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The Relationship Between Body Composition and Growth Hormone, SIRT Signaling, Protein Turnover and Insulin Sensitivity

This study has been completed.
Aarhus University Hospital
Information provided by (Responsible Party):
University of Aarhus Identifier:
First received: January 21, 2011
Last updated: May 23, 2014
Last verified: May 2014
The purpose of this study is to investigate signaling pathways in fat and muscle, as well as turnover of protein, sugar and fat after stimulation with growth hormone and during fasting in lean and obese subjects. This will help clarify differences in the human metabolism between lean and obese subject and provide us with a better understanding of the molecular mechanisms regulating the basic metabolism during prolonged fasting.

Condition Intervention
Behavioral: 72 hour fast
Behavioral: control, 12 hour fast
Drug: Growth hormone
Drug: Olbetam

Study Type: Interventional
Study Design: Allocation: Randomized
Intervention Model: Crossover Assignment
Masking: Open Label
Primary Purpose: Basic Science
Official Title: THE RELATIONSHIP BETWEEN BODY COMPOSITION AND GROWTH HORMONE, SIRT SIGNALING, PROTEIN TURNOVER AND INSULIN SENSITIVITY. Studies of Signaling Pathways in Fat and Muscle, and Turnover of Protein, Sugar and Fat After Stimulation With Growth Hormone and During Fasting in Lean and Obese Subjects

Resource links provided by NLM:

Further study details as provided by University of Aarhus:

Primary Outcome Measures:
  • Measurements of changes in metabolism [ Time Frame: 6 hours ]
    Measurements of the switch to lipid metabolism during fasting in lean and obese human subjects.

Secondary Outcome Measures:
  • Signaling pathways in muscle and fat tissue involved in regulation of metabolism [ Time Frame: 6 hours ]
    Protein and gene-exspression, phosphorylation and acetylation of specific proteins involved in lipid-, glucose and protein metabolism.

Enrollment: 19
Study Start Date: January 2011
Study Completion Date: December 2013
Primary Completion Date: December 2013 (Final data collection date for primary outcome measure)
Arms Assigned Interventions
Experimental: 72 hour fast Behavioral: 72 hour fast
The participants will be fasting 72 hours prior to the start of the study day, drinking water is allowed.
Experimental: 12 hours fast Behavioral: control, 12 hour fast
The 12 hour fast will be used as a basic metabolic control
Experimental: 12 hour fast, growth hormone bolus Drug: Growth hormone
Genotropin bolus(0,005 mg/kg over 20 min.) will be administered at the beginning of the study day after a 12 hour fast.
Experimental: 72 hour fast, inhibition of lipolysis Drug: Olbetam

The participants will be fasting 72 hours prior to the start of the study day, drinking water is allowed.

During the last 12 hours of fasting and the study day lipolysis will be inhibited with one tablet of olbetam 250 mg every 4 hours.

Detailed Description:

In an evolutionary context, it is likely that "inherited" obesity provides a survival advantage when there are shortages of food, but also increases the risk of lifestyle diseases in times of prosperity. This may explain the high incidence of obesity, diabetes and cardiovascular disease in the western world today. Obese individuals have high levels of free fatty acids (FFAs) in the blood and FFAs are both protein sparing (giving an evolutionary survival advantage) but also cause increased insulin resistance (which increases the risk of diabetes and cardiovascular disease). Obesity also leads to low growth hormone (GH)-levels, whereas fasting is accompanied by high GH- and FFA-levels and increased IGF-I mRNA in muscle. It is likely that obese individuals are more capable of fasting than lean individuals and will lose less protein during fasting, have increased activation of GH signaling and altered activation of other signaling proteins. And obese individuals are likely to be more sensitive to growth hormone than lean individuals based on FFA-responses, intracellular signaling, protein loss and insulin sensitivity.

We would like to test 3 hypotheses: (1) Obese individuals are more capable of fasting than lean individuals and will lose less protein during fasting (2) Activation of lipolysis is an important prerequisite for limiting protein loss during fasting in both slim as obese individuals. (3) Obese individuals are more sensitive to growth hormone than lean individuals based on FFA responses and activation of intracellular signals. The hypotheses are tested in 8 lean and 8 obese healthy young men, who are studied 4 times: (i) after 12 hours of fasting (ii) after 72 hours of fasting (iii) after GH-bolus (0.005 mg/kg over 20 min.) and (iv) after 72 hours of fasting with inhibition of fat metabolism (tablet acipimox 250 mg every 4 hours) during the last 12 hours of fasting and during the study period.

Each study period consists of a 4-hour basal period and a 2 hour hyperinsulinemic euglycemic clamp (30 mU/m2/min). Muscle- and fat-biopsies are taken and analyzed for enzyme expression and activation of various signaling pathways. The study subjects are given glucose-, amino acid-, urea- and palmitate-tracers and specific hormones and metabolites are measured for assessment of underlying molecular mechanisms regulating the basic human energy metabolism.


Ages Eligible for Study:   20 Years to 35 Years   (Adult)
Sexes Eligible for Study:   Male
Accepts Healthy Volunteers:   Yes

Inclusion Criteria:

  • healthy lean (BMI19-25) and healthy obese (BMI 32-40) men
  • written consent before study start

Exclusion Criteria:

  • known medical conditions
  • any medication
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Please refer to this study by its identifier: NCT01299831

Department of medical endocrinology, University Hospital of Aarhus
Aarhus, Denmark, 8000
Sponsors and Collaborators
University of Aarhus
Aarhus University Hospital
  More Information

Responsible Party: University of Aarhus Identifier: NCT01299831     History of Changes
Other Study ID Numbers: M-2010082
Study First Received: January 21, 2011
Last Updated: May 23, 2014

Additional relevant MeSH terms:
Insulin Resistance
Glucose Metabolism Disorders
Metabolic Diseases
Hormones, Hormone Substitutes, and Hormone Antagonists
Physiological Effects of Drugs
Hypoglycemic Agents
Hypolipidemic Agents
Molecular Mechanisms of Pharmacological Action
Lipid Regulating Agents processed this record on April 27, 2017