Effect of Low-Magnitude, High-Frequency Vibration Treatment on Retardation of Sarcopenia: Senescence-Accelerated Mouse-P8 Model

Styxl2 regulates de novo sarcomere assembly by binding to non-muscle myosin IIs and promoting their degradation

Styxl2, a poorly characterized pseudophosphatase, was identified as a transcriptional target of the Jak1-Stat1 pathway during myoblast differentiation in culture. Styxl2 is specifically expressed in vertebrate striated muscles. By gene knockdown in zebrafish or genetic knockout in mice, we found that Styxl2 plays an essential role in maintaining sarcomere integrity in developing muscles. To further reveal the functions of Styxl2 in adult muscles, we generated two inducible knockout mouse models: one with Styxl2 being deleted in mature myofibers to assess its role in sarcomere maintenance, and the other in adult muscle satellite cells (MuSCs) to assess its role in de novo sarcomere assembly. We find that Styxl2 is not required for sarcomere maintenance but functions in de novo sarcomere assembly during injury-induced muscle regeneration. Mechanistically, Styxl2 interacts with non-muscle myosin IIs, enhances their ubiquitination, and targets them for autophagy-dependent degradation. Without Styxl2, the degradation of non-muscle myosin IIs is delayed, which leads to defective sarcomere assembly and force generation. Thus, Styxl2 promotes de novo sarcomere assembly by interacting with non-muscle myosin IIs and facilitating their autophagic degradation.

Prevention of age-related neuromuscular junction degeneration in sarcopenia by low-magnitude high-frequency vibration

Neuromuscular junction (NMJ) degeneration is one of pathological factors of sarcopenia. Low-magnitude high-frequency vibration (LMHFV) was reported effective in alleviating the sarcopenia progress. However, no previous study has investigated treatment effects of LMHFV targeting NMJ degeneration in sarcopenia. We first compared morphological differences of NMJ between sarcopenic and non-sarcopenic subjects, as well as young and old C57BL/6 mice. We then systematically characterized the age-related degeneration of NMJ in SAMP8 against its control strain, SAMR1 mice, from 3 to 12 months old. We also investigated effects of LMHFV in SAMP8 on the maintenance of NMJ during the onset of sarcopenia with respect to the Agrin-LRP4-MuSK-Dok7 pathway and investigated the mechanism related to ERK1/2 signaling. We observed sarcopenic/old NMJ presented increased acetylcholine receptors (AChRs) cluster fragmentation and discontinuity than non-sarcopenic/young NMJ. In SAMP8, NMJ degeneration (morphologically at 6 months and functionally at 8 months) was observed associated with the sarcopenia onset (10 months). SAMR1 showed improved NMJ morphology and function compared with SAMP8 at 10 months. Skeletal muscle performance was improved at Month 4 post-LMHFV treatment. Vibration group presented improved NMJ function at Months 2 and 6 posttreatment, accompanied with alleviated morphological degeneration at Month 4 posttreatment. LMHFV increased Dok7 expression at Month 4 posttreatment. In vitro, LMHFV could promote AChRs clustering in myotubes by increasing Dok7 expression through suppressing ERK1/2 phosphorylation. In conclusion, NMJ degeneration was observed associated with the sarcopenia onset in SAMP8. LMHFV may attenuate NMJ degeneration and sarcopenia progression by increasing Dok7 expression through suppressing ERK1/2 phosphorylation.

Therapeutic Approach of Whole-Body Vibration Exercise on Wound Healing in Animal Models: A Systematic Review

