葛根素对胰岛素抵抗大鼠脂肪细胞葡萄糖转运蛋白4的影响

目的 :探讨葛根素对高糖高脂饮食诱导的胰岛素抵抗大鼠脂肪细胞葡萄糖转运蛋白 4 (GLUT4 )表达水平及其转位机制的影响。方法 :实验大鼠随机分为正常组、模型组和葛根素组 ,每组 10只。模型组和葛根素组大鼠喂以高糖高脂饲料 ,4周后葛根素组大鼠予以葛根素 10 0mg·kg-1·d-1腹腔注射。以Westernblot法检测各组大鼠脂肪细胞GLUT4的含量 ,定期检测实验大鼠的体质量、血甘油三酯和胆固醇、空腹血糖及血浆胰岛素水平 ,并计算胰岛素敏感指数。结果 :模型组大鼠脂肪细胞内膜GLUT4含量较正常组减少 38.72 % (P <0 .0 5 ) ,细胞外膜减少2 1.91% (P <0 .0 5 )。给予葛根素治疗 6周后 ,大鼠脂肪细胞内膜GLUT4的含量与模型组相比无明显变化 ,而细胞外膜GLUT4含量增加 2 1.4 6 % (P <0 .0 5 )。结论 :葛根素可提高胰岛素抵抗大鼠脂肪细胞GLUT4蛋白表达水平 ,且能够改善其转位机制 ,从而加强葡萄糖的摄取和利用。     

The role of resistin in obesity-induced insulin resistance

Resistin is a 12.5-kDa polypeptide hormone produced by adipocytes and immunocompetent cells. It was originally proposed as a link between obesity and insulin resistance/diabetes. Later, studies revealed that substantial inter-species differences exist between the major sites of resistin production in rodents (adipocytes) and humans (immunocompetent cells). While in rodents resistin appears to have an important role in the development of liver insulin resistance, its role in humans is less clear, and it is probably involved in the regulation of inflammatory processes rather than in insulin sensitivity. Current experimental and clinical data concerning resistin physiology and pathophysiology, and its possible role in the development of insulin resistance and atherosclerosis are detailed in this review.     

葛根素对胰岛素抵抗大鼠脂肪组织中糖原合成酶激酶3β表达的影响

目的探讨葛根素对高脂饮食诱导的胰岛素抵抗大鼠脂肪组织中糖原合成酶激酶3β(GSK-3β)表达的影响。方法30只SPF级雄性Wister大鼠随机分为2组,正常对照组10只,常规饲料喂养,模型组20只,高脂饲料喂养;4周后模型形成,模型组随机分为2组(胰岛素抵抗组、葛根素干预组,每组10只),继以高脂饲料喂养,葛根素干预组同时给予葛根素注射液100mg·kg-1·d-1腹腔注射。干预6周后,用Western-blot方法检测各组大鼠附睾脂肪组织中GSK-3β的表达,分析对比各组的表达差异;定期检测大鼠体重、空腹血糖及血浆胰岛素、血甘油三酯和胆固醇,并计算胰岛素敏感指数。结果高脂饲料喂养4周后,与正常对照组比较,模型组大鼠体重(BW)、空腹血糖(FPG)、胰岛素(FINS)、胆固醇(TC)、甘油三酯(TG)显著升高(P<0.05或P<0.01),胰岛素敏感指数ISI显著下降(P<0.01),胰岛素抵抗模型诱导成功;葛根素干预6周后,与胰岛素抵抗组大鼠比较,脂肪组织中GSK-3β的表达显著下降(P<0.05),和正常对照组比较,无显著差异。结论葛根素显著下调脂肪组织GSK-3β的表达,并且可能参与其改善胰岛素抵抗的机制。     

