Sarita Gupta

Glucose lowering effect of aqueous extract of Enicostemma littorale Blume in diabetes: a possible mechanism of action.

Diabetes mellitus is a chronic metabolic disorder characterized by hyperglycemia. Enicostemma littorale Blume is a small herb and recently we have reported its blood glucose lowering potential in alloxan induced diabetic rats. A single dose of aqueous extract of E. littorale (15 g dry plant equivalent extract per kg) had shown significant increase in the serum insulin levels in alloxan-induced diabetic rats at 8 h. The insulinotropic action of aqueous extract of E. littorale was further investigated using rat pancreatic islets. Extract has the potential to enhance glucose-induced insulin release at 11.1 mM glucose from isolated rat pancreatic islets and was partially able to reverse the effect of diazoxide (0.25 mM). Incubation with Ca(2+) chelator (EGTA) and Ca(2+) channel blocker (nimodipine) did not affect the glucose-induced insulin release augmented by the extract. Above results suggest the glucose lowering effect of aqueous extract of E. littorale to be associated with potentiation of glucose-induced insulin release through K(+)-ATP channel dependent pathway but did not require Ca(2+) influx.

Dose dependent hypoglycemic effect of aqueous extract of Enicostemma littorale Blume in alloxan induced diabetic rats

Previous studies in our lab had confirmed the blood glucose lowering effect of E. littorale Blume in alloxan induced diabetic rats with no change in normoglycemic control rats. Present paper deals with dose dependent (0.5, 1.0, 1.5, 2.5, 3.5 g dry plant equivalent extract/100 g body wt., p.o.) blood glucose lowering effect of aqueous extract of E. littorale Blume in alloxan induced diabetic rats. The effective dose was found to be 1.5 g dry plant equivalent extract/100 g body wt.. The above dose caused significant decrease in glycosylated haemoglobin, liver glucose-6-phosphatase activity and significant increase in serum insulin levels of the diabetic rats. No significant changes were observed in the toxicity parameters of extract treated diabetic rats as compared to diabetic control rats. The above results suggest that E. littorale is a potent antidiabetic agent without any toxic effect at this particular dose (1.5 g dry plant equivalent extract/100 g body wt.).

Effects of combined exposure to lead and cadmium on the hypothalamic-pituitary axis function in proestrous rats.

The effects of lead and cadmium on the hypothalamic-pituitary axis were studied in proestrous rats. Adult female rats were treated intraperitonially with either lead acetate and cadmium acetate alone or in combination at a dose of 0.05 mg/kg daily for 15 days. Serotonin (5-HT) and norepinephrine (NE) levels decreased in individually and combined metal treated groups whereas dopamine (DA) levels were decreased only in the cadmium-exposed group. The pituitary levels of luteinizing hormone (LH) and follicle stimulating hormone (FSH) were decreased significantly in cadmium and combined treatment groups. In contrast, lead exposure failed to cause any change in serum LH and FSH levels, whereas cadmium and combined treatments showed significant decrease in serum LH and FSH levels as compared with control. The accumulation of both metals increased in the hypothalamus and pituitary after treatment. These data suggest that the metal accumulation disrupts the regulatory mechanisms of the hypothalamic-pituitary axis where the effects produced by the combined treatment of metals are not additive.

Antioxidant enzyme activity and lipid peroxidation in liver of female rats co-exposed to lead and cadmium: Effects of vitamin E and Mn2+

The oxidative status of liver of female rats exposed to lead acetate and cadmium acetate either alone or in combination at a dose of 0.05 mg/kg body wt intraperitoneally for 15 days was studied. After the administration of lead alone, the activity of superoxide dismutase (SOD) decreased in liver, whereas no changes were observed in catalase (CAT) activity, and glutathione (GSH) and thiobarbituric acid (TBARS) levels. Cadmium exposure and combined exposure to lead and cadmium led to decrease in GSH content and increased TBARS levels. Moreover, animals exposed to either cadmium alone or in combination with lead showed a decrease in SOD activity and an increase in CAT activity. The in vitro experiments showed that vitamin E failed to restore the antioxidant enzyme activities in metal treated postmitochondrial supernatant fraction of liver. But Mn2+ ions protected the mitochondria from lipid peroxidation and could completely restore Mn-superoxide dismutase (Mn-SOD) activity following metal intoxication. The results of this study indicate that despite the ability of lead and cadmium to induce oxidative stress the effect in liver is not intensified by combined exposure to both lead and cadmium. The observed changes in various oxidative stress parameters in the liver of rats co-exposed to lead and cadmium may result from an independent effect of lead and /cadmium and also from their interaction such as changes in metal accumulation and content of essential elements like Cu, Zn and Fe. These results suggest that when lead and cadmium are present together in similar concentrations, cadmium mediates major effects due to its more reactive nature.

