The disulfide bonds formed in the SAPA domain of a recombinant version of the NH2-terminal propeptide (SP-BN) from the precursor of human pulmonary surfactant protein B (SP-B) were identified through ...sequential digestion of SP-BN with GluC/trypsin or thermolysin/GluC, followed by mass spectrometry (MS) analysis. MS spectra allowed identification of disulfide bonds between Cys32-Cys49 and Cys40-Cys55, and we propose a disulfide connectivity pattern of 1–3 and 2–4 within the SAPA domain, with the Cys residues numbered according to their position from the N-terminus of the propeptide sequence. The peaks with m/z ∼ 2136 and ∼ 1780 in the MS spectrum of the GluC/trypsin digest were assigned to peptides 24AWTTSSLACAQGPE37 and 45QALQCR50 linked by Cys32-Cys49 and 38FWCQSLE44 and 51ALGHCLQE58 linked by Cys40-Cys55 respectively. Tandem mass spectrometry (MS/MS) analysis verified the position of the bonds. The results of the series ions, immonium ions and internal fragment ions were all compatible with the proposed 1–3/2–4 position of the disulfide bonds in the SAPA domain. This X-pattern differs from the kringle-type found in the SAPB domain of the SAPLIP proteins, where the first Cys in the sequence links to the last, the second to the penultimate and the third to the fourth one. Regarding the SAPB domain of the SP-BN propeptide, the MS analysis of both digests identified the bond Cys100-Cys112, numbered 7–8, which is coincident with the bond position in the kringle motif.
The SAPLIP (saposin-like proteins) family encompasses several proteins with homology to saposins (sphingolipids activator proteins). These are proteins with mainly alpha-helical folds, compact packing including well conserved disulfide bonds and ability to interact with phospholipids and membranes. There are two types of saposin-like domains termed as Saposin A (SAPA) and Saposin B (SAPB) domains. While disulfide connectivity has been well established in several SAPB domains, the position of disulfide bonds in SAPA domains is still unknown. The present study approaches a detailed proteomic study to determine disulfide connectivity in the SAPA domain of the precursor of human pulmonary surfactant-associated protein SP-B. This task has been a challenge requiring the combination of different sequential proteolytic treatments followed by MS analysis including MALDI-TOF and tandem mass MS/MS spectrometry. The determination for first time of the position of disulfide bonds in SAPA domains is an important step to understand the structural determinants defining its biological functions.
Display omitted
•GluC/trypsin double digestion followed by MS and MS/MS determined the disulfide connectivity in a SAPA domain.•A theoretical handy work assigned internal and terminal disulfide linked ions to peak signals in MS/MS spectra.•A pattern 1–3 and 2–4 is found for disulfide bonds in the SAPA domain of the human proSP-B precursor.•The disulphide pattern determined by this SAPA domain differs from the established SAPB kringle domain.
Bone turnover: Biology and assessment tools Szulc, Pawel
Best Practice & Research Clinical Endocrinology & Metabolism,
October 2018, 2018-10-00, 20181001, Letnik:
32, Številka:
5
Journal Article
Recenzirano
Bone turnover includes two processes: resorption (removal of old bone) and formation (laying down of new bone). N-terminal propeptide of type I procollagen (PINP) and C-telopeptide of type I collagen ...(CTX-I) are markers of bone formation and resorption, respectively, that the International Osteoporosis Foundation and the International Federation of Clinical Chemistry recommend for clinical use. Bone turnover markers (BTM) are subject to sources of variability, including feeding (lower resorption) and recent fracture (increased levels of all markers). Controllable patient-related factors should be adapted as much as possible (eg blood collection after an overnight fast) to minimize pre-analytical variability. Uncontrollable factors should be considered in the interpretation of the BTM measurements. BTM do not improve prediction of bone loss or fracture within an individual. In osteoporotic patients, BTM may help to assess the response to anabolic and antiresorptive therapies, to assess compliance to the treatment, or to indicate possible secondary causes of osteoporosis. BTM reflect changes in bone metabolism induced by anti-osteoporotic treatment. Anti-resorptive drugs induce a rapid dose-dependent decrease in bone resorption, whereas bone formation stimulating medications increase the levels of bone formations markers. BTM may be used for monitoring anti-osteoporosis therapy. The expected effect during the anti-resorptive therapy is to decrease the PINP by at least 10 ng/mL and to attain the target level of less than 35 ng/mL. The expected effect during the bone formation-stimulating therapy is to increase the PINP by at least 10 ng/mL and to attain the target level of more than 69 ng/mL.
