Citation
C-Reactive Protein as a Biomarker for Aging

Material Information

Title:
C-Reactive Protein as a Biomarker for Aging
Creator:
Kalani, Rizwan
Leeuwenburgh, Christiaan ( Mentor )
Place of Publication:
Gainesville, Fla.
Publisher:
University of Florida
Publication Date:
Language:
English

Subjects

Genre:
serial ( sobekcm )

Record Information

Source Institution:
University of Florida
Holding Location:
University of Florida
Rights Management:
All applicable rights reserved by the source institution and holding location.

Downloads

This item has the following downloads:


Full Text




journal orf in.n err.3du.3-e : R-:ese-arch

,,Oluine ., issue 5 - la.3rch 2.1'.Ls



C-Reactive Protein as a Biomarker for Aging

Rizvian Kalani and Christiaan Leeuvienburgh


ABSTRACT


Purpose


Inflammation has shown to be involved with the aging process and many age-related pathologies.

Persistent, unwarranted immunological episodes and other pivotal inflammatory agents have the ability to

reduce antioxidant levels. The two most prevalent life-prolonging strategies, life-long wheel running and life-

long caloric restriction (CR), have been shown to increase mean and maximum life span, respectively, but

the mechanisms by which the interventions work remain unclear. Hence, we evaluated the effects of age on

plasma inflammatory markers, C-reactive protein (CRP), interleukin-6 (IL-6), and total antioxidant capacity

(TAC); and we determined the ability of short-term CR, long-term CR and life-long exercise to

attenuate inflammation and restore total antioxidant potential.



Methods


Stored plasma samples were used for these studies. For the caloric restriction study, we used 6-month-old ad

libitum fed (6AL, young; n=8), 26-month-old ad libitum fed (26AL, old; n=8), 6-month-old calorie restricted

(6CR, young CR; n=8), and 26-month-old calorie restricted (26CR, old CR; n=8) male Fisher-344 rats. For the

wheel running study, we used 24-month-old sedentary ad libitum fed (ad libitum; n=8), 24-month-old sedentary

8% food restricted (sedentary; n=8), and 24-month-old wheel running 8% food restricted (runners; n=8)

male Fisher-344 rats.



Results


Short-term CR dramatically reduced CRP levels (61%), but had no significant effect on IL-6 or total

plasma antioxidant status. Plasma CRP levels increased dramatically (357%) in the old 26-month old

animals compared to the young 6-month old rats, whereas 26-month old life-long caloric restricted rats only

showed a 42% increase compared to 6-month old animals. Antioxidant status was significantly decreased in the

26-month old animals and tended to be higher in the 26CR rats compared to the 26-month old animals. Circulating

IL-6 levels, on the other hand, did not show significant changes with age or life-long calorie restriction. Life-

long exercise (and 8% CR) showed a marked decrease in CRP levels (38%) compared to the 8% CR

sedentary control rats and an even greater reduction (53%) compared to the ad libitum fed rats. In contrast,





plasma antioxidant levels were the highest in the life-long exercising 8% CR group compared to either the 8% CR

or ad libitum fed animals. Again, no changes were found in IL-6 levels between any of these treatment groups.



Conclusions


CR and wheel running, the two most prevalent life-prolonging strategies, significantly attenuate chronic

inflammation that is shown to increase with age. These studies show that CRP levels may be useful as a

biomarker for longevity studies, but surprisingly IL-6 levels remained unchanged with all interventions. In

addition, the heightened levels of inflammation were clearly associated with a reduced level of total

plasma antioxidant status.



