Comparative analysis of obesity-related cardiometabolic and renal biomarkers in human plasma and serum

A Walnut-Enriched Diet for 2 Years Changes the Serum Oxylipin Profile in Healthy Older Persons

BACKGROUND

Oxylipins are products derived from polyunsaturated fatty acids (PUFAs) that play a role in cardiovascular disease and aging. Fish oil-derived n-3 PUFAs promote the formation of anti-inflammatory and vasodilatory oxylipins; however, there are little data on oxylipins derived from α-linolenic acid (C18:3n-3), the primary plant-derived n-3 PUFA. Walnuts are a source of C18:3n-3.

OBJECTIVES

To investigate the effect on serum oxylipins of a diet enriched with walnuts at 15% energy (30-60 g/d; 2.6-5.2 g C18:3n-3/d) for 2 y compared to a control diet (abstention from walnuts) in healthy older males and females (63-79 y).

METHODS

The red blood cell proportion of α-linolenic acid was determined by gas chromatography as a measure of compliance. Ultra-performance liquid chromatography-tandem mass spectrometry was used to measure serum concentrations of 53 oxylipins in participants randomly assigned to receive the walnut diet (n = 64) or the control diet (n = 51). Two-year concentration changes (final minus baseline) were log-transformed (base log-10) and standardized (mean-centered and divided by the standard deviation of each variable). Volcano plots were then generated (fold change ≥1.5; false discovery rate ≤0.1). For each oxylipin delta surviving multiple testing, we further assessed between-intervention group differences by analysis of covariance adjusting for age, sex, BMI, and the baseline concentration of the oxylipin.

RESULTS

The 2-y change in red blood cell C18:3n-3 in the walnut group was significantly higher than that in the control group (P < 0.001). Compared to the control diet, the walnut diet resulted in statistically significantly greater increases in 3 C18:3n-3-derived oxylipins (9-HOTrE, 13-HOTrE, and 12,13-EpODE) and in the C20:5n-3 derived 14,15-diHETE, and greater reductions of the C20:4n-6-derived 5-HETE, 19-HETE, and 5,6-diHETrE.

CONCLUSIONS

Long-term walnut consumption changes the serum oxylipin profile in healthy older persons. Our results add novel mechanistic evidence on the cardioprotective effects of walnuts.

TRIAL REGISTRATION

Clinicaltrials.gov Identifier: NCT01634841.

Oxylipin profiling by LC-ESI-MS/MS in canine serum and plasma to investigate ovulation-specific changes

New biomarkers that are directly associated with canine ovulation would be of value to ensure mating on optimal days of heat. In this study, canine plasma and serum were analyzed with liquid chromatography electrospray ionization tandem mass spectrometry (LC-ESI-MS/MS) to quantify a broad range of oxylipins for the purpose of developing a method for biomarker discovery studies in canine reproduction. A majority of the 67 oxylipins probed for were detected at comparable levels in both sample types, but more oxylipins at higher concentrations were detected in serum than in plasma. Nine of the oxylipins were detected in a pilot study of serum at levels that significantly differed (p ≤ 0.1) between time-points before (n = 10), during (n = 10) and after (n = 10) ovulation, and might serve as putative biomarkers for canine ovulation. One oxylipin (20-HETE) was significantly altered after adjusting for multiple comparisons. In conclusion, the results showed that the LC-ESI-MS/MS method was suitable for quantification of canine oxylipins, revealing important similarities and differences between plasma and serum profiles as well as preliminary ovulation-specific changes in a subset of the investigated oxylipins.

Serum proteomic profiling of carotid arteriopathy: A population outcome study

BACKGROUND AND AIMS

Circulating proteins reflecting subclinical vascular disease may improve prediction of atherosclerotic cardiovascular disease (ASCVD). We applied feature selection and unsupervised clustering on proteomic data to identify proteins associated with carotid arteriopathy and construct a protein-based classifier for ASCVD event prediction.

METHODS

491 community-dwelling participants (mean age, 58 ± 11 years; 51 % women) underwent carotid ultrasonography and proteomic profiling (CVD II panel, Olink Proteomics). ASCVD outcome was collected (median follow-up time: 10.2 years). We applied partial least squares (PLS) to identify proteins linked to carotid intima-media thickness (cIMT). Next, we assessed the association between future ASCVD events and protein-based phenogroups derived by unsupervised clustering (Gaussian Mixture modelling) based on proteins selected in PLS.