早发型子痫前期患者血清脂肪型脂肪酸结合蛋白水平与胰岛素抵抗关系的研究

目的：探讨早发型子痫前期患者血清脂肪型脂肪酸结合蛋白（FABP4）水平变化及其与胰岛素抵抗的关系。方法：选取2010年10月～2012年10月在青岛医学院第二附属医院产科住院分娩的早发型子痫前期（发病时孕周≤34周）患者30例为观察组,同期我院产科门诊检查的孕妇30例为对照组,采用酶联免疫吸附法检测两组空腹血清脂肪型脂肪酸结合蛋白（FABP4）,同时测定各组的血压、体重指数、血糖、空腹胰岛素等指标,采用稳态模型法计算胰岛素抵抗指数。结果：①观察组血清FABP4水平显著高于对照组（P〈0.05）;②观察组胰岛素抵抗指数显著高于对照组（P〈0.05）;③观察组血清FABP4与胰岛素抵抗指数呈正相关（r=0.96,P≤0.05）。结论：FABP4与胰岛素抵抗在早发型子痫前期发病中起重要作用。     

二甲双胍对胰岛素抵抗状态下脂肪细胞的作用

目的探讨二甲双胍对胰岛素抵抗状态下3T3-L1脂肪细胞的作用以及可能的作用机制。方法体外培养3T3-L1前脂肪细胞,诱导分化成熟后,将分化成熟的3T3-L1脂肪细胞分为空白组、模型组和不同浓度二甲双胍（0．01、0．10、0．50、1．00mmol／L）组,观察药物处理48h后培养基中葡萄糖含量及腺苷酸活化蛋白激酶（AMPK）mRNA水平。结果①模型组细胞上清培养液的葡萄糖吸光度值（2．5390±0．0024）明显高于空白组（1．4778±0．0033）（P〈0．05）,1．00、0．50、0．10、0．01mmol／L浓度的二甲双胍组培养液的葡萄糖吸光度值（分别为1．7400±0．0024、1．7418±0．0028、2．1785±0．0019、2．3693±0．0029）均低于模型组（2．5390±0．0024）（均P〈0．05）。②模型组的AMPKmRNA水平（0．120±0．006）明显低于空白组（1．000±0．000）（P〈0．05）。0．01、0．10、0．50、1．00mmol／L浓度的二甲双胍组AMPKmRNA水平（分别为0．240±0．006、0．530±0．035、0．850±0．020、0．890±0．041）明显高于模型组（均P〈0．05）。结论二甲双胍改善胰岛素抵抗状态下葡萄糖摄取,可能通过上调3T3-L1脂肪细胞AMPK水平增加胰岛素抵抗状态下脂肪细胞葡萄糖摄取。     

抵抗素在肝脏胰岛素抵抗中的作用及其机制探讨

目的探讨抵抗素在肝脏胰岛素抵抗中的作用及其可能的机制。方法将载有抵抗素基因的重组腺病毒经尾静脉注射构建高抵抗素血症小鼠模型,同时设正常对照组及病毒对照组,取肝脏组织切片行PAS糖原染色半定量观察肝糖代谢变化;以Western blot检测肝腺苷酸活化蛋白激酶(AMPK)的磷酸化,以磷酸化AMPK/总AMPK的比值代表AMPK激活程度;以实时PCR检测肝组织糖异生关键酶葡萄糖6磷酸酶(G6Pase)和磷酸烯醇式丙酮酸羧激酶(PEP-CK)mRNA表达水平的变化。结果重组腺病毒注射d5获得血中抵抗素高表达构建了高抵抗素血症动物模型,糖原染色示高抵抗素血症小鼠肝糖原含量较正常对照及病毒对照组降低(P<0.05);高抵抗素血症组肝AMPK磷酸化水平较正常对照及病毒对照组下降,磷酸化AMPK/总AMPK比值分别为0.78±0.06vs0.93±0.13,0.89±0.05(P<0.05)。高抵抗素血症小鼠G6Pase和PEPCK的mRNA表达升高,G6Pase分别为2.136±0.857vs1.353±0.49,1.250±0.77;PEPCK分别为3.54±0.90vs2.75±0.78,2.63±0.67(P<0.05)。结论抵抗素可能通过抑制肝脏AMPK活性,增加肝糖异生关键酶的表达而影响机体肝糖代谢,降低肝糖储量,参与肝脏胰岛素抵抗的形成。     

