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

Rikke Hjortebjerg*, Lars Melholt Rasmussen, Mette Faurholdt Gude, Akhmadjon Irmukhamedov, Lars P. Riber, Jan Frystyk, Jo G.R. De Mey

*Corresponding author for this work

Research output: Contribution to journalJournal articleResearchpeer-review

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.

Original languageEnglish
JournalThe Journal of clinical endocrinology and metabolism
Volume105
Issue number11
Pages (from-to)e4083–e4093
ISSN0021-972X
DOIs
Publication statusPublished - Nov 2020

Keywords

  • Cardiovascular disease
  • insulin like growth factor binding protein-4
  • insulin-like growth factor
  • pregnancy-associated plasma protein-A
  • stanniocalcin-2

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