Apolipoprotein gene expression in analbuminemic rats and in rats with Heymann nephritis

Xihua Sun, Harbin Jones, Jaap A. Joles, Arie Van Tol, George Kaysen

Research output: Contribution to journalArticle

40 Scopus citations

Abstract

The nephrotic syndrome results from altered glomerular permselectivity, causing urinary protein loss, reduced albumin concentration, oncotic pressure (π) and hyperlipidemia. Hepatic lipid and apolipoprotein synthesis increases and lipoprotein catabolism decreases. Decreased lipoprotein catabolism follows the onset of proteinuria but is not associated with hereditary analbuminemia [Nagase analbuminemic rat (NAR)] if proteinuria is absent. We measured plasma apolipoproteins (apo) AI, B, and E levels, their mRNA concentrations in liver, and the transcription rate of each mRNA in rats with Heymann nephritis (HN) or NAR to determine which alterations occurred in NAR alone without proteinuria. Plasma apo AI, B, and E were increased in both HN and NAR. Cholesterol and apo AI were inversely proportional to π and independent of urinary protein loss or the presence of albumin in plasma. In contrast, triglycerides (TGs) were significantly greater in HN and were increased out of proportion to apo B. The concentration of apo AI mRNA increased in liver of both HN and NAR as did apo AI transcription. Apo E mRNA increased in neither HN nor NAR, whereas apo B mRNA increased only in HN. Transcription of neither apo B nor E increased. Plasma apo AI levels are likely to be regulated transcriptionally at the level of protein synthesis, whereas plasma apo B and E levels are regulated either posttranscriptionally, at the level of protein catabolism, or at both sites. Lipoproteins rich in TG and poor in apo B appear after the development of proteinuria but not as a consequence of analbuminemia alone. The accumulation of TG-rich apo B containing lipoproteins in rats with HN may result from impaired lipolysis occurring as a consequence of proteinuria.

Original languageEnglish (US)
JournalAmerican Journal of Physiology - Renal Fluid and Electrolyte Physiology
Volume262
Issue number5 31-5
StatePublished - 1992

Keywords

  • Apolipoproteins AI, B, E, and AIV
  • Lipid
  • Nephrotic syndrome
  • Oncotic pressure
  • Proteinuria
  • Transcription

ASJC Scopus subject areas

  • Physiology

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