Indiana University-Purdue University Indianapolis (IUPUI) / Type 2 diabetes mellitus (T2DM) is a growing problem globally and is associated with increased fracture risk and delayed bone healing. Novel approaches are needed in the treatment of T2DM and the resulting diabetic osteopathy. Recent studies highlight the role of bone as an endocrine organ producing factors that communicate with distant tissues to modulate systemic glucose metabolism. Ca2+/calmodulin (CaM)-dependent protein kinase kinase 2 (CaMKK2) is a potent regulator of whole-body energy metabolism, inflammation, bone remodeling and fracture healing. Genetic ablation of CaMKK2 protects from diet-induced obesity, insulin resistance and inflammation, while enhancing pancreatic β cell survival and insulin secretion. Deletion or inhibition of CaMKK2 promotes bone accrual by stimulating osteoblast-mediated bone formation and suppressing osteoclast-mediated bone resorption; however, its specific role in osteocytes, the master regulator of bone remodeling remains unknown. Here we demonstrate that conditional deletion of CaMKK2 from osteocytes enhances bone mass in 3-month-old female, but not male mice, due to suppression of osteoclasts. Conditioned media experiments and proteomics analysis revealed that female osteocytes lacking CaMKK2 suppressed osteoclast formation and function through enhanced secretion of calpastatin, a potent inhibitor of calpains, which are calciumdependent cysteine proteases that support osteoclasts. Further, to determine if CaMKK2- deficient osteocytes regulate whole-body glucose homeostasis, we placed these mice on a high-fat diet (HFD) for a period of 16 weeks. Although the diet did not significantly impact bone mass or strength, we found that conditional deletion of CaMKK2 in osteocytes enhanced bone microarchitecture in 6-month-old male and female mice. We also observed that conditional deletion of CaMKK2 from osteocytes protected male and female mice from HFD-induced obesity and insulin insensitivity. Taken together, these findings highlight CaMKK2 as a potent regulator of osteocyte-mediated modulation of bone remodeling and whole-body energy metabolism. / 2024-08-02

Inherited rickets of Corriedale sheep is a newly discovered skeletal disease of sheep with simple autosomal recessive inheritance. The clinical signs resemble rickets in other species and include decreased growth rate, thoracic lordosis and angular limb deformities. Radiographic features include physeal thickening, blurred metaphyseal trabeculae and thickened porous cortices. Computed tomography scanning of long bones reveals increased bone mineral content and cortical area, but decreased bone mineral density. Gross lesions include segmental thickening of physes, growth arrest lines, collapse of subchondral bone of the humeral head, thickened cortices and enthesophytes around distal limb joints. Microscopically there is persistence of hypertrophic chondrocytes at sites of endochondral ossification, inappropriate and excessive osteoclastic resorption, microfractures and wide, unmineralised osteoid seams lining trabeculae and filling secondary osteons. Affected sheep are persistently hypophosphataemic and hypocalcaemic. Normal serum 25-hydroxyvitamin D3 concentration accompanied by a two-fold elevation in 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) suggested a defect in endorgan responsiveness to vitamin D as a likely mechanism, but this was not supported by in vitro studies using cultured skin fibroblasts. These studies revealed normal vitamin D receptor function and the presence of 24- hydroxylase mRNA in cells from affected sheep, even without induction by 1,25(OH)2D3. Inappropriate overexpression of 25-hydroxyvitamin D3-24- hydroxylase, the enzyme that breaks down active vitamin D, is therefore considered the probable cause of inherited rickets in Corriedale sheep. Such a mechanism has not previously been described as a cause of inherited rickets in humans or other animal species. Treatment of affected sheep with high oral doses of vitamin D3 weekly for 3 months showed a trend towards increased bone mineral density, thus supporting an intact vitamin D receptor. Preliminary studies on immune function revealed reduced numbers of CD4+ and CD8+ lymphocytes and reduced interferon-? production by lymphocytes stimulated with parasite antigen. This new form of inherited rickets may be widespread in

