miércoles, 30 de marzo de 2016

Las hojas de Stevia rebaudiana ayudan mucho a luchar contra la diabetes

 Puedes verlo en español dándole al traductor de esta página

Treatment of diabetes with sulfonylurea drugs (glibenclamide) causes hypoglycemia followed by greater reduction in body weight, which are the most worrisome effects of these drugs. Stevia extract was found to antagonize the necrotic action of alloxan and thus had a re-vitalizing effect on β-cells of pancreas.

Stevia rebaudiana (Bertoni) is one of the 950 genera of the Compositae (Asteraceae). The plant was rediscovered by Dr. Moises Santiago Bertoni in 1887. The plant was used extensively by Gaurani Indians for more than 1500 years. [4] Stevia has a long history of medicinal use in Paraguay and Brazil, and while many of the therapeutic applications of Stevia are anecdotal, they must be considered in that they have spanned generations. There are now known to be more than 150 Stevia species but this is the only one with significant sweetening properties; other species do contain other biochemicals of interest. Leaves contain approximately 4–15% of steviosides, which are intensely sweet compounds (150–300 times sweeter than sugar). The leaves have been traditionally used for hundreds of years in Paraguay and Brazil to sweeten local teas, medicines and as a “sweet treat”. [5]
S. rebaudiana possesses various activities like antimicrobial, [6] antifungal, [7] hepatoprotective, [8] hypoglycemic (water extract), [9] antitumor, [6] antirotavirus, [10] anti-HIV, [11] anti-hypertension, [12,13] antiviral activity, [14] etc. Other folk applications of Stevia and stevioside (primarily in Latin America and the Orient) include the following: stimulate alertness and counter fatigue; facilitate digestion and gastrointestinal functions; regulate blood glucose levels (BGLs); nourish the liver, pancreas and spleen; help the body sustain a feeling of vitality and well-being and external application for blemishes. Some Stevia and stevioside users report a decrease in desire for sweets and fatty foods. Additionally, some users have reported that drinking Stevia tea or Stevia enhanced teas helped to reduce their desire for tobacco and alcoholic beverages. [15] Stevia and stevioside have been shown in studies to inhibit the growth and reproduction of some bacteria that are responsible for tooth decay. [15,16]
Studies on the comparative effects of leaves and stevioside on glycemia and hepatic gluconeogenesis have already been reported. [17] Hypoglycemic effect [18] of stevioside has also been studied, together with protective effects of stevioside against the toxic actions of alloxan. [19] Chen et al.[18] suggested that stevioside was able to regulate BGLs by enhancing not only insulin secretion, but also insulin utilization in insulin-deficient rats; the latter was due to decreased PEPCK gene expression in rat liver by stevioside's action of slowing down gluconeogenesis.

Results and Discussion

Alloxan, a β-cytotoxin, destroys β-cells of islets of Langerhans of pancreas, resulting in a decrease in endogenous insulin secretion and paves the way for the decreased utilization of glucose by the tissues. [2931] In vitro studies have shown that alloxan is selectively toxic to pancreatic β-cells, leading to the induction of cell necrosis. [32,33] The cytotoxic action of alloxan is mediated by reactive oxygen species, with a simultaneous massive increase in cystolic calcium concentration, leading to a rapid destruction of β-cells. [34] Decreased utilization of glucose by the tissues results in the elevation of BGL.
Expression of elevated fasting BGL confirms induction of diabetes in alloxan-induced experimental rats. The experiment focused on exploring the competence of medium-polar (benzene:acetone, 1:1, v/v) extract from the leaves of S. rebaudiana for medication of diabetes against positive control reference drug glibenclamide. The difference in the initial and final fasting BGLs of different groups in long-term (10-day) studies exposed a significant elevation in BGL in diabetic controls as compared with that of normal control, extract treated and glibenclamide treated rats. Treatment of BGL with Stevia extract indicates the effectiveness of the extract in experimental diabetic animals.
Medium-polar extract from leaves of S. rebaudiana, when administered orally (200 and 400 mg/kg) for 10 days, produced a significant (P < 0.01) dose-dependent reduction in BGL [Table 2] as well as in the body weight [Table 3], although body weight was regained by rats treated with both glibenclamide and Stevia extract. Stevia extract exhibited a significant control of BGLs in diabetic rats, together with lowest decrease in the body weight, as compared with glibenclamide. Alternative exogenous treatments to diabetes include dosage of insulin and sulfonylurea drugs (e.g., glibenclamide), which cause hypoglycemia followed by greater reduction in body weight are the most worrisome effects. Treatment with Stevia extract did not cause hypoglycemia as well as significant decrease in body weight of diabetic rats. Stevia extract was found to revitalize β-cells of pancreas, antagonizing β-necrotic action of alloxan.
Excessive hepatic glycogenolysis and gluconeogenesis associated with decreased utilization of glucose by tissue is the fundamental mechanism underlying hyperglycemia in the diabetic state. [35] Aberration of liver glycogen synthesis or glycogenolysis in diabetes may be due to lack of or resistance to insulin, which is essential to activate glycogen synthase system. The significant increase of liver glycogen level in Stevia extract-treated groups may be due to reactivation of the glycogen synthase system by improving insulin secretion. Diabetes is associated with weight loss. [36] The reversal of weight loss in extract-treated diabetic group indicates that the restorative effect of the extract may be due to the reversal of gluconeogenesis and glycogenolysis.
Experimental results also reflect that the Stevia extract is capable of reducing the oxidative state associated with diabetes. Alloxan produces diabetes by liberating oxygen-free radicals which cause lipid peroxide-mediated pancreatic injury. [37] The extract may scavenge free radicals and facilitate reconstruction of pancreatic cells to release more insulin and ultimately produces an antidiabetic effect.

Effects on blood glucose level

Administration of benzene:acetone extract (200 and 400 mg/kg) produced a significant (P < 0.01) dose-dependant reduction in BGL of alloxan-induced diabetic rats. Alloxanized rats of group II (negative control) suffered from hyperglycemia as they did not receive any drug, whereas alloxanized rats of group III (positive control) treated with the reference antidiabetic drug glibenclamide showed significant reduction in BGL to the required standard blood glucose level on the 7th day and the levels were continuously maintained up to 10th day. Rats of group IV treated with Stevia extract (200 mg/kg) showed nearly normal BGL (99.00 ± 7.98 mg/dL) value on the 10 th day, whereas group V rats treated with Stevia extract (400 mg/kg) also showed decrease in blood glucose level to nearly normal (93.69 ± 9.33 mg/dL) value, which is very close to 0 day BGL of group V. Table 2 shows that positive control glibenclamide treated rats attained normalized BGL on the 7th day of treatment, whereas Stevia extract treated rats attained nearby normal BGL on the 10th day.

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