Whole-body vibration mediates mechanical hypersensitivity through Aβ-fiber and C-fiber thermal sensation in a chronic pain model

Astaxanthin has a beneficial influence on pain-related symptoms and opioid-induced hyperalgesia in mice with diabetic neuropathy-evidence from behavioral studies

BACKGROUND

The treatment of painful diabetic neuropathy is still a clinical problem. The aim of this study was to determine whether astaxanthin, a substance that inhibits mitogen-activated protein kinases, activates nuclear factor erythroid 2-related factor 2 and influences N-methyl-D-aspartate receptor, affects nociceptive transmission in mice with diabetic neuropathy.

METHODS

The studies were performed on streptozotocin-induced mouse diabetic neuropathic pain model. Single intrathecal and intraperitoneal administrations of astaxanthin at various doses were conducted in both males and females. Additionally, repeated twice-daily treatment with astaxanthin (25 mg/kg) and morphine (30 mg/kg) were performed. Hypersensitivity was evaluated with von Frey and cold plate tests.

RESULTS

This behavioral study provides the first evidence that in a mouse model of diabetic neuropathy, single injections of astaxanthin similarly reduce tactile and thermal hypersensitivity in both male and female mice, regardless of the route of administration. Moreover, repeated administration of astaxanthin slightly delays the development of morphine tolerance and significantly suppresses the occurrence of opioid-induced hyperalgesia, although it does not affect blood glucose levels, body weight, or motor coordination. Surprisingly, astaxanthin administered repeatedly produces a better analgesic effect when administered alone than in combination with morphine, and its potency becomes even more pronounced over time.

CONCLUSIONS

These behavioral results provide a basis for further evaluation of the potential use of astaxanthin in the clinical treatment of diabetic neuropathy and suggest that the multidirectional action of this substance may have positive effects on relieving neuropathic pain in diabetes.

Therapeutic effects of whole-body vibration on postmenopausal women with osteoporosis: a systematic review and meta-analysis

The objective of this study was to assess the efficacy of whole-body vibration (WBV) on bone mineral density (BMD), pain levels, and body composition in postmenopausal women with osteoporosis (PMOP). Relevant studies were retrieved from the PubMed, EMBASE, Web of science, CENTRAL, and PEDro databases. Thirteen randomized controlled trials with 783 patients were enrolled. The meta-analysis results showed that WBV can significantly increase lumbar spine BMD (WMD=0.018; 95%CI: 0.004 to 0.032; P=0.011), femoral neck BMD (WMD=0.005, 95%CI: 0.001 to 0.011, P=0.0493), and reduce pain degree (WMD=-0.786; 95%CI: -1.300 to -0.272; P=0.0027) in PMOP, but has no significant effect on patients' muscle mass (WMD=0.547; 95%CI: -1.104 to 2.199; P=0.5158) as well as fat mass (WMD=0.530; 95%CI: -2.389 to 3.448; P=0.7222). To conclude, WBV showed the potential to provide positive benefits in improving BMD and relieving pain of PMOP.

Whole Body Vibration: A Valid Alternative Strategy to Exercise?

Several studies agree that mechanical vibration can induce physiological changes at different levels, improving neuromuscular function through postural control strategies, muscle tuning mechanisms and tonic vibration reflexes. Whole-body vibration has also been reported to increase bone mineral density and muscle mass and strength, as well as to relieve pain and modulate proprioceptive function in patients with osteoarthritis or lower back pain. Furthermore, vibratory training was found to be an effective strategy for improving the physical performance of healthy athletes in terms of muscle strength, agility, flexibility, and vertical jump height. Notably, several benefits have also been observed at the brain level, proving to be an important factor in protecting and/or preventing the development of age-related cognitive disorders. Although research in this field is still debated, certain molecular mechanisms responsible for the response to whole-body vibration also appear to be involved in physiological adaptations to exercise, suggesting the possibility of using it as an alternative or reinforcing strategy to canonical training. Understanding these mechanisms is crucial for the development of whole body vibration protocols appropriately designed based on individual needs to optimize these effects. Therefore, we performed a narrative review of the literature, consulting the bibliographic databases MEDLINE and Google Scholar, to i) summarize the most recent scientific evidence on the effects of whole-body vibration and the molecular mechanisms proposed so far to provide a useful state of the art and ii) assess the potential of whole-body vibration as a form of passive training in place of or in association with exercise.

