视黄醇结合蛋白4与2型糖尿病微血管病变的研究进展

视黄醇结合蛋白4(Retinolbindingprotein4,RBP4)是一种分泌型视黄醇结合蛋白,主要由肝脏合成,在协助视黄醇发挥生理功能中起着重要的作用。近年研究发现,RBP4是一种新的循环性脂肪因子,亦能由脂肪组织特异性分泌,它不仅能够抑制肌肉组织中的胰岛素信号通路,而且能够促进糖异生,增加肝糖输出,从而导致胰岛素抵抗的发生,增加糖尿病的发病风险。目前RBP4与2型糖尿病(Type2diabetes mellitus,T2DM)关系逐渐受到人们的重视,本文就RBP4的生理功能、RBP4与T2DM微血管病变的研究进展作一综述。     

2型糖尿病患者尿视黄醇结合蛋白与视网膜病变的相关性

目的 探讨2型糖尿病患者尿视黄醇结合（RBP）与视网膜病变相关性。方法 采用酶联免疫法检测158例2型糖尿病患者24h尿视黄醇结合蛋白排泄（24hURBP）及24h尿白蛋白排泄（24hUAE）,并同时用眼底镜仔细检查其眼氏。结果 糖尿病视网膜病变（DR）发生率随着24hURBP、24hUAE增加而显著增高,24hURBP、24hUAE也随DR的程度加重而显著增加。结论 2型糖尿病患者DR与尿RBP、尿白蛋白呈正相关。     

锌转运蛋白8与1型和2型糖尿病的研究进展

ZnT8(zinc transporter,member8)是锌离子转运蛋白,主要定位于胰岛β细胞,能将胞浆锌离子转运至胰岛素储存/分泌性囊泡内,其转运功能降低会影响胰岛素合成、储存和分泌,能增加2型糖尿病(T2DM)的发病风险。ZnT8蛋白也可作为抗原引起β细胞自身免疫损伤,诱发1型糖尿病(T1DM)。ZnT8基因多态性是引起其锌离子转运功能和免疫原性变化的重要因素,与糖尿病的发生、发展密切相关。该文综述了ZnT8与T1DM和T2DM的研究进展,提示ZnT8可作为糖尿病防治的新药物靶点。     

2型糖尿病大鼠心肌IR、IRS-1的表达与罗格列酮及APP5肽类似物P165的干预效应

目的研究2型糖尿病大鼠心肌胰岛素信号转导通路蛋白胰岛素受体（IR）、胰岛素受体底物-1（IRS-1）的表达与正常SD大鼠的区别,并探讨进行罗格列酮及APP5肽类似物P165干预后对上述蛋白表达的影响。方法60只SD大鼠随机分为正常对照组（C组）、正常对照＋罗格列酮组（C＋RSG组）、2型糖尿病组（T2DM组）、2型糖尿病＋罗格列酮组（T2DM＋RSG组）、糖尿病给予P165小剂量组（T2DM＋P165小剂量组）、糖尿病给予P165大剂量组（T2DM＋P165大剂量组）,其中糖尿病动物采用高脂饮食后给予小剂量STZ腹腔注射的方法造模。后将各组SD大鼠处死,采用免疫组织化学染色和Western blot的方法检测心肌组织IR、IRS-1的表达。结果（1）2型糖尿病组（T2DM组）心肌组织IR、IRS-1的表达水平显著低于对照组（C组）;（2）2型糖尿病＋罗格列酮组（T2DM＋RSG组）心肌组织IR、IRS-1的表达水平显著高于T2DM组;（3）免疫组化染色发现2型糖尿病＋P165小/大剂量组（T2DM＋P165小/大剂量组）心肌组织IR、IRS-1免疫反应阳性颗粒沉着的累积光密度值显著高于T2DM组;Western blot结果显示T2DM＋P165小/大剂量组心肌组织IRS-1的表达水平显著高于T2DM组;而IR的表达水平与T2DM组相比无差别。结论（1）2型糖尿病大鼠心肌存在胰岛素抵抗或信号转导障碍;（2）罗格列酮干预后可以改善2型糖尿病心肌的胰岛素信号转导异常;（3）P165对2型糖尿病大鼠心肌胰岛素信号转导具有调节作用,其作用靶点可能为胰岛素受体底物。     

