The anabolic catabolic transforming agent (ACTA) espindolol increases muscle mass and decreases fat mass in old rats

Abstract

Background: Sarcopenia, the age-related, progressive loss of skeletal muscle mass, strength, and function, is a considerable socioeconomic burden by increasing risks of falls, fractures, and frailty. Moreover, sarcopenic patients are often obese and therapeutic options are very limited.

Methods: Here, we assessed the efficacy of espindolol on muscle mass in 19-month-old male Wistar Han rats (weight, 555 ± 18 g), including safety issues. Rats were randomized to treatment with 3 mg/kg/day espindolol (n = 8) or placebo (n = 14) for 31 days.

Results: Placebo-treated rats progressively lost body weight (-15.5 ± 7.2 g), lean mass (-1.5 ± 4.2 g), and fat mass (-15.6 ± 2.7 g), while espindolol treatment increased body weight (+8.0 ± 6.1 g, p < 0.05), particularly lean mass (+43.4 ± 3.5 g, p < 0.001), and reduced fat mass further (-38.6 ± 3.4 g, p < 0.001). Anabolic/catabolic signaling was assessed in gastrocnemius muscle. Espindolol decreased proteasome and caspase-3 proteolytic activities by approximately 50 % (all p < 0.05). Western blotting showed a reduced expression of key catabolic regulators, including NFκB, MuRF1, and LC-3 (all p < 0.01). The 50- and 26-kDa forms of myostatin were downregulated fivefold and 20-fold, respectively (both p < 0.001). Moreover, 4E-BP-1 was reduced fivefold (p < 0.01), while phospho-PI3K was upregulated fivefold (p < 0.001), although Akt expression and phosphorylation were lower compared to placebo (all p < 0.05). No regulation of p38 and expression of ERK1/2 were observed, while phosphorylation of p38 was reduced (-54 %, p < 0.001) and ERK1/2 was increased (115 and 83 %, respectively, both p < 0.01). Espindolol did not affect cardiac function (echocardiography) or clinical plasma parameters.

Conclusion: Espindolol reversed the effects of aging/sarcopenia, particularly loss of muscle mass and increased fat mass. Thus, espindolol is an attractive candidate drug for the treatment of sarcopenia patients.

Figures

Fig. 1

Effect of espindolol treatment on body weight and body composition. Absolute change in body weight (a, b), lean body mass (d, e), and fat mass (g, h) and relative change (c, f, i, respectively) during the study. While placebo-treated rats lost weight, lean mass, and fat mass, espindolol-treated animals gained weight, increased lean mass, and lost more fat mass. Black bar placebo, gray bars 3 mg/kg/day espindolol. *p < 0.05, **p < 0.01, ***p < 0.001. Placebo: n = 14, espindolol: n = 8

Fig. 2

Spontaneous activity (a), food intake (b), and water intake (c) over 24 h on day 28. Activity was not affected by treatment, while food and water intake were increased by espindolol. Black bar placebo, gray bars: 3 mg/kg/day espindolol. *p < 0.05, **p < 0.01. Placebo n = 14, espindolol n = 8

Fig. 3

Catabolic signaling in the gastrocnemius muscle. Expression is shown as relative to the mean of placebo. Expression of the atrophy driving transcription factors FoxO3a (a) and NFκB (b) were lower in espindolol-treated rats, resulting in a reduced expression of the E3 ubiquitin ligases MuRF-1 (c) and MAFbx (d). This led to a reduced activity of the proteasome (e–g). Moreover, the activity of caspase-3 was lowered by treatment (h). Both the preform (i) and the mature form (j) of myostatin were strongly reduced, as well as the autophagy marker LC-3 (k, l). Black bar placebo, gray bars 3 mg/kg/day espindolol. PGPH peptidyl-glutamyl protein-hydrolyzing. *p < 0.05, **p < 0.01, ***p < 0.001. All proteins: placebo n = 13, espindolol n = 8

Fig. 4

Anabolic signaling in the gastrocnemius muscle. Expression is shown as relative to the mean of placebo. Increased phosphorylation of PI3K (a) by espindolol did not result in higher phosphorylation of Akt (b–d). However, the inhibitor of protein synthesis 4E-BP1 was downregulated (e–g) and MyoD was unchanged (h). Black bar placebo, gray bars: 3 mg/kg/day espindolol. *p < 0.05, **p < 0.01, ***p < 0.001. All proteins: placebo n = 13, espindolol n = 8

Fig. 5

Expression and phosphorylation of p38 MAPK and p42/44 ERK1/2. Expression is shown as relative to the mean of placebo. Espindolol reduced activation of p38 MAPK (a, b), while it increased activation of p42 (c, d) and p44 (e, f). Black bar placebo, gray bars 3 mg/kg/day espindolol. **p < 0.01, ***p < 0.001. All proteins: placebo n = 13, espindolol n = 8