The RANKL/RANK/OPG signaling pathway mediates medial arterial calcification in diabetic Charcot neuroarthropathy

Novel Glycomimetics Protect against Glycated Low-Density Lipoprotein-Induced Vascular Calcification In Vitro via Attenuation of the RAGE/ERK/CREB Pathway

Heparan sulphate (HS) can act as a co-receptor on the cell surface and alterations in this process underpin many pathological conditions. We have previously described the usefulness of mimics of HS (glycomimetics) in protection against β-glycerophosphate-induced vascular calcification and in the restoration of the functional capacity of diabetic endothelial colony-forming cells in vitro. This study aims to investigate whether our novel glycomimetic compounds can attenuate glycated low-density lipoprotein (g-LDL)-induced calcification by inhibiting RAGE signalling within the context of critical limb ischemia (CLI). We used an established osteogenic in vitro vascular smooth muscle cell (VSMC) model. Osteoprotegerin (OPG), sclerostin and glycation levels were all significantly increased in CLI serum compared to healthy controls, while the vascular calcification marker osteocalcin (OCN) was down-regulated in CLI patients vs. controls. Incubation with both CLI serum and g-LDL (10 µg/mL) significantly increased VSMC calcification vs. controls after 21 days, with CLI serum-induced calcification apparent after only 10 days. Glycomimetics (C2 and C3) significantly inhibited g-LDL and CLI serum-induced mineralisation, as shown by a reduction in alizarin red (AR) staining and alkaline phosphatase (ALP) activity. Furthermore, secretion of the osteogenic marker OCN was significantly reduced in VSMCs incubated with CLI serum in the presence of glycomimetics. Phosphorylation of cyclic AMP response element-binding protein (CREB) was significantly increased in g-LDL-treated cells vs. untreated controls, which was attenuated with glycomimetics. Blocking CREB activation with a pharmacological inhibitor 666-15 replicated the protective effects of glycomimetics, evidenced by elevated AR staining. In silico molecular docking simulations revealed the binding affinity of the glycomimetics C2 and C3 with the V domain of RAGE. In conclusion, these findings demonstrate that novel glycomimetics, C2 and C3 have potent anti-calcification properties in vitro, inhibiting both g-LDL and CLI serum-induced VSMC mineralisation via the inhibition of LDLR, RAGE, CREB and subsequent expression of the downstream osteogenic markers, ALP and OCN.

Biomarkers for Early Detection of Charcot Arthropathy: A Prospective Study on Type 2 Diabetes Patients with Severe Neuropathy

BACKGROUND

Charcot arthropathy (CA) is a progressive noninfectious inflammatory disease that causes irreversible destruction to pedal architecture in diabetic neuropathy (DN) patients. The debilitating prognosis demands early detection to prevent the development and progression of this disorder. Dysregulated and persistent production of inflammatory cytokines is reported as the key element in initiating osteoclastogenesis in CA. The study analyzed the potential association of markers of inflammation and bone turnover of prediagnostic serum samples on CA.

METHODS

Seventy-one type 2 severe DN patients were selected based on inclusion-exclusion criteria. Serum samples of interleukin 6 (IL-6), osteoprotegerin (OPG), bone alkaline phosphatase (BALP), and C-reactive protein (CRP) were analyzed. These patients were followed for the development of symptoms of CA for 12 months. In the year of monitoring, 7 patients developed CA (group 1), whereas the remaining 64 patients did not develop CA (group 2).

RESULTS

The rate of development of CA in patients with severe DN was 9.8%. In this group, significantly increased median values of HbA1c (group 2: 8.00 [7.00-9.00], group 1: 10.00 [9.25-11.50], P = .013); IL-6 (group 2: 1.21 [0.72-2.16], group 1: 11.08 [6.65-63.64], P = .008); and CRP (group 2: 1.25 [0.78-3.20], group 1: 3.31 [1.18-41.33], P = .041) were found. The receiver operating characteristic analysis showed that IL-6 was more strongly associated with the onset of CA (IL-6: area under the curve = 0.808; P = .008) than CRP. Cut-off values of ≥6.6 for IL-6 show potential to rule out CA in high-risk patients, with a positive predictive value of 26.1%, a negative predictive value of 97.9%, a sensitivity of 85.7%, and a specificity of 73.4%.

CONCLUSION

In our study population, we found that an exacerbated inflammatory state, reflected by IL-6 values, generally occurred in DN patients before the clinical detection of CA.

LEVEL OF EVIDENCE

Level II, prospective comparative study.

The role of miR-433-3p in vascular calcification in type 2 diabetic patients: targeting WNT/β-Catenin and RANKL/RANK/OPG signaling pathways

BACKGROUND

Vascular calcification (VC) is a major predictor of cardiovascular diseases that represent the principal cause of mortality among type-2 diabetic patients. Accumulating data suggest the vital role of some microRNAs on vascular calcification as an epigenetic regulator. Thus, we assessed herein, the role of serum miR-433-3p in vascular calcification in type-2 diabetic patients.

METHODS

Twenty healthy subjects (control group) and forty diabetic patients (20 without VC and 20 with VC) were involved in the study. miR-433-3p gene expression was measured. Runx2, Dickkopf-1 (DKK1), β-catenin, Receptor activator of nuclear factor kappa-B ligand (RANKL), and osteoprotegerin (OPG) levels in serum were assessed by ELISA technique.

RESULTS

Diabetes patients had significantly lower levels of miR-433-3p expression in comparison to the control group, with the lowest levels being found in diabetic patients with VC. Furthermore, Runx2, β-catenin, and RANKL levels were significantly increased with concomitant lower DKK1 and OPG levels detected in the two diabetic groups especially those with VC.

CONCLUSION

Collectively, the study documented that down-regulation of miR-433-3p may contribute to the development of VC through activating WNT/β-Catenin and RANKL/RANK/OPG signaling pathways.

Association of rs2073618 polymorphism and osteoprotegerin levels with hypertension and cardiovascular risks in patients with type 2 diabetes mellitus

There are reports of link of osteoprotegerin (OPG) gene polymorphism to type-2 diabetes (T2D) and hypertension (HTN). The objective of the study was to assess the allele frequency of OPG (rs2073618) gene polymorphism and its association with heart rate variability (HRV) and blood pressure variability profile as CVD risks in diabetes mellitus patients with hypertension undergoing treatment. T2D patients on treatment without hypertension (n = 172), with hypertension (n = 177) and 191 healthy volunteers were recruited for the study. Their blood pressure variability including baroreflex sensitivity (BRS), heart rate variability (HRV), OPG, insulin, lipid profile, receptor-activator for NFkB (RANK), receptor-activator for NFkB-Ligand (RANKL), and tumor necrosis factor-α (TNF-α) were estimated. Allele frequency of OPG (rs2073618) gene polymorphism was assessed from the DNA samples. BRS and HRV indices were decreased, and RANKL/OPG and TNF-α were increased in T2D and T2D + HTN groups, respectively compared to healthy control group. The reduction in BRS was contributed by increased inflammation and reduced SDNN of HRV in GG genotype in T2D + HTN. In GG + GC subgroup, it was additionally contributed by rise in RANKL/OPG level (β - 0.219; p 0.008). Presence of mutant GG genotype contributed to the risk of hypertension among T2D patients (OR 3.004) as well as in general population (OR 2.79). It was concluded that CV risks are more in T2D patients with HTN expressing OPG rs2073618 gene polymorphism.