新诊断2型糖尿病患者血清Pannexin-1、Apelin、RBP4、VEGF水平与糖脂代谢和胰岛素抵抗的关系研究

摘要 目的：探讨新诊断2型糖尿病患者血清缝隙连接蛋白-1(Pannexin-1)、爱帕琳肽（Apelin）、视黄醇结合蛋白4(RBP4)、血管内皮生长因子（VEGF）水平与糖脂代谢和胰岛素抵抗的关系。方法：选择2018年2月至2020年2月我院诊治的120例新诊断2型糖尿病患者作为糖尿病组,选择同期在我院进行体检的120例健康者作为对照组。检测所有受试者甘油三酯（TG）、总胆固醇（TC）、谷草转氨酶（AST）、谷丙转氨酶(ALT)、高密度脂蛋白（HDL）和低密度脂蛋白（LDL）水平、空腹血糖（FPG）、空腹胰岛素(FINS)、Pannexin-1、Apelin、RBP4、VEGF水平,计算胰岛素抵抗指数(HOMA-IR)、胰岛素敏感性指数（ISI）和胰岛?茁细胞功能指数(HOMA-β)。分析Pannexin-1、Apelin、RBP4、VEGF水平与糖脂代谢和胰岛素抵抗相关指标的关系,分析影响上述指标表达的相关因素。结果：与对照组相比,糖尿病组体质量指数（BMI）、TG、TC、FPG、FINS、Pannexin-1、Apelin、RBP4、VEGF水平,HOMA-IR明显升高（P<0.05）,ISI和HOMA-β明显下降（P<0.05）。新诊断2型糖尿病患者血清Pannexin-1、Apelin、RBP4、VEGF水平与ISI和HOMA-β均呈负相关（P<0.05）,与BMI、TG、TC、FPG、FINS、HOMA-IR均呈正相关（P<0.05）。TG与Pannexin-1表达联系密切（β=0.006,P<0.05）,ISI和HOMA-IR与Apelin表达联系密切（β=-6.673、0.049,P<0.05）,FPG和TC与RBP4表达联系密切（β=22.309、0.506,P<0.05）,HOMA-IR与VEGF表达联系密切（β=0.574,P<0.05）。结论：新诊断2型糖尿病患者血清Pannexin-1、Apelin、RBP4、VEGF水平异常升高,并参与新诊断2型糖尿病患者的糖脂代谢和胰岛素抵抗,在2型糖尿病的诊断和预防中有一定临床价值。     

干扰视黄醇结合蛋白4对猪脂肪细胞PI3K/Akt信号通路的影响

视黄醇结合蛋白4(Retinol binding protein 4,RBP4)是一种脂肪细胞分泌因子,其表达水平的升高与胰岛素抵抗及Ⅱ型糖尿病等疾病密切相关,但具体作用机制尚不清楚。为明确此机制,通过包装RBP4干扰慢病毒并侵染猪前体脂肪细胞。运用胰岛素激活及诱导胰岛素抵抗模型,利用QRT-PCR及Western blotting方法检测RBP4的干扰效率及处理组PI3K/Akt信号通路相关基因的表达。结果显示RBP4的基因及蛋白的干扰效率达到60%(P<0.01)以上。进一步研究发现在胰岛素诱导及胰岛素抵抗的情况下,LH1-shRBP4干扰后可显著提高胰岛素信号通路AKT2、PI3K、GLUT4和IRS1基因mRNA的表达;明显促进AKT2、PI3K和IRS1蛋白的磷酸化;提高AKT2、PI3K和GLUT4基因的总蛋白水平。总之,RBP4干扰通过上调PI3K/Akt胰岛素信号通路相关因子的表达及其磷酸化水平,提高了胰岛素敏感性。此研究将为胰岛素抵抗相关疾病的治疗提供新思路。     

