Detection of oxidized and glycated proteins in clinical samples using mass spectrometry — A user's perspective

Background

Proteins in human tissues and body fluids continually undergo spontaneous oxidation and glycation reactions forming low levels of oxidation and glycation adduct residues. Proteolysis of oxidised and glycated proteins releases oxidised and glycated amino acids which, if they cannot be repaired, are excreted in urine.

Scope of Review

In this review we give a brief background to the classification, formation and processing of oxidised and glycated proteins in the clinical setting. We then describe the application of stable isotopic dilution analysis liquid chromatography-tandem mass spectrometry (LC-MS/MS) for measurement of oxidative and glycation damage to proteins in clinical studies, sources of error in pre-analytic processing, corroboration with other techniques – including how this may be improved – and a systems approach to protein damage analysis for improved surety of analyte estimations.

Major conclusions

Stable isotopic dilution analysis LC-MS/MS provides a robust reference method for measurement of protein oxidation and glycation adducts. Optimised pre-analytic processing of samples and LC-MS/MS analysis procedures are required to achieve this.

General significance

Quantitative measurement of protein oxidation and glycation adducts provides information on level of exposure to potentially damaging protein modifications, protein inactivation in ageing and disease, metabolic control, protein turnover, renal function and other aspects of body function. Reliable and clinically assessable analysis is required for translation of measurement to clinical diagnostic use. Stable isotopic dilution analysis LC-MS/MS provides a “gold standard” approach and reference methodology to which other higher throughput methods such as immunoassay and indirect methods are preferably corroborated by researchers and those commercialising diagnostic kits and reagents. This article is part of a Special Issue entitled Current methods to study reactive oxygen species - pros and cons and biophysics of membrane proteins. Guest Editor: Christine Winterbourn.     

Slight phenotypic variation in predators and prey causes complex predator-prey oscillations

Predator-prey oscillations are expected to show a 1/4-phase lag between predator and prey. However, observed dynamics of natural or experimental predator-prey systems are often more complex. A striking but hardly studied example are sudden interruptions of classic 1/4-lag cycles with periods of antiphase oscillations, or periods without any regular predator-prey oscillations. These interruptions occur for a limited time before the system reverts to regular 1/4-lag oscillations, thus yielding intermittent cycles. Reasons for this behaviour are often difficult to reveal in experimental systems. Here we test the hypothesis that such complex dynamical behaviour may result from minor trait variation and trait adaptation in both the prey and predator, causing recurrent small changes in attack rates that may be hard to capture by empirical measurements. Using a model structure where the degree of trait variation in the predator can be explicitly controlled, we show that a very limited amount of adaptation resulting in 10–15% temporal variation in attack rates is already sufficient to generate these intermittent dynamics. Such minor variation may be present in experimental predator-prey systems, and may explain disruptions in regular 1/4-lag oscillations.     

慢性间歇性缺氧降低SD大鼠精子数量和活力的研究

摘要 目的：通过制备大鼠慢性间歇性缺氧的动物模型,观察间歇性缺氧对雄性大鼠精子数量和活力的影响,并初步探讨其可能的发生机制。方法：16只雄性SD大鼠随机分为对照组和缺氧组。间歇性缺氧8周后分别测定两组大鼠精子活力和精子浓度,睾丸组织中P53的表达量和细胞的凋亡水平,以及血清睾酮（T）、促卵泡素（FSH）和黄体生成素（LH）的浓度。结果：与对照组比较,缺氧组大鼠精子的浓度和活力均降低（P>0.05),并且前向运动的精子数明显减少（P<0.05）。同时,缺氧组睾丸组织P53 mRNA的表达和睾丸组织中凋亡的细胞均多于对照组,血清T、LH的浓度低于对照组（P<0.05）。结论：间歇性缺氧时可能影响了下丘脑-垂体-性腺轴,不仅使睾酮合成减少,还降低了对P53的抑制作用而诱导了大量细胞的凋亡,最终降低了SD大鼠的精子数量和活力。     

Firing pattern of bursting neurons under sinusoidal drive in mean-field modeling

Bursting has been observed in many sensory neurons, and is thought to be important in neural signaling, sleep, and some disorders of the brain. Bursting neurons have been studied via various types of conductance-based models at the single-neuron level. Important features of bursting have been reproduced by this type of model, but it is not certain how well the behavior of populations of bursting neurons can be represented solely by that of individual neurons. To study bursting neurons at the population level, a conductance-based model is incorporated into a mean-field model to yield a mean-field bursting model. The responses of the model to sinusoidal inputs are studied, showing that neurons with various different initial states are capable of phase-locked or intermittent firing, depending on their baseline voltage. Furthermore, depending on this voltage, the bursting frequency either slaves to the original unperturbed bursting frequency or approaches a steady value when the external driving frequency increases. Finally, use of white noise perturbations shows that the bursting frequency of the neurons remains the same even under a more general external stimulus.     

