Exercise is highly beneficial in patients with type-2 diabetes (T2DM) for improving clinical risk factors like obesity and insulin resistance. However, the exact biological mechanisms that result in the improved clinical outcomes are not fully understood. Identifying potential biomarkers that are differentially regulated by exercise in T2DM, such as circulating microRNAs (miRNAs), and associating these responses with improved insulin resistance and other clinical risk factors, may offer new insights to optimise exercise prescription in T2DM patients.
26 men and 7 women with ≥6.1mM fasting glucose with and without T2DM completed 16wks of different exercise programs: i) moderate-intensity continuous training (MICT, n=7, 5x/wk); ii) high-volume high-intensity interval training (4HIIT, n=13, 3x/wk); iii) low-volume HIIT (1HIIT, n=13, 3x/wk). miRNA was extracted from resting blood samples taken before and after the 16wks intervention. Pre-selected miRNAs were detected by qPCR using Exiqon Kits and data were analysed with GenEx software.
Plasma abundance of mir-28-3p, mir-126-3p, mir-146a-5p, mir-27a-3p and mir-223-3p was decreased (p<0.05) in hyperglycaemic patients following MICT intervention. Only mir-34a-5p expression levels significantly increased (p<0.05) after 4HIIT, while no changes in plasma miRNA expression were observed after 1HIIT.
MICT caused a greater impact on the plasma miRNA expression profile than HIIT, significantly reducing the abundance of mir-28-3p, mir-146a-5p and mir-27a-3p, known to be increased in T2DM patients  but also downregulating mir-223-3p and mir-126-3p found to be reduced in diabetic settings  and involved in glucose uptake and insulin resistance in peripheral tissues [2, 3]. Together, these data indicate that HIIT and MICT differentially alter the plasma miRNA expression profile in hyperglycaemic patients, which may mediate the different training-induced changes on the metabolism.