Enzyme-generated fragments of tau have been linked to neuronal death and may serve as serum biomarkers of cognitive loss. Two competitive ELISAs detecting an ADAM10-generated fragment (Tau-A) or a caspase-3-generated fragment (Tau-C) were measured in baseline serum samples from patients with mild to moderate Alzheimer's disease (AD) from a Phase III clinical trial, and correlated to change in the Alzheimer's Disease Assessment Scale-Cognitive subscale (ADAS-Cog11) and Clinical Dementia Rating-Sum of Boxes (CDR-SB) over a 64-week period using an MMRM-analysis. Relationship between the biomarkers and changes in ADAS-Cog11 score as a function of time were observed for Tau-C and change in ADAS-Cog11 (p = 0.06), and for Tau-A and change in CDR-SB (p = 0.04). The correlation of Tau-A/Tau-C ratio with cognitive change assessed by ADAS-Cog11 was even more significant (p < 0.006). These data indicate that measuring the balance between tau fragments in serum may provide a marker of the rate of progression of AD and warrant studies in larger cohorts.
Alzheimer's disease is the public health crisis of the 21st century. There is a clear need for a widely available, inexpensive and reliable method to diagnosis Alzheimer's disease in the earliest stages, track disease progression, and accelerate clinical development of new therapeutics. One avenue of research being explored is blood based biomarkers. In April 2012, the Alzheimer's Association and the Alzheimer's Drug Discovery Foundation convened top scientists from around the world to discuss the state of blood based biomarker development. This manuscript summarizes the meeting and the resultant discussion, including potential next steps to move this area of research forward.
Treatment of Alzheimer's disease (AD) is significantly hampered by the lack of easily accessible biomarkers that can detect disease presence and predict disease risk reliably. Fluid biomarkers of AD currently provide indications of disease stage; however, they are not robust predictors of disease progression or treatment response, and most are measured in cerebrospinal fluid, which limits their applicability. With these aspects in mind, the aim of this article is to underscore the concerted efforts of the Blood-Based Biomarker Interest Group, an international working group of experts in the field. The points addressed include: (1) the major challenges in the development of blood-based biomarkers of AD, including patient heterogeneity, inclusion of the "right" control population, and the blood-brain barrier; (2) the need for a clear definition of the purpose of the individual markers (e.g., prognostic, diagnostic, or monitoring therapeutic efficacy); (3) a critical evaluation of the ongoing biomarker approaches; and (4) highlighting the need for standardization of preanalytical variables and analytical methodologies used by the field.
The present study investigated a novel oral dual amylin and calcitonin receptor agonist (DACRA), KBP-042, in head-to-head comparison with salmon calcitonin (sCT) with regard to in vitro receptor pharmacology, ex vivo pancreatic islet studies, and in vivo proof of concept studies in diet-induced obese (DIO) and Zucker diabetic fatty (ZDF) rats. In vitro, KBP-042 demonstrated superior binding affinity and activation of amylin and calcitonin receptors, and ex vivo, KBP-042 exerted inhibitory action on stimulated insulin and glucagon release from isolated islets. In vivo, KBP-042 induced a superior and pronounced reduction in food intake in conjunction with a sustained pair-fed corrected weight loss in DIO rats. Concomitantly, KBP-042 improved glucose homeostasis and reduced hyperinsulinemia and hyperleptinemia in conjunction with enhanced insulin sensitivity. In ZDF rats, KBP-042 induced a superior attenuation of diabetic hyperglycemia and alleviated impaired glucose and insulin tolerance. Concomitantly, KBP-042 preserved insulinotropic and induced glucagonostatic action, ultimately preserving pancreatic insulin and glucagon content. In conclusion, oral KBP-042 is a novel DACRA, which exerts antiobesity and antidiabetic efficacy by dual modulation of insulin sensitivity and directly decelerating stress on the pancreatic ?- and ?-cells. These results could provide the basis for oral KBP-042 as a novel therapeutic agent in type 2 diabetes.
Matrix metalloproteinase-3 (MMP-3) plays an important role in the pathology of rheumatoid arthritis (RA) and ankylosing spondylitis (AS). Measurement of active MMP-3 in clinical samples could provide information about progression of rheumatoid diseases, and potentially response to treatment. Hence, we aimed to develop a sensitive assay specifically measuring the active form of MMP-3 (act-MMP-3) both in ex vivo models and in human sera.
The lack of readily available biomarkers is a significant hindrance toward progressing to effective therapeutic and preventative strategies for Alzheimer's disease (AD). Blood-based biomarkers have potential to overcome access and cost barriers and greatly facilitate advanced neuroimaging and cerebrospinal fluid biomarker approaches. Despite the fact that preanalytical processing is the largest source of variability in laboratory testing, there are no currently available standardized preanalytical guidelines. The current international working group provides the initial starting point for such guidelines for standardized operating procedures (SOPs). It is anticipated that these guidelines will be updated as additional research findings become available. The statement provides (1) a synopsis of selected preanalytical methods utilized in many international AD cohort studies, (2) initial draft guidelines/SOPs for preanalytical methods, and (3) a list of required methodological information and protocols to be made available for publications in the field to foster cross-validation across cohorts and laboratories.
