FGF21对糖尿病Beagle犬降糖作用的研究

[目的]探讨成纤维细胞生长因子-21(FGF21)对糖尿病Beagle犬的降糖作用。[方法]通过注射四氧嘧啶(ALX)50 mg/kg和链脲霉素(STZ)30 mg/kg溶液,建立糖尿病Beagle犬动物模型。糖尿病模型复制成功后,考察25μg/kg、50μg/kg和100μg/kg的FGF21以及阳性对照50μg/kg的地特胰岛素注射液(Det),每72 h给药1次,连续给药10次后,对糖尿病Beagle犬血糖等生化指标和肝脏、胰腺组织切片的影响。[结果]与模型组相比,FGF21各剂量给药组Beagle犬体重呈现升高趋势(p0.05),各给药组血糖、糖化血红蛋白水平均显著降低,并呈剂量依赖性,即随着FGF21给药剂量的增加,治疗效果更明显,其中高剂量组治疗效果最佳,治疗后空腹血糖达到8.77±5.74 mmol/L,糖化血红蛋白浓度4.89±1.36%,C肽浓度为0.010±0.000 nmol/L,与模型组存在显著差异(p0.01、p0.05、p0.01)。FGF21各剂量组肝脏和胰腺组织病变程度明显减轻。[结论]FGF21对Beagle犬有明显的降低血糖作用,FGF21各剂量组肝脏和胰腺组织病变程度明显减轻,为糖尿病治疗提供了新思路。     

FGF21的代谢调控及临床应用

成纤维细胞生长因子21(fibroblast growth factor 21,FGF21)是一种新型的参与代谢调控的关键分子,对降低体重和增加机体胰岛素敏感性具有十分显著的作用。大量的临床前和临床研究结果显示,FGF21是治疗肥胖和2型糖尿病潜在的药物靶点,该文从肝脏、脂肪和神经系统等组织入手,对FGF21调控代谢的分子作用机制及临床研究进展作一综述。     

不同活动、饥饿和饮食成分状态下FGF21的动力学表达

成纤维细胞生长因子21（fibroblast growth factor,FGF21）是FGF家族中的新成员．目前研究显示,FGF21是一个新的糖脂代谢调节因子,有望成为治疗糖尿病的新型药物．为探讨FGF21的生理功能,利用real-time PCR和Western印迹,检测FGF21在不同生理或病理状态下基因水平和蛋白水平的表达量变化规律．实验结果显示,在全天24 h中,小鼠肝脏中FGF21在晚18点至21点,表达量显著升高,这可能与啮齿类动物傍晚活动加强及进食习性有关|FGF21在饥饿后表达量显著升高,在饥饿后喂食FGF21的表达量下降,并且随着饥饿时间的延长,FGF21的表达量升高,说明FGF21与饥饿程度呈正相关|灌注葡萄糖后20 min内,FGF21的表达量下降,而灌注脂肪乳20 min内,FGF21的表达量上升,说明葡萄糖是FGF21的负调节因子,而脂肪乳是FGF21的正调节因子|利用谷氨酸钠造模的肥胖小鼠,肝脏中FGF21的表达量显著高于同龄对照组,说明肥胖可诱导FGF21高表达．综上所述,FGF21的表达量变化与小鼠夜间活动取食、饥饿程度、饮食中不同的成分以及肥胖有关.     

老年2型糖尿病患者的血清FGF21水平与临床参数的相关性研究

目的目的对老年糖尿病患者的空腹血浆成纤维细胞生长因子（Fibroblast growth factor21,FGF21）的水平与其临床参数进行相关性分析。方法对辽宁省沈阳市部分社区进行糖尿病普查,对78名65岁以上老年糖尿病患者的空腹血浆FGF21的水平与其临床参数进行相关性分析。其中包括腰围、体重指数（BMI）、血生化学指标、应用针对糖尿病,高血压和血脂异常治疗药物的情况等。结果在单变量分析中,2型糖尿病患者的FGF21水平与是否使用贝特类药物、甘油三酯水平、肌酐水平、腰围和BMI有独立相关性。经过校正年龄,性别和BMI之后进行多元线性回归分析发现,血清FGF21水平与贝特类药物的使用、TG水平、肌酐水平、LDL-C水平、胰高血糖素水平等独立相关。结论在老年2型糖尿病患者中,空腹血清FGF21水平与使用贝特类降脂药物,血脂水平,肾功等密切相关,说明FGF21水平在此类患者的糖脂代谢中占有重要地位。     

