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Evaluation of Antidiabetic Effects of the Traditional Medicinal Plant Gynostemma pentaphyllum and the Possible Mechanisms of Insulin Release.

Lokman EF, Gu HF, Wan Mohamud WN, Östenson CG - Evid Based Complement Alternat Med (2015)

Bottom Line: Opening of ATP-sensitive potassium (K-ATP) channels by diazoxide and inhibition of calcium channels by nifedipine significantly decreased insulin response to GP.Conclusion.The antidiabetic effect of GP is associated with the stimulation of insulin release from the islets.

View Article: PubMed Central - PubMed

Affiliation: Department of Molecular Medicine and Surgery, Karolinska Institutet, Karolinska University Hospital, SE-171 76 Stockholm, Sweden ; Diabetes and Endocrine Unit, Cardiovascular, Diabetes and Nutrition Research Centre (CDNRC), Institute for Medical Research, Jalan Pahang, 50588 Kuala Lumpur, Malaysia.

ABSTRACT
Aims. To evaluate the antidiabetic effects of Gynostemma pentaphyllum (GP) in Goto-Kakizaki (GK) rat, an animal model of type 2 diabetes, and to investigate the mechanisms of insulin release. Methods. Oral glucose tolerance test was performed and plasma insulin levels were measured. Results. An oral treatment with GP (0.3 g/kg of body weight daily) for two weeks in GK rats improved glucose tolerance versus placebo group (P < 0.01). Plasma insulin levels were significantly increased in the GP-treated group. The insulin release from GP-treated GK rats was 1.9-fold higher as compared to the control group (P < 0.001). GP stimulated insulin release in isolated GK rat islets at high glucose. Opening of ATP-sensitive potassium (K-ATP) channels by diazoxide and inhibition of calcium channels by nifedipine significantly decreased insulin response to GP. Furthermore, the protein kinase A (PKA) inhibitor H89 decreased the insulin response to GP (P < 0.05). In addition, GP-induced insulin secretion was decreased after preincubation of GK islets with pertussis toxin to inhibit exocytotic Ge proteins (P < 0.05). Conclusion. The antidiabetic effect of GP is associated with the stimulation of insulin release from the islets. GP-induced insulin release is partly mediated via K-ATP and L-type Ca(2+) channels, the PKA system and also dependent on pertussis toxin sensitive Ge-protein.

No MeSH data available.


Related in: MedlinePlus

Effects of Gynostemma pentaphyllum (GP) on insulin secretion in GK rat islets with or without 24 hours incubation with 100 ng/mL of pertussis toxin. ∗P < 0.05, ∗∗P < 0.01 (when compared with control group with no addition at 16.7 mM glucose); #P < 0.05 (when compared with islets incubated with GP at 16.7 mM glucose without exposure to pertussis toxin) using paired t-test. Results of insulin release (μU/islet/hour) are the means ± SEM of three independent experiments with three replicates for each experiment.
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fig6: Effects of Gynostemma pentaphyllum (GP) on insulin secretion in GK rat islets with or without 24 hours incubation with 100 ng/mL of pertussis toxin. ∗P < 0.05, ∗∗P < 0.01 (when compared with control group with no addition at 16.7 mM glucose); #P < 0.05 (when compared with islets incubated with GP at 16.7 mM glucose without exposure to pertussis toxin) using paired t-test. Results of insulin release (μU/islet/hour) are the means ± SEM of three independent experiments with three replicates for each experiment.

Mentions: To understand if GP stimulates insulin release via exocytotic Ge proteins, pertussis toxin (PTX) was used as an inhibitor. PTX prevents the G proteins from interacting with their associated G protein-coupled receptors [27]. The preincubation of GK rat islets with pertussis toxin in the presence of GP at 11.1 mM glucose decreased the insulin secretion compared to the control group, from 29.6 ± 2.2 to 13.8 ± 0.7 μU/islet/hour at 16.7 mM glucose (P < 0.05) (Figure 6).


