Open Access Research article

The effect of proatherogenic pathogens on adipose tissue transcriptome and fatty acid distribution in apolipoprotein E-deficient mice

Kati Hyvärinen1*, Anita M Tuomainen1, Saara Laitinen2, Georg Alfthan3, Irma Salminen3, Maija Leinonen4, Pekka Saikku5, Petri T Kovanen6, Matti Jauhiainen37 and Pirkko J Pussinen1

Author Affiliations

1 Institute of Dentistry, University of Helsinki, P.O. Box 63, 00014 Helsinki, Finland

2 Finnish Red Cross Blood Service, Helsinki, Finland

3 National Institute for Health and Welfare, Helsinki, Finland

4 National Institute for Health and Welfare, Oulu, Finland

5 Department of Medical Microbiology, University of Oulu, Oulu, Finland

6 Wihuri Research Institute, Helsinki, Finland

7 FIMM, Institute for Molecular Medicine, Helsinki, Finland

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BMC Genomics 2013, 14:709  doi:10.1186/1471-2164-14-709

Published: 17 October 2013

Abstract

Background

Chronic infections have been demonstrated to maintain low-grade systemic inflammation and associate with atherosclerosis. We studied the inflammation- and lipid homeostasis-related effects of Aggregatibacter actinomycetemcomitans (Aa) and Chlamydia pneumoniae (Cpn) infections on the epididymal and inguinal adipose tissue (AT) transcriptomes and fatty acid distribution in apolipoprotein (apo) E-deficient mice. Chow-fed apoE-deficient mice were exposed to 1) chronic intranasal infection with C. pneumoniae (Cpn group), 2) recurrent intravenous infection with A. actinomycetemcomitans (Aa group), 3) a combination of both types of infection (Cpn + Aa group), or 4) infection with the vehicle (control group). Epididymal and inguinal AT gene expression was analyzed using an Illumina Mouse WG-6 v2.0 platform and quantitative PCR (QPCR). Microarray data were analyzed using Gene Ontology enrichment analysis. AT fatty acid analysis was performed using gas–liquid chromatography.

Results

The transcriptomics data revealed significant enrichment in inflammation-associated biological pathways in both AT depots derived from the Aa and Cpn + Aa treated mice compared with the control group. The proportion of saturated fatty acids was higher in the inguinal AT in Aa (p = 0.027) and Cpn + Aa (p = 0.009) groups and in the epididymal AT in Aa group (p = 0.003). The proportion of polyunsaturated fatty acids was significantly lower among all Aa-infected groups in both depots. Chronic Cpn infection displayed only minor effects on transcriptomics and fatty acids of the AT depots.

Conclusions

Systemic infection with A. actinomycetemcomitans activates inflammation-related biological pathways and modulates cellular lipid homeostasis. The adverse changes in adipose tissues during chronic infection may promote atherosclerosis.

Keywords:
A. actinomycetemcomitans; C. pneumoniae; Adipose tissue; apoE-deficient mice; Transcriptome; Fatty acid distribution