Preanalytic and analytic sources of variations in C-reactive protein measurement: implications for cardiovascular disease risk assessment

The cross-sectional relationship between vitamin C and high-sensitivity C-reactive protein levels: insights from NHANES database

Background

Ascorbic acid or vitamin C has antioxidant and anti-inflammatory properties that may impact markers of inflammation like C-reactive protein (CRP). However, studies specifically on vitamin C and high-sensitivity CRP (hs-CRP) have been scarce.

Methods

We conducted a cross-sectional analysis of the National Health and Nutrition Examination Survey 2017-2018 dataset including 5,380 U.S. adults aged ≥20 years. Multiple regression models examined the relationship between plasma vitamin C and serum hs-CRP while adjusting for potential confounders. Stratified analyses and curve fitting assessed effect modification and nonlinearity.

Results

An inverse association was found between plasma vitamin C and serum hs-CRP overall (β = -0.025, 95% CI: -0.033 to -0.017, p < 0.00001) and in subgroups except for the "other Hispanic" subgroup in model II (β = -0.009, 95% CI: (-0.040, 0.023), p = 0.5885). The relationship was nonlinear, with the greatest hs-CRP reduction observed up to a plasma vitamin C level of 53.1 μmol/L.

Conclusion

The results showed a non-linear negative correlation between vitamin C levels and hs-CRP in adults. These results suggest vitamin C intake may reduce inflammation and cardiovascular risk, but only up to 53.1 μmol/L plasma vitamin C.

Alcohol consumption and epigenetic age acceleration across human adulthood

The alcohol-associated biological aging remains to be studied across adulthood. We conducted linear regression analyses to investigate the associations between alcohol consumption and two DNA methylation-based biological age acceleration metrics in 3823 Framingham Heart Study participants (24-92 years and 53.8% women) adjusting for covariates. We also investigated whether the two epigenetic aging metrics mediated the association of alcohol consumption with hypertension. We found that higher long-term average alcohol consumption was significantly associated with biological age acceleration assessed by GrimAge acceleration (GAA) and PhenoAge acceleration (PAA) in middle-aged (45-64 years, n = 1866) and older (65-92 years, n = 1267) participants while not in young participants (24-44 years, n = 690). For example, one additional standard drink of alcohol (~14 grams of ethanol per day) was associated with a 0.71 ± 0.15-year (p = 2.1e-6) and 0.60 ± 0.18-year (p = 7.5e-4) increase in PAA in middle-aged and older participants, respectively, but the association was not significant in young participants (p = 0.23). One additional standard serving of liquor (~14 grams of ethanol) was associated with a greater increase in GAA (0.82-year, p = 4.8e-4) and PAA (1.45-year, p = 7.4e-5) than beer (GAA: 0.45-year, p = 5.2e-4; PAA: 0.48-year, p = 0.02) and wine (GAA: 0.51-year, p = 0.02; PAA: 0.91-year, p = 0.008) in middle-aged participant group. We observed that up to 28% of the association between alcohol consumption and hypertension was mediated by GAA or PAA in the pooled sample. Our findings suggest that alcohol consumption is associated with greater biological aging quantified by epigenetic aging metrics, which may mediate the association of alcohol consumption with quantitative traits, such as hypertension.

WEIGHT REGAIN AND THE METABOLIC PROFILE OF WOMEN IN THE POSTOPERATIVE PERIOD OF BARIATRIC SURGERY: A MULTIVARIATE ANALYSIS

BACKGROUND

Weight regain in the postoperative period after bariatric surgery is directly related to the relapse of preoperative comorbidities and a negative impact on the patients' biochemical profile.

AIMS

To assess the metabolic impact of weight regain on preoperative comorbidities and on patients' biochemical profiles, in order to show the impact of the complications on the metabolic outcomes of bariatric surgery.

METHODS

A retrospective study was carried out with 75 women in the late postoperative period of bariatric surgery who presented pathological weight regain (≥20% of the maximum weight loss). Data of interest consisted of glycemic, lipid, and inflammatory profile measurements at three different moments of evaluation: preoperative period, at the weight nadir (minimum weight), and after weight regain. A multivariate analysis was performed.

RESULTS

The mean age was 46.39±12.09 years. Preoperative body mass index was 40.10±4.11 kg/m2. There was an overall increase of 3.36 points in the mean body mass index between the nadir and after regain: from 26.30±3.9 kg/m2 to 29.66±4.66 kg/m2. The mean time to reach the nadir was 18±7.6 months, with an average percentage of excess weight loss of 91.08±11.8%. The median time for pathological weight regain was 48 months, and the mean regain amongst the sample was 8.85±5.65 kg. There was a significant correlation between pathological weight regain and levels of insulin (r=0.351; p<0.011), C-peptide (r=0.303; p<0.011), C-reactive protein (r=0.402; p<0.001), and vitamin D (r=-0.435; p<0.001), the last two being the most influenced by the percentage of weight regained.

CONCLUSIONS

The pathological weight regain in the postoperative period of bariatric surgery results in losses in the patients' metabolic and inflammatory profiles. However, the biochemical benefits are sustained up to the preoperative levels of the parameters analyzed.

You look stressed: A pilot study on facial action unit activity in the context of psychosocial stress

Quality and quantity of the human stress response are highly individual. Not only are there differences in terms of psychological and physiological stress reactivity, but also with regard to facial muscle stress reactivity. In a first correlative pilot study to decipher the signature of stress as it presents in the physiognomy of a stressed individual, we investigated how stress-induced muscle movement activity in the face is associated with stress marker activation during a standardized laboratory stress test. Female and male participants (N = 62) completed the Trier Social Stress Test and provided multiple measurements of salivary cortisol, subjective experience, heart rate, and high-frequency heart rate variability. In addition, participants were filmed during stress induction to derive the activation of 13 individual muscles or muscle groups, also termed action units (AU). Mean AU intensity and occurrence rates were measured using the opensource software OpenDBM. We found that facial AU activity correlated with different aspects of the psychosocial stress response. Higher stress-induced cortisol release was associated with more frequent upper eyelid raiser (AU05) and upper lip raiser (AU10) occurrences, while more lip corner pulling (AU12) went along with lower cortisol reactivity. More frequent eyelid tightener (AU07) occurrences were linked to higher subjective stress reactivity but decreased heart rate and HF-HRV reactivity. Last, women showed greater stress-induced smiling intensity and occurrence rates than men. We conclude that psychosocial stress reactivity is systematically linked to facial muscle activity, with distinct facial stress profiles emerging for different stress markers. From all the AUs studied, eyelid tightening (AU07) seems to provide the strongest potential for future attempts of diagnosing phases of acute stress via facial activity.

