Summary The variability of serum osteoprotegerin (OPG) and soluble RANKL (sRANKL) along the 24-h cycle was assessed in 20 healthy women. No rhythmic variations of serum OPG, sRANKL or sRANKL/OPG ratio were detected as a group phenomenon. Timing of sampling is unlikely to influence the results of measurements of circulating OPG and sRANKL. Introduction Physiological bone turnover shows diurnal variations. The aim of the study was to assess variability of OPG and sRANKL serum levels along the 24-h cycle. Methods Blood was collected from 20 healthy women (median age 31 years, range 25-65 years) at 4-h intervals between 08:00 and 24:00 and at 2-h intervals between 24:00 and 08:00. Serum albumin, cortisol, osteocalcin (OC), Cterminal telopeptide of type I collagen (CTX), OPG and total sRANKL were measured. Temporal variations were assessed by the COSINOR model. Results Circadian rhythms of cortisol and albumin documented a normal synchronization within the circadian structure. Serum OC and CTX showed rhythmic variations, peaking at night-time. Rhythmic variations of serum OPG, sRANKL and sRANKL/OPG ratio were not detected as a group phenomenon. On an individual basis, rhythmic changes were detected in ten patients for OPG and eight patients for sRANKL, with very small amplitudes and heterogeneous acrophases. Conclusions The absence of consistent rhythmic variations of circulating OPG and sRANKL levels may reflect the absence of rhythmic variations of their expression in the bone microenvironment. Were this the case, the nocturnal rise of bone resorption should be accounted for by different, not RANKL/OPG-mediated factors. Since circulating OPG and sRANKL may derive from sources other than bone, rhythmicity could be masked by non-rhythmic or nonsynchronized rhythmic expression in these sources. Timing of sampling is unlikely to influence the results of measurements of circulating OPG and sRANKL.

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Persistent circadian rhythm of bone turnover in bone metastatic breast cancer suggests greater skeletal retention of bisphosphonates if administered in the night. We assessed differential effects of night vs morning administration of zoledronic acid (ZA) on bone turnover. Forty-four breast cancer patients with bone metastases were randomised to receive intravenous ZA (4 mg) at 1100 or 2300 hours every 28 days for four times. Urinary concentration N-telopeptide of type-I collagen (NTX) and deoxypyridinolines, and serum C-telopeptide of type-I collagen (CTX), bone alkaline phosphatase (ALP), osteocalcin and Parathyroid hormone (PTH) was measured in the morning at baseline and after 4, 7, 14, 28, 56 and 84 days. Urinary ZA concentration was also measured. Zoledronic acid caused significant decreases of NTX and CTX (Po0.001), without any difference in percent changes between night and morning arms. Bone ALP and osteocalcin were also significantly affected by ZA (P ¼ 0.001), without any difference between arms. Parathyroid hormone significantly increased in both the arms; PTH increase was lower in the night arm (P ¼ 0.001). From the second administration onwards, urinary ZA level was significantly higher in the night arm (Po0.01). Administration of ZA at two opposite phases of the circadian cycle causes similar changes of bone-turnover marker levels, but has differential effects on the level of serum PTH.

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BackgroundSmall supernumerary marker chromosomes (sSMCs) are additional, structurally abnormal chromosomes, generally smaller than chromosome 20 of the same metaphase spread. Due to their small size, they are difficult to characterize by conventional cytogenetics alone. In regard to their clinical effects, sSMCs are a heterogeneous group: in particular, sSMCs containing pericentromeric euchromatin are likely to be associated with abnormal outcomes, although exceptions have been reported. To improve characterization of the genetic content of sSMCs, several approaches might be applied based on different molecular and molecular-cytogenetic assays, e.g., fluorescent in situ hybridization (FISH), array-based comparative genomic hybridization (array CGH), and multiplex ligation-dependent probe amplification (MLPA).To provide a complementary tool for the characterization of sSMCs, we constructed and validated a new, FISH-based, pericentromeric Bacterial Artificial Chromosome (BAC) clone set that with a high resolution spans the most proximal euchromatic sequences of all human chromosome arms, excluding the acrocentric short arms.ResultsBy FISH analysis, we assayed 561 pericentromeric BAC probes and excluded 75 that showed a wrong chromosomal localization. The remaining 486 probes were used to establish 43 BAC-based pericentromeric panels. Each panel consists of a core, which with a high resolution covers the most proximal euchromatic ~0.7 Mb (on average) of each chromosome arm and generally bridges the heterochromatin/euchromatin junction, as well as clones located proximally and distally to the core. The pericentromeric clone set was subsequently validated by the characterization of 19 sSMCs. Using the core probes, we could rapidly distinguish between heterochromatic (1/19) and euchromatic (11/19) sSMCs, and estimate the euchromatic DNA content, which ranged from approximately 0.13 to more than 10 Mb. The characterization was not completed for seven sSMCs due to a lack of information about the covered region in the reference sequence (1/19) or sample insufficiency (6/19).ConclusionsOur results demonstrate that this pericentromeric clone set is useful as an alternative tool for sSMC characterization, primarily in cases of very small SMCs that contain either heterochromatin exclusively or a tiny amount of euchromatic sequence, and also in cases of low-level or cryptic mosaicism. The resulting data will foster knowledge of human proximal euchromatic regions involved in chromosomal imbalances, thereby improving genotype–phenotype correlations.