Metabolic Syndrome and Bone: Pharmacologically Induced Diabetes has Deleterious Effect on Bone in Growing Obese Rats.

Metabolic syndrome and osteoporosis share similar risk factors. Also, patients with diabetes have a higher risk of osteoporosis and fracture. Liver manifestations, such as non-alcoholic steatohepatitis (NASH), of metabolic syndrome are further aggravated in diabetics and often lead to liver failure. Our objective was to create a rat model of human metabolic syndrome and determine the long-term impact of early-onset T1D on bone structure and strength in obese growing rats. Male rats were given either standard chow and RO water (Controls) or a high-fat, high-cholesterol diet and sugar water containing 55% fructose and 45% glucose (HFD). A third group of rats received the HFD diet and a single dose of streptozotocin to induce type 1 diabetes (HFD/Sz). Body weight and glucose tolerance tests were conducted several times during the course of the study. Serum chemistry, liver enzymes, and biomarkers of bone metabolism were evaluated at 10 and 28 weeks. Shear wave elastography and histology were used to assess liver fibrosis. Cancellous bone structure and cortical bone geometry were evaluated by mCT and strength by the 3-point bending method. Body mass and fat accumulation was significantly higher in HFD and HFD/Sz rats compared to Controls. Rats in both the HFD and HFD/Sz groups developed NASH, although the change was more severe in diabetic rats. Although both groups of obese rats had larger bones, their cancellous structure and cortical thickness were reduced, resulting in diminished strength that was further aggravated by diabetes. The HFD and HFD/Sz rats recapitulate MeSy in humans with liver pathology consistent with NASH. Our data provide strong indication that obesity accompanied by type 1 diabetes significantly aggravates comorbidities of MeSy, including the development of osteopenia and weaker bones. The juvenile rat skeleton seems to be more vulnerable to damage imposed by obesity and diabetes and may offer a model to inform the underlying pathology associated with the unusually high fracture rates in obese adults with diabetes.

A novel endpoint for the assessment of chemotherapy-induced peripheral neuropathy in rodents: biomechanical properties of peripheral nerve.

Chemotherapy-induced peripheral neuropathy (CiPN) is a frequent adverse effect in patients and a leading safety consideration in oncology drug development. Although behavioral assessment and microscopic examination of the nerves and dorsal root ganglia can be incorporated into toxicity studies to assess CiPN risk, more sensitive and less labor-intensive endpoints are often lacking. In this study, rats and mice administered vincristine (75 µg kg-1  day-1 , i.p., for 10 days in rats and 100 µg kg-1  day-1 , i.p., for 11 days in mice, respectively) were employed as the CiPN models. Behavioral changes were assessed during the dosing phase. At necropsy, the sural or sciatic nerve was harvested from the rats and mice, respectively, and assessed for mechanical and histopathological endpoints. It was found that the maximal load and the load/extension ratio were significantly decreased in the nerves collected from the animals dosed with vincristine compared with the vehicle-treated animals (P < 0.05). Additionally, the gait analysis revealed that the paw print areas were significantly increased in mice (P < 0.01), but not in rats following vincristine administration. Light microscopic histopathology of the nerves and dorsal root ganglia were unaffected by vincristine administration. We concluded that ex vivo mechanical properties of the nerves is a sensitive endpoint, providing a new method to predict CiPN in rodent. Gait analysis may also be a useful tool in these pre-clinical animal models.

Correlation between µCT imaging, histology and functional capacity of the osteoarthritic knee in the rat model of osteoarthritis.

BACKGROUND: To acquire the most meaningful understanding of human arthritis, it is essential to select the disease model and methodology translatable to human conditions. The primary objective of this study was to evaluate a number of analytic techniques and biomarkers for their ability to accurately gauge bone and cartilage morphology and metabolism in the medial meniscal tear (MMT) model of osteoarthritis (OA). METHODS: MMT surgery was performed in rats to induce OA. A dynamic weight bearing system (DWB) system was deployed to evaluate the weight-bearing capacity of the front and hind legs in rats. At the end of a 10-week study cartilage pathology was evaluated by micro computed tomography (µCT), contrast enhanced µCT (EPIC µCT) imaging and traditional histology. Bone tissue was evaluated at the tibial metaphysis and epiphysis, including the subchondral bone. Histological techniques and dynamic histomorphometry were used to evaluate cartilage morphology and bone mineralization. RESULTS: The study results showed a negative impact of MMT surgery on the weight-bearing capacity of the operated limb. Surgery caused severe and extensive deterioration of the articular cartilage at the medial tibial plateau, as evidenced by elevated CTX-II in serum, EPIC µCT and histology. Bone analysis by µCT showed thickening of the subchondral bone beneath the damaged cartilage, loss of cancellous bone at the metaphysis and active osteophyte formation. CONCLUSIONS: The study emphasizes the need for using various methodologies that complement each other to provide a comprehensive understanding of the pathophysiology of OA at the organ, tissue and cellular levels. Results from this study suggest that use of histology, µCT and EPIC µCT, and functional DWB tests provide powerful combination to fully assess the key aspects of OA and enhance data interpretation.

