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Huang R, Shi J, Wei R, Li J. Challenges of insulin-like growth factor-1 testing. Crit Rev Clin Lab Sci 2024:1-16. [PMID: 38323343 DOI: 10.1080/10408363.2024.2306804] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2023] [Accepted: 01/15/2024] [Indexed: 02/08/2024]
Abstract
Insulin-like growth factor 1 (IGF-1), primarily synthesized in the liver, was initially discovered due to its capacity to replicate the metabolic effects of insulin. Subsequently, it emerged as a key regulator of the actions of growth hormone (GH), managing critical processes like cell proliferation, differentiation, and apoptosis. Notably, IGF-1 displays a longer half-life compared to GH, making it less susceptible to factors that may affect GH concentrations. Consequently, the measurement of IGF-1 proves to be more specific and sensitive when diagnosing conditions such as acromegaly or GH deficiency. The recognition of the existence of IGFBPs and their potential to interfere with IGF-1 immunoassays urged the implementation of various techniques to moderate this issue and provide accurate IGF-1 results. Additionally, in response to the limitations associated with IGF-1 immunoassays and the occurrence of discordant IGF-1 results, modern mass spectrometric methods were developed to facilitate the quantification of IGF-1 levels. Taking advantage of their ability to minimize the interference caused by IGF-1 variants, mass spectrometric methods offer the capacity to deliver robust, reliable, and accurate IGF-1 results, relying on the precision of mass measurements. This also enables the potential detection of pathogenic mutations through protein sequence analysis. However, despite the analytical challenges, the discordance in IGF-1 reference intervals can be attributed to a multitude of factors, potentially leading to distinct interpretations of results. The establishment of reference intervals for each assay is a demanding task, and it requires nationwide multicenter collaboration among laboratorians, clinicians, and assay manufacturers to achieve this common goal in a cost-effective and resource-efficient manner. In this comprehensive review, we examine the challenges associated with the standardization of IGF-1 measurement methods, the minimization of pre-analytical factors, and the harmonization of reference intervals. Particular emphasis will be placed on the development of IGF-1 measurement techniques using "top-down" or "bottom-up" mass spectrometric methods.
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Affiliation(s)
- Rongrong Huang
- Department of Pathology and Immunology, Baylor College of Medicine, Houston, TX, USA
- Department of Pathology and Laboratory Medicine, Harris Health System Ben Taub Hospital, Houston, TX, USA
| | - Junyan Shi
- Department of Pathology and Laboratory Medicine, Vancouver General Hospital, Vancouver Coastal Health, Vancouver, British Columbia, Canada
- Department of Pathology and Laboratory Medicine, University of British Columbia, Vancouver, British Columbia, Canada
| | - Ruhan Wei
- Department of Pathology, Duke University School of Medicine, Durham, NC, USA
| | - Jieli Li
- Department of Pathology, Wexner Medical Center, The Ohio State University, Columbus, OH, USA
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2
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Development and characterization of an enzyme-linked DNA aptamer-magnetic bead-based assay for human IGF-I in serum. Microchem J 2016. [DOI: 10.1016/j.microc.2015.08.002] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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3
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Frysak Z, Schovanek J, Iacobone M, Karasek D. Insulin-like Growth Factors in a clinical setting: Review of IGF-I. Biomed Pap Med Fac Univ Palacky Olomouc Czech Repub 2015; 159:347-51. [PMID: 26365932 DOI: 10.5507/bp.2015.041] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2015] [Accepted: 07/28/2015] [Indexed: 11/23/2022] Open
Abstract
BACKGROUND AND AIMS Interest in growth hormone (GH) is inextricably linked to the need for in depth understanding of the somatomedins (insulin-like growth factors) which are polypeptides structurally similar to insulin and with broad physiological activity. To date, the most commonly known is Insulin-Like Growth Factor I (IGF-I). Despite considerable current knowledge of IGF-I, however, its bioactivity is incompletely understood. Measurement of IGF-I is of the utmost importance in the diagnosis and treatment of, for example acromegaly and growth hormone deficiency. The development of recombinant IGF-I, has allowed its use in such cases. Clinical practice, however, shows that few young/adult patients will benefit from treatment with the rIGF-I, mecasermin, given the number of adverse effects found. This review focuses on current knowledge mainly related to IGF-I and the use of its recombinant form (rIGF-I) in clinical practice. Several functions of IGI-II have been elucidated but their clinical significance is unclear.
