No evidence of ectopic lipid accumulation in the pathophysiology of the acromegalic cardiomyopathy

Context: Patients with acromegaly frequently display disturbances of glucose and lipid metabolism, which might contribute to their increased cardiovascular risk. Since insulin resistance and increased lipolysis have been linked to ectopic lipid deposition, altered lipid accumulation in the liver and the myocardium might contribute to metabolic and cardiac complications in these patients. Objective: The aim of this study was to investigate myocardial (MYCL) and hepatic lipid content (HCL), insulin sensitivity and cardiac function in active acromegaly and after control of GH-excess through transsphenoidal surgery. Patients: Ten patients with newly diagnosed acromegaly (ACRO active) were compared to 12 healthy controls (CON), matched for age, BMI and gender. In seven patients GH-excess was controlled (ACRO PS) and they were compared to their active state. Methods: MYCL and HCL were assessed by 1H-magnetic-resonance(MR)-spectroscopy, pericardial fat and cardiac function by MR-imaging; insulin sensitivity and secretion by an oral glucose tolerance test. Results: While MYCL tended to be lower, HCL was significantly lower in ACRO active compared to CON (HCL: 1.2±1.2 vs.4.3±3.5% of MRS-signal,p<0.02). Parameters of systolic function and hypertrophy were significantly increased in ACRO active compared to CON, as were insulin secretion and -resistance. Following control of GH-excess, HCL and MYCL remained unchanged, but pericardial fat was increased in ACRO PS (from 11.6±5.5 to 14.7±6.2cm2,p=0.02). Conclusion: Acromegaly represents a unique condition characterized by low myocardial and hepatic lipid content despite decreased insulin sensitivity, hyperinsulinemia and hyperglycemia. Hence, ectopic lipid accumulation does not appear to contribute to cardiac morbidity and increased lipid oxidation might counteract ectopic lipid accumulation GH-excess.