FGF21类似物治疗动脉粥样硬化机制研究进展

动脉粥样硬化是冠心病、脑梗死、外周血管病的主要诱因,近年来发病率越来越高,严重威胁着人类生命健康。脂质代谢障碍是动脉粥样硬化的病理基础。成纤维细胞生长因子21(FGF21)是FGF家族的一种内分泌因子,它能够增加葡萄糖的摄取,调节脂质代谢,并使代谢活跃的器官（如肝脏和脂肪组织）中胰岛素反应敏感。FGF21水平与动脉粥样硬化的发生率和严重程度密切相关。然而,FGF21原型在血浆的半衰期短、体外易聚集,严重限制了其临床应用。近年来,对FGF21类似物的研究取得了突破性进展。综述了FGF21的生理作用,并讨论了基于FGF21类似物治疗动脉粥样硬化的主要突破和局限性,为FGF21蛋白类新药的开发提供了理论依据。     

精氨酸修饰成纤维细胞生长因子21及修饰后蛋白体内稳定性和糖代谢调节作用的研究

成纤维细胞生长因子21(fibroblast growth factor21,FGF21)是2000年发现的一个不依赖胰岛素调节血糖的细胞因子,有望成为治疗糖尿病的候选药物.但是,野生型FGF21由于半衰期较短,在体内不稳定,从而影响其成药性.为提高FGF21的稳定性,本实验在FGF21的C端添加了2个精氨酸(arginine,Arg),命名为FGF21-2A,用Compute pI/Mw软件计算之后,等电点(isoelectric point,pI)从5.43上升到5.84,随后进行了蛋白质的表达、分离纯化、体内稳定性及糖代谢调节作用的研究.诱导表达后菌液的SDS-PAGE图经BandScan5.0分析后显示FGF21-2A的表达量相对于野生型FGF21提高了10.6%.家兔体内半衰期检测实验结果显示FGF21-2A的半衰期显著延长.GOD-POD法检测HepG2肝癌细胞葡萄糖吸收实验、糖尿病小鼠降血糖实验和肝糖原检测实验的结果证明,FGF21-2A的降糖效果得到了增强,并且持续时间相对于野生型FGF21显著延长.Real-time PCR结果发现,长期注射FGF21-2A显著提高了糖尿病小鼠肝脏内葡萄糖转运蛋白(GLUT)1和葡萄糖激酶(GK)mRNA的表达量,降低了葡萄糖-6-磷酸酶(G6P)的mRNA表达量,表明FGF21-2A调节糖代谢的机制与野生型FGF21一致.综上所述,精氨酸修饰的FGF21其蛋白质稳定性提高,进而增加了对血糖的调控效果,有望成为新型糖尿病药物.     

不同运动方式对肥胖大鼠肝脏脂质沉积及FGF21分泌的影响*

目的: 研究持续性运动训练(CT)与高强度间歇运动训练(HIIT)对正常和肥胖大鼠血清和肝脏FGF21蛋白含量及肝脏脂肪代谢的影响。方法: 雄性SD大鼠随机分为两组:普通饲料及45%高脂饲料喂养,8周后以普通饲料喂养,大鼠体重增加20%为肥胖造模成功标准。将正常大鼠随机分为正常安静组(LC)、正常高强度间歇运动训练组(LHI)、正常持续性运动训练组(LCT),肥胖大鼠随机分为肥胖安静组(OC)、肥胖高强度间歇运动训练组(OHI)及肥胖持续性运动训练组(OCT),每组10只,运动干预组大鼠进行8周不同方式负重游泳运动训练干预,末次运动干预间隔24 h后取血液检测血清炎症因子、FGF21水平,取肝脏组织检测脂质含量、脂代谢酶含量及FGF21表达水平。结果: 与LC组比较,OC组大鼠体重、血清炎症因子、肝脏甘油三酯(TG)含量显著增高(P＜0.05),LHI组肝脏TG含量显著降低,LCT组肝脏FGF21表达水平显著增高(P＜0.05)。与OC组比较,OHI组大鼠肝脏TG含量显著降低(P＜0.05),线粒体CPT-1β、β-HAD酶含量显著升高(P＜0.05),OCT组大鼠肝脏LPL、FAT/CD36酶含量显著增高,血清、肝脏FGF21水平均显著上升(P＜0.05)。结论: 两种运动方式均能降低正常、肥胖大鼠体重及肥胖大鼠肝脏脂质沉积现象,其中HIIT上调线粒体脂肪氧化水平,显著降低正常、肥胖大鼠肝脏TG含量,而CT通过提高正常、肥胖大鼠肝脏FGF21蛋白表达及血清FGF21水平,促进肝脏摄取脂肪酸,对缓解肥胖大鼠肝脏脂质沉积效果有限。     

