The effects of a Kenyan antidiabetic plant on insulin homeostasis

• Main Author: Suleiman, Khairunisa Yahya
• Format: Others
• Language: English
• Published: Nelson Mandela Metropolitan University 2009
• Subjects: Medicinal plants > Kenya; Insulin resistance
• Online Access: http://hdl.handle.net/10948/1055

The metabolic disorder diabetes; is a global epidemic affecting people in developed countries and increasingly in developing countries. In two decades time, 350 million people will be diabetic at the current rate of prevalence. In a preliminary study, insulin resistant rats were treated with Prunus Africana (plant A) for 28 days. Plasma samples obtained from P. africana treated rats had increased insulin levels compared to normal and untreated insulin resistant rats (Karachi, 2009). The treatment of insulin resistant rats with P. africana also showed increased glucose uptake in rat adipose tissue (Karachi, 2009), suggesting that P. africana had anti-diabetic properties. The aim of the study was to investigate the mechanism of the anti-diabetic properties of P africana extract. Increased insulin secretion was confirmed by the increased Cpeptide concentration in plasma samples of rats treated with P. africana. In order to explain the high insulin levels, several hypothesis’ were investigated: (1) P. africana may increase insulin secretion in β cells, hence the effect of P. africana on insulin secretion by INS-1 cells was investigated; (2) P. africana may increase insulin secretion by prolonging the half-life of glucagon like peptide-1 (GLP-1) by decreasing dipeptidyl peptidase IV (DPP IV) activity; the effect of P. africana on DPP IV activity was determined spectrophotometrically, (3) P. africana may increase the half-life of insulin in the plasma by decreasing the activity of insulin degrading enzyme (IDE); the effect of P. africana on IDE in rat muscle and spleen samples was investigated. To explain the increased glucose uptake in adipose tissue observed in the previous study two parameters were investigated: (1) increased GLUT4 expression in P. africana treated rats; the effect of P. africana treatment on the expression of glucose transporter 4 (GLUT4) was determined using real-time polymerase chain reaction (RT-PCR), (2) P. africana may increase glucose utilization; the effect of P. africana on glucose utilization was determined in 3T3-L1 cells. The plant extract did not significantly increase insulin secretion by INS-1 cells in the absence of glucose. P. africana decreased DPP IV activity in rat plasma when compared to the untreated insulin resistant rats and this could be a mechanism by which insulin secretion is increased during plant treatment. P. africana decreased IDE activity (however not significantly) when compared to the untreated insulin resistant The effects of a Kenyan antidiabetic plant on insulin homeostasis KY Suleiman VII rats. P. africana appeared to have no effect on GLUT4 expression. The plant appeared to increase glucose utilization in 3T3-L1 cells in the absence of insulin suggesting that P. africana may have insulin like activity. In summary, this study indicates that P. africana is indirectly involved in inhibiting DDPIV. This in turn can increase the half life of GLP-1, which in turn can enhance the secretion of insulin. P. africana increases glucose utilization although there was no evidence that the GLUT 4 transporter has a higher expression in the plant treated rats. Further studies should be conducted to investigate the expression of GLUT1 under the same conditons.