RESULTS

PLS identified 19 proteins as important, which were all associated with cIMT in multivariable-adjusted linear regression. 8 of the 19 proteins were excluded from the clustering analysis because of high collinearity. Based on the 11 remaining proteins, the clustering algorithm subdivided the cohort into two phenogroups. Compared to the first phenogroup (n = 177), participants in the second phenogroup (n = 314) presented: i) a more unfavorable lipid profile with higher total cholesterol and triglycerides and lower HDL cholesterol (p ≤ 0.014); ii) higher cIMT (p = 0.0020); and iii) a significantly higher risk for future ASCVD events (multivariable-adjusted hazard ratio (95 % CI) versus phenogroup 1: 2.05 (1.26-3.52); p = 0.0093). The protein-based phenogrouping supplemented ACC/AHA 10-year ASCVD risk scoring for prediction of a first ASCVD event.

CONCLUSIONS

Focused protein-based phenogrouping identified individuals at high risk for future ASCVD and may complement current risk stratification strategies.

Comparative predictive power of serum vs plasma proteomic signatures in feto-maternal medicine

BACKGROUND

Blood proteins are frequently measured in serum or plasma, because they provide a wealth of information. Differences in the ex vivo processing of serum and plasma raise concerns that proteomic health and disease signatures derived from serum or plasma differ in content and quality. However, little is known about their respective power to predict feto-maternal health outcomes. Predictive power is a sentinel characteristic to determine the clinical use of biosignatures.

OBJECTIVE

This study aimed to compare the power of serum and plasma proteomic signatures to predict a physiological pregnancy outcome.

STUDY DESIGN

Paired serum and plasma samples from 73 women were obtained from biorepositories of a multinational prospective cohort study on pregnancy outcomes. Gestational age at the time of sampling was the predicted outcome, because the proteomic signatures have been validated for such a prediction. Multivariate and cross-validated models were independently derived for serum and plasma proteins.

RESULTS

A total of 1116 proteins were measured in 88 paired samples from 73 women with a highly multiplexed platform using proximity extension technology (Olink Proteomics Inc, Watertown, MA). The plasma proteomic signature showed a higher predictive power (R=0.64; confidence interval, 0.42-0.79; P=3.5×10^-6) than the serum signature (R=0.45; confidence interval, 0.18-0.66; P=2.2×10^-3). The serum signature was validated in plasma with a similar predictive power (R=0.58; confidence interval, 0.34-0.75; P=4.8×10^-5), whereas the plasma signature was validated in serum with reduced predictive power (R=0.53; confidence interval, 0.27-0.72; P=2.6×10^-4). Signature proteins largely overlapped in the serum and plasma, but the strength of association with gestational age was weaker for serum proteins.

CONCLUSION

Findings suggest that serum proteomics are less informative than plasma proteomics. They are compatible with the view that the partial ex-vivo degradation and modification of serum proteins during sample processing are an underlying reason. The rationale for collecting and analyzing serum and plasma samples should be carefully considered when deriving proteomic biosignatures to ascertain that specimens of the highest scientific and clinical yield are processed. Findings suggest that plasma is the preferred matrix.

Association between lipocalin-2 and mild cognitive impairment or dementia: A systematic review and meta-analysis of population-based evidence

BACKGROUND

The associations between lipocalin-2 (LCN2) with mild cognitive impairment (MCI) and dementia have gained growing interest. However, population-based studies have yielded inconsistent findings. Therefore, we conducted this essential systematic review and meta-analysis to analyze and summarize the existing population-based evidence.

METHODS

PubMed, EMBASE, and Web of Science were systematically searched until Mar 18, 2022. Meta-analysis was performed to generate the standard mean difference (SMD) of peripheral blood and cerebrospinal fluid (CSF) LCN2. A qualitative review was performed to summarize the evidence from postmortem brain tissue studies.

