Monoamine oxidase is a source of oxidative stress in obese patients with chronic inflammation 1.

Obesity is an important preventable risk factor for morbidity and mortality from cardiometabolic disease. Oxidative stress (including in visceral adipose tissue) and chronic low-grade inflammation are the major underlying pathomechanisms. Monoamine oxidase (MAO) has recently emerged as an important source of cardiovascular oxidative stress. The present study was conducted to evaluate the role of MAO as contributor to reactive oxygen species (ROS) production in white adipose tissue and vessels harvested from patients undergoing elective abdominal surgery. To this aim, visceral adipose tissue and mesenteric artery branches were isolated from obese patients with chronic inflammation and used for organ bath, ROS production, quantitative real-time PCR, and immunohistology studies. The human visceral adipose tissue and mesenteric artery branches contain mainly the MAO-A isoform, as shown by the quantitative real-time PCR and immunohistology experiments. A significant upregulation of MAO-A, the impairment in vascular reactivity, and increase in ROS production were found in obese vs. non-obese patients. Incubation of the adipose tissue samples and vascular rings with the MAO-A inhibitor (clorgyline, 30 min) improved vascular reactivity and decreased ROS generation. In conclusion, MAO-A is the predominant isoform in human abdominal adipose and vascular tissues, is overexpressed in the setting of inflammation, and contributes to the endothelial dysfunction.