Light-intensity exercise improves memory dysfunction with the restoration of hippocampal MCT2 and miRNAs in type 2 diabetic mice

Cognitive decline associated with type 2 diabetes mellitus (T2DM) is a risk factor to impair human health. Although light-intensity exercise prevents hippocampal memory dysfunction in pre-symptomatic T2DM animals by altering hippocampal lactate transport and neurotrophic factors, the effects of light-intensity exercise in an advanced stage of T2DM animals remain unclear. Here, ob/ob mice, an animal model of T2DM, were subjected to light-intensity exercise (5.0 m/min) for 30 min/day, five days/week for four weeks. The effects of light-intensity exercise on hippocampal complications, mRNA expressions of monocarboxylate transporter (MCT), and miRNA levels were assessed. The light-intensity exercise improved hippocampal memory retention in ob/ob mice. Downregulated hippocampal Mct2 mRNA levels in T2DM were improved with light-intensity exercise. Hippocampal mRNA levels of Mct1 and Mct4 were unchanged within groups. Based on miRNA sequencing, sedentary ob/ob mice exhibited that 71 miRNAs were upregulated, and 77 miRNAs were downregulated in the hippocampus. In addition, the exercise significantly increased 24 miRNAs and decreased 4 miRNAs in the T2DM hippocampus. The exercise reversed T2DM-induced alterations of hippocampal 9 miRNAs, including miR-200a-3p. Our findings imply that miR-200a-3p/Mct2 in the hippocampus would be a possible clinical target for treating T2DM-induced memory dysfunction.