Hemodynamics, Salt Sensitivity and Body Composition in Patients With Morbid Obesity

Official Title: “Hemodynamics, Salt Sensitivity and Body Composition in Patients With Morbid Obesity - Effect of Weight Loss Following Laparoscopic Gastric Bypass”

The purpose of this study is to evaluate the impact of laparoscopic gastric bypass on blood pressure, salt sensitivity and body composition in morbidly obese patients and to describe the hemodynamic mechanisms involved in the amelioration of blood pressure during long-term weight loss.

Overweight and obesity are rapidly increasing in Western countries and are associated with increased mortality and morbidity. The increased morbidity is assumed to be mediated mainly by insulin resistance, diabetes, hypertension and lipid disturbances, but obesity also represents an independent risk factor for cardiovascular disease.

Obesity is associated with an increased risk of hypertension but the pathophysiological basis is not fully established. Several studies have demonstrated that blood pressure of obese patients is more dependent on dietary sodium intake than the blood pressure of non-obese patients, and that this sodium sensitivity of blood pressure is lost after weight loss.

To date, bariatric surgery is the only therapy resulting in substantial and durable long-term weight loss, and the beneficial effects on obesity-related co-morbidities have been well documented. Laparoscopic gastric bypass results in a remarkable improvement of glucose homeostasis and a resolution of diabetes, that typically occurs too fast to be accounted for by weight loss alone. Furthermore, an immediate reduction of blood pressure following laparoscopic gastric bypass has been demonstrated in morbidly obese patients with hypertension as early as one week after the operation. As with the rapid reduction of diabetes, the antihypertensive effect of the procedure might be a consequence of the rearrangement of the gastrointestinal anatomy.

With this study, we want to evaluate the impact of laparoscopic gastric bypass on blood pressure, salt sensitivity and body composition in morbidly obese patients and we would like to describe the hemodynamic mechanisms involved in the amelioration of blood pressure during long-term weight loss.

Patients are examined before, 4-6 weeks after and one year after laparoscopic gastric bypass.

Before and one year after the operation, the patients are examined two times; in a five days period of a low dietary sodium consumption and in a five days period of a high sodium consumption respectively. Four-six weeks following the operation, the patients are examined once on their usual diet.

Intervention(s) in this Clinical Trial

• Other: 24-hour blood pressure
  • Blood pressure is measured every 20 minutes in the daytime and every 30 minutes at night
• Other: Echocardiography
  • Standard 2-D and m-mode echocardiography with determination of dimensions, systolic, and diastolic function.
• Other: Inert gas rebreathing
  • Cardiac output, stroke volume and total peripheral resistance are tested at rest and during exercise (bicycle ergometer) using non-invasive equipment (inert gas rebreathing - Innocor)
• Radiation: Dexa-scan
  • Fat mass and fat free mass is determined with a whole body Dexa scan, and bone mineral density is tested with Dexa-scans of the lumbar spine and proximal femur.
• Radiation: Plasma volume
  • The test is performed using 5 MBq technetium-labeled albumine (99mTc-albumine - Vasculosis) with several postinjection samples for accurate zero-time extrapolation.
• Radiation: Glomerular filtration rate (GFR)
  • GFR and ECV are determined following injection of 3,7 MBq 51Cr-EDTA and postinjection samples three-four hours after injection.
• Other: Blood samples
  • p-glucose, p-insulin, NT-proBNP, hemoglobin, potassium, sodium, creatinine, albumine
• Other: Urine analyses
  • 24-hour urine collections with determination of u-sodium, u-potassium and u-creatinine.

Arms, Groups and Cohorts in this Clinical Trial

• : Obese, hypertension
  • Obese patients with hypertension and a body mass index 40-50 kg/m2
• : Control
  • Control subjects without hypertension and body mass index < 30 kg/m2

Primary Measures

• 24-hour blood pressure before and one year after laparoscopic gastric bypass.
  • Time Frame: One year
    Safety Issue?: No

Secondary Measures

• Echocardiography: Dimensions, systolic and diastolic function before and one year after laparoscopic gastric bypass
  • Time Frame: One year
    Safety Issue?: No
• Non-invasive hemodynamic measurements (inert gas rebreathing) before and one year after laparoscopic gastric bypass
  • Time Frame: One year
    Safety Issue?: No
• Body composition: Dexa-scan, plasma volume and extracellular volume before and one year after laparoscopic gastric bypass
  • Time Frame: One year
    Safety Issue?: No
• Blood samples: NT-proBNP, p-glucose, p-insulin
  • Time Frame: One year
    Safety Issue?: No

Inclusion Criteria (cases):

• Caucasians fulfilling the criteria for laparoscopic gastric bypass.
• Hypertension, defined as blood pressure > 140/90 and/or use of antihypertensive medication.
• Body mass index 40-50 kg/m2

Inclusion Criteria (controls):

• Caucasian.
• No hypertension or use of antihypertensive medication.
• Body mass index < 30 kg/m2

Exclusion Criteria (all):

• Pregnancy
• Chronic obstructive pulmonary disease
• Diabetes mellitus
• Medical treatment with sibutramine.

Gender Eligibility for this Clinical Trial: Both

Minimum Age for this Clinical Trial: 18 Years

Maximum Age for this Clinical Trial: 70 Years

Are Healthy Volunteers Accepted for this Clinical Trial?: Accepts Healthy Volunteers

Lead Investigator: Roskilde County Hospital Other

Overall Clinical Trial Officials and Contacts

Peter K Bonfils, MD Principal Investigator University Hospital Koege  

Overall Contact: Peter K Bonfils, MD +45 47 32 58 24 pkbo@regionsjaelland.dk

Information obtained from ClinicalTrials.gov on February 02, 2012

Link to the current ClinicalTrials.gov record. http://clinicaltrials.gov/show/NCT00998465

Study ID Number: SJ-99

ClinicalTrials.gov Identifier: NCT00998465

Health Authority: Denmark: The Regional Committee on Biomedical Research Ethics