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Background: Obesity is a public health problem worldwide; it has reached pandemic proportions in the last 40 years. Its prevalence in children and adolescents increased from 0.7% to 7.8% between 1975 and 2016. Recently, microRNAs (miRNAs) have been reported as regulatory factors related to molecular functions under different conditions. These can be used as biomarkers of a disease to estimate risks in the early stages. Objective: This study aimed to determine the expression levels of miRNAs associated with childhood obesity and their relationships with biochemical parameters and Health-related Physical Fitness (HRPF). Methods: This was a descriptive cross-sectional study in which a population of 40 children between 6 and 10 years of age of both sexes from Cali, Colombia, was evaluated; the children were classified as 20 normal-weight and 20 obese. Blood biochemistry, HRPF, and miRNA expression levels were determined (hsa-miR-122-5p, hsa-miR-15b-5p, hsa-miR-191-5p, hsa-miR-486-3p, hsa-miR-222-3p. Comparisons were made between the groups, miRNA associations between the studied variables, and linear regression analysis. Results: Twenty normal-weight and 20 obese patients were evaluated. Both groups had an average age of eight years old. The miRNA hsa-miR-122-5p (p < 0.05) was overexpressed in the obese group. According to the linear regression analysis, the amount of adipose tissue may be associated with the production of miRNAs (hsa-miR-15b-5p, hsa-miR-222-3p, hsa-miR-122-5p, and hsamiR- 191-5p). Conclusion: Four miRNAs (hsa-miR-15b-5p, hsa-miR-222-3p, hsa-miR-122-5p, and hsa-miR- 191-5p) are associated with modifications in biochemical variables of HRPF in this group. Adipose tissue mass could be associated with the production of these miRNAs, thus making them biomarkers of childhood obesity risk.

Background: Overweight and obesity prevalence has risen substantially in the last years. MicroRNAs (miRNAs) are factors that regulate gene expression through binding to a complementary sequence of mRNA. Objective: The objective of this review is to determine the association between the expression of miRNAs with overweight and obesity in children. Methods: A systematic search was carried out in Medline (Ovid), EMBASE, LILACS, and CENTRAL. Clinical trials, cohort studies, cases and controls, and cross-section studies were included. Quasi-experimental, prognostic studies, animal experiments, in silico studies, and studies on the adult population were excluded. Results: Seven studies (684 children) were included in this review. Three hundred and sixty-one children had obesity/overweight and 323 had normal weight. 40.64% (278) of the children were boys. The classification of obesity was inconsistent between the studies with several classifications used. A total of 65 miRNAs were reported to be associated with obesity and overweight; at least two studies reported miR-122, miR-122-5p, miR-15b, miR15b-5p, miR191-5p, miR-222, miR-222-3p, miR 486, miR-486-3p and miR-486-5p. Blood samples were the most common samples used to measure miRNAs, and the approaches to select miRNAs were diverse, with four articles performing high-throughput techniques (sequencing and microarrays) before the validation of the miRNAs associated with obesity. Pathway analysis of the repeated miRNAs showed that they were involved in the regulation of metabolic and signaling pathways, including fatty acid metabolism. Conclusion: miRNAs are potential biomarkers of the development of pathologies, such as obesity. It was found a heterogeneous group of these molecules was associated with obesity in children. miR- 15b-5p, miR-486-5p, and hsa-miR-122-5p were considered as good candidates for obesity biomarkers.