Increase of insulin sensitivity by stevioside in fructose-rich chow-fed rats.

The intake of dietary fructose has undergone a marked increase around the world, especially the developed countries, in recent times. Stevioside, a glycoside contained in the leaves of Stevia rebaudiana Bertoni (Compositae), was used to screen the effect induced by a diet containing 60% fructose on insulin resistance in rats. Single oral administration of stevioside for 90 min decreased plasma glucose concentrations in a dose-dependent manner in rats receiving fructose-rich chow for four weeks. In addition, insulin action on glucose disposal rate was measured using the glucose-insulin index, the product of the areas under the curve of glucose, and insulin during the intraperitoneal glucose tolerance test. Oral administration of stevioside (5.0 mg/kg) in rats given four weeks of fructose-rich chow for 90 min reversed the value of glucose-insulin index, indicating that stevioside has the ability to improve insulin sensitivity in this insulin-resistant animal model. Time for the loss of plasma glucose lowering response to tolbutamide (10.0 mg/kg, i. p.) in fructose-rich chow fed rats was also markedly delayed by repeated stevioside treatment three times daily compared to the vehicle-treated group. The plasma glucose-lowering activity of tolbutamide was introduced to account for varying levels of endogenous insulin secretion, and is widely used as the indicator of insulin resistance development. Thus, it provided the supportive data that repeated oral administration of stevioside delayed the development of insulin resistance in rats on a high-fructose diet. Increased insulin sensitivity by stevioside administration was further identified using the plasma glucose-lowering action of exogenous insulin in streptozotocin-induced diabetic rats (STZ-diabetic rats). Oral administration of stevioside at 0.2 mg/kg three times daily into STZ-diabetic rats for ten days increased the response to exogenous insulin. Taken together, this demonstrated that oral administration of stevioside improves insulin sensitivity, and seems suitable as an adjuvant for diabetic patients and/or those that consume large amounts of fructose.     

Improvement of insulin resistance by panax ginseng in fructose-rich chow-fed rats.

In an attempt to probe a new target for handling insulin resistance, we used Panax ginseng root to screen the effect on insulin resistance induced by fructose-rich chow in rats. Insulin action on glucose disposal rate was measured using the glucose-insulin index, which is the product of the areas under the curve of glucose and insulin during the intraperitoneal glucose tolerance test. Oral administration of Panax ginseng root (125.0 mg/kg) into rats three times daily for three days after receiving fructose-rich chow for four weeks reversed the increased glucose-insulin index, indicating that Panax ginseng root has the ability to improve insulin sensitivity. In addition, the plasma glucose concentrations in rats repeatedly treated with Panax ginseng root were not elevated as markedly as those of the vehicle-treated group during the fructose-rich chow-feeding period. Also, the time in which the plasma glucose-lowering response to tolbutamide (10.0 mg/kg, i. p.) receded in fructose-rich chow fed rats was markedly delayed by repeated Panax ginseng root treatment compared to the vehicle-treated group. The plasma glucose-lowering activity of tolbutamide is believed to depend on the secretion of endogenous insulin, which is widely used as an indicator of insulin resistance development. Thus, it provided supportive data that oral administration of Panax ginseng root could delay the development of insulin resistance in rats. In conclusion, our results suggest that oral administration of Panax ginseng root improves insulin sensitivity and may be used as an adjuvant therapy for treating diabetic patients with insulin resistance.     

Effects of macro elements and nitrogen source on adventitious root growth and ginsenoside production in ginseng (Panax ginseng C. A. Meyer)

We investigated the effects on ginseng adventitious root growth and ginsenoside production when macro-element concentrations and nitrogen source were manipulated in the culture media. Biomass growth was greatest in the medium supplemented with 0.5-strength NH₄PO₃, whereas ginsenoside accumulation was highest (9.90 mg g^-1 DW) in the absence of NH₄PO₃. At levels of 1.0-strength KNO₃, root growth was maximum, but a 2.0 strength of KNO₃ led to the greatest ginsenoside content (9.85 mg g^-l). High concentrations of MgSO₄ were most favorable for both root growth and ginsenoside accumulation (up to 8.89 mg g^-1 DW). Root growth and ginsenoside content also increased in proportion to the concentration of CaCI₂ in the medium, with the greatest accumulation of ginsenoside (8.91 mg g^-1 DW) occurring at a 2.0 strength. The NH₄/NO₃ ^-- ratio also influenced adventitious root growth and ginsenoside production; both parameters were greater when the NO₃ ^- concentration was higher than that of NH₄ ⁺. Maximum root growth was achieved at an NH₄ ⁺/NO₃ ^- ratio of 7.19/18.50, while ginsenoside production was greatest (83.37 mg L^-1) when NO₃ ^- was used as the sole N source.     

