Obesity-induced Hyperfiltration Clinical Trial
Official title:
Effect of Acetazolamide and Furosemide on Obesity-induced Glomerular Hyperfiltration
Background:
Obesity is associated with a high prevalence of chronic kidney disease.The glomerular
hyperfiltration associated with obesity may play a role in the pathogenesis of obesity
associated chronic kidney disease. Attenuation of hyperfiltration by pharmacological means
may slow down the development and progression of chronic renal failure. The investigators
have previously shown that acetazolamide, a proximally acting diuretic that activates
tubuloglomerular feedback(TGF) by increasing solute delivery to the Macula DENSA, abates
glomerular hyperfiltration. The present study was designed to test the hypothesis that this
decrease in hyperfiltration is specific to acetazolamide and not due to a non specific
diuretic effect. The aim of the present study is to compare the effects of furosemide and
acetazolamide on glomerular hemodynamics in subjects with severe obesity.
Methods:
A randomized double-blind crossover controlled design will be used. Fifteen obese subjects
and ten subjects with normal body weight will participate in the study. Obese subjects will
undergo measurement of glomerular filtration rate (GFR)(inulin clearance), renal plasma flow
(RPF) (p-aminohippuric acid clearance), filtration fraction, fractional excretion of lithium
(FE LI) and blood pressure, before and after intravenous administration of furosemide 2 mg.
and acetazolamide 5 mg/kg BW. Ten subjects with normal body weight will undergo measurement
of renal function without administration of diuretics.
BACKGROUND Almost half of the causes of death in the industrial world are due to
cardio-vascular (CV) disease. Two of the main risk factors for CV disease have become much
more prevalent during the last decades, reaching epidemic dimensions in the 21st century:
hypertension and obesity. In 2003-2004, 66% of the adult USA population had a body mass
index(BMI)over 25, while 32% had a BMI over 30 .Hypertension is more prevalent in obese than
in lean subjects .The cause and effect relationship between these two conditions is
supported by the fact that weight loss is associated with a decrease in blood pressure .
Salt retention by the kidney is one of the important mechanisms involved in the pathogenesis
of hypertension in obesity. Studies in animal models and in humans showed that increased
salt reabsorption occurs in the tubules in obesity. Another renal functional abnormality
occurring in obesity is glomerular hyperfiltration, characterized by increased renal plasma
flow (RPF) and increased glomerular filtration rate(GFR) up to twice the normal level . The
structural basis to these functional abnormalities is renal hypertrophy and glomerular
enlargement.
These functional and structural abnormalities have deleterious consequences:
1. Increased urinary albumin excretion. Microalbuminuria, an important risk factor for CV
disease, has a high prevalence in obese subjects .
2. Increased risk for the development of focal segmental glomerulosclerosis, the so-called
obesity related glomerulopathy. The incidence of this disease has multiplied 10 times
within 15 yrs in the USA .
3. Increased rate of progression of chronic renal insufficiency in kidney disease not
primarily caused by obesity. Following initial glomerular damage from any cause, the
number of remnant functioning glomeruli decreases. The consequent compensatory increase
in single nephron filtration rate of these remnant glomeruli leads to further
glomerular damage in kidney disease not related to obesity . In the obese with chronic
renal damage, the obesity related hyperfiltration amplifies the compensatory
augmentation in single nephron GFR of remnant nephrons, thus worsening glomerular
damage, irrespective of the cause of the primary insult.
The clinical relevance of these abnormalities is reflected in the sharp increase in the risk
of developing end stage renal disease in the obese. This relative risk, independently of
confounders as diabetes mellitus, hypertension and dyslipidemia, is 3 to 5 depending on the
severity of obesity .
Considering the role of hyperfiltration in the pathogenesis of chronic kidney disease (CKD)
in the obese, attenuation of hyperfiltration by pharmacological means may slow down the
development and progression of chronic renal failure. One of the tools available is
activating tubuloglomerular feedback (TGF). Tubuloglomerular feedback (TGF) refers to the
alterations in GFR that can be induced by changes in tubular flow rate. An increase in the
delivery of chloride to the Macula DENSA results in a reduction in GFR, resulting in a
decrease in the tubular flow rate delivered to the Macula DENSA. An increase in chloride
delivery to the Macula DENSA can be obtained by administrating acetazolamide, a diuretic
acting on the proximal tubule. We have previously shown that administration of acetazolamide
to obese subjects results in attenuation of glomerular hyperfiltration.
