Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0851184 (thinning)
 11,252 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Twenty-seven thalassaemic patients (13 F, 14 M, aged 8.1-14.9 yr), regularly transfused and chelated with desferrioxamine (30-40 mg/kg/day) were studied. Every patient was submitted to auxological evaluations, dual X-ray absorptiometry to measure bone mineral density (BMD), and to the determination of bone metabolic markers of osteoclastic activity (total urinary hydroxylysylpyridinoline crosslinks, carboxyterminal pyridinoline crosslinked telopeptide of type I collagen [ICTP]) and of osteoblastic activity (bone Gla protein [BGP] and carboxyterminal propeptide of type I procollagen [PIPC]). The evaluations were repeated after 1 year, during which 13 patients continued desferrioxamine chelation while 14 underwent deferiprone chelation (75 mg/kg/day in 3 doses). The data demonstrate widespread bone alterations consisting of osteoporosis, growth failure and bone age delay. Lumber spine (L2-L4) BMD areal values (Z score) inversely correlated with age, as did height SDS of both male and female patients, indicating osteoporosis progressing with age in parallel with growth insufficiency. No clear-cut alterations in bone mineral metabolism were found in basal state and after 1 year. Extensive MR imaging studies are needed to define the contribution of residual bone marrow hyperplasia to thalassaemic osteopathy suggested by subtle radiological signs as enlargement of bone marrow cavities with thinning of the cortical bone and abnormalities of the trabecules of spongy bone.
 ...
PMID:Bone density and metabolism in thalassaemia. 1009 Nov 47

In this research we utilized tail-suspended rats as an in vivo model for bone loss studies in order to investigate the effects of the tail suspension on the structure of the suspended bones and in ex vivo cultures the activities of trabecular osteoblasts, marrow-derived osteogenic cells, and osteoclasts obtained from treated animals, compared with untreated controls. After a 5-day hind limb unloading, trabecular thinning was already evidenced in the tibial primary spongiosa. In the secondary spongiosa, the bone formation activity was reduced whereas osteoclastic parameters were not yet altered. Bone marrow-derived osteogenic cells and differentiated osteoblasts from enzymatic digestion of posterior limb trabecular bone were prepared from 5 day tail-suspended rats and from normally loaded rats as controls. Cell morphology, alkaline phosphatase (ALPH) activity, production of mineral matrix, osteocalcin, and IL-6 secretion were evaluated in both cell populations. Tail suspension reduced the osteogenic potential of stromal marrow cells and of already differentiated osteoblasts. In fact, ALP positive colonies were significantly reduced in number and were smaller in size compared with controls and bone nodules formed in permissive conditions were also significantly fewer and smaller, whereas in cultures of cells from control conditions, large mineralizing nodules were formed. Osteocalcin secretion was not affected by unloading. Finally, IL-6 concentration was increased in marrow-derived cells from treated rats compared with controls. Primary cultures of osteoclasts were obtained from the nonadherent fraction of the bone marrow of the same animals. The number of TRAP positive cells in culture from tail-suspended rats was significantly increased, as well as bone resorption activity, measured as resorbed surfaces of a suitable synthetic hydroxyapatite, compared with controls. These data clearly suggest that skeletal unloading not only reduces the osteogenic potential of osteoblastic cells but induces an increased osteoclastogenesis and osteoclast activity in ex vivo cultures. They also indicate for the first time that a possible mediator responsible for the increased osteoclastogenesis could be represented by the IL-6 whose secretion by bone marrow cells was significantly enhanced by unloading.
 ...
PMID:Rat hindlimb unloading by tail suspension reduces osteoblast differentiation, induces IL-6 secretion, and increases bone resorption in ex vivo cultures. 1190 15

An excessive intake of vitamin A has been associated with an increased risk of fractures in humans. In animals, a high vitamin A intake leads to a reduction of long bone diameter and spontaneous fractures. Studies in rodents indicate that the bone thinning is due to increased periosteal bone resorption and reduced radial growth. Whether the latter is a consequence of direct effects on bone or indirect effects on appetite and general growth is unknown. In this study we therefore used pair-feeding and dynamic histomorphometry to investigate the direct effect of a high intake of vitamin A on bone formation in rats. Although there were no differences in body weight or femur length compared to controls, there was an approximately halved bone formation and mineral apposition rate at the femur diaphysis of rats fed vitamin A. To try to clarify the mechanism(s) behind this reduction, we treated primary human osteoblasts and a murine preosteoblastic cell line (MC3T3-E1) with the active metabolite of vitamin A; retinoic acid (RA), a retinoic acid receptor (RAR) antagonist (AGN194310), and a Cyp26 inhibitor (R115866) which blocks endogenous RA catabolism. We found that RA, via RARs, suppressed in vitro mineralization. This was independent of a negative effect on osteoblast proliferation. Alkaline phosphatase and bone gamma carboxyglutamate protein (Bglap, Osteocalcin) were drastically reduced in RA treated cells and RA also reduced the protein levels of Runx2 and Osterix, key transcription factors for progression to a mature osteoblast. Normal osteoblast differentiation involved up regulation of Cyp26b1, the major enzyme responsible for RA degradation, suggesting that a drop in RA signaling is required for osteogenesis analogous to what has been found for chondrogenesis. In addition, RA decreased Phex, an osteoblast/osteocyte protein necessary for mineralization. Taken together, our data indicate that vitamin A is a negative regulator of osteoblast mineralization.
...
PMID:Vitamin a is a negative regulator of osteoblast mineralization. 2434 23