The role of subcutaneous adipose tissue in supporting the copper balance in rats with a chronic deficiency in holo-ceruloplasmin

PLoS One. 2017 Apr 5;12(4):e0175214. doi: 10.1371/journal.pone.0175214. eCollection 2017.

Abstract

We have previously shown that (1) an acute deficiency in blood serum holo-ceruloplasmin (Cp) developed in rats that were fed fodder containing silver ions (Ag-fodder) for one month and (2) the deficiency in holo-Cp was compensated by non-hepatic holo-Cp synthesis in rats that were chronically fed Ag-fodder for 6 months (Ag-rats). The purpose of the present study is to identify the organ(s) that compensate for the hepatic holo-Cp deficiency in the circulation. This study was performed on rats that were fed Ag-fodder (40 mg Ag·kg-1 body mass daily) for 6 months. The relative expression levels of the genes responsible for copper status were measured by RT-PCR. The in vitro synthesis and secretion of [14C]Cp were analyzed using a metabolic labeling approach. Oxidase activity was determined using a gel assay with o-dianisidine. Copper status and some hematological indexes were measured. Differential centrifugation, immunoblotting, immunoelectrophoresis, and atomic absorption spectrometry were included in the investigation. In the Ag-rats, silver accumulation was tissue-specific. Skeletal muscles and internal (IAT) and subcutaneous (SAT) adipose tissues did not accumulate silver significantly. In SAT, the mRNAs for the soluble and glycosylphosphatidylinositol-anchored ceruloplasmin isoforms were expressed, and their relative levels were increased two-fold in the Ag-rats. In parallel, the levels of the genes responsible for Cp metallation (Ctr1 and Atp7a/b) increased correspondingly. In the SAT of the Ag-rats, Cp oxidase activity was observed in the Golgi complex and plasma membrane. Moreover, full-length [14C]Cp polypeptides were released into the medium by slices of SAT. The possibilities that SAT is part of a system that controls the copper balance in mammals, and it plays a significant role in supporting copper homeostasis throughout the body are discussed.

MeSH terms

  • Animals
  • Ceruloplasmin / deficiency*
  • Ceruloplasmin / metabolism
  • Copper / metabolism*
  • Female
  • Immunoblotting
  • Immunoprecipitation
  • Male
  • Muscle, Skeletal / metabolism
  • Rats
  • Rats, Wistar
  • Silver / metabolism
  • Subcutaneous Fat / metabolism*

Substances

  • Silver
  • Copper
  • Ceruloplasmin

Grants and funding

The work was supported by Russian Foundation for Basic Research grants 16-34-60219 (EYI), 14-04-01640 (NVT), 15-04-06770-a (LVP), http://www.rfbr.ru/rffi/eng. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.