Effect of lead and cadmium co-exposure on testicular steroid metabolism and antioxidant system of adult male rats.

The mechanism of testicular toxicity of lead (Pb) and cadmium (Cd) is poorly understood. Previous studies focused on single metal‐related changes in testicular toxicity. This study points towards the possible involvement of Pb‐ and Cd‐induced oxidative stress in the suppression of steroidogenesis. The oxidative status of testis of adult male rats exposed to Pb acetate and cadmium acetate either alone or in combination at a dose of 0.025 mg kg−1 body weight of metal intraperitoneally for 15 days was studied. Pb and Cd caused an increase in reactive oxygen species (ROS) by elevating testicular malondialdehydes (MDA) and decrease in activities of testicular antioxidant enzymes superoxide dismutase (SOD), catalase, glucose 6 phosphate dehydrogenase (G6PDH) and glutathione‐S‐transferase (GST) in mitochondrial and/or post‐mitochondrial fraction. Activities of steroidogenic enzymes 3β and 17β‐hydroxysteroid dehydrogenase also decreased significantly leading to altered testosterone production. Metal‐exposed groups showed significantly decreased testicular and epididymal sperm count. Epididymal sperm motility and viability was also decreased on Pb and Cd exposure. Cd exposure showed more toxic effect than lead exposure, while combined exposure demonstrated least toxicity. In vitro experiments showed that vitamin C restores steroidogenic enzyme activities, suggesting that Pb‐ and Cd‐induced ROS inhibits the testicular steroidogenesis.

Insulin resistance: an additional risk factor in the pathogenesis of cardiovascular disease in type 2 diabetes

Sedentary life style and high calorie dietary habits are prominent leading cause of metabolic syndrome in modern world. Obesity plays a central role in occurrence of various diseases like hyperinsulinemia, hyperglycemia and hyperlipidemia, which lead to insulin resistance and metabolic derangements like cardiovascular diseases (CVDs) mediated by oxidative stress. The mortality rate due to CVDs is on the rise in developing countries. Insulin resistance (IR) leads to micro or macro angiopathy, peripheral arterial dysfunction, hampered blood flow, hypertension, as well as the cardiomyocyte and the endothelial cell dysfunctions, thus increasing risk factors for coronary artery blockage, stroke and heart failure suggesting that there is a strong association between IR and CVDs. The plausible linkages between these two pathophysiological conditions are altered levels of insulin signaling proteins such as IR-β, IRS-1, PI3K, Akt, Glut4 and PGC-1α that hamper insulin-mediated glucose uptake as well as other functions of insulin in the cardiomyocytes and the endothelial cells of the heart. Reduced AMPK, PFK-2 and elevated levels of NADP(H)-dependent oxidases produced by activated M1 macrophages of the adipose tissue and elevated levels of circulating angiotensin are also cause of CVD in diabetes mellitus condition. Insulin sensitizers, angiotensin blockers, superoxide scavengers are used as therapeutics in the amelioration of CVD. It evidently becomes important to unravel the mechanisms of the association between IR and CVDs in order to formulate novel efficient drugs to treat patients suffering from insulin resistance-mediated cardiovascular diseases. The possible associations between insulin resistance and cardiovascular diseases are reviewed here.

Transplantation of islet-like cell clusters derived from human dental pulp stem cells restores normoglycemia in diabetic mice.

BACKGROUND AIMS The success of islet transplantation for diabetes depends on the availability of an adequate number of allogeneic or autologous islets. Postnatal stem cells are now considered for the generation of physiologically competent, insulin-producing cells. Our group showed earlier that it is possible to generate functional islets from human dental pulp stem cells by using a serum-free cocktail in a three-step protocol. METHODS We compared the yield of generated islet-like cell clusters (ICCs) from stem cells from pulps of human exfoliated deciduous teeth (SHED) and dental pulp stem cells from permanent teeth (DPSCs). ICCs derived from SHED were packed in immuno-isolatory biocompatible macro-capsules and transplanted into streptozotocin (STZ)-induced diabetic mice. Non-diabetic and diabetic controls were transplanted with macro-capsules with or without islets. RESULTS SHED were superior to DPSCs. STZ diabetic mice alone and mice transplanted with empty macro-capsules exhibited hyperglycemia throughout the experiment, whereas mice transplanted with macro-capsules containing ICCs were restored to normoglycemia within 3-4 weeks, which persisted for >60 days. CONCLUSIONS Our results demonstrate for the first time that ICCs derived from SHED reverse STZ diabetes in mice without immunosuppression and offer an autologous and non-controversial source of human tissue that could be used for stem cell therapy in diabetes.