We previously reported that oral delivery of salmon calcitonin (sCT) improved energy and glucose homeostasis and attenuated diabetic progression in animal models of diet-induced obesity (DIO) and type 2 diabetes, although the glucoregulatory mode of action was not fully elucidated. In the present study we hypothesized that oral sCT as pharmacological intervention 1) exerted anti-hyperglycemic efficacy, and 2) enhanced insulin action in DIO-streptozotocin (DIO-STZ) diabetic rats. Diabetic hyperglycemia was induced in male selectively bred DIO rats by a single low dose (30mg/kg) injection of STZ. Oral sCT by gavage was delivered as once-daily administration with lead-in (2mg/kg) and maintenance (0.5mg/kg) dose of oral sCT for a total of 21 days. Food intake, body weight, blood glucose, HbA1c, glucose and insulin tolerance test, and parameters of insulin sensitivity were investigated. Plasma glucoregulatory hormones and pancreatic insulin content were analyzed. Oral sCT treatment induced a pronounced anorectic action during the 7 days lead-in period and markedly reduced food intake and body weight in conjunction with improved glucose homeostasis. During the maintenance period, oral sCT normalized food intake and attenuated weight loss, albeit sustained glycemic control by reducing fasting blood glucose and HbA1c levels compared to those of vehicle-treated rats at the end of study. Notably, plasma levels of insulin, glucagon, leptin and adiponectin were unaltered, albeit insulin action was enhanced in conjunction with protection of pancreatic insulin content. The results of the present study indicate that oral sCT exerts a novel insulin-sensitizing effect to improve glucose metabolism in obesity and type 2 diabetes.
Osteopetrosis due to lack of acid secretion by osteoclasts is characterized by abolished bone resorption, increased osteoclast numbers, but normal or even increased bone formation. In contrast, osteoclast-poor osteopetrosis appears to have less osteoblasts and reduced bone formation, indicating that osteoclasts are important for regulating osteoblast activity. To illuminate the role of the osteoclast in controlling bone remodeling, we transplanted irradiated skeletally mature 3-month old wild-type mice with hematopoietic stem cells (HSCs) to generate either an osteoclast-rich or osteoclast-poor adult osteopetrosis model. We used fetal liver HSCs from (1) oc/oc mice, (2) RANK KO mice, and (3) compared these to wt control cells. TRAP5b activity, a marker of osteoclast number and size, was increased in the oc/oc recipients, while a significant reduction was seen in the RANK KO recipients. In contrast, the bone resorption marker CTX-I was similarly decreased in both groups. Both oc/oc and Rank KO recipients developed a mild osteopetrotic phenotype. However, the osteoclast-rich oc/oc recipients showed higher trabecular bone volume (40 %), increased bone strength (66 %), and increased bone formation rate (54 %) in trabecular bone, while RANK KO recipients showed only minor trends compared to control recipients. We here show that maintaining non-resorbing osteoclasts, as opposed to reducing the osteoclasts, leads to increased bone formation, bone volume, and ultimately higher bone strength in vivo, which indicates that osteoclasts are sources of anabolic molecules for the osteoblasts.
Salmon calcitonin (sCT) and human calcitonin (hCT) are pharmacologically distinct. However, the reason for the differences is unclear. Here we analyze the differences between sCT and hCT on the human calcitonin receptor (CT(a)R) with respect to activation of cAMP signaling, ?-arrestin recruitment, ligand binding kinetics and internalization. The study was conducted using mammalian cell lines heterologously expressing the human CT(a) receptor. CT(a)R downstream signaling was investigated with dose response profiles for cAMP production and ?-arrestin recruitment for sCT and hCT during short term (<2 hours) and prolonged (up to 72 hours) stimulation. CT(a)R kinetics and internalization was investigated with radio-labeled sCT and hCT ligands on cultured cells and isolated membrane preparations from the same cell line. We found that sCT and hCT are equipotent during short-term stimulations with differences manifesting themselves only during long-term stimulation with sCT inducing a prolonged activation up to 72 hours, while hCT loses activity markedly earlier. The prolonged sCT stimulation of both cAMP accumulation and ?-arrestin recruitment was attenuated, but not abrogated by acid wash, suggesting a role for sCT activated internalized receptors. We have demonstrated a novel phenomenon, namely that two distinct CT(a)R downstream signaling activation patterns are activated by two related ligands, thereby highlighting qualitatively different signaling responses in vitro that could have implications for sCT use in vivo.
The osteoclast is vital for establishment of normal hematopoiesis in the developing animal. However, its role for maintenance of hematopoiesis in adulthood is more controversial. To shed more light on this process, we transplanted hematopoietic stem cells from two osteopetrotic mouse models, with lack of osteoclasts or defective osteoclast function, to normal adult mice and examined the bone phenotype and hematopoiesis in the recipients. B6SJL mice were lethally irradiated and subsequently transplanted with oc/oc, Receptor Activator of Nuclear Factor Kappa B knockout or control fetal liver cells. Osteoclasts derived from the recipient animals were tested in vitro for osteoclastogenesis and resorptive function. Bone remodeling changes were assessed using biomarkers of bone turnover and micro-CT. Hematopoiesis was assessed by flow cytometry and colony formation, and hematopoietic stem cell function by secondary competitive transplantations and cell cycle analysis. After transplantation, a donor chimerism of 97-98% was obtained, and by 15 weeks mild osteopetrosis had developed in recipients of cells from osteopetrotic mice. There were no alterations in the number of bone marrow cells. Colony formation was slightly reduced in Receptor Activator of Nuclear Factor Kappa B knockout recipients but unchanged in oc/oc recipients. Phenotypically, stem cells were marginally reduced in recipients of cells from osteopetrotic mice, but no significant difference was seen in cell cycle status and in competitive secondary transplantations all three groups performed equally well. Our results indicate that osteoclast function is not crucial for hematopoietic stem cell maintenance in adult mice.
