Effect of DPP4 Inhibition on Vasoconstriction

Study Overview
=================
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.

Official Title
-----------------
Contribution of Neuropeptide Y (NPY) to Vasoconstriction and Sympathetic Activation in the Setting of Dipeptidyl Peptidase IV (DPP4) Inhibition

Conditions
-----------------
Type 2 Diabetes Mellitus

Intervention / Treatment
-----------------
* Drug: Sitagliptin
* Drug: Placebo
* Drug: Neuropeptide Y
* Drug: Enalaprilat
* Drug: Valsartan 160mg


Participation Criteria
=================
Eligibility Criteria
-----------------
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

Ages Eligible for Study
-----------------
Minimum Age: 18 Years
Maximum Age: 55 Years

Sexes Eligible for Study
-----------------
All

Accepts Healthy Volunteers
-----------------
No

Study Plan
=================
How is the study designed?
-----------------

Design Details

Primary Purpose: Basic Science
Allocation: Randomized
Intervention Model: Crossover Assignment
Interventional Model Description: Crossover Arms 1 and 2, Crossover Arms 3 and 4
Masking: Quadruple


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Other: Sitagliptin then Placebo<br>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. | Drug: Sitagliptin<br>* Subjects will receive sitagliptin 100 mg daily for 7 days prior to one of the study days.<br>* Other names: Januvia;Drug: Placebo<br>* Subjects will receive a placebo capsule daily for 7 days prior to one of the study days.<br>* Other names: Microcrystalline cellulose;Drug: Neuropeptide Y<br>* During the study days, neuropeptide Y will be infused through an intra-arterial line. There will be four doses of neuropeptide Y used (0.1, 0.3, 1.0, and 3.0 nmol/min) and each dose will be infused for 10 minutes.<br>* Other names: NPY;Drug: Enalaprilat<br>* Ninety minutes after the last dose of neuropeptide Y, enalaprilat will be infused through the intra-arterial line at 0.33 µg/min/100mL of forearm volume. After 30 minutes, a second infusion of neuropeptide Y will begin. Similar to the previous neuropeptide infusion, four doses of neuropeptide Y will be used (0.1, 0.3, 1.0, and 3.0 nmol/min) and each dose will be infused for 10 minutes.<br>* Other names: Vasotec I.V.;|
| Other: Placebo then Sitagliptin<br>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. | Drug: Sitagliptin<br>* Subjects will receive sitagliptin 100 mg daily for 7 days prior to one of the study days.<br>* Other names: Januvia;Drug: Placebo<br>* Subjects will receive a placebo capsule daily for 7 days prior to one of the study days.<br>* Other names: Microcrystalline cellulose;Drug: Neuropeptide Y<br>* During the study days, neuropeptide Y will be infused through an intra-arterial line. There will be four doses of neuropeptide Y used (0.1, 0.3, 1.0, and 3.0 nmol/min) and each dose will be infused for 10 minutes.<br>* Other names: NPY;Drug: Enalaprilat<br>* Ninety minutes after the last dose of neuropeptide Y, enalaprilat will be infused through the intra-arterial line at 0.33 µg/min/100mL of forearm volume. After 30 minutes, a second infusion of neuropeptide Y will begin. Similar to the previous neuropeptide infusion, four doses of neuropeptide Y will be used (0.1, 0.3, 1.0, and 3.0 nmol/min) and each dose will be infused for 10 minutes.<br>* Other names: Vasotec I.V.;|
| Placebo Comparator: Sitagliptin then Placebo: Valsartan<br>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. | Drug: Sitagliptin<br>* Subjects will receive sitagliptin 100 mg daily for 7 days prior to one of the study days.<br>* Other names: Januvia;Drug: Placebo<br>* Subjects will receive a placebo capsule daily for 7 days prior to one of the study days.<br>* Other names: Microcrystalline cellulose;Drug: Valsartan 160mg<br>* Valsartan 160 mg/d for 7 days prior to one of the study days.<br>* Other names: valsartan p.o.;|
| Placebo Comparator: Placebo then Sitagliptin: Valsartan<br>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. | Drug: Sitagliptin<br>* Subjects will receive sitagliptin 100 mg daily for 7 days prior to one of the study days.<br>* Other names: Januvia;Drug: Placebo<br>* Subjects will receive a placebo capsule daily for 7 days prior to one of the study days.<br>* Other names: Microcrystalline cellulose;Drug: Valsartan 160mg<br>* Valsartan 160 mg/d for 7 days prior to one of the study days.<br>* Other names: valsartan p.o.;|

What is the study measuring?
-----------------
Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Forearm Blood Flow | Forearm blood flow measured by strain gauge plethysmography in response to 1.0 nmol/min neuropeptide Y, the highest dose that all received. | 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. | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Arterial Norepinephrine | Arterial norepinephrine concentration measured by high-performance liquid chromatography. | 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 | Venous norepinephrine concentration measured by high-performance liquid chromatography | 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. | 
| NPY Metabolites | 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. | 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. | 
| Insulin | Plasma insulin measured by radioimmunoassay. | 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. | 
| GLP-1 | GLP--1 was not analyzed as subjects were studied in the fasting state. | 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 | Glucose was measured by the glucose oxidase method using a YSI glucose analyzer | 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 | 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. | 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 | DPP4 activity was measured by detection of cleavage of a colorimetric substrate. | 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. | 
| Low Frequency Variability of Blood Pressure Activity | Measured using the VITAL-GARD 450c monitor Ivy Biomedical Systems, Branford, CT, USA) | 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 tPA | Measured using an ELISA. | 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. | 
| Venous tPA | 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. | 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. | 
| 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. | 

 Terms related to the study
=================
Keywords Provided by Centre Hospitalier Valida
-----------------
Type 2 Diabetes Mellitus, Sitagliptin, Dipeptidyl Peptidase IV Inhibitors, Angiotensin Converting Enzyme Inhibitors, Enalaprilat, Neuropeptide Y