Hemodynamics, Salt Sensitivity and Body Composition in Patients With Morbid Obesity
Condition: Obesity; Hypertension
MeSH terms: Hypertension; Obesity; Obesity, Morbid; Hypersensitivity
Study type: Observational

Summary: 
      The purpose of this study is to evaluate the effect of high vs. low sodium intake on blood
      pressure and system hemodynamics in patients with morbid obesity and to evaluate the impact
      of laparoscopic gastric bypass on blood pressure, salt sensitivity and body composition in
      morbidly obese patients. Furthermore, we wants to describe the hemodynamic mechanisms
      involved in the amelioration of blood pressure during long-term weight loss.
    

Detailed description: 
      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 indicated that blood pressure of obese
      patients could be more dependent on dietary sodium intake than the blood pressure of
      non-obese patients(as it is the case for patients with essential hypertension)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 effect of high vs. low sodium intake on blood
      pressure and system hemodynamics in patients with morbid obesity and to evaluate the impact
      of laparoscopic gastric bypass on blood pressure, salt sensitivity and body composition in
      morbidly obese patients. Furthermore, we wants to describe the hemodynamic mechanisms
      involved in the amelioration of blood pressure during long-term weight loss. Therefore,
      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.

      The protocol comprise three sub studies:

        1. The effect of high vs low sodium intake on blood pressure and hemodynamics in the morbid
           obese patient - preoperative study.

        2. Effect of gastric bypass surgery on blood pressure, hemodynamics and salt-sensitivity -
           1 year follow-up.

        3. Effect of gastric bypass surgery on echocardiographic parameters - 1 year follow-up.
    

Intervention name(s): 24-hour blood pressure; Echocardiography; Inert gas rebreathing; Dexa-scan; Plasma volume; Glomerular filtration rate (GFR); Blood samples; Urine analyses; Diets with low and high sodium content
Intervention type(s): Other; Other; Other; Radiation; Radiation; Radiation; Other; Other; Dietary Supplement
Intervention description(s): Blood pressure is measured every 15 minutes in the daytime and every 30 minutes at night; Standard 2-D and m-mode echocardiography with determination of dimensions, systolic, and diastolic function.; 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); 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.; The test is performed using 5 MBq technetium-labeled albumine (99mTc-albumine - Vasculosis) with several postinjection samples for accurate zero-time extrapolation.; GFR and ECV are determined following injection of 3,7 MBq 51Cr-EDTA and postinjection samples three-four hours after injection.; p-glucose, p-insulin, NT-proBNP, hemoglobin, potassium, sodium, creatinine, albumine; 24-hour urine collections with determination of u-sodium, u-potassium and u-creatinine.; Participants are subjected to 5 days of low (90 mmol/day) and high (250 mmol/day) sodium intake in a randomized order before and 1 year after laparoscopic gastric bypass surgery.
Observational model: Case-Control
Time perspective: Cross-Sectional
Sampling method: Non-Probability Sample
Study population: 
        The cases are recruited from the Bariatric Clinics at Glostrup Hospital, Koege Hospital and
        The Private Hospital Hamlet.

        Controls are recruited through public advertisement
      
Biospecimen description: 
      Blood samples: p-glucose, p-insulin, MR-proANP, hemoglobine, sodium, potassium, creatinine,
      albumine.

      Urine collections: u-sodium, u-potassium, u-creatinine
    
Keywords: Obesity; Hypertension; Salt sensitivity; Laparoscopic gastric bypass; Bariatric surgery