Local IGF Bioactivity Associates with High PAPP-A Activity in the Pericardial Cavity of Cardiovascular Disease Patients

• Published in: The journal of clinical endocrinology and metabolism Vol. 105; no. 11; pp. e4083 - e4093
• Main Authors: Hjortebjerg, Rikke, Rasmussen, Lars Melholt, Gude, Mette Faurholdt, Irmukhamedov, Akhmadjon, Riber, Lars P, Frystyk, Jan, De Mey, Jo G R
• Format: Journal Article
• Language: English
• Published: US Oxford University Press 01.11.2020; Copyright Oxford University Press
• Subjects: Aged; Arteriosclerosis; Atherosclerosis; Biological activity; Cardiac patients; Cardiovascular disease; Cardiovascular diseases; Cardiovascular Diseases - metabolism; Cardiovascular Diseases - surgery; Coronary Artery Bypass; Coronary artery disease; Diabetes mellitus (non-insulin dependent); Diabetes Mellitus, Type 2 - metabolism; Ethylenediaminetetraacetic acid; Glycoproteins - metabolism; Heart surgery; Humans; Insulin; Insulin-like growth factor I; Insulin-like growth factor-binding protein 4; Insulin-like growth factors; Intercellular Signaling Peptides and Proteins - metabolism; Male; Medical research; Medicine, Experimental; Middle Aged; Pericardial Fluid - metabolism; Pericardium - metabolism; Plasma; Pregnancy; Pregnancy-Associated Plasma Protein-A - metabolism; Protein binding; Proteins; Proteolysis; Somatomedins - metabolism; Stanniocalcin; Type 2 diabetes; Denmark; Cardiovascular disease; insulin-like growth factor; insulin like growth factor binding protein-4; pregnancy-associated plasma protein-A; stanniocalcin-2
• ISSN: 0021-972X; 1945-7197; 1945-7197
• DOI: 10.1210/clinem/dgaa617

Abstract Objective Pregnancy-associated plasma protein-A (PAPP-A) has been suggested as a proatherogenic enzyme by its ability to locally increase insulin-like growth factor (IGF) activity through proteolytic cleavage of IGF binding protein-4 (IGFBP-4). Recently, stanniocalcin-2 (STC2) was discovered as an inhibitor of PAPP-A. This study aimed to investigate IGFBP-4, PAPP-A, and STC2 as local regulators of IGF bioactivity in the cardiac microenvironment by comparing levels in the pericardial fluid with those in the circulation of patients with cardiovascular disease. Methods Plasma and pericardial fluid were obtained from 39 patients undergoing elective cardiothoracic surgery, hereof 15 patients with type 2 diabetes. Concentrations of IGF-I, intact and fragmented IGFBP-4, PAPP-A, and STC2 were determined by immunoassays and IGF bioactivity by a cell-based assay. Results In pericardial fluid, the concentrations of total IGF-I, intact IGFBP-4, and STC2 were 72 ± 10%, 91 ± 5%, and 40 ± 24% lower than in plasma, while PAPP-A was 15 times more concentrated. The levels of the 2 IGFBP-4 fragments generated by PAPP-A and reflecting PAPP-A activity were elevated by more than 25%. IGF bioactivity was 62 ± 81% higher in the pericardial fluid than plasma. Moreover, pericardial fluid levels of both IGFBP-4 fragments correlated with the concentration of PAPP-A and with the bioactivity of IGF. All protein levels were similar in pericardial fluid from nondiabetic and diabetic subjects. Conclusions PAPP-A increases IGF bioactivity by cleavage of IGFBP-4 in the pericardial cavity of cardiovascular disease patients. This study provides evidence for a distinct local activity of the IGF system, which may promote cardiac dysfunction and coronary atherosclerosis.