Dammarane-type triterpene extracts of Panax notoginseng root ameliorates hyperglycemia and insulin sensitivity by enhancing glucose uptake in skeletal muscle

Skeletal muscle is an important organ for controlling the development of type 2 diabetes. We discovered Panax notoginseng roots as a candidate to improve hyperglycemia through in vitro muscle cells screening test. Saponins are considered as the active ingredients of ginseng. However, in the body, saponins are converted to dammarane-type triterpenes, which may account for the anti-hyperglycemic activity. We developed a method for producing a dammarane-type triterpene extract (DTE) from Panax notoginseng roots and investigated the extract’s potential anti-hyperglycemic activity. We found that DTE had stronger suppressive activity on blood glucose levels than the saponin extract (SE) did in KK-A^y mice. Additionally, DTE improved oral glucose tolerance, insulin sensitivity, glucose uptake, and Akt phosphorylation in skeletal muscle. These results suggest that DTE is a promising agent for controlling hyperglycemia by enhancing glucose uptake in skeletal muscle.     

人参毛状根及愈伤组织中ATP动态变化的生物发光法测定

人参 (ＰａｎａｘｇｉｎｓｅｎｇＣ .Ａ .Ｍｅｙ)系五加科 (Ａｒａｌｉａｃｅａｅ)人参属 (ＰａｎａｘＬ .)植物 ,是一种贵重药材。随着植物生物技术的发展 ,Ｒｉ质粒介导产生的植物毛状根培养是植物基因工程和细胞工程相结合的一项新技术[1 ,2 ] 。人参毛状根系统的建立是对人参资源开发和利用的新形式。ＡＴＰ是生物体的能量“通货”及重要的代谢调节物质 ,对生命活动至关重要。随着生物有机体的生长发育 ,ＡＴＰ含量也呈一定的变化趋势 ,并反映出生物体的生长代谢情况。由于ＡＴＰ测定操作复杂 ,仪器试剂昂贵[3 ] ,不便于进行动态监测。…     

Improvement of ginsenoside production by jasmonic acid and some other elicitors in hairy root culture of ginseng (Panax ginseng C. A. Meyer)

Summary Hairy root cultures of Panax ginseng, established after the infection of root sections with Agrobacterium rhizogenes KCTC 2703, were cultured in phytohormone-free Murashige and Skoog (MS) liquid medium containing different concentrations of jasmonic acid and some other elicitors, in order to promote ginsenoside accumulation. Jasmonic acid in the range 1.0−5.0 mg l⁻¹ (4.8–23.8 μM) strongly improved total ginsenoside production in ginseng hairy roots. Peptone (300 mg l⁻¹) also showed some effect on ginsenoside improvement; however its effect was much weaker than that of jasmonic acid. Ginsenoside content and productivity were 58.65 and 504.39 mg g⁻¹, respectively. The Rb group of ginsenoside content was increased remarkably by jasmonic acid, while Rg group ginsenoside content changed only slightly compared to controls. However, jasmonic acid also strongly inhibited ginseng hairy root growth.     

Enhanced Ginsenoside Productivity by Combination of Ethephon and Methyl Jasmoante in Ginseng (Panax ginseng C.A. Meyer) Adventitious Root Cultures

Ethephon at 50 μM enhanced both root growth and ginsenoside accumulation in ginseng (Panax ginseng C.A. Meyer) adventitious root cultures, but at 100 μM it inhibited only ginsenoside accumulation. Ginsenoside productivity with 50 μM ethephon was the highest at 1.7 mg l⁻¹ d⁻¹ after 8 days of elicitation. However, elicitation with 50 μM ethephon and 100 μM methyl jasmonate (MJ) improved productivity (6.3 mg l⁻¹ d⁻¹) whereas elicitation with 100 μM MJ alone gave only 2.9 mg l⁻¹ d⁻¹.     

Effect of aging on the sensitivity of pancreatic beta-cells to insulin secretagogues in rats.

Glucose-stimulated insulin release from rat pancreas is known to be blunted by aging. In the present study, we examined the effect of aging on insulin release induced by various secretagogues using the isolated perfused pancreas of female rats. Insulin release from the perfused pancreas in response to 16.7 mM glucose in 8-month-old rats (older rats) was much less than that in 2-month-old rats (young rats). The first phase of insulin release after glucose stimulation was attenuated in older rats. The addition of 0.1 mM 3-isobutyl-1-methylxanthine (IBMX) potentiated glucose-induced insulin secretion in both groups of rats. However, the second phase of insulin secretion in older rats was lower than that in younger rats. The phorbol ester 12-O-tetradecanoyl phorbol ester (TPA, 200 nM) enhanced both the first and the second phases of insulin release induced by glucose in both groups of rats. The amount of first phase insulin release induced by TPA with glucose in young rats was greater than that in older rats, whereas the second phase of insulin release was similar in both groups of rats. On the other hand, tolbutamide (200 uM) similarly stimulated the first phase of insulin release in both age groups of rat. In addition, the amount of cumulative insulin secretion induced by tolbutamide during the second phase was slightly but significantly greater in older rats than in young controls. Insulin content in the pancreas was significantly greater in older rats than in young rats and increased after the stimulation with TPA and tolbutamide.(ABSTRACT TRUNCATED AT 250 WORDS)     

