Rapamycin-induced insulin resistance is mediated by mTORC2 loss and uncoupled from longevity

Rapamycin, an inhibitor of mechanistic target of rapamycin complex 1 (mTORC1), extends the life spans of yeast, flies, and mice. Calorie restriction, which increases life span and insulin sensitivity, is proposed to function by inhibition of mTORC1, yet paradoxically, chronic administration of rapamycin substantially impairs glucose tolerance and insulin action. We demonstrate that rapamycin disrupted a second mTOR complex, mTORC2, in vivo and that mTORC2 was required for the insulin-mediated suppression of hepatic gluconeogenesis. Further, decreased mTORC1 signaling was sufficient to extend life span independently from changes in glucose homeostasis, as female mice heterozygous for both mTOR and mLST8 exhibited decreased mTORC1 activity and extended life span but had normal glucose tolerance and insulin sensitivity. Thus, mTORC2 disruption is an important mediator of the effects of rapamycin in vivo.     

Brain IRS2 signaling coordinates life span and nutrient homeostasis

Reduced insulin-like signaling extends the life span of Caenorhabditis elegans and Drosophila. Here, we show that, in mice, less insulin receptor substrate-2 (Irs2) signaling throughout the body or just in the brain extended life span up to 18%. At 22 months of age, brain-specific Irs2 knockout mice were overweight, hyperinsulinemic, and glucose intolerant; however, compared with control mice, they were more active and displayed greater glucose oxidation, and during meals they displayed stable superoxide dismutase-2 concentrations in the hypothalamus. Thus, less Irs2 signaling in aging brains can promote healthy metabolism, attenuate meal-induced oxidative stress, and extend the life span of overweight and insulin-resistant mice.     

Extension of life-span by loss of CHICO, a Drosophila insulin receptor substrate protein

The Drosophila melanogaster gene chico encodes an insulin receptor substrate that functions in an insulin/insulin-like growth factor (IGF) signaling pathway. In the nematode Caenorhabditis elegans, insulin/IGF signaling regulates adult longevity. We found that mutation of chico extends fruit fly median life-span by up to 48% in homozygotes and 36% in heterozygotes. Extension of life-span was not a result of impaired oogenesis in chico females, nor was it consistently correlated with increased stress resistance. The dwarf phenotype of chico homozygotes was also unnecessary for extension of life-span. The role of insulin/IGF signaling in regulating animal aging is therefore evolutionarily conserved.     

A mechanism of extreme growth and reliable signaling in sexually selected ornaments and weapons

Many male animals wield ornaments or weapons of exaggerated proportions. We propose that increased cellular sensitivity to signaling through the insulin/insulin-like growth factor (IGF) pathway may be responsible for the extreme growth of these structures. We document how rhinoceros beetle horns, a sexually selected weapon, are more sensitive to nutrition and more responsive to perturbation of the insulin/IGF pathway than other body structures. We then illustrate how enhanced sensitivity to insulin/IGF signaling in a growing ornament or weapon would cause heightened condition sensitivity and increased variability in expression among individuals--critical properties of reliable signals of male quality. The possibility that reliable signaling arises as a by-product of the growth mechanism may explain why trait exaggeration has evolved so many different times in the context of sexual selection.     

Role of brain insulin receptor in control of body weight and reproduction

Insulin receptors (IRs) and insulin signaling proteins are widely distributed throughout the central nervous system (CNS). To study the physiological role of insulin signaling in the brain, we created mice with a neuron-specific disruption of the IR gene (NIRKO mice). Inactivation of the IR had no impact on brain development or neuronal survival. However, female NIRKO mice showed increased food intake, and both male and female mice developed diet-sensitive obesity with increases in body fat and plasma leptin levels, mild insulin resistance, elevated plasma insulin levels, and hypertriglyceridemia. NIRKO mice also exhibited impaired spermatogenesis and ovarian follicle maturation because of hypothalamic dysregulation of luteinizing hormone. Thus, IR signaling in the CNS plays an important role in regulation of energy disposal, fuel metabolism, and reproduction.     