The Association of Serum High-Sensitivity C-Reactive Protein Level With the Risk of Site-Specific Cancer Mortality: The Health Examinees (HEXA) Study Cohort

Few studies have investigated the association between high-sensitivity C-reactive protein (hsCRP) level and site-specific cancer mortality. In this study, we aimed to examine the associations of hsCRP with overall and site-specific cancer mortality among South Koreans using data on the Health Examinees (HEXA) Study cohort (41,070 men and 81,011 women aged ≥40 years). We obtained mortality information from the National Statistical Office of Korea, which provided the dates and causes of all deaths occurring through December 31, 2015, by linking mortality data with each participant's unique national identifier. Cox proportional hazards and restricted cubic spline models were used to assess the association between hsCRP and cancer mortality with adjustment for covariates. An analysis of site-specific cancer mortality was focused on 5 major cancers (lung, liver, gastric, colorectal, and breast/prostate). Median hsCRP levels were 0.77 mg/L and 0.59 mg/L for men and women, respectively. A dose-response association between hsCRP and overall cancer mortality was observed in men but disappeared in women after exclusion of deaths occurring in the first 1 or 2 years of follow-up. Elevated hsCRP levels increased the risks of lung, liver, and gastric cancer mortality in men, but the risks of colorectal and breast cancer mortality were not increased. The dose-response association between hsCRP and cancer mortality was observed differently depending on site-specific cancer mortality by sex.

Association of serum high-sensitivity C reactive protein with risk of mortality in an Asian population: the Health Examinees cohort

OBJECTIVES

This study aimed to examine the association of high-sensitivity C reactive protein (hsCRP) with mortality risk and the attenuated effect of non-communicable disease history (NCD _history ) on the association.

DESIGN

Prospective cohort study.

SETTING

Health Examinees cohort.

PARTICIPANTS

A total of 41 070 men and 81 011 women aged ≥40 years were involved (follow-up: 6.8 years).

OUTCOME MEASURES

Data and cause of death occurring until 31 December 2015 were confirmed by death statistics from the National Statistical Office. We conducted advanced analysis after stratification by NCD _history and sensitivity analysis after excluding death before 1 or 2 years from recruitment. Cox proportional hazard and restricted cubic spline models were used to assess the association.

RESULTS

The association between serum hsCRP and risk of all-cause mortality was observed with strong linearity in both genders and was not influenced by NCD _history . The association of serum hsCRP with risk of cancer mortality was not observed in women with NCD _history , but the association with risk of cardiovascular disease (CVD) mortality was predominantly observed in men with NCD _history .

CONCLUSIONS

This study suggests a dose-response association of hsCRP with mortality risk, including cancer and CVD mortality, in Koreans with low serum hsCRP, although the association with cancer and CVD mortality risk could be influenced by gender and NCD _history .

Moderating effect of ppar-γ on the association of c-reactive protein and ischemic stroke in patients younger than 60

AIM

The aim of this study was to evaluate the moderating effect of peroxisome proliferator activated receptor-γ (PPAR-γ) gene variants on the association of serum C-reactive protein level (CRP) and ischemic stroke (IS).

MATERIAL AND METHODS

A total of 114 patients with IS and 135 healthy controls were included.

RESULTS

After adjustment for age, sex, total cholesterol, LDL and HDL cholesterol, triglycerides, hypertension, smoking, body mass index and previous therapy with antihypertensive and/or statins, PPAR-γ had statistically significant moderating effect on association of serum CRP level and IS in patients younger than 60. In participants with PPAR CG or GG genotype level of CRP and IS were not statistically significantly associated (OR = 1.00; 95% CI 0.90-1.10; p = 0.933), but in participants with PPAR CC genotype, the association of serum CRP level and IS was significant (OR = 1.67; 95% CI 1.21-2.31; p = 0.002).

CONCLUSION

In patients with PPAR CC genotype the association of serum CRP level and IS was significant.

Inflammatory markers in acute myocardial infarction and the correlation with the severity of coronary heart disease

INTRODUCTION

The inflammatory hypothesis of atherosclerosis is appealing in acute coronary syndromes, but the dynamics and precise role are not established.

OBJECTIVES

The study investigates the levels of C reactive protein (CRP), interleukin 1β (IL-1β) and stromal-derived factor 1α (SDF-1α) at the time of acute myocardial infarction (AMI) and at 1 and 6 months afterwards, compared with a control group.

RESULTS

In the acute phase of AMI, CRP and SDF-1α were significantly higher, while IL-1β showed lower levels compared with controls. CRP positively correlated with coronary stenosis severity (rho = 0.3, p=.05) and negatively related with left ventricle ejection fraction (LVEF) at 1 month (rho= -0.43, p=.05). IL-1β weakly correlated with the severity of coronary lesions (rho =0.29, p=.02) and strongly with LVEF (rho= -0.8, p=.05). SDF-1α, slightly correlated with LVEF at 1 month (rho = 0.22, p=.01) and with the severity of coronary atherosclerosis (rho= -0.41, p=.003).

CONCLUSIONS

CRP, IL-1β and SDF-1α have important dynamic in the first 6 months after AMI and CRP and SDF-1α levels correlated with the severity of coronary lesions and LVEF at 1 month after the acute ischaemic event.

