FIG. 2.

Differential thresholds of PTP1B and JNK to ROS. Insulin signaling is balanced by the negative regulators PTP1B (A) and JNK (B). Low doses of H₂O₂ are sufficient to inhibit PTP1B activity (A), whereas high doses of H₂O₂ are required for JNK activation (B) (14). The different thresholds of PTP1B and JNK may cause the dual action of H₂O₂ in insulin signaling. Therefore, insulin signaling becomes enhanced under weak oxidative stress, whereas it is impaired under strong oxidative stress (14). **p < 0.01, versus untreated control. Color images are available online.