Augmented Wnt signaling in a mammalian model of accelerated aging

The contribution of stem and progenitor cell dysfunction and depletion in normal aging remains incompletely understood. We explored this concept in the Klotho mouse model of accelerated aging. Analysis of various tissues and organs from young Klotho mice revealed a decrease in stem cell number and an increase in progenitor cell senescence. Because klotho is a secreted protein, we postulated that klotho might interact with other soluble mediators of stem cells. We found that klotho bound to various Wnt family members. In a cell culture model, the Wnt-klotho interaction resulted in the suppression of Wnt biological activity. Tissues and organs from klotho-deficient animals showed evidence of increased Wnt signaling, and ectopic expression of klotho antagonized the activity of endogenous and exogenous Wnt. Both in vitro and in vivo, continuous Wnt exposure triggered accelerated cellular senescence. Thus, klotho appears to be a secreted Wnt antagonist and Wnt proteins have an unexpected role in mammalian aging.     

缢蛏IGFALS基因的表达特征及IGF系统对生长的调控作用

类胰岛素生长因子(insulin-like growth factor,IGF)信号通路在机体的发育、繁殖以及生长等过程中起着重要的调控作用。类胰岛素生长因子酸不稳定亚基(IGF acid-labile subunit,IGFALS)是IGF系统中的重要一员,可通过延长IGF的半衰期参与IGF信号通路的调控。本研究首次在缢蛏转录组数据库中筛选鉴定了两个IGFALS基因,包含完整的开放阅读框,分别命名为IGFALSa和IGFALSb。IGFALSa基因的cDNA序列为4809 bp,编码996个氨基酸;IGFALSb基因的cDNA序列为1925 bp,编码546个氨基酸。在缢蛏不同发育期的表达分析中发现,IGFALSa和IGFALSb在幼虫的前期发育阶段均只有少量表达,而随着幼虫的发育,其表达量逐渐上升;组织表达分析表明,IGFALSa在外套膜和性腺中高表达,IGFALSb则在水管中高表达。利用不同质量浓度胰岛素短期刺激缢蛏稚贝,当质量浓度为10 mg/L时,两个IGFALS基因表达量均显著上调,其下游基因IRS、PDK1、MPKP1的表达量也显著上调;进一步利用10 mg/L胰岛素长期喂养缢蛏稚贝,结果显示其壳长和壳宽的日生长率均显著提升。     

Insulin resistance and a diabetes mellitus-like syndrome in mice lacking the protein kinase Akt2 (PKB beta)

Glucose homeostasis depends on insulin responsiveness in target tissues, most importantly, muscle and liver. The critical initial steps in insulin action include phosphorylation of scaffolding proteins and activation of phosphatidylinositol 3-kinase. These early events lead to activation of the serine-threonine protein kinase Akt, also known as protein kinase B. We show that mice deficient in Akt2 are impaired in the ability of insulin to lower blood glucose because of defects in the action of the hormone on liver and skeletal muscle. These data establish Akt2 as an essential gene in the maintenance of normal glucose homeostasis.     

Increased insulin sensitivity and obesity resistance in mice lacking the protein tyrosine phosphatase-1B gene

Protein tyrosine phosphatase-1B (PTP-1B) has been implicated in the negative regulation of insulin signaling. Disruption of the mouse homolog of the gene encoding PTP-1B yielded healthy mice that, in the fed state, had blood glucose concentrations that were slightly lower and concentrations of circulating insulin that were one-half those of their PTP-1B+/+ littermates. The enhanced insulin sensitivity of the PTP-1B-/- mice was also evident in glucose and insulin tolerance tests. The PTP-1B-/- mice showed increased phosphorylation of the insulin receptor in liver and muscle tissue after insulin injection in comparison to PTP-1B+/+ mice. On a high-fat diet, the PTP-1B-/- and PTP-1B+/- mice were resistant to weight gain and remained insulin sensitive, whereas the PTP-1B+/+ mice rapidly gained weight and became insulin resistant. These results demonstrate that PTP-1B has a major role in modulating both insulin sensitivity and fuel metabolism, thereby establishing it as a potential therapeutic target in the treatment of type 2 diabetes and obesity.     