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Affiliation(s)
- Zdenek Frysak
- Department of Internal Medicine III-Nephrology, Rheumatology and Endocrinology, University Hospital and Faculty of Medicine and Dentistry, Palacky University Olomouc, Czech Republic, I.P.Pavlova 6 - 779 00, - Olomouc, Czech Republic
| | - Jan Schovanek
- Department of Internal Medicine III-Nephrology, Rheumatology and Endocrinology, University Hospital and Faculty of Medicine and Dentistry, Palacky University Olomouc, Czech Republic, I.P.Pavlova 6 - 779 00, - Olomouc, Czech Republic
| | - Maurizio Iacobone
- Minimally Invasive Endocrine Surgery Unit, Department of Surgery, Oncology and Gastroenterology, University of Padova, Italy, Via Giustiniani 2 - 35128 - Padova, Italy
| | - David Karasek
- Department of Internal Medicine III-Nephrology, Rheumatology and Endocrinology, University Hospital and Faculty of Medicine and Dentistry, Palacky University Olomouc, Czech Republic, I.P.Pavlova 6 - 779 00, - Olomouc, Czech Republic
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Ramadhin C, Pillay B, Olaniran AO. Cell-based assays for IGF-I bioactivity measurement: overview, limitations and current trends. Growth Factors 2014; 32:130-8. [PMID: 25060037 DOI: 10.3109/08977194.2014.939806] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Insulin-like growth factor-I (IGF-I) is an important growth promoting protein that is involved in numerous cellular responses and multiple biological systems. Although the molecular structure, function and recombinant production of IGF-I in various hosts have been the subject of much researches over the recent past, methods to determine the bioactivity of this protein have not been fully explored. Several assays have traditionally been used to measure IGF-I bioactivity, but have not become a routine laboratory practice due to the high cost involved and technical problems. Thus, there is still a need for a rapid, technically simple and accurate assay to determine IGF-I bioactivity. This review highlights the various cell-based assays currently commercially available for measuring the bioactivity of IGF-I along with their limitations. This is aimed at presenting the modern-day IGF researcher with a holistic overview of the current trends and future prospects regarding IGF-I bioactivity determinations.
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Affiliation(s)
- Charlotte Ramadhin
- Discipline of Microbiology, School of Life Sciences, College of Agriculture, Engineering and Science, University of KwaZulu-Natal , Durban , Republic of South Africa
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Smits NGE, Ludwig SKJ, Van der Veer G, Bremer MGEG, Nielen MWF. Multiplex flow cytometric immunoassay for serum biomarker profiling of recombinant bovine somatotropin. Analyst 2014; 138:111-7. [PMID: 22805655 DOI: 10.1039/c2an35226e] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Recombinant bovine somatotropin (rbST) is licensed for enhancing milk production in dairy cows in some countries, for instance the United States, but is banned in Europe. Serum biomarker profiling can be an adequate approach to discriminate between treated and untreated groups. In this study a multiplex screening tool of a small set of biomarkers for pinpointing recombinant bovine somatotropin (rbST) (ab)use was developed and evaluated: insulin-like growth factor 1 (IGF-1), IGF binding protein 2 (IGFBP2) and rbST-induced antibodies were selected as rbST dependent markers and combined in one parallel assay format. For this, the color-encoded microspheres were used in a suspension array, with a dedicated flow cytometer. Serum samples obtained from an animal experiment with rbST-treated and untreated dairy cows were measured with the developed triplex immunoassay and biomarker responses on rbST treatment were evaluated. This resulted in characteristic treatment-dependent responses for all three individual biomarkers. Combining these results with the statistical prediction model k-nearest neighbours (kNN), resulted in good discrimination of treated and untreated animals: an overall sensitivity (true positive rate) of 89.1% and an overall specificity (true negative rate) of 97.7% were reached. Therefore, this is the first multiplex method which can be applied with high confidence for screening of unknown herds of cattle pinpointing at rbST (ab)use.
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Guha N, Cowan DA, Sönksen PH, Holt RIG. Insulin-like growth factor-I (IGF-I) misuse in athletes and potential methods for detection. Anal Bioanal Chem 2013; 405:9669-83. [DOI: 10.1007/s00216-013-7229-y] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2013] [Revised: 07/02/2013] [Accepted: 07/08/2013] [Indexed: 11/30/2022]
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Douglas NC, Thornton MH, Nurudeen SK, Bucur M, Lobo RA, Sauer MV. Differential expression of serum glycodelin and insulin-like growth factor binding protein 1 in early pregnancy. Reprod Sci 2013; 20:1376-81. [PMID: 23585335 DOI: 10.1177/1933719113485290] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
This prospective study evaluated whether serum glycodelin and insulin-like growth factor binding protein 1 (IGFBP-1) predict the likelihood of embryo implantation in recipients undergoing donor egg in vitro fertilization. We measured glycodelin and IGFBP-1 at 6 points from lining check to lutenizing hormone (LH) + 31. β-Human chorionic gonadotropin levels were first measured at LH + 17. The recipients were divided into those without embryo implantation (group 1, n = 6) and those with successful implantation (group 2, n = 30). Although this is a negative study in that neither glycodelin nor IGFBP-1 alone reflected endometrial (EM) receptivity, the glycodelin/IGFBP-1 ratio on the day of blastocyst transfer was higher in recipients who achieved pregnancy (P = .05). At LH + 17, glycodelin was higher (P = .04), and IGFBP-1 was lower (P = .004) in recipients who achieved pregnancy when compared to those who did not. These observations are likely due to EM changes induced by successful embryo implantation.
