ABSTRACT
BACKGROUND: Dipeptidyl peptidase 4 (DPP-4, also known as CD26) binds with adenosine deaminase (ADA) to activate T lymphocytes. Here, we investigated whether ADA activity is specifically affected by treatment with DPP-4 inhibitor (DPP4I) compared with other anti-diabetic agents. METHODS: Fasting ADA activity, in addition to various metabolic and biochemical parameters, were measured in 262 type 2 diabetes mellitus (T2DM) patients taking various anti-diabetic agents and in 46 non-diabetic control subjects. RESULTS: ADA activity was increased in T2DM patients compared with that in non-diabetic control subjects (mean+/-standard error, 23.1+/-0.6 U/L vs. 18.6+/-0.8 U/L; P9%) showed significantly increased ADA activity (21.1+/-0.8 U/L vs. 25.4+/-1.6 U/L; P<0.05). The effect of DPP4I on ADA activity in T2DM patients did not differ from those of other oral anti-diabetic agents or insulin. T2DM patients on metformin monotherapy showed a lower ADA activity (20.9+/-1.0 U/L vs. 28.1+/-2.8 U/L; P<0.05) compared with that of those on sulfonylurea monotherapy. CONCLUSION: Our results show that ADA activity is increased in T2DM patients compared to that in non-diabetic patients, is positively correlated with blood glucose level, and that DPP4I has no additional specific effect on ADA activity, except for a glycemic control- or HbA1c-dependent effect.