Development of immunoassays for serum tartrate-resistant acid phosphatase isoform 5a

Intensive weight gain therapy in patients with anorexia nervosa results in improved serum tartrate-resistant acid phosphatase (TRAP) 5a and 5b isoform protein levels

AIM

Tartrate-resistant acid phosphatase (TRAP) exists as isoforms 5a and 5b. TRAP 5a is a biomarker of chronic inflammation and influences adipose tissue and 5b associates with bone metabolism/pathologies. The aim was to investigate the association of serum TRAP 5a/5b isoforms with fat and bone markers and anthropometric parameters in patients with anorexia nervosa (AN) during weight gain therapy.

METHODS

Twenty-five Swedish female AN patients, age 16-24 years, were treated for 12 weeks with a high-energy diet with six meals daily. Serum TRAP 5a/5b, markers of fat/glucose metabolism, markers of bone resorption and formation were measured. Parameters of bone and body composition were assessed by dual-energy X-ray absorptiometry and peripheral quantitative computed tomography.

RESULTS

BMI increased from median 15.4 kg/m² to 19.0 kg/m², p < 0.0001. TRAP 5a and 5a/5b ratio increased but TRAP 5b decreased during the study. TRAP Δ5a and Δ5b correlated with Δinsulin and Δadiponectin, respectively. TRAP 5b correlated with trabecular density at start but not at week 12. At 12 weeks, TRAP 5b correlated with CTX, and Δ decrease in TRAP 5b correlated to Δ increase in bone-specific alkaline phosphatase.

CONCLUSIONS

This clinical interventional study resulted in increased BMI in patients with AN. The decreased TRAP 5b protein levels confirm a role for TRAP 5b as a marker of bone resorption, whereas increased TRAP 5a seemed to derive from systemic changes in bone as well as metabolic changes. The combined detection of TRAP 5a and TRAP 5b in serum could be an indicator of improved bone metabolism.

LEVEL OF EVIDENCE

Level III, prospective interventional cohort study.

Elevated serum tartrate-resistant acid phosphatase isoform 5a levels in metabolic syndrome

Background

Tartrate-resistant phosphatase isoform 5a is expressed in tumor-associated macrophages and is a biomarker of chronic inflammation. Herein, we correlated serum tartrate-resistant phosphatase isoform 5a levels with metabolic syndrome status and made comparisons with traditional markers of inflammation, including c-reactive protein and interleukin-6.

Methods

One hundred healthy volunteers were randomly selected, and cut-off points for metabolic syndrome related inflammatory biomarkers were determined using receiver operating characteristic curves. Linear and logistic regression models were subsequently used to correlate inflammatory markers with the risk of metabolic syndrome.

Results

Twenty-two participants met the criteria for metabolic syndrome, and serum tartrate-resistant phosphatase isoform 5a levels of >5.8 μg/L were associated with metabolic syndrome (c-statistics, 0.730; p = 0.001; 95% confidence interval, 0.618-0.842). In addition, 1 μg/L increases in tartrate-resistant phosphatase isoform 5a levels were indicative of a 1.860 fold increase in the risk of metabolic syndrome (p = 0.012).

Conclusions

Elevated serum tartrate-resistant phosphatase isoform 5a levels are associated with the risk of metabolic syndrome, with a cut-off level of 5.8 μg/L.

Association of Tartrate-Resistant Acid Phosphatase-Expressed Macrophages and Metastatic Breast Cancer Progression

Infiltrating neutrophils, lymphocytes, macrophages, and cytokines constitute a state of chronic inflammation within the tumor microenvironment. Tartrate-resistant acid phosphatase 5a (TRACP5a) protein, a novel product of activated macrophage, is postulated to be a biomarker for systemic inflammatory burden in states of chronic inflammation. We aimed to investigate the clinical significance of TRACP5a expression in tumor-infiltrating macrophages and serum TRACP5a in patients with metastatic breast cancer (BC). We retrospectively analyzed the clinical data from 34 BC patients with confirmed skeletal/visceral metastasis upon or during first-line palliative treatment. Patients were stratified into 3 groups based on the therapeutic responses and follow-up disease course. The association of TRACP5a protein with other inflammatory and cancer biomarkers was assessed among the clinically distinct group of patients. Higher TRACP5a protein was significantly correlated with earlier disease progression and survival (P = 0.0045) in comparison to other inflammatory markers, CRP or IL-6. Patients with higher serum TRACP5a level and shorter survival and treatment refractoriness also had more TRACP+ tumor-infiltrating macrophages. Our data support a hypothesis that serum TRACP5a protein can potentially be a predictive and prognostic marker to evaluate disease progression and therapeutic response in BC patients with bone/visceral metastasis. The associations between overall survival and TRACP expression by macrophages require further prospective investigation.