Human skin wounds pose a gathering threat to the public health, carrying an immense epidemiologic and financial burden. Pharmacological and non-pharmacological (NP) treatments have been proposed to the management of wound healing. Physical exercise is a strong NP intervention considered for patients in wound healing. Particularly, a type of exercise intervention known as whole-body vibration (WBV) exercise has gained increasing interest. WBV exercise is generated due to the transmission of mechanical vibrations, produced by a vibrating platform, to the body. The aim of this review was to summarize studies in experimental animal models using WBV exercise in wound healing. Searches were performed in EMBASE, PubMed, Scopus and Web of Science including publications on 21 November 2022 using the string "whole body vibration" AND "wound healing" (animal or mice or mouse or rat or rodent). The SYRCLE tool was used to assess the risk of bias (RoB). From 48 studies, five studies met the inclusion criteria. RoB indicated that none of the studies fulfilled all methodological analyzed criteria, resulting in possible biases. The studies were homogeneous, and results suggest beneficial effects of WBV exercise in wound healing, mainly related to enhancing angiogenesis, granulation tissue formation, reducing the blood glucose level and enhancing blood microcirculation, by increasing myofiber growth and rapid re-epithelialization. In conclusion, the various biological effects of the response to the WBV exercise indicate the relevance of this intervention in wound healing in animals. Moreover, considering the translation approach, it is possible to speculate that the beneficial effects of this non-pharmacological therapy might justify clinical trials for wound healing also in humans, after criterion evaluation.

A Phytomolecule Icariin Protects from Sarcopenia Partially by Suppressing Myosin Heavy Chain Degradation in Orchiectomized Rats

Treatments are lacking for sarcopenia, which is an age-related disease characterized by loss of skeletal muscle mass, strength, and/or physical performance. Icariin is a phytomolecule from herbal Epimedium, a traditional Chinese medicine widely used to treat musculoskeletal disorders for thousands of years. Here the effects of icariin against sarcopenia are investigated and the underlying mechanism is elucidated. A classic rat model of bilaterally orchiectomized (ORX) is used to induce sarcopenia. After administration for 8 weeks, compared to the control group, the forelimb grip strength, the specific tetanic forces of the soleus (SOL) and extensor digitorum longus muscle (EDL) are higher, and the fiber cross-sectional areas (CSAs) of the gastrocnemius and tibialis anterior muscle are larger in the icariin group. In addition, icariin promotes mRNA and protein expressions of myosin heavy chain (MyHC) both in SOL and EDL. Mechanistically, icariin significantly suppresses the mRNA and protein expressions of FOXO3a, atrogin-1, and MuRF-1, which are related to the degradation of myosin heavy chain. Collectively, icariin protects from sarcopenia in ORX rats characterized by enhancing grip strength and skeletal muscle contraction, as well as increasing skeletal muscle CSA by inhibiting the ubiquitination degradation of the MyHC in skeletal muscle fibers.

Coapplication of Magnesium Supplementation and Vibration Modulate Macrophage Polarization to Attenuate Sarcopenic Muscle Atrophy through PI3K/Akt/mTOR Signaling Pathway

Sarcopenia is an age-related geriatric syndrome characterized by the gradual loss of muscle mass and function. Low-magnitude high-frequency vibration (LMHFV) was shown to be beneficial to structural and functional outcomes of skeletal muscles, while magnesium (Mg) is a cofactor associated with better indices of skeletal muscle mass and strength. We hypothesized that LMHFV, Mg and their combinations could suppress inflammation and sarcopenic atrophy, promote myogenesis via PI3k/Akt/mTOR pathway in senescence-accelerated mouse P8 (SAMP8) mice and C2C12 myoblasts. Results showed that Mg treatment and LMHFV could significantly decrease inflammatory expression (C/EBPα and LYVE1) and modulate a CD206-positive M2 macrophage population at month four. Mg treatment also showed significant inhibitory effects on FOXO3, MuRF1 and MAFbx mRNA expression. Coapplication showed a synergistic effect on suppression of type I fiber atrophy, with significantly higher IGF-1, MyoD, MyoG mRNA (p < 0.05) and pAkt protein expression (p < 0.0001) during sarcopenia. In vitro inhibition of PI3K/Akt and mTOR abolished the enhancement effects on myotube formation and inhibited MRF mRNA and p85, Akt, pAkt and mTOR protein expressions. The present study demonstrated that the PI3K/Akt/mTOR pathway is the predominant regulatory mechanism through which LMHFV and Mg enhanced muscle regeneration and suppressed atrogene upregulation.