Peroxidase-mimicking nanozyme with surface-dispersed Pt atoms for the colorimetric lateral flow immunoassay of C-reactive protein

Platinum-containing nanozymes with peroxidase-mimicking activity (PMA) have found a broad application in bioanalytical methods and are potentially able to compete with enzymes as the labels. However, traditionally used methods for the synthesis of nanozymes result in only a small fraction of surface-exposed Pt atoms, which participate in catalysis. To overcome this limitation, we propose a new approach for the synthesis of nanozymes with the efficient dispersion of Pt atoms on particles' surfaces. The synthesis of nanozymes includes three steps: the synthesis of gold nanoparticles (Au NPs), the overgrowth of a silver layer over Au NPs (Au@Ag NPs, 6 types of NPs with different thicknesses of Ag shell), and the galvanic replacement of silver with PtCl₆^2- leading to the formation of trimetallic Au@Ag-Pt NPs with uniformly deposited catalytic sites and high Pt-utilization efficiency. Au@Ag-Pt NPs (23 types of NPs with different concentrations of Pt) with various sizes, morphology, optical properties, and PMA were synthesized and comparatively tested. Using energy-dispersive spectroscopy mapping, we confirm the formation of core@shell Au@Ag NPs and dispersion of surface-exposed Pt. The selected Au@Ag-Pt NPs were conjugated with monoclonal antibodies and used as the colorimetric and catalytic labels in lateral flow immunoassay of the inflammation biomarker: C-reactive protein (CRP). The colorimetric signal enhancement was achieved by the oxidation of 3,3'-diaminobenzidine by H₂O₂ catalyzed by Au@Ag-Pt NPs directly on the test strip. The use of Au@Ag-Pt NPs as the catalytic label produces a 65-fold lower limit of CRP detection in serum (15 pg mL^-1) compared with Au NPs and ensures the lowest limit of detection for equipment-free lateral flow immunoassays. The assay shows a high correlation with data of enzyme-linked immunosorbent assay (R² = 0.986) and high recovery (83.7-116.2%) in serum and plasma. The assay retains all the benefits of lateral flow immunoassay as a point-of-care method.

C-reactive protein predicts complications in community-associated S. aureus bacteraemia: a cohort study

Background

Staphylococcus aureus (S. aureus) bacteraemia is increasingly acquired from community settings and is associated with a mortality rate of up to 40% following complications. Identifying risk factors for complicated S. aureus bacteraemia would aid clinicians in targeting patients that benefit from expedited investigations and escalated care.

Methods

In this prospective observational cohort study, we aimed to identify risk factors associated with a complicated infection in community-onset S. aureus bacteraemia. Potential risk factors were collected from electronic medical records and included: - patient demographics, symptomology, portal of entry, and laboratory results.

Results

We identified several potential risk factors using univariate analysis. In a multiple logistic regression model, age, haemodialysis, and entry point from a diabetic foot ulcer were all significantly protective against complications. Conversely, an unknown entry point of infection, an entry point from an indwelling medical device, and a C-reactive protein concentration of over 161 mg/L on the day of admission were all significantly associated with complications.

Conclusions

We conclude that several factors are associated with complications including already conducted laboratory investigations and portal of entry of infection. These factors could aid the triage of at-risk patients for complications of S. aureus bacteraemia.

Pathological cardiac remodeling seen by the eyes of proteomics

Cardiac remodeling involves cellular and structural changes that occur as consequence of multifactorial events to maintain the homeostasis. The progression of pathological cardiac remodeling involves a transition from adaptive to maladaptive changes that eventually leads to impairment of ventricular function and heart failure. In this scenario, proteins are key elements that orchestrate molecular events as increased expression of fetal genes, neurohormonal and second messengers' activation, contractile dysfunction, rearrangement of the extracellular matrix and alterations in heart geometry. Mass spectrometry based-proteomics has emerged as a sound method to study protein dysregulation and identification of cardiac diseases biomarkers in plasma. In this review, we summarize the main findings related to large-scale proteome modulation of cardiac cells and extracellular matrix occurred during pathological cardiac remodeling. We describe the recent proteomic progresses in the selection of protein targets and introduce the renin-angiotensin system as an interesting target for the treatment of pathological cardiac remodeling.

Variability of C-reactive protein in first-generation Ecuadorian immigrants living in the United States

OBJECTIVES

Establish the variability of C-reactive protein (CRP) within a population of first-generation immigrants living in the United States. Prior work has theorized that individuals with high levels of childhood pathogen exposure may have lower CRP levels in adulthood, and therefore that for these individuals, CRP may not be as accurate an index of chronic disease risk related to low-level inflammation as is presumed based on data from wealthy populations. This potentially has major implications for the interpretation of CRP as a biomarker of chronic inflammation.

METHODS

This longitudinal study collected a total of 125 dried blood spot (DBS) samples from 31 participants (median 4 samples each) and CRP levels in these DBS were assayed by enzyme-linked immunosorbant assay. Surveys were administered to characterize childhood pathogen exposure, and current illness. Variance was estimated using mixed effects regression models.

RESULTS

On average, participants were adults (mean = 41.9 years old) who had immigrated to the United States nearly 20 years prior to the study and had nearly universally experienced childhood helminth infection and other major pathogen exposures. Median serum-equivalent CRP was 0.77 mg/L. Individuals reliably differed in subacute CRP levels, and, depending on whether untransformed or log-transformed CRP was the outcome variable, 45% or 62% of variance in CRP was attributable to between-individual differences.

CONCLUSIONS

The variability of CRP levels in individuals with relatively high childhood pathogen exposure is comparable to previously reported studies in North America and Europe. However, CRP values are relatively low. CRP is an appropriate measure of subacute inflammation in this sample.

An Association Between the Inflammatory Biomarker GlycA and Depressive Symptom Severity

OBJECTIVE

The underlying mechanisms of depression remain unclear; however, current literature suggests a relationship between inflammation and depression. The association between the inflammatory biomarker high-sensitivity C-reactive protein (hs-CRP) and depression has been previously investigated, but the relationship between GlycA, a novel spectroscopic inflammatory biomarker, and depression does not appear to have been examined.

METHODS

Data were obtained from The Dallas Heart Study (DHS, conducted between 2000 and 2002), which consisted of a large community-based sample of Dallas County residents (N = 3,033). Depressive symptom severity was assessed with the Quick Inventory of Depressive Symptomatology-Self-Report (QIDS-SR). It was hypothesized that the serum GlycA level would be a statistically significant predictor of QIDS-SR scores after control for demographic covariates. Multiple linear regression was used to assess the relationship between GlycA level and QIDS-SR scores. The role of hs-CRP in predicting QIDS-SR scores was also explored.

RESULTS

GlycA level was a statistically significant positive predictor of QIDS-SR score (β = .053, P = .038) with control for sex, age, antidepressant use, ethnicity, smoking status, drinking status, body mass index, and years of education. In a subset of adults with moderate-to-severe depression, GlycA level was not associated with QIDS-SR scores. Additionally, hs-CRP level was not a statistically significant predictor of QIDS-SR scores.

