Assessment of Changes in Metabolic Activity in Liver & Skeletal Muscle in Patients Suffering From Acromegaly

Study Overview
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Brief Summary
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Growth hormone (GH) plays a pivotal role in the regulation of body composition including ectopic lipid deposition in insulin sensitive organs like liver and skeletal muscle. Recent evidence indicates that the GH-IGF1 axis affects body composition via regulating mitochondrial oxidation capacity. Thus, excessive GH secretion by a pituitary adenoma (Acromegaly) might be accompanied by increased mitochondrial activity leading to inappropriately low intracellular lipid depots, especially in metabolically active tissue like liver and skeletal muscle. This study aims to assess metabolic activity and intracellular lipid content in skeletal muscle and liver in patients suffering from acromegaly compared to controls by 31P/1H Magnetic resonance spectroscopy before and in follow up examinations 3, 6 and 12 months after initiation of GH lowering treatments including surgery, somatostatinanalogs or pegvisomant, as well as oral glucose tolerance tests at each examination to assess treatment responses and calculate validated parameters for insulin sensitivity and resistance.

Detailed Description
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Background: Growth hormone (GH) plays a pivotal role in the regulation of body composition including ectopic lipid deposition in insulin sensitive organs like liver and skeletal muscle. Direct inhibition of growth hormone action by a receptor antagonist has been shown to induce hepatic steatosis and growth hormone replacement decreases liver fat content in obese humans. Of note, recent evidence indicates that the GH-IGF1 axis affects body composition via regulating mitochondrial oxidation capacity. Hypothesis: Direct and/or indirect effects of GH on mitochondrial function might mediate the changes in body composition and lipid deposition. Thus, excessive GH secretion by a pituitary adenoma (Acromegaly) might be accompanied by increased mitochondrial activity leading to inappropriately low intracellular lipid depots, especially in metabolically active tissue like liver and skeletal muscle. Aim: Assessment of metabolic activity and intracellular lipid content in skeletal muscle and liver in patients suffering from acromegaly compared to controls. Methods: Non-interventional study: 31P/1H Magnetic resonance spectroscopy before and in follow up examinations 3, 6 and 12 months after initiation of GH lowering treatments including surgery, somatostatinanalogs or pegvisomant. oral glucose tolerance tests at each examination to assess treatment responses and calculate validated parameters for insulin sensitivity and resistance.

Official Title
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Assessment of Changes in Metabolic Activity in Liver & Skeletal Muscle in Patients Suffering From Acromegaly - a 31P/1H Magnetic Resonance Spectroscopy Pilot Study

Conditions
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Acromegaly

Intervention / Treatment
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* Other: 1H/31P Magnetic Resonance Spectroscopy
* Other: oral glucose tolerance testing
* Other: Thyroid sonography


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: age between 18-75 years Exclusion Criteria: (known) overt diabetes mellitus known coronary artery disease (history of myocardial infarction or angina pectoris) acute or chronic (inflammatory, metabolic [hyperlipidemia, arterial hypertension, thyroid disorder]) disease (healthy controls) intake of medication potentially affecting glucose or lipid metabolism metal devices or other magnetic material in or on the subjects body which will be hazardous for NMR investigation [heart pacemaker, brain (aneurysm) clip, nerve stimulators, electrodes, ear implants, post coronary by-pass graft (epicardial pace wires), penile implants, colored contact lenses, patch to deliver medications through the skin, coiled spring intrauterine device, vascular filter for blood clots, orthodontic braces, shunt- spinal or ventricular, any metal implants (rods, joints, plates, pins, screws, nails, or clips without MR-authorization), embolization coil, or any metal fragments or shrapnel in the body]. tendency toward claustrophobia severe liver disorders (plasma transaminases elevated > 3fold) any acute inflammatory disease within 2 weeks prior the study pregnancy nursing clinically relevant anemia

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 75 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Acromegalic patients<br>Acromegalic patients before and after initiation of individual therapy will be investigated by 1H/31P magnetic resonance spectroscopy, thyroid sonography and oral glucose tolerance testing | Other: 1H/31P Magnetic Resonance Spectroscopy<br>* The 31P-MRS examinations will be performed in a 7 T MR system (Siemens Healthcare, Erlangen, Germany) using a double-tuned (31P/1H) surface coil (Rapid Biomedical Ltd, Rimpar, Germany), with a diameter of 10 cm. Participants will be investigated lying in lateral position with the right lobe of the liver positioned over the coil.<br>Other: oral glucose tolerance testing<br>* In patients without overt diabetes, glucose tolerance will be assessed by an oral glucose tolerance test, routinely performed at the outpatients clinic. The test will be performed in the morning after an overnight fast of at least 8 hours. Blood will be drawn via a catheter placed in an antecubital vein of one arm. Blood samples for the assessment of glucose, insulin, C-peptide, free fatty acids and growth hormone will be drawn at baseline as well as 30, 60, 90 and 120 minutes after ingestion of 75g glucose in a solution. Concentrations of glucose, insulin and C-peptide will be used to derive parameters of insulin secretion and insulin sensitivity by mathematical modelling.<br>Other: Thyroid sonography<br>* In acromegalic patients thyroid morphology will be assessed at the outpatient clinic of the Division of Endocrinology and Metabolism, using standard ultrasound technique. Measurements will be performed by a well- experienced physician at baseline and at each follow up examination in an out-patient care setting.<br>|
| Healthy control subjects<br>Age and Body mass index matched control subjects will be investigated by 1H/31P magnetic resonance spectroscopy and oral glucose tolerance testing | Other: 1H/31P Magnetic Resonance Spectroscopy<br>* The 31P-MRS examinations will be performed in a 7 T MR system (Siemens Healthcare, Erlangen, Germany) using a double-tuned (31P/1H) surface coil (Rapid Biomedical Ltd, Rimpar, Germany), with a diameter of 10 cm. Participants will be investigated lying in lateral position with the right lobe of the liver positioned over the coil.<br>Other: oral glucose tolerance testing<br>* In patients without overt diabetes, glucose tolerance will be assessed by an oral glucose tolerance test, routinely performed at the outpatients clinic. The test will be performed in the morning after an overnight fast of at least 8 hours. Blood will be drawn via a catheter placed in an antecubital vein of one arm. Blood samples for the assessment of glucose, insulin, C-peptide, free fatty acids and growth hormone will be drawn at baseline as well as 30, 60, 90 and 120 minutes after ingestion of 75g glucose in a solution. Concentrations of glucose, insulin and C-peptide will be used to derive parameters of insulin secretion and insulin sensitivity by mathematical modelling.<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Changes in hepatic energy metabolism | The 31P-MRS examinations will be performed in a 7 T MR system (Siemens Healthcare, Erlangen, Germany) using a double-tuned (31P/1H) surface coil (Rapid Biomedical Ltd, Rimpar, Germany), with a diameter of 10 cm. | before & 3,6,9, and 12 months after initiation of therapy | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Changes in hepatic lipid content | Hepatic lipid content will be assessed using localized single voxel 1H MRS as published by our study group. STEAM sequence (VOI= 3×3×3 cm3; TE= 30, 50, 70, 120 ms; NA= 4 for each TE) data acquisition will be performed during repetitive single breath holds. Hepatocellular lipid (HCL) content will be calculated from ration of summed area of methylene and methyl resonance to that of water following the individual spin-spin relaxation correction as per cent of total tissue MRS signal (water + methylene + methyl). | before, as well as 3,6,9 &12 months after initiation of therapy |