Accelerated skeletal muscle wasting is a shared trait among many pathologies and aging. Acupuncture has been used as a therapeutic intervention to control pain; however, little is known about its effects on skeletal muscle atrophy and function. The study's purpose was to compare the effects of acupuncture, electro-acupuncture, and electrical stimulation on cast-induced skeletal muscle atrophy. Forty female Sprague Dawley rats were randomly divided into groups: Control, casted (CAST), CAST+Acupuncture (CAST-A), 4) CAST+Electro-acupuncture (CAST-EA), and CAST+Electrical stimulation (CAST-ES) (n = 8). Plaster casting material was wrapped around the left hind limb. Acupuncture and electro-acupuncture (10 Hz, 6.4 mA) treatments were applied by needling acupoints (stomach-36 and gallbladder-34). Electrical stimulation (10 Hz, 6.4 mA) was conducted by needling the lateral and medial gastrocnemius muscles. Treatments were conducted for 15 min, three times/week for 14 days. Muscle atrophy F-box (MAFbx), muscle RING finger 1 (MuRF1), and contractile properties were assessed. Fourteen days of cast-immobilization decreased muscle fiber CSA by 56% in the CAST group (p = 0.00); whereas, all treatment groups demonstrated greater muscle fiber CSA than the CAST group (p = 0.00). Cast-immobilization increased MAFbx and MuRF1 protein expression in the CAST group (p<0.01) while the CAST-A, CAST-EA, and CAST-ES groups demonstrated lower levels of MAFbx and MuRF1 protein expression (p<0.02) compared to the CAST group. Following fourteen days of cast-immobilization, peak twitch tension did not differ between the CAST-A and CON groups (p = 0.12). Skeletal muscle atrophy, induced by 14 days of cast-immobilization, was significantly attenuated by acupuncture, electro-acupuncture, or electrical stimulation.

Mechanical unloading during microgravity causes skeletal muscle atrophy and impairs mitochondrial energetics. The elevated production of reactive oxygen species (ROS) by mitochondria and Nox2, coupled with impairment of stress protection (e.g., SIRT1, antioxidant enzymes), contribute to atrophy. We tested the hypothesis that the SIRT1 activator, SRT2104 would rescue unloading-induced mitochondrial dysfunction. Mitochondrial function in rat gastrocnemius and soleus muscles were evaluated under three conditions (10 days): ambulatory control (CON), hindlimb unloaded (HU), and hindlimb-unloaded-treated with SRT2104 (SIRT). Oxidative phosphorylation, electron transfer capacities, H₂O₂ production, and oxidative and antioxidant enzymes were quantified using high-resolution respirometry and colorimetry. In the gastrocnemius, (1) integrative (per mg tissue) proton LEAK was lesser in SIRT than in HU or CON; (2) intrinsic (relative to citrate synthase) maximal noncoupled electron transfer capacity (E_CI+II) was lesser, while complex I-supported oxidative phosphorylation to E_CI+II was greater in HU than CON; (3) the contribution of LEAK to E_CI+II was greatest, but cytochrome c oxidase activity was lowest in HU. In both muscles, H₂O₂ production and concentration was greatest in SIRT, as was gastrocnemius superoxide dismutase activity. In the soleus, H₂O₂ concentration was greater in HU compared to CON. These results indicate that SRT2104 preserves mitochondrial function in unloaded skeletal muscle, suggesting its potential to support healthy muscle cells in microgravity by promoting necessary energy production in mitochondria.

Muscle atrophy leads to debilitating loss of physical capacity, particularly when alternative treatments are needed. Acupuncture is proposed as a potential therapy for disuse atrophy, but its effects on muscle biology remain unclear. This study evaluated the effects of acupuncture on soleus muscle mass and mitochondrial function in a rat model of immobilization-induced atrophy. Female Sprague Dawley rats were assigned to three groups: Control (CON), casting-induced immobilization (CT), and CT with acupuncture (CT-A) (n = 8). Immobilization of the left hindlimb lasted for 14 days, and acupuncture was performed at specific acupoints (stomach-36, gallbladder-34) three times per week for 15 min. Mitochondrial function was assessed in saponin-permeabilized fibers, and signaling molecules regulating muscle mass were analyzed by Western blot. CT-A attenuated soleus muscle atrophy compared to CT. Under fatty acid substrate conditions, CT reduced complex I and II-supported oxidative phosphorylation (OXPHOS) compared to CON, while CT-A decreased respiratory leak and enhanced OXPHOS coupling relative to CT. Without fatty acids, CT-A decreased both respiratory leak and complex I and II-supported OXPHOS compared to CON, but differences between CT and CT-A were not significant. AMPKα activity (p-AMPKα/AMPKα) was significantly elevated in the CT group compared to the CON group, but returned to CON levels in the CT-A group. However, there were no changes in proteins associated with muscle atrophy or autophagy markers among the groups. Acupuncture mitigates immobilization-induced muscle atrophy and preserves mitochondrial function, suggesting its potential as a therapeutic approach for muscle disuse conditions.

Heat shock proteins (HSPs) are a family of conserved molecular chaperons present in both prokaryotic and eukaryotic species, playing a crucial role in maintaining cellular proteostasis and enhancing stress resilience. HSPs have a multitude of roles in regulating cell signaling transduction, antioxidant defenses, apoptosis, and protein folding, thereby contributing to overall cellular homeostasis. Insulin resistance is characterized by elevated oxidative stress, dysregulated pro-inflammatory signaling, and impaired cellular stress response, ultimately leading to deficient glucose uptake in skeletal muscle. Many studies have illustrated the benefits of exercise in improving insulin resistance and reducing the risk of metabolic disorders, such as type 2 diabetes. Habitual exercise and lifestyle modifications have been shown to activate heat shock response, enhancing HSP70 expression and promoting cellular adaptations that protect against metabolic dysfunction. However, the link between HSPs, particularly HSP70, and skeletal muscle insulin resistance remains complex and not fully elucidated. In this review, we discuss the mechanistic pathways by which HSP70 modulates insulin resistance, mitochondrial function, and inflammatory responses in skeletal muscle. Additionally, we discuss the protective effects of exercise-induced HSP70 expression and its potential as a therapeutic target for improving insulin sensitivity and metabolic health.