MDA-LDL levels ( mean S.E. ) decreased significantly with increasing the dose of metformin ( from 94.40 6.35 to 77.83 4.74 U/L , P < 0.005 ) , but remained unchanged with add-on sitagliptin treatment ( from 89.94 5.59 to 98.46 6.78 U/L , p > 0.05 ) .