Effects of whole-body vibration on neuropathic pain and the relationship between pain and spasticity in persons with spinal cord injury

OBJECTIVE

Whole-body vibration (WBV) appears to modulate reflex hyperexcitability and spasticity. Due to common underlying neural mechanisms between spasticity and neuropathic pain, WBV may also reduce chronic pain after spinal cord injury (SCI). Our objective was to determine whether there are dose-related changes in pain following WBV and to examine the relationships between neuropathic pain and reflex excitability.

STUDY DESIGN

Secondary analysis of a sub-population (participants with neuropathic pain, n = 16) from a larger trial comparing the effects of two different doses of WBV on spasticity in persons with SCI.

SETTING

Hospital/Rehabilitation Center in Atlanta, GA, USA.

METHODS

Participants were randomized to 8-bout or 16-bout WBV groups. Both groups received ten sessions of sham intervention, followed by ten sessions of WBV. Primary measures included the Neuropathic Pain Symptom Inventory (NPSI) for pain symptom severity and H-reflex paired-pulse depression (PPD) for reflex excitability.

RESULTS

Mean change in NPSI scores were not significantly different between the groups (7 ± 6; p = 0.29; ES = 0.57); however, 8-bouts of WBV were consistently beneficial for participants with high neuropathic pain symptom severity (NPSI total score >30), while 16-bouts of WBV appeared to increase pain in some individuals with high NPSI scores. A baseline NPSI cut score of 30 predicted PPD response (sensitivity = 1.0, specificity = 0.83), with higher NPSI scores associated with decreased PPD in response to WBV.

CONCLUSIONS

WBV in moderate doses appears to decrease neuropathic pain symptoms and improve reflex modulation. However, at higher doses neuropathic pain symptoms may be aggravated. Lower baseline NPSI scores were associated with improved reflex modulation.

Glycosides for Peripheral Neuropathic Pain: A Potential Medicinal Components

Neuropathic pain is a refractory disease that occurs across the world and pharmacotherapy has limited efficacy and/or safety. This disease imposes a significant burden on both the somatic and mental health of patients; indeed, some patients have referred to neuropathic pain as being 'worse than death'. The pharmacological agents that are used to treat neuropathic pain at present can produce mild effects in certain patients, and induce many adverse reactions, such as sedation, dizziness, vomiting, and peripheral oedema. Therefore, there is an urgent need to discover novel drugs that are safer and more effective. Natural compounds from medical plants have become potential sources of analgesics, and evidence has shown that glycosides alleviated neuropathic pain via regulating oxidative stress, transcriptional regulation, ion channels, membrane receptors and so on. In this review, we summarize the epidemiology of neuropathic pain and the existing therapeutic drugs used for disease prevention and treatment. We also demonstrate how glycosides exhibit an antinociceptive effect on neuropathic pain in laboratory research and describe the antinociceptive mechanisms involved to facilitate the discovery of new drugs to improve the quality of life of patients experiencing neuropathic pain.

Effects of whole-body vibration training in a cachectic C26 mouse model

Targeted exercise combined with nutritional and pharmacological strategies is commonly considered to be the most optimal strategy to reduce the development and progression of cachexia. For COPD patients, this multi-targeted treatment has shown beneficial effects. However, in many, physical activity is seriously hampered by frailty and fatigue. In the present study, effects of whole-body-vibration-training (WBV) were investigated, as potential alternative to active exercise, on body mass, muscle mass and function in tumour bearing mice. Twenty-four male CD2F1-mice (6–8 weeks, 21.5 ± 0.2 g) were stratified into four groups: control, control + WBV, C26 tumour-bearing, and C26 tumour-bearing + WBV. From day 1, whole-body-vibration was daily performed for 19 days (15 min, 45 Hz, 1.0 g acceleration). General outcome measures included body mass and composition, daily activity, blood analysis, assessments of muscle histology, function, and whole genome gene expression in m. soleus (SOL), m. extensor digitorum longus (EDL), and heart. Body mass, lean and fat mass and EDL mass were all lower in tumour bearing mice compared to controls. Except from improved contractility in SOL, no effects of vibration training were found on cachexia related general outcomes in control or tumour groups, as PCA analysis did not result in a distinction between corresponding groups. However, analysis of transcriptome data clearly revealed a distinction between tumour and trained tumour groups. WBV reduced the tumour-related effects on muscle gene expression in EDL, SOL and heart. Gene Set Enrichment Analysis showed that these effects were associated with attenuation of the upregulation of the proteasome pathway in SOL. These data suggest that WBV had minor effects on cachexia related general outcomes in the present experimental set-up, while muscle transcriptome showed changes associated with positive effects. This calls for follow-up studies applying longer treatment periods of WBV as component of a multiple-target intervention.