The aim of the present study is to show that the effect of acetazolamide on GFR is specific
and not due to its diuretic effect. We will study the effects of furosemide, a diuretic
which does not activate TGF ,on GFR and RPF in obese subjects in comparison with
acetazolamide.
Methods:
A 24-hour urine collection will be performed during the week prior to the renal function
test studies for assessment of sodium intake.
Obese subjects: A randomized double-blind crossover controlled design will be used. Two
renal function studies will be performed: one before and after intravenous furosemide and
the second before and after intravenous acetazolamide. Subjects will receive 300 mg of
lithium carbonate at 22.00 the day before the renal function tests. They will be instructed
to drink 250 ml of water at bedtime. Renal function tests will start at 08.00 a.m. after a
10-hour fast, excepting a drink of 250 ml of water at 07.00 a.m. Intravenous catheters will
be placed in each upper limb for infusion of clearance markers and blood sampling. After
blood sampling for urea, creatinine, proteins, glucose, electrolytes, blood gases, insulin,
renin, aldosterone, Hba1c, CBC. A priming dose of inulin (50 mg/kg) and p-aminohippuric acid
(8 mg/kg) will be administered and a 200-300 ml p.o water load will be given. Thereafter,
inulin and p-aminohippuric acid will be infused continuously. After the first 60 minutes, 8
accurately timed urine collections of 30 to 40 minutes will be obtained by spontaneous
voiding. Peripheral venous blood will be drawn to bracket each urine collection. Arterial
pressure will be measured by a trained observer, after 30 minutes of rest in the supine
position, using an electronic oscillometric blood pressure measuring device. The cuff will
be appropriately sized to the diameter of the arm and the arm positioned at the heart level.
At least 8 measurements will be performed during the study, each measurement being the mean
of 3 readings. After the first 4 timed urine collections, participants will receive
intravenous furosemide 2 mg/5min or intravenous acetazolamide 5 mg/kg/5 min. Four other
times urine collections will be performed thereafter. Subjects will be randomized to receive
during the first study either furosemide or acetazolamide. The second study will be
performed one to two weeks after the first study, using the drug that had not administrated
during the first study.
Subjects with normal body weight: will undergo measurement of renal function without
administration of diuretics (one renal function study, same protocol like obese subjects,
with 4 urine collections only).
Laboratory procedures: Plasma and urinary concentrations of inulin and p-aminohippuric acid
will be analyzed by colorimetric methods .Lithium in serum and urine will be measured .
Urine microalbumin will be determined by competitive chemiluminescent enzyme immunoassay .
Calculations: GFR will be determined from the average value for the timed inulin clearances,
and renal plasma flow (RPF) - from the average value for the timed p-aminohippurate
clearances. The fractional excretion of lithium (FE Li) will be calculated as lithium
clearance / GFR, using two timed urine collections. FE Li will be determined as the average
value for these two measurements Statistical Analysis: The significance of differences
between groups will be evaluated by paired and unpaired two-tailed Student's t-test. The
Student's t-test will be applied to non-normally distributed data (albumin excretion rate
and fractional lithium excretion) after log transformation. P<0.05 will be considered as
significant. The response to treatment with furosemide will be compared to the response to
treatment with acetazolamide using ANOVA.
;
Allocation: Randomized, Endpoint Classification: Efficacy Study, Intervention Model: Crossover Assignment, Masking: Double Blind (Subject, Caregiver, Investigator, Outcomes Assessor), Primary Purpose: Treatment
| Status | Clinical Trial | Phase | |
|---|---|---|---|
| Terminated |
NCT00962286 -
Effect of Furosemide on Obesity-induced Glomerular Hyperfiltration
|
N/A |