Activation of GPR55 Receptors Exacerbates oxLDL-Induced Lipid Accumulation and Inflammatory Responses,while Reducing Cholesterol Efflux from Human Macrophages

The G protein-coupled receptor GPR55 has been proposed as a new cannabinoid receptor associated with bone remodelling, nervous system excitability, vascular homeostasis as well as in several pathophysiological conditions including obesity and cancer. However, its physiological role and underlying mechanism remain unclear. In the present work, we demonstrate for the first time its presence in human macrophages and its increased expression in ox-LDL-induced foam cells. In addition, pharmacological activation of GPR55 by its selective agonist O-1602 increased CD36- and SRB-I-mediated lipid accumulation and blocked cholesterol efflux by downregulating ATP-binding cassette (ABC) transporters ABCA1 and ABCG1, as well as enhanced cytokine- and pro-metalloprotease-9 (pro-MMP-9)-induced proinflammatory responses in foam cells. Treatment with cannabidiol, a selective antagonist of GPR55, counteracted these pro-atherogenic and proinflammatory O-1602-mediated effects. Our data suggest that GPR55 could play deleterious role in ox-LDL-induced foam cells and could be a novel pharmacological target to manage atherosclerosis and other related cardiovascular diseases.     

Effects of Puerarin on Lipid Accumulation and Metabolism in High-Fat Diet-Fed Mice

In order to investigate the mechanisms by which puerarin from kudzu root extract regulates lipid metabolism, fifty mice were randomly assigned to five groups: normal diet, high-fat diet (HFD), and HFD containing 0.2%, 0.4% or 0.8% puerarin for 12 weeks. Body weight, intraperitioneal adipose tissue (IPAT) weight, serum biochemical parameters, and hepatic and feces lipids were measured. Activity and mRNA and protein expressions of hepatic lipid metabolism-related enzymes were analyzed. Compared with HFD, 0.4% and 0.8% puerarin significantly decreased body and IPAT weight. There was a significant decrease in the serum and hepatic concentrations of total cholesterol, triglycerides and leptin in mice fed the 0.4% and 0.8% puerarin diets compared with HFD. Fatty acid synthase activity was suppressed in mice fed the 0.4% and 0.8% puerarin diets, while the activities of AMP-activated protein kinase (AMPK), carnitine acyltransferase (CAT) and hormone-sensitive lipase (HSL) were increased. mRNA expression of peroxisome proliferator-activated receptor γ 2 (PPARγ 2) was down-regulated in liver of mice fed the 0.8% diet compared with HFD, while mRNA expression of CAT and HSL was considerably up-regulated by 0.4% and 0.8% puerarin diets. The protein expression of PPARγ2 in liver was decreased and those of p-AMPK, HSL and p-HSL were increased in mice fed 0.4% and 0.8% puerarin diets. These results suggest that > 0.4% puerarin influenced the activity, mRNA and protein levels of hepatic lipid metabolism-related enzymes, decreasing serum and liver lipids, body weight gain and fat accumulation. Puerarin might be beneficial to prevent lifestyle-related diseases.     

Effect of Short-Term Salinity on Lipid Metabolism and Ion Accumulation in Tomato Roots

To examine the ion accumulation and membrane lipid metabolism in response to salinity we compared two tomato cvs. Pera and Hellfrucht Fruhstamm (HF), considered to be salt-tolerant and sensitive respectively. Na⁺ and K⁺ accumulation was significantly higher in roots of cv. Pera after 24 h and 72 h of 100 mM NaCl. While in cv. HF, a temporary increase in K⁺ accumulation at 24 h was accompanied by a sustained increase in Na⁺ content. Both cultivars enhanced incorporation of [³²P]orthophosphate into phosphatidylinositol 4,5-bisphosphate at 24 h and 72 h of NaCl. In parallel to the increase of phosphatidylinositol 4,5-bisphosphate a decrease in phosphorylation of phosphatidic acid and phosphatidylcholine were observed in the sensitive cv. HF. Structural and signal lipid changes in response to salinity were more evident in the sensitive cv. HF. Salt tolerant cv. Pera accumulated Na⁺ ions in the roots without considerable modifications in lipid metabolism. This revised version was published online in July 2006 with corrections to the Cover Date.     

