血清镁离子浓度与直肠癌患者谷氨酰转肽酶的关系

Relationship between Serum Magnesium Ion Concentration and Glutamyl Transferase in Rectal Cancer Patients

直肠癌患者血清镁离子(Mg^(2+))浓度对γ-谷氨酰转肽酶(γ-GT)的影响尚不明确,收集分析临床数据,Mg^(2+)浓度不呈正态分布(D=0.737,P<0.05),按照中位数分组,比较不同组间临床病理特征的差异,用局部加权散点平滑(LOWESS)、分段线性回归方法,拟合血清Mg^(2+)浓度与γ-GT的关系。结果发现,与Mg^(2+)浓度小于0.92 mmol/L组的直肠癌患者比较,Mg^(2+)浓度≥0.92 mmol/L组的γ-GT和血清总胆固醇较高(P均<0.05)。LOWESS的结果表明,原始数据中血清Mg^(2+)浓度的两个变化点分别为0.92 mmol/L和0.99 mmol/L,自然对数转换的数据中血清Mg^(2+)浓度的另外两个变化点分别为-0.167和-0.01。利用原始数据建立的两段线性回归模型表明,血清Mg^(2+)浓度的变化点为0.98 mmol/L,Mg^(2+)浓度<0.98 mmol/L对γ-GT有正向影响,Mg^(2+)≥0.98 mmol/L时有负向影响。另一个使用自然对数转换数据的两段线性回归模型显示,血清Mg^(2+)浓度的变化点为0.01,其中Mg^(2+)浓度的自然对数<0.01对γ-GT有正向影响,当Mg^(2+)浓度的自然对数≥0.01时则有负向影响。用原始数据LOWESS回归的2个拐点,即0.92 mmol/L和0.99 mmol/L的Mg^(2+)浓度,进行三段线性回归分析,结果显示,<0.980 mmol/L的Mg^(2+)浓度,对γ-GT的影响是正向的,且与<0.929 mmol/L的Mg^(2+)浓度区间的系数不同,影响程度不同,而在≥0.980 mmol/L的Mg^(2+)浓度区间,对γ-GT的影响是负向的,此外,用对数转换数据LOWESS的2个拐点进行的三段线性回归,也显示Mg^(2+)浓度的自然对数以-0.020为分界点时,对γ-GT的影响方向是相反的,但三段线性回归模型均没有统计学意义,总之,具有较高Mg^(2+)浓度的直肠癌患者,其γ-GT的水平也较高,Mg^(2+)浓度对γ-GT的影响存在拐点效应,为γ-GT的关联因素研究提供了基础。

The effect of serum magnesium ion(Mg ^(2+))concentration onγ-glutamyl transferase(γ-GT)in rectal cancer patients is not yet clear.The clinical data were collected and analyzed in this paper.The concentration of serum Mg ^(2+)did not exhibit a normal distribution(D=0.737,P<0.05).The clinical data was grouped according to the median concentration of Mg ^(2+).The differences in clinical and pathological characteristics between different groups were compared.The relationship between the serum concentration of Mg ^(2+)andγ-GT levels were fitted by locally weighted scatterplot smoothing(LOWESS)and piecewise linear regression methods.The results showed that compared with rectal cancer patients with Mg ^(2+)concentration less than 0.92 mmol/L,those patients with Mg ^(2+)concentration more than 0.92 mmol/L had higherγ-GT and serum total cholesterol levels(P<0.05 respectively).The results from LOWESS indicated that two change points of serum Mg ^(2+)concentration in the original data were 0.92 mmol/L and 0.99 mmol/L,respectively.The other two change points of serum Mg ^(2+)concentration in the data converted from natural logarithms were-0.167 and-0.01,respectively.A two-piecewise linear regression model established using original data showed that the change point of serum Mg ^(2+)concentration was 0.98 mmol/L,with Mg ^(2+)concentration less than 0.98 mmol/L performed a positive impact onγ-GT and negative impact when Mg ^(2+)more than 0.98 mmol/L.Another two-piecewise linear regression model using natural logarithms transformed data showed that the change point of serum Mg ^(2+)concentration was 0.01,with the natural logarithm of Mg ^(2+)concentration less than 0.01 having a positive impact onγ-GT and negative impact when the natural logarithm of Mg ^(2+)concentration more than 0.01.The two inflection points of Mg ^(2+)concentrations(0.92 mmol/L and 0.99 mmol/L)was from LOWESS regression for the original data,and a three-stage linear regression analysis was conducted.The results showed that Mg ^(2+)concentrations less than 0.980 mmol/L had positively impact onγ-GT,and different from the coefficient and degree of influence in the Mg ^(2+)concentration range of less than 0.929 mmol/L.However,in the Mg ^(2+)concentration range of more than 0.980 mmol/L,it had a negative impact onγ-GT.In addition,a three-stage linear regression using the two inflection points from LOWESS regression for the logarithmic transformed data also showed that when the natural logarithm of Mg ^(2+)concentration was at the cut-off point of-0.020,its impact direction ofγ-GT was opposite,but the three stage linear regression models were not statistically significant.In summary,rectal cancer patients with high Mg ^(2+)concentrations had higher levels ofγ-GT,the concentration of Mg ^(2+)affectedγ-GT through turning point effects,and provided foundations for studies on the associated factors ofγ-GT in rectal cancer patients.