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Xinhua Chen, Theresa O. Scholl, Maria J. Leskiw, Melissa R. Donaldson, T. Peter Stein, Authors’ Response: Association of Glutathione Peroxidase Activity with Insulin Resistance and Dietary Fat Intake during Normal Pregnancy, The Journal of Clinical Endocrinology & Metabolism, Volume 89, Issue 9, 1 September 2004, Pages 4773–4774, https://doi.org/10.1210/jc.2004-1200
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To the editor:
In his letter, Hawkes (1) suggests that our findings on glutathione peroxidase (GPx) during pregnancy were the result of residual confounding by changes in maternal hemoglobin with gestation and by differences in hemoglobin between ethnic groups. Consequently, we reexamined our data using absolute erythrocyte GPx activity in lieu of computing the ratio of GPx to hemoglobin, the usual method of expressing the concentration (2–4). These results confirmed our original findings. The absolute GPx activity increased significantly between entry to care and the third trimester (2196 mU/ml at entry vs. 2382 mU/ml, third trimester; P < 0.001), and the effect persisted even when hemoglobin was used as a covariate in the models. Ethnic differences in absolute GPx activity were present both at entry and in the third trimester. At entry, African-Americans (2344 ± 65 mU/ml) had absolute levels of GPx that were significantly higher (P < 0.01) than Hispanics (2079 ± 60 mU/ml) but not whites (2166 ± 114 mU/ml). During the third trimester, GPx levels in African-American gravidas exceeded both ethnic groups (P < 0.02) [2515 ± 60 mU/ml (African-Americans), 2316 ± 56 mU/ml (Hispanics), 2207 ± 103 mU/ml (whites)]; use of hemoglobin as a covariate did not alter this result. On both occasions, African-American women had significantly higher absolute GPx activity, despite having lower levels of hemoglobin.
