Growth Hormone as a Model for Reversible Activation of Adipose Tissue Fibrosis

May 25, 2023 updated by: University of Aarhus

Background: Adipose tissue fibrosis denotes excessive pathological accumulation of extracellular matrix (ECM) in adipose tissue and is a marker of dysfunction. Growth hormone (GH) activates adipose tissue lipolysis and stimulates collagen synthesis in lean tissues. Intriguingly, we have novel pilot data to suggest that GH excess (acromegaly) also induces reversible fibrosis in vivo and potently activates the expression of fibroblast activation protein alpha (FAPα).

Hypothesis: GH induces adipose tissue fibrosis by increased FAPα expression together with proliferation and fibrogenic differentiation of fibro-adipogenic progenitor (FAP) cells.

Aim: To unravel the mechanisms underlying GH-induced adipose tissue fibrosis with emphasis on FAPα expression and proliferation of FAP cells.

Subjects and methods: In a single blinded, randomized, double-dummy crossover design, 10 adult, moderately overweight individuals will be subjected to one week of GH and GH receptor blockade (Pegvisomant). We will use single-cell technologies, fluorescence-activated cell sorting (FACS), RNA sequencing, and cell culture studies on adipose tissue samples, combined with in vivo assessment of adipose tissue turnover and metabolism.

Perspectives: Understanding fibrosis formation in human models may identify new targets for treatment of obesity-associated disorders.

Study Overview

Status

Active, not recruiting

Conditions

Intervention / Treatment

Detailed Description

Background and preliminary data: Adipose tissue is a multicellular tissue surrounded by an extracellular matrix, which undergoes continuous remodeling. Pertubations in the remodeling processes may cause accumulation of excess extracellular matrix protein and hence fibrosis. Adipose tissue fibrosis is recognized as a component of the metabolic syndrome together with insulin resistance, dyslipidemia and obesity, and fibrosis is likely to play a causative role (1,2). In this context, it is fascinating that prolonged GH exposure in vivo induces insulin resistance despite a concomitant mobilization and reduction of fat mass (3). This effect of GH is expressed in patients with a GH-producing pituitary tumor (acromegaly) (4). Moreover, GH is a potent activator of collagen turnover and it also promotes fibrosis in human tendons and skeletal muscles (5-7). Increased AT fibrosis has been reported in a GH transgenic mice model (8) and we have preliminary data showing AT fibrosis in patients with active acromegaly, which reverses after disease control.

Little is known about the mechanisms underlying GH-induced fibrosis, but recent evidence points to a potential involvement of FAPα, an enzyme that is highly expressed in mouse AT FAP cells (9). Moreover, we have recently reported that human skeletal muscle FAP cells upregulate FAPα (DPP4) during fibrogenic differentiation (19). FAPα is a subunit of a heterodimeric proteinase complex attached to the cell membrane in addition to a soluble form also present in the circulation (10). Several proteins are recognized as FAPα substrates, including collagen type I (11) and III (12), and FAPα appears to play a significant role in hepatic tissue remodeling (13) and in lung fibrosis (14). We have recently recorded elevated circulating levels of FAPα in active acromegaly, which correlates with collagen turnover reverses after disease control (15). Fibro-adipogenic progenitor cells are mesenchymal progenitors with the intrinsic potential to differentiate into either collagen-producing fibroblasts or adipocytes. They have been studied in murine cardiac and skeletal muscle, where they contribute to either fibrosis or fat deposition during muscle-impaired regeneration or degeneration (16-18). We have recently demonstrated that a subset of FAP cells drives the accumulation of ECM protein and adipocytes in the muscle from patients with type 2 diabetes and likely contributes to the poor metabolic and mechanical muscle function (19). Whether GH affects adipose tissue FAP cell proliferation and differentiation is unknown, but FAP cell proliferation is regulated by IGF-I (16), which is a strongly GH-dependent peptide. Increased FAP proliferation has also been reported to contribute to intramuscular adipose tissue (IMAT) in several conditions, and we have observed IMAT after treatment in acromegaly (unpublished data). Furthermore, we have preliminary data from FACS-isolated adipose tissue FAP cells incubated with serum from acromegaly patients, which suggest GH-dependent increased FAP cell proliferation and fibrogenic appearance. Collectively, these findings suggest that GH promotes a pro-proliferative and fibrogenic FAP phenotype at the expense of adipogenic differentiation.