不同品种鸭胚胎期骨骼肌成肌细胞GHR和IGF 1 mRNA表达差异分析

为探讨生长激素受体（growth hormone receptor,GHR）和胰岛素样生长因子 1（Insulin like growth factor 1,IGF 1）在不同品种鸭胚胎期骨骼肌成肌细胞中的表达差异。选择生长速度不同的金定鸭和高邮鸭为试验动物,采用实时荧光定量PCR方法检测鸭13,15,17,19,21和23胚龄时胸肌和腿肌成肌细胞GHR,IGF 1 mRNA的表达情况,并进行了品种间比较。结果发现：13胚龄时,高邮鸭胸肌和腿肌成肌细胞IGF 1的表达均显著高于金定鸭（P<0.05）;17胚龄是两个品种鸭GHR和IGF 1共同的表达高峰期;17胚龄之后,鸭胸肌和腿肌成肌细胞GHR和IGF 1表达均显著降低。在19,21胚龄时,高邮鸭胸肌成肌细胞2个基因的表达均显著高于金定鸭（P<0.05）,而腿肌成肌细胞GHR和IGF 1表达在品种间无显著差异（P>0.05）。鸭胚胸肌和腿肌成肌细胞GHR和IGF 1表达呈现极显著的正线性相关（P<0.01）。提示：GHR和IGF 1的表达谱及各自在品种间的变化规律基本一致;鸭胚骨骼肌成肌细胞GHR和IGF 1 mRNA表达有组织特异性,二者之间可能存在正调控的作用机制。     

TRB3: a tribbles homolog that inhibits Akt/PKB activation by insulin in liver

Insulin resistance is a major hallmark in the development of type II diabetes, which is characterized by the failure of insulin to promote glucose uptake in muscle and to suppress glucose production in liver. The serine-threonine kinase Akt (PKB) is a principal target of insulin signaling that inhibits hepatic glucose output when glucose is available from food. Here we show that TRB3, a mammalian homolog of Drosophila tribbles, functions as a negative modulator of Akt. TRB3 expression is induced in liver under fasting conditions, and TRB3 disrupts insulin signaling by binding directly to Akt and blocking activation of the kinase. Amounts of TRB3 RNA and protein were increased in livers of db/db diabetic mice compared with those in wild-type mice. Hepatic overexpression of TRB3 in amounts comparable to those in db/db mice promoted hyperglycemia and glucose intolerance. Our results suggest that, by interfering with Akt activation, TRB3 contributes to insulin resistance in individuals with susceptibility to type II diabetes.     

Continuous fatty acid oxidation and reduced fat storage in mice lacking acetyl-CoA carboxylase 2

Malonyl-coenzyme A (malonyl-CoA), generated by acetyl-CoA carboxylases ACC1 and ACC2, is a key metabolite in the regulation of energy homeostasis. Here, we show that Acc2-/- mutant mice have a normal life span, a higher fatty acid oxidation rate, and lower amounts of fat. In comparison to the wild type, Acc2-deficient mice had 10- and 30-fold lower levels of malonyl-CoA in heart and muscle, respectively. The fatty acid oxidation rate in the soleus muscle of the Acc2-/- mice was 30% higher than that of wild-type mice and was not affected by addition of insulin; however, addition of insulin to the wild-type muscle reduced fatty acid oxidation by 45%. The mutant mice accumulated 50% less fat in their adipose tissue than did wild-type mice. These results raise the possibility that pharmacological manipulation of ACC2 may lead to loss of body fat in the context of normal caloric intake.     