Oral salmon calcitonin (sCT) has demonstrated clinical efficacy in treating osteoporosis in postmenopausal women. The postmenopausal state is also associated with obesity-related insulin resistance (IR) and type 2 diabetes. The aim of this study was to investigate the preventive effects of oral sCT on energy and glucose homeostasis in high-fat diet (HFD)- and ovariectomy (OVX)-induced obese rats. Furthermore, the weight-regulatory and gluco-regulatory effects of short-term oral sCT intervention on HFD-induced obese rats were explored.
The degree of inflammation in auto-immune diseases such as rheumatoid arthritis is often assessed in serum and used for diagnostic and prognostic purposes. The serum levels of acute inflammatory signaling molecules (C-reactive protein and serum amyloid A) in conjunction with the important pro-inflammatory cytokines themselves may have limited utility due to several limitations. (1) These traditional biomarkers are associated with substantial variation due to biological not technical issues. (2) The combined burden of cytokines rather than one single player may be responsible for the progression of disease. (3) The cellular and tissue origins of cytokines that are detected systemically are difficult to determine as the cytokines lack tissue specificity. (4) There is substantial redundancy in the signaling potential of cytokines. Despite these major limitations, the total burden of inflammatory signaling molecules and pro-inflammatory cytokines are important in assessing the degree of inflammation in conjunction with a diagnosis of disease. The total burden of signaling ultimately results in protease expression, tissue destruction and disease progression. One of the pivotal events in the downstream inflammatory signaling is the generation of pathological enzymes, which results in the release of small but tissue-specific protein fragments into the serum that may be used as molecular biochemical markers. We discuss the potential of this new class of biochemical markers, which may be viewed as "end products of tissue destruction". These so-called protein fingerprints may also be considered end-products of the convergence cytokine signaling pathways, as they are the final end-result of tissue destruction.
Loss of musculoskeletal mass and function is a natural ageing trait, reinforced by an unhealthy life style. Loss of bone (osteoporosis) and muscle (sarcopaenia) are conditions whose prevalence are increasing because of the change in population distribution in the western world towards an older mean age. Improvements in lifestyle factors, such as diet, smoking and exercise, are the most powerful tools to combat this decline efficiently; however, public health interventions aimed at tackling these problems have shown abysmal success at the population level, mostly due to failure in compliance. With these issues in mind, we believe that the primary prevention modality in coming decades will be pharmacological. We review the basic biology of musculoskeletal ageing and what measures can be taken to prevent ageing-associated loss of musculoskeletal mass and function, with particular emphasis on pharmacological means.
Infantile malignant osteopetrosis (IMO) is a rare, lethal, autosomal recessive disorder characterized by non-functional osteoclasts. More than 50% of the patients have mutations in the TCIRG1 gene, encoding for a subunit of the osteoclast proton pump. The aim of this study was to restore the resorptive function of IMO osteoclasts by lentiviral mediated gene transfer of the TCIRG1 cDNA. CD34(+) cells from peripheral blood of five IMO patients and from normal cord blood were transduced with lentiviral vectors expressing TCIRG1 and GFP under a SFFV promoter, expanded in culture and differentiated on bone slices to mature osteoclasts. qPCR analysis and western blot revealed increased mRNA and protein levels of TCIRG1, comparable to controls. Vector corrected IMO osteoclasts generated increased release of Ca(2+) and bone degradation product CTX-I into the media as well as increased formation of resorption pits in the bone slices, while non-corrected IMO osteoclasts failed to resorb bone. Resorption was approximately 70-80% of that of osteoclasts generated from cord blood. Furthermore, transduced CD34(+) cells successfully engrafted in NSG-mice. In conclusion we provide the first evidence of lentiviral-mediated correction of a human genetic disease affecting the osteoclastic lineage.
Immobilization-induced loss of muscle mass is a complex phenomenon with several parallels to sarcopenic and cachectic muscle loss. Muscle is a large organ with a protein turnover that is orders of magnitude larger than most other tissues. Thus, we hypothesize that muscle loss and regain is reflected by peptide biomarkers derived from type VI collagen processing released in the circulation.
In the bone remodeling process that takes place throughout the skeleton at bone multicellular units, intercellular communication processes are crucial. The osteoblast lineage has long been known to program osteoclast formation and hence resorption, but the preservation of bone mass and integrity requires tight control of remodeling. This needs local controls that ensure availability of mesenchymal precursors and the provision of local signals that promote differentiation through the osteoblast lineage. Some signals can come from growth factors released from resorbed bone matrix, and there is increasing evidence that the osteoclast lineage itself produces factors that can either enhance or inhibit osteoblast differentiation and hence bone formation. A number of such factors have been identified from predominantly in vitro experiments. The coupling of bone formation to resorption is increasingly recognized as a complex, dynamic process that results from the input of many local factors of cell and matrix origin that can either promote or inhibit bone formation.
