Abdominal Fat and Sarcopenia in Women Significantly Alter Osteoblasts Homeostasis In Vitro by a WNT/-Catenin Dependent Mechanism

Obesity and sarcopenia have been associated with mineral metabolism derangement and low bone mineral density (BMD). We
investigated whether imbalance of serum factors in obese or obese sarcopenic patients could affect bone cell activity in vitro. To
evaluate and characterize potential cellular and molecular changes of human osteoblasts, cells were exposed to sera of four groups
of patients: (1) affected by obesity with normal BMD (O), (2) affected by obesity with low BMD (OO), (3) affected by obesity and
sarcopenia (OS), and (4) affected by obesity, sarcopenia, and lowBMD(OOS) as compared to subjects with normal bodyweight and
normalBMD(CTL). Patients were previously investigated and characterized for body composition, biochemical and bone turnover
markers. Then, sera of different groups of patients were used to incubate human osteoblasts and evaluate potential alterations in cell
homeostasis. Exposure to OO, OS, and OOS sera significantly reduced alkaline phosphatase, osteopontin, and BMP4 expression
compared to cells exposed toOand CTL, indicating a detrimental effect on osteoblast differentiation. Interestingly, sera of all groups
of patients induced intracellular alteration in Wnt/-catenin molecular pathway, as demonstrated by the significant alteration of
specific target genes expression and by altered -catenin cellular compartmentalization and GSK3 phosphorylation. In conclusion
our results show for the first time that sera of obese subjects with low bone mineral density and sarcopenia significantly alter
osteoblasts homeostasis in vitro, indicating potential detrimental effects of trunk fat on bone formation and skeletal homeostasis.