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Hydrogen peroxide inhibits insulin signaling in vascular smooth muscle cells
Carla D Gardner1, Satoru Eguchi, Cherilynn M Reynolds
1Department of Anatomy and Physiology, Meharry Medical College, Nashville, Tennessee 37208, USA.
Abstract:
Both insulin resistance and reactive oxygen species (ROS) have been reported to play essential pathophysiological roles in cardiovascular diseases, such as hypertension and atherosclerosis. However, the mechanistic link between ROS, such as H2O2 and insulin resistance in the vasculature, remains undetermined. Akt, a Ser/Thr kinase, mediates various biological responses induced by insulin. In this study, we examined the effects of H2O2 on Akt activation in the insulin-signaling pathway in vascular smooth muscle cells (VSMCs). In VSMCs, insulin stimulates Akt phosphorylation at Ser473. Pretreatment with H2O2 concentration- and time-dependently inhibited insulin-induced Akt phosphorylation with significant inhibition observed at 50 microM for 10 min. A ROS inducer, diamide, also inhibited insulin-induced Akt phosphorylation. In addition, H2O2 inhibited insulin receptor binding partially and inhibited insulin receptor autophosphorylation almost completely. However, pretreatment with a protein kinase C inhibitor, GF109203X (2 microM), for 30 min did not block the inhibitory effects of H2O2 on insulin-induced Akt phosphorylation, suggesting that protein kinase C is not involved in the inhibition by H2O2. We conclude that ROS inhibit a critical insulin signal transduction component required for Akt activation in VSMCs, suggesting potential cellular mechanisms of insulin resistance, which would require verification in vivo.
Insights
Reactive oxygen species (ROS) impair insulin signaling in blood vessel cells. Hydrogen peroxide (H2O2) inhibits Akt activation, a key step in insulin response, contributing to vascular insulin resistance.
Area of Science:
- Biochemistry
- Cell Biology
- Cardiovascular Research
Background:
- Insulin resistance and reactive oxygen species (ROS) are implicated in cardiovascular diseases like hypertension and atherosclerosis.
- The precise connection between ROS and vascular insulin resistance is not fully understood.
Purpose of the Study:
- To investigate the impact of hydrogen peroxide (H2O2), a type of ROS, on the insulin-signaling pathway in vascular smooth muscle cells (VSMCs).
- To elucidate the cellular mechanisms linking ROS to insulin resistance in the vasculature.
Main Methods:
- VSMCs were treated with varying concentrations and durations of H2O2.
- Insulin-induced Akt phosphorylation was measured.
- Insulin receptor binding and autophosphorylation were assessed.
- The role of protein kinase C was evaluated using an inhibitor.
Main Results:
- H2O2 inhibited insulin-induced Akt phosphorylation in a concentration- and time-dependent manner.
- A ROS inducer, diamide, also suppressed insulin-induced Akt phosphorylation.
- H2O2 partially reduced insulin receptor binding and almost completely blocked insulin receptor autophosphorylation.
- Protein kinase C inhibition did not prevent H2O2-induced suppression of Akt phosphorylation.
Conclusions:
- ROS, specifically H2O2, interfere with crucial components of insulin signal transduction in VSMCs, leading to impaired Akt activation.
- These findings suggest a potential cellular mechanism for vascular insulin resistance mediated by ROS.
- Further in vivo studies are needed to confirm these observations.