Mechanisms of insulin resistance in non-oxidative glucose metabolism: the role of glycogen synthase

Insulin-mediated non-oxidative glucose metabolism is more or less identical to glycogen synthesis in skeletal muscle and that is why this pathway is specifically discussed in this paper. All three major steps in non-oxidative glucose processing--glucose transport, phosphorylation and glycogen synthesis--are found to be reduced in response to insulin in insulin-resistant type 2 diabetic subjects compared with controls. The insulin-signalling cascade from the insulin receptor to PI-3-K was also found to be abnormal, resulting in a severely reduced phosphorylation degree of the IRS-1 (IRS-2?)-PI-3-K complex, which can explain both reduced glucose transport and glycogen synthesis. The most pronounced finding in our studies is reduced glycogen synthase activation by insulin which is found in prediabetic subjects with normal glucose tolerance as well as in type 2 diabetics, but more severely. This defect was not reversible after treatment (normalization of blood glucose) and is therefore a candidate for the primary defect which is likely to be of genetic origin, but also could be caused by genetic imprinting, intrauterine malnutrition and social inheritance (obesity). Most of the abnormalities in non-oxidative glucose metabolism may be of secondary origin due to hyperglycemia itself or obesity. Both events may stimulate production of glucosamine, malonyl CoA and intramuscular triglyceride accumulation. These metabolites can theoretically induce most of the defects in glucose processing and furthermore impair insulin signalling. Whether the primary defect in activation of glycogen synthase is due to an abnormality in the enzyme complex itself or in the insulin signalling cascade still has to be investigated.     

The role of the adipocyte hormone adiponectin in cardiovascular disease

Adiponectin, a novel hormone made by fat tissue, regulates energy metabolism and endothelial activation. Serum levels of adiponectin are reduced in conditions that are associated with an increased risk of cardiovascular disease, such as diabetes and the metabolic syndrome. Adiponectin trimers assemble into higher-order oligomers, which have different signaling properties. Adiponectin trimers and a C-terminal globular domain activate AMP-activated protein kinase, whereas hexamer and high-molecular weight isoforms activate nuclear factor-kappa B signaling pathways. Exogenous adiponectin corrects metabolic defects that are associated with insulin resistance, and might protect the endothelium from the progression of cardiovascular disease. Receptors for adiponectin have been described and might provide future therapeutic targets for the treatment of cardiovascular disease.     

The role of insulin resistance in the pathogenesis of Alzheimer's disease: implications for treatment

An emerging body of evidence suggests that an increased prevalence of insulin abnormalities and insulin resistance in Alzheimer's disease may contribute to the disease pathophysiology and clinical symptoms. It has long been known that insulin is essential for energy metabolism in the periphery. In the past 2 decades, convergent findings have begun to demonstrate that insulin also plays a role in energy metabolism and other aspects of CNS function. Investigators reported 20 years ago that insulin and insulin receptors were densely but selectively expressed in the brain, including the medial temporal regions that support the formation of memory. It has recently been demonstrated that insulin-sensitive glucose transporters are localised to the same regions supporting memory and that insulin plays a role in memory functions. Collectively, these findings suggest that insulin may contribute to normal cognitive functioning and that insulin abnormalities may exacerbate cognitive impairments, such as those associated with Alzheimer's disease. Insulin may also play a role in regulating the amyloid precursor protein and its derivative beta-amyloid (Abeta), which is associated with senile plaques, a neuropathological hallmark of Alzheimer's disease. It has been proposed that insulin can accelerate the intracellular trafficking of Abeta and interfere with its degradation. These findings are consistent with the notion that insulin abnormalities may potentially influence levels of Abeta in the brains of patients with Alzheimer's disease. The increased occurrence of insulin resistance in Alzheimer's disease and the numerous mechanisms through which insulin may affect clinical and pathological aspects of the disease suggest that improving insulin effectiveness may have therapeutic benefit for patients with Alzheimer's disease. The thiazolidinedione rosiglitazone has been shown to have a potent insulin-sensitising action that appears to be mediated through the peroxisome proliferator-activated receptor-gamma (PPAR-gamma). PPAR-gamma agonists, such as rosiglitazone, also have anti-inflammatory effects that may be of therapeutic benefit in patients with Alzheimer's disease. This review presents evidence suggesting that insulin resistance plays a role in the pathophysiology and clinical symptoms of Alzheimer's disease. Based on this evidence, we propose that treatment of insulin resistance may reduce the risk or retard the development of Alzheimer's disease.     