INTRODUCTION



An increase in chronic inflammation has been shown to play a vital role in numerous disease states and has

been linked with the aging process. 2-4 It has been implicated in a diverse range of diseases including

arthritis, cancer, diabetes and Alzheimer's disease. 6, 20, 23, 27 Moreover, inflammation has been recognized

as playing a major, deleterious role in arteriosclerosis and as an integral component in the pathogenesis of

other cardiovascular disease. 1, 8, 28 C-reactive protein (CRP), an inflammatory biomarker, is increasingly

receiving more attention due to its potential in predicting cardiovascular disease. 7 It is a non-glycosylated protein

of the pentraxin family involved in the acute phase reaction, a non-specific physiological response to tissue

injury, infection, inflammation, and disease activity, which is characterized by an increase in certain cytokines

and hormones. CRP primarily functions to recognize and eliminate pathogens and damaged cells by activating

the complement system and phagocytic cells.40 Moreover, interleukin-6 (IL-6), an acute phase cytokine, has

also been implicated in enhancing the inflammatory response persistent in cardiovascular disease. 36 The

production of circulating CRP levels is primaly modulated by interleukin-6 (IL-6) in hepatocytes, although

trace amounts of mRNA for CRP have been found in lymphocytes and kidney. 22,29 In addition, monokines IL-1

and TNF-_ and interferons are other pro-inflammatory stimulus associated with increased production of CRP.

11 Expression is regulated through activation of transcription factors C/EBP_ and C/EBP_ from the C/EBP

family, STAT3, and Rel proteins such as NF-_B. 11 Hence, the primary objectives of these studies were to

determine the relationship between CRP and IL-6 with age and life-long prolonging interventions.



The two most prevalent life-prolonging strategies, life-long caloric restriction and life-long wheel running

exercise, have not been investigated extensively regarding their ability to attenuate chronic systemic

inflammation. Life-long caloric restriction has shown to increase both the mean and maximum life span in rats,

while chronic exercise only increases mean life span. 15, 39, 41 The mechanisms by which these interventions

extend life span remain unclear. Here, these studies were designed to investigate the effect of age, short-term

(40%) and long-term (8% and 40%) caloric restriction as well as life-long wheel running on plasma cytokine levels

of CRP and IL-6 as well as total antioxidant status. These studies provide further insight into how long-term

caloric restriction and exercise affect inflammatory response, in addition to establishing a relationship between IL-





6 and CRP levels in the plasma.


MATERIALS AND METHODS



Subjects


Stored plasma samples were used for these studies. For the caloric restriction study, we used 6-month-old ad

libitum fed (6AL, young; n=8), 26-month-old ad libitum fed (26AL, old; n=8), 6-month-old calorie restricted

(6CR, young CR; n=8), and 26-month-old calorie restricted (26CR, old CR; n=8) male Fisher-344 rats

(National Institutes of Aging Colony, Harlan Sprague Dawley, Indianapolis, IN). For the wheel running study, we

used 24-month-old sedentary ad libitum fed (ad libitum; n=8), 24-month-old sedentary 8% food

restricted (sedentary; n=8), and 24-month-old wheel running 8% food restricted (runners; n=8) male Fisher-

344 rats (National Institutes of Aging Colony, Harlan Sprague Dawley, Indianapolis, IN). The rats were

euthanized with isoflurane, in accordance with the Guiding Principles for Research involving Animals with

all experimental procedures approved by the University of Florida's Institute on Animal Care and Use

Committee. Blood was removed by cardiac puncture, drawn into tubes containing ethylene diamine tetra-acetic

acid and heparin. The aliquots of blood were centrifuged at 40C at 1500 x g for ten minutes and plasma stored at

-806C until use.



Plasma levels of C-reactive protein


C-Reactive protein was measured using a solid-phase sandwich enzyme-linked immunosorbent assay (ELISA)

(BD Biosciences, San Diego, CA) with a minimum detectable CRP concentration of 0.35 ng/ml and inter-

assay coefficient of variation <10%. Sample absorbencies were read in triplicate at 450 nm, with

wavelength correction at 630 nm of a standard curve and expressed in _g/ml. CRP concentrations were normalized

to total protein content, measured by the Bradford method.



