Hindlimb Grip Strength Research Articles

Melatonin Regulates Rheumatoid Synovial Fibroblasts-Related Inflammation: Implications for Pathological Skeletal Muscle Treatment.

Melatonin has been reported to regulate circadian rhythms and have anti-inflammatory characteristics in various inflammatory autoimmune diseases, but its effects in diseases-associated muscle atrophy remain controversial. This study is aimed to determine the evidence of melatonin in rheumatoid arthritis (RA)-related pathological muscle atrophy. We used initially bioinformatics results to show that melatonin regulated significantly the correlation between pro-inflammation and myogenesis in RA synovial fibroblasts (RASF) and myoblasts. The conditioned medium (CM) from melatonin-treated RASF was incubated in myoblasts with growth medium and differentiated medium to investigate the markers of pro-inflammation, atrophy, and myogenesis. We found that melatonin regulated RASF CM-induced pathological muscle pro-inflammation and atrophy in myoblasts and differentiated myocytes through NF-κB signaling pathways. We also showed for the first time that miR-30c-1-3p is negatively regulated by three inflammatory cytokines in human RASF, which is associated with murine-differentiated myocytes. Importantly, oral administration with melatonin in a collagen-induced arthritis (CIA) mouse model also significantly improved arthritic swelling, hind limb grip strength as well as pathological muscle atrophy. In conclusion, our study is the first to demonstrate not only the underlying mechanism whereby melatonin decreases pro-inflammation in RA-induced pathological muscle atrophy but also increases myogenesis in myoblasts and differentiated myocytes.

Effects of a ketogenic diet on motor function and motor unit number estimation in aged C57BL/6 mice

ObjectivePathological, age-related loss of muscle function, commonly referred to as sarcopenia, contributes to loss of mobility, impaired independence, as well as increased risk of adverse health events. Sarcopenia has been attributed to changes in both neural and muscular integrity during aging. Current treatment options are primarily limited to exercise and dietary protein fortification, but the therapeutic impact of these approaches are often inadequate. Prior work has suggested that a ketogenic diet (KD) might improve healthspan and lifespan in aging mice. Thus, we sought to investigate the effects of a KD on neuromuscular indices of sarcopenia in aged C57BL/6 mice. DesignA randomized, controlled pre-clinical experiment consisting of longitudinal assessments performed starting at 22-months of age (baseline) as well as 2, 6 and 10 weeks after the start of a KD vs. regular chow intervention. SettingPreclinical laboratory study. Sample sizeThirty-six 22-month-old mice were randomized into 2 dietary groups: KD [n = 22 (13 female and 9 male)], and regular chow [n = 15 (7 female and 8 male)]. MeasurementsMeasures included body mass, hindlimb and all limb grip strength, rotarod for motor performance, plantarflexion muscle contractility, motor unit number estimations (MUNE), and repetitive nerve stimulation (RNS) as an index of neuromuscular junction transmission efficacy recorded from the gastrocnemius muscle. At end point, muscle wet weight and blood samples were collected to assess blood beta-hydroxybutyrate levels. Statistical analysisPrimary analyses were two-way mixed effects ANOVA (diet and time × diet) to determine the effect of a KD on indices of motor function (grip, rotarod) and indices of motor unit (MUNE) and muscle (contractility) function. ResultsBeta-hydroxybutyrate (BHB) was significantly higher at 10 weeks in mice on a KD vs control group (0.83 ± 0.44 mmol/l versus 0.42 ± 0.21 mmol/l, η2 = 0.265, unpaired t-test, p = 0.0060). Mice on the KD intervention demonstrated significantly increased hindlimb grip strength (diet, p = 0.0001; time × diet, p = 0.0030), all limb grip strength (diet, p = 0.0005; time × diet, p = 0.0523), and rotarod latency to fall (diet, p = 0.0126; time × diet, p = 0.0021). Mice treated with the KD intervention also demonstrated increased MUNE (diet, p = 0.0465; time × diet, p = 0.0064), but no difference in muscle contractility (diet, p = 0.5248; time × diet, p = 0.5836) or RNS (diet, p = 0.3562; time × diet, p = 0.9871). ConclusionKD intervention improved neuromuscular and motor function in aged mice. This pre-clinical work suggests that further research is needed to assess the efficacy and physiological effects of a KD on indices of sarcopenia.

