| Outcome Measures: |
Primary: Mean Arterial Blood Pressure, The primary analyses will focus on mean arterial blood pressure, heart rate, and norepinephrine (NE) concentrations during ramipril versus ramipril+sitagliptin, and during ramipril+sitagliptin versus ramipril+sitagliptin+aprepitant. We will make similar comparisons within the valsartan- and placebo-treated groups. In addition, we will compare blood pressure and heart rate parameters among the ramipril-treated, valsartan-treated, and placebo-treated groups during comparable concurrent treatment., 4.5 hours on the 7th day of each intervention (placebo, sitagliptin, or sitagliptin+aprepitant)|Heart Rate, The primary analyses will focus on blood pressure, heart rate, and norepinephrine (NE) concentrations during ramipril versus ramipril+sitagliptin, and during ramipril+sitagliptin versus ramipril+sitagliptin+aprepitant. We will make similar comparisons within the valsartan- and placebo-treated groups. In addition, we will compare blood pressure and heart rate parameters among the ramipril-treated, valsartan-treated, and placebo-treated groups during comparable concurrent treatment., 4.5 hours on the 7th day of each intervention (placebo, sitagliptin, or sitagliptin+aprepitant)|Norepinephrine (NE) Concentrations, The primary analyses will focus on blood pressure, heart rate, and norepinephrine (NE) concentrations during ramipril versus ramipril+sitagliptin, and during ramipril+sitagliptin versus ramipril+sitagliptin+aprepitant. We will make similar comparisons within the valsartan- and placebo-treated groups. In addition, we will compare blood pressure and heart rate parameters among the ramipril-treated, valsartan-treated, and placebo-treated groups during comparable concurrent treatment., 4.5 hours on the 7th day of each intervention (placebo, sitagliptin, or sitagliptin+aprepitant) | Secondary: Low Frequency Variability of Blood Pressure Activity, Low frequency variability of systolic blood pressure will be measured using spectral analysis., for 5 minutes on the 7th day of each intervention (placebo, sitagliptin, sitagliptin+aprepitant)|Glucose, measure of effectiveness of DPP4 inhibitor, fasting at 3 hours on the 7th day of each intervention (placebo, sitagliptin, sitagliptin+aprepitant)|Insulin, Measure of insulin resistance., fasting insulin measured at 3 hours on the 7th day of each intervention (placebo, sitagliptin, sitatliptin+aprepitant)|Dipeptidyl Peptidase IV (DPP4) Activity, Measure of DPP4 inhibitor administration., for 4.5 hours on the 7th day of each intervention (placebo, sitagliptin, sitagliptin+aprepitant)|Angiotensin Converting Enzyme (ACE) Activity, This is a measure of activity of the angiotensin-converting enzyme (ACE). The assay is a kinetic assay (Labcore) that measures the rate of cleavage of an added ACE substrate over time and the results are reported in Units, which represent the rate of increase in fluorescent metabolite over 30 minutes under standard conditions at 37C., for 4.5 hours on the 7th day of each intervention (placebo, sitagliptin, sitagliptin+aprepitant)|Mean Arterial Blood Pressure, Average of measurements made every five minutes beginning just prior to (time 0) and for four hours after the ingestion of a mixed meal, Value provided is the AVERAGE of measurements made every five minutes prior to (time 0) and for four four hours after ingestion of a mixed meal.|Heart Rate, The average of measurements made every five minutes prior to (time 0) and for four four hours after ingestion of a mixed meal, Value provided is the average of measurements made every five minutes prior to (time 0) and for four four hours after ingestion of a mixed meal.|Neuropeptide Y, Measurement of Neuropeptide Y (NPY) concentrations, Neuropeptide Y concentration prior to ingestion of the mixed meal.|24hr Urinary Testing for Sodium, Subjects will collect 24hr urine sample and bring with to the study day for analysis, Urine was collected for sodium for 24 hrs prior to each of the study days listed below. Study days occurred after each 7-day treatment arm (placebo/placebo, sitagliptin/placebo, or sitagliptin/aprepitant) within 3 anti-hypertensive groups. | Other: Aldosterone, Angiotensin II, and Plasma Renin Activity (PRA), renin-angiotensin system measurements were not done because there were not significant differences in blood pressure, for 4.5 hours on the 7th day of each intervention
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