Impaired function of fibroblast growth factor 23 / Klotho protein axis in prediabetes and diabetes mellitus: Promising predictor of cardiovascular risk

The discovery of clear molecular mechanisms of early cardiac and vascular complications in patients with prediabetes and known diabetes mellitus are core element of stratification at risk with predictive model creation further. Previous clinical studies have shown a pivotal role of impaired signaling axis of fibroblast growth factor 23 (FGF23), FGF23 receptor isoforms and its co-factor Klotho protein in cardiovascular (CV) complications in prediabetes and diabetes. Although there were data received in clinical studies, which confirmed a causative role of altered function of FGF-23/Klotho protein axis in manifestation of CV disease in prediabetes and type 2 diabetes mellitus (T2DM), the target therapy of these diseases directing on improvement of metabolic profiles, systemic and adipokine-relating inflammation by beneficial restoring of dysregulation in FGF-23/Klotho protein axis remain to be not fully clear. The aim of the review was to summarize findings regarding the role of impaired FGF-23/Klotho protein axis in developing CV complications in patients with prediabetes and type 2 diabetes mellitus. It has been elucidated that elevated levels of FGF-23 and deficiency of Klotho protein in peripheral blood are predictors of CV disease and CV outcomes in patients with (pre) diabetes, while predictive values of dynamic changes of the concentrations of these biomarkers require to be elucidated in detail in the future.     

Melatonin Attenuates Memory Impairment Induced by Klotho Gene Deficiency Via Interactive Signaling Between MT2 Receptor,ERK, and Nrf2-Related Antioxidant Potential

Background:

We demonstrated that oxidative stress plays a crucial role in cognitive impairment in klotho mutant mice, a genetic model of aging. Since down-regulation of melatonin due to aging is well documented, we used this genetic model to determine whether the antioxidant property of melatonin affects memory impairment.

Methods:

First, we examined the effects of melatonin on hippocampal oxidative parameters and the glutathione/oxidized glutathione (GSH/GSSG) ratio and memory dysfunction of klotho mutant mice. Second, we investigated whether a specific melatonin receptor is involved in the melatonin-mediated pharmacological response by application with melatonin receptor antagonists. Third, we examined phospho-extracellular-signal-regulated kinase (ERK) expression, nuclear factor erythroid 2-related factor 2 (Nrf2) nuclear translocation, Nrf2 DNA binding activity, and glutamate-cysteine ligase (GCL) mRNA expression. Finally, we examined effects of the ERK inhibitor SL327 in response to antioxidant efficacy and memory enhancement mediated by melatonin.

Results:

Treatment with melatonin resulted in significant attenuations of oxidative damage, a decrease in the GSH/GSSG ratio, and a significant amelioration of memory impairment in this aging model. These effects of melatonin were significantly counteracted by the selective MT2 receptor antagonist 4-P-PDOT. Importantly, 4-P-PDOT or SL327 also counteracted melatonin-mediated attenuation in response to the decreases in phospho-ERK expression, Nrf2 nuclear translocation, Nrf2 DNA-binding activity, and GCL mRNA expression in the hippocampi of klotho mutant mice. SL327 also counteracted the up-regulation of the GSH/GSSG ratio and the memory enhancement mediated by melatonin in klotho mutant mice.

Conclusions:

Melatonin attenuates oxidative stress and the associated memory impairment induced by klotho deficiency via signaling interaction between the MT2 receptor and ERK- and Nrf2-related antioxidant potential.     