Plasma levels of IL-6


IL-6 concentrations were measured using an ELISA (Endogen, Rockford, IL). Sample absorbencies were read

in triplicate at 450 nm, with wavelength correction at 550 nm of a standard curve and expressed in pg/ml.

The sensitivity was < Ipg/ml and inter-assay coefficient of variation <10%. IL-6 concentrations were normalized

to total protein content, measured by the Bradford method.



Total antioxidant status


Total Antioxidant Potential was assayed using a commercially available kit (Calbiochem, La Jolla, CA). The rationale

to use the total antioxidant potential capacity was to determine the totality of all low molecular weight

antioxidants, such as vitamin C, glutathione (GSH), and Uric acid in the plasma. This temperature-

dependent, spectrophotometric assay relies on the ability of the sample antioxidants to inhibit the oxidation of






ABTS (2,2'-Azino-di-[3-ethylbenzthiazoline sulphonate]) to ABTSI+. The amount of ABTSI+ produced

was monitored by reading the absorbance at 600 nm. The degree of suppression of the absorbance at 600 nm by

the antioxidants in the sample is proportional to their concentration.



Statistical analysis


Two-tailed, unpaired t tests were used to determine significant differences between groups. Significance was set

at p<0.05.



RESULTS



Effect of short-term calorie restriction on CRP, IL-6, and total plasma antioxidant levels


First, we determined the effects of 2-month calorie restriction (40% less compared to ad libitum fed animals)

on cytokine levels (Fig. 1; Table 1). Short-term CR dramatically reduced CRP levels (Fig. 1A; 61 %), but had

no significant effect on IL-6 concentrations (Table 1). Moreover, inflammation is linked to an increase production

of oxidant, which may have affected the consumption of total plasma antioxidant levels. Total plasma

antioxidant status tended to decrease but changes were not significant (Fig. 1B; p=0.12).


125-


le 1O-



0)
. 0.75-

E 050-

025-


0.00-


e-
0
C-
"25-

E

E


B


4ko


Figure 1. Effects of short-term calorie restriction on plasma concentration of C-reactive protein (CRP)






and total antioxidant capacity in young (6-months) and age-matched calorie restricted (CR) Fisher-

344 male rats. CR was started at 4 months of age at 40% compared to ad libitum fed animals

(See Methods). Values are means � SEM. E denotes significant ( p<0.0001) difference from

young animals. Young rats, n = 8 for CR group n= 8.




Table 1
Effects of short-term calorie restriction on plasma concentration of Interleukin-6 (IL-6) in
young (6-months) and age-matched calorie restricted (CR) Fisher-344 male rats

Protein 6-month 6-month CR

Interleukin-6
1.78 � 0.23 1.40 �0.18
(pg / mg protein)

Values are means � SEM. For all groups of rats, n = 8.



Long-term calorie restriction


Circulating levels of C-reactive protein are shown to increase with age (Fig. 2A) as the old 26AD rats

had substantially higher plasma levels of CRP compared to the young 6AD group. In contrast, the old 26CR rats

had significantly lower levels of CRP compared to the 26AD group. Plasma levels of Interleukin-6 did not

change significantly with age or life-long calorie restriction (Table 2). Total plasma antioxidant levels

were significantly decreased in the old animals compared to the young (Fig. 2B), whereas the old CR group

tended to show an increase compared to old animals (p= 0.074). Taken together, life-long calorie restriction is

a potent intervention to halt inflammation and to attenuate the age associated decrease in antioxidant potential.




4-
A

- 0 3
o -
0.
S2-





O- B






E ii

O-







Figure 2. Effects of long-term calorie restriction on plasma concentration of C-reactive protein (CRP)

and total antioxidant capacity in young (6-months) and old (26-months) and old (26-month)






age-matched calorie restricted Fisher-344 male rats. CR was started at 4 months of age at

40% compared to ad libitum fed animals (See Methods). Values are means � SEM. For CRP, E

denotes significant (p<0.0001) differences from young animals; _ denotes significant

(p<0.0001) differences from old animals. For total antioxidant capacity, E denotes significant

(p=0.0113) difference from young animals. Total antioxidant capacity was not different (p= 0.1472

NS) between old CR and old rats. For all groups of rats, n = 8.