RESULTS

In peripheral blood, the overall pooled results showed no significant difference in LCN2 across Alzheimer's disease (AD), MCI and control groups. Further subgroup analysis revealed higher serum LCN2 levels in AD compared to controls (SMD =1.28 [0.44;2.13], p = 0.003), while the difference remained insignificant in plasma (SMD =0.04 [-0.82;0.90], p = 0.931). Besides, peripheral blood LCN2 were higher in AD when age difference between AD and controls ≥ 4 years (SMD =1.21 [0.37;2.06], p = 0.005). In CSF, no differences were found in LCN2 across groups of AD, MCI and controls. However, CSF LCN2 was higher in vascular dementia (VaD) compared to controls (SMD =1.02 [0.17;1.87], p = 0.018), as well as compared to AD (SMD =1.19 [0.58;1.80], p < 0.001). Qualitative analysis supported that LCN2 was increased in the brain tissue of AD-related areas, especially in astrocytes and microglia; while LCN2 increased in infarct-related brain areas and over-expressed in astrocytes and macrophages in mixed dementia (MD).

CONCLUSION

The difference in peripheral blood LCN2 between AD and controls may be affected by the type of biofluid and age. No differences were found in CSF LCN2 across AD, MCI and controls groups. In contrast, CSF LCN2 was elevated in VaD patients. Moreover, LCN2 was increased in AD-related brain areas and cells in AD, while in infarcts-related brain areas and cells in MD.

Peripheral high levels of CRP predict progression from normal cognition to dementia: A systematic review and meta-analysis

OBJECTIVE

Several cross-sectional studies have demonstrated a relationship between inflammation and dementia. Uncertainty exists over the ability of C-reactive protein (CRP), one of the most investigated markers of inflammation, to predict the progression of normal cognition to dementia. A systematic review and meta-analysis were performed to assess whether high peripheral levels of CRP are associated with cognitive impairment and whether CRP is a risk factor for predicting progression from normal cognition to cognitive decline or dementia.

METHODS

Literature published before November 2022 was retrieved from PubMed, Embase, and Web of Science. Prospective cohort studies that employed recognized evaluation instruments to assess global cognitive function or used accepted diagnostic criteria to ascertain dementia were selected. Subgroup analysis was conducted on specific cognitive domains and causes of dementia (i.e., Alzheimer's disease and vascular dementia). Odds ratios (ORs) and hazard ratios (HRs) were extracted and merged to facilitate data analysis. A random-effects model was used for the meta-analysis and a descriptive analysis of the data that could not be merged was conducted.

RESULTS

A total of 13 articles (14 cohort studies) were included for meta-analysis and six articles were included for descriptive analysis. The results showed that high CRP levels were not related to future cognitive decline (OR = 1.115; 95 % CI: 0.830-1.497; p = 0.469) but were associated with an increased risk of conversion to dementia. (HR = 1.473; 95 % CI: 1.037-2.090; p = 0.0394). This association persisted after full adjustment for potential covariates, with an OR of 1.044 (95 % CI:0.767-1.421, p = 0.785) for cognitive decline and an HR of 1.429 (95 % CI:1.088-1.876, p = 0.010) for dementia. The subgroup analysis showed that a higher level of CRP was related to a decline in visual-spatial ability (OR = 1.402, 95 % CI: 1.045-1.882, p = 0.024) and the risk of conversion to vascular dementia (total effect size of OR and HR = 2.769, 95 % CI: 1.586-4.83, p = 0.000).

CONCLUSIONS

Higher CRP levels as an indicator of chronic systemic inflammation cannot predict future cognitive decline but may indicate a higher risk of conversion to dementia.