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Affiliation(s)
- Nataki C Douglas
- 1Division of Reproductive Endocrinology, Department of Obstetrics and Gynecology, Columbia University Medical Center, New York, NY, USA
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Abstract
The growth hormone/insulin-like growth factor (GH/IGF) axis is widely investigated in disorders of growth, development, and anterior pituitary function. Methods are described for three hormones in this axis (growth hormone, IGF-I, and IGF binding protein-3). Enzyme-linked immunosorbent assays (ELISAs) are described as they combine the specificity of antibody-antigen interactions with the sensitivity of simple enzyme assays. Many commercial immunoassays are available for the measurement of GH and IGF-I, and the main problems encountered in the measurement of these clinically important hormones are discussed.
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Affiliation(s)
- Nishan Guha
- Department of Clinical Biochemistry, John Radcliffe Hospital, Oxford, UK
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9
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Electrochemical impedimetric immunosensor for insulin like growth factor-1 using specific monoclonal antibody-nanogold modified electrode. Biosens Bioelectron 2011; 26:2130-4. [DOI: 10.1016/j.bios.2010.09.020] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2010] [Revised: 09/06/2010] [Accepted: 09/07/2010] [Indexed: 11/18/2022]
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10
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Frystyk J, Freda P, Clemmons DR. The current status of IGF-I assays--a 2009 update. Growth Horm IGF Res 2010; 20:8-18. [PMID: 19818658 PMCID: PMC7748085 DOI: 10.1016/j.ghir.2009.09.004] [Citation(s) in RCA: 114] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/15/2009] [Accepted: 09/16/2009] [Indexed: 10/20/2022]
Abstract
For almost three decades, the measurement of circulating IGF-I has constituted a highly important biochemical tool in the management of GH disorders. In fact, in acromegaly the importance of circulating IGF-I has increased following the introduction of the GH receptor antagonist pegvisomant, as the use of this drug makes it impossible to use circulating GH as a monitor of disease activity. In addition, determination of circulating IGF-I constitutes a valuable scientific tool in various research areas, from epidemiological investigations through clinical trials and experimental studies. The multiple facets of IGF-I physiology and patho-physiology may explain why numerous endocrine laboratories have invested in IGF-I assays, by means of either in-house assays or commercial kits. However, despite its widespread use, the measurement of IGF-I is by no means trivial. On the contrary, the pronounced binding of IGF-I to the high-affinity IGF-binding proteins (IGFBPs) constitutes a notorious source of error, which has necessitated the development of methods that more or less successfully circumvent interference from the IGFBPs. Furthermore, there are some unsolved issues with the international standardization of the different IGF-I assays and there is no consensus regarding the procedures used when collecting and storing samples for measurement of circulating IGF-I. The aim of this review is to discuss the current state of the art of IGF-I immunoassays and to present the current analytical problems with IGF-I measurements. Finally, we would like to suggest an agenda that may be used when trying to produce internationally accepted uniform requirements for future IGF-I assays.
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Affiliation(s)
- Jan Frystyk
- The Medical Research Laboratories, Clinical Institute of Medicine, and Medical Department M (Diabetes & Endocrinology), Aarhus University Hospital, Nørrebrogade 44, DK-8000 Aarhus C, Denmark.
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11
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Bremer MGEG, Smits NGE, Haasnoot W, Nielen MWF. Multiplex ready flow cytometric immunoassay for total insulin like growth factor 1 in serum of cattle. Analyst 2010; 135:1147-52. [DOI: 10.1039/b925372f] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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12
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Abstract
The diagnosis of disorders of growth hormone (GH) is dependent upon accurate measurement of insulin-like growth factor-I (IGF-I) concentrations since serum IGF-I assays have been found to be useful as a screening tests for the presence of growth hormone deficiency (GHD) in children and in both children and adults they have been found very useful in establishing the diagnosis of acromegaly. IGF-I is also used extensively to monitor the response to GH treatment in children and adults and to monitor the response to treatment in acromegaly. Since IGF-I is influenced by several other hormones and physiologic factors as well as GH, a knowledge of its regulation is essential to understanding how to properly interpret the measurements. Several technical criteria are required for successful laboratory estimation of IGF-I values. These include elimination of interference of IGF-I-binding proteins (IGFBP), utilization of adequate numbers of normal subjects to define the normal ranges and importantly the use of high affinity, high specificity antisera that allow precise and reproducible measurements of the biologically active peptide. Cross comparisons of various commercial assays show that the results generally are similar when values are in the normal range. However, the assays have different performance characteristics when concentrations are either above or below the normal range. To obtain cross laboratory standardization for values outside the normal range requires utilization of similar, high-quality reagents and techniques that are reasonably comparable. Without this degree of standardization, cross comparisons among various reference laboratories are likely to continue to show wide divergence for values that are above or below the 95% confidence interval. A future goal should be the development of standard procedures and reagents that eliminate this degree of variability.