Prdx2 Inhibits Macrophage Lipid Accumulation Through ROS-NF-κB-miR-33a-ABCA1 Pathway

Previous studies have unraveled that peroxiredoxin 2 (Prdx2) inhibits atherogenesis in mice, whereas its role in macrophage lipid accumulation or the underlying mechanisms remain unknown. THP-1 monocyte-derived foam cells were transfected with Prdx2-overexpressing plasmid vectors (pcDNA3.1-Prdx2) or Prdx2 siRNA. The expression of ABCA1, NF-κB p65 and miR-33a were detected by RT-PCR and Western blotting. Percentage of cholesterol efflux was evaluated by liquid scintillation counting. Cellular lipid droplets were assessed using Oil Red O staining. Intracellular cholesterol contents were measured using high performance liquid chromatography (HPLC). Furthermore, cells were pre-treated with NF-κB inhibitor PDTC and/or miR-33a inhibitor, followed by detection of the indices above. The results showed that overexpression of Prdx2 in THP-1 monocyte-derived foam cells significantly increased ABCA1 expression and the percentage of ［³H］-cholesterol efflux to apoA-1 (P＜0.05), whereas NF-κB p65 and miR-33a levels as well as lipid accumulation were decreased (P＜0.05). After pre-treatment with PDTC and/or miR-33a inhibitor, these effects were more obvious (P＜0.05). In contrast, silencing of Prdx2 significantly diminished ABCA1 expression and increased NF-κB p65 and miR-33a levels. At last, we found that Prdx2 overexpression obviously down-regulated the ROS level in THP-1 monocyte-derived foam cells. Altogether, Prdx2 promotes macrophage cholesterol efflux and inhibits intracellular lipid accumulation through the ROS-NF-κB-miR-33a-ABCA1 pathway.     

Mitochondrial Integrity Regulated by Lipid Metabolism Is a Cell-Intrinsic Checkpoint for Treg Suppressive Function

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Class IIa Histone Deacetylases Drive Toll-like Receptor-Inducible Glycolysis and Macrophage Inflammatory Responses via Pyruvate Kinase M2

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高脂饮食联合链脲佐菌素对小鼠糖脂代谢及炎症的影响

观察高脂饮食联合链脲佐菌素(STZ)对小鼠糖脂代谢及胰岛功能损伤的影响。将体质量为18~20 g的SPF级雄性C57BL/6J小鼠40只,随机分为对照组和模型组,每组20只。对照组小鼠饲喂对照饲料,模型组小鼠饲喂高脂饲料。1周后,禁食16 h,测量小鼠体质量与空腹血糖;尾静脉采血,分离血清;每周1次,连续4周。4周后,对照组小鼠腹腔注射柠檬酸缓冲液,模型组小鼠腹腔注射STZ,剂量为40 mg·kg~(-1),每天1次,连续3 d。继续饲养2周后,测量随机血糖,以小鼠血糖≥16.7 mmol·L~(-1)者即判定为2型糖尿病。对照组及2型糖尿病小鼠经腹腔注射葡萄糖以进行糖耐量试验。与对照组同一时间的体质量和血糖进行比较,模型组小鼠体质量、血糖均升高,除第1周血糖外,差别均有统计学意义(P0.05)。采用重复测量方差分析,发现喂养时间对体质量(F=200.831)和血糖(F=7.025)均有影响,差异有统计学意义(P0.05);不同喂养时间对低密度脂蛋白(F=30.793)、甘油三酯(F=34.027)和高密度脂蛋白(F=30.793)均有影响,差异有统计学意义(P0.05)。不同饲料喂养与不同喂养时间对体质量和甘油三酯存在交互作用(P0.05)。比较糖耐量曲线发现,成模小鼠较对照组小鼠糖耐量降低。采用ELISA试剂盒检测小鼠血清中TNF-α含量,成模小鼠的TNF-α含量高于对照组,差异有统计学意义(P0.05)。高脂饮食可导致C57BL/6J小鼠糖脂代谢紊乱,给予STZ后引起了小鼠糖耐量降低及炎症损伤,高脂饮食联合STZ可提高小鼠2型糖尿病模型的成模率。     

细胞因子与巨噬细胞脂质稳态

在动脉粥样硬化发生发展过程中,巨噬细胞发挥了重要作用。巨噬细胞泡沫化是动脉粥样硬化发生过程中的一个标志性事件。一旦巨噬细胞脂质稳态动态平衡被打破会引起细胞泡沫化。细胞因子可通过不同途径调控相应的酶或受体表达,以及细胞因子与巨噬细胞的相互作用,从而调控细胞脂质稳态。本文就近年细胞因子与巨噬细胞脂质稳态方面的研究进行综述。     

Chronic Endocannabinoid System Stimulation Induces Muscle Macrophage and Lipid Accumulation in Type 2 Diabetic Mice Independently of Metabolic Endotoxaemia

Aims

Obesity and type 2 diabetes are characterised by low-grade inflammation, metabolic endotoxaemia (i.e., increased plasma lipopolysaccharides [LPS] levels) and altered endocannabinoid (eCB)-system tone. The aim of this study was to decipher the specific role of eCB-system stimulation or metabolic endotoxaemia in the onset of glucose intolerance, metabolic inflammation and altered lipid metabolism.