OBJECTIVE: Oral salmon calcitonin (sCT) has demonstrated clinical efficacy in treating osteoporosis in postmenopausal women. The postmenopausal state is also associated with obesity-related insulin resistance (IR) and type 2 diabetes. The aim of this study was to investigate the preventive effects of oral sCT on energy and glucose homeostasis in high-fat diet (HFD)- and ovariectomy (OVX)-induced obese rats. Furthermore, the weight-regulatory and gluco-regulatory effects of short-term oral sCT intervention on HFD-induced obese rats were explored. METHODS: For prevention, female rats exposed to HFD with or without OVX were treated with oral sCT for 5 weeks. As intervention, HFD-induced obese male rats were treated with oral sCT for 4 days. Body weight, food intake, and plasma glucose, insulin, and leptin levels were measured, and the clinical homeostasis model assessment for insulin resistance (HOMA-IR) index was calculated. In addition, oral glucose tolerance was evaluated in the systemic and portal circulations. RESULTS: For prevention, oral sCT reduced body weight by ?16% to 19% (P < 0.001), reduced plasma insulin and leptin by ?50%, and improved impaired fasting glycemia (P < 0.05) concomitantly with amelioration of IR (HOMA-IR; P < 0.01) in HFD- and OVX-induced obesity. Furthermore, oral sCT significantly reduced the incremental area under the curve for plasma glucose and insulin by ?40% and ?70%, respectively, during glucose tolerance testing. As intervention in HFD-induced obese rats, oral sCT reduced body weight, fasting glycemia, and insulinemia in conjunction with HOMA-IR (P < 0.001). Finally, oral sCT alleviated glucose intolerance predominantly in the portal circulation. CONCLUSIONS: Oral sCT treatment displays weight-regulatory and glucoregulatory efficacy in HFD- and OVX-induced obese rats, indicating the clinical usefulness of oral sCT in postmenopausal obesity-related IR and type 2 diabetes.
The controversy surrounding the results from the Womens Health Initiative (WHI) trials published a decade ago caused a significant decline in the use of menopausal hormone replacement therapy. However, these results have been vehemently contested and several lines of evidence suggest that in perimenopausal and non-obese women, estrogen therapy may indeed be of benefit. There is ample proof that menopause causes a loss of musculoskeletal tissue mass and quality, thereby causing a loss of health and quality of life. There is also solid evidence that hormone replacement therapy in itself prevents most of these effects in connective tissue in it self. Besides the independent, direct effects on the musculoskeletal tissues, estrogen deficiency also reduces the ability to adequately respond and adapt to external mechanical and metabolic stressors, e.g. exercise, which are otherwise the main stimuli that should maintain musculoskeletal integrity and metabolic function. Thus, normophysiological estrogen levels appear to exert a permissive effect on musculoskeletal adaptations to loading, thereby likely improving the outcome of rehabilitation following critical illness, musculoskeletal trauma or orthopedic surgical therapy. These effects add to the evidence supporting the use of estrogen therapy, particularly accelerated gain of functional capacity and independence following musculoskeletal disuse.
Systematic studies of autosomal dominant osteopetrosis (ADO) were followed by the identification of underlying mutations giving unique possibilities to perform translational studies. What was previously designated ADO1 turned out to be a high bone mass phenotype caused by a missense mutation in the first propeller of LRP5, a region of importance for binding inhibitory proteins. Thereby, ADO1 cannot be regarded as a classical form of osteopetrosis but must now be considered a disease of LRP5 activation. ADO (Albers-Schönberg disease, or previously ADO2) is characterized by increased number of osteoclasts and a defect in the chloride transport system (ClC-7) of importance for acidification of the resorption lacuna (a form of Chloride Channel 7 Deficiency Osteopetrosis). Ex vivo studies of osteoclasts from ADO have shown that cells do form normally but have reduced resorption capacity and an expanded life span. Bone formation seems normal despite decreased osteoclast function. Uncoupling of formation from resorption makes ADO of interest for new strategies for treatment of osteoporosis. Recent studies have integrated bone metabolism in whole-body energy homeostasis. Patients with ADO may have decreased insulin levels indicating importance beyond bone metabolism. There seems to be a paradigm shift in the treatment of osteoporosis. Targeting ClC-7 might introduce a new principle of dual action. Drugs affecting ClC-7 could be antiresorptive, still allowing ongoing bone formation. Inversely, drugs affecting the inhibitory site of LRP5 might stimulate bone formation and inhibit resorption. Thereby, these studies have highlighted several intriguing treatment possibilities, employing novel modes of action, which could provide benefits to the treatment of osteoporosis.
Alzheimers disease (AD) is a devastating neurological disease characterized by pathological proteolytic cleavage of tau protein, which appears to initiate death of the neurons. The objective of this study was to investigate whether a proteolytic fragment of the tau protein could serve as blood-based biomarker of cognitive function in AD.
The present study describes the assessment of true formation of type III collagen in different pathologies using a neo-epitope specific competitive Enzyme-linked immunosorbent assay (ELISA) towards the N-terminal propeptide of type III collagen (PRO-C3).
