Effects of Curcumin and Ursolic Acid on the Mitochondrial Coupling Efficiency and Hydrogen Peroxide Emission of Intact Skeletal Myoblasts

• Main Author: Tueller, Daniel J.
• Format: Others
• Published: BYU ScholarsArchive 2017
• Subjects: curcumin; mitochondria; skeletal muscle; ursolic acid; Nutrition
• Online Access: https://scholarsarchive.byu.edu/etd/6911; https://scholarsarchive.byu.edu/cgi/viewcontent.cgi?article=7911&context=etd

Curcumin is a natural compound that improves blood glucose management. While some evidence from isolated mitochondria indicates that curcumin uncouples electron transport from oxidative phosphorylation, the effects of curcumin on mitochondrial respiration and hydrogen peroxide emission in intact skeletal muscle cells are not known. By assessing rates of oxygen consumption, we demonstrated for the first time that curcumin (40 µM) reduced the mitochondrial coupling efficiency (percentage of oxygen consumption that supports ATP synthesis) of intact skeletal muscle cells. A 30-minute incubation with curcumin decreased mitochondrial coupling efficiency by 17.0 ± 0.4% relative to vehicle (p < 0.008). Curcumin also decreased the rate of hydrogen peroxide emission by 43 ± 13% compared to vehicle (p < 0.05). Analysis of cell respiration in the presence of curcumin revealed a 40 ± 4% increase in the rate of oxygen consumption upon curcumin administration (p < 0.05 compared to vehicle). In additional experiments, no difference in mitochondrial coupling efficiency was observed between vehicle- and curcumin-pretreated cells after permeabilization of cell membranes (p > 0.7). The possibility of synergistic effects between curcumin and ursolic acid, another natural compound that improves blood glucose management, was also examined. Interestingly, ursolic acid (0.12 µM) increased mitochondrial coupling efficiency by 4.1 ± 1.1% relative to vehicle (p < 0.008) and attenuated the effect of curcumin when the two compounds were used in combination (decreased mitochondrial coupling efficiency by 8.0 ± 0.9% compared to vehicle, p < 0.008). These results provide evidence for lower mitochondrial coupling efficiency and hydrogen peroxide emission as possible contributors to the increased glucose uptake and insulin sensitivity of subjects after treatment with curcumin but not ursolic acid. Unless cells are assessed in the intact condition, changes to mitochondrial coupling efficiency after curcumin treatment may go unnoticed.