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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. [ABSTRACT FROM AUTHOR]

Branched-chain amino acids (BCAA) are considered markers of insulin resistance (IR) in subjects with obesity. In this study, we evaluated whether the presence of the SNP of the branched-chain aminotransferase 2 (BCAT2) gene can modify the effect of a dietary intervention (DI) on the plasma concentration of BCAA in subjects with obesity and IR. A prospective cohort study of adult subjects with obesity, BMI ≥ 30 kg/m2, homeostatic model assessment-insulin resistance (HOMA-IR ≥ 2·5) no diagnosed chronic disease, underwent a DI with an energy restriction of 3140 kJ/d and nutritional education for 1 month. Anthropometric measurements, body composition, blood pressure, resting energy expenditure, oral glucose tolerance test results, serum biochemical parameters and the plasma amino acid profile were evaluated before and after the DI. SNP were assessed by the TaqMan SNP genotyping assay. A total of eighty-two subjects were included, and fifteen subjects with a BCAT2 SNP had a greater reduction in leucine, isoleucine, valine and the sum of BCAA. Those subjects also had a greater reduction in skeletal muscle mass, fat-free mass, total body water, blood pressure, muscle strength and biochemical parameters after 1 month of the DI and adjusting for age and sex. This study demonstrated that the presence of the BCAT2 SNP promotes a greater reduction in plasma BCAA concentration after adjusting for age and sex, in subjects with obesity and IR after a 1-month energy-restricted DI. [ABSTRACT FROM AUTHOR]

Purpose: We compared the effect of diets with different amounts and sources of dietary protein on insulin sensitivity (IS) in subjects with obesity and insulin resistance (IR). Methods: Eighty subjects with obesity (BMI ≥ 30 kg/m2) and IR (Matsuda index < 4.3 and HOMA-IR ≥ 2.5) over 18 years old were randomized to four groups for a one-month period: a normal protein diet (< 20%) with a predominance of animal protein (Animal NP) or vegetable protein (Vegetable NP) and a high-protein diet (25–30%) with a predominance of animal protein (Animal HP) or vegetable protein (Vegetable HP). Baseline and final measurements of body weight, body composition, biochemical parameters, blood pressure (BP), resting energy expenditure and plasma amino acid profiles were performed. Results: Body weight, BMI and waist circumference decreased in all groups. Interestingly, the IS improved more in the Animal HP (Matsuda index; 1.39 vs 2.58, P = 0.003) and in the Vegetable HP groups (Matsuda index; 1.44 vs 3.14, P < 0.0001) after one month. The fat mass, triglyceride levels, C-reactive protein levels and the leptin/adiponectin index decreased; while, the skeletal muscle mass increased in the Animal and Vegetable HP groups. The BP decreased in all groups except the Animal NP group. Conclusion: Our study demonstrates that a high-protein hypocaloric diets improves IS by 60–90% after one month in subjects with obesity and IR, regardless of weight loss and the source of protein, either animal or vegetable. Trial registration: The trial is registered at clinicaltrials.gov (NCT03627104), August 13, 2018. [ABSTRACT FROM AUTHOR]