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C-reactive protein (CRP) is an acute inflammatory protein that increases up to 1,000-fold at sites of infection or inflammation. CRP is produced as a homopentameric protein, termed native CRP (nCRP), which can irreversibly dissociate at sites of inflammation and infection into five separate monomers, termed monomeric CRP (mCRP). CRP is synthesized primarily in liver hepatocytes but also by smooth muscle cells, macrophages, endothelial cells, lymphocytes, and adipocytes. Evidence suggests that estrogen in the form of hormone replacement therapy influences CRP levels in the elderly. Having been traditionally utilized as a marker of infection and cardiovascular events, there is now growing evidence that CRP plays important roles in inflammatory processes and host responses to infection including the complement pathway, apoptosis, phagocytosis, nitric oxide (NO) release, and the production of cytokines, particularly interleukin-6 and tumor necrosis factor-α. Unlike more recent publications, the findings of early work on CRP can seem somewhat unclear and at times conflicting since it was often not specified which particular CRP isoform was measured or utilized in experiments and whether responses attributed to nCRP were in fact possibly due to dissociation into mCRP or lipopolysaccharide contamination. In addition, since antibodies for mCRP are not commercially available, few laboratories are able to conduct studies investigating the mCRP isoform. Despite these issues and the fact that most CRP research to date has focused on vascular disorders, there is mounting evidence that CRP isoforms have distinct biological properties, with nCRP often exhibiting more anti-inflammatory activities compared to mCRP. The nCRP isoform activates the classical complement pathway, induces phagocytosis, and promotes apoptosis. On the other hand, mCRP promotes the chemotaxis and recruitment of circulating leukocytes to areas of inflammation and can delay apoptosis. The nCRP and mCRP isoforms work in opposing directions to inhibit and induce NO production, respectively. In terms of pro-inflammatory cytokine production, mCRP increases interleukin-8 and monocyte chemoattractant protein-1 production, whereas nCRP has no detectable effect on their levels. Further studies are needed to expand on these emerging findings and to fully characterize the differential roles that each CRP isoform plays at sites of local inflammation and infection.

C-reactive protein (CRP) is a non-specific diagnostic marker of inflammation and an evolutionarily conserved protein with roles in innate immune signaling. Natural CRP is composed of five identical globular subunits that form a pentamer, but the role of pentameric CRP (pCRP) during inflammatory pathogenesis remains controversial. Emerging evidence suggests that pCRP can be dissociated into monomeric CRP (mCRP) that has major roles in host defenses and inflammation. Here, we discuss our current knowledge of the dissociation mechanisms of pCRP and summarize the stepwise conformational transition model to mCRP to elucidate how CRP dissociation contributes to proinflammatory activity. These discussions will evoke new understanding of this ancient protein.

Background Exploratory analysis to determine the effect of semaglutide versus comparators on high-sensitivity C-reactive protein (hsCRP) in subjects with type 2 diabetes. Methods Trials of once-weekly subcutaneous (SUSTAIN 3) and once-daily oral (PIONEER 1, 2, 5) semaglutide with hsCRP data were analyzed. Subjects with type 2 diabetes (N = 2482) received semaglutide (n = 1328) or comparators (placebo, n = 339; exenatide extended-release, n = 405; empagliflozin, n = 410). hsCRP ratio to baseline at end-of-treatment was analyzed overall, by clinical cutoff (< 1.0, ≥ 1.0 to ≤ 3.0, or > 3.0 mg/L), by tertile, and by estimated glomerular filtration rate in PIONEER 5 (a trial which was conducted in a population with type 2 diabetes and chronic kidney disease [CKD]). Mediation analyses assessed the effect of change in glycated hemoglobin (HbA 1c ) and/or change in body weight (BW) on hsCRP reductions. Results Geometric mean baseline hsCRP was similar across trials (range 2.7–3.0 mg/L). Semaglutide reduced hsCRP levels by clinical cutoffs and tertiles from baseline to end-of-treatment in all trials versus comparators (estimated treatment ratios [ETRs] versus comparators: 0.70–0.76; p < 0.01) except versus placebo in PIONEER 5 (ETR [95% CI]: 0.83 [0.67–1.03]; p > 0.05). The effect of semaglutide on hsCRP was partially mediated (20.6–61.8%) by change in HbA 1c and BW. Conclusions Semaglutide reduced hsCRP ratios-to-baseline versus comparators in subjects with type 2 diabetes (not significant with CKD). This effect was partially mediated via reductions in HbA 1c and BW and potentially by a direct effect of semaglutide. Semaglutide appears to have an anti-inflammatory effect, which is being further investigated in ongoing trials. Trial registrations: ClinicalTrials.gov identifiers: NCT01885208 (first registered June 2013), NCT02906930 (first registered September 2016), NCT02863328 (first registered August 2016), NCT02827708 (first registered July 2016).

