Experiments with mice and humans showed that exercise training increased the expression in adipose tissue of a key enzyme for the organism’s metabolic health, combating the harmful effects of aging and obesity.
Adipose tissue is not just a simple reservoir of energy for periods of food scarcity. It contributes significantly to regulation of the metabolism, releasing various molecules into the bloodstream, including microRNAs that modulate the expression of key genes in different parts of the organism, including the liver, pancreas, and muscles.
Research has shown that both aging and obesity can impair the production of these regulatory microRNAs by adipose tissue and favor the development of diseases such as diabetes and dyslipidemia, medicalxpress.com reported.
The good news is that this degenerative process can be reversed by practicing regular aerobic exercise, according to a study published in Proceedings of the National Academy of Sciences (PNAS).
"Experiments with mice and humans have shown that aerobic exercise stimulates expression of an enzyme called DICER, which is essential to the processing of these microRNAs. We, therefore, observed an increase in production of these regulatory molecules by adipose cells, with several benefits for the metabolism," said Marcelo Mori, a professor at the University of Campinas's Institute of Biology (IB-UNICAMP) in the state of São Paulo, Brazil, and one of the principal investigators for the project, which was supported by FAPESP (São Paulo Research Foundation) and conducted in partnership with groups at the University of Copenhagen in Denmark and Harvard University in the United States.
The experiments were performed during the postdoctoral research of Bruna Brasil Brandão, formerly Mori's Ph.D. student and now at Harvard Medical School working as a research fellow in the laboratory of Professor C. Ronald Kahn.
The results showed the occurrence of communication between muscle and adipose tissue during aerobic exercise via signaling molecules secreted into the bloodstream. This exchange of information makes energy consumption by adipose cells more efficient, enabling the metabolism to adapt to exercise and enhancing the performance of the muscles.
The mice were subjected to a 60-minute treadmill running protocol for eight weeks. As they became fitter, treadmill speed and inclination were increased. At the end, in addition to the improvement in performance, the scientists found a significant elevation in adipocyte levels of DICER expression, which was accompanied by a reduction in body weight and visceral fat.
When they repeated the experiment with mice that were genetically modified not to express DICER in adipose cells, the researchers found that the beneficial effects of aerobic exercise were far smaller. "The animals didn't lose weight or visceral fat, and their overall fitness didn't improve," Mori said. "We also observed that adipose cells used the energy substrate differently in these GM mice than in wild mice, leaving less glucose available for muscles."
In humans, six weeks of high-intensity interval training (HIIT) were sufficient to yield a fivefold increase in the amount of DICER in adipose tissue on average. The effect was observed in both younger volunteers, aged about 36, and older subjects, aged about 63. The response varied considerably between individuals, however, with DICER increasing as much as 25 times in some, and very little in others.