The effect of insulin resistance and exercise on the percentage of CD16(+) monocyte subset in obese individuals.

UNLABELLED: Obesity is a low-grade chronic inflammation condition, and macrophages, and possibly monocytes, are involved in the pathological outcomes of obesity. Physical exercise is a low-cost strategy to prevent and treat obesity, probably because of its anti-inflammatory action. We evaluated the percentage of CD16(-) and CD16(+) monocyte subsets in obese insulin-resistant individuals and the effect of an exercise bout on the percentage of these cells. Twenty-seven volunteers were divided into three experimental groups: lean insulin sensitive, obese insulin sensitive and obese insulin resistant. Venous blood samples collected before and 1 h after an aerobic exercise session on a cycle ergometer were used for determination of monocyte subsets by flow cytometry. Insulin-resistant obese individuals have a higher percentage of CD16(+) monocytes (14.8 ± 2.4%) than the lean group (10.0 ± 1.3%). A positive correlation of the percentage of CD16(+) monocytes with body mass index and fasting plasma insulin levels was found. One bout of moderate exercise reduced the percentage of CD16(+) monocytes by 10% in all the groups evaluated. Also, the absolute monocyte count, as well as all other leukocyte populations, in lean and obese individuals, increased after exercise. This fact may partially account for the observed reduction in the percentage of CD16(+) cells in response to exercise. Insulin-resistant, but not insulin-sensitive obese individuals, have an increased percentage of CD16(+) monocytes that can be slightly modulated by a single bout of moderate aerobic exercise. These findings may be clinically relevant to the population studied, considering the involvement of CD16(+) monocytes in the pathophysiology of obesity. Copyright © 2016 John Wiley & Sons, Ltd.

SIGNIFICANCE OF THE STUDY: Obesity is now considered to be an inflammatory condition associated with many pathological consequences, including insulin resistance. It is proposed that insulin resistance contributes to the aggravation of the inflammatory dysfunction in obesity. The effect of obesity on the percentage of monocytes was previously observed in class II and III obese individuals who presented other alterations in addition to insulin resistance. In this study we observed that insulin-resistant obese individuals, but not insulin-sensitive ones, had an increased percentage of CD14(+) CD16(+) monocytes. This fact shows that a dysfunction of the monocyte percentage in class I obese individuals is only seen when this condition is associated with insulin resistance.