Blockade of angiotensin II modulates insulin-like growth factor 1-mediated skeletal muscle homeostasis in experimental steatohepatitis

Sarcopenia is associated with mortality in patients with nonalcoholic steatohepatitis (NASH). Angiotensin II receptor blocker (ARB) has been suggested to prevent sarcopenia, but reports on its effect on NASH-derived skeletal muscle atrophy in conjunction with insulin-like growth factor 1 (IGF-1)-mediated muscle homeostasis are few. Our aim was to examine the combined effect of the ARB losartan and IGF-1 replacement on skeletal muscle atrophy in a methionine–choline deficient (MCD) diet-fed murine steatohepatitis model. The MCD-fed mice developed steatohepatitis and skeletal muscle atrophy, as indicated by the reduction of psoas muscle mass and attenuation of forelimb and hindlimb grip strength. Significantly suppressed steatohepatitis and skeletal muscle atrophy was observed after single treatment with ARB or IGF-1, and these effects were augmented after combination treatment. Treatment with ARB and IGF-1 effectively inhibited ubiquitin proteasome-mediated protein degradation by reducing forkhead box protein O1 (FOXO1) and FOXO3a transcriptional activity in the skeletal muscle. Combined ARB and IGF-1 decreased the intramuscular expression of proinflammatory cytokines (i.e., TNFα, IL6, and IL1β) and increased the Trolox equivalent antioxidant capacity and antioxidant enzymes (CAT, GPX1, SOD2, and CYTB). This antioxidant effect was based on downregulation of NADPH oxidase (NOX) 2, normalization of mitochondrial biogenesis and dynamics. Moreover, ARB increased the hepatic and plasma IGF-1 levels and improved steatohepatitis, leading to enhanced skeletal muscle protein synthesis mediated by IGF-1/ AKT/ mechanistic target of rapamycin signaling. Collectively, combined ARB and IGF-1 replacement could be a promising new therapeutic target for NASH-derived skeletal muscle wasting.

Glycine and N-Acetylcysteine (GlyNAC) Combined with Body Weight Support Treadmill Training Improved Spinal Cord and Skeletal Muscle Structure and Function in Rats with Spinal Cord Injury.

Skeletal muscle atrophy is a frequent complication after spinal cord injury (SCI) and can influence the recovery of motor function and metabolism in affected patients. Delaying skeletal muscle atrophy can promote functional recovery in SCI rats. In the present study, we investigated whether a combination of body weight support treadmill training (BWSTT) and glycine and N-acetylcysteine (GlyNAC) could exert neuroprotective effects, promote motor function recovery, and delay skeletal muscle atrophy in rats with SCI, and we assessed the therapeutic effects of the double intervention from both a structural and functional viewpoint. We found that, after SCI, rats given GlyNAC alone showed an improvement in Basso-Beattie-Bresnahan (BBB) scores, gait symmetry, and results in the open field test, indicative of improved motor function, while GlyNAC combined with BWSTT was more effective than either treatment alone at ameliorating voluntary motor function in injured rats. Meanwhile, the results of the skeletal muscle myofiber cross-sectional area (CSA), hindlimb grip strength, and acetylcholinesterase (AChE) immunostaining analysis demonstrated that GlyNAC improved the structure and function of the skeletal muscle in rats with SCI and delayed the atrophication of skeletal muscle.

Mesenchymal stem cells alleviate dexamethasone-induced muscle atrophy in mice and the involvement of ERK1/2 signalling pathway

BackgroundHigh dosage of dexamethasone (Dex) is an effective treatment for multiple diseases; however, it is often associated with severe side effects including muscle atrophy, resulting in higher risk of falls and poorer life quality of patients. Cell therapy with mesenchymal stem cells (MSCs) holds promise for regenerative medicine. In this study, we aimed to investigate the therapeutic efficacy of systemic administration of adipose-derived mesenchymal stem cells (ADSCs) in mitigating the loss of muscle mass and strength in mouse model of DEX-induced muscle atrophy.Methods3-month-old female C57BL/6 mice were treated with Dex (20 mg/kg body weight, i.p.) for 10 days to induce muscle atrophy, then subjected to intravenous injection of a single dose of ADSCs (1times {10}^{6} cells/kg body weight) or vehicle control. The mice were killed 7 days after ADSCs treatment. Body compositions were measured by animal DXA, gastrocnemius muscle was isolated for ex vivo muscle functional test, histological assessment and Western blot, while tibialis anterior muscles were isolated for RNA-sequencing and qPCR. For in vitro study, C2C12 myoblast cells were cultured under myogenic differentiation medium for 5 days following 100 muM Dex treatment with or without ADSC-conditioned medium for another 4 days. Samples were collected for qPCR analysis and Western blot analysis. Myotube morphology was measured by myosin heavy chain immunofluorescence staining.ResultsADSC treatment significantly increased body lean mass (10–20%), muscle wet weight (15–30%) and cross-sectional area (CSA) (~ 33%) in DEX-induced muscle atrophy mice model and down-regulated muscle atrophy-associated genes expression (45–65%). Hindlimb grip strength (~ 37%) and forelimb ex vivo muscle contraction property were significantly improved (~ 57%) in the treatment group. Significant increase in type I fibres (~ 77%) was found after ADSC injection. RNA-sequencing results suggested that ERK1/2 signalling pathway might be playing important role underlying the beneficial effect of ADSC treatment, which was confirmed by ERK1/2 inhibitor both in vitro and in vivo.ConclusionsADSCs restore the pathogenesis of Dex-induced muscle atrophy with an increased number of type I fibres, stronger muscle strength, faster recovery rate and more anti-fatigue ability via ERK1/2 signalling pathway. The inhibition of muscle atrophy-associated genes by ADSCs offered this treatment as an intervention option for muscle-associated diseases. Taken together, our findings suggested that adipose-derived mesenchymal stem cell therapy could be a new treatment option for patient with Dex-induced muscle atrophy.