Evaluating Classification Systems of Diabetic Foot Ulcer Severity: A 12-Year Retrospective Study on Factors Impacting Survival

(1) Background: This study examines the survival of patients after their first presentation with diabetic foot ulcers (DFUs) to the regional Diabetes, Nutrition, and Metabolic Diseases Clinic within the Emergency Clinical Hospital "Sf. Spiridon", Iaşi, and analyzes the factors associated with this outcome. (2) Methods: In this retrospective study, patients with DFUs consecutively referred between 1 January 2007 and 31 December 2017 were followed up until 31 December 2020 (for 13 years). The study group included 659 subjects. (3) Results: During the study period, there were 278 deaths (42.2%) and the average survival time was 9 years. The length of hospitalization, diabetic nephropathy, chronic kidney disease, glomerular filtration rate, cardiovascular disease, hypertension, anemia, and DFU severity were the most significant contributors to the increase in mortality. Patients with severe ulcers, meaning DFUs involving the tendon, joint, or bone, had a higher mortality risk than those with superficial or pre-ulcerative lesions on initial presentation (Texas classification HR = 1.963, 95% CI: 1.063-3.617; Wagner-Meggitt classification HR = 1.889, 95% CI: 1.024-3.417, SINBAD Classification System and Score HR = 2.333, 95% CI: 1.258-4.326) after adjusting for confounding factors. (4) Conclusions: The findings of this study suggested that patients presenting with severe ulcers involving the tendon, joint, or bone exhibited a significantly higher risk of mortality, even when potential confounders were taken into consideration.

Biomarkers for Prostate Cancer Bone Metastasis Detection and Prediction

Prostate cancer (PCa) causes deaths worldwide, ranking second after lung cancer. Bone metastasis (BM) frequently results from advanced PCa, affecting approximately 90% of patients, and it also often results in severe skeletal-related events. Traditional diagnostic methods for bone metastases, such as tissue biopsies and imaging, have substantial drawbacks. This article summarizes the significance of biomarkers in PCa accompanied with BM, including (1) bone formation markers like osteopontin (OPN), pro-collagen type I C-terminal pro-peptide (PICP), osteoprotegerin (OPG), pro-collagen type I N-terminal pro-peptide (PINP), alkaline phosphatase (ALP), and osteocalcin (OC); (2) bone resorption markers, including C-telopeptide of type I collagen (CTx), N-telopeptide of type I collagen (NTx), bone sialoprotein (BSP), tartrate-resistant acid phosphatase (TRACP), deoxypyridinoline (D-PYD), pyridoxine (PYD), and C-terminal pyridinoline cross-linked telopeptide of type I collagen (ICTP); (3) prostate-specific antigen (PSA); (4) neuroendocrine markers, such as chromogranin A (CgA), neuron-specific enolase (NSE), and pro-gastrin releasing peptide (ProGRP); (5) liquid biopsy markers, such as circulating tumor cells (CTCs), microRNA (miRNA), circulating tumor DNA (ctDNA), and cell-free DNA (cfDNA) and exosomes. In summary, some of these markers are already in widespread clinical use, while others still require further laboratory or clinical studies to validate their value for clinical application.

Therapeutics of Charcot neuroarthropathy and pharmacological mechanisms: A bone metabolism perspective

Charcot neuroarthropathy (CN) is a chronic, destructive, and painless damage of the skeletal system that affects the life quality of patients. CN, with an unclear mechanism, is characterized with invasive destruction of bones and a serious abnormality of bone metabolism. Unfortunately, development of an effective prevention and treatment strategy for CN is still a great challenge. Of note, recent studies providing an insight into the molecular mechanisms of bone metabolism and homeostasis have propelled development of novel CN therapeutic strategies. Therefore, this review aims to shed light on the pathogenesis, diagnosis, and treatment of CN. In particular, we highlight the eminent role of the osteoprotegerin (OPG)-receptor activator of nuclear factor-κB (RANK)-RANK ligand (RANKL) system in the development of CN. Furthermore, we summarize and discuss the diagnostic biomarkers of CN as well as the potential pharmacological mechanisms of current treatment regimens from the perspective of bone metabolism. We believe that this review will enhance the current state of knowledge on the diagnosis, prevention, and therapeutic efficacy of CN.

Roles of osteoprotegerin in endocrine and metabolic disorders through receptor activator of nuclear factor kappa-B ligand/receptor activator of nuclear factor kappa-B signaling

Endocrine and metabolic diseases show increasing incidence and high treatment costs worldwide. Due to the complexity of their etiology and mechanism, therapeutic strategies are still lacking. Osteoprotegerin (OPG), a member of the tumor necrosis factor receptor superfamily, appears to be a potential candidate for the treatment of these diseases. Studies based on clinical analysis and rodent animal models reveal the roles of OPG in various endocrine and metabolic processes or disorders, such as bone remodeling, vascular calcification, and β-cell proliferation, through the receptor activator of nuclear factor kappa-B ligand (RANKL) and the receptor activator of NF-κB (RANK). Thus, in this review, we mainly focus on relevant diseases, including osteoporosis, cardiovascular disease (CVD), diabetes, and gestational diabetes mellitus (GDM), to summarize the effects of the RANKL/RANK/OPG system in endocrine and metabolic tissues and diseases, thereby providing a comprehensive insight into OPG as a potential drug for endocrine and metabolic diseases.

Beaming the Charcot Foot

The Charcot diabetic foot presents unique challenges to the podiatric surgeon in the quest to salvage the limb. This disorder is an intersection of prototypical metabolic diseases and neurodegenerative disorder. Furthermore, it can be considered a disease of bone and ligaments that is often complicated by peripheral vascular disease and serious deep infection. Presently, simplistic ablative surgical procedures and the brace-makers art, still have a valid place in treating this disorder. Newer methods of surgical reconstruction are rapidly evolving to address distorted and nonfunctional limb. This article seeks to evidence the principles and practice of beaming the Charcot midfoot. As will be presented, the beam is a load-sharing device, which can be surgically introduced in an intramedullary method to restore architecture and strength to the Charcot foot. Problems with beam failure and migration have resulted in unsatisfactory outcomes as will be discussed. New Charcot-specific beams are currently reaching the podiatric surgeon with hopes of improving durability. In this article, we aim to address the surgical art of the beam, the engineering principles of beaming, and the novel introduction of a truss/tie rod configuration of beaming.

Bone Metabolism in Charcot

Bone metabolism in the healthy, young adult is identified as a relatively stable process. Normal bone turnover is a dynamic state, which is conferred through intracellular signaling and complex cellular pathways. It has been well described in the literature that Charcot neuro-osteoarthropathy is a disease state, which is marked by intense bone turnover leading to structural collapse and dissolution of skeletal features of the foot and ankle. Within the last two decades, extensive interest has been placed in characterizing the metabolic pathogenesis of Charcot bone metabolism. Despite this work, there remains an incomplete understanding of this devastating disorder. In this article, we review bone histology, physiologic bone metabolism, biomarkers of bone metabolism, pathologic bone metabolism in Charcot diabetics, and potential avenues for intervention.

Etiology, Epidemiology, and Outcomes of Managing Charcot Arthropathy

Surgical intervention for Charcot arthropathy is becoming more common; this is driven by an increased prevalence, better understanding of the cause, identifying patient risk factors that influence outcomes, and how to best optimize these. This article aims to summarize the cause of Charcot, look at the factors that influence the outcomes, and the financial cost of managing what is a very challenging condition.

The Charcot Foot Reflects a Response to Injury That Is Critically Distorted by Preexisting Nerve Damage: An Imperfect Storm

It has been recognized since comprehensive descriptions by Jean-Martin Charcot in 1868 and 1883 that development of what is usually known as neuropathic osteoarthropathy (or the Charcot foot) requires the coincidence of neuropathy and inflammation. Despite this, detailed understanding of the causes has remained remarkably limited in the succeeding century and a half. The aim of this descriptive account is to draw particular attention to the processes involved in both the onset and resolution of the inflammation that is an essential component of active disease. The principal observation is that while neuropathy is common in people with diabetes, the inflammation and secondary skeletal damage that characterize neuropathic osteoarthropathy are observed in only a small minority of people with diabetes and with neuropathy. We therefore argue that the key to understanding the causes of the Charcot foot is to focus equally on those who have active disease as well as those who do not. Although neuropathy is essential for development of the disorder, neuropathy also has an adverse impact on the mechanisms involved in the onset of inflammation, and these may be critically affected in the majority of those who are susceptible. The Charcot foot is uncommon in people with diabetes (or any other cause of neuropathy) because the large majority of those with neuropathy may have also lost the capacity to mount the specific inflammatory reaction that is essential for its development.

