The tendency of anemia of inflammation in periodontal diseases.

"Competing Interests The authors declare that there are no competing interests associated with the manuscript."

"Funding This work was supported by the research funds from the National Natural Science Foundation of China [grant number 82071117]; the Natural Science Foundation of Beijing [grant number 7212136]; and the Youth Program of National Natural Science Foundation of China [grant number 81800976]."

"The protocol of the human study was approved by the Ethics Committee of Peking University Health Science Center (Approval No. PKUSSIRB-202056090) and registered in the International Clinical Trials Registry Platform under the ID: ChiCTR2000040451. The research had been carried out in accordance with the World Medical Association Declaration of Helsinki, and written informed consent was obtained from all subjects. About 60 patients with periodontitis were recruited from the Department of Periodontology, Peking University School, and Hospital of Stomatology. The diagnosis of periodontitis was based on the diagnostic criteria proposed by 2017 Workshop for the Classification of Periodontal Diseases and Conditions []. In addition, 60 healthy subjects were selected with probing depth (PD) ≤3 mm, percentage of sites with bleeding on probing <10%, and no attachment loss (AL). Individuals who were current or previous smokers, and those with any systemic disease, pregnancy, history of iron supplementation or other drugs for the treatment of anemia, periodontal therapy or antimicrobial therapy, or use of any medication (including oral contraceptive drugs) within the previous 6 months were excluded. Ethics Approval: The clinical study was approved by the Ethics Committee of Peking University Health Science Center (Approval No. PKUSSIRB-202056090) and registered in the International Clinical Trials Registry Platform under the ID: ChiCTR2000040451. All of the procedures performed on the animals followed the protocol approved by the Experimental Animal Welfare Ethics Branch of Peking University Biomedical Ethics Committee (LA2013-32)."