected Markers

BACKGROUND

Sustained hyperglycaemia leads to the development of haematological alterations which, if left untreated, is associated with cardiovascular complications. Insulin is the mainstay drug in type 1 diabetes mellitus (T1D); however, the use of insulin is associated with haematological alterations that could further worsen cardiovascular complications. Therefore, the aim of the study was to investigate the haematological effects of oleanolic acid (OA) in streptozotocin- (STZ-) induced diabetic rats.

METHODS

The animals were separated into five groups; the nondiabetic group (ND), the diabetic control group (DC), and the treatment groups of insulin (170 μg/kg, s.c), metformin (500 mg/kg, p.o), and OA (80 mg/kg, p.o). OA was administered orally twice a day. Thereafter, the animals were sacrificed, and blood and tissues were collected for haematological, hormonal, and oxidative status analysis.

RESULTS

Untreated diabetic rats exhibited hyperglycaemia, elevated glycated haemoglobin (HbA1c), oxidative stress, and a reduced erythropoietin (EPO) concentration when compared to ND rats. However, administration of OA attenuated hyperglycaemia, HbA1c, and EPO concentrations compared to DC rats. The reduction of blood glucose concentration, HbA1c, and improved EPO concentrations was further associated with a notable increase in red blood cell (RBC) count and other RBC indices. We also observed an increase in the antioxidant status of the RBCs with a concomitant decrease in oxidative stress.

CONCLUSION

These findings suggest that OA improves diabetes-induced haematological changes caused by hyperglycaemia and attenuates the progression of cardiovascular complications in DM individuals.

The protective effect of neonatal oral administration of oleanolic acid against the subsequent development of fructose-induced metabolic dysfunction in male and female rats

BACKGROUND

Consumption of fructose-rich diets has been implicated in the increasing global prevalence of metabolic syndrome (MetS). Interventions during periods of early ontogenic developmental plasticity can cause epigenetic changes which program metabolism for positive or negative health benefits later in life. The phytochemical oleanolic acid (OA) possesses anti-diabetic and anti-obesity effects. We investigated the potential protective effects of neonatal administration of OA on the subsequent development of high fructose diet-induced metabolic dysfunction in rats.

METHOD

Male and female (N = 112) suckling rats were randomly assigned to four groups and administered orally: distilled water (DW), oleanolic acid (OA; 60 mg/kg), high-fructose solution (HF; 20% w/v) or OA + HF for 7 days. The rats were weaned onto normal commercial rat chow up to day 55. From day 56, half of the rats in each treatment group were continued on plain water and the rest on a high fructose solution as drinking fluid for 8 weeks. On day 110, the rats were subjected to an oral glucose tolerance test and then euthanased on day 112. Tissue and blood samples were collected to determine the effects of the treatments on visceral fat pad mass, fasting plasma levels of cholesterol, insulin, glucose, triglycerides, insulin resistance (HOMA-IR) and glucose tolerance.

RESULTS

Rats which consumed fructose as neonates and then later as adults (HF + F) and those which consumed fructose only in adulthood (DW + F) had significant increases in terminal body mass (females only), visceral fat mass (males and females), serum triglycerides (females only), epididymal fat (males only), fasting plasma glucose (males and females), impaired glucose metabolism (females only), β-cell dysfunction and insulin resistance (males and females) compared to the other treatment groups (P < 0.05). There were no differences in fasting serum cholesterol levels across all treatment groups in both male and female rats (P > 0.05).

CONCLUSION

We conclude that neonatal oral administration of OA during the critical window of developmental plasticity protected against the development of health outcomes associated with fructose-induced metabolic disorders in the rats.

The Effects of Plant-Derived Oleanolic Acid on Selected Parameters of Glucose Homeostasis in a Diet-Induced Pre-Diabetic Rat Model

Prolonged exposure to high energy diets has been implicated in the development of pre-diabetes, a long-lasting condition that precedes type 2 diabetes mellitus (T2DM). A combination of pharmacological and dietary interventions is used to prevent the progression of pre-diabetes to T2DM. However, poor patient compliance leads to negligence of the dietary intervention and thus reduced drug efficiency. Oleanolic acid (OA) has been reported to possess anti-diabetic effects in type 1 diabetic rats. However, the effects of this compound on pre-diabetes have not yet been established. Consequently, this study sought to evaluate the effects OA on a diet-induced pre-diabetes rat model. Pre-diabetic male Sprague Dawley rats were treated with OA in both the presence and absence of dietary intervention for a period of 12 weeks. The administration of OA with and without dietary intervention resulted in significantly improved glucose homeostasis through reduced caloric intake, body weights, plasma ghrelin concentration and glycated haemoglobin by comparison to the pre-diabetic control. These results suggest that OA may be used to manage pre-diabetes as it was able to restore glucose homeostasis and prevented the progression to overt type 2 diabetes.