视黄醇结合蛋白4在病理妊娠中的研究进展

视黄醇结合蛋白4(Retinol binding protein 4,RBP4)是近年来新发现的一种脂肪细胞因子,在动物与人类的研究中均发现其与胰岛素抵抗的发生及糖、脂代谢的调节密切相关,随着机体胰岛素抵抗及糖脂代谢异常程度的增加,RBP4水平上升。在妊娠期,母体脂肪量增加并伴有不同程度的胰岛素抵抗。在正常妊娠时,RBP4随着妊娠的进展而升高,且与胰岛素抵抗程度增加相一致。与正常妊娠相比,妊娠期糖尿病(gestational diabetes mellitus,GDM)患者的RBP4升高更明显,且RBP4的升高水平与GDM预后相关。研究发现早期RBP4的升高可以预测GDM的发生,此外控制RBP4水平可能干预GDM发展。RBP4在妊娠期高血压疾病中升高;RBP4在脐血中的水平与胎儿生长密切相关,在小于胎龄儿中水平下降,在大于胎龄儿中升高;RBP4与早产的关系并不明确。进一步研究RBP4在病理妊娠的作用机制,可为病理妊娠的发生发展和防治提供新方向。     

视黄醇结合蛋白4对肾脏疾病早期诊断的评估

视黄醇结合蛋白4(RBP4)是一类合成于肝脏且广泛分布于人体血液、尿液等其它体液中的维生素A运载蛋白,它在协助维生素A发挥生理功能中起着决定性的作用。近年来的研究表明:当近端肾小管受损时,人体血液或尿液中视黄醇结合蛋白4的含量会出现不同程度的升高。同时它与糖尿病肾病、营养性疾病的发展等其它疾病都在临床上存在着一定的相关性。临床上已将RBP4的含量测定作为判定肾功能有效且成熟的指标之一。目前临床上对视黄醇结合蛋白4的检测主要是传统的酶联免疫法、免疫比浊法等,近年来随着研究水平的不断提高,对RBP4的检测方法已有逐渐转向新型的快速检测方法的趋势。本文在对视黄醇结合蛋白4的理化性质、在肾脏等各类疾病方面的应用以及新型临床检测方法等方面作一综述,随着研究的不断完善,视黄醇结合蛋白4的更多临床意义将逐渐显现。     

胰高血糖素样多肽-1拮抗2型糖尿病胰岛细胞凋亡损伤

胰高血糖素样多肽-1（glucogen like peptide 1, GLP-1）在胰岛素分泌过程中扮演重要角色,并在改善β细胞功能方面有着令人瞩目的效应,但有关其作用机制尚需更深入研究。本研究探讨GLP-1对2型糖尿病（type 2 diabetes mellitus, T2DM）大鼠模型胰岛细胞损伤的影响,观察GLP-1在T2DM大鼠胰岛细胞凋亡损伤机制中所发挥的作用。HE染色结果发现,糖尿病大鼠胰岛损伤。ELISA结果表明,糖尿病患者和糖尿病大鼠血清中GLP-1表达水平上调。放射免疫结果表明,GLP-1和谷氧还蛋白1（Grx1）促进HIT-T 15细胞分泌胰岛素,Cd抑制胰岛素的分泌。免疫组化结果表明,糖尿病大鼠GLP-1加药处理后,各组与糖尿病组相比,药物提高了Grx1和胰岛素表达水平,降低了胰高血糖素表达水平,同时降低了活性胱天蛋白酶3（caspase-3）的表达。本研究结果提示,GLP-1在肥胖T2DM大鼠胰岛细胞凋亡中起保护作用,同时可调节胰岛素和胰高血糖素水平,其机制可能与Grx1相关     

Ⅱ型糖尿病大鼠海马Alzheimer病样Tau蛋白过度磷酸化修饰及机制探讨

Tau蛋白过度磷酸化是Alzheimer病 (Alzheimer′s disease, AD) 的一个重要特征.本研究检测了Ⅱ型糖尿病大鼠海马tau蛋白磷酸化水平,对其形成机制进行探讨. 以同龄正常Wistar大鼠作为对照,高脂高蛋白高糖饮食加小剂量链脲佐菌素（streptozotocin,STZ）注射诱导造Ⅱ型糖尿病模型（T2DM组）.放免法检测血浆胰岛素;葡萄糖氧化酶法检测血浆葡萄糖;蛋白质印迹技术检测各组大鼠海马内总tau蛋白、tau蛋白上部分位点磷酸化、神经细胞膜上胰岛素受体及葡萄糖转运子3（glucose transport 3,GLUT3）水平;表面等离子共振技术（surface plasmon resonance, SPR）检测细胞膜上胰岛素受体与血浆胰岛素结合力;γ32-P标记的ATP和特异性底物肽检测海马内胰岛素信号传导系统中的关键酶糖原合酶激酶-3β（glycogen synthase kinase-3β, GSK-3β）活性.结果显示,T2DM组血浆血糖、血浆胰岛素及运用HOMA-IR公式计算的胰岛素抵抗指数显著高于对照组.蛋白质印迹结果显示两组大鼠海马回总tau蛋白水平无差异;T2DM组中tau蛋白在Ser199、Thr212、Ser214、Thr217、Ser396及Ser422位点上的磷酸化水平均显著高于对照组;T2DM组海马神经细胞膜上胰岛素受体水平及与胰岛素结合的功能均显著低于对照组;GSK-3β活性检测结果显示,T2DM组大鼠模型海马回中GSK-3β活性明显增高.研究结果表明,Ⅱ型糖尿病中由于胰岛素抵抗导致GSK-3β激活从而出现AD样tau蛋白的过度磷酸化,葡萄糖代谢紊乱也可能在tau蛋白的过度磷酸化起一定作用.     

