Nr5a1-Cre-mediated Tspo conditional knockout mice with low growth rate and prediabetes symptoms – A mouse model of stress diabetes

Translocator protein (TSPO) is a high-affinity cholesterol- and drug-binding mitochondrial protein. Nuclear receptor subfamily 5 group A member 1 or steroidogenic factor 1 (Nr5a1)-Cre mice were previously used to generate steroidogenic cell-specific Tspo gene conditional knockout (cKO) mice. TSPO-depleted homozygotes showed no response to adrenocorticotropic hormone (ACTH) in stimulating adrenal cortex corticosterone production but showed increased epinephrine synthesis in the medulla. No other phenotype was observed under normal growth conditions. During these studies, we noted that pairing two cKO mice resulted in the generation of small pups. These pups showed low growth rate at weaning, which has been linked to the development of type 2 diabetes (T2D) in adulthood. Experimental verification of T2D symptoms via blood testing of the adult mice, including glycated hemoglobin and insulin C-peptide measurements, showed that these Tspo cKO mice exhibited sustained hyperglycemia, a sign of prediabetes, likely due to the augmentation of hepatic glucose production mediated by the increased epinephrine. We also observed increased expression of the S100a8 gene, which is upregulated after chronic glucose stimulation. Taken together, the observed prediabetes phenotype and lack of response to ACTH indicate that Tspo cKO mice (Nr5a1-Cre^+/?, Tspo^fl/fl) could provide a useful model to study the link between diabetes and stress.     

Oxidized LDL autoantibodies are related to apolipoprotein E phenotype,independently of postprandial change in plasma triglycerides and LDL size,among patients with angiographically verified coronary artery disease and healthy controls

OBJECTIVE: Oxidized low-density lipoprotein (LDL) autoantibodies (oxLDLab), apolipoprotein E (apoE) phenotype, postprandial triglyceride changes and LDL size are suggested to be risk factors for coronary artery disease (CAD). Our aim was to study the interaction between these new risk factors among patients with CAD and healthy controls. METHODS: oxLDLab from 31 men with angiographically verified CAD and 31 healthy men were analyzed by enzyme-linked immunosorbent assay. Isoelectric focusing and immunoblotting were used for apoE phenotyping. Triglyceride level was measured after 12 h of fasting and 3, 5 and 7 h after a high-fat meal. Nondenaturing gradient gel electrophoresis was used to separate LDL particles according to size. RESULTS: oxLD- Lab levels increased according to apoE phenotype in the following order: E2 < E3 < E4 (p = 0.004, ANOVA). The postprandial response of triglycerides, the size of LDL particles and the concentration of LDL and high-density lipoprotein (HDL) cholesterol did not differ between apoE phenotypes, and the use of these variables as covariates did not change the statistically significant difference in oxLDLab levels between apoE phenotypes (p = 0.01, ANCOVA). oxLDLab levels did not differ between the patient and control groups. CONCLUSION: We found an association between apoE allele epsilon2 and decreased levels of oxLDLab, which was independent of the postprandial response of triglycerides, the size of LDL particles and plasma LDL and HDL cholesterol levels. The mechanism by which apoE affects oxidation of LDL remains unknown.     

有氧运动对小鼠高脂血症及脂蛋白代谢的影响

本研究以高胆固醇饮食小鼠为实验对象,观察有氧运动对脂质水平异常的动物个体血脂及脂蛋白代谢的影响。结果显示,经１１周有氧耐力训练后,高脂膳食＋运动组小鼠血浆ＴＧ、ＴＣ及ＬＤＬ－Ｃ水平均显著低于高脂膳食组（Ｐ＜０．０５）,而ＨＤＬ－Ｃ／ＴＣ和ＨＤＬ－Ｃ／ＬＤＬ－Ｃ比值均显著高于高脂膳食组（Ｐ＜０．０５）。表明长期有氧耐力训练能显著改善高胆固醇饮食小鼠血脂及脂蛋白代谢状况。     

PPARγ2 Pro12Ala polymorphism is associated with improved lipoprotein lipase functioning in adipose tissue of insulin resistant obese women

