SPP1 and left ventricular hypertrophy: Under normal circumstances, OPN expression in the heart is low (Singh et al., 2014); however, plasma OPN has been used as a causative biomarker for various cardiac pathologic states such as myocardial infarction (Trueblood et al., 2001), left ventricular hypertrophy (Graf et al., 1997), and heart failure (Stawowy et al., 2002; Li et al., 2017; Yousefi et al., 2019).