Puerarin improves skeletal muscle strength by regulating gut microbiota in young adult rats

Background

Sarcopenia is an age-related skeletal muscle dysfunction syndrome that is lacking validated treatments. Maximizing muscle strength in young adulthood may be a promising way to prevent sarcopenia in the elderly. The phytomolecule puerarin has been extensively used in clinical practice and reported to increase energy metabolism in skeletal muscle by directly targeting the skeletal muscle fiber. However, the bioavailability of puerarin is very poor, and almost 93% of puerarin stays in the intestine until excretion. Therefore, we hypothesize that puerarin may regulate gut microbiota to improve skeletal muscle strength and/or mass in adults.

Methods

Twenty three-month old male Sprague Dawley rats were divided into two groups according to average weights, puerarin group (puerarin dissolved in 0.5% CMC-Na, 150 ​mg/kg/day, N ​= ​10), and control group (equal volume 0.5% CMC-Na, N ​= ​10). The treatment lasted for 8 weeks. Muscle weight, muscle fiber types and cross-sectional area (CSA), ex vivo muscle contraction test and grip strength were measured. 16S rDNA sequencing was employed to evaluate the gut microbiota composition in the sample of cecal content. Short-chain fatty acids (SCFAs) in cecal and serum were analyzed by gas chromatography-mass spectrometry. Adenosine triphosphate (ATP) concentration in skeletal muscle was also detected. Pearson's correlation was used to analyze the relations between SCFAs, ATP concentration and muscle function.

Results

After puerarin treatment, grip strength, the specific twitch force, and the tetanic forces in the soleus (SOL) and extensor digitorum longus (EDL) muscle were significantly higher than those of the control group. The percentage and CSA of type II muscle fiber in EDL was higher in the puerarin group than those in the control group. Puerarin treatment significantly changed the gut microbial constitutes. Two SCFAs-productive microbiota, the families Peptococcaceae and Closteridiales, were significantly higher in the puerarin group than those in the control group, while the ratio of Prevotellaceae/Bacteroidaceae (P/B), a muscle atrophy indicator, was lower in the puerarin group. As expected, there were significant linear correlations between the concentrations of SCFAs, including cecal total SCFAs, serum n-butyric acid and total SCFAs, and skeletal muscle strength and function, including the twitch force and tetanic force of SOL and EDL, as well as the forelimb grip strength.

Conclusion

In conclusion, puerarin improved the forelimb grip strength and muscle contraction function in young adult rats. The underlying mechanism may include that puerarin increased SCFAs production by regulating gut microbiota, augmented ATP synthesis and skeletal muscle strength.

The translational potential of this article: Our study finds that a clinical used phytomolecule puerarin has the potential of improving skeletal muscle strength in young adult rats. As puerarin has long-term clinical experience and shows good safety, it might be a potential candidate for developing muscle strengthening agents.

HR-pQCT for the Evaluation of Muscle Quality and Intramuscular Fat Infiltration in Ageing Skeletal Muscle

