Differential Associations of Subcutaneous and Visceral Fat with Bone Turnover Markers: A Study on Bariatric Surgery Patients with Severe Obesity and Individuals Without Obesity

Backgrounds Obesity is associated with alterations in bone turnover markers (BTMs). However, the association between regional fat distribution and bone metabolism has received less attention. This study therefore aimed to identify which specific fat compartments (i.e., abdominal and femoral subcutaneous fat, intra- and extraperitoneal fat, and total visceral fat) exert the most significant influence on circulating BTMs. Methods The study comprised a cohort of individuals with severe obesity (n = 46), studied both before and after weigh loss induced by metabolic bariatric surgery, and individuals without obesity and surgery who served as controls (n = 25). The BTMs included Tartrate-Resistant Acid Phosphatase 5b, C-terminal Telopeptide of Type I Collagen (CTX), Procollagen Type I N-terminal Propeptide (PINP), and Total (TotalOC), Carboxylated (cOC), and Undercarboxylated (ucOC) osteocalcin. Results In the pooled data, significant negative associations were observed between intraperitoneal and total visceral fat and CTX, TotalOC, cOC, and ucOC (all with p < 0.05). Similarly, extraperitoneal fat showed a significant negative relationship with cOC. Conversely, no significant associations were observed between abdominal and femoral subcutaneous fat and any of the measured BTMs in the study participants (all p > 0.05). Conclusions Distinct deleterious implications for bone formation and resorption were associated with intraperitoneal, extraperitoneal, and total visceral fat. These findings emphasize the importance of fat distribution in the body to skeletal health. ClinicalTrials.gov registration numbers : NCT00793143 and NCT01373892.