Antihyperglycaemic and antiperoxidative effect of Helicteres isora L. bark extracts in streptozotocin-induced diabetic rats

Vitexin restores pancreatic β-cell function and insulin signaling through Nrf2 and NF-κB signaling pathways

Chronic hyperglycemia induces pancreatic β-cell dysfunction through several cell signaling pathways. The β-cell loss by apoptosis appears to play a crucial role in the onset and progression of diabetes. This study was aimed to investigate the role of vitexin against high glucose-induced β-cells apoptosis and the underlying mechanisms involved therein. INS-1 cells were pretreated with vitexin (20 and 40 μM) followed by high glucose (33 mM) exposure and the cytotoxicity was assessed by MTT. The effect of vitexin on nuclear factor erythroid 2-related factor 2 (Nrf2) and NF-kB signaling molecules have been studied. Vitexin-mediated stimulation of Nrf2 was assessed. Vitexin protected the cells against high glucose toxicity in a concentration-dependent manner. Vitexin improved insulin signaling as analyzed by the levels of functional proteins in the insulin pathways, viz., insulin receptor (IR), insulin receptor substrate (IRS)-1 and IRS-2, glucose transporter -2, and glucose-stimulated insulin secretion. Vitexin improved the high glucose-induced nuclear transcription factor system by suppressing Rel A, Rel B, P50/p105, and IκB expression resulting in decreased cell apoptosis, further confirmed by the reduction in the percentage of Annexin-V positive cells. Our data suggest that vitexin improves insulin secretion by activating key proteins, including NF-κB and Nrf2 in β-cells regulating apoptosis.

Efficacy and Mechanisms of Flavonoids against the Emerging Opportunistic Nontuberculous Mycobacteria

Nontuberculous mycobacteria (NTM) are the causative agent of severe chronic pulmonary diseases and is accountable for post-traumatic wound infections, lymphadenitis, endometritis, cutaneous, eye infections and disseminated diseases. These infections are extremely challenging to treat due to multidrug resistance, which encompasses the classical and existing antituberculosis agents. Hence, current studies are aimed to appraise the antimycobacterial activity of flavonoids against NTM, their capacity to synergize with pharmacological agents and their ability to block virulence. Flavonoids have potential antimycobacterial effects at minor quantities by themselves or in synergistic combinations. A cocktail of flavonoids used with existing antimycobacterial agents is a strategy to lessen side effects. The present review focuses on recent studies on naturally occurring flavonoids and their antimycobacterial effects, underlying mechanisms and synergistic effects in a cocktail with traditional agents.

Anti-Diabetic Effects and Mechanisms of Dietary Polysaccharides

Diabetes mellitus is a multifactorial, heterogeneous metabolic disorder, causing various health complications and economic issues, which apparently impacts the human's life. Currently, commercial diabetic drugs are clinically managed for diabetic treatment that has definite side effects. Dietary polysaccharides mainly derive from natural sources, including medicinal plants, grains, fruits, vegetables, edible mushroom, and medicinal foods, and possess anti-diabetic potential. Hence, this review summarizes the effects of dietary polysaccharides on diabetes and underlying molecular mechanisms related to inflammatory factors, oxidative stress, and diabetes in various animal models. The analysis of literature and appropriate data on anti-diabetic polysaccharide from electronic databases was conducted. In vivo and in vitro trials have revealed that treatment of these polysaccharides has hypoglycemic, hypolipidemic, antioxidant, and anti-inflammatory effects, which enhance pancreatic β-cell mass and alleviates β-cell dysfunction. It enhances insulin signaling pathways through insulin receptors and activates the PI3K/Akt pathway, and eventually modulates ERK/JNK/MAPK pathway. In conclusion, dietary polysaccharides can effectively ameliorate hyperglycemia, hyperlipidemia, low-grade inflammation, and oxidative stress in type 2 diabetes mellitus (T2DM), and, thus, consumption of polysaccharides can be a valuable choice for diabetic control.

Antidiabetic effect of S-allylcysteine: effect on thyroid hormone and circulatory antioxidant system in experimental diabetic rats

OBJECTIVE

It is considered that diabetes mellitus and thyroid disease are the two common endocrine disorders and also suggested that insulin and thyroid hormones influence each other actions. The present study was designed to investigate the effect of the administration of S-allylcysteine (SAC), a sulfur containing amino acid derived from garlic on blood glucose, insulin, HbA1C, total protein, albumin, Thyroid hormone (T3, T4), TSH, TBARS and circulatory antioxidant levels (SOD, CAT, GSH and GPx) in STZ-induced diabetic rats.

METHODS

SAC was administered orally for 45 days to control and STZ induced diabetic rats. The effects of SAC on glucose, plasma insulin, HbA1C, total protein, albumin, Thyroid hormone, TSH and circulatory antioxidant levels were studied.