Inflammation and hyperlipidaemia jointly contribute to atherothrombotic disease. However, when people are treated with intensive statin therapy, the relative contributions of inflammation and hyperlipidaemia to the risk of future cardiovascular events might change, which has implications for the choice of adjunctive cardiovascular therapeutics. We aimed to evaluate the relative importance of high-sensitivity C-reactive protein (CRP) and low-density lipoprotein cholesterol (LDLC) as determinants of risk for major adverse cardiovascular events, cardiovascular death, and all-cause-death among patients receiving statins. We did a collaborative analysis of patients with—or at high risk of—atherosclerotic disease, who were receiving contemporary statins and were participants in the multinational PROMINENT (NCT03071692), REDUCE-IT (NCT01492361), or STRENGTH (NCT02104817) trials. Quartiles of increasing baseline high-sensitivity CRP (a biomarker of residual inflammatory risk) and of increasing baseline LDLC (a biomarker of residual cholesterol risk) were assessed as predictors of future major adverse cardiovascular events, cardiovascular death, and all-cause death. Hazard ratios (HRs) for cardiovascular events and deaths were calculated across quartiles of high-sensitivity CRP and LDLC in analyses adjusted for age, gender, BMI, smoking status, blood pressure, previous history of cardiovascular disease, and randomised treatment group assignment. 31 245 patients were included in the analysis from the PROMINENT (n=9988), REDUCE-IT (n=8179), and STRENGTH (n=13 078) trials. The observed ranges for baseline high-sensitivity CRP and LDLC, and the relationships of each biomarker to subsequent cardiovascular event rates, were almost identical in the three trials. Residual inflammatory risk was significantly associated with incident major adverse cardiovascular events (highest high-sensitivity CRP quartile vs lowest high-sensitivity CRP quartile, adjusted HR 1·31, 95% CI 1·20–1·43; p<0·0001), cardiovascular mortality (2·68, 2·22–3·23; p<0·0001), and all-cause mortality (2·42, 2·12–2·77; p<0·0001). By contrast, the relationship of residual cholesterol risk was neutral for major adverse cardiovascular events (highest LDLC quartile vs lowest LDLC quartile, adjusted HR 1·07, 95% CI 0·98–1·17; p=0·11), and of low magnitude for cardiovascular death (1·27, 1·07–1·50; p=0·0086) and all-cause death (1·16, 1·03–1·32; p=0·025). Among patients receiving contemporary statins, inflammation assessed by high-sensitivity CRP was a stronger predictor for risk of future cardiovascular events and death than cholesterol assessed by LDLC. These data have implications for the selection of adjunctive treatments beyond statin therapy and suggest that combined use of aggressive lipid-lowering and inflammation-inhibiting therapies might be needed to further reduce atherosclerotic risk. Kowa Research Institute, Amarin, AstraZeneca.

The humoral arm of innate immunity includes diverse molecules with antibody-like functions, some of which serve as disease severity biomarkers in coronavirus disease 2019 (COVID-19). The present study was designed to conduct a systematic investigation of the interaction of human humoral fluid-phase pattern recognition molecules (PRMs) with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Of 12 PRMs tested, the long pentraxin 3 (PTX3) and mannose-binding lectin (MBL) bound the viral nucleocapsid and spike proteins, respectively. MBL bound trimeric spike protein, including that of variants of concern (VoC), in a glycan-dependent manner and inhibited SARS-CoV-2 in three in vitro models. Moreover, after binding to spike protein, MBL activated the lectin pathway of complement activation. Based on retention of glycosylation sites and modeling, MBL was predicted to recognize the Omicron VoC. Genetic polymorphisms at the MBL2 locus were associated with disease severity. These results suggest that selected humoral fluid-phase PRMs can play an important role in resistance to, and pathogenesis of, COVID-19, a finding with translational implications.Stravalaci et al. examined recognition of SARS-CoV-2 by human soluble innate pattern recognition receptor. They report that pentraxin 3 and mannose-binding protein recognize viral nucleoprotein and spike, respectively. Mannose-binding lectin has antiviral activity, and human genetic polymorphisms of MBL2 are associated with more severe COVID-19.

