Preservation of Cognitive Function by Lepidium meyenii (Maca) Is Associated with Improvement of Mitochondrial Activity and Upregulation of Autophagy-Related Proteins in Middle-Aged Mouse Cortex

Abstract

Maca has been used as a foodstuff and a traditional medicine in the Andean region for over 2,000 years. Recently the neuroprotective effects of maca also arouse interest of researchers. Decrease in mitochondrial function and decline in autophagy signaling may participate in the process of age-related cognitive decline. This study aimed to investigate if maca could improve cognitive function of middle-aged mice and if this effect was associated with improvement of mitochondrial activity and modulation of autophagy signaling in mouse cortex. Fourteen-month-old male ICR mice received maca powder administered by gavage for five weeks. Maca improved cognitive function, motor coordination, and endurance capacity in middle-aged mice, accompanied by increased mitochondrial respiratory function and upregulation of autophagy-related proteins in cortex. Our findings suggest that maca is a newly defined nutritional plant which can improve mitochondrial function and upregulate autophagy-related proteins and may be an effective functional food for slowing down age-related cognitive decline.

Figure 1

Analysis of macamides in maca powder measured by HPLC using standard maca product from Peru as a reference. (1–4): macamides.

Figure 2

The effects of maca on body weight of middle-aged mice.

Figure 3

Timeline for experimental design. The mice were allowed to acclimatize to the environment for the first week. Then the mice in MACA were treated with maca powder suspension administered by gavage once a day for 5 weeks. From the 25th day of maca treatment, all mice underwent Morris water maze test (1 w), rotarod test (1 d), and endurance capacity test (1 d) in succession. Sample collection was performed 48 h after the endurance capacity test to minimize the influence of behavioral tests.

Figure 4

Maca improves spatial learning and memory of middle-aged mice. Values are the mean ± SD. ^∗ p < 0.05 and ^∗∗ p < 0.01 versus CON.

Figure 5

Maca improves motor coordination of middle-aged mice. Values are the mean ± SD. ^∗ p < 0.05 versus CON.

Figure 6

Maca improves endurance capacity in middle-aged mice. All mice were subject to a progressive load test in the swimming apparatus to determine the endurance capacity. Values are the mean ± SD. ^∗ p < 0.05 versus CON.

Figure 7

Maca increases the protein expression of subunits of mitochondrial respiratory chain complexes in cortex of middle-aged mice. The cortex was extracted from different groups of mice and subjected to Western blot analysis of OXPHOS. Representative immunoblot images (a) and quantification of mitochondrial OXPHOS complexes I–IV (b–f) in the hippocampal extracts of mice. Values are the mean ± SD. ^∗ p < 0.05 and ^∗∗ p < 0.01 versus CON.

Figure 8

Maca upregulates autophagy-related proteins in cortex of middle-aged mice. The cortex was extracted from different groups of mice and subjected to Western blot analysis of LC3, Atg7, and Beclin1. (a) LC3; (b) Atg7; (c) Beclin1. Values are the mean ± SD. ^∗ p < 0.05 and ^∗∗ p < 0.01 versus CON.