By secreting proteases such as cathepsins and matrix metalloproteinases (MMPs), macrophage foam cells may be a major cause of ruptured atherosclerotic plaques. The aims of the present study were to investigate in vitro role of human macrophage foam cells in degrading type I collagen, a major component of extracellular matrix (ECM) in plaques, and to establish whether the pro-inflammatory molecules, tumor necrosis factor (TNF)-alpha, and receptor activator of nuclear factor-?B ligand (RANK-L) increase this degradation. CD14+ monocytes isolated from peripheral blood were differentiated into macrophage foam cells and cultured on a type I collagen matrix in the presence of TNF-alpha and RANK-L. Matrix degradation was measured by the cathepsin K-generated C-terminal cross-linked telopeptide of type I collagen (CTX-I) and the MMP-generated carboxyterminal telopeptide of type I collagen (ICTP) in supernatants showing that macrophage foam cells secrete MMPs and cathepsin K, resulting in release of ICTP and CTX-I. Stimulation with TNF-alpha increased CTX-I and ICTP dose dependently, with ICTP levels increasing by 59% and CTX-I levels increasing by 43%. RANK-L enhanced the release of CTX-I and ICTP by 56% and 72%, respectively. This is, to our knowledge, the first data describing a simple in vitro system in which macrophage foam cells degradation of matrix proteins can be monitored. This degradation can be enhanced by cytokines since TNF-alpha and RANK-L significantly increased the matrix degradation. This in vitro system in part is a model system for the macrophage-mediated proteolytic degradation of the ECM, which is found in many diseases with an inflammatory component.
Glucocorticoids are known to attenuate bone formation in vivo leading to decreased bone volume and increased risk of fractures, whereas effects on the joint tissue are less characterized. However, glucocorticoids appear to have a reducing effect on inflammation and pain in osteoarthritis. This study aimed at characterizing the effect of glucocorticoids on chondrocytes, osteoclasts, and osteoblasts.
Osteopetrosis caused by defective acid secretion by the osteoclast, is characterized by defective bone resorption, increased osteoclast numbers, while bone formation is normal or increased. In contrast the bones are of poor quality, despite this uncoupling of formation from resorption.To shed light on the effect of uncoupling in adult mice with respect to bone strength, we transplanted irradiated three-month old normal mice with hematopoietic stem cells from control or oc/oc mice, which have defective acid secretion, and followed them for 12 to 28 weeks.Engraftment levels were assessed by flow cytometry of peripheral blood. Serum samples were collected every six weeks for measurement of bone turnover markers. At termination bones were collected for µCT and mechanical testing. An engraftment level of 98% was obtained. From week 6 until termination bone resorption was significantly reduced, while the osteoclast number was increased when comparing oc/oc to controls. Bone formation was elevated at week 6, normalized at week 12, and reduced onwards. µCT and mechanical analyses of femurs and vertebrae showed increased bone volume and bone strength of cortical and trabecular bone.In conclusion, these data show that attenuation of acid secretion in adult mice leads to uncoupling and improves bone strength.
Rheumatoid arthritis (RA) is a chronic systemic autoimmune disease associated with potentially debilitating joint inflammation, as well as altered skeletal bone metabolism and co-morbid conditions. Early diagnosis and aggressive treatment to control disease activity offers the highest likelihood of preserving function and preventing disability. Joint inflammation is characterized by synovitis, osteitis, and/or peri-articular osteopenia, often accompanied by development of subchondral bone erosions, as well as progressive joint space narrowing. Biochemical markers of joint cartilage and bone degradation may enable timely detection and assessment of ongoing joint damage, and their use in facilitating treatment strategies is under investigation. Early detection of joint damage may be assisted by the characterization of biochemical markers that identify patients whose joint damage is progressing rapidly and who are thus most in need of aggressive treatment, and that, alone or in combination, identify those individuals who are likely to respond best to a potential treatment, both in terms of limiting joint damage and relieving symptoms. The aims of this review are to describe currently available biochemical markers of joint metabolism in relation to the pathobiology of joint damage and systemic bone loss in RA; to assess the limitations of, and need for additional, novel biochemical markers in RA and other rheumatic diseases, and the strategies used for assay development; and to examine the feasibility of advancement of personalized health care using biochemical markers to select therapeutic agents to which a patient is most likely to respond.
Treatment of patients with perioxisome proliferator-activated receptor-? full agonists are associated with weight gain, heart failure, peripheral oedema, and bone loss. However, the safety of partial perioxisome proliferator-activated receptor-? agonists has not been established in a clinical trial. The BALaglitazone glucose Lowering Efficacy Trial aimed to establish the glucose-lowering effects and safety parameters of the perioxisome proliferator-activated receptor-? partial agonist balaglitazone in diabetic patients on stable insulin therapy.
How do pharmaceutical companies find new uses for old or failed drugs? Is there a way to manage serendipity at the very first stage of identifying compounds that could be developed into new drugs? Several approaches are now being pursued by various companies that are dedicated to drug repositioning cross a spectrum of technologies and scientific bases. Biochemical markers could provide significant shortcuts for drug development. In this review, we introduce drug repositioning, approaches to it and their associated challenges. We also highlight a novel class of serological biomarkers, namely neo-epitopes, which have proven successful in repositioning drugs in clinical settings.