Hypotheses: Growth hormone: 1) Activates FAPα protein expression, 2) Increases proliferation and fibrogenic differentiation of FAP cells, and 3) Induces reversible fibrosis in adipose tissue in humans

Subjects and methods: In a single blinded, randomized, double-dummy crossover design, 10 adult, moderately overweight individuals will be subjected to one week of GH and GH receptor blockade (Pegvisomant). Pegvisomant is a modfied GH molecule that selectively blocks the GH receptor and is a licensed drug for the treatment of acromegaly. We include Pegvisomant as an 'active control' in order to suppress endogenous GH actions. The participants will receive daily subcutaneous injections of growth hormone, 0.6-2.0 mg depending on age, for 7 days in the GH intervention. In the control intervention, the participants will receive daily subcutaneous injections of either Pegvisomant or saline. Pegvisomant in a dose of 30 mg is given two times, in the beginning and in the end of the control intervention, whereas saline is given on the other 5 days of the control intervention period. The two intervention periods are separated by a wash out period of 1-4 months. The participants will be randomized to either start with the GH intervention and next be subjected to the control intervention, or start with the control intervention and next be subjected to the GH intervention. The participants will meet at the hospital daily for the injections and a small blood sample. Each intervention period is initiated by an initiation day where there will be taken blood samples, adipose tissue and muscle samples, be performed temperature measurements and bioimpedance, and be administered heavy water and the first injection of intervention either GH or control intervention. On the first initiation day a DXA scan will be performed for assessment of body composition. Each intervention period will be terminated with a study day where there will be taken blood samples, adipose tissue and muscle samples, be performed temperature measurements, indirect calorimetry, palmitate tracer kinetics and bioimpedance, and be administered the last injection of intervention either GH or control intervention. The participants will be fasting for the initiation and study days, and during the intervention periods, they will log their intake of food and beverages.

Study outcomes:

Primary: FAP cell function, FAPα protein expression and markers of fibrosis in AT biopsies obtained before and after intervention. In particular, we will perform:

  • FACS to quantify and isolate cell populations, including quantification of FAP cells in adipose tissue, and in vitro determination of proliferation and fibro-/adipogenic differentiation potential
  • FAPα expression in blood and adipose tissue
  • Markers of fibrosis in adipose tissue assessed by light microscopy and immunohistochemically, RNA sequencing and heavy water labeled connective tissue turnover

Secondary: to study the impact of GH exposure on:

  • Circulating biomarkers of collagen turnover (PINP, PIIINP)
  • Whole body energy metabolism and fatty acid turnover (indirect calorimetry and palmitate tracer kinetics)
  • Connective tissue turnover in muscle tissue (heavy water (D2O) labeling)
  • Temperature measurements

Statistical analysis plan: Comparison between groups will be performed using standard statistical methods (t-test or equivalent nonparametric test). Within group comparison will be performed using paired t-test of equivalent nonparametric test. Moreover, ANOVA (repeated measures) will be used. A p-value less than 0.05 will be regarded as statistically significant.

Perspective and relevance: This is the first study to investigate GH effects on adipose tissue fibrosis in humans, which has implications beyond GH pathophysiology. A deeper understanding of the pathways controlling fibroblast and adipocyte balance in fat tissue is essential groundwork and may unravel new targets for combating adipose tissue dysfunction and related disorders. As recently demonstrated in type 2 diabetic patients these progenitor cells are key mediators of tissue plasticity and function in humans (19).