Environmental Enrichment Improves Motor Function and Muscle Transcriptome of Aged Mice.

Aging results in the progressive decline of muscle strength. Interventions to maintain muscle strength may mitigate the age-related loss of physical function, thus maximizing health span. The work on environmental enrichment (EE), an experimental paradigm recapitulating aspects of an active lifestyle, has revealed EE-induced metabolic benefits mediated by a brain-fat axis across the lifespan of mice. EE initiated at 18-month of age shows a trend toward an increased mean lifespan. While previous work described EE's influences on the aging dynamics of several central-peripheral processes, its influence on muscle remained understudied. Here, the impact of EE is investigated on motor function, neuromuscular physiology, and the skeletal muscle transcriptome. EE is initiated in 20-month-old mice for a five-month period. EE mice exhibit greater relative lean mass that is associated with improved mobility and hindlimb grip strength. Transcriptomic profiling of muscle tissue reveals an EE-associated enrichment of gene expression within several metabolic pathways related to oxidative phosphorylation and the TCA cycle. Many mitochondrial-related genes-several of which participate in the electron transport chain-are upregulated. Stress-responsive signaling pathways are downregulated because of EE. The results suggest that EE improves motor function-possibly through preservation of mitochondrial function-even late in life.

N-acetylcysteine treatment attenuates hemodialysis access-related limb pathophysiology in mice with chronic kidney disease.

The objective of the present study was to determine if treatment with N-acetylcysteine (NAC) could reduce access-related limb dysfunction in mice. Male and female C57BL6J mice were fed an adenine-supplemented diet to induce chronic kidney disease (CKD) prior to the surgical creation of an arteriovenous fistula (AVF) in the iliac vascular bundle. AVF creation significantly increased peak aortic and infrarenal vena cava blood flow velocities, but NAC treatment had no significant impact, indicating that fistula maturation was not impacted by NAC treatment. Hindlimb muscle and paw perfusion recovery and muscle capillary density in the AVF limb were unaffected by NAC treatment. However, NAC treatment significantly increased the mass of the tibialis anterior (P = 0.0120) and soleus (P = 0.0452) muscles post-AVF. There was a significant main effect of NAC treatment on hindlimb grip strength at postoperative day 12 (POD 12) (P = 0.0003), driven by significantly higher grip strength in both male (P = 0.0273) and female (P = 0.0031) mice treated with NAC. There was also a significant main effect of NAC treatment on the walking speed at postoperative day 12 (P = 0.0447), and post hoc testing revealed an improvement in NAC-treated male mice (P = 0.0091). The area of postsynaptic acetylcholine receptors (P = 0.0263) and motor endplates (P = 0.0240) was also increased by NAC treatment. Interestingly, hindlimb skeletal muscle mitochondrial oxidative phosphorylation trended higher in NAC-treated female mice but was not statistically significant (P = 0.0973). Muscle glutathione levels and redox status were not significantly impacted by NAC treatment in either sex. In summary, NAC treatment attenuated some aspects of neuromotor pathology in mice with chronic kidney disease following AVF creation.NEW & NOTEWORTHY Hemodialysis via autogenous arteriovenous fistula (AVF) is the preferred first-line modality for renal replacement therapy in patients with end-stage kidney disease. However, patients undergoing AVF surgery frequently experience a spectrum of hand disability symptoms postsurgery including weakness and neuromotor dysfunction. Unfortunately, no treatment is currently available to prevent or mitigate these symptoms. Here, we provide evidence that daily N-acetylcysteine supplementation can attenuate some aspects of limb neuromotor function in a preclinical mouse model of AVF.