Inflammation proteomics datasets in the ALSPAC cohort

Proteomics is the identification, detection and quantification of proteins within a biological sample. The complete set of proteins expressed by an organism is known as the proteome. The availability of new high-throughput proteomic technologies, such as Olink Proteomic Proximity Extension Assay (PEA) technology has enabled detailed investigation of the circulating proteome in large-scale epidemiological studies. In particular, the Olink® Target 96 inflammatory panel allows the measurement of 92 circulating inflammatory proteins. The Avon Longitudinal Study of Parents and Children (ALSPAC) is a prospective population-based cohort study which recruited pregnant women in 1991-1992 and has followed these women, their partners, and their offspring ever since. In this data note, we describe the proteomic data available in ALSPAC. Ninety-two proteins were analysed in 9000 blood plasma samples using the Olink® Target 96 inflammatory panel. Samples were derived from 2968 fasted mothers (mean age 47.5; Focus on Mothers 1 (FOM1)), 3005 non-fasted offspring at age 9 (Focus@9) and 3027 fasted offspring at age 24 (Focus@24). Post sample filtering, 1834 offspring have data at both timepoints and 1119 of those have data from their mother available. We performed quality control analyses using a standardised data processing workflow (metaboprep) to produce a filtered dataset of 8983 samples for researchers to use in future analyses. Initial validation analyses indicate that IL-6 measured using the Olink® Target 96 inflammatory panel is highly correlated with IL-6 previously measured by clinical chemistry (Pearson’s correlation = 0.77) and we are able to reproduce the reported positive correlation between body mass index (BMI) and IL-6. The pre-processing and validation analyses indicate a rich proteomic dataset to further characterise the role of inflammation in health and disease.

Folliculin-interacting protein FNIP2 impacts on overweight and obesity through a polymorphism in a conserved 3' untranslated region

BACKGROUND

Overweight and obesity are defined by an anomalous or excessive fat accumulation that may compromise health. To find single-nucleotide polymorphisms (SNPs) influencing metabolic phenotypes associated with the obesity state, we analyze multiple anthropometric and clinical parameters in a cohort of 790 healthy volunteers and study potential associations with 48 manually curated SNPs, in metabolic genes functionally associated with the mechanistic target of rapamycin (mTOR) pathway.

RESULTS

We identify and validate rs2291007 within a conserved region in the 3'UTR of folliculin-interacting protein FNIP2 that correlates with multiple leanness parameters. The T-to-C variant represents the major allele in Europeans and disrupts an ancestral target sequence of the miRNA miR-181b-5p, thus resulting in increased FNIP2 mRNA levels in cancer cell lines and in peripheral blood from carriers of the C allele. Because the miRNA binding site is conserved across vertebrates, we engineered the T-to-C substitution in the endogenous Fnip2 allele in mice. Primary cells derived from Fnip2 C/C mice show increased mRNA stability, and more importantly, Fnip2 C/C mice replicate the decreased adiposity and increased leanness observed in human volunteers. Finally, expression levels of FNIP2 in both human samples and mice negatively associate with leanness parameters, and moreover, are the most important contributor in a multifactorial model of body mass index prediction.

CONCLUSIONS

We propose that rs2291007 influences human leanness through an evolutionarily conserved modulation of FNIP2 mRNA levels.

Links between ectopic and abdominal fat and systemic inflammation: New insights from the SHIP-Trend study

BACKGROUND

Excessive fat accumulation in adipose tissue depots and organs such as the pancreas and the liver is associated with systemic low-grade chronic inflammation.

AIMS

To investigate the association between abdominal, hepatic, and pancreatic fat and the circulating level of inflammatory biomarkers.

METHODS

We used data from a subsample of the Study of Health in Pomerania (SHIP-Trend, n = 469). The plasma concentration of 37 inflammatory biomarkers was measured using the Bio-Plex-Pro™-Human-Inflammation-Panel-1. Subcutaneous and visceral adipose tissue (SAT and VAT), as well as hepatic and pancreatic fat, were determined by magnetic resonance imaging. We assessed the associations between fat content and inflammatory biomarkers using multiple linear regression.

RESULTS

Hepatic fat was associated with MMP-2 (β -0.11), PTX3 (β -0.14), and TNFSF12 (β -0.06). Pancreatic fat was associated with sTNFR1 (β 0.15), sTNFR2 (β 0.11), and sCD163 (β 0.13). VAT and SAT were associated with sCD163 (β^VAT 0.20, β^SAT 0.16), MMP-2 (β^VAT -0.12, β^SAT -0.10), OSTCN (β^VAT -0.16, β^SAT -0.10), sTNFR1 (β^VAT 0.13, β^SAT 0.13), sTNFR2 (β^VAT 0.13, β^SA 0.12), TNFSF12 (β^VAT -0.11, β^SAT -0.08), and TNFSF14 (β^VAT 0.21, β^SAT 0.20). VAT was additionally associated with TNFSF13B (β 0.08) and CHI3L1 (β 0.07).

