Effect of DPP4 Inhibition on Vasoconstriction

Phase 4

Completed

Conditions: Type 2 Diabetes Mellitus

Interventions: Drug: Sitagliptin
Drug: Placebo
Drug: Valsartan 160mg
Drug: Neuropeptide Y
Drug: Enalaprilat

Registration Number: NCT02639637

Lead Sponsor: Vanderbilt University

Brief Summary: The purpose of this study is to understand how dipeptidyl peptidase IV (DPP4) inhibition in diabetics affects hemodynamic parameters and sympathetic activation in the setting of increasing concentrations of neuropeptide Y, an endogenous peptide. The central hypothesis is that DPP4 inhibition decreases degradation of neuropeptide Y, resulting in increased vasoconstriction and sympathetic activation.

Detailed Description: Dipeptidyl peptidase IV (DPP4) inhibitors are routinely used for the treatment of type II diabetes mellitus (T2DM). Since the prevalence of hypertension is 1.5-3 times greater in diabetics compared to sex-aged matched controls, the use of antihypertensives such as ACE inhibitors is also common in diabetics. DPP4 is involved in the degradation of multiple vasoactive peptides, one of which is neuropeptide Y. This peptide is thought to play a role in blood pressure regulation and sympathetic nervous system activation. The aim of this study is to investigate how DPP4 inhibition affects vasoconstriction in response to increasing neuropeptide Y concentrations. Additionally, the investigators want to understand how the combination of DPP4 inhibition and ACE inhibition affects vasoconstriction and sympathetic activation. Understanding the hemodynamic and neurohumoral changes associated with DPP4 and ACE inhibitors has important implications for the millions of patients with T2DM who take these drugs concurrently.

Recruitment & Eligibility

Status: COMPLETED

Sex: All

Target Recruitment: 18

Inclusion Criteria

Type 2 Diabetes Mellitus, as defined by one or more of the following,

Hgb A1C ≥6.5%, or
Fasting plasma glucose ≥126mg/dL, or
Two hour plasma glucose ≥200 mg/dL following 75gr oral glucose load

For female subjects the following conditions must be met:

Postmenopausal status for at least 1 year, or
Status post-surgical sterilization, or
If of childbearing potential, utilization of some form of birth control and willingness to undergo β-HCG testing prior to drug treatment and on every study day

Exclusion Criteria

Type 1 diabetes.
Poorly controlled T2DM, defined as Hgb A1C>8.7%.
Use of anti-diabetic medications other than metformin.
Hypertension.
Subjects who have participated in a weight-reduction program during the last 6 months and whose weight has increased or decreased more than 5 kg over the preceding 6 months.
Pregnancy. Breast-feeding.
Treatment with any of the following drugs: cisapride, pimozide, terfenadine, astemizol
Clinically significant gastrointestinal impairment that could interfere with drug absorption
Cardiovascular disease that would pose risk for the subject to participate in the study, such as: myocardial infarction within 6 months prior to enrollment, presence of angina pectoris, significant arrhythmia, congestive heart failure (LV hypertrophy acceptable), deep vein thrombosis, pulmonary embolism, second- or third-degree AV block, mitral valve stenosis, or hypertrophic cardiomyopathy.
Impaired hepatic function (aspartate amino transaminase [AST] and/or alanine amino transaminase [ALT] >2 x upper limit of normal range)
Impaired renal function (eGFR< 60mL/min/1.73m2 as determined by the MDRD equation).
History or presence of immunological or hematological disorders.
History of pancreatitis or known pancreatic lesions.
History of angioedema or cough while taking an ACE inhibitor.
Hematocrit <35%.
Treatment with anticoagulants.
Growth hormone deficiency.
Diagnosis of asthma requiring use of an inhaled β-2 agonist more than 1 time per week.
Any underlying or acute disease requiring regular medication which could possibly pose a threat to the subject or make implementation of the protocol or interpretation of the study results difficult
Treatment with systemic glucocorticoids within the last 6 months.
Treatment with lithium salts
Ongoing tobacco use or recreational drug use.
Treatment with any investigational drug in the 1 month preceding the study
Mental conditions rendering the subject unable to understand the nature, scope, or possible consequences of the study
Inability to comply with the protocol, e.g., uncooperative attitude, inability to return for follow-up visits, and unlikelihood of completing the study

