No evidence for a role of adipose tissue-derived serum amyloid a in the development of insulin resistance or obesity-related inflammation in hSAA1(+/-) transgenic mice

PLoS One. 2013 Aug 15;8(8):e72204. doi: 10.1371/journal.pone.0072204. eCollection 2013.

Abstract

Obesity is associated with a low-grade inflammation including moderately increased serum levels of the acute phase protein serum amyloid A (SAA). In obesity, SAA is mainly produced from adipose tissue and serum levels of SAA are associated with insulin resistance. SAA has been described as a chemoattractant for inflammatory cells and adipose tissue from obese individuals contains increased numbers of macrophages. However, whether adipose tissue-derived SAA can have a direct impact on macrophage infiltration in adipose tissue or the development of insulin resistance is unknown. The aim of this study was to investigate the effects of adipose tissue-derived SAA1 on the development of insulin resistance and obesity-related inflammation. We have previously established a transgenic mouse model expressing human SAA1 in the adipose tissue. For this report, hSAA1(+/-) transgenic mice and wild type mice were fed with a high fat diet or normal chow. Effects of hSAA1 on glucose metabolism were assessed using an oral glucose tolerance test. Real-time PCR was used to measure the mRNA levels of macrophage markers and genes related to insulin sensitivity in adipose tissue. Cytokines during inflammation were analyzed using a Proinflammatory 7-plex Assay. We found similar insulin and glucose levels in hSAA1 mice and wt controls during an oral glucose tolerance test and no decrease in mRNA levels of genes related to insulin sensitivity in adipose tissue in neither male nor female hSAA1 animals. Furthermore, serum levels of proinflammatory cytokines and mRNA levels of macrophage markers in adipose tissue were not increased in hSAA1 mice. Hence, in this model we find no evidence that adipose tissue-derived hSAA1 influences the development of insulin resistance or obesity-related inflammation.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adipose Tissue / metabolism*
  • Animals
  • Biomarkers / blood
  • Biomarkers / metabolism
  • Blood Glucose
  • Body Composition
  • Disease Models, Animal
  • Gene Expression
  • Glucose / metabolism
  • Glucose Tolerance Test
  • Humans
  • Inflammation / etiology
  • Insulin / blood
  • Insulin / metabolism
  • Insulin Resistance*
  • Male
  • Mice
  • Mice, Transgenic
  • Obesity / complications
  • Obesity / genetics*
  • Obesity / metabolism*
  • Serum Amyloid A Protein / genetics*
  • Serum Amyloid A Protein / metabolism*

Substances

  • Biomarkers
  • Blood Glucose
  • Insulin
  • SAA1 protein, human
  • Serum Amyloid A Protein
  • Glucose

Grants and funding

The work was funded by the Swedish Research Council (K2008-65X-20753-01-4), the Swedish federal government under the LUA/ALF agreement, the Swedish Foundation for Strategic Research to Sahlgrenska Center for Cardiovascular and Metabolic Research, the Åke Wiberg Foundation, the Foundations of the National Board of Health and Welfare, the Emelle Foundation and the Swedish Knowledge Foundation through the Industrial PhD program in Medical Bioinformatics at Corporate Alliances, Karolinska Institutet, the Jeansson Foundations, the Magnus Bergvall Foundation, the Royal Physiographic Society (Nilsson-Ehle Foundation), the Tore Nilsson Foundation, the Arosenius Foundation, the Clas Groschinsky Foundation, the Torsten and Ragnar Söderberg Foundation, the VINNOVA-VINNMER program, the Sahlgrenska University Hospital Foundation, the Längmanska foundation, and the Wilhelm and Martina Lundgren foundation. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.