CONCLUSIONS

Our findings provide new insights into the involvement of hepatic and pancreatic fat on systemic inflammation.

Lipoxins reduce obesity-induced adipose tissue inflammation in 3D-cultured human adipocytes and explant cultures

Adipose tissue inflammation drives obesity-related cardiometabolic diseases. Enhancing endogenous resolution mechanisms through administration of lipoxin A4, a specialized pro-resolving lipid mediator, was shown to reduce adipose inflammation and subsequently protects against obesity-induced systemic disease in mice. Here, we demonstrate that lipoxins reduce inflammation in 3D-cultured human adipocytes and adipose tissue explants from obese patients. Approximately 50% of patients responded particularly well to lipoxins by reducing inflammatory cytokines and promoting an anti-inflammatory M2 macrophage phenotype. Responding patients were characterized by elevated systemic levels of C-reactive protein, which causes inflammation in cultured human adipocytes. Responders appeared more prone to producing anti-inflammatory oxylipins and displayed elevated prostaglandin D2 levels, which has been interlinked with transcription of lipoxin-generating enzymes. Using explant cultures, this study provides the first proof-of-concept evidence supporting the therapeutic potential of lipoxins in reducing human adipose tissue inflammation. Our data further indicate that lipoxin treatment may require a tailored personalized-medicine approach.

Lipoxins modulate neutrophil oxidative burst, integrin expression and lymphatic transmigration differentially in human health and atherosclerosis

Dysregulated chronic inflammation plays a crucial role in the pathophysiology of atherosclerosis and may be a result of impaired resolution. Thus, restoring levels of specialized pro‐resolving mediators (SPMs) to promote the resolution of inflammation has been proposed as a therapeutic strategy for patients with atherosclerosis, in addition to standard clinical care. Herein, we evaluated the effects of the SPM lipids, lipoxin A₄ (LXA₄) and lipoxin B₄ (LXB₄), on neutrophils isolated from patients with atherosclerosis compared with healthy controls. Patients displayed altered endogenous SPM production, and we demonstrated that lipoxin treatment in whole blood from atherosclerosis patients attenuates neutrophil oxidative burst, a key contributor to atherosclerotic development. We found the opposite effect in neutrophils from healthy controls, indicating a potential mechanism whereby lipoxins aid the endogenous neutrophil function in health but reduce its excessive activation in disease. We also demonstrated that lipoxins attenuated upregulation of the high‐affinity conformation of the CD11b/CD18 integrin, which plays a central role in clot activation and atherosclerosis. Finally, LXB₄ enhanced lymphatic transmigration of human neutrophils isolated from patients with atherosclerosis. This finding is noteworthy, as impaired lymphatic function is now recognized as an important contributor to atherosclerosis. Although both lipoxins modulated neutrophil function, LXB₄ displayed more potent effects than LXA₄ in humans. This study highlights the therapeutic potential of lipoxins in atherosclerotic disease and demonstrates that the effect of these SPMs may be specifically tailored to the need of the individual.

Healthy Subcutaneous and Omental Adipose Tissue Is Associated with High Expression of Extracellular Matrix Components

Obesity is associated with extensive expansion and remodeling of the adipose tissue architecture, including its microenvironment and extracellular matrix (ECM). Although obesity has been reported to induce adipose tissue fibrosis, the composition of the ECM under healthy physiological conditions has remained underexplored and debated. Here, we used a combination of three established techniques (picrosirius red staining, a colorimetric hydroxyproline assay, and sensitive gene expression measurements) to evaluate the status of the ECM in metabolically healthy lean (MHL) and metabolically unhealthy obese (MUO) subjects. We investigated ECM deposition in the two major human adipose tissues, namely the omental and subcutaneous depots. Biopsies were obtained from the same anatomic region of respective individuals. We found robust ECM deposition in MHL subjects, which correlated with high expression of collagens and enzymes involved in ECM remodeling. In contrast, MUO individuals showed lower expression of ECM components but elevated levels of ECM cross-linking and adhesion proteins, e.g., lysyl oxidase and thrombospondin. Our data suggests that subcutaneous fat is more prone to express proteins involved in ECM remodeling than omental adipose tissues. We conclude that a more dynamic ability to deposit and remodel ECM may be a key signature of healthy adipose tissue, and that subcutaneous fat may adapt more readily to changing metabolic conditions than omental fat.

