Effects of Sclerocarya birrea Stem-Bark Extracts on Glucose Uptake, InsulinSynthesis and Expression of Selected Genes Involved in the Synthesis andSecretion of Insulin in Rat Insulinoma Pancreatic Beta Cells

The present study reported the effects of Sclerocarya birrea stem-bark (SBSB) extracts on glucose uptake, insulin synthesis and theexpression of glucose transporter 2 (GLUT2), glucokinase, pancreatic duodenal homeobox-1 (PDX-1), musculoaponeurotic fibrosarcomaoncogene homolog A (MafA) and pre-proinsulin genes in rat insulinoma (RIN)-m5F pancreatic beta cells. The amount of glucose takenupby RIN-m5F cells was measured using a glucose oxidase-based assay kit. Intracellular and secreted insulin were measured using anenzyme linked immunoassay kit. Pre-proinsulin gene expression was determined using the conventional polymerase chain reaction(PCR) technique, while the expressions of GLUT2, glucokinase, PDX-1 and MafA genes were evaluated using quantitative real-timePCR technique. Of the four SBSB extracts investigated in the study, only the SBSB hexane extract positively affected all the studyvariables in RIN-m5F cells compared with the DMSO control. Thus, the SBSB hexane extract contains phytochemicals capable ofenhancing insulin synthesis partly through up-regulation of the expression of GLUT2, glucokinase, PDX-1, MafA and pre-proinsulin genes.