Pathophysiology and Molecular Imaging of Diabetic Foot Infections

Diabetic foot infection is the leading cause of non-traumatic lower limb amputations worldwide. In addition, diabetes mellitus and sequela of the disease are increasing in prevalence. In 2017, 9.4% of Americans were diagnosed with diabetes mellitus (DM). The growing pervasiveness and financial implications of diabetic foot infection (DFI) indicate an acute need for improved clinical assessment and treatment. Complex pathophysiology and suboptimal specificity of current non-invasive imaging modalities have made diagnosis and treatment response challenging. Current anatomical and molecular clinical imaging strategies have mainly targeted the host's immune responses rather than the unique metabolism of the invading microorganism. Advances in imaging have the potential to reduce the impact of these problems and improve the assessment of DFI, particularly in distinguishing infection of soft tissue alone from osteomyelitis (OM). This review presents a summary of the known pathophysiology of DFI, the molecular basis of current and emerging diagnostic imaging techniques, and the mechanistic links of these imaging techniques to the pathophysiology of diabetic foot infections.

Pathophysiology and Molecular Imaging of Diabetic Foot Infections

Diabetic foot infection is the leading cause of non-traumatic lower limb amputations worldwide. In addition, diabetes mellitus and sequela of the disease are increasing in prevalence. In 2017, 9.4% of Americans were diagnosed with diabetes mellitus (DM). The growing pervasiveness and financial implications of diabetic foot infection (DFI) indicate an acute need for improved clinical assessment and treatment. Complex pathophysiology and suboptimal specificity of current non-invasive imaging modalities have made diagnosis and treatment response challenging. Current anatomical and molecular clinical imaging strategies have mainly targeted the host's immune responses rather than the unique metabolism of the invading microorganism. Advances in imaging have the potential to reduce the impact of these problems and improve the assessment of DFI, particularly in distinguishing infection of soft tissue alone from osteomyelitis (OM). This review presents a summary of the known pathophysiology of DFI, the molecular basis of current and emerging diagnostic imaging techniques, and the mechanistic links of these imaging techniques to the pathophysiology of diabetic foot infections.

Resveratrol Ameliorates Aortic Calcification in Ovariectomized Rats via SIRT1 Signaling

Postmenopausal women are at an increased risk of vascular calcification which is defined as the pathological deposition of minerals in the vasculature, and is strongly linked with increased cardiovascular disease risk. Since estrogen-replacement therapy is associated with increased cancer risk, there is a strong need for safer therapeutic approaches. In this study we aimed to investigate the protective and therapeutic effects of the phytoestrogen resveratrol against vascular calcification in ovariectomized rats, a preclinical model of postmenopause. Furthermore, we aimed to compare the effects of resveratrol to those of estrogen and to explore the mechanisms underpinning those effects. Treatment with resveratrol or estrogen ameliorated aortic calcification in ovariectomized rats, as shown by reduced calcium deposition in the arterial wall. Mechanistically, the effects of resveratrol and estrogen were mediated via the activation of SIRT1 signaling. SIRT1 protein expression was downregulated in the aortas of ovariectomized rats, and upregulated in rats treated with resveratrol or estrogen. Moreover, resveratrol and estrogen reduced the levels of the osteogenic markers: runt-related transcription factor 2 (RUNX2), osteocalcin and alkaline phosphatase (ALP) which have been shown to play a role during vascular calcification. Additionally, the senescence markers (p53, p16 and p21) which were also reported to play a role in the pathogenesis of vascular calcification, were reduced upon treatment with resveratrol and estrogen. In conclusion, the phytoestrogen resveratrol may be a safer alternative to estrogen, as a therapeutic approach against the progression of vascular calcification during postmenopause.

Association between Osteoprotegerin and Charcot Neuroarthropathy: a systematic review

AIMS

Osteoprotegerin (OPG) has been associated with Charcot Neuroarthropathy (CN); however, three studied OPG polymorphisms (1181C > G, 245A > C and 950 T > C) have yielded conflicting results. Therefore, this meta-analysis was conducted to determine the difference in serum OPG concentrations between healthy controls and diabetics with and without CN and the effect OPG polymorphisms have on CN development.

METHODS

PubMed, LILAC, SCOPUS, and EBSCO databases and retrieved publications' bibliographies were searched for studies that examined for OPG and CN. Depending on the heterogeneity, fixed or random effects were used to calculate the pooled odds ratio (OR) or standard difference in means (SDM) with 95% confidence intervals (95%CI) for 5 genetic models (heterozygous, homozygous, dominant, recessive, and allelic) and serum concentrations, respectively.

RESULTS

Seven publications (12 studies) demonstrated that serum OPG concentrations were more elevated in subjects with CN (SDM = 0.719, 95%CI = 0.555-0.883, p < 0.001). When CN was compared to healthy controls or diabetics, the difference was more prominent for healthy controls (SDM = 1.043, 95%CI = 0.676-1.409, p < 0.001) than diabetics (SDM = 0.639, 95%CI = 0.456-0.821, p < 0.001) and the SDM difference was significant (p = 0.013). Using 6 publications (9 studies), neither the 1181C > G or the 950 T > C polymorphisms showed any significant associations for any genetic model. For the 245A > C polymorphism, only the homozygous genetic model showed a significant association between the polymorphism and CN (OR = 2.850, 95%CI: 1.051-7.729, p = 0.040).

CONCLUSIONS

Here, we determined a potential correlation between the CN and serum OPG concentrations and that only the CC genotype of the 245A > C polymorphism showed an increased risk of developing CN.

The role of RANKL and FGF23 in Assessing Bone Turnover in Type 2 Diabetic Patients

CONTEXT

Type 2 diabetes is a chronic metabolic disease which affects bone. There is evidence in the literature about some serum markers that reflect the bone turnover metabolism, such as RANKL (Receptor Activator of Nuclear factor Kappa-b Ligand) and Fibroblast Growth Factor (FGF) 23.

OBJECTIVE

We aimed to investigate the correlations between RANKL and FGF23 and other diabetes-related factors possibly influencing early bone turnover changes.

SUBJECTS AND METHOD

We conducted a cross-sectional analytical study on a group of 171 patients with type 2 diabetes, without Charcot's arthropathy or a history of amputations, in which a complete history and anthropometric, clinical, biochemical and dietary evaluation were performed. We evaluated the serum level of RANKL and FGF 23.

RESULTS

RANKL was significantly lower in patients with macroangiopathy (0.42±0.15 pmol/L vs. 0.47±0.2 pmol/L, p=0.001). The level of FGF23 was lower in patients with neuropathy (0.37±0.36 pmol/L vs. 0.41±0.17 pmol/L, p=0.001). We found that FGF23 increased with age, but decreased with the duration of diabetes. We also found an inverse relationship between FGF23 levels and HbA1c, triglycerides, diastolic blood pressure, total proteins, albuminemia.

CONCLUSIONS

RANKL was significantly lower in patients with macroangiopathy, and FGF 23 in patients with neuropathy. Therefore, more studies are needed to elucidate their role in early bone turnover changes.

Loss of SIRT1 in diabetes accelerates DNA damage-induced vascular calcification

AIMS

Vascular calcification is a recognized predictor of cardiovascular risk in the diabetic patient, with DNA damage and accelerated senescence linked to oxidative stress-associated pathological calcification. Having previously shown that systemic SIRT1 is reduced in diabetes, the aim was to establish whether SIRT1 is protective against a DNA damage-induced senescent and calcified phenotype in diabetic vascular smooth muscle cells (vSMCs).

METHODS AND RESULTS

Immunohistochemistry revealed decreased SIRT1 and increased DNA damage marker expression in diabetic calcified arteries compared to non-diabetic and non-calcified controls, strengthened by findings that vSMCs isolated from diabetic patients show elevated DNA damage and senescence, assessed by the Comet assay and telomere length. Hyperglycaemic conditions were used and induced DNA damage and enhanced senescence in vSMCs in vitro. Using H2O2 as a model of oxidative stress-induced DNA damage, pharmacological activation of SIRT1 reduced H2O2 DNA damage-induced calcification, prevented not only DNA damage, as shown by reduced comet tail length, but also decreased yH2AX foci formation, and attenuated calcification. While Ataxia Telanglectasia Mutated (ATM) expression was reduced following DNA damage, in contrast, SIRT1 activation significantly increased ATM expression, phosphorylating both MRE11 and NBS1, thus allowing formation of the MRN complex and increasing activation of the DNA repair pathway.