运动调控FGF21在改善肥胖相关代谢性疾病中的作用

肥胖是糖尿病、脂肪肝、心血管疾病等慢性代谢性疾病发生发展的重要风险因素。运动可以改善肥胖,对相关代谢性疾病的预防与康复具有积极作用。成纤维细胞生长因子21 (fibroblast growth factor 21,FGF21)是一种对机体能量稳态、糖脂代谢有积极调控作用的内分泌因子,是代谢性疾病预防和治疗的有效靶点之一。FGF21抵抗是机体对FGF21反应性减弱的现象,表现为靶组织生物学效应降低,机体FGF21代偿性合成增加。这可能是由FGF21受体(fibroblast growth factor receptors,FGFRs)和β-klotho蛋白(β-klotho,KLB)表达减少或敏感性降低所致。肥胖患者常出现FGF21抵抗,改善FGF21抵抗是治疗肥胖及相关代谢性疾病的新思路。运动不仅可以增加部分组织FGF21表达量,还可以刺激FGFRs与KLB的表达来敏化FGF21的作用,改善FGF21抵抗。     

FGF21与代谢性疾病防治及其运动干预

成纤维细胞生长因子21(fibroblast growth factor 21, FGF21)属于成纤维细胞生长因子家族FGF19(fibroblast growth factor 19, FGF19)的亚型,不具有促成纤维细胞生长活性,且不与肝素特异性结合,是一种调节机体代谢的分泌型蛋白。在骨骼肌、肾脏、心脏以及血管和脂肪组织中 fgf21 表达比肝脏中高约7~10倍。FGF21可靶向脑、心脏、骨骼肌以及肾脏和肠等多种组织器官发挥作用。近来证实,FGF21已广泛应用于肝脂、糖脂代谢以及心血管疾病等代谢性疾病的预防与康复,可能成为代谢性疾病预防和康复的有效靶点之一。急性运动后骨骼肌FGF21表达显著升高,耐力运动可改善FGF21对肝脏脂肪调节的抵抗,有氧运动和抗阻运动可显著提高肝脏FGF21表达水平,单次急性运动后小鼠血清FGF21水平呈上升趋势。表明运动可显著提高循环和靶器官FGF21水平。积极开展运动介导的FGF21表达与肝脂、糖脂代谢紊乱及心血管等疾病康复研究,将为代谢性疾病预防与康复及其相关药物筛选提供新思路和新靶点。     

