Institute of Toxicology, Core Unit Proteomics, Hannover Medical School, 30623, Hannover, Germany.
Institute of Toxicology, Core Unit Proteomics, Hannover Medical School, Carl-Neuberg-Strasse 1, 30625, Hannover, Germany.
Amino Acids. 2019 Jun;51(6):961-971. doi: 10.1007/s00726-019-02737-y. Epub 2019 Apr 26.
The importance of L-arginine (Arg) and relatives, including L-homoarginine (hArg) and asymmetric dimethylarginine (ADMA), in humans infected with Helicobacter pylori (Hp) is little understood. ADMA is produced by asymmetric dimethylation of the guanidine group of Arg residues in certain proteins and is released by proteolysis. High concentrations of circulating free ADMA are considered a risk factor for morbidity and mortality in adults. This risk is considered to arise from the inhibition of the synthesis of nitric oxide (NO), which is a potent vasodilator and inhibitor of platelet aggregation. In the present study, we quantified by stable isotope dilution gas chromatography-mass spectrometry (GC-MS) the concentration of free (f) and total (t) ADMA, Arg, hArg, lysine (Lys) and the sum of citrulline (Cit) and ornithine (Orn) (6 M HCl, 20 h, 110 °C) in serum samples of apparently healthy elderly subjects (n = 27; age, 31-105 years) who were tested for Hp infection. Nine subjects (5 males, 4 females) were found to be Hp seropositive (Hp+) and 18 subjects (8 males, 9 females) were found to be Hp seronegative (Hp‒). Proteinic (p) concentrations were determined by difference. fADMA (0.493 ± 0.068 vs 0.466 ± 0.081 µM, P = 0.382), pADMA (113 ± 73 vs 76 ± 59 nM, P = 0.169) and tADMA (0.606 ± 0.126 vs 0.543 ± 0.121 µM, P = 0.280) serum concentrations were found not to differ between the Hp+ and Hp- subjects. Serum concentrations of fArg (162 ± 30 vs 177 ± 36 µM, P = 0.471), fhArg (1.600 ± 0.638 vs 1.831 ± 0.742 µM, P = 0.554), and fLys (388 ± 170 vs 395 ± 149 µM, P = 0.700) also did not differ statistically between Hp+ and Hp- subjects. tArg (12.4 ± 1.49 vs 13.0 ± 1.33 mM, P = 0.190), tLys (23.0 ± 2.65 vs. 23.9 ± 2.66 mM, P = 0.456) and tCit + Orn (2.53 ± 0.76 vs 2.63 ± 0.85 mM, P = 0.817) did not differ between Hp+and Hp‒ subjects as well. phArg concentration was close to the limit of quantitation of the method (Hp+: 30 ± 210 nM; Hp-: 42 ± 205 nM), suggesting that hArg is virtually absent in serum proteins of the investigated subjects. pCit + Orn did not differ between infected and non-infected subjects. Our study suggests that Hp infection is not associated with elevated asymmetric dimethylation and citrullination of Arg proteins present in the serum or with the hArg synthesis from free Arg in elderly subjects. However, asymmetric Arg dimethylation was found to correlate inversely with Arg citrullination in Hp- (r = 0.408, P = 0.004) but not in Hp+ (r = 0.065, P = 0.506), with Arg citrullination decreasing and Arg asymmetric dimethylation increasing with subjects' age.
在感染幽门螺杆菌（Hp）的人群中，精氨酸（Arg）及其相关物质（包括 L-同型精氨酸（hArg）和不对称二甲基精氨酸（ADMA））的重要性尚未被充分认识。ADMA 是由 Arg 残基胍基的不对称二甲基化产生的，并通过蛋白水解释放。循环中游离 ADMA 浓度升高被认为是成年人发病率和死亡率的一个风险因素。这种风险被认为是由于抑制了一氧化氮（NO）的合成，NO 是一种强有力的血管扩张剂和血小板聚集抑制剂。在本研究中，我们通过稳定同位素稀释气相色谱-质谱法（GC-MS）定量检测了血清样品中游离（f）和总（t）ADMA、Arg、hArg、赖氨酸（Lys）以及瓜氨酸（Cit）和鸟氨酸（Orn）的总和（6M HCl，20h，110°C）浓度。血清样本来自 27 名看似健康的老年受试者（年龄 31-105 岁），他们接受了 Hp 感染检测。9 名受试者（5 名男性，4 名女性）被检测为 Hp 血清阳性（Hp+），18 名受试者（8 名男性，9 名女性）被检测为 Hp 血清阴性（Hp-）。蛋白（p）浓度通过差值确定。fADMA（0.493±0.068 对 0.466±0.081µM，P=0.382）、pADMA（113±73 对 76±59nM，P=0.169）和 tADMA（0.606±0.126 对 0.543±0.121µM，P=0.280）血清浓度在 Hp+和 Hp-受试者之间没有差异。fArg（162±30 对 177±36µM，P=0.471）、fhArg（1.600±0.638 对 1.831±0.742µM，P=0.554）和 fLys（388±170 对 395±149µM，P=0.700）在 Hp+和 Hp-受试者之间也没有统计学差异。tArg（12.4±1.49 对 13.0±1.33mM，P=0.190）、tLys（23.0±2.65 对 23.9±2.66mM，P=0.456）和 tCit+Orn（2.53±0.76 对 2.63±0.85mM，P=0.817）在 Hp+和 Hp-受试者之间也没有差异。phArg 浓度接近方法的定量下限（Hp+：30±210nM；Hp-：42±205nM），这表明 hArg 实际上不存在于研究对象的血清蛋白中。感染和未感染的受试者之间 pCit+Orn 没有差异。我们的研究表明，Hp 感染与血清或 Arg 蛋白中 Arg 的不对称二甲基化和瓜氨酸化增加无关，也与老年受试者中游离 Arg 合成 hArg 无关。然而，不对称 Arg 二甲基化与 Hp-（r=0.408，P=0.004）但与 Hp+（r=0.065，P=0.506）受试者的 Arg 瓜氨酸化呈负相关，Arg 瓜氨酸化减少，Arg 不对称二甲基化增加。