帕立骨化醇抑制糖尿病肾病大鼠肾小管间质纤维化

目的:探讨帕立骨化醇(paricalcitol,P)对糖尿病肾病(DN)肾小管间质纤维化的干预作用及可能机制。方法:大鼠禁食后,采用单次无菌腹腔注射链脲佐菌素建立DN模型。将DN大鼠随机分为:(1)帕立骨化醇干预组(P组):帕立骨化醇溶于丙二醇中,于造模成功后第2天以0.4μg/kg的剂量腹腔注射,每周3次;(2)糖尿病肾病组(D组):给予等体积的丙二醇腹腔注射。设置正常对照组(C组)。帕立骨化醇连续干预12周后,测血、尿生化指标;进行肾脏病理学检查;利用免疫组化及Western blotting检测肾组织TGF-β1、Wnt-4、β-catenin及Klotho蛋白的表达;并进行指标间的相关分析。结果:(1)与C组比较,D组大鼠SCr、BUN及24 h尿蛋白水平均升高,而P组均较D组降低(P0.05)。(2)与C组比较,D组大鼠肾小管间质纤维化面积增加,而P组较D组减小(P0.05)。(3)D组大鼠肾组织Klotho蛋白表达低于C组,而P组高于D组(P0.05);与C组比较,D组大鼠肾组织TGF-β1、Wnt-4及β-catenin蛋白表达增加,而P组表达均较D组减少(P0.05)。(4)Klotho与纤维化面积、TGF-β1、Wnt-4及β-catenin均呈负相关(P0.05)。结论:帕立骨化醇可抑制DN大鼠肾小管间质纤维化,其作用可能与增加肾组织Klotho表达,抑制Wnt/β-catenin信号通路激活,同时减少TGF-β1合成相关。     

Clinical implication of alterations in serum Klotho levels in patients with type 2 diabetes mellitus and its associated complications

Aim

To investigate the clinical significance of serum α-Klotho and β-Klotho levels in patients with type 2 diabetes mellitus (T2DM) and its associated complications.

东亚人群Klotho G-395A基因多态性与冠心病的Meta分析

目的 应用Meta分析探讨东亚人群Klotho G-395A基因多态性与冠心病易感性的关系。方法 分别检索中英文数据,获取2013年12月之前发表的有关Klotho G-395A基因多态性与冠心病易感性的病例对照研究,应用Meta分析方法对纳入的研究结果进行定量合并,采用Stata12.0软件进行统计分析,同时进行异质性检验及敏感性分析。结果 共纳入文献6篇,累计病例组1560例,对照组1459例。以显性模型比较做Meta分析,异质性检验显示无统计学意义（P0.2,I²30.8%）,以固定效应模型合并,表明Klotho G-395A基因多态性与冠心病易感性的关系有统计学意义（OR1.24,95%CI：1.06～1.45,P0.009）。按照病例组是否完全行冠状动脉造影做亚组分析,显示两组内部均无明显异质性,均以固定效应模型合并,冠状动脉造影组显示GA/AA基因型个体患冠心病的风险高于GG基因型个体（OR1.38,95%CI：1.12～1.70,P0.003）。非完全冠状动脉造影组则显示GA/AA基因型个体与GG基因型个体之间患冠心病的风险无统计学差异（OR1.07,95%CI：0.84～1.37,P0.587）。分别采取随机效应模型或去除权重最大的研究或去除等位基因差异最大的研究行敏感性分析,所得OR值与总体模型类似,有统计学意义。Begg’s检验提示无明显发表偏倚。结论 Klotho G-395A基因多态性可能与东亚人群冠心病易感性有关。     

Klotho与心血管疾病的关系及其生物学机制

Klotho是重要的内源性多效蛋白,参与衰老和钙磷代谢等病理生理过程,与心血管疾病密切相关。近期的临床研究发现低水平的Klotho与更多的心血管危险因素关联,并能预测心血管疾病的发病风险和不良预后;基础研究也表明Klotho在维持血管稳态和正常心功能中发挥了至关重要的作用。Klotho可以促进一氧化氮(NO)的生成,抑制炎症因子和黏附分子的表达,介导抗氧化、抗凋亡、抗衰老的生物学效应,延缓动脉粥样硬化及血管钙化,并抑制心肌肥厚和纤维化。Klotho或可作为一个新的干预靶点,为心血管疾病的防治提供新的思路。文章就Klotho与心血管疾病的关系及其潜在的生物学机制做一综述。     