Myosteatosis is the infiltration of fat in skeletal muscle during the onset of sarcopenia. The quantification of intramuscular adipose tissue (IMAT) can be a feasible imaging modality for the clinical assessment of myosteatosis, important for the early identification of sarcopenia patients and timely intervention decisions. There is currently no standardized method or consensus for such an application. The aim of this study was to develop a method for the detection and analysis of IMAT in clinical HR-pQCT images of the distal tibia to evaluate skeletal muscle during the ageing process, validated with animal and clinical experimentation. A pre-clinical model of ovariectomized (OVX) rats with known intramuscular fat infiltration was used, where gastrocnemii were scanned by micro-computed tomography (micro-CT) at an 8.4 μm isotropic voxel size, and the images were analyzed using our modified IMAT analysis protocol. IMAT, muscle density (MD), and muscle volume (MV) were compared with SHAM controls validated with Oil-red-O (ORO) staining. Furthermore, the segmentation and IMAT evaluation method was applied to 30 human subjects at ages from 18 to 81 (mean = 47.3 ± 19.2). Muscle-related parameters were analyzed with functional outcomes. In the animal model, the micro-CT adipose tissue-related parameter of IMAT% segmented at −600 HU to 100 HU was shown to strongly associate with the ORO-positively stained area (r = 0.898, p = 0.002). For the human subjects, at an adjusted threshold of −600 to −20 HU, moderate positive correlations were found between MV and MD (r = 0.642, p < 0.001), and between MV and IMAT volume (r = 0.618, p < 0.01). Moderate negative correlations were detected between MD and IMAT% (r = −0.640, p < 0.001). Strong and moderate associations were found between age and MD (r = −0.763, p < 0.01), and age and IMAT (r = 0.559, p < 0.01). There was also a strong correlation between IMAT% and chair rise time (r = 0.671, p < 0.01). The proposed HR-pQCT evaluation protocol for intramuscular adipose-tissue produced MD and IMAT results that were associated with age and physical performance measures, and were of good predictive value for the progression of myosteatosis or sarcopenia. The protocol was also validated on animal skeletal muscle samples that showed a good representation of histological lipid content with positive correlations, further supporting the clinical application for the rapid evaluation of muscle quality and objective quantification of skeletal muscle at the peripheral for sarcopenia assessment.

Magnesium supplementation alleviates corticosteroid-associated muscle atrophy in rats

PURPOSE

Corticosteroid (CS) therapy for infectious and rheumatological diseases showed to decrease serum magnesium (Mg++) level and induce muscle atrophy in patients. The present study investigated the effects of Mg++ supplementation on preventing CS-induced muscle atrophy in an animal model, which provided experimental data for potential clinical translation.

METHODS

Twelve 24-week-old male Sprague-Dawley rats were treated with lipopolysaccharide (LPS) and CS methylprednisolone (MPS) to induce muscle atrophy, with half of the rats also given daily 50 mg/kg Mg++ oral supplementation. Additional six rats without LPS + CS treatments were used as normal controls. After treatment for 6 weeks, serum was collected for Mg++ quantification, animal dual-energy X-ray absorptiometry (DXA) was performed for tissue composition, and the extensor digitorum longus (EDL) was collected for muscle functional test and histology including muscle fiber size, intramuscular fat infiltration and fiber typing. In vitro myotube atrophy model was used to study the in vitro effect associated with in vivo muscle atrophy.

RESULTS

LPS + CS treatments induced hypomagnesemia while the serum Mg++ level was in normal range after Mg++ supplementation. DXA showed 53.0% lower fat percent and 29.7% higher lean mass in LPS + CS + Mg group when compared to LPS + CS group. Muscle functional test showed 22.2% higher specific twitch force and 40.3% higher specific tetanic force in LPS + CS + Mg group when compared to LPS + CS group. Histological analysis showed 4.1% higher proportion of muscle fibers area to total area and 63.6% lower intramuscular fat infiltration in EDL sections in LPS + CS + Mg group when compared to LPS + CS group. LPS + CS + Mg group had 33.0% higher area proportion and 29.4% higher cross-sectional area (CSA) of type IIb muscle fiber. Myoblast culture results showed that Mg++ supplementation group had larger myotube diameter. The mRNA expressions of the muscle atrophy marker genes MuRF1 and MAFbx were lower in Mg++ supplementation group both in vitro and in vivo.

CONCLUSION

The current study demonstrated that Mg++ supplementation successfully alleviated CS-associated muscle atrophy in rats at both functional and morphology levels, indicating a translational potential for patients undergoing CS therapy. This study provided the evidence for the first time that Mg++ supplementation could prevent muscle atrophy-an adverse effect of CS therapy, currently also adopted for treating coronavirus disease 2019 (COVID-19).