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Affiliation(s)
- David R Clemmons
- CB# 7170, 8024 Burnett-Womack, Division of Endocrinology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-7170, USA.
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13
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Khosravi J, Krishna RG, Bodani U, Diamandi A, Khaja N, Kalra B, Kumar A. Immunoassay of serine-phosphorylated isoform of insulin-like growth factor (IGF) binding protein (IGFBP)-1. Clin Biochem 2006; 40:86-93. [PMID: 17005169 DOI: 10.1016/j.clinbiochem.2006.07.004] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2006] [Revised: 06/29/2006] [Accepted: 07/21/2006] [Indexed: 11/17/2022]
Abstract
OBJECTIVES Development of an ELISA for phosphorylated isoform of IGFBP-1. Serine phosphorylation is an important regulator of IGFBP-1 bioactivity, but specific immunoassays for its measurement are currently lacking. DESIGN AND METHODS Assay design was based on a novel approach of first capturing the phosphorylated and non-phosphorylated IGFBP-1 by an anti-IGFBP-1 antibody and then selectively detecting the phosphorylated form by an anti-phosphoserine antibody. Method development involved pair-wise evaluation of the candidate antibodies and determinations of analytical performance and specificity. Specificity was monitored by reactivity with dephosphorylated IGFBP-1, with antibodies against other phosphorylated residues that are not expressed, and by comparative analysis of sample containing different IGFBP-1 phosphorylation profile. RESULTS Analytical evaluation demonstrated acceptable performance; detection limit 0.3 microg/L, dynamic range 1.56-100 microg/L; intra- and inter-assay CVs 2.1-8.6%; mean recovery (+/-SD) 97.8+/-9.2%, and mean recovery of sample dilution 93.4+/-6.0%. The phosphorylated and total IGFBP-1 medians in non-pregnant adult serum, which mostly contain the highly phosphorylated isoform, were 11.9 and 18.6 microg/L, respectively, and the sample values were tightly correlated (r=0.99). As expected, the corresponding medians in 1st trimester (17.4 and 63.0 microg/L) and 2nd trimester (30.9 and 75.8) samples with altered IGFBP-1 phosphorylation were significantly different (p<0.001). Similarly, a fraction (1.29%) of total IGFBP-1 (13.3 mg/L) in amniotic fluids was found to be phosphorylated (0.172 mg/L). There was no reactivity with dephosphorylated IGFBP-1. CONCLUSIONS The present ELISA is highly specific for the phosphorylated isoform of IGFBP-1 and its availability should help expedite further investigations of IGFBP-1 phosphorylation.
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Affiliation(s)
- Javad Khosravi
- Diagnostic Systems Laboratories (Canada) Inc., Toronto, Ontario, Canada M5G 1L7.
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14
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Nindl BC, Tuckow AP, Alemany JA, Harman EA, Rarick KR, Staab JS, Faupel ML, Khosravi MJ. Minimally invasive sampling of transdermal body fluid for the purpose of measuring insulin-like growth factor-I during exercise training. Diabetes Technol Ther 2006; 8:244-52. [PMID: 16734553 DOI: 10.1089/dia.2006.8.244] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Insulin-like growth factor-I (IGF-I) is a ubiquitous hormone that is secreted in both an endocrine and an autocrine/paracrine manner. IGF-I has conventionally been measured in serum; however, transdermal body fluid (TDF) remains as an unexplored biocompartment in which IGF-I also resides and may be more biologically relevant because of its proximity to tissues and cells. The purpose of this study was to compare IGF-I in serum versus IGF-I in TDF before and after 8 weeks of physical training. Twenty-eight healthy men (28 +/- 5 years old, 176 +/- 8 cm tall, weighing 83 +/- 11 kg) had TDF obtained by a novel, minimally invasive method that included the application of continuous vacuum pressure on forearm skin perforated with tiny micropores created by a focused beam from a laser system and also had blood obtained by venipuncture. An enzyme-linked immunosorbent assay measured total IGF-I concentrations. A repeated-measures analysis of variance (biocompartment x time) and Pearson Product Moment Correlation coefficients (P < or = 0.05) were used for statistical analyses. Data are presented as mean +/- SE. Total TDF IGF-I was significantly lower than serum IGF-I both before (TDF, 91 +/- 6 ng/mL; serum, 375 +/- 17 ng/mL) and after (TDF, 83 +/- 5 ng/mL; serum, 363 +/- 19 ng/mL) the exercise training. Serum and TDF IGF-I values were not significantly different pre- to post-training. Serum and TDF IGF-I levels were significantly correlated pre-training (r = 0.41), but not post-training (r = 0.34). The percent change between serum and TDF was not correlated (r = 0.09). This study has demonstrated that total IGF-I can be sampled and measured in TDF via a minimally invasive manner and is appreciably (approximately 76%) less than total IGF-I measured in serum. Additionally, the IGF-I measurements in these two biocompartments were not closely associated, possibly indicating an uncoupled, rather than a linked, regulation of IGF-I among the body's biocompartments.