Periodontitis has been associated with low-grade inflammation as assessed by C-reactive protein (CRP) levels and its treatment can decrease CRP serum levels. The aim of this systematic review was to critically appraise the evidence comparing CRP serum levels (standard and high-sensitivity [hs]) of otherwise healthy patients suffering from periodontitis when compared to controls. The impact of intensive and non-intensive nonsurgical periodontal treatment (NSPT) on hs-CRP was also investigated. Four electronic databases (Pubmed, The Cochrane Central Register of Controlled Trials [CENTRAL], EMBASE and Web of Science) were searched up to February 2021 and the review was completed according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines (PROSPERO No. CRD42020167454). Observational and intervention studies that: 1) evaluated CRP and hs-CRP serum levels in patients with and without periodontitis, and; 2) hs- CRP levels after NSPT were included. Following risk of bias appraisal, both qualitative and quantitative analyses were performed. Pooled estimates were rendered through ratio of means (RoM) random-effects meta-analyses. After screening 485 studies, 77 case-control studies and 67 intervention trials were included. Chronic and aggressive periodontitis diagnoses were consistently associated with higher levels of CRP and hs-CRP (p<0.001). Patients with aggressive periodontitis exhibited on average more than 50% higher levels of CRP (RoM [95% confidence interval [CI]]: 1.56 [1.15; 2.12], p=0.0039) than patients with chronic periodontitis. Intensive NSPT induced an immediate increase of hs-CRP followed by a progressive decrease whilst non-intensive NSPT consistently decreased hs-CRP after treatment up to 180 days (p<0.001). These findings provide robust evidence that periodontitis is associated with systemic inflammation as measured by serum CRP levels. Periodontitis treatment induces a short-term acute inflammatory increase when performed in an intensive session, whilst a progressive reduction up to 6 months was demonstrated when performed in multiple visits.

C-reactive protein (CRP) is a widely known, hepatically synthesized protein whose blood levels change rapidly and pronouncedly in response to any tissue damaging event associated with an inflammatory response. The synthesis and secretion of CRP is stimulated by interleukin-6, an early pleiotropic cytokine released by macrophages, endothelial, and other cells that are activated when localized normal tissue structures are compromised by trauma or disease. Serum CRP levels can change rapidly and robustly from 10-100-fold within 6-72 h of any tissue damaging event. Elevated blood levels correlate with the onset and extent of both activated inflammation and the acute phase biochemical response to the tissue insult. Because its functional bioactivity as the prototypic acute phase reactant has eluded clear definition for decades, diagnosticians of various conditions and diseases use CRP blood levels as a simple index for ongoing inflammation. In many pathologies, which involves many different tissues, stages of disease, treatments, and responses to treatments, its interpretive diagnostic value requires a deeper understanding of the localized tissue processes and events that contribute signals which regulate protective or pathological host defense bioactivities. This report presents concepts that describe how local tissue activation events can lead to a non-proteolytic, conformational rearrangement of CRP into a unique isoform with distinctive solubility, antigenicity, binding reactivities and bioactivities from that protein widely known and measured in serum. By describing factors that control the expression, tissue localization, half-life and pro-inflammatory amplification activity of this CRP isoform, a unifying explanation for the diagnostic significance of CRP measurement in disease is advanced.