Table 2
Effects of long-term calorie restriction on plasma concentration of Interleukin-6 (IL-6) in
young (6-months), old (26-months), and old (26-month) age-matched calorie restricted (CR)
Fisher-344 male rats

Protein 6-month 26-month 26-month CR

Interleukin-6
0.70 �0.034 0.74 � 0.045 0.73 � 0.056
(pg / mg protein)

Values are means � SEM. For all groups of rats, n = 8.


Long-term exercise


Life-long exercise (and 8% CR) showed a marked decrease (38%) in CRP levels compared to the 8% CR

sedentary control rats and an even greater reduction (53%) was observed when compared with the ad libitum

fed rats (Fig. 3A). In contrast, plasma antioxidant levels were the highest (p <0.001) in the life-long exercising

8% CR group compared to 8% CR and ad libitum fed animals (Fig. 3B). No changes were found in IL-6

levels between these treatment groups (Table 3). In summary, life-long 8% calorie restriction has already

a remarkable ability to reduce CRP levels, and this group shows increases in total antioxidant status compared to

old animals. Exercise has an additional beneficial effect in reducing inflammation (CRP) and shows the highest

total plasma antioxidant status of all three groups.





41 A










o 6
0 C L


CE
'C -


r E25







Figure 3. Effects of long-term calorie restriction combined with exercise on plasma concentration of

C-reactive protein (CRP) and total antioxidant capacity in old (24-months) ad libitum fed, old (24-

month) calorie restricted (CR O/8%) as well as old (24-month) life-long wheel running calorie

restricted (8%) Fisher-344 male rats. CR was started at 4 months of age at 8% compared to ad

libitum fed animals (See Methods). Values are means � SEM. For CRP, E denotes significant

(p=0.0010) differences from old animals; _ denotes significant (p<0.0001) differences from old 8%/

CR rats. For total antioxidant capacity, E denotes significant (p= 0.0276) differences from old animals;

_ denotes significant (p= 0.0004) differences from old 8% CR rats. For all groups of rats, n = 8.



Table 3
Effects of long-term calorie restriction and exercise on plasma concentration of interleukin-6
(IL-6) in old (24-months) ad libitum fed, old (24-month) calorie restricted (CR 8%), and old (24-
month) life-long wheel running calorie restricted (8%) Fisher-344 male rats

Protein 24-month 24-month 8% CR 26-month 8% CR Excercise

Interleukin-6
1.31 � 0.14 1.41 � 0.12 1.39 � 0.09
(pg / mg protein)

Values are means � SEM. For all groups of rats, n = 8.



DISCUSSION



The objective of these studies was to examine the effects of caloric restriction and chronic exercise on the

circulating levels of CRP and IL-6 and the effect on total antioxidant potential. We found that short-term CR

(2-months) was highly effective in reducing plasma CRP levels by 61%. Life-long 40% CR and 8% CR showed

also significantly lower levels of plasma CRP compared to age-matched ad libitum fed control animals (reductions

of 60% and 25%, respectively). Moreover, life-long exercise (and 8% CR) reduced the levels of CRP by

38% compared to the 8% CR sedentary controls and by 53% compared to ad libitum fed rats. In contrast,

circulating IL-6 levels were not affected by age, diet, or exercise. Taken together, interventions known to

extend maximum and mean life span in rodent studies were effective in reducing a general systemic biomarker

of inflammation (CRP) but had no effect on the cytokine IL-6.