The osteoclast initiates resorption by creating a resorption lacuna. The ruffled border surrounding the lacunae arises from exocytosis of lysosomes. To dissolve the inorganic phase of the bone, the vacuolar adenosine triphosphatase, located in the ruffled border, pumps protons into the resorption lacunae. The electroneutrality of the lacunae is maintained by chloride transport through the chloride-proton antiporter chloride channel 7. Inhibition of either proton or chloride transport prevents bone resorption. The aims of this study were to validate the human osteoclastic microsome- based influx assay with respect to lysosomal acidification and assess whether it is a reliable test of a compounds ability to inhibit acidification. Investigated were the expression levels of the lysosomal acidification machinery, the activation of the assay by adenosine triphosphate, H(+) and Cl(-) dependency, the effect of valinomycin, inhibitor sensitivity, and the ion profile of the human osteoclast microsomes. The expression level of chloride channel 7 was increased in the human osteoclastic microsomes compared with whole osteoclasts. Acid influx was induced by 1.25 mM adenosine triphosphate. Further 1.1 ?M valinomycin increased the acid influx by 129%. Total abrogation of acid influx was observed using both H(+) and Cl(-) ionophores. Finally, investigation of the anion profile demonstrated that Cl(-) and Br(-) are the preferred anions for the transporter. In conclusion, the acid influx assay based on microsomes from human osteoclasts is a useful tool for detection of inhibitors of the osteoclastic acidification machinery, and thus may aid the identification of effective drugs for osteoporosis that target the acid secretion by osteoclasts.
Bone resorption is initiated by osteoclastic acidification of the resorption lacunae. This process is mediated by secretion of protons through the V-ATPase and chloride through the chloride antiporter ClC-7. To shed light on the intracellular signalling controlling extracellular acidification, we screened a protein kinase inhibitor library in human osteoclasts.
Osteoporosis is a slow progressive disease with develops over decades, and where intervention is needed for an extended number of years. This highlights the need for safe intervention possibilities, which have sustained beneficial effects post-treatment.
ClC-7 is a ubiquitous transporter which is broadly expressed in mammalian tissues. It is implied in the pathogenesis of lysosomal storage disease and osteopetrosis. Because of its endosomal/lysosomal localization it is still poorly characterized.
Normal osteoclasts resorb bone by secretion of acid and proteases. Recent studies of patients with loss of function mutations affecting either of these processes have indicated a divergence in osteoclastic phenotypes. These difference in osteoclast phenotypes may directly or indirectly have secondary effects on bone remodeling, a process which is of importance for the pathogenesis of both osteoporosis and osteoarthritis. We treated human osteoclasts with different inhibitors and characterized their resulting function.
The aim of this review is to discuss the potential usefulness of novel advances in the class of biochemical markers, neo-epitopes. Neo-epitopes are post-translational modifications (PTMs) of proteins formed by processes such as protease cleavage, citrullination, nitrosylation, glycosylation and isomerization. Each modification results from a specific local physiological or pathobiologial process. Identification of each modification, and the affected tissue-specific protein, may produce a unique disease-specific biochemical marker. One example of neo-epitopes detectable in protein fragments are type II collagen degradation products. These 2nd generation biochemical markers have proven useful for research on joint damage. Such neo-epitopes are being utilized in translational medicine to estimate safety and efficacy in both preclinical models and clinical settings. More advanced, 3rd generation biochemical markers, which may more accurately identify both the affected tissue and the disease stage, might be developed through research into multiple PTMs occurring during specific disease pathogenesis. The end-product of these investigations is one single measurement for each disease. To date, advanced biochemical markers have been identified in bone, cardiovascular, fibrosis and cartilage diseases and continue research in Alzheimers and chronic obstructive pulmonary diseases. These advanced biochemical marker assays relying on analytes that are modified by multiple PTMs may become optimal tools that meet the BIPED (Burden of disease, Investigatory, Prognostic, Efficacy of intervention and Diagnosis) biochemical marker "usefulness" criteria. For some of these markers it may be interesting to also investigate whether the PTMs are the cause or consequence of a certain disease.
Osteoarthritis (OA) is a disease of the entire joint. Different treatment strategies for OA have been proposed and tested clinically without the desired efficacy. One reason for the scarcity of current chondroprotective agents may be the insufficient understanding of the patho-physiology of the joint and whether the joint damage is reversible or irreversible. In this review, we compile emerging data on cellular and pathological aspects of OA, and ask whether these data could give clue to when cartilage degradation is reversible and whether a point-of-no-return exists. We highlight different stages of OA, and speculate whether different intervention strategies (e.g. DMOAD vs. SMOADs) may only be efficacious at distinct stages of OA.
The aims of the study were to investigate interindividual variations in the bioavailability of salmon calcitonin (sCT) following single oral 0.8 mg doses at three different times of the day, and intraindividual variation in sCT bioavailability at each end of a 14-day treatment period. We also investigated correlations between exposure to sCT and levels of the bone resorption biomarker serum C-terminal telopeptide of collagen type I (CTX-I).
Agonists of Perioxisome Proliferator-Activator Receptor gamma (PPARgamma), which work as insulin sensitizers, are approved for type 2 diabetes. However, adverse effects, such as oedemas, infarctions, and increased fracture rates, limit their applicability. We performed a head-to-head comparison of equipotent glucose lowering concentrations of the partial PPARgamma agonist balaglitazone and the full agonist pioglitazone in male diet-induced obese rats, to investigate effects on bone formation, fluid retention and fat accumulation. Sixty male dio induced obese rats were divided into five categories: vehicle, pioglitazone 10 mg/kg, pioglitazone 30 mg/kg, balaglitazone 5 mg/kg, balaglitazone 10 mg/kg. At day -7, 21 and 42 fasting serum samples were collected and whole body tissue composition was evaluated by MR scanning. Food intake and bodyweights were monitored during the study period. At day 42, an oral glucose tolerance test was performed to evaluate glucose homeostasis in the rats. During oral glucose tolerance test both pioglitazone and balaglitazone lowered baseline glucose and maintained the suppression during the oral glucose tolerance test. Both lowered basal insulin, peak insulin secretion and total insulin during oral glucose tolerance test. Both drugs increased bodyweight, although this was more pronounced in the pioglitazone 30 group. MR scans of body fat and water showed that all treatment groups increased their fat mass, whereas only the pioglitazone 30 group accumulated water. Pioglitazone treatment led to reduction of the bone formation marker osteocalcin, whereas balaglitazone treatment did not affect it. Balaglitazone is a novel PPARgamma agonist, which potently lowers glucose levels, while it neither affects fluid retention nor bone formation parameters.
