Changes of dipeptidyl peptidase IV (DPP-IV) in obese children with weight loss: relationships to peptide YY, pancreatic peptide, and insulin sensitivity.

Aim: Gastrointestinal (GI) hormones are involved in satiety regulation and in glucose metabolism. Most GI hormones are hydrolyzed and inactivated by the same enzyme, dipeptidyl peptidase IV (DPP-IV). We analyzed changes of DPP-IV after weight loss in obese children and its relationships to the GI hormones pancreatic peptide (PP), peptide YY (PYY), and insulin sensitivity.

Methods: We measured at baseline and one year later anthropometrics, percentage body fat based on skinfold thickness, DPP-IV, PP, PYY, insulin, and glucose concentrations in 18 obese children (mean age 10.9 years, 44% male, mean BMI 28.5 kg/m2) who participated in a one-year lifestyle intervention program based on physical activity, nutrition course, and behavioral therapy. Insulin sensitivity was calculated using QUICKI.

Results: Changes of DPP-IV correlated significantly to the changes of percentage body fat (r = 0.47) and BMI SDS (r = 0.60). In partial regression analysis adjusted for change in weight status, changes of DPP-IV correlated significantly to changes of PYY (r = -0.43), PP (r = -0.49), QUICKI (r = -0.53), and insulin (r = 0.57). The 10 children with substantial weight loss significantly reduced their DPP-IV and insulin concentrations, while QUICKI, PYY, and PP levels significantly increased. In children without substantial weight loss no significant changes were observed.

Conclusions: These findings suggest that the increase of fasting PP and PYY in weight loss is influenced at least in part by a decrease of their cleavage enzyme DPP-IV. Further research is necessary to evaluate the mechanisms in weight loss leading to a decrease of DPP-IV activity and consequently to an improvement of insulin sensitivity.