Therapeutic Effects of FGF23 c-tail Fc in a Murine Preclinical Model of X-Linked Hypophosphatemia Via the Selective Modulation of Phosphate Reabsorption.

Fibroblast growth factor 23 (FGF23) is the causative factor of X-linked hypophosphatemia (XLH), a genetic disorder effecting 1:20,000 that is characterized by excessive phosphate excretion, elevated FGF23 levels and a rickets/osteomalacia phenotype. FGF23 inhibits phosphate reabsorption and suppresses 1α,25-dihydroxyvitamin D (1,25D) biosynthesis, analytes that differentially contribute to bone integrity and deleterious soft-tissue mineralization. As inhibition of ligand broadly modulates downstream targets, balancing efficacy and unwanted toxicity is difficult when targeting the FGF23 pathway. We demonstrate that a FGF23 c-tail-Fc fusion molecule selectively modulates the phosphate pathway in vivo by competitive antagonism of FGF23 binding to the FGFR/α klotho receptor complex. Repeated injection of FGF23 c-tail Fc in Hyp mice, a preclinical model of XLH, increases cell surface abundance of kidney NaPi transporters, normalizes phosphate excretion, and significantly improves bone architecture in the absence of soft-tissue mineralization. Repeated injection does not modulate either 1,25D or calcium in a physiologically relevant manner in either a wild-type or disease setting. These data suggest that bone integrity can be improved in models of XLH via the exclusive modulation of phosphate. We posit that the selective modulation of the phosphate pathway will increase the window between efficacy and safety risks, allowing increased efficacy to be achieved in the treatment of this chronic disease. © 2017 American Society for Bone and Mineral Research.

Effect of antiresorptive and anabolic bone therapy on development of osteoarthritis in a posttraumatic rat model of OA.

INTRODUCTION: Osteoarthritis (OA) is a leading cause of disability, but despite the high unmet clinical need and extensive research seeking dependable therapeutic interventions, no proven disease-modifying treatment for OA is currently available. Due to the close interaction and interplay between the articular cartilage and the subchondral bone plate, it has been hypothesized that antiresorptive drugs can also reduce cartilage degradation, inhibit excessive turnover of the subchondral bone plate, prevent osteophyte formation, and/or that bone anabolic drugs might also stimulate cartilage synthesis by chondrocytes and preserve cartilage integrity. The benefit of intensive zoledronate (Zol) and parathyroid hormone (PTH) therapy for bone and cartilage metabolism was evaluated in a rat model of OA. METHODS: Medial meniscectomy (MM) was used to induce OA in male Lewis rats. Therapy with Zol and human PTH was initiated immediately after surgery. A dynamic weight-bearing (DWB) system was deployed to evaluate the weight-bearing capacity of the front and hind legs. At the end of the 10-week study, the rats were euthanized and the cartilage pathology was evaluated by contrast (Hexabrix)-enhanced µCT imaging and traditional histology. Bone tissue was evaluated at the tibial metaphysis and epiphysis, including the subchondral bone. Histological techniques and dynamic histomorphometry were used to evaluate cartilage morphology and bone mineralization. RESULTS: The results of this study highlight the complex changes in bone metabolism in different bone compartments influenced by local factors, including inflammation, pain and mechanical loads. Surgery caused severe and extensive deterioration of the articular cartilage at the medial tibial plateau, as evidenced by contrast-enhanced µCT and histology. The study results showed the negative impact of MM surgery on the weight-bearing capacity of the operated limb, which was not corrected by treatment. Although both Zol and PTH improved subchondral bone mass and Zol reduced serum CTX-II level, both treatments failed to prevent or correct cartilage deterioration, osteophyte formation and mechanical incapacity. CONCLUSIONS: The various methods utilized in this study showed that aggressive treatment with Zol and PTH did not have the capacity to prevent or correct the deterioration of the hyaline cartilage, thickening of the subchondral bone plate, osteophyte formation or the mechanical incapacity of the osteoarthritic knee.