CONCLUSIONS

This study found a positive association between the inflammatory biomarker GlycA, but not hs-CRP, and depressive symptom severity in a large multiethnic and multiracial community-based sample. Thus, these results provide the first indication that GlycA may be a potentially useful novel biomarker of depression.

Circulating angiopoietin-like protein 2 levels and arterial stiffness in patients receiving maintenance hemodialysis: A cross-sectional study

BACKGROUND AND AIMS

Chronic low-grade inflammation is receiving much attention as a critical pathology that induces various aging phenotypes, a concept known as "inflammaging". Uremic patients undergoing hemodialysis therapy show vascular aging phenotypes characterized by greater arterial stiffness and calcification compared to healthy controls of the same generation. In the current study, we investigated whether levels of inflammaging markers in the circulation were associated with vascular aging phenotypes in hemodialysis patients, as estimated by the cardio-ankle vascular index (CAVI).

METHODS

We conducted a multicenter cross-sectional study of 412 patients receiving hemodialysis and evaluated the relationship between circulating hs-CRP or ANGPTL2 levels, as markers of inflammaging, and CAVI.

RESULTS

Of 412 patients, 376 were analyzed statistically. While circulating hs-CRP levels had no significant association with CAVI, generalized linear models revealed that high circulating ANGPTL2 levels were significantly associated with increasing CAVI after adjustment for classical metabolic factors and hemodialysis-related parameters [β 0.63 (95%CI 0.07-1.18)]. Exploratory analysis revealed that high circulating ANGPTL2 levels were also strongly associated with increased CAVI, particularly in patients with conditions of increased vascular mechanical stress, such elevated blood pressure [β 1.00 (95%CI 0.23-1.76)], elevated pulse pressure [β 0.75 (95%CI 0.52-0.98)], or excess body fluid [β 1.25 (95%CI 0.65-1.84)].

CONCLUSIONS

We conclude that circulating levels of ANGPTL2 rather than hs-CRP are positively associated with CAVI in the uremic population and that ANGPTL2 could be a unique marker of progression of vascular aging in patients receiving hemodialysis.

Contribution of Predictive and Prognostic Biomarkers to Clinical Research on Chronic Kidney Disease

Chronic kidney disease (CKD), defined as the presence of albuminuria and/or reduction in estimated glomerular filtration rate (eGFR) < 60 mL/min/1.73 m2, is considered a growing public health problem, with its prevalence and incidence having almost doubled in the past three decades. The implementation of novel biomarkers in clinical practice is crucial, since it could allow earlier diagnosis and lead to an improvement in CKD outcomes. Nevertheless, a clear guidance on how to develop biomarkers in the setting of CKD is not yet available. The aim of this review is to report the framework for implementing biomarkers in observational and intervention studies. Biomarkers are classified as either prognostic or predictive; the first type is used to identify the likelihood of a patient to develop an endpoint regardless of treatment, whereas the second type is used to determine whether the patient is likely to benefit from a specific treatment. Many single assays and complex biomarkers were shown to improve the prediction of cardiovascular and kidney outcomes in CKD patients on top of the traditional risk factors. Biomarkers were also shown to improve clinical trial designs. Understanding the correct ways to validate and implement novel biomarkers in CKD will help to mitigate the global burden of CKD and to improve the individual prognosis of these high-risk patients.

Evaluation of the modulatory effects of Piper guineense leaves and seeds on egg albumin-induced inflammation in experimental rat models

ETHNOPHARMACOLOGICAL RELEVANCE

Inflammation processes are implicated in many degenerative diseases. Piper guineense, a West African spice belonging to the Piperaceae family has been reported to contain anti-inflammatory agents.

AIM OF STUDY

This study determined the modulatory effects of methanolic extracts of Piper guineense leaves and seeds on egg albumin-induced inflammation in rats.

STUDY DESIGN AND METHODS

Inflammation in the hind paw was induced by injecting 0.1ml egg albumin subcutaneously. Treatments including diclofenac were given orally. Rectal temperature and paw size were monitored hourly for the first 3 h' post-induction of inflammation and then at the 6th and 24th hour. Serum levels of CRP, MDA, LDH and GGT activities were determined at these hours.

RESULTS

Results showed that egg albumin-induced inflammation caused a significant (p < 0.05) increase in paw size and rectal temperature. It further showed that treatment with the leaves and seed extracts reversed the effect of inflammation on serum levels of CRP and MDA, and on LDH and GGT activities similar to diclofenac in rats.

CONCLUSION

Extracts of the Piper guineense seed and leaves have potentials of being used as an anti-inflammatory agent but further studies need to be done to determine their toxicity and effects on immunological markers of inflammation.

Only vulnerable adults show change in chronic low-grade inflammation after contemplative mental training: evidence from a randomized clinical trial

Growing evidence suggests that chronic low-grade inflammation can be reduced through mindfulness-based mental training interventions. However, these results are inconsistent and based on patient populations with heterogeneous conditions. Similar research in healthy adults is lacking. Moreover, common intervention protocols involve varying combinations of different contemplative practices, such that it remains unclear which types of training most effectively influence biomarkers of inflammation. The present study investigated the effect of three distinct 3-month training modules cultivating a) interoception and present-moment focus (Presence), b) socio-affective skills (Affect), or c) socio-cognitive skills (Perspective) on the inflammatory biomarkers interleukin-6 (IL-6) and high sensitive C-reactive protein (hs-CRP) in 298 healthy adults. We observed no group-level effect of training on either biomarker, but trend-level interactions of training type and participant sex. In additionally exploring the influence of participants' baseline inflammation, a selective training effect emerged: Following the Presence module, participants with relatively higher inflammatory load showed stronger reduction in IL-6 on average, and in hs-CRP if they were male. Mindfulness- and attention-based mental practice thus appears most effective when targeting chronic low-grade inflammation in healthy adults, particularly in men. Overall, our data point to a floor effect in the reduction of inflammatory markers through contemplative mental training, suggesting that mental training may be less effective in improving basal biological health outcomes in healthy, low-stressed adults than in vulnerable populations.

