416 - Mitochondrial Oxidative Stress Induced by Downregulation of Antioxidant Enzymes Leads to Nuclear Protein Carbonylation by Retrograde Signaling in 3T3-L1 Adipocytes

Abstract

Obesity-linked insulin resistance is mechanistically connected to local inflammation of adipose tissue, which produces a metabolic state characterized by oxidative stress and mitochondrial dysfunction. Antioxidants enzymes such as Glutathione S-transferase A4 (GSTA4), peroxiredoxin 3 (Prdx3) and glutathione peroxidase 4 (GPx4) expressions are selectively downregulated in adipose tissue of obese insulin-resistant mice and in human obesity-linked insulin resistance. Also, TNFα treatment of 3T3-L1 adipocytes resulted in decreased expression of GSTA4, GPx4, and Prdx3 and increased protein carbonylation. In addition, protein carbonylation is implicated as an initiating factor in mitochondrial dysfunction and ER-stress, providing a mechanistic connection between oxidative stress and metabolic disease. Histones are the primary components of chromatin and are notably susceptible to carbonylation because of their long lysine-rich tails. These modifications may have effects on histone code, leading to long lasting implications of human health, including insulin resistance. In this study GSTA4-Prdx3-GPx4-silenced 3T3-L1 adipocytes were evaluated for reactive oxygen species production (ROS), mitochondrial function and histones carbonylation. Downregulation of GSTA4, Prdx3 and GPx4 led to an significant increase in ROS, a significant increase in H3 and H4 histones carbonylation, and mitochondrial dysfunction. These results indicate that a downregulation of antioxidant enzymes in adipocytes leads to increased ROS production, mitochondrial dysfunction and nuclear protein carbonylation, and may contribute to the development of insulin resistance and type 2 diabetes.