Methods

Mice were treated with either a cannabinoid (CB) receptor agonist (HU210) or low-dose LPS using subcutaneous mini-pumps for 6 weeks. After 3 weeks of the treatment under control (CT) diet, one-half of each group of mice were challenged with a high fat (HF) diet for the following 3-week period.

Results

Under basal conditions (control diet), chronic CB receptor agonist treatment (i.e., 6 weeks) induced glucose intolerance, stimulated metabolic endotoxaemia, and increased macrophage infiltration (CD11c and F4/80 expression) in the muscles; this phenomenon was associated with an altered lipid metabolism (increased PGC-1α expression and decreased CPT-1b expression) in this tissue. Chronic LPS treatment tended to increase the body weight and fat mass, with minor effects on the other metabolic parameters. Challenging mice with an HF diet following pre-treatment with the CB agonist exacerbated the HF diet-induced glucose intolerance, the muscle macrophage infiltration and the muscle''s lipid content without affecting the body weight or the fat mass.

Conclusion

Chronic CB receptor stimulation under basal conditions induces glucose intolerance, stimulates metabolic inflammation and alters lipid metabolism in the muscles. These effects worsen following the concomitant ingestion of an HF diet. Here, we highlight the central roles played by the eCB system and LPS in the pathophysiology of several hallmarks of obesity and type 2 diabetes.     

The Relationship between Inorganic Nitrogen Metabolism and Proline Accumulation in Osmoregulatory Responses of Two Euryhaline Microalgae

Chlorella autotrophica, a euryhaline marine alga, and Stichococcus bacillaris, a salt-tolerant soil alga, grow in the presence of methionine sulfoximine (MSX), an inhibitor of glutamine synthetase, by maintaining high levels of NADPH-glutamate dehydrogenase. Nitrate reductase showed no change in MSX-adapted cells. For both species, MSX-adapted cells retained their capacity to accumulate proline in response to salinity, and in S. bacillaris no major shift was observed in the presence of MSX toward the accumulation of sorbitol. Following transfer from 33 to 150% artificial seawater (ASW), both algae exhibited increases in organic solute levels without a lag. Within 6 h of this sudden increase in salinity, the levels of proline in C. autotrophica and of proline and sorbitol in S. bacillaris were similar to those found in steady state 150% ASW cultures. Following transfer from 33 to 150% ASW, S. bacillaris continued [¹⁴C] bicarbonate photoassimilation at a normal rate and maintained active enzymes of nitrogen assimilation. The incorporation of [¹⁴C]phenylalanine into proteins was inhibited for about 30 minutes in MSX-free cells and 90 minutes in MSX-adapted cells following transfer from 33 to 150% ASW; the recovery after these lag periods was almost complete.     

脂肪代谢的整合调控

脂肪组织是人体内甘油三酯的主要储存场所,脂肪分解产生的甘油和游离脂肪酸对机体能量代谢起着至关重要的作用。肝脏在脂类运输和代谢中起重要作用。在餐后、饥饿不同状态机体内脂肪代谢不同。脂肪代谢失调是肥胖发生发展的重要原因,内脏脂肪和胰岛素抵抗等与疾病关系密切。     

Hepatic FoxO1 Integrates Glucose Utilization and Lipid Synthesis through Regulation of Chrebp O-Glycosylation

