Title: Maternal periodontal disease promotes changes in microRNA expression patterns in adult offspring
The fetal programming hypothesis suggests that stimuli or aggressions during intrauterine life may result in permanent physiological and metabolic changes in the offspring, increasing the risk of disease in adult life. Changes in microRNA expression patterns are considered one of the molecular mechanisms responsible for this programming. Previous studies have demonstrated that maternal periodontal disease (PD) promotes insulin resistance, increased plasma concentrations of cytokines, reduced GLUT4 content, plasma membrane, translocation index and expression in adult offspring. In addition, maternal periodontal disease was able to activate inflammatory pathways in the skeletal muscle of adult offspring. This activation was confirmed by increased expression of TNF-alpha, NF-kBp65, NF-kBp50, IKK alpha/beta and ERK1/2. However, no changes in DNA methylation of the GLUT4 gene and JNK expression were observed in adult offspring. It was possible to infer that one of the reasons for the observed reduction of GLUT4 expression in the muscular tissue of adult rats with PD occurred through the activation of inflammatory pathways. These findings evidenced the need for further studies to verify other mechanisms involved, such as miRNAs expression patterns in the adult offspring. Therefore, the aims of the present study are to evaluate in adult rats, offspring of rats with periodontal disease: a) body weight; b) global expression of miRNAs in gastrocnemius skeletal muscle. Rats were distributed into two groups: 1) with periodontal disease (PED), induced by ligation with silk thread around the 1st molar, 2) control rats (CN). Seven days after ligature placement, rats of both groups were mated, and copulation was verified by daily vaginal smears. Pregnant rats were separated into individual boxes. After weaning, male offspring were distributed into control offspring (CN-o) and periodontal disease offspring (PED-o) groups. Body weights were measured from 0–75 days of age. At day 75, analysis of the global expression of miRNAs was performed by microarray in total RNA extracted from gastrocnemius skeletal muscle samples. There was a significantly lower birth weight in the PED-o group compared to the CN-o group. However, body weight did not differ at the weekly weighing, carried out until 75 days of age, between the CN-o and PED-o groups. We identified 11 miRNAs that were modulated in adult offspring of rats with periodontal disease (fold change ± 1.5; p < 0.05) when compared to control rats. Among these, 5 miRNAs were upregulated and 6 downregulated. Therefore, maternal periodontal disease is capable of promoting low birth weight, catch-up growth and, in adulthood, changes in microRNA profile in muscle. These findings reinforce the importance of caring for maternal oral health during pregnancy in order to avoid adverse pregnancy outcomes and epigenetic modifications in their adult offspring. This study was supported by the Sao Paulo Research Foundation (FAPESP) [grant #2019/04183-9] Sao Paulo, SP, Brazil.