In HL-1 cardiomyocytes, sitagliptin did not suppress PKC activity over the tested time and concentration ranges, whereas saxagliptin did. In isolated adult mouse ventricular cardiomyocytes, 2 μM sitagliptin for 5 min did not significantly prolong APD90. These findings are specific to the tested cellular conditions. [2]
Sitagliptin responses differed between isolated artery models. At 1–10 μM it did not restore acetylcholine-dependent relaxation in high-glucose-treated WKY mesenteric arteries. In SHR arteries, 1 μM was ineffective while 10 μM produced a slight improvement. These ex vivo findings do not establish an antihypertensive effect in treated animals. [3]
Human DPP4 inhibition and selectivity at 37°C
Biochemical assay · Isolated cloned human DPP4, DPP8 and DPP9; gly-pro-pNA substrate [1]
Sitagliptin inhibited human DPP4 competitively with much weaker DPP8 and DPP9 inhibition under the same assay conditions. Reported values are Ki, not IC50 or treatment doses.
Literature-Reported Treatment Conditions
- Treatment concentration
- Inhibitor concentration series; individual concentrations not enumerated in the read Methods. Substrate: 120 or 1000 μM gly-pro-pNA.
- Exposure duration
- 40 min inhibitor–enzyme preincubation; reaction followed for 40 min at 37°C
- Method
- Chromogenic assay at 405 nm; initial velocities; IC50 converted to Ki assuming competitive inhibition and averaged across the two substrate concentrations.
- Vehicle
- 1% DMSO in the final assay
- Reported limits
- Enzyme amount is not specified in the read steady-state Methods paragraph. Exact test-material salt/solid form is not specified.
Methods and source locations
Compound reported in the paper: Sitagliptin; Compound label in the paper: Sitagliptin; exact salt/solid form not specified
Evidence concerns the named sitagliptin active compound in the reported preparation. It does not validate this SKU, a particular free-base/salt preparation or an Adooq lot; no salt-to-base conversion is made.
Table 2, sitagliptin row and footnote; Methods: Reagents and Steady-state inhibition of isolated cloned human and cynomolgus monkey DPP4, 8 and 9 in vitro at 37°C
Human DPP4 inhibition: Gly-pro-pNA cleavage assay at 37°C; competitive-inhibition calculation. — Table 2: sitagliptin row, DPP4 column and table footnote
Human DPP8 inhibition: Gly-pro-pNA cleavage assay at 37°C; competitive-inhibition calculation. — Table 2: sitagliptin row, DPP8 column and table footnote
Human DPP9 inhibition: Gly-pro-pNA cleavage assay at 37°C; competitive-inhibition calculation. — Table 2: sitagliptin row, DPP9 column and table footnote
Rapid dissociation from human DPP4
Biochemical assay · Human DPP4; inhibitor dissociation measured by recovery of substrate cleavage after free-inhibitor removal [1]
Sitagliptin dissociated within the method’s temporal resolution: reported half-life <2 min at 37°C. This is an enzyme-complex dissociation limit, not a plasma elimination half-life.
Literature-Reported Treatment Conditions
- Treatment concentration
- 20 nM enzyme and 500 nM inhibitor during preincubation; 250 μM substrate during the dissociation assay
- Exposure duration
- 30 min preincubation at 37°C; subsequent dissociation monitored at 37°C
- Method
- Remove excess free inhibitor with a P-30 spin column, dilute approximately 10-fold into excess substrate and fit activity recovery.
- Reported limits
- Replicate count and exact salt form are not supplied for the sitagliptin Table 4 entry; assay vehicle is not specified in this separate kinetics paragraph.
Methods and source locations
Compound reported in the paper: Sitagliptin; Compound label in the paper: Sitagliptin; exact salt/solid form not specified
Evidence concerns the named sitagliptin active compound in the reported preparation. It does not validate this SKU, a particular free-base/salt preparation or an Adooq lot; no salt-to-base conversion is made.
Table 4; Results: Saxagliptin and 5-hydroxysaxagliptin are long-acting DPP4 inhibitors in vitro; Methods: Slow binding kinetics at 37°C for human DPP4
Dissociation of sitagliptin from human DPP4: Free-inhibitor removal/dilution followed by recovery of DPP4 activity. — Table 4, sitagliptin row, t1/2 column; corresponding Results paragraph
No detectable suppression of PKC activity in HL-1 cardiomyocytes
Cell-based study · HL-1 murine cardiomyocyte cell line [2]
Sitagliptin did not suppress active PKC in the tested time and concentration series, whereas saxagliptin reduced PKC activity. The result limits extrapolation of saxagliptin-associated signaling to sitagliptin.
Literature-Reported Treatment Conditions
- Treatment concentration
- 2 μM in the time series; 0, 0.1, 0.2, 0.5, 1 and 2 μM in the 10-min concentration series
- Exposure duration
- 0, 2.5, 5, 7.5, 10, 15 and 30 min in Figure 5A; 10 min in Figure 5B
- Method
- Commercial PKC kinase activity kit (ADI-EKS-420A); active PKC normalized to total cell protein.
- Vehicle
- DMSO; final concentration 0.01% (v/v)
- Reported limits
- No numerical PKC inhibition magnitude is tabulated for the selected sitagliptin series; exact salt/solid form and sitagliptin catalog/lot not stated.
Methods and source locations
Compound reported in the paper: Sitagliptin; Compound label in the paper: Sitagliptin; exact salt/solid form not specified
Evidence concerns the named sitagliptin active compound in the reported preparation. It does not validate this SKU, a particular free-base/salt preparation or an Adooq lot; no salt-to-base conversion is made.