In liver, glucose utilization and lipid synthesis are inextricably intertwined. When glucose availability exceeds its utilization, lipogenesis increases, leading to increased intrahepatic lipid content and lipoprotein secretion. Although the fate of three-carbon metabolites is largely determined by flux rate through the relevant enzymes, insulin plays a permissive role in this process. But the mechanism integrating insulin receptor signaling to glucose utilization with lipogenesis is unknown. Forkhead box O1 (FoxO1), a downstream effector of insulin signaling, plays a central role in hepatic glucose metabolism through the regulation of hepatic glucose production. In this study, we investigated the mechanism by which FoxO1 integrates hepatic glucose utilization with lipid synthesis. We show that FoxO1 overexpression in hepatocytes reduces activity of carbohydrate response element binding protein (Chrebp), a key regulator of lipogenesis, by suppressing O-linked glycosylation and reducing the protein stability. FoxO1 inhibits high glucose- or O-GlcNAc transferase (OGT)-induced liver-pyruvate kinase (L-PK) promoter activity by decreasing Chrebp recruitment to the L-PK promoter. Conversely, FoxO1 ablation in liver leads to the enhanced O-glycosylation and increased protein level of Chrebp owing to decreased its ubiquitination. We propose that FoxO1 regulation of Chrebp O-glycosylation is a mechanism linking hepatic glucose utilization with lipid synthesis.     

Spastin Binds to Lipid Droplets and Affects Lipid Metabolism

Mutations in SPAST, encoding spastin, are the most common cause of autosomal dominant hereditary spastic paraplegia (HSP). HSP is characterized by weakness and spasticity of the lower limbs, owing to progressive retrograde degeneration of the long corticospinal axons. Spastin is a conserved microtubule (MT)-severing protein, involved in processes requiring rearrangement of the cytoskeleton in concert to membrane remodeling, such as neurite branching, axonal growth, midbody abscission, and endosome tubulation. Two isoforms of spastin are synthesized from alternative initiation codons (M1 and M87). We now show that spastin-M1 can sort from the endoplasmic reticulum (ER) to pre- and mature lipid droplets (LDs). A hydrophobic motif comprised of amino acids 57 through 86 of spastin was sufficient to direct a reporter protein to LDs, while mutation of arginine 65 to glycine abolished LD targeting. Increased levels of spastin-M1 expression reduced the number but increased the size of LDs. Expression of a mutant unable to bind and sever MTs caused clustering of LDs. Consistent with these findings, ubiquitous overexpression of Dspastin in Drosophila led to bigger and less numerous LDs in the fat bodies and increased triacylglycerol levels. In contrast, Dspastin overexpression increased LD number when expressed specifically in skeletal muscles or nerves. Downregulation of Dspastin and expression of a dominant-negative variant decreased LD number in Drosophila nerves, skeletal muscle and fat bodies, and reduced triacylglycerol levels in the larvae. Moreover, we found reduced amount of fat stores in intestinal cells of worms in which the spas-1 homologue was either depleted by RNA interference or deleted. Taken together, our data uncovers an evolutionarily conserved role of spastin as a positive regulator of LD metabolism and open up the possibility that dysfunction of LDs in axons may contribute to the pathogenesis of HSP.     

Lipid Metabolism,Oxidative Stress and Cell Death Are Regulated by PKC Delta in a Dietary Model of Nonalcoholic Steatohepatitis

Steatosis, oxidative stress, and apoptosis underlie the development of nonalcoholic steatohepatitis (NASH). Protein kinase C delta (PKCδ) has been implicated in fatty liver disease and is activated in the methionine and choline-deficient (MCD) diet model of NASH, yet its pathophysiological importance towards steatohepatitis progression is uncertain. We therefore addressed the role of PKCδ in the development of steatosis, inflammation, oxidative stress, apoptosis, and fibrosis in an animal model of NASH. We fed PKCδ^−/− mice and wildtype littermates a control or MCD diet. PKCδ^−/− primary hepatocytes were used to evaluate the direct effects of fatty acids on hepatocyte lipid metabolism gene expression. A reduction in hepatic steatosis and triglyceride levels were observed between wildtype and PKCδ^−/− mice fed the MCD diet. The hepatic expression of key regulators of β-oxidation and plasma triglyceride metabolism was significantly reduced in PKCδ^−/− mice and changes in serum triglyceride were blocked in PKCδ^−/− mice. MCD diet-induced hepatic oxidative stress and hepatocyte apoptosis were reduced in PKCδ^−/− mice. MCD diet-induced NADPH oxidase activity and p47^phox membrane translocation were blunted and blocked, respectively, in PKCδ^−/− mice. Expression of pro-apoptotic genes and caspase 3 and 9 cleavage in the liver of MCD diet fed PKCδ^−/− mice were blunted and blocked, respectively. Surprisingly, no differences in MCD diet-induced fibrosis or pro-fibrotic gene expression were observed in 8 week MCD diet fed PKCδ^−/− mice. Our results suggest that PKCδ plays a role in key pathological features of fatty liver disease but not ultimately in fibrosis in the MCD diet model of NASH.