Factor for adipocyte differentiation 158 gene disruption prevents the body weight gain and insulin resistance induced by a high-fat diet

To clarify the molecular mechanism of adipocyte differentiation, we previously isolated a novel gene, factor for adipocyte differentiation (fad) 158, whose expression was induced during the earliest stages of adipogenesis, and its product was localized to the endoplasmic reticulum. We found that the knockdown of fad158 expression prevented the differentiation of 3T3-L1 cells into adipocytes. In addition, over-expression of fad158 promoted the differentiation of NIH-3T3 cells, which do not usually differentiate into adipocytes. Although these findings strongly suggest that fad158 has a crucial role in regulating adipocyte differentiation, the physiological role of the gene is still unclear. In this study, we generated mice in which fad158 expression was deleted. The fad158-deficient mice did not show remarkable changes in body weight or the weight of white adipose tissue on a chow diet, but had significantly lower body weights and fat mass than wild-type mice when fed a high-fat diet. Furthermore, although the disruption of fad158 did not influence insulin sensitivity on the chow diet, it improved insulin resistance induced by the high-fat diet. These results indicate that fad158 is a key factor in the development of obesity and insulin resistance caused by a high-fat diet.     

The role of IGF-1 resistance in obesity and type 2 diabetes-mellitus-related insulin resistance and vascular disease

Importance of the field: The insulin-resistant conditions of type 2 diabetes mellitus (T2DM) and obesity are a major cause of cardiovascular disease on a global scale. These disorders are not only a cause of ill health but are a huge financial drain on healthcare systems. T2DM leads to an increased risk of cardiovascular mortality equivalent to over 10 years of ageing while obesity independent of T2DM also leads to a substantially increased risk of acute myocardial infarction. Recent trials of therapeutic agents and approaches to preventing the cardiovascular complications of type 2 diabetes have been disappointing.

Areas covered in this review: The role of insulin resistance in the endothelium in the regulation of the anti-atherosclerotic signalling molecule NO and a potential important role for IGF-1 in vascular NO production.

What the reader will gain: A comprehensive understanding of how insulin and IGF-1 regulate vascular function and the effect of type 2 diabetes on these pathways.

Take home message: The roles of insulin and IGF-1 in vascular function are complex and intimately related. Nevertheless IGF-1 signalling in the arterial wall has the potential to be manipulated to protect the vasculature against the development of atherosclerosis and its devastating complications.     

Defining the role of insulin detemir in Basal insulin therapy

Insulin detemir is a novel long-acting insulin analogue with a unique mechanism underlying its prolonged duration of action. Unlike neutral protamine Hagedorn (NPH) insulin (insulin suspension isophane) and insulin glargine, which precipitate after administration, insulin detemir remains soluble after it is injected. The prolonged duration of action of insulin detemir is a result of the ability to self-associate into hexamers and dihexamers, and to bind reversibly to albumin. This mechanism of protraction provides a more prolonged, consistent and predictable glycaemic effect in patients with type 1 or type 2 diabetes mellitus compared with NPH insulin. Clinical studies have demonstrated that insulin detemir administered once or twice daily is at least as effective as NPH insulin and insulin glargine in achieving glycaemic control. Most trials have also shown that insulin detemir exhibits less intrapatient variability in glycaemic control compared with NPH insulin and insulin glargine. One of the benefits of insulin detemir is its favourable effect on bodyweight. Insulin detemir has shown weight neutrality in patients with type 1 diabetes and is associated with less weight gain than NPH insulin in clinical studies. Patients with type 2 diabetes using insulin detemir gain less weight than patients using NPH insulin and insulin glargine. In addition, a reduced risk of hypoglycaemia, particularly nocturnal hypoglycaemia, has been reported with insulin detemir compared with NPH insulin in patients with type 1 and type 2 diabetes. A reduced risk of major and nocturnal hypoglycaemia compared with insulin glargine in patients with type 1 diabetes has also been observed. Together, these data indicate that insulin detemir is a valuable new option for basal insulin therapy in patients with type 1 or type 2 diabetes.     