RESULTS

The levels of glucose, TBARS, hydroperoxide and HbA1C were increased significantly whereas the levels of plasma insulin, reduced glutathione, superoxide dismutase, catalase, GSH, GPx, total protein, albumin, Thyroid hormone and TSH were decreased in STZ induced diabetic rats. Administration of SAC to diabetic rats showed a decrease in plasma glucose, TBARS, hydroperoxide and HbA1C. In addition, the levels of plasma insulin, SOD, CAT, GPx, GSH, total protein, albumin, Thyroid hormone and TSH were increased in SAC treated diabetic rats. The effect of SAC was compared with gliclazide, a well-known antioxidant and antihyperglycemic drug.

CONCLUSION

From these findings, it is indicated that SAC might be acting through activation in the synthesis and/or secretion of circulating thyroid hormones which in turn stimulate the synthesis of insulin.

Effects of training and nitric oxide on diabetic nephropathy progression in type I diabetic rats

The aim of the paper is to assess nitric oxide (NO) production during aerobic training and its role on the progression of diabetic nephropathy in rats. Induction of diabetes mellitus (DM) was achieved in adult male Wistar rats with streptozotocin. Half of the animals underwent training on a treadmill and the others (sedentary) stayed on a turned-off treadmill for the same period according to the following groups: sedentary control (CTL + SE); training control (CTL + EX); sedentary diabetic (DM + SE); and training diabetic (DM + EX) (n = 9 for all groups). The training on treadmill was carried out at a work rate of 16 m/min, 60 min/d, 5 d/week for eight weeks. Before and after the exercises, rats were placed in individual metabolic cages with standard chow and water ad libitum, for 24-h urine collection, followed by three hours' fasting blood sample withdrawal from the retro-orbital plexus, under anesthesia. Diabetic animals showed reduction of body weight, creatinine and urea depurations and NO excretion, increased blood glucose concentrations, albuminuria and thiobarbituric acid reactive substance (TBARS) excretion, when compared with the respective controls. All these alterations induced by DM were attenuated in the DM + EX versus DM + SE group. Analysis of insulin concentrations at the end of the protocol showed no significant change between the DM + SE and DM + EX groups. In conclusion, our data show that a routine physical exercise resulted in a better control of glycemia with an increased NO bioavailability and oxidative stress control, associated with an amelioration of renal function. We suggest aerobic training and the control of oxidative and nitrosative stress as useful non-pharmacological tools to delay the progression of diabetic nephropathy.

Attenuation of Helicteres isora L. bark extracts on streptozotocin-induced alterations in glycogen and carbohydrate metabolism in albino rats

The present study was undertaken to assess the effect of Helicteres isora L. on four important enzymes of carbohydrate metabolism (glucokinase [GK], hexokinase [HK] phosphofructokinase [PFK] and fructose-1, 6-bisphosphatase [FBP]) along with glycogen content of insulin-dependent (skeletal muscle and liver) and insulin-independent tissues (kidneys and brain) in streptozotocin (STZ; 60 mg/kg)-induced model of diabetes for 30 days. Administration of bark extracts (100, 200 mg/kg) for 30 days led to decrease in plasma glucose levels by approximately 9.60% and 22.04% and 19.18% and 33.93% on 15th and 30th day, respectively, of the experiment. Liver and two-kidney weight expressed as percentage of body weight significantly increased in diabetics (P < 0.05) versus normal controls. Renal glycogen content increased by 10 folds while hepatic and skeletal muscle glycogen content decreased by 75% and 68% in diabetic controls versus controls. H. isora did not affect glycogen content in any tissue. The decreased activities of PFK, GK, FBP and HK in diabetic controls were 40%, 50%, 50% and 60% and bark extract of H. isora partially corrected this alteration. The efficacy of the bark extract was comparable with Tolbutamide, a well-known hypoglycemic drug.

Hypolipidaemic activity of Helicteres isora L. bark extracts in streptozotocin induced diabetic rats

In this study, the hypolipidaemic effect of an aqueous extract of the bark of Helicteres isora was investigated in streptozotocin (STZ)-induced diabetic rats. Administration of the bark extract of Helicteres isora (100 and 200 mg/kgb.w.) for 21 days resulted in significant reduction in serum and tissue cholesterol, phospholipids, free fatty acids and triglycerides in STZ diabetic rats. In addition to that, significant (p<0.05) decrease in high-density lipoprotein (HDL) whereas significant increase (p<0.05) low-density lipoprotein (LDL) and very low-density lipoprotein (VLDL) were observed in STZ diabetic rats, which were normalized after 21 days of bark extract treatment. The bark extract at a dose of 200 mg/kgb.w. showed much significant hypolipidaemic effect than at the dose of 100 mg/kgb.w.