Is subcutaneous adipose tissue expansion in people living with lipedema healthier and reflected by circulating parameters?

Lipedema may be considered a model for healthy expandability of subcutaneous adipose tissue (SAT). This condition is characterized by the disproportional and symmetrical SAT accumulation in the lower-body parts and extremities, avoiding the abdominal area. There are no circulating biomarkers facilitating the diagnosis of lipedema. We tested the hypothesis that women living with lipedema present a distinct pattern of circulating parameters compared to age- and BMI-matched women. In 26 women (Age 48.3 ± 13.9 years, BMI 32.6 ± 5.8 kg/m2; lipedema group: n=13; control group: n=13), we assessed circulating parameters of glucose and lipid metabolism, inflammation, oxidative stress, sex hormones and a proteomics panel. We find that women with lipedema have better glucose metabolism regulation represented by lower HbA1c (5.55 ± 0.62%) compared to controls (6.73 ± 0.85%; p&lt;0.001); and higher adiponectin levels (lipedema: 4.69 ± 1.99 mmol/l; control: 3.28 ± 1.00 mmol/l; p=0.038). Despite normal glycemic parameters, women with lipedema have significantly higher levels of total cholesterol (5.84 ± 0.70 mmol/L vs 4.55 ± 0.77 mmol/L in control; p&lt;0.001), LDL-C (3.38 ± 0.68 mmol/L vs 2.38 ± 0.66 mmol/L in control; p=0.002), as well as higher circulating inflammation (top 6 based on p-values: TNFSF14, CASP8, EN-RAGE, EIF4EBP1, ADA, MCP-1) and oxidative stress markers (malondialdehyde, superoxide dismutase and catalase). Our findings suggest that the expected association between activation of inflammatory and oxidative stress pathways and impaired glucose metabolism are counterbalanced by protective factors in lipedema.

Genetic and environmental influences on serum oxylipins, endocannabinoids, bile acids and steroids

Lipid bioactivity is a result of direct action and the action of lipid mediators including oxylipins, endocannabinoids, bile acids and steroids. Understanding the factors contributing to biological variation in lipid mediators may inform future approaches to understand and treat complex metabolic diseases. This research aims to determine the contribution of genetic and environmental influences on lipid mediators involved in the regulation of inflammation and energy metabolism. This study recruited 138 monozygotic (MZ) and dizygotic (DZ) twins aged 18-65 years and measured serum oxylipins, endocannabinoids, bile acids and steroids using liquid chromatography mass-spectrometry (LC-MS). In this classic twin design, the similarities and differences between MZ and DZ twins are modelled to estimate the contribution of genetic and environmental influences to variation in lipid mediators. Heritable lipid mediators included the 12-lipoxygenase products 12-hydroxyeicosatetraenoic acid [0.70 (95% CI: 0.12,0.82)], 12-hydroxyeicosatetraenoic acid [0.73 (95% CI: 0.30,0.83)] and 14‑hydroxy-docosahexaenoic acid [0.51 (95% CI: 0.07,0.71)], along with the endocannabinoid docosahexaenoy-lethanolamide [0.52 (95% CI: 0.15,0.72)]. For others such as 13-hydroxyoctadecatrienoic acid and lithocholic acid the contribution of environment to variation was stronger. With increased understanding of lipid mediator functions in health, it is important to understand the factors contributing to their variance. This study provides a comprehensive analysis of lipid mediators and extends pre-existing knowledge of the genetic and environmental influences on the human lipidome.

Proteomic profiling of low muscle and high fat mass: a machine learning approach in the KORA S4/FF4 study

BACKGROUND

The coexistence of low muscle mass and high fat mass, two interrelated conditions strongly associated with declining health status, has been characterized by only a few protein biomarkers. High-throughput proteomics enable concurrent measurement of numerous proteins, facilitating the discovery of potentially new biomarkers.

