FP09-2 Bone Loss Following Bariatric Surgery: Comparison of Different Modalities

Program: Abstracts - Orals, Featured Poster Presentations, and Posters
Session: FP09-Obesity: Physiologic Responses to Energy Balance Disruption
Bench to Bedside
Saturday, June 15, 2013: 11:00 AM-11:30 AM
Presentation Start Time: 11:05 AM
Room 307 (Moscone Center)

Poster Board SAT-661
Malgorzata M Brzozowska*1, Angel Hong2, John Jorgensen3, Michael Talbot3, Nguyen D Nguyen4, Weiwen Chen1, Nicholas A Pocock5, John A Eisman1, Christopher P White2, Paul A Baldock4 and Jacqueline R Center1
1Garvan Institute of Medical Research and St Vincent's Hospital, Sydney, Australia, 2Prince of Wales Hospital, Sydney, Australia, 3St George Private Hospital, Sydney, Australia, 4Garvan Institute of Medical Research, Sydney, Australia, 5St Vincent's Hospital, Sydney, Australia
Obesity rates have increased markedly in recent decades and bariatric surgery remains the most effective therapy for weight loss. However, its skeletal consequences are not fully elucidated. We examined the skeletal response to 3 weight loss modalities: Medical Managed Dieting (MMD), Gastric Banding (GB) and Gastric Sleeve (GS).

These data represent 12 mth follow-up from a 24 mth prospective trial. Data include DXA at 0 and 12 mths, calcium intake, 25-OH vit D, PTH, gut hormones and adipokines.

The participants included 15 MMD, 7 GB and 20 GS subjects. At baseline, average age was 53 ±12 yrs (MMD 57 ±10, GB 46 ±13, GS 52 ±12, ns). BMI was 39 ±6 (MMD 38 ±7, GB 37 ±3, GS 42 ±5, ns). Calcium intake, 25-OH vit D and PTH were normal throughout.

At 12 mths, differences were evident between groups. % weight change was small in MMD (-5: -8, -1 (mean: Q1, Q3)), greater in GB (-12: -17,-7) and greatest in GS (-27: -31,-22), ANOVA, F=35, P<0.0001. % loss in total hip (TH) BMD was evident in GS (-6.1: -8,-4) but non-significant in MMD (-0.95: -2, 0.1) and GB (-1.76: -3,-0.3) ANOVA, F=18, P<0.001, despite weight loss in the other groups.

We examined factors affecting bone loss:

1. Weight loss in GS occurred in the first 6 mths post-surgery, however bone loss was ongoing: 3.5% by 6 mths, 6% by 12 mths. Moreover the 8 patients with 24 mth data had further BMD loss of 10% (-10%: -12,-9) with decrease in mean TH 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 TH area did not change between visits, p=0.29, hence areal BMD at TH (24m) declined by 10% p<0.001. Loss of TH BMD was significantly correlated to weight loss at 12mth (r = 0.57, p<0.02) with weight loss accounting for 28% of the 12mth decrease in BMD (adj R2=0.28).

2. Bone turnover markers increased in GS from baseline to 12 mths: osteocalcin (9 ±3 µg/L to 15 ±7, P<0.001) and uNTX (30 ±10nmol/mMCr to 55 ± 26, P<0.001), without any comparable change in MMD and GB.

3. Calcium intake, 25-OH vit D and PTH remained normal throughout.

4. The gut-derived, pro-satiety hormone Peptide YY has a negative effect on bone. At baseline, no post-prandial PYY increase was evident in any group. At 12 mths, difference in %PYY increment at 90 minutes post meal was significant between groups (mean: Q1, Q3), MMD (32.9: 13, 53), GB (42.8: -11, 96), GS (138.4: 86, 191) ANOVA, F=7.7, P<0.002. GLP-1 response was not significantly altered. % adiponectin increase between 0 and 12 mths was significantly different between groups: MMD (4.3: -9, 17), GB (24.7: -4, 53), GS (70.3: 37, 103), ANOVA, F=7.7, P<0.002 and negatively correlated with % fat loss (r = -0.37) p< 0.04.

Different weight loss modalities produced varied skeletal responses. Bone loss was apparent in GS but not with GB despite weight loss. Bone loss associated with GS was not accounted for by weight loss alone and may involve changes in factors such as PYY and adiponectin.

Disclosure: JAE: Scientific Board Member, Merck & Co., Scientific Board Member, Novartis Pharmaceuticals, Scientific Board Member, Sanofi, Scientific Board Member, Servier, Scientific Board Member, Eli Lilly & Company, Scientific Board Member, Amgen. JRC: Speaker, Amgen, Speaker, Merck & Co., Speaker, Novartis Pharmaceuticals, Speaker, Sanofi. Nothing to Disclose: MMB, AH, JJ, MT, NDN, WC, NAP, CPW, PAB

*Please take note of The Endocrine Society's News Embargo Policy at http://www.endo-society.org/endo2013/media.cfm

Sources of Research Support: This work was supported by National Health and Medical Research Council (NHMRC) Postgraduate Research Scholarship to Dr MM Brzozowska