CONCLUSION

DNA damage-induced calcification is accelerated within a diabetic environment and can be attenuated in vitro by SIRT1 activation. This occurs through enhancement of the MRN repair complex within vSMCs and has therapeutic potential within the diabetic patient.

Circulating Receptor Activator of Nuclear Factor kB Ligand and triglycerides are associated with progression of lower limb arterial calcification in type 2 diabetes: a prospective, observational cohort study

Background

Lower limb arterial calcification is a frequent, underestimated but serious complication of diabetes. The DIACART study is a prospective cohort study designed to evaluate the determinants of the progression of lower limb arterial calcification in 198 patients with type 2 diabetes.

Methods

Lower limb arterial calcification scores were determined by computed tomography at baseline and after a mean follow up of 31.20 ± 3.86 months. Serum RANKL (Receptor Activator of Nuclear factor kB Ligand) and bone remodeling, inflammatory and metabolic parameters were measured at baseline. The predictive effect of these markers on calcification progression was analyzed by a multivariate linear regression model.

Results

At baseline, mean ± SD and median lower limb arterial calcification scores were, 2364 ± 5613 and 527 respectively and at the end of the study, 3739 ± 6886 and 1355 respectively. Using multivariate analysis, the progression of lower limb arterial log calcification score was found to be associated with (β coefficient [slope], 95% CI, p-value) baseline log(calcification score) (1.02, 1.00–1.04, p < 0.001), triglycerides (0.11, 0.03–0.20, p = 0.007), log(RANKL) (0.07, 0.02–0.11, p = 0.016), previous ischemic cardiomyopathy (0.36, 0.15–0.57, p = 0.001), statin use (0.39, 0.06–0.72, p = 0.023) and duration of follow up (0.04, 0.01–0.06, p = 0.004).

Conclusion

In patients with type 2 diabetes, lower limb arterial calcification is frequent and can progress rapidly. Circulating RANKL and triglycerides are independently associated with this progression. These results open new therapeutic perspectives in peripheral diabetic calcifying arteriopathy.

Trial registration NCT02431234

Metformin, resveratrol, and exendin-4 inhibit high phosphate-induced vascular calcification via AMPK-RANKL signaling

Vascular calcification increases the risk of developing cardiovascular disease, and it is closely associated with metabolic disorders such as diabetes mellitus and non-alcoholic fatty liver disease. We investigated whether the activators of AMP-activated protein kinase (AMPK), metformin, resveratrol, and exendin-4, improved inorganic phosphate (Pi)-induced vascular calcification in rat vascular smooth muscle cells (VSMCs) and whether these effects were via AMPK. Pi increased calcium deposition in a dose-dependent manner, and metformin, resveratrol, and exendin-4 significantly decreased calcium deposition in the Pi-treated VSMCs. Moreover, metformin and exendin-4 increased the expression of a SMC marker gene, α-smooth muscle actin, and Ampk and reduced the receptor activator of nuclear factor kappa-Β ligand (Rankl)/osteoprotegerin ratio. Metformin, resveratrol, and exendin-4 reduced the expression of osteoblast differentiation-associated factors, such as runt-related transcription factor 2, bone morphogenic protein-2, p-small mothers against decapentaplegic 1/5/8, and Rankl. Inhibition of AMPK by siRNA adversely affected the anti-calcification effects of metformin, resveratrol, and exendin-4 and reversed the reduction of the expression of Rankl by metformin and exendin-4 in the Pi-treated VSMCs. These data suggest that metformin, resveratrol, and exendin-4 ameliorate Pi-induced vascular calcification by inhibiting osteoblast differentiation of VSMCs, which is mediated by AMPK.

Mechanisms of the Osteogenic Switch of Smooth Muscle Cells in Vascular Calcification: WNT Signaling, BMPs, Mechanotransduction, and EndMT

Characterized by the hardening of arteries, vascular calcification is the deposition of hydroxyapatite crystals in the arterial tissue. Calcification is now understood to be a cell-regulated process involving the phenotypic transition of vascular smooth muscle cells into osteoblast-like cells. There are various pathways of initiation and mechanisms behind vascular calcification, but this literature review highlights the wingless-related integration site (WNT) pathway, along with bone morphogenic proteins (BMPs) and mechanical strain. The process mirrors that of bone formation and remodeling, as an increase in mechanical stress causes osteogenesis. Observing the similarities between the two may aid in the development of a deeper understanding of calcification. Both are thought to be regulated by the WNT signaling cascade and bone morphogenetic protein signaling and can also be activated in response to stress. In a pro-calcific environment, integrins and cadherins of vascular smooth muscle cells respond to a mechanical stimulus, activating cellular signaling pathways, ultimately resulting in gene regulation that promotes calcification of the vascular extracellular matrix (ECM). The endothelium is also thought to contribute to vascular calcification via endothelial to mesenchymal transition, creating greater cell plasticity. Each of these factors contributes to calcification, leading to increased cardiovascular mortality in patients, especially those suffering from other conditions, such as diabetes and kidney failure. Developing a better understanding of the mechanisms behind calcification may lead to the development of a potential treatment in the future.

The role of genetic factors and monocyte-to-osteoclast differentiation in the pathogenesis of Charcot neuroarthropathy

Charcot neuroarthropathy is a chronic, progressive condition of the skeletal system that affects some patients with diabetic neuropathy. It results in progressive destruction of bones of the foot and disorganisation of pedal joints and ligaments. Effective prevention and treatment for Charcot neuroarthropathy remain a challenge. Currently, there are no reliable repeatable markers to identify patients with diabetes who are at higher risk of developing Charcot neuroarthropathy. The pathogenesis underlying the development of Charcot neuroarthropathy also remains unclear. In this review, we provide an overview of the history, prevalence, symptoms, risk factors, diagnostics and treatment of Charcot neuroarthropathy. We also discuss the potential for OPG and RANKL gene variants to act as predictive markers for the development of Charcot neuroarthropathy. Finally, we summarise the latest research on the role of monocyte-to-osteoclast differentiation in the development of acute Charcot neuroarthropathy.

Diabetes and calcification: The potential role of anti-diabetic drugs on vascular calcification regression

Vascular calcification (VC) has been well-established as an independent and strong predictor of cardiovascular diseases (CVD) as well as major cardiac adverse events (MACE). VC is associated with increased mortality in patients with CVD. Pathologically, VC is now believed to be a multi-directional active process ultimately resulting in ectopic calcium deposition in vascular beds. On the other hand, prevalence of diabetes mellitus (DM) is gradually increasing thus making the current population more prone to future CVD. Although the mechanisms involved in development and progression of VC in DM patients are not fully understood, a series of evidences demonstrated positive association between DM and VC. It has been highlighted that different cellular pathways are involved in this process. These intermediates such as tumor necrosis factor alpha (TNF-α), various interleukins (ILs) and different cell-signaling pathways are over-expressed in DM patients leading to development of VC. Thus, considering the burden and significance of VC it is of great importance to find a therapeutic approach to prevent or minimize the development of VC in DM patients. Over the past few years various anti diabetic drugs (ADDs) have been introduced and many of them showed desired glucose control. But no study demonstrated the effects of these medications on regression of VC. In this review, we will briefly discuss the current understanding on DM and VC and how commonly used ADDs modulate the development or progression of VC.

