Diabetes mellitus (DM) affects bone metabolism and leads to osteoporosis; however, its pathogenetic mechanisms remain unknown. We found that high glucose (HG) conditions induced the production of reactive oxygen species (ROS) and the expression of proteins related to MAPKs [phosphorylated (p)‐ERK, p‐JNK, and p‐p38], NF‐κB(NF‐κB, p‐IαB, and IKK), and NACHT‐LRR‐PYD domains‐containing protein 3 (NALP3) (NLRP3) [apoptosis‐associated speck‐like protein containing a caspase activation and recruitment domain (ASC), caspase‐1, IL‐18, IL‐1β, and NLRP3] in osteoclasts (OCs) in vitro. Further analysis showed that in HG‐induced OCs, ROS is an upstream signal for MAPKs, NF‐κB, and the NLRP3 inflammasome. Moreover, MAPKs mediated the activation of NF‐κB and NLRP3, whereas NF‐κB up‐regulated the NLRP3 inflammasome response. Interestingly, HG inducement enhanced the bone resorption of OCs but inhibited their efferocytosis, whereas insulin and lipoxin A4 (4) treatment reversed this phenomenon. In streptozotocin‐induced diabetic rats in vivo, the numbers and the bone‐resorption capacity of OCs as well as the serum levels of TRACP‐5b were significantly increased, and the expression of MAPK‐, NF‐κB‐, and NLRP3 inflammasome‐related proteins in the proximal tibia were also significantly elevated; however, treatment with insulin and LXA4 reversed this elevation. Together, these results demonstrated that the activation of ROS/MAPKs/NF‐κB/NLRP3 and the inhibition of efferocytosis in OCs are the main causes of osteoporosis in DM.—An, Y., Zhang, H., Wang, C., Jiao, F., Xu, H., Wang, X., Luan, W., Ma, F., Ni, L., Tang, X., Liu, M., Guo, W., Yu, L. Activation of ROS/MAPKs/NF‐κB/NLRP3 and inhibition of efferocytosis in osteoclast‐mediated diabetic osteoporosis. FASEB J. 33, 12515–12527 (2019). http://www.fasebj.org

are contributed equally to this work. AbstractObjective To explore the effect of cordycepin on reducing lipid droplets in adipocytes. Methods Rats were fed a 60% high-fat diet to construct a hyperlipidaemia animal model and then treated with cordycepin at different concentrations for 8 weeks. Adipocytes were extracted, and BODIPY staining was used to detect the size of the lipid droplets. The adipocyte membrane proteins ASC-1, PAT2 and P2RX5 were assessed to determine the transformation of white adipocytes to beige and brown adipocytes. In an in vitro study, 3T3-L1 cells were cultured, and Western blotting was used to determine the expression of the lipid dropletrelated genes Fsp27, perilipin 3, perilipin 2, PPAR-c, Rab5, Rab7, Rab11, perilipin 1, ATGL and CGI-58. Results We found that cordycepin could promote the transformation of white adipocytes into beige and brown adipocytes. Cordycepin also downregulated the lipid droplet-associated genes Fsp27, perilipin 3, perilipin 2, Rab5, Rab11 and perilipin 1. Moreover, cordycepin reduced the expression of protein CGI-58, which inhibits lipid droplet degradation. In addition, cordycepin significantly increased the expression of ATGL, suggesting that cordycepin might stimulate lipolysis by upregulating the expression of ATGL instead of CGI-58 and by downregulating the expression of perilipin 1. Conclusions Cordycepin could blockade lipid droplet formation and promote lipid droplet degradation.

Cordycepin is an extract from the insect fungus Cordyceps. militaris with various biological function. In previous studies, cordycepin had been reported with excellent anti-obesity effect, but the mechanism is unclear. Evidences also showed that prolactin played an important role in body weight regulation, hyperprolactinemia can promote appetite and accelerate fat deposition. In this study, we explored the molecular mechanism of the anti-obesity effect of cordycepin. In vivo, obese rats model was induced by high fat diet for 5 weeks, the serum and liver lipids coupled with serum prolactin were reduced by treatment of cordycepin (P＜0.01) , the results suggested that cordycepin is a potential drug for lowering blood and liver lipids and reducing body weight which related with prolactin. Cordycepin also protects adipocytes from enlargement and hepatocytes from lipotoxicity caused inflammation. In vitro, cordycepin could inhibit prolactin secretion in GH3 cells via upregulating the expression of adenosine A1 receptor, the inhibition effect could be blocked by an antagonist of adenosine receptor A1 DPDPX, which demonstrated that cordycepin may work as an adenosine agonist. In addition, cordycepin could inhibit ERK/AKT/PI3K pathway in GH3 cells. Meanwhile, cordycepin could block prolactin induced the upregulation of lipogenesis genes PRLR, and phosphorylation of JAK2 in 3T3-L1 cells. In vivo study, cordycepin would down-regulate the expression of prolactin receptor (PRLR) but not phosphorylation of JAK2. Thus, we concluded that cordycepin modulate body weight by reducing prolactin release via an adenosine A1 receptor.

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