Lactobacillus paracasei PS23 decelerated age-related muscle loss by ensuring mitochondrial function in SAMP8 mice

Sarcopenia is a common impairment in the elderly population responsible for poor outcomes later in life; it can be caused by age-related alternations. Only a few strategies have been reported to reduce sarcopenia. Lactobacillus paracasei PS23 (LPPS23) has been reported to delay some age-related disorders. Therefore, here we investigated whether LPPS23 decelerates age-related muscle loss and its underlying mechanism. Female senescence-accelerated mouse prone-8 (SAMP8) mice were divided into three groups (n=6 each): non-aging (16-week-old), control (28-week-old), and PS23 (28-week-old) groups. The control and PS23 groups were given saline and LPPS23, respectively. We evaluated the effects of LPPS23 by analyzing body weight and composition, muscle strength, protein uptake, mitochondrial function, reactive oxygen species (ROS), antioxidant enzymes, and inflammation-related cytokines. LPPS23 significantly attenuated age-related decreases of muscle mass and strength. Compared to the control group, the non-aging and PS23 groups exhibited higher mitochondrial function, IL10, antioxidant enzymes, and protein uptake. Moreover, inflammatory cytokines and ROS were lower in the non-aging and PS23 groups than the control group. Taken together, LPPS23 extenuated sarcopenia progression during aging; this effect might have been enacted by preserving the mitochondrial function via reducing age-related inflammation and ROS and by retaining protein uptake in the SAMP8 mice.

Vibration and β-hydroxy-β-methylbutyrate treatment suppresses intramuscular fat infiltration and adipogenic differentiation in sarcopenic mice

BACKGROUND

Sarcopenia is an aging-induced deterioration of skeletal muscle mass and function. Low-magnitude high-frequency vibration (LMHFV) was shown to improve muscle functions and β-hydroxy-β-methylbutyrate (HMB) to increase muscle mass and strength. Muscle-derived stem cells (MDSCs) are progenitor cells important for muscle regeneration. We hypothesized that LMHFV and HMB could retard sarcopenia by reducing fat infiltration through inhibiting adipogenesis in MDSCs.

METHODS

Senescence-accelerated mouse P8 male mice were randomized into control (CTL), HMB, LMHFV (VIB), and combined (COM) groups. Interventions started at age of month 7 and assessed at 1, 2, and 3 months post-intervention by densitometry, histology, and functional tests. In vitro, MDSCs isolated from gastrocnemius of senescence-accelerated mouse P8 mice were characterized, randomized into CTL, VIB, HMB, and COM groups, and assessed by oil red O staining, mRNA, and protein expression.

RESULTS

At 2 months post-intervention, percentage lean mass of HMB, VIB, and COM groups were significantly higher than CTL group. Twitch, tetanic, and specific tetanic forces of COM group were higher, while specific twitch force of both VIB and COM groups were higher. Grip strength of HMB, VIB, and COM groups were higher. Histologically, both VIB and COM groups presented lower oil red O area than CTL group. Type I muscle fibre in CTL group was higher than HMB, VIB, and COM groups. MDSC were detected in situ by immunofluorescence stain with stem cell antigen-1 signals confirmed with higher β-catenin expression in the COM group. The observations were also confirmed in vitro, MDSCs in the HMB, VIB, and COM groups presented lower adipogenesis vs. the CTL group. β-Catenin mRNA and protein expressions were lower in the CTL group while their relationship was further validated through β-catenin knock-down approach.

CONCLUSIONS

Our results showed that combined LMHFV and HMB interventions enhanced muscle strength and decreased percentage fat mass and intramuscular fat infiltration as compared with either treatment alone. Additive effect of LMHFV and HMB was demonstrated in β-catenin expression than either treatment in MDSCs and altered cell fate from adipogenesis to myogenesis, leading to inhibition of intramuscular lipid accumulation. Wnt/β-catenin signalling pathway was found to be the predominant regulatory mechanism through which LMHFV and HMB combined treatment suppressed MDSCs adipogenesis.