肾元颗粒对db/db糖尿病肾病小鼠血管钙化的改善作用及其机制

目的：通过高磷诱导db/db糖尿病肾病（DN）小鼠血管钙化,探讨肾元颗粒对db/db DN小鼠血管钙化的改善作用及其可能机制。方法：将20只SPF级db/db小鼠随机分为模型组和肾元颗粒组（n=10）,同系背景野生型（WT）小鼠作为空白组（n=10）。给药12周后,取各组小鼠血清、肾脏和胸主动脉组织。ELISA法检测各组小鼠血清FGF23水平,HE和von Kossa法检测各组小鼠胸主动脉病理形态表现以及钙盐沉积情况,实时荧光定量PCR （Real-time PCR）法检测各组小鼠肾脏组织中KlothomRNA和胸主动脉组织中Pit-1、Runx2及SM22α mRNA表达水平,Western blotting法检测各组小鼠肾脏组织中Klotho蛋白和胸主动脉组织中Pit-1、Runx2及SM22α蛋白表达水平,免疫组织化学法检测各组小鼠胸主动脉组织中Pit-1蛋白表达水平,免疫荧光法检测各组小鼠胸主动脉组织中SM22α和Runx2蛋白表达水平。结果：与空白组比较,模型组小鼠血清FGF23水平明显升高（P<0.05）,肾脏组织中Klotho mRNA和蛋白表达水平明显降低（P<0.01）,胸主动脉组织中Pit-1和Runx2 mRNA及蛋白表达水平明显升高（P<0.01）,SM22α mRNA和蛋白表达水平明显降低（P<0.01）,胸主动脉组织中Pit-1和Runx2蛋白表达水平明显升高（P<0.01）,SM22α蛋白表达水平明显降低（P<0.01）。与模型组比较,肾元颗粒组小鼠血清FGF23水平降低（P<0.05）,肾脏组织中Klotho mRNA和蛋白表达水平明显升高（P<0.01）,胸主动脉组织中Pit-1和Runx2 mRNA及蛋白表达水平明显降低（P<0.01）,胸主动脉组织中SM22α mRNA和蛋白表达水平明显升高（P<0.01）。结论：肾元颗粒可通过上调小鼠肾脏组织中Klotho蛋白表达水平,减少Pit-1表达水平,抑制FGF23/Pit-1信号通路,调节血管平滑肌细胞（VSMC）的表型转化,达到血管保护作用。     

Effects of salt intervention on serum levels of Klotho influenced by salt sensitivity

Klotho was involved in sodium reabsorption and the regulation of blood pressure. Animal studies indicated Klotho deficiency could mediate the development of salt‐sensitive hypertension, indicating its correlation with salt sensitivity. We aimed to explore the responses of Klotho to salt intake through dietary intervention in Chinese adults. Forty‐four participants were enrolled from Lantian county of Shaanxi, China. All participants sequentially underwent a 3‐day normal diet, a 7‐day low‐Na⁺ diet, and a 7‐day high‐Na⁺ diet. The concentrations of serum Klotho were assessed by using ELISA kits. Serum level of Klotho was 360.44 ± 93.89 pg/mL at baseline and increased while changed to low‐salt diet (478.65 ± 183.25 vs 360.44 ± 93.89 pg/mL, P < .001). During high‐salt diet, serum Klotho decreased to 354.37 ± 98.16 pg/mL (P < .001, compared to low‐salt diet). The overall responses of Klotho were more prominent in salt‐resistant participants. Serum Klotho of salt‐resistant group changed from 353.92 ± 97.65 pg/mL to 496.76 ± 196.21 pg/mL while changed from normal diet to low‐salt diet (P < .001) and decreased to 350.37 ± 99.50 pg/mL during high‐salt intake (P < .001). Furthermore, the response of serum Klotho to low‐salt intervention was much greater in salt‐resistant individuals than in salt‐sensitive ones. The responses of serum Klotho to dietary salt intervention were influenced by salt sensitivity, which was more prominent in salt‐resistant participants.     

