The Role of Insulin-like Growth Factor Binding Protein 2 in Bone Loss After Vertical Sleeve Gastrectomy: A Pilot Study
*Alison N Pletch
Maine Medical Center, Portland, ME
Objective: Insulin-like Growth Factor Binding Protein 2 (IGFBP2) plays an important role in bone loss; its deletion results in resistance to bone loss in mice. Bone loss is also a known side effect of vertical sleeve gastrectomy (VSG). We aim to determine which VSG technique yields greater bone loss when performed on mice, to characterize this bone turnover, and to evaluate IGFBP2 response.
Design: Nonrandomized control trial.
Setting: Maine Medical Center Research Institute, Scarborough, Maine.
Patients: Regular C57BL/6J mice.
Interventions: 12 mice underwent a stapled VSG (S-VSG), a hand-sewn VSG (HS-VSG), or a sham procedure (4 mice per group).
Main Outcome Measures: Mice were scanned at 3 weeks after surgery using a Lunar PIXImus densitometer to estimate bone mineral density (BMD), bone mineral content (BMC), and body composition. Mice were eye bled at 2 weeks and terminally bled at 3 weeks after surgery. IGFBP2, CTx and P1NP assays were performed on blood samples to characterize bone turnover.
Results: Areal BMD and BMC analysis showed significant bone loss after HS-VSG versus sham procedure (p=0.0312 and p=0.0980). Femoral BMD and BMC analysis revealed even more significant bone loss between the same groups (p=0.0042 and p=0.0037). IGFBP2 levels fell significantly for both the S-VSG and HS-VSG groups (p=0.0183 and p=0.0020). CTx levels significantly increased after HS-VSG (p=0.0160). All mice gained weight 3 weeks after surgery.
Conclusions: Bone loss was more significant after HS-VSG, perhaps due to the larger gastrectomy achieved using a hand-sewn technique. Bone loss is likely driven by bone resorption rather then mechanical unloading. IGFBP2’s role remains unclear but may be clarified after a repeat study using IGFBP2 null and wild type mice.
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