Bone remodeling is required for healthy calcium homeostasis and for repair of damage occurring with stress and age. Osteoclasts resorb bone and osteoblasts form bone. These processes normally occur in a tightly regulated sequence of events, where the amount of formed bone equals the amount of resorbed bone, thereby restoring the removed bone completely. Osteocytes are the third cell type playing an essential role in bone turnover. They appear to regulate activation of bone remodeling, and they exert both positive and negative regulation on both osteoclasts and osteoblasts. In this review, we consider the intricate communication between these bone cells in relation to bone remodeling, reviewing novel data from patients with mutations rendering different cell populations inactive, which have shown that these interactions are more complex than originally thought. We highlight the high probability that a detailed understanding of these processes will aid in the development of novel treatments for bone metabolic disorders, i.e. we discuss the possibility that bone resorption can be attenuated pharmacologically without a secondary reduction in bone formation.
The aim of this study was to assess the bioavailability and pharmacodynamic efficacy of synthetic salmon calcitonin (ssCT) and recombinant salmon calcitonin (rsCT) in healthy postmenopausal women. The study was a single-blind, randomized study. Participants were 36 postmenopausal women 62 to 74 years old, randomly assigned to a comparison of dosing with ssCT (n = 12) or rsCT (n = 24) given in the morning at 08:00. Study parameters were plasma CT levels measured up to 2 hours postdose and changes in the bone resorption marker serum CTX-I and the cartilage degradation marker urine CTX-II measured up to 4 hours postdose. For both formulations, peak plasma concentrations were obtained 15 minutes after dosage, and no statistically significant differences in the uptake of CT were observed. Measurement of bone resorption and cartilage degradation markers displayed comparable responses, with AUCs of relative change of serum CTX-I of -250% x hours and relative change of urine CTX-II of -180% x hours during the 4-hour observation period. In conclusion, oral synthetic and recombinant calcitonin displayed comparable pharmacodynamic and kinetic properties.
The chloride-proton antiporter ClC-7 has been speculated to be involved in acidification of the lysosomes and the resorption lacunae in osteoclasts; however, neither direct measurements of chloride transport nor acidification have been performed. Human osteoclasts harboring a dominant negative mutation in ClC-7 (G215R) were isolated, and used these to investigate bone resorption measured by CTX-I, calcium release and pit scoring. The actin cytoskeleton of the osteoclasts was also investigated. ClC-7 enriched membranes from the osteoclasts were isolated, and used to test acidification rates in the presence of a V-ATPase and a chloride channel inhibitor, using a H(+) and Cl(-) driven approach. Finally, acidification rates in ClC-7 enriched membranes from ADOII osteoclasts and their corresponding controls were compared. Resorption by the G215R osteoclasts was reduced by 60% when measured by both CTX-I, calcium release, and pit area when comparing to age and sex matched controls. In addition, the ADOII osteoclasts showed no differences in actin ring formation. Finally, V-ATPase and chloride channel inhibitors completely abrogated the H(+) and Cl(-) driven acidification. Finally, the acid influx was reduced by maximally 50% in the ClC-7 deficient membrane fractions when comparing to controls. These data demonstrate that ClC-7 is essential for bone resorption, via its role in acidification of the lysosomes and resorption lacunae in osteoclasts.
To investigate whether increased levels of vimentin citrullinated peptides identified by MS in articular cartilage can be measured in pathologies other than rheumatoid arthritis and be utilised for diagnostic purposes.
Disease heterogeneity is as major issue in Type II Diabetes Mellitus (T2DM), and this patient inter-variability might not be sufficiently reflected by measurements of glycated haemoglobin (HbA1c).?-cell dysfunction and ?-cell death are initiating factors in development of T2DM. In fact, ?-cells are known vanish prior to the development of T2DM, and autopsy of overt T2DM patients have shown a 60% reduction in ?-cell mass.As the decline in ?-cell function and mass have been proven to be pathological traits in T2DM, methods for evaluating ?-cell loss is becoming of more interest. However, evaluation of ?-cell death or loss is currently invasive and unattainable for the vast majority of diabetes patients. Serological markers, reflecting ?-cell loss would be advantageous to detect and monitor progression of T2DM. Biomarkers with such capacities could be neo-epitopes of proteins with high ?-cell specificity containing post translational modifications. Such tools may segregate T2DM patients into more appropriate treatment groups, based on their ?-cell status, which is currently not possible. Presently individuals presenting with adequately elevated levels of both insulin and glucose are classified as T2DM patients, while an important subdivision of those is pending, namely those patients with sufficient ?-cell capacity and those without. This may warrant two very different treatment options and patient care paths.Serological biomarkers reflecting ?-cell health status may also assist development of new drugs for T2DM and aid physicians in better characterization of individual patients and tailor individual treatments and patient care protocols.
