Effect of six months' exercise training on C-reactive protein levels in healthy elderly subjects

The relative influences of fitness and fatness on inflammatory factors

OBJECTIVE

Inflammatory processes contribute to disease pathways and may be affected by behavioral lifestyle factors. The relative contributions of fatness and cardiorespiratory fitness to inflammatory factors remain unclear. The present review examines the hypothesis that the association between fitness and inflammatory factors is independent of fatness.

METHODS

Data were examined from 40 observational studies on the association between fitness/physical activity and inflammatory factors after making statistical adjustment for measures of fatness, and from 12 randomized controlled trials that considered the impact of improved fitness and weight loss.

RESULTS

Two thirds of the observational studies report an inverse relationship between inflammatory factors and fitness after adjustment for fatness. Evidence from randomized controlled trials does not consistently support the hypothesis. Inconsistencies in the literature may be related to various factors such as age, gender, and disease status.

CONCLUSIONS

Both fitness and fatness appear to contribute to inflammatory factors, although it is unclear whether fatness is a mediator or if both fitness and fatness share the same causal pathways. Lifestyle interventions for primary prevention in the general public should therefore focus on both increasing physical activity and the prevention of excess adiposity, although the optimal exercise dose and body composition for preventing chronic inflammatory processes is not well established.

Effects of aerobic exercise on C-reactive protein, body composition, and maximum oxygen consumption in adults: a meta-analysis of randomized controlled trials

The aim of the study was to use the meta-analytic approach to examine the effects of aerobic exercise on C-reactive protein (CRP) in adults. Secondary outcomes included changes in body weight in kilograms, percentage of body fat, and maximum oxygen consumption (VO2max) in mL kg(-1) min(-1). Studies were retrieved using computerized literature searches, cross-referencing, and hand searching. Inclusion criteria were assessment of CRP in randomized controlled trials published in the English language between January 1, 1990, and January 1, 2006. Studies were also limited to aerobic exercise interventions lasting 4 weeks or more in adults 18 years or older. Five studies representing 323 male and female subjects (171 exercise, 152 control) and 6 outcomes for CRP were available for pooling. A nonsignificant reduction of approximately 3% was observed for CRP in the exercise groups (mean +/- SEM, -0.11 +/- 0.14 mg/L; 95% confidence interval [CI], -0.39 to 0.17 mg/L) using a random-effects model. Statistically significant reductions of approximately 4% were found for body weight (mean +/- SEM, -3.4 +/- 1.0 kg; 95% CI, -5.3 to -1.5 kg) and percentage of body fat (mean +/- SEM, -1.4% +/- 0.4%; 95% CI, -2.3% to -0.6%), whereas a statistically significant increase of 12% was found for VO2max (mean +/- SEM, 3.3 +/- 0.9 mL kg(-1) min(-1); 95% CI, 1.5 to 5.1 mL kg(-1) min(-1)). The results of our study suggest that aerobic exercise does not reduce CRP levels in adults, but does improve measures of body composition and physical fitness.

Response of high-sensitivity C-reactive protein to exercise training in an at-risk population

BACKGROUND

High-sensitivity C-reactive protein (hsCRP) is promoted as an independent predictor of atherosclerotic risk. In addition, cardiorespiratory fitness is inversely related to hsCRP in single-sex cross-sectional analyses. Our objective was to determine if modulating fitness with exercise training imposes changes in high-sensitivity C-reactive protein in a mixed-sex population at risk for cardiovascular disease.

METHODS

We studied baseline and postintervention plasma hsCRP in 193 sedentary, overweight to mildly obese, dyslipidemic men and women who were randomized to 6 months of inactivity or 1 of 3 aerobic exercise groups: low amount-moderate intensity (energy equivalent of approximately 19.3 km/wk at 40%-55% peak VO2), low amount-high intensity (energy equivalent of approximately 19.3 km/wk at 65%-80% peak VO2), or high amount-high intensity (energy equivalent of approximately 32.2 km/wk at 65%-80% peak VO2).

