Biochemistry of Exercise Training: Effects on Bone
Peter M. Tiidus, Rebecca E. K. MacPherson, Paul J. LeBlanc, Andrea R. Josse in The Routledge Handbook on Biochemistry of Exercise, 2020
In understanding the pathophysiology of osteoporosis, bone turnover is an essential concept because it is this process which governs how bone is replaced, lost, or gained at certain sites and ultimately determines bone's three-dimensional structure (35). Bone turnover is considered a continuous process of constant removal and replacement of volumes of bone tissue, conducted by osteoclasts and osteoblasts, in both cortical and trabecular bone (35). Under normal conditions, the processes of bone formation and resorption are coupled to one another, and the maintenance of skeletal balance is achieved through the action of various hormones and local mediators (140). Osteoclasts burrow into bone, forming cavities where osteoblasts can deposit new bone resulting in the formation of new osteons. This process also results in the liberation of calcium and phosphate into the bloodstream. Bone homeostasis is achieved when the amount of bone resorbed is replaced by a similar amount of newly synthesized bone. A sustained increase in the ratio of osteoclast to osteoblast activity may eventually result in osteoporosis. Therefore, the activity of osteoclasts and osteoblasts is not only important in establishing the calcium and phosphate levels necessary for particular bodily functions but also in maintaining the structural integrity of bone.
Metabolic and endocrine bone disorders
Ashley W. Blom, David Warwick, Michael R. Whitehouse in Apley and Solomon’s System of Orthopaedics and Trauma, 2017
Drugs for treating osteoporosis can also be used to treat bone fragility in CKD patients, but in CKD stages 4 and 5 this is somewhat controversial. Oral bisphosphonates are probably safe but may need to be administered at lower dose or greater dosage interval. IV zoledronate should be avoided as it may precipitate acute renal failure. Denosumab runs the risk of acute hypocalcaemia, hence calcium levels should be checked 1–2 weeks after administration. Aside from general safety and renal toxicity, the efficacy of these agents in reducing fracture risk in CKD stages 4 and 5 is unclear. Extrapolation of their benefits in osteoporosis may justify their use, particularly in high bone turnover states given their anti-resorptive action. Theoretically, these agents may be less effective or even harmful in adynamic bone disease where bone turnover is already suppressed. Some advocate performing a bone biopsy to exclude adynamic bone disease before using these agents, but this is often not practical, and there is currently no clinical data to suggest that the efficacy of anti-osteoporotic drugs in CKD is predicted from bone biopsy.
Bones and fractures
Henry J. Woodford in Essential Geriatrics, 2022
Plain X-rays of the thoracic and lumbar spine can be used to detect vertebral fractures in people reporting height loss or with clinical evidence of kyphosis. Quantitative computerised tomography (CT) measurements allow accurate bone density assessment but its use is associated with increased costs and radiation exposure. Quantitative ultrasound measurements are taken at peripheral sites, such as the calcaneum. It is a simple, quick and radiation-free technique but its accuracy has not been fully proven. A bone biopsy may be considered when there is diagnostic uncertainty. This can exclude certain conditions, including malignancy, but is rarely performed. Biochemical markers of bone turnover have been detected in serum and urine samples. They may have the advantage of reflecting responses to treatment before BMD changes are detectable on DEXA scans. They include bone-specific ALP, various breakdown products of collagen and the non-collagenous bone protein called osteocalcin. They are often utilised in the setting of clinical trials but are not recommended for use in routine clinical practice.21
Umbilical cord N-terminal procollagen of type l collagen (P1NP) and beta C-terminal telopeptide (βCTX) levels in term pregnancies with vitamin D deficiency
Published in Gynecological Endocrinology, 2021
Mefkure Eraslan Sahin, Erdem Sahin, Yusuf Madendag, Ilknur Col Madendag, Cigdem Karakukcu, Gokhan Acmaz
Bone turnover is a dynamic and complex process that is initiated by several substances and factors and that restores damaged bone and helps maintain calcium homeostasis through bone resorption and formation. This process can be assessed using measurements of specific biochemical markers, such as proteins and enzymes [8]. During bone resorption, beta C-terminal telopeptide (βCTX) fragments of collagen type I are released. These telopeptides are specific fractions of the C-terminal end of collagen and are especially in large numbers at the beginning of collagen depletion. As bone increasingly degrades, elevated amounts of these segments can be observed in the blood. N-terminal procollagen of type l collagen (P1NP) is produced by enzymatic hydrolysis of the N-terminal and is a marker specific to osteoblast activity [9]. P1NP/βCTX is a useful new biomarker for predicting bone mineral density [10,11]. In the current study, we hypothesized that umbilical cord P1NP and βCTX can help to identify a vitamin D deficiency that affects the bone health of the fetus; therefore, we aimed to evaluate the umbilical cord P1NP and βCTX levels in uncomplicated term pregnancies in women with vitamin D deficiency.
Predicting bone turnover following tobacco exposure using bone alkaline phosphatase and N-telopeptide biomarkers and possible variability and effect modification of these markers by race/ethnicity
Published in Biomarkers, 2020
Ogbebor E. Omoike, Liang Wang, Adekunle O. Oke, Kiana R. Johnson
Bone turnover involves the process of bone formation and mineralization by osteoblast cells, and bone resorption by osteoclast cells (Hlaing and Compston 2014). These processes are tightly regulated events in the human body (Wheater et al.2013). An alteration in this regulation could result in abnormal bone events and disease conditions such as osteoporosis. Bone Mineral Density (BMD), although the gold standard for diagnosis of osteoporosis with high specificity, has relatively poor sensitivity, suggesting that many potential fractures will be missed and undetected if used alone (Biver et al. 2012; Wheater et al. 2013). Hence the use of Bone Turnover Markers (BTMs) which have the advantages of relative ease of measurement, real time results and low cost for a single measurement. In addition, BTMs have the advantage of a rapid response to treatment, especially when compared to BMD measurement (Bell et al. 2012).
Irradiation affects the structural, cellular and molecular components of jawbones
Published in International Journal of Radiation Biology, 2022
Sridhar Reddy Padala, Bina Kashyap, Hannah Dekker, Jopi J. W. Mikkonen, Anni Palander, Nathalie Bravenboer, Arja M. Kullaa
Bone remodeling is a dynamic process; it occurs throughout the lifetime of an organism in a coordinated and tightly regulated manner in order to maintain a functional skeletal system. The bone remodeling process involves two opposing processes – bone resorption and bone formation (Mello et al. 2018) executed by three distinct cell types present in bone cells; osteoclasts, osteoblasts, and osteocytes. The physiological process of bone remodeling is based on the interactions not only between these cells but also multiple molecular agents including hormones, growth factors, and cytokines (Feng and McDonald 2011). Bone turnover is necessary to allow new bone to replace the existing bone, ensuring the adaptation of the newly formed bone to its microenvironment (Misch et al. 2001). Exposure to radiation causes a deterioration of the quantity and quality of bone by interfering with bone remodeling/turnover activity which ultimately impacts on the bone’s microstructure (Costa and Reagan 2019).
Related Knowledge Centers
- Bone
- Bone Resorption
- Osteology
- Skeleton
- Ossification
- Bone Fracture
- Osteoporosis
- Osteoblast
- Homeostasis
- Microdamage In Bone