Elevated hepatic DPP4 activity promotes insulin resistance and non-alcoholic fatty liver disease

Baumeier, Christian; Schlüter, Luisa; Saussenthaler, Sophie; Laeger, Thomas; Rödiger, Maria; Alaze, Stella Amelie; Fritsche, Louise; Häring, Hans-Ulrich; Stefan, Norbert; Fritsche, Andreas; Schwenk, Robert Wolfgang; Schürmann, Annette

For the quantification of plasma DPP4 activity, 348 subjects with prediabetes from the ongoing Tübingen family (TUEF) study for type 2 diabetes were selected [24] . Each participant underwent a standardized 5 point oral glucose tolerance test with 75 g of glucose after an overnight fasting period. Venous blood samples were obtained at time points 0, 30, 60, 90, and 120 min for the measurement of glucose (ADVIA 1800 Chemistry Analyzer, Siemens Healthcare Diagnostics) and insulin (ADVIA Centaur XP Immunoassay System, Siemens Healthcare Diagnostics). Insulin sensitivity was calculated with the composite whole-body insulin sensitivity index (ISI) [25] . Liver fat was quantified by localized 1H-MR spectroscopy using a 1.5 T MR scanner (Magnetom Sonata, Siemens Healthcare). The cohort was divided into quartiles according to liver fat content. For quantification of plasma DPP4 activity, 158 samples from subjects of the first and fourth quartile, matched for age and sex, were used. DPP4 activity was measured in 25 ml plasma as described before [23] . The work described has been carried out in accordance with the code of ethics of the World Medical Association (Declaration of Helsinki).