Significance: Dg complex integrity and balance are required for a proper hematopoietic cell function, in that its disruption might contribute to leukemia pathophysiology.3

Coronavirus disease 2019 (COVID-19) is a disease produced by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and it is currently causing a catastrophic pandemic affecting humans worldwide. This disease has been lethal for approximately 3.12 million people around the world since January 2020. Globally, among the most affected countries, Mexico ranks third in deaths after the United States of America and Brazil. Although the high number of deceased people might also be explained by social aspects and lifestyle customs in Mexico, there is a relationship between this high proportion of deaths and comorbidities such as high blood pressure (HBP), type 2 diabetes, obesity, and metabolic syndrome. The official epidemiological figures reported by the Mexican government have indicated that 18.4% of the population suffers from HBP, close to 10.3% of adults suffer from type 2 diabetes, and approximately 36.1% of the population suffers from obesity. Disbalances in the gut microbiota (GM) have been associated with these diseases and with COVID-19 severity, presumably due to inflammatory dysfunction. Recent data about the association between GM dysbiosis and metabolic diseases could suggest that the high levels of susceptibility to SARS-CoV-2 infection and COVID-19 morbidity in the Mexican population are primarily due to the prevalence of type 2 diabetes, obesity, and metabolic syndrome.

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Mammary gland secretory cells produce miRNA-rich milk. In humans, these miRNAs reach infant/neonate bloodstream, playing diverse roles, like neural system development, metabolism, and immune system maturation. Notwithstanding, still few works explore human milk miRNA content, and there are no reports at the population level. Our hypothesis was that miR-146b-5p, miR148a-3p, miR155-5p, mir181a-5p, and mir200a-3p immunoregulatory miRNAs are expressed in human colostrum/milk at a higher level than infant milk formulae. The aim of this work was to evaluate the expression of the five immunoregulatory miRNAs in human milk and compare it with their expression in infant milk formula. For this purpose, miRNA relative expression was measured by qPCR in cDNA prepared from total RNA extracted from sixty human colostrum/milk samples and six different formulae. The comparative Cт method 2−ΔCт using exogenous cel-miR-39 as internal control was employed, followed by statistical analysis. We found the relative expression levels of miRNAs are comparable among colostrum/milk samples, and these miRNAs are present in infant milk formulae but at very low concentrations. We conclude that the relative expression of the immunomodulatory miRNAs is comparable in all the human colostrum/milk samples and is higher than the expression in formulae.