RESULTS

At baseline, the study population was at intermediate to high cardiovascular risk as defined by hsCRP. Cardiorespiratory fitness was inversely related to hsCRP (P < .001) even after adjusting for significant and expected sex differences. Fitness, hormone replacement therapy use, and high-density lipoprotein cholesterol accounted for the sex difference in baseline hsCRP. Fitness, high-density lipoprotein cholesterol, fasting insulin, hormone replacement therapy, and visceral adiposity were all independent predictors for baseline hsCRP (r2 = 0.34 for the entire model, P < .0001). However, despite significant improvements in fitness, visceral adiposity, subcutaneous adiposity, and insulin sensitivity, hsCRP did not change in response to exercise training (P > .20).

CONCLUSIONS

Cardiorespiratory fitness is inversely related to hsCRP independent of sex and accounts for most of the large sex disparity in hsCRP. Nonetheless, in the absence of a significant change in diet, 6 months of aerobic exercise training does not produce a significant change in hsCRP in an at-risk population.

Effects of lifestyle modifications on C-reactive protein: contribution of weight loss and improved aerobic capacity

High-sensitivity C-reactive protein (hs-CRP) is associated with an increased risk of cardiovascular disease and the development of type 2 diabetes mellitus. We analyzed the effects of lifestyle modifications including exercise training on hs-CRP in 47 overweight and obese adults. Subjects were divided into a lifestyle modification group (n=23) (exercise and diet instruction) and a control group (n=24) who did not participate in any lifestyle modification. After 3 months, body weight (80.8+/-11.5 to 73.5+/-10.7 kg, P<.01), total cholesterol (217+/-38.4 to 178.0+/-25.6 mg/dL, P<.01), low-density lipoprotein cholesterol (151.3+/-34.9 to 116.7+/-27.8 mg/dL, P<.01), Vo(2)peak (30.3+/-5.1 to 37.1+/-6.9 mL/[kg . min], P<.01), and log hs-CRP (0.75+/-0.4 to 0.56+/-0.3 mg/dL, P=.01) were significantly improved in the lifestyle modification group, but there was no significant improvement in the control group. Changes in log hs-CRP were associated with changes in Vo(2)peak (r=-0.41, P=.004) and changes in weight loss (r=0.42, P=.004). In stepwise multiple regression analysis, weight loss (P=.034) and improved Vo(2)peak (P=.039) were independent predictors of the changes in hs-CRP. When grouped into quartiles according to decreasing weight and increasing Vo(2)peak, levels of changes in log hs-CRP improved across quartiles of weight loss (P<.05) and improved Vo(2)peak (P<.01). Thus, lifestyle changes including regular exercise training in overweight and obese adults decreased hs-CRP, and this was associated with weight loss and improved Vo(2)peak.

Aerobic exercise, but not flexibility/resistance exercise, reduces serum IL-18, CRP, and IL-6 independent of beta-blockers, BMI, and psychosocial factors in older adults