Elevation of tumor necrosis factor alpha levels is associated with restless legs symptoms in clinically depressed patients

BACKGROUND

Restless legs syndrome is a sensorimotor disorder associated with several mental illnesses particularly depression.

METHODS

A cross-sectional study of primary care patients. The prevalence of restless legs symptoms was studied in 706 patients with depressive symptoms and 426 controls without a psychiatric diagnosis by using a structured questionnaire. The depressive symptoms were evaluated with the BDI and the psychiatric diagnosis was confirmed by means of a diagnostic interview (M.I.N.I.). The subjects with elevated depressive symptoms were divided into two groups subjects with depressive symptoms with and without clinical depression.

RESULTS

The prevalence of restless legs symptoms was 24.8% in the controls, 50.0% in the patients with clinical depression and 42.4% in the patients with depressive symptoms. CRP value was significantly higher (p = .003) in the clinically depressed patients than in the other groups. There was a higher concentration of TNF-α in the subjects with restless legs symptoms (7.4 ng/l ± 3.2) compared with the subjects without symptoms (6.7 ng/l ± 2.3)(p < .001). There was a significant difference in the TNF-α levels between the subjects with and without restless legs symptoms in the depression group (p < .001) and among the patients with depressive symptoms but no a depression diagnosis (p = .022). In these groups, restless legs symptoms were associated with elevated levels of TNF-α.

CONCLUSIONS

TNF-α level was associated with restless legs symptoms only among subjects with depressive symptoms whether they had clinical depression or not. We suggest that TNF-α could be an underlying factor between restless legs symptoms and comorbidities.

Markers of Atherosclerosis: Part 1 - Serological Markers

Atherosclerosis is a major contributor to morbidity and mortality worldwide. With therapeutic consequences in mind, several risk scores are being used to differentiate individuals with low, intermediate or high cardiovascular (CV) event risk. The most appropriate management of intermediate risk individuals is still not known, therefore, novel biomarkers are being sought to help re-stratify them as low or high risk. This narrative review is presented in two parts. Here, in Part 1, we summarise current knowledge on serum (serological) biomarkers of atherosclerosis. Among novel biomarkers, high sensitivity C-reactive protein (hsCRP) has emerged as the most promising in chronic situations, others need further clinical studies. However, it seems that a combination of serum biomarkers offers more to risk stratification than either biomarker alone. In Part 2, we address genetic and imaging markers of atherosclerosis, as well as other developments relevant to risk prediction.

Exploring the multidimensional complex systems structure of the stress response and its relation to health and sleep outcomes

To gain a comprehensive understanding of the multidimensional complex systems structure of the stress response and related health outcomes, we utilized network analysis in a sample of 328 healthy participants in two steps. In a first step, we focused on associations between measures of basal hypothalamic-pituitary-adrenal axis functioning and subjective stress perceptions. In a second step, we linked these diverse stress-related measures to biomarkers and self-reports of health and sleep. Overall, measures clustered depending on their method of assessment, with high correlations between different saliva-based indices of diurnal cortisol regulation, between cortisol and cortisone levels in hair, between different biological health indicators (systemic inflammatory activity and body mass index), between state (experience sampling) and trait (questionnaire-based) self-reports of stress and wellbeing, and between different self-reports of sleep. Bridges between clusters suggested that if individuals perceive stress throughout their daily lives this is reflected in their total salivary cortisol output possibly contributing to long-term cortisol accumulation in hair. Likewise, earlier awakening time may contribute to cortisol accumulation in hair via an influence on awakening cortisol processes. Our results show that while meaningful connections between measures exist, stress is a highly complex construct composed of numerous aspects. We argue that network analysis is an integrative statistical approach to address the multidimensionality of the stress response and its effects on the brain and body. This may help uncover pathways to stress-related disease and serve to identify starting points for prevention and therapeutic intervention.

Markers of Atherosclerosis: Part 2 - Genetic and Imaging Markers

This is Part 2 of a two-part review summarising current knowledge on biomarkers of atherosclerosis. Part 1 addressed serological biomarkers. Here, in part 2 we address genetic and imaging markers, and other developments in predicting risk. Further improvements in risk stratification are expected with the addition of genetic risk scores. In addition to single nucleotide polymorphisms (SNPs), recent advances in epigenetics offer DNA methylation profiles, histone chemical modifications, and micro-RNAs as other promising indicators of atherosclerosis. Imaging biomarkers are better studied and already have a higher degree of clinical applicability in cardiovascular (CV) event prediction and detection of preclinical atherosclerosis. With new methodologies, such as proteomics and metabolomics, discoveries of new clinically applicable biomarkers are expected.

Cardiovascular biomarkers in clinical studies of type 2 diabetes

When planning cardiovascular (CV) studies in type 2 diabetes (T2D), selection of CV biomarkers is a complex issue. Because the pathophysiology of CV disease (CVD) in T2D is multifactorial, ideally, the selected CV biomarkers should cover all aspects of the known pathophysiology of the disease. This will allow the researcher to distinguish between effects on different aspects of the pathophysiology. To this end, we discuss a host of biomarkers grouped according to their role in the pathogenesis of CVD, namely: (1) cardiac damage biomarkers; (2) inflammatory biomarkers; and (3) novel biomarkers (oxidative stress and endothelial dysfunction biomarkers). Within each category we present the best currently validated biomarkers, with special focus on the population of interest (people with T2D). For each individual biomarker, we discuss the physiological role, validation in the general population and in people with T2D, analytical methodology, modifying factors, effects of glucose-lowering drugs, and interpretation. This approach will provide clinical researchers with the information necessary for planning, conducting and interpreting results from clinical trials. Furthermore, a systematic approach to selection of CV biomarkers in T2D research will improve the quality of future research.