Altered Circulating Levels of Retinol Binding Protein 4 and Transthyretin in Relation to Insulin Resistance,Obesity, and Glucose Intolerance in Asian Indians

Objective: Retinol binding protein 4 (RBP4) has been implicated in metabolic disorders including type 2 diabetes mellitus (T2DM), but few studies have looked at transthyretin (TTR) with which RBP4 is normally bound to in the circulation. We report on the systemic levels of RBP4 and TTR and their associations with insulin resistance, obesity, prediabetes, and T2DM in Asian Indians.Methods: Age-matched individuals with normal glucose tolerance (NGT, n = 90), impaired glucose tolerance (IGT, n = 70) and T2DM (n = 90) were recruited from the Chennai Urban Rural Epidemiology Study (CURES). Insulin resistance was estimated using the homeostasis model assessment of insulin resistance (HOMA-IR). RBP4 and TTR levels were measured by enzyme-linked immunosorbent assay (ELISA).Results: Circulatory RBP4 and TTR levels (in μg/mL) were highest in T2DM (RBP4: 13 ± 3.9, TTR: 832 ± 310) followed by IGT (RBP4: 10.5 ± 3.2; TTR: 720 ± 214) compared to NGT (RBP4: 8.7 ± 2.5; TTR: 551 ± 185; P<.001). Compared to nonobese NGT individuals, obese NGT, nonobese T2DM, and obese T2DM had higher RBP4 (8.1 vs. 10.6, 12.1, and 13.2 μg/mL, P<.01) and TTR levels (478 vs. 737, 777, and 900 μg/mL, P<.01). RBP4 but not TTR was significantly (P<.001) correlated with insulin resistance even among NGT subjects. In regression analysis, RBP4 and TTR showed significant associations with T2DM after adjusting for confounders (RBP4 odds ratio [OR]: 1.107, 95% confidence interval [CI]: 1.008–1.216; TTR OR: 1.342, 95% CI: 1.165–1.547).Conclusion: Circulatory levels of RBP4 and TTR showed a significant associations with glucose intolerance, obesity, T2DM and RBP4 additionally, with insulin resistance.Abbreviations: BMI = body mass index CI = confidence interval HDL = high-density lipoprotein IGT = impaired glucose tolerance LDL = low-density lipoprotein NGT = normal glucose tolerance OGTT = oral glucose tolerance test OR = odds ratio RBP4 = retinol binding protein 4 T2DM = type 2 diabetes mellitus TTR = transthyretin WC = waist circumference     

Application of an allosteric model to describe the interactions among retinol binding protein 4, transthyretin, and small molecule retinol binding protein 4 ligands

Retinol binding protein 4 (RBP4) is a serum protein that serves as the major transport protein for retinol (vitamin A). Recent reports suggest that elevated levels of RBP4 are associated with insulin resistance and that insulin sensitivity may be improved by reducing serum RBP4 levels. This can be accomplished by administration of small molecules, such as fenretinide, that compete with retinol for binding to RBP4 and disrupt the protein-protein interaction between RBP4 and transthyretin (TTR), another serum protein that protects RBP4 from renal clearance. We developed a fluorescence resonance energy transfer (FRET) assay that measures the interaction between RBP4 and TTR and can be used to determine the binding affinities of RBP4 ligands. We present an allosteric model that describes the pharmacology of interaction among RBP4, TTR, retinol, and fenretinide, and we show data that support the model. We show that retinol increases the affinity of RBP4 for TTR by a factor of 4 and determine the affinity constants of fenretinide and retinyl acetate. The assay may be useful for characterizing small molecule ligands that bind to RBP4 and disrupt its interaction with TTR. In addition, such a model could be used to describe other protein-protein interactions that are modulated by small molecules.     