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Affiliation(s)
- Bradley C Nindl
- Military Performance Division, U.S. Army Research Institute of Environmental Medicine, Natick, Massachusetts 01760, USA.
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15
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Khosravi J, Diamandi A, Bodani U, Khaja N, Krishna RG. Pitfalls of immunoassay and sample for IGF-I: comparison of different assay methodologies using various fresh and stored serum samples. Clin Biochem 2005; 38:659-66. [PMID: 15885685 DOI: 10.1016/j.clinbiochem.2005.04.001] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2004] [Revised: 02/17/2005] [Accepted: 04/08/2005] [Indexed: 11/26/2022]
Abstract
OBJECTIVE Determination of insulin-like growth factor (IGF)-I is now a routine adjunct to multiple research and clinical investigations. Evidence has associated higher IGF-I levels with various human pathologies, but the reported associations have not been invariably confirmed. We examined the potential for post-sampling proteolysis and evaluated the impact of such events on IGF-I immunoassays. DESIGN AND METHODS We compared IGF-I in different sets of fresh and frozen old samples using four different and commonly used immunoassays. The potential for post-sampling proteolysis was further examined by assaying fresh samples stored for 4 weeks at various temperatures in the absence or presence of protease inhibitors. RESULTS IGF-I levels in fresh serum samples from adult males, females, and pregnant subjects by all methods were similar and were highly correlated (r=0.85-0.97). The same was true for levels in frozen ( approximately 2 years at --80 degrees C) samples from diabetic patients, which are reportedly associated with enhanced proteolytic activity. In contrast, in another set of frozen adult male and female samples ( approximately 8 years at --20 degrees C), the inter-method median IGF-I levels varied by approximately 3- to 4-fold and the values poorly correlated. Similar variability in the inter-method response was also observed when IGF-I in the replicates of fresh samples stored at 4 degrees C for 4 weeks was measured. However, the 4 degrees C storage effect could be completely blocked by the addition of protease inhibitors, allowing for all assays to detect 92--101% of the expected mean levels. CONCLUSIONS The data indicate susceptibility of IGF-I to significant post-sampling proteolysis and suggest the importance of immunoassays for the intact molecule. Immunoassays that lack specificity for intact IGF-I may mask the potential pathophysiological effects of proteolysis and generate misleading results, particularly in studies involving inappropriately stored and/or proteolyzed samples. In such cases, underestimation of the in vivo levels by the intact assays would occur, but the findings of low IGF-I levels may be indicative of questionable sample quality.
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Affiliation(s)
- Javad Khosravi
- Diagnostic Systems Laboratories (Canada) Inc., Mount Sinai Hospital, Toronto, Ontario, Canada M5G 1X5.
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16
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Khosravi J, Krishna RG, Khaja N, Bodani U, Diamandi A. Enzyme-linked immunosorbent assay of total inhibin: direct determination based on inhibin alpha subunit-specific monoclonal antibodies. Clin Biochem 2004; 37:370-6. [PMID: 15087252 DOI: 10.1016/j.clinbiochem.2004.01.011] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2003] [Revised: 01/27/2004] [Accepted: 01/27/2004] [Indexed: 11/19/2022]
Abstract
OBJECTIVE Inhibin circulates in various molecular weight forms. Alpha (alpha)-subunit-directed total inhibin immunoassays, which detect all forms of alpha subunits plus the alpha/beta inhibin dimers, have been found valuable in the diagnosis and monitoring of ovarian cancer. Because of the dependency of the published methods on boiling sample pre-treatment with SDS and unavailability of a commercial assay, we developed an enzyme-linked immunosorbent assay (ELISA) for direct determination of total inhibin. DESIGN AND METHODS Method development involved a pair of well-characterized inhibin alpha subunit-directed antibodies and determination of the effects of various assay parameters. Selection of the optimized protocol was guided by the outcome of comparative sample analysis using previously reported boiling sample pre-treatment reagents and protocols. RESULTS We report development of a simplified ELISA for total inhibin. Method evaluation data demonstrated acceptable analytical performance characteristics with detection limit of 2 ng/l (recombinant inhibin-A), dynamic range of 12.5-500 ng/l, and intra- and inter-assay imprecision of 2.3-4.6% and 3.3-5.1% at total inhibin concentrations of approximately 60-400 ng/l, respectively. The mean (+/-SD) recovery from spiked serum samples averaged 109 +/- 14% and recovery in response to serial sample dilution was 99 +/- 10%. Serum values by the direct method (n = 40) correlated strongly with those obtained after sample pre-treatment by boiling with SDS (r = 0.97). As expected, the total inhibin immunoreactivity in human follicular fluid fractionated by HPLC gel filtration in multiple immunoreactive peaks (8-250 kDa). In serum samples from postmenopausal women with ovarian cancer, the assay detected significantly higher total inhibin levels than in samples from normal postmenopausal controls. CONCLUSION The development of a fast and simplified ELISA should facilitate wider investigations of pathophysiology and diagnostic potential of total inhibin measurement.