Maternal music exposure during pregnancy influences reflexive motor behaviors in mice offspring.

Evidence supports that music can modulate many physiological roles, exerting clear effects on the central nervous system. For this effect to be positive, music should be tuned at a frequency of 432 Hz. This study aims to determine the effects of prenatal exposure to music on reflexive motor behaviors in mice offspring. Six pregnant female NMRI mice (8-10weeks old) were randomly and equally allocated into two groups. Group 1 as control was placed in a normal housing area (average room noise 35 dB), and Group 2 was exposed to music pitched at 432 Hz for 2h a day played at constant volume (75/80 dB) during pregnancy. Following delivery, four pups from each pregnant mouse were selected, and reflexive motor behaviors including ambulation, hind-limb foot angle, surface righting, grip strength, front- and hind-limb suspension, and negative geotaxis were determined. Based on the findings, prenatal exposure to music significantly increased ambulation score, grip strength, and front- and hind-limb suspension compared to the control group (P< 0.05). Also, prenatal exposure to music significantly decreased hind-limb foot angle, negative geotaxis, and surface righting compared to the control group (P< 0.05). These results suggested that music exposure during pregnancy had a significant positive effect on all tested reflexive motor behaviors in mice offspring.

Impact of N-acetylcysteine supplementation on skeletal muscle myopathy in a mouse model of access-related hand dysfunction

Introduction: Hemodialysis is a life-line therapy for end-stage kidney disease patients that requires long-term arteriovenous access. Arteriovenous fistula (AVF) is the most durable and commonly employed access strategy. However, access-related hand dysfunction (ARHD) including ischemia, weakness, and neuromotor discoordination is prevalent (~50%) following AVF placement. Unfortunately, there are no pre-emptive non-surgical therapeutic studies available. We hypothesized that N-acetylcysteine (NAC) supplementation would attenuate hindlimb disability in a mouse model of ARHD. Methods: Adult male and female C57BL/6J mice (N=9/group) were fed adenine diet to induce kidney disease. Thereafter, animals were randomly allocated to receive NAC (150 mg/kg in 0.2 ml of 0.9% saline) or placebo (0.2 ml of saline) via oral gavage beginning 3 days prior to the AVF surgery and until euthanasia. Limb perfusion to the ischemic hindlimb and hindlimb grip strength were assessed post-operatively (POD) in vivo. Muscle contractile and mitochondrial function, and histological assessments of muscle and the neuromuscular junction were also performed. Results: Laser Doppler perfusion to the ventral paw was decreased immediately after AVF creation on the left common iliac artery (~25% of the contralateral limb) and recovered (~40-60%) at POD13 without a treatment effect. NAC treatment improved muscle mass in the tibialis anterior (TA) (+13~21%, P&lt;0.05) and soleus (+17~21%, P&lt;0.05) muscles in both male and female mice compared with placebo-treated animals. NAC female, not male, mice had significant improvement in grip strength (~20% greater at POD4 and POD12, P&lt;0.05) and maximal mitochondrial respiration (~30% higher at POD14, P&lt;0.05) compared with control animals. Muscle contractile function and myofiber area and capillarization in TA and soleus muscles were similar between NAC and placebo groups (P&gt;0.05). Interestingly, the area of the post-synaptic acetylcholine receptor clusters was significantly greater in the animals that received NAC treatment (+10~22%, P&lt;0.05) in both male and female mice. Conclusion: Daily treatment with a thiol reducing antioxidant, NAC, has beneficial effects on the recovery of muscle mass and neuromuscular junction morphology in both male and female mice with additional improvement in grip strength and mitochondrial function in female mice suggesting a potential therapeutic strategy targeting antioxidant defense to ameliorate ARHD. Funding Support: National Institutes of Health grant R01HL148597 and American Heart Association grant POST903198. This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Knock-in mouse models for CMTX1 show a loss of function phenotype in the peripheral nervous system

The X-linked form of Charcot-Marie-Tooth disease (CMTX1) is the second most common form of CMT. In this study we used CRISPR/Cas9 to develop new “knock-in” models of CMTX1 that are more representative of the spectrum of mutations seen with CMTX1 than the Cx32 knockout (KO) mouse model used previously. We compared mice of four genotypes - wild-type, Cx32KO, p.T55I, and p.R75W. Sciatic motor conduction velocity slowing was the most robust electrophysiologic indicator of neuropathy, showing reductions in the Cx32KO by 3 months and in the p.T55I and p.R75W mice by 6 months. At both 6 and 12 months, all three mutant genotypes showed reduced four limb and hind limb grip strength compared to WT mice. Performance on 6 and 12 mm width balance beams revealed deficits that were most pronounced at on the 6 mm balance beam at 6 months of age. There were pathological changes of myelinated axons in the femoral motor nerve in all three mutant lines by 3 months of age, and these became more pronounced at 6 and 12 months of age; sensory nerves (femoral sensory and the caudal nerve of the tail) appeared normal at all ages examined. Our results demonstrate that mice can be used to show the pathogenicity of human GJB1 mutations, and these new models for CMTX1 should facilitate the preclinical work for developing treatments for CMTX1.

