Fig 1: Linagliptin decreases F passsive by increasing titin phosphorylation at N2Bus S4010 in human cardiomyocytes in vitro. A, Cardiomyocyte passive stiffness in human cardiomyocytes treated with 300 ng/mL DPP‐4, 100 nmol/L linagliptin and 300 ng/mL DPP‐4, or control (DMSO/PBS) for 30 min (n = 3 different left ventricular tissues measuring at least 12 cardiomyocytes from each left ventricular tissue per condition). B, PKA‐mediated N2Bus S4010 phosphorylation and representative Coomassie Blue stained‐PVDF membranes and (C) PKG‐dependent N2Bus S4099 phosphorylation in human cardiomyocytes (n = 5 different left ventricular tissues) treated with vehicle control (DMSO/PBS), 300 ng/mL DPP‐4, 300 ng/mL DPP‐4 and 100 nmol/L linagliptin, or 100 nmol/L linagliptin for 2 h. F passive, passive stiffness; N2Bus, N2B unique sequence. Panel A was analysed using a two‐tailed unpaired Student t test with *P < .05. Panel B and C were analysed using a one‐way ANOVA with Dunnett's multiple comparison post hoc test with *P < .05 and ***P < .001 comparing control, DPP‐4 + Lina and Lina to DPP‐4
Fig 2: Linagliptin prevents DPP‐4‐mediated titin cleavage in human cardiomyocytes in vitro. A‐B, Western blots of total titin, containing the two isoforms N2BA and N2B and the known degradation product titin‐2 (T2) of human intact non‐permeabilized (A) and non‐intact permeabilized (B) human cardiomyocytes exposed to control PBS/DMSO (Ctrl) for 0 or 2 h (lane 1 and 2, respectively), 300 ng/mL DPP‐4 for 30 min and 2 h (lane 3 and 4, respectively), 300 ng/mL DPP‐4 and 100 nmol/L linagliptin for 2 h (lane 5) or 100 nmol/L linagliptin alone for 2 h (lane 6) in vitro (n = 3 different left ventricular tissues). Titin cleavage is indicated by red asterisks. Western blots of the specific N2Bus region (C; cross‐species conserved sequence QELLSKETLFP) and PEVK region (D; cross‐species conserved sequence KLRPGSGGEKPP) of human cardiomyocytes exposed to control PBS/DMSO (Ctrl) for 0 or 2 h (lane 1 and 2, respectively), 300 ng/mL DPP‐4 for 30 min and 2 h (lane 3 and 4, respectively), 300 ng/mL DPP‐4 and 100 nmol/L linagliptin for 2 h (lane 5) or 100 nmol/L linagliptin alone for 2 h (lane 6) (n = 3 different left ventricular tissues). Titin cleavage is indicated by red asterisks. The framed area represents the location for the zoomed images presented on the right side. Ctrl, control; DPP‐4, dipeptidyl peptidase‐4; F passive, passive stiffness; Lina, linagliptin; N2Bus, N2B unique sequence. Data are expressed as mean ± SEM
Fig 3: Linagliptin improves left ventricular relaxation in obese ZSF1 rats. Plasma DPP‐4 activity (A), aGIP levels (B), fasting glucose levels (C), bodyweight (D), mitral valve deceleration time (E) and E/E’ ratio (F) in 20‐wk‐old linagliptin‐ (Obese + Lina) and placebo‐treated obese (Obese) ZSF1 rats (n = 7 per group). aGIP, active glucose‐dependent insulinotropic peptide; DPP‐4, dipeptidyl peptidase‐4; E, early mitral inflow peak velocity; E’, early diastolic mitral annulus peak velocity; ND, not detected; RFU, relative fluorescence units. Data are expressed as mean ± SEM. Data were analysed using a two‐tailed unpaired Student t test, except D was analysed by a Mann‐Whitney U test. * Indicates P < .05, **P < .01 and ***P < .001
Supplier Page from Sino Biological, Inc. for Mouse DPP4 / CD26 Protein (His Tag)