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Growth Hormone as a Determinant of Weight Regulation

This study has been completed.
Sponsor:
Collaborator:
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Information provided by (Responsible Party):
JEFFREY F HOROWITZ, University of Michigan
ClinicalTrials.gov Identifier:
NCT00355784
First received: July 24, 2006
Last updated: December 2, 2015
Last verified: December 2015
  Purpose
With the alarming increase in the prevalence of obesity, identifying factors that predispose individuals to weight-gain is of critical importance. Even when caloric intake and physical activity levels are well controlled, susceptibility for weight-gain is heterogeneous. Basal metabolic rate (BMR) represents the largest portion of daily energy expenditure in normal adults, and as such, variability in BMR among individuals can be a major factor in determining the susceptibility for gaining weight. However, factors responsible for this variability in BMR and resistance to weight-gain remain unclear. Our preliminary data indicate that high-normal growth hormone (GH) concentration is associated with resistance to weight-gain in rats when overfed and greater weight-loss in humans when underfed. In addition, the investigators have found that the pulsatility of GH secretion has profound effects on several metabolic processes. Therefore, together these findings suggest that endogenous GH secretion is associated with body weight regulation, and the pulsatility (peak amplitude) of GH secretion, rather than the absolute GH concentration, per se, may be responsible for this effect. Because GH influences many of the key metabolic processes that contribute to BMR (e.g.; protein synthesis, proteolysis, substrate cycling), the investigators anticipate that the resistance to weight-gain in persons with elevated GH concentrations will be associated with an increase in BMR due to acceleration of some or all of these processes. Our overall hypothesis is that increased GH secretion can protect against weight-gain due to an augmentation of major metabolic processes that contribute to BMR. Identifying factors responsible for predisposing individuals to weight-gain will lead to establishing improved methods for reducing the prevalence of obesity.

Condition Intervention
Obesity Other: overfeeding Drug: growth hormone treatment

Study Type: Interventional
Study Design: Allocation: Randomized
Intervention Model: Parallel Assignment
Masking: None (Open Label)
Primary Purpose: Diagnostic
Official Title: Growth Hormone as a Determinant of Weight Regulation.

Resource links provided by NLM:


Further study details as provided by JEFFREY F HOROWITZ, University of Michigan:

Primary Outcome Measures:
  • 24 Hour Average Plasma Growth Hormone Concentration [ Time Frame: 2 weeks ]
  • Changes in Body Weight [ Time Frame: 2 weeks ]
  • Baseline Whole Body Protein Turnover [ Time Frame: baseline ]
    Whole body proteolytic rate (Leucine Ra)

  • Baseline Skeletal Muscle Protein Synthesis [ Time Frame: baseline ]
    after an overnight fast

  • Lipolytic Rate [ Time Frame: 2 weeks ]
  • Whole Body Protein Turnover After 2 Week Intervention [ Time Frame: 2 weeks ]
    whole body proteolytic rate (leucine Ra)

  • 2 Week Skeletal Muscle Protein Synthesis [ Time Frame: 2 weeks ]
    after an overnight fast

  • Changes in Fat Mass [ Time Frame: 2 weeks ]
  • Changes in Fat-free Mass [ Time Frame: 2 weeks ]

Enrollment: 24
Study Start Date: September 2005
Study Completion Date: December 2015
Primary Completion Date: December 2011 (Final data collection date for primary outcome measure)
Arms Assigned Interventions
Control
9 non-obese (initial body mass index 23.5 +/- 0.3 kg/m2), weight stable, relatively sedentary (physical activity </- 2h/week), healthy adults not taking any medications were admitted to the hospital for 2 weeks during which time they ate ~4000 kcal/day and their plasma growth hormone concentration was allowed to decline naturally.
Other: overfeeding
overfeeding 2000kcals/day above energy requirements for 14d
Experimental: Growth Hormone Treatment
8 non-obese (initial body mass index 23.5 +/- 0.3 kg/m2), weight stable, relatively sedentary (physical activity </- 2h/week), healthy adults not taking any medications were admitted to the hospital for 2 weeks during which time they ate ~4000 kcal/day and received exogenous growth hormone treatment administered in 4 daily injections to mimic physiological growth hormone secretion throughout the 2-week overeating period.
Other: overfeeding
overfeeding 2000kcals/day above energy requirements for 14d
Drug: growth hormone treatment
growth hormone administrated for 2 weeks (dose = 1.0 mg/m2/d)
Experimental: High Growth Hormone Treatment
5 non-obese (initial body mass index 23.5 +/- 0.3 kg/m2), weight stable, relatively sedentary (physical activity </- 2h/week), healthy adults not taking any medications were admitted to the hospital for 2 weeks during which time they ate ~4000 kcal/day and received a relatively high daily dose of growth hormone.
Other: overfeeding
overfeeding 2000kcals/day above energy requirements for 14d
Drug: growth hormone treatment
growth hormone administrated for 2 weeks (dose = 1.0 mg/m2/d)