用抗糖尿病药物GLP-1及其类似物治疗阿尔茨海默病

流行病学和基础研究表明阿尔茨海默病（Alzheimert＇s disease,AD）与2型糖尿病（type 2 diabetes mellitus,T2DM）存在密切关联：T2DM是AD的危险因素之一;而AD脑内也出现胰岛素信号异常、胰岛素抵抗状态,因而被称为“第3类型的糖尿病”。近年来治疗T2DM的新药——胰高血糖素样肽-1（glucagon-1ike peptide-1,GLP-1）及其类似物,已被证实具有神经保护作用,且能改善AD模型的记忆和认知功能,为AD治疗药物的研究提供了新的策略。     

长春新碱对糖尿病兔肾小管间质损伤的影响

目的观察长春新碱对糖尿病兔肾小管-间质损伤的影响。方法 24只日本大白兔随机分成正常对照组（control组）、糖尿病组（DM组）、糖尿病长春新碱治疗组（DV组）;耳缘静脉注射四氧嘧啶造成糖尿病兔模型,DV组每周进行一次长春新碱耳缘静脉注射;胰岛素控制DM组、DV组血糖16.0～25.0mmol/L。8周时测各组兔血糖、肾重、体重、尿β2-MG、RBP、NAG,肾组织病理观察肾小管-间质变化。结果给药后7hDV组、DM组血糖明显升高形成稳定糖尿病模型;8周时,DV组体重明显高于DM组（P〈0.05）、肾重/体重值明显低于DM组（P〈0.05）;DM组、DV组尿β2-MG阳性反应率较低;DM组尿RBP、NAG明显高于control组（P〈0.05）,长春新碱可抑制糖尿病兔尿RBP、NAG增加（P〈0.05）,并减轻糖尿病兔肾小管间质损伤指数（P〈0.05）。结论长春新碱可减轻糖尿病兔肾小管间质损伤。     

Retinol‐binding Protein 4 (RBP4) Protein Expression Is Increased in Omental Adipose Tissue of Severely Obese Patients

Visceral fat has been linked to insulin resistance and type 2 diabetes mellitus (T2DM); and emerging data links RBP4 gene expression in adipose tissue with insulin resistance. In this study, we examined RBP4 protein expression in omental adipose tissue obtained from 24 severely obese patients undergoing bariatric surgery, and 10 lean controls (4 males/6 females, BMI = 23.2 ± 1.5 kg/m²) undergoing elective abdominal surgeries. Twelve of the obese patients had T2DM (2 males/10 females, BMI: 44.7 ± 1.5 kg/m²) and 12 had normal glucose tolerance (NGT: 4 males/8 females, BMI: 47.6 ± 1.9 kg/m²). Adipose RBP4, glucose transport protein‐4 (GLUT4), and p85 protein expression were determined by western blot. Blood samples from the bariatric patients were analyzed for serum RBP4, total cholesterol, triglycerides, and glucose. Adipose RBP4 protein expression (NGT: 11.0 ± 0.6; T2DM: 11.8 ± 0.7; lean: 8.7 ± 0.8 arbitrary units) was significantly increased in both NGT (P = 0.03) and T2DM (P = 0.005), compared to lean controls. GLUT4 protein was decreased in both NGT (P = 0.02) and T2DM (P = 0.03), and p85 expression was increased in T2DM subjects, compared to NGT (P = 0.03) and lean controls (P = 0.003). Regression analysis showed a strong correlation between adipose RBP4 protein and BMI for all subjects, as well as between adipose RBP4 and fasting glucose levels in T2DM subjects (r = 0.76, P = 0.004). Further, in T2DM, serum RBP4 was correlated with p85 expression (r = 0.68, P = 0.01), and adipose RBP4 protein trended toward an association with p85 protein (r = 0.55, P = 0.06). These data suggest that RBP4 may regulate adiposity, and p85 expression in obese‐T2DM, thus providing a link to impaired insulin signaling and diabetes in severely obese patients.     

