CYP27A1 and type 2 diabetes mellitus: Notably, serum SIRT1 levels in the T2DM group were markedly reduced than those in the control group (P < 0.05).No significant differences were observed between the two groups regarding lumbar BMD, osteocalcin (OC), 25-hydroxyvitamin D [25(OH)D], and β-C-terminal telopeptide of type I collagen (β-CTX) (P > 0.05).