Detailed Description:
The susceptibility to gain weight is highly variable even when caloric intake and physical activity are well controlled. Because basal metabolic rate (BMR) represents ~70% of total daily energy expenditure (TDEE), even a small difference in BMR can affect daily energy balance, thereby increasing the susceptibility for gaining weight. Our preliminary data indicate that high-normal growth hormone (GH) secretion is associated with resistance to weight-gain in rats when overfed and greater weight-loss in humans when underfed. Given that GH influences many of the key metabolic processes that contribute to BMR, the investigators hypothesize that persons with high-normal GH will be resistant to weight-gain because of a high BMR, resulting from accelerated rates of these processes. The investigators will measure basal 24h GH secretion and BMR in 106 non-obese men and women. The investigators will also measure protein synthesis, proteolysis, triglyceride/fatty acid cycling (all measured using stable isotope tracer methods) to determine the relationships among these processes, BMR, and GH [Specific Aim 1]. Subjects identified as having "low-normal" (<1.5 ug/L) and "high-normal" (>3 ug/L) 24h GH will then be admitted to the hospital for a 2 wk overfeeding protocol (~2000 kcal/d >TDEE - with restricted physical activity), immediately followed by a 4 wk caloric restriction protocol (~750 kcal/d <TDEE) to compare changes in weight, body composition and intra-abdominal adiposity between these groups that differ markedly in their GH secretion (GH measured before the diet) [Specific Aim 2]. A subset of subjects with low-normal GH will receive intravenous GH throughout the 2 wk overfeeding period at either: 1. a constant rate or 2. as a pulsatile infusion (to mimic endogenous secretion). BMR will be assessed daily and protein synthesis, proteolysis, and triglyceride/fatty acid cycling will be measured at the end of the 2 wks [Specific Aim 3]. The investigators anticipate that a higher GH pulsatility (peak amplitude), rather than elevated GH concentration, per se, will increase protein synthesis, proteolysis, and triglyceride/fatty acid cycling with a resultant increase in BMR and resistance to weight-gain. Identifying factors responsible for predisposing individuals to weight-gain will help combat the alarming rise in the prevalence of obesity.
  Eligibility

Ages Eligible for Study:   18 Years to 35 Years   (Adult)
Sexes Eligible for Study:   All
Accepts Healthy Volunteers:   Yes
Criteria

Inclusion Criteria:

Age = 21-35 years Weight stable (< ± 5 pound over past 6 months) Premenopausal (women only) Body mass index 18 - 26 kg/m2 Must be willing to be randomized to receive GH infusion during 2 week Michigan Clinical Research Unit (MCRU) visit

Exclusion Criteria:

  • Evidence of metabolic or cardiovascular disease Pregnancy (women only) Hyperlipidemia (fasting plasma triglyceride concentration > 150 mg/dl) Hematocrit < 34% Liver Function test abnormalities participating in a regular exercise program (> 2 h/week) taking any prescription medication (except birth control)
  Contacts and Locations
Choosing to participate in a study is an important personal decision. Talk with your doctor and family members or friends about deciding to join a study. To learn more about this study, you or your doctor may contact the study research staff using the Contacts provided below. For general information, see Learn About Clinical Studies.

Please refer to this study by its ClinicalTrials.gov identifier: NCT00355784

Locations
United States, Michigan
University of Michigan
Ann Arbor, Michigan, United States, 48109
Sponsors and Collaborators
University of Michigan
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Investigators
Principal Investigator: Jeffrey F. Horowitz, PhD University of Michigan
  More Information

Responsible Party: JEFFREY F HOROWITZ, Associate Professor, Movement Science, School of Kinesiology, University of Michigan
ClinicalTrials.gov Identifier: NCT00355784     History of Changes
Other Study ID Numbers: R01DK071955-01 ( U.S. NIH Grant/Contract )
R01DK071955 ( U.S. NIH Grant/Contract )
Study First Received: July 24, 2006
Results First Received: March 13, 2013
Last Updated: December 2, 2015

Keywords provided by JEFFREY F HOROWITZ, University of Michigan:
growth hormone
overfeeding
energy expenditure
protein metabolism
lipid metabolism

Additional relevant MeSH terms:
Hormones
Hormones, Hormone Substitutes, and Hormone Antagonists
Physiological Effects of Drugs

ClinicalTrials.gov processed this record on September 21, 2017