Saliva as a potential and non-invasive approach to identify upregulated genes associated with comorbidities of T1DM: a brief report.

Background: One of the main challenges in Type 1 diabetes mellitus (T1DM) research is the sample size of the participants and the invasive process of collecting an adequate number of blood samples from young patients with T1DM. Therefore, it is of great interest to investigate the possibility of using saliva as a non-invasive tool to investigate the genetic factors that are associated with T1DM comorbidities. The present study aims to identify differentially expressed genes (DEGs) in saliva samples of T1DM patients with various comorbidities using transcriptomic profiling.

Methods: A total of 56 participants were recruited from the University Hospital Sharjah, Dubai Hospital and Rashid Hospital, United Arab Emirates. Participants were divided into various groups: Control Group: healthy Emirati (n = 13), Group 1: patients with T1DM without any comorbidities (G1; n = 14), Group 2: patients with T1DM and hyperlipidemia (G2; n = 10), Group 3: patients with T1DM and neuropathy (G3; n = 5), Group 4: patients with T1DM and ketoacidosis (G4; n = 6), Group 5: patients with T1DM and hypothyroidism (G5; n = 6) and Group 6: patients with T1DM and polycystic ovary syndrome (PCOS, G6; n = 5). Saliva samples and blood were collected from all participants and RNA was extracted for transcriptomic analysis.

Results: The transcriptomic analysis of saliva samples of T1DM patients showed several DEGs that were associated with T1DM comorbidities. Interestingly, the number of upregulated genes in blood (n = 350) and saliva (n = 353) was comparable in the PCOS group (G6). In addition, the number of DEGs was more than double in saliva (n = 270) compared to blood (n = 118) samples in the ketoacidosis group (G4). Ten common upregulated genes between saliva and blood were identified in T1DM patients with hyperlipidemia (G2): LYPD5, TCF15, PRKY, CYHR1, CCDC173, CHRNA5, MIAT, HBA2, RAD54L, and TSHZ3. In addition, two common upregulated genes were identified in the neuropathy group (G3): KCTD19, FAM209B. Moreover, the following upregulated genes were observed in ketoacidosis (G4), hypothyroidism (G5) and PCOS (G6): (NCKAP5, ADAD2, C20orf144), (ZFY, KCTD19, P2RY14, RPS60) and (C4orf19, RSAD2, MEGF10, CMPK2, CHRNA5, TSHZ3, CCDC77, CLEC12A, RTP4), respectively.

Conclusions: The present findings demonstrated that the number of upregulated genes can be comparable between saliva and blood of T1DM patients with comorbidities, and in some groups, the number of upregulated genes was higher in the saliva compared to blood, emphasizing that saliva can be a potential non-invasive tool to identify DEGs in T1DM comorbidities.