Time-Course Changes in Bone Turnover Markers and Fat-Soluble Vitamins After Obesity Surgery

Background The available evidence indicates a progressive increase in the incidence and severity of the deficiency of certain vitamins and related clinical conditions (i.e., metabolic bone disease). Because of the potential role of fat-soluble vitamins and carotenoids in bone metabolism, our aim was to assess the time-course changes of fat-soluble vitamins and serum markers of bone metabolism in candidates for obesity surgery and following two bariatric procedures. Methods Sixty-five candidates for bariatric surgery and 150 serum samples after obesity surgery (i.e., Roux-en-Y gastric bypass, n=85; biliopancreatic diversion, n=65) were consecutively analyzed over a period of more than 2 years. Retinol, alpha- and gamma-tocopherol, 25-OH-vitamin D3, beta-cryptoxanthin, and beta-carotene were analyzed by high-performance liquid chromatography. Calcium, phosphorus, alkaline phosphatase, intact parathyroid hormone (iPTH), osteocalcin, beta-crosslaps, and N-terminal peptide of procollagen I (P1NP) were determined using commercial kits. Results Retinol, beta-cryptoxanthin, beta-carotene, and alpha- and gamma-tocopherol levels were significantly lower in post-surgery samples while osteocalcin, b-crosslaps, and P1NP were significantly increased. Along the time and regardless of the surgical procedure, P1NP, b-crosslaps, and osteocalcin increased during the first 12-24 months but declined afterward. 25-OH-vitamin D increased during the first 12 months and tended to decrease afterward while iPTH remained constant or decreased but increased after 1 year in both groups. Vitamin A remained constant but alpha- and gamma-tocopherol, beta-cryptoxanthin, and beta-carotene decreased in both groups. Conclusions In addition to the nutritional assessment, regular monitoring of bone markers seems necessary in these patients and the early introduction of preventive strategies (i.e., the use of antiresorptive agents) should be evaluated.