Basal myokine levels are associated with quality of life and depressed mood in older adults

Abstract

In an aging society, late‐life depression has become an increasing problem. There is evidence that physical activity ameliorates depressive symptoms and increases the quality of life (QoL). However, the underlying mechanisms are still poorly understood. Myokines are molecules secreted in response to muscle contraction. Some of them can cross the blood‐brain barrier, making them promising candidates for mediating the beneficial effects of physical activity on mood. The present study aims to compare circulating myokine levels to depression/QoL in older athletes and controls. 55 athletes, 57 controls >59 years were enrolled. The assessment included ergometry, magnetic resonance imaging, blood withdrawal, and neuropsychological testing. Serum interleukin‐6 (IL‐6), irisin, brain‐derived neurotrophic factor (BDNF), kynurenine, and cathepsin B were analyzed and compared to surrogates of depression and quality of life. Athletes presented with higher levels of Cathepsin B. Among controls, all myokines but irisin were associated with age. Also, among controls, kynurenine and IL‐6 correlated inversely with specific dimensions of quality of life questionnaires, and IL‐6 further with depressive symptoms and decreased physical performance. No such associations could be found among athletes. Irisin levels were inversely associated with mild depression and low‐grade white matter‐lesions in the brain and predicted impaired QoL. The circulating levels of several myokines/muscle activity‐related factors appear to be associated with depressive symptoms and impaired QoL among older adults. However, in athletes, some of these connections seem ameliorated, suggesting additional stressors (as f.e. age) or a different pathomechanism among athletes.

Effects of Aerobic Exercise Training on Systemic Biomarkers and Cognition in Late Middle-Aged Adults at Risk for Alzheimer’s Disease

“…Plasma CTSB is upregulated by aerobic exercise training and associated with cognition in young adults ( 25 ). In the present study we show that CTSB is increased in late-middle-aged adults after 26 weeks of aerobic training, indicating that CTSB levels change after prolonged activity ( 25 , 54 , 55 ) whereas shorter term aerobic exercise protocols ( 56 , 57 ), and resistance training ( 58 , 59 ) show no change. The present findings in late-middle aged adults at risk for AD extend findings from healthy younger adults that CTSB levels were positively correlated with a hippocampus-dependent visual memory task after a four-month aerobic exercise intervention ( 25 ).…”

“…In addition, these subjects participated in a variety of athletic activities. Indeed, older marathon runners have been shown to harbor elevated CTSB levels ( 55 ). It is also noteworthy our study included both males and females, and that females may drive the myokine CTSB increase and correlations with cognitive function.…”

“…Moreover, while this study extends and confirms a link between CTSB and cognition, additional older and younger study populations, and memory tests will be needed to further explore this finding. Finally, resistance exercise training may also support brain health ( 131 ); however, aerobic exercise was employed in this study due to its upregulation of CTSB and klotho ( 25 , 31 , 55 ), favorable effect on cardiorespiratory fitness ( 36 ), and well-established link to cognitive function ( 5 , 6 , 132 ).…”

Beyond muscles: Investigating immunoregulatory myokines in acute resistance exercise – A systematic review and meta‐analysis

“…5,10,11 Released by concentric muscle contractions, 8 they mediate the health-promoting effects of exercise via, for example, activating IL-6-sensitive natural killer (NK) cells, 12 therefore contributing to the protection against diseases associated with low-grade inflammation. [13][14][15] Given these characteristics, myokines have also been described to belong to the group of exerkines, along with other signaling units that are released in response to exercise. 16,17 Myokines are not only released by muscle fibers, but also in the regenerating muscle from infiltrating neutrophils and macrophages, 18 fibro-adipogenic progenitors, 19 and satellite cells.…”

Cathepsin B and Muscular Strength are Independently Associated with Cognitive Control

“…Subsequent studies have examined the association between exercise and CTSB and reported mixed results. Chronic exercise studies have reported no changes in serum CTSB following a six-week high intensity interval training intervention [ 30 ], an inverse association between habitual exercise and plasma CTSB [ 31 ], higher levels of CTSB in older athletes compared to age-matched sedentary controls [ 32 ], and increased CTSB following twelve-weeks of resistance training [ 33 ] and twenty-six weeks of moderate-to-vigorous aerobic training [ 34 ]. Acute exercise studies have reported more consistent findings with one study reporting a significant, albeit small, increase in CTSB following a single bout of high-intensity interval training [ 35 ] and another reporting increased CTSB following an acute bout of exercise for fencers but not swimmer or sedentary individuals [ 36 ].…”