Neuropathy-induced osteopenia in rats is not due to a reduction in weight born on the affected limb

Effects of 4-Aminopyridine on Combined Nerve and Muscle Injury and Bone Loss

PURPOSE

Musculoskeletal injuries are common, and peripheral nerve injury (PNI) causes significant muscle and bone loss within weeks. After PNI, 4-aminopyridine (4-AP) improves functional recovery and muscle atrophy. However, it is unknown whether 4-AP has any effect on isolated traumatic muscle injury and PNI-induced bone loss.

METHODS

A standardized crush injury was performed on the sciatic nerve and muscles in mice, and the mice were assigned to receive normal saline or 4-AP treatment daily for 21 days. The postinjury motor and sensory function recovery was assessed, injured muscles were processed for histomorphometry, and the tibial bone was scanned for bone density.

RESULTS

4-Aminopyridine significantly accelerated the postinjury motor and sensory function recovery, improved muscle histomorphometry, increased muscle satellite cell numbers, and shifted muscle fiber types after combined nerve and muscle injury. Importantly, the 4-AP treatment significantly reduced PNI-induced bone loss. In contrast, in the case of isolated muscle injury, 4-AP had no effect on functional recovery and bone density, but it improved muscle-specific histomorphometry to a limited extent.

CONCLUSIONS

These findings demonstrate the potential beneficial effects of 4-AP on the recovery of muscle morphology and bone density after combined muscle and nerve injury.

CLINICAL RELEVANCE

Nerve injuries frequently involve muscle and result in rapid muscle and bone atrophy. In this scenario, 4-AP, in addition to accelerating nerve functional recovery, might work as an adjunctive agent to improve the recovery of injured muscle and attenuate PNI-induced bone loss.

Effect of peripheral neuropathy on bone mineral density in adults with diabetes: A systematic review of the literature and meta-analysis

INTRODUCTION

Peripheral neuropathy occurs in two thirds of patients with diabetes mellitus (DM). It can lead to severe pathological changes in the feet, and it increases the risk of fracture more than any other diabetic complication. The objective of this review is to analyze available literature on the effect of peripheral neuropathy on BMD of the foot, spine, or hip. We hypothesize that the presence of diabetic neuropathy leads to lower BMD in adults with diabetes.

METHODS

Original studies investigating the effects of diabetic neuropathy on bone density were searched for inclusion in this systematic review. Studies were eligible if they met the following criteria: 1) participants included adults with either Type 1 DM or Type 2 DM; 2) Method used for the diagnosis of neuropathy described in the manuscript 3) DXA scan, ultrasound, or CT scan was used to measure proximal femur, spine, or foot bone mineral density were reported, and 4) bone parameters were analyzed based on the presence and absence of neuropathy.

RESULTS

Among the 5 studies that met eligibility criteria, 4 did not find a significant effect of neuropathy on BMD. One study showed a significant negative impact of neuropathy on calcaneal BMD in patients with type 1 diabetes. The meta-analysis did not show a significant effect of peripheral neuropathy on BMDs of proximal femur, spine, and calcaneus in diabetic adults.

CONCLUSION

Our study shows no evidence that peripheral neuropathy affects bone density or bone turnover in DM. However, this conclusion should be taken with caution since only a very limited number of studies were available for inclusion in the analysis and included both type 1 and type 2 DM patients. Improved measures of peripheral neuropathy and more advanced imaging technologies are needed to better assess the effect of diabetes on bone health.

Pharmacology of bisphosphonates in pain

The treatment of pain, in particular, chronic pain, remains a clinical challenge. This is particularly true for pain associated with severe or rare conditions, such as bone cancer pain, vulvodynia, or complex regional pain syndrome. Over the recent years, there is an increasing interest in the potential of bisphosphonates in the treatment of pain, although there are few papers describing antinociceptive and anti-hypersensitizing effects of bisphosphonates in various animal models of pain. There is also increasing evidence for clinical efficacy of bisphosphonates in chronic pain states, although the number of well-controlled studies is still limited. However, the mechanisms underlying the analgesic effects of bisphosphonates are still largely elusive. This review provides an overview of preclinical and clinical studies of bisphosphonates in pain and discusses various pharmacological mechanisms that have been postulated to explain their analgesic effects. LINKED ARTICLES: This article is part of a themed issue on The molecular pharmacology of bone and cancer-related bone diseases. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v178.9/issuetoc.

