A role for SPARC in the moderation of human insulin secretion

PLoS One. 2013 Jun 28;8(6):e68253. doi: 10.1371/journal.pone.0068253. Print 2013.

Abstract

Aims/hypothesis: We have previously shown the implication of the multifunctional protein SPARC (Secreted protein acidic and rich in cysteine)/osteonectin in insulin resistance but potential effects on beta-cell function have not been assessed. We therefore aimed to characterise the effect of SPARC on beta-cell function and features of diabetes.

Methods: We measured SPARC expression by qRT-PCR in human primary pancreatic islets, adipose tissue, liver and muscle. We then examined the relation of SPARC with glucose stimulated insulin secretion (GSIS) in primary human islets and the effect of SPARC overexpression on GSIS in beta cell lines.

Results: SPARC was expressed at measurable levels in human islets, adipose tissue, liver and skeletal muscle, and demonstrated reduced expression in primary islets from subjects with diabetes compared with controls (p< = 0.05). SPARC levels were positively correlated with GSIS in islets from control donors (p< = 0.01). Overexpression of SPARC in cultured beta-cells resulted in a 2.4-fold increase in insulin secretion in high glucose conditions (p< = 0.01).

Conclusions: Our data suggest that levels of SPARC are reduced in islets from donors with diabetes and that it has a role in insulin secretion, an effect which appears independent of SPARC's modulation of obesity-induced insulin resistance in adipose tissue.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adipose Tissue / metabolism
  • Adult
  • Cells, Cultured
  • Diabetes Mellitus / genetics
  • Diabetes Mellitus / metabolism
  • Female
  • Glucose / metabolism
  • Humans
  • Insulin / genetics
  • Insulin / metabolism*
  • Insulin Resistance / genetics
  • Insulin-Secreting Cells / metabolism
  • Islets of Langerhans / metabolism
  • Liver / metabolism
  • Male
  • Middle Aged
  • Muscles / metabolism
  • Osteonectin / genetics*
  • Osteonectin / metabolism*

Substances

  • Insulin
  • Osteonectin
  • SPARC protein, human
  • Glucose

Grant support

This study was funded by the Diabetes Research Wellness Foundation. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.