Objective To construct the platelet-specific Metrnl gene knockout （Plt-Metrnl^-/-）mice model. Methods Based on the Cre-LoxP system, Metrnl^loxp/loxp mice, previously constructed in our laboratory, were mated with Pf4-Cre mice to generate Plt-Metrnl^-/- mice. The genotypes of the offspring were identified, and tissues of the platelet, other peripheral blood cells, heart, liver, spleen, lung, kidney, brain, colon, and bone marrow were collected. The expression of the Metrnl gene in Plt-Metrnl^-/- mice was investigated by quantitative real-time PCR and western blot. Also, the blood routine index was tested in Plt-Metrnl^-/- mice. Results Compared with wild-type mice, the level of Metrnl protein in platelets was significantly decreased in Plt-Metrnl^-/- mice. There was no significant difference in mRNA and protein levels of other peripheral blood cells and tissues, as well as in blood routine index, growth, and development between Plt-Metrnl^-/- mice and WT mice. Conclusion Platelet-specific Metrnl knockout mice（Plt-Metrnl^-/- mice）model was successfully constructed.

Objective To explore the effects of nicotinamide mononucleotide （NMN） on hypertensive rats. Methods Two rat hypertension models including spontaneously hypertensive rats（SHR）and two-kidney two-clip （2K2C） rats were used to be given single, long-term or lifelong administration of NMN respectively. NMN’s effects were assessed comprehensively by monitoring survival time, blood pressure levels, and the extent of organ damage in hypertensive model rats. Results It was revealed that NMN did not exhibit protective effects in terms of lowering blood pressure levels, reducing organ damage or increasing survival time in hypertensive rats. Conclusion This study suggested that NMN did not demonstrate anti-hypertensive effects in rat hypertension models and could provide valuable insights for future clinical observation on NMN.

Objective To investigate the effects of the H₃ receptor inverse agonist pitolisant on wakefulness and cognitive behavior in mice subjected to sleep deprivation, and assess its potential wake-promoting and pro-cognitive properties. Methods A mouse model of sleep deprivation was utilized, in which sleep deprivation was performed for 6, 12, and 24 h by an automatic rotating rod system. Pitolisant （20 mg/kg, i.p.） or saline control was administered prior to the end of deprivation. Quantitative wakefulness was monitored by polysomnographic recordings and spontaneous locomotion, spatial learning and memory were assessed through open field test and Morris water maze test, respectively. Results Pitolisant significantly increased wake duration after all sleep deprivation periods, with the most prominent effect observed in the early recovery phase. In the 24 h deprivation model, pitolisant also significantly improved spontaneous locomotor activity and showed a potential enhancement of spatial learning and memory, although the effects did not reach statistical significance. Conclusion Pitolisant not only enhanced wakefulness but also showed partial pro-cognitive effects following sleep loss, which supported its potential application in improving cognitive impairment associated with various sleep disorders.

Objective To generate mice with whole-body overexpression of human METRNL gene.Methods Based on Cre-loxP system,Dppa3-Cre mice were mated with Rosa26-LSL-METRNL knock-in mice(R26-LSL-METRNL+/-)to generate R26-L-METRNL+/-mice.The genotypes of the offsprings were identified,and tissues of the blood,heart,liver,spleen,lung,kidney,brain,white adipose and muscle were collected.The expression of human METRNL gene in mice was investigated by quantitative real-time PCR,western blot and enzyme linked immunosorbent assay.Results Compared with wild type control mice,human METRNL in R26-L-METRNL+/-mice significantly expressed at both mRNA and protein levels in tissues,with abundant METRNL protein in blood.Conclusion The mouse model overexpressing human METRNL gene(R26-L-METRNL+/-mouse)was successfully constructed.

Objective To study the effect of MT-1207 on blood glucose,blood lipids and atherosclerosis in mice.Methods The apolipoprotein E knockout(ApoE-/-)mice were fed with normal feed,drug feed containing losartan and drug feed containing MT-1207 at a dosage of 30 mg/kg.The body weight,blood glucose and blood lipids were detected,and the plaque area of atherosclerotic was evaluated.8-week-old male C57 mice were fed a high fat diet and given intragastric administration of MT-1207 and losartan at a dose of 30 mg/kg per day.The body weight,blood glucose and lipids levels were also examined to further evaluate the effects of MT-1207 on blood glucose and lipids levels.Results ApoE-/-mice treated with MT-1207 and losartan gained weight faster.There was no significant improvement in blood glucose and lipid levels,and no significant change in atherosclerotic plaque area.MT-1207 and losartan had no significant improvement effect on blood glucose and blood lipids of C57 mice.Conclusion MT-1207 and losartan couldn't improve the levels of blood glucose,blood lipids and atherosclerosis,and couldn't aggravate atherosclerosis.

The injury of vascular endothelial cell function is the beginning of the pathological process of atherosclerosis. Mitochondrial oxidative stress is closely related to vascular endothelial cell function, which causes the dysfunction of vascular endothelial cell by inducing mitophagy, reducing nitric oxide production, inflammation, cellular metabolic imbalance and apoptosis. Meanwhile, vascular endothelial cell could also maintain their homeostasis by regulating mitochondrial oxidative stress. The molecular signaling pathways of the vascular endothelial cell injury caused by mitochondrial oxidative stress in the pathological process of atherosclerosis were outlined in this review, which provided reference for further research on the molecular mechanism between mitochondrial oxidative stress and endothelial damage.

