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Androgens and bone function
Published in Barry G. Wren, Progress in the Management of the Menopause, 2020
Watts and associates19 studied surgically menopausal women who were treated with either oral esterified estrogen (1.25 mg) or esterified estrogen (1.25 mg) and methyl- testosterone (2.5 mg) daily for 2 years. Bone loss at the spine and hip was prevented by both treatment regimens; however, combined estrogen/androgen therapy was associated with an increase in spinal BMD compared with baseline19. The effects of estrogen alone, and estrogen plus androgen, on biochemical markers of bone formation and resorption in postmenopausal women have also been investigated. Postmenopausal women were treated for 9 weeks with either a combination of 1.25 mg esterified estrogen and 2.5 mg methyltestosterone orally, or 1.25 mg conjugated equine estrogen (CEE) given alone. A similar decrease in the urinary excretion of the bone absorption markers deoxy- pyridinoline, pyridinoline and hydroxyproline occurred in both groups. However, women treated with CEE had a reduction in the serum markers of bone formation, bone-specific alkaline phosphatase, osteocalcin and C- terminal procollagen peptide, whereas the women treated with estrogen plus androgen had increases in all of these markers of bone formation.
Osteoporosis
Published in Peter V. Giannoudis, Thomas A. Einhorn, Surgical and Medical Treatment of Osteoporosis, 2020
Ippokratis Pountos, Peter V. Giannoudis
Pyridinoline (PYD) and deoxypyridinoline (DPD) are trifunctional cross-links that stabilize the mature collagen molecule. During bone resorption, collagen is proteolytically broken down to its components; hence, PYD and DPD are released in the peripheral circulation and excreted in the urine. PYD is found in bone, cartilage, and other extraskeletal tissues, while DPD is mainly found in bone and dentin. Urinary excretion of PYD and DPD is independent to dietary intake as neither is taken up from food. The degradation of newly formed collagen does not influence their levels.
Sex Hormones and Their Impact on Sarcopenia and Osteoporosis
Published in Kohlstadt Ingrid, Cintron Kenneth, Metabolic Therapies in Orthopedics, Second Edition, 2018
Estrogen also has a positive effect on markers of bone remodeling. The rate of bone turnover in a patient can be evaluated indirectly by examining biochemical markers. The main part of the organic bone matrix is made of type I collagen. When bone is reabsorbed, collagen is broken down into breakdown products that are excreted in the urine. These breakdown products can be measured, including hydroxyproline, pyridinoline, and doxypyridinoline. These bone resorption markers are a good way to evaluate the effectiveness of therapies such as estrogen replacement [94]. Another study showed that the level of bone remodeling was reduced and the bone mass was increased with hormone replacement. The placebo group did not show any increase in bone mass [95]. Likewise, in clinical trials, estrogen has been shown to reverse bone loss in areas of trabecular and cortical bone due to postmenopausal hormone loss [96–98]. Both osteoblasts and osteoclasts have been shown to have estrogen receptor sites [99, 100]. As you have seen, studies have revealed that estrogen has positive direct effects on both the osteoblasts and osteoclasts and also helps prevent bone loss in postmenopausal women.
Glimpses into the molecular pathogenesis of Peyronie’s disease
Published in The Aging Male, 2020
Evert-Jan P. M. ten Dam, Mels F. van Driel, Igle Jan de Jong, Paul M. N. Werker, Ruud A. Bank
Using immunohistochemical studies, we have shown that in PD plaques contains increased amounts of collagen types I and III, higher numbers of myofibroblasts, and increased levels of β-catenin, Wnt4, and YAP1 (but normal levels of Wnt2, Wnt5a, Wnt7b, and WISP1). The mRNA tissue expression levels indicate differences in ratios between the different fibrillar collagen types (in favor of collagen types III and V compared to collagen type I), which is in agreement with the thinner collagen fibrils as previously observed in PD. The fibrotic nature of the plaque is confirmed by the increased mRNA levels of collagen types IV and VI, and fibronectin. Not only the quantity of collagen is affected but also the quality of the collagen, as concluded from the increased mRNA levels of PLOD3. Differences in extracellular matrix composition and post-translational modifications all contribute to aberrations in supramolecular assemblages. The low mRNA level of cathepsin K is also noteworthy, as this enzyme is capable of effectively degrading pyridinoline cross-linked collagen. The lower levels of cathepsin K may further contribute to the consistent collagen accumulation in the plaque. Clearly, the homeostasis of the extracellular matrix is compromised, and should be targeted in future treatments.
Proteomic exploration of cystathionine β-synthase deficiency: implications for the clinic
Published in Expert Review of Proteomics, 2020
Collagen is a major structural protein component of connective tissues (e.g., skin, tendons, bone), which accounts for 25 to 35% of the total protein weight in mammals [93]. Normal function of collagenous fibers depends on inter-chain crosslinks, which stabilize triple helical structures [94]. Crosslinking is initiated by the oxidation of specific lysine and hydroxylysine residues to the aldehydes allysine and hydroxyallysine, respectively. The enzymatic oxidation reactions are catalyzed by lysine oxidase (LOX) [95,96]. Spontaneous chemical reactions between the allysine/hydroxyallysine residues and the ε-amino group of lysine residue afford a Schiff-base adduct, which converts to a stable pyridinoline crosslink [97]. Each triple-helical collagen unit contains one to two crosslinks. The fibril-forming type I, II, and III collagens have four cross-linking sites: one in each of the short non-helical ends, called telopeptides, and two in the triple-helical region, close to the N- and C-terminal ends of collagen molecules. The pyridinoline crosslinks, which occur in collagens of cartilage, bone, and skeletal tissues, provide the stability and tensile strength to collagen fibrils, which is important for the mechanical function of connective tissues [93,94].
Suppression of joint destruction with subcutaneous tocilizumab for Japanese patients with rheumatoid arthritis in clinical practice
Published in Modern Rheumatology, 2020
Yasuharu Nakashima, Masakazu Kondo, Eisuke Shono, Takashi Ishinishi, Hiroshi Tsukamoto, Koji Kuroda, Akira Maeyama, Hiroshi Harada, Masayuki Maekawa, Takashi Shimauchi, Ryuji Nagamine, Hiroshi Jojima, Seiji Yoshizawa, Tomomi Tsuru, Takeshi Otsuka, Hisaaki Miyahara, Eiichi Suematsu, Ken Wada, Shigeru Yoshizawa, Yasushi Inoue, Takaaki Fukuda, Satoshi Ikemura, Akihisa Haraguchi
TCZ administration has frequently been reported to increase bone formation markers. Gernero et al. have reported that serum osteocalcin, a bone formation marker, increased in the OPTION study [27]. In the same way, BAP increased significantly from the baseline in the present study showing the positive effects on bone formation. However, it is not consistent with the bone resorption markers with TCZ treatment. The OPTION study showed that carboxy-terminal pyridinoline cross-linked telopeptide of type I collagen (CTX1), a bone resorption marker, decreased after TCZ administration, but the LITHE study showed the increased CTX1 at 52 weeks after TCZ treatment [28]. In this study, both BAP and TRACP5b increased. This paradoxical increase of TRACP5b was also seen with TNF inhibitor. Toussirot et al reported elevated TRAP5b despite increase in lumber spine bone mineral density [29]. There is no clear explanation for these findings at present, and it needs further clarification.