Liver Retinol Transporter and Receptor for Serum Retinol-binding Protein (RBP4)

Vitamin A (retinol) is absorbed in the small intestine, stored in liver, and secreted into circulation bound to serum retinol-binding protein (RBP4). Circulating retinol may be taken up by extrahepatic tissues or recycled back to liver multiple times before it is finally metabolized or degraded. Liver exhibits high affinity binding sites for RBP4, but specific receptors have not been identified. The only known high affinity receptor for RBP4, Stra6, is not expressed in the liver. Here we report discovery of RBP4 receptor-2 (RBPR2), a novel retinol transporter expressed primarily in liver and intestine and induced in adipose tissue of obese mice. RBPR2 is structurally related to Stra6 and highly conserved in vertebrates, including humans. Expression of RBPR2 in cultured cells confers high affinity RBP4 binding and retinol transport, and RBPR2 knockdown reduces RBP4 binding/retinol transport. RBPR2 expression is suppressed by retinol and retinoic acid and correlates inversely with liver retinol stores in vivo. We conclude that RBPR2 is a novel retinol transporter that potentially regulates retinol homeostasis in liver and other tissues. In addition, expression of RBPR2 in liver and fat suggests a possible role in mediating established metabolic actions of RBP4 in those tissues.     

Tissue-specific alterations of glucose transport and molecular mechanisms of intertissue communication in obesity and type 2 diabetes.

Insulin resistance plays a major role in the pathogenesis of type 2 diabetes. Insulin regulates blood glucose levels primarily by promoting glucose uptake from the blood into multiple tissues and by suppressing glucose production from the liver. The glucose transporter, GLUT4, mediates insulin-stimulated glucose uptake in muscle and adipose tissue. Decreased GLUT4 expression in adipose tissue is a common feature of many insulin resistant states. GLUT4 expression is preserved in skeletal muscle in many insulin resistant states. However, functional defects in the intracellular trafficking and plasma membrane translocation of GLUT4 result in impaired insulin-stimulated glucose uptake in muscle. Tissue-specific genetic knockout of GLUT4 expression in adipose tissue or muscle of mice has provided new insights into the pathogenesis of insulin resistance. We recently determined that the expression of serum retinol binding protein (RBP4) is induced in adipose tissue as a consequence of decreased GLUT4 expression. We found that RBP4 is elevated in the serum of insulin resistant humans and mice. Furthermore, we found that increasing serum RBP4 levels by transgenic overexpression or by injection of purified RBP4 protein into normal mice causes insulin resistance. Therefore, RBP4 appears to play an important role in mediating adipose tissue communication with other insulin target tissues in insulin resistant states.     

Retinol-binding protein 4 inhibits insulin signaling in adipocytes by inducing proinflammatory cytokines in macrophages through a c-Jun N-terminal kinase- and toll-like receptor 4-dependent and retinol-independent mechanism

Retinol-binding protein 4 (RBP4), the sole retinol transporter in blood, is secreted from adipocytes and liver. Serum RBP4 levels correlate highly with insulin resistance, other metabolic syndrome factors, and cardiovascular disease. Elevated serum RBP4 causes insulin resistance, but the molecular mechanisms are unknown. Here we show that RBP4 induces expression of proinflammatory cytokines in mouse and human macrophages and thereby indirectly inhibits insulin signaling in cocultured adipocytes. This occurs through activation of c-Jun N-terminal protein kinase (JNK) and Toll-like receptor 4 (TLR4) pathways independent of the RBP4 receptor, STRA6. RBP4 effects are markedly attenuated in JNK1-/- JNK2-/- macrophages and TLR4-/- macrophages. Because RBP4 is a retinol-binding protein, we investigated whether these effects are retinol dependent. Unexpectedly, retinol-free RBP4 (apo-RBP4) is as potent as retinol-bound RBP4 (holo-RBP4) in inducing proinflammatory cytokines in macrophages. Apo-RBP4 is likely to be physiologically significant since RBP4/retinol ratios are increased in serum of lean and obese insulin-resistant humans compared to ratios in insulin-sensitive humans, indicating that higher apo-RBP4 is associated with insulin resistance independent of obesity. Thus, RBP4 may cause insulin resistance by contributing to the development of an inflammatory state in adipose tissue through activation of proinflammatory cytokines in macrophages. This process reveals a novel JNK- and TLR4-dependent and retinol- and STRA6-independent mechanism of action for RBP4.