Short-time recovery skeletal muscle from dexamethasone-induced atrophy and weakness in old female rats

BackgroundSeveral pathological conditions (atrophy, dystrophy, spasticity, inflammation) can change muscle biomechanical parameters. Our previous works have shown that dexamethasone treatment changes skeletal muscle tone, stiffness, elasticity. Exercise training may oppose the side effects observed during dexamethasone treatment. The purpose of this study was to examine the changes in biomechanical parameters (tone, stiffness, elasticity) of skeletal muscle occurring during dexamethasone treatment and subsequent short-time recovery from glucocorticoid-induced muscle atrophy and weakness, as well as the effect of mild therapeutic exercise. Methods17 old female rats, aged 22 months were used in this study. The hand-held and non-invasive device (MyotonPRO, Myoton Ltd., Tallinn, Estonia) was used to study changes in biomechanical properties of muscle. Additionally, body and muscle mass, hind limb grip strength were assessed. FindingsResults showed that dexamethasone treatment alters muscle tone, stiffness and elasticity. During 20-day recovery period all measured parameters gradually improved towards the average baseline, however, remaining significantly lower than these values. The body and muscle mass, hind limb grip strength of the rats decreased considerably in the groups that received glucocorticoids. After 20 days of recovery, hind limb grip strength of the animals was slightly lower than the baseline value and mild therapeutic exercise had a slight but not significant effect on hind limb grip strength. Biomechanical parameters improved during the recovery period, but only dynamic stiffness and decrement retuned to baseline value. InterpretationThe study results show that monitoring muscle biomechanical parameters allows to assess the recovery of atrophied muscle from steroid myopathy.

Prenatal Exposure to L-Citrulline Has Positive Effects on Reflexive Motor Behavior in Newborn Mice.

L-citrulline (L-cit) is a nonessential amino acid that interacts with the veracity of neurotransmitters in the brain and might have a positive effect on fetal growth. However, there is no information about the possible effect of L-cit on reflexive motor behavior. Thus, this study aimed to determine the effects of prenatal exposure to L-cit on reflexive motor behavior in mice offspring. Forty pregnant female mice were allocated into four groups. In the control group, mice received water, while in groups 2-4, female mice orally gavage with L-cit (25, 50, and 100 mg/kg) at 5, 8, 11, 14, and 17 days of gestation (GD). Following delivery, pups were selected, and reflexive motor behaviors were determined using ambulation, hind-limb foot angle, surface righting, hind-limb strength, grip strength, front limb suspension, and negative geotaxis tests. Also, serum Nitric oxide (NO), malondialdehyde (MDA), superoxide dismutase (SOD) and glutathione peroxidase (GPx) were determined. Based on the findings, maternal exposure to L-cit improved ambulation score, hind-limb suspension score, grip strength, and front-limb suspension in offspring (P<0.05). Prenatal exposure to L-cit decreased surface righting, hind-limb foot angle, and negative geotaxis in offspring (P<0.05). L-cit decreased immobility time in forced swimming test (FST), tail suspension test (TST), and increased number of squares crossed in the open field test (OFT) and spending time on rotarod on postpartum mice (P<0.05). L-cit increased serum NO levels (P<0.05). L-cit decreased blood MDA and increased SOD and GPx levels in offspring (P<0.05). Findings revealed that L-cit improves postpartum behaviors in mice and reflexive motor in their pups.

Amelioration of muscle and nerve pathology of Lama2-related dystrophy by AAV9-laminin-αLN linker protein.