Increased attention is paid to the structural components of tissues. These components are mostly collagens and various proteoglycans. Emerging evidence suggests that altered components and noncoded modifications of the matrix may be both initiators and drivers of disease, exemplified by excessive tissue remodeling leading to tissue stiffness, as well as by changes in the signaling potential of both intact matrix and fragments thereof. Although tissue structure until recently was viewed as a simple architecture anchoring cells and proteins, this complex grid may contain essential information enabling the maintenance of the structure and normal functioning of tissue. The aims of this review are to (1) discuss the structural components of the matrix and the relevance of their mutations to the pathology of diseases such as fibrosis and cancer, (2) introduce the possibility that post-translational modifications (PTMs), such as protease cleavage, citrullination, cross-linking, nitrosylation, glycosylation, and isomerization, generated during pathology, may be unique, disease-specific biochemical markers, (3) list and review the range of simple enzyme-linked immunosorbent assays (ELISAs) that have been developed for assessing the extracellular matrix (ECM) and detecting abnormal ECM remodeling, and (4) discuss whether some PTMs are the cause or consequence of disease. New evidence clearly suggests that the ECM at some point in the pathogenesis becomes a driver of disease. These pathological modified ECM proteins may allow insights into complicated pathologies in which the end stage is excessive tissue remodeling, and provide unique and more pathology-specific biochemical markers.
The skeletal muscle mass is the largest organ in the healthy body, comprising 30-40 % of the body weight of an adult man. It confers protection from trauma, locomotion, ventilation, and it represents a "sink" in glucose metabolism and a reservoir of amino acids to other tissues such as the brain and blood cells. Naturally, loss of muscle has dire consequences for health as well as functionality. Muscle loss is a natural consequence of especially aging, inactivity, and their associated metabolic dysfunction, but it is strongly accelerated in critical illness such as organ failure, sepsis, or cancer. Whether this muscle loss is considered a primary or secondary condition, it is known that muscle loss is a symptom that predicts morbidity and mortality and one that is known to impact quality of life and independence. Therefore, monitoring of muscle mass is relevant in a number of pathologies as well as in clinical trials as measures of efficacy as well as safety.
Salmon calcitonin has chondroprotective effect both in vitro and in vivo, and is therefore being tested as a candidate drug for cartilage degenerative diseases. Recent studies have indicated that different chondrocyte phenotypes may express the calcitonin receptor (CTR) differentially. We tested for the presence of the CTR in chondrocytes from tri-iodothyronin (T3)-induced bovine articular cartilage explants. Moreover, investigated the effects of human and salmon calcitonin on the explants.
Osteoclasts are known to be important for the coupling process between bone resorption and formation. The aim of this study was to address when osteoclasts are anabolically active. Human monocytes were differentiated into mature osteoclasts by treatment with M-CSF and RANKL. Conditioned medium was collected from macrophages, pre-osteoclasts, and mature functional or non-resorbing osteopetrotic osteoclasts on either bone, plastic, decalcified bone or dentine with or without diphyllin, E64 or GM6001. Osteoclasts numbers were measured by TRACP activity. Bone resorption was evaluated by CTX-I and calcium release. The osteoblastic cell line 2T3 was treated with 50% of CM or non-CM for 12days. Bone formation was assessed by Alizarin Red extraction. CM from mature osteoclasts induced bone formation, while CM from macrophages did not. Non-resorbing osteoclasts generated from osteopetrosis patients showed little resorption, but still an induction of bone formation by osteoblasts. Mimicking the reduction in bone resorption using the V-ATPase inhibitor Diphyllin, the cysteine proteinase inhibitor E64 and the MMP-inhibitor GM6001 showed that CM from diphyllin and E64 treated osteoclasts showed reduced ability to induce bone formation compared to CM from vehicle treated osteoclasts, while CM from GM6001 treated osteoclasts equaled vehicle CM. Osteoclasts on either dentine or decalcified bone showed strongly attenuated anabolic capacities. In conclusion, we present evidence that osteoclasts, both dependent and independent of their resorptive activity, secrete factors stimulating osteoblastic bone formation.
Articular cartilage deterioration, which includes cartilage degradation and chondrocyte hypertrophy, is a hallmark of degenerative joint diseases (DJD). Chondrocyte hypertrophy is initiated in the deep layer of the cartilage; thus, a robust explants model for investigation of hypertrophy should include this zone. The aim of this study was to characterize and investigate the hypertrophy-promoting potential of different endogenous factors on an ex vivo articular cartilage model. The full-depth cartilage explants were harvested from bovine femoral condyle and cultured for 13 days in different conditions: 10 ng/ml oncostatin M + 20 ng/ml TNF-?; 100 ng/ml IGF1; 10-100 ng/ml bFGF; 10-100 ng/ml BMP2; 50 ?g/ml ascorbic acid in combination with 10 mM ?-glycerophosphate; and 20-100 ng/ml triiodothyronine. The cellular activity and morphology, degradation, formation and calcification, and expression level of hypertrophic markers were investigated. The hypertrophic factors tested all induced cellular activity and marked morphological changes starting at day 4, however, not in a synchronized manner. Both cartilage degradation and formation were induced by T3 (P < 0.05). Only T3 had a full hypertrophic gene expression profile (P < 0.05). We developed and characterized a novel model for investigation of chondrocyte hypertrophy. We speculated that this can become an important investigatory tool for investigation of matrix turnover, chondrocyte hypertrophy and cartilage calcification that are associated with DJD pathogenesis.
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