成纤维细胞生长因子21对1型糖尿病动物模型的肝糖代谢影响及机制研究

成纤维细胞生长因子(FGF)-21是FGF家族的成员之一.作为近年发现的一种新的糖代谢调节因子,大量研究表明,FGF-21是一种不依赖胰岛素,能够独立降糖的2型糖尿病治疗潜力型药物.但是,能否应用于1型糖尿病的治疗,国内外目前尚无报道.通过改良传统造模方法,诱导小鼠缓慢产生糖耐量异常,研究FGF-21对此类模型的糖代谢影响及肝糖代谢机制.通过检测FGF-21短期注射和长期注射后模型动物血糖的变化,研究FGF-21在模型动物上对血糖的调控效果.采用实时定量PCR检测FGF-21对模型动物肝脏中葡萄糖转运蛋白(GLUT)1、4 mRNA的表达影响.利用蒽酮法检测模型动物肝脏中糖原合成量.实验结果显示,FGF-21能够调节1型糖尿病动物的血糖水平,并呈剂量依赖性.同时,首次在1型糖尿病动物模型上证实了低剂量FGF-21(0.125 mg/kg)与胰岛素的协同作用效果优于相同剂量FGF-21和胰岛素单独注射的效果.治疗结果表明,FGF-21能够维持1型糖尿病动物模型血糖在正常范围,效果优于胰岛素.实时定量PCR结果发现,与胰岛素上调GLUT4 mRNA表达量不同的是,FGF-21作用动物模型8周后,GLUT1 mRNA表达量显著提高,长期的FGF-21与胰岛素协同注射使GLUT1、4 mRNA表达量同时显著提高.长期FGF-21与胰岛素协同注射组和高剂量FGF-21注射均可显著提高模型动物肝糖原的合成.结果表明,FGF-21促进动物模型糖代谢机制与增加GLUT1表达、增加糖原合成作用有关.为临床应用FGF-21治疗1型糖尿病,增加胰岛素敏感性提供了理论依据.     

Rush to the fire: FGF21 extinguishes metabolic stress,metaflammation and tissue damage

FGF21 is a master regulator of homeostasis of local and systemic lipid, glucose and energy metabolism. Since its discovery a decade ago, significant progress has been made in understanding the basic molecular, cellular and physiological mechanisms underlying its metabolic roles, and characterizing its beneficial pharmacological activities and possible pathological roles in obesity, diabetes, dyslipidemia, fatty liver disease and their collateral complications and tissue damage. Under basal or normal conditions, FGF21 appears to play a dispensable role in metabolism. However, in response to a variety of cellular and metabolic stress, FGF21 is significantly upregulated to serve as a potent catabolic factor leading to the clearance of excessive lipids and glucose, and therefore, antagonizes metabolic and energy imbalance in a negative fashion. Furthermore, FGF21 treatment ameliorates tissue damage resulted from the harmful effects of metabolic abnormalities, which often ensue an oxidative, pro-inflammatory, inflammatory and/or immune stress state, the so-called metaflammation. Most notably, studies focusing on the liver, pancreas, cardio-vasculature and kidney have revealed its significant protective effects against the structural and functional damages induced by the obese, diabetic or other abnormal metabolic conditions. In this review, we will summarize the current progress on the roles of FGF21 against metaflammation and metabolic tissue damage.     

Dietary protein dilution limits dyslipidemia in obesity through FGF21-driven fatty acid clearance

Recent studies have demonstrated that dietary protein dilution (PD) can promote metabolic inefficiency and improve glucose metabolism. However, whether PD can promote other aspects of metabolic health, such as improve systemic lipid metabolism, and mechanisms therein remains unknown. Mouse models of obesity, such as high-fat-diet-fed C57Bl/6 N mice, and New Zealand Obese mice were fed normal (i.e., 20%P) and protein-dilute (i.e., 5%EP) diets. FGF21−/− and Cd36−/− and corresponding littermate +/+ controls were also studied to examine gene-diet interactions. Here, we show that chronic PD retards the development of hypertrigylceridemia and fatty liver in obesity and that this relies on the induction of the hepatokine fibroblast growth factor 21 (FGF21). Furthermore, PD greatly enhances systemic lipid homeostasis, the mechanisms by which include FGF21-stimulated, and cluster of differentiation 36 (CD36) mediated, fatty acid clearance by oxidative tissues, such as heart and brown adipose tissue. Taken together, our preclinical studies demonstrate a novel nutritional strategy, as well as highlight a role for FGF21-stimulated systemic lipid metabolism, in combating obesity-related dyslipidemia.     

PPARalpha is a key regulator of hepatic FGF21

The metabolic regulator fibroblast growth factor 21 (FGF21) has antidiabetic properties in animal models of diabetes and obesity. Using quantitative RT-PCR, we here show that the hepatic gene expression of FGF21 is regulated by the peroxisome proliferator-activated receptor alpha (PPARalpha). Fasting or treatment of mice with the PPARalpha agonist Wy-14,643 induced FGF21 mRNA by 10-fold and 8-fold, respectively. In contrast, FGF21 mRNA was low in PPARalpha deficient mice, and fasting or treatment with Wy-14,643 did not induce FGF21. Obese ob/ob mice, known to have increased PPARalpha levels, displayed 12-fold increased hepatic FGF21 mRNA levels. The potential importance of PPARalpha for FGF21 expression also in human liver was shown by Wy-14,643 induction of FGF21 mRNA in human primary hepatocytes, and PPARalpha response elements were identified in both the human and mouse FGF21 promoters. Further studies on the mechanisms of regulation of FGF21 by PPARalpha in humans will be of great interest.     