Inhibition of osteoclasts prevents cartilage loss and pain in a rat model of degenerative joint disease

OBJECTIVE

To investigate the relationship between efficacy of a bisphosphonate, pain and extent of joint damage in the monosodium iodoacetate (MIA) model of painful degenerative joint disease.

METHODS

Zoledronate treatment was initiated prior to and at various times following model induction, including late time points representing advanced disease. Radiographic and histological structural parameters were correlated with pain as measured by weight bearing.

RESULTS

Intraarticular (IA) MIA resulted in a progressive loss of bone mineral density (BMD) and chondrocytes, thinning of cartilage, loss of proteoglycan, resorption of calcified cartilage and subchondral bone, as well as pain. This was completely prevented by pre-emptive chronic zoledronate treatment with joint sections being histologically indistinguishable from saline-injected controls. When initiation of treatment was delayed efficacy was reduced. In animals with advanced joint degeneration, treatment partially restored BMD and had a significant, but limited, effect on pain. We confirmed these radiographic and behavioral findings in the medial meniscal tear model. To understand the mechanism-of-action of zoledronate we investigated an early time point 4 days post-model induction when chondrocytes were histologically viable, with minor loss of proteoglycan and generalized synovitis. Osteoclast-mediated resorption of the calcified cartilage was observed and was prevented by two doses of zoledronate.

CONCLUSION

Subchondral bone remodeling plays an important role in nociception and the pathobiology of the MIA model with osteoclasts being implicated in both bone and cartilage resorption. Inhibition of osteoclastic activity when initiated early leads to improved efficacy.

Diabetes medications related to an increased risk of falls and fall-related morbidity in the elderly

OBJECTIVE

To review literature regarding the effect of diabetes medications as a contributing risk for falls and fall-related morbidity in elderly patients with type 2 diabetes.

DATA SOURCES

Primary literature was identified through PubMed MEDLINE (1966-November 2009) using the search terms elderly, aged, older adults, diabetes type 2, diabetes mellitus, falls, fractures, medication, hypoglycemia, and vitamin B(12) deficiency. Each drug class and the individual agents within the classes were also included in the search. Additional references were obtained through review of references from articles obtained.

STUDY SELECTION AND DATA EXTRACTION

Clinical studies evaluating diabetes medications and their association with falls, as well as studies evaluating their association with the complications of falls, were considered for inclusion. Selection emphasis was placed on randomized studies evaluating diabetes medications and falls.

DATA SYNTHESIS

There is no direct link between metformin and falls; however, an indirect association caused by neuropathy secondary to vitamin B(12) deficiency may be of concern. Although hypoglycemia is a risk factor, to date, there are no trials specifically linking insulin secretagogues to falls. Insulin use has been demonstrated to increase the risk of falls in the elderly. Thiazolidinediones increase fracture risk and thus may worsen fall-related outcomes. There are no studies to date linking other agents to an increased risk of falls.

CONCLUSIONS

Special considerations should be made when treating elderly patients with diabetes. At this time, a patient's functional level and risk factors for falls should weigh into decision-making regarding drug selection. The risk of falls and fall-related complications associated with diabetes medications should not be ignored.

Thiazolidinedione use and the longitudinal risk of fractures in patients with type 2 diabetes mellitus

CONTEXT

Thiazolidinedione (TZD) use has recently been associated with an increased risk of fractures.

OBJECTIVE

The aim of this study was to determine the time-dependent relationship between TZD use and fracture risk.

DESIGN

We conducted a retrospective cohort study in a large health system in southeast Michigan.