Biomarkers of cartilage and surrounding joint tissue

The identification and clinical demonstration of efficacy and safety of osteo- and chondro-protective drugs are met with certain difficulties. During the last few decades, the pharmaceutical industry has, in the field of rheumatology, experienced disappointments associated with the development of disease modification. Today, the vast amount of patients suffering from serious, chronic joint diseases can only be offered treatments aimed at improving symptoms, such as pain and acute inflammation, and are not aimed at protecting the joint tissue. This huge, unmet medical need has been the driver behind the development of improved analytical techniques allowing better and more efficient clinical trial design, implementation and analysis. With this review, we aim to provide a brief and general overview of biochemical markers of joint tissue, with special focus on neoepitopes. Furthermore, we highlight recent studies applying biochemical markers in joint degenerative diseases. These disorders, including osteoarthritis, rheumatoid arthritis and spondyloarthropathies, are the most predominant disorders in Europe and the USA, and have enormous socioeconomical impact.

Tartrate-resistant acid phosphatase 5a in sarcoidosis: further evidence for a novel macrophage biomarker in chronic inflammation

BACKGROUND/PURPOSE

Tartrate-resistant acid phosphatase (TRACP) 5a is expressed strongly in inflammatory macrophages (MΦ). Serum TRACP5a is elevated in rheumatoid arthritis patients with extra-articular manifestations of rheumatoid nodules, in a percentage of patients with end-stage chronic kidney disease, and may be a risk marker for acute myocardial infarction. This proof-of-concept study was undertaken in patients with sarcoidosis to further substantiate our hypothesis that TRACP5a protein is a biomarker for macrophages in other chronic inflammatory diseases.

METHODS

Immunohistochemical staining for TRACP5a and CD68 was performed in tissues of 19 patients with sarcoidosis. We also measured circulating TRACP5a protein and other inflammation biomarkers including interkeukin-6, angiotensin-converting enzyme, and C-reactive protein in 13 patients. Twenty healthy age-matched nonsmoking individuals were used as the reference group.

RESULTS

All sarcoidosis tissues showed strong staining for TRACP5a and CD68 in the non-caseating granulomatous lesions and localized specifically to MΦ, multinucleate giant cells, and epithelioid MΦ. Serum TRACP5a protein was elevated significantly in active sarcoidosis patients compared with the control group, and levels fluctuated with disease activity in one patient studied longitudinally.

CONCLUSION

TRACP5a protein is expressed abundantly in the granulomatous tissues and may be elevated in a significant proportion of sarcoidosis patients. These findings further support our hypothesis that serum TRACP5a is derived from systemic inflammatory MΦ and thereby may be a biomarker of inflammation for sarcoidosis and also reflect its disease activity.

Serum tartrate-resistant acid phosphatase isoform 5a (TRACP5a) as a potential risk marker in cardiovascular disease

OBJECTIVE

This study was undertaken to determine the association between serum tartrate-resistant acid phosphatase 5a (TRACP5a) and cardiovascular disease (CVD) risk.

METHODS

Four hundred patients were enrolled including, 291 asymptomatic subjects grouped by the number of traditional risk factors, 36 patients undergoing cardiac arteriography, 34 undergoing percutaneous cardiac intervention, and 39 with acute myocardial infarction. Serum was collected at baseline and, in arteriograpy and intervention groups, periodically for 1 week afterward. In addition to laboratory and clinical evaluation for risk assessment, serum TRACP5a, C-reactive protein (CRP) and interleukin-6 (IL-6) were determined.

RESULTS

All biomarkers rose with increasing CVD risk. Only serum TRACP5a, logCRP and cholesterol were elevated in symptomatic patients. Serum TRACP5a was higher in men and correlated with age, logCRP, logIL-6 and log-triglycerides, and in symptomatic patients, with the number of diseased coronary arteries. IL-6 and CRP showed acute phase responses, whereas TRACP5a did not change over 1 week after arteriography or intervention. After adjustment for all other variables and risk factors, TRACP5a and logCRP were the only biomarkers to associate with symptomatic disease. TRACP5a was more specific than CRP to predict myocardial infarction among all subjects.

CONCLUSIONS

Serum TRACP5a is a macrophage-derived inflammation marker associated with CVD risk, and with coronary vessel disease and its severity and may be a useful marker for screening and assessment of CVD risk.

Tartrate-resistant acid phosphatase deficiency causes a bone dysplasia with autoimmunity and a type I interferon expression signature

We studied ten individuals from eight families showing features consistent with the immuno-osseus dysplasia spondyloenchondrodysplasia (SPENCD). Of particular note was the diverse spectrum of autoimmune phenotypes observed in these patients, including systemic lupus erythematosus (SLE), Sjögren's syndrome, haemolytic anemia, thrombocytopenia, hypothyroidism, inflammatory myositis, Raynaud's disease, and vitiligo. Haplotype data indicated the disease gene to be on chromosome 19p13 and linkage analysis yielded a combined multipoint lod score of 3.6. Sequencing of the ACP5 gene, encoding tartrate resistant acid phosphatase (TRAP), identified biallelic mutations in each of the patients studied, and in vivo testing confirmed a loss of expressed protein. All eight patients assayed demonstrated elevated serum interferon alpha activity, and gene expression profiling in whole blood defined a type I interferon signature. Our findings reveal a previously unrecognised link between TRAP activity and interferon metabolism, and highlight the importance of type I interferon in the genesis of autoimmunity.

