FFA-Induced Hypertension and Endothelial Dysfunction

Not Applicable

Completed

Conditions: Endothelial Dysfunction
Hypertension

Interventions: Drug: Intralipid 20%@ 40cc/hour
Drug: Intralipid 20% @ 20cc/hour
Dietary Supplement: 64-gram oral fat load
Drug: Normal Saline
Dietary Supplement: 32-gram oral fat load

Registration Number: NCT00589888

Lead Sponsor: Emory University

Brief Summary: The study is a prospective open label study to examine the effects of oral and intravenous fat load on blood pressure, endothelial function, sympathetic activity, and oxidative stress in obese healthy subjects. Subjects will receive either 8-hour of intravenous or oral fat loads in either low or high doses or normal saline in random order. Blood samples are drawn and vitals are measured before and after the infusions. Endothelial function and plasma glucose and lipid levels are measured to study the effects.

Detailed Description: Insulin resistance has been implicated as the central mechanism in the development of several cardiovascular risk factors including hypertension, diabetes, lipid disorders, and coagulation disorders. Recent evidence suggests that increased levels of a circulation fat (free fatty acids or FFAs) are a leading candidate causing insulin resistance. Our preliminary studies in indicate that, in addition to insulin resistance, the infusion of Intralipid and heparin to increase FFAs resulted in a significant rise in systolic and diastolic blood pressure, impaired endothelial (vascular) function, and increased inflammatory markers in obese African Americans with and without diabetes. The effects of FFA on insulin action are well established; however, the blood pressure and vascular effects of FFAs infusion in obese subjects have not been fully investigated. We hypothesize that observed changes in blood pressure are the result of acute endothelial dysfunction, and/or increased activation of the autonomic nervous system. No previous studies have attempted to determine a dose response effect of increasing FFA on blood pressure. In addition, it is not know if increased FFAs by repeated oral fat load results in similar blood pressure than intravenous lipid infusion. Accordingly, we propose: 1) a systematic evaluation of the effects of increasing FFA levels on blood pressure and endothelial (vascular) function, and 2) determine the effects of comparable increases in FFA concentration via intravenous infusion of Intralipid or by repeated oral fat load on blood pressure, insulin resistance and endothelial dysfunction in obese subjects.

A group of obese normotensive subjects will be admitted to the Grady Clinical Research Center or to the Outpatient Research Unit in the Grady Diabetes Clinic on five occasions. In four of these admissions, research subjects will receive an 8-hour intravenous infusion, in random order, of increasing Intralipid concentration (10 ml, 20 ml, 40 ml per hour) or normal saline (40 ml per hour). During the final admission, research subjects will receive an oral liquid fat diet every 2 hours for 8-hours. The effect of increased FFAs on blood pressure and endothelial (vascular) function via intravenous infusion and via oral fat load therapy will be assessed.

Recruitment & Eligibility

Status: COMPLETED

Sex: All

Target Recruitment: 13

Inclusion Criteria

Males or females between the ages of 18 and 65 years.
Definition: obese = BMI ≥ 30 kg/m2
Blood pressure < 140/80 mm Hg and no prior history of hypertension

Exclusion Criteria

History of hypertension or previous history of antihypertensive drug therapy.
Current tobacco use
Fasting triglyceride levels > 250 mg/dL during the stabilization period.
Liver disease (ALT 2.5x > upper limit of normal), or other significant medical or surgical illness, including myocardial ischemia, congestive heart failure, liver failure, and infectious processes.
Serum creatinine ≥1.5 mg/dL for males, or ≥ 1.4 mg/dL for females.
History of drug or alcohol abuse within the last 5 years.
Mental condition rendering the subject unable to understand the nature, scope, and possible consequences of the study.
Female subjects are pregnant or breast feeding at time of enrollment into the study.

Study & Design

Study Type: INTERVENTIONAL

Study Design: CROSSOVER

Arm && Interventions

Group	Intervention	Description
Intralipid 20% @ 40cc/hour	Intralipid 20%@ 40cc/hour	Intralipid 20% IV infusion at 40cc/hour
Intralipid 20%@ 20cc/hour	Intralipid 20% @ 20cc/hour	Intralipid 20% IV infusion at 20cc/hour
64-gram oral fat load	64-gram oral fat load	64-gram oral fat load once
Normal Saline infusion @ 40cc/hour	Normal Saline	Normal Saline continuous IV infusion at 40cc/hour for 8 hours
32-gram oral fat load	32-gram oral fat load	32-gram oral fat load once

