Proteomic profile of bone in patients with acromegaly: new insights from a pilot exploratory study

Introduction: Bone metabolism is typically impaired in patients with acromegaly due to increased bone turnover, increased bone resorption, and impaired bone neoformation. The pathogenetic mechanisms underlying skeletal fragility in patients with acromegaly remain not fully clarified. We aim to compare the bone proteome of patients with acromegaly to that of a control group of patients with non-secreting pituitary tumors (NSPTs). Methods: A Liquid Chromatography-Mass Spectrometry was conducted on ethmoid samples (after processing and digestion of the sample) of five patients with acromegaly and five patients with NSPTs, to identify and assay the proteome. Biological functions were investigated for proteins that were found quantitatively up- and down-regulated in the bone of acromegalic patients, with a ratio of variation based on Fold-Change (FC) >|1.50| and statistical significance (p-value < 0.05). Results: 312 proteins belonging to each group were identified. Six proteins with positive FC (up-regulated) and 12 proteins with negative FC (down-regulated) significantly differ in patients with acromegaly than in patients with NSPTs. Among up- and down-regulated proteins, profilin-1, isoform 5 of the periostin, apolipoprotein E, and caveolin-1 were known to be involved in bone metabolism. In our cohort, a positive correlation was detected between the profilin-1, the isoform 5 of the periostin, GH, and IGF-I levels; and a negative correlation was detected between caveolin-1 and serum GH and IGF-I levels, and with apolipoprotein E and serum IGF-I levels. Conclusion: Our results proved that the bone of patients with acromegaly is characterized by a specific proteomic profile, which is closely correlated to GH and IGF-I hypersecretion.