An elevated inflammatory milieu are among the physiological changes deemed synonymous with the aging

process and have been cited as significant indicators of mortality in older populations. 10, 24, 28, 38 Given the

social and economic impact of inflammation and cardiovascular heart disease and subclinical inflammation with

age, 28, 38 our research attempted to elucidate some potential mechanisms driving these outcomes. A

recently emerging and potentially important area of aging research closely associated with inflammation is

biological redox status. The presence of an aging effect on systemic levels of inflammation was confirmed

by increased levels of the CRP in the plasma of old animals, which significantly reduced plasma total

antioxidant redox status. Plasma contains several key cellular thiols (i.e., GSH), vitamin C and uric acid, which

are important in maintaining the plasma redox potential and largely reflect to total antioxidant capacity. Hence,





the reduction of antioxidant potential could reflect an increased consumption of antioxidants by oxidants or

a decreased synthesis of low molecular antioxidants. Further studies should explore the numerous

potential antioxidants which were affected, but it is clear from these studies that inflammation level can

significantly affect the total antioxidant potential in the plasma.



Inflammatory cell types are sensitive to reactive oxygen species and regulate their function based on the presence

of oxidants. 19, 34 In other words, specific pro-inflammatory enzymes induciblee nitric oxide synthase;

iNOS, cyclooxygenase-2; COX 2, and xanthine oxidase; XOD) can be activated by gene regulators (NF-kB

activation) in response to the formation of oxidants. This fact presents the possibility that a pro-inflammatory

state may become more chronic in association with advancing age. Key mediators of inflammatory pathways, such

as tumor necrosis factor-alpha (TNF-a) and nuclear factor-kappa B (NF-kB), have been extensively studies

by laboratories (including ours) with regard to a possible role in aging. 4, 9, 13, 21, 26, 30-32 Moreover,

several laboratories have explored the attenuation of inflammation through use of life-long calorie restriction.

Indeed, an overall chronic inflammation present in rodents was blunted with this intervention. 4, 21 Based on

these studies, researchers formulated the inflammation theory of aging, which complements the free radical

oxidative stress theory of aging and the glycooxidation theory of aging. However, whether IL-6 and CRP are

molded by interplay between oxidative stress and inflammatory mediators has not been investigated in

animal models used for aging.



We assessed CRP and IL-6 levels and antioxidant status in the plasma and observed an age-associated increase

in CRP levels (and reduction in antioxidant status), which calorie restriction (40%) attenuated. Even with short-

term CR at the age of 6 months, there is a 60% decrease in CRP levels compared to the same age rats, which

were fed an ad libitum diet. Surprisingly, 8% CR was also highly effective in reducing circulating CRP levels.

Recent studies showed that long-term calorie restriction is highly effective in reducing the risk for atherosclerosis

in humans, and this finding was strongly associated with a reduction in plasma CRP levels. 10 Hence,

caloric restriction is exceptionally effective in reducing inflammation, which may contribute to the aging process.



Wheel running (combined with 8% CR) was also very effective in modulation CRP concentration in the

plasma compared to 8% CR only. We found that plasma C-reactive protein levels were decreased by

caloric restriction (8%) and were even lower when 8% CR was combined with exercise. Combining both 8%

calorie restriction and chronic exercise decreases the levels of CRP by approximately 53%. Previous studies

have investigated whether exercise can modulate inflammatory responses. 12, 25, 42 It has been shown that

physical activity and exercise decrease levels of inflammatory markers, achieved by a decrease in the

inflammatory response. 5, 33 Exercise can also reduce the risk of numerous chronic diseases including

cardiovascular disease, hypertension, diabetes, metabolic syndrome and several forms of cancer, all of which have

an inflammatory component. 37



In our studies, IL-6 levels in the plasma did not change to a significant degree with age, caloric restriction,

or exercise. We found these data very interesting because CRP levels did increase significantly with age, and





plasma CRP is mainly under the transcriptional control of IL-6 produced by hepatocytes. However, no

quantitative relation between the circulating levels of the two markers was found. This finding implies that

other cytokines may have a more significant role in regulating CRP production with age and CR or that

inflammation may not be the only condition that causes an elevation in CRP levels. Future studies should