Study & Design

Study Type: INTERVENTIONAL

Study Design: CROSSOVER

Arm && Interventions

Group	Intervention	Description
Sitagliptin then Placebo	Placebo	Subjects in this arm will receive sitagliptin 100 mg daily. After one week of treatment, subjects will report for study day #1. During the study day subjects will be given intra-aterial neuropeptide Y and enalaprilat. A four week washout of medications will occur after the study day. Subjects will then receive placebo for one week followed by study day #2.
Placebo then Sitagliptin	Placebo	Subjects in this arm will receive placebo for one week. After this, subjects will report for study day #1. During the study day subjects will be given intra-aterial neuropeptide Y and enalaprilat. A four week washout of medications will occur after the study day. Subjects will then receive 100 mg of sitagliptin daily for one week followed by study day #2.
Sitagliptin then Placebo: Valsartan	Placebo	Subjects in this arm will receive sitagliptin 100 mg/d for one week as well as valsartan 160 mg/d for one week. After this subjects will report for study day #1. During the study day, subjects will be given intra-arterial neuropeptide Y. A four week washout of medication will occur after the study day. Subjects will then receive placebo/d and valsartan 160 mg/d for one week followed by study day #2.
Placebo then Sitagliptin: Valsartan	Sitagliptin	Subjects in this arm will receive placebo/d for one week as well as valsartan 160 mg/d for one week. After this subjects will report for study day #1. During the study day, subjects will be given intra-arterial neuropeptide Y. A four week washout of medication will occur after the study day. Subjects will then receive sitagliptin 100mg/d and valsartan 160 mg/d for one week followed by study day #2.
Placebo then Sitagliptin: Valsartan	Placebo	Subjects in this arm will receive placebo/d for one week as well as valsartan 160 mg/d for one week. After this subjects will report for study day #1. During the study day, subjects will be given intra-arterial neuropeptide Y. A four week washout of medication will occur after the study day. Subjects will then receive sitagliptin 100mg/d and valsartan 160 mg/d for one week followed by study day #2.
Sitagliptin then Placebo: Valsartan	Valsartan 160mg	Subjects in this arm will receive sitagliptin 100 mg/d for one week as well as valsartan 160 mg/d for one week. After this subjects will report for study day #1. During the study day, subjects will be given intra-arterial neuropeptide Y. A four week washout of medication will occur after the study day. Subjects will then receive placebo/d and valsartan 160 mg/d for one week followed by study day #2.
Placebo then Sitagliptin: Valsartan	Valsartan 160mg	Subjects in this arm will receive placebo/d for one week as well as valsartan 160 mg/d for one week. After this subjects will report for study day #1. During the study day, subjects will be given intra-arterial neuropeptide Y. A four week washout of medication will occur after the study day. Subjects will then receive sitagliptin 100mg/d and valsartan 160 mg/d for one week followed by study day #2.
Sitagliptin then Placebo	Sitagliptin	Subjects in this arm will receive sitagliptin 100 mg daily. After one week of treatment, subjects will report for study day #1. During the study day subjects will be given intra-aterial neuropeptide Y and enalaprilat. A four week washout of medications will occur after the study day. Subjects will then receive placebo for one week followed by study day #2.
Sitagliptin then Placebo	Enalaprilat	Subjects in this arm will receive sitagliptin 100 mg daily. After one week of treatment, subjects will report for study day #1. During the study day subjects will be given intra-aterial neuropeptide Y and enalaprilat. A four week washout of medications will occur after the study day. Subjects will then receive placebo for one week followed by study day #2.
Placebo then Sitagliptin	Sitagliptin	Subjects in this arm will receive placebo for one week. After this, subjects will report for study day #1. During the study day subjects will be given intra-aterial neuropeptide Y and enalaprilat. A four week washout of medications will occur after the study day. Subjects will then receive 100 mg of sitagliptin daily for one week followed by study day #2.
Placebo then Sitagliptin	Enalaprilat	Subjects in this arm will receive placebo for one week. After this, subjects will report for study day #1. During the study day subjects will be given intra-aterial neuropeptide Y and enalaprilat. A four week washout of medications will occur after the study day. Subjects will then receive 100 mg of sitagliptin daily for one week followed by study day #2.
Sitagliptin then Placebo: Valsartan	Sitagliptin	Subjects in this arm will receive sitagliptin 100 mg/d for one week as well as valsartan 160 mg/d for one week. After this subjects will report for study day #1. During the study day, subjects will be given intra-arterial neuropeptide Y. A four week washout of medication will occur after the study day. Subjects will then receive placebo/d and valsartan 160 mg/d for one week followed by study day #2.
Sitagliptin then Placebo	Neuropeptide Y	Subjects in this arm will receive sitagliptin 100 mg daily. After one week of treatment, subjects will report for study day #1. During the study day subjects will be given intra-aterial neuropeptide Y and enalaprilat. A four week washout of medications will occur after the study day. Subjects will then receive placebo for one week followed by study day #2.
Placebo then Sitagliptin	Neuropeptide Y	Subjects in this arm will receive placebo for one week. After this, subjects will report for study day #1. During the study day subjects will be given intra-aterial neuropeptide Y and enalaprilat. A four week washout of medications will occur after the study day. Subjects will then receive 100 mg of sitagliptin daily for one week followed by study day #2.