海带多糖的抗衰老作用及其机理的研究

以果蝇(Drosophila melanogaster)作为试验动物,探讨了海带多糖(Laminaria japonicapolysaccharide,LJP)延缓衰老的作用及其机理。试验将未交配的果蝇雌雄分开并随机分成4组,每组100只,用含不同浓度海带多糖的培养基喂养,培养基中所含海带多糖的浓度分别为0(对照组)、0.25%、0.50%、1.00%。用果蝇寿命试验检测其抗衰老作用,分别使用邻苯三酚自氧化法、钼酸铵比色法、硫代巴比妥酸(TBA)法测定果蝇体内超氧化物岐化酶(SOD)、过氧化氢酶(CAT)活性及丙二醛(MDA)含量。利用统计学软件SAS v6.12对试验数据进行分析。结果表明:培养基中添加海带多糖能延长果蝇平均寿命,寿命延长的百分率与喂食果蝇的海带多糖浓度有一定的量效关系,培养基中海带多糖浓度为0.25%、0.50%、1.00%时,与对照组相比,雌果蝇寿命延长百分率分别为5.20%、6.20%、9.20%,雄果蝇寿命延长百分率分别为4.60%、5.00%、6.00%;饲喂海带多糖后果蝇体内的SOD、CAT活性提高,与对照组相比,海带多糖添加量为0.50%和1.00%时,雌性果蝇SOD、CAT活性提高量达到显著水平(P<0.05),MDA降低量达到显著水平(P<0.05);海带多糖添加量为1.00%时,雄性果蝇SOD与CAT活性提高量达到显著水平(P<0.05),MDA含量降低。提示提高生物体内抗氧化酶活力,降低衰老物质前体的含量可能是海带多糖抗衰老的途径之一。     

Protein kinase C beta and prolyl isomerase 1 regulate mitochondrial effects of the life-span determinant p66Shc

The 66-kilodalton isoform of the growth factor adapter Shc (p66Shc) translates oxidative damage into cell death by acting as reactive oxygen species (ROS) producer within mitochondria. However, the signaling link between cellular stress and mitochondrial proapoptotic activity of p66Shc was not known. We demonstrate that protein kinase C beta, activated by oxidative conditions in the cell, induces phosphorylation of p66Shc and triggers mitochondrial accumulation of the protein after it is recognized by the prolyl isomerase Pin1. Once imported, p66Shc causes alterations of mitochondrial Ca2+ responses and three-dimensional structure, thus inducing apoptosis. These data identify a signaling route that activates an apoptotic inducer shortening the life span and could be a potential target of pharmacological approaches to inhibit aging.     

Transgenic mice with a reduced core body temperature have an increased life span

Reduction of core body temperature has been proposed to contribute to the increased life span and the antiaging effects conferred by calorie restriction (CR). Validation of this hypothesis has been difficult in homeotherms, primarily due to a lack of experimental models. We report that transgenic mice engineered to overexpress the uncoupling protein 2 in hypocretin neurons (Hcrt-UCP2) have elevated hypothalamic temperature. The effects of local temperature elevation on the central thermostat resulted in a 0.3 degrees to 0.5 degrees C reduction of the core body temperature. Fed ad libitum, Hcrt-UCP2 transgenic mice had the same caloric intake as their wild-type littermates but had increased energy efficiency and a greater median life span (12% increase in males; 20% increase in females). Thus, modest, sustained reduction of core body temperature prolonged life span independent of altered diet or CR.     

石斛多糖对延缓秀丽隐杆线虫衰老作用的影响

石斛是中国传统中药材,其多糖含量丰富,具有提高免疫力、抗氧化、延缓衰老等多种功效。本文以多糖含量丰富的铁皮石斛、细茎石斛和鼓槌石斛为对象,探讨了石斛多糖对模式生物秀丽隐杆线虫寿命、产卵量、运动行为能力、热应激能力等的影响。结果表明：三种石斛多糖在不影响秀丽隐杆线虫正常生殖能力的条件下显著延长线虫的平均寿命和最长寿命,其中80mg/L的细茎石斛多糖与对照组相比,平均寿命提高了33.2%;不同浓度的石斛多糖能明显提升线虫的运动能力,其头部摆动频率、身体弯曲频率、热应激能力均随着多糖浓度的升高而增加,与延长线虫寿命正相关。论文结果为阐述石斛多糖延缓衰老功能的作用机理,更好地开发利用石斛提供理论依据。     

Reversal of obesity- and diet-induced insulin resistance with salicylates or targeted disruption of Ikkbeta

We show that high doses of salicylates reverse hyperglycemia, hyperinsulinemia, and dyslipidemia in obese rodents by sensitizing insulin signaling. Activation or overexpression of the IkappaB kinase beta (IKKbeta) attenuated insulin signaling in cultured cells, whereas IKKbeta inhibition reversed insulin resistance. Thus, IKKbeta, rather than the cyclooxygenases, appears to be the relevant molecular target. Heterozygous deletion (Ikkbeta+/-) protected against the development of insulin resistance during high-fat feeding and in obese Lep(ob/ob) mice. These findings implicate an inflammatory process in the pathogenesis of insulin resistance in obesity and type 2 diabetes mellitus and identify the IKKbeta pathway as a target for insulin sensitization.     