Increased serum levels of inflammatory mediators have been associated with numerous disease states including atherosclerosis, Type II diabetes, hypertension, depression, and overall mortality. We hypothesized that a long-term exercise intervention among older adults would reduce serum inflammatory cytokines, and this reduction would be mediated, in part, by improvements in psychosocial factors and/or by beta-adrenergic receptor mechanisms. Adults age 64 were randomly assigned to either an aerobic exercise treatment (CARDIO) or a flexibility/strength exercise treatment (FLEX) 3 days/week, 45 min/day for 10 months. A subgroup of subjects treated with non-selective beta(1)beta(2) adrenergic antagonists were included to evaluate the potential role of beta-adrenergic receptor adaptations as mediators of an exercise-induced change in inflammation. The inflammatory mediators [C-reactive protein (CRP), IL-6, tumor necrosis factor (TNF)-alpha, and IL-18] and the psychosocial factors (depression, perceived stress, optimism, sense of coherence, and social support) were measured pre- and post-intervention. The CARDIO treatment resulted in significant reductions in serum CRP, IL-6, and IL-18 compared to the FLEX treatment (significant treatment x time interaction, p<.05), whereas TNFalpha declined in both groups (main effect of time, p=.001). However, several psychosocial factors (depression, optimism, and sense of coherence) improved in both groups suggesting that the reduction of CRP, IL-6, and IL-18 in the CARDIO group was not mediated by improvements in psychosocial scores. With respect to the potential role of beta-adrenergic receptors, both CARDIO subjects treated with beta-adrenergic antagonists and those who were not treated with those medications demonstrated similar reductions in serum CRP, IL-6, IL-18, and TNFalpha. In summary, we have observed that an aerobic exercise intervention can significantly reduce serum inflammatory mediators, but beta-adrenergic receptors and psychosocial factors do not appear to be involved.

Endurance training reduces circulating inflammatory markers in persons at risk of coronary events: Impact on plaque stabilization?

Inflammatory pathways are involved in destabilization of atherosclerotic plaques. We assessed the hypothesis that endurance training decreases circulating concentrations of inflammatory markers in persons with coronary artery disease (CAD) and cardiovascular risk factors (CVRFs). Thirty-two subjects with CAD and/or CVRFs joined a 12-week supervised endurance training. We found a significant decrease of the chemokines interleukin (IL)-8 (pre: 3.9+/-0.6, change: -1.2+/-0.4 pg/ml, -21%, p=0.002) and monocyte chemoattractant protein-1 (pre: 213+/-9, change: -20.4+/-8.2 pg/ml, -5%, p=0.03). Diabetes mellitus (DM) significantly influenced changes of IL-8 (p=0.002). IL-8 substantially dropped by 39% in diabetics. Moreover, matrix metalloproteinase-9 (MMP-9) highly significantly decreased in response to training (pre: 750+/-98, change: -278+/-77 ng/ml, -18%, p=0.005). Exercise-induced changes of MMP-9 were influenced by concomitant use of statins (p=0.038). We observed a particularly strong MMP-9 reduction of 44% in patients treated with statins. Acute phase reactants IL-6 (pre: 1.7+/-0.3, change: +0.25+/-0.7 pg/ml, +4%, p=0.58) and high sensitivity C-reactive protein (pre: 2.1+/-0.5, change: -0.25+/-0.4 mg/l, -9%, p=0.54) did not change in response to training. In conclusion, endurance training decreased circulating chemokines and MMP-9, which may in part explain its beneficial effect on coronary risk. Patients with DM or treated with statins because of hypercholesterolemia may particularly take advantage.

Effects of exercise training on 5 inflammatory markers associated with cardiovascular risk

BACKGROUND

Cross-sectional studies suggest that regular exercise has anti-inflammatory effects, leading to lower levels of several proatherogenic inflammatory markers. However, this has yet to be confirmed by randomized prospective trials. We performed a randomized controlled trial to assess whether exercise training decreases levels of 5 inflammatory markers linked to future cardiovascular risk: white blood cell count, fibrinogen, C-reactive protein, soluble intercellular adhesion molecule 1, and soluble CD40 ligand.

METHODS

One hundred fifty-two healthy female smokers were randomized to either 12 weeks of exercise training or health education as part of a smoking cessation program. Smoking was held steady for the first 6 weeks, and thereafter, smoking cessation was actively attempted. One hundred four participants completed 6 weeks, and 88 completed 12 weeks. Fitness and circulating inflammatory marker levels were measured at baseline, 6 weeks, and 12 weeks. To avoid potential confounding from changes in smoking exposure during the second 6 weeks of the trial, the primary end point was change in inflammatory marker levels from baseline to 6 weeks. Change in inflammatory markers from baseline to 12 weeks was a secondary end point.

