3-Hydroxybutyrate, originating from the increased β-oxidation of free fatty acids [40], is found in higher concentrations in the plasma of T2DM patients [41] and has been shown to ameliorate insulin resistance in T2DM mice through the HCAR2/Ca2+/cAMP/PKA/Raf1/ERK1/2/PPARγ pathway [42]. This evidence concerns the gene MAPK3 and type 2 diabetes mellitus.