DPP4 and metabolic syndrome: Previous studies have shown the participation of DPP4 in the pathogenesis of hyperglycemia, IR, dyslipidemia, oxidative stress, inflammation (Zhao et al., 2006; Lamers et al., 2011; Zheng et al., 2014; Zheng T. et al., 2015), fatty liver (FL) (Baumeier et al., 2017) and SA (Zheng T. P. et al., 2015).