Comparative bone anatomy of commonly used laboratory animals: implications for drug discovery.

To accommodate functional demands, the composition and organization of the skeleton differ among species. Microcomputed tomography has improved our ability markedly to assess structural parameters of cortical and cancellous bone. The current study describes differences in cortical and cancellous bone structure, bone mineral density, and morphology (geometry) at the proximal femur, proximal femoral diaphysis, lumbar vertebrae, and mandible in mice, rats, rabbits, dogs, and nonhuman primates. This work enhances our understanding of bone gross and microanatomy across lab animal species and likely will enable scientists to select the most appropriate species and relevant bone sites for research involving skeleton. We evaluated the gross and microanatomy of the femora head and neck, lumbar spine, and mandible and parameters of cancellous bone, including trabecular number, thickness, plate separation, and connectivity among species. The skeletal characteristics of rabbits, including a very short femoral neck and small amounts of cancellous bone at the femoral neck, vertebral body, and mandible, seem to make this species the least desirable for preclinical research of human bone physiology; in comparison, nonhuman primates seem the most applicable for extrapolation of data to humans. However, rodent (particularly rat) models are extremely useful for conducting basic research involving the skeleton and represent reliable and affordable alternatives to dogs and nonhuman primates. Radiology and microcomputed tomography allow for reliable evaluation of bone morphology, microarchitecture, and bone mineral density in preclinical and clinical environments.

Age-related changes in marmoset trabecular and cortical bone and response to alendronate therapy resemble human bone physiology and architecture.

In older humans, bone elongation ceases, periosteal expansion continues, and bone remodeling remains a dominant metabolic process. An appropriate animal model of type I and type II osteoporosis would be a species with sealed growth plates and persistence of bone remodeling. The rat is commonly used as a primary model, but due to delayed epiphyseal closure with continuous modeling and lack of Haversian remodeling, Food and Drug Administration guidelines recommend assessment of bone quality in an additional, non rodent, remodeling species. This study investigated the skeletal characteristics of senescent marmosets to evaluate their suitability as an osteoporosis model. Animals were randomized across three experimental groups; controls for both sexes and marmosets receiving alendronate for either 30 or 60 days (28 microg/kg, sc, twice per week). Outcome measures included serum chemistry and bone biomarkers, DEXA, histomorphometry, micro-computed tomography, and histopathology. Results showed that the adult marmoset skeleton has similar anatomical characteristics to the adult human, including the absence of growth plates, presence of Haversian system, and true remodeling of cancellous and cortical bone. Structural analyses of senescent marmoset cancellous bone demonstrated loss of trabecular mass and architecture similar to skeletal changes described for elderly men and women. Treatment with alendronate improved trabecular volume and number by reducing bone resorption, although bone formation was also reduced through coupling of bone remodeling. The common marmoset may provide a valuable model for research paradigms targeting human bone pathology and osteoporosis due to skeletal features that are similar to age-related changes and response to bisphosphonate therapy reported for humans.

Impact of Mrp2 on the biliary excretion and intestinal absorption of furosemide, probenecid, and methotrexate using Eisai hyperbilirubinemic rats.

PURPOSE: This study assesses the impact of rat multidrug resistance-associated protein 2 (Mrp2) on the biliary excretion and oral absorption of furosemide, probenecid, and methotrexate using Eisai hyperbilirubinemic rats (EHBR). METHODS: To assess Mrp2-mediated biliary excretion, rats received a 2-h intravenous infusion of furosemide, probenecid, or methotrexate. Blood and bile samples were collected at specified intervals. To assess Mrp2's impact on oral absorption, rats received furosemide, probenecid, or methotrexate orally at 5 mg/kg. Jugular and portal blood samples were obtained at timed intervals. All samples were analyzed by LC-MS/MS. Pharmacokinetic parameters were estimated using WinNonlin and standard pharmacokinetic equations. RESULTS: Thirty seven- and 39-fold reductions in biliary clearance were observed in EHBR as compared to control rats for probenecid and methotrexate, respectively. Biliary clearance was comparable between EHBR and control rats for furosemide. In all cases, no significant difference in absorption was observed between EHBR and control rats. CONCLUSIONS: This study provides the first evidence that Mrp2 mediates the biliary excretion of probenecid but not furosemide. Additionally, Mrp2 apparently has a less profound impact on intestinal absorption than biliary excretion of its substrates. Furthermore, alteration in systemic clearance in EHBR indicates that a potential compensatory mechanism may occur in EHBR.