Patients implanted with osseointegrated (OI) prosthetic systems have reported vastly improved upper and lower extremity prosthetic function compared with their previous experience with ...socket‐suspension systems. However, OI systems have been associated with superficial and deep‐bone infections and implant loosening due, in part, to a failure of the osseointegration process. Although monitoring the osseointegration using circulating biomarkers has clinical relevance for understanding the progression of osseointegration with these devices, it has yet to be established. Ten patients were enrolled in this study. Blood samples were collected at pre‐selected times, starting before implantation surgery, and continuing to 12 months after the second surgery. Bone formation markers, bone resorption markers, and circulating amino acids were measured from blood samples. A linear mixed model was generated for each marker, incorporating patient ID and age with the normalized marker value as the response variable. Post hoc comparisons were made between 1 week before Stage 1 Surgery and all subsequent time points for each marker, followed by multiple testing corrections. Serial radiographic imaging of the residual limb containing the implant was obtained during follow‐up, and the cortical index (CI) was calculated for the bone at the porous region of the device. Two markers of bone formation, specifically bone‐specific alkaline phosphatase (Bone‐ALP) and amino‐terminal propeptide of type I procollagen (PINP), exhibited significant increases when compared with the baseline levels of unloaded residual bone prior to the initial surgery, and they subsequently returned to their baseline levels by the 12‐month mark. Patients who experienced clinically robust osseointegration experienced increased cortical bone thickness at the porous coated region of the device. A medium correlation was observed between Bone‐ALP and the porous CI values up to PoS2‐M1 (p = .056), while no correlation was observed for PINP. An increase in bone formation markers and the lack of change observed in bone resorption markers likely reflect increased cortical bone formation induced by the end‐loading design of the Utah OI device used in this study. A more extensive study is required to validate the correlation observed between Bone‐ALP and porous CI values.
With metabolic dysfunction-associated fatty liver disease (MAFLD) incidence and prevalence increasing, it is necessary to identify patients with advanced fibrosis (F3-F4 stages). We evaluated the ...performance of new biomarkers and algorithms for diagnosing advanced fibrosis in an Asian population.
Data from two Asian cohorts (including 851 biopsy-proven MAFLD 578 from Wenzhou, 273 from Hong Kong) were studied. The association between N-terminal propeptide of type 3 collagen (PRO-C3) and the histologic stage of liver fibrosis was analyzed by multivariable linear regression. The area under the receiver operating characteristic curve (AUROC) was used to test the diagnostic performance of serum PRO-C3 and the ADAPT score for advanced fibrosis and compared them to other established non-invasive tests.
Serum PRO-C3 levels increased progressively across liver fibrosis stages and correlated with advanced fibrosis (P < 0.001). The ADAPT score had an AUROC of 0.865 (95% confidence interval 0.829–0.901) for advanced fibrosis; the accuracy, sensitivity and negative predictive values were 81.4%, 82.2% and 96.1%, respectively. This result was better compared to that of PRO-C3 alone or other non-invasive fibrosis biomarkers (aspartate aminotransferase-to-platelet ratio index, Fibrosis-4, BARD, and NAFLD fibrosis score). In subgroup analyses (including sex, age, diabetes, NAFLD activity score, body mass index or serum alanine aminotransferase levels), the ADAPT score had good diagnostic performance.
PRO-C3 and the ADAPT score reliably exclude advanced fibrosis in MAFLD patients and reduce the need for liver biopsy.