METHODS

Data derived from the prospective population-based Cooperative Health Research in the Region of Augsburg S4/FF4 cohort study (median follow-up time: 13.5 years) included 1478 participants (756 men and 722 women) aged 55-74 years in the cross-sectional and 608 participants (315 men and 293 women) in the longitudinal analysis. Appendicular skeletal muscle mass (ASMM) and body fat mass index (BFMI) were determined through bioelectrical impedance analysis at baseline and follow-up. At baseline, 233 plasma proteins were measured using proximity extension assay. We implemented boosting with stability selection to enable false positives-controlled variable selection to identify new protein biomarkers of low muscle mass, high fat mass, and their combination. We evaluated prediction models developed based on group least absolute shrinkage and selection operator (lasso) with 100× bootstrapping by cross-validated area under the curve (AUC) to investigate if proteins increase the prediction accuracy on top of classical risk factors.

RESULTS

In the cross-sectional analysis, we identified kallikrein-6, C-C motif chemokine 28 (CCL28), and tissue factor pathway inhibitor as previously unknown biomarkers for muscle mass [association with low ASMM: odds ratio (OR) per 1-SD increase in log2 normalized protein expression values (95% confidence interval (CI)): 1.63 (1.37-1.95), 1.31 (1.14-1.51), 1.24 (1.06-1.45), respectively] and serine protease 27 for fat mass [association with high BFMI: OR (95% CI): 0.73 (0.61-0.86)]. CCL28 and metalloproteinase inhibitor 4 (TIMP4) constituted new biomarkers for the combination of low muscle and high fat mass [association with low ASMM combined with high BFMI: OR (95% CI): 1.32 (1.08-1.61), 1.28 (1.03-1.59), respectively]. Including protein biomarkers selected in ≥90% of group lasso bootstrap iterations on top of classical risk factors improved the performance of models predicting low ASMM, high BFMI, and their combination [delta AUC (95% CI): 0.16 (0.13-0.20), 0.22 (0.18-0.25), 0.12 (0.08-0.17), respectively]. In the longitudinal analysis, N-terminal prohormone brain natriuretic peptide (NT-proBNP) was the only protein selected for loss in ASMM and loss in ASMM combined with gain in BFMI over 14 years [OR (95% CI): 1.40 (1.10-1.77), 1.60 (1.15-2.24), respectively].

CONCLUSIONS

Proteomic profiling revealed CCL28 and TIMP4 as new biomarkers of low muscle mass combined with high fat mass and NT-proBNP as a key biomarker of loss in muscle mass combined with gain in fat mass. Proteomics enable us to accelerate biomarker discoveries in muscle research.

Rapid Decline of Serum Proprotein Convertase Subtilisin/Kexin 9 (PCSK9) in Non-Cirrhotic Patients with Chronic Hepatitis C Infection Receiving Direct-Acting Antiviral Therapy

Direct-acting antivirals (DAAs) efficiently eradicate the hepatitis C virus (HCV). Low-density lipoprotein (LDL) levels increase rapidly upon DAA treatment. Proprotein convertase subtilisin/kexin 9 (PCSK9) induces degradation of the hepatic LDL receptor and thereby elevates serum LDL. The aim of this study was to determine serum PCSK9 concentrations during and after DAA therapy to identify associations with LDL levels. Serum PCSK9 was increased in 82 chronic HCV-infected patients compared to 55 patients not infected with HCV. Serum PCSK9 was low in HCV patients with liver cirrhosis, but patients with HCV-induced liver cirrhosis still exhibited higher serum PCSK9 than patients with non-viral liver cirrhosis. Serum PCSK9 correlated with measures of liver injury and inflammation in cirrhotic HCV patients. In patients without liver cirrhosis, a positive association of serum PCSK9 with viral load existed. Serum PCSK9 was not different between viral genotypes. Serum PCSK9 did not correlate with LDL levels in HCV patients irrespective of cirrhotic status. Serum PCSK9 was reduced, and LDL was increased at four weeks after DAA therapy start in non-cirrhotic HCV patients. Serum PCSK9 and LDL did not change upon DAA treatment in the cirrhotic group. The rapid decline of PCSK9 after the start of DAA therapy in conjunction with raised LDL levels in non-cirrhotic HCV patients shows that these changes are not functionally related.