Longitudinal study of serum zinc and copper levels in hemodialysis patients and their relation to biochemical markers

A 6-mo longitudinal study of 48 hemodialysis patients (HPs) with chronic renal failure was performed. Three blood samplings were done. Samples of whole blood from each patient were collected during hemodialysis sessions after passing through the artificial kidney. Zinc and copper levels were measured by atomic absorption spectrometry. Additionally, 36 biochemical indexes were evaluated during the study. Fifty-two healthy matched controls were also considered. Mean serum zinc and copper concentrations in HPs were significantly decreased (Zn) and increased (Cu), when compared with healthy controls (p<0.01). Zinc concentrations found in the first and second blood samplings from patients were significantly lower than those measured for the third sampling (p<0.01). The etiology of chronic renal failure influenced the statistically serum Zn levels of patients (p<0.05). Serum copper levels of HPs were significantly diminished by the existence of secondary associated diseases (p<0.01). Uric acid and parathyroid hormone, and total-cholesterol and glutamic-pyruvic-transaminase levels were significantly (p<0.05) and linearly related with serum zinc and copper concentrations, respectively. From all of indexes, creatinine, direct bilirubin, magnesium, calcium, parathyroid hormone, transferrin, and albumin were statistically modified along the longitudinal study (p<0.05). Transferrin serum levels were significantly diminished in the third blood sampling, indicating the tendency toward anemia in the patients. This result is reinforced by low levels of biochemical and hematological indexes related with iron body staus.     

间歇性θ脉冲刺激联合有氧运动训练对老年2型糖尿病合并轻度认知功能障碍患者糖脂代谢、认知功能和听觉诱发电位P300的影响

摘要 目的：探讨间歇性θ脉冲刺激（iTBS）联合有氧运动训练对老年2型糖尿病（T2DM）合并轻度认知功能障碍（MCI）患者糖脂代谢、认知功能和听觉诱发电位P300的影响。方法：选取2020年3月~2021年11月期间来我院接受治疗的老年T2DM合并MCI患者117例。按照随机数字表法分为对照组（有氧运动训练,58例）和观察组（iTBS联合有氧运动训练,59例）。观察两组干预前后糖脂代谢、认知功能和听觉诱发电位P300的变化情况。结果：观察组干预后空腹血糖（FBG）、糖化血红蛋白（HbA1c）低于对照组（P<0.05）。两组干预后总胆固醇（TC）、三酰甘油（TG）、低密度脂蛋白胆固醇（LDL-C）、高密度脂蛋白胆固醇（HDL-C）组间对比,统计学无差异（P>0.05）。观察组干预后蒙特利尔量表（MoCA）各维度及总分高于对照组（P<0.05）。观察组干预后中央区（Cz）潜伏期、组顶区（Pz）潜伏期短于对照组,Cz波幅、Pz波幅高于对照组（P<0.05）。结论：iTBS联合有氧运动训练用于老年T2DM合并MCI患者,可有效降低血糖,改善机体认知功能和听觉诱发电位P300。     

NT-702 (parogrelil hydrochloride, NM-702), a novel and potent phosphodiesterase inhibitor, improves reduced walking distance and lowered hindlimb plantar surface temperature in a rat experimental intermittent claudication model

NT-702 (parogrelil hydrochloride, NM-702), 4-bromo-6-[3-(4-chlorophenyl)propoxy]-5-[(pyridin-3-ylmethyl)amino]pyridazin-3(2H)-one hydrochloride, a novel phosphodiesterase (PDE) inhibitor synthesized as a potent vasodilatory and antiplatelet agent, is being developed for the treatment of intermittent claudication (IC) in patients with peripheral arterial disease. We assessed the efficacy of NT-702 in an experimental IC model as compared with cilostazol and additionally investigated the pharmacological property in vitro and ex vivo. NT-702 selectively inhibited PDE3 (IC(50)=0.179 and 0.260 nM for PDE3A and 3B) more potently than cilostazol (IC(50)=231 and 237 nM for PDE3A and 3B) among recombinant human PDE1 to PDE6. NT-702 inhibited in vitro human platelet aggregation induced by various agonists (IC(50)=11 to 67 nM) and phenylephrine-induced rat aortic contraction (IC(50)=24 nM). Corresponding results for cilostazol were 4.1 to 17 microM and 1.0 microM, respectively. NT-702 (3 mg/kg or more) significantly inhibited ex vivo rat platelet aggregation after a single oral dose. For cilostazol, 300 mg/kg was effective. In a rat femoral artery ligation model, NT-702 at 5 and 10 mg/kg repeated oral doses twice a day (BID) for 13 days significantly improved the reduced walking distance while the lowered plantar surface temperature was improved at 2.5 mg/kg and more. Cilostazol also improved the walking distance and surface temperature at 300 mg/kg BID but significant difference was only observed for surface temperature on day 8. These results suggest that NT-702 can be expected to have therapeutic advantage for IC.     