Lipoprotein lipase (LPL) plays a pivotal role in lipid metabolism, contributes to metabolic disorders related to insulin action and body weight regulation, and is influenced by inflammation. The Pro12Ala polymorphism of the peroxisome proliferator-activated receptor (PPAR)γ2 gene seems to influence LPL functioning, but its role in obesity and insulin resistance status, which usually coexist in the clinical setting, has not been explored. Our aim was to analyze the association of obesity and insulin resistance with adipose LPL activity and expression, and the influence of the PPARγ2 Pro12Ala polymorphism. A cross-sectional study was conducted in 58 reproductive-age women who underwent elective abdominal surgery. Free-fatty acids, glucose, insulin, and selected adipokines were measured in fasting blood samples. DNA was isolated and the polymorphism genotyped. Biopsies of abdominal subcutaneous adipose tissue obtained during surgery were used to determine enzymatic LPL activity and expression; and expression of selected cytokines. Overweight/obese women presented lower LPL activity (P = 0.022) and higher circulating TNF-α (P = 0.020) than controls. Insulin resistant women also showed borderline lower LPL activity than non-resistant (P = 0.052), but adiposity and inflammatory molecules were comparable. Nevertheless, LPL activity was higher in Pro12Ala carriers than in non-carriers after adjusting for obesity, insulin resistance and inflammation. Likewise, adipose LPL expression was increased in carriers while expression of cytokines was decreased. Our data suggest that insulin resistance is associated with low adipose LPL activity independently of obesity, but the PPARγ2 Pro12Ala polymorphism seems to protect the LPL functioning of obese insulin resistant women, likely through regulating inflammation in adipose tissue.     

Skeletal muscle damage and impaired regeneration due to LPL-mediated lipotoxicity

According to the concept of lipotoxicity, ectopic accumulation of lipids in non-adipose tissue induces pathological changes. The most prominent effects are seen in fatty liver disease, lipid cardiomyopathy, non-insulin-dependent diabetes mellitus, insulin resistance and skeletal muscle myopathy. We used the MCK(m)-hLPL mouse distinguished by skeletal and cardiac muscle-specific human lipoprotein lipase (hLPL) overexpression to investigate effects of lipid overload in skeletal muscle. We were intrigued to find that ectopic lipid accumulation induced proteasomal activity, apoptosis and skeletal muscle damage. In line with these findings we observed reduced Musculus gastrocnemius and Musculus quadriceps mass in transgenic animals, accompanied by severely impaired physical endurance. We suggest that muscle loss was aggravated by impaired muscle regeneration as evidenced by reduced cross-sectional area of regenerating myofibers after cardiotoxin-induced injury in MCK(m)-hLPL mice. Similarly, an almost complete loss of myogenic potential was observed in C2C12 murine myoblasts upon overexpression of LPL. Our findings directly link lipid overload to muscle damage, impaired regeneration and loss of performance. These findings support the concept of lipotoxicity and are a further step to explain pathological effects seen in muscle of obese patients, patients with the metabolic syndrome and patients with cancer-associated cachexia.     

人参皂甙Rg1抗OxLDL诱导内皮细胞凋亡及分子机制

目的 探讨人参皂甙Rg1抑制氧化低密度脂蛋白（oxidized low-density lipoprotein,OxLDL)诱导血管内皮细胞凋亡的作用及其相关分子机制。方法 以体外培养的牛主动脉内皮细胞为模型。分别加入OxLDL200μg/ml(OxLDL组）和OxLDL200μg/ml Rg140μg/ml（Rg1组）;对照组不加任何诱导物,培养24小时后观察细胞形态变化,DNA电泳,TUNEL染色检测细胞有无凋亡及凋亡的程度,Western blot分析各组内皮细胞型一氧化氮合酶（endothelial Nitric Oxide Synthase,eNOS)的表达水平。结果 （1）对照组和OxLDL组血管内皮细胞凋亡比例分别为8%和41.35%;(2)Rg1组血管内皮细胞凋亡比例为13.29%;(3)OxLDL抑制牛主动脉内皮细胞的eNOS表达水平,此抑制作用具有剂量依赖性。人参皂甙Rg1可使被OxLDL抑制的eNOS表达水平回升。结论 （1）OxLDL能诱导血管内皮细胞凋亡。（2）人参皂甙Rg1能抑制OxLDL诱导的血管内皮细胞凋亡。（3）此作用可能与上调内皮细胞的eNOS水平,减轻细胞的脂质过氧化损伤有关。     

