Journal Articles

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Author: search.filters.author.Dittmer KESubject: search.filters.subject.osteoporosis

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    Insights into the pathogenesis of catastrophic spontaneous humeral fractures in first-lactation dairy cows
    (CSIRO Publishing, Australia, 2025-05-06) Wehrle-Martinez AS; Lawrence KE; Back PJ; Rogers CW; Gibson MJ; Dittmer KE; Eastwood C
    Spontaneous humeral fractures in first-lactation dairy cows have introduced significant challenges to the dairy industry in New Zealand, impacting animal welfare, farm economics, and veterinary practices. This review synthesizes current knowledge on the pathogenesis of these fractures and identifies potential key risk factors. The majority of bones from affected first-lactation dairy cows have osteoporosis, which is associated with inadequate bone formation and increased bone resorption. In addition, low total collagen content in bones from most affected dairy cows supports the hypothesis that inadequate bone formation is an important risk factor associated with humeral fractures in these cows. Spectroscopic analyses further confirmed a significant reduction in bone quality and strength. Novel findings suggest that low liver copper concentration in many of the affected cows' results from the mobilisation of copper to the bone. Although limited, the accumulated evidence suggests that to mitigate the incidence of catastrophic fractures, adequate nutrition (especially protein-energy) should be supplied during important growth periods. While significant progress has been made in understanding the cause of these fractures, many uncertainties and areas requiring further research remain.
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    Debilitating Musculoskeletal Disease in Two Free-Ranging Juvenile American Black Bears (Ursus americanus).
    (MDPI (Basel, Switzerland), 2024-07-17) Fahrenholz IC; Dennis MM; Morandi F; Dittmer KE; Sheldon JD; Gottdenker N; Tinelli A
    Severe musculoskeletal disease characterized by marked joint laxity was the cause of euthanasia in two wild juvenile American black bears (Ursus americanus) admitted to a rehabilitation facility in eastern Tennessee in 2023. Previously, almost all reported musculoskeletal diseases in this population were of traumatic etiology, even in malnourished yearlings. Case 1 was an orphaned 11-month-old male cub exhibiting disproportionate dwarfism, progressive immobility, and joint laxity. Necropsy findings suggested either chondrodysplasia or rickets, and imaging findings supported a skeletal dysplasia. Case 2 was a 14-month-old emaciated male yearling exhibiting joint laxity and immobility. Necropsy findings showed osteoporosis and serous atrophy of fat, and imaging findings were inconsistent with a skeletal dysplasia. Both cases were clinically inconsistent with rickets based on normal calcium, phosphorous, and parathyroid hormone concentrations; however, Case 1 had hypovitaminosis D (9 nmol/L) compared to healthy juvenile black bears. We hypothesize that Case 1 had a genetic chondrodysplasia while the osteoporosis of Case 2 was due to chronic malnutrition. The goal of this case report is to inform wildlife agencies and facilities to monitor for similar, non-trauma-related debilitating musculoskeletal disease in free-ranging bears and evaluate cases that allow us to further understand the disease processes involved.
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    Expression of Renal Vitamin D and Phosphatonin-Related Genes in a Sheep Model of Osteoporosis
    (MDPI (Basel, Switzerland), 2022-01) Dittmer KE; Chernyavtseva A; Marshall JC; Cabrera D; Wolber FM; Kruger M; Bienko M; Radzki RP
    Osteoporosis is a significant public health issue around the world, with post-menopausal osteoporosis due to estrogen deficiency resulting in approximately ¾ of cases. In this study, 18 aged Merino ewes were ovariectomized, and 10 were controls. Three of the ovariectomized ewes were treated weekly with 400 mg of methylprednisolone for 5 months and three were treated weekly for 2 months, followed by a 3-month recovery period. At 2 months, five control animals and six ovariectomized animals were euthanized. At 5 months, all the remaining ewes were euthanized. Kidney samples were collected postmortem for qPCR analysis of NPT1, PTH1R, NPT2a, NPT2c, Klotho, FGFR1IIIc, VDR, CYP24A1, CYP27B1, TRPV5, TRPV6, CalD9k, CalD28k, PMCA and NCX1. Ovariectomized sheep had significantly greater VDR expression compared with other groups. Ovariectomized sheep treated with glucocorticoids for 2 months followed by euthanasia at 5 months showed significant differences in TRPV5, CYP24A1 and klotho gene expression compared to other groups. Differences in klotho expression were most marked after adjustment for repeated measures (p = 0.1). Klotho is known as the "anti-aging" hormone and is involved in calcium and phosphorus metabolism. Klotho may be involved in the recovery of bone mineral density in ovariectomized sheep treated with glucocorticoids for 2 months followed by euthanasia at 5 months. Further research on the role of klotho is recommended.
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    Osteoporosis is the cause of spontaneous humeral fracture in dairy cows from New Zealand.
    (2023-01) Wehrle-Martinez A; Lawrence K; Back PJ; Rogers CW; Gibson M; Dittmer KE
    Outbreaks of humeral fractures in dairy cows have been reported in New Zealand for several years. Gross, histologic, and histomorphometric findings in the humerus from primiparous cows with spontaneous humeral fracture were compared to age-matched control cows. Affected cows had a complete nonarticular spiral fracture of the humerus. Histologically affected humeri had a thicker growth plate with abnormal architecture, thinner cortex with increased abnormal resorption, increased resorption in the distal humerus, decreased trabecular density, abnormal trabecular architecture, presence of growth arrest lines and woven bone formation. Histomorphometry showed reduction in bone volume, trabecular perimeter, and trabecular width. Cows grazed on fodder beet had thicker growth plates with an abnormal appearance compared with cows grazed on pasture, and cows with low/marginal liver copper concentration had more resorption cavities in the distal humerus and thinner cortical bone compared with cows with adequate liver copper concentration. Decreased trabecular density (OR = 249.5), abnormal cortical resorption (OR = 54.2), presence of woven bone formation in the proximal metaphysis (OR = 37.2), and the number of resorption cavities in the distal humerus were significantly associated with a high probability of fracture. Ribs had enlargement of the costochondral junction with fractures in different stages of healing. Histology of the ribs revealed abnormal growth plate appearance, presence of fracture lines, callus tissue, fibrosis, and microfractures. Cows with humeral fracture have osteoporosis due to decreased bone formation and increased bone resorption, likely associated with inadequate feed quality and perhaps copper deficiency leading to a reduction in bone strength and fracture.