Figure 5A–B and caption; Results: Saxagliptin Inhibits PKC Activity, Dependent on DPP9; Methods: Incubation Protocol and PKC Activity Assay
Active PKC in sitagliptin-treated HL-1 cells: PKC kinase activity assay; baseline and saxagliptin comparator. — Figure 5A–B, caption and corresponding Results paragraph
No significant acute action-potential prolongation in isolated ventricular cardiomyocytes
Cell-based study · Isolated adult mouse ventricular cardiomyocytes; donor mice 14–18 weeks old, either sex [2]
At 2 μM for 5 min, sitagliptin did not significantly prolong APD90; saxagliptin did. These are isolated-cell recordings, not an animal treatment or a clinical cardiac safety experiment.
Literature-Reported Treatment Conditions
- Treatment concentration
- 2 μM
- Exposure duration
- 5 min superfusion
- Method
- Whole-cell patch clamp at 37°C with 1-Hz stimulation; before/after recordings with external-solution rundown control.
- Vehicle
- Standard external solution; drug stock vehicle for this superfusion is not specified separately.
- Reported limits
- Exact salt/solid form and primary-cell drug stock vehicle are not specified. No tabulated APD90 values are extracted.
Methods and source locations
Compound reported in the paper: Sitagliptin; Compound label in the paper: Sitagliptin; exact salt/solid form not specified
Evidence concerns the named sitagliptin active compound in the reported preparation. It does not validate this SKU, a particular free-base/salt preparation or an Adooq lot; no salt-to-base conversion is made.
Figure 6C–D and caption; Methods: Cardiomyocyte Isolation and Patch Clamp; Statistical Analysis
Action-potential duration at 90% repolarization (APD90): Whole-cell patch clamp, paired before/after exposure with external-solution rundown comparator; ANCOVA. — Figure 6C–D and caption
No recovery of relaxation in high-glucose WKY arteries
Cell-based study · Isolated endothelium-intact mesenteric arteries from male Wistar-Kyoto rats; 50 mM glucose challenge [3]
Sitagliptin at 1 or 10 μM did not recover acetylcholine-induced endothelium-dependent relaxation impaired by 50 mM glucose.
Literature-Reported Treatment Conditions
- Treatment concentration
- 1 and 10 μM sitagliptin; 50 mM glucose challenge
- Exposure duration
- 2 h pretreatment
- Method
- Ex vivo dual-wire myography; cumulative acetylcholine 0.1 nM–10 μM after 5 μM phenylephrine precontraction; relaxation normalized to precontraction.
- Vehicle
- DMSO below 0.5% total, as stated in shared Methods.
- Reported limits
- Exact sitagliptin form/catalog/lot is not given. Matched vehicle balancing and an osmotic control are not described in the read Methods. Animal-to-artery allocation is not specified.
Methods and source locations
Compound reported in the paper: Sitagliptin; Compound label in the paper: Sitagliptin; exact salt/solid form not specified
Evidence concerns the named sitagliptin active compound in the reported preparation. It does not validate this SKU, a particular free-base/salt preparation or an Adooq lot; no salt-to-base conversion is made.
Figure 2A,C,D and caption; Results: Effects of gemigliptin, sitagliptin, and saxagliptin on the EDR impaired by HG condition; Methods: Isometric tension measurement, Drugs and chemicals, Statistical analysis
Acetylcholine-induced endothelium-dependent relaxation: Wire myography with phenylephrine precontraction and acetylcholine concentration-response curves. — Figure 2A,C,D and caption; Results: Effects of gemigliptin, sitagliptin, and saxagliptin on the EDR impaired by HG condition
Concentration-dependent relaxation response in SHR arteries
Cell-based study · Isolated endothelium-intact mesenteric arteries from male spontaneously hypertensive rats (SHR) [3]
Sitagliptin at 1 μM did not recover impaired acetylcholine-induced relaxation in SHR arteries; 10 μM produced a slight improvement. This differs from the negative response in high-glucose WKY arteries.
Literature-Reported Treatment Conditions
- Treatment concentration
- 1 and 10 μM sitagliptin
- Exposure duration
- 2 h pretreatment
- Method
- Ex vivo dual-wire myography; cumulative acetylcholine 0.1 nM–10 μM after 5 μM phenylephrine precontraction; relaxation normalized to precontraction.
- Vehicle
- DMSO below 0.5% total, as stated in shared Methods.
- Reported limits
- Exact sitagliptin form/catalog/lot is not given. Matched vehicle balancing and an osmotic control are not described in the read Methods. Animal-to-artery allocation is not specified.
Methods and source locations
Compound reported in the paper: Sitagliptin; Compound label in the paper: Sitagliptin; exact salt/solid form not specified
Evidence concerns the named sitagliptin active compound in the reported preparation. It does not validate this SKU, a particular free-base/salt preparation or an Adooq lot; no salt-to-base conversion is made.
Figure 3A,C,D and caption; Results: Effects of gemigliptin, sitagliptin and saxagliptin on EDR in MAs of SHR rats; Methods: Isometric tension measurement, Drugs and chemicals, Statistical analysis
Acetylcholine-induced endothelium-dependent relaxation: Wire myography with phenylephrine precontraction and acetylcholine concentration-response curves. — Figure 3A,C,D and caption; Results: Effects of gemigliptin, sitagliptin and saxagliptin on EDR in MAs of SHR rats