Contaminant removal efficiency depending on primary treatment and operational strategy in horizontal subsurface flow treatment wetlands

This study aimed to evaluate the contaminant removal efficiency of shallow horizontal subsurface flow treatment wetlands (SSF TWs) as a function of (1) primary treatment (hydrolytic upflow sludge blanket (HUSB) reactor vs. conventional settling) and (2) operation strategy (alternation of saturated/unsaturated phases vs. permanently saturated). An experimental plant was constructed, operated and surveyed for the main water quality parameters over a period of 2.5 years. The plant had 3 treatment lines: a control line (settler-wetland permanently saturated), a batch line (settler-wetland operated with saturated/unsaturated phases) and an anaerobic line (HUSB reactor-wetland permanently saturated). In each line wetlands had a surface area of 2.80 m², a water depth of 25 cm and a granular medium D₆₀ = 7.3 mm, and were planted with common reed. During the study period the wetlands were operated at a hydraulic and organic load of 28.5 mm/d and about 4.7 g BOD/m² d, respectively. Effluent average redox potential was lower for the anaerobic line (−45 ± 78 mV) than for the other two lines (3 ± 92.7 and −5 ± 71 mV for control and batch, respectively). Overall, chemical oxygen demand (COD), biochemical oxygen demand (BOD₅) and ammonium mass removal efficiencies were slightly greater for the batch line (88%, 96% and 87%, respectively) than for the control line (83%, 94% and 80%) and the anaerobic line (80%, 87% and 73%). During cold seasons, COD and ammonium removal in the batch line was around 30% and 50% higher than in the control line, respectively. The results of this study indicate that the implementation of a HUSB reactor as primary treatment did not enhance the treatment capacity of the system (in comparison with a conventional settler). The efficiency of treatment wetland systems with horizontal subsurface flow can be improved using a batch operation strategy.     

平衡型氨基酸透析液对维持性血液透析患者血浆游离氨基酸含量的影响

目的:研究一种平衡型氨基酸透析液,探讨其对维持性血透患者血游离氨基酸含量的影响。方法:实验采用自身对照设计,应用蛋白水解法测定、分析应用氨基酸透析液血透前后患者血浆氨基酸含量,并同时测定应用碳酸盐透析液患者及健康人血浆游离氨基酸作为比较。结果:经碳酸盐透析后,患者血浆大多数游离氨基酸和总氨基酸含量显著降低。给予平衡氨基酸透析液能不同程度改善患者血浆游离氨基酸的含量。结论:平衡型氨基酸透析液能减少血中部分氨基酸的丢失。     

Hybrid cooling vest for cooling between exercise bouts in the heat: Effects and practical considerations

While continuous cooling strategies may induce some ergonomic problems to occupational workers, cooling between work bouts may be an alternative for cooling them down in hot environments. The purpose of this study was to assess the effects of wearing a newly designed hybrid cooling vest (HCV) between two bouts of exercise. Inside a climatic chamber set at an air temperature of 37 °C and a relative humidity of 60%, twelve male participants underwent two bouts of intermittent exercise interspersed with a 30 min between-bout recovery session, during which HCV or a passive rest without any cooling (PAS) was administered. The results indicated that thermoregulatory, physiological, and perceptual strains were significantly lower in HCV than those in PAS during the recovery session (p≤0.022), which were accompanied with a large effect of cooling (Cohen's d=0.84–2.11). For the second exercise bout, the exercise time following HCV (22.13±12.27 min) was significantly longer than that following PAS (11.04±3.40 min, p=0.005, d=1.23) During this period, core temperature T_c was significantly lower by 0.14±0.0.15 °C in HCV than that in PAS. The heart rate drift over time was declined by 2±2 bpm min⁻¹ (p=0.001, d=1.00) and the rise in physiological strain index was reduced by 0.11±0.12 unit min⁻¹ (p=0.010, d=0.96) following the use of HCV. These findings suggested that using HCV could accelerate between-bout recovery and improve subsequent exercise performance by the enlarged body core temperature margin and blunted cardiovascular drift.