抗脂肪细胞膜蛋白多克隆抗体对猪脂类和内分泌代谢的影响

 给15kg体重仔猪分别腹腔注射0,10,20,30mg抗脂肪细胞膜蛋白多克隆抗体。结果显示,抗脂肪细胞膜蛋白抗体可显著提高血清脂蛋白脂酶（LPL）的活性和低密度脂蛋白（LDL）的含量（P<0.05）,降低游离脂肪酸（FFA）和极低密度脂蛋白（VLDL）的含量（P<0.05）,对血清总脂、甘油三酯（TG）、血清总胆固醇（CHO）和高密度脂蛋白（HDL）的含量无明显影响（P>0.05）。此外,该抗体可显著降低血清胰岛素（Ins）的水平（P<0.05）,提高三碘甲状腺原氨酸（T3）的水平（P<0.05）,而对血清生长激素（GH）和胰岛素样生长因子-1（IGF-1）的水平无明显影响（P>0.05）。表明抗脂肪细胞膜蛋白抗体可通过影响血液脂类代谢和激素的水平而减少体内脂肪沉积。     

西方蜜蜂工蜂不同虫态发育的转录组学分析

【目的】基于转录组学对西方蜜蜂工蜂不同虫态间的差异表达基因（DEGs）进行筛选和功能注释分析,揭示与工蜂生长发育相关的信号通路,为深入解析工蜂生长发育的分子调控机理提供基础数据。【方法】以西方蜜蜂工蜂的3日龄幼虫、1日龄蛹和1日龄羽化工蜂3个虫态为研究对象,利用llumina NovaSeq 6000平台进行转录组测序,采用DESeq2筛选不同虫态样品间的表达差异基因,然后分别进行GO功能注释分析及KEGG信号通路富集分析,并通过实时荧光定量PCR进行验证。【结果】经转录组测序,在西方蜜蜂工蜂3日龄幼虫与1日龄蛹间筛选出4823个差异表达基因（51.86%上调,48.14%下调）,在1日龄蛹与1日龄羽化工蜂间筛选出3295个差异表达基因（57.51%上调,42.49%下调）,在3日龄幼虫与1日龄羽化工蜂间筛选出5267个差异表达基因（52.95%上调,47.05%下调）。GO功能注释分析结果显示,3日龄幼虫与1日龄蛹间的差异表达基因注释到43个GO功能条目,1日龄蛹与1日龄羽化工蜂间的差异表达基因注释到45个GO功能条目,3日龄幼虫与1日龄羽化工蜂间的差异表达基因注释到44个GO功能条目,主要涉及细胞过程、细胞部分及结合等。KEGG信号通路富集分析发现,3日龄幼虫与1日龄蛹间有2905个差异表达基因富集到332条KEGG信号通路上,其中17条KEGG信号通路呈显著富集,涉及核糖体、氧化磷酸化和昆虫激素生物合成等;1日龄蛹与1日龄羽化工蜂间有1644个差异表达基因富集到331条KEGG信号通路上,其中45条KEGG信号通路呈显著富集,涉及氧化磷酸化、生热作用和胰岛素分泌等;3日龄幼虫与1日龄羽化工蜂间有2958个差异表达基因富集到337条KEGG信号通路上,其中14条KEGG信号通路呈显著富集,涉及核糖体、蛋白酶体和胰岛素分泌等。6个随机挑选差异表达基因的实时荧光定量PCR检测结果与转录组测序结果相符,即转录组测序结果可靠。【结论】昆虫激素生物合成通路相关差异表达基因调控与西方蜜蜂工蜂各虫态JH滴度变化规律一致,氧化磷酸化信号通路则与各虫态的营养摄入和活动行为相关,而胰岛素分泌通路涉及各虫态的营养调控、脂肪体合成及细胞凋亡。可见,昆虫激素生物合成、胰岛素分泌和氧化磷酸化3种信号通路在西方蜜蜂工蜂幼虫、蛹和成虫的发育调控中发挥着重要作用。