Circulating Irisin and Myostatin as Markers of Muscle Strength and Physical Condition in Elderly Subjects

Abstract

Background and objective Aging is a physiological process known to produce changes in body composition, affecting the musculature and leading to decreased muscle strength. Muscle in response to exercise acts as an endocrine organ, producing and releasing myokines such as irisin and myostatin that modulate muscular growth. Here, we aimed to evaluate the effects of low intensity resistance exercise, with or without protein supplementation, on body composition, anthropometric parameters and circulating irisin and myostatin in elderly subjects. Methods This is a prospective and controlled clinical trial in which subjects were randomized into 3 groups: (1) control group ( n = 20), (2) low intensity resistance exercise group (RE) ( n = 14), and (3) low intensity resistance exercise and nutritional support group (RENS) ( n = 9). Participants, aged 60–75 years, were studied at baseline and 16 weeks thereafter. Body composition was evaluated through bioelectric impedance. Serum irisin and myostatin was measured using ELISA. Results At follow-up, RENS resulted in a significant increase in fat free mass (47.4 ± 7.4 vs. 46.5 ± 7.4, p = 0.046), the calf muscle circumference (36.4 ± 1.3 vs. 32.3 ± 4.3, p = 0.025), and circulating irisin (3 ± 1.1 vs. 2.6 ± 1.3, p = 0.030) compared to baseline. RE resulted in a significant increase in grip strength (17.2 ± 4.6 vs. 15.3 ± 4.6, p = 0.011) and irisin (3.1 ± 0.8 vs. 2.4 ± 0.3, p = 0.011) and decreased walking speed at different distance ( p < 0.02). Opposite findings in these parameters were observed in control intervention. In line with these findings, the percent change of calf muscle circumference ( p = 0.003) and fat free mass ( p < 0.0001) were significantly increased in RENS compared to control, whereas fat mass ( p = 0.033) was decreased. Interestingly, in this group, strength was positively correlated with fat free mass ( r = 0.782, p = 0.008), and circulating irisin was significantly decreased in those participants with strength loss at the end of the study ( p = 0.002). No significant correlation between circulating irisin and myostatin in any group was observed. Conclusion Circulating irisin, but not myostatin, constitutes a marker for improved muscular performance in elderly subjects.

Myostatin as a Biomarker of Muscle Wasting and other Pathologies-State of the Art and Knowledge Gaps

“…Although a number of novel research studies have been focused on the relationship between serum myostatin and muscle mass and function, and thus, its potential as a biomarker, the results seem unclear. Most studies indicate that a higher circulating myostatin concentration can be found in patients with higher muscle mass [ 79 , 80 , 81 , 82 , 83 , 84 , 85 ], but a few research studies resulted in finding such an association only in men [ 86 , 87 ], and some did not show any correlation with muscle mass parameters at all [ 88 , 89 , 90 , 91 ]. A study on healthy, obese and metabolically unhealthy participants found a contradictory, significantly negative correlation between muscle mass and serum myostatin, suggesting a major influence of metabolic syndrome on circulating myostatin level [ 92 ].…”

“…Similarly, contradictory findings have been made regarding the relationship between serum myostatin and muscle function. Some studies found increased circulating myostatin concentrations in patients with better muscle function or physical performance [ 80 , 81 , 83 , 84 , 87 ], and several indicated such a relationship to be more apparent in the male population [ 85 , 93 ], while others did not show any clear correlation between those parameters [ 82 , 88 , 89 , 92 , 94 ].…”

“…It is worth mentioning that a significant negative correlation between myostatin and CRP was reported [ 81 , 82 , 84 , 87 ]. In one of those studies, a regression analysis stratified for the baseline CRP was conducted, resulting in a significantly steeper dependence curve between myostatin and hand-grip strength in patients with CRP <10 mg/L than in patients with CRP >10 mg/L, suggesting that inflammatory status impacts the performance of myostatin as a biomarker of muscle strength [ 87 ].…”

Concentrations of Circulating Irisin and Myostatin in Race and Endurace Purebred Arabian Horses—Preliminary Study

“…They both play a significant role in bone metabolism as factors influencing bone microstructure and mechanical properties [79]. Irisin plays a crucial role in enhancing bone remodelling and increasing cortical bone mass in experimental animals, which ultimately increases bone strength [23,80]. In contrast, myostatin exerts negative effects on bone mass through osteoclast activation, which leads to increased bone remodeling, where bone resorption outpaces bone formation [81].…”

Irisin Rendah dalam Serum sebagai Faktor Risiko Sarkopenia pada Lanjut Usia

“…Kadar irisin berkorelasi secara positif dengan massa dan kekuatan otot. 18 Terdapat beberapa penjelasan tentang efek protektif irisin terhadap otot rangka untuk mencegah terjadinya sarkopenia. Hal ini dihubungkan dengan beberapa faktor seperti inflamasi kronis, status nutrisi, keadaan uremia, atau resistensi insulin.…”