Impaired Fracture Healing in Sarco-Osteoporotic Mice Can Be Rescued by Vibration Treatment Through Myostatin Suppression

Sarcopenia is highly prevalent in fragility fracture patients and is associated with delayed healing. In this study, we investigated the effect of low-magnitude high-frequency vibration (LMHFV) on osteoporotic fracture with sarcopenia and the potential role of myostatin. Osteoporotic fractures created in sarcopenic SAMP8, non-sarcopenic SAMR1 were randomized to control or LMHFV (SAMP8, SAMR1, SAMP8-V, or SAMR1-V) groups. Healing and myostatin expression were evaluated at 2, 4, and 6 weeks post-fracture. In vitro, conditioned-media were collected from myofibers isolated from aged and young SAMP8 or C2C12 myoblasts with or without LMHFV. Osteoblastic MC3T3-E1 under osteogenic differentiation were treated with plain or conditioned-medium (±myostatin propeptide). LMHFV significantly enhanced callus formation was in non-sarcopenic SAMR1 mice; but the enhancement effect was not significant in SAMP8 mice at week 2. Myostatin expressions in callus and biceps femoris of SAMP8 group were significantly higher all groups with significant negative correlation with callus size (R²  = 0.7256; p = 0.0004). Mechanical properties (week 4) and callus remodeling (week 6) were inferior in SAMP8 versus SAMR1 and were significantly enhanced by LMHFV. Alkaline Phosphatase (ALP) and Runx2 expression of MC3T3-E1 was lower in aged myofiber compared with young, but upregulated by LMHFV or myostatin inhibition; also confirmed with C2C12. LMHFV enhanced early callus formation, microarchitecture, callus remodeling and mechanical properties of fracture healing in both SAMP8 and SAMR1; however, more effective in non-sarcopenic SAMR1 mice. Impaired fracture healing in sarcopenic SAMP8 mice is attributed by elevated myostatin expression in callus and muscle, which correlated negatively with callus formation. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 38:277-287, 2020.

A study protocol for a randomized controlled trial evaluating vibration therapy as an intervention for postural training and fall prevention after distal radius fracture in elderly patients

Background

Fractures of the distal radius are one of the most common osteoporotic fractures in elderly men and women. These fractures are a particular health concern amongst the elderly, who are at risk of fragility fractures, and are associated with long-term functional impairment, pain and a variety of complications. This is a sentinel event, as these fractures are associated with a two to four times increased risk of subsequent hip fractures in elderly patients. This is an important concept, as it is well established that these patients have an increased risk of falling. Fall prevention is therefore crucial to decrease further morbidity and mortality. The purpose of this study is to investigate the effect of low-magnitude high-frequency vibration (LMHFV) on postural stability and prevention of falls in elderly patients post distal radius fracture.

Methods

This is a prospective single-blinded randomized controlled trial. Two hundred patients will be recruited consecutively with consent, and randomized to either LMHFV (n = 100) or a control group (n = 100). The primary outcome is postural stability measured by the static and dynamic ability of patients to maintain centre of balance on the Biodex Balance System SD. Secondary outcomes are the occurrence of fall(s), the health-related quality of life 36-item short form instrument, the Timed Up and Go test for basic mobility skills, compliance and adverse events. Outcome assessments for both groups will be performed at baseline (0 month) and at 6 weeks, 3 months and 6 months time points.

Discussion

Previous studies have stressed the importance of reducing falls after distal radius fracture has occurred in elderly patients, and an effective intervention is crucial. Numerous studies have proven vibration therapy to be effective in improving balancing ability in normal patients; However, no previous study has applied the device for patients with fractures. Our study will attempt to translate LMHFV to patients with fractures to improve postural stability and prevent recurrent falls. Positive results would provide a large impact on the prevention of secondary fractures and save healthcare costs.

Trial registration

ClinicalTrials.gov, NCT03380884. Registered on 21 December 2017.

Low-Magnitude High-Frequency Vibration Decreases Body Weight Gain and Increases Muscle Strength by Enhancing the p38 and AMPK Pathways in db/db Mice

OBJECTIVE

To evaluate the effect LMHFV on body weight gain, NAFLD and muscle strength and explore effect in mitochondrial biogenesis, AMPKα and p38 pathways.

METHODS

Vibration platform used in this study provides specific whole-body cyclic mechanical stimulation at low magnitude (0.3 g) and high frequency (50 Hz). Diabetic mice (8-9 mice per group) (C57BL/KsJ-m+/+Lepr^db) were randomly divided into untreated group (no vibration) and two vibration groups. Lean mice (8 mice) were used as non-diabetic control for both groups. Two diabetic vibration groups received LMHFV every day for 20 min/day and 40 min/day separately.