RESULTS

At baseline, greater physical fitness was associated with lower white blood cell, fibrinogen, and C-reactive protein levels, but these associations were not statistically significant after adjusting for body mass index (P > .1 for all). Fitness improved significantly in the exercise group at both 6 and 12 weeks. However, there were no differences in levels of any inflammatory marker between the exercise and control groups at either 6 weeks (primary end point) or 12 weeks (secondary end point) (P > .05 for all comparisons).

CONCLUSION

In female smokers, baseline associations between fitness and inflammatory markers were largely attributable to differences in body fat; regular exercise did not reduce levels of any of the inflammatory markers studied despite a significant improvement in fitness at both 6 and 12 weeks.

Physical Activity and High-Sensitivity C-Reactive Protein

Cardiovascular disease (CVD) remains one of the leading causes of death and disability in developed countries around the world despite the documented success of lifestyle and pharmacological interventions. This illustrates the multifactorial nature of atherosclerosis and the use of novel inflammatory markers as an adjunct to risk factor reduction strategies. As evidence continues to accumulate that inflammation is involved in all stages of the development and progression of atherosclerosis, markers of inflammation such as high-sensitivity C-reactive protein (CRP) may provide additional information regarding the biological status of the atherosclerotic lesion. Recent investigations suggest that physical activity reduces CRP levels. Higher levels of physical activity and cardiorespiratory fitness are consistently associated with 6-35% lower CRP levels. Longitudinal training studies that have demonstrated reductions in CRP concentrations range from 16% to 41%, an effect that may be independent of baseline levels of CRP, body composition or weight loss. The average change in CRP associated with physical activity appears to be at least as good, if not better, than currently prescribed pharmacological interventions in similar populations. The primary purpose of this review will be to present evidence from both cross-sectional and longitudinal investigations that physical activity lowers CRP levels in a dose-response manner. Finally, this review will examine factors such as body composition, sex, blood sample timing, diet and smoking, which may influence the CRP response to physical activity.

Effect of exercise training on C-reactive protein in postmenopausal breast cancer survivors: a randomized controlled trial

The objective of this study was to determine the effects of exercise training on changes in C-reactive protein (CRP) and other cardiovascular risk factors in postmenopausal breast cancer survivors. Fifty-three postmenopausal breast cancer survivors were randomly assigned to an exercise (n = 25) or control group (n = 28). The exercise group trained on cycle ergometers 3 times per week for 15 weeks. The control group did not train. The primary end point was change in CRP between baseline and week 15. Secondary end points were changes in RHR, HRR, SBP, DBP, TC, LDL-C, HDL-C, TG, and TC:HDL-C ratio. Fifty-two participants completed the trial. Baseline values did not differ between groups except that TG (p = .007) and TC:HDL-C ratio (p = .023) were higher in the exercise group. Intention-to-treat analysis showed that CRP decreased by 1.39 mg/L in the exercise group whereas it increased by 0.10 mg/L in the control group (mean between group change, -1.49 mg/L; 95% CI, -3.09 to 0.10 mg/L; p = .066). Intention-to-treat analysis also showed a clinically and statistically significant difference between groups for change in HRR (mean change, +10.6 beats/min; 95% CI, +3.4 to +17.7 beats/min; p = .004) and clinically but not statistically significant differences between groups for change in RHR (mean change, -5.5 beats/min; 95% CI, -11.5 to +0.5 beats/min; p = .073), SBP (mean change, -5.5 mmHg; 95% CI, -14.5 to +3.4 mmHg; p = .218), DBP (mean change,-3.6 mmHg; 95% CI, -9.3 to +2.1 mmHg; p = .214), and HDL-C (mean change, +0.05 mmol/L; 95% CI, -0.03 to 0.14 mmol/L; p = .214). These data suggest that exercise training may have beneficial effects on CRP and other cardiovascular risk factors in postmenopausal breast cancer survivors. Larger randomized controlled trials are warranted.