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.
Bruno
Carolina
C
Indiana University School of Medicine, 541 North Clinical Drive, Clinical Building 455, Indianapolis, Indiana 46202-5111. rconsidi@iupui.edu.
Fulford
Angie D
AD
Potts
Jenna R
JR
McClintock
Ronald
R
Jones
Rosemarie
R
Cacucci
Brenda M
BM
Gupta
Christine E
CE
Peacock
Munro
M
Considine
Robert V
RV
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