LAMA2 deficiency, resulting from a defective or absent laminin α2 subunit, is a common cause of congenital muscular dystrophy. It is characterized by muscle weakness from myofiber degeneration and neuropathy from Schwann cell amyelination. Previously it was shown that transgenic muscle-specific expression of αLNNd, a laminin γ1–binding linker protein that enables polymerization in defective laminins, selectively ameliorates the muscle abnormality in mouse disease models. Here, adeno-associated virus was used to deliver linker mini-genes to dystrophic dy2J/dy2J mice for expression of αLNNd in muscle, or αLNNdΔG2′, a shortened linker, in muscle, nerve, and other tissues. Linker and laminin α2 levels were higher in αLNNdΔG2′-treated mice. Both αLNNd- and αLNNdΔG2′-treated mice exhibited increased forelimb grip strength. Further, αLNNdΔG2′-treated mice achieved hind limb and all-limb grip strength levels approaching those of WT mice as well as ablation of hind limb paresis and contractures. This was accompanied by restoration of sciatic nerve axonal envelopment and myelination. Improvement of muscle histology was evident in the muscle-specific αLNNd-expressing mice but more extensive in the αLNNdΔG2′-expressing mice. The results reveal that an αLN linker mini-gene, driven by a ubiquitous promoter, is superior to muscle-specific delivery because of its higher expression that extends to the peripheral nerve. These studies support a potentially novel approach of somatic gene therapy.

Assessment of hindlimb myopathy and mitochondrial bioenergetics in a unique mouse model of access‐related hand dysfunction

IntroductionAccess‐related hand dysfunction (ARHD) such as steal syndrome, neuromotor discoordination, and weakness is prevalent following arteriovenous fistula (AVF) placement in patients with end‐stage renal disease. Despite the progressive increase in symptomatic hemodialysis patients, currently no preclinical animal model exists to examine underlying mechanisms or develop novel therapeutics. Herein, we characterize the hindlimb pathology in a novel mouse model of iliac AVF.MethodsMale 8‐week‐old C57BL/6J mice were randomly assigned to casein‐based chow (CON: n=6) or adenine diet (CKD: n=16) for 3 weeks and glomerular filtration rate (GFR) using FIT‐C inulin clearance was measured. On the day of operation, animals were allocated to receive either left common iliac AVF (CKD_AVF: n=10) or Sham (CON_Sham: n=6, CKD_Sham: n=6) surgery and remained on their original diet throughout the study. Hemodynamic changes, hindlimb grip strength, and gait pattern were assessed prior to and post‐operatively. After two weeks of surgery, the animals were euthanized to assess gastrocnemius mitochondrial respiratory capacity and morphological alterations in tibialis anterior (TA), extensor digitorum longus (EDL), and soleus (SOL) muscles.ResultsAnimals exposed to adenine diet had impaired kidney function (GFR in CON:441.3±54.2 µL/min vs. CKD: 165.1±118.3 µL/min, p&lt;0.01) prior to surgery. AVF placement increased inferior vena cava diameter (1.4‐fold at POD3 and 1.6‐fold at POD13, P&lt;0.05) and peak velocity (3.3‐fold at POD3 and 3.8‐fold at POD13, P&lt;0.05) when compared to the pre‐surgery values. In contrast to the animals with sham surgery, AVF mice had decreases in perfusion to the ventral paw (‐77.4±17.4% at POD0 and ‐30.7±15.8% at POD13, P&lt;0.05), grip strength (‐58.6±35.1% at POD4 and ‐42.6±30.9% at POD12, P&lt;0.05), and gait speed (‐5.7±5.2cm/sec at POD4, P&lt;0.05 and ‐3.2±4.3 cm/sec at POD12, P=0.10). Gastrocnemius mitochondrial oxidative phosphorylation conductance in response to stress mimic conditions was decreased by both fistula formation and kidney insufficiency (P&lt;0.05). Morphological analysis of limb muscles revealed that AVF mice exhibited ~60% of fibers with central nuclei and had ~35% smaller myofiber cross‐sectional area in TA and SOL muscles compared to CON_Sham (P&lt;0.05) and ~50% lower capillary contacts in TA, EDL, and SOL muscles compared to both sham surgered groups (P&lt;0.05).ConclusionIliac AVF creation resulted in central and peripheral hemodynamic alterations, impaired hindlimb neuromotor function, mitochondrial dysfunction, and morphological deformation. Taken together, we identify several key pathophysiological aspects of ARHD in a pre‐clinical model providing a platform to facilitate mechanistic and therapeutic studies aimed to reduce ARHD prevalence in CKD patients.

Parental exposure of Tadalafil has beneficial effect on reflexive motor behaviors in mice offspring.

