Hydrogen peroxide induces activation of insulin signaling pathway via AMP-dependent kinase in podocytes.

Podocytes are cells that form the glomerular filtration barrier in the kidney. Insulin signaling in podocytes is critical for normal kidney function. Insulin signaling is regulated by oxidative stress and intracellular energy levels. We cultured rat podocytes to investigate the effects of hydrogen peroxide (H(2)O(2)) on the phosphorylation of proximal and distal elements of insulin signaling. We also investigated H(2)O(2)-induced intracellular changes in the distribution of protein kinase B (Akt). Western blots showed that H(2)O(2) (100 μM) induced rapid, transient phosphorylation of the insulin receptor (IR), the IR substrate-1 (IRS1), and Akt with peak activities at 5 min (Δ 183%, P<0.05), 3 min (Δ 414%, P<0.05), and 10 min (Δ 35%, P<0.05), respectively. Immunostaining cells with an Akt-specific antibody showed increased intensity at the plasma membrane after treatment with H(2)O(2)>. Furthermore, H(2)O(2) inhibited phosphorylation of the phosphatase and tensin homologue (PTEN; peak activity at 10 min; Δ -32%, P<0.05) and stimulated phosphorylation of the AMP-dependent kinase alpha subunit (AMPKα; 78% at 3 min and 244% at 10 min). The stimulation of AMPK was abolished with an AMPK inhibitor, Compound C (100 μM, 2h). Moreover, Compound C significantly reduced the effect of H(2)O(2) on IR phosphorylation by about 40% (from 2.07 ± 0.28 to 1.28 ± 0.12, P<0.05). In addition, H(2)O(2) increased glucose uptake in podocytes (from 0.88 ± 0.04 to 1.29 ± 0.12 nmol/min/mg protein, P<0.05), and this effect was attenuated by Compound C. Our results suggested that H(2)O(2) activated the insulin signaling pathway and glucose uptake via AMPK in cultured rat podocytes. This signaling may play a potential role in the prevention of insulin resistance under conditions associated with oxidative stress.