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Bone loss associated with sleeve but not banding
A comparison of different modalities of bone loss has reported that patients undergoing laparoscopic sleeve gastrectomy had reduced bone, compared with patients who underwent gastric banding. The study, presented at ENDO2013, the annual meeting of the Endocrine Society, in San Francisco, concluded that bone loss associated with sleeve patients was not accounted for by weight loss alone, and may involve changes in factors such as Peptide YY and adiponectin.
Despite the rise of obesity and bariatric surgery procedures, the study researchers from the Garvan Institute of Medical Research and St Vincent's Hospital, Prince of Wales Hospital, St George Private Hospital and St Vincent's Hospital, Sydney, Australia, said that the skeletal consequences from surgery have not been fully explored and explained.
As a result, they examined the skeletal response in 42 patients to three weight loss modalities: medical managed dieting (n=15), gastric banding (n=7) and gastric sleeve (n=20).
At baseline, average age was 53 ±12 years (medical managed dieting 57±10, gastric banding 46±13 and gastric sleeve 52±12) and the differences were not significant. Average BMI was 39 ±6 (medical managed dieting 38±7, gastric banding 37±3, and gastric sleeve 42±5) and the differences were not significant.
They reported 12 month data including DXA at 0 and 12 months, calcium intake, 25-OH vitamin D, PTH, gut hormones and adipokines, from a 24 month prospective trial. Calcium intake, 25-OH vitamin D and PTH were normal throughout.
The 12 months results showed that percentage weight change was the least in medical managed dieting group (-5: -8, -1 (mean: Q1, Q3)), greater in in the banding patients (-12: -17,-7) and greatest in the sleeve patients (-27: -31,-22), ANOVA, F=35, p<0.0001. % loss in total hip bone mineral density was evident in sleeve patients (-6.1: -8,-4) but non-significant in medical managed dieting (-0.95: -2, 0.1) and banding patients (-1.76: -3,-0.3) ANOVA, F=18, p<0.001, despite weight loss in the other groups.
According to the researchers, there were several factors that affected bone loss. Weight loss in the sleeve group occurred in the first six months post-surgery and bone loss continued throughout the study period: 3.5% by three months, 6% by 12 months. The eight patients with 24 month data had further BMD loss of 10% (-10%: -12,-9) with decrease in mean total hip T-score from +0.9 to 0.0, p<0.001, suggesting that weight loss may not be the sole determinant of bone loss. The total hip area did not change between visits, p=0.29, hence areal bone mineral density at total hip (24 months) declined by 10% p<0.001. Loss of total hip bone mineral density was significantly correlated to weight loss at 12 month (r=0.57, p<0.02) with weight loss accounting for 28% of the 12 month decrease in bone mineral density (adj R2=0.28).
Bone turnover markers increased in sleeve patients from baseline to 12 months: osteocalcin (9±3µg/L to 15±7, p<0.001) and uNTX (30±10nmol/mMCr to 55±26, p<0.001), compared with no noticeable change in the two other groups.
It was also reported that Peptide YY has a negative effect on bone, as at baseline there were no post-prandial PYY increase evident in any of the groups. However, at 12 months, the difference in %PYY increment at 90 minutes post meal was significant between groups (mean: Q1, Q3), medical managed dieting (32.9: 13, 53), banding (42.8: -11, 96), sleeve (138.4: 86, 191) ANOVA, F=7.7, p<0.002. GLP-1 response was not significantly altered.
Percentage adiponectin increase between 0 and 12 months was significantly different between groups: medical managed dieting (4.3: -9, 17), banding (24.7: -4, 53), sleeve (70.3: 37, 103), ANOVA, F=7.7, p<0.002 and negatively correlated with % fat loss (r= -0.37) p< 0.04.