A hook effect-free immunochromatographic assay (HEF-ICA) for measuring the C-reactive protein concentration in one drop of human serum

The immunochromatographic (ICA) assay is a highly promising platform for rapid and simple detection of C-reactive protein (CRP) which is an indicator of the different phases of various diseases, as well as of inflammation and infection. However, the hook effect in the ICA assay limits the quantification of CRP levels at high CRP concentrations. Methods: In this study, we developed a hook effect-free immunochromatographic assay (HEF-ICA) to detect CRP over a wide concentration range. The hook effect results from the simultaneous reaction of an excess target antigens with both immobilized and labeled antibodies respectively. To reduce the potential occurrence of this simultaneous reaction, we separated the migration of the target antigen and gold nanoparticle (AuNP)-labeled antibodies on a nitrocellulose membrane and analyzed the time profiles by modifying the ICA structure. Results: The signal intensity of HEF-ICA was saturated at high CRP concentrations, without decreasing. The titration curve of HEF-ICA was adjusted with the Hill equation, and HEF-ICA was performed with the following parameters: limit of detection, 43 ng mL^-1; dynamic range, 119 ng mL^-1 to 100 µg mL^-1. The accuracy of the newly developed assay was evaluated using 33 clinical samples via comparison with a clinical chemistry analyzer. Conclusion: HEF-ICA enabled the measurement of a wide range of CRP concentrations without the hook effect, and was suitable for point-of-care testing with fingertip blood sampling, as only a minute sample volume (2.5 µL) was required.

Specific reduction in cortisol stress reactivity after social but not attention-based mental training

Psychosocial stress is a public health burden in modern societies. Chronic stress-induced disease processes are, in large part, mediated via the activation of the hypothalamic-pituitary-adrenal (HPA) axis and the sympathetic-adrenal-medullary system. We asked whether the contemplative mental training of different practice types targeting attentional, socio-affective (for example, compassion), or socio-cognitive abilities (for example, perspective-taking) in the context of a 9-month longitudinal training study offers an effective means for psychosocial stress reduction. Using a multimethod approach including subjective, endocrine, autonomic, and immune markers and testing 313 participants in a standardized psychosocial laboratory stressor, we show that all three practice types markedly reduced self-reported stress reactivity in healthy participants. However, only the training of intersubjective skills via socio-affective and socio-cognitive routes attenuated the physiological stress response, specifically the secretion of the HPA axis end-product cortisol, by up to 51%. The assessed autonomic and innate immune markers were not influenced by any practice type. Mental training focused on present-moment attention and interoceptive awareness as implemented in many mindfulness-based intervention programs was thus limited to stress reduction on the level of self-report. However, its effectiveness was equal to that of intersubjective practice types in boosting the association between subjective and endocrine stress markers. Our results reveal a broadly accessible low-cost approach to acquiring psychosocial stress resilience. Short daily intersubjective practice may be a promising method for minimizing the incidence of chronic social stress-related disease, thereby reducing individual suffering and relieving a substantial financial burden on society.

Obesity and inflammation: the linking mechanism and the complications

Obesity is the accumulation of abnormal or excessive fat that may interfere with the maintenance of an optimal state of health. The excess of macronutrients in the adipose tissues stimulates them to release inflammatory mediators such as tumor necrosis factor α and interleukin 6, and reduces production of adiponectin, predisposing to a pro-inflammatory state and oxidative stress. The increased level of interleukin 6 stimulates the liver to synthesize and secrete C-reactive protein. As a risk factor, inflammation is an imbedded mechanism of developed cardiovascular diseases including coagulation, atherosclerosis, metabolic syndrome, insulin resistance, and diabetes mellitus. It is also associated with development of non-cardiovascular diseases such as psoriasis, depression, cancer, and renal diseases. On the other hand, a reduced level of adiponectin, a significant predictor of cardiovascular mortality, is associated with impaired fasting glucose, leading to type-2 diabetes development, metabolic abnormalities, coronary artery calcification, and stroke. Finally, managing obesity can help reduce the risks of cardiovascular diseases and poor outcome via inhibiting inflammatory mechanisms.

Novel Protein Glycan-Derived Markers of Systemic Inflammation and C-Reactive Protein in Relation to Glycemia, Insulin Resistance, and Insulin Secretion

OBJECTIVE

N-acetylglucosamine/galactosamine (GlycA) and sialic acid (GlycB) moieties of glycosylated serum proteins are nonspecific measures of inflammation, but conclusive data on their relationship with insulin resistance or insulin secretion are missing. Therefore, we aimed to examine the relation of GlycA, GlycB, and C-reactive protein (CRP) to direct measures of insulin sensitivity (insulin sensitivity index [S_I]) and insulin secretion (acute insulin response [AIR]).

RESEARCH DESIGN AND METHODS

This study used cross-sectional analyses and included 1,225 participants with and without type 2 diabetes in the Insulin Resistance Atherosclerosis Study (IRAS). S_I and AIR were measured using the frequently sampled intravenous glucose tolerance test, and GlycA and GlycB were measured using nuclear magnetic resonance spectroscopy.

RESULTS

GlycA and GlycB had a strong correlation with CRP (r = 0.60 [P < 0.001] and r = 0.46 [P < 0.001], respectively). In a linear regression model with both GlycA and CRP as independent variables, GlycA (β × 1 SD, -0.04 ± 0.02; P < 0.01) and CRP (-0.06 ± 0.02; P < 0.001) were independently associated with S_I even after adjusting for demographics, smoking, physical activity, plasma glucose, and BMI. However, neither CRP nor GlycA had an independent relationship with AIR.

CONCLUSIONS

GlycA may complement CRP in evaluating the relationship between inflammation, glucose tolerance, and insulin resistance.

Mass spectrometry-based approaches to targeted quantitative proteomics in cardiovascular disease

Mass spectrometry-based proteomics methodology has become an important tool in elucidating some of the underlying mechanisms involved in cardiovascular disease. The present review provides details on selected important protein targets where highly selective and specific mass spectrometry-based approaches have led to important new findings and provided new mechanistic information. The role of six proteins involved in the etiology of cardiovascular disease (acetylated platelet cyclooxygenase-1, serum apolipoprotein A1, apolipoprotein C-III, serum C-reactive protein, serum high mobility group box-1 protein, insulin-like growth factor I) and their quantification has been discussed. There are an increasing number of examples where highly selective mass spectrometry-based quantification has provided new important data that could not be obtained with less labor intensive and cheaper immunoassay-based procedures. It is anticipated that these findings will lead to significant advances in a number of important issues related to the role of specific proteins in cardiovascular disease. The availability of a new generation of high-resolution high-sensitivity mass spectrometers will greatly facilitate these studies so that in the future it will be possible to analyze serum proteins of relevance to cardiovascular disease with levels of specificity and/or sensitivity that cannot be attained by immunoassay-based procedures.