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Affiliation(s)
- Javad Khosravi
- Diagnostic Systems Laboratories Inc., Toronto, Ontario, Canada.
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Hennies M, Sauerwein H. Purification of bovine IGFBP-3 and the development of an enzyme immunoassay for the protein. J Immunol Methods 2003; 281:9-15. [PMID: 14580877 DOI: 10.1016/s0022-1759(03)00195-9] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Insulin-like growth factor binding protein-3 (IGFBP-3), the most prominent IGF-binding protein in serum, has been demonstrated to modulate the effects of the IGFs but also to exert IGF-independent actions. Quantification of IGFBP-3 in livestock species, in particular ruminants, is commonly limited to blotting methods in spite of the importance of these species. Here we describe the development of a specific homologous enzyme-linked immunosorbent assay (ELISA) to measure bovine IGFBP-3 in bovine plasma, serum and milk. IGFBP-3 purified from bovine serum was used both as standard and also for tracer synthesis. A specific antiserum was raised in rabbits using a synthetic peptide based on the sequence of bovine IGFBP-3. The measuring range of the assay was between 50 and 1000 ng IGFBP-3 per milliliter of plasma or milk. Mean recovery was 97.3% for plasma and 100.1% for milk. Intra- and interassay coefficients of variation were 6.2% and 9.3%, respectively. For the biological verification of the assay, IGFBP-3 was determined in plasma obtained from 12 dairy cows before and after being injected with a depot-formulated growth hormone (GH) preparation. GH, a well-characterized stimulator of IGFBP-3, led to a 1.3-fold increase of basal IGFBP-3 concentrations during days 3 to 19 after the injection. The availability of an ELISA procedure which permits precise and sufficiently sensitive quantification of bovine IGFBP-3 and which can be used on large sample numbers thereby avoiding the need for radioactive labels, should facilitate further research studies.
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Affiliation(s)
- Mark Hennies
- Institut für Physiologie, Biochemie und Hygiene der Tiere, Rheinische Friedrich Wilhelms-Universität Bonn, Katzenburgweg 7-9, 53115 Bonn, Germany
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Scorilas A, Plebani M, Mazza S, Basso D, Soosaipillai AR, Katsaros N, Pagano F, Diamandis EP. Serum human glandular kallikrein (hK2) and insulin-like growth factor 1 (IGF-1) improve the discrimination between prostate cancer and benign prostatic hyperplasia in combination with total and %free PSA. Prostate 2003; 54:220-9. [PMID: 12518327 DOI: 10.1002/pros.10186] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
BACKGROUND There is growing evidence describing an association of hK2 and IGFs with cancer. The aim of this study is to investigate the differences in serum levels of hK2 and IGFs in a large group of patients with benign prostatic hyperplasia (BPH) or prostatic carcinoma (CaP) and to examine the value of these variables, as well as their various combinations with PSA, for discriminating between these two clinical entities. METHODS Human glandular kallikrein 2 (hK2), insulin-like growth factor-1 (IGF-1), free and total PSA concentrations were measured with non-competitive immunological procedures. Receiver operating characteristic (ROC) analysis as well as univariate and multivariate logistic regression analysis were performed to investigate the potential utility of the various markers and their combinations for discriminating between BPH and CaP. RESULTS hK2 and IGF-1 concentrations were increased in CaP patients, in comparison to BPH patients. hK2/free PSA and free/total PSA ratios (area under the curve, AUC = 0.70) were stronger predictors of prostate cancer than the IGF-1/total PSA ratio (AUC = 0.56) in the group of patients with total PSA <4 microg/L. The hK2/free PSA ratio (AUC = 0.74) was found to have significant discriminatory value in patients with total PSA within the "gray zone" (4-10 microg/L). Multivariate logistic regression models confirmed the observed relationships and identified IGF-1/free PSA and hK2/free PSA as independent predictors of CaP. CONCLUSIONS hK2/free PSA and IGF-1/free PSA ratios may be useful adjuncts in improving patient selection for prostate biopsy.