Evaluation of Antidiabetic Effects of the Traditional Medicinal Plant Gynostemma pentaphyllum and the Possible Mechanisms of Insulin Release.

Lokman EF, Gu HF, Wan Mohamud WN, Östenson CG - Evid Based Complement Alternat Med (2015)

Effects of Gynostemma pentaphyllum (GP) on insulin secretion in GK rat islets with or without 24 hours incubation with 100 ng/mL of pertussis toxin. ∗P < 0.05, ∗∗P < 0.01 (when compared with control group with no addition at 16.7 mM glucose); #P < 0.05 (when compared with islets incubated with GP at 16.7 mM glucose without exposure to pertussis toxin) using paired t-test. Results of insulin release (μU/islet/hour) are the means ± SEM of three independent experiments with three replicates for each experiment.
© Copyright Policy - open-access
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC4493304&req=5

fig6: Effects of Gynostemma pentaphyllum (GP) on insulin secretion in GK rat islets with or without 24 hours incubation with 100 ng/mL of pertussis toxin. ∗P < 0.05, ∗∗P < 0.01 (when compared with control group with no addition at 16.7 mM glucose); #P < 0.05 (when compared with islets incubated with GP at 16.7 mM glucose without exposure to pertussis toxin) using paired t-test. Results of insulin release (μU/islet/hour) are the means ± SEM of three independent experiments with three replicates for each experiment.
Mentions: To understand if GP stimulates insulin release via exocytotic Ge proteins, pertussis toxin (PTX) was used as an inhibitor. PTX prevents the G proteins from interacting with their associated G protein-coupled receptors [27]. The preincubation of GK rat islets with pertussis toxin in the presence of GP at 11.1 mM glucose decreased the insulin secretion compared to the control group, from 29.6 ± 2.2 to 13.8 ± 0.7 μU/islet/hour at 16.7 mM glucose (P < 0.05) (Figure 6).

Bottom Line: Opening of ATP-sensitive potassium (K-ATP) channels by diazoxide and inhibition of calcium channels by nifedipine significantly decreased insulin response to GP.Conclusion.The antidiabetic effect of GP is associated with the stimulation of insulin release from the islets.

View Article: PubMed Central - PubMed

Affiliation: Department of Molecular Medicine and Surgery, Karolinska Institutet, Karolinska University Hospital, SE-171 76 Stockholm, Sweden ; Diabetes and Endocrine Unit, Cardiovascular, Diabetes and Nutrition Research Centre (CDNRC), Institute for Medical Research, Jalan Pahang, 50588 Kuala Lumpur, Malaysia.

ABSTRACT
Aims. To evaluate the antidiabetic effects of Gynostemma pentaphyllum (GP) in Goto-Kakizaki (GK) rat, an animal model of type 2 diabetes, and to investigate the mechanisms of insulin release. Methods. Oral glucose tolerance test was performed and plasma insulin levels were measured. Results. An oral treatment with GP (0.3 g/kg of body weight daily) for two weeks in GK rats improved glucose tolerance versus placebo group (P < 0.01). Plasma insulin levels were significantly increased in the GP-treated group. The insulin release from GP-treated GK rats was 1.9-fold higher as compared to the control group (P < 0.001). GP stimulated insulin release in isolated GK rat islets at high glucose. Opening of ATP-sensitive potassium (K-ATP) channels by diazoxide and inhibition of calcium channels by nifedipine significantly decreased insulin response to GP. Furthermore, the protein kinase A (PKA) inhibitor H89 decreased the insulin response to GP (P < 0.05). In addition, GP-induced insulin secretion was decreased after preincubation of GK islets with pertussis toxin to inhibit exocytotic Ge proteins (P < 0.05). Conclusion. The antidiabetic effect of GP is associated with the stimulation of insulin release from the islets. GP-induced insulin release is partly mediated via K-ATP and L-type Ca(2+) channels, the PKA system and also dependent on pertussis toxin sensitive Ge-protein.

No MeSH data available.


Related in: MedlinePlus