ABSTRACT
BACKGROUND: Oestrogen deficiency leads to metabolic disturbances such as insulin resistance and impairment of adipose tissue or lipid metabolism. Marantodes pumilum (Blume) Kuntze (Primulaceae) is believed to have phytoestrogenic properties and is claimed to have beneficial effects in the treatment of diabetes mellitus (DM), but the mechanism behind its phytoestrogenic effects on estrogen-deficient diabetic condition have not been fully examined. PURPOSE: The present study investigated the effects of oral treatment with M. pumilum var. alata (MPA) extracts on the estrogen receptor, metabolic characteristics and insulin signaling pathway in pancreas and liver of ovariectomised nicotidamide streptozotocin-induced diabetes in female rats. MATERIALS AND METHODS: Ovariectomised diabetic (OVXS) Sprague-Dawley rats were orally administered with either aqueous leaf extract and ethanol (50%) stem-root extract of MPA (50 or 100â¯mg/kg) respectively for 28 days. Metabolic parameters were evaluated by measuring fasting blood glucose, serum insulin, oral glucose and insulin tolerance test. Distribution and expression level of insulin, oxidative stress and inflammatory marker in the pancreatic islets and liver were evaluated by immunohistochemistry and western blot, respectively. RESULTS: Oral treatment with aqueous leaf and ethanol (50%) stem-root extracts of MPA (100â¯mg/kg) significantly reversed the elevated fasting blood glucose, impaired glucose and insulin tolerance. The protein expression of insulin, glucose transporter (GLUT-2 and GLUT-4) increased in the pancreatic islets and liver. Furthermore, marked improvement in the tissue morphology following treatment with MPA was observed. Similarly, the western blots analysis denotes improved insulin signaling in the liver and decreased reactive oxygen species producing enzymes, inflammatory and pro-apoptotic molecules with MPA treatment. CONCLUSIONS: Taken together, this work demonstrate that 100â¯mg/kg of aqueous leaf extract and ethanol (50%) stem-root extract of MPA improves ß-cell function and insulin signaling in postmenopausal diabetes through attenuation of oxidative stress and partially mediated by oestrogen receptor stimulation.