•The N-terminal propeptide of type 3 collagen can be used for the staging fibrosis.•The ADAPT score has better diagnostic performance for identifying advanced fibrosis.•The ADAPT score can be used as new noninvasive tests for diagnosing advanced fibrosis.
Background Biomarkers simplifying the diagnostic workup by discriminating between non–ST‐segment–elevation myocardial infarction (NSTEMI) and infarct‐like myocarditis are an unmet clinical need. ...Methods and Results A total of 105 subjects were categorized into groups as follows: ST‐segment−elevation myocardial infarction (n=36), NSTEMI (n=22), infarct‐like myocarditis (n=19), cardiomyopathy‐like myocarditis (n=18), and healthy control (n=10). All subjects underwent cardiac magnetic resonance imaging, and serum concentrations of matrix metalloproteinase‐1 (MMP‐1) and procollagen type I carboxy terminal propeptide (PICP) were measured. Biomarker concentrations in subjects presenting with acute coronary syndrome and non‐ST‐segment‐elevation, for example NSTEMI or infarct‐like myocarditis, categorized as the non−ST‐segment−elevation acute coronary syndrome−like cohort, were of particular interest for this study. Compared with healthy controls, subjects with myocarditis had higher serum concentrations of MMP‐1 and PICP, while no difference was observed in individuals with myocardial infarction. In the non−ST‐segment−elevation acute coronary syndrome−like cohort, MMP‐1 concentrations discriminated infarct‐like myocarditis and NSTEMI with an area under the receiver operating characteristic curve (AUC) of 0.95 (95% CI, 0.89−1.00), whereas high‐sensitivity cardiac troponin T performed inferiorly (AUC, 0.74 95% CI, 0.58−0.90; P =0.012). Application of an optimal MMP‐1 cutoff had 94.4% sensitivity (95% CI, 72.7%−99.9%) and 90.9% specificity (95% CI, 70.8%−98.9%) for the diagnosis of infarct‐like myocarditis in this cohort. The AUC of PICP in this context was 0.82 (95% CI, 0.68−0.97). As assessed by likelihood ratio tests, incorporating MMP‐1 or PICP with age and C‐reactive protein into composite prediction models enhanced their diagnostic performance. Conclusions MMP‐1 and PICP could potentially be useful biomarkers for differentiating between NSTEMI and infarct‐like myocarditis in individuals with non−ST‐segment−elevation acute coronary syndrome‐like presentation, though further research is needed to validate their clinical applicability.
Summary
The National Bone Health Alliance (NBHA) recommends standardized sample handling and patient preparation for C-terminal telopeptide of type I collagen (CTX-I) and N-terminal propeptide of ...type I procollagen (PINP) measurements to reduce pre-analytical variability. Controllable and uncontrollable patient-related factors are reviewed to facilitate interpretation and minimize pre-analytical variability.
Introduction
The IOF and the International Federation of Clinical Chemistry (IFCC) Bone Marker Standards Working Group have identified PINP and CTX-I in blood to be the reference markers of bone turnover for the fracture risk prediction and monitoring of osteoporosis treatment. Although used in clinical research for many years, bone turnover markers (BTM) have not been widely adopted in clinical practice primarily due to their poor within-subject and between-lab reproducibility. The NBHA Bone Turnover Marker Project team aim to reduce pre-analytical variability of CTX-I and PINP measurements through standardized sample handling and patient preparation.
Methods
Recommendations for sample handling and patient preparations were made based on review of available publications and pragmatic considerations to reduce pre-analytical variability. Controllable and un-controllable patient-related factors were reviewed to facilitate interpretation and sample collection.
Results
Samples for CTX-I must be collected consistently in the morning hours in the fasted state. EDTA plasma is preferred for CTX-I for its greater sample stability. Sample collection conditions for PINP are less critical as PINP has minimal circadian variability and is not affected by food intake. Sample stability limits should be observed. The uncontrollable aspects (age, sex, pregnancy, immobility, recent fracture, co-morbidities, anti-osteoporotic drugs, other medications) should be considered in BTM interpretation.
