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Hypertension results from the interaction of genetic and acquired factors. IgG occurs in the form of different subclasses, of which the effector functions show significant variation. The detailed differences between the glycosylation profiles of the individual IgG subclasses may be lost in a profiling method for total IgG N-glycosylation. In this study, subclass-specific IgG Fc glycosylation profile was investigated in the four northwestern Chinese minority populations, namely, Uygur (UIG), Kazak (KZK), Kirgiz (KGZ), and Tajik (TJK), composed of 274 hypertensive patients and 356 healthy controls. The results showed that ten directly measured IgG N-glycan traits (i.e., IgG1G0F, IgG2G0F, IgG2G1FN, IgG2G1FS, IgG2G2S, IgG4G0F, IgG4G1FS, IgG4G1S, IgG4G2FS, and IgG4G2N) representing galactosylation and sialylation are significantly associated with hypertension, with IgG4 consistently showing weaker associations of its sialylation, across the four ethnic groups. We observed a modest improvement on the AUC of ROC curve when the IgG Fc N-glycan traits are added into the glycan-based model (difference between AUCs, 0.044, 95% CI: 0.016-0.072, P = 0.002). The AUC of the diagnostic model indicated that the subclass-specific IgG Fc N-glycan profiles provide more information reinforcing current models utilizing age, gender, BMI, and ethnicity, and demonstrate the potential of subclass-specific IgG Fc N-glycosylation profiles to serve as a biomarker for hypertension. Further research is however required to determine the additive value of subclass-specific IgG Fc N-glycosylation on top of biomarkers, which are currently used.

Next-generation (postgenomic) biomarkers from the nascent field of glycomics now offer fresh vistas for innovation in chronic disease biomarkers and system diagnostics in clinical medicine. Our previous work has shown an association between hypertension and immunoglobulin G (IgG) glycome composition, suggesting that individual variation in N-glycosylation of IgG might contribute to hypertension pathogenesis. The present study examined, for the first time to the best of our knowledge, the IgG N-glycans as potential biomarkers for hypertension in the Kazakh population. The profile of 60 N-glycopeptides of IgG subclass isolated from plasma samples of 150 Kazakh study participants was analyzed by nano ultra-performance liquid chromatography with mass spectrometry. Fourteen IgG subclass-specific Fc N-glycopeptide structures, along with one derived glycosylation trait in subclasses IgG2/3 and IgG4, were found to correlate with systolic blood pressure and/or diastolic blood pressure. For differentiation of hypertension and healthy status in the Kazakh population sample, the receiver operating characteristic curve analysis showed that the performance of the model, including nine IgG N-glycans, was greater than the traditional gender, age, and body mass index based model (p < 0.05). This study indicates that alteration in Fc N-glycopeptide profiles of plasma IgG subclasses is associated with blood pressure status in the Kazakh population. IgG N-glycosylation profiles may serve as potential biomarkers for hypertension in the Kazakhs, thus contributing to move toward personalized medicine. Further studies of postgenomic glycomic biomarkers in cardiovascular and chronic diseases are timely and called for.