Human Nek6 is a monomeric mostly globular kinase with an unfolded short N-terminal domain

Background  

The NIMA-related kinases (Neks) are widespread among eukaryotes. In mammalians they represent an evolutionarily conserved family of 11 serine/threonine kinases, with 40-45% amino acid sequence identity to the Aspergillus nidulans mitotic regulator NIMA within their catalytic domains. Neks have cell cycle-related functions and were recently described as related to pathologies, particularly cancer, consisting in potential chemotherapeutic targets. Human Nek6, -7 and -9 are involved in the control of mitotic spindle formation, acting together in a mitotic kinase cascade, but their mechanism of regulation remain elusive.     

MicroRNA-21介导非对称性二甲基精氨酸诱导的内皮细胞衰老

目的：观察非对称性二甲基精氨酸（ADMA）对内皮细胞中microRNA-21（miR-21）表达的影响,探讨microRNA-21在ADMA诱导的内皮细胞衰老中的作用。方法：人脐静脉内皮细胞（HUVEC）与10uM的ADMA孵育48小时后收集细胞提取总RNA及蛋白,荧光定量实时RT—PCR检测miR-21表达,Westernblot检测超氧化物歧化酶2（SOD2）表达,衰老相关半乳糖苷酶（SA-β-gal）染色鉴定衰老的内皮细胞;然后HUVEC与miR-21抑制剂转染6小时后继续与10uM的ADMA孵育48小时留取细胞按上述方法检测相关指标。结果：HUVEC与ADMA孵育后miR-21表达量明显增加（P〈0．01）,同时衰老的内皮细胞数量增多（P〈0．05）,而SOD2表达减少（P〈0．01）;MiR-21抑制剂转染HUVEC后ADMA诱导的miR-21表达明显减少,同时衰老的内皮细胞减少,而SOD2表达明显增加（所有P〈0．01）。结论：ADMA诱导了HUVEC中miR-21表达及细胞衰老,miR-21介导了ADMA诱导的内皮细胞衰老作用,其机制可能与其抑制SOD2表达有关。     

Metoclopramide-induced central nervous system depression in the chicken

Background

Metoclopramide is a dopamine D2-receptor antagonist used as an antiemetic and gastroprokinetic agent in man and animals. The drug causes sedation as a side effect in man. Such a sedative action of metoclopramide has not been documented in the chicken as the drug is not used clinically in this species. The present study examines the central nervous system depressant effects of metoclopramide in 7–14 days old broiler chicks.

Results

Injection of metoclopramide at 50, 100 and 200 mg/kg, subcutaneously (s.c.) induced sedation in the chicks in a dose dependent manner. The chicks manifested, within 3.6–19 minutes of metoclopramide injection, signs of sedation characterized by drooping of the head and wings, closed eyelids, reduced motility and decreased distress calls. The duration of sedation ranged between 37.2 to 163.4 minutes. Metoclopramide at 100 and 200 mg/kg induced, within 12.2 and 6.2 minutes, sleep (loss of righting reflex) for 43.8 and 158.6 minutes, respectively. The median effective doses of metoclopramide for induction of sedation and sleep in the chicks were 11 and 53 mg/kg, s.c., respectively. Lower doses of metoclopramide (5 and 10 mg/kg, s.c.) significantly decreased the open-field activity of the chicks and increased the durations of their tonic immobility. All treated-chicks recovered from the central nervous system depressant effect of metoclopramide without any observable adverse effects.

Conclusion

The data suggest that metoclopramide induces central nervous system depression in chicks, and the drug could have potential clinical applications as a sedative-hypnotic agent in avian species not intended for human consumptions.     

22-Hydroxycholesterols regulate lipid metabolism differently than T0901317 in human myotubes

The nuclear liver X receptors (LXRalpha and beta) are regulators of lipid and cholesterol metabolism. Oxysterols are known LXR ligands, but the functional role of hydroxycholesterols is at present unknown. In human myotubes, chronic exposure to the LXR ligand T0901317 promoted formation of diacylglycerol (DAG) and triacylglycerol (TAG), 22-R-hydroxycholesterol (22-R-HC) had no effect, and 22-S-hydroxycholesterol (22-S-HC) reduced the formation. In accordance with this, 22-HC and T0901317 regulated the expression of fatty acid transporter CD36, stearoyl-CoA desaturase-1, acyl-CoA synthetase long chain family member 1 and fatty acid synthase (FAS) differently; all genes were increased by T0901317, 22-R-HC did not change their expression level, while 22-S-HC reduced it. Transfection studies confirmed that the FAS promoter was activated by T0901317 and repressed by 22-S-HC through an LXR response element in the promoter. Both 22-R-HC and T0901317 increased gene expression of LXRalpha, sterol regulatory element-binding protein 1c and ATP-binding cassette transporter A1, while 22-S-HC had little effect. In summary, 22-R-HC regulated lipid metabolism and mRNA expression of some LXR target genes in human myotubes differently than T0901317. Moreover, 22-S-HC did not behave like an inactive ligand; it reduced synthesis of complex lipids and repressed certain genes involved in lipogenesis and lipid handling.     

