Quantitative analysis of dipeptidyl peptidase inhibitor P32/98 and its main metabolite in rat, dog, mouse, monkey, human plasma and human urine using liquid chromatography–tandem mass spectrometry: application to pharmacokinetic evaluation

Effects of dipeptidyl peptidase iv inhibition on arterial blood pressure

1. The aim of the present study was to determine whether inhibition of dipeptidyl peptidase IV (DPP IV) elevates arterial blood pressure and whether any such effect is dependent on genetic background, the sympathetic nervous system and Y(1) receptors. The rationale behind this study was that: (i) neuropeptide (NP) Y(1-36) and peptide YY(1-36) (PYY(1-36)) are endogenous Y(1) receptor agonists and are metabolised by DPP IV to NPY(3-36) and PYY(3-36), which are not Y(1) but rather selective Y(2) receptor agonists; (ii) Y(1) receptors mediate vasoconstriction, whereas Y(2) receptors have little effect on vascular tone; (iii) vaso-constrictor effect of the Y(1) receptor is enhanced in spontaneously hypertensive rats (SHR) compared with normotensive Wistar-Kyoto (WKY) rats; and (iv) NPY(1-36) is released from sympathetic nerve terminals. 2. We examined the effects of acute administration of 3-N-[(2S,3S)-2-amino-3-methylpentanoyl]-1,3-thiazolidine (P32/98; a DPP IV inhibitor) on arterial blood pressure in anaesthetized adult SHR and WKY rats in the absence and presence of either captopril, hydralazine or chlorisondamine to lower basal mean arterial blood pressure (MABP) by different mechanisms (inhibition of angiotensin-converting enzyme, direct vasodilation and ganglionic blockade, respectively). 3. In naïve SHR with severely elevated basal blood pressures (MABP = 176 +/- 3 mmHg; n = 4), i.v. boluses (1, 3 and 10 mg/kg) of P32/98 did not affect blood pressure. 4. When basal blood pressure was reduced by pretreatment of SHR with either captopril (30 mg/kg, i.v.; MABP = 116 +/- 3 mmHg; n = 9) or hydralazine (5 mg/kg, i.p.; MABP = 84 +/- 3 mmHg; n = 7), P32/98 (1, 3 and 10 mg/kg) caused significant dose-related increases in arterial blood pressure (4 +/- 2, 10 +/- 2 and 12 +/- 3 mmHg in the captopril-pretreated group, respectively (P < 0.01); 5 +/- 2, 8 +/- 3 and 11 +/- 4 mmHg in the hydralazine-pretreated group, respectively (P < 0.01)). 5. The increases in arterial blood pressure induced by P32/98 in captopril- or hydralazine-pretreated SHR were entirely blocked by pretreatment with the selective Y(1) receptor antagonist N2-(diphenylacetyl)-N-[(4-hydroxyphenyl)methyl]-d-arginine amide (BIBP 3226; 6 mg/kg per h). 6. When basal blood pressure was reduced in SHR by pretreatment with chlorisondamine (10 mg/kg, s.c.; MABP = 108 +/- 4 mmHg; n = 7), inhibition of DPP IV with P32/98 did not affect arterial blood pressure. Basal heart rate in chlorisondamine-treated SHR was significantly reduced compared with naïve SHR, captopril-pretreated SHR and hydralazine-pretreated SHR, indicating effectiveness of ganglionic blockade. 7. Unlike the results in genetically hypertensive animals, in normotensive WKY rats pretreated with captopril (30 mg/kg, i.v.; MABP = 81 +/- 4 mmHg; n = 6), or hydralazine (5 mg/kg, i.p.; MABP = 63 +/- 4 mmHg; n = 4) or chlorisondamine (10 mg/kg, s.c.; MABP = 63 +/- 4 mmHg; n = 5), P32/98 did not affect arterial blood pressure. 8. We conclude that, in genetically susceptible animals, inhibition of DPP IV increases arterial blood pressure via Y(1) receptors when elevated blood pressure is reduced with antihypertensive drugs provided that the sympathetic nervous system is functional. The results suggest vigilance because DPP IV inhibitors are used more widely in hypertensive patients treated with antihypertensive drugs.

Type 2 diabetes—Therapy with dipeptidyl peptidase IV inhibitors

The sole application of an inhibitor of the dipeptidyl peptidase DP IV (also DP 4, CD26, DPP-IV or DPP-4) to a mammal subsequently leading to improved glucose tolerance marks a major breakthrough in metabolic research bearing the potential of a new revolutionary diabetes therapy. This was demonstrated in rat applying the specific DP IV inhibitor isoleucyl thiazolidine. It was published in 1996 for the first time that a specific DP IV inhibitor in a given dose was able to completely block glucagon-like peptide-1 (GLP-1) degradation in vivo resulting in improved insulin response accompanied, by accelerated peripheral glucose disposal. Later on, these results were confirmed by several research teams applying DP IV inhibitors intravenously or orally. Today, the DP IV inhibition for the treatment of metabolic disorders is a validated principle. Now, more than 10 years after the initial animal experiments, first DP IV inhibitors as investigational drugs are tested in phase 3 clinical trials.

Improvement of glucose tolerance in Zucker diabetic fatty rats by long-term treatment with the dipeptidyl peptidase inhibitor P32/98: comparison with and combination with rosiglitazone

AIM

The aim of this study was to investigate the effect of long-term treatment with the dipeptidyl peptidase inhibitor P32/98 and its combination with rosiglitazone on blood glucose control and islet of Langerhans histology in male Zucker diabetic fatty (ZDF) rats, when treatment begins before or after the development of overt diabetes.

METHODS

ZDF rats were treated with P32/98 from the age of 9, 12 or 15 weeks. Rosiglitazone maleate was given to a separate group from the age of 13 weeks. P32/98 was given to all of these rosiglitazone-treated rats from 16 weeks of age. Rosiglitazone maleate was also given from 16 weeks of age to half the rats that were given P32/98 from 9 weeks of age. The compounds were given by oral gavage until the rats were 14 weeks old and then in the diet. The experiment was terminated at the age of 20-21 weeks. Blood glucose, plasma insulin and oral glucose tolerance were measured at intervals; islet histology was assessed terminally.

RESULTS

P32/98 improved glucose tolerance after both single and multiple doses when treatment started at 9 weeks of age, also after the third week of treatment when treatment began at 12 or 15 weeks of age. P32/98 reduced daytime blood glucose when treatment began at 12 weeks. Treatment with rosiglitazone increased food intake and body weight, and after 2 weeks, reduced daytime blood glucose, water intake and the area under the glucose tolerance curve. A single dose of P32/98 markedly improved glucose tolerance in rosiglitazone-treated rats. When treatment had begun at 9 weeks of age, P32/98 stimulated insulin secretion in some glucose tolerance tests. Neither P32/98 nor rosiglitazone affected pancreatic insulin content, nor did they have clear effects on islet histology.

CONCLUSION

P32/98 elicited a sustained improvement in glucose tolerance in both prediabetic and diabetic ZDF rats. The effects of P32/98 on glucose and insulin were similar to those of rosiglitazone, and in contrast to rosiglitazone, P32/98 did not increase food intake or body weight. However, neither compound was especially effective at improving diabetes in ZDF rats when treatment began at 9, 12 or 15 (P32/98) or 13 (rosiglitazone) weeks of age.