Abstract
The mechanisms whereby regular exercise reduces chronic inflammation remain unclear. We investigated whether regular aerobic exercise alters basal levels of interleukin (IL)‐10 and IL‐4 in two randomized trials of physical activity. The Alberta Physical Activity and Breast Cancer Prevention Trial (ALPHA, n = 320) and the Breast Cancer and Exercise Trial in Alberta (BETA, n = 400) were two‐center, two‐armed randomized trials in inactive, healthy, postmenopausal women. Both trials included an exercise intervention prescribed five times/week and no dietary changes. In ALPHA, the exercise group was prescribed 225 min/week versus no activity in the controls. BETA examined dose‐response effects comparing 300 (HIGH) versus 150 (MODERATE) min/week. Plasma concentrations of IL‐10 and IL‐4 were measured at baseline, 6, and 12 months. Intention‐to‐treat (ITT) analysis was performed using linear mixed models adjusted for baseline biomarker concentrations. Circulating anti‐inflammatory cytokine levels decreased among all groups, with percent change ranging from −3.4% (controls) to −8.2% (HIGH) for IL‐4 and −1.6% (controls) to −7.5% (HIGH) for IL‐10. No significant group differences were found for IL‐4 (ALPHA P = 0.54; BETA P = 0.32) or IL‐10 (ALPHA P = 0.84; BETA P = 0.68). Some evidence for moderation of the effect of exercise by baseline characteristics was found for IL‐10 but not for IL‐4. Results from these two large randomized aerobic exercise intervention trials suggest that aerobic exercise does not alter IL‐10 or IL‐4 in a manner consistent with chronic disease and cancer prevention.
Highlights
Chronic systemic inflammation has been implicated in the etiology and pathogenesis of cardiovascular disease [1,2,3,4], type 2 diabetes [5,6,7], and cancer [8,9,10]
It is plausible that physical activity offers protection against chronic inflammation, and thereby chronic disease and breast cancer development, by exerting systemic anti-inflammatory effects mediated through the production of myokines via contracting skeletal muscles with a subsequent increase in anti-inflammatory cytokines [21,22,23,24]
To address the limitations of these studies and the lack of data from randomized controlled exercise intervention trials (RCTs) in healthy subjects, we investigated whether varying volumes of moderate intensity aerobic exercise (150, 225 and 300 min per week) in the two trials (ALPHA and BETA) increase circulating levels of IL-4 and IL-10
Summary
Chronic systemic inflammation has been implicated in the etiology and pathogenesis of cardiovascular disease [1,2,3,4], type 2 diabetes [5,6,7], and cancer [8,9,10]. High circulating C-reactive protein (CRP), as a nonspecific marker of systemic inflammation, is a putative risk factor for postmenopausal breast cancer [11,12,13]. It is plausible that physical activity offers protection against chronic inflammation, and thereby chronic disease and breast cancer development, by exerting systemic anti-inflammatory effects mediated through the production of myokines via contracting skeletal muscles with a subsequent increase in anti-inflammatory cytokines [21,22,23,24]. Exercise-induced muscle-d erived cytokines have been found to inhibit mammary cancer cell growth in vitro [28]
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