DPP4 and Osteopenia: Of note, plasma DPP4 activity tended to be marginally higher in the osteoporosis group compared with the osteopenia group and normal bone mineral density group (7.7 ± 0.8 vs. 7.5 ± 0.9 and 7.3 ± 0.8 nmol/min/ml, respectively; P=0.07).