Alteration of Bone Mineral Density Differs between Genders in Obese Subjects after Laparoscopic Sleeve Gastrectomy—Bone Morphogenetic Protein 4 May Count

Laparoscopic sleeve gastrectomy (LSG) has proven to be successful in weight reduction but with potential loss of bone mass. Previous studies indicated that bone morphogenetic protein 4 (BMP4) plays an important role in both bone formation and glucose–lipid metabolism. This study aimed to investigate the changes in bone mineral density (BMD), bone metabolic parameters, and serum BMP4 levels in obese Chinese subjects after LSG. Seventy-one obese patients (34 males, age 31.70 ± 9.61 years and 37 females, age 32.80 ± 11.45 years) were enrolled. BMD (at the right hip, femoral neck, and lumbar spine 1–4 (L1–L4)) was measured by dual-energy X-ray absorptiometry, bone metabolic markers, and routine anthropometric/laboratory biochemical parameters at baseline, 3, 6, and 12 months after LSG (abbreviated as 3, 6, and 12 M post-LSG, respectively) were recorded. Serum BMP4 levels were measured by enzyme-linked immunosorbent assay. LSG led to dramatic weight loss with improved glucose–lipid metabolism in all patients. In females, BMD was significantly decreased at the right hip at all time points studied and at the femoral neck at 6 and 12 M post-LSG (P   0.05). Intriguingly, serum BMP4 levels were reduced slightly at 3 M post-LSG (P = 0.463) and were significantly at 6 M post-LSG (from 75.51 ± 16.54 to 65.40 ± 10.51 pg/mL, P = 0.048) in females, but unchanged in males (all P > 0.05). Vitamin D and 25-hydroxy vitamin D were increased in males at 12 M post-LSG (all P < 0.05). Osteocalcin was increased in males at all time points studied and in females at 3 and 6 M post-LSG (all P < 0.05). Type I collagen was increased in males at 3 and 6 M post-LSG and in females at all the time points studied (all P < 0.05). The effect of LSG on BMD differs between genders, decreasing significantly in females while remaining unchanged in males. Moreover, decreased BMP4 levels may partly account for the diminished BMD in obese Chinese female patients after LSG.