Study Type

Interventional

Enrollment (Estimated)

10

Phase

  • Not Applicable

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Locations

  • Denmark
      • Aarhus, Denmark, DK-8200
        • Aarhus University

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Ages Eligible for Study

18 years to 50 years (Adult)

Accepts Healthy Volunteers

Yes

Description

Inclusion Criteria:

  • Written and oral consent before enrollment
  • Legally competent subjects
  • Healthy (except uncomplicated hypertension and hypercholesterolemia)
  • Male sex
  • Age ≥ 18 years and ≤ 50 years
  • BMI 25-35

Exclusion Criteria:

  • Any condition which the investigator considers might affect the participant's ability to complete the study
  • Known of presumed acute of chronic illness

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

  • Primary Purpose: Basic Science
  • Allocation: Randomized
  • Interventional Model: Crossover Assignment
  • Masking: Single

Arms and Interventions

Participant Group / Arm
Intervention / Treatment
Experimental: GH intervention - control intervention
Participants will receive daily subcutaneous injections of growth hormone for 7 days. Approximately 1-4 months later, the participants will receive daily subcutaneous injections of control intervention for 7 days consisting of saline and GH receptor blockade (Pegvisomant).
Biological: Growth hormone, saline and GH receptor blockade (Pegvisomant)
This study aims to uncover physiological effects of growth hormone (GH). The intervention with GH and GH receptor blockade (Pegvisomant) will therefore be used as tools to activate a well-known physiological response. Thus, this study is not a drug trial.
Experimental: Control intervention - GH intervention
Participants will receive daily subcutaneous injections of control intervention for 7 days consisting of saline and GH receptor blockade (Pegvisomant). Approximately 1-4 months later, the participants will receive daily subcutaneous injections of growth hormone for 7 days.
Biological: Growth hormone, saline and GH receptor blockade (Pegvisomant)
This study aims to uncover physiological effects of growth hormone (GH). The intervention with GH and GH receptor blockade (Pegvisomant) will therefore be used as tools to activate a well-known physiological response. Thus, this study is not a drug trial.

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Fibro-adipogenic progenitor (FAP) cells
Time Frame: Anticipated approximately 1-5 months
Quantification of FAP cells in adipose tissue, and in vitro determination of proliferation and fibro-/adipogenic differentiation potential
Anticipated approximately 1-5 months
Fibroblast activation protein (FAPα)
Time Frame: Anticipated approximately 1-5 months
FAPα concentration and activity in blood, and expression in adipose tissue
Anticipated approximately 1-5 months
Adipose tissue fibrosis
Time Frame: Anticipated approximately 1-5 months
Markers of fibrosis in adipose tissue assessed by light microscopy and immunohistochemically, RNA sequencing and heavy water labeled connective tissue turnover
Anticipated approximately 1-5 months

Secondary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Circulating biomarkers of collagen turnover
Time Frame: Anticipated approximately 1-5 months
(PINP, PIIINP)
Anticipated approximately 1-5 months
Protein turnover in muscle tissue
Time Frame: Anticipated approximately 1-5 months
Heavy water labeled protein and connective tissue turnover in muscle tissue to compare with protein turnover in adipose tissue
Anticipated approximately 1-5 months
Metabolism and fatty acid turnover
Time Frame: Anticipated approximately 1-5 months
Whole body energy metabolism and fatty acid turnover (indirect calorimetry and palmitate tracer kinetics)
Anticipated approximately 1-5 months
Temperature
Time Frame: Anticipated approximately 1-5 months
Temperature measurements
Anticipated approximately 1-5 months

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

University of Aarhus

Collaborators

University of Copenhagen

Investigators

  • Principal Investigator: Amanda Bæk, MD, University of Aarhus
  • Study Director: Jens Otto L Jørgensen, Professor, University of Aarhus

Publications and helpful links

The person responsible for entering information about the study voluntarily provides these publications. These may be about anything related to the study.

General Publications

Helpful Links

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Actual)

August 1, 2021

Primary Completion (Estimated)

December 31, 2023

Study Completion (Estimated)

December 31, 2023

Study Registration Dates

First Submitted

August 9, 2021

First Submitted That Met QC Criteria

August 9, 2021

First Posted (Actual)

August 10, 2021

Study Record Updates

Last Update Posted (Actual)

May 30, 2023

Last Update Submitted That Met QC Criteria

May 25, 2023

Last Verified

May 1, 2023

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

  • 1-10-72-283-20

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

No

Studies a U.S. FDA-regulated device product

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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