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Affiliation(s)
- Andreas Scorilas
- National Center for Scientific Research Demokritos, IPC, Athens, Greece
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Khosravi J, Diamandi A, Krishna RG, Bodani U, Mistry J, Khaja N. Pregnancy associated plasma protein-A: ultrasensitive immunoassay and determination in coronary heart disease. Clin Biochem 2002; 35:531-8. [PMID: 12493581 DOI: 10.1016/s0009-9120(02)00359-4] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
OBJECTIVES Markers of myocardial injury have been vital in the assessment of patients with coronary heart disease. Pregnancy associated plasma protein A (PAPP)-A is an insulin-like growth factor (IGF) binding protein (IGFBP)-4 protease and a potential early indicator of unstable angina. We developed an ultrasensitive enzyme-linked immunosorbent assay (ELISA) for PAPP-A and measured serum PAPP-A in patients with biochemical evidence of acute coronary syndrome. DESIGN AND METHODS Method development was based on pair-wise evaluation of a panel of antibodies and determination of PAPP-A specificity and sensitivity relative to those of a conventional method. Association of PAPP-A with myocardial damage was assessed in serum samples classified based on serum creatine kinase (CK)-MB or cardiac troponin-T levels. RESULTS Serum PAPP-A was significantly higher in samples with elevated CK-MB or troponin-T than in samples with normal CK-MB (p < 0.001). Marker-association studies showed strong correlation between PAPP-A and troponin-T (r = 0.59, p < 0.001) in a subset of troponin-T positive samples. Indications for both parallel as well as divergence in the expression of PAPP-A and troponin-T was also evident when serial timed samples available from a number of patients were analyzed. CONCLUSIONS The data are consistent with the conclusion that expression of PAPP-A is enhanced in patients with biochemical evidence of acute coronary syndrome and suggest strongly that demonstration of PAPP-A association with other cardiac markers might be influenced by their relative release dynamics (timing and duration). The availability of the ultrasensitive PAPP-A ELISA should facilitate systematic investigations of PAPP-A expression in this and other pathophysiological conditions that might involve altered expression of the IGF/PAPP-A system.
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Affiliation(s)
- Javad Khosravi
- Diagnostic Systems Laboratories (Canada) Inc., Toronto, Ontario, Canada.
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De Palo EF, Gatti R, Lancerin F, Cappellin E, Soldà G, De Palo CB, Spinella P. Urinary insulin-like growth factor I in athletes, before and after physical exercise, and in sedentary subjects. Clin Chim Acta 2002; 322:51-7. [PMID: 12104081 DOI: 10.1016/s0009-8981(02)00136-5] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
BACKGROUND Insulin-like growth factor I (IGF-I), like growth hormone (GH), is excreted in urine in a smaller fraction than the concentration found in blood. Exercising subjects undergo post-exercise proteinuria. The present work aims to propose a method for urinary IGF-I analysis (uIGF-I) by defining urinary concentration in sedentary individuals and athletes before and after strenuous exercise. METHODS Urine samples were collected from 30 sedentary healthy male individuals during the morning and from 30 well-trained cyclists, before and after a competition of about 3 h (150 km). uIGF-I was measured in undiluted acidified urine by radioimmunoassay (RIA) method using a purified polyclonal rabbit antibody, human 125I-IGF-I and a second anti-rabbit antiserum. The acidification of the urine samples and the excess of IGF-II addition in the incubation medium of the assay were used to dissociate the binding and to block the interference from IGF binding proteins (IGFBPs). Urinary growth hormone (uGH), total protein (utPr) and creatinine (ucr) concentrations were also measured by immunoradiometric assay (IRMA), colorimetric and capillary electrophoresis methods, respectively. RESULTS The analysis range was 0-2500 ng/l (0-327 pmol/l), the intra- and inter-assay coefficients of variations (CVs) ranged from 2.3% to 7.8%, respectively. The detection limit was 0.6 pg/tube. The uIGF-I/creatinine (cr) ratio in healthy subjects was 70 +/- 8 pg/mg cr. The uIGF-I/creatinine ratio (pg/mg cr) was different (p<0.001) in athletes before vs. after competition 93 +/- 27 vs. 136 +/- 13. Athletes' [uIGF-I/total proteins] ratio (ng/mg tPr) before and post-exercise was 2.3 +/- 0.5 and 2.5 +/- 0.3, respectively. CONCLUSIONS uIGF-I assay appears to be an effective way of monitoring IGF-I excretion. In the cyclists, in the pre-exercise state, uIGF-I was comparable with that measured in sedentary healthy individuals. In the cyclists, after strenuous exercise, the increased uIGF-I/cr and uGH/cr ratios suggested a relation with the post-exercise proteinuria. In conclusion, proteinuria physiologically obtained, such as post-exercise proteinuria, might be a new approach in IGF-I system investigation.
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Affiliation(s)
- Elio F De Palo
- Section of Clinical Biochemistry, Department of Medical Diagnostic Sciences and Special Therapies, University of Padova-Medical School, Via Ospedale 105, 35128 Padua, Italy.