to determine if monokines IL-1, TNF-_, and/or interferons are responsible for the changes observed in CRP

levels, because those inflammatory markers are associated with CRP production (especially since TNF-_ has

been shown to increase with age). 31



In summary, since CRP has been shown to be a good clinical marker in predicting cardiovascular disease and

other diseases associated with inflammation, effective strategies in attenuating and maintaining this

inflammation that should be considered are caloric restriction and chronic exercise. 7 Our results imply that

the mechanisms by which caloric restriction and exercise enhance health and life span are involved with

inflammation and inflammatory pathways. Finally, life-long (40%) calorie restriction may always remain the

most robust intervention to extend maximum life span; however, moderate (8%) CR combined with exercise may

be more easily achieved in humans and is worthy of further investigation in human populations for

reducing inflammation and maintaining good health.






ACKNOWLEDGEMENTS



We are very grateful to all current and past members of the Biochemistry of Aging Laboratory for their

technical assistance in this study. This research was supported by grants to Dr. Christiaan Leeuwenburgh from

the National Institute on Aging (R01-AG17994 and AG21042). Rizwan Kalani is a University Scholar and funding

was provided by The University of Florida Scholar's Program.







REFERENCES



1. Berliner, J. A. and J. W. Heinecke. The role of oxidized lipoproteins in atherogenesis. Free Radic Biol Med.

20:707-727, 1996.

2. Chung, H. Y., K. Q. Cheng, and G. J. Chung. [Molecular inflammation in aging process]. Nippon Ronen Igakkai

Zasshi. 41:357-364, 2004.

3. Chung, H. Y., H. J. Kim, J. W. Kim, and B. P. Yu. The inflammation hypothesis of aging: molecular modulation

by calorie restriction. Ann N YAcad Sci. 928:327-335, 2001.

4. Chung, H. Y., H. J. Kim, K. W. Kim, J. S. Choi, and B. P. Yu. Molecular inflammation hypothesis of aging based on

the anti-aging mechanism of calorie restriction. Microsc Res Tech. 59:264-272, 2002.






5. Colbert, L. H., M. Visser, E. M. Simonsick, R. P. Tracy, A. B. Newman, S. B. Kritchevsky, M. Pahor, D. R. Taaffe,

J. Brach, S. Rubin, and T. B. Harris. Physical Activity, Exercise, and Inflammatory Markers in Older Adults:

Findings from The Health, Aging and Body Composition Study. J Am Geriatr Soc. 52:1098-1104, 2004.

6. Coussens, L. M. and Z. Werb. Inflammation and cancer. Nature. 420:860-867, 2002.

7. Danesh, J., J. G. Wheeler, G. M. Hirschfield, S. Eda, G. Eiriksdottir, A. Rumley, G. D. 0. Lowe, M. B. Pepys, and

V. Gudnason. C-Reactive Protein and Other Circulating Markers of Inflammation in the Prediction of Coronary

Heart Disease. N Engl J Med. 350:1387-1397, 2004.

8. de Boer, 0. J., A. C. van der Wal, and A. E. Becker. Atherosclerosis, inflammation, and infection. J Pathol.

190:237-243, 2000.

9. Dirks, A. J. and C. Leeuwenburgh. Aging and lifelong calorie restriction result in adaptations of skeletal

muscle apoptosis repressor, apoptosis-inducing factor, X-linked inhibitor of apoptosis, caspase-3, and caspase-

12. Free Radic Biol Med. 36:27-39, 2004.

10. Fontana, L., T. E. Meyer, S. Klein, and J. 0. Holloszy. Long-term calorie restriction is highly effective in reducing

the risk for atherosclerosis in humans. Proc Nat/ Acad Sci U S A. 101:6659-6663, 2004.

11. Gabay, C. and I. Kushner. Acute-Phase Proteins and Other Systemic Responses to Inflammation. N Eng J

Med. 340:448-454, 1999.

