Reversible insulin resistance in muscle and fat unrelated to the metabolic syndrome in patients with acromegaly
Mai C. Arlien-Søborg,
Jakob Dal,
Michael Alle Madsen,
Morten Lyng Høgild,
Astrid Johannesson Hjelholt,
Steen B. Pedersen,
Niels Møller,
Niels Jessen,
Jens O.L. Jørgensen
Affiliations
Mai C. Arlien-Søborg
Department of Endocrinology and Internal Medicine, Aarhus University Hospital, Denmark; Medical Research Laboratory, Department of Clinical Medicine, Aarhus University Hospital, Denmark; Corresponding author at: Department of Endocrinology and Internal Medicine, Aarhus University Hospital, Denmark.
Jakob Dal
Department of Endocrinology and Internal Medicine, Aarhus University Hospital, Denmark; Department of Endocrinology, Aalborg University Hospital, Denmark; Steno Diabetes Centre North, Aalborg University Hospital, Aalborg, Denmark
Michael Alle Madsen
Department of Endocrinology and Internal Medicine, Aarhus University Hospital, Denmark; Department of Nuclear Medicine & PET Centre, Aarhus University Hospital, Denmark
Morten Lyng Høgild
Department of Endocrinology and Internal Medicine, Aarhus University Hospital, Denmark; Medical Research Laboratory, Department of Clinical Medicine, Aarhus University Hospital, Denmark
Astrid Johannesson Hjelholt
Department of Endocrinology and Internal Medicine, Aarhus University Hospital, Denmark; Medical Research Laboratory, Department of Clinical Medicine, Aarhus University Hospital, Denmark
Steen B. Pedersen
Steno Diabetes Centre, Aarhus, Denmark
Niels Møller
Department of Endocrinology and Internal Medicine, Aarhus University Hospital, Denmark; Medical Research Laboratory, Department of Clinical Medicine, Aarhus University Hospital, Denmark
Niels Jessen
Steno Diabetes Centre, Aarhus, Denmark; Department of Clinical Pharmacology, University of Aarhus, Aarhus, Denmark; Department of Biomedicine, Aarhus University, Denmark
Jens O.L. Jørgensen
Department of Endocrinology and Internal Medicine, Aarhus University Hospital, Denmark; Medical Research Laboratory, Department of Clinical Medicine, Aarhus University Hospital, Denmark
Summary: Background: Patients with active acromegaly exhibit insulin resistance despite a lean phenotype whereas controlled disease improves insulin sensitivity and increases fat mass. The mechanisms underlying this paradox remain elusive, but growth hormone (GH)-induced lipolysis plays a central role. The aim of the study was to investigative the molecular mechanisms of insulin resistance dissociated from obesity in patients with acromegaly. Methods: In a prospective study, twenty-one patients with newly diagnosed acromegaly were studied at diagnosis and after disease control obtained by either surgery alone (n=10) or somatostatin analogue (SA) treatment (n=11) with assessment of body composition (DXA scan), whole body and tissue-specific insulin sensitivity and GH and insulin signalling in adipose tissue and skeletal muscle. Findings: Disease control of acromegaly significantly reduced lean body mass (p<0.001) and increased fat mass (p<0.001). At diagnosis, GH signalling (pSTAT5) was constitutively activated in fat and enhanced expression of GH-regulated genes (CISH and IGF-I) were detected in muscle and fat. Insulin sensitivity in skeletal muscle, liver and adipose tissue increased after disease control regardless of treatment modality. This was associated with enhanced insulin signalling in both muscle and fat including downregulation of phosphatase and tensin homolog (PTEN) together with reduced signalling of GH and lipolytic activators in fat. Interpretation: In conclusion, the study support that uncontrolled lipolysis is a major feature of insulin resistance in active acromegaly, and is characterized by upregulation of PTEN and suppression of insulin signalling in both muscle and fat. Funding: This work was supported by a grant from the Independent Research Fund, Denmark (7016-00303A) and from the Alfred Benzon Foundation, Denmark.
