A Dipeptidyl Peptidase-4 Inhibitor Suppresses Macrophage Foam Cell Formation in Diabetic db/db Mice and Type 2 Diabetes Patients
Effects of the dipeptidyl peptidase-4 (DPP-4) inhibitor teneligliptin on oxidized low-density lipoprotein accumulation and its related gene expression levels in macrophages extracted from diabetic db/db mice and db/db misty mice at 13 weeks old. Four days after an intraperitoneal injection of thioglycolate, the exudate peritoneal cells were isolated from diabetic db/db (C57BLKS/J Iar -+Leprdb/+Leprdb) mice and db/db misty (C57BLKS/J Iar -m+/m+) mice at 13 weeks of age. For cholesterol accumulation, adherent macrophages were incubated at 37°C in 5% CO2 for 18 hours with RPMI 1640 medium containing 5% fetal bovine serum (FBS) and 10 μg/mL oxidized low-density lipoprotein (ox-LDL) in the presence of 0.1 mmol/L [3H] oleate or 10 μg/mL Dil-ox-LDL, which were added with/without 10 nmol/L teneligliptin (Te) ex vivo (a-k). For gene expression levels, adherent macrophages were incubated at 37°C in 5% CO2 for 18 hours with RPMI 1640 medium with 5% FBS in the presence/absence 10 nmol/L teneligliptin ex vivo without the addition of ox-LDL (l-n). (a-i) Representative immunofluorescent staining images of the peritoneal macrophages isolated from diabetic db/db mice or db/db misty mice. F4/80-expressing cells were in green, Dil-ox-LDL-stained cells were in red, and DAPI-stained cells were in blue. Scale bars represent 50 μm. (j) Relative fluorescence ratio per area of Dil-ox-LDL in peritoneal macrophages isolated from mice was imaged and analyzed with a BZ-X710 microscope/software. (k) Foam cell formation in exudate peritoneal macrophages isolated from diabetic db/db mice and db/db misty mice. The cellular lipids were extracted, and the radioactivity of the cholesterol [3H] oleate was determined by thin-layer chromatography. (l-n) Gene expression levels related to foam cell formation in peritoneal macrophages isolated from diabetic db/db mice and db/db misty mice. Gene expression levels of CD36 (l), acyl-coenzyme A: cholesterol acyltransferase-1 (ACAT-1) (m), and interleukin-6 (IL-6) (n) and the association with GAPDH were analyzed by real-time RT-PCR without the addition of ox-LDL. Data information: db/db misty mice, db/db mice, and db/db mice with ex vivo teneligliptin treatment. Results are presented as mean values ± SEM and analyzed with one-way ANOVA: , vs. db/db misty mice. ,, vs. db/db mice without teneligliptin.
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