Abstract

It has been reported that 58% of individuals with chronic kidney disease (CKD) have moderate to advanced periodontitis due to alterations of pH and biochemical composition in the saliva. In fact, the composition of this important biofluid may be modulated by systemic disorders. Here we investigate the micro-reflectance Fourier-transform infrared spectroscopy (FTIR) spectra of saliva that CKD patients submitted to periodontal treatment, aiming to identify spectral biomarkers of kidney disease evolution and the effectiveness of periodontal treatment, proposing possible biomarkers of disease evolution. Saliva from 24 CKD patients—stage-5 men, 29 to 64 years old—was evaluated in (i) patients starting periodontal treatment; (ii) patients 30 days after periodontal treatment; and (iii) patients 90 days after periodontal treatment. Our findings indicated that there are statistically relevant changes among the groups after 30 and 90 days of periodontal treatment, when considering the overall spectra in the fingerprint region ($800 {-} 1800\;{\text{cm}^{- 1}}$). The key bands presenting good prediction power (area under the receiver operating characteristic curve ${\gt}\;{0.70}$) were related to poly (ADP-ribose) polymerase (PARP) conjugated to DNA at 883, 1031, and $1060\;{\text{cm}^{- 1}}$ (carbohydrates at 1043 and $1049\;{\text{cm}^{- 1}}$) and triglycerides ($1461\;{\text{cm}^{- 1}}$). Interestingly when analyzing the derivative spectra in the secondary structure region ($1590 {-} 1700\;{\text{cm}^{- 1}}$), we detected over-expression of the $\beta$-sheet class of secondary structures in 90 days of periodontal treatment, possibly related to over-expression of human B-defensins. Conformational changes in ribose sugar in this region corroborate the interpretation concerning PARP detection. To our knowledge, PARP was detected for the first time in saliva samples of stage-5 CKD patients by FTIR. All observed changes were correctly interpreted in terms of intensive apoptosis and dyslipidemia due to kidney disease progression. Biomarkers due to CKD predominate in saliva, and the relative improvement in the periodontal state did not cause remarkable changes in the spectra of saliva.

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