Cucurbita ficifolia Bouché increases insulin secretion in RINm5F cells through an influx of Ca²⁺ from the endoplasmic reticulum

详细信息    查看全文

• 作者：Maria Elizabeth Miranda-Perez^a ; ^{mirandapme@hotmail.com" class="auth_mail" title="E-mail the corresponding author} ; Clara Ortega-Camarillo^b ; ^{cocamarillo2014@gmail.com" class="auth_mail" title="E-mail the corresponding author} ; Maria Del Carmen Escobar-Villanueva^c ; ^{macaresvi@yahoo.com.mx" class="auth_mail" title="E-mail the corresponding author} ; Gerardo Blancas-Flores^c ; ^{gera_1024@yahoo.com.mx" class="auth_mail" title="E-mail the corresponding author} ; Francisco Javier Alarcon-Aguilar^c ; ^{aaaf@xanum.uam.mx" class="auth_mail" title="E-mail the corresponding author}
• 关键词：2-APB ; Inositol 1 ; 4 ; 5-trisphosphate (IP3)-receptor-selective inhibitor 2 amino-ethoxydiphenylborate ; ([Ca2+]I ; Concentration of intracellular calcium ; C. ficifolia ; Cucurbita ficifolia Bouché ; DCI ; D-chiro-inositol ; Dz ; Diazoxide ; ER ; Endoplasmic reticulum ; Fluo 4AM ; Fluorescent dye fluo4-acetoxymethyl ester (AM) ; IP3Rs ; Inositol 1 ; 4 ; 5-trisphosphate receptors ; K+ATP ; ATP-dependent potassium channel ; Kir6.2 ; A component of the K+ATP channel activated by sulphonylurea ; MTT ; 3&ndash ; (4 ; 5&nda
• 刊名：Journal of Ethnopharmacology
• 出版年：2016
• 出版时间：21 July 2016
• 年：2016
• 卷：188
• 期：Complete
• 页码：159-166
• 全文大小：1250 K

文摘

Cucurbita ficifolia Bouché(C. ficifolia) is a plant used in Mexican traditional medicine to control type 2 diabetes (T2D). The hypoglycemic effect of the fruit of C. ficifolia has been demonstrated in different experimental models and in T2D patients. It has been proposed that D-chiro-inositol (DCI) is the active compound of the fruit. Additionally, it has been reported that C. ficifolia increases the mRNA expression of insulin and Kir 6.2 (a component of the ATP-sensitive potassium (K⁺_ATP) channel, which is activated by sulphonylurea) in RINm5F cells. However, it remains unclear whether C. ficifolia and DCI causes the secretion of insulin by increasing the concentration of intracellular calcium ([Ca²⁺]i) through K⁺_ATP channel blockage or from the reservoir in the endoplasmic reticulum (ER).

Material and methods

The aqueous extract of C. ficifolia was obtained and standardized with regard to its DCI content. RINm5F pancreatic β-cells were incubated with different concentrations (50, 100, 200 and 400 μM) of DCI alone or C. ficifolia (9, 18, 36 and 72 µg of extract/mL), and the [Ca²⁺]i of the cells was quantified. The cells were preloaded with the Ca²⁺ fluorescent dye fluo4-acetoxymethyl ester (AM) and visualized by confocal microscopy. Insulin secretion was measured by an ELISA method. Subsequently, the effect of C. ficifolia on the K⁺_ATP channel was evaluated. In this case, the blocker activator diazoxide was used to inhibit the C. ficifolia-induced calcium influx. In addition, the inositol 1,4,5-trisphosphate (IP3)-receptor-selective inhibitor 2-amino-thoxydiphenylborate (2-APB) was used to inhibit the influx of calcium from the ER that was induced by C. ficifolia.

Results

It was found that DCI alone did not increase [Ca²⁺]i or insulin secretion. In contrast, treatment with C. ficifolia increased [Ca²⁺]i 10-fold compared with the control group. Insulin secretion increased by 46.9%. In the presence of diazoxide, C. ficifolia decreased [Ca²⁺]i by 50%, while insulin secretion increased by 36.4%. In contrast, in the presence of 2-APB, C. ficifolia increased [Ca²⁺]i 18-fold, while insulin secretion remained constant, indicating an additive effect. Therefore, C. ficifolia was not found to block the K⁺_ATP channel. However, it did exert an effect by increasing [Ca²⁺]i from the ER, which may partly explain the insulin secretion observed following treatment with C. ficifolia.

Conclusions

The hypoglycemic properties of C. ficifolia can be explained in part by its effect as a secretagogue for insulin through an increase in [Ca²⁺]i from the calcium reservoir in the ER. Therefore, the mechanism of action of C. ficifolia is different to those of the currently used hypoglycemic drugs, such as sulfonylureas. These results support that C. ficifolia may be a potential natural resource for new agents to control T2D.