12. Gielen, S., V. Adams, S. Mobius-Winkler, A. Linke, S. Erbs, J. Yu, W. Kempf, A. Schubert, G. Schuler, and

R. Hambrecht. Anti-inflammatory effects of exercise training in the skeletal muscle of patients with chronic

heart failure. J Am Coil Cardiol. 42:861-868, 2003.

13. Greiwe, J. S., B. Cheng, D. C. Rubin, K. E. Yarasheski, and C. F. Semenkovich. Resistance exercise decreases

skeletal muscle tumor necrosis factor alpha in frail elderly humans. Faseb J. 15:475-482, 2001.

14. Holloszy, J. 0. Longevity of exercising male rats: effect of an antioxidant supplemented diet. Mech Ageing

Dev. 100:211-219, 1998.

15. Holloszy, J. 0. Mortality rate and longevity of food-restricted exercising male rats: a reevaluation. J Appl

Physiol. 82:399-403, 1997.

16. Holloszy, J. 0. and K. B. Schechtman. Interaction between exercise and food restriction: effects on longevity of

male rats. JAppl Physiol. 70:1529-1535, 1991.

17. Holloszy, J. 0. and K. B. Schechtman. Interaction between exercise and food restriction: effects on longevity of

male rats. JAppl Physiol. 70:1529-1535, 1991.

18. Holloszy, J. 0., E. K. Smith, M. Vining, and S. Adams. Effect of voluntary exercise on longevity of rats. JAppl

Physiol. 59:826-831, 1985.

19. Janssen-Heininger, Y. M., M. E. Poynter, and P. A. Baeuerle. Recent advances towards understanding

redox mechanisms in the activation of nuclear factor kappaB. Free Radic Biol Med. 28:1317-1327, 2000.


20. Jones, R. W. Inflammation and Alzheimer's disease. The Lancet. 358:436-437, 2001.







21. Kim, H. J., K. J. Jung, B. P. Yu, C. G. Cho, J. S. Choi, and H. Y. Chung. Modulation of redox-sensitive

transcription factors by calorie restriction during aging. Mech Ageing Dev. 123:1589-1595, 2002.

22. Kuta, A. and L. Baum. C-reactive protein is produced by a small number of normal human peripheral

blood lymphocytes. J. Exp. Med. 164:321-326, 1986.

23. Libby, P., P. M. Ridker, and A. Maseri. Inflammation and Atherosclerosis. Circulation. 105:1135-1143, 2002.

24. Lindmark, E., E. Diderholm, L. Wallentin, and A. Siegbahn. Relationship between interleukin 6 and mortality

in patients with unstable coronary artery disease: effects of an early invasive or noninvasive strategy.

Jama. 286:2107-2113., 2001.

25. Pastva, A., K. Estell, T. R. Schoeb, T. P. Atkinson, and L. M. Schwiebert. Aerobic exercise attenuates

airway inflammatory responses in a mouse model of atopic asthma. Immunol. 172:4520-4526, 2004.

26. Payne, A. M., S. L. Dodd, and C. Leeuwenburgh. Life-long calorie restriction in Fischer 344 rats attenuates

age-related loss in skeletal muscle-specific force and reduces extracellular space. J Appl Physiol. 95:2554-2562, 2003.

27. Pearson, T. A., G. A. Mensah, R. W. Alexander, J. L. Anderson, R. O. Cannon, III, M. Criqui, Y. Y. Fadl, S.

P. Fortmann, Y. Hong, G. L. Myers, N. Rifai, S. C. Smith, Jr, K. Taubert, R. P. Tracy, and F. Vinicor. Markers

of Inflammation and Cardiovascular Disease: Application to Clinical and Public Health Practice: A Statement

for Healthcare Professionals From the Centers for Disease Control and Prevention and the American

Heart Association. Circulation. 107:499-511, 2003.