Coupled OPG-Fc on Decellularized Aortic Valves by EDC/NHS Attenuates Rat MSCs Calcification In Vitro

Valve calcification commonly damages natural human heart valves and tissue-engineered heart valves (TEHVs), and no ideal intervention is available in clinical practice. It is increasingly considered that osteoprotegerin (OPG) inhibits vascular calcification. Herein we aimed to explore whether free OPG-Fc fusion protein or coupled OPG-Fc on decellularized aortic valves attenuates calcification. Calcification of rat bone marrow-derived mesenchymal stromal cells (MSCs) was induced by osteogenic differentiation media, and the effects of free OPG-Fc or OPG-Fc coupled on the decellularized porcine aortic heart valve leaflet scaffolds by coupling agents 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC)/N-hydroxysuccinimide (NHS) on calcification were observed. Mineralization of the extracellular matrix, alkaline phosphatase (ALP) activity, and expression of osteoblastic markers were assessed to determine the calcification kinetics. Our results indicated that the matrix calcium content and the ALP activity, as well as the mRNA expression levels of a bone morphogenetic protein-2 (BMP-2), osteopontin (OPN), and osteocalcin (OC), of the MSCs seeded on plates with free OPG-Fc or on the OPG-Fc-coupled scaffolds decreased compared with their control MSCs without coupled OPG-Fc. The results suggest that both free and immobilized OPG-Fc on the decellularized aortic valve scaffolds by EDC/NHS can attenuate the calcification of MSCs induced by osteogenic differentiation media, implying that OPG-Fc might be a new treatment or prevention strategy for the calcification of natural human heart valves and TEHVs in the future.

New Concepts in the Management of Charcot Neuroarthropathy in Diabetes

Charcot Neuroarthropathy (CN) is an uncommon, debilitating and often underdiagnosed complication of chronic diabetes mellitus though, it can also occur in other medical conditions resulting from nerve injury. Till date, the etiology of CN remains unknown, but enhanced osteoclastogenesis is believed to play a central role in the pathogenesis of CN, in the presence of neuropathy. CN compromises the overall health and quality of life. Delayed diagnosis can result in a severe deformity that can act as a gateway to ulceration, infection and in the worst case, can lead to limb loss. In an early stage of CN, immobilization with offloading plays a key role to a successful treatment. Medical therapies seem to have limited role in the treatment of CN.In case of severe deformity, proper footwear or bracing may help prevent further deterioration and development of an ulcer. In individuals with a concomitant ulcer with osteomyelitis, soft tissue infection and severe deformity, where conservative measures fall short, surgical intervention becomes the only choice of treatment. Early diagnosis and proper management at an early stage can help prevent the occurrence of CN and amputation.

Low bone mass is associated with carotid calcification plaque in Chinese postmenopausal women: the Chongqing osteoporosis study

Background: The aim of this study was to examine the relationship between low bone mass and the risk of carotid calcification plaques in Chinese postmenopausal women.Methods: We conducted a 5 years prospective study. Bone mineral density (BMD) was measured by dual-energy X-ray absorptiometry (DXA) scanning. Carotid computed tomography angiography (CTA) was conducted using a 64-multidetector row scanner to assess carotid arterial plaque at baseline and during follow-up. Cox proportional hazards analysis was used to evaluate the association of BMD and risk of carotid calcification plaques.Results: Four hundred and eighty-eight women sustained prospective carotid plaques during the follow-up. Women with carotid calcification plaques had low BMD than those with carotid non-calcification plaques. After adjustment for potential confounders, BMD, age, years since menopause, levels of plasma osteoprotegerin and adiponectin, hypertension, diabetes mellitus and hyperlipidemia were independently associated with increased risk of carotid calcification plaques. For carotid calcification plaques, a significant inverse correlation was indicated between BMD and the plaques, and a significant positive correlation was indicated between bone loss and plaques.Conclusions: This study suggested that lower BMD and increased loss rate of BMD were associated with a higher risk of carotid calcification plaques in Chinese postmenopausal women.

Charcot Neuroarthropathy Advances: Understanding Pathogenesis and Medical and Surgical Management

Understanding new theories of the epidemiology of Charcot neuroarthropathy is practice changing. Treatment of Charcot neuroarthropathy is evolving from a passive approach to one that sees the urgency of proactive, early recognition, thereby avoiding the cascading events that lead to the complex, limb-threatening deformities. Preventive medicine is the most efficient at avoiding severe deformity, with prolonged offloading and immobilization as the current mainstay of treatment. However, with recent advancements in medical and surgical modalities, this may become the treatment of the past as clinicians begin to favor medical management and early surgical intervention.

Ginsenoside Rb1 ameliorates CKD-associated vascular calcification by inhibiting the Wnt/β-catenin pathway

Vascular calcification (VC) is a pathological process underpinning major cardiovascular conditions and has attracted public attention due to its high morbidity and mortality. Chronic kidney disease (CKD) is a common disease related to VC. Ginsenoside Rb1 (Rb1) has been reported to protect the cardiovascular system against vascular diseases, yet its role in VC and the underlying mechanisms remain unclear. In this study, we established a CKD‐associated VC rat model and a β‐glycerophosphate (β‐GP)‐induced vascular smooth muscle cell (VSMC) calcification model to investigate the effects of Rb1 on VC. Our results demonstrated that Rb1 ameliorated calcium deposition and VSMC osteogenic transdifferentiation both in vivo and in vitro. Rb1 treatment inhibited the Wnt/β‐catenin pathway by activating peroxisome proliferator‐activated receptor‐γ (PPAR‐γ), and confocal microscopy was used to show that Rb1 inhibited β‐catenin nuclear translocation in VSMCs. Furthermore, SKL2001, an agonist of the Wnt/β‐catenin pathway, compromised the vascular protective effect of Rb1. GW9662, a PPAR‐γ antagonist, reversed Rb1's inhibitory effect on β‐catenin. These results indicate that Rb1 exerted anticalcific properties through PPAR‐γ/Wnt/β‐catenin axis, which provides new insights into the potential theraputics of VC.

RANKL Gene Polymorphism as a Potential Biomarker to Identify Acute Charcot Foot Among Indian Population With Type 2 Diabetes: A Preliminary Report

Studies addressing the link between gene polymorphism and Charcot neuropathic osteoarthopathy (CN) have been limited to analyse osteoprotegerin gene. Aim is to understand the association of RANKL gene variants on the susceptibility of diabetic neuropathy and CN and to measure the serum levels of sRANKL among Indian population with type 2 diabetes. 77 subjects (48 males: 29 females) were recruited and divided into 3 groups. Group 1 Control: normal glucose tolerance (NGT). Group 2: Type 2 diabetes mellitus and neuropathy (DPN). Group 3: Established type 2 diabetes mellitus, DPN, and CN. Subjects were genotyped for RANKL SNP 693 C/G and 643 C/T using polymerase chain reaction-restriction fragment length polymorphism. sRANKL levels were measured using ELISA (enzyme-linked immunosorbent assay). The serum levels of sRANKL were significantly different between the 3 groups. In RANKL -643 C/T the frequency of “CT” genotype and the minor allele “T” was greater among the DPN and CN group compared with the NGT. Further statistical analysis found a significant difference in genotypic frequencies between DPN and NGT subjects with CT genotype. In RANK L -693 C/G the frequency of homozygote mutant “GG” and the minor allele “G” was greater among the DPN and CN group compared with the NGT. Significant differences in genomic frequencies were observed among “GG” genotype. RANKL -643 C/T was significantly associated with DPN alone while -693 C/G was significantly associated with both DPN and CN. Thus, the study suggests RANKL polymorphism might be considered as an independent risk factor for the development of CN.

Effect of Bushen Huoxue decoction on inhibiting osteogenic differentiation of vascular smooth cells by regulating OPG/RANK/RANKL system in vascular calcification

BACKGROUND

To investigate the effects of Bushen Huoxue Decoction (BSHXD) and its underlying molecular mechanisms on inhibiting osteogenic differentiation of vascular smooth muscle cells (VSMCs) in vascular calcification via regulating the mRNA expression of osteoprotegerin (OPG) and the receptor activator of the nuclear factor-kappa B ligand (RANKL).

METHODS

VSMCs from the aortas of rats were cultured in vitro. Osteogenic differentiation of VSMCs was induced by high levels of an inorganic phosphate medium (2.4 mM). BSHXD-containing serum was prepared using the serum-pharmacological method. VSMCs were plated using 6-well plates at an approximate density of 4.0×104 cells/mL and cultured for 10 days. This was followed by the application of different concentrations of BSHXD-containing serum. The percentage of concentrations of BSHXD-containing serum in high, middle and low dosage group was 20%, 10% and 5%, respectively. Calcium nodules were evaluated by alizarin red S staining, and alkaline phosphatase (ALP) activity and calcium deposition were both examined as per the instruction of the test kits on the 3rd, 6th, and 10th days. Protein expression level of ALP and α-smooth muscle actin (α-SMA) were detected by Western blot on the 3rd, 6th, and 10th days. The mRNA expression of the OPG and RANKL were also detected by real-time PCR on the 3rd, 6th, and 10th days.

