Evaluation of Exosomal Coding and Non-Coding RNA Signature in Obese Adolescents

Modulation of MicroRNAs and Exosomal MicroRNAs after Dietary Interventions for Obesity and Insulin Resistance: A Narrative Review

MicroRNAs (miRNAs) are small noncoding RNAs approximately 22 nucleotides in length. Their main function is to regulate gene expression at the posttranscriptional level by inhibiting the translation of messenger RNAs (mRNAs). miRNAs originate in the cell nucleus from specific genes, where they can perform their function. However, they can also be found in serum, plasma, or other body fluids travelling within vesicles called exosomes and/or bound to proteins or other particles such as lipoproteins. miRNAs can form complexes outside the cell where they are synthesized, mediating paracrine and endocrine communication between different tissues. In this way, they can modulate the gene expression and function of distal cells. It is known that the expression of miRNAs can be affected by multiple factors, such as the nutritional or pathological state of the individual, or even in conditions such as obesity, insulin resistance, or after any dietary intervention. In this review, we will analyse miRNAs whose expression and circulation are affected in conditions of obesity and insulin resistance, as well as the changes generated after a dietary intervention, with the purpose of identifying new possible biomarkers of early response to nutritional treatment in these conditions.

The Regulatory Role of MicroRNAs in Obesity and Obesity-Derived Ailments

Obesity is a condition that is characterized by the presence of excessive adipose tissue in the body. Obesity has become one of the main health concerns worldwide since it can lead to other chronic ailments, such as type 2 diabetes or fatty liver disease, and it could be an aggravating factor in infections. MicroRNAs (miRNAs) are small, non-coding RNA molecules that regulate gene expression and can play an important role in controlling crucial biological processes involved in the onset of obesity, such as lipogenesis, adipogenesis, lipid metabolism, or the regulation of cytokines and chemokines. Moreover, chemical compounds present in food or food packaging can alter miRNA expression and regulate the aforementioned biological mechanisms related to diabetes onset and progression. Furthermore, therapies, such as bariatric surgery and aerobic exercise training, can also influence the expression profile of miRNAs in obesity. Therefore, the present review provides insight into the current research on the role of miRNAs in obesity and obesity-derived ailments, intending to develop novel therapies to effectively manage these disorders.

Circulating and Exosomal microRNA-33 in Childhood Obesity

BACKGROUND

MicroRNA-33 may control a wide range of different metabolic functions.

METHODS

This study aims to assess the miR-33a circulating profile in normal-weight (N = 20) and obese (O = 30) adolescents and to correlate its expression levels to their metabolic parameters. In a subset of subjects, we compared circulating miR-33a with exosomal miR-33a.

RESULTS

Metabolic parameters were altered in O, with initial hyperinsulinemia. Circulating miR-33a was significantly higher in O than in N (p = 0.0002). Significant correlations between miR-33a and auxological and metabolic indices (Insulin p = 0.01; Cholesterol p = 0.01; LDL p = 0.01; HbA1c p = 0.01) were found. Splitting our population (O + N) into two groups, according to the median value of mRNA expression miR-33a levels (0.701), irrespective of the presence or absence of obesity, we observed that those having a higher expression of miR-33a were more frequently obese (87.5% vs. 12.5%; p < 0.0001) and had significantly increased values of auxological and metabolic parameters. Exosomes extracted from plasma of N and O carried miR-33a, and its expression was lower in O (p = 0.026). No correlations with metabolic parameters were observed.

CONCLUSION

While exosome miR-33a does not provide any advantage, circulating miR-33a can provide important indications in an initial phase of metabolic dysfunction, stratifying obese adolescents at higher cardiometabolic risk.