Site-1 protease ablation in the osterix-lineage in mice results in bone marrow neutrophilia and hematopoietic stem cell alterations

Differential Gene Expression Involved in Bone Turnover of Mice Expressing Constitutively Active TGFβ Receptor Type I

Transforming growth factor beta (TGF-β) is ubiquitously found in bone and plays a key role in bone turnover. Mice expressing constitutively active TGF-β receptor type I (Mx1;TβRICA mice) are osteopenic. Here, we identified the candidate genes involved in bone turnover in Mx1;TβRICA mice using RNA sequencing analysis. A total of 285 genes, including 87 upregulated and 198 downregulated genes, were differentially expressed. According to the KEGG analysis, some genes were involved in osteoclast differentiation (Fcgr4, Lilrb4a), B cell receptor signaling (Cd72, Lilrb4a), and neutrophil extracellular trap formation (Hdac7, Padi4). Lilrb4 is related to osteoclast inhibition protein, whereas Hdac7 is a Runx2 corepressor that regulates osteoblast differentiation. Silencing Lilrb4 increased the number of osteoclasts and osteoclast marker genes. The knocking down of Hdac7 increased alkaline phosphatase activity, mineralization, and osteoblast marker genes. Therefore, our present study may provide an innovative idea for potential therapeutic targets and pathways in TβRI-associated bone loss.

L2Δ13, a splicing isoform of lysyl oxidase-like 2, causes adipose tissue loss via the gut microbiota and lipid metabolism

Obesity is primarily characterized by the dysregulation of lipid metabolism and gut microbiota. Here, we found that the body weight of transgenic mice overexpressing L2Δ13, a selectively spliced isoform of lysyl oxidase-like 2 (LOXL2), was lower than that of wild-type (WT) mice. Numerous microbiotas were significantly changed and most microbial metabolites were abnormal in L2Δ13 mice. Lipid metabolites in feces were negatively correlated with those in plasma, suggesting that L2Δ13 may affect lipid uptake, and potentially, adipose tissue homeostasis. This was supported by the weight loss and decreased area of adipose tissue in L2Δ13 mice. Adipogenic differentiation of primary stromal vascular fraction cells showed that the lipid droplets of L2Δ13 cells were significantly smaller than those of WT cells. Adipocyte differentiation-associated genes were also downregulated in adipose tissue from L2Δ13 mice. Thus, L2Δ13 can induce adipose tissue loss in mice by affecting gut microbiota homeostasis and multi-tissue lipid metabolism.

Enterically derived high-density lipoprotein restrains liver injury through the portal vein

The biogenesis of high-density lipoprotein (HDL) requires apoA1 and the cholesterol transporter ABCA1. Although the liver generates most of the HDL in the blood, HDL synthesis also occurs in the small intestine. Here, we show that intestine-derived HDL traverses the portal vein in the HDL3 subspecies form, in complex with lipopolysaccharide (LPS)-binding protein (LBP). HDL3, but not HDL2 or low-density lipoprotein, prevented LPS binding to and inflammatory activation of liver macrophages and instead supported extracellular inactivation of LPS. In mouse models involving surgical, dietary, or alcoholic intestinal insult, loss of intestine-derived HDL worsened liver injury, whereas outcomes were improved by therapeutics that elevated and depended upon raising intestinal HDL. Thus, protection of the liver from injury in response to gut-derived LPS is a major function of intestinally synthesized HDL.