PATIENTS

PATIENTS who received care from the health system were included if they were at least 18 yr of age, had a diagnosis of diabetes, and had at least one prescription for an oral diabetes medication. These criteria identified 19,070 individuals (9,620 women and 9,450 men).

INTERVENTION

This study compared patients treated with TZDs to patients without TZD treatment. Cox proportional hazard models were used to assess the relationship between exposure and outcomes.

MAIN OUTCOME MEASURES

The primary outcome was the time to fracture. Secondary analyses examined the risk of fractures in subgroups defined by sex and age.

RESULTS

TZD use was associated with an increased risk of fracture in the cohort overall [adjusted hazard ratio (aHR), 1.35; 95% confidence interval (CI), 1.05-1.71] and in women (aHR, 1.57; 95% CI, 1.16-2.14), but not in men (aHR, 1.05; 95% CI, 0.70-1.58). Women more than 65 yr of age appeared to be at greatest risk for fracture (aHR, 1.72; 95% CI, 1.17-2.52). Among women, the increased fracture risk was not apparent until after 1 yr of TZD treatment.

CONCLUSIONS

TZD use was associated with an increased risk for fractures in women, particularly at ages above 65 yr. Clinicians should be aware of this association when considering TZD therapy so as to appropriately manage and counsel their patients.

Thiazolidinedione-induced skeletal fragility--mechanisms and implications

Recent evidence suggests that the risk of several types of fracture is increased in type 2 diabetes mellitus (T2DM). Thiazolidinediones (TZDs) are now widely used in the management of T2DM, and their use may increase in other diseases characterized by insulin resistance. The PPAR-gamma, the molecular target of the TZDs currently in clinical use, is expressed in skeletal tissue. Evidence from preclinical studies has demonstrated that activation of PPAR-gamma (i) inhibits bone formation by diverting mesenchymal stem cells from the osteogenic to the adipocytic lineage and (ii) may increase bone resorption by stimulating the development of osteoclasts. There is also potential for indirect adverse skeletal effects of PPAR-gamma activation by modulation of circulating levels of hormones and cytokines known to influence bone metabolism. Recent studies in humans have demonstrated that TZDs decrease markers of bone formation decrease bone mass, and increase fracture rates, at least in women. The implication of these findings is that fracture risk should be considered in patients with T2DM for whom TZD therapy is being considered, and appropriate therapy instigated to prevent fractures in individuals ascertained to be at high risk.

Bone health and back pain: what do we know and where should we go?

Bone health is generally not considered in patients who present with chronic back pain. Nonetheless, bone health and back pain share common genetic and environmental correlates suggesting a co-dependence. Evidence exists for a relationship between back pain and impaired bone health. Here we present the evidence, theoretic framework and clinical relevance. Bone health and back pain are important determinants of musculoskeletal health. Back pain experienced in youth is a risk factor for future back pain, while suboptimal bone health during development increases the risk of skeletal fragility in later life. Generally, bone health is not considered in patients with chronic back pain who do not demonstrate other well-recognised bone health risk factors or associated conditions. Nonetheless, evidence suggests that back pain and impaired bone health share common environmental and genetic correlates, indicating that bone health ought to be considered in the context of back pain in otherwise healthy individuals. This review describes the likely mechanisms explaining the relationship between back pain and impaired bone health, evidence concerning the relationship and suggestions for future research. A narrative literature search was conducted using CINAHL, Medline, PubMed and Web of Science electronic databases. A history of back pain is associated with decreased bone mineral density in adults, yet this tends to be site-specific. No studies were identified examining this association in youth, yet the negative effects of childhood skeletal trauma and obesity on bone and spinal health provide indirect evidence for an association. Further research is required to clarify the impact of back pain on bone health at different lifespan stages using prospective cohort designs.