Primary Outcome Measures

Name	Time	Method
Change in Systolic Blood Pressure From Baseline to After Completing an Oral 32-gram Fat Load in Obese Normotensive Subjects.	Baseline and at the end of the 8-hours	To study the effects of oral low dose fat load on systolic blood pressure (SBP) in healthy obese subjects, subject's baseline SBP is compared to SBP after the infusion. Blood Pressure (BP) was measured with a manual cuff in triplicate on admission when patient was in Supine position.The Blood pressure was measured at admission and at end of the fat load. The BP from the admission are compared to BP after the fat load. A normal systolic blood pressure is lower than 120 mmHg; elevated blood pressure if the systolic reading is 120-129 mmHg. A level above 140 mmHg is considered hypertension.
Change in Systolic Blood Pressure to After Completing an 8-hour Normal Saline Infusion in Obese Normotensive Subjects.	Baseline and at the end of the 8-hours	To study the effects of high dose oral fat load on systolic blood pressure (SBP) in healthy obese subjects, subject's baseline SBP is compared to SBP after the infusion. Blood Pressure (BP) was measured with a manual cuff in triplicate on admission when patient was in Supine position. The Blood pressure was measured at admission and at end of the fat load. The BP from the admission are compared to BP after the fat load. A normal systolic blood pressure is lower than 120 mmHg; elevated blood pressure if the systolic reading is 120-129 mmHg. A level above 140 mmHg is considered hypertension.
Change in Systolic Blood Pressure From Baseline to After Completing an 8-hour 20% Intralipid @ 20cc/hr Infusion in Obese Normotensive Subjects.	Baseline and at the end of the 8-hours	To study the effects of low dose intravenous (IV) fat infusion on systolic blood pressure (SBP) in healthy obese subjects, subject's baseline SBP is compared to SBP after the infusion. Blood Pressure (BP) was measured with a manual cuff in triplicate on admission when patient was in Supine position. The Blood pressure was measured at admission and at every 2 hours till the end of infusion. The BP from the admission are compared to BP after the infusion.A normal systolic blood pressure is lower than 120 mmHg; elevated blood pressure if the systolic reading is 120-129 mmHg. A level above 140 mmHg is considered hypertension.
Changes in Systolic Blood Pressure From Baseline to After Completing an 8-hour 20% Intralipid @ 40cc/hr Infusion in Obese Normotensive Subjects	Baseline and at the end of the 8-hours	To study the effects of high dose intravenous (IV) fat infusion on systolic blood pressure (SBP) in healthy obese subjects, subject's baseline SBP is compared to SBP after the infusion. Blood Pressure (BP) was measured with a manual cuff in triplicate on admission when patient was in Supine position. The Blood pressure was measured at admission and at every 2 hours till the end of infusion. The BP from the admission are compared to BP after the infusion. A normal systolic blood pressure is lower than 120 mmHg; elevated blood pressure if the systolic reading is 120-129 mmHg. A level above 140 mmHg is considered hypertension.
Changes in Systolic Blood Pressure From Baseline to After Completing an Oral 64-gram Fat Load in Obese Normotensive Subjects	at the end of the 8 hours	To study the effects of high dose oral fat load on systolic blood pressure (SBP) in healthy obese subjects, subject's baseline SBP is compared to SBP after the infusion. Blood Pressure (BP) was measured with a manual cuff in triplicate on admission when patient was in Supine position. The Blood pressure was measured at admission and at end of the fat load. The BP from the admission are compared to BP after the fat load. A normal systolic blood pressure is lower than 120 mmHg; elevated blood pressure if the systolic reading is 120-129 mmHg. A level above 140 mmHg is considered hypertension.

Secondary Outcome Measures

Name	Time	Method
Change in Flow-mediated Dilation (FMD) of Endothelium-dependent Brachial Artery From Baseline to After Completing a Specific Intervention in Obese Normotensive Subjects.	Baseline and at the end of the 8-hours	Endothelium-dependent brachial artery dilatation was assessed as a measurement of endothelial function using established methodology. Briefly, ultrasound images of the brachial artery were obtained at baseline under standardized conditions and 60 s after induction of reactive hyperemia by 5-min cuff occlusion of the forearm. Image landmarks as well as surface markers were utilized to ensure anatomic consistency between serial imaging studies. All images were digitized online, and arterial diameters were measured with customized software by individuals blinded to the clinical and laboratory status of the subjects. Flow-mediated dilatation (FMD) was expressed as the percentage increase in diameter from baseline. It is measured in percentage.
Change in C-peptide Concentration Levels From Baseline to After Specific Intervention Among the Healthy Obese Subjects	baseline and after 8 hours after admission	C-peptide is a peptide composed of 31 amino acids. It is released from the pancreatic beta-cells during cleavage of insulin from proinsulin. It is mainly excreted by the kidney, and its half-life is 3-4 times longer than that of insulin. The reference range of C-peptide is 0. 8-3 ng/ml. The C-peptide test is a tool to monitor and treat diabetes. It shows how well your body makes insulin, which moves sugar (or "glucose") from your blood into your cells.
Change in Blood Glucose Levels From Baseline to 6-8 Hours After Intervention Among Obese Healthy Subjects	Baseline and at the end of the 8-hours	The blood glucose level is the amount of glucose present in the blood of humans. Many factors affect a person's blood sugar level. The body's homeostatic mechanism of blood sugar regulation (known as glucose homeostasis), when operating normally, restores the blood sugar level to a narrow range of about 4.4 to 6.1 mmol/L (79 to 110 mg/dL) (as measured by a fasting blood glucose test). The study aims to study the effects of these interventions on blood glucose levels among obese healthy subjects.
Change in Blood Insulin Levels From Baseline to After Intervention Among the Normal Obese Subjects	Baseline and at the end of the 8-hours	Insulin is an anabolic hormone that promotes glucose uptake, glycogenesis, lipogenesis, and protein synthesis of skeletal muscle and fat tissue through the tyrosine kinase receptor pathway. In addition, insulin is the most important factor in the regulation of plasma glucose homeostasis, as it counteracts glucagon and other catabolic hormones like epinephrine, glucocorticoid, and growth hormone. Normal fasting insulin levels is \< 25 milli-International unit/litre