RESULTS

After 8 weeks of treatment, results showed that body weight, liver weight, fat pad weight, glucose level and insulin level were lower in vibration group when compared with the untreated group. The ratio of fat in liver was significantly decreased after vibration treatment. Muscle strength was significantly increased after vibration. Mitochondrial biogenesis-related gene expression was increased in soleus, gastrocnemius and liver. AMPKα mRNA expression level was increased in soleus and gastrocnemius after vibration treatment. p38 and AMPKα mRNA expression level and protein expression level in liver were enhanced with vibration treatment. Moreover, phosphorylation of p38 and AMPKα was enhanced in liver.

CONCLUSION

LMHFV applied in our study decreases body weight gain and improves muscle strength and NAFLD in diabetic mice which were partly through improving mitochondrial biogenesis by enhancing p38 and AMPKα pathway.

Low-Magnitude High-Frequency Vibration Accelerated the Foot Wound Healing of n5-streptozotocin-induced Diabetic Rats by Enhancing Glucose Transporter 4 and Blood Microcirculation

Delayed wound healing is a Type 2 diabetes mellitus (DM) complication caused by hyperglycemia, systemic inflammation, and decreased blood microcirculation. Skeletal muscles are also affected by hyperglycemia, resulting in reduced blood flow and glucose uptake. Low Magnitude High Frequency Vibration (LMHFV) has been proven to be beneficial to muscle contractility and blood microcirculation. We hypothesized that LMHFV could accelerate the wound healing of n5-streptozotocin (n5-STZ)-induced DM rats by enhancing muscle activity and blood microcirculation. This study investigated the effects of LMHFV in an open foot wound created on the footpad of n5-STZ-induced DM rats (DM_V), compared with no-treatment DM (DM), non-DM vibration (Ctrl_V) and non-DM control rats (Ctrl) on Days 1, 4, 8 and 13. Results showed that the foot wounds of DM_V and Ctrl_V rats were significantly reduced in size compared to DM and Ctrl rats, respectively, at Day 13. The blood glucose level of DM_V rats was significantly reduced, while the glucose transporter 4 (GLUT4) expression and blood microcirculation of DM_V rats were significantly enhanced in comparison to those of DM rats. In conclusion, LMHFV can accelerate the foot wound healing process of n5-STZ rats.

An animal model of co-existing sarcopenia and osteoporotic fracture in senescence accelerated mouse prone 8 (SAMP8)

Sarcopenia and osteoporotic fracture are common aging-related musculoskeletal problems. Recent evidences report that osteoporotic fracture patients showed high prevalence of sarcopenia; however, current clinical practice basically does not consider sarcopenia in the treatment or rehabilitation of osteoporotic fracture. There is almost no report studying the relationship of the co-existing of sarcopenia and osteoporotic fracture healing. In this study, we validated aged senescence accelerated mouse prone 8 (SAMP8) and senescence accelerated mouse resistant 1 (SAMR1) as animal models of senile osteoporosis with/without sarcopenia. Bone mineral density (BMD) at the 5th lumbar and muscle testing of the two animal strains were measured to confirm the status of osteoporosis and sarcopenia, respectively. Closed fracture was created on the right femur of 8-month-old animals. Radiographs were taken weekly post-fracture. MicroCT and histology of the fractured femur were performed at week 2, 4 and 6 post-fracture, while mechanical test of both femora at week 4 and 6 post-fracture. Results showed that the callus of SAMR1 was significantly larger at week 2 but smaller at week 6 post-fracture than SAMP8. Mechanical properties were significantly better at week 4 post-fracture in SAMR1 than SAMP8, indicating osteoporotic fracture healing was delayed in sarcopenic SAMP8. This study validated an animal model of co-existing sarcopenia and osteoporotic fracture, where a delayed fracture healing might be resulted in the presence of sarcopenia.