Objective To investigate the effect of intestinal Metrnl on dextran sodium sulfate (DSS)-induced ulcerative colitis mouse model and the regulation mechanism of intestinal microbiota. Methods Different concentrations of DSS (3% DSS and 1% DSS) were used to induce ulcerative colitis on C57 mice to determine the experimental conditions. Intestinal epithelial Metrnl specific knockout mice (Metrnl^(-/-)) and its control mice (Metrnl^(+/+)) were administrated with 3% DSS for 5 d. Then the survival time, body weight, DAI (disease activity index), colon length and pathological changes in colon tissues were observed. 16S ribosomal RNA gene sequencing was used to detect the composition of intestinal microbiota. Results Compared with 1% DSS, 3% DSS could significantly aggravate ulcerative colitis on C57 mice, such as lower survival rate (P<0.05), more weight loss (P<0.05), higher DAI score (P<0.05), shorter colon length (P<0.05) and higher pathology score (P<0.05). After administrated to 3% DSS for 5 d, comparing with Metrnl^(+/+) mice, Metrnl^(-/-) mice showed more weight loss (P<0.05), higher DAI score (P<0.05), shorter colon length (P<0.05) and higher pathology score (P<0.05). The 16S ribosomal RNA results showed that the diversity of intestinal microbiota in Metrnl^(-/-) mice significantly decreased. Furthermore, Bacteroidetes and Proteobacteria significantly decreased, while Firmicutes increased. Conclusion Metrnl could protect the DSS-induced ulcerative colitis mouse through regulating intestinal microbiota.

METRNL is a recently identified secreted protein with emerging functions. This study is to find major cellular source of circulating METRNL and to determine METRNL novel function. Here, we show METRNL is abundant in human and mouse vascular endothelium and released by endothelial cells using endoplasmic reticulum-Golgi apparatus pathway. By creating endothelial cell-specific Metrnl knockout mice, combined with bone marrow transplantation to produce bone marrow-specific deletion of Metrnl, we demonstrate that most of circulating METRNL (approximately 75%) originates from the endothelial cells. Both endothelial and circulating METRNL decrease in atherosclerosis mice and patients. By generating endothelial cell-specific Metrnl knockout in apolipoprotein E-deficient mice, combined with bone marrow-specific deletion of Metrnl in apolipoprotein E-deficient mice, we further demonstrate that endothelial METRNL deficiency accelerates atherosclerosis. Mechanically, endothelial METRNL deficiency causes vascular endothelial dysfunction including vasodilation impairment via reducing eNOS phosphorylation at Ser1177 and inflammation activation via enhancing NFκB pathway, which promotes the susceptibility of atherosclerosis. Exogenous METRNL rescues METRNL deficiency induced endothelial dysfunction. These findings reveal that METRNL is a new endothelial substance not only determining the circulating METRNL level but also regulating endothelial function for vascular health and disease. METRNL is a therapeutic target against endothelial dysfunction and atherosclerosis.

Objective To explore the expression of CRELD2 at the gene and protein levels of mouse tissues, and to provide a reference for studying the biological function of CRELD2 in various tissues. Methods The expression level of CRELD2 in the liver, pancreas, stomach, and lung of C57BL/6J mice was determined by real-time PCR and Western Blot. Results RT-PCR and WB showed that CRELD2 was expressed in mouse liver, pancreas, stomach, and lung. The relative expression levels of CRELD2 from high to low were pancreas, stomach, liver, and lung at the gene level, and pancreas, liver, stomach, and lung at protein level respectively. The result suggested that the relative expression levels of the CRELD2 gene and protein in different tissues were not completely consistent, suggesting that it is related to transcriptional regulation. Conclusion CRELD2 is expressed in mouse liver, pancreas, stomach, and lung, and the relative expression levels of CRELD2 are not completely parallel at the gene and protein level.

Objective Nicotinamide phosphoribosyltransferase (Nampt) is a new therapeutic target for ischemic stroke. The aim of this study was to investigate protective effect of liver-derived Nampt on ischemic stroke. Methods Liver-specific Nampt knockout mice were generated using the Cre/loxP system. Nampt^loxP/loxP mice were crossed with liver-specific Cre recombinase expression mice (Alb-Cre), and the progeny genotypes were identified by polymerase chain reaction. Body weight of knockout mice and control mice were measured. Nampt in liver and brain was determined by Western blot assay. Middle cerebral artery occlusion (MCAO), a classical ischemic stroke model, was generated in liver-specific Nampt knockout mice and control mice by electrocoagulation. After 24 h of modeling, neurological deficit scores of each group were evaluated and TTC staining was performed to determine the cerebral infarction volume. The level of plasma Nampt in each group was determined by ELISA. Results Liver-specific Nampt knockout mice with the genotype of Nampt^loxP/loxPAlb-Cre were successfully constructed. The hepatic Nampt expression in knockout mice was significantly decreased by 74.2% compared to control mice, while there was no significant difference in the expression of brain Nampt protein between the knockout group and the control group. Specific knockout of liver Nampt gene expression had no effect on the body weight of mice. Under normal physiological conditions, there was no significant difference in plasma Nampt levels between liver-specific Nampt knockout mice and control mice of the same gender. 24 h after MCAO modeling, there were no significant differences in neurological deficit scores, cerebral infarct volume and plasma Nampt concentration between liver-specific Nampt knockout group and control group. Conclusion Liver-specific Nampt knockout mice are successfully constructed. Liver-derived Nampt has no significant protective effects on ischemic stroke.