RESULTS

Compared with the control group, BSHXD significantly attenuated the calcium nodules that were examined by alizarin red-S staining. Protein expression levels of α-SMA were up-regulated and ALP were down-regulated on the BSHXD group (P<0.05). BSHXD also attenuated the ALP activity and calcium deposition of the VSMCs (P<0.05). These changes were associated with the effect of BSHXD on up-regulating the expression of OPG mRNA and down-regulating the expression of RANKL mRNA in the process of osteogenic differentiation of VSMCs.

CONCLUSIONS

BSHXD has a beneficial effect on inhibiting osteogenic differentiation of VSMCs induced by high levels of phosphate. The underlying mechanism appears to be related to the modulation of expressions of OPG mRNA and RANKL mRNA in the VSMCs, thereby preventing the phenotypic changes of VSMCs to an osteogenic phenotype.

Charcot Pathogenesis: A Study of In Vivo Gene Expression

Charcot neuroarthropathy is a rare but often difficult to manage disease in the neuropathic patient. Early signs such as unremarkable edema, marginal trauma, or minor infection can activate a cascade of bony destruction and lead to gross prominence or deformity, with dire consequences. The exact molecular mechanism is poorly understood. Current theory states that an inflammatory reaction leads to the activation of osteoclasts mediated by specific cytokines. Our study sought to test the genetic expression of certain biomarkers in diabetic patients with and without Charcot neuroarthropathy compared with patients with and without diabetes or neuropathy. A total of 30 patients participated in the study, 17 (57%) males and 13 (43%) females. Peripheral blood samples were drawn, and gene expression was measured using real-time polymerase chain reaction. The expression levels of receptor activator of nuclear factor kappa-B ligand and osteoprotegerin showed no significant increase in the Charcot neuroarthropathy group compared with the healthy control group. We determined that the levels of receptor activator of nuclear factor kappa-B ligand and osteoprotegerin were not significantly increased in Charcot neuroarthropathy patients compared with healthy control patients. These results demonstrate a need for further investigation into alternative molecular pathways to determine the exact mechanism of the disease process.

Suppression of SIRT1 in Diabetic Conditions Induces Osteogenic Differentiation of Human Vascular Smooth Muscle Cells via RUNX2 Signalling

Vascular calcification is associated with significant morbidity and mortality within diabetes, involving activation of osteogenic regulators and transcription factors. Recent evidence demonstrates the beneficial role of Sirtuin 1 (SIRT1), an NAD⁺ dependant deacetylase, in improved insulin sensitivity and glucose homeostasis, linking hyperglycaemia and SIRT1 downregulation. This study aimed to determine the role of SIRT1 in vascular smooth muscle cell (vSMC) calcification within the diabetic environment. An 80% reduction in SIRT1 levels was observed in patients with diabetes, both in serum and the arterial smooth muscle layer, whilst both RUNX2 and Osteocalcin levels were elevated. Human vSMCs exposed to hyperglycaemic conditions in vitro demonstrated enhanced calcification, which was positively associated with the induction of cellular senescence, verified by senescence-associated β-galactosidase activity and cell cycle markers p16 and p21. Activation of SIRT1 by SRT1720 reduced Alizarin red staining by a third, via inhibition of the RUNX2 pathway and prevention of senescence. Conversely, inhibition of SIRT1 via Sirtinol and siRNA increased RUNX2 by over 50%. These findings demonstrate the key role that SIRT1 plays in preventing calcification in a diabetic environment, through the inhibition of RUNX2 and senescence pathways, suggesting a downregulation of SIRT1 may be responsible for perpetuating vascular calcification in diabetes.

Endogenous Calcification Inhibitors in the Prevention of Vascular Calcification: A Consensus Statement From the COST Action EuroSoftCalcNet

The physicochemical deposition of calcium-phosphate in the arterial wall is prevented by calcification inhibitors. Studies in cohorts of patients with rare genetic diseases have shed light on the consequences of loss-of-function mutations for different calcification inhibitors, and genetic targeting of these pathways in mice have generated a clearer picture on the mechanisms involved. For example, generalized arterial calcification of infancy (GACI) is caused by mutations in the enzyme ecto-nucleotide pyrophosphatase/phosphodiesterase-1 (eNPP1), preventing the hydrolysis of ATP into pyrophosphate (PP_i). The importance of PP_i for inhibiting arterial calcification has been reinforced by the protective effects of PP_i in various mouse models displaying ectopic calcifications. Besides PP_i, Matrix Gla Protein (MGP) has been shown to be another potent calcification inhibitor as Keutel patients carrying a mutation in the encoding gene or Mgp-deficient mice develop spontaneous calcification of the arterial media. Whereas PP_i and MGP represent locally produced calcification inhibitors, also systemic factors contribute to protection against arterial calcification. One such example is Fetuin-A, which is mainly produced in the liver and which forms calciprotein particles (CPPs), inhibiting growth of calcium-phosphate crystals in the blood and thereby preventing their soft tissue deposition. Other calcification inhibitors with potential importance for arterial calcification include osteoprotegerin, osteopontin, and klotho. The aim of the present review is to outline the latest insights into how different calcification inhibitors prevent arterial calcification both under physiological conditions and in the case of disturbed calcium-phosphate balance, and to provide a consensus statement on their potential therapeutic role for arterial calcification.

Charcot Neuroarthropathy: From the Laboratory to the Bedside

BACKGROUND

The diabetic Charcot foot syndrome is a serious and potentially limbthreatening lower-extremity complication of diabetes.

INTRODUCTION

The present review provides a concise account of the advances made over the last twentyfive years in understanding the pathogenesis and management of Charcot neuroarthropathy (CN).

METHODS

In this study, the widely known pathogenetic mechanisms underpinning CN are brought into focus, particularly the role of RANKL/RANK/OPG system and advanced glycation end production in the pathogenesis of CN. Furthermore, other potential triggering factors, namely nitric oxide, endothelial dysfunction, macro calcifications and body weight that influence CN have also been discussed.

RESULTS

The wide range of diagnostic tools available to clinicians for accurate staging of this pathology has been examined, particularly radiological and nuclear medicine imaging. Additionally, the difficult differential diagnosis between osteomyelitis and CN is also elucidated.

CONCLUSION

The review concludes with the comprehensive summary of the major promising therapeutic strategies, including conservative treatment involving orthopedic devices, pharmacological approach, and the most common surgical techniques currently employed in the diagnosis and treatment of this acute disease.

Circulating osteogenic proteins are associated with coronary artery calcification and increase after myocardial infarction

BACKGROUND

Coronary artery calcification (CAC) and atherosclerotic inflammation associate with increased risk of myocardial infarction (MI). Vascular calcification is regulated by osteogenic proteins (OPs). It is unknown whether an association exists between CAC and plasma OPs and if they are affected by atherothrombotic inflammation. We tested the association of osteogenic and inflammatory proteins with CAC and assessed these biomarkers after MI.

METHODS

Circulating OPs (osteoprotegerin, RANKL, fetuin-A, Matrix Gla protein [MGP]) and inflammatory proteins (C-reactive protein, oxidized-LDL, tumoral necrosis factor-α, transforming growth factor [TGF]-β1) were compared between stable patients with CAC (CAC ≥ 100 AU, n = 100) and controls (CAC = 0 AU, n = 30). The association between biomarkers and CAC was tested by multivariate analysis. In patients with MI (n = 40), biomarkers were compared between acute phase and 1-2 months post-MI, using controls as a baseline.

RESULTS

MGP and fetuin-A levels were higher within individuals with CAC. Higher levels of MGP and RANKL were associated with CAC (OR 3.12 [95% CI 1.20-8.11], p = 0.02; and OR 1.75 [95% CI 1.04-2.94] respectively, p = 0.035). After MI, C-reactive protein, OPG and oxidized-LDL levels increased in the acute phase, whereas MGP and TGF-β1 increased 1-2 months post-MI.