Risk Stratification for Primary Prevention of Coronary Artery Disease: Roles of C-Reactive Protein and Coronary Artery Calcium

Risk stratification of individuals at risk for atherosclerotic cardiovascular disease (ASCVD) plays an important role in primary prevention of cardiovascular disease. In addition to risk scores derived from conventional cardiovascular risk factors, high sensitivity C-reactive protein (hs-CRP) and coronary artery calcium (CAC) have emerged as two of the widely accepted non traditional risk factors for atherosclerotic disease that have shown incremental prognostic value in predicting cardiovascular events. This review systematically assesses the role of hs-CRP and CAC in various studies and demonstrates meta-analyses of the incremental prognostic value of hs-CRP and CAC in identifying patients at risk of future CVD events. Compared with this, CAC showed better incremental prognostic value and might be a better indicator of ASCVD risk in asymptomatic adults.

Localizing factors in atherosclerosis

Atherosclerotic vascular disease is the leading cause of death worldwide. Although the entire vascular bed is constantly exposed to the same risk factors, atheromatous lesions present a distinct intra-individual pattern of localization and progression, being consistently more frequent in specific segments of the arterial vascular bed. This peculiar distribution may be related to selective sensitivity of such locations to the influence of risk factors or to histopathological and flow differences, and has relevant clinical implications, as the prognosis of the disease varies according to localization. We here review the theories that have been formulated to explain such preferential locations, as its understanding can be useful to pursue diagnostic screening strategies and focused preventive measures.

Prevalence of glutamine deficiency in ICU patients: a cross-sectional analytical study

BACKGROUND

Not only is glutamine deficiency an independent predictor of mortality in intensive care unit (ICU) patients, but glutamine supplementation is also recommended for its proven outcome benefits. However, recent data suggest that early glutamine supplementation in certain patient groups increase mortality. The aim of this study was to investigate plasma glutamine levels of adult ICU patients in the South African setting and to determine relationships between glutamine levels, gender, diagnostic categories and selected inflammatory markers. The data from this study will be used as baseline measurement to support a large scale study that will be undertaken in the South African ICU population.

METHODS

This cross-sectional, analytical study included 60 mixed adult ICU patients within 24 h post ICU admission. Plasma glutamine levels were determined on admission. The relationship between glutamine levels, Interleukin-6 (IL-6) and C-reactive protein (CRP); as well as gender- and diagnosis-related differences in glutamine levels were also investigated. A non-parametric ROC curve was computed to determine the CRP concentration cut-off point above which glutamine becomes deficient.

RESULTS

The median plasma glutamine level (497 μmol/L) was in the normal range; however, 38.3 % (n = 23) of patients had deficient (<420 μmol/L) and 6.7 % (n = 4) had supra-normal glutamine levels (>930 μmol/L). No significant difference could be detected between glutamine levels and gender or diagnosis categories as a group. When only the medical and surgical categories were compared, the median plasma glutamine level of the medical patients were significantly lower than that of the surgical patients (p = 0.042). Glutamine showed inverse associations with CRP levels (r = -0.44, p < 0.05) and IL-6 concentrations (r = -0.23, p = 0.08). A CRP cut-off value of 95.5 mg/L was determined above which glutamine levels became deficient.

CONCLUSIONS

About a third of patients (38 %) were glutamine deficient on admission to ICU, whereas some presented with supra-normal levels. While glutamine levels correlated inversely with inflammatory markers, and a CRP value of above 95.5 mg/L indicated potential glutamine deficiency, the clinical application of this finding needs further investigation.

A Retrospective Evaluation of the Inflammatory Marker C-Reactive Protein (CRP), Cholesterol and High-Density Lipoproteins in Patients with Major Depression: Preliminary Findings

The aim of this study was to retrospectively evaluate the role of C-reactive protein, total cholesterol and high-density lipoprotein cholesterol in patients suffering from Major Depression (MD). Data of C-reactive protein, total cholesterol (TC) and high-density lipoprotein cholesterol of 37 adult outpatients (17 men, 20 women) with a DSM-IV diagnosis of MD were analyzed. Depression was measured with the 17-item Hamilton Depression Rating Scale (HAM-D) and with the Beck Depression Inventory (BDI). Suicide risk was evaluated with the Scale of Suicide Ideation (SSI). Patients with a lifetime history of attempted suicide were categorized as having higher suicide risk. Higher suicide risk patients showed higher C-reactive protein levels and lower high-density lipoprotein cholesterol levels than lower suicide risk patients whereas total cholesterol levels were not statistically different. C-reactive protein positively correlated with BDI, HAM-D, SSI scores and with number of previous depressive episodes. High-density lipoprotein cholesterol correlated inversely with BDI, HAM-D and SSI scores, whereas, no significant correlations were found between Total Cholesterol and other variables including C-reactive protein. In linear regression models, C-reactive protein was predictor of more severe depression and increased suicide risk. Lower high-density lipoprotein cholesterol levels were significantly predictive of increased suicide risk.

The Association of Peroxisome Proliferator-Activated Receptor δ and Additional Gene-Gene Interaction with C-Reactive Protein in Chinese Population

Aims. To examine the association between 4 single nucleotide polymorphisms (SNPs) of peroxisome proliferator-activated receptors δ (PPARδ) polymorphisms and C-reactive protein (CRP) level and additional gene-gene interaction. Methods. Line regression analysis was performed to verify polymorphism association between SNP and CRP levels. Generalized multifactor dimensionality reduction (GMDR) was employed to analyze the interaction. Results. A total of 1028 subjects (538 men, 490 women) were selected. The carriers of the C allele (TC or CC) of rs2016520 were associated with a significant decreased level of CRP, regression coefficients was -0.338, and standard error was 0.104 (p = 0.001). The carriers of the G allele (CG or GG) of rs9794 were also significantly associated with decreased level of CRP, regression coefficients was -0.219, and standard error was 0.114 (p = 0.012). We also found a potential gene-gene interaction between rs2016520 and rs9794. Subjects with rs2016520-TC or CC, rs9794-CG or GG genotypes have lowest CRP level, difference (95% CI) = -0.50 (-0.69 to -0.21) (p < 0.001), compared to subjects with rs2016520-TT and rs9794-CC genotypes. Conclusions. rs2016520 and rs9794 minor allele of PPARδ and combined effect between the two SNP were associated with decreased CRP level.

