Effect of Testosterone on Inflammatory Markers in the Development of Early Atherogenesis in the Testicular-Feminized Mouse Model

Abstract

Background. Low levels of serum testosterone in men are associated with cardiovascular disease. Clinical studies show that testosterone replacement therapy (TRT) can improve symptoms of cardiovascular disease and reduce the inflammatory burden evident in atherosclerosis. Aim. We used an in vivo animal model to determine whether testosterone influences mediators of vascular inflammation as part of its beneficial effects on atherogenesis. Methods. Testicular-feminized (Tfm) mice, which express low endogenous testosterone and a non-functional androgen receptor (AR), were used to assess the effect of androgen status on atheroma formation, serum lipids, and inflammatory mediators. Tfm mice were fed a high-cholesterol diet, received saline or physiological (TRT), and were compared to saline-treated XY littermates. Results. A total of 28 weeks of high-cholesterol diet caused fatty streak formation in the aortic root of XY littermates and Tfm mice, an effect significantly amplified in Tfm mice. Tfm mice on normal diet showed elevated serum tumor necrosis factor-α (TFN-α) and interleukin-6 compared to XY littermates. High-cholesterol diet induced increased monocyte chemoattractant protein-1 (MCP-1) in Tfm mice, and TFN-α and MCP-1 in XY littermates. TRT reduced fatty streak formation and serum interleukin-6 in Tfm mice but had no significant effects on lipid profiles. Monocyte/macrophage staining indicated local inflammation in aortic root fatty streak areas of all mice, with TRT reducing local inflammation through plaque reduction in Tfm mice. Fractalkine (CX₃CL1) and its receptor (CX₃CR1) were present in fatty streaks of all mice fed a high-cholesterol diet, independent of androgen status. Conclusion. These results are consistent with AR-dependent and AR-independent anti-inflammatory actions of testosterone in atheroprotection, although the local anti-inflammatory mechanisms via which testosterone acts remain unknown.

• Androgen receptor
• Fatty streak
• Cytokine
• Lipid
• Chemokine

Acknowledgments

The authors thank Philip Craddock from Department of Clinical Chemistry, Sheffield Children’s Hospital, Sheffield, UK, for performing the serum cholesterol measurements and Susan Newton from the University of Sheffield Core Research Facilities for her assistance with the multiplex bead array assays.

Declarations of interest

There is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported.

This research was supported by the Cardiology Research Fund, Sheffield NHS Foundation Trust, and the Biomedical Research Centre, Sheffield Hallam University.