Physical activity unveils the relationship between mitochondrial energetics, muscle quality, and physical function in older adults

Abstract

BackgroundThe concept of mitochondrial dysfunction in ageing muscle is highly controversial. In addition, emerging evidence suggests that reduced muscle oxidative capacity and efficiency underlie the aetiology of mobility loss in older adults. Here, we hypothesized that studying well‐phenotyped older cohorts across a wide range of physical activity would unveil a range of mitochondrial function in skeletal muscle and in turn allow us to more clearly examine the impact of age per se on mitochondrial energetics. This also enabled us to more clearly define the relationships between mitochondrial energetics and muscle lipid content with clinically relevant assessments of muscle and physical function.MethodsThirty‐nine volunteers were recruited to the following study groups: young active (YA, n = 2 women/8 men, age = 31.2 ± 5.4 years), older active (OA, n = 2 women/8 men, age = 67.5 ± 2.7 years), and older sedentary (OS, n = 8 women/11 men, age = 70.7 ± 4.7 years). Participants completed a graded exercise test to determine fitness (VO2peak), a submaximal exercise test to determine exercise efficiency, and daily physical activity was recorded using a tri‐axial armband accelerometer. Mitochondrial energetics were determined by (i) 31P magnetic resonance spectroscopy and (ii) respirometry of fibre bundles from vastus lateralis biopsies. Quadriceps function was assessed by isokinetic dynamometry and physical function by the short physical performance battery and stair climb test.ResultsDaily physical activity energy expenditure was significantly lower in OS, compared with YA and OA groups. Despite fitness being higher in YA compared with OA and OS, mitochondrial respiration, maximum mitochondrial capacity, Maximal ATP production/Oxygen consumption (P/O) ratio, and exercise efficiency were similar in YA and OA groups and were significantly lower in OS. P/O ratio was correlated with exercise efficiency. Time to complete the stair climb and repeated chair stand tests were significantly greater for OS. Interestingly, maximum mitochondrial capacity was related to muscle contractile performance and physical function.ConclusionsOlder adults who maintain a high amount of physical activity have better mitochondrial capacity, similar to highly active younger adults, and this is related to their better muscle quality, exercise efficiency, and physical performance. This suggests that mitochondria could be an important therapeutic target for sedentary ageing associated conditions including sarcopenia, dynapenia, and loss of physical function.

In vivo assessment of mitochondrial capacity using NIRS in locomotor muscles of young and elderly males with similar physical activity levels

“…In the VL, a 25% slower mVȮ 2 recovery in older individuals was observed, reflecting a decrease in mitochondrial capacity with age. This finding is in agreement with studies measuring PCr recovery in the VL (Conley et al 2000;Johannsen et al 2012;Larsen et al 2012;Choi et al 2016;Adelnia et al 2019) and with studies measuring ex vivo oxygen consumption using high-resolution respirometry (Porter et al 2015;Distefano et al 2018). Specifically, Larsen et al found a 23% decrease in PCr recovery in older adults compared to younger adults in a similar-aged and physical activity-matched population (Larsen et al 2012).…”

“…However, this result should be interpreted with care, due to the low number of measurements that were included in the correlation. Furthermore, inactive or sedentary older individuals do show a lower mitochondrial capacity than their more active counterparts, indicating that a protective effect of physical activity on the VL may not be excluded (Larsen et al 2012;Distefano et al 2018). The lower number of measurements in VL were the result of insufficient activation of the muscle during the NIRS protocol.…”

Differences in mitochondrial efficiency explain individual variation in growth performance

“…Consequently, some fish on the low ration treatment were actually faster growing than others on the high ration treatment that were consuming three times as much food. While it has previously been shown that increased mitochondrial efficiency promotes fitness-related traits (physical performance [34], growth performance [9,[21][22][23]35], reproductive output [36] and ageing [9,14,36,37]), here we demonstrate that this relationship can even occur when animals are experiencing similar rates of food intake. As well as varying among Table 1.…”

Sarcopenia as a Mediator of the Effect of a Gerontogymnastics Program on Cardiorespiratory Fitness of Overweight and Obese Older Women: A Randomized Controlled Trial

“…People who have a higher risk of cardiovascular disease (CVD) and mortality are those who have a lower CRF [ 33 ]. For older individuals, regular aerobic exercise helps them to attain better VO 2 values [ 34 ]. With age, exercise that includes long-term aerobic exercise can help combat the effects of sarcopenia [ 35 ].…”