Korean J Physiol Pharmacol.  2018 Nov;22(6):713-719. 10.4196/kjpp.2018.22.6.713.

Potentiation of endothelium-dependent vasorelaxation of mesenteric arteries from spontaneously hypertensive rats by gemigliptin, a dipeptidyl peptidase-4 inhibitor class of anti-diabetic drug

• Kim HJ
• Baek EB
• Kim SJ

• KMID: 2430094
• DOI: http://doi.org/10.4196/kjpp.2018.22.6.713

Abstract

Dipeptidyl peptidase4 (DPP4) inhibitors such as gemigliptin are anti-diabetic drugs elevating plasma concentration of incretins such as GLP-1. In addition to the DPP4 inhibition, gemigliptin might directly improve the functions of vessels under pathological conditions. To test this hypothesis, we investigated whether the acetylcholine-induced endothelium dependent relaxation (ACh-EDR) of mesenteric arteries (MA) are altered by gemigliptin pretreatment in Spontaneous Hypertensive Rats (SHR) and in Wistar-Kyoto rats (WKY) under hyperglycemia-like conditions (HG; 2 hr incubation with 50 mM glucose). ACh-EDR of WKY was reduced by the HG condition, which was significantly recovered by 1 µM gemigliptin while not by saxagliptin and sitagliptin up to 10 µM. The ACh-EDR of SHR MA was also improved by 1 µM gemigliptin while similar recovery was observed with higher concentration (10 µM) of saxagliptin and sitagliptin. The facilitation of ACh-EDR by gemigliptin in SHR was not observed under pretreatment with NOS inhibitor, L-NAME. In the endotheliumdenuded MA of SHR, sodium nitroprusside induced dose-dependent relaxation was not affected by gemigliptin. The ACh-EDR in WKY was decreased by treatment with 30 µM pyrogallol, a superoxide generator, which was not prevented by gemigliptin. Exendin-4, a GLP-1 analogue, could not enhance the ACh-EDR in SHR MA. The present results of ex vivo study suggest that gemigliptin enhances the NOS-mediated EDR of the HG-treated MA as well as the MA from SHR via GLP-1 receptor independent mechanism.

Keyword

Dipeptidyl peptidase-4; Endothelium dependent relaxation; Gemigliptin; Hypertension; Hyperglycemia

MeSH Terms

Animals
Endothelium
Glucagon-Like Peptide 1
Glucagon-Like Peptide-1 Receptor
Hyperglycemia
Hypertension
Incretins
Mesenteric Arteries*
NG-Nitroarginine Methyl Ester
Nitroprusside
Plasma
Pyrogallol
Rats
Rats, Inbred SHR*
Relaxation
Sitagliptin Phosphate
Superoxides
Vasodilation*
Glucagon-Like Peptide 1
Glucagon-Like Peptide-1 Receptor
Incretins
NG-Nitroarginine Methyl Ester
Nitroprusside
Pyrogallol
Sitagliptin Phosphate
Superoxides

Figure

• 

  Fig. 1 Blood pressure and body weights of WKY (n=16) and SHR (n=23) rats.(A) Systolic and diastolic blood pressures were measured by tail-cuff methods. The blood pressures were significantly higher in SHR than WKY rats (***p<0.001). (B) SHR rats weighed less than WKY significantly (***p<0.001).

• 

  Fig. 2 Improvement of ACh-EDR by gemigliptin in WKY MA exposed to 50 mM glucose (HG).Cumulative concentration-dependent relaxation of endothelium-intact MA were obtained in the presence of 5 µM PhE (ACh-EDR), and normalized to the steady-state contraction by PhE. HG condition (n=31) attenuated ACh-EDR of WKY MA (A), and the treatment with gemigliptin (1 µM; n=18, 10 µM; n=18) induced partial recovery of ACh-EDR (B). However, other DPP-4 inhibitors, sitagliptin (1 µM; n=12, 10 µM; n=12) and saxagliptin (1 µM; n=12, 10 µM; n=12) did not (C, D). n indicated the number of experiments. The concentration-response curves were plotted by using different colored symbols for each group. Statistical differences were analyzed between the tested groups at each concentration of ACh. The significance was marked by asterisks of the corresponding color (**p<0.01, ***p<0.001).

• 

  Fig. 3 More effective improvement of ACh-EDR by gemigliptin than sitagliptin and saxagliptin in SHR MA.The normalized concentration-response curves to ACh were obtained. Statistical differences were analyzed between the tested groups at each concentration of ACh, and the significance was marked by asterisks of the color corresponding to each group symbol (*p<0.05, **p<0.01, ***p<0.001). The sensitivity to ACh was lower in SHR (n=23) than WKY (n=24) (A). Incubation with gemigliptin at both 1 (n=8) and 10 µM (n=8) similarly improved the sensitivity to ACh in SHR MA (B). However, pretreatment with 1 µM sitagliptin (n=8) or 1 µM saxagliptin (n=8) did not recover ACh-EDR in SHR MA (C). Treatment of 10 µM sitagliptin (n=8) improved ACh-EDR slightly in SHR MA, whereas the treatment of 10 µM saxagliptin (n=8) did not (D). n indicated the number of experiments.

• 

  Fig. 4 Pharmacological investigation of the mechanism underlying the EDR improvement by gemigliptin.Cumulative concentration-response curves to ACh (A, C, D) or to SNP (B) in MAs of WKY (C) and SHR (A, B, D). (A) No effect of gemigliptin on ACh-induced EDR in the presence of L-NAME (n=12). (B) No difference of SNP-induced relaxation in the absence of functional endothelium. (C) No improving effect of gemigliptin on EDR under the pretreatment with 30 µM pyrogallol (n=12). (D) No improvement of ACh-EDR by 1 µM exendin-4 pretreatment in SHR MA (n=10). In each group of experiments, tonic contraction of MA was initially induced by 5 µM PhE. Statistical significance was marked by asterisks of the color corresponding to each group symbol. n indicated the number of experiments.

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