Introduction First described in 2002, osteonecrosis of the jaw (ONJ, or avascular necrosis of the jaw) is an uncommon but potentially serious side effect of treatment with bisphosphonates. Although typically identified in patients with multiple myeloma and other malignancies, a few cases have been reported in patients taking bisphosphonates - a potent drug class used in the treatment of osteoclast-mediated bone resorption issues, including postmenopausal osteoporosis, Paget's disease, multiple myeloma, and malignant hypercalcemia. The clinical diagnosis of ONJ can be obscured by jaw pain, abscess, swelling, and fistulas, but exposed bone is a distinctive sign. This reports a case of ONJ secondary to bisphosphonate use in a 65-year-old woman and clinical management complications. Case Presentation A 65-year-old lady with history of age-related osteoporosis and compression fractures on alendronate for 4 years, squamous cell carcinoma of neck status post excision and radiotherapy 11-years prior, Sjogren's syndrome and discoid lupus on hydroxychloroquine, diabetes, hypertension, stroke and multiple dental abscesses presents with persistent neck pain. Initial CT neck with contrast showed diffuse fat stranding. Subsequently, alendronate was discontinued due to jaw necrosis suspicion. Eight months later, repeat CT scan showed new non-mass-like soft tissue thickening in the subcutaneous fat abutting the right anterior mandible with mandibular teeth cavities and periapical lucencies, likely to be periodontal cellulitis versus radiation osteonecrosis. Later, patient complained of a piece of bone penetrating the skin of her chin and presented with continuous drainage from sinus tract in her mandible, which was diagnosed as osteonecrosis attributed to bisphosphonates, previous radiation therapy, and dental abscesses. Patient was started on abaloparatide, an osteo-anabolic medication for osteoporosis and enrolled in hyperbaric oxygen therapy which immensely helped in controlling sinus drainage. Patient is currently awaiting mandibular reconstruction surgery. Discussion ONJ, often associated with pain, swelling, exposed bone, local infection, and pathologic fracture of the jaw, is a rare complication of bisphosphonate therapy. Currently, no prospective data exists to advise the benefits of therapy discontinuation however most clinical practices tend to discontinue at least temporarily. The incidence increases with longer treatment duration, particularly when therapy exceeds four years. Risk factors for developing ONJ while taking bisphosphonates include IV administration, anticancer therapy, dose and duration of exposure, dental extractions/implants, glucocorticoids, smoking, diabetes, and preexisting dental disease. Case reports and series suggest benefit from hyperbaric oxygen therapy in wound healing, pain, and quality of life at three months, however no significant differences exist with outcomes beyond three months. Patients being considered for therapy with a bisphosphonate should be thoroughly evaluated for dental issues, prior to initiating therapy. Conservative management with limited debridement, antibiotic therapy as needed, and topical mouth rinses rather than aggressive surgical resection are recommended. Conservative therapy may result in healing in a significant proportion of patients. Surgical resection of necrotic bone should be reserved for refractory or advanced cases. Providers should remain cautious while prescribing high doses of bisphosphonates in patients with increased risk factors to prevent, timely diagnose and treat this condition. References Edwards BJ, Gounder M, McKoy JM, et al. Pharmacovigilance and reporting oversight in US FDA fast-track process: bisphosphonates and osteonecrosis of the jaw. Lancet Oncol 2008; 9:1166. Khosla S, Burr D, Cauley J, et al. Bisphosphonate-associated osteonecrosis of the jaw: report of a task force of the American Society for Bone and Mineral Research. J Bone Miner Res 2007; 22:1479. Hoff AO, Toth BB, Altundag K, et al. Frequency and risk factors associated with osteonecrosis of the jaw in cancer patients treated with intravenous bisphosphonates. J Bone Miner Res 2008; 23:826.