Adipophilin在动脉粥样硬化病变和脂质负荷细胞中的作用研究(英)

Adipophilin是细胞内脂质聚集和与脂质聚集有关疾病的标志物,巨噬细胞源性泡沫细胞的形成是动脉粥样硬化性疾病发生的重要环节.为了探讨adipophilin在动脉粥样硬化性疾病的作用,通过高胆固醇饲料喂养新西兰白兔12周,复制动脉粥样硬化疾病模型,同时测定血脂的变化和动脉壁胆固醇,使用HE染色、苏丹Ⅳ染色观察动脉粥样硬化病变的形成,使用免疫组织化学的方法观察动脉粥样硬化病变处和动物肝脏中adipophilin的表达.结果发现,高胆固醇饲料喂养组血清总胆固醇、低密度脂蛋白胆固醇和动脉壁胆固醇明显增高,动脉粥样硬化病变面积增加到(40.06±7.29)%,动脉粥样硬化病变处adipophilin表达呈阳性;而adipophilin在肝脏中的表达无论是高胆固醇饲料喂养组或对照组均为阴性.使用80 mg/L OxLDL与小鼠腹膜巨噬细胞共孵育,复制脂质负荷细胞,然后把构建的1 mmol/L adipophilin反义寡核苷酸与该细胞共孵育.结果发现,使用油红O染色观察的细胞内脂滴明显减少,生化测定细胞内胆固醇酯显著降低,与对照组相比,差别有显著性.说明adipophilin与动脉粥样硬化病变有密切的关系,控制adipophilin的表达能够减少巨噬细胞细胞内胆固醇酯的聚集.     

Molecular action of vitamin E in lipoprotein oxidation: implications for atherosclerosis

The oxidation theory of atherosclerosis proposes that the oxidative modification of low-density lipoproteins (LDL) plays a central role in the disease. Although a direct causative role of LDL oxidation for atherogenesis has not been established, oxidized lipoproteins are detected in atherosclerotic lesions, and in vitro oxidized LDL exhibits putative pro-atherogenic activities. alpha-Tocopherol (alpha-TOH; vitamin E), the major lipid-soluble antioxidant present in lipoproteins, is thought to be antiatherogenic. However, results of vitamin E interventions on atherosclerosis in experimental animals and cardiovascular disease in humans have been inconclusive. Also, recent mechanistic studies demonstrate that the role of alpha-TOH during the early stages of lipoprotein lipid peroxidation is complex and that the vitamin does not act as a chain-breaking antioxidant. In the absence of co-antioxidants, compounds capable of reducing the alpha-TOH radical and exporting the radical from the lipoprotein particle, alpha-TOH exhibits anti- or pro-oxidant activity for lipoprotein lipids depending on the degree of radical flux and reactivity of the oxidant. The model of tocopherol-mediated peroxidation (TMP) explains the complex molecular action of alpha-TOH during lipoprotein lipid peroxidation and antioxidation. This article outlines the salient features of TMP, comments on whether TMP is relevant for in vivo lipoprotein lipid oxidation, and discusses how co-antioxidants may be required to attenuate lipoprotein lipid oxidation in vivo and perhaps atherosclerosis.     

氧化修饰使HDL促动脉平滑肌细胞胆固醇流出减少

为了研究氧化修饰对高密度脂蛋白（ＨＤＬ）转运细胞胆固醇地＾３Ｈ－胆固醇负荷的培养人动脉平滑肌细胞（ＳＭＣ）分别与天然ＨＤＬ及Ｃｕ＾２＋ａｋｇ ＨＯＣｌ氧化修饰的ＨＤＬ在３７℃温育不同时间后,分别测定细胞＾３Ｈ－胆固醇清除率。结果发现,温育２４ｈ后,经Ｃｕ＾２＋或ＨＯＬｌ氧修饰后的ＨＤＬ其细胞胆因醇清除率分别较天然ＨＤＬ下降了３０．０％和４３．１％（ｐ〈０．０１）。结果还发现,Ｃｕ＾２＋或ＨＯＣｌ氧