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Plasma Osteopontin Increases After Bariatric Surgery and Correlates with Markers of Bone Turnover But Not with Insulin Resistance

Division of Endocrinology and Metabolism, Department of Medicine III (M.R., G.V., C.M., A.H., A.K.-W., B.L., M.C., A.L.), Division of General Surgery, Department of Surgery (S.S.-M., G.P.), and Clinical Institute of Medical and Chemical Laboratory Diagnostics (O.W.), Medical University of Vienna, A-1090, Vienna, Austria

Address all correspondence and requests for reprints to: Michaela Riedl, Department of Medicine III, Medical University of Vienna, Waehringer Guertel 18-20, A-1090, Vienna, Austria. E-mail: michaela.riedl{at}meduniwien.ac.at.

Context: Osteopontin (OPN) is a multifunctional protein involved in bone metabolism, cardiovascular disease, diabetes, and obesity. OPN levels are elevated in the plasma and adipose tissue of obese subjects, and are decreased with diet-induced weight loss.

Objective: We investigated the effect of bariatric surgery on plasma OPN concentrations in morbidly obese patients.

Setting: The study was performed at a university hospital.

Subjects: We investigated 40 obese patients aged 43.1 ± 1.8 yr, scheduled to undergo bariatric surgery. Roux-en-Y gastric bypass (RYGB) was performed in 30 subjects (27 females, three males), and laparoscopic adjustable gastric banding (LAGB) in 10 subjects (eight females, two males).

Study Design: All patients were studied before and 1 yr (10.3–14.8 months) after the intervention.

Main Outcome Measures: OPN, leptin, C-reactive protein, insulin, the homeostatic model assessment insulin resistance index, calcium, 25-hydroxyvitamin D, C telopeptide, and osteocalcin were determined.

Results: Both bariatric procedures significantly reduced body weight, body mass index, insulin, leptin, and C-reactive protein 1 yr after surgery. Plasma OPN increased from 31.4 ± 3.8 to 52.8 ± 3.7 ng/ml after RYGB (P < 0.001) and from 29.8 ± 6.9 to 46.4 ± 10.6 ng/ml after LAGB (P = 0.042). Preoperative OPN correlated with age, insulin, the homeostatic model assessment insulin resistance index, and postoperative OPN. Postoperative OPN correlated with C telopeptide and osteocalcin.

Conclusions: One year after RYGB and LAGB, plasma OPN levels significantly increased and correlated with biomarkers of bone turnover. Unlike other proinflammatory cytokines, OPN does not normalize but increases further after bariatric surgery.