Increasing Age Associated with Higher Dipeptidyl Peptidase-4 Inhibition Rate Is a Predictive Factor for Efficacy of Dipeptidyl Peptidase-4 Inhibitors

BACKGROUND: It is not known which type 2 diabetes mellitus (T2DM) patients would most benefit from dipeptidyl peptidase-4 (DPP-4) inhibitor treatment. We aimed to investigate the predictors of response to DPP-4 inhibitors considering degree of DPP-4 inhibition. METHODS: This study is a post hoc analysis of a 24-week, randomized, double-blind, phase III trial that compared the efficacy and safety of a DPP-4 inhibitor (gemigliptin vs. sitagliptin) in patients with T2DM. Subjects were classified into tertiles of T1 <65.26%, T2=65.26%–76.35%, and T3 ≥76.35% by DPP-4 inhibition. We analyzed the change from baseline in glycosylated hemoglobin (HbA1c) according to DPP-4 inhibition with multiple linear regression adjusting for age, ethnicity, body mass index, baseline HbA1c, and DPP-4 activity at baseline. RESULTS: The mean age was greater in the high tertile group compared with the low tertile group (T1: 49.8±8.3 vs. T2: 53.1±10.5 vs. T3: 55.3±9.5, P<0.001) of DPP-4 inhibition. Although HbA1c at baseline was not different among tertiles of DPP-4 inhibition (P=0.398), HbA1c after 24-week treatment was lower in the higher tertile compares to the lower tertile (T1: 7.30%±0.88% vs. T2: 7.12%±0.78% vs. T3: 7.00%±0.78%, P=0.021). In multiple regression analysis, DPP-4 enzyme inhibition rate was not a significant determent for HbA1c reduction due to age. In subgroup analysis by tertile of DPP-4 inhibition, age was the only significant predictor and only in the highest tertile (R(2)=0.281, B=–0.014, P=0.024). CONCLUSION: This study showed that HbA1c reduction by DPP-4 inhibitor was associated with increasing age, and this association was linked with higher DPP-4 inhibition.