Conclusion
Adopting standardized sample handling and patient preparation procedures will significantly reduce controllable pre-analytical variability. The successful adoption of such recommendations necessitates the close collaboration of various stakeholders at the global stage, including the laboratories, the medical community, the reagent manufacturers and the regulatory agencies.
Background Peripheral venous pressure (PVP) has been shown to be a reliable surrogate for right atrial pressure in assessing congestion in patients with heart failure (HF). Liver fibrosis markers and ...scores can be useful in assessing organ injury in patients with acute HF. This study aimed to investigate the association of liver fibrosis markers and scores with PVP in patients with acute HF. Methods and Results The 7S domain of the collagen type IV N-terminal propeptide (P4NP 7S), aspartate aminotransferase-to-platelet ratio index, fibrosis-4, and nonalcoholic fatty liver disease fibrosis score were determined along with PVP measurements before discharge in 229 patients with acute HF. The strongest correlation with PVP was found for P4NP 7S (Pearson
=0.40). Patients with high P4NP 7S levels (≥median 6.2 ng/mL) had an increased risk of cardiovascular death or HF hospitalization (adjusted hazard ratio HR, 1.80 95% CI, 1.09-3.04,
=0.02). The concomitant high PVP (≥mean 8 mm Hg)/high P4NP 7S group, in contrast to the high PVP/low P4NP 7S or low PVP/high P4NP 7S group, had a significant risk relative to the low PVP/low P4NP 7S group for cardiovascular death or HF hospitalization (adjusted HR, 2.63 95% CI, 1.43-5.05,
=0.002). A sustained elevation in PVP for 1 month postdischarge was associated with a persistent increase in P4NP 7S. Conclusions The study demonstrated the relationship between the liver fibrosis marker P4NP 7S and congestion. PVP and P4NP 7S could be useful for assessing congestion-related organ injury and predicting prognosis in patients with acute HF.
Background The management of chronic kidney disease–mineral and bone disorder requires the assessment of bone turnover, which most often is based on parathyroid hormone (PTH) concentration, the ...utility of which remains controversial. Study Design Cross-sectional retrospective diagnostic test study. Setting & Participants 492 dialysis patients from Brazil, Portugal, Turkey, and Venezuela with prior bone biopsy and stored (−20°C) serum. Index Tests Samples were analyzed for PTH (intact iPTH and whole PTH), bone-specific alkaline phosphatase (bALP), and amino-terminal propeptide of type 1 procollagen (P1NP). Reference Test Bone histomorphometric assessment of turnover (bone formation rate/bone surface BFR/BS) and receiver operating characteristic curves for discriminating diagnostic ability. Results The biomarkers iPTH and bALP or combinations thereof allowed discrimination of low from nonlow and high from nonhigh BFR/BS, with an area under the receiver operating characteristic curve > 0.70 but < 0.80. Using iPTH level, the best cutoff to discriminate low from nonlow BFR/BS was <103.8 pg/mL, and to discriminate high from nonhigh BFR/BS was >323.0 pg/mL. The best cutoff for bALP to discriminate low from nonlow BFR/BS was <33.1 U/L, and for high from nonhigh BFR/BS, 42.1 U/L. Using the KDIGO practice guideline PTH values of greater than 2 but less than 9 times the upper limit of normal, sensitivity and specificity of iPTH level to discriminate low from nonlow turnover bone disease were 65.7% and 65.3%, and to discriminate high from nonhigh were 37.0% and 85.8%, respectively. Limitations Cross-sectional design without consideration of therapy. Potential limited generalizability with samples from 4 countries. Conclusions The serum biomarkers iPTH, whole PTH, and bALP were able to discriminate low from nonlow BFR/BS, whereas iPTH and bALP were able to discriminate high from nonhigh BFR/BS. Prospective studies are required to determine whether evaluating trends in biomarker concentrations could guide therapeutic decisions.
PDF
