Suppressed brain-derived neurotrophic factor response to 6 min walking exercise in mild cognitive impairment.

Myokines and cytokines are signaling proteins released by skeletal muscle cells during exercise that act as messengers, influencing the function of various organs, including the brain. We examined whether a single bout of walking exercise induces distinct changes in plasma myokine and cytokine concentrations in older adults with and without mild cognitive impairment (MCI). In 146 older adults characterized based on the Montreal Cognitive Assessment (MoCA) scores in non-MCI (MoCA score ≥26, n = 55) vs MCI (MoCA score <26, n = 91), we measured cognitive performance by battery, body composition by DXA, and functional performance by 6 min walk test (6MWT) distance. In addition, plasma myokine and cytokine concentrations were assessed before and immediately after 6MWT by MILLIPLEX® Human Myokine Magnetic Bead Panel (HMYOMAG-56K) and Immunology Multiplex Assay (HCYTA-60K-PXBK38) using Luminex® 200™ and MagPix system. Analysis was performed by GLMM to test the effects of group (Non-MCI vs MCI) and walking exercise. The MCI group had worse cognitive performance on trail-making test, stroop color word test (SCWT), phonemic and semantic fluency test, digit span backward, and the Rey auditory verbal learning test (AVLT) delayed memory (all P < 0.02). Body weight, BMI, lean mass, and (visceral) fat mass were comparable between non-MCI and MCI groups. There was a trend toward significantly lower 6MWT distance in the MCI (P = 0.067). We found lower baseline GM-csF concentration (P = 0.006) and a smaller increase in BDNF, FABP-3, and Osteocrin concentration in response to 6MWT in the MCI, even after adjustment for age and 6MWT distance (P < 0.003). Lower BDNF response to exercise was further associated with advancing age and worse cognitive function (MoCA, SCWT) (P < 0.04), but not with changes in lifestyle (habitual physical activity or dietary intake). We observed 6MWT-induced increases for the other myokines (apelin, BDNF, EPO, osteonectin, IL-15, myostatin, FABP-3, FSTL-1, IL-6, FGF-21, and osteocrin), and nearly all cytokines were independent of the group studied (all P < 0.02). A single bout of 6-minute walking exercise elicits a suppressed increase in BDNF, FABP-3, and Osteocrin in individuals with MCI, with a particularly blunted BDNF response in those who are older and more cognitively impaired. Whether disturbances in muscle-brain crosstalk, mediated by suppressed exercise induced BDNF response, contribute to cognitive decline in older adults warrants further investigation.