Graphical abstract

Farnesoid X receptor (FXR) is a nuclear hormone receptor involved in bile acid synthesis and homeostasis. Dysfunction of FXR is involved in cholestasis and atherosclerosis. FXR is prevalent in liver, gallbladder, and intestine, but it is not yet clear whether it modulates neurobehavior. In the current study, we tested the hypothesis that mouse FXR deficiency affects a specific subset of neurotransmitters and results in an unique behavioral phenotype. The FXR knockout mice showed less depressive-like and anxiety-related behavior, but increased motor activity. They had impaired memory and reduced motor coordination. There were changes of glutamatergic, GABAergic, serotoninergic, and norepinephrinergic neurotransmission in either hippocampus or cerebellum. FXR deletion decreased the amount of the GABA synthesis enzyme GAD65 in hippocampus but increased GABA transporter GAT1 in cerebral cortex. FXR deletion increased serum concentrations of many bile acids, including taurodehydrocholic acid, taurocholic acid, deoxycholic acid (DCA), glycocholic acid (GCA), tauro-α-muricholic acid, tauro-ω-muricholic acid, and hyodeoxycholic acid (HDCA). There were also changes in brain concentrations of taurocholic acid, taurodehydrocholic acid, tauro-ω-muricholic acid, tauro-β-muricholic acid, deoxycholic acid, and lithocholic acid (LCA). Taken together, the results from studies with FXR knockout mice suggest that FXR contributes to the homeostasis of multiple neurotransmitter systems in different brain regions and modulates neurobehavior. The effect appears to be at least partially mediated by bile acids that are known to cross the blood-brain barrier (BBB) inducing potential neurotoxicity.

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As the main inorganic component of human hard tissue, hydroxyapatite (HAp) has attracted extensive interest in biomedical and clinical applications, especially for HAp nanoparticles. In this study, HAp nanorods with a controllable aspect ratio were successfully prepared using NH3·H2O and CO­(NH2)2 as aspect ratio modifier by a high-gravity reactive precipitation in a rotating packed bed (RPB) combined with hydrothermal treatment. The influences of the molar ratio of NH3·H2O and CO­(NH2)2 and the rotating speed on the average size and aspect ratio of HAp nanorods were systematically explored. The as-synthesized HAp nanorods were investigated with TEM, XRD, and FTIR. The results indicated that the average aspect ratio of HAp nanorods could be facilely controlled in the range 2.2–39. As compared to a traditional batch stirred tank reactor, the RPB reactor had HAp nanorods with a smaller particle width and a wider range of aspect ratio, and a much shorter reaction time from 20 min to 1 s. Further, the potential use of HAp nanorods in the pectin/HAp nanocomposite cements was investigated. The pectin/HAp nanocomposite cement with the highest compressive strength of 29.7 MPa was achieved with the addition of HAp nanorods with the aspect ratio of 15.

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