| dc.description.abstract | Skeletal muscle insulin resistance is a common precursor to type II diabetes. Phytochemicals in fruits have shown to have bioactive properties that could alleviate some of the symptoms and causes of insulin resistance in peripheral tissues. In this thesis, stone fruits of peach, plum, and nectarine were viewed for their bioactive properties against insulin resistant murine C2C12 myotubes in vitro. Fruits were characterized using HPLC-DAD and TLC, removed of sugars and organic acids by SPE reverse phase C18 silica gel, and tested on a palmitic acid induced insulin resistant skeletal muscle model for cytotoxicity levels and glucose 6-phosphate accumulation. Peach extracts investigated in depth analysis in this study. Using SPE the peach extract was fractionated into major phenolic compound categories, identified with HPLC-DAD, and quantified with wet based chemistry assays. The standardized peach fractions were tested on the cell model for cytotoxicity levels, glucose uptake, glucose 6-phosphate, ROS accumulation, and immunochemistry.
Isolated and identified extracts were used at 0-300 μg/mL for cytotoxicity testing. From these results, stone fruit phenolic levels used for glucose 6-phosphate quantification were 1, 10, and 100 μg/mL. Of the stone fruits, peach and nectarine had the most pronounced effect on glucose 6-phosphate concentration at 1 and 10 μg/mL. Further isolated peach extract was separated using SPE, identified using HPLC-DAD and quantified with a wet based chemical assay. These peach phenolic fractions were tested in the murine insulin resistant model for their effect on glucose uptake, with the most effective doses in the cell used for further assays (phenolic acid fraction: 1μg/mL; anthocyanin and flavonoid fractions: 0.1μg/mL; catechin fraction: 0.5 μg/mL). All fractions were able to restore intracellular glucose 6-phosphate to levels comparable to normal and control cells with the exception of F3 which showed no difference from IR induced cells. The fractions had no significant effect on ROS accumulation but were able to increase AKT phosphorylation and decrease phosphorylation of negative regulators of insulin signaling (JNK and IRS1ser307). Further research is needed to view if these compounds act directly on insulin receptors, or work through the AMPK mechanism similar to the positive control, metformin. | en |
