Study of insulin resistance in cybrid cells harboring diabetes-susceptible and diabetes-protective mitochondrial haplogroups.

AIM

This study aims to elucidate the independent role of mitochondria in the pathogenesis of insulin resistance (IR).

METHODS

Cybrids derived from 143B osteosarcoma cell line and harboring the same nuclear DNA but different mitochondrial haplogroups were studied. Cybrid B4 (the major diabetes-susceptible haplogroup in Chinese population), cybrid D4 (the major diabetes-resistant haplogroup in Chinese population) and cybrid N9 (the diabetes-resistant haplogroup in Japanese population) were cultured in a medium containing 25 mM glucose and stimulated with 0 μM, 0.1 μM, and 1.0 μM insulin. We compared the insulin activation of PI3K-Akt (glucose uptake) and ERK-MAPK (pro-inflammation) signaling pathways, intracellular and mitochondrial oxidative stress (DCF and MitoSOX Red), and their responses to the antioxidant N-acetylcysteine (NAC).

RESULTS

Upon insulin treatment, the translocation of cytoplasmic GLUT1/GLUT4 to the cell membrane in cybrid D4 and N9 cells increased significantly, whereas the changes in B4 cells were not or less significant. On the contrary, the ratio of insulin-induced JNK and P38 to Akt phosphorylation was significantly greater in cybrid B4 cells than in cybrid D4 and N9 cells. The levels of DCF and MitoSOX Red, which are indicative of the oxidative stress, were significantly higher in the B4 cells in basal conditions and after insulin treatment. Following treatment with the antioxidant NAC, cybrid B4 cells showed significantly reduced insulin-induced phosphorylation of P38 and increased GLUT1/GLUT4 translocation to the cell membrane, suggesting that NAC may divert insulin signaling from pro-inflammation to glucose uptake.

CONCLUSIONS

Mitochondria play an independent role in the pathogenesis of IR, possibly through altered production of intracellular ROS.