Hypothesis: food for thoughtAnti-inflammatory nature of exercise
Introduction
Exercise improves mood, insulin sensitivity, and plasma lipoprotein profiles and reduces blood pressure.1 Regular exercise decreases the risk of cardiovascular disease.2 Studies have associated low amounts of exercise at moderate or high intensity (which is equivalent to walking or jogging 12 mi/wk, respectively) with beneficial changes in the plasma lipoprotein profile.3 A graded response of the plasma lipoprotein levels to increasing amounts of exercise was reported, suggesting that improvements are related to the amount of exercise but not necessarily to the intensity of exercise. An increasing physical activity score shows a strong, graded, inverse association with the risk of coronary and total cardiovascular events, suggesting that exercise prevents cardiovascular mortality.4 Exercise increases insulin sensitivity and decreases and/or prevents the development or progression of type 2 diabetes mellitus in adults.5, 6 Although these studies have documented the beneficial actions of exercise, the underlying mechanisms by which exercise exerts its beneficial actions are poorly understood. I suggest that exercise is anti-inflammatory in nature and thus brings about its benefits.
Section snippets
Exercise suppresses inflammatory indices and augments antioxidant capacity
The ability of mononuclear cells in subjects who exercised for a mean of 2.5 h/wk to produce antiatherogenic and anti-inflammatory cytokines such as interleukin (IL)–4, IL-10, and transforming growth factor-β (TGF-β) rose by almost 36%. Simultaneously, the serum levels of C-reactive protein (CRP) and proinflammatory cytokines such as tumor necrosis factor-α (TNF-α) and IL-6 declined compared with control subjects.7, 8, 9 IL-4, IL-10, and TGF-β not only have anti-inflammatory actions but also
Exercise and eicosanoids
In addition, exercise enhances the formation of prostacyclin, a vasodilator and platelet anti-aggregator; decreases that of thromboxane A2, a vasoconstrictor and platelet aggregator; increases plasma levels of high-density lipoprotein cholesterol14; and preserves prostaglandin-induced dilation of epicardial coronary artery15 by enhancing the conversion of arachidonic acid to prostacyclin. Exercise increases parasympathetic tone and heart rate variability, which prevents cardiac arrhythmias
Exercise and TGF-β
The ability of exercise to enhance tissue levels of TGF-β is noteworthy because TGF-β has desirable actions in preserving myocardial function and preventing cardiac damage. In animal studies, when given before or immediately after experimental coronary occlusion, TGF-β diminished the amount of superoxide anion (O2−•) in the coronary circulation, maintained and/or restored endothelial-dependent coronary relaxation, and prevented myocardial damage.16 This protective action of TGF-β can be
Mechanism(s) of exercise-induced anti-inflammatory action
In this context, it is interesting to note that the initial stimulus for the increased generation of anti-inflammatory cytokines, O2−•, NO, and Mn-SOD is due to the enhanced production of proinflammatory cytokines such as TNF-α, IL-1β, and IL-6. Exercise causes release of these proinflammatory cytokines that in turn trigger the activation of Mn-SOD and production of anti-inflammatory cytokines such as IL-10, IL-1 receptor antagonist, and TGF-β.20, 21, 22, 23, 24 Moreover, endurance exercise
Exercise and adiponectin
Adiponectin is a recently detected secretory protein of white adipose tissue. It has been shown to have insulin-sensitizing and anti-inflammatory properties.44, 45 Women generally showed a higher mean adiponectin concentration than men. Decreased concentrations of adiponectin have been shown to precede the onset of type 2 diabetes. Alternatively, high concentrations of adiponectin prevent the onset of type 2 diabetes.46
In a case-control study, Lindsay et al.47 found that Pima Indians who had
Conclusions
It is evident from the preceding discussion that the beneficial actions of physical exercise may be related to its ability to suppress the production of inflammatory markers IL-6, TNF-α, CRP, and intracellular adhesion molecule-1 and enhance the anti-inflammatory indices TGF-β, IL-4, IL-10, and adiponectin. In addition, regular exercise stimulates the synthesis of eNO, prostacyclin from the vascular endothelial cells, and tissue Mn-SOD. Vigorous exercise induces the generation of free radicals
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