A novel method to detect in vivo oxidant production reveals microvascular endothelial dysfunction linked to NADPH oxidase in obese human skeletal muscle

Abstract

Excessive production of reactive oxygen species (ROS) contributes to the development of endothelial dysfunction and progression of vascular diseases that are observed in obesity. Three microdialysis probes were inserted into the vastus lateralis of young, sedentary lean (LN; n=7), overweight (OW; n=8) and obese (OB; n=7) individuals, allowing sampling of extracellular fluid. To measure extracellular ROS, probes were perfused with saline containing 5 mM ethanol, 100 μM Amplex Ultrared, 1 U/ml horseradish peroxidase, and 10 U/ml superoxide dismutase, with or without 300 μM apocynin (Apo; an NADPH oxidase inhibitor). Dialysate fluorescence was measured at the outlet. Endothelial function was assessed with addition of acetylcholine (ACh) to the perfusate, with local blood flow calculated from the ethanol outflow:inflow ratio. Extracellular ROS was elevated in OB 3.2‐fold over OW, and 5.6‐fold over LN (p < 0.05), which was prevented by Apo (p < 0.01). ACh‐stimulated blood flow was depressed 60% in OB vs. OW, and 68% vs. LN (p = 0.01). Apo augmented ACh‐stimulated blood flow only in OB (p = 0.02). Microvascular endothelial dysfunction was evident in OB, which was largely reversed by NADPH oxidase inhibition. It can be concluded that the substantial elevation in ROS in OB was predominantly driven by NADPH oxidase.Supported by a doctoral student grant from the American College of Sports Medicine.