Association of Plasma Carnitine Levels with Bone Mineral Density and Recent Osteoporotic Fracture

Zhaoyue Shang^1,2Xinwei Wang²Yongliang Du²Xiaohua Zhang²Yanlin Duan²William Leslie³Lisa Lix⁴Bo Kan⁵Shuman Yang^1,6*

• ¹First Affiliated Hospital of Jinzhou Medical University, Jinzhou, China
• ²Jilin University School of Public Health, Changchun, China
• ³University of Manitoba Department of Internal Medicine, Winnipeg, Canada
• ⁴University of Manitoba Department of Community Health Sciences, Winnipeg, Canada
• ⁵The Second Hospital of Jilin University, Changchun, China
• ⁶Jilin University, Changchun, China

Abstract Background The carnitine system may play an essential role in bone metabolism. However, existing epidemiological studies on the association between carnitine and bone mineral density (BMD) are still controversial. No human study has examined the association of carnitine and osteoporotic fracture. The objective of this research was to examine the association of carnitine levels with BMD and recent osteoporotic fracture. Methods We used cross-sectional and case-control studies to examine the associations of carnitine levels with BMD and recent osteoporotic fracture. The cross-sectional study identified 135 participants aged ≥45 years from the Second Hospital of Jilin University. The case-control study identified 44 recent fracture cases and 88 healthy controls aged 50 and older. Multivariable linear regression models were used to test the associations of carnitine with BMD, and conditional logistic regression models were used to analyze the association between carnitine levels and fracture. We used targeted metabolomics technology to measure 27 types of plasma carnitine levels. Results In the cross-sectional study, the average age was 57.6 ± 5.0 years, with 29 participants (21.5%) being female. We observed no significant association between total carnitine levels and BMD (P > 0.05). In the case-control study, 23 participants (52.3%) were diagnosed with hip fracture. Greater total carnitine levels were negatively associated with the risk of osteoporotic fractures (adjusted odds ratio: 0.43, 95% confidence interval: 0.22-0.85). The magnitude of the associations was comparable for hip and non-hip fractures. Conclusions Carnitine was not associated with BMD but was negatively associated with osteoporotic fracture. The low carnitine levels among fracture cases may be due to the post-fracture inflammatory and catabolic stress.