Protein array test detected three osteoporosis related plasma inflammatory cytokines in Chinese postmenopausal women.

Inflammatory cytokines were involved in pathological conditions of osteoporosis (OP). However, the specific OP-associated inflammatory cytokines are still awaiting to be detected by using a systemic method. Herein, we adopted an extreme sampling scheme and examined inflammatory cytokines between subjects with low and high bone mineral density (BMD) through protein microarray. First, 8 candidate cytokines including B lymphocyte chemoattractant (BLC), osteopontin (OPN) and insulin-like growth factor-binding protein 4 (IGFBP4) were identified in the discovery extreme sampling subgroup. Then, the different expressions for BLC, OPN and IGFBP4 were validated and replicated in two independent extreme sampling subgroups. Further functional experiments showed that the cytokine BLC was involved in bone metabolism by inhibiting bone formation and promoting bone resorption. Together, this study further revealed that inflammatory cytokines were closely related with OP, and that they highlighted critical roles of BLC in the pathogenesis of OP.

Relative abundance of mature myostatin rather than total myostatin is negatively associated with bone mineral density in Chinese.

Myostatin is mainly secreted by skeletal muscle and negatively regulates skeletal muscle growth. However, the roles of myostatin on bone metabolism are still largely unknown. Here, we recruited two large populations containing 6308 elderly Chinese and conducted comprehensive statistical analyses to evaluate the associations among lean body mass (LBM), plasma myostatin, and bone mineral density (BMD). Our data revealed that total myostatin in plasma was mainly determined by LBM. The relative abundance of mature myostatin (mature/total) was significantly lower in high versus low BMD subjects. Moreover, the relative abundance of mature myostatin was positively correlated with bone resorption marker. Finally, we carried out in vitro experiments and found that myostatin has inhibitory effects on the proliferation and differentiation of human osteoprogenitor cells. Taken together, our results have demonstrated that the relative abundance of mature myostatin in plasma is negatively associated with BMD, and the underlying functional mechanism for the association is most likely through inhibiting osteoblastogenesis and promoting osteoclastogenesis.

Association of Plasma Irisin with Bone Mineral Density in a Large Chinese Population Using an Extreme Sampling Design.

Irisin, a myokine produced by skeletal muscle in response to physical exercise, promotes trans-differentiation of white adipose tissue into brown adipose tissue. Recent evidences suggested that irisin also plays an important role in the control of bone metabolism. This study aimed to ascertain the relationship between plasma irisin and bone mineral density (BMD) in Chinese population by adoption of an extreme sampling method. Based on a large and screened Chinese elderly population (N = 6308), two subgroups with extremely high and low hip BMD were selected for discovery (N = 80, high vs. low BMD = 44:36) and validation (N = 60, high vs. low BMD = 30:30), respectively. Plasma irisin, P1NP, and ß-CTx were measured using commercially available ELISA kits. Other metabolic parameters (e.g., blood glucose, total cholesterol and triglycerides) were collected. Student's t test and Spearman correlation analyses were conducted in SPSS. Significant difference was discovered for plasma irisin between females and age-matched males (N = 80, male vs. female = 42:38, P = 0.002). The plasma irisin levels were significantly higher in high BMD subjects than in low BMD subjects, which was observed in both discovery (P = 0.012) and validation samples (P = 0.022). However, such observation was limited to males only. Further correlation analyses in males showed that plasma irisin was correlated with BMD (r = 0.362, P = 0.025) and triglyceride (r = - 0.354, P = 0.032). Plasma irisin levels were associated with hip BMD in Chinese elderly men. This study represented the first effort of investigating the relationship of plasma irisin and BMD in elderly population. The positive correlation between plasma irisin and BMD hints intrinsic communication between muscle and bone.