PAPP-A, IGFBP-4 and IGF-II are secreted by human adipose tissue cultures in a depot-specific manner

Mette Faurholdt Gude, Rikke Hjortebjerg, Claus Oxvig, Anne Anker Thyoø, Nils Erik Magnusson, Mette Bjerre, Steen Boønloøkke Pedersen, Jan Frystyk*

*Corresponding author for this work

Research output: Contribution to journalJournal articleResearchpeer-review

Abstract

Objective: Adipose tissue secretes pregnancy-Associated plasma protein-A (PAPP-A), which may increase local IGF action through cleavage of IGF-binding protein-4 (IGFBP-4). We tested whether this mechanism was operational in human visceral and subcutaneous adipose tissue (i.e. VAT and SAT). Design: Explants of VAT and SAT from 26 obese subjects (hereof 17 women, BMI 39.5 (37.2; 42.8) kg/m2 (median (25%; 75% confidence interval) and SAT from eight lean, age-matched women (BMI 23.6 (22.4; 24.9) kg/m2) were incubated with or without GH (100 ?g/L) and the media were harvested. Methods: Media were assessed for concentrations of PAPP-A, intact and PAPP-A-cleaved IGFBP-4, IGF-I and IGF-II, and IGF-I receptor (IGF-IR) activation by bioassay. Results: In obese subjects, VAT media contained higher concentrations than SAT of PAPP-A (4.4-fold) and both PAPP-A-generated IGFBP-4 fragments (C-Terminal: 3.3-fold, N-Terminal: 1.5-fold) (all P < 0.0005). Intact IGFBP-4 levels were similar in SAT and VAT. VAT media contained elevated IGF-II (1.4-fold; P < 0.005), but similar IGF-I concentrations compared with SAT. Still, VAT media contained a 1.8-fold increased ability to stimulate the IGF-IR (P < 0.005). IGF-I protein concentration and IGF-IR activation increased more in VAT media than SAT media following GH stimulation (both P < 0.05). At baseline, SAT media protein levels from lean and obese women were similar, with the exception of PAPP-A being 1.8-fold elevated in VAT media (P < 0.05). GH induced a similar increase in IGF-I media levels in SAT from obese and lean women. Conclusion: Human adipose tissue cultures secrete enzymatically active PAPP-A, IGFBP-4 and IGF-II in a depot-specific manner, suggesting differential regulation of IGF activity. Further, IGF-II appears to be more prominent than IGF-I. Finally, VAT appears more GH responsive than SAT.

Original languageEnglish
JournalEuropean Journal of Endocrinology
Volume175
Issue number6
Pages (from-to)509-517
Number of pages9
ISSN0804-4643
DOIs
Publication statusPublished - 1. Dec 2016
Externally publishedYes

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