CONCLUSIONS

Higher MGP and RANKL levels associate with CAC. These findings highlight the potential role of these proteins as modulators and markers of CAC. In addition, the post-MI increase in OPG and MGP, as well as of inflammatory proteins suggest that the regulation of these OPs is affected by atherothrombotic inflammation.

Updates on Diabetic Foot and Charcot Osteopathic Arthropathy

PURPOSE OF REVIEW

Diabetes mellitus affects approximately 30.8 million people currently living in the USA. Chronic diabetes complications, including diabetic foot complications, remain prevalent and challenging to treat. We review clinical diagnosis and challenges providers may encounter when managing diabetic foot ulcers and Charcot neuroarthropathy.

RECENT FINDINGS

Mechanisms controlling these diseases are being elucidated and not fully understood. Offloading is paramount to heal and manage diabetic foot ulcers and Charcot neuroarthropathy. Diabetic foot ulcers recur and the importance of routine surveillance and multidisciplinary approach is essential. Several predictors of failure in Charcot foot include a related diabetic foot ulcer, midfoot or rearfoot location of the Charcot event, and progressive bony changes on interval radiographs. Patients with diabetic foot ulcer and/or Charcot neuroarthropathy are in need of consistent and regular special multidisciplinary care. If not diagnosed early and managed effectively, morbidity and mortality significantly increase.

Type 2 diabetes affects bone cells precursors and bone turnover

BACKGROUND

Here we study the effect of type 2 diabetes (T2DM) on bone cell precursors, turnover and cytokines involved in the control of bone cell formation and activity.

METHODS

We enrolled in the study 21 T2DM women and 21 non diabetic controls matched for age and body mass index (BMI). In each subject we measured bone cell precursors, Receptor Activator of Nuclear Factor κB (RANKL), Osteoprotegerin (OPG), Sclerostin (SCL) and Dickoppf-1 (DKK-1) as cytokines involved in the control of osteoblast and osteoclast formation and activity, bone density (BMD) and quality trough trabecular bone score (TBS) and bone turnover. T2DM patients and controls were compared for the analyzed variables by one way ANOVA for Gaussian ones and by Mann-Whitney or Kruskal-Wallis test for non-Gaussian variables.

RESULTS

RANKL was decreased and DKK-1 increased in T2DM. Accordingly, patients with T2DM have lower bone turnover compared to controls. BMD and TBS were not significantly different from healthy controls. Bone precursor cells were more immature in T2DM. However the number of osteoclast precursors was increased and that of osteoblasts decreased.

CONCLUSIONS

Patients with T2DM have more immature bone cells precursors, with increased number of osteoclasts and decreased osteoblasts, confirming low bone turnover and reduced cytokines such as RANKL and DKK-1. BMD and TBS are not significantly altered in T2DM although, in contrast with other studies, this may be due to the match of patients and controls for BMI rather than age.

Role of bisphosphonates in the management of acute Charcot foot

Diabetes mellitus is the most common cause of Charcot neuropathy affecting foot and ankle. Acute Charcot foot (CF) presents with a red and swollen foot in contrast to the painless deformed one of chronic CF. Enhanced osteoclastogenesis plays a central role in the pathogenesis of acute CF. Many studies have shown elevated levels of bone turnover markers in patients with acute CF confirming it. These findings have led clinicians to use anti-resorptive agents [bisphosphonates (BP), calcitonin, and denosumab] along with immobilization and offloading in acute CF patients. The maximum evidence among all anti-resorptive agents is available for BPs, although its quality is low. Pamidronate has been shown to reduce the markers of activity of CF like raised skin temperature, pain, edema, and bone turnover markers in the majority of studies. Intravenous BPs are known to cause acute phase reactions leading to flu-like illness following their first infusion, which can be ameliorated by oral acetaminophen. Alendronate is the only oral BP used in these patients. It needs to be taken on an empty stomach with a full glass of water to avoid esophagitis. The side-effects and contraindications to BPs should be kept in mind while treating acute CF patients with them.

Strontium ranelate inhibits wear particle-induced aseptic loosening in mice

The imbalance between bone formation and osteolysis plays a key role in the pathogenesis of aseptic loosening. Strontium ranelate (SR) can promote bone formation and inhibit osteolysis. The aim of this study was to explore the role and mechanism of SR in aseptic loosening induced by wear particles. Twenty wild-type (WT) female C57BL/6j mice and 20 sclerostin-/- female C57BL/6j mice were used in this study. Mice were randomly divided into four groups: WT control group, WT SR group, knockout (KO) control group, and KO SR group. We found that SR enhanced the secretion of osteocalcin (0.72±0.007 in WT control group, 0.98±0.010 in WT SR group, P=0.000), Runx2 (0.34±0.005 in WT control group, 0.47±0.010 in WT SR group, P=0.000), β-catenin (1.04±0.05 in WT control group, 1.22±0.02 in WT SR group, P=0.000), and osteoprotegerin (OPG) (0.59±0.03 in WT control group, 0.90±0.02 in WT SR group, P=0.000). SR significantly decreased the level of receptor activator for nuclear factor-κB ligand (RANKL) (1.78±0.08 in WT control group, 1.37±0.06 in WT SR group, P=0.000) and improved the protein ratio of OPG/RANKL, but these effects were not observed in sclerostin-/- mice. Our findings demonstrated that SR enhanced bone formation and inhibited bone resorption in a wear particle-mediated osteolysis model in wild-type mice, and this effect relied mainly on the down-regulation of sclerostin levels to ameliorate the inhibition of the canonical Wnt pathway.

A review of bone metabolism and developments in medical treatment of the diabetic Charcot foot

Charcot foot is a rare but severe, and possibly limb-threatening, complication to neuropathy and diabetes mellitus. The current treatment consists of long-term off-loading, and has a large negative impact on the patient's life. Much research has gone into understanding the condition and its biochemical mechanisms, however, the underlying pathogenesis of a Charcot foot is not yet fully understood. In the recent decades several key advances in our understanding of the Charcot foot have been made, both in regards to the changes in bone metabolism and structure an acute Charcot foot can cause, and to the molecular pathways involved in this. This review summerizes the available research into the bone metabolism around a Charcot foot, with an emphasis on the biochemical profile. The existing data regarding attempts at medical treatment is also reviewed, including novel trials targetting specific inflammatory pathways upregulated in the acute diabetic Charcot foot.

Neuroarthropathy in diabetes: pathogenesis of Charcot arthropathy

Charcot neuroarthropathy is a rare but serious complication of diabetes, causing progressive destruction of the bones and joints of the foot leading to deformity, altered biomechanics and an increased risk of ulceration.

Management is complicated by a lack of consensus on diagnostic criteria and an incomplete understanding of the pathogenesis. In this review, we consider recent insights into the development of Charcot neuroarthropathy.

It is likely to be dependent on several interrelated factors which may include a genetic pre-disposition in combination with diabetic neuropathy. This leads to decreased neuropeptides (nitric oxide and calcitonin gene-related peptide), which may affect the normal coupling of bone formation and resorption, and increased levels of Receptor activator of nuclear factor kappa-B ligand, potentiating osteoclastogenesis.

Repetitive unrecognized trauma due to neuropathy increases levels of pro-inflammatory cytokines (interleukin-1β, interleukin-6, tumour necrosis factor α) which could also contribute to increased bone resorption, in combination with a pre-inflammatory state, with increased autoimmune reactivity and a profile of monocytes primed to transform into osteoclasts - cluster of differentiation 14 (CD14).

Increased blood glucose and loss of circulating Receptor for Advanced Glycation End-Products (AGLEPs), leading to increased non-enzymatic glycation of collagen and accumulation of AGLEPs in the tissues of the foot, may also contribute to the pathological process.

An understanding of the relative contributions of each of these mechanisms and a final common pathway for the development of Charcot neuroarthropathy are still lacking.

