C-reactive protein - biological functions, cardiovascular disease and physical exercise

Abstract

C-reactive protein (CRP) is an acute-phase reactant that increases in response to noxious stimuli that inevitably induce cellular and/or tissue injury. The increased synthesis of CRP occurs predominantly in the liver and peaks 24 - 48 hours after the inciting stimulus. CRP forms an integral component of innate immunity and serves primarily to recognise potential pathogens and damaged cells. It facilitates the removal of these cells through opsonisation and activates the complement system. With increasing evidence supporting the classification of artherosclerosis as inflammatory in nature, CRP has received considerable attention as a marker, and in some cases a contributor towards this cardiovascular disease. Traditionally, CRP has been measured within exercise studies to provide evidence that an acute-phase inflammatory response can or has been initiated. Although the elevation in CRP following exercise has largely been attributed to muscle damage, evidence is mounting to contest this premise. Participation in chronic exercise has been associated with a reduced risk of cardiovascular disease. Numerous studies have now shown an inverse relationship between physical activity levels and resting concentrations of CRP. Thus, exercise may prove beneficial in lowering systemic inflammatory markers such as CRP, and consequently contribute towards preventing the progression of inflammatory disorders. South African Journal of Sports Medicine Vol. 18 (1) 2006: pp. 24-28

Effects of the 5-m Shuttle Run Test on Markers of Muscle Damage, Inflammation, and Fatigue in Healthy Male Athletes

“…In fact, the higher levels of ALAT are indicative of muscle injury in the absence of liver disease, which is consistent with the higher levels of CK and LDH after the 5mSRT. Moreover, muscle damage induced by the 5mSRT is indicative of inflammatory responses, which is confirmed in this study by the elevation of CRP [ 23 , 50 , 51 , 52 ].…”

C-Reactive Protein: An In-Depth Look into Structure, Function, and Regulation

“…CRP concentration in circulation is primarily determined by its synthesis rate [ 28 ]. Although the liver is the main site for production and release of CRP, its mRNA has been found in a myriad of extrahepatic sites, including adipose tissue [ 29 ], lungs [ 30 ], epithelial cells of renal cortical tubules [ 31 ], lymphocytes, and atherosclerotic lesions, in both macrophages and smooth muscle cells [ 32 – 34 ]. Numerous studies have focused on identifying other extrahepatic sources of CRP production that may underlie the lower and more sustained CRP concentrations which appear to predict cardiovascular risk; these include findings of CRP synthesis in coronary smooth muscle cells in response to inflammatory cytokines.…”

Revisiting the clinical usefulness of C-reactive protein in the set of cancer cachexia

“… 49 An increase in CRP circulating levels is not immediately noticed, being detected after 6 to 8 hours, peaking at 24 to 48 hours. Although CRP is mainly synthesized in the liver, its mRNA was also detected in respiratory tract epithelial cells, T-lymphocytes, 50 adipose tissues, epithelial cells of renal cortical tubules, and in smooth muscle cells and macrophages from atherosclerotic plaques. 51 …”