Biochemical effects of gestational coexposure to lead and cadmium on reproductive performance, placenta, and ovary.

Adult virgin 4‐day cycling synchronized Charles foster females were treated subcutaneously (0.05 mg/kg body wt/day) with sodium acetate (control), lead acetate or cadmium acetate alone, or both during gestational period, with pretreatment of 5 days prior to mating. There were no alterations in reproductive performance in all metal‐treated groups. Implantation enzymes, cathepsin‐D and alkaline phosphatase, activity were altered, but no change in the reproductive performance was observed. The key steroidogenic enzymes of ovary and placenta (3β‐HSD and 17β‐HSD), along with gonadal steroids, were affected the most in cadmium and combined treated animals whereas lead‐treated animals showed a minimum change compared to the control group. Maximum displacement of zinc bound to metallothionein was more in cadmium and combined treated rats when compared to other metal‐treated groups. Biomolecules such as glycogen, protein, RNA, DNA, and protein content were affected in all metal‐treated groups, whereas cadmium‐treated animals showed greater effect. General parameters of toxicity such as alkaline phosphatase, serum glutamate pyruvate transaminase, and creatinine were altered but were within the normal range. Biochemical effects are correlated with metals accumulated in blood, reproductive tissue such as placenta and ovary.

Antidiabetic Efficacy of Enicostemma littorale Methanol Extract in Alloxan-Induced Diabetic Rats

The glucose lowering and antioxidant effect of a methanol extract of Enicostemma littorale Blume was evaluated in alloxan-induced diabetic rats. Administration of methanol extract (2.5 g/kg body weight/day) to diabetic rats for 20 days reduced blood glucose levels from 466.50 ± 37.07 to 237.20 ± 28.22 (P < 0.01). E. littorale also increased the serum insulin levels of diabetic rats and improved the antioxidant status of diabetic rats. Extract treatment to the diabetic rats significantly increased reduced glutathione levels and decreased erythrocyte catalase activity and lipid peroxidation. These results support the use of E. littorale as an antidiabetic agent by traditional healers in rural pockets of Gujarat.

Embryonic fibroblasts represent a connecting link between mesenchymal and embryonic stem cells

It is well established that fibroblasts and mesenchymal stem cells (MSC) share several characteristics with subtle differences. However, no study highlighting the versatility of fibroblasts beyond their multipotentiality has been reported so far. Mouse embryonic fibroblasts (MEFs) are widely used as feeder layers to support the growth of embryonic stem cells (ESC). We hypothesized that MEF may retain ES‐like features in concurrence to their developmental hierarchy in addition to their multipotent nature. Hence, we performed a comparative assessment of MEF and ESC to determine their ability to differentiate into cell types other than mesoderm as well as capacity to form teratoma using routine in vitro and in vivo techniques. MEF were derived by trypsin/ EDTA (ethylenediaminetetraacetic acid) digestion from E13.5 embryos after removing heads and viscera following plastic adherence. MEFs robustly proliferated in culture until passage 15 and formed aggregates by hanging drop method. Flow cytometry, reverse transcription–polymerase chain reaction (RT–PCR) and immunocytochemistry revealed the presence of key MSC markers such as CD90, CD73, Sca‐1, CD44, CD29, Vimentin and absence of CD45. Additionally, they expressed SSEA‐1, Oct‐4, Nanog, Sox‐2 and ABCG2 as pluripotency markers; Nestin, β‐III tubulin, Otx‐2 (ectoderm); MEF‐2, Mesp2, GATA‐2 (mesoderm) and GATA‐4, α‐amylase, PDX‐1 (endoderm) as tri‐lineage markers. Furthermore, MEFs formed representative tissues from all three germ layers upon transplantation into Balb/c mice. These unique abilities of MEF to exhibit pluripotency, in addition to fibroblast characteristics and their ready availability with less ethical concerns and low maintenance requirements make them an attractive model for further exploration as a possible tool for regenerative medicine.