Mindfulness intervention improves cognitive function in older adults by enhancing the level of miRNA-29c in neuron-derived extracellular vesicles

Abstract

Although mindfulness-based stress reduction (MBSR) improves cognitive function, the mechanism is not clear. In this study, people aged 65 years and older were recruited from elderly communities in Chitose City, Japan, and assigned to a non-MBSR group or a MBSR group. Before and after the intervention, the Japanese version of the Montreal Cognitive Assessment (MoCA-J) was administered, and blood samples were collected. Then, neuron-derived extracellular vesicles (NDEVs) were isolated from blood samples, and microRNAs, as well as the target mRNAs, were evaluated in NDEVs. A linear mixed model analysis showed significant effects of the MBSR x time interaction on the MoCA-J scores, the expression of miRNA(miR)-29c, DNA methyltransferase 3 alpha (DNMT3A), and DNMT3B in NDEVs. These results indicate that MBSR can improve cognitive function by increasing the expression of miR-29c and decreasing the expression of DNMT3A, as well as DNMT3B, in neurons. It was also found that intracerebroventricular injection of miR-29c mimic into 5xFAD mice prevented cognitive decline, as well as neuronal loss in the subiculum area, by down-regulating Dnmt3a and Dnmt3b in the hippocampus. The present study suggests that MBSR can prevent neuronal loss and cognitive impairment by increasing the neuronal expression of miR-29c.

Figure 1

Flow chart of the study design. (a) Waiting list controls are assigned to Group 1. In this group, no intervention is performed for 4 weeks, then MBSR is done for 4 weeks. In Group 2, people perform only MBSR for 4 weeks. During the intervention, three MBSR sessions are performed per week for a total of 12 sessions within 4 weeks. Each MBSR session is performed for 60 min. Before and after the intervention, the MoCA-J and blood sampling are conducted. (b) A total of 46 older adults aged over 65 years participated in this study (Group 1: n = 21, Group 2: n = 25). The data of participants who performed the MBSR program fewer than eight times or who did not undergo the second assessment were excluded. For the analysis, Group 1 is considered the non-MBSR group (n = 10), and Group 2 is considered the MBSR group (n = 19).

Figure 2

Changes in the scores of the MoCA-J at pre and post intervention in the non-MBSR and MBSR groups. A linear mixed model was used to evaluate the P values of the MBSR x time interaction on the total MoCA-J scores and the seven domains of MoCA-J, including delayed recall, visuospatial/executive function, attention, abstraction, language, naming, and orientation. Values are the means ± 95% CI. Non-MBSR group (n = 10), MBSR group (n = 19).

Figure 3

Western blotting for CD81 in NDEVs. NDEVs were isolated from the blood samples, and the presence of the common extracellular vesicle marker of CD81 is confirmed in NDEVs.

Figure 4

Luciferase assays of miR-29c on DNMT3A, DNMT3B, and BACE1. The binding sites of miR-29c on the 3’UTR regions of DNMT3A, DNMT3B, and BACE1 mRNA are shown in (a–c), respectively. (a–c) Luciferase reporter assays show that DNMT3A, DNMT3B, and BACE1 are target genes of miR-29c. Values are the means ± SD. The experiment was repeated four times. **P < 0.01, unpaired t-test.

Figure 5

Effect of intracerebroventricular injection of the miR-29c mimic into 5xFAD mice. (a) Experimental protocol. Negative control miRNA (140 pmol) or miR-29c mimic (140 pmol) is injected intracerebroventricularly into 5-month-old 5xFAD mice four times at 1-week intervals. At 1 week after the last injection, Y maze tests are conducted, and mice are sacrificed at 6 months of age. (b) The results of Y maze tests. Total numbers of arm entries and the percentages of alternations are shown. Values are the means ± SEM. *P < 0.05, unpaired t-test. Negative control mimic group (n = 6), miR-29c mimic group (n = 6). (c) The expressions of miR-29c, Dnmt3a, Dnmt3b, and Bace1. Values are the means ± SEM. *P < 0.05, unpaired t-test. Negative control mimic group (n = 6), miR-29c mimic group (n = 6). (d) The Aβ-positive area. Values are the means ± SEM. Negative control mimic group (n = 6), miR-29c mimic group (n = 6). (e) The number of NeuN-positive cells. Values are the means ± SEM. *P < 0.05, unpaired t-test. Negative control mimic group (n = 6), miR-29c mimic group (n = 6).