On the role of liver X receptors in lipid accumulation in adipocytes

The pivotal role of liver X receptors (LXRs) in the metabolic conversion of cholesterol to bile acids in mice is well established. More recently, the LXRalpha promoter has been shown to be under tight regulation by peroxisome proliferator-activated receptors (PPARs), implying a role for LXRalpha in mediating the interplay between cholesterol and fatty acid metabolism. We have studied the role of LXR in fat cells and demonstrate that LXR is regulated during adipogenesis and augments fat accumulation in mature adipocytes. LXRalpha expression in murine 3T3-L1 adipocytes as well as in human adipocytes was up-regulated in response to PPARgamma agonists. Administration of a PPARgamma agonist to obese Zucker rats also led to increased LXRalpha mRNA expression in adipose tissue in vivo. LXR agonist treatment of differentiating adipocytes led to increased lipid accumulation. An increase of the expression of the LXR target genes, sterol regulatory binding protein-1 and fatty acid synthase, was observed both in vivo and in vitro after treatment with LXR agonists for 24 h. Finally, we demonstrate that fat depots in LXRalpha/beta-deficient mice are smaller than in age-matched wild-type littermates. These findings imply a role for LXR in controlling lipid storage capacity in mature adipocytes and point to an intriguing physiological interplay between LXR and PPARgamma in controlling pathways in lipid handling.     

Trans10, cis12-conjugated linoleic acid prevents triacylglycerol accumulation in adipocytes by acting as a PPARgamma modulator

A group of polyunsaturated fatty acids called conjugated linoleic acids (CLAs) are found in ruminant products, where the most common isomers are cis9, trans11 (c 9,t11) and trans10, cis12 (t10,c12) CLA. A crude mixture of these isomers has been shown in animal studies to alter body composition by a reduction in body fat mass as well as an increase in lean body mass, with the t10,c12 isomer having the most pronounced effect. The objective of this study was to establish the molecular mechanisms by which t10,c12 CLA affects lipid accumulation in adipocytes. We have shown that t10,c12 CLA prevents lipid accumulation in human and mouse adipocytes at concentrations as low as 5 microM and 25 microM, respectively. t10,c12 CLA fails to activate peroxisome proliferator-activated receptor gamma (PPARgamma) but selectively inhibits thiazolidinedione-induced PPARgamma activation in 3T3-L1 adipocytes. Treatment of mature adipocytes with t10,c12 CLA alone or in combination with Darglitazone down-regulates the mRNA expression of PPARgamma as well as its target genes, fatty acid binding protein (aP2) and liver X receptor alpha (LXRalpha). Taken together, our results suggest that the trans10, cis12 CLA isomer prevents lipid accumulation in adipocytes by acting as a PPARgamma modulator.     

LXRβ deficient mice have reduced hepatic insulin clearance during hyperinsulinemic euglucemic clamp

The present study addresses the insulin sensitivity in mice deficient in LXRβ (LXRβ^−/−) as well as in wild type (wt) mice assessed by hyperinsulinemic euglycemic clamp. Wt and LXRβ^−/− mice were fed either a normal chow diet or a high fat and high cholesterol diet (HFCD), and insulin sensitivity was assessed by hyperinsulinemic euglycemic clamps. We show that LXRβ^−/− mice have reduced insulin clearance during hyperinsulinemic clamps upon feeding both HFCD and a regular chow diet. Moreover we also observed reduced hepatic inflammation in LXRβ^−/− mice compared to wt mice upon feeding an HFCD, despite equal levels of hepatic steatosis. In summary, our results indicate that LXRβ^−/− mice have reduced insulin clearance during hyperinsulinemic euglycemic clamps and also reduced hepatic inflammation upon feeding an HFCD for 26 weeks.