miR-301b在调节脂肪细胞分化中的作用

摘要： 目的 研究 miR-301b 在调节间充质干细胞向脂肪细胞分化过程中的作用。方法 对小鼠骨髓基质细胞 ST2 进行脂肪细胞诱导分化, 并利用 qRT-PCR 检测细胞分化过程中成脂分化诱导组相对于阴性对照组的 miR-301b 表达变化。对 ST2 细胞转染 miR-301b mimics 并进行成脂诱导分化, 利用 qRT-PCR 和 Western blot 技术检测 miR- 301b mimics 转染组和阴性对照片段 （NC） 转染组细胞的脂肪特异性基因和蛋白表达水平的变化。结果 成脂分化诱导组 miR-301b 相对表达水平 （0.219±0.021） 较对照组 （1.000±0.425） 减少 （P＜0.05）。miR-301b mimics 转染组的脂肪细胞特异性转录因子过氧化物酶体增殖物激活受体 （PPARγ）、 CCAAT 增强子结合蛋白 （C/EBPα） 和脂肪型脂肪酸结合蛋白 （aP2） 的相对表达量均较 NC 转染组降低 （P＜0.05）。miR-310b mimics 转染组与 NC 转染组相比, 标志基因aP2、 转录因子PPARγ 和C/EBPα 蛋白的表达量均减少 （P＜0.05）。结论 miR-301b可抑制脂肪细胞分化。     

The role of glycogen synthase kinase-3 in insulin resistance and type 2 diabetes

Glycogen synthase kinase-3 (GSK-3) is a ubiquitous cytosolic serine/threonine protein kinase that has been implicated in multiple receptor-mediated intracellular processes. Its unique feature, which distinguishes it from other protein kinases, is that it is constitutively active in resting conditions and acts as a suppressor of signalling pathways. The fact that the function of two key targets of insulin action, glycogen synthase and insulin receptor substrate-1, are suppressed by GSK-3, as well as the fact that GSK-3 activity is higher in diabetic tissues, makes it a promising drug discovery target for insulin resistance and Type 2 diabetes. Thus, the development of GSK-3 inhibitors has received attention as an attempt to control both the spread of the disease and its severity.     

黄芩苷对大鼠脂肪细胞胰岛素抵抗的改善作用

目的:探讨黄芩苷对大鼠脂肪细胞胰岛素抵抗的改善作用及可能机制。方法:无菌条件下取大鼠腹股沟处的脂肪组织采用酶消化法进行原代培养,将前脂肪细胞诱导分化为成熟的脂肪细胞后,以地塞米松诱导建立胰岛素抵抗模型,待其抗性成立后予随机分组干预,分为4组:正常组、模型组、黄芩苷干预组和阳性药物(罗格列酮)干预组。以葡萄糖氧化酶法检测各组细胞上清液中的葡萄糖浓度,ELISA方法检测上清液中细胞因子脂连素(adiponectin)、抵抗素(resistin)的浓度,免疫组化法检测PPARγ的表达。结果:黄芩苷干预组、阳性药物(罗格列酮)组与模型组相比能明显增加脂肪细胞葡萄糖消耗量(P<0.01),升高脂连素的水平(P<0.05,P<0.01)、降低抵抗素水平(P<0.05),PPARγ的表达增加(P<0.05,P<0.01)。结论:黄芩苷能增加胰岛素抵抗脂肪细胞的葡萄糖消耗,改善胰岛素抵抗,其机制可能是通过上调PPARγ的表达升高脂连素水平并降低抵抗素水平。     

Long-lasting partnership between insulin resistance and endothelial dysfunction: role of metabolic memory

Background and Purpose

The persistence of deleterious effects of hyperglycaemia even after glucose normalization is referred to as ‘metabolic memory’. However, similar persistent effects of the metabolic consequences of a high fat diet (HFD) have not been described.