Primary Outcome Measures

Name	Time	Method
Forearm Blood Flow	FBF measured after 5 min of the 1 nmol/min dose of neuropeptide Y on study days 1 and 2. Study days 1 and two were separated by five weeks.	Forearm blood flow measured by strain gauge plethysmography in response to 1.0 nmol/min neuropeptide Y, the highest dose that all received.

Secondary Outcome Measures

Name	Time	Method
Insulin	Measured at baseline (time 0) of each study day prior to the infusion of neuropeptide Y. Study days 1 and 2 were separated by five weeks, a four-week washout and one-week treatment period.	Plasma insulin measured by radioimmunoassay.
GLP-1	Measured at baseline (time 0) of each study day prior to the infusion of neuropeptide Y. Study days were separated by five weeks, a four-week washout and one-week treatment period.	GLP--1 was not analyzed as subjects were studied in the fasting state.
Glucose	Measured at baseline (time 0) of each study day prior to the infusion of neuropeptide Y. Study days were separated by five weeks, a four-week washout and one-week treatment period.	Glucose was measured by the glucose oxidase method using a YSI glucose analyzer
ACE Activity	Measured at baseline (time 0) of each study day prior to the infusion of neuropeptide Y. Study days were separated by five weeks, a four-week washout and one-week treatment period.	ACE activity was measured using a commercially available assay (Olympus AU400/AU600, Alpco Diagnotics, Salem, NH.) The lower level of detection was 15 U/L and values below the level of detection were reported at half the level of detection.
DPP4 Activity	Measured at baseline (time 0) of each study day prior to the infusion of neuropeptide Y. Study days were separated by five weeks, a four-week washout and one-week treatment period.	DPP4 activity was measured by detection of cleavage of a colorimetric substrate.
Low Frequency Variability of Blood Pressure Activity	Measured at baseline (time 0) of each study day prior to the infusion of neuropeptide Y. Study days were separated by five weeks, a four-week washout and one-week treatment period.	Measured using the VITAL-GARD 450c monitor Ivy Biomedical Systems, Branford, CT, USA)
Arterial tPA	Measured at baseline (time 0) of each study day prior to the infusion of neuropeptide Y. Study days were separated by five weeks, a four-week washout and one-week treatment period.	Measured using an ELISA.
Venous tPA	Measured at baseline (time 0) of each study day prior to the infusion of neuropeptide Y. Study days were separated by five weeks, a four-week washout and one-week treatment period.	Measured using an ELISA. This was measured in a few subjects. After it was determined that there was no change in net t-PA release it was not measured in the remainder.
Mean Arterial Pressure	Measured at baseline (time 0) of each study day prior to the infusion of neuropeptide Y. Study days were separated by five weeks, a four-week washout and one-week treatment period.
Heart Rate	Measured at baseline (time 0) of each study day prior to the infusion of neuropeptide Y. Study days were separated by five weeks, a four-week washout and one-week treatment period.
Arterial Norepinephrine	Measured at baseline (time 0) prior to the infusion of neuropeptide Y on each study day. Study days 1 and 2 were separated by five weeks.	Arterial norepinephrine concentration measured by high-performance liquid chromatography.
Venous Norepinephrine	Measured at baseline (time 0) prior to the infusion of neuropeptide Y on each study day. Study days 1 and 2 were separated by five weeks.	Venous norepinephrine concentration measured by high-performance liquid chromatography
NPY Metabolites	Measured after 5 min infusion of the 1.0 nmol/min dose of neuropeptide Y on study days 1 and 2. Study days 1 and 2 were separated by five weeks.	NPY (3-36) concentration measured by micro ultra-hgih pressure liquid chromatography tandem mass spectrometry. NPY (3-36) is the degradation product of NPY by dipeptidyl peptidase 4. It was measured only in the diabetics studied.