Differential specificity of endocrine FGF19 and FGF21 to FGFR1 and FGFR4 in complex with KLB

Background

Recent studies suggest that betaKlotho (KLB) and endocrine FGF19 and FGF21 redirect FGFR signaling to regulation of metabolic homeostasis and suppression of obesity and diabetes. However, the identity of the predominant metabolic tissue in which a major FGFR-KLB resides that critically mediates the differential actions and metabolism effects of FGF19 and FGF21 remain unclear.

Methodology/Principal Findings

We determined the receptor and tissue specificity of FGF21 in comparison to FGF19 by using direct, sensitive and quantitative binding kinetics, and downstream signal transduction and expression of early response gene upon administration of FGF19 and FGF21 in mice. We found that FGF21 binds FGFR1 with much higher affinity than FGFR4 in presence of KLB; while FGF19 binds both FGFR1 and FGFR4 in presence of KLB with comparable affinity. The interaction of FGF21 with FGFR4-KLB is very weak even at high concentration and could be negligible at physiological concentration. Both FGF19 and FGF21 but not FGF1 exhibit binding affinity to KLB. The binding of FGF1 is dependent on where FGFRs are present. Both FGF19 and FGF21 are unable to displace the FGF1 binding, and conversely FGF1 cannot displace FGF19 and FGF21 binding. These results indicate that KLB is an indispensable mediator for the binding of FGF19 and FGF21 to FGFRs that is not required for FGF1. Although FGF19 can predominantly activate the responses of the liver and to a less extent the adipose tissue, FGF21 can do so significantly only in the adipose tissue and adipocytes. Among several metabolic and endocrine tissues, the response of adipose tissue to FGF21 is predominant, and can be blunted by the ablation of KLB or FGFR1.

Conclusions

Our results indicate that unlike FGF19, FGF21 is unable to bind FGFR4-KLB complex with affinity comparable to FGFR1-KLB, and therefore, at physiological concentration less likely to directly and significantly target the liver where FGFR4-KLB predominantly resides. However, both FGF21 and FGF19 have the potential to activate responses of primarily the adipose tissue where FGFR1-KLB resides.     

LY2405319, an Engineered FGF21 Variant,Improves the Metabolic Status of Diabetic Monkeys

Fibroblast growth factor 21 (FGF21) is a novel metabolic regulator that represents a promising target for the treatment of several metabolic diseases. Administration of recombinant wild type FGF21 to diabetic animals leads to a dramatic improvement in glycaemia and ameliorates other systemic measures of metabolic health. Here we report the pharmacologic outcomes observed in non-human primates upon administration of a recently described FGF21 analogue, LY2405319 (LY). Diabetic rhesus monkeys were treated subcutaneously with LY once daily for a period of seven weeks. The doses of LY used were 3, 9 and 50 mg/kg each delivered in an escalating fashion with washout measurements taken at 2, 4, 6 and 8 weeks following the final LY dose. LY therapy led to a dramatic and rapid lowering of several important metabolic parameters including glucose, body weight, insulin, cholesterol and triglyceride levels at all doses tested. In addition, we observed favorable changes in circulating profiles of adipokines, with increased adiponectin and reduced leptin indicative of direct FGF21 action on adipose tissue. Importantly, and for the first time we show that FGF21 based therapy has metabolic efficacy in an animal with late stage diabetes. While the glycemic efficacy of LY in this animal was partially attenuated its lipid lowering effect was fully preserved suggesting that FGF21 may be a viable treatment option even in patients with advanced disease progression. These findings support continued exploration of the FGF21 pathway for the treatment of metabolic disease.     

