Serum markers of bone turnover are increased at six and 18 months after Roux-en-Y bariatric surgery: correlation with the reduction in leptin.
OBJECTIVE
The aim of the study was to examine serum markers of bone turnover at 6 and 18 months after Roux-en-Y gastric bypass surgery.


METHODS
Ten women and 10 men [body mass index (BMI), 50.2 +/- 8.4 kg/m(2)] were studied at 6 months; 10 women and nine men (BMI, 47.2 +/- 6.6 kg/m(2)) were studied at 18 months after surgery.


METHODS
Serum osteocalcin, bone specific alkaline phosphatase (BAP), N-telopeptide of type 1 collagen (NTX), PTH, 25-hydroxy vitamin D, and leptin were measured.


RESULTS
BMI was reduced 32.7 +/- 6.2% at 6 months after surgery. Serum osteocalcin (6.9 +/- 2.4 to 10.9 +/- 2.6 ng/ml; P < 0.0001), BAP (14.2 +/- 3.7 to 16.4 +/- 4.5 ng/ml; P = 0.04), and NTX (10.9 +/- 1.7 to 19.6 +/- 5.3 nm bone collagen equivalents; P < 0.0001) were increased. Calcium, phosphate, and PTH were unchanged, but 25-hydroxy vitamin D increased (16.0 +/- 8.9 vs. 26.9 +/- 10.6 ng/ml; P <0.0001). The increase in NTX correlated with reduction in serum leptin (r = 0.58; P = 0.007). BMI was reduced 40.9 +/- 7.5% at 18 months after surgery. Serum BAP (17.6 +/- 5.3 to 22.2 +/- 7.8 ng/ml; P = 0.0017) and NTX (10.8 +/- 2.7 to 16.9 +/- 5.5 nm bone collagen equivalents; P < 0.0001) were increased. Calcium, phosphate, and PTH were unchanged, but 25-hydroxy vitamin D increased (17.7 +/- 7.6 to 25.6 +/- 6.8 ng/ml; P < 0.0001). The increase in NTX correlated with reduction in BMI (r = 0.58; P = 0.009) and leptin (r = 0.45; P = 0.04) and the increase in serum 25-hydroxy vitamin D (r = 0.43; P = 0.05). In multiple regression (adjusted model R(2) 0.263; P = 0.013), reduction in leptin was a significant predictor of increase in NTX (P = 0.016), but changes in BMI and 25-hydroxy vitamin D were not.


CONCLUSIONS
Weight loss after bariatric surgery is associated with long-term increase in serum markers of bone turnover. The increase in NTX is related to the decrease in leptin, which may signal caloric restriction to the skeleton.
Indiana University School of Medicine, 541 North Clinical Drive, Clinical Building 455, Indianapolis, Indiana 46202-5111. rconsidi@iupui.edu.
Carolina
C
Bruno
Angie D
AD
Fulford
Jenna R
JR
Potts
Ronald
R
McClintock
Rosemarie
R
Jones
Brenda M
BM
Cacucci
Christine E
CE
Gupta
Munro
M
Peacock
Robert V
RV
Considine
D000328:Adult; D050110:Bariatric Surgery / Q000009:adverse effects / Q000534:rehabilitation; D015415:Biomarkers / Q000097:blood*; D015992:Body Mass Index; D016723:Bone Remodeling / Q000502:physiology; D024042:Collagen Type I / Q000097:blood; D005260:Female; D015390:Gastric Bypass / Q000009:adverse effects / Q000534:rehabilitation*; D006801:Humans; D020738:Leptin / Q000097:blood*; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000097:blood / Q000534:rehabilitation / Q000601:surgery; D010281:Parathyroid Hormone / Q000097:blood; D010455:Peptides / Q000097:blood; D011184:Postoperative Period; D013997:Time Factors; D014807:Vitamin D / Q000031:analogs & derivatives / Q000097:blood; D015431:Weight Loss / Q000502:physiology; D055815:Young Adult
D015415:Biomarkers; D024042:Collagen Type I; D020738:Leptin; D010281:Parathyroid Hormone; D010455:Peptides; C052929:collagen type I trimeric cross-linked peptide; D014807:Vitamin D; C104450:25-hydroxyvitamin D