Citrate is essential to biomineralization of the bone especially as an integral part of apatite nanocomposite. Citrate precipitate of apatite is hypothesized to be derived from mesenchymal stem/stromal cells (MSCs) upon differentiation into mature osteoblasts. Based on ¹³C‐labeled signals identified by solid‐state multinuclear magnetic resonance analysis, boosted mitochondrial activity and carbon‐source replenishment of tricarboxylic acid cycle intermediates coordinate to feed forward mitochondrial anabolism and deposition of citrate. Moreover, zinc (Zn²⁺) is identified playing dual functions: (i) Zn²⁺ influx is influenced by ZIP1 which is regulated by Runx2 and Osterix to form a zinc‐Runx2/Osterix‐ZIP1 regulation axis promoting osteogenic differentiation; (ii) Zn²⁺ enhances citrate accumulation and deposition in bone apatite. Furthermore, age‐related bone loss is associated with Zn²⁺ and citrate homeostasis; whereas, restoration of Zn²⁺ uptake alleviates age‐associated declining osteogenic capacity and amount of citrate deposition. Together, these results indicate that citrate is not only a key metabolic intermediate meeting the emerging energy demand of differentiating MSCs but also participates in extracellular matrix mineralization, providing mechanistic insight into Zn²⁺ homeostasis and bone formation.

Significance: Signaling pathways regulate the self-renewal and differentiation of embryonic stem cells (ESCs). Suppression of Mek/Erk signaling by pharmacological inhibitors promotes self-renewal and pluripotency maintenance of mouse ESCs, supporting the prevailing view that Erk signaling is dispensable for ESC self-renewal. However, using inducible Erk knockout ESCs, we demonstrate that Erk signaling is critical for ESC self-renewal. ESCs cannot be maintained for more than four passages after Erk depletion, associated with misregulated expression of pluripotency genes, reduced proliferation rate, G1 cell-cycle arrest, increased apoptosis, rapid shortening of telomeres, and impaired genomic stability. We further demonstrate an Erk-independent function of Mek, which may explain the diverse effects of Mek inhibition and Erk knockout on ESC self-renewal.

Rationale: Men and postmenopausal women are more prone to developing non-alcoholic fatty liver disease/steatohepatitis (NAFLD/NASH) than premenopausal women. However, the pathological links and underlying mechanisms of this disparity are still elusive. The sex-difference in hepatic very low-density lipoprotein (VLDL) assembly and secretion may contribute to NAFLD development. Estrogen-related receptor alpha (ERRα) is a key regulator of several metabolic processes. We hypothesized that ERRα plays a role contributing to the sex-difference in hepatic VLDL assembly and secretion.

Nonalcoholic fatty liver disease (NAFLD) is the most common cause of chronic liver disease and may progress to cirrhosis or even hepatocellular carcinoma. A number of steroid hormones are important regulators of lipid homeostasis through fine tuning the expression of genes related to lipid synthesis, export, and metabolism. Dysregulation of such pathways has been implicated in the pathogenesis of NAFLD. The aim of this review is to clarify the potential impact of steroid hormones on NAFLD. We also highlight potential interventions through modulating steroid hormone levels or the activities of their cognate receptors as therapeutic strategies for preventing NAFLD.

Nuclear receptors, including Esrrb, Dax1, and Nr5a2, have been shown to be involved in pluripotency maintenance. Yet, the role of their coactivators in mouse embryonic stem cells remains unexplored. Here, we demonstrated that the nuclear receptor coactivator 3 (Ncoa3) is essential for pluripotency maintenance. Knockdown of Ncoa3 not only compromises the expression of pluripotency markers but also impairs in vitro and in vivo differentiation potential of mouse ESCs. Ncoa3 binds to the Nanog promoter and recruits the histone acetyltransferase CREB binding protein (CBP) and the histone arginine methyltransferase CARM1 to activate Nanog expression. Moreover, glycogen synthase kinase 3 GSK3 signaling down-regulates the Ncoa3 protein level to suppress Nanog expression. Thus, Ncoa3 not only contributes to self-renewal by activating Nanog but also facilitates ESC differentiation as a break point to disrupt the core transcriptional circuitry of pluripotency.