Cite this article: S. E. Johnson-Lynn, A. W. McCaskie, A. P. Coll, A. H. N. Robinson. Neuroarthropathy in diabetes: pathogenesis of Charcot arthropathy. Bone Joint Res 2018;7:373–378. DOI: 10.1302/2046-3758.75.BJR-2017-0334.R1.

The role of OPG/RANKL in the pathogenesis of diabetic cardiovascular disease

Cardiovascular (CV) disease is the leading cause of mortality in patients with type 2 diabetes mellitus. A major factor in the pathogenesis of CV disease is vascular calcification (VC), which is accelerated in type 2 diabetes mellitus. Calcification of the vessel wall contributes to vascular stiffness and left ventricular hypertrophy whereas intimal calcification may predispose to plaque rupture and CV death. The pathogenesis of VC is complex but appears to be regulated by the osteoprotegerin (OPG)/receptor activator of nuclear factor-κB ligand (RANKL) signaling pathway, which is involved in bone remodeling. Within the bone, OPG prevents RANKL from binding to receptor activator of nuclear factor-κB and inhibiting bone resorption. Outside of the bone, the clinical significance of OPG blocking RANKL is not well understood, but OPG knockout mice that lack OPG develop early and severe VC. This minireview outlines some of the research on OPG/RANKL in the pathogenesis of VC and discusses potential therapies, which may reduce VC and CV burden in humans.

Regulation of Vascular Calcification by Growth Hormone-Releasing Hormone and Its Agonists

RATIONALE

Vascular calcification (VC) is a marker of the severity of atherosclerotic disease. Hormones play important roles in regulating calcification; estrogen and parathyroid hormones exert opposing effects, the former alleviating VC and the latter exacerbating it. To date no treatment strategies have been developed to regulate clinical VC.

OBJECTIVE

The objective of this study was to investigate the effect of growth hormone-releasing hormone (GHRH) and its agonist (GHRH-A) on the blocking of VC in a mouse model.

METHODS AND RESULTS

Young adult osteoprotegerin-deficient mice were given daily subcutaneous injections of GHRH-A (MR409) for 4 weeks. Significant reductions in calcification of the aortas of MR409-treated mice were paralleled by markedly lower alkaline phosphatase activity and a dramatic reduction in the expression of transcription factors, including the osteogenic marker gene Runx2 and its downstream factors, osteonectin and osteocalcin. The mechanism of action of GHRH-A was dissected in smooth muscle cells isolated from human and mouse aortas. Calcification of smooth muscle cells induced by osteogenic medium was inhibited in the presence of GHRH or MR409, as evidenced by reduced alkaline phosphatase activity and Runx2 expression. Inhibition of calcification by MR409 was partially reversed by MIA602, a GHRH antagonist, or a GHRH receptor-selective small interfering RNA. Treatment with MR409 induced elevated cytosolic cAMP and its target, protein kinase A which in turn blocked nicotinamide adenine dinucleotide phosphate oxidase activity and reduced production of reactive oxygen species, thus blocking the phosphorylation of nuclear factor κB (p65), a key intermediate in the ligand of receptor activator for nuclear factor-κ B-Runx2/alkaline phosphatase osteogenesis program. A protein kinase A-selective small interfering RNA or the chemical inhibitor H89 abolished these beneficial effects of MR409.

CONCLUSIONS

GHRH-A controls osteogenesis in smooth muscle cells by targeting cross talk between protein kinase A and nuclear factor κB (p65) and through the suppression of reactive oxygen species production that induces the Runx2 gene and alkaline phosphatase. Inflammation-mediated osteogenesis is thereby blocked. GHRH-A may represent a new pharmacological strategy to regulate VC.

Bone mineral density and markers of bone turnover and inflammation in diabetes patients with or without a Charcot foot: An 8.5-year prospective case-control study

BACKGROUND AND AIMS

Charcot foot is a rare but severe complication to diabetes and peripheral neuropathy. It is still unclear if an acute Charcot foot has long-term effects on the bone metabolism. To investigate this, we conducted a follow-up study to examine if a previously acute Charcot foot has any long-term effects on bone mineral density (BMD) or local or systemic bone metabolism.

METHODS

An 8.5-year follow-up case-control study of 44 individuals with diabetes mellitus, 24 of whom also had acute or chronic Charcot foot at the baseline visit in 2005-2007, who were followed up in 2015 with DXA scans and blood samples.

RESULTS

21 of the 44 baseline participants participated in the follow-up. There were no difference in the change in total hip BMD from baseline to follow-up in either the Charcot or the control group (p = 0.402 and 0.517), and no increased risk of osteoporosis in the previous Charcot feet either. From baseline to follow-up, there was a significant difference in the change in levels of fsRANK-L in the Charcot group, but not in the control group (p = 0.002 and 0.232, respectively). At follow-up, there were no differences in fsRANK-L between the groups. The fsRANK-L/OPG ratio also significantly decreased from baseline to follow-up in the Charcot group (3.4 versus 0.5) (p = 0.009), but not in the control group (1.3 versus 1.1) (p = 0.302).

CONCLUSION

We found that diabetes patients with an acute Charcot foot have an elevated fsRANK-L/OPG ratio, and that the level decreased from baseline to follow-up to be comparable to the level in diabetes patients without previous or current Charcot foot. We found no permanent effect of an acute Charcot foot on hip or foot BMD.

Markers of Local Inflammation and Bone Resorption in the Acute Diabetic Charcot Foot

OBJECTIVE

Due to the localized nature of Charcot foot, systemically altered levels of inflammation markers can be difficult to measure. The aim of this study was to investigate whether it is possible to detect an arteriovenous (A-V) flux in any locally produced inflammatory biomarkers from an acute Charcot foot by comparing local and systemic measurements.

METHODS

We included patients with acute diabetic Charcot foot. Blood was sampled from the vena saphena magna on the distal part of the crus bilaterally as well as from the arteria radialis. To minimize the A-V shunting effect, the feet were externally cooled with ice water prior to resampling.

RESULTS

Both before and after cooling, the A-V flux of interleukin-6 (IL-6) between the Charcot feet and the arterial level was significantly higher than the flux between the healthy feet and the arterial level (Δvalue_before: 7.25 versus 0.41 pg/mL, resp., p = 0.008; Δvalue_after: 10.04 versus 1.68 pg/mL, resp., p = 0.032). There were no differences in the fluxes for other markers of inflammation.

CONCLUSION

We have found an increased A-V flux of IL-6 in the acute diabetic Charcot foot compared to the healthy foot in the same patients.

Strontium ranelate reduces the progression of titanium particle-induced osteolysis by increasing the ratio of osteoprotegerin to receptor activator of nuclear factor-κB ligand in vivo

The present study aimed to investigate the effects of strontium ranelate (SR), an anti‑osteoporotic drug, on osteolysis in an experimental mouse model of aseptic loosening. A total of 45 female C57BL/6J mice each received implantation of one titanium alloy pin into the tibia, followed by intraarticular injection of titanium particles. One week following surgery, mice were randomly divided into three groups: Control group (no additional treatment), SR625 group (treated with SR at a dose of 625 mg/kg/day), and SR1800 group (treated with SR at a dose of 1,800 mg/kg/day). SR was administered via oral gavage once every day for 12 weeks. Micro‑computed tomography scanning and hematoxylin/eosin staining were used to assess osteolysis around the prosthesis. Immunohistochemistry and reverse transcription-quantitative polymerase chain reaction analysis were used to measure the expression of receptor activator of nuclear factor‑κB ligand (RANKL) and osteoprotegerin (OPG). Compared with the control, the SR625 and SR1800 groups exhibited a significantly increased pulling force of the titanium alloy pin. Bone volume and the bone surface/volume ratio in the periprosthetic tissue were significantly increased in the SR‑treated groups. Significant differences were observed between the SR1800 group and control group with respect to trabecular thickness and trabecular number. Mechanistically, SR downregulated the expression of RANKL and upregulated the expression of OPG in the periprosthetic tissue. In addition, SR was observed to inhibit wear particle‑associated osteolysis in a dose‑dependent manner. In conclusion, the present data illustrated that SR inhibited titanium particle‑induced osteolysis in vivo.