Assessment of the antidiabetic potential of selected medicinal plants using in vitro bioassays of muscle glucose transport and liver glucose production

Type 2 diabetes mellitus (T2DM) is the most common type of diabetes mellitus. It is caused by decreased insulin sensitivity in target organs like liver, muscle and adipose tissue, and/or a deficiency in insulin secretion. In T2DM, increased hepatic glucose output and decreased glucose uptake by skeletal muscle cells are the principal contributors to the associated hyperglycemic state. The aim of this study was to assess the antidiabetic potential of five medicinal plant extracts using in vitro cell based assays targeting glucose uptake in C2C12 skeletal muscle cells [1] and glucose-6-phosphatase activity (G6Pase) [2] in rat hepatoma H4IIE. Cells were treated for 18h with maximal non-toxic concentrations (50 µg/mL) of the ethanolic extract of Psidium guajava (leaf and bark), Phyllanthus niruri (aerial parts), Eugenia jambolana (dried fruit) and Rhizophora mucronata (bark), which were determined by the lactate dehydrogenase (LDH) cytotoxicity assay. None of the extracts were able to reduce G6Pase activity. In contrast, one plant extract (P. guajava leaf extract) was found to significantly increase deoxyglucose uptake in C2C12 muscle cells (161%, p ≤0.001), to levels higher that of the positive control metformin (144%, p ≤0.05) and insulin (142% p ≤0.05) in comparison to the vehicle control (DMSO). In addition, the activity of extracts of P. niruri aerial parts and Eugenia jambolana dried fruit (both at 142%, p ≤0.05) was close to those of the positive controls. In conclusion, our results demonstrated that P. guajava (leaves), P. niruri (aerial parts) and E. jambolana (dried fruit) extracts improve muscle glucose uptake and may thus have potential applications in treatment of type 2 diabetes.

Keywords: Diabetes, glucose uptake, muscle cell, medicinal plant.

References:

[1] Martineau LC, Adeyiwola-Spoor DC, Vallerand D, Afshar A, Arnason JT, Haddad PS. Enhancement of muscle cell glucose uptake by medicinal plant species of Canada's native populations is mediated by a common, Metformin-like mechanism. J Ethnopharmacol 2010; 127: 396 – 406

[2] Nachar A, Saleem A, Arnason JT, Haddad PS. Regulation of liver cell glucose homeostasis by dehydroabietic acid, abietic acid and squalene isolated from balsam fir (Abies balsamea (L.) Mill.) a plant of the Eastern James Bay Cree traditional pharmacopeia. Phytochemistry 2015; 117: 373 – 379