Inflammation, insulin resistance, and diabetes-mendelian randomization using CRP haplotypes points upstream

Background Raised C-reactive protein (CRP) is a risk factor for type 2 diabetes. According to the Mendelian randomization method, the association is likely to be causal if genetic variants that affect CRP level are associated with markers of diabetes development and diabetes. Our objective was to examine the nature of the association between CRP phenotype and diabetes development using CRP haplotypes as instrumental variables. Methods and Findings We genotyped three tagging SNPs (CRP + 2302G > A; CRP + 1444T > C; CRP + 4899T > G) in the CRP gene and measured serum CRP in 5,274 men and women at mean ages 49 and 61 y (Whitehall II Study). Homeostasis model assessment-insulin resistance (HOMA-IR) and hemoglobin A1c (HbA1c) were measured at age 61 y. Diabetes was ascertained by glucose tolerance test and self-report. Common major haplotypes were strongly associated with serum CRP levels, but unrelated to obesity, blood pressure, and socioeconomic position, which may confound the association between CRP and diabetes risk. Serum CRP was associated with these potential confounding factors. After adjustment for age and sex, baseline serum CRP was associated with incident diabetes (hazard ratio = 1.39 [95% confidence interval 1.29-1.51], HOMA-IR, and HbA1c, but the associations were considerably attenuated on adjustment for potential confounding factors. In contrast, CRP haplotypes were not associated with HOMA-IR or HbA1c (p=0.52-0.92). The associations of CRP with HOMA-IR and HbA1c were all null when examined using instrumental variables analysis, with genetic variants as the instrument for serum CRP. Instrumental variables estimates differed from the directly observed associations (p=0.007-0.11). Pooled analysis of CRP haplotypes and diabetes in Whitehall II and Northwick Park Heart Study II produced null findings (p=0.25-0.88). Analyses based on the Wellcome Trust Case Control Consortium (1,923 diabetes cases, 2,932 controls) using three SNPs in tight linkage disequilibrium with our tagging SNPs also demonstrated null associations. Conclusions Observed associations between serum CRP and insulin resistance, glycemia, and diabetes are likely to be noncausal. Inflammation may play a causal role via upstream effectors rather than the downstream marker CRP

Levels of C-reactive protein associated with high and very high cardiovascular risk are prevalent in patients with rheumatoid arthritis.

ObjectiveC-reactive protein (CRP) levels>3 mg/L and>10 mg/L are associated with high and very high cardiovascular risk, respectively, in the general population. Because rheumatoid arthritis (RA) confers excess cardiovascular mortality, we determined the prevalence of these CRP levels among RA patients stratified on the basis of their RA disease activity.MethodsWe evaluated physician and patient global assessments of disease activity, tender and swollen 28 joint counts, erythrocyte sedimentation rate (ESR), and CRP measured in a single clinic visit for 151 RA patients. Disease activity was calculated using the Clinical Disease Activity Index (CDAI) and the Disease Activity Score 28 Joints (DAS28-ESR and DAS28-CRP).ResultsMedian CRP level was 5.3 mg/L. 68% of patients had CRP>3 mg/L, and 25% had CRP>10 mg/L. Of those with 0-1 swollen joints (n = 56), or 0-1 tender joints (n = 81), 64% and 67%, respectively, had CRP>3 mg/L, and 23% and 20%, respectively, had CRP>10 mg/L. Of those with remission or mildly active disease by CDAI (n = 58), DAS28-ESR (n = 39), or DAS28-CRP (n = 70), 49-66% had CRP>3 mg/L, and 10-14% had CRP>10 mg/L. Of patients with moderate disease activity by CDAI (n = 51), DAS28-ESR (n = 78), or DAS28-CRP (n = 66), 67-73% had CRP>3 mg/L, and 25-33% had CRP>10 mg/L.ConclusionEven among RA patients whose disease is judged to be controlled by joint counts or standardized disease scores, a substantial proportion have CRP levels that are associated high or very high risk for future cardiovascular events in the general population

Identification of the CRP regulon using in vitro and in vivo transcriptional profiling

The Escherichia coli cyclic AMP receptor protein (CRP) is a global regulator that controls transcription initiation from more than 100 promoters by binding to a specific DNA sequence within cognate promoters. Many genes in the CRP regulon have been predicted simply based on the presence of DNA-binding sites within gene promoters. In this study, we have exploited a newly developed technique, run-off transcription/microarray analysis (ROMA) to define CRP-regulated promoters. Using ROMA, we identified 176 operons that were activated by CRP in vitro and 16 operons that were repressed. Using positive control mutants in different regions of CRP, we were able to classify the different promoters into class I or class II/III. A total of 104 operons were predicted to contain Class II CRP-binding sites. Sequence analysis of the operons that were repressed by CRP revealed different mechanisms for CRP inhibition. In contrast, the in vivo transcriptional profiles failed to identify most CRP-dependent regulation because of the complexity of the regulatory network. Analysis of these operons supports the hypothesis that CRP is not only a regulator of genes required for catabolism of sugars other than glucose, but also regulates the expression of a large number of other genes in E.coli. ROMA has revealed 152 hitherto unknown CRP regulons