Experimental Approach

Rats were given a normal pellet diet (NPD) or a HFD for 3 months. The animals from the HFD group were then returned to the NPD to observe the long-term effects of insulin resistance. Endothelial dysfunction was assessed by carbachol-mediated vasorelaxation and eNOS phosphorylation.

Key Results

As expected, HFD consumption resulted in insulin resistance and endothelial dysfunction. Phosphorylation of eNOS at S1177 was decreased in HFD rats, compared with that in the NPD group. Rats on 3 months of HFD showed glucose intolerance and impaired insulin sensitivity and were then switched back to NPD (REV group). Levels of cholesterol and triglyceride, and adiposity returned to normal in REV rats. However, endothelium-dependent vascular responses to carbachol which were impaired in HFD rats, continued to be impaired in REV rats. Similarly, decreased eNOS phosphorylation after HFD was not improved after 1 or 6 months of REV.

Conclusions and Implications

Our data indicate that returning to NPD did not improve the insulin sensitivity or the endothelial dysfunction induced by HFD. Although some biochemical parameters responsible for insulin resistance and endothelial dysfunction were normalized, molecular and vascular abnormalities, involving NO, persisted for several months, highlighting the long-lasting effects of metabolic memory.     

From excess adiposity to insulin resistance: The role of free fatty acids

With a positive caloric balance, adipocytes undergo excessive hypertrophy, which causes adipocyte dysfunction, as well as adipose tissue endocrine and immune responses. A preferential site of fat accumulation is the abdominal-perivisceral region, due to peculiar factors of the adipose tissue in such sites, namely an excess of glucocorticoid activity, which promotes the accumulation of fat; and the greater metabolic activity and sensitivity to lipolysis, due to increased number and activity of β3-adrenoceptors and, partly, to reduced activity of α2-adrenoceptors. As a consequence, more free fatty acids (FFA) are released into the portal system. Hypertrophic adipocytes begin to secrete low levels of TNF-α, which stimulate preadipocytes and endothelial cells to produce MCP-1, in turn responsible for attracting macrophages to the adipose tissue, thus developing a state of chronic low-grade inflammation which is causally linked to insulin resistance. Excess of circulating FFA, TNF-α and other factors induces insulin resistance. FFA cause insulin resistance by inhibiting insulin signaling through the activation of serin-kinases, i.e. protein kinase C-Θ, and the kinases JNK and IKK, which promote a mechanism of serine phosphorylation of Insulin Receptor Substrates (IRS), leading to interruption of the downstream insulin receptor (IR) signaling. TNF-α, secreted by hypertrophic adipocytes and adipose tissue macrophages, also inhibits IR signaling by a double mechanism of serine-phosphorylation and tyrosine-dephosphorylation of IRS-1, causing inactivation and degradation of IRS-1 and a consequent stop of IR signaling. Such mechanisms explain the transition from excess adiposity to insulin resistance, key to the further development of type 2 diabetes.     

Measurement of insulin resistance in vivo

Insulin sensitivity, which can be impaired in both glucose-intolerant and non-glucose-intolerant individuals, is a valuable parameter because of its potential as a marker for the future development of diabetes and increased cardiovascular risk. Techniques available for the determination of insulin sensitivity include the glucose clamp, insulin tolerance test, insulin suppression test, the frequently sampled intravenous glucose tolerance test and the regional artero-venous balance. Model assessment methods are also available for the measurement of insulin sensitivity at steady-state plasma glucose and insulin levels or after a standardised glucose infusion. Methods vary in their complexity, and the choice between them depends on the nature of the information required. There is also evidence for a strong genetic contribution to insulin sensitivity; although identification of the relevant gene(s) has not yet been successful, accurate phenotyping should still be carried out as part of the assessment of a patient's clinical status.