Effects of exercise on insulin sensitivity, inflammatory cytokines, and serum tartrate-resistant acid phosphatase 5a in obese Chinese male adolescents

The benefits of exercise on glucose metabolism, inflammation, and serum tartrate-resistant acid phosphatase 5a (TRACP 5a) protein levels in Chinese male adolescents have not been extensively analyzed. Therefore, we examined the effects of a 12-week exercise program on weight, adiposity, insulin sensitivity (IS), and inflammatory marker expression, including the novel macrophage marker TRACP 5a, in obese Chinese male adolescents. A total of 106 male adolescents were recruited from the Army Academy in Taiwan and classified as lean (body mass index [BMI], 20.9 +/- 0.2 kg/m(2)) or obese (BMI, 27.7 +/- 0.2 kg/m(2)). Body composition, IS, and inflammatory markers were measured in both groups at baseline and in the obese group after completion of a 12-week exercise program. Body weight, BMI, waist circumference, body fat mass and percentage, homeostasis model assessment for insulin resistance, fasting plasma glucose, fasting serum insulin, 2-hour postchallenge plasma glucose concentration, interleukin-6, C-reactive protein, and serum TRACP 5a were significantly higher in the obese group as compared with the lean group. In addition, serum TRACP 5a was positively correlated with body mass and fat indices. After completion of the exercise program, significant reductions in all anthropometric, metabolic, and inflammatory indicators, with the exception of serum TRACP 5a were observed. Although the obese participants remained obese, exercise training significantly improved IS and reduced interleukin-6 and C-reactive protein. Tartrate-resistant acid phosphatase 5a remained unaffected by exercise training, consistent with our hypothesis that it is associated with increased adipose tissue in obese individuals.

Biology and clinical significance of tartrate-resistant acid phosphatases: new perspectives on an old enzyme

Type 5 tartrate-resistant acid phosphatase (TRAP) has been a clinically relevant biomarker for about 50 years. It has always been a reliable and specific cytochemical marker for hairy cell leukemia and for differentiated cells of monocytic lineage. Only recently has the test for serum TRAP activity been accepted as sensitive and specific enough for clinical use as a marker of osteoclasts and bone resorption. This has come about through steady advances in knowledge about TRAP enzymology, structure, function, and molecular regulation and a consequent appreciation that TRAP isoforms 5a and 5b have very different clinical significance. As a measure of osteoclast number and bone resorption, TRAP 5b has diagnostic and prognostic applications in osteoporosis, cancers with bone metastasis, chronic renal failure, and perhaps other metabolic and pathologic bone diseases. Serum TRAP 5a, on the other hand, has no relationship to bone metabolism but seems instead to be a measure of activated macrophages and chronic inflammation. Exploration of the real clinical usefulness of serum TRAP 5a for diagnosis and disease management in a wide variety of chronic inflammatory diseases is only now beginning. This perspective traces the important basic scientific developments that have led up to the refinement of serum TRAP isoform immunoassays and their validation as biomarkers of disease. Many unanswered questions remain, providing a wealth of opportunity for continued research of this multifaceted enzyme.

Significance of serum TRACP in rheumatoid arthritis

Human serum contains two related isoforms of TRACP: TRACP 5a and TRACP 5b. Serum TRACP 5a protein is increased in about one third of rheumatoid arthritis (RA) sera. This study was undertaken to examine the significance of serum TRACP isoforms 5a and 5b as disease markers of inflammation and bone destruction in RA. One hundred eighteen patients were recruited including 50 with RA (25 with nodules), 26 with osteoarthritis (OA), and 42 with other rheumatic diseases. Twenty-six healthy adults served as controls. Serum TRACP 5a activity, TRACP 5a protein, and TRACP 5b activity were determined by in-house immunoassays. C-reactive protein (CRP) was determined by in-house immunoassay using commercial antibodies and CRP. Other commercial markers included bone-specific alkaline phosphatase (BALP), C-telopeptides of type-I collagen (ICTP), cartilage glycoprotein-39 (YKL-40), and IgM rheumatoid factors (IgM-RF). Mean TRACP 5a protein was significantly elevated only in RA compared with healthy controls and other disease groups. TRACP 5a protein correlated significantly only with IgM-RF in RA. Among RA patients, mean TRACP 5a protein and IgM RF were significantly higher in nodule formers. In contrast, TRACP 5b activity was slightly elevated in RA and correlated with BALP, ICTP, and YKL-40 but not with IgM-RF or CRP. Mean TRACP 5b activity was no different in RA patients with or without nodules. TRACP isoforms could be useful disease markers in RA; TRACP 5a protein may be a measure of systemic inflammatory macrophage burden and disease severity. TRACP 5b activity is a marker for osteoclast number and perhaps local or systemic bone destruction.