Tadalafil has positive effects on neurodevelopment and antioxidant defense system, but there is no information for its possible role during gestation on reflexive motor behavior in offspring. So current study determined the effect of prenatal exposure to the Tadalafil on reflexive motor behaviors and antioxidant activity in mice offspring and antidepressive behaviors in postpartum dams. Forty pregnant female NMRI mice were allocated into four groups. In control group, mice received water while in Groups 2-4, female mice orally gavage with Tadalafil (0.4, 0.8, and 1.6mg/kg) at gestation day (GD) 5, 8, 11, 14, and 17, respectively. Following delivery, pups were selected and reflexive motor behaviors determined using ambulation, hind-limb foot angle, surface righting, hind-limb strength, grip strength, front-limb suspension, and negative geotaxis tests. Also, serum malondialdehyde (MDA), superoxide dismutase (SOD), glutathione peroxidase (GPx), and total antioxidant status (TAS) were determined in offspring. On Day 2 postpartum, antidepressant activity of Tadalafil was determined by open field test (OFT), rotarod, forced swimming test (FST), and tail suspension test (TST) in dams. Based on the findings, maternal exposure to Tadalafil improved ambulation score, hind-limb suspension score, grip strength, and front-limb suspension in offspring (P < 0.05). Prenatal exposure to Tadalafil decreased surface righting, hind-limb foot angle, and negative geotaxis in offspring (P < 0.05). Tadalafil decreased blood MDA and increased SOD and GPx levels in offspring (P < 0.05). Tadalafil significantly decreased immobility time in FST and TST and increased number of squares crossed in OFT and spending time on rotarod on postpartum mice (P < 0.05). These results suggested that parental exposure of Tadalafil has positive effect on reflexive motor and postpartum behaviors.

Hematopoietic Prostaglandin D Synthase Inhibitor PK007 Decreases Muscle Necrosis in DMD mdx Model Mice.

Duchenne muscular dystrophy (DMD) is characterized by progressive muscle weakness and wasting due to the lack of dystrophin protein. The acute phase of DMD is characterized by muscle necrosis and increased levels of the pro-inflammatory mediator, prostaglandin D2 (PGD2). Inhibiting the production of PGD2 by inhibiting hematopoietic prostaglandin D synthase (HPGDS) may alleviate inflammation and decrease muscle necrosis. We tested our novel HPGDS inhibitor, PK007, in the mdx mouse model of DMD. Our results show that hindlimb grip strength was two-fold greater in the PK007-treated mdx group, compared to untreated mdx mice, and displayed similar muscle strength to strain control mice (C57BL/10ScSn). Histological analyses showed a decreased percentage of regenerating muscle fibers (~20% less) in tibialis anterior (TA) and gastrocnemius muscles and reduced fibrosis in the TA muscle in PK007-treated mice. Lastly, we confirmed that the DMD blood biomarker, muscle creatine kinase activity, was also reduced by ~50% in PK007-treated mdx mice. We conclude that our HPGDS inhibitor, PK007, has effectively reduced muscle inflammation and fibrosis in a DMD mdx mouse model.

Nimodipine Promotes Functional Recovery After Spinal Cord Injury in Rats.

Spinal cord injury (SCI) is a devastating condition that results in severe motor, sensory, and autonomic dysfunction. The L-/T-type calcium channel blocker nimodipine (NMD) exerts a protective effect on neuronal injury; however, the protective effects of long-term administration of NMD in subjects with SCI remain unknown. Thus, the aim of this study was to evaluate the role of long-term treatment with NMD on a clinically relevant SCI model. Female rats with SCI induced by 25 mm contusion were subcutaneously injected with vehicle or 10 mg/kg NMD daily for six consecutive weeks. We monitored the motor score, hind limb grip strength, pain-related behaviors, and bladder function in this study to assess the efficacy of NMD in rats with SCI. Rats treated with NMD showed improvements in locomotion, pain-related behaviors, and spasticity-like symptoms, but not in open-field spontaneous activity, hind limb grip strength or bladder function. SCI lesion areas and perilesional neuronal numbers, gliosis and calcitonin gene-related peptide (CGRP+) fiber sprouting in the lumbar spinal cord and the expression of K+–Cl− cotransporter 2 (KCC2) on lumbar motor neurons were also observed to further explore the possible protective mechanisms of NMD. NMD-treated rats showed greater tissue preservation with reduced lesion areas and increased perilesional neuronal sparing. NMD-treated rats also showed improvements in gliosis, CGRP+ fiber sprouting in the lumbar spinal cord, and KCC2 expression in lumbar motor neurons. Together, these results indicate that long-term treatment with NMD improves functional recovery after SCI, which may provide a potential therapeutic strategy for the treatment of SCI.