Probiotic culture supernatant improves metabolic function through FGF21-adiponectin pathway in mice

High-fat/high-fructose diet plus intermittent hypoxia exposure (HFDIH) causes metabolic disorders such as insulin resistance, obesity, nonalcoholic fatty liver disease (NAFLD) and type 2 diabetes. The purpose of this study is to examine the effects and understand the mechanism of action of Lactobacillus rhamnosus GG culture supernatant (LGGs) on HFDIH-induced metabolic dysfunction. Mice were fed high-fat:high-fructose diet for 15 weeks. After 3 weeks of feeding, the mice were exposed to chronic intermittent hypoxia for the next 12 weeks (HFDIH), and LGGs was supplemented over the entire experiment. HFDIH exposure significantly led to metabolic disorders. LGGs treatment showed significant improvements in indices of metabolic disorders including fat mass, energy expenditure, glucose intolerance, insulin resistance, increased hepatic steatosis and liver injury. HFDIH mice markedly increased adipose inflammation and adipocyte size, and reduced circulating adiponectin, which was restored by LGGs treatment. LGGs treatment increased hepatic FGF21 mRNA expression and circulating FGF21 protein levels, which were associated with increased hepatic PPARα expression and fecal butyrate concentration. In addition, HFDIH-induced hepatic fat accumulation and apoptosis were significantly reduced by LGGs supplementation. In summary, LGGs treatment increased energy expenditure and insulin sensitivity and prevented metabolic abnormalities in HFDIH mice, and this is associated with the FGF21-adiponectin signaling pathway. LGGs may be a potential prevention/treatment strategy in subjects with the metabolic syndrome.     

Aging is associated with increased FGF21 levels but unaltered FGF21 responsiveness in adipose tissue

Fibroblast growth factor 21 (FGF21) has been proposed to be an antiaging hormone on the basis of experimental studies in rodent models. However, circulating FGF21 levels are increased with aging in rodents and humans. Moreover, despite the metabolic health‐promoting effects of FGF21, the levels of this hormone are increased under conditions such as obesity and diabetes, an apparent incongruity that has been attributed to altered tissue responsiveness to FGF21. Here, we investigated serum FGF21 levels and expression of genes encoding components of the FGF21‐response molecular machinery in adipose tissue from healthy elderly individuals (≥70 years old) and young controls. Serum FGF21 levels were increased in elderly individuals and were positively correlated with insulinemia and HOMA‐IR, indices of mildly deteriorated glucose homeostasis. Levels of β‐Klotho, the coreceptor required for cellular responsiveness to FGF21, were increased in subcutaneous adipose tissue from elderly individuals relative to those from young controls, whereas FGF receptor‐1 levels were unaltered. Moreover, total ERK1/2 protein levels were decreased in elderly individuals in association with an increase in the ERK1/2 phosphorylation ratio relative to young controls. Adipose explants from aged and young mice respond similarly to FGF21 “ex vivo”. Thus, in contrast to what is observed in obesity and diabetes, high levels of FGF21 in healthy aging are not associated with repressed FGF21‐responsiveness machinery in adipose tissue. The lack of evidence for impaired FGF21 responsiveness in adipose tissue establishes a distinction between alterations in the FGF21 endocrine system in aging and chronic metabolic pathologies.     

FGF21 Can Be Mimicked In Vitro and In Vivo by a Novel Anti-FGFR1c/β-Klotho Bispecific Protein

The endocrine hormone FGF21 has attracted considerable interest as a potential therapeutic for treating diabetes and obesity. As an alternative to the native cytokine, we generated bispecific Avimer polypeptides that bind with high affinity and specificity to one of the receptor and coreceptor pairs used by FGF21, FGFR1c and β-Klotho. These Avimers exhibit FGF21-like activity in in vitro assays with potency greater than FGF21. In a study conducted in obese male cynomolgus monkeys, animals treated with an FGFR1c/β-Klotho bispecific Avimer showed improved metabolic parameters and reduced body weight comparable to the effects seen with FGF21. These results not only demonstrate the essential roles of FGFR1c and β-Klotho in mediating the metabolic effects of FGF21, they also describe a first bispecific activator of this unique receptor complex and provide validation for a novel therapeutic approach to target this potentially important pathway for treating diabetes and obesity.