Effect of obesity on the association between common variations in the PPAR gene and C-reactive protein level in Chinese Han population

The peroxisome proliferator-activated receptors (PPARs)-α, -β/δ, and -γ are the ligand-activated transcription factors that function as the master regulators of glucose, fatty acid and lipoprotein metabolism, inflammation, and atherosclerosis. Our aim was to test the association between ten single nucleotide polymorphisms of PPARs and CRP level, as well as their interaction with overweight/obesity. A sample population of 643 subjects was recruited from the prevention of MetS and multi-metabolic disorders in Jiangsu Province of China Study. The selected SNPs in PPAR α (rs135539, rs4253778, rs1800206), PPAR β/δ (rs2016520 and rs9794), and PPAR γ (rs10865710, rs1805192, rs709158, rs3856806, and rs4684847) were genotyped. After adjustment for smoking, alcohol consumption, SBP, DBP, TG, and HDL-C, rs1800206, rs709158, rs1805192, and rs4684847 polymorphisms were significantly associated with CRP level in normal weight subjects (P < 0.05). In the overweight/obese subjects, rs1800206 was also significant associated with CRP level (P<0.01). In addition, the rs709158, rs1805192, and rs4684847 polymorphisms were shown interactions with overweight/obesity to influence CRP level (P<0.05). PPARs polymorphisms are independently associated with CRP levels in Chinese Han population. Further, PPARs polymorphisms interact with overweight/obesity to set CRP levels.

A novel haplotype within C-reactive protein gene influences CRP levels and coronary heart disease risk in Northwest Indians

According to several epidemiological and clinical studies, the concentration of C-reactive protein (CRP) in blood is associated with the risk of coronary heart disease (CHD). However, these studies are limited in high incidence and prevalence area of North-West India. The present case control study investigated the contribution of three relevant CRP single nucleotide polymorphisms: -717A>G located in the promoter region (rs2794521), +1059G>C on exon2 (rs1800947) and +1444C>T in the 3' UTR (rs1130864) in 180 angiographically verified CHD cases and 175 control subjects. Minor allele frequencies (G, C and T) of rs2794521, rs1800947 and rs1130864 are observed to be 21.1, 11.7, 29.4 and 11.4, 10.0, 19.7 % in CHD cases and controls respectively. AA genotype of -717A>G and TT genotype of +1444C>T were significantly associated (P = 0.02 & 0.03 respectively) with the risk of CHD whereas, +1059G and +1444T were found to be strongly related (P = 0.023 & P = 0.008 respectively) with multivariable adjusted CRP levels. AGT Haplotype was significantly associated with the adjusted CRP levels (P < 0.05). Disease association analysis revealed that haplotype AGT influences CHD risk (OR 2.4, 95 % CI 1.23-4.84, P = 0.006) which exacerbates after correcting the confounding effects of risk variables (OR 2.5, 95 % CI 1.27-4.99, P = 0.004). With the global index of Akaike information criterion, it has been observed that the carrying each single unit of this susceptibility haplotype increases CHD risk by a value of 2.41 ± 0.439 (β ± SE) in the recessive mode.

Hematological and biochemical markers of iron status in a male, young, physically active population

The aim of this study was to establish reference intervals (RIs) for the hemogram and iron status biomarkers in a physically active population. The study population included male volunteers (n = 150) with an average age of 19 ± 1 years who had participated in a regular and controlled exercise program for four months. Blood samples were collected to determine hematological parameters using a Sysmex XE-5000 analyzer (Sysmex, Kobe, Japan). Iron, total iron-binding capacity (TIBC), transferrin saturation and ferritin, and high-sensitivity C-reactive protein (CRP) concentrations in serum samples were measured using commercial kits (Roche Diagnostics, GmbH, Mannheim, Germany) and a Roche/Hitachi 902 analyzer. The RIs were established using the RefVal program 4.1b. The leucocyte count, TIBC, and CRP and ferritin concentrations exhibited higher RIs compared with those in a nonphysically active population. Thirty volunteers (outliers) were removed from the reference population due to blood abnormalities. Among the outliers, 46% exhibited higher CRP concentrations and lower concentrations of iron and reticulocyte hemoglobin compared with the nonphysically active population (P < 0.001). Our results showed that it is important to establish RIs for certain laboratory parameters in a physically active population, especially for tests related to the inflammatory response and iron metabolism.

Inflammatory markers in the second trimester prior to clinical onset of preeclampsia, intrauterine growth restriction, and spontaneous preterm birth

Low-grade inflammation has been associated with pregnancy complications including preeclampsia (PE), intrauterine growth restriction (IUGR), and spontaneous preterm birth (SPB). In an unmatched, nested case-control study, we assessed the possible predictive association of maternal C-reactive protein (CRP), interferon-γ-inducible protein 10 (IP-10), and soluble urokinase plasminogen activator receptor (suPAR) in second trimester plasma samples in relation to later development of PE (n = 29), IUGR (n = 53), and SPB (n = 9). Inflammatory marker levels in these groups were compared to normotensive healthy pregnant controls (n = 127). We found no statistically significant difference in CRP, IP-10, or suPAR in second trimester plasma samples from pregnant women with later PE, IUGR, and SPB when compared to normotensive healthy controls. Second trimester plasma samples of CRP, IP-10, and suPAR cannot be used as a prognostic marker for PE, IUGR, and SPB.

Physical activity - an important preanalytical variable

The concentration of several biochemical and hematological biomarkers is strongly influenced by a number of preanalytical variables. Several lines of evidence attest that short, middle, and long-term exercise, as well as the relative intensity of physical effort (from mild to strenuous), may influence a broad array of laboratory variables. The amount of extracellular release and clearance from blood of most of these biomarkers is markedly influenced by the biological characteristics of the molecule(s), level of training, type, intensity and duration of exercise, and time of recovery after training. It is hence noteworthy that test results that fall outside the conventional reference ranges in athletes not only may reflect the presence of a given disease, but may frequently mirror an adaptation to regular training or changes that have occurred during and/or following strenuous exercise, and which should be clearly acknowledged to prevent misinterpretation of laboratory data. The aim of this narrative review is to provide an update about the most significant changes of some biochemical and hematological biomarkers in response to physical exercise, for appropriate interpretation of these changes in the context of physically active subjects.