Background Both the triglyceride-glucose (TyG) index, as a surrogate marker of insulin resistance, and systemic inflammation are predictors of cardiovascular diseases; however, little is known about the coexposures and relative contributions of TyG index and inflammation to cardiovascular diseases. Using the nationally representative data from the China Health and Retirement Longitudinal Study (CHARLS), we conducted longitudinal analyses to evaluate the joint and mutual associations of the TyG index and high-sensitivity C-reactive protein (hsCRP) with cardiovascular events in middle-aged and older Chinese population. Methods This study comprised 8 658 participants aged at least 45 years from the CHARLS 2011 who are free of cardiovascular diseases at baseline. The TyG index was calculated as Ln [fasting triglyceride (mg/dL) × fasting glucose (mg/dL)/2]. Cardiovascular events were defined as the presence of physician-diagnosed heart disease and/or stroke followed until 2018.We performed adjusted Cox proportional hazards regression and mediation analyses. Results The mean age of the participants was 58.6 ± 9.0 years, and 3988 (46.1%) were females. During a maximum follow-up of 7.0 years, 2606 (30.1%) people developed cardiovascular diseases, including 2012 (23.2%) cases of heart diseases and 848 (9.8%) cases of stroke. Compared with people with a lower TyG index (< 8.6 [median level]) and hsCRP < 1 mg/L, those concurrently with a higher TyG and hsCRP had the highest risk of overall cardiovascular disease (adjusted hazard ratio [aHR], 1.300; 95% CI 1.155–1.462), coronary heart disease (aHR, 1.294; 95% CI 1.130–1.481) and stroke (aHR, 1.333; 95% CI 1.093–1.628), which were predominant among those aged 70 years or below. High hsCRP significantly mediated 13.4% of the association between the TyG index and cardiovascular disease, while TyG simultaneously mediated 7.9% of the association between hsCRP and cardiovascular risk. Conclusions The findings highlight the coexposure effects and mutual mediation between the TyG index and hsCRP on cardiovascular diseases. Joint assessments of the TyG index and hsCRP should be underlined for the residual risk stratification and primary prevention of cardiovascular diseases, especially for middle-aged adults.

Objective C-reactive protein-triglyceride-glucose index (CTI) has been proposed as a novel biomarker for insulin resistance and inflammation. However, the association between CTI and the risk of stroke, particularly in individuals with different glycemic status, remains unclear. Methods A total of 10,443 middle-aged and elderly participants were enrolled from the China Health and Retirement Longitudinal Study (CHARLS). The primary endpoint was the occurrence of stroke events. The CTI was calculated using the formula 0.412* Ln (CRP [mg/L]) + Ln (TG [mg/dl] × FPG [mg/dl])/2. The Kaplan–Meier curves, Cox proportional hazard models, and restricted cubic spline analysis were applied to explore the association between CTI and the risk of stroke according to gender, age and glycemic status. Results During a median follow-up of 9 years, 960 (9.2%) participants experienced a stroke. Our findings revealed a significant positive linear relationship between CTI and the occurrence of stroke. The association was similar between male and female, despite the HR tended to be higher in females (HR 1.22, 95% CI 1.09, 1.36) than males (HR 1.15, 95% CI 1.02, 1.29), and similar in middle-aged (HR 1.25, 95% CI 1.11, 1.41) and elderly participants (HR 1.12, 95% CI 1.00, 1.26). In different glycemic status, high levels of CTI were found to be linked to an increased risk of stroke in individuals with normal glucose regulation (NGR) (HR 1.33, 95% CI 1.11, 1.59) and prediabetes mellitus (Pre-DM) (HR 1.20, 95% CI 1.04, 1.39). However, this association was not observed in individuals with diabetes mellitus (DM). Conclusions Our findings revealed a significant positive linear relationship between CTI and the occurrence of stroke. The association between CTI and stroke was similar between male and female, and similar in middle-aged and elderly participants. In different glycemic status, the association was significant in individuals with NGR and Pre-DM. Graphical abstract What is currently known about this topic? CTI has been proposed as a novel biomarker for insulin resistance and inflammation. What is the key research question? What is the relationship between CTI and stroke risk under different genders, ages, and glycemic status? What is new? This is the first large-scale study to demonstrate this relationship between the CTI and stroke risk, and assessed this relationship according to gender, ages and glycemic status. How might this study influence clinical practice? Our research findings demonstrate a significant positive linear relationship between CTI and the incidence of stroke. To reduce the risk of stroke, different strategies must be adopted to manage CTI levels based on gender, age, and glycemic status.

Excess adiposity is a reversible etiologic risk factor for obstructive sleep apnea. In this trial, tirzepatide reduced the apnea–hypopnea index of participants with obstructive sleep apnea and obesity.