28. Penninx, B. W., S. B. Kritchevsky, A. B. Newman, B. J. Nicklas, E. M. Simonsick, S. Rubin, M. Nevitt, M. Visser,

T. Harris, and M. Pahor. Inflammatory markers and incident mobility limitation in the elderly. JAm Geriatr

Soc. 52:1105-1113, 2004.

29. Pepys, M. B. and G. M. Hirschfield. C-reactive protein: a critical update. J. Clin. Invest. 111:1805-1812, 2003.

30. Phillips, T., A. C. Childs, D. M. Dreon, S. Phinney, and C. Leeuwenburgh. A dietary supplement attenuates IL-6

and CRP after eccentric exercise in untrained males. Med Sci Sports Exerc. 35:2032-2037, 2003.

31. Phillips, T. and C. Leeuwenburgh. Muscle fiber specific apoptosis and TNF-a signaling in sarcopenia is attenuated

by life-long calorie restriction. Faseb J, 2005.

32. Pollack, M. and C. Leeuwenburgh. Molecular Mechanisms of Oxidative Stress and Aging: Free radicals,

aging, antioxidants, and disease. In: Handbook of Oxidants and Antioxidants in Exercise. L. P. a. O. H. C.K.

Sen (Ed.): Elsevier Science, 1999.

33. Rauramaa, R., P. Halonen, S. B. Vaisanen, T. A. Lakka, A. Schmidt-Trucksass, A. Berg, I. M. Penttila, T.

Rankinen, and C. Bouchard. Effects of Aerobic Physical Exercise on Inflammation and Atherosclerosis in Men:

The DNASCO Study: A Six-Year Randomized, Controlled Trial. Ann Intern Med. 140:1007-1014, 2004.

34. Reid, M. B. and Y. P. Li. Cytokines and oxidative signalling in skeletal muscle. Acta Physiol Scand. 171:225-232, 2001.

35. Ridker, P. M. High-sensitivity C-reactive protein: potential adjunct for global risk assessment in the





primary prevention of cardiovascular disease. Circulation. 103:1813-1818., 2001.


36. Ridker, P. M., M. Cushman, M. J. Stampfer, R. P. Tracy, and C. H. Hennekens. Inflammation, aspirin, and the risk

of cardiovascular disease in apparently healthy men. N Engl J Med. 336:973-979., 1997.

37. Roberts, C. K. and R. J. Barnard. Effects of exercise and diet on chronic disease. JAppl Physiol. 98:3-30, 2005.

38. Roubenoff, R., H. Parise, H. A. Payette, L. W. Abad, R. D'Agostino, P. F. Jacques, P. W. Wilson, C. A. Dinarello, and

T. B. Harris. Cytokines, insulin-like growth factor 1, sarcopenia, and mortality in very old community-dwelling

men and women: the Framingham Heart Study. Am J Med. 115:429-435, 2003.

39. Sohal, R. S., R. J. Mockett, and W. C. Orr. Mechanisms of aging: an appraisal of the oxidative stress hypothesis.

Free Radic Biol Med. 33:575-586, 2002.

40. Volanakis, J. E. Human C-reactive protein: expression, structure, and function. Molecular Immunology. 38:189-

197, 2001.

41. Weindruch, R. and R. S. Sohal. Seminars in medicine of the Beth Israel Deaconess Medical Center. Caloric intake

and aging.N Engl J Med. 337:986-994, 1997.

42. You, T., D. M. Berman, A. S. Ryan, and B. J. Nicklas. Effects of hypocaloric diet and exercise training on

inflammation and adipocyte lipolysis in obese postmenopausal women. 3 Clin Endocrinol Metab. 89:1739-1746, 2004.


--top--



Back to the Journal of Undergraduate Research


College of Liberal Arts and Sciences I University Scholars Program I University of Florida I


U* 1 UNIVERSITY of
UF FLORIDA
The f,,rrillili hr Tr Tfir Color ahoqn


� University of Florida, Gainesville, FL 32611; (352) 846-2032.