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Yu H, Mistry J, Nicar MJ, Khosravi MJ, Diamandis A, van Doorn J, Juul A. Insulin-like growth factors (IGF-I, free IGF-I, and IGF-II) and insulin-like growth factor binding proteins (IGFBP-2, IGFBP-3, IGFBP-6, and ALS) in blood circulation. J Clin Lab Anal 1999. [DOI: 10.1002/(sici)1098-2825(1999)13:4<166::aid-jcla5>3.0.co;2-x] [Citation(s) in RCA: 111] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
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Diamandi A, Khosravi MJ, Mistry J, Martinez V, Guevara-Aguirre J. Filter paper blood spot assay of human insulin-like growth factor I (IGF-I) and IGF-binding protein-3 and preliminary application in the evaluation of growth hormone status. J Clin Endocrinol Metab 1998; 83:2296-301. [PMID: 9661598 DOI: 10.1210/jcem.83.7.4923] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
To facilitate broader applications of insulin-like growth factor I (IGF-I) and IGF-binding protein-3 (IGFBP-3) analysis, we developed procedures for their measurements in extracts of whole blood dried on filter paper. A single 8-mm diameter filter paper disc containing about 13 microL blood was used. IGFBP-3 was efficiently extracted in a buffer within 1 h of incubation. IGF-I extraction involved incubation in buffer followed by acidification and neutralization steps. Blood spot assays showed intra- and interassay coefficients of variation (including interspot variations) of 5.4-16.7% for IGF-I and 6.6-11.7% for IGFBP-3; recoveries were 97 +/- 7.1% and 101 +/- 8.7%, respectively. Recoveries of IGF-I and IGFBP-3 in response to 4- to 8-fold variations in extraction buffer volume were 97 +/- 8.2% and 107 +/- 6.1%, respectively. Dried blood spot IGF-I and IGFBP-3 showed greater than 1-month stability at -20 C, 4 C, and room temperature and retained more than 65% of the immunoreactivity after approximately 1 month at 37 C. Both IGF-I and IGFBP-3 were contained within the plasma fraction of whole blood, and variations (mean +/- SD) in IGF-I (204 +/- 29 micrograms/L) and IGFBP-3 (4.4 +/- 0.48 mg/L) measured in extracts of dried blood spot with adjusted hematocrit of 0.2-0.62 were acceptable. IGF-I and IGFBP-3 in paired plasma and dried blood spot extracts of random samples (n = 46) showed excellent correlation (r > 0.94) with slopes of near unity. Compared to conventional methods, the filter paper procedures were equally effective in distinguishing IGF-I and IGFBP-3 levels in untreated GH receptor-deficient (n = 11) and age-matched normal controls (n = 16). We conclude that blood collected on filter paper is ideal for IGF-I and IGFBP-3 analysis and may find applications in pediatric and large scale infant screening programs.
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Affiliation(s)
- A Diamandi
- Diagnostic Systems Laboratories (Canada), Inc., Toronto, Ontario, Canada
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Ginjala V, Pakkanen R. Determination of transforming growth factor-beta 1 (TGF-beta 1) and insulin-like growth factor (IGF-1) in bovine colostrum samples. JOURNAL OF IMMUNOASSAY 1998; 19:195-207. [PMID: 9682131 DOI: 10.1080/01971529808005480] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
The major growth factors in bovine colostrum are transforming growth factor-beta s (TGF-beta 1 and TGF-beta 2) and insulin-like growth factors (IGF-1 and IGF-2). Recently, TGF-beta 2 content of bovine colostrum was measured using a TGF-beta 2 specific ELISA (1) and now we have validated ELISAs for for bovine TGF-beta 1 and IGF-1. The concentrations of IGF-1 and TGF-beta 1 in the first milking after calving were 248-1850 ng/ml and 12.4-42.6 ng/ml, respectively, and they declined in correlation with total protein concentration to 27.0-101 ng/ml (IGF-1) and 0.80-3.49 ng/ml(TGF-beta 1) by the fifth milkings. The amount of TGF-beta 1 was on average 5.3 +/- 1.4% of that of TGF-beta 2 and there is a high correlation (r = 0.966) between the concentrations of these growth factors in the same samples. No free TGF-beta 1 form of could be detected.
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Affiliation(s)
- V Ginjala
- Department of Biochemistry and Food Chemistry, University of Turku, Finland
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Abstract
AbstractAccurate measurement of insulin-like growth factor (IGF) binding protein-1 (IGFBP-1) is important for precise definition of its physiological roles and potential diagnostic values. Because altered phosphorylation results in altered IGFBP-1 immunoreactivity, current assays may significantly underestimate or fail to detect physiological changes in the IGFBP-1 concentrations. We developed three ELISAs (ELISA 1–3) using a common capture but three different detection antibodies. IGFBP-1 in serum, synovial fluid (SF), cerebrospinal fluid (CSF), and amniotic fluid (AF) were measured before and after treatment with alkaline phosphatase (ALP). Among the methods, only ELISA-1 was unaffected by IGFBP-1 phosphorylation and generated identical results before and after ALP treatment. The serum and SF values by ELISA-2 and -3 were lower by ∼4- to 10-fold, but increased after ALP treatment to within 66–98% of those by ELISA-1. The medians in AF, and to a lesser extent in CSF, by all methods were similar and did not change significantly after dephosphorylation. ELISA-1 showed excellent correlation with ELISA-2, ELISA-3, and a commercial IGFBP-1 IRMA only after ALP-treated samples were analyzed by the comparative methods. ELISA-1 is highly specific for IGFBP-1 and demonstrated acceptable analytical performance characteristics.
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Affiliation(s)
- M Javad Khosravi
- Diagnostic Systems Laboratories (Canada) Inc., Toronto, ON, Canada
- Department of Clinical Biochemistry, University of Toronto, Toronto, ON, Canada
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