Cost-Effectiveness of Point-of-Care C-Reactive Protein Tests for Respiratory Tract Infection in Primary Care in England

Introduction Despite recommendations that general practitioners (GPs) delay antibiotic prescribing for respiratory tract infections (RTIs), antibiotic prescriptions in primary care in England increased by 4.1% from 2010 to 2013. C-reactive protein (CRP) point-of-care tests (POCT), for example, the Afinion™ Analyzer (Alere Ltd, Stockport, UK) device, are widely used in several countries in the European Union. Studies suggest that CRP POCT use, either alone or in combination with communication training, reduces antibiotic prescribing and improves quality of life for patients presenting with RTI symptoms. The aim of this study is to evaluate the cost-effectiveness of CRP POCT for RTIs in primary care in England over 3 years for three different strategies of care compared to standard practice. Methods An economic evaluation was carried out to compare the costs and benefits of three different strategies of CRP testing (GP plus CRP; practice nurse plus CRP; and GP plus CRP and communication training) for patients with RTI symptoms as defined by National Institute for Health and Care Excellence guideline CG69, compared with current standard GP practice without CRP testing. Analysis consisted of a decision tree and Markov model to describe the quality-adjusted life years (QALYs) and cost per 100 patients, together with the number of antibiotic prescriptions and RTIs for each group. Results Compared with current standard practice, the GP plus CRP and practice nurse plus CRP test strategies result in increased QALYs and reduced costs, while the GP plus CRP testing and communication training strategy is associated with increased costs and reduced QALYs. Additionally, all three CRP arms led to fewer antibiotic prescriptions and infections over 3 years. Conclusion The additional cost per patient of the CRP test is outweighed by the associated cost savings and QALY increment associated with a reduction in infections in the long term

Low prevalence of an acute phase response in asymptomatic children from a malaria-endemic area of Papua New Guinea

Levels of C-reactive protein (CRP), a classic marker for the acute phase response (APR), were measured in children with asymptomatic malaria infection in the Amele region of Papua New Guinea (PNG). Despite the presence of parasitemia, the prevalence of CRP levels consistent with an APR (CRP > 10 (xg/mL) was very low (< 10%). Splenomegaly was significantly associated with increased parasitemia (P < 0.001) and CRP levels (P < 0.001), highlighting the importance of splenomegaly as an indicator of recent high density infection in this population. Multivariate analysis showed that CRP levels were significantly associated with splenomegaly, fever, hemoglobin, and age (P < 0.002). CRP levels also increased with increasing parasitemia (P < 0.001) but remained < 3.5 (xg/mL. The low levels of CRP indicate that children in the Amele modulate inflammation associated with malaria

Inflammation and endothelial function: Direct vascular effects of human C-reactive protein on nitric oxide bioavailability

Background - Circulating concentrations of the sensitive inflammatory marker C-reactive protein (CRP) predict future cardiovascular events, and CRP is elevated during sepsis and inflammation, when vascular reactivity may be modulated. We therefore investigated the direct effect of CRP on vascular reactivity. Methods and Results - The effects of isolated, pure human CRP on vasoreactivity and protein expression were studied in vascular rings and cells in vitro, and effects on blood pressure were studied in rats in vivo. The temporal relationship between changes in CRP concentration and brachial flow-mediated dilation was also studied in humans after vaccination with Salmonella typhi capsular polysaccharide, a model of inflammatory endothelial dysfunction. In contrast to some previous reports, highly purified and well-characterized human CRP specifically induced hyporeactivity to phenylephrine in rings of human internal mammary artery and rat aorta that was mediated through physiological antagonism by nitric oxide (NO). CRP did not alter endothelial NO synthase protein expression but increased protein expression of GTP cyclohydrolase-1, the rate-limiting enzyme in the synthesis of tetrahydrobiopterin, the NO synthase cofactor. In the vaccine model of inflammatory endothelial dysfunction in humans, increased CRP concentration coincided with the resolution rather than the development of endothelial dysfunction, consistent with the vitro findings; however, administration of human CRP to rats had no effect on blood pressure. Conclusions - Pure human CRP has specific, direct effects on vascular function in vitro via increased NO production; however, further clarification of the effect, if any, of CRP on vascular reactivity in humans in vivo will require clinical studies using specific inhibitors of CRP. © 2005 American Heart Association, Inc

Broad-Scale Relations between Conservation Reserve Program and Grassland Birds: Do Cover Type, Configuration and Contract Age Matter?