Proteome of Oriental ginseng Panax ginseng C. A. Meyer and the potential to use it as an identification tool

Oriental ginseng (Panax ginseng C. A. Meyer) and American ginseng (Panax quinquefolius) are two widely used valuable traditional Chinese medicines (TCM). Previously, the identification of ginseng was mainly performed by analyzing the ginsengnosides using high performance liquid chromatography and amplification of polymorphic DNA using polymerase chain reaction. However, these methods cannot be used to distinguish TCM samples which are from different parts (main root, lateral roots, rhizome head and skin) of ginseng and ginseng culture cells from wild-grown ginseng. The present study aimed to identify different species of ginseng, different parts of the same ginseng and cultured cells of ginseng using a proteomic approach. Two-dimensional electrophoresis (2-DE) maps were established from the American ginseng main root, different parts (main root, lateral roots, rhizome head and skins) of Oriental ginseng and Oriental ginseng culture cells. Our results show that the 2-DE maps of different ginseng samples contain sufficient differences to permit easy discrimination. We have also identified common and specific protein spots in the 2-DE maps of different ginseng samples. The use of these "marker proteins" may help to speed up the identification process.     

Enhanced in vivo sensitivity of vanadyl-treated diabetic rats to insulin

Vanadium has been reported to have insulin-like properties and has recently been demonstrated to be beneficial in the treatment of diabetic animals. In the present study, concentration dependence of the therapeutic effects of vanadium and the nature of interaction under in vivo conditions between vanadium and insulin were examined in streptozotocin-diabetic rats. During a 2-week period, blood glucose levels in all treated animals were decreased. At higher concentrations of vanadyl this decrease was greater and more rapid, and remained consistently lower for the entire treatment period. Daily intake of vanadyl, however, reached a similar steady state in all groups. Acute administration of submaximal doses of insulin, which had minimal effects in untreated diabetic rats, lowered blood glucose concentrations in vanadyl-treated and vanadyl-withdrawn animals to control levels. Chronic treatment of streptozotocin-diabetic rats with submaximal levels of vanadyl and insulin, ineffective alone, also produced significant decreases in blood glucose levels when used in combination. Finally, the insulin dosage required to maintain a nonglycosuric state in spontaneously diabetic (BB) rats was reduced in the presence of vanadyl. These studies indicate that chronic oral vanadyl treatment (a) produces a concentration-related lowering of blood glucose in diabetic rats, (b) potentiates the in vivo glucose lowering effects of acute and chronic administrations of insulin in streptozotocin-diabetic rats, and (c) substitutes for, or potentiates, the effects of chronic insulin therapy in spontaneously diabetic BB rats.     

Involvement of Putrescine,Nitric Oxide,and Hydrogen Peroxide in Methyl Jasmonate-Induced Ginsenoside Synthesis in Adventitious Root Cultures of Panax ginseng C.A. Meyer

Journal of Plant Growth Regulation - The adventitious root (AR) culture of Panax ginseng C.A. Meyer is an alternative route for mass production of ginsenosides. During the AR culture of P. ginseng,...     

Rosiglitazone and fenofibrate improve insulin sensitivity of pre-diabetic OLETF rats by reducing malonyl-CoA levels in the liver and skeletal muscle

AimsRosiglitazone and fenofibrate, specific agonists of the peroxisome proliferator activated receptors-γ (PPARγ) and -α (PPARα), respectively, improve insulin sensitivity in diabetic animals and in patients with type 2 diabetes. Here we investigated how pre-diabetic Otsuka Long–Evans Tokushima Fatty (OLETF) rats fed with normal and high-fat diets respond to these PPAR agonists.Main methodsPre-diabetic OLETF rats were subjected to high-fat or standard diets with or without rosiglitazone or fenofibrate for 2 weeks. The metabolism of the rats and the levels of malonyl-CoA and activities of malonyl-CoA decarboxylase (MCD), acetyl-CoA carboxylase (ACC), and AMP-activated protein kinase (AMPK) in metabolic tissues were assessed.Key findingsRosiglitazone and fenofibrate significantly improved insulin sensitivity and reduced the levels of plasma triglycerides and free fatty acids in OLETF rats fed with a high-fat diet. Fenofibrate particularly reduced the body weight, fat, and total cholesterol in high fat diet OLETF rats. The highly elevated malonyl-CoA levels in the skeletal muscle and liver of OLETF rat were significantly reduced by rosiglitazone or fenofibrate due to, in part, the increased MCD activities and expression. On the other hand, ACC activities were unchanged in skeletal muscle and decreased in liver in high fat diet group. AMPK activities were dramatically decreased in OLETF rats and not affected by these agonists.SignificanceThese results demonstrate that treatment of pre-diabetic OLETF rats–particularly those fed a high-fat diet–with rosiglitazone and fenofibrate significantly improves insulin sensitivity and fatty acid metabolism by increasing the activity of MCD and reducing malonyl-CoA levels in the liver and skeletal muscle.