β-Aminoisobutyric Acid Suppresses Atherosclerosis in Apolipoprotein E-Knockout Mice

Endurance exercise training has been shown to induce peroxisome proliferator-activated receptor-7 coactivator-1 alpha (PGC-1 alpha) expression in skeletal muscle. We recently reported that skeletal muscle-specific PGC-1 alpha overexpression suppressed atherosclerosis in apolipoprotein E-knockout (ApoE(-/-)) mice. beta-Aminoisobutyric acid (BAIBA) is a PGC-1 alpha-dependent myokine secreted from myocytes that affects multiple organs. We have also reported that BAIBA suppresses tumor necrosis factor-alpha-induced vascular cell adhesion molecule-1 (VCAM-1) and monocyte chemoattractant protein-1 (MCP-1) gene expression in endothelial cells. In the present study, we hypothesized that BAIBA suppresses atherosclerosis progression, and tested that hypothesis with ApoE(-/-) mice. The mice were administered water containing BAIBA for 14 weeks, and were then sacrificed at 20 weeks of age. Atherosclerotic plaque area, plasma BAIBA concentration, and plasma lipoprotein profiles were assessed. Immunohistochemical analyses of the plaque were performed to assess VCAM-1 and MCP-1 protein expression levels and macrophage infiltration. The results showed that BAIBA administration decreased atherosclerosis plaque area by 30%, concomitant with the elevation of plasma BAIBA levels. On the other hand, plasma lipoprotein profiles were not changed by the administration. Immunohistochemical analyses indicated reductions in VCAM-1, MCP-1, and Mac-2 protein expression levels in the plaque. These results suggest that BAIBA administration suppresses atherosclerosis progression without changing plasma lipoprotein profiles. We propose that the mechanisms of this suppression are reductions in both VCAM-1 and MCP-1 expression as well as macrophage infiltration into the plaque.