The Conservation Reserve Program (CRP) is a voluntary cropland set-aside program where environmentally-sensitive cropland is retired to a conservation practice. Grassland birds should benefit because most CRP is grass habitat and because amount of land in CRP is highest in agriculture-dominated areas of the United States where grassland habitat has been most impacted. We used the Breeding Bird Survey and Common Land Unit (CLU) data (spatially-explicit data of farm field boundaries and land cover) to identify relations between types and configurations of CRP and grassland bird abundance in 3 Midwestern states. All 13 species we studied were related to at least one aspect of CRP habitat - specific conservation practices (e.g., native vs. exotic grass), CRP habitat configuration, or habitat age. Treating all types of CRP as a single habitat type would have obscured bird-CRP relations. Based on our results, creating a mosaic of large and small set-aside patches could benefit both area-sensitive and edge-associated grassland birds. Additionally, northern bobwhite and other birds that use early successional grasslands would benefit from periodic disturbances. CRP, agrienvironment schemes, and other government-sponsored set-aside programs may be most successful when administered as part of a targeted, regional conservation plan

Constraining the population of cosmic ray protons in cooling flow clusters with gamma-ray and radio observations: Are radio mini-halos of hadronic origin?

We wish to constrain the cosmic-ray proton (CRp) population in galaxy clusters. By hadronic interactions with the thermal gas of the intra-cluster medium (ICM), the CRp produce gamma-rays for which we develop an analytic formalism to deduce their spectral distribution. Assuming the CRp-to-thermal energy density ratio X_CRp and the CRp spectral index to be spatially constant, we derive an analytic relation between the gamma-ray and bolometric X-ray fluxes, F_gamma and F_X. Based on our relation, we compile a sample of suitable clusters which are promising candidates for future detection of gamma-rays resulting from hadronic CRp interactions. Comparing to EGRET upper limits, we constrain the CRp population in the cooling flow clusters Perseus and Virgo to X_CRp < 20%. Assuming a plausible value for the CRp diffusion coefficient kappa, we find the central CRp injection luminosity of M 87 to be limited to 10^43 erg s^-1 kappa/(10^29 cm^2 s^-1). The synchrotron emission from secondary electrons generated in CRp hadronic interactions allows even tighter limits to be placed on the CRp population using radio observations. We obtain excellent agreement between the observed and theoretical radio brightness profiles for Perseus, but not for Coma without a radially increasing CRp-to-thermal energy density profile. Since the CRp and magnetic energy densities necessary to reproduce the observed radio flux are very plausible, we propose synchrotron emission from secondary electrons as an attractive explanation of the radio mini-halos found in cooling flow clusters. This model can be tested with future sensitive gamma-ray observations of the accompanying pi0-decays. We identify Perseus (A 426), Virgo, Ophiuchus, and Coma (A 1656) as the most promising candidate clusters for such observations.Comment: 20 pages, 8 figures. Corrected Figure 3 to match the erratum accepted by A&

A systematic review of the association between circulating concentrations of C reactive protein and cancer.

The objective of this study was to review and summarise the published evidence for an association between circulating concentrations of C reactive protein (CRP) and cancer through a systematic review. 90 discrete studies were identified. 81 (90%) were prevalent case-control or cross-sectional studies, and only 9 studies had a prospective design. In most prevalent studies, CRP concentrations were found to be higher in patients with cancer than in healthy controls or controls with benign conditions. Of the nine large prospective studies identified in this review, four reported no relationship between circulating CRP levels and breast, prostate or colorectal cancers, and five studies found that CRP was associated with colorectal or lung cancers. Most of the studies evaluating CRP as a diagnostic marker of cancer did not present relevant statistical analyses. Furthermore, any association reported in the prevalent studies might reflect reverse causation, survival bias or confounding. The prospective studies provided no strong evidence for a causal role of CRP in cancer. Instead of further prevalent studies, more large prospective studies and CRP gene-cancer association studies would be valuable in investigating the role of CRP in cancer

A new nanocrystalline diamond-based biosensor for the detection of cardiovascular risk markers

In this paper, a new method to probe associative interactions of C-reactive protein (CRP) antigen with CRP antibody immobilized on a gold-interdigitated diamond electrodes was investigated. The CRP antigen detection was performed by capacitive/dielectric-constant measurements. Our results showed that the dynamic detection range using optimized conditions for a given antibody concentration (100 μg/ml) was found to be in the range 25-800 ng/ml of CRP-antigen. Biosensor developed in this study can be potentially used for detection of elevated CRP levels in suspected subjects for early diagnosis