Sodium thiosulfate attenuates high phosphorous induced vascular calcification in rats with 5/6 nephrectomy

Objective To observe the expression of Klotho and Na+/Pi cotransporter in high phosphorous-induced rats with 5/6 nephrectomy and its relationship with vascular calcification, as well as to investigate the effect of early intervention by sodium thiosulfate (STS) on the progression of vascular calcification. Methods Either 5/6 nephrectomy (n=21) or sham operation (n=14) was conducted on 35 Sprague Dawley rats, who were then fed with high phosphorus (HP) diet or normal phosphorus (NP) diet for 16 weeks respectively. The rats were divided into 5 groups as follows: (1) remnant kidney rats receiving HP diet (NHP, n=7), (2) remnant kidney rats receiving NP diet (NNP, n=7), (3) sham operation rats receiving NP diet (SNP, n=7), (4) sham operation rats receiving HP diet (SHP, n=7), (5) remnant kidney rats receiving HP diet with STS (THP, n=7). The treatment group was given STS intraperitoneally three times a week for 16 weeks. At the end of the 16th week, rats tail artery blood pressures were tested, serum creatinine (Scr), calcium (Ca2+), phosphorus (P3+), FGF23, iPTH and urine protein were examined. Throacic aorta and kidney were then removed. Vascular calcification was confirmed by Von kossa staining. Klotho and Pit-1 expression in aortas were determined by immunohistochemistry. Renal lesion was determined by PASM-Masson staining. Renal Klotho and NaPi-2a mRNA were determined by real time RT-PCR. Results After 16 weeks, Scr, P3+, FGF23, iPTH, uric protein and blood pressure were significantly higher in NHP than those in SNP rats (all P＜0.05). PASM-Masson staining revealed typical renal pathology of chronic renal failure in NHP group. With the treatment of STS, THP rats showed significant decrease in Scr, P3+, FGF23, iPTH, uric protein and blood pressure by comparison with NHP group (all P＜0.05). Significant vascular calcification was found in NHP group while NNP and SHP group occasionally had vascular calcification; THP group had marked alleviation of vascular calcification. The aorta and renal expression of Klotho decreased remarkably while expression of Pit-1 and NaPi-2a increased significantly in NHP compared with SNP group (all P＜0.05). Accordingly, the aorta and renal expression of Klotho increased and Pit-1 and NaPi-2a decreased significantly in THP compared with NHP group (P＜0.05). Conclusions The early intervention of sodium thiosulfate might regulate Klotho and Na+/Pi cotransporter expression in both aorth and kidney, decreasing serum phosphate, delaying progression of vascular calcification and improving renal function.     

重型颅脑损伤患者血清可溶性α-Klotho蛋白水平动态变化及临床意义研究

背景 血清可溶性α-Klotho蛋白对多种神经系统疾病有保护作用,但关于颅脑损伤后其水平动态变化及与预后相关性的研究鲜有报道。 目的 探讨重型颅脑损伤患者术后血清可溶性α-Klotho蛋白水平的动态变化及其对预后的预测价值。 方法 选取2019年7月至2020年9月山西白求恩医院重症医学科收治的重型颅脑损伤行手术治疗需术后监护的患者103例作为病例组,另选取同期在本院体检的健康志愿者50例作为对照组。根据病例组患者住院28 d的生存结局将其分为生存亚组（n=74）与死亡亚组（n=29）。收集患者的临床资料,并采用酶联免疫吸附试验（ELISA）检测患者入重症医学科第1、3、5、7天血清可溶性α-Klotho蛋白水平,对照组入组第1天进行血清可溶性α-Klotho蛋白水平检测。 结果 病例组第1、3、5、7天血清可溶性α-Klotho蛋白水平均高于对照组（P<0.05）。病例组第3、5天血清可溶性α-Klotho蛋白水平均高于第1天,第5、7天血清可溶性α-Klotho蛋白水平均低于第3天,第7天血清可溶性α-Klotho蛋白水平低于第5天（P<0.05）。生存亚组第1、7天血清可溶性α-Klotho蛋白水平高于死亡亚组（P<0.05）。术后第1、7天血清可溶性α-Klotho蛋白水平预测重型颅脑损伤患者生存结局的受试者工作特征（ROC）曲线下面积（AUC）分别为0.686〔95%CI（0.587,0.774）〕、0.710〔95%CI（0.612,0.796）〕,两者AUC比较,差异无统计学意义（Z=0.265,P=0.791）。 结论 重型颅脑损伤可引起血清可溶性α-Klotho蛋白水平升高,且在伤后第3天达最高峰,对其动态监测有利于指导临床病情及预后的判断。