Linoleic Acid-Rich Diet Improves Glucose Clearance, Increases Grip Strength, and Alters Skeletal Muscle Cardiolipin Species in a Mouse Model of Diet-Induced Obesity

Abstract Objectives Compare the effects of high-fat diets containing linoleic-acid (LA)-rich oil and lard on measures of whole-body energy metabolism and skeletal muscle function in a mouse model of diet-induced obesity. Methods 9-week old male C57BL6/J mice (n = 24) were assigned to high fat isocaloric diets (24% fat by wt) containing LA-rich safflower oil (SO) or lard (LD) for 18 weeks. Food intake and body weight were measured every 2 days. EchoMRI was used at Days 0, 65, and 100 to determine the effects of each diet on body composition. Grip strength was measured to assess muscle strength at Day 113. Fasting blood glucose was measured and an insulin tolerance test (ITT) was performed on Day 85 to measure insulin sensitivity and glucose uptake. After 130 days, quadriceps muscle mitochondrial and cardiolipin remodeling gene expression was measured by qRT-PCR. Cardiolipin (CL) speciation of muscle was measured by normal phase liquid chromatography coupled to electrospray ionization mass spectrometry. Results Although LD-fed mice gained body mass at a faster rate, there was no difference in body mass or cumulative food intake after 130 days. Similarly, % adiposity of LD-fed mice increased at Day 65 compared to those fed the SO diet, but not at Day 100. Mice consuming the SO diet exhibited increased hindlimb grip strength. SO-fed mice exhibited lower blood glucose levels at 90 and 120 minutes post-insulin injection, demonstrating improved glucose clearance over time. Significant differences in CL speciation, particularly that of LA-containing species, were observed. Conclusions When compared to the LD diet, mice consuming the SO diet exhibited early reductions in adiposity that were undistinguishable after 130 days of dietary intervention. However, mice fed SO diet exhibited improved grip strength, insulin-stimulated glucose clearance and significant differences in skeletal muscle cardiolipin speciation. Future studies will address the relationship between LA-derived metabolites, CL speciation, and improved muscle function. Funding Sources Funding was provided by NIH, Ohio Agriculture Research and Development Center and the Carol S. Kennedy Professorship. DBS received support from the AOCS Thomas H. Smouse Memorial Fellowship.

Profiling age-related muscle weakness and wasting: neuromuscular junction transmission as a driver of age-related physical decline.

Pathological age-related loss of skeletal muscle strength and mass contribute to impaired physical function in older adults. Factors that promote the development of these conditions remain incompletely understood, impeding development of effective and specific diagnostic and therapeutic approaches. Inconclusive evidence across species suggests disruption of action potential signal transmission at the neuromuscular junction (NMJ), the crucial connection between the nervous and muscular systems, as a possible contributor to age-related muscle dysfunction. Here we investigated age-related loss of NMJ function using clinically relevant, electrophysiological measures (single-fiber electromyography (SFEMG) and repetitive nerve stimulation (RNS)) in aged (26 months) versus young (6 months) F344 rats. Measures of muscle function (e.g., grip strength, peak plantarflexion contractility torque) and mass were assessed for correlations with physiological measures (e.g., indices of NMJ transmission). Other outcomes also included plantarflexion muscle contractility tetanic torque fade during 1-s trains of stimulation as well as gastrocnemius motor unit size and number. Profiling NMJ function in aged rats identified significant declines in NMJ transmission stability and reliability. Further, NMJ deficits were tightly correlated with hindlimb grip strength, gastrocnemius muscle weight, loss of peak contractility torque, degree of tetanic fade, and motor unit loss. Thus, these findings provide direct evidence for NMJ dysfunction as a potential mechanism of age-related muscle dysfunction pathogenesis and severity. These findings also suggest that NMJ transmission modulation may serve as a target for therapeutic development for age-related loss of physical function.

Age of Peak Performance Differs by Functional Task in Mice Tracked Over 2 Years.

Mouse models are often used to validate novel interventions prior to human testing, although biological differences between mice and humans limit the translatability of outcomes. A common assumption in animal research is that maximal physical performance will be present at a young age, and that differences in task performance between young and old can be attributed to the aging process. However, this may not be true for all physical function tasks, and leaving out intermediate time points could drastically alter data interpretation. Here, we document age-related changes in forelimb and hindlimb grip strength, balance and coordination, and body composition in mice (n = 43) collected at multiple time points between 4 and 24 months of age. Maximal forelimb grip strength was recorded at 4 months of age, but maximal hindlimb grip strength was recorded at 15 months of age. Balance performance was stable from 4 to 15 months of age, declining significantly at 18 months. Both lean and fat mass peaked at 18 months before declining steadily. We conclude that the inclusion of intermediate time points is essential for the accurate evaluation of physical function status in mice, particularly in the context of translating intervention outcomes into strategies to be tested in humans.