Inflammatory osteolysis in diabetic neuropathic (charcot) arthropathies of the foot

OBJECTIVE

Osteolysis and low bone mineral density (BMD) are underappreciated consequences of several chronic diseases that may elevate the risk for fracture. The purpose of this study was to assess tarsal BMD associated with acute inflammation (ie, inflammatory osteolysis) in individuals with chronic diabetes mellitus (DM), peripheral neuropathy (PN), and recent-onset neuropathic (Charcot) arthropathy (NCA) of the foot.

RESEARCH DESIGN AND METHODS

This was a case-control study of 32 people (11 men, 21 women) with DM, PN, and NCA of the foot or ankle. The subjects with DM, PN, and NCA were compared with 64 age-, sex-, and race-matched control subjects (24 men, 40 women) without DM, PN or NCA. Within the first 3 weeks of cast immobilization, BMD was estimated in both calcanei using quantitative ultrasonometry. Acute inflammation was confirmed by comparing skin temperature differences between the feet of the subjects with DM, PN, and NCA and the feet of the control subjects.

RESULTS

Skin temperature differences averaged 6.7 degrees F (SD=4.0 degrees F) (involved foot minus noninvolved foot) in the feet of the subjects with DM, PN, and NCA compared with 0.0 degrees F (SD=1.3 degrees F) in the feet of the control subjects. Calcaneal BMD averaged 384 mg/cm(2) (SD=110) in the involved feet and 467 mg/cm(2) (SD=123) in the noninvolved feet of the subjects with DM, PN, and NCA and 545 mg/cm(2) (SD=121) in combined right and left feet of the control subjects.

CONCLUSIONS

Inflammation in individuals with DM, PN, and NCA may contribute to or exacerbate a rapid loss of BMD. Inflammatory osteolysis may be a prominent factor responsible for both the spontaneous onset of neuropathic fracture and the insidious and progressive foot deformity that is the hallmark of the chronic Charcot foot.

Skeletal consequences of thiazolidinedione therapy

Thiazolidinediones (TZDs) are agonists of the peroxisome proliferator-activated receptor gamma (PPARgamma) nuclear transcription factor. Two members of this drug class, rosiglitazone and pioglitazone, are commonly used in the management of type II diabetes mellitus, and play emerging roles in the treatment of other clinical conditions characterized by insulin resistance. Over the past decade, a consistent body of in vitro and animal studies has demonstrated that PPARgamma signaling regulates the fate of pluripotent mesenchymal cells, favoring adipogenesis over osteoblastogenesis. Treatment of rodents with TZDs decreases bone formation and bone mass. Until recently, there were no bone-related data available from studies of TZDs in humans. In the past year, however, several clinical studies have reported adverse skeletal actions of TZDs in humans. Collectively, these investigations have demonstrated that the TZDs currently in clinical use decrease bone formation and accelerate bone loss in healthy and insulin-resistant individuals, and increase the risk of fractures in the appendicular skeleton in women with type II diabetes mellitus. These observations should prompt clinicians to evaluate fracture risk in patients for whom TZD therapy is being considered, and initiate skeletal protection in at-risk individuals.

Predictive validity of animal pain models? A comparison of the pharmacokinetic-pharmacodynamic relationship for pain drugs in rats and humans

A number of previous reviews have very eloquently summarized pain models and endpoints in animals. Many of these reviews also discuss how animal models have enhanced our understanding of pain mechanisms and make forward-looking statements as to our proximity to the development of effective mechanism-based treatments. While a number of reports cite failures of animal pain models to predict efficacy in humans, few have actually analyzed where these models have been successful. This review gives a brief overview of those successes, both backward, providing validation of the models, and forward, predicting clinical efficacy. While the largest dataset is presented on treatments for neuropathic pain, this review also discusses acute and inflammatory pain models. Key to prediction of clinical efficacy is a lack of side effects, which may incorrectly suggest efficacy in animals and an understanding of how pharmacokinetic parameters translate from animals to man. As such, this review focuses on a description of the pharmacokinetic-pharmacodynamic relationship for